@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{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} }
 @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.Copyright © 2015 by ASME}, 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} }
 @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} }
 @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={Both intrinsic material properties and topographical features are critical in influencing cell‐biomaterial interactions. We present a systematic investigation of regulating mouse pre‐osteoblastic MC3T3‐E1 cell behavior on biodegradable polymer substrates with distinct mechanical properties and concentric microgrooves. The precursors for fabricating substrates used here were two poly(ϵ‐caprolactone) triacrylates (PCLTAs) synthesized from poly(ϵ‐caprolactone) triols with molecular weights of ∼7000 and ∼10000 g mol−1. These two PCLTAs were photo‐crosslinked into PCL networks with distinct thermal, rheological, and mechanical properties at physiological temperature because of their different crystallinities and melting temperatures. Microgrooved substrates with four groove widths of 7.5, 16.1, 44.2, and 91.2 μm and three groove depths of 0.2, 1, and 10 μm were prepared through replica molding, i.e., photo‐crosslinking PCLTA on micro‐fabricated silicon wafers with pre‐designed concentric groove patterns. MC3T3‐E1 cell attachment and proliferation could be better supported by the stiffer substrates while not significantly influenced by the microgrooves. Microgroove dimensions could regulate MC3T3‐E1 cell alignment, nuclear shape and distribution, mineralization, and gene expression. Among the microgrooves with a fixed depth of 10 μm, the smallest width of 7.5 μm could align and elongate the cytoskeleton and nuclei most efficiently. Strikingly, higher mineral deposition and upregulation of osteocalcin gene expression were found in the narrower microgrooves when the groove depth was 10 μm.}, 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{zhang_dong_2012, title={Design, fabrication, and testing of a SOI-MEMS-based active microprobe for potential cellular force sensing applications}, journal={Advances in Mechanical Engineering}, author={Zhang, L. and Dong, J.}, year={2012}, pages={324–349} }
 @article{zhang_dong_2012, title={High-rate tunable ultrasonic force regulated nanomachining lithography with an atomic force microscope}, volume={23}, number={8}, journal={Nanotechnology}, author={Zhang, L. and Dong, J. Y.}, year={2012} }
 @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} }