@misc{kim_kim_jiang_kim_2021, title={Static Force Measurement Using Piezoelectric Sensors}, volume={2021}, ISBN={1687-7268}, DOI={10.1155/2021/6664200}, abstractNote={In force measurement applications, a piezoelectric force sensor is one of the most popular sensors due to its advantages of low cost, linear response, and high sensitivity. Piezoelectric sensors effectively convert dynamic forces to electrical signals by the direct piezoelectric effect, but their use has been limited in measuring static forces due to the easily neutralized surface charge. To overcome this shortcoming, several static (either pure static or quasistatic) force sensing techniques using piezoelectric materials have been developed utilizing several unique parameters rather than just the surface charge produced by an applied force. The parameters for static force measurement include the resonance frequency, electrical impedance, decay time constant, and capacitance. In this review, we discuss the detailed mechanism of these piezoelectric-type, static force sensing methods that use more than the direct piezoelectric effect. We also highlight the challenges and potentials of each method for static force sensing applications.}, journal={JOURNAL OF SENSORS}, author={Kim, Kyungrim and Kim, Jinwook and Jiang, Xiaoning and Kim, Taeyang}, year={2021} }
 @article{kim_kim_kim_jiang_2020, title={A Face-Shear Mode Piezoelectric Array Sensor for Elasticity and Force Measurement}, volume={20}, ISSN={["1424-8220"]}, DOI={10.3390/s20030604}, abstractNote={We present the development of a 6 × 6 piezoelectric array sensor for measuring elasticity and force. The proposed sensor employs an impedance measurement technique, sensing the acoustic load impedance of a target by measuring the electrical impedance shift of face-shear mode PMN–PT (lead magnesium niobate–lead titanate) single crystal elements. Among various modes of PMN–PT single crystals, the face-shear mode was selected due to its especially high sensitivity to acoustic loads. To verify the elasticity sensing performance, gelatin samples with different elastic moduli were prepared and tested. For the force measurement test, different magnitudes of force were loaded to the sensing layer whose acoustic impedance was varied with applied forces. From the experimental results, the fabricated sensor showed an elastic stiffness sensitivity of 23.52 Ohm/MPa with a resolution of 4.25 kPa and contact force sensitivity of 19.27 Ohm/N with a resolution of 5.19 mN. In addition, the mapping experiment of elasticity and force using the sensor array was successfully demonstrated.}, number={3}, journal={SENSORS}, author={Kim, Kyungrim and Kim, Taeyang and Kim, Jinwook and Jiang, Xiaoning}, year={2020}, month={Feb} }
 @article{huang_kim_kim_bakshi_williams_matthieu_loboa_shung_zhou_jiang_2016, title={A Novel Ultrasound Technique for Non-Invasive Assessment of Cell Differentiation}, volume={16}, ISSN={["1558-1748"]}, DOI={10.1109/jsen.2015.2477340}, abstractNote={A novel technique for the characterization of mammalian cells during cell culture was studied using a lead magnesium niobate-lead titanate single crystal piezoelectric resonator. Tests were conducted to observe changes in material properties of human adipose derived stem cells during both proliferation and osteogenic differentiation. The resonator electrical impedance was recorded as a function of the cell acoustic impedance, an indicator of cell viscoelasticity. Observed electrical impedance change (in percentage) from day 1 to day 14 for human adipose derived stem cells undergoing chemical-induced osteogenic differentiation was ~1.7× that observed for proliferating stem cells maintained in complete growth medium.}, number={1}, journal={IEEE SENSORS JOURNAL}, author={Huang, Wenbin and Kim, Jinwook and Kim, Kyngrim and Bakshi, Saurabh and Williams, John and Matthieu, Pattie and Loboa, Elizabeth and Shung, Koping Kirk and Zhou, Qifa and Jiang, Xiaoning}, year={2016}, month={Jan}, pages={61–68} }
 @inproceedings{kim_jiang_2014, title={Acoustic wave microsensor array for tactile sensing}, DOI={10.1115/imece2013-66098}, abstractNote={Tactile perception is a critical requirement for surgery procedures such as minimally invasive surgery (MIS). In this study, an acoustic wave tactile sensor array for force and shear modulus sensing was investigated. This device can sense the magnitude of the applied force change and the tissue’s shear modulus change by means of detecting an electrical impedance change. The 6×6 array with a pitch of 1.3 mm was fabricated using a face-shear mode PMN-PT piezoelectric resonator which is highly sensitive to acoustic impedance load. External forces (0–5 N) were applied to the sensor and the electric impedance shift was measured. The sensitivity was found to be 56.87 Ohm/N. Imaging test results for different force and load stiffnesses were also obtained. The proposed tactile sensing technique is also favorable for a number of other biomedical applications including haptic sensors for the robotic surgery and artificial skin or fingers.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2013, vol 3B}, author={Kim, K. and Jiang, X. N.}, year={2014} }
 @inproceedings{johnson_kim_zhang_jiang_2014, title={Crack propagation testing using a YCOB acoustic emission sensor}, volume={9063}, DOI={10.1117/12.2045091}, abstractNote={Piezoelectric crystals are popular for passive sensors, such as accelerometers and acoustic emission sensors, due to their robustness and high sensitivity. These sensors are widespread in structural health monitoring among civil and industrial structures, but there is little application in high temperature environments (e.g. > 1000°C) due to the few materials that are capable of operating at elevated temperatures. Most piezoelectric materials suffer from a loss of electric properties above temperatures in the 500-700°C range, but rare earth oxyborate crystals, such as Yttrium calcium oxyborate (YCOB), retain their piezoelectric properties above 1000 °C. Our previous research demonstrated that YCOB can be used to detect transient lamb waves via Hsu-Nielsen tests, which replicate acoustic emission waves, up to 1000°C. In this paper, YCOB piezoelectric acoustic emission sensors were tested for their ability to detect crack progression at elevated temperatures. The sensor was fabricated using a YCOB single crystal and Inconel electrodes and wires. The sensor was mounted onto a stainless steel bar substrate, which was machined to include a pre-crack notch. A dynamic load was induced on the bar with a shaker in order to force the crack to advance along the thickness of the substrate. The obtained raw data was processed and analyzed in the frequency domain and compared to the Lamb wave modes that were evaluated in previous Hsu-Nielsen testing for the substrate.}, booktitle={Nondestructive characterization for composite materials, aerospace engineering, civil infrastructure, and homeland security 2014}, author={Johnson, J. A. and Kim, K. and Zhang, S. J. and Jiang, X. N.}, year={2014} }
 @misc{jiang_kim_zhang_johnson_salazar_2014, title={High-Temperature Piezoelectric Sensing}, volume={14}, ISSN={["1424-8220"]}, DOI={10.3390/s140100144}, abstractNote={Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented.}, number={1}, journal={SENSORS}, author={Jiang, Xiaoning and Kim, Kyungrim and Zhang, Shujun and Johnson, Joseph and Salazar, Giovanni}, year={2014}, month={Jan}, pages={144–169} }
 @article{johnson_kim_zhang_wu_jiang_2014, title={High-temperature acoustic emission sensing tests using a yttrium calcium oxyborate sensor}, volume={61}, DOI={10.1109/tuffc.2014.6805694}, abstractNote={Piezoelectric materials have been broadly utilized in acoustic emission sensors, but are often hindered by the loss of piezoelectric properties at temperatures in the 500°C to 700°C range or higher. In this paper, a piezoelectric acoustic emission sensor was designed and fabricated using yttrium calcium oxyborate (YCOB) single crystals, followed by Hsu-Nielsen tests for high-temperature (>700°C) applications. The sensitivity of the YCOB sensor was found to have minimal degradation with increasing temperature up to 1000°C. During Hsu-Nielsen tests with a steel bar, this YCOB acoustic sensor showed the ability to detect zero-order symmetric and antisymmetric modes at 30 and 120 kHz, respectively, as well as distinguish a first-order antisymmetric mode at 240 kHz at elevated temperatures up to 1000°C. The frequency characteristics of the signal were verified using a finite-element model and wavelet transformation analysis.}, number={5}, journal={IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control}, author={Johnson, J. A. and Kim, K. and Zhang, S. J. and Wu, D. and Jiang, X. N.}, year={2014}, pages={805–814} }
 @article{johnson_kim_zhang_wu_jiang_2013, title={High-temperature (> 1000 degrees C) acoustic emission sensor}, volume={8694}, ISSN={["1996-756X"]}, DOI={10.1117/12.2009301}, abstractNote={Piezoelectric crystals have shown promising results as acoustic emission sensors, but are often hindered by the loss of electric properties above temperatures in the 500-700°C range. Yttrium calcium oxyborate, (YCOB), however, is a promising high temperature piezoelectric material due to its high resistivity at high temperatures and its relatively stable electromechanical and piezoelectric properties across a broad temperature range. In this paper, a piezoelectric acoustic emission sensor was designed, fabricated, and tested for use in high temperature applications using a YCOB single crystal. An acoustic wave was generated by a Hsu-Nielsen source on a stainless steel bar, which then propagated through the substrate into a furnace where the YCOB acoustic emission sensor is located. Charge output of the YCOB sensor was collected using a lock-in charge amplifier. The sensitivity of the YCOB sensor was found to have small to no degradation with increasing temperature up to 1000 °C. This oxyborate crystal showed the ability to detect zero order symmetric and antisymmetric modes, as well as distinguishable first order antisymmetric modes at elevated temperatures up to 1000 °C.}, journal={NONDESTRUCTIVE CHARACTERIZATION FOR COMPOSITE MATERIALS, AEROSPACE ENGINEERING, CIVIL INFRASTRUCTURE, AND HOMELAND SECURITY 2013}, author={Johnson, Joseph A. and Kim, Kyungrim and Zhang, Shujun and Wu, Di and Jiang, Xiaoning}, year={2013} }
 @article{kim_jiang_2013, title={Tissue characterization using an acoustic wave tactile sensor array}, volume={8695}, ISSN={["1996-756X"]}, DOI={10.1117/12.2009518}, abstractNote={Tactile perception of different types of tissue is important in order for surgeons to perform procedures correctly and safely. This is especially true in minimally invasive surgery (MIS) where the surgeon must be able to locate the target tissue without a direct line of sight or direct finger touch. In this study, tissue characterization using an acoustic wave tactile sensor array was investigated. This type of tactile sensor array can detect the acoustic impedance change of target materials. Abnormal tissues can have different Young’s moduli and shear moduli caused by composition change compared to those of healthy tissues. This also leads to a difference in acoustic impedance which can be detected using our sensor array. The array was fabricated using a face-shear mode PMN-PT piezoelectric resonator which is highly sensitive to acoustic impedance load. Gelatin and water mixtures with weight concentration of 5 wt % - 30 wt % were prepared as tissue phantoms. The shear modulus of each phantom was measured using bulk face-shear mode crystal resonators, and it was found that shear modulus change from 120 kPa to 430 kPa resulted on 30 % electrical impedance shift from the resonator. Imaging display of elastic properties of prepared phantoms was also tested using the fabricated sensor array. The proposed tissue characterization technique is promising for the development of effective surgical procedures in minimally invasive surgery.}, journal={HEALTH MONITORING OF STRUCTURAL AND BIOLOGICAL SYSTEMS 2013}, author={Kim, Kyungrim and Jiang, Xiaoning}, year={2013} }
 @article{kim_zhang_salazar_jiang_2012, title={Design, fabrication and characterization of high temperature piezoelectric vibration sensor using YCOB crystals}, volume={178}, ISSN={["0924-4247"]}, DOI={10.1016/j.sna.2012.02.003}, abstractNote={A shear-mode piezoelectric accelerometer using YCa4O(BO3)3 single crystals (YCOB) was designed, fabricated and successfully tested for high temperature vibration sensing applications. Dynamic modeling of the accelerometer was presented first, followed by YCOB single crystal sample preparation, sensor assembly and experimental setup establishment. The prototyped accelerometer was tested at temperatures ranging from room temperature to 1000 °C and at frequencies ranging from 50 Hz to 350 Hz. The sensitivity of the prototype was found to be 5.9 ± 0.06 pC/g throughout the tested frequency, temperature and acceleration ranges. In addition, YCOB piezoelectric accelerometers retained the same sensitivity at 1000 °C for a dwell time of 9 h, exhibiting a high stability and reliability.}, journal={SENSORS AND ACTUATORS A-PHYSICAL}, author={Kim, Kyungrim and Zhang, Shujun and Salazar, Giovanni and Jiang, Xiaoning}, year={2012}, month={May}, pages={40–48} }
 @article{kim_zhang_tian_han_jiang_2012, title={Face-shear Mode Ultrasonic Tactile Sensor Array}, ISBN={["978-1-4673-4561-3"]}, ISSN={["1948-5719"]}, DOI={10.1109/ultsym.2012.0265}, abstractNote={Ultrasonic sensors using piezoelectric resonators are widely used for the chemical and biomedical applications because of their high sensitivity to applied loads, simple structures, and relatively low cost. In this study, we investigated an ultrasonic tactile sensing array using face-shear mode PMN-PT single crystal resonators, based on the sensing mechanism that electric impedance of a piezoelectric resonator is dependent on its surface acoustic load. An 8 × 8 sensing array was designed, fabricated and characterized. The electrical impedance changes induced by the applied surface loads including acoustic loads and surface forces were measured, and then, the contact shape of applied object was mapped by recording electric impedances of 64 elements.}, journal={2012 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS)}, author={Kim, Kyungrim and Zhang, Shujun and Tian, Jian and Han, Pengdi and Jiang, Xiaoning}, year={2012}, pages={1059–1062} }
 @inproceedings{huang_kim_zhang_yuan_jiang_2012, title={Flexoelectric materials and structures for M/NEMS}, DOI={10.1115/imece2011-64520}, abstractNote={Recent research progress on flexoelectricity suggests that dramatic enhancement of effective piezoelectric properties desirable for advanced M/NEMS, in principle, is attainable through flexoelectric (FE) effect and scale effect. In this paper, the transverse flexoelectric coefficient μ12 of barium strontium titanate (BST) microcantilevers with thicknesses ranging from 1.4 mm down to 30 μm was measured at room temperature. It was found that μ12 remains to be constant (8.5 μC/m) for all fabricated microcantilevers. Effective piezoelectric coefficients of these microcantilevers were also calculated, indicating that significantly increased effective piezoelectric coefficients can be obtained from microcantilevers with thickness of microns and nanometers, which is promising for micro/nano electromechanical systems (M/NEMS).}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2011, vol 11}, author={Huang, W. B. and Kim, K. and Zhang, S. J. and Yuan, F. G. and Jiang, X. N.}, year={2012}, pages={761–766} }
 @article{kim_zhang_jiang_2012, title={Surface Acoustic Load Sensing Using a Face-Shear PIN-PMN-PT Single-Crystal Resonator}, volume={59}, ISSN={["1525-8955"]}, DOI={10.1109/tuffc.2012.2488}, abstractNote={Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) resonators for surface acoustic load sensing are presented in this paper. Different acoustic loads are applied to thickness mode, thickness-shear mode, and face-shear mode resonators, and the electrical impedances at resonance and anti-resonance frequencies are recorded. More than one order of magnitude higher sensitivity (ratio of electrical impedance change to surface acoustic impedance change) at the resonance is achieved for the face-shear-mode resonator compared with other resonators with the same dimensions. The Krimholtz, Leedom, and Matthaei (KLM) model is used to verify the surface acoustic loading effect on the electrical impedance spectrum of face-shear PIN-PMN-PT single-crystal resonators. The demonstrated high sensitivity of face-shear mode resonators to surface loads is promising for a broad range of applications, including artificial skin, biological and chemical sensors, touch screens, and other touch-based sensors.}, number={11}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Kim, Kyungrim and Zhang, Shujun and Jiang, Xiaoning}, year={2012}, month={Nov}, pages={2548–2554} }
 @article{kim_jiang_zhang_2011, title={A High Temperature Piezoelectric Sensor for Structure Health Monitoring}, volume={7983}, ISSN={["1996-756X"]}, DOI={10.1117/12.880163}, abstractNote={High temperature sensors play a significant role in aerospace, automotive and energy industries. In this paper, a shearmode piezoelectric accelerometer using YCa4O(BO3)3 single crystals (YCOB) was designed and fabricated for high temperature sensing applications. The prototype sensor was tested at the temperature ranging from room temperature to 1000°C. The sensitivity of the sensor was found to be 1.9±04 pC/g throughout the tested frequency and temperature range. Moreover, YCOB piezoelectric accelerometers remained stable performance at 1000°C for a dwell time of three hours.}, journal={NONDESTRUCTIVE CHARACTERIZATION FOR COMPOSITE MATERIALS, AEROSPACE ENGINEERING, CIVIL INFRASTRUCTURE, AND HOMELAND SECURITY 2011}, author={Kim, Kyungrim and Jiang, Xiaoning and Zhang, Shujun}, year={2011} }
 @article{huang_kim_zhang_yuan_jiang_2011, title={Scaling effect of flexoelectric (Ba,Sr)TiO3 microcantilevers}, volume={5}, ISSN={["1862-6254"]}, DOI={10.1002/pssr.201105326}, abstractNote={Abstract}, number={9}, journal={PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS}, author={Huang, Wenbin and Kim, Kyungrim and Zhang, Shujun and Yuan, Fuh-Gwo and Jiang, Xiaoning}, year={2011}, month={Sep}, pages={350–352} }
 @article{kim_zhang_huang_yu_jiang_2011, title={YCa4O(BO3)(3) (YCOB) high temperature vibration sensor}, volume={109}, ISSN={["1089-7550"]}, DOI={10.1063/1.3598115}, abstractNote={A shear-mode piezoelectric accelerometer using YCa4O(BO3)3 (YCOB) single crystal was designed, fabricated and successfully tested for high temperature vibration sensing applications. The prototyped sensor was tested at temperatures ranging from room temperature to 1000 °C and at frequencies ranging from 80 Hz to 1 kHz. The sensitivity of the sensor was found to be 5.7 pC/g throughout the tested frequency and temperature range. In addition, YCOB piezoelectric accelerometers remained the same sensitivity at 1000 °C for a dwell time of four hours, exhibiting high stability and reliability.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Kim, Kyungrim and Zhang, Shujun and Huang, Wenbin and Yu, Fapeng and Jiang, Xiaoning}, year={2011}, month={Jun} }
 @misc{jiang_kim_kim, title={Relaxor-PT single crystal piezoelectric sensors}, volume={4}, number={3}, journal={Crystals}, author={Jiang, X. N. and Kim, J. and Kim, K.}, pages={351–376} }