@article{kwon_huang_zhang_yuan_jiang_2014, title={A new type of microphone using flexoelectric barium strontium titnate}, volume={9062}, ISSN={["1996-756X"]}, DOI={10.1117/12.2045072}, abstractNote={A flexoelectric bridge-structured microphone using bulk barium strontium titanate (Ba0.65Sr0.35TiO3 or BST) ceramic was investigated in this study. The flexoelectric microphone was installed in an anechoic box and exposed to the sound pressure emitted from a loud speaker. Charge sensitivity of the flexoelectric microphone was measured and calibrated using a reference microphone. The 1.5 mm×768 μm×50 μm micro-machined bridge-structured flexoelectric microphone has a sensitivity of 0.92 pC/Pa, while its resonance frequency was calculated to be 98.67 kHz. The analytical and experimental results show that the flexoelectric microphone has both high sensitivity and broad bandwidth, indicating that flexoelectric microphones are potential candidates for many applications.}, journal={SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS INTEGRATION 2014}, author={Kwon, Seol Ryung and Huang, Wenbin and Zhang, Shujun and Yuan, Fuh-Gwo and Jiang, Xiaoning}, year={2014} }
 @article{huang_kwon_zhang_yuan_jiang_2014, title={A trapezoidal flexoelectric accelerometer}, volume={25}, ISSN={["1530-8138"]}, DOI={10.1177/1045389x13491021}, abstractNote={ In this article a new acceleration sensor using flexoelectric barium strontium titanate cantilever was designed, fabricated, and tested for vibration monitoring. The flexoelectric sensors were configured as a trapezoidal unimorph with a barium strontium titanate layer bonded onto a steel substrate. Seismic mass was attached to the unimorph tip to amplify the transverse flexoelectric response of the barium strontium titanate layer. The theoretical model was developed and validated by vibration tests using the prototyped flexoelectric unimorph. The prototyped accelerometer with thickness of 0.1 mm and length and width in millimeters showed a stable sensitivity of 0.84 pC/g over the frequency range of 100 Hz–1.6 kHz. The aging property of the flexoelectric material was demonstrated to be much better than that of the reported piezoelectric materials right after poling. Scaling effect analysis was also performed for flexoelectric unimorphs. The test results and initial scaling effect analysis indicate that micro/nano flexoelectric sensing holds promise for a broad range of applications. }, number={3}, journal={JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES}, author={Huang, Wenbin and Kwon, Seol-Ryung and Zhang, Shujun and Yuan, Fuh-Gwo and Jiang, Xiaoning}, year={2014}, month={Feb}, pages={271–277} }
 @article{shu_huang_kwon_wang_li_wei_zhang_lanagan_yao_jiang_2014, title={Converse flexoelectric coefficient f(1212) in bulk Ba0.67Sr0.33TiO3}, volume={104}, ISSN={["1077-3118"]}, DOI={10.1063/1.4882060}, abstractNote={The converse flexoelectric effect, referred as the electric field gradient induced strain, widely exists in dielectric materials, but its experimental studies have been reported by few research groups so far. In this Letter, we report our studies on the converse flexoelectric behavior of (Ba0.67Sr0.33)TiO3 ceramics and present the measured value of its flexoelectric coefficient f1212. In the experiments, the electric field gradient was generated by applying an electric field across the two lateral sides of trapezoid (Ba0.67Sr0.33)TiO3 samples. The shear displacement was measured using a laser vibrometer. The converse flexoelectric coefficient f1212 was found to be 124 ± 14 μC/m at room temperature. This result was in good agreement with the theoretical prediction of the flexoelectricity of the (Ba, Sr)TiO3 ceramics.}, number={23}, journal={APPLIED PHYSICS LETTERS}, author={Shu, Longlong and Huang, Wenbin and Kwon, Seol Ryung and Wang, Zhao and Li, Fei and Wei, Xiaoyong and Zhang, Shujun and Lanagan, Michael and Yao, Xi and Jiang, Xiaoning}, year={2014}, month={Jun} }
 @article{huang_shu_kwon_zhang_yuan_jiang_2014, title={Fabrication and measurement of a flexoelectric micro-pyramid composite}, volume={4}, ISSN={["2158-3226"]}, DOI={10.1063/1.4904024}, abstractNote={A fabrication method by combining precision mechanical dicing and wet etching was developed to prepare micro-pyramid structures based on (Ba0.67Sr0.33)TiO3 ceramics. The effective piezoelectric properties of flexoelectric pyramid structures in ten micrometers scale were investigated and measured through converse flexoelectric effect. The scaling effect of the flexoelectric response was demonstrated as the structure size shrinks down. The results do suggest the great potential of flexoelectric micro pyramids as an alternative to lead-free piezoelectric material.}, number={12}, journal={AIP ADVANCES}, author={Huang, Wenbin and Shu, Longlong and Kwon, Seol Ryung and Zhang, Shujun and Yuan, Fuh-Gwo and Jiang, Xiaoning}, year={2014}, month={Dec} }
 @article{kwon_huang_shu_yuan_maria_jiang_2014, title={Flexoelectricity in barium strontium titanate thin film}, volume={105}, ISSN={["1077-3118"]}, DOI={10.1063/1.4898139}, abstractNote={Flexoelectricity, the linear coupling between the strain gradient and the induced electric polarization, has been intensively studied as an alternative to piezoelectricity. Especially, it is of interest to develop flexoelectric devices on micro/nano scales due to the inherent scaling effect of flexoelectric effect. Ba0.7Sr0.3TiO3 thin film with a thickness of 130 nm was fabricated on a silicon wafer using a RF magnetron sputtering process. The flexoelectric coefficients of the prepared thin films were determined experimentally. It was revealed that the thin films possessed a transverse flexoelectric coefficient of 24.5 μC/m at Curie temperature (∼28 °C) and 17.44 μC/m at 41 °C. The measured flexoelectric coefficients are comparable to that of bulk BST ceramics, which are reported to be 10–100 μC/m. This result suggests that the flexoelectric thin film structures can be effectively used for micro/nano-sensing devices.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Kwon, Seol Ryung and Huang, Wenbin and Shu, Longlong and Yuan, Fuh-Gwo and Maria, Jon-Paul and Jiang, Xiaoning}, year={2014}, month={Oct} }
 @article{yan_huang_kwon_yang_jiang_yuan_2013, title={A sensor for the direct measurement of curvature based on flexoelectricity}, volume={22}, ISSN={["1361-665X"]}, DOI={10.1088/0964-1726/22/8/085016}, abstractNote={A direct curvature sensing measurement based on the flexoelectricity of Ba0.64Sr0.36TiO3 (BST) material through electromechanical coupling is proposed and developed in this paper. The curvature sensing was demonstrated in four point bending tests of a beam with bonded BST curvature sensors under different applied loads with low time-harmonic frequencies from 0.5 to 3 Hz. A shear lag concept which describes the efficiency of the loading transfer from the epoxy bonding layer was taken into account in extracting the actual curvature from the sensor measurement. A finite element analysis has been performed to estimate the curvature transfer efficiency and the bonding layer thickness is found to be a critical parameter in determining the curvature transfer. Experimental results showed a good linearity of charge output dependence on curvature inputs in a limited frequency range and showed a curvature sensitivity of 30.78 pC m, in comparison with 32.48 pC m from theoretical predictions. Using the measured curvature, the bending stiffness of the beam was then obtained from the experimentally obtained moment–curvature curve. This work demonstrated that the flexoelectric BST sensor provides a direct curvature measurement instead of using a traditional strain gage sensor through interpolation, and thus offers an important avenue for on-line and in situ structural health monitoring.}, number={8}, journal={SMART MATERIALS AND STRUCTURES}, author={Yan, Xiang and Huang, Wenbin and Kwon, Seol Ryung and Yang, Shaorui and Jiang, Xiaoning and Yuan, Fuh-Gwo}, year={2013}, month={Aug} }
 @article{yan_huang_kwon_yang_jiang_yuan_2013, title={Design of a curvature sensor using a flexoelectric material}, volume={8692}, ISSN={["1996-756X"]}, DOI={10.1117/12.2009941}, abstractNote={A curvature sensor based on flexoelectricity using Ba0.64Sr0.36TiO3 (BST) material is proposed and developed in this paper. The working principle of the sensor is based on the flexoelectricity, exhibiting coupling between mechanical strain gradient and electric polarization. A BST curvature sensor is lab prepared using a conventional solid state processing method. The curvature sensing is demonstrated in four point bending tests of the beam under harmonic loads. BST sensors are attached on both side surfaces of an aluminum beam, located symmetrically with respect to its neutral axis. Analyses have shown that the epoxy bonding layer plays a critical role for curvature transfer. Consequently a shear lag effect is taken into account for extracting actual curvature from the sensor measurement. Experimental results demonstrated good linearity from the charge outputs under the frequencies tests and showed a sensor sensitivity of 30.78pC•m in comparison with 32.48pC•m from theoretical prediction. The BST sensor provides a direct curvature measure instead of using traditional strain gage through interpolation and may offer an optional avenue for on-line and in-situ structural health monitoring.}, journal={SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2013}, author={Yan, X. and Huang, W. B. and Kwon, S. R. and Yang, S. R. and Jiang, X. N. and Yuan, F. G.}, year={2013} }
 @article{kwon_huang_zhang_yuan_jiang_2013, title={Flexoelectric sensing using a multilayered barium strontium titanate structure}, volume={22}, ISSN={["1361-665X"]}, DOI={10.1088/0964-1726/22/11/115017}, abstractNote={The flexoelectric effect has been recently explored for its promise in electromechanical sensing. However, the relatively low flexoelectric coefficients of ferroelectrics inhibit the potential to develop flexoelectric sensing devices. In this paper, a multilayered structure using flexoelectric barium strontium titanate (Ba0.65Sr0.35TiO3 or BST) ceramic was fabricated in an attempt to enhance the effective flexoelectric coefficients using its inherent scale effect, and hence to improve the flexoelectric sensitivity. The performances of piezoelectric and flexoelectric cantilevers with the same dimensions and under the same conditions were compared. Owing to the flexoelectric scaling effect, under the same force input, the BST flexoelectric structure generated a higher charge output than its piezoelectric P(VDF-TrFE) and PMN-30PT counterparts when its thickness was less than 73.1 μm and 1.43 μm, respectively. Also, amplification of the charge output using the multilayered structure was then experimentally verified. The prototyped structure consisted of three layers of 350 μm-thick BST plates with a parallel electric connection. The charge output was approximately 287% of that obtained using a single-layer structure with the same total thickness of the multilayered structure under the same end deflection input, which suggests high sensitivity sensing can be achieved using multilayer flexoelectric structures.}, number={11}, journal={SMART MATERIALS AND STRUCTURES}, author={Kwon, S. R. and Huang, W. B. and Zhang, S. J. and Yuan, F. G. and Jiang, X. N.}, year={2013}, month={Nov} }
 @article{huang_yan_kwon_zhang_yuan_jiang_2012, title={Flexoelectric strain gradient detection using Ba0.64Sr0.36TiO3 for sensing}, volume={101}, ISSN={["0003-6951"]}, DOI={10.1063/1.4772803}, abstractNote={Strain gradient sensing offers an alternative avenue for in-situ monitoring of onset and growth of cracks in structural health monitoring, where the strain gradient is the most sensitive measurand. In this study, flexoelectric strain gradient sensing structures using Ba0.64Sr0.36TiO3 (BST) were attached on the proximity of an open hole in an aluminum plate, to monitor strain gradient variations of the specimen under a uniaxial dynamic load. Charge outputs of the BST micro-bars showed good linearity with the average strain gradients, with a sensitivity of 88 pC m, which is in good agreement with the theoretical estimation by assuming a 30 μm bonding thickness.}, number={25}, journal={APPLIED PHYSICS LETTERS}, author={Huang, Wenbin and Yan, Xiang and Kwon, Seol Ryung and Zhang, Shujun and Yuan, Fuh-Gwo and Jiang, Xiaoning}, year={2012}, month={Dec} }