@article{ren_song_zhu_o'connor_dong_2023, title={All Electrohydrodynamic Printed Flexible Organic Thin Film Transistors}, volume={6}, ISSN={["2365-709X"]}, url={https://doi.org/10.1002/admt.202300410}, DOI={10.1002/admt.202300410}, abstractNote={Abstract}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Ren, Ping and Song, Runqiao and Zhu, Yong and O'Connor, Brendan and Dong, Jingyan}, year={2023}, month={Jun} }
 @article{ren_dong_2023, title={Direct printing of conductive polymer PEDOT:PSS for foldable transient electronics}, volume={35}, ISSN={["2213-8463"]}, url={http://dx.doi.org/10.1016/j.mfglet.2023.08.024}, DOI={10.1016/j.mfglet.2023.08.024}, abstractNote={With the increased demand on portability, electronics have progressed from rudimentary flexible electronics to foldable electronics. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a conductive polymer, is a promising material for achieving foldable electronics, due to its mechanical stability. In foldable electronics, however, inadequate physical adhesion between electrodes and substrates under folding deformation has been a challenge. It can cause interfacial delamination and electronic failure during the folding and unfolding processes. In this study, electrohydrodynamic (EHD) printing is utilized for the fast, low-cost, and high-resolution fabrication of PEDOT:PSS circuits onto polyvinyl alcohol (PVA) films to improve the interface binding force for foldable electronics. The morphology and electrical properties of PEDOT:PSS patterns with different printed conditions were experimentally investigated. The adhesion between the printed PEDOT:PSS circuits and the PVA film was characterized by tape adhesion test, and the electrical property remained almost unchanged after 50 peeling tests. We demonstrated excellent foldability of the printed electronics. After 4 folds (16 layers), the resistance of PEDOT:PSS circuits varied minimally, and the external LED lights remained operational while folding and unfolding. Moreover, using the water soluble and degradable PVA substrate, the printed circuits can be simply dissolved in water, which provide a promising approach toward transient electronics and green electronics, and reduce the electronic waste.}, journal={MANUFACTURING LETTERS}, publisher={Elsevier BV}, author={Ren, Ping and Dong, Jingyan}, year={2023}, month={Aug}, pages={215–220} }
 @article{ren_dong_2023, title={Electrohydrodynamic Printed Pedot:Pss/Graphene/Pva Circuits for Sustainable and Foldable Electronics}, volume={8}, ISSN={["2365-709X"]}, url={https://doi.org/10.1002/admt.202301045}, DOI={10.1002/admt.202301045}, abstractNote={Abstract}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Ren, Ping and Dong, Jingyan}, year={2023}, month={Aug} }
 @article{song_ren_liu_zhu_dong_brendan t. o'connor_2023, title={Stretchable Organic Transistor Based Pressure Sensor Employing a Porous Elastomer Gate Dielectric}, volume={4}, ISSN={["2365-709X"]}, url={http://dx.doi.org/10.1002/admt.202202140}, DOI={10.1002/admt.202202140}, abstractNote={Abstract}, journal={ADVANCED MATERIALS TECHNOLOGIES}, publisher={Wiley}, author={Song, Runqiao and Ren, Ping and Liu, Yuxuan and Zhu, Yong and Dong, Jingyan and Brendan T. O'Connor}, year={2023}, month={Apr} }
 @article{liu_zheng_o'connor_dong_zhu_2022, title={Curvilinear soft electronics by micromolding of metal nanowires in capillaries}, volume={8}, ISSN={["2375-2548"]}, url={https://doi.org/10.1126/sciadv.add6996}, DOI={10.1126/sciadv.add6996}, abstractNote={
            Soft electronics using metal nanowires have attracted notable attention attributed to their high electrical conductivity and mechanical flexibility. However, high-resolution complex patterning of metal nanowires on curvilinear substrates remains a challenge. Here, a micromolding-based method is reported for scalable printing of metal nanowires, which enables complex and highly conductive patterns on soft curvilinear and uneven substrates with high resolution and uniformity. Printing resolution of 20 μm and conductivity of the printed patterns of ~6.3 × 10
            6
            S/m are achieved. Printing of grid structures with uniform thickness for transparent conductive electrodes (TCEs) and direct printing of pressure sensors on curved surfaces such as glove and contact lens are also realized. The printed hybrid soft TCEs and smart contact lens show promising applications in optoelectronic devices and personal health monitoring, respectively. This printing method can be extended to other nanomaterials for large-scale printing of high-performance soft electronics.
          }, number={46}, journal={SCIENCE ADVANCES}, author={Liu, Yuxuan and Zheng, Michael and O'Connor, Brendan and Dong, Jingyan and Zhu, Yong}, year={2022}, month={Nov} }
 @article{ren_dong_2022, title={Direct electrohydrodynamic printing of aqueous silver nanowires ink on hydrophobic substrates for flexible and stretchable electronics}, volume={33}, url={http://dx.doi.org/10.1016/j.mfglet.2022.07.021}, DOI={10.1016/j.mfglet.2022.07.021}, abstractNote={Stretchable conductors based on metal nanowires, such as silver nanowires (AgNWs), are essential for the fabrication of stretchable electronics. Electrohydrodynamic (EHD) printing has been developed as a promising technique for patterning various conductive nanomaterials on stretchable substrates. However, the printing performance is adversely affected by poor wettability of the ink on the surface of the stretchable substrates, which are mostly low-surface-energy elastomeric polymers, like polydimethylsiloxane (PDMS). The surface treatments of the substrate surface could improve the printability of the ink on these substrates, but also impose many limitations, as the surface treatment could unfavorably affect the mechanical properties of the polymer and may cause damage to the underlying layer or other existing features on the substrate. The paper investigates EHD direct printing of aqueous AgNWs ink on untreated PDMS using surfactant (i.e., Capstone FS30) modified ink for the fabrication of stretchable electronics. The static contact angles at the different FS30 ratios were measured to analyze their effect on regulating the ink wettability. A set of printing experiments were performance to select the right ink composition to tailor and optimize the ink printability and printing performance. The morphology and electrical properties of printed AgNWs-based conductors can be controlled by selecting different the EHD printing speed. Furthermore, to illustrate the potential for reliable EHD direct printing of AgNWs for stretchable electronics, a wearable electronic patch with a fractal design of the AgNWs pattern was printed on an untreated PDMS substrate using the surfactant modified AgNWs ink, which provides stable electronic response under the bending, tension and compression.}, journal={Manufacturing Letters}, publisher={Elsevier BV}, author={Ren, Ping and Dong, Jingyan}, year={2022}, month={Sep}, pages={161–166} }
 @article{cao_dong_2022, title={Fabrication, modeling, and characterization of soft twisting electrothermal actuators with directly printed oblique heater}, volume={32}, ISSN={["1361-6439"]}, url={https://doi.org/10.1088/1361-6439/ac4956}, DOI={10.1088/1361-6439/ac4956}, abstractNote={Abstract}, number={3}, journal={JOURNAL OF MICROMECHANICS AND MICROENGINEERING}, publisher={IOP Publishing}, author={Cao, Yang and Dong, Jingyan}, year={2022}, month={Mar} }
 @article{cao_dong_2022, title={Freeform printing and modeling of soft twisting electrothermal actuators}, volume={33}, url={http://dx.doi.org/10.1016/j.mfglet.2022.07.013}, DOI={10.1016/j.mfglet.2022.07.013}, abstractNote={Soft electrothermal actuators have drawn extensive attention in recent years for their promising applications in biomimetic and biomedical areas. Most soft electrothermal actuators reported so far demonstrated uniform bending deformation, due to the deposition-based fabrication of the conductive heater layer from nanomaterial-based solutions, resulting in uniform heating and bending. Twisting represents another degree-of-freedom for soft actuators to enhance their versatility and functionality. In this paper, a soft electrothermal actuator that can provide twisting deformation was designed and fabricated. The two structural layers of the actuator are made of polyimide (PI) and polydimethylsiloxane (PDMS), which are selected due to their distinct thermal expansion properties. Embedded in between the two structural layers is a metallic microfilament heater layer that is directly printed using electrohydrodynamic (EHD) printing. Assisted by the freeform direct patterning capabilities of EHD printing, a skewed heater pattern was designed and printed. This skewed heater pattern not only produces a skewed parallelogram-shaped temperature field, but also changes the stiffness anisotropy of the actuator, leading to twisting deformation with coupled bending. The fabricated twisting actuator was characterized on its heating and twisting performance at different supply voltages. Finite element analysis (FEA) was utilized for the thermal and deformation analysis of the actuator. Using three twisting actuators, a soft gripper was designed and fabricated to implement pick-and-place operations of delicate objects.}, journal={Manufacturing Letters}, publisher={Elsevier BV}, author={Cao, Yang and Dong, Jingyan}, year={2022}, month={Sep}, pages={41–47} }
 @article{cheng_zhai_dong_2022, title={Investigation of Gaussian mixture clustering model for online diagnosis of tip-wear in nanomachining}, volume={77}, ISSN={["2212-4616"]}, url={http://dx.doi.org/10.1016/j.jmapro.2022.03.012}, DOI={10.1016/j.jmapro.2022.03.012}, abstractNote={This paper studied an unsupervised machine learning method to achieve real-time diagnosis of tip wear in tip-based nanomachining with an Atomic Force Microscope (AFM). The unsupervised Gaussian Mixture Model (GMM) was applied for online pattern recognition using the collected process data. In this work, the time varying signal of machining force was collected and managed in the form of moving data windows. The characteristics of the nanomachining force signal, including the maximum force, peak to peak force, and the variance, were calculated as the data of extracted features to indicate the tip wear conditions. Outliers were identified and removed using the Mahalanobis Distance Detection. A GMM model was trained using the historical processing data, in which the tip wear states were identified by clustering the feature parameters of each data frame. The change of the tip conditions was detected and tracked through the changing numbers of the tip failure points in the data windows. Experiment results showed that the highest and the average recognition accuracy of the proposed model was 1 and 0.8367 with the longest and the average calculation time of 0.031 s and 0.025 s. Compared with supervised and semi-supervised machine learning algorithms, the GMM based on unsupervised machine learning model has slightly lower recognition accuracy, but much shorter calculation time, which is suitable for online automatic diagnosis of tool wear in large-scale nanomanufacturing in real time.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, publisher={Elsevier BV}, author={Cheng, Fei and Zhai, Shi-Chen and Dong, Jingyan}, year={2022}, month={May}, pages={114–124} }
 @article{behera_sousa_oleksik_dong_fritzen_2022, title={Student perceptions of remote learning transitions in engineering disciplines during the COVID-19 pandemic: a cross-national study}, volume={48}, ISSN={["1469-5898"]}, url={https://doi.org/10.1080/03043797.2022.2080529}, DOI={10.1080/03043797.2022.2080529}, abstractNote={ABSTRACT This study captures student perceptions of the effectiveness of remote learning and assessment in two associated engineering disciplines, mechanical and industrial, during the COVID-19 pandemic in a cross-national study. A structured questionnaire with 24 items on a 5-point Likert scale was used. Parallel and exploratory factor analyses identified three primary subscales. The links between student perceptions and assessment outcomes were also studied. There was a clear preference for face-to-face teaching, with the highest for laboratories. Remote live lectures were preferred over recorded. Although students found the switch to remote learning helpful, group work and communication were highlighted as concern areas. Mean scores on subscales indicate a low preference for remote learning (2.23), modest delivery effectiveness (3.05) and effective digital delivery tools (3.61). Gender effects were found significant on all subscales, along with significant interactions with university and year-group. Preference for remote delivery of design-based modules was significantly higher than others.}, number={1}, journal={EUROPEAN JOURNAL OF ENGINEERING EDUCATION}, publisher={Informa UK Limited}, author={Behera, Amar Kumar and Sousa, Ricardo Alves and Oleksik, Valentin and Dong, Jingyan and Fritzen, Daniel}, year={2022}, month={Jun} }
 @article{deng_jiang_si_zhou_dong_cohen_2021, title={AFM-Based nanofabrication and quality inspection of three-dimensional nanotemplates for soft lithography}, volume={66}, ISSN={["2212-4616"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85105693471&partnerID=MN8TOARS}, DOI={10.1016/j.jmapro.2021.04.051}, abstractNote={Soft lithography is one of the most promising nanofabrication technologies for scalable nanomanufacturing. It uses flexible molds or stamps to fabricate extremely high-resolution nanopatterns in a low cost and rapid fashion on both flat and curved surfaces. Although two-dimensional soft lithography has been widely investigated and applied for some applications, there is a lack of quantitative research on using nanometer scale 3D patterns fabricated by atomic force microscope (AFM) for 3D soft lithography. In this paper, we demonstrated the effectiveness of ultrasonic vibration assisted AFM-based nanomachining in fabricating 3D master nanotemplates for 3D soft lithography. We successfully applied Polydimethylsiloxane (PDMS) daughter molds, casted from a nanometer scale 3D master template, using a soft lithography technique solvent-assisted micromolding. In addition, we investigated the quality and reusability of the master nanotemplates, and the quality of the PDMS patterns by quantifying the volume differences using an automatic imaging registration algorithm. Results show that there are zero or little PDMS residuals in the polymethyl methacrylate (PMMA) master nanotemplate with a simple contour for the first and second daughter mold casting, but 7% residuals for the third casting. And a more complex master nanotemplate shows slightly higher residual levels.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, publisher={Elsevier BV}, author={Deng, Jia and Jiang, Lan and Si, Bing and Zhou, Huimin and Dong, Jingyan and Cohen, Pual}, year={2021}, month={Jun}, pages={565–573} }
 @article{ren_liu_song_o'connor_dong_zhu_2021, title={Achieving High-Resolution Electrohydrodynamic Printing of Nanowires on Elastomeric Substrates through Surface Modification}, volume={3}, ISSN={["2637-6113"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85099220488&partnerID=MN8TOARS}, DOI={10.1021/acsaelm.0c00747}, abstractNote={Stretchable electronics based on nanomaterials has received much interest recently. However, it is challenging to print 1D nanomaterials (e.g., nanowires) with high resolution on stretchable elasto...}, number={1}, journal={ACS APPLIED ELECTRONIC MATERIALS}, publisher={American Chemical Society (ACS)}, author={Ren, Ping and Liu, Yuxuan and Song, Runqiao and O'Connor, Brendan and Dong, Jingyan and Zhu, Yong}, year={2021}, month={Jan}, pages={192–202} }
 @article{cheng_dong_2021, title={Data-driven online detection of tip wear in tip-based nanomachining using incremental adaptive support vector machine}, volume={69}, ISSN={["2212-4616"]}, url={http://dx.doi.org/10.1016/j.jmapro.2021.08.013}, DOI={10.1016/j.jmapro.2021.08.013}, abstractNote={This paper presented an online statistical pattern recognition method to detect the severe tip wear in nanomachining using an incremental adaptive support vector machine (IASVM). From the time series data of the collected nanomachining force, the two feature variables (i.e., peak-to-peak force and variance of each machining cycle) were calculated to classify the state of the nanomachining process. To enable online detection, the data was collected in the form of a moving window, sliding once every 0.2 s to add 20 sets of new feature data to update the data set each time. For each data window, the support vector machine (SVM) was restructured by modifying the regularization parameter and the Kernel parameter adaptively. The solution structure of the updated SVM was calculated to classify the incremental data and the disturbing data with the best accuracy. The number of tip failure points in each window was counted to determine the tip wear severity and the moment when the AFM tip needs to be replaced by monitoring the trend of tip failure points. From experimental data, it was shown that the average accuracy of IASVM's recognition of the tip wear conditions was 95% and the average calculation time was 0.166 s, which makes it a promising approach for online detection of tip damage in nanomachining process.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, publisher={Elsevier BV}, author={Cheng, Fei and Dong, Jingyan}, year={2021}, month={Sep}, pages={412–421} }
 @article{ren_dong_2021, title={Direct Fabrication of VIA Interconnects by Electrohydrodynamic Printing for Multi-Layer 3D Flexible and Stretchable Electronics}, volume={6}, ISSN={["2365-709X"]}, url={https://doi.org/10.1002/admt.202100280}, DOI={10.1002/admt.202100280}, abstractNote={Abstract}, number={9}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Ren, Ping and Dong, Jingyan}, year={2021}, month={Jun} }
 @article{cao_dong_2021, title={Programmable soft electrothermal actuators based on free-form printing of the embedded heater}, volume={17}, ISSN={["1744-6848"]}, url={https://doi.org/10.1039/D0SM02062A}, DOI={10.1039/d0sm02062a}, abstractNote={We report soft electrothermal actuators with programmable deformations. By configuring the design of the printed heater, complex programmable deformations, including uniform bending, customized bending, folding, and twisting, can be achieved.}, number={9}, journal={SOFT MATTER}, publisher={Royal Society of Chemistry (RSC)}, author={Cao, Yang and Dong, Jingyan}, year={2021}, month={Mar}, pages={2577–2586} }
 @article{cao_dong_2021, title={Self-Sensing and Control of Soft Electrothermal Actuator}, volume={26}, ISSN={["1941-014X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85098780878&partnerID=MN8TOARS}, DOI={10.1109/TMECH.2020.3009237}, abstractNote={Soft electrothermal actuators have been of particular interest to researchers in soft mechatronic/robotic systems due to their large deformation, lightweight, and low power actuation. Closed-loop control of soft actuators is critical for high-precision applications, due to the nonlinear relationship between actuation voltage and output bending motion. In this article, a resistive self-sensing approach was developed for the soft electrothermal actuator, which enables the closed-loop control of the actuator without external sensors. The self-sensing of the actuator's deformation is achieved by measuring the resistance change of the embedded microfilament heater of the soft electrothermal actuator. When the bimorph electrothermal actuator deflects under the temperature change, its deflection can be detected by the temperature-incurred resistance change of the embedded heater. A closed-loop controller was designed using the self-sensed deflection signal. To handle the different responses of the actuator in the heating and cooling stages, a switching proportional-integral-derivative control algorithm was designed. Specifically, two sets of control parameters were tuned and used for the heating and cooling stages, respectively. The performance of the designed control algorithm was evaluated for step response, tracking of complex wave signals, and disturbance rejection. Compared with the open-loop operation, the closed-loop controlled actuator demonstrated a much more rapid and accurate response (the rising time and settling time were reduced over 80%) and excellent tracking and disturbance rejection capabilities.}, number={2}, journal={IEEE-ASME TRANSACTIONS ON MECHATRONICS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Cao, Yang and Dong, Jingyan}, year={2021}, month={Apr}, pages={854–863} }
 @inproceedings{cao_dong_2020, title={Fabrication and self-sensing control of soft electrothermal actuator}, volume={48}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85095111823&partnerID=MN8TOARS}, DOI={10.1016/j.promfg.2020.05.018}, abstractNote={Soft electrothermal actuators have attracted wide attention due to their high flexibility, adaptability and light weight. These characteristics give them great potentials to be used in biomimetic and soft robotics applications. In this paper, an electrothermal actuator with directly printed microfilament heater was designed, fabricated and characterized. The soft actuator used polyimide (PI) and polydimethylsiloxane (PDMS) as the structural materials due to their large mismatch of thermal expansion. A microfilament heater was electrohydrodynamic (EHD) printed using a low melting point alloy Bi58/Sn42, and embedded in-between the PI and PDMS layers. The fabricated actuator achieved a maximum curvature of 1.0 cm−1 under a supply voltage as low as 3 V. Resistive self-sensing technology was used to sense the deflection of the actuator and to develop the closed-loop control of the actuator. The bending curvature of the actuator is resulted from the temperature change of the actuator, which can be detected by the electrical resistance change of the embedded heater as they are linearly related. A PID controller was designed for the closed-loop operation of the actuator. Compared with the open-loop operation, the closed-loop controlled actuator demonstrated more rapid and precise response. The developed electrothermal actuator was successfully demonstrated for applications as a soft lifter and soft gripper.}, booktitle={Procedia Manufacturing}, publisher={Elsevier BV}, author={Cao, Y. and Dong, J.}, year={2020}, pages={43–48} }
 @article{song_yao_liu_wang_dong_zhu_brendan t. o'connor_2020, title={Facile Approach to Fabricating Stretchable Organic Transistors with Laser-Patterned Ag Nanowire Electrodes}, volume={12}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.0c15339}, DOI={10.1021/acsami.0c15339}, abstractNote={Stretchable electronics are poised to revolutionize personal healthcare and robotics, where they enable distributed and conformal sensors. Transistors are fundamental building blocks of electronics, and there is a need to produce stretchable transistors using low-cost and scalable fabrication techniques. Here, we introduce a facile fabrication approach using laser patterning and transfer printing to achieve high-performance, solution-processed intrinsically stretchable organic thin-film transistors (OTFTs). The device consists of Ag nanowire (NW) electrodes, where the source and drain electrodes are patterned using laser ablation. The Ag NWs are then partially embedded in a poly(dimethylsiloxane) (PDMS) matrix. The electrodes are combined with a PDMS dielectric and polymer semiconductor, where the layers are individually transfer printed to complete the OTFT. Two polymer semiconductors, DPP-DTT and DPP-4T, are considered and show stable operation under the cyclic strain of 20 and 40%, respectively. The OTFTs maintain electrical performance by adopting a buckled structure after the first stretch-release cycle. The conformability and stretchability of the OTFT is also demonstrated by operating the transistor while adhered to a finger being flexed. The ability to pattern highly conductive Ag NW networks using laser ablation to pattern electrodes as well as interconnects provides a simple strategy to produce complex stretchable OTFT-based circuits.}, number={45}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Song, Runqiao and Yao, Shanshan and Liu, Yuxuan and Wang, Hongyu and Dong, Jingyan and Zhu, Yong and Brendan T. O'Connor}, year={2020}, month={Nov}, pages={50675–50683} }
 @article{kong_deng_dong_cohen_2020, title={Study of tip wear for AFM-based vibration-assisted nanomachining process}, volume={50}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85076704783&partnerID=MN8TOARS}, DOI={10.1016/j.jmapro.2019.12.013}, abstractNote={Nanofabrication technologies have many applications in science and engineering. Among different nanofabrication technologies, the tip-based vibration-assisted nanomachining using an Atomic Force Microscope (AFM) provides a low-cost, easy-to-setup approach for the production of nano-scale structures. As the resolution and quality of the machined features are greatly affected by the radius and sharpness of the tip, it is critical to investigate the behavior of tip wear during the nanomachining process and to estimate the tip life. In this work, the evolvement of the tip wear was characterized and modeled to predict tip wear and tip life for the nanomachining process. Besides the direct inspection of the tip radius using a Scanning Electron Microscope (SEM), the pull-off force between the AFM tip and the sample surface was found to correlate well with the tip radius, which enabled the measurement of tip wear directly without unloading the tip from the AFM. To study the tip wear at different conditions, the tip radius was measured from the pull-off force under a wide range of machining conditions. The change rates of the tip radius were significantly affected by the machining parameters, such as setpoint force and feed rate. Moreover, during the nanomachining process, three regions were identified for the tip wear evolvement as initial tip wear region, transition region, and tip failure region. Regression models were developed to describe the tip wear at different stages, and to estimate the tip life (i.e. when the tip needs to be changed), which provide usefully information for future process planning and process optimization.}, journal={Journal of Manufacturing Processes}, publisher={Elsevier BV}, author={Kong, Xiangcheng and Deng, Jia and Dong, Jingyan and Cohen, Paul H.}, year={2020}, pages={47–56} }
 @article{dong_2019, title={Editorial: Welcome to engineering research express}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85092512436&partnerID=MN8TOARS}, DOI={10.1088/2631-8695/ab2758}, abstractNote={On behalf of the Editorial Board and IOPPublishing I ampleased to announce the opening of the inaugural issue ofEngineering Research Express (ERX), a newmultidisciplinary journal that will serve all areas of engineering science. Characterized by a broad subject coverage, fast-track peer-review process and an inclusive editorial selection process focused on the scientific rigour and validity of thework, rather than its perceived impact or novelty, ERXwill publish experimental and theoretical research covering topics extending across all aspects of engineering. Encompassing interdisciplinary fields that at the interface engineering and the physical sciences, particular areas of interest will include:}, number={1}, journal={Engineering Research Express}, author={Dong, Jingyan}, year={2019} }
 @article{cao_dong_2019, title={High-performance low-voltage soft electrothermal actuator with directly printed micro-heater}, volume={297}, ISSN={["0924-4247"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85070218690&partnerID=MN8TOARS}, DOI={10.1016/j.sna.2019.111546}, abstractNote={Soft actuators are widely studied due to their high flexibility and adaptability. In this paper, a soft electrothermal actuator with directly printed microfilament heater was designed, fabricated, and tested. In this soft actuator, a polyimide (PI) film and a polydimethylsiloxane (PDMS) layer were selected as the two structural layers because of their distinct thermal expansion properties. Embedded between these two layers, a metallic microfilament heater that was made of low-melting-point metal alloy (i.e. Bi58/Sn42) was directly printed with custom-designed pattern using an electrohydrodynamic (EHD) printing process. The pattern of the microfilament heater and the thickness of the soft thermoelectric actuator were carefully designed towards the improved actuation capability. When an electric current was applied, the high temperature generated by the resistive heater causes large mismatch in the thermal expansion of the two structural layers, which bent the actuator. The fabricated soft actuator can achieve a maximum bending curvature of 1.0 cm−1 under an extremely low voltage about 3V. The soft actuator has been demonstrated for potential applications in soft robotics as a soft lifter and a soft gripper. At the full capability, the soft lifter provided a maximum actuation force about 3 mN, and was able to fully lift a load that was twice of its own weight. A four-finger soft gripper was designed and fabricated using four soft actuators to mimic humanoid motions and was implemented for pick-and-place operation for delicate objects.}, journal={SENSORS AND ACTUATORS A-PHYSICAL}, author={Cao, Yang and Dong, Jingyan}, year={2019}, month={Oct} }
 @article{cheng_dong_2019, title={Monitoring tip-based nanomachining process by time series analysis using support vector machine}, volume={38}, ISSN={["2212-4616"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85059695774&partnerID=MN8TOARS}, DOI={10.1016/j.jmapro.2019.01.011}, abstractNote={In this paper, time-series data analysis and pattern recognition using a multi-class support vector machine (SVM) were studied to monitor the state changes of the AFM tip-based nanomachining process with respect to the machining performance and tip wear. Time series data (i.e. machining force from the process), which has transient, nonlinear, and non-stationary characteristics, was collected by a data acquisition system. Three status detection features including the maximum force, peak-to-peak force value, and the variance of the collected lateral machining force, were extracted to classify the state of the nanomachining process. Directed Acyclic Graph Support Vector Machines (DAGSVM) with a Gaussian Radial Basis Kernel Function (RBF Kernel) was constructed to identify the different process states. Using this multi-class SVM, the machining process and the tip wear can be classified into three regions, which are effective machining with a sharp tip, transition region and bad/no machining with severe tip wear. The experimental data showed that the accuracy of the SVM was over 94.73% in both binary and ternary classifications, which confirmed that the SVM-based pattern recognition technology via time series data could successfully monitor the tip wear and process performance for tip-based nanomachining process.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Cheng, Fei and Dong, Jingyan}, year={2019}, month={Feb}, pages={158–166} }
 @article{cheng_dong_2019, title={Nano-machining AFM Tip Wear Monitoring Based on Time Series Data and Support Vector Machine,基于时间序列数据和支持向量机的纳米加工AFM刀尖损伤监测}, volume={40}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85072176043&partnerID=MN8TOARS}, DOI={10.3969/j.issn.1000-1158.2019.04.17}, number={4}, journal={Jiliang Xuebao/Acta Metrologica Sinica}, author={Cheng, F. and Dong, J.-Y.}, year={2019}, pages={647–654} }
 @article{yao_ren_song_liu_huang_dong_o'connor_zhu_2019, title={Nanomaterial‐Enabled Flexible and Stretchable Sensing Systems: Processing, Integration, and Applications}, volume={32}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.201902343}, DOI={10.1002/adma.201902343}, abstractNote={Abstract}, number={15}, journal={Advanced Materials}, publisher={Wiley}, author={Yao, Shanshan and Ren, Ping and Song, Runqiao and Liu, Yuxuan and Huang, Qijin and Dong, Jingyan and O'Connor, Brendan T. and Zhu, Yong}, year={2019}, month={Aug}, pages={1902343} }
 @inproceedings{deng_zhou_dong_cohen_2019, title={Three-dimensional nanomolds fabrication for nanoimprint lithography}, volume={34}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85072394935&partnerID=MN8TOARS}, DOI={10.1016/j.promfg.2019.06.143}, abstractNote={Nanoimprint lithography is a fabrication method by applying nanomolds on resists to form inversed patterns. It can be utilized to fabricate high-resolution nanopatterns in a low cost and rapid fashion on both flat and curved surfaces. The fidelity of fabricated master nanopatterns and elastomer nanomolds are essential to the quality of the nanoimprinted features. Although two-dimensional nanoimprint lithography has been widely investigated, there are limited researches about three-dimensional master nanopatterns and nanomolds. Even less of them discussed the fidelity of entire procedures throughout the initial master fabrication to the final nanoimprinting. In this paper, we demonstrated the effectiveness of our approach, atomic force microscope (AFM) based ultrasonic vibration assisted nanomachining, in fabricating three-dimensional master nanopatterns with complex contours and continuously height changes. Nanomolds for nanoimprint lithography were fabricated subsequently based on the master nanopatterns with a positive draft, which is naturally generated from the AFM tip. We investigated the fidelity of the nanomachining results and the residual effect of reusing mater patterns. Besides, we demonstrated the 3D nanoimprinting capability of the solvent-assisted microcontact molding process, discovering the possibility of tuning the layer-thickness of imprinted 3D nanopatterns.}, booktitle={Procedia Manufacturing}, author={Deng, J. and Zhou, H. and Dong, J. and Cohen, P.}, year={2019}, pages={228–232} }
 @article{kong_wei_zhu_cohen_dong_2018, title={Characterization and Modeling of Catalyst-free Carbon-Assisted Synthesis of ZnO Nanowires}, volume={32}, ISSN={["1526-6125"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85044172611&partnerID=MN8TOARS}, DOI={10.1016/j.jmapro.2018.03.018}, abstractNote={ZnO nanowires have been widely studied due to their unique material properties and many potential applications in electronic and optoelectronic devices. Many growth processes have been developed to synthesize ZnO nanowires. It is critically important to develop predictive process models so as to maximize the output of the nanowire synthesis. Here we report a method to characterize, quantify, and model a catalyst-free carbon-assisted ZnO nanowire growth process. Two key factors were identified for the synthesis conditions, which are reaction temperature and flow rate. Based on a factorial design method, we conducted experiments with different combinations of the two factors to study their effects on the process output (i.e. density of the nanowires), which was evaluated by a scanning electron microscope (SEM). The experimental results were analyzed using ANOVA test, and then a semi-empirical model was built to correlate the ZnO nanowire output with synthesis conditions. This model was able to describe the ZnO nanowire density with respect to synthesis conditions, which can provide guideline for synthesis parameters selection and process optimization.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Kong, Xiangcheng and Wei, Chuang and Zhu, Yong and Cohen, Paul and Dong, Jingyan}, year={2018}, month={Apr}, pages={438–444} }
 @article{deng_dong_cohen_2018, title={Development and Characterization of Ultrasonic Vibration Assisted Nanomachining Process for Three-Dimensional Nanofabrication}, volume={17}, ISSN={["1941-0085"]}, url={https://doi.org/10.1109/TNANO.2018.2826841}, DOI={10.1109/tnano.2018.2826841}, abstractNote={This paper develops and characterizes a three-dimensional (3-D) nanofabrication process using ultrasonic vibration assisted nanomachining based on an atomic force microscope (AFM). The superiorities of height control over force control in the process are explained and are demonstrated by the fabrication results. Three factors impacting actual feature depths are investigated, including the ultrasonic z-vibrational amplitude, the assigned base feature depth, and the machining speed. 3-D nanostructures with continuous height variations were successfully fabricated on polymethyl methacrylate (PMMA) films with the feature height manipulated through controlling the absolute height of the cantilever tip in AFM. By selecting machining parameters based on characterizations, feature dimensions can be controlled as desired values within small variances. The capability of transferring 3-D nanostructures from PMMA films to silicon substrates is further explored in this paper. After selecting recipes of the reactive ion etching process, 3-D nanostructures are successfully transferred to silicon substrates with controllable selectivity. The reported ultrasonic vibration assisted nanomachining process in height control provides a robust approach of fabricating 3-D nanostructures.}, number={3}, journal={IEEE TRANSACTIONS ON NANOTECHNOLOGY}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Deng, Jia and Dong, Jingyan and Cohen, Paul H.}, year={2018}, month={May}, pages={559–566} }
 @article{han_dong_2018, title={Electrohydrodynamic (EHD) Printing of Molten Metal Ink for Flexible and Stretchable Conductor with Self‐Healing Capability}, volume={3}, url={https://doi.org/10.1002/admt.201700268}, DOI={10.1002/admt.201700268}, abstractNote={Abstract}, number={3}, journal={Advanced Materials Technologies}, author={Han, Yiwei and Dong, Jingyan}, year={2018}, month={Mar} }
 @article{han_dong_2018, title={Electrohydrodynamic Printing for Advanced Micro/Nanomanufacturing: Current Progresses, Opportunities, and Challenges}, volume={6}, ISSN={["2166-0476"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85057826433&partnerID=MN8TOARS}, DOI={10.1115/1.4041934}, abstractNote={The paper provides an overview of high-resolution electrohydrodynamic (EHD) printing processes for general applications in high-precision micro/nanoscale fabrication and manufacturing. Compared with other printing approaches, EHD printing offers many unique advantages and opportunities in the printing resolution, tunable printing modes, and wide material applicability, which has been successfully applied in numerous applications that include additive manufacturing, printed electronics, biomedical sensors and devices, and optical and photonic devices. In this review, the EHDs-based printing mechanism and the resulting printing modes are described, from which various EHD printing processes were developed. The material applicability and ink printability are discussed to establish the critical factors of the printable inks in EHD printing. A number of EHD printing processes and printing systems that are suitable for micro/nanomanufacturing applications are described in this paper. The recent progresses, opportunities, and challenges of EHD printing are reviewed for a range of potential application areas.}, number={4}, journal={JOURNAL OF MICRO AND NANO-MANUFACTURING}, author={Han, Yiwei and Dong, Jingyan}, year={2018}, month={Dec} }
 @article{cui_han_huang_dong_zhu_2018, title={Electrohydrodynamic printing of silver nanowires for flexible and stretchable electronics}, volume={10}, ISSN={["2040-3372"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85045850487&partnerID=MN8TOARS}, DOI={10.1039/c7nr09570h}, abstractNote={High-resolution, large-scale printing of highly conductive AgNWs for flexible and stretchable electronics using EHD printing is presented. The printed patterns show the smallest line width of 45 μm and electrical conductivity as high as ∼5.6 × 106S m−1. AgNW-based wearable heaters and ECG electrodes are fabricated.}, number={15}, journal={NANOSCALE}, author={Cui, Zheng and Han, Yiwei and Huang, Qijin and Dong, Jingyan and Zhu, Yong}, year={2018}, month={Apr}, pages={6806–6811} }
 @article{han_dong_2018, title={Fabrication of self-recoverable flexible and stretchable electronic devices}, volume={48}, ISSN={["1878-6642"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85046344028&partnerID=MN8TOARS}, DOI={10.1016/j.jmsy.2018.04.011}, abstractNote={In this paper, we developed an EHD printing process for the fabrication of high-resolution self-recoverable flexible and stretchable electronics using low-melting-point metal inks. Three different metal inks were tested for their printability on four different substrates separately to demonstrate the capability of EHD printing technology. EHD printing enables low-cost direct fabrication of metallic conductors with sub-50 μm resolution, which represents a promising way to create electronic features with metallic conductivity and excellent flexibility and stretchability. When properly designed, the EHD printed electronics provided a stable resistance under hundreds of bending cycles and many stretching and releasing cycles with high tensile strain, which demonstrates their good flexibility and stretchability in electronics applications. The printed electronics was capable of self-healing under low temperature treatment to recover from failures without sacrificing its electrical properties. Moreover, a high-resolution capacitive sensor array was designed and fabricated. A Finite Element Analysis (FEA) model was developed to study the performance of the designed touch sensor. The results from FEA model agreed well with experimental results, which demonstrated the high-resolution capability of the EHD printing for the direction fabrication of flexible and stretchable devices.}, journal={JOURNAL OF MANUFACTURING SYSTEMS}, author={Han, Yiwei and Dong, Jingyan}, year={2018}, month={Jul}, pages={24–29} }
 @article{kong_wei_zhu_cohen_dong_2018, title={Modeling of Catalyst-free Growth Process of ZnO Nanowires}, volume={26}, ISSN={2351-9789}, url={http://dx.doi.org/10.1016/J.PROMFG.2018.07.043}, DOI={10.1016/j.promfg.2018.07.043}, abstractNote={ZnO nanowires have been widely studied due to their unique material properties and many potential applications in electronic and optoelectronic devices. Many growth processes have been developed to synthesize ZnO nanowires. It is critically important to develop predictive process models so as to maximize the output of the nanowire synthesis. Here we report a method to characterize, quantify, and model a catalyst-free carbon-assisted ZnO nanowire growth process. Two key factors were identified for the synthesis conditions, which are reaction temperature and flow rate. Based on a factorial design method, we conducted experiments with different combinations of the two factors to study their effects on the process output (i.e. density of the nanowires), which was evaluated by a scanning electron microscope (SEM). The experimental results were analyzed using ANOVA test, and then a semi-empirical model was built to correlate the ZnO nanowire output with synthesis conditions. This model was able to describe the ZnO nanowire density with respect to synthesis conditions, which can provide a guideline for synthesis parameters selection and process optimization.}, journal={Procedia Manufacturing}, publisher={Elsevier BV}, author={Kong, Xiangcheng and Wei, Chuang and Zhu, Yong and Cohen, Paul and Dong, Jingyan}, year={2018}, pages={349–358} }
 @article{deng_dong_cohen_2018, title={Rapid Fabrication and Characterization of SERS Substrates}, volume={26}, ISSN={2351-9789}, url={http://dx.doi.org/10.1016/J.PROMFG.2018.07.068}, DOI={10.1016/j.promfg.2018.07.068}, abstractNote={Surface enhanced Raman spectroscopy (SERS) is a surface-sensitive detection technique that dramatically increases the scattering signals of the analytes compared to traditional Raman spectroscopy. Rapid and low-cost fabrication of SERS substrates with easily tunable features remains a challenge, although many SERS substrates with high enhancement factors (EF) were investigated. Here, we report a novel and rapid approach of fabricating SERS substrates using ultrasonic vibration assisted nanomachining. Grids patterns with easily tuned dimensions were fabricated on PMMA surfaces. SERS substrates were fabricated after coating an 80 nm gold layer on the patterned silicon after reactive ion etching (RIE) using the patterned PMMA as the mask. Probing molecules of R6G with the area density of 2.8 × 10-12 M/mm2 can be detected, achieving an EF of 3.11 × 103. Results show a pattern with higher grids density tends to achieve a higher EF.}, journal={Procedia Manufacturing}, publisher={Elsevier BV}, author={Deng, Jia and Dong, Jingyan and Cohen, Paul}, year={2018}, pages={580–586} }
 @article{qin_dong_lee_2017, title={AC-pulse modulated electrohydrodynamic jet printing and electroless copper deposition for conductive microscale patterning on flexible insulating substrates}, volume={43}, ISSN={["1879-2537"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000385603000021&KeyUID=WOS:000385603000021}, DOI={10.1016/j.rcim.2015.09.010}, abstractNote={This paper presents a novel micro-manufacturing method for fabrication of electrical features and patterns on highly insulating substrates and flexible substrates based on high-resolution AC-pulse modulated electrohydrodynamic jet (e-jet) printing of silver nanoink as seed layer followed by electroless copper deposition. Traditional ink jet printing method is limited in printing resolution which is determined by dimension of printing nozzle and dimension of droplets. Traditional e-jet printing has the disadvantage of residual charge problem especially for highly insulating substrates which cannot dredge remained charge of printed droplets, resulting in distorted electrostatic field and low printing controllability. Meanwhile, for printing of liquid phase ink, feature resolution contradicts with the required thickness, which is a key factor of conductivity of printed patterns. In this paper, a novel AC-modulated e-jet printing technique is applied to neutralize charges on substrates by switching polarity of consequent droplets for direct printing of high-resolution conductive silver patterns on insulating substrates. Electroless copper deposition is introduced in the fabrication process to solve the thickness problem of the resulting features. Variables of fabrication process, including amplitude and frequency of AC-pulsed voltage, plotting speed, curing temperature, number of layers, concentration of solution for copper growth, were identified to achieve reliable and conductive printed patterns. Sub-20 µm silver tracks with resistivity about 3.16 times of bulk silver were successfully fabricated. We demonstrated that ac-pulse modulated e-jet printing followed by electroless copper deposition can produce high resolution conductive patterns with improved thickness on insulating substrates and flexible substrates, which can be applied to direct printing and micro scale patterning for flexible electronics and wearable devices applications.}, journal={ROBOTICS AND COMPUTER-INTEGRATED MANUFACTURING}, author={Qin, Hantang and Dong, Jingyan and Lee, Yuan-Shin}, year={2017}, month={Feb}, pages={179–187} }
 @article{han_dong_2017, title={Design, modeling and testing of integrated ring extractor for high resolution electrohydrodynamic (EHD) 3D printing}, volume={27}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000400073800001&KeyUID=WOS:000400073800001}, DOI={10.1088/1361-6439/aa5966}, abstractNote={This paper presents an integrated ring extractor design in electrohydrodynamic (EHD) printing, which can overcome the standoff height limitation in the EHD printing process, and improve printing capability for 3D structures. Standoff height in the EHD printing will affect printing processes and limit the height of the printed structure when the ground electrode is placed under the substrate. In this work, we designed and integrated a ring electrode with the printing nozzle to achieve a self-working printer head, which can start and maintain the printing process without the involvement of the substrate. We applied a FEA method to model the electric field potential distribution and strength to direct the ring extractor design, which provides a similar printing capability with the system using substrate as the ground electrode. We verified the ring electrode design by experiments, and those results from the experiments demonstrated a good match with results from the FEA simulation. We have characterized the printing processes using the integrated ring extractor, and successfully applied this newly designed ring extractor to print polycaprolactone (PCL) 3D structures.}, number={3}, journal={Journal of Micromechanics and Microengineering}, author={Han, Yiwei and Dong, Jingyan}, year={2017} }
 @article{qin_wei_dong_lee_2017, title={Direct Printing and Electrical Characterization of Conductive Micro-Silver Tracks by Alternating Current-Pulse Modulated Electrohydrodynamic Jet Printing}, volume={139}, ISSN={["1528-8935"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000393881400008&KeyUID=WOS:000393881400008}, DOI={10.1115/1.4033903}, abstractNote={In this paper, a rapid prototyping method for fabrication of highly conductive micropatterns on insulating substrates was developed and evaluated. Sub-20 μm microstructures were printed on flexible insulating substrates using alternating current (AC) modulated electrohydrodynamic jet (e-jet) printing. The presented technique resolved the challenge of current rapid prototyping methods in terms of limited resolution and conductivity for microelectronic components for flexible electronics. Significant variables of fabrication process, including voltage, plotting speeds, curing temperature, and multilayer effect, were investigated to achieve reliable printing of silver tracks. Sub-20 μm silver tracks were successfully fabricated with resistivity about three times than bulk silver on flexible substrates, which indicates the potential applications of electrohydrodynamic printing in flexible electronics and medical applications, such as lab-on-chip systems.}, number={2}, journal={JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME}, author={Qin, Hantang and Wei, Chuang and Dong, Jingyan and Lee, Yuan-Shin}, year={2017}, month={Feb} }
 @article{qin_cai_dong_lee_2017, title={Direct Printing of Capacitive Touch Sensors on Flexible Substrates by Additive E-Jet Printing With Silver Nanoinks}, volume={139}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000395125000011&KeyUID=WOS:000395125000011}, DOI={10.1115/1.4034663}, abstractNote={In this paper, techniques of direct printing of capacitive touch sensors on flexible substrates are presented. Capacitive touch sensors were fabricated by using electrohydrodynamic inkjet (E-jet) printing onto flexible substrates. Touch pad sensors can be achieved with optimized design of silver nanoink tracks. An analytical model was developed to predict touch pad capacitance, and experiments were conducted to study the effects of sensor design (e.g., number of electrodes, electrode length, and electrode distance) on the capacitance of printed coplanar capacitance touch sensors. Details of the fabrication techniques were developed to enable rapid prototype flexible sensors with simple structure and good sensitivity. The presented techniques can be used for the on-demand fabrication of different conductive patterns for flexible electronics with high resolution and good transparency}, number={3}, journal={Journal of Manufacturing Science and Engineering-Transactions of the Asme}, author={Qin, Hantang and Cai, Yi and Dong, Jingyan and Lee, Yuan-Shin}, year={2017} }
 @article{qin_dong_lee_2017, title={Fabrication and electrical characterization of multi-layer capacitive touch sensors on flexible substrates by additive e-jet printing}, volume={28}, ISSN={["1526-6125"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85020067130&partnerID=MN8TOARS}, DOI={10.1016/j.jmapro.2017.04.015}, abstractNote={Current consumer electronics, in particular touch displays and flexible electronics, were limited by the properties of existing commercial transparent conductor materials used as electrodes both in flat panel display and capacitive touch sensors. In this paper, an alternative fabrication technique using silver nanoink that can be used for rapid prototyping of high-resolution electrode arrays to replace indium tin oxide (ITO) for flexible electronics was presented. By direct printing silver nanoparticles on flexible substrates, capacitive touch sensors were fabricated onto polyethylene terephthalate (PET) film. Experiments were conducted to study the feasibility of electrohydrodynamic inkjet printing (e-jet printing) of high-resolution electrodes for touch sensors. Sensitivity of sub-20 μm capacitance sensor array was investigated in the study for droplet and humidity detection applications. The rapid prototyping method makes a significant impact in enabling simultaneously (1) customized and flexible touch sensors, (2) cost-effective manufacturing, and (3) high resolution and good sensitivity. The presented techniques can be used for the on-demand fabrication of customized conductive patterns for flexible and wearable electronics.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Qin, Hantang and Dong, Jingyan and Lee, Yuan-Shin}, year={2017}, month={Aug}, pages={479–485} }
 @inproceedings{han_dong_2017, title={High-Resolution Electrohydrodynamic (EHD) Direct Printing of Molten Metal}, volume={10}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85023644286&partnerID=MN8TOARS}, DOI={10.1016/j.promfg.2017.07.070}, abstractNote={In this paper, we developed a high-resolution direct printing process for molten metal using Elctrohydrodynamic (EHD) printing technology. We characterized and verified the effect of the electric field on the printing process, which can continuously print fine molten metal filament from the nozzle without requiring any pneumatic pressure. By comparing direct extrusion with pneumatic pressure and EHD printing with a voltage, we found that the EHD printing can effectively reduce the printed filament dimension down to less than 50 μm and achieve better quality (uniformity and shape) of the printed features. We successfully applied EHD printing to print high-resolution 2D patterns and some high aspect-ratio 3D structures, which demonstrated the potential capabilities of EHD printing process in producing fine metal structures and microelectronic fabrication.}, booktitle={Procedia Manufacturing}, author={Han, Y. and Dong, J.}, year={2017}, pages={845–850} }
 @article{han_dong_2017, title={High-resolution direct printing of molten-metal using electrohydrodynamic jet plotting}, volume={12}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85018610949&partnerID=MN8TOARS}, DOI={10.1016/j.mfglet.2017.04.001}, abstractNote={In this paper, a high-resolution direct printing process was developed for molten metal using Electrohydrodynamic (EHD) printing technology. The effect of the critical printing conditions, such as voltage and printing speed, on the printing process was characterized. Compared with direct extrusion using pneumatic pressure, the EHD printing can effectively reduce the dimension of the printed filament down to less than 50 μm with better quality of the printed features. We successfully applied EHD printing to print high-resolution 2D patterns and some high aspect-to-ratio 3D structures, which demonstrated the potential capabilities of EHD printing process in producing fine metal structures.}, journal={Manufacturing Letters}, author={Han, Y. and Dong, J.}, year={2017}, pages={6–9} }
 @article{kong_dong_cohen_2017, title={Modeling of the dynamic machining force of vibration-assisted nanomachining process}, volume={28}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000407982200011&KeyUID=WOS:000407982200011}, DOI={10.1016/j.jmapro.2017.05.028}, abstractNote={Nanofabrication technology is very important for many emerging engineering and scientific applications. Among different nanofabrication technologies, vibration-assisted nanomachining provides a low-cost easy-to-setup approach for producing structures with nano-scale resolution. It is very important to understand the mechanism for this nanomachining process and predict the involved machining force, so as to provide guidelines to achieve higher productivity and reduce tip wear. In this work, a machining force model for the tip-based nanomachining process was developed and validated. We analyzed the instantaneous engagement between the cutting tool (AFM tip) and the workpiece (PMMA film) during each tip rotation cycle for the vibration-assisted nanomachining process. A discrete voxel method was adopted to calculate the material removal rate at each moment, and an empirical machining force model is developed by correlating the machining force with material removal rate, which is a function of the input parameters of the nanomachining process. The machining force model was verified by experiments over a large range of machining conditions, and the coefficients in the force model were obtained by minimizing the Mean Square Error (MSE) method by comparing the predicted machining force from the model and measured machining force from the experiments. The results show a good fit between the predicted machining force and the measured machining force.}, journal={Journal of Manufacturing Processes}, author={Kong, Xiangcheng and Dong, Jingyan and Cohen, Paul H.}, year={2017}, pages={101–108} }
 @article{deng_zhang_dong_cohen_2016, title={AFM-based 3D nanofabrication using ultrasonic vibration assisted nanomachining}, volume={24}, ISSN={["1526-6125"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000389393500022&KeyUID=WOS:000389393500022}, DOI={10.1016/j.jmapro.2016.09.003}, abstractNote={This paper presents a novel AFM-based 3D nanofabrication process using ultrasonic vibration assisted nanomachining. A set of three dimensional nanostructures on polymethyl methacrylate (PMMA) samples are fabricated with the assistance of high frequency in-plane circular xy-vibration and ultrasonic tip-sample z-vibration. Two methods for fabricating 3D nanostructures were investigated in this study, which are layer-by-layer nanomachining and one pass nanomachining with the depth controlled by setpoint force. Critical parameters in the process are identified, including setpoint force, overlap percentage, amplitude of z vibration and machining speed. By regulating these process parameters, multi-level 3D nanostructures were fabricated by multi-layer machining in vector mode and raster scan mode. Using different setpoint forces for regulating feature depths, other nanostructures, such as convex and concave circles, were fabricated in raster scan mode from gray-scale bitmap pattern images. Under each mode, 3D nanostructure over microscale area can be fabricated in just a few minutes with sub-10 nm resolution in z direction.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Deng, Jia and Zhang, Li and Dong, Jingyan and Cohen, Paul H.}, year={2016}, month={Oct}, pages={195–202} }
 @article{qin_cai_dong_lee_asme_2016, title={DIRECT PRINTING OF CAPACITIVE TOUCH SENSORS ON FLEXIBLE SUBSTRATES BY ADDITIVE E-JET PRINTING WITH SILVER NANOINKS}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000388159100032&KeyUID=WOS:000388159100032}, journal={Proceedings of the Asme 11th International Manufacturing Science and Engineering Conference, 2016, Vol 1}, author={Qin, Hantang and Cai, Yi and Dong, Jingyan and Lee, Yuan-Shin and ASME}, year={2016} }
 @article{han_dong_shih_wang_2016, title={Design of Integrated Ring Extractor for High Resolution Electrohydrodynamic (EHD) 3D Printing}, volume={5}, ISSN={["2351-9789"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000387592400079&KeyUID=WOS:000387592400079}, DOI={10.1016/j.promfg.2016.08.070}, abstractNote={This paper presents an integrated ring extractor design in electrohydrodynamic (EHD) printing, which can overcome the standoff height limitation in the EHD printing process, and improve printing capability for 3D structures. Standoff height in EHD printing will affect printing processes and limit the height of the printed structure when the ground electrode is placed under the substrate. In this work, we designed and integrated a ground ring electrode with the printing nozzle to achieve a self-working printer head, which can start and maintain the printing process without the involvement of the substrate. We applied FEA method to model the electrostatic field distribution and strength to direct the ring extractor design, which has the similar printing capability with the system using substrate as the ground electrode. We verified the ring electrode design by experiments, and the results from experiments demonstrated a good match with results in the FEA simulation. We have characterized the printing processes using the integrated ring extractor, and successfully applied newly designed ring extractor to print polycaprolactone (PCL) 3D structures.}, journal={44TH NORTH AMERICAN MANUFACTURING RESEARCH CONFERENCE, NAMRC 44}, author={Han, Yiwei and Dong, Jingyan and Shih, A and Wang, L}, year={2016}, pages={1031–1042} }
 @inproceedings{qin_cai_dong_lee_2016, title={Direct printing of capacitive touch sensors on flexible substrates by additive e-jet printing with silver nanoinks}, volume={139}, DOI={10.1115/msec2016-8740}, abstractNote={In this paper, techniques of direct printing of capacitive touch sensors on flexible substrates are presented. Capacitive touch sensors were fabricated by using electrohydrodynamic inkjet (E-jet) printing onto flexible substrates. Touch pad sensors can be achieved with optimized design of silver nanoink tracks. An analytical model was developed to predict touch pad capacitance, and experiments were conducted to study the effects of sensor design (e.g. number of electrodes, electrode length, and electrode distance) on the capacitance of printed coplanar capacitance touch sensors. Details of the fabrication techniques were developed to enable rapid prototype flexible sensors with simple structure and good sensitivity. The presented techniques can be used for the on-demand fabrication of different conductive patterns for flexible electronics with high-resolution and good transparency.}, number={3}, booktitle={Proceedings of the ASME 11th International Manufacturing Science and Engineering Conference, 2016, vol 1}, author={Qin, H. T. and Cai, Y. and Dong, Jingyan and Lee, Yuan-Shin}, year={2016} }
 @inproceedings{qin_cai_dong_lee_2016, title={Direct printing of capacitive touch sensors on flexible substrates by additive e-jet printing with silver nanoinks}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84991808752&partnerID=MN8TOARS}, DOI={10.1115/MSEC20168740}, booktitle={ASME 2016 11th International Manufacturing Science and Engineering Conference, MSEC 2016}, author={Qin, H. and Cai, Y. and Dong, J. and Lee, Y.-S.}, year={2016} }
 @article{bharathi_dong_2016, title={Feedrate optimization for smooth minimum-time trajectory generation with higher order constraints}, volume={82}, ISSN={["1433-3015"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000368996000024&KeyUID=WOS:000368996000024}, DOI={10.1007/s00170-015-7447-x}, number={5-8}, journal={INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY}, author={Bharathi, Akilan and Dong, Jingyan}, year={2016}, month={Feb}, pages={1029–1040} }
 @article{deng_dong_cohen_shih_wang_2016, title={High Rate 3D Nanofabrication by AFM-Based Ultrasonic Vibration Assisted Nanomachining}, volume={5}, ISSN={["2351-9789"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000387592400096&KeyUID=WOS:000387592400096}, DOI={10.1016/j.promfg.2016.08.100}, abstractNote={This paper introduces a high precision 3D nanofabrication approach using ultrasonic vibration assisted nanomachining using an AFM operating in constant height control mode. Nanostructures with 3D features were successfully fabricated on PMMA film with the feature height manipulated through controlling the absolute heights of z-scanner in AFM. Two methods were used to move the AFM tip to create desire features, vector mode and raster scan mode. Relatively simple features, such as stair-like nanostructure with five steps was successfully fabricated in vector mode. Complex nanostructure with discrete height levels and continuous changes were successfully fabricated in raster scan mode. By carefully selecting the machining parameters, the feature dimension and height can be precisely controlled with only small variation from the designed value. Moreover, this paper explores the capability of transferring 3D nanostructures from PMMA film onto silicon substrate. After calibrating the recipe of Reactive Ion Etching (RIE) process, 3D nanostructures are successfully transferred to silicon wafer with controllable selectivity between PMMA and silicon. The results of fabricating 3D structures on silicon substrates show promising potential of many applications, such as mold preparation in nanoimprint lithography.}, journal={44TH NORTH AMERICAN MANUFACTURING RESEARCH CONFERENCE, NAMRC 44}, author={Deng, Jia and Dong, Jingyan and Cohen, Paul and Shih, A and Wang, L}, year={2016}, pages={1283–1294} }
 @article{kong_cohen_dong_2016, title={Predictive modeling of feature dimension for tip-based nano machining process}, volume={24}, ISSN={["1526-6125"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000389166500004&KeyUID=WOS:000389166500004}, DOI={10.1016/j.jmapro.2016.06.013}, abstractNote={The tip-based vibration-assisted nanomachining process can fabricate three-dimensional (3D) features with nanometer scale resolution. To control the feature dimension accurately in process planning, we need to understand the relationship between feature dimension and machining parameters including setpoint force, XY vibration amplitude and feed rate. In this article, we conducted full factorial experiments to analyze the relationship between feature dimension and machining parameters. Based on analysis of variance (ANOVA), we determined the significant factors in determining the feature dimension. The feature width is mainly controlled by XY vibration amplitude, and the feature depth is controlled XY vibration, setpoint force and feed rate. In order to predict the feature dimension in nanomachining and provide instructions for machining parameter selection, a semi-empirical mechanical model was built first. Then simplified regression models were also investigated, with all models displaying good predictive capability. The results show good fit between predicted feature depth and measured feature depth, for most machining conditions. These models provide good capability in process planning for implementation of this process.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Kong, Xiangcheng and Cohen, Paul H. and Dong, Jingyan}, year={2016}, month={Oct}, pages={338–345} }
 @article{bharathi_dong_shih_wang_2015, title={A Smooth Trajectory Generation Algorithm for Addressing Higher-Order Dynamic Constraints in Nanopositioning Systems}, volume={1}, ISSN={["2351-9789"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000380512300019&KeyUID=WOS:000380512300019}, DOI={10.1016/j.promfg.2015.09.006}, abstractNote={The generation of a time-optimal feedrate trajectory has received significant attention in CNC machining and robotics applications. Most of the existing feedrate planning algorithms take velocity and acceleration into the consideration for capability constraints. The introduction of higher order dynamic states, such as jerk and/or jounce into the feedrate scheduling problem makes generating computationally efficient solutions while simultaneously guaranteeing optimality a challenging problem, as the dimension of the planning problem is increased accordingly. This paper proposes a heuristic trajectory planning algorithm that can provide a near optimal trajectory for problems with higher order dynamic states. The algorithm starts with a non-optimal but feasible velocity trajectory, which is interpolated from a number of knot points by piece-wise spline interpolation with high order continuity. Then the trajectory is improved by scanning the interpolating knot points and increasing the velocity at each knot points while maintaining the feasibility of the resulting trajectory. A near optimal trajectory is achieved when the improvement in travel time is neglectable from the last scan iteration. The algorithm supports the incorporation of high order dynamic states (up to fifth order derivative of position) in constraints for optimization without sacrificing the computational efficiency. Examples including linear and curved toolpaths are presented to illustrate the effectiveness of this algorithm for high-speed contouring.}, journal={43RD NORTH AMERICAN MANUFACTURING RESEARCH CONFERENCE, NAMRC 43}, author={Bharathi, Akilan and Dong, Jingyan and Shih, AJ and Wang, LH}, year={2015}, pages={216–225} }
 @article{deng_zhang_dong_cohen_shih_wang_2015, title={AFM-based 3D Nanofabrication using Ultrasonic Vibration Assisted Nanomachining}, volume={1}, ISSN={["2351-9789"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000380512300051&KeyUID=WOS:000380512300051}, DOI={10.1016/j.promfg.2015.09.036}, abstractNote={This paper explores AFM-based 3D nanomachining process assisted by ultrasonic vibration. 3D structures on polymethyl methacrylate (PMMA) substrates are fabricated by ultrasonic vibration-assisted nanomachining process. Two fabrication approaches for 3D structures are investigated in this study, which are layer-by-layer nanomachining and one pass nanomachining with the depth controlled by setpoint force. Critical parameters in the process are identified, including set-point force, overlap rate, amplitude of z vibration and machining speed. By regulating these parameters, stair-like 3D nanostructures are fabricated by multi-layer machining in Vector mode and Raster scan mode. Using different setpoint force for different feature depth, other nanostructures, such as convex and concave circles, are fabricated in Raster scan mode from grey-scale image. Under each mode, 3D nanostructure over microscale area can be fabricated in just a few minutes with the assistance of high frequency in-plane circular xy-vibration and ultrasonic tip-sample z-vibration.}, journal={43RD NORTH AMERICAN MANUFACTURING RESEARCH CONFERENCE, NAMRC 43}, author={Deng, Jia and Zhang, Li and Dong, Jingyan and Cohen, Paul H. and Shih, AJ and Wang, LH}, year={2015}, pages={584–592} }
 @article{dai_huan_gao_dong_liu_pan_wang_bi_2015, title={Development of a high-resolution micro-torsion tester for measuring the shear modulus of metallic glass fibers}, volume={26}, ISSN={0957-0233 1361-6501}, url={http://dx.doi.org/10.1088/0957-0233/26/2/025902}, DOI={10.1088/0957-0233/26/2/025902}, abstractNote={A high-resolution micro-torsion tester is developed based on electromagnetism, and the shear modulus of metallic glass fiber (Pd40Cu30Ni10P20) is measured using this tester. The torque is measured by a coil-magnet component and the rotation angle is measured by an inductive angular transducer. The calibration results show that the torque capacity of this tester is 1.1  ×  10−3 N m with resolution of 3  ×  10−8 N m and the rotation angle capacity is 90° with a resolution of 0.01°. A set of metallic glass fibers, with diameter of about 90 µm, are tested using this tester. The average shear modulus is obtained as 20.2 GPa (±6%).}, number={2}, journal={Measurement Science and Technology}, publisher={IOP Publishing}, author={Dai, Y J and Huan, Y and Gao, M and Dong, J and Liu, W and Pan, M X and Wang, W H and Bi, Z L}, year={2015}, month={Jan}, pages={025902} }
 @article{wei_qin_chiu_lee_dong_2015, title={Drop-on-demand E-jet printing of continuous interconnects with AC-pulse modulation on highly insulating substrates}, volume={37}, ISSN={["1878-6642"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000367698200008&KeyUID=WOS:000367698200008}, DOI={10.1016/j.jmsy.2014.07.005}, abstractNote={In this paper, we present a novel AC-pulse modulated electrohydrodynamic (EHD) jet printing technology that enables high resolution fabrication of electrical features and interconnects using the silver nanoink on highly insulating substrates. In traditional EHD jet printing, the remained charge of the printed droplets changes the electrostatic field distribution and interrupts the follow-on printing behavior, especially for highly insulating substrates having a slow charge decay rate. In this paper, a modulated AC-pulsed voltage was used for the EHD jet printing process that can alternate the charge polarity of the consequent droplets to neutralize the residue charge on the substrate. The effect of the residue charge is minimized, which enables high resolution printing of continuous patterns. With three printing parameters (e.g. pulse frequency, voltage, and duration), the EHD jet printing speed and droplet size can be controlled independently. We demonstrated that AC-pulse modulated EHD jet printing can overcome the charge accumulation challenge on highly insulating substrates, and investigated the variables of fabrication process to achieve reliable jet printing of conductive silver tracks.}, journal={JOURNAL OF MANUFACTURING SYSTEMS}, author={Wei, Chuang and Qin, Hantang and Chiu, Chia-Pin and Lee, Yuan-Shin and Dong, Jingyan}, year={2015}, month={Oct}, pages={505–510} }
 @article{han_wei_dong_2015, title={Droplet formation and settlement of phase-change ink in high resolution electrohydrodynamic (EHD) 3D printing}, volume={20}, ISSN={["2212-4616"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000367634700007&KeyUID=WOS:000367634700007}, DOI={10.1016/j.jmapro.2015.06.019}, abstractNote={This paper presents a modeling framework to model the droplet formation and settlement on substrate of phase-change ink in high resolution electrohydrodynamic (EHD) printing process, which can successfully produce sub 10-μm droplet footprints and 3D microstructure. We have used Finite Element Analysis (FEA) to develop the model for droplet formation and droplet settlement. Two important competitive forces in EHD printing, electrostatic force and surface tension force are modeled by FEA. The droplet size is obtained by balancing the electrostatic force and surface tension of the pending droplets at the tip of the meniscus under different printing conditions. With the results from FEA analysis about the charge on a droplet and electrostatic field distribution, the droplets in-flight velocity and impact velocity on the substrate are derived numerically. With the derived impact velocity, the droplet spreading and settlement on the substrate is also modeled by FEA. The results from FEA models are compared with the experimental measured droplet dimensions at different process conditions to validate the developed model, which demonstrate very good agreement between the experimental results and model prediction. We have successfully applied EHD printing process for phase-change wax material, which is widely used in 3D printing or additive manufacturing for supporting and model material, to achieve high resolution sub 10-μm 3D structures.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Han, Yiwei and Wei, Chuang and Dong, Jingyan}, year={2015}, month={Oct}, pages={485–491} }
 @article{qin_dong_lee_2015, title={ELECTROHYDRODYNAMIC JET PRINTING OF SILVER SEEDS: MICRO SCALE PATTERNING BY ELECTROLESS COPPER DEPOSITION}, ISBN={["978-0-7918-5682-6"]}, DOI={10.1115/msec2015-9487}, abstractNote={The paper describes a new method for micro scale patterning of highly conductive features on flexible and flat surfaces. The method uses electrohydrodynamic jet printing to deposit silver seeds on-demand that serve as catalysts for subsequent electroless deposition of copper. The electroless deposition of copper on substrates occurred only where silver seeds exist. In the study, ethylenediaminetetraacetic acid (EDTA) and triethanolamine (TEA) were used as chelating agents, and formaldehyde as reducing agent. Copper growth rate and resistivity were investigated using microscopic and profilometer to determine optimal concentration of each agents in reaction solution. The results indicated that EDTA significantly affects copper growth rate, playing an important role in complexing, while TEA in the dual-complexing system will balance deposition rate and stability of solution. Optimal temperature and time for copper deposition on silver nanoparticles were also discussed in the study. The techniques of activating substrates by selective printing and electroless metallization was successfully used to pattern on glass, and flexible polymer films, and both flat and curved substrates were used. The proposed technique was also capable of fabricating metal structures on flexible substrates with excellent conductivity. Metal filaments with resistivity four times bulk copper and thickness up to 15μm were demonstrated in the research.}, journal={PROCEEDINGS OF THE ASME 10TH INTERNATIONAL MANUFACTURING SCIENCE AND ENGINEERING CONFERENCE, 2015, VOL 1}, author={Qin, Hantang and Dong, Jingyan and Lee, Yuan-Shin}, year={2015} }
 @article{qin_dong_lee_asme_2015, title={ELECTROHYDRODYNAMIC JET PRINTING OF SILVER SEEDS: MICRO SCALE PATTERNING BY ELECTROLESS COPPER DEPOSITION}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000365146800073&KeyUID=WOS:000365146800073}, journal={Proceedings of the Asme 10th International Manufacturing Science and Engineering Conference, 2015, Vol 1}, author={Qin, Hantang and Dong, Jingyan and Lee, Yuan-Shin and ASME}, year={2015} }
 @inproceedings{qin_dong_lee_2015, title={Electrohydrodynamic jet printing of silver seeds: Micro scale patterning by electroless copper deposition}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84945400860&partnerID=MN8TOARS}, DOI={10.1115/MSEC20159487}, booktitle={ASME 2015 International Manufacturing Science and Engineering Conference, MSEC 2015}, author={Qin, H. and Dong, J. and Lee, Y.-S.}, year={2015} }
 @article{bharathi_dong_2015, title={Feedrate optimization and trajectory control for micro/nanopositioning systems with confined contouring accuracy}, volume={229}, ISSN={["2041-2975"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000358335700010&KeyUID=WOS:000358335700010}, DOI={10.1177/0954405414548467}, abstractNote={ This article focuses on identifying and fully utilizing the dynamic capabilities of a nanopositioning system to optimally trace a given trajectory. This work develops a framework for abstracting the capabilities of the piezo-actuated nanopositioning systems and a methodology for using these capabilities to generate an optimal trajectory for a particular tool path on a given nanopositioning system while satisfying all the process-related requirements. Several dynamic capabilities of a typical nanopositioning system are identified and modeled as the constraints to drive the optimization problem. First, the velocity and acceleration capabilities of each individual axes are constrained by developing a simplified dynamic model of the performance envelope, which couple velocity and acceleration capabilities of each axis, as a function of displacement. Second, input command bandwidth constraints are introduced to mitigate frequency-related tracking difficulties encountered when traversing sharp geometric features at high velocity. Finally, the accuracy requirement is satisfied by developing a dynamic model of the instantaneous following error to estimate the contour error as a function of the velocity and acceleration at each moment. The above constraints are incorporated into a computationally efficient two-pass algorithm to generate a minimum time feedrate profile for a particular positioning system for any given trajectory. Linear zigzag and cubic spline airfoil trajectories are used to demonstrate the significant improvements in time and contouring accuracy realized through such an approach. }, number={7}, journal={PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART B-JOURNAL OF ENGINEERING MANUFACTURE}, author={Bharathi, Akilan and Dong, Jingyan}, year={2015}, month={Jul}, pages={1193–1205} }
 @article{kong_zhang_dong_cohen_asme_2015, title={MACHINING FORCE MODELING OF VIBRATION-ASSISTED NANO-MACHINING PROCESS}, volume={2}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000365147200005&KeyUID=WOS:000365147200005}, DOI={10.1115/MSEC20159423}, journal={Proceedings of the Asme 10th International Manufacturing Science and Engineering Conference, 2015, Vol 2}, author={Kong, Xiangcheng and Zhang, Li and Dong, Jingyan and Cohen, Paul H. and ASME}, year={2015} }
 @inproceedings{kong_zhang_dong_cohen_2015, title={Machining force modeling of vibration-assisted nano-machining process}, DOI={10.1115/MSEC2015-9423}, abstractNote={Nanofabrication technology is very important for many emerging engineering and scientific applications. Among different nanofabrication technologies, vibration-assisted nano-machining provides a low cost easy-to-setup approach to produce structures with nano-scale resolution. It is critical to understand the mechanism for the nano-machining process and predict the cutting force, so as to provide guidelines to achieve higher productivity and reduce tip wear. In this article, a machining force model for tip-based nano-machining process is developed and validated. We analyze the instantaneous engagement area between cutting tool (AFM tip) and workpiece (PMMA film) at the given tip position for the vibration-assisted nano-machining process. A discrete voxel method is adopted to calculate the material removal rate at each moment, and an empirical machining force model is developed by correlating the cutting force with material removal rate. The model was verified by experiments over a large range of machining conditions, and the coefficients and parameters in the force model was obtained using Mean Square Error (MSE) method by comparing the predicted machining force from the force model and measured machining force from experiments. The results show good fit between predicted machining force and measured machining force.}, booktitle={Proceedings of the ASME 10th International Manufacturing Science and Engineering Conference, 2015, vol 2}, author={Kong, X. C. and Zhang, L. and Dong, J. Y. and Cohen, P. H.}, year={2015} }
 @article{henry_cai_liu_zhang_dong_chen_wang_wang_2015, title={Roles of Hydroxyapatite Allocation and Microgroove Dimension in Promoting Preosteoblastic Cell Functions on Photocured Polymer Nanocomposites through Nuclear Distribution and Alignment}, volume={31}, ISSN={["0743-7463"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000350918500029&KeyUID=WOS:000350918500029}, DOI={10.1021/la504994e}, abstractNote={This study clarifies how hydroxyapatite (HA) allocation and microgroove dimension affect mouse preosteoblastic MC3T3-E1 cell functions on microgrooved substrates of polymer nanocomposites. Using replica molding from micromachined silicon wafer templates, we fabricated photocured poly(ε-caprolactone) triacrylate (PCLTA)/HA nanocomposite substrates with parallel microgrooves (two groove widths of 5 and 15 μm and one groove depth of 5 μm). Four types of microgrooved substrates were made: "homogeneous" ones of PCLTA and PCLTA/HA with uniform distribution and two "heterogeneous" laminated microgrooved substrates with HA only in the PCLTA matrix in the ridges or bottom. These substrates were used to regulate MC3T3-E1 cell attachment, proliferation, alignment, nuclear circularity and distribution, and mineralization. MC3T3-E1 cell attachment and proliferation were much higher on the microgrooved substrates of PCLTA/HA than on those of PCLTA, in particular, on the 5 μm wide microgrooved substrate with PCLTA/HA ridges and PCLTA bottom. The shape and distribution of MC3T3-E1 cytoskeleton and nuclei were altered by the substrate topography and HA allocation. For 5 μm wide heterogeneous microgrooved substrates with HA only in the ridges, MC3T3-E1 cells exhibited better spreading perpendicular to the microgrooves but tended to extend along the microgrooves containing HA in the bottom. The widest cells and the roundest/largest cell nuclei were observed on the heterogeneous substrate with PCLTA/HA ridges, while the narrowest cells with the best elongation were found on the homogeneous PCLTA/HA substrate. The trend in MC3T3-E1 cell mineralization on the substrates was consistent with that in cell/nuclear elongation. Osteocalcin mRNA expression was significantly higher on the PCLTA/HA substrates than on the PCLTA ones and also on the microgrooved substrates of PCLTA/HA than on the flat ones, regardless of the groove width of 5 or 15 μm.}, number={9}, journal={LANGMUIR}, author={Henry, Michael G. and Cai, Lei and Liu, Xifeng and Zhang, Li and Dong, Jingyan and Chen, Liang and Wang, Zaiqin and Wang, Shanfeng}, year={2015}, month={Mar}, pages={2851–2860} }
 @inbook{dong_2015, title={Ultrasonic Vibration-Assisted Nanomachining}, ISBN={9789400761780}, url={http://dx.doi.org/10.1007/978-94-007-6178-0_100921-1}, DOI={10.1007/978-94-007-6178-0_100921-1}, booktitle={Encyclopedia of Nanotechnology}, publisher={Springer Netherlands}, author={Dong, Jingyan}, year={2015}, pages={1–9} }
 @inproceedings{qin_wei_dong_lee_2014, title={AC-pulse modulated electrohydrodynamic (EHD) direct printing of conductive micro silver tracks for micro-manufacturing}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84960928060&partnerID=MN8TOARS}, booktitle={FAIM 2014 - Proceedings of the 24th International Conference on Flexible Automation and Intelligent Manufacturing: Capturing Competitive Advantage via Advanced Manufacturing and Enterprise Transformation}, author={Qin, H. and Wei, C. and Dong, J. and Lee, Y.-S.}, year={2014}, pages={763–770} }
 @article{qin_wei_dong_lee_2014, title={DIRECT FABRICATION OF HIGHLY CONDUCTIVE MICRO SILVER TRACKS USING ELECTROHYDRODYNAMIC JET PRINTING FOR SUB-20 mu M MICRO-MANUFACTURING}, volume={2}, ISBN={["978-0-7918-4581-3"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84908429027&partnerID=MN8TOARS}, DOI={10.1115/msec2014-4163}, abstractNote={This paper presents a direct fabrication method of highly conductive silver tracks with sub-20 μm microstructures on glass substrate by using electrohydrodynamic jet printing (EHDJP) with alternative current (AC) voltage. Traditional ink jet printing fabrication approaches are limited in the achievable resolution. EHDJP has been used in directly printing by generating a fine jet through a large electrical potential between nozzle and substrate. When charge accumulates on the ink meniscus at the nozzle, a fine jet down to nano scale can be generated. In the paper, we successfully applied EHDJP for fabrication of highly conductive silver tracks using AC voltage. It was the first time that sub-20 μm silver tracks were demonstrated and printed with resistivity about 3.16 times than bulk silver. The variables of fabrication process were investigated to achieve reliable jet printing of conductive silver tracks. The topography of printed tracks was characterized and verified in the study. The presented technique can be used for micro-manufacturing of three-dimensional microstructures and biomedical device fabrications.}, journal={PROCEEDINGS OF THE ASME 9TH INTERNATIONAL MANUFACTURING SCIENCE AND ENGINEERING CONFERENCE, 2014, VOL 2}, author={Qin, Hantang and Wei, Chuang and Dong, Jingyan and Lee, Yuan-Shin}, year={2014} }
 @article{wei_dong_2014, title={Development and Modeling of Melt Electrohydrodynamic-Jet Printing of Phase-Change Inks for High-Resolution Additive Manufacturing}, volume={136}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000344393000012&KeyUID=WOS:000344393000012}, DOI={10.1115/1.4028483}, abstractNote={This paper presents the development and modeling a high-resolution electrohydrodynamic-jet (EHD-jet) printing process using phase-change ink (i.e., wax), which is capable of producing sub-10 μm footprints (sub-10 fL in volume) for super-resolution additive manufacturing. In this study, we successfully apply EHD-jet printing for phase-change ink (wax), which is widely used as modeling and supporting material for additive manufacturing, to achieve micron-scale features. The resolution for single droplet on substrate is around 5 μm with the thickness in the range of 1–2 μm, which provides great potential in both high-resolution 3D printing and 2D drop-on-demand microfabrication. The droplet formation in EHD printing is modeled by finite element analysis (FEA). Two important forces in EHD printing, electrostatic force and surface tension force, are modeled separately by FEA. The droplet size is obtained by balancing the electrostatic force and surface tension of the pending droplets around meniscus apex. Furthermore, to predict the droplet dimension at different process conditions, a dimensionless scaling law is identified to describe the relationship between dimensionless droplet diameter and modified nondimensional electrical bond number. Finally, the droplets in-flight velocity and impact characteristics (e.g., Reynolds number and Weber number) are modeled using the results from FEA analysis.}, number={6}, journal={Journal of Manufacturing Science and Engineering-Transactions of the Asme}, author={Wei, Chuang and Dong, Jingyan}, year={2014} }
 @inproceedings{wei_qin_chiu_lee_dong_2014, title={Drop-on-demand E-Jet printing of continuous features with AC-pulse modulation on highly insulating substrates}, volume={42}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84938054378&partnerID=MN8TOARS}, number={January}, booktitle={Transactions of the North American Manufacturing Research Institution of SME}, author={Wei, C. and Qin, H. and Chiu, C.-P. and Lee, Y.-S. and Dong, J.}, year={2014}, pages={345–352} }
 @article{wei_qin_ramirez-iglesias_chiu_lee_dong_2014, title={High-resolution ac-pulse modulated electrohydrodynamic jet printing on highly insulating substrates}, volume={24}, ISSN={["1361-6439"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84897548526&partnerID=MN8TOARS}, DOI={10.1088/0960-1317/24/4/045010}, abstractNote={This paper presents a new high-resolution ac-pulse modulated electrohydrodynamic (EHD)-jet printing technology on highly insulating substrates for drop-on-demand fabrication of electrical features and interconnects using silver nanoink. In traditional EHD-jet printing, the remained charge of the printed droplets changes the electrostatic field distribution and interrupts the follow-on printing behavior, especially for highly insulating substrates which have slow charge decay rates. The residue charge makes the control of EHD-jet printing very challenging for high-resolution continuous features. In this paper, by using modulated ac-pulsed voltage, the EHD-jet printing process switches the charge polarity of the consequent droplets to neutralize the charge on the substrate. The effect of the residue charge is minimized, which enables high-resolution printing of continuous patterns. Moreover, by modulating the pulse frequency, voltage, and duration, the EHD-jet printing behavior can be controlled with respect to printing speed/frequency and droplet size. Printing frequency is directly controlled by the pulse frequency, and the droplet dimension is controlled by the voltage and the duration of the pulse. We demonstrated that ac-pulse modulated EHD-jet printing can overcome the long-predicated charge accumulation problem on highly insulating substrates, and potentially be applied to many flexible electronics applications.}, number={4}, journal={JOURNAL OF MICROMECHANICS AND MICROENGINEERING}, author={Wei, Chuang and Qin, Hantang and Ramirez-Iglesias, Nakaira A. and Chiu, Chia-Pin and Lee, Yuan-shin and Dong, Jingyan}, year={2014}, month={Apr} }
 @article{wei_dong_2014, title={Hybrid hierarchical fabrication of three-dimensional scaffolds}, volume={16}, ISSN={["2212-4616"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000349566600012&KeyUID=WOS:000349566600012}, DOI={10.1016/j.jmapro.2013.10.003}, abstractNote={Three-dimensional (3D) porous structures facilitating cell attachment, growth, and proliferation is critical to tissue engineering applications. Traditional solid freeform fabrication (SFF) methods have limited capabilities in the fabrication of high resolution micro-scale features to implement advanced biomedical functions. In this work, we present a hybrid scaffold fabrication approach by integrating electrohydrodynamic (EHD) printing technology with extrusion deposition together to fabricate hierarchical 3D scaffolds with well controlled structures at both macro and micro scale. We developed a hybrid fabrication platform and a robust fabrication process to achieve 3D hierarchical structures. The melting extrusion by pneumatic pressure was used to fabricate 3D scaffolds with filaments dimension of hundreds of microns using thermoplastic biopolymer polycaprolactone (PCL). An electrohydrodynamic (EHD) melt jet plotting process was developed to fabricate micro-scale features on the scaffolds with sub-10 μm resolution, which has great potential in advanced biomedical applications, such as cell alignment and cell guidance.}, number={2}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Wei, Chuang and Dong, Jingyan}, year={2014}, month={Apr}, pages={257–263} }
 @article{zhang_koo_salapaka_dong_ferreira_2014, title={Robust control of a MEMS probing device}, volume={19}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84895061380&partnerID=MN8TOARS}, DOI={10.1109/TMECH.2012.2224122}, abstractNote={In this paper, a systematic design based on the robust control theory is developed for a microelectromechanical systems nanopositioning/probing device. The device is fabricated on a silicon-on-insulator substrate, and provides decoupled XY motion by using a parallel kinematics mechanism design. Each axis of the device is actuated by linear comb-drives and the corresponding displacements are sensed by separate comb structures. To improve the sensing resolution, the sensing and driving combs are electrically isolated. The nonlinear dynamic model between the actuation voltage and the sensed displacement will increase the complexity of model identification and control design. We circumvent the nonlinear model by redefining the input and output (I/O) signals during the model definition and identification, which results in linear and time-invariant models. A dynamical model of the system is identified through experimental input-output frequency-domain identification. The implemented H∞ control design achieves a significant improvement over the response speed, where the bandwidths from the closed-loop sensitivity and complementary sensitivity functions, respectively, are 68 and 74 Hz. When compared to open-loop characteristics, enhancement in reliability and repeatability (robustness to uncertainties) as well as noise attenuation (by over 12%) is demonstrated through this design.}, number={1}, journal={Ieee-Asme Transactions on Mechatronics}, author={Zhang, X. and Koo, B. and Salapaka, S.M. and Dong, Jingyan and Ferreira, P.M.}, year={2014}, pages={100–108} }
 @article{han_wei_dong_2014, title={Super-resolution electrohydrodynamic (EHD) 3D printing of micro-structures using phase-change inks}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84908304909&partnerID=MN8TOARS}, DOI={10.1016/j.mfglet.2014.07.005}, abstractNote={This paper presents a super-resolution 3D printing process using electrohydrodynamic (EHD) printing technology for the direct fabrication of micro-scale structures with phase-change inks (i.e. wax). In this work, we successfully apply EHD printing process for phase-change ink (wax), which is widely used modeling and supporting material for additive manufacturing and 3D printing, to achieve micro-scale droplet dimension. Moreover, a Finite Element Analysis (FEA) model is developed to predict the droplet formation and droplet size of the EHD printing at different printing voltage. The EHD printing process is capable of producing high aspect-of-ratio 3D structures with sub-10 μm feature resolution.}, number={4}, journal={Manufacturing Letters}, author={Han, Y. and Wei, C. and Dong, J.}, year={2014}, pages={96–99} }
 @inproceedings{bharathi_dong_2014, title={Time-optimal feed-rate scheduling for nanopositioning systems with confined contouring error}, volume={42}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84938059294&partnerID=MN8TOARS}, number={January}, booktitle={Transactions of the North American Manufacturing Research Institution of SME}, author={Bharathi, A. and Dong, J.}, year={2014}, pages={372–380} }
 @article{wei_dong_2013, title={Direct fabrication of high-resolution three-dimensional polymeric scaffolds using electrohydrodynamic hot jet plotting}, volume={23}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878127942&partnerID=MN8TOARS}, DOI={10.1088/0960-1317/23/2/025017}, abstractNote={This paper presents the direct three-dimensional (3D) fabrication of polymer scaffolds with sub-10 µm structures using electrohydrodynamic jet (EHD-jet) plotting of melted thermoplastic polymers. Traditional extrusion-based fabrication approaches of 3D periodic porous structures are very limited in their resolution, due to the excessive pressure requirement for extruding highly viscous thermoplastic polymers. EHD-jet printing has become a high-resolution alternative to other forms of nozzle deposition-based fabrication approaches by generating micro-scale liquid droplets or a fine jet through the application of a large electrical voltage between the nozzle and the substrate. In this study, we successfully apply EHD-jet plotting technology with melted biodegradable polymer (polycaprolactone, or PCL) for the fabrication of 2D patterns and 3D periodic porous scaffold structures in potential tissue engineering applications. Process conditions (e.g. electrical voltage, pressure, plotting speed) have been thoroughly investigated to achieve reliable jet printing of fine filaments. We have demonstrated for the first time that the EHD-jet plotting process is capable of the fabrication of 3D periodic structures with sub-10 µm resolution, which has great potential in advanced biomedical applications, such as cell alignment and guidance.}, number={2}, journal={Journal of Micromechanics and Microengineering}, author={Wei, Chuang and Dong, Jingyan}, year={2013} }
 @inproceedings{wei_dong_2013, title={Hybrid hierarchical fabrication of three-dimensional scaffolds}, volume={41}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84892703159&partnerID=MN8TOARS}, booktitle={Transactions of the North American Manufacturing Research Institution of SME}, author={Wei, C. and Dong, J.}, year={2013}, pages={541–547} }
 @inproceedings{zhang_dong_cohen_2013, title={Machining depth regulation and friction reduction in AFM-based ultrasonic vibration assisted nanomachining}, volume={41}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84892764978&partnerID=MN8TOARS}, booktitle={Transactions of the North American Manufacturing Research Institution of SME}, author={Zhang, L. and Dong, J. and Cohen, P.H.}, year={2013}, pages={482–488} }
 @article{zhang_dong_cohen_2013, title={Material-Insensitive Feature Depth Control and Machining Force Reduction by Ultrasonic Vibration in AFM-Based Nanomachining}, volume={12}, ISSN={["1941-0085"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84883779535&partnerID=MN8TOARS}, DOI={10.1109/tnano.2013.2273272}, abstractNote={This paper investigates the effect of ultrasonic tip-sample vibration in regulating the fabricated feature depth and reducing machining force in ultrasonic vibration-assisted nanomachining with an atomic force microscope (AFM). Nanopatterns on aluminum and polymethyl methacrylate (PMMA) substrates are fabricated by the ultrasonic vibration-assisted nanomachining approach. It is demonstrated that using a small set-point force and the same vibration amplitude for machining PMMA and aluminum, nearly the same feature depth is achieved. The fabrication depth is mainly controlled by the amplitude of the tip-sample z-vibration, and is insensitive to sample materials. A theoretical analysis of the sample contact stiffness and dynamic stiffness of the cantilever is used to explain the observed material-insensitive depth regulation by ultrasonic tip-sample vibration. The ultrasonic vibration also effectively reduces the normal force and friction during nanomachining. On both PMMA and aluminum samples, experimental results demonstrate significant reduction in set-point force and lateral friction force in ultrasonic vibration-assisted nanomachining compared with nanomachining without ultrasonic z-vibration. Smaller tip wear is observed in ultrasonic vibration-assisted nanomachining for the fabrication of PMMA samples.}, number={5}, journal={IEEE TRANSACTIONS ON NANOTECHNOLOGY}, author={Zhang, Li and Dong, Jingyan and Cohen, Paul H.}, year={2013}, month={Sep}, pages={743–750} }
 @article{zhu_tracy_dong_jiang_jones_childers_2013, title={Teaching a Multidisciplinary Nanotechnology Laboratory Course to Undergraduate Students}, volume={5}, ISSN={1936-7449}, url={http://dx.doi.org/10.1166/jne.2013.1032}, DOI={10.1166/jne.2013.1032}, abstractNote={Here we report our efforts to teach the first multidisciplinary undergraduate nanotechnology laboratory course in the College of Engineering at North Carolina State University (NCSU). The course was designed to provide undergraduate students with hands-on experience in nanoscience and nanotechnology. The theme of this laboratory course is the integration of nanotechnology with microsystem technology, i.e., bottom-up synthesis meeting top-down fabrication. This course consists of seven carefully designed lab modules that bridge the major “pillars” of nanotechnology– nanomaterials, nanofabrication, nanoscale characterization, and nanodevices. Final projects provide students opportunities to conduct nanotechnology research through problem-based learning and to improve their communication and presentation skills for educating the public about nanotechnology. A pedagogical approach that features problem-based learning, group learning, visual/tactile assistance and interdisciplinary interaction was employed during the offering of this course.}, number={1}, journal={Journal of Nano Education}, publisher={American Scientific Publishers}, author={Zhu, Yong and Tracy, Joseph B. and Dong, Jingyan and Jiang, Xiaoning and Jones, M. Gail and Childers, Gina}, year={2013}, month={Jun}, pages={17–26} }
 @article{koo_zhang_dong_salapaka_ferreira_2012, title={A 2 Degree-of-Freedom SOI-MEMS Translation Stage With Closed-Loop Positioning}, volume={21}, ISSN={["1941-0158"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84858438834&partnerID=MN8TOARS}, DOI={10.1109/jmems.2011.2174425}, abstractNote={This paper presents the design, analysis, fabrication, and characterization of a closed-loop XY micropositioning stage. The stage design is based on a 2 degree-of-freedom parallel kinematic mechanism with linear characteristics. Integrated with sensing combs, and fabricated in SOI wafers, the design provides a promising pathway to closed-loop positioning microelectromechanical systems platform with applications in nanomanufacturing and metrology. The XY stage provides a motion range of 20 micrometers in each direction at the driving voltage of 100 V. The resonant frequency of the XY stage under ambient conditions is 600 Hz. The positioning loop is closed using a capacitance-to-voltage conversion IC and a feedback controller is used to control position with an uncertainty characterized by a standard distribution of 5.24 nm and a closed-loop bandwidth of about 30 Hz.}, number={1}, journal={JOURNAL OF MICROELECTROMECHANICAL SYSTEMS}, author={Koo, Bonjin and Zhang, Xuemeng and Dong, Jingyan and Salapaka, Srinivasa M. and Ferreira, Placid M.}, year={2012}, month={Feb}, pages={13–22} }
 @article{zhang_dong_asme_2012, title={A SOI-MEMS-BASED SINGLE AXIS ACTIVE PROBE FOR CELLULAR FORCE SENSING AND CELL MANIPULATION}, volume={10}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000320481100072&KeyUID=WOS:000320481100072}, DOI={10.1115/IMECE2010-37924}, abstractNote={This paper presents the design, analysis, fabrication, and characterization of an electrostatically driven single axis active probing device for cellular force sensing and cell manipulation applications. The active probe is actuated by linear comb driver to create the motion in the probing direction. Both actuation and sensing comb drives are designed for the probing stage. The sensing comb structures enable us to sense the probe displacement when it is actuated, which enables application of force balanced sensing. The designed active probing device has an overall size of 5 mm × 4.5 mm, is fabricated on a silicon-on-insulator (SOI) substrate through surface micromachining technologies and deep reactive-ion etching (DRIE) process. The probe stage structure is fabricated on the 10-μm-thick device layer of SOI wafer. The handle layer beneath probe stage is etched away by DRIE process to decrease the film damping between the stage and the handle wafer thus achieving high quality factor. The proposed single axis probe is aimed at sensing cellular force which ranges from pN to μN and cell manipulation applications.}, journal={Proceedings of the Asme International Mechanical Engineering Congress and Exposition (Imece 2010), Vol 10}, author={Zhang, Li and Dong, Jingyan and ASME}, year={2012}, pages={537–542} }
 @inproceedings{kazemi-tutunchi_wei_shirwaiker_dong_2012, title={A process engineering perspective of scaffold fabrication methods in regenerative medicine: A review}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900330276&partnerID=MN8TOARS}, booktitle={62nd IIE Annual Conference and Expo 2012}, author={Kazemi-Tutunchi, G. and Wei, C. and Shirwaiker, R.A. and Dong, J.}, year={2012}, pages={3096–3105} }
 @inproceedings{zhang_dong_2012, title={A soi-mems-based single axis active probe for cellular force sensing and cell manipulation}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition (IMECE 2010), vol 10}, author={Zhang, L. and Dong, J. Y.}, year={2012}, pages={537–542} }
 @article{wang_cai_zhang_dong_wang_2012, title={Biodegradable Photo-Crosslinked Polymer Substrates with Concentric Microgrooves for Regulating MC3T3-E1 Cell Behavior}, volume={1}, ISSN={["2192-2659"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878117340&partnerID=MN8TOARS}, DOI={10.1002/adhm.201200030}, abstractNote={Abstract}, number={3}, journal={ADVANCED HEALTHCARE MATERIALS}, author={Wang, Kan and Cai, Lei and Zhang, Li and Dong, Jingyan and Wang, Shanfeng}, year={2012}, month={May}, pages={292–301} }
 @article{polit_dong_asme_2012, title={DESIGN OF A HIGH-BANDWIDTH XY NANOPOSITIONING STAGE FOR HIGH-THROUGHPUT MICRO/NANO MANUFACTURING}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000320286400084&KeyUID=WOS:000320286400084}, journal={Proceedings of the Asme International Mechanical Engineering Congress and Exposition 2010, Vol 3, Pts a and B}, author={Polit, Sebastian and Dong, Jingyan and ASME}, year={2012}, pages={709–718} }
 @article{wei_sonawane_cai_wang_dong_asme_2012, title={DIRECT-DEPOSITION AND MULTIPLE MATERIALS INTEGRATION OF TISSUE ENGINEERING SCAFFOLDS}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000320286400130&KeyUID=WOS:000320286400130}, journal={Proceedings of the Asme International Mechanical Engineering Congress and Exposition 2010, Vol 3, Pts a and B}, author={Wei, Chuang and Sonawane, Bhushan and Cai, Lei and Wang, Shanfeng and Dong, Jingyan and ASME}, year={2012}, pages={1083–1088} }
 @inproceedings{polit_dong_2012, title={Design of a high-bandwidth XY nanopositioning stage for high-throughput micro/nano manufacturing}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition 2010, vol 3, pts A and B}, author={Polit, S. and Dong, J. Y.}, year={2012}, pages={709–718} }
 @article{zhang_dong_2012, title={Design, Fabrication, and Testing of a SOI-MEMS-Based Active Microprobe for Potential Cellular Force Sensing Applications}, volume={2012}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000308153700001&KeyUID=WOS:000308153700001}, DOI={10.1155/2012/785798}, abstractNote={ This paper presents the design, analysis, fabrication, and characterization of an electrostatically driven single-axis active probing device for the applications of cellular force sensing and materials characterization. The active microprobe is actuated by linear comb drivers to generate the motion in the probing direction. Both actuation and sensing comb-drive structures are designed for the probing stage. The sensing comb structures enable us to sense the probe displacement when the device is actuated, which enables applications of force-balanced sensing and provides the capability of closed-loop control towards better accuracy. The designed active probing device is fabricated on a silicon-on-insulator (SOI) substrate with a 10 μm thick device layer through surface micromachining technologies and deep reactive-ion etching (DRIE) process. The handle layer beneath probe stage is etched away by DRIE process to decrease the film damping between the stage and the handle wafer thus achieving high-quality factor. The fabricated stage provides a motion range of 14 μm at actuation voltage of 140 V. The measured natural frequency of the stage is 1.5 kHz under ambient conditions. A sensitivity of 6 fF/ μm has been achieved. The proposed single-axis probe is aimed at sensing cellular force which ranges from a few nano-Newton to μN and micromanipulation applications. }, journal={Advances in Mechanical Engineering}, author={Zhang, Li and Dong, Jingyan}, year={2012}, pages={324–349} }
 @inproceedings{wei_sonawane_cai_wang_dong_2012, title={Direct-deposition and multiple materials integration of tissue engineering scaffolds}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition 2010, vol 3, pts A and B}, author={Wei, C. and Sonawane, B. and Cai, L. and Wang, S. F. and Dong, J. Y.}, year={2012}, pages={1083–1088} }
 @article{wei_cai_sonawane_wang_dong_2012, title={High-precision flexible fabrication of tissue engineering scaffolds using distinct polymers}, volume={4}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000304524700010&KeyUID=WOS:000304524700010}, DOI={10.1088/1758-5082/4/2/025009}, abstractNote={Three-dimensional porous structures using biodegradable materials with excellent biocompatibility are critically important for tissue engineering applications. We present a multi-nozzle-based versatile deposition approach to flexibly construct porous tissue engineering scaffolds using distinct polymeric biomaterials such as thermoplastic and photo-crosslinkable polymers. We first describe the development of the deposition system and fabrication of scaffolds from two types of biodegradable polymers using this system. The thermoplastic sample is semi-crystalline poly(ε-caprolactone) (PCL) that can be processed at a temperature higher than its melting point and solidifies at room temperature. The photo-crosslinkable one is polypropylene fumarate (PPF) that has to be dissolved in a reactive solvent as a resin for being cured into solid structures. Besides the direct fabrication of thermoplastic PCL scaffolds, we specifically develop a layer molding approach for the fabrication of crosslinkable polymers, which traditionally can only be fabricated by stereolithography. In this approach, a thermoplastic supporting material (paraffin wax) is first deposited to make a mold for each specific layer, and then PPF is deposited on demand to fill the mold and cured by the UV light. The supporting material can be removed to produce a porous scaffold of crosslinked PPF. Both PCL and crosslinked PPF scaffolds fabricated using the developed system have been characterized in terms of compressive mechanical properties, morphology, pore size and porosity. Mouse MC3T3-E1 pre-osteoblastic cell studies on the fabricated scaffolds have been performed to demonstrate their capability of supporting cell proliferation and ingrowth, aiming for bone tissue engineering applications.}, number={2}, journal={Biofabrication}, author={Wei, Chuang and Cai, Lei and Sonawane, Bhushan and Wang, Shanfeng and Dong, Jingyan}, year={2012} }
 @article{zhang_dong_2012, title={High-rate tunable ultrasonic force regulated nanomachining lithography with an atomic force microscope}, volume={23}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000300173200012&KeyUID=WOS:000300173200012}, DOI={10.1088/0957-4484/23/8/085303}, abstractNote={This paper describes a high-rate tunable nanomachining-based nanolithography technique using an atomic force microscope (AFM). Controlled vibration between the cantilever tip and the sample is introduced to increase the lithographical speed and controllability of the nanomachining process. In this approach, an ultrasonic z vibration of the sample and the resulting ultrasonic force from the nonlinear force–distance interaction between the sample and the cantilever tip are utilized to regulate fabrication depth. A high frequency in-plane circular vibration is introduced between the tip and the sample to control the width of the fabricated features, and to improve the speed of nanolithography. Features (e.g. slots) with dimensions spanning from tens of nanometers to hundreds of nanometers are fabricated in one scan. A lithography speed of tens of microns per second can be achieved, which is significantly higher than other known mechanical-modification-based nanolithography methods. The patterns, that are machined on a thin PMMA film, are transferred to silicon substrate through a reactive ion etching process, which provides a cost-effective tunable approach for the fabrication of nanostructures.}, number={8}, journal={Nanotechnology}, author={Zhang, Li and Dong, Jingyan}, year={2012} }
 @inproceedings{wei_lei_wang_dong_2012, title={Multi-material fabrication of tissue engineering scaffold}, volume={40}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84869826114&partnerID=MN8TOARS}, booktitle={Transactions of the North American Manufacturing Research Institution of SME}, author={Wei, C. and Lei, C. and Wang, S. and Dong, J.}, year={2012}, pages={126–132} }
 @article{cai_zhang_dong_wang_2012, title={Photocured Biodegradable Polymer Substrates of Varying Stiffness and Microgroove Dimensions for Promoting Nerve Cell Guidance and Differentiation}, volume={28}, ISSN={["0743-7463"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000307988700018&KeyUID=WOS:000307988700018}, DOI={10.1021/la302868q}, abstractNote={Photocross-linkable and biodegradable polymers have great promise in fabricating nerve conduits for guiding axonal growth in peripheral nerve regeneration. Here, we photocross-linked two poly(ε-caprolactone) triacrylates (PCLTAs) with number-average molecular weights of ~7000 and ~10,000 g mol(-1) into substrates with parallel microgrooves. Cross-linked PCLTA7k was amorphous and soft, while cross-linked PCLTA10k was semicrystalline with a stiffer surface. We employed different dimensions of interests for the parallel microgrooves, that is, groove widths of 5, 15, 45, and 90 μm and groove depths of 0.4, 1, 5, and 12 μm. The behaviors of rat Schwann cell precursor line (SpL201) cells with the glial nature and pheochromocytoma (PC12) cells with the neuronal nature were studied on these microgrooved substrates, showing distinct preference to the substrates with different mechanical properties. We found different threshold sensitivities of the two nerve cell types to topographical features when their cytoskeleton and nuclei were altered by varying the groove depth and width. Almost all of the cells were aligned in the narrowest and deepest microgrooves or around the edge of microgrooves. Oriented SpL201 cell movement had a higher motility as compared to unaligned ones. After forskolin treatment, SpL201 cells demonstrated significantly upregulated S-100 and O4 on stiffer substrates or narrower microgrooves, suggesting more differentiation toward early Schwann cells (SCs). PC12 neurites were oriented with enhanced extension in narrower microgrooves. The present results not only improve our fundamental understanding on nerve cell-substrate interactions, but also offer useful conduit materials and appropriate feature dimensions to foster guidance for axonal growth in peripheral nerve regeneration.}, number={34}, journal={LANGMUIR}, author={Cai, Lei and Zhang, Li and Dong, Jingyan and Wang, Shanfeng}, year={2012}, month={Aug}, pages={12557–12568} }
 @inproceedings{zhang_dong_2012, title={Ultrasonic vibration assisted nanomachining on PMMA with an AFM}, volume={TP12PUB71}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84880696152&partnerID=MN8TOARS}, booktitle={Technical Paper - Society of Manufacturing Engineers}, author={Zhang, L. and Dong, J.}, year={2012}, pages={631–637} }
 @inproceedings{koo_dong_ferreira_2011, title={A two degree-of-freedom soi-mems translation stage with closed loop positioning}, volume={52}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84884296523&partnerID=MN8TOARS}, booktitle={Proceedings - ASPE 2011 Annual Meeting}, author={Koo, B. and Dong, J. and Ferreira, P.M.}, year={2011}, pages={87–89} }
 @article{wang_cai_zhang_dong_wang_2011, title={Biodegradable elastomeric substrates with concentric microgrooves for regulating MC3T3 cell behavior}, volume={242}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000299378306557&KeyUID=WOS:000299378306557}, journal={Abstracts of Papers of the American Chemical Society}, author={Wang, Kan and Cai, Lei and Zhang, Li and Dong, Jingyan and Wang, Shanfeng}, year={2011} }
 @article{cai_zhang_dong_wang_2011, title={Biodegradable elastomeric substrates with micro-fabricated grooves for promoting neurite extension}, volume={242}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000299378306551&KeyUID=WOS:000299378306551}, journal={Abstracts of Papers of the American Chemical Society}, author={Cai, Lei and Zhang, Li and Dong, Jingyan and Wang, Shanfeng}, year={2011} }
 @article{polit_dong_2011, title={Development of a High-Bandwidth XY Nanopositioning Stage for High-Rate Micro-/Nanomanufacturing}, volume={16}, ISSN={["1941-014X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79956125765&partnerID=MN8TOARS}, DOI={10.1109/tmech.2010.2052107}, abstractNote={This paper presents the design analysis fabrication and testing of a high-bandwidth piezo-driven parallel kinematic nanopositioning XY stage. The monolithic stage design has two axes and each axis is composed of a doubly clamped beam and a parallelogram hybrid flexure with compliant beams and circular flexure hinges. The doubly clamped beam that is actuated by a piezoelectric actuator acts as a linear prismatic axis. The parallelogram hybrid flexures are used to decouple the actuation effect from the other axis. The mechanism design decouples the motion in the X- and Y-directions and restricts parasitic rotations in the XY plane while allowing for an increased bandwidth with linear kinematics in the operating region. Kinematic and dynamic analysis shows that the mechanical structure of the stage has decoupled motion in XY-direction while achieving high bandwidth and good linearity. The stage is actuated by piezoelectric stack actuators, and two capacitive gauges were added to the system to build a closed-loop positioning system. The results from frequency tests show that the resonant frequencies of the two vibrational modes are over 8 kHz. The stage is capable of about 15 μm of motion along each axis with a resolution of about 1 nm. Due to parallel kinematic mechanism design, a uniform performance is achieved across the workspace. A PI controller is implemented for the stage and a closed-loop bandwidth of 2 kHz is obtained.}, number={4}, journal={IEEE-ASME TRANSACTIONS ON MECHATRONICS}, author={Polit, Sebastian and Dong, Jingyan}, year={2011}, month={Aug}, pages={724–733} }
 @article{helfrich_lee_bristow_xiao_dong_alleyne_salapaka_ferreira_2010, title={Combined H-infinity-Feedback Control and Iterative Learning Control Design With Application to Nanopositioning Systems}, volume={18}, ISSN={["1558-0865"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77649187283&partnerID=MN8TOARS}, DOI={10.1109/tcst.2009.2018835}, abstractNote={This paper examines a coordinated feedback and feedforward control design strategy for precision motion control (PMC) systems. It is assumed that the primary exogenous signals are repeated; including disturbances and references. Therefore, an iterative learning control (ILC) feedforward strategy can be used. The introduction of additional non-repeating exogenous signals, including disturbances, noise, and reset errors, necessitates the proper coordination between feedback and feedforward controllers to achieve high performance. A novel ratio of repeated versus non-repeated signal power in the frequency domain is introduced and defined as the repetitive-to-non-repetitive (RNR) ratio. This frequency specific ratio allows for a new approach to delegating feedback and feedforward control efforts based on RNR value. A systematic procedure for control design is given whereby the feedback addresses the non-repeating exogenous signal content (RNR ≪ 0 dB) and the feedforward ILC addresses the repeating signal content (RNR ≫ 0 dB). To illustrate the design approach, two case studies using different nano-positioning devices are given.}, number={2}, journal={IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY}, author={Helfrich, Brian E. and Lee, Chibum and Bristow, Douglas A. and Xiao, X. H. and Dong, Jingyan and Alleyne, A. G. and Salapaka, Srinivasa M. and Ferreira, Placid M.}, year={2010}, month={Mar}, pages={336–351} }
 @inproceedings{polit_dong_2010, title={Design of a high-bandwidth XY nanopositioning stage for high-throughput micro/nano manufacturing}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84881461863&partnerID=MN8TOARS}, DOI={10.1115/IMECE2010-37794}, abstractNote={A high natural frequency (open-loop bandwidth) is a critical requirement for nanopositioners in high-throughput nanomanufacturing and nano-metrology applications. This paper presents the design and analysis of a high-bandwidth nanopositioning XY stage. The monolithic stage design has two axes and each axis is comprised of a doubly-clamped beam and a parallelogram hybrid flexure with complaint beams and circular flexure hinges. The doubly-clamped beam that is actuated by a piezoelectric actuator acts as a linear prismatic axis. The parallelogram hybrid flexures are used to decouple the actuation effect from the other axis. The mechanism design decouples the motion in the X and Y directions and restricts parasitic rotations in the XY plane while allowing for an increased bandwidth with linear kinematics in the operating region (or workspace). Kinematic and dynamic analysis shows that the mechanical structure of the stage has decoupled motion in XY direction, while achieving high bandwidth and good linearity. Finite element analysis is adapted to verify the dynamic responses from theoretical analysis. The stage is actuated by piezoelectric stack actuators, and two capacitive gauges were added to the system to build a closed-loop positioning system. The results from frequency test show that the resonation frequencies of the two vibrational modes are over 8K Hz. The stage is capable of about 15 microns of motion along each axis with a resolution of about 1 nanometer. Due to parallel kinematic mechanism design, a uniform performance is achieved across the workspace. A PI controller is implemented for the stage and a high closed-loop bandwidth is obtained.}, number={PARTS A AND B}, booktitle={ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)}, author={Polit, S. and Dong, J.}, year={2010}, pages={709–718} }
 @inproceedings{wei_sonawane_cai_wang_dong_2010, title={Direct-deposition and multiple materials integration of tissue engineering scaffolds}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84881452711&partnerID=MN8TOARS}, DOI={10.1115/IMECE2010-37922}, abstractNote={High-aspect-ratio three-dimensional structures using biocompatible materials are critical for tissue engineering applications. This study develops a multi-nozzle direct-write approach to construct tissue engineering scaffolds with complex three-dimensional structures utilizing polymeric materials. This approach provides the capability to fabricate three dimensional scaffolds by depositing biocompatible UV-curable polymeric material and thermoplastic material (paraffin wax) layer-by-layer, which respectively are used as structural material and supporting material that will be removed later on. The designed structure is built by selectively extruding drops and/or filament through a set of syringes that host different functional materials, following a layer-by-layer sequence. The location of the deposition is precisely controlled by a high precision three-dimensional translational stage. After different structural/functional materials and the supporting material are deposited with predesigned pattern, the supporting material is removed by using appropriate chemical solvent which will not affect physical and chemical properties of the designed structure. The mechanical property of the structure, the equilibrium modulus and dynamic stiffness, can be engineered by designing different pore size for the scaffold. The multi-nozzle based direct writing approach provides a practical solution to build scaffolds for tissue engineering and integrate multiple functional materials together into a single scaffold structure.}, number={PARTS A AND B}, booktitle={ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)}, author={Wei, C. and Sonawane, B. and Cai, L. and Wang, S. and Dong, J.}, year={2010}, pages={1083–1088} }
 @article{dong_ferreira_asme_2010, title={NANO-MANIPULATION DEVICE WITH PARALLEL KINEMATIC MICRO-POSITIONING STAGE AND INTEGRATED ACTIVE CANTILEVER}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000280203700060&KeyUID=WOS:000280203700060}, journal={Imece 2009: Proceedings of the Asme International Mechanical Engineering Congress and Exposition, Vol 12, Pts a and B}, author={Dong, Jingyan and Ferreira, Placid M. and ASME}, year={2010}, pages={405–413} }
 @inproceedings{dong_ferreira_asme_2010, title={Nano-manipulation device with parallel kinematic micro-positioning stage and integrated active cantilever}, volume={12}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77954308617&partnerID=MN8TOARS}, DOI={10.1115/IMECE2009-10336}, abstractNote={This paper discusses the design, analysis, fabrication and characterization of a MEMS device for nano-manufacturing and nano-metrology applications. The device includes an active cantilever as its manipulator that is integrated with a high-bandwidth two degree-of-freedom translational (XY) micro positioning stage. The cantilever is actuated electrostatically through a separate electrode that is fabricated underneath the cantilever. Torsion bars that connect the cantilever to the rest of the structure provide the required compliance for cantilever’s out-of-plane rotation. The active cantilever is carried by a micro-positioning stage, which enables high-bandwidth scanning to allow manipulation in three dimensions. The design of the MEMS (Micro-Electro-Mechanical Systems) stage is based on a parallel kinematic mechanism (PKM). The PKM design decouples the motion in the X and Y directions and restricts rotations in the XY plane while allowing for an increased motion range with linear kinematics in the operating region (or workspace). The truss-like structure of the PKM also results in increased stiffness and reduced mass of the stage. The integrated cantilever device is fabricated on a Silicon-On-Insulator (SOI) wafer using surface micromachining and deep reactive ion etching (DRIE) processes. The actuation electrode of the cantilever is fabricated on the handle layer, while the cantilever and XY stage are at the device layer of the SOI wafer. Two sets of electrostatic linear comb drives are used to actuate the stage mechanism in X and Y directions. The cantilever provides an out-of-plane motion of 7 microns at 4.5V, while the XY stage provides a motion range of 24 microns in each direction at the driving voltage of 180V. The resonant frequency of the XY stage under ambient conditions is 2090 Hz. A high quality factor (∼210) is achieved from this parallel kinematics XY stage. The fabricated stages will be adapted as chip-scale manufacturing and metrology devices for nanomanufacturing and nano-metrology applications.}, number={PART A}, booktitle={Imece 2009: Proceedings of the Asme International Mechanical Engineering Congress and Exposition, Vol 12, Pts a and B}, author={Dong, Jingyan and Ferreira, Placid M. and ASME}, year={2010}, pages={405–413} }
 @article{polit_dong_2009, title={Design of high-bandwidth high-precision flexure-based nanopositioning modules}, volume={28}, ISSN={["1878-6642"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000278240700004&KeyUID=WOS:000278240700004}, DOI={10.1016/j.jmsy.2010.01.001}, abstractNote={This paper presents the design of a single degree-of-freedom high-bandwidth high-precision nanopositioning module for high-throughput nanomanufacturing applications. Compared with widely used lumped-compliance mechanisms (using notch-flexure hinges) and distributed-compliance mechanisms (using compliant flexure beams), this nanopositioning module adopts a hybrid compliant-notch-flexure-based structure. This flexure design decouples the performance requirements for the structural bandwidth and parasitic accuracy that are correlated in the lumped-compliance mechanisms and distributed-compliance mechanisms. The parallelogram hybrid compliant-notch-flexure-based structure enables simultaneous achievement of a higher structural bandwidth and a smaller parasitic motion. The behavior of the nanopositioning module is analyzed theoretically with respect to its design parameters and performance objectives. Finite element analysis is adapted to study the dynamic responses and parasitic displacement of the designed nanopositioning module. The results from the theoretical and FEA analysis demonstrate the effectiveness of the hybrid compliant-notch-flexure design over commonly used lumped-compliance mechanisms and distributed-compliance mechanisms, especially when a high structural bandwidth is required for high-throughput nanomanufacturing applications.}, number={2-3}, journal={JOURNAL OF MANUFACTURING SYSTEMS}, author={Polit, Sebastian and Dong, Jingyan}, year={2009}, month={Jul}, pages={71–77} }
 @article{dong_ferreira_2009, title={Electrostatically Actuated Cantilever With SOI-MEMS Parallel Kinematic XY Stage}, volume={18}, ISSN={["1057-7157"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000266723700015&KeyUID=WOS:000266723700015}, DOI={10.1109/JMEMS.2009.2020371}, abstractNote={This paper presents the design, analysis, fabrication, and characterization of an active cantilever device integrated with a high-bandwidth 2-DOF translational (XY) micropositioning stage. The cantilever is actuated electrostatically through a separate electrode that is fabricated underneath the cantilever. Torsion bars that connect the cantilever to the rest of the structure provide the required compliance for the cantilever's out-of-plane rotation. The active cantilever is carried by a micropositioning stage, which enables high-bandwidth scanning to allow manipulation in three dimensions. The design of the microelectromechanical system stage is based on a parallel kinematic mechanism (PKM). The PKM design decouples the motion in the X- and Y-directions while allowing for an increased motion range with linear kinematics in the operating region (or workspace). The trusslike structure of the PKM also results in increased stiffness and reduced mass of the stage. The integrated cantilever device is fabricated on a silicon-on-insulator (SOI) wafer using surface micromachining and deep reactive ion etching processes. The actuation electrode of the cantilever is fabricated on the handle layer, while the cantilever and the XY stage are at the device layer of the SOI wafer. Two sets of electrostatic linear comb drives are used to actuate the stage mechanism in the X- and Y-directions. The cantilever provides an out-of-plane motion of 7 mum at 4.5 V, while the XY stage provides a motion range of 24 mum in each direction at the driving voltage of 180 V. The resonant frequency of the XY stage under ambient conditions is 2090 Hz. A high quality factor (~210) is achieved from this parallel kinematic XY stage. The fabricated stages will be adapted as chip-scale manufacturing and metrology devices for nanomanufacturing and nanometrology applications.}, number={3}, journal={JOURNAL OF MICROELECTROMECHANICAL SYSTEMS}, author={Dong, Jingyan and Ferreira, Placid M.}, year={2009}, month={Jun}, pages={641–651} }
 @article{mukhopadhyay_dong_pengwang_ferreira_2008, title={A SOI-MEMS-based 3-DOF planar parallel-kinematics nanopositioning stage}, volume={147}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000259017500047&KeyUID=WOS:000259017500047}, DOI={10.1016/j.sna.2008.04.018}, abstractNote={This paper presents the design, kinematic and dynamic analysis, fabrication and characterization of a monolithic micro/nanopositioning three degrees-of-freedom (DOF) (XYθ) stage. The design of the proposed MEMS (micro-electro-mechanical system) stage is based on a parallel-kinematic mechanism (PKM) scheme that allows for translation in the XY plane and rotation about the Z axis, an increased motion range, and linear kinematics in the operating region (or work area) of the stage. The truss-like structure of the PKM results in higher modal frequencies by increasing the structural stiffness and reducing the moving mass of the stage. The stage is fabricated on a silicon-on-insulator (SOI) wafer using surface micromachining and deep reactive ion etching (DRIE) processes. Three sets of electrostatic linear comb drives jointly actuate the mechanism to produce motion in the X, Y and θ (rotation) directions. The fabricated stage provides a motion range of 18 μm and 1.72° at a driving voltage of 85 V. The resonant frequency of the stage under ambient conditions is 465 Hz. Additionally a high Q factor (∼66) is achieved from this parallel-kinematics mechanism design.}, number={1}, journal={Sensors and Actuators a-Physical}, author={Mukhopadhyay, Deepkishore and Dong, Jingyang and Pengwang, Eakkachai and Ferreira, Placid}, year={2008}, pages={340–351} }
 @article{dong_yao_ferreira_2008, title={A novel parallel-kinematics mechanism for integrated, multi-axis nanopositioning - Part 2: Dynamics, control and performance analysis}, volume={32}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000251753400003&KeyUID=WOS:000251753400003}, DOI={10.1016/j.precisioneng.2007.03.002}, abstractNote={In this paper, we discuss the dynamics, controls and performance of a parallel-kinematics, integrated, multi-axis nanopositioner, the PKXYZNP [Yao Q, Dong J, Ferreira PM. A novel parallel-kinematics mechanisms for integrated, multi-axis nano-positioning. Part 1: Kinematics and design for fabrications]. The paper focuses on computing the workspace of the stage, characterization of its dynamic behavior, synthesis of a controller for it, and the testing of its contour tracking and positioning performance. For this system, because of the coupled nature of the axes, a MIMO control scheme is adopted to directly close the loop around the kinematics of the stage, i.e., the position of the table/end-effector is fed back to control the actuators. This scheme has the added advantage of not requiring complex and fragile kinematic calibration of the stage as the accuracy becomes a function of only the accuracy of the sensing system and the servo performance. To make the MIMO control scheme tractable by reducing its order, the controller design is performed in the modal space of the system. A resolution of 2–4 nm is achieved from this stage. Linear and circular tests were performed to evaluate the contouring performance of the PKXYZ stage. In spite of a relatively heavy load condition (the weight of a solid target), the linear and circular contouring errors are less than 40 and 150 nm, respectively, with contouring speeds ranging up to 40 μm/s.}, number={1}, journal={Precision Engineering-Journal of the International Societies For Precision Engineering and Nanotechnology}, author={Dong, Jingyan and Yao, Qing and Ferreira, Placid M.}, year={2008}, pages={20–33} }
 @article{yao_dong_ferreira_2008, title={A novel parallel-kinematics mechanisms for integrated, multi-axis nanopositioning - Part 1. Kinematics and design for fabrication}, volume={32}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35748956659&partnerID=MN8TOARS}, DOI={10.1016/j.precisioneng.2007.03.001}, abstractNote={Abstract Multi-axis micro and nanopositioning systems are increasingly used in much of the metrology and process equipment related to the field of nanotechnology. This, the first of a two-part series of papers on a novel piezo-driven, parallel-kinematics XYZ nanopositioning (PKXYZNP) stage, concentrates on the development of a viable scheme to achieve pure spatial translation. First, the mechanism is shown to admit closed-form solutions to both; the forward and reverse kinematic problems. The Jacobian and the dynamics of the system indicate that the mechanical structure produces a relatively large work volume, and is capable of high bandwidth and uniform performance across it. The fabrication of the system is described along with some basic testing of its Jacobian and its modal frequencies. Using capacitive gages, the stage is capable of about 85 μm of motion along each axis with a resolution of about 2–4 nm. The controls, testing and performance are discussed in detail in the companion paper [Dong J, Yao Q, Ferreira PM. A novel parallel-kinematics mechanism for integrated, multi-axis nanopositioning. Part 2. Dynamics, control and performance analysis. Precis Eng].}, number={1}, journal={Precision Engineering-Journal of the International Societies For Precision Engineering and Nanotechnology}, author={Yao, Qing and Dong, Jingyan and Ferreira, Placid M.}, year={2008}, pages={7–19} }
 @inbook{helfrich_lee_bristow_xiao_dong_alleyne_salapaka_ferreira_ieee_2008, title={Combined H-infinity-feedback and Iterative Learning Control design with application to nanopositioning systems}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000259261502211&KeyUID=WOS:000259261502211}, DOI={10.1109/ACC.2008.4587101}, abstractNote={This paper presents a coordinated design framework for precision motion control (PMC) systems. In particular, the focus is on the design of feedback and feedforward controllers operating on systems that repeatedly perform the same tasks. The repetitive nature of the tasks suggests the use of Iterative Learning Control (ILC). However, in addition to the repeatability of the desired trajectory, the class of systems under study examines the effect of non-repeating disturbances and possible reset errors. The rejection of uncertain, but bounded, disturbances suggests the use of H infin design. The non-repeating disturbances and reset errors necessitate coordination of the feedback and feedforward designs. The assumption that the disturbances have a particular frequency distribution affords a frequency domain separation between the two controller degrees of freedom. Experimental results are given on a piezo-driven nanopositioning device demonstrating the benefits to the presented approach.}, booktitle={2008 American Control Conference, Vols 1-12}, author={Helfrich, B. E. and Lee, C. and Bristow, D. A. and Xiao, X. H. and Dong, J. and Alleyne, A. G. and Salapaka, S. M. and Ferreira, P. M. and IEEE}, year={2008}, pages={3893–3900} }
 @article{bristow_dong_alleyne_ferreira_salapaka_2008, title={High bandwidth control of precision motion instrumentation}, volume={79}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55349127406&partnerID=MN8TOARS}, DOI={10.1063/1.2980377}, abstractNote={This article presents a high-bandwidth control design suitable for precision motion instrumentation. Iterative learning control (ILC), a feedforward technique that uses previous iterations of the desired trajectory, is used to leverage the repetition that occurs in many tasks, such as raster scanning in microscopy. Two ILC designs are presented. The first design uses the motion system dynamic model to maximize bandwidth. The second design uses a time-varying bandwidth that is particularly useful for nonsmooth trajectories such as raster scanning. Both designs are applied to a multiaxis piezoelectric-actuated flexure system and evaluated on a nonsmooth trajectory. The ILC designs demonstrate significant bandwidth and precision improvements over the feedback controller, and the ability to achieve precision motion control at frequencies higher than multiple system resonances.}, number={10}, journal={Review of Scientific Instruments}, author={Bristow, Douglas A. and Dong, Jingyan and Alleyne, Andrew G. and Ferreira, Placid and Salapaka, Srinivas}, year={2008} }
 @article{dong_salapaka_ferreira_asme_2008, title={MIMO H-infinity control of a parallel kinematic XYZ nano-positioner}, journal={International Mechanical Engineering Congress and Exposition 2007, Vol 11 Pt a and Pt B: Micro and Nano Systems}, author={Dong, Jingyan and Salapaka, Srinivasa M. and Ferreira, Placid M. and ASME}, year={2008}, pages={145–153} }
 @inproceedings{dong_salapaka_ferreira_2008, title={MIMO H<inf>∞</inf> control of a parallel kinematic XYZ nano-positioner}, volume={11 PART A}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44349157652&partnerID=MN8TOARS}, DOI={10.1115/IMECE2007-41868}, abstractNote={This paper presents the design, model identification and control of a parallel-kinematics XYZ nano positioning stage for general nano-manipulation and nano-manufacturing applications. The stage features a low degree of freedom monolithic parallel kinematic mechanism with flexure joints. The stage is driven by piezoelectric actuators and its displacement is detected by capacitance gauges. The control loop is closed at the end-effector instead of the each joint, so as to avoid calibration difficulties and guarantee high positioning accuracy. Instead of a single input and single output (SISO) system with joint space control configuration, this design has strongly coupled dynamics with each actuator input producing along multiple axes. The nano-positioner is modeled as a multiple input and multiple output (MIMO) system, where the control design forms an important constituent that accounts for the strongly coupled dynamics. The dynamics that model the MIMO plant is identified by time-domain identification method. A pseudo-random binary signal is used to excite the system while avoiding violent vibrations at resonant frequencies, which comes from the low damping feature of flexure based structure. The order of the model is reduced to make controller efficient and implementable. The control design based on modern robust control theory that gives a high bandwidth closed loop nanopositioning system which is robust to physical model uncertainties arising from flexure-based mechanisms is presented. The nonlinear effects from piezoelectric actuators, such as hysteresis and creep, are compensated effectively by closed loop robust controller. The bandwidth, resolution and repeatability are characterized experimentally, which demonstrate the effectiveness of the robust control approach.}, booktitle={ASME International Mechanical Engineering Congress and Exposition, Proceedings}, author={Dong, J. and Salapaka, S.M. and Ferreira, P.M.}, year={2008}, pages={145–153} }
 @inbook{mukhopadhyay_dong_ferreira_maher_chiao_resnick_2008, title={Parallel kinematic mechanism based monolithic XY micro-positioning stage with rotary comb drive actuators - art. no. 688209}, volume={6882}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-41149116083&partnerID=MN8TOARS}, DOI={10.1117/12.762358}, abstractNote={Micro-positioning stages fabricated using Micro Electro Mechanical Systems (MEMS) based processes have been critical in enabling micro/nano manipulation and probing. These stages have been extensively used in micro-force sensors, scanning probe microscopy and micro optical lens scanners. This paper presents the design, kinematic and dynamic analysis, fabrication and characterization of a novel monolithic micro-positioning XY stage. The design of the proposed micro-positioning stage is based on a Parallel Kinematic Mechanism (PKM). The PKM based design decouples the motion in the XY direction. Additionally, it restricts the parasitic rotation of the end-effector (table) of the micro-positioning stage while providing an increased motion range. The motion of the stage is linear in the operating range thus simplifying its kinematics. The truss like parallel kinematic mechanism design of the stage structure reduces its mass while keeping the stage stiffness high. This leads to a high natural frequency of the micro-positioning stage (1250Hz) and a high Q-factor of 156. The stage mechanism is fabricated on a Silicon-On-Insulator (SOI) substrate and is actuated by integrated electrostatic rotary comb drives. The fabrication process uses multi-layer patterning along with an Inductively Coupled Plasma Deep Reactive Ion Etching (ICP-DRIE). The use of ICP-DRIE enables the high aspect ratio etching that is required for the stage fabrication and its optimal actuation using the integrated electrostatic rotary comb drives. The fabricated stages have a motion range of more than 30 microns of decoupled displacements along the X and Y directions at a driving voltage of 200V.}, booktitle={Micromachining and Microfabrication Process Technology Xiii}, author={Mukhopadhyay, Deepkishore and Dong, Jingyan and Ferreira, Placid M. and Maher, MA and Chiao, JC and Resnick, PJ}, year={2008}, pages={88209} }
 @inproceedings{dong_mukhopadhyay_pengwang_ferreira_2008, title={Parallel-kinematics mems stages for high precision nanopositioning and manipulation}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84884962392&partnerID=MN8TOARS}, booktitle={Proceedings of the 23rd Annual Meeting of the American Society for Precision Engineering, ASPE 2008 and the 12th ICPE}, author={Dong, J. and Mukhopadhyay, D. and Pengwang, E. and Ferreira, P.M.}, year={2008} }
 @article{dong_salapaka_ferreira_2008, title={Robust control of a parallel-kinematic nanopositioner}, volume={130}, url={http://dx.doi.org/10.1115/1.2936861}, DOI={10.1115/1.2936861}, abstractNote={This paper presents the design, model identification, and control of a parallel-kinematic XYZ nanopositioning stage for general nanomanipulation and nanomanufacturing applications. The stage has a low degree-of-freedom monolithic parallel-kinematic mechanism featuring single-axis flexure hinges. The stage is driven by piezoelectric actuators, and its displacement is detected by capacitance gauges. The control loop is closed at the end effector instead of at each joint, so as to avoid calibration difficulties and guarantee high positioning accuracy. This design has strongly coupled dynamics with each actuator input producing in multiaxis motions. The nanopositioner is modeled as a multiple input and multiple output (MIMO) system, where the control design forms an important constituent in view of the strongly coupled dynamics. The dynamics that model the MIMO plant is identified by frequency domain and time-domain identification methods. The control design based on modern robust control theory that gives a high bandwidth closed loop nanopositioning system, which is robust to physical model uncertainties arising from flexure-based mechanisms, is presented. The bandwidth, resolution, and repeatability are characterized experimentally, which demonstrate the effectiveness of the robust control approach.}, number={4}, journal={Journal of Dynamic Systems, Measurement, and Control}, publisher={ASME International}, author={Dong, Jingyan and Salapaka, Srinivasa M. and Ferreira, Placid M.}, year={2008}, pages={0410071–04100715} }
 @inbook{jeong_dong_ferreira_2008, place={Bellingham}, title={Self-calibration of a dual-actuated single-axis nanopositioner using measurement transitivity with extensions to calibration of two-axis systems}, volume={7042}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-56249115562&partnerID=MN8TOARS}, DOI={10.1117/12.796101}, abstractNote={In this paper we discuss a self-calibration technique for a dual-actuated, single-axis nanopositioner and extend ideas from this method to develop a calibration technique for a two-axis system. The proposed methods exploit concepts of measurement transitivity and redundancy that are will established in self-calibration theory. The developed method has been applied to a dual-actuated single-axis nanopositioner equipped with capacitive displacement sensors with a calibration error in the sub-nanometer range. For the two-axis system, the technique uses a right angle prism as an artifact to calibrate two orthogonal axes. Transitivity between the axes is obtained through the use of a redundant or 'dummy' uncalibrated sensor that maintains the hypotenuse of the right angle prism invariant during sets of measurements. Because, the approach relies on the accuracy of the prism, it cannot be considered to be a self-calibration technique. Nevertheless, experiments indicate that it calibrates a two-axis stage to within 1 nm of the prism.}, booktitle={Instrumentation, Metrology, and Standards for Nanomanufacturing Ii}, author={Jeong, Y. H. and Dong, J. and Ferreira, P. P.}, editor={Postek, M. T. and Allgair, J. A.Editors}, year={2008} }
 @article{jeong_dong_ferreira_2008, title={Self-calibration of dual-actuated single-axis nanopositioners}, volume={19}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-42549100721&partnerID=MN8TOARS}, DOI={10.1088/0957-0233/19/4/045203}, abstractNote={The rapid growth in nanosciences and technology has increased the need for high-precision nanopositioning stage technology, an important aspect of which is calibration to a traceable length standard with nanometre resolution. Direct calibration of the entire displacement range to a traceable length standard is generally difficult and time consuming because of the dearth of suitable and stable references and the need to remove all environmental disturbances during the calibration procedure. This paper introduces an approach to implementing self-calibration on a single-axis, dual-actuated, nanopositioning stage. It demonstrates how dual actuation on such a system can be used to implement the transitivity and redundancy conditions required for dimensional self-calibration so that only a single scaling input is required. The approach is verified by a series of simulations and experiments to demonstrate repeatable self-calibration of the axis to within 1 nm over a displacement range of 30 µm.}, number={4}, journal={Measurement Science & Technology}, author={Jeong, Y. H. and Dong, J. and Ferreira, P. M.}, year={2008} }
 @article{dong_ferreira_2008, title={Simultaneous actuation and displacement sensing for electrostatic drives}, volume={18}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-42549097297&partnerID=MN8TOARS}, DOI={10.1088/0960-1317/18/3/035011}, abstractNote={This paper presents a method for driving a MEMS electrostatic actuator, while simultaneously sensing the resulting displacement/capacitance without the use of an additional physical sensing structure. The approach superposes the sensing and actuation signals into a single input into the system and obtains its mechanical (displacement) response from the modulation (amplitude or phase) it produces on the sensing input. The approach is analyzed and experimentally shown to produce an amplitude modulation of 0.1857 mV µm−1 of displacement on electrostatic drive that produces a displacement of 14 µm at 100 V and a 0.55 pF capacitance change from a nominal capacitance of 0.35 Pico farads. The approach enables a very cost-effective and convenient approach to detect the displacement of MEMS devices for a variety of applications in the laboratory environment, and provide a potential feedback signal for closed-loop control of electrostatically driven MEMS devices.}, number={3}, journal={Journal of Micromechanics and Microengineering}, author={Dong, Jingyan and Ferreira, Placid M.}, year={2008} }
 @article{yao_dong_ferreira_2007, title={Design, analysis, fabrication and testing of a parallel-kinematic micropositioning XY stage}, volume={47}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33846817319&partnerID=MN8TOARS}, DOI={10.1016/j.ijmachtools.2006.07.007}, abstractNote={This paper reports on a novel piezo-driven, parallel-kinematic, micropositioning XY stage. This monolithic design is comprised of parallelogram four-bar linkages, flexure hinges, and piezoelectric actuators. Kinematic and dynamic analysis shows that the mechanical structure of the stage has a large work space, high bandwidth and good linearity. The stage system was run in open-loop mode to measure the step response and frequency response. The results show that the resonation frequencies of the two vibration modes are 563 and 536 Hz and the damping ratios are 0.049 and 0.0228. Two fiber optic sensors were added to the system to build a closed-loop positioning system. Linear and circular contouring performance in closed-loop mode suggests high scanning performance for such parallel-kinematic stages. The positioning resolution of the stage, limited only by the feedback sensors used, is about 20 nm.}, number={6}, journal={International Journal of Machine Tools & Manufacture}, author={Yao, Qing and Dong, J. and Ferreira, P. M.}, year={2007}, pages={946–961} }
 @article{dong_mukhopadhyay_ferreira_2007, title={Design, fabrication and testing of a silicon-on-insulator (SOI) MEMS parallel kinematics XY stage}, volume={17}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34249718527&partnerID=MN8TOARS}, DOI={10.1088/0960-1317/17/6/008}, abstractNote={This paper presents the design, kinematics, fabrication and characterization of a monolithic micro positioning two degree-of-freedom translational (XY) stage. The design of the proposed MEMS (micro-electro-mechanical system) stage is based on a parallel kinematics mechanism (PKM). The stage is fabricated on a silicon-on-insulator (SOI) substrate. The PKM design decouples the motion in the XY directions. The design restricts rotations in the XY plane while allowing for an increased motion range and produces linear kinematics in the operating region (or workspace) of the stage. The truss-like structure of the PKM also results in increased stiffness by reducing the mass of the stage. The stage is fabricated on a silicon-on-insulator (SOI) wafer using surface micromachining and a deep reactive ion etching (DRIE) process. Two sets of electrostatic linear comb drives are used to actuate the stage mechanism in the X and Y directions. The fabricated stage provides a motion range of more than 15 µm in each direction at a driving voltage of 45 V. The resonant frequency of the stage under ambient conditions is 960 Hz. A high Q factor (∼100) is achieved from this parallel kinematics mechanism design.}, number={6}, journal={Journal of Micromechanics and Microengineering}, author={Dong, Jingyan and Mukhopadhyay, Deepkishore and Ferreira, Placid M.}, year={2007}, pages={1154–1161} }
 @article{dong_ferreira_stori_2007, title={Feed-rate optimization with jerk constraints for generating minimum-time trajectories}, volume={47}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34547670801&partnerID=MN8TOARS}, DOI={10.1016/j.ijmachtools.2007.03.006}, abstractNote={Competitive pressure requires manufacturers to simultaneously address increasingly stringent constraints on both productivity and quality. From the perspective of numerically controlled (NC) machine tools, this means higher machining performance in terms of speed and accuracy. Conventional approaches to programming NC operations involve selecting a constant feedrate for a given operation to produce acceptable performance (operation time and contouring accuracy). In this paper, we examine the possibility of scheduling or varying the feedrate by taking into consideration the geometry of the contour that the machine is expected to follow and the physical capabilities of the machine (i.e., its maximum velocity, acceleration and jerk constraints). Previous work by the authors has addressed the efficient, off-line computation of time-optimal trajectories with constraints on velocity and acceleration. This paper introduces additional constraints on the permissible jerk (rate of change of acceleration) on the machine's axis. From a practical perspective, excessive jerk leads to excitation of vibrations in components in the machine assembly, accelerated wear in the transmission and bearing elements, noisy operations and large contouring errors at discontinuities (such as corners) in the machining path. The introduction of jerk into the feedrate scheduling problem makes generating computationally efficient solutions while simultaneously guaranteeing optimality a challenging problem. This paper approaches this problem as an extension of our previous bi-directional scan algorithm [23], [29]. A new acceleration-continuation procedure is added to the feedrate optimization algorithm to address jerk constraints and remove discontinuities in the acceleration profile. The algorithm maintains computational efficiency and supports the incorporation of a variety of state-dependent (such as position, velocity, acceleration and jerk) constraints. By carefully organizing the local search and acceleration continuity enforcing steps, a globally optimal solution is achieved. Singularities, or critical points, and critical curves on the trajectory, which are difficult to deal within optimal control approaches, are treated in a natural way in this algorithm. Several application examples and tests are performed to verify the effectiveness of this approach for high-speed contouring.}, number={12-13}, journal={International Journal of Machine Tools & Manufacture}, author={Dong, Jingyan and Ferreira, P. M. and Stori, J. A.}, year={2007}, pages={1941–1955} }
 @inproceedings{dong_salapaka_ferreira_2007, title={MIMO H∞ control of a parallel kinematic XYZ nano-positioner}, volume={11}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84928615975&partnerID=MN8TOARS}, DOI={10.1115/IMECE200741868}, booktitle={ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)}, author={Dong, J. and Salapaka, S.M. and Ferreira, P.M.}, year={2007}, pages={145–153} }
 @article{dong_stori_2007, title={Optimal feed-rate scheduling for high-speed contouring}, volume={129}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34248167120&partnerID=MN8TOARS}, DOI={10.1115/1.2280549}, abstractNote={The majority of efforts to improve the contouring performance of high-speed CNC systems has focused on advances in feedback control techniques at the single-axis servo level. Regardless of the dynamic characteristics of an individual system, performance will inevitably suffer when that system is called upon to execute a complex trajectory beyond the range of its capabilities. The intent of the present work is to provide a framework for abstracting the capabilities of an individual multiaxis contouring system, and a methodology for using these capabilities to generate a time-optimal feed-rate profile for a particular trajectory on a particular machine. Several constraints are developed to drive the feed-rate optimization algorithm. First, simplified dynamic models of the individual axes are used to generate performance envelopes that couple the velocity versus acceleration capabilities of each axis. Second, bandwidth limitations are introduced to mitigate frequency related problems encountered when traversing sharp geometric features at high velocity. Finally, a dynamic model for the instantaneous following error is used to estimate the contour error as a function of the instantaneous velocity and acceleration state. We present a computationally efficient algorithm for generating a minimum-time feed-rate profile subject to the above constraints, and demonstrate that significant improvements in contouring accuracy can be realized through such an approach. Experimental results are presented on a conventional two-axis X−Y stage executing a complex trajectory.}, number={1}, journal={Journal of Manufacturing Science and Engineering-Transactions of the Asme}, author={Dong, J. and Stori, J. A.}, year={2007}, pages={63–76} }
 @article{baca_meitl_ko_mack_kim_dong_ferreira_rogers_2007, title={Printable single-crystal silicon micro/nanoscale ribbons, platelets and bars generated from bulk wafers}, volume={17}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-36148942881&partnerID=MN8TOARS}, DOI={10.1002/adfm.200601161}, abstractNote={Abstract}, number={16}, journal={Advanced Functional Materials}, author={Baca, Alfred J. and Meitl, Matthew A. and Ko, Heung Cho and Mack, Shawn and Kim, Hoon-Sik and Dong, Jingyan and Ferreira, Placid M. and Rogers, John A.}, year={2007}, pages={3051–3062} }
 @inproceedings{dong_salapaka_ferreira_2007, title={Robust MIMO control of a parallel kinematics nano-positioner for high resolution high bandwidth tracking and repetitive tasks}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-41949092731&partnerID=MN8TOARS}, DOI={10.1109/CDC.2007.4434317}, abstractNote={This paper presents the design and implementation of robust control schemes for two applications of a nanopositioning stage (1) reference trajectory tracking with high resolution over a given bandwidth (2) control design for repetitive motions. The stage has a low degree of freedom monolithic parallel kinematic mechanism using flexure hinges. It is driven by piezoelectric actuators and its displacement is detected by capacitance gauges. The design has strongly coupled dynamics with each actuator input producing in multi- axis motions. The nano-positioner is modeled as a multiple input and multiple output (MIMO) system, and the MIMO plant model is identified by time-domain identification methods. The design of the nano-positioner relies heavily on the control design to account for the high coupling in the system. The proposed Hinfin MIMO controller achieves a good performance in terms of resolution, bandwidth and robustness to the modeling uncertainty. In the second part of the paper, we present control design for tasks that require repetitive motion of nano positioning system. These tasks are quite common in micro/nano manipulation and manufacturing. This paper presents a robust control design that gives a significant (over thirty fold) improvement in tracking of repetitive motions on a prespecified frequency band. This design, unlike other schemes, is robust to modeling uncertainties that arise in flexure based mechanisms, and does not require any learning steps during its real time implementation. This design scheme is implemented on a parallel-kinematics XYZ nano positioning stage for repetitive nano-manipulation and nano-manufacturing applications.}, booktitle={Proceedings of the IEEE Conference on Decision and Control}, author={Dong, J. and Salapaka, S.M. and Ferreira, P.M.}, year={2007}, pages={4495–4500} }
 @inbook{dong_salapaka_ferreira_ieee_2007, title={Robust MIMO control of a parallel kinematics nano-positioner for high resolution high bandwidth tracking and repetitive tasks}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000255181701011&KeyUID=WOS:000255181701011}, booktitle={Proceedings of the 46th Ieee Conference on Decision and Control, Vols 1-14}, author={Dong, Jingyan and Salapaka, Srinivasa M. and Ferreira, Placid M. and IEEE}, year={2007}, pages={1899–1904} }
 @article{meitl_feng_dong_menard_ferreira_huang_rogers_2007, title={Stress focusing for controlled fracture in microelectromechanical systems}, volume={90}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33847216124&partnerID=MN8TOARS}, DOI={10.1063/1.2679072}, abstractNote={This letter describes a strategy for controlling fracture in microelectromechanical systems (MEMSs) based on the control of corner sharpness. Studies of model MEMS structures with round (radius of approximately microns), intermediate, and sharp (<10nm) corners demonstrate the effects of corner sharpness on the concentration of applied stress. Finite-element analysis reveals that stress distributions intensify and localize as sharpness increases, and transfer printing experiments demonstrate the influence of stress concentration on breakability.}, number={8}, journal={Applied Physics Letters}, author={Meitl, Matthew A. and Feng, Xue and Dong, Jingyan and Menard, Etienne and Ferreira, Placid M. and Huang, Yonggang and Rogers, John A.}, year={2007} }
 @article{dong_stori_2006, title={A generalized time-optimal bidirectional scan algorithm for constrained feed-rate optimization}, volume={128}, url={http://dx.doi.org/10.1115/1.2194078}, DOI={10.1115/1.2194078}, abstractNote={The problem of generating an optimal feed-rate trajectory has received a significant amount of attention in both the robotics and machining literature. The typical objective is to generate a minimum-time trajectory subject to constraints such as system limitations on actuator torques and accelerations. However, developing a computationally efficient solution to this problem while simultaneously guaranteeing optimality has proven challenging. The common constructive methods and optimal control approaches are computationally intensive. Heuristic methods have been proposed that reduce the computational burden but produce only near-optimal solutions with no guarantees. A two-pass feedrate optimization algorithm has been proposed previously in the literature by multiple researchers. However, no proof of optimality of the resulting solution has been provided. In this paper, the two-pass feed-rate optimization algorithm is generalized and a proof of global optimality is provided. The generalized algorithm maintains computational efficiency, and supports the incorporation of a variety of state-dependent constraints. By carefully arranging the local search steps, a globally optimal solution is achieved. Singularities, or critical points on the trajectory, which are difficult to deal with in optimal control approaches, are treated in a natural way in the generalized algorithm. A detailed proof is provided to show that the algorithm does generate a globally optimal solution under various types of constraints. Several examples are presented to illustrate the application of the algorithm.}, number={2}, journal={Journal of Dynamic Systems, Measurement, and Control}, publisher={ASME International}, author={Dong, J and Stori, JA}, year={2006}, pages={379–390} }
 @inproceedings{dong_stori_2004, title={A generalized time-optimal Bi-directional scan algorithm for constrained feedrate optimization}, volume={15}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-23244457491&partnerID=MN8TOARS}, DOI={10.1115/IMECE2004-61365}, abstractNote={The problem of generating an optimal feedrate trajectory has received a significant amount of attention in both the robotics and machining literature. The typical objective is to generate a minimum-time trajectory subject to constraints such as system limitations on actuator torques and accelerations. However, developing a computationally efficient solution to this problem while simultaneously guaranteeing optimality has proven challenging. The common constructive methods and optimal control approaches are computationally intensive. Heuristic methods have been proposed that reduce the computational burden but produce only near-optimal solutions with no guarantees. A two-pass feedrate optimization algorithm has been proposed previously in the literature by multiple researchers. However, no proof of optimality of the resulting solution has been provided. In this paper, the two-pass feedrate optimization algorithm is extended and generalized. The generalized algorithm maintains computationally efficiency, and supports the incorporation of a variety of state dependent constraints. By carefully arranging the local search steps, a globally optimal solution is achieved. Singularities, or critical points on the trajectory, which are difficult to deal with in optimal control approaches, are treated in a natural way in the generalized algorithm. A detailed proof is provided to show that the algorithm does generate a globally optimal solution under various types of constraints.}, booktitle={American Society of Mechanical Engineers, Manufacturing Engineering Division, MED}, author={Dong, J. and Stori, J.A.}, year={2004}, pages={725–739} }
 @article{dong_yuan_stori_ferreira_2004, title={Development of a high-speed 3-axis machine tool using a novel parallel-kinematics X-Y table}, volume={44}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-3042775775&partnerID=MN8TOARS}, DOI={10.1016/j.ijmachtools.2004.04.009}, abstractNote={In this paper we discuss the development and performance evaluation of a high-speed, 3-axis milling machine using a novel parallel kinematics x-y table. The x-y table is based on a an inversion of the Oldham coupling. The advantages of this kinematic configuration include low inertia, uniform kinematic conditioning, and dynamically matched axes. The design of the x-y table makes this system particularly well suited for high-speed contouring in the x-y plane. The kinematics, dynamics, and mechanical design of the system are described. Linear and circular contouring experiments are conducted to evaluate the system capabilities. The stiffness of both the mechanism as well as the direct drive actuation system are measured and reported. The experimental results demonstrate that the proposed mechanism offers an attractive combination of performance characteristics for high-speed contouring and high-speed machining.}, number={12-13}, journal={International Journal of Machine Tools & Manufacture}, author={Dong, J and Yuan, C and Stori, JA and Ferreira, PM}, year={2004}, pages={1355–1371} }
 @inproceedings{dong_stori_2003, title={Optimal feed-rate scheduling for high-speed contouring}, volume={14}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-1842590525&partnerID=MN8TOARS}, DOI={10.1115/IMECE2003-42357}, abstractNote={The majority of efforts to improve the contouring performance of high-speed CNC systems have focused on advances in feed-back control techniques at the single-axis servo level. Regardless of the dynamic characteristics of an individual system, performance will inevitably suffer when that system is called upon to execute a complex trajectory beyond the range of its capabilities. The intent of the present work is to provide a framework for abstracting the capabilities of an individual multi-axis contouring system, and a methodology for using these capabilities to generate a time-optimal feed-rate profile for a particular trajectory on a particular machine. Several constraints are developed to drive the feed-rate optimization algorithm. First, simplified dynamic models of the individual axes are used to generate performance envelopes that couple the velocity vs. acceleration capabilities of each axis. Second, bandwidth limitations are introduced to mitigate frequency related problems encountered when traversing sharp geometric features at high velocity. Finally, a dynamic model for the instantaneous following error is used to estimate the contour-error as function of the instantaneous velocity and acceleration state. We present a computationally efficient algorithm for generating a minimum-time feed-rate profile subject to the above constraints, and demonstrate that significant improvements in contouring accuracy can be realized through such an approach. Experimental results are presented on a conventional two-axis X-Y stage executing a complex trajectory.}, booktitle={Manufacturing}, publisher={ASMEDC}, author={Dong, J. and Stori, J.A.}, year={2003}, pages={497–513} }