Piezoelectric resonators are widely used in applications

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1 548 IEEE Transations on Ultrasonis, Ferroeletris, and Frequeny Control, vol. 59, no., November 0 Surfae Aousti Load Sensing Using a Fae-Shear PIN PMN PT Single-Crystal Resonator Kyungrim Kim, Shujun hang, and Xiaoning Jiang Abstrat Pb(In 0.5 Nb 0.5 )O 3 Pb(Mg /3 Nb /3 )O 3 PbTiO 3 (PIN PMN PT) resonators for surfae aousti load sensing are presented in this paper. Different aousti loads are applied to thikness mode, thikness-shear mode, and fae-shear mode resonators, and the eletrial impedanes at resonane and anti-resonane frequenies are reorded. More than one order of magnitude higher sensitivity (ratio of eletrial impedane hange to surfae aousti impedane hange) at the resonane is ahieved for the fae-shear-mode resonator ompared with other resonators with the same dimensions. The Krimholtz, Leedom, and Matthaei (KLM) model is used to verify the surfae aousti loading effet on the eletrial impedane spetrum of fae-shear PIN PMN PT single-rystal resonators. The demonstrated high sensitivity of fae-shear mode resonators to surfae loads is promising for a broad range of appliations, inluding artifiial skin, biologial and hemial sensors, touh sreens, and other touh-based sensors. Manusript reeived Marh 5, 0; aepted August 8, 0. The work is partially supported by the North Carolina State Career Development Fund provided to X. Jiang. K. Kim and X. Jiang are with the Department of Mehanial and Aerospae Engineering, North Carolina State University, Raleigh, NC ( xjiang5@nsu.edu). S. hang is with Materials Researh Institute, The Pennsylvania State University, University Park, PA. DOI I. Introdution Piezoeletri resonators are widely used in appliations in the hemial, bio-medial, semiondutor, and information industries beause of their merits of simple struture and low ost. For example, mirobalanes whih are made of quartz or other piezoeletri material an be used for sensing the degradation of fuel ells by measuring the orrosion on the surfae area of eletrodes []. They also have been used as highly sensitive humidity sensors beause the mirobalanes are very stable devies, and thus, an detet small mass hanges (less than a nanogram) of vapor deposition []. In the medial field, piezoeletri tatile sensors have been developed for measuring the elasti stiffness of tissues [3] [6], for the endosopi sensor in minimally invasive surgery (MIS) [7], [8], for the smart skin used in diagnosing breast tumors or prostate gland disease [9], and also for sensing the intraoular pressure (IOP) in the human eye [0]. Information-industry appliations inlude touh input devies, fingerprint identifiation, and virtual reality video game devies []. Typially, these types of sensors use diret piezoeletri effet or measure hanges in the resonant frequeny of osillation aused by interation between piezoeletri resonator arrays and target materials. The hange in the resonant frequeny is diretly proportional to the applied fore by the Sauerbrey equation []. Thus, the loal distribution of the applied mehanial stress an be deteted by measuring the fundamental frequeny shift of the resonator array. However, to obtain the tatile information from the objet, the time duration of applied stress must exeed the required time for array sanning and data proessing. In this ase, the parallel sanning proess an be used to speed up the sanning of the sensor array [3]. A relatively new tatile sensing tehnique, whih uses the relationship between eletrial impedane of the piezoeletri resonator and aousti load impedane of the front load, has been developed for the fingerprinting appliation [4], [5]. The sensing omponent was made of a piezoeletri omposite [lead zironate titanate (PT)/epoxy 3 omposite] with died eletrodes forming a -D array. When an objet is applied to the front surfae of sensor, the eletrial impedane of piezoeletri elements at a partiular frequeny is hanged. This hange is related to the aousti impedane of applied objets. As a result, the distribution of aousti load impedane of the objet an be mapped by measuring the eletrial impedane of eah element of the array in a rapid fashion. This devie an be highly sensitive as a biometri sensor ompared with apaitive and thermal tatile sensors beause the ontrast ratio of aousti impedane between air and tissue is 4000:, whereas that of thermal ondutivity is about 8: and dieletri permittivity is 3: [6]. For these reasons, this aousti impedane sensing is promising for appliations in biomedial industry (artifiial skin sensor) and servie robotis (touh sreen and fingerprint reader). The PT eramis are ommonly used piezoeletri materials for the aforementioned sensors beause of their high dieletri onstants, large eletromehanial oupling fators, and ease of manufaturing [7]. Lead magnesium niobate lead titanate (PMN PT) single rystals have also been investigated as promising andidates with advaned properties ompared with PT [8], [9]. For example, the elasti ompliane of PMN PT is about 6 times higher than that of PT 5H. A high elasti ompliane leads to redued element and devie size for a given resonane frequeny. The piezoeletri oeffiient of PMN-PT is 3 to 5 times higher than that of PT 5H, whih determines the performane of the piezoeletri devie. In addition, PMN PT has a higher eletromehanial oupling fator (longitudinal mode, k 33 ): greater than 0.90 ompared /$ IEEE

2 kim et al.: surfae aousti load sensing using a fae-shear resonator 549 TABLE I. Measured Properties of the Crystal. f r f a E s 66 d 36 N 36 (khz) (khz) ε33 / ε0 (m /N) k 36 (pc/n) (Hz m) Values with 0.75 of PT 5H [0], []. A muh broader operating bandwidth an be ahieved with a large oupling fator [8], []. For these reasons, PMN-PT rystals have been used in various devies suh as sensors, atuators, and other eletromehanial devies in advaned medial appliations [8]. However, the low oerive field (.5 kv/ m) of binary PMN-PT rystal an limit its appliation, whih requires a high exitation signal [8], [3]. Furthermore, the low depoling temperature (T R/T = 75 C to 95 C) an be a ause for redued performane of the devies [4]. Reently developed ternary PIN PMN PT rystals retain similar eletromehanial ouplings (k 33 > 0.9) and piezoeletri oeffiients (d 33 > 500 pc/n) ompared with the binary PMN PT, but have signifiantly improved oerive field (5 kv/m), and T R/T (7 C) [8], [5], [6]. In the ase of the thikness-shear mode, the high shear piezoeletri oeffiients (d 5 ) and eletromehanial oupling fators (k 5 ) for different domain onfigurations were also observed to be >000 pc/n and >0.85, respetively [7]. More reently, the fae-shear mode PIN PMN PT rystals have been given attention beause of their ultralow frequeny onstant (500 Hz m) and high piezoeletri oeffiient (000 to 500 pc/n) [8]. The low frequeny onstant allows the piezoeletri devie to be small for ultra-low-frequeny appliations suh as sonar transduers. More importantly, unlike thikness-shear-mode rystals, the fae-shear-mode rystals an be easily repolarized beause the poling eletrode is the same as the ative eletrode. Moreover, the fae-shear-mode PIN PMN PT rystals have signifiantly higher mehanial quality fator Q m (50 to 80) than that of thikness-shear rystal (0 to 30) [8], [8], whih is promising in resonator appliations. In this paper, the fae-shear-mode PIN PMN PT single-rystal resonators were first fabriated and haraterized by measuring properties suh as shear piezoeletri oeffiients (d 36 ), eletromehanial oupling fators (k 36 ), elasti ompliane (s 66 ), and frequeny onstant (N 36 ) using the resonane method. Different aousti loads were then applied to the thikness-mode, thikness-shear-mode, and fae-shear-mode rystal resonators to ompare the sensitivity to eletrial impedane hange indued by the applied aousti loads. The experimental results were verified by a Krimholtz, Leedom, and Matthaei (KLM) model simulation. II. Fae-Shear PIN PMN PT Single Crystal In this study, [0]-ut rhombohedral PIN PMN PT single rystals were used, whih have the marosopi symmetry mm. The rystals were oriented using a realtime bak-refletion Laue system. Fae-shear-mode samples were prepared by rotating a 45 angle about the - axis [0] diretion, with dimensions of 0 0 mm. Eletrodes were deposited on the (0) surfae of eah rystal. The samples were poled along the rystallographi [0] diretion. The apaitane of the fae-shear PIN PMN PT single rystal was measured at khz and the free dieletri onstant ( ε33 T / ε0) was found to be 940. The resonant frequeny (f r ) and anti-resonant frequeny (f a ) were also measured using an impedane analyzer (HP494A, Agilent Tehnologies In., Santa Clara, CA) and found to be 68.5 and khz, respetively. Properties of the rystals an be alulated aording to the IRE standards [9], [30]. Table I shows the measured and alulated properties of the fae-shear PIN PMN PT single rystal. Compared to the published data [30], the overall properties showed slightly lower values. This might be attributed to the fat that the sample properties are related to the rystal omposition of the sample used. Fig.. The shemati of the single-surfae loaded piezoeletri faeshear-mode resonator. Fig.. The equivalent iruit for a single-side loaded piezoeletri rystal using the Krimholtz, Leedom, and Matthaei (KLM) model.

3 550 IEEE Transations on Ultrasonis, Ferroeletris, and Frequeny Control, vol. 59, no., November 0 Fig. 3. Eletrial impedane spetrum of the fae-shear-mode resonator with the front load. III. Surfae Load Sensing Model Fig. indiates the shemati of the single surfae loaded piezoeletri fae-shear mode resonator. The surfae load an be any material, inluding air, water, metal, and rubber. AB represents the eletrial impedane of piezoeletri resonator. The aousti impedane hanges from the surfae load of the resonator an be sensed by measuring the hange of the eletrial impedane ( AB ). The KLM model [3] was used to verify the effet of the aousti loading on the fae-shear-mode PIN PMN PT rystal. Fig. represents the equivalent iruit of the KLM model [3]. The aousti impedane at the port CD is a ombination of the right aousti impedane ( r ) and the left aousti impedane ( l ). r and l are given by [33] EF + tanh( γ l / ) r = + EFtanh( γ l / ) GH + tanh( γ l / ) l = + tanh( γ l / ), GH where is the harateristi impedane [aousti shear impedane, (ρ 66 ) /, where 66 is the shear elasti modulus of the rystal], γ is the omplex wave propagation fator [= jω(ρ / 66 ) / ], and l is the length of the resonator rystal. EF and GH represent the aousti load impedane at the ports EF and GH. The total aousti impedane ( CD ) at position CD is the parallel arrangement of r and l. Thus, CD is CD = r l () () +. (3) The eletrial impedane ( AB ) at port AB an be alulated from Fig. 4. Shear aousti impedane and sound veloity of rubber and alumina mixtures. where and AB = + jx + jωc N 0 CD, (4) k 36 jx = sin α, j ω C0 α (5) 4k 36 α = sin, N ω C α (6) 0 α = ωl ρ. (7) v N, X, C 0, and α represent the turn ratio of the transformer, additional reatane of the equivalent iruit, lamped apaitane of the rystal, and the omplex aousti wave phase shift (= πω/ω 0 ), respetively. ρ is the rystal density and v is the speed of shear sound waves in the rystal. Beause the aousti load ( L ) was applied to one side of the rystal, we an assume that the load at the port GH ( GH ) is zero and at the port EF ( EF ) is L, as shown in Fig.. Finally, the eletrial impedane ( AB ) an be obtained for a single-side loaded piezoeletri rystal using () (7) [3] [36]: AB L k j = 36 α tan j C. (8) ω L 0 α j otα Fig. 3 shows the alulated eletrial impedane spetrum of the fae-shear-mode resonator with the front load using l (mm) TABLE II. Input Parameters for KLM Model. v (m/s) ρ (kg/m 3 ) C 0 (nf) (Mrayl) L,air (rayl) L,water (Mrayl) Values

4 kim et al.: surfae aousti load sensing using a fae-shear resonator 55 TABLE III. Speifiations of Single Crystal Resonators. Mode Crystal Dimensions (mm) Thikness (d 33 ) PMN PT Thikness-shear (d 5 ) PMN PT 0 0 Fae-shear (d 36 ) PIN PMN PT 0 0 the KLM model. At the resonant frequeny and anti-resonant frequeny, the eletrial impedane is hanged with different loads suh as air and water. Input parameters used for the modeling of fae-shear mode resonator are shown in Table II. IV. Experimental Results and Disussion For the aousti impedane sensing test, we used rystal resonators operating in three different modes, inluding thikness mode (or d 33 mode), thikness-shear mode (or d 5 mode) and fae-shear mode (or d 36 mode). The dimensions of all resonators are listed in Table III. Cr/ Au eletrodes were sputtered onto 0 0 mm surfaes. For eletrial onnetion to the impedane analyzer, 0- m o-axial wires (AWG 5, Hitahi Cable Ltd., Tokyo, Japan) were bonded to both eletrodes on the resonators using silver epoxy. The silion rubber (Sylgard 70, Dow Corning Corp., Midland, MI) was used as the arrier material for ontrol of aousti load variations. Aluminum oxide (Al O 3 ) powders in different perentages by weight were mixed with the liquid silion rubber. The amount of mixed alumina oxide was 0%, 0%, 30%, and 40% of the silion rubber by weight. The liquid silion rubber with or without Al O 3 powders was applied to one side of eah rystal and ured for 4 h in a vauum desiator. The thikness of rubber or rubber/aluminum oxide omposite was about mm. The longitudinal sound veloities of rubber mixtures were measured using the pulse eho method and then the shear sound veloities were alulated. For pulse eho tests, the rubber mixture sample was immersed in a water tank and a 30-MHz transduer was loated 5 mm away from the top surfae of the rubber sample in water. This Fig. 6. Relative eletrial impedane of eah mode at the resonant frequeny. transduer transmitted ultrasound waves into the water and reeived ultrasound eho signals from the top and bottom surfaes of the rubber targets. The time of flight of pulse-eho waves between the top and bottom surfaes of rubber samples was measured [37]. The shear veloity was alulated from the longitudinal veloity using the Poisson s ratio of rubbers (υ = 0.5). The dimension and the weight of the rubber mixture were measured using a digital aliper and a miro balane to determine the density of the rubber mixtures. The shear aousti impedane ( s ) of rubber mixtures was alulated using s = ρ v, (9) where ρ and ν s are the density and the shear sound veloity of the rubber mixtures, respetively. Fig. 4 shows the shear aousti impedane and shear sound veloity of the s Fig. 5. Measured fae-shear-mode resonator behavior with different aousti load impedanes. Fig. 7. Relative eletrial impedane of eah mode at the anti-resonant frequeny.

5 55 IEEE Transations on Ultrasonis, Ferroeletris, and Frequeny Control, vol. 59, no., November 0 Fig. 8. Calulated sensitivity of fae-shear, thikness-shear, and thikness-mode resonators at the resonant frequeny under different surfae loadings ( to 0 Mrayl). Fig. 9. Eletrial impedane of fae-shear-mode resonator with different thikness of rubber layers at the resonant and anti-resonant frequenies. rubber mixtures. The aousti impedane and veloity of the rubber mixtures inreased with the omposition ratio of aluminum oxide powders. The eletrial impedane spetrum of eah resonator was measured using an impedane analyzer (HP494A). Fig. 5 shows the measured eletrial impedane of fae-shear-mode rystal with different aousti loads for the frequeny range from 30 to 0 khz. The insets show lose-ups of the impedane hanging with the appliation of different aousti loads. The eletrial impedane inreased at the resonant frequeny, whereas it dereased at the anti-resonant frequeny, as the aousti load impedane inreased. To ompare the performane of resonators operating in different modes, the eletrial impedane of eah resonator was normalized by the referene impedane (pure rubber loaded resonator). Figs. 6 and 7 present the relative eletrial impedane for eah vibration mode at the resonane and anti-resonane, respetively. In the ase of thikness-shear mode, it was hard to find the relationship between the surfae load and the eletrial impedane beause the hange in eletrial impedane was too small and the resonane peak was not lear. The sensitivity (S ) of eletrial impedane to applied surfae loads an be alulated by using S z = d d AB L, (0) where d AB is the eletrial transmitting impedane and d L is the aousti load impedane. The sensitivity of fae-shear mode, thikness-shear mode, and thikness mode were ompared, as shown in Table IV. At the resonane, the sensitivity of fae-shear mode was about 0 times higher than that of thikness-shear mode and 85 times higher than that of thikness mode. Similarly, at the anti-resonane, fae-shear mode showed 95 times and 400 times higher sensitivity than thikness-shear mode and thikness mode, respetively. As a result, the fae-shearmode resonator was found to be muh more sensitive to the surfae aousti loads than its thikness-shear and thikness-mode ounterparts at both resonane and antiresonane. The KLM modeling results for sensitivity of eah resonator under different surfae loadings are shown in Fig. 8. The alulated sensitivity of the fae-shear mode at the resonant frequeny was 63 Ω/Mrayl, whih was 55 times higher than other modes. The higher mehanial quality fator than other modes, whih determines the quality of resonane and the sensitivity to the load, an be the main reason for high sensitivity. These measured sensitivities were slightly lower than the alulated sensitivity values. This was beause the wires onneted to the resonator ould at as an additional resistane and the silver epoxy used for the wire bonding on the resonator surfae ould be onsidered as an additional surfae load. This unique property of fae-shear-mode resonator an be a merit for a broad range of appliations suh as artifiial skins, biologial and hemial sensors, touh sreens, and other tatile-based sensors whih require high sensitivity to the surfae load. Fig. 9 shows the impedane of the fae-shear resonator with different thikness of rubber layers ( to 4 mm) at the resonane and anti-resonane. The impedane hanges were found to be less than 5%. Beause these hanges were very small, we assumed that the effet from thikness of rubber was not signifiant in ases in whih the front load thikness is > mm. Fig. 0 shows the lateral size effet of the fae-shear resonator with different operational frequeny. The resonator dimension is TABLE IV. Measured Sensitivity of Different Mode Crystals (Ω/Mrayl). Fae-shear mode Thikness-shear mode Thikness mode Sensitivity at resonane Sensitivity at anti-resonane

6 kim et al.: surfae aousti load sensing using a fae-shear resonator 553 Crystal length (mm) TABLE V. Calulated Sensitivity and Resonant Frequeny of Fae-Shear Mode Resonator. Sensitivity (Ω/Mrayl) related to the resonator sensitivity beause the dimension determines the resonant frequeny of the resonator. As the resonant frequeny inreases, the amount of impedane hange that is, the sensitivity to the surfae load inreased. Table V indiates the sensitivity of the fae-shear mode resonators with different lateral sizes and resonant frequenies. The sensitivity is inversely proportional to the rystal length, but proportional to the resonant frequeny. For example, ideally, the sensitivity of the -mm-length resonator was 0 times higher than that of the 0-mmlength resonator. This result supports the idea that miniaturized fae-shear resonator arrays are very promising for surfae load sensing appliations. V. Conlusion Resonant frequeny (khz) In onlusion, the sensitivity to the aousti surfae load impedane of PIN PMN PT resonator was investigated. Different aousti loads were applied to the thikness-mode, thikness-shear-mode, and fae-shear-mode resonators. The highest sensitivity was found from the fae-shear-mode resonator, whih was found to be about ten times higher than other modes, and whih was suessfully verified by the KLM model results. It was also found that surfae load sensitivity inreases with dereased lateral sizes of resonators, whih favors large area surfae Fig. 0. The size effet of fae-shear-mode resonators with lateral sizes from to 0 mm. sensing using an array of fae-shear resonators. The high sensitivity of the fae shear mode to the surfae load an be promising for appliations suh as artifiial skins, biologial sensors, hemial sensors, touh sreens, and other tatile-based sensors. Aknowledgments The author thank their lab members, S. Bakshi, L. Tolliver, and S. Guo, for their insightful omments. Referenes [] B. Wikman, H. Grönbek, P. Hanarp, and B. Kasemo, Corrosion indued degradation of Pt/C model eletrodes measured with eletrohemial quartz rystal mirobalane, J. Eletrohem. So., vol. 57, no. 4, pp. B59 B598, 00. [] X. Wang, B. Ding, J. Yu, M. Wang, and F. Pan, A highly sensitive humidity sensor based on a nanofibrous membrane oated quartz rystal mirobalane, Nanotehnology, vol., no. 5, art. no , 00. [3] V. Jalkanen, B. Andersson, and O. Lindahl, Stiffness of a small tissue phantom measured by a tatile resonane sensor, in th Mediterranean Conf. Medial and Biologial Engineering and Computing, 00, pp [4] T. Hemsel, R. Stroop, D. Oliva Uribe, and J. Wallashek, Resonant vibrating sensors for tatile tissue differentiation, J. Sound Vibrat., vol. 308, no. 3 5, pp , 007. [5] T. Oie, H. Suzuki, Y. Murayama, T. Fukuda, S. Omata, K. Kanda, K. Takamizawa, and Y. Nakayama, Surfae elastiity imaging of vasular tissues in a liquid environment by a sanning hapti mirosope, J. Artif. Organs, vol. 3, no., pp. 5, 00. [6] Y. Murayama, M. Yoshida, J. Mizuno, H. Nakamura, S. Inoue, Y. Watanabe, K. Akaishi, H. Inui, C. E. Constantinou, and S. Omata, Elastiity measurement of zona pelluida using a miro tatile sensor to evaluate embryo quality, J. Mamm. Ova Res, vol. 5, pp. 8 6, Apr [7] A. Bonakdar and N. Narayanan, Determination of tissue properties using mirofabriated piezoeletri tatile sensor during minimally invasive surgery, Sensor Rev., vol. 30, no. 3, pp. 33 4, 00. [8] J. Dargahi, R. Sedaghati, H. Singh, and S. Najarian, Modeling and testing of an endosopi piezoeletri-based tatile sensor, Mehatronis, vol. 7, no. 8, pp , 007. [9] C. H. Chuang, Flexible piezoeletri tatile sensors with strutural eletrodes array, Reent Adv. Sens. Tehnol., vol. 49, pt. 6, pp. 89 0, 009. [0] O. Lindahl, C. Constantinou, A. Eklund, Y. Murayama, P. Hallberg, and S. Omata, Tatile resonane sensors in mediine, J. Med. Eng. Tehnol., vol. 33, no. 4, pp , 009. [] C. Chuang, Piezoeletri tatile sensor, U.S. Patent 88 80, Jul., 00. [] E. Benes, M. Gröshl, W. Burger, and M. Shmid, Sensors based on piezoeletri resonators, Sens. Atuators A, vol. 48, no., pp., 995. [3] V. Todorova and D. Kolev, Design and modeling problems of resonane piezoeletri tatile arrays, in IEEE Control Appliations, (CCA) and Intelligent Control, (ISIC), 009, pp [4] R. M. Shmitt, W. G. Sott, R. D. Irving, J. Arnold, C. Bardons, D. Halpert, and L. Parker, Ultrasoni imaging of fingerprints using aoustial impediography, in IEEE Int. Ultrasonis Symp., 004, pp [5] R. M. Shmitt and J. Owen, Aousti impediography: Imaging surfae aousti impedane using 3 piezo-omposite for Integrated fingerprinting, in IEEE 6st Eletroni Components and Tehnology Conf., 0, pp [6] R. M. Shmitt, Method and system for multi-mode mehanial resonator, U.S. Patent 7 468, May 8, 008. [7] K. B. Kim, D. K. Hsu, B. Ahn, Y. G. Kim, and D. J. Barnard, Fabriation and omparison of PMN-PT single rystal, PT and PT-based -3 omposite ultrasoni transduers for NDE appliations, Ultrasonis, vol. 50, no. 8, pp , 00.

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Kino, The design of effiient broad-band piezoeletri transduers, IEEE Trans. Sonis Ultrason., vol. 5, no. 3, pp. 5 5, 978. [37] I. Kuo, B. Hete, and K. Shung, A novel method for the measurement of aousti speed, J. Aoust. So. Am., vol. 88, no. 4, pp , 990. Kyungrim Kim reeived his B.S. degree in mehanial and automotive engineering from Kookmin University in Korea. In fall 009, he started his work as a Ph.D. student in the Department of Mehanial and Aerospae Engineering, North Carolina State University. Currently, he is working as a Researh Assistant in the Miro/Nano Engineering Laboratory under Dr. Jiang. His main researh interests are high-temperature piezoeletri sensors and ultrasoni sensors. Shujun hang reeived his Ph.D. degree from The State Key Laboratory of Crystal Materials, Shandong University, China, in 000. He is urrently Senior Researh Assoiate at the Material Researh Institute and an Assoiate Professor in the Materials Siene and Engineering Department, The Pennsylvania State University. He is an assoiate editor of the IEEE Transations on Ultrasonis, Ferroeletris, and Frequeny Control (UFFC) and the Journal of the Amerian Cerami Soiety. He was a reipient of the Ferroeletris Young Investigator Award of the IEEE UFFC Soiety in 0. He has oauthored more than 00 papers in the area of funtional single rystals and eramis. He is now fousing on the struture property performane relationship of high-temperature, high-power, and high-performane piezoeletri rystals and eramis for sensor and transduer appliations. Xiaoning Jiang reeived his Ph.D. degree from Tsinghua University in 997 and postdotoral training from the Nanyang Tehnologial University and The Pennsylvania State University (997 00). He worked in industry (Standard MEMS In. and TRS Tehnologies In.) before joining North Carolina State University in 009 as an Assoiate Professor of mehanial and aerospae engineering. Dr. Jiang is the author or oauthor of two book hapters, one book, more than 0 US patents and patent appliations, and more than 50 tehnial papers and presentations on piezoeletri omposite miromahined ultrasound transduers (PC-MUT), ultrasound for medial imaging and NDE, smart materials and strutures, and M/NEMS.