@article{wan_luo_kim_chung_chang_yamashita_jiang_2022, title={<p>The overpoling effect of alternating current poling on rhombohedral Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals</p>}, volume={120}, ISSN={["1077-3118"]}, DOI={10.1063/5.0086057}, abstractNote={The overpoling effect of alternating current poling (ACP) was studied on [001]-orientated rhombohedral Pb(Mg1/3Nb2/3)O3-0.26PbTiO3 (PMN-0.26PT) single crystals. Our experimental results showed that the property enhancement from the ACP was remarkable only when the poling cycle number (NL) was kept low. When ACP was continued after the saturation, dielectric and piezoelectric properties gradually dropped down to traditional direct current poled levels or even lower. Such a decrease in material properties caused by the large NL during ACP was defined as the “overpoling effect of ACP” in this study. The following lattice symmetry and domain structure characterization studies were performed through x-ray diffraction (XRD) and piezoelectric force microscopy (PFM) to find the origin of the overpoling effect. The XRD measurements combined with temperature dependence of dielectric properties demonstrated that the field-induced phase transition continued when the samples became overpoled. Further PFM measurements illustrated that the domain density of the overpoled ACP sample was significantly lower than that of the normal one, while the “2R” domain configuration was maintained through the ACP process. In addition, the hysteresis loop characterization indicated large decreases in the coercive fields. The discovered overpoling effect of ACP could help us understand the mechanisms of ACP and optimize the ACP process.}, number={19}, journal={APPLIED PHYSICS LETTERS}, author={Wan, Haotian and Luo, Chengtao and Kim, Hwang-Pill and Chung, Ching-Chang and Chang, Wei-Yi and Yamashita, Yohachi and Jiang, Xiaoning}, year={2022}, month={May} }
 @article{wan_luo_liu_chang_yamashita_jiang_2021, title={Alternating current poling on sliver-mode rhombohedral Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals}, volume={208}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2021.116759}, abstractNote={Sliver-mode 0.73Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystals were poled by the alternating current electric field (ACP) along the [001] direction for low-frequency transducer applications. Under ACP with optimized conditions (2.89 kVrms, 0.1 Hz, 10 cycles), the free dielectric constant (εT33/ε0) was enhanced from 5300 to 7220 and piezoelectric coefficient (d33) was improved from 1410 to 1920 pC/N, both are about 36% higher than those under traditional direct current poling. The piezoresponse force microscopy observation and phase-field simulation show the similar domain morphologies evolution. During the ACP process, the domain morphology first changes from ‘4R’ to ‘2R’ configuration, and then the length of the 109° domain wall keeps increasing, which leads to a longer range of ordering and a stable lamellar domain structure in the end. The correlation between the domain morphology and the coercive field is also found in both the experiment and simulation. These findings on the effect and mechanism of ACP will help develop advanced low-frequency single crystal transducer arrays.}, journal={ACTA MATERIALIA}, author={Wan, Haotian and Luo, Chengtao and Liu, Chang and Chang, Wei-Yi and Yamashita, Yohachi and Jiang, Xiaoning}, year={2021}, month={Apr} }
 @article{luo_chang_gao_chang_li_viehland_tian_jiang_2020, title={Multi-layered domain morphology in relaxor single crystals with nano-patterned composite electrode}, volume={182}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2019.10.017}, abstractNote={(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystals, especially with compositions near its morphotropic phase boundary (MPB), have been employed for a broad range of applications such as ultrasound transducers, sensors, and actuators. To further enhance the properties of PMN-PT, electrode patterning, as a method of domain engineering, was proved to be an effective approach. In our previous report, a 200 nm grating pattern electrode (Ti/Au–MnOx) (nano-electrode) was prepared on one surface of PMN-PT crystal, exhibiting 30% d33 enhancement. In this work, the multi-layered domain morphology and the domain engineering from nano-electrode were characterized using piezoresponse force microscopy (PFM). A hypothetical domain engineering model for nano-electrodes is established to explain the experimental results as well as the property enhancement from the nano-electrode. The electrode patterning proves that the nano-scale modification can tune the macro-scale piezoelectric properties of the bulk material.}, journal={ACTA MATERIALIA}, author={Luo, Chengtao and Chang, Wei-Yi and Gao, Min and Chang, Chih-Hao and Li, Jiefang and Viehland, Dwight and Tian, Jian and Jiang, Xiaoning}, year={2020}, month={Jan}, pages={10–17} }
 @article{gao_luo_chang_leung_tian_li_jiang_viehland_2019, title={Apparent phase stability and domain distribution of PMN-30PT single crystals with nanograted Au/MnOx electrodes}, volume={169}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2019.02.039}, abstractNote={X-ray diffraction (XRD) reciprocal space mapping (RSM) was used to investigate how nanograted electrodes affect the nanodomain distribution and average crystal structure in near-surface regions of poled Pb(Mg1/3Nb2/3)O3-30%PbTiO3 (PMN-30PT) single crystals. The RSM scans revealed a transverse broadening along the (H00) direction, which was quite different from that of either the rhombohedral (R) or monoclinic A (MA) phase. This broadening provides evidence of a non-uniform distribution of tilt angles between neighboring nanodomains, induced by a gradient in the applied electric field (E). Investigations of the front and back surfaces of the crystals revealed significant differences in the RSM scans. Gradients in the domain distribution and apparent symmetry may extend throughout the crystal thickness. The data evidence changes in the nanodomain distribution that results in adaptations of the average symmetry.}, journal={ACTA MATERIALIA}, author={Gao, Min and Luo, Chengtao and Chang, Wei-Yi and Leung, Chung Ming and Tian, Jian and Li, Jiefang and Jiang, Xiaoning and Viehland, D.}, year={2019}, month={May}, pages={28–35} }
 @article{kim_kim_chang_huang_jiang_dayton_2019, title={Candle-Soot Carbon Nanoparticles in Photoacoustics Advantages and challenges for laser ultrasound transmitters}, volume={13}, ISSN={["1942-7808"]}, DOI={10.1109/MNANO.2019.2904773}, abstractNote={This article provides a review of candle-soot nanoparticle (CSNP) composite laser ultrasound transmitters (LUTs) and compares and contrasts this technology with other carbon-composite designs. Among many carbon-based composite LUTs, a CSNP composite has demonstrated its advantages of maximum energy conversion and fabrication simplicity for developing highly efficient ultrasound transmitters. We focus on the advantages and challenges of the CSNP-composite transmitter in the areas of nanostructure design, fabrication procedure, and promising applications.}, number={3}, journal={IEEE NANOTECHNOLOGY MAGAZINE}, author={Kim, Jinwook and Kim, Howuk and Chang, Wei-Yi and Huang, Wenbin and Jiang, Xiaoning and Dayton, Paul A.}, year={2019}, month={Jun}, pages={13–28} }
 @article{luo_wan_chang_yamashita_paterson_jones_jiang_2019, title={Effect of low-frequency alternating current poling on 5-mm-thick 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) single crystals}, volume={115}, ISSN={["1077-3118"]}, DOI={10.1063/1.5127292}, abstractNote={Alternating current (electric field) poling (ACP) was applied on [001]-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-0.3PT) single crystal samples with dimensions of 5 × 1.25 × 1.25 mm3 (with electrodes on the 1.25 × 1.25 mm2 surfaces), and the influence of ACP frequency (fACP) was studied. Compared to those from traditional direct (electric field) poling samples, the piezoelectric coefficient (d33) and free dielectric constant (εT33/ε0) of ACP samples could gain up to a 67% increase to 3200 pC/N and 10 500, respectively. The influence of fACP was studied on two main aspects: saturated properties and dynamic saturation process. In general, ACP samples with lower fACP had higher saturated d33, εT33/ε0, and coupling factor k33, as well as lower dielectric loss and faster saturation speed. The ACP dynamics during the saturation process were studied by measuring the polarization-vs-electric field hysteresis loops (P-E loops). The P-E loops illustrated that the coercive field of ACP samples could be further tuned from 1.84 kV/cm to 3.03 kV/cm by changing fACP (0.1–10 Hz). This work demonstrated the enormous potential of ACP optimization in relaxor-PT single crystal-based low-frequency transducer applications.}, number={19}, journal={APPLIED PHYSICS LETTERS}, author={Luo, Chengtao and Wan, Haotian and Chang, Wei-Yi and Yamashita, Yohachi and Paterson, Alisa R. and Jones, Jacob and Jiang, Xiaoning}, year={2019}, month={Nov} }
 @article{luo_wan_chang_yamashita_paterson_jones_jiang_2019, title={Effect of low-frequency alternating current poling on 5-mm-thick 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) single crystals (vol 115, 192904, 2019)}, volume={115}, ISSN={["1077-3118"]}, DOI={10.1063/1.5139662}, abstractNote={First Page}, number={26}, journal={APPLIED PHYSICS LETTERS}, author={Luo, Chengtao and Wan, Haotian and Chang, Wei-Yi and Yamashita, Yohachi and Paterson, Alisa R. and Jones, Jacob and Jiang, Xiaoning}, year={2019}, month={Dec} }
 @article{wan_luo_chang_yamashita_jiang_2019, title={Effect of poling temperature on piezoelectric and dielectric properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals under alternating current poling}, volume={114}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.5094362}, DOI={10.1063/1.5094362}, abstractNote={In this work, the piezoelectric and dielectric properties of [001]-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals under alternating current poling (ACP) at different temperatures were studied. The piezoelectric coefficients (d33 ∼ 1930 pC/N, d31 ∼ −850 pC/N) and free dielectric permittivity (εT33/ε0 ∼ 7570) reached their highest values when the poling temperature (Tpoling) was 70 °C. Compared with traditional direct current electric field poling at 20 °C, 70 °C-ACP samples showed an enhancement of 40%, 35%, and 49% for d33, d31, and εT33/ε0, respectively. Meanwhile, d33 and εT33/ε0 were enhanced by about 9% when Tpoling increased from 20 °C to 70 °C under ACP, while d31 remained the same value and the dielectric loss was lowered from 0.29% to 0.22%. Moreover, ACP samples with different Tpoling have similar electromechanical coupling factors (k31 ∼ 0.44, kt ∼ 0.60). A discussion of the mechanism for the ACP enhancement was based on the domain observation using piezoresponse force microscopy, and the results showed that the domain densities of ACP samples with different Tpoling were positively correlated with their piezoelectric properties. This work demonstrated the enormous potential of ACP optimization for relaxor-PT single crystal applications.}, number={17}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Wan, Haotian and Luo, Chengtao and Chang, Wei-Yi and Yamashita, Yohachi and Jiang, Xiaoning}, year={2019}, month={Apr}, pages={172901} }
 @article{kim_chang_kim_jiang_2019, title={Narrow band photoacoustic lamb wave generation for nondestructive testing using candle soot nanoparticle patches}, volume={115}, ISSN={["1077-3118"]}, DOI={10.1063/1.5100292}, abstractNote={The generation of ultrasonic surface waves with a photoacoustic-laser-source has become useful for the noncontact nondestructive testing and evaluation (NDT&E) of materials and structures. In this work, a hybrid ultrasound based NDT&E method is proposed based on the photoacoustic-laser-source as a noncontact Lamb wave generator by incorporating a line-arrayed patterned candle soot nanoparticle-polydimethylsiloxane (CSNPs-PDMS) patch as the signal amplifier and with a narrow bandwidth. The CSNP-PDMS composite has been investigated as the functional patch for its laser energy absorption efficiency, fast thermal diffusion, and large thermoelastic expansion capabilities. The signal amplitude (in mW) from the CSNP-PDMS patch exhibits 2.3 times higher amplitude than the no patch condition and a narrower bandwidth than other conditions. Furthermore, improvement in the sensitivity is also achieved through the selection of the aluminum nitride sensing system. The overall combination of the Lamb wave generation and receiver-sensing system in this study is found to be very promising for a broad range of noncontact NDT&E applications.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Kim, Taeyang and Chang, Wei-Yi and Kim, Howuk and Jiang, Xiaoning}, year={2019}, month={Sep} }
 @article{kim_chang_kim_huang_jiang_2019, title={Stress Measurement of a Pressurized Vessel Using Candle Soot Nanocomposite Based Photoacoustic Excitation}, volume={10971}, ISSN={["1996-756X"]}, DOI={10.1117/12.2515211}, abstractNote={This article aims to develop a pressure sensing method by utilizing both a contacting active sensor and a non-contacting laser ultrasound transmitter. An overloaded stress in an industrial pressure tank such as a nuclear reactor may cause a catastrophic explosion; thus, it is essential to monitor the mechanical stress in a reliable manner for the structural safety. Among many different types of stress sensing methods, ultrasound sensing has been attractive due to its non-invasive measurement feature. For the recent decades, subsurface longitudinal (SSL) ultrasonic wave has been widely used since it is not only less dependent on the internal medium and the surface condition, but also has the fastest wave speed without wave distortion. In our work, laser source and Aluminum nitride (AlN) wafer are used to generate and to receive SSL ultrasonic waves, respectively. In order to increase the photoacoustic efficacy, a composite of carbon-soot nanoparticles (CSNP) and polydimethylsiloxane (PDMS) was attached onto the intermediate wedge at the transmitter side. The photoacoustic experiment results demonstrate a reasonable linear relationship between the stress level and the time-of-flight variation of the propagated wave signal.}, journal={NONDESTRUCTIVE CHARACTERIZATION AND MONITORING OF ADVANCED MATERIALS, AEROSPACE, CIVIL INFRASTRUCTURE, AND TRANSPORTATION XIII}, author={Kim, Ho-Wuk and Chang, Wei-Yi and Kim, Taeyang and Huang, Shujin and Jiang, Xiaoning}, year={2019} }
 @article{chang_chung_luo_kim_yamashita_jones_jiang_2018, title={Dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O-3-0.3 PbTiO3 single crystal poled using alternating current}, volume={6}, ISSN={["2166-3831"]}, DOI={10.1080/21663831.2018.1498812}, abstractNote={ABSTRACT In this paper, 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-30%PT) single crystal samples were poled using an alternating current (electric field) poling (ACP) method. Compared to the traditional poling method, the piezoelectric coefficient, free and clamped dielectric constants were improved more than 21%. X-ray diffraction result suggests the existence of monoclinic phase (MA) in ACP samples and piezoresponse force microscopy (PFM) result further depicts the finer engineered domain structures. The ACP sample also showed the unique phase transition sequences during the depoling process. Our work could provide a novel domain engineered method to enhance piezoelectric properties of PMN-PT single crystal. GRAPHICAL ABSTRACT IMPACT STATEMENT Piezoelectric and dielectric properties of relaxor-PT single crystals can be significantly enhanced by employing the new alternating current poling method, attributing to the unique heterogenous domain structure containing unprecedented domain wall density.}, number={10}, journal={MATERIALS RESEARCH LETTERS}, author={Chang, Wei-Yi and Chung, Ching-Chang and Luo, Chengtao and Kim, Taeyang and Yamashita, Yohachi and Jones, Jacob L. and Jiang, Xiaoning}, year={2018}, pages={537–544} }
 @article{yuan_sang_sun_qi_chang_zhang_yang_jiang_cao_2018, title={Domain engineering and full matrix material constants of the [111](c)-poled 0.63Pb(Mg1/3Nb2/3)-0.37PbTiO(3) single crystal}, volume={20}, ISSN={["1466-8033"]}, DOI={10.1039/c8ce00831k}, abstractNote={Domain engineering was performed on a [111]c-oriented tetragonal ferroelectric 0.63Pb(Mg1/3Nb2/3)-0.37PbTiO3 (PMN-0.37PT) single crystal in order to achieve better piezoelectric properties.}, number={33}, journal={CRYSTENGCOMM}, author={Yuan, Zhongyuan and Sang, Shijing and Sun, Enwei and Qi, Xudong and Chang, Wei-Yi and Zhang, Rui and Yang, Bin and Jiang, Xiaoning and Cao, Wenwu}, year={2018}, month={Sep}, pages={4745–4751} }
 @article{chang_zhang_kim_huang_bagal_chang_fang_wu_jiang_2018, title={Evaluation of Photoacoustic Transduction Efficiency of Candle Soot Nanocomposite Transmitters}, volume={17}, ISSN={["1941-0085"]}, url={https://doi.org/10.1109/TNANO.2018.2845703}, DOI={10.1109/TNANO.2018.2845703}, abstractNote={Candle soot nanoparticles (CSNP) and polydimethyl-siloxane (PDMS) composite has shown the highly efficient photoacoustic transduction owing to their high light absorption coefficient and low interfacial thermal resistance. In this study, we report the effect of candle soot structure and thickness on the photoacoustic transduction efficiency. Optical properties of the CSNP/PDMS nanocomposites were characterized through both experimental measurements and finite difference time domain analysis in the visible wavelength range, indicating that the carbon volume fraction and thickness of CS/PDMS composite are highly relevant with light absorption. With a low laser energy input ( <inline-formula><tex-math notation="LaTeX">$< {\text{1 mJ/pulse}}$</tex-math></inline-formula>), the CS/PDMS composite with 2.15 <italic>μ</italic>m thickness exerts an output pressure of 3.78 MPa and a conversion efficiency of <inline-formula><tex-math notation="LaTeX">${\text{9.69}}\,\times \,{\text{10}}^{- 3}$</tex-math> </inline-formula>, which is two orders of magnitude higher than previously reported results.}, number={5}, journal={IEEE TRANSACTIONS ON NANOTECHNOLOGY}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Chang, Wei-Yi and Zhang, Xu A. and Kim, Jinwook and Huang, Wenbin and Bagal, Abhijeet and Chang, Chih-Hao and Fang, Tiegang and Wu, Hanchang Felix and Jiang, Xiaoning}, year={2018}, month={Sep}, pages={985–993} }
 @article{chang_chung_yuan_chang_tian_viehland_li_jones_jiang_2018, title={Patterned nano-domains in PMN-PT single crystals}, volume={143}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2017.10.016}, abstractNote={The domain structure, dielectric, and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single crystals with nanocomposite electrode, which includes MnOx semiconductor nanogratings and a Ti/Au conductive layer, were studied in this paper. These artificial MnOx nanogratings can alter the electric field distribution and then enhance the domain density. PMN-PT crystals with Ti/Au-MnOx nanocomposite electrodes showed high piezoelectric constant of 2250 p.m./V and dielectric constant of 5400 at 1 kHz, respectively. Compared to ones with conventional planar electrodes, the piezoelectric and dielectric constants of the samples with nanocomposite electrodes were increased 36.7% and 38.3%, respectively. Piezoresponse force microscopy (PFM) images revealed the domain pattern near the electrode/single crystal interface. A linear domain structure induced by the MnOx nanocomposite electrode was found in the samples with thickness less than 200 μm. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) results showed the diffusion of Mn about 300 nm in depth in PMNPT crystal after heat treatment during MnOx nanocomposite electrode. It is believed that the localized high electric fields induced by fringe effects caused by the nanocomposite electrode can enhance nucleation of new domains, and that diffusion from the patterned Mn layer may also lead to an enhancement in domain wall mobility. Our findings open up a new domain engineering technique for tailoring the dielectric and piezoelectric properties of PMN-PT single crystals.}, journal={Acta Materialia}, author={Chang, W.-Y. and Chung, C.-C. and Yuan, Z. and Chang, C.-H. and Tian, J. and Viehland, D. and Li, J.-F. and Jones, J.L. and Jiang, X.}, year={2018}, month={Jan}, pages={166–173} }
 @article{berik_chang_jiang_2018, title={Piezoelectric torsional actuation in d(36) shear-mode PMN-PT single crystals}, volume={10598}, ISSN={["1996-756X"]}, DOI={10.1117/12.2292672}, abstractNote={This paper presents an experimental and numerical characterization of a piezoelectric d36 shear-based torsion actuator made of xPb(Mg1/3Nb2/3)O3-(1-x)PbTiO3 (PMN-PT) single crystals embedded between Polydimethylsiloxane (PDMS) layers. The generated rate of twist value of the piezoelectric d36-mode PMN-PT single crystal composite torsion actuator was obtained using a laser vibrometer from the maximum detected transverse deflection measurement. The quasi–static torsion actuation experiments were conducted on the piezoelectric d36 torsion actuator by applying different AC voltages at 1 Hz. The experimental benchmark was further modelled by Finite Element (FE) code ABAQUS® using three dimensional (3D) piezoelectric finite elements. The experimental results and Finite Element computations showed good agreement. Findings reveal that more rate of twist is produced by PMN-PT single crystals in comparison to piezoceramic alternatives. This piezoelectric PMN-PT d36-mode composite torsion actuator can be effectively used in torsional deformation control.}, journal={SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2018}, author={Berik, Pelin and Chang, Wei-Yi and Jiang, Xiaoning}, year={2018} }
 @article{kim_lindsey_chang_dai_stavas_dayton_jiang_2017, title={Intravascular forward-looking ultrasound transducers for microbubble-mediated sonothrombolysis}, volume={7}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-017-03492-4}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Kim, Jinwook and Lindsey, Brooks D. and Chang, Wei-Yi and Dai, Xuming and Stavas, Joseph M. and Dayton, Paul A. and Jiang, Xiaoning}, year={2017}, month={Jun} }
 @article{berik_chang_jiang_2017, title={Piezoelectric d(36) in-plane shear-mode of lead-free BZT-BCT single crystals for torsion actuation}, volume={110}, ISSN={["1077-3118"]}, DOI={10.1063/1.4975587}, abstractNote={We report the study of piezoelectric direct torsion actuation mechanism using lead-free piezoelectric d36 in-plane shear-mode BZT-BCT single crystals. The generated angle of twist of the piezoelectric torsion actuator was obtained from the transverse deflection measurement using a laser vibrometer. The bi-morph torsional actuator, consisting of two lead-free piezoelectric BZT-BCT in-plane shear-mode single crystals with a giant piezoelectric d36 shear strain coefficient of 1590 pC/N, provided a rate of twist of 34.12 mm/m under a quasi-static 15 V drive. The experimental benchmark was further modelled and verified by the ANSYS software using three dimensional (3D) piezoelectric finite elements. The experimental results revealed that lead-free piezoelectric BZT-BCT d36-mode single crystal is a superior candidate for piezoelectric torsion actuation. This lead-free piezoelectric BZT-BCT d36-mode torsion actuator can be effectively applied in torsional deformation control by taking into account the environmental considerations.}, number={5}, journal={APPLIED PHYSICS LETTERS}, author={Berik, P. and Chang, W. -Y. and Jiang, X.}, year={2017}, month={Jan} }
 @inproceedings{li_huang_chang_jiang_2016, title={40-MHz micromachined PMN-PT composite ultrasound array for medical imaging}, DOI={10.1115/imece2015-52540}, abstractNote={Ultrasonography is well known as a relatively low cost and non-invasive modality for real-time imaging. In recent years, various high frequency array transducers have been developed and used for ophthalmology, dermatology, and small animal studies. This paper reports the development of a 48-element 40-MHz ultrasonic array using micromachined lead magnesium niobate-lead titanate (PMN-PT) single crystal 1–3 composite material. Array elements with a pitch of 100-micron were interconnected via a customized flexible circuit. Pulse-echo test showed an average center frequency of 40 MHz and a −6 dB fractional bandwidth of 52%. The −20 dB pulse length was evaluated as 120 ns. The electrical and acoustical separation showed the crosstalk less than - 24 dB. An image of a steel wire target phantom was acquired by stacking multiple A-lines. The results demonstrate resolutions exceeding 70 μm axially and 800 μm laterally. Those results imply the great potential of the developed array transducer for the high frequency medical imaging.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2015, vol 3}, author={Li, S. B. and Huang, W. B. and Chang, W. Y. and Jiang, X. N.}, year={2016} }
 @article{huang_chang_kim_li_huang_jiang_2016, title={A Novel Laser Ultrasound Transducer Using Candle Soot Carbon Nanoparticles}, volume={15}, ISSN={["1941-0085"]}, DOI={10.1109/tnano.2016.2536739}, abstractNote={As a novel composite material for laser ultrasound transducer, candle soot nanoparticles polydimethylsiloxane (CSPs-PDMS) has been demonstrated to generate high frequency, broadband, and high-amplitude ultrasound waves. In this study, we investigated the mechanism of the high-optoacoustic conversion efficiency exhibited by the composite. A thermal-acoustic coupling model was proposed for analyzing the performance of the composite. The theoretical result matches well with the experimental observation. The acoustic beam profile was compared with Field II simulation results. The 4.41 × 10-3 energy conversion coefficient and 21 MHz--6 dB frequency bandwidth of the composite suggest that CSPs-PDMS composites is promising for a broad range of ultrasound therapy and non-destructive testing applications.}, number={3}, journal={IEEE TRANSACTIONS ON NANOTECHNOLOGY}, author={Huang, Wenbin and Chang, Wei-Yi and Kim, Jinwook and Li, Sibo and Huang, Shujin and Jiang, Xiaoning}, year={2016}, month={May}, pages={395–401} }
 @inproceedings{kim_chang_lindsey_dayton_dai_stavas_jiang_2016, title={Laser-generated-focused ultrasound transducers for microbubble-mediated, dual-excitation sonothrombolysis}, DOI={10.1109/ultsym.2016.7728473}, abstractNote={A laser-generated-focused ultrasound (LGFU) transducer generates high-pressure (up to 20 MPa), high-frequency (>10 MHz) shock waves with a tight focal spot. In this work, we aim to demonstrate the feasibility of using LGFU transducers for sonothrombolysis in vitro. A carbon black LGFU transducer was designed, fabricated and characterized. The prototyped LGFU was applied with in-vitro thrombolysis tests involving microbubble contrast agent (MCA). A conventional piezo ultrasound transducer was used as a secondary excitation source to enhance the cavitation effect by dual-frequency excitation. The in vitro test results showed that microbubble-mediated LGFU treatment can yield the lytic rate of approximately 2 mg/min, suggesting that LGFU transducers may be useful in precision high lytic rate sonothrombolysis.}, booktitle={2016 ieee international ultrasonics symposium (ius)}, author={Kim, J. and Chang, W. Y. and Lindsey, B. D. and Dayton, P. A. and Dai, X. M. and Stavas, J. M. and Jiang, X. N.}, year={2016} }
 @inproceedings{kim_chang_huang_jiang_2016, title={Nanocomposite transducer with a laser ultarsound transmitter and a piezoelectric receiver}, DOI={10.1109/nano.2016.7751440}, abstractNote={Laser ultrasound transducers, converting the laser pulses into acoustic waves with high frequency, broadband and high pressure amplitude, is attractive to many biomedical and industrial applications. In this paper, nanocomposites consisting of carbon nanomaterials, PDMS and PVDF were incorporated into a transducer structure for ultrasound transmitting and receiving. The prototyped nanocomposite transducers were characterized by conducting pulse-echo tests. The obtained center frequency is 12 MHz, -6 dB fractional bandwidth is 138%, and the signal-to-noise ratio of 42 dB with an excitation of ~5 mJ of 532 nm, 6 ns pulsed laser. These initial findings strongly suggest that laser ultrasound transducers are promising for advanced ultrasound imaging applications.}, booktitle={2016 IEEE 16th International Conference on Nanotechnology (IEEE-nano)}, author={Kim, J. and Chang, W. Y. and Huang, S. J. and Jiang, X. N.}, year={2016}, pages={191–192} }
 @inproceedings{chang_kim_li_huang_jiang_2015, title={A novel laser ultrasound transducer using candle soot carbon nanoparticles}, DOI={10.1109/nano.2015.7388855}, abstractNote={Laser ultrasound provides a useful method to generate high frequency, broadband and high intensity acoustic waves. In this study, we demonstrated a novel optoacoustic transducer with high-energy conversion efficiency by using candle soot nanoparticles polydimethylsiloxane (CSPs-PDMS) composite. Carbon nanoparticles are used because of their excellent properties of light absorption and heat transfer. The mean diameter of collected candle soot carbon nanoparticles is about 40 nm, and the light absorption ratio at 532 nm wavelength is up to 96.24%. The prototyped CSPs-PDMS composite laser ultrasound transducer was excited by laser pulses, and the acoustic beam profile was measured and compared with Field II simulation results. Energy conversion coefficient and -6 dB frequency bandwidth of CSPs-PDMS composite laser ultrasound transducer were measured to be 4.41 × 10-3 and 21 MHz, respectively. The unprecedented laser ultrasound transduction performance using CSNPs-PDMS nano-composites is promising for a broad range of ultrasound therapy and non-destructively testing applications.}, booktitle={2015 IEEE 15th International Conference on Nanotechnology (IEEE-NANO)}, author={Chang, W. Y. and Kim, J. and Li, S. B. and Huang, W. B. and Jiang, X. N.}, year={2015}, pages={1243–1246} }
 @article{chang_huang_kim_li_jiang_2015, title={Candle soot nanoparticles-polydimethylsiloxane composites for laser ultrasound transducers}, volume={107}, ISSN={["1077-3118"]}, DOI={10.1063/1.4934587}, abstractNote={Generation of high power laser ultrasound strongly demands the advanced materials with efficient laser energy absorption, fast thermal diffusion, and large thermoelastic expansion capabilities. In this study, candle soot nanoparticles-polydimethylsiloxane (CSNPs-PDMS) composite was investigated as the functional layer for an optoacoustic transducer with high-energy conversion efficiency. The mean diameter of the collected candle soot carbon nanoparticles is about 45 nm, and the light absorption ratio at 532 nm wavelength is up to 96.24%. The prototyped CSNPs-PDMS nano-composite laser ultrasound transducer was characterized and compared with transducers using Cr-PDMS, carbon black (CB)-PDMS, and carbon nano-fiber (CNFs)-PDMS composites, respectively. Energy conversion coefficient and −6 dB frequency bandwidth of the CSNPs-PDMS composite laser ultrasound transducer were measured to be 4.41 × 10−3 and 21 MHz, respectively. The unprecedented laser ultrasound transduction performance using CSNPs-PDMS nano-composites is promising for a broad range of ultrasound therapy applications.}, number={16}, journal={APPLIED PHYSICS LETTERS}, author={Chang, Wei-Yi and Huang, Wenbin and Kim, Jinwook and Li, Sibo and Jiang, Xiaoning}, year={2015}, month={Oct} }