@article{li_kim_wang_kasoji_lindsey_dayton_jiang_2018, title={A Dual-Frequency Colinear Array for Acoustic Angiography in Prostate Cancer Evaluation}, volume={65}, ISSN={["1525-8955"]}, DOI={10.1109/TUFFC.2018.2872911}, abstractNote={Approximately 80% of men who reach 80 years of age will have some form of prostate cancer. The challenge remains to differentiate benign and malignant lesions. Based on recent research, acoustic angiography, a novel contrast-enhanced ultrasound imaging technique, can provide high-resolution visualization of tissue microvasculature and has demonstrated the ability to differentiate vascular characteristics between healthy and tumor tissue in preclinical studies. We hypothesize that transrectal acoustic angiography may enhance the assessment of prostate cancer. In this paper, we describe the development of a dual frequency, dual-layer colinear array transducer for transrectal acoustic angiography. The probe consists of 64 transmitting (TX) elements with a center frequency of 3 MHz and 128 receiving (RX) elements with a center frequency of 15 MHz. The dimensions of the array are 18 mm in azimuth and 9 mm in elevation. The pitch is  $280~\mu \text{m}$  for TX elements and 140  $\mu \text{m}$  for RX elements. Pulse-echo tests of TX/RX elements and aperture acoustic field measurements were conducted, and both results were compared with the simulation results. Real-time contrast imaging was performed using a Verasonics system and a tissue-mimicking phantom. Nonlinear acoustic responses from microbubble contrast agents at a depth of 35 mm were clearly observed. In vivo imaging in a rodent model demonstrated the ability to detect individual vessels underneath the skin. These results indicate the potential use of the array described herein for acoustic angiography imaging of prostate tumor and identification of regions of neovascularization for the guidance of prostate biopsies.}, number={12}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Li, Sibo and Kim, Jinwook and Wang, Zhuochen and Kasoji, Sandeep and Lindsey, Brooks D. and Dayton, Paul A. and Jiang, Xiaoning}, year={2018}, month={Dec}, pages={2418–2428} }
 @article{kim_lindsey_li_dayton_jiang_2017, title={Dual-Frequency Transducer with a Wideband PVDF Receiver for Contrast-Enhanced, Adjustable Harmonic Imaging}, volume={10170}, ISBN={["978-1-5106-0825-2"]}, ISSN={["0277-786X"]}, DOI={10.1117/12.2258571}, abstractNote={Acoustic angiography is a contrast-enhanced, superharmonic microvascular imaging method. It has shown the capability of high-resolution and high-contrast-to-tissue-ratio (CTR) imaging for vascular structure near tumor. Dual-frequency ultrasound transducers and arrays are usually used for this new imaging technique. Stacked-type dual-frequency transducers have been developed for this vascular imaging method by exciting injected microbubble contrast agent (MCA) in the vessels with low-frequency (1-5 MHz), moderate power ultrasound burst waves and receiving the superharmonic responses from MCA by a high-frequency receiver (>10 MHz). The main challenge of the conventional dual-frequency transducers is a limited penetration depth (<25 mm) due to the insufficient receiving sensitivity for highfrequency harmonic signal detection. A receiver with a high receiving sensitivity spanning a wide superharmonic frequency range (3rd to 6th) enables selectable bubble harmonic detection considering the required penetration depth. Here, we develop a new dual-frequency transducer composed of a 2 MHz 1-3 composite transmitter and a polyvinylidene fluoride (PVDF) receiver with a receiving frequency range of 4-12 MHz for adjustable harmonic imaging. The developed transducer was tested for harmonic responses from a microbubble-injected vessel-mimicking tube positioned 45 mm away. Despite the long imaging distance (45 mm), the prototype transducer detected clear harmonic response with the contrast-to-noise ratio of 6-20 dB and the -6 dB axial resolution of 200-350 μm for imaging a 200 um-diameter cellulose tube filled with microbubbles.}, journal={HEALTH MONITORING OF STRUCTURAL AND BIOLOGICAL SYSTEMS 2017}, author={Kim, Jinwook and Lindsey, Brooks D. and Li, Sibo and Dayton, Paul A. and Jiang, Xiaoning}, year={2017} }
 @book{jiang_li_kim_ma_2017, title={High frequency piezo-composite micromachined ultrasound transducer array technology for biomedical imaging}, DOI={10.1115/1.860441}, abstractNote={in this monograph, the authors report the current advancement in high frequency piezoelectric crystal micromachined ultrasound transducers and arrays and their biomedical applications. piezoelectric ultrasound transducers operating at high frequencies (>20 mhz) are of increasing demand in recent years for medical imaging and biological particle manipulation involved therapy. The performances of transducers greatly rely on the properties of the piezoelectric materials and transduction structures, including piezoelectric coefficient (d), electromechanical coupling coefficient (k), dielectric permittivity (e) and acoustic impedance (Z). piezo-composite structures are preferred because of their relatively high electromechanical coupling coefficient and low acoustic impedance. a number of piezo-composite techniques have been developed, namely “dice and fill”, “tape-casting”, “stack and bond”, “interdigital phase bonding”, “laser micromachining” and “micro-molding”. however, these techniques are either difficult to achieve fine features or not suitable for manufacturing of high frequency ultrasound transducers (>20 mhz). The piezo-composite micromachined ultrasound transducers (pc-mUT) technique discovered over the last 10 years or so has demonstrated high performance high frequency piezo-composite ultrasound transducers. in this monograph, piezoelectric materials used for high frequency transducers is introduced first. Next, the benefits and theory of piezo composites is presented, followed by the design criteria and fabrication methods. Biomedical applications using pc-mUT and arrays will also be reported, in comparison with other ultrasound transducer techniques. The final part of this monograph describes challenges and future perspectives of this technique for biomedical applications. ASME_Bionano Monograph Jiang_FM.indd vi Manila Typesetting Company 08/29/2017 09:58PM ASME_Bionano Monograph Jiang_FM.indd vii Manila Typesetting Company 08/29/2017 09:58PM Downloaded From: http://asmedigitalcollection.asme.org on 10/21/2018 Terms of Use: http://www.asme.org/about-asme/terms-of-use Downloaded From: http://asmedigitalcollection.asme.org on 10/21/2018 Terms of Use: http://www.asme.org/about-asme/terms-of-use}, publisher={New York, NY, USA: ASME Press}, author={Jiang, X. and Li, S. and Kim, J. and Ma, J.}, year={2017} }
 @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{li_kim_wang_jiang_kasoji_lindsey_dayton_2016, title={A dual-frequency co-linear array for prostate acoustic angiography}, DOI={10.1109/ultsym.2016.7728718}, abstractNote={Approximately 80% of men who reach 80-years of age will have some form of prostate cancer. The challenge remains to differentiate indolent from aggressive disease. Based on recent research, acoustic angiography, a novel contrast enhanced ultrasound imaging technique, can provide high-resolution visualization of tissue microvasculature and has demonstrated the ability to differentiate vascular characteristics between healthy and tumor tissue. We hypothesize that transrectal acoustic angiography may enhance assessment of prostate cancer. In this paper, we describe the development of a dual layer co-linear array ultrasound transducer for transrectal acoustic angiography. The KLM model and Field II were used for the element design and acoustic field simulation, respectively. The probe consists of 64 transmit elements with a center frequency of 3 MHz and 128 receive elements with a center frequency of 15 MHz. The dimensions of the array are 18 mm in azimuth and 8 mm in elevation. The pitch is 280 μm for transmitting (TX) elements and 140 μm for receiving (RX) elements. Pulse-echo test of TX/RX elements were conducted and compared with the simulation results. Real-time contrast imaging was tested using a Verasonics system. Non-linear responses from microbubble contrast agents at a depth of 18 mm were clearly observed. The axial beam width (-6 dB) and CTR were calculated from the measured signals to be 400 μm and 20 dB, respectively. These results suggest that the prototype co-linear array is capable of performing dual-frequency superharmonic imaging of microbubbles for prostate cancer assessment.}, booktitle={2016 ieee international ultrasonics symposium (ius)}, author={Li, S. B. and Kim, J. and Wang, Z. C. and Jiang, X. N. and Kasoji, S. and Lindsey, B. and Dayton, P. A.}, year={2016} }
 @article{wang_li_czernuszewicz_gallippi_liu_geng_jiang_2016, title={Design, Fabrication, and Characterization of a Bifrequency Colinear Array}, volume={63}, ISSN={["1525-8955"]}, DOI={10.1109/tuffc.2015.2506000}, abstractNote={Ultrasound imaging with high resolution and large penetration depth has been increasingly adopted in medical diagnosis, surgery guidance, and treatment assessment. Conventional ultrasound works at a particular frequency, with a - 6-dB fractional bandwidth of ~ 70% , limiting the imaging resolution or depth of field. In this paper, a bifrequency colinear array with resonant frequencies of 8 and 20 MHz was investigated to meet the requirements of resolution and penetration depth for a broad range of ultrasound imaging applications. Specifically, a 32-element bifrequency colinear array was designed and fabricated, followed by element characterization and real-time sectorial scan (S-scan) phantom imaging using a Verasonics system. The bifrequency colinear array was tested in four different modes by switching between low and high frequencies on transmit and receive. The four modes included the following: 1) transmit low, receive low; 2) transmit low, receive high; 3) transmit high, receive low; and 4) transmit high, receive high. After testing, the axial and lateral resolutions of all modes were calculated and compared. The results of this study suggest that bifrequency colinear arrays are potential aids for wideband fundamental imaging and harmonic/subharmonic imaging.}, number={2}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Wang, Zhuochen and Li, Sibo and Czernuszewicz, Tomasz J. and Gallippi, Caterina M. and Liu, Ruibin and Geng, Xuecang and Jiang, Xiaoning}, year={2016}, month={Feb}, pages={266–274} }
 @article{li_kim_wang_jiang_kasoji_lindsey_dayton_2015, title={A 3 MHz/18 MHz Dual-layer Co-Linear Array for Transrectal Acoustic Angiography}, ISSN={["1948-5719"]}, DOI={10.1109/ultsym.2015.0030}, abstractNote={In this paper, a novel dual layer co-linear array ultrasound transducer was developed for transrectal dual-frequency superharmonic imaging. The KLM model and Field II were used for the acoustic stack design and simulation of the acoustic field of the array, respectively. The newly designed and fabricated probe consists of 50 transmit elements with a center frequency of 3 MHz and 100 receive elements with a center frequency of 18 MHz. The dimensions of the array are 15 mm in azimuth and 9 mm in elevation. The pitch is 270 μm for the transmitting elements and 135 μm for the receiving element. Pulse-echo testing of TX/RX elements corresponded with the simulation results. Real-time contrast imaging was tested using a multi-channel imaging system. The non-linear responses from microbubble contrast agents flowing through a 200 μm cellulose tube at a distance of 30 mm from the probe were clearly observed and displayed in the image. The axial beam width and CNR were calculated to be 200 μm and 18 dB, respectively. These results suggest that the prototyped co-linear array is capable of performing dual-frequency superharmonic imaging of microbubbles (“acoustic angiography”) for prostate cancer assessment.}, journal={2015 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS)}, author={Li, Sibo and Kim, Jinwook and Wang, Zhuochen and Jiang, Xiaoning and Kasoji, Sunny and Lindsey, Brooks and Dayton, Paul A.}, year={2015} }
 @article{li_jiang_tian_han_zhang_2015, title={A PMN- PT Micromachined 1-3 Composite Circular Array for IVUS}, ISSN={["1948-5719"]}, DOI={10.1109/ultsym.2015.0117}, abstractNote={In this paper, a single crystal PMN-PT micromachined 1-3 composite circular array (50 element, ~2.2 mm in diameter) was developed for intravascular ultrasound (IVUS) imaging. Micromachined 1-3 composites with frequency of XX MHz were first fabricated and tested. Array elements with a pitch of 140-micron were interconnected via a customized flexible circuit. Pulse-echo tests showed the average center frequency of 40 MHz and the -6 dB fractional bandwidth of 62% for array elements. The -20 dB pulse length was evaluated as 118 ns. The measured crosstalk is less than - 24 dB between adjacent elements. An image of 50 μm steel wire targets was acquired by stacking multiple A-lines. The results demonstrated beam widths exceeding 70 μm axially. Those results imply the great potential of the developed array transducer for the high frequency medical imaging.}, journal={2015 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS)}, author={Li, Sibo and Jiang, Xiaoning and Tian, Jian and Han, Pengdi and Zhang, Chao}, year={2015} }
 @inproceedings{wang_li_liu_geng_jiang_2015, title={A bi-frequency co-linear array transducer for biomedical ultrasound imaging}, DOI={10.1115/imece2014-38871}, abstractNote={Ultrasound imaging with high resolution and large field of depth has been increasingly adopted in medical diagnosis, surgery guidance and treatment assessment because of its relatively low cost, non-invasive and capability of real-time imaging. There is always a tradeoff between the resolution and depth of field in ultrasound imaging. Conventional ultrasound works at a particular frequency, with −6 dB fractional bandwidth of < 100%, limiting the resolution or field of depth in many ultrasound imaging cases.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2014, vol 3}, author={Wang, Z. C. and Li, S. B. and Liu, R. B. and Geng, X. C. and Jiang, X. N.}, year={2015} }
 @article{hsieh_kim_zhu_li_zhang_jiang_2015, title={A laser ultrasound transducer using carbon nanofibers-polydimethylsiloxane composite thin film}, volume={106}, ISSN={["1077-3118"]}, url={https://publons.com/publon/2826301/}, DOI={10.1063/1.4905659}, abstractNote={The photoacoustic effect has been broadly applied to generate high frequency and broadband acoustic waves using lasers. However, the efficient conversion from laser energy to acoustic power is required to generate acoustic waves with high intensity acoustic pressure (>10 MPa). In this study, we demonstrated laser generated high intensity acoustic waves using carbon nanofibers–polydimethylsiloxane (CNFs-PDMS) thin films. The average diameter of the CNFs is 132.7 ± 11.2 nm. The thickness of the CNFs film and the CNFs-PDMS composite film is 24.4 ± 1.43 μm and 57.9 ± 2.80 μm, respectively. The maximum acoustic pressure is 12.15 ± 1.35 MPa using a 4.2 mJ, 532 nm Nd:YAG pulsed laser. The maximum acoustic pressure using the CNFs-PDMS composite was found to be 7.6-fold (17.62 dB) higher than using carbon black PDMS films. Furthermore, the calculated optoacoustic energy conversion efficiency K of the prepared CNFs-PDMS composite thin films is 15.6 × 10−3 Pa/(W/m2), which is significantly higher than carbon black-PDMS thin films and other reported carbon nanomaterials, carbon nanostructures, and metal thin films. The demonstrated laser generated high intensity ultrasound source can be useful in ultrasound imaging and therapy.}, number={2}, journal={APPLIED PHYSICS LETTERS}, publisher={AIP Publishing}, author={Hsieh, Bao-Yu and Kim, Jinwook and Zhu, Jiadeng and Li, Sibo and Zhang, Xiangwu and Jiang, Xiaoning}, year={2015}, month={Jan} }
 @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} }
 @inproceedings{ma_li_wang_jiang_2015, title={Anti-matching design for wave isolation in dual frequency transducer for intravascular super-harmonic imaging}, DOI={10.1115/imece2014-38844}, abstractNote={Intravascular super-harmonic imaging of microvessels is expected to assist understanding of atherosclerotic cardiovascular disease. A dual frequency intravascular (IVUS) ultrasound transducer is a core component transmitting at low frequency and receiving high order harmonics. A significant challenge in developing high performance dual frequency IVUS transducers is the isolation of the high frequency ultrasound echoes from the low frequency element while keeping the low frequency transmission pressure. An anti-matching layer with low impedance and quarter wavelength thickness was designed based on wave propagation theory. In both KLM modeling and prototype validation, the anti-matching layer successfully suppressed the aliasing echo to less than −20 dB. Transmission pressure of the prototype transducer was still high enough for microbubble nonlinear responses. High resolution (<0.2 mm) and high CTR (>12 dB) image was generated from super-harmonic imaging, which elucidated the capability of the transducer for intravascular microvessel detection.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2014, vol 3}, author={Ma, J. G. and Li, S. B. and Wang, Z. C. and Jiang, X. N.}, year={2015} }
 @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} }
 @article{kim_li_kasoji_dayton_jiang_2015, title={Dual-frequency Super Harmonic Imaging Piezoelectric Transducers for Transrectal Ultrasound}, volume={9438}, ISSN={["0277-786X"]}, DOI={10.1117/12.2084459}, abstractNote={In this paper, a 2/14 MHz dual-frequency single-element transducer and a 2/22 MHz sub-array (16/48-elements linear array) transducer were developed for contrast enhanced super-harmonic ultrasound imaging of prostate cancer with the low frequency ultrasound transducer as a transmitter for contrast agent (microbubble) excitation and the high frequency transducer as a receiver for detection of nonlinear responses from microbubbles. The 1-3 piezoelectric composite was used as active materials of the single-element transducers due to its low acoustic impedance and high coupling factor. A high dielectric constant PZT ceramic was used for the sub-array transducer due to its high dielectric property induced relatively low electrical impedance. The possible resonance modes of the active elements were estimated using finite element analysis (FEA). The pulse-echo response, peak-negative pressure and bubble response were tested, followed by in vitro contrast imaging tests using a graphite-gelatin tissue-mimicking phantom. The single-element dual frequency transducer (8 × 4 × 2 mm3) showed a -6 dB fractional bandwidth of 56.5% for the transmitter, and 41.8% for the receiver. A 2 MHz-transmitter (730 μm pitch and 6.5 mm elevation aperture) and a 22 MHz-receiver (240 μm pitch and 1.5 mm aperture) of the sub-array transducer exhibited -6 dB fractional bandwidth of 51.0% and 40.2%, respectively. The peak negative pressure at the far field was about -1.3 MPa with 200 Vpp, 1-cycle 2 MHz burst, which is high enough to excite microbubbles for nonlinear responses. The 7th harmonic responses from micro bubbles were successfully detected in the phantom imaging test showing a contrast-to-tissue ratio (CTR) of 16 dB.}, journal={HEALTH MONITORING OF STRUCTURAL AND BIOLOGICAL SYSTEMS 2015}, author={Kim, Jinwook and Li, Sibo and Kasoji, Sandeep and Dayton, Paul A. and Jiang, Xiaoning}, year={2015} }
 @article{jian_li_huang_cui_jiang_2015, title={Electromechanical response of micromachined 1-3 piezoelectric composites: Effect of etched piezo-pillar slope}, volume={26}, ISSN={["1530-8138"]}, DOI={10.1177/1045389x14546657}, abstractNote={ Micromachined single-crystal piezoelectric 1-3 composites are known for high electromechanical coupling coefficients, low acoustic impedance, high processing precision and uniformity, which are desired for high-frequency ultrasound transducers. In this article, based on Smith and Auld’s 1-3 composite thickness-mode oscillation model, the effect of etched side wall slope on the electromechanical characteristics of micromachined piezoelectric 1-3 composites was studied. In specific, strain constant, stiffness, dielectric constant, electromechanical coupling coefficient, acoustic impedance, longitudinal velocity, and frequency of micromachined 1-3 composites were deduced using the developed model. The analytical model was then verified by a COMSOL simulation and experimental measurements of a micromachined composite sample with pitch of 15.9 µm, thickness of 42.8 µm, and etched pillar slope angle of 83.8°. The measured center frequency was 49.05 MHz, electromechanical coupling coefficient was 0.66, dielectric constant was 1178, and strain constant was 26.90 C/m2, which all agreed well with the analytical calculations. These results will be helpful in design and fabrication of high-frequency micromachined ultrasound transducers. }, number={15}, journal={JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES}, author={Jian, Xiaohua and Li, Sibo and Huang, Wenbin and Cui, Yaoyao and Jiang, Xiaoning}, year={2015}, month={Oct}, pages={2011–2019} }
 @article{kim_li_kasoji_dayton_jiang_2015, title={Phantom evaluation of stacked-type dual-frequency 1-3 composite transducers: A feasibility study on intracavitary acoustic angiography}, volume={63}, ISSN={["1874-9968"]}, DOI={10.1016/j.ultras.2015.06.009}, abstractNote={In this paper, we present phantom evaluation results of a stacked-type dual-frequency 1-3 piezoelectric composite transducer as a feasibility study for intracavitary acoustic angiography. Our previous design (6.5/30 MHz PMN-PT single crystal transducer) for intravascular contrast ultrasound imaging exhibited a contrast-to-tissue ratio (CTR) of 12 dB with a penetration depth of 2.5 mm. For improved penetration depth (>3 mm) and comparable contrast-to-tissue ratio (>12 dB), we evaluated a lower frequency 2/14 MHz PZT 1-3 composite transducer. Superharmonic imaging performance of this transducer and a detailed characterization of key parameters for acoustic angiography are presented. The 2/14 MHz arrangement demonstrated a -6 dB fractional bandwidth of 56.5% for the transmitter and 41.8% for the receiver, and produced sufficient peak-negative pressures (>1.5 MPa) at 2 MHz to induce a strong nonlinear harmonic response from microbubble contrast agents. In an in-vitro contrast ultrasound study using a tissue mimicking phantom and 200 μm cellulose microvessels, higher harmonic microbubble responses, from the 5th through the 7th harmonics, were detected with a signal-to-noise ratio of 16 dB. The microvessels were resolved in a two-dimensional image with a -6dB axial resolution of 615 μm (5.5 times the wavelength of 14 MHz waves) and a contrast-to-tissue ratio of 16 dB. This feasibility study, including detailed explanation of phantom evaluation and characterization procedures for key parameters, will be useful for the development of future dual-frequency array transducers for intracavitary acoustic angiography.}, journal={ULTRASONICS}, author={Kim, Jinwook and Li, Sibo and Kasoji, Sandeep and Dayton, Paul A. and Jiang, Xiaoning}, year={2015}, month={Dec}, pages={7–15} }
 @article{li_jiang_tian_han_2014, title={Development of Dual-layer Micromachined Composite Transducers for Broadband Ultrasound Imaging}, ISSN={["1948-5719"]}, DOI={10.1109/ultsym.2014.0164}, abstractNote={We presented in this paper the development of micromachined 1-3 composite dual layer transducers for multifrequency imaging. The effective electromechanical coupling coefficient and acoustic impedance of the micromachined PMN-PT 1-3 composite material was measured to be 0.73 and 18 MRayl, respectively. Based on the material, a dual-layer transducer prototype was developed. The probe was operated at both 15 MHz and 48 MHz. To characterize the transducer, pulse echo test was conducted, achieved a 73% and 70% bandwidth at low and high resonance, respectively. At fundamental mode, it showed transmitting sensitivity of 26 KPa/V, These results suggested great potential for medical broadband imaging applications.}, journal={2014 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS)}, author={Li, Sibo and Jiang, Xiaoning and Tian, Jian and Han, Pengdi}, year={2014}, pages={667–670} }
 @article{kim_li_jiang_kasoji_dayton_2014, title={Development of Transmitters in Dual-Frequency Transducers for Interventional Contrast Enhanced Imaging and Acoustic Angiography}, ISSN={["1948-5719"]}, DOI={10.1109/ultsym.2014.0167}, abstractNote={Spatial limitation can be a challenge to interventional ultrasound transducers for dual-frequency contrast-enhanced ultrasound imaging, or acoustic angiography. A low frequency (<; 3 MHz) transmission with moderate peak negative pressure (PNP) and short pulse length is not easily attainable within limited dimensions. In this paper, a new design of the low frequency transmitter of dual-frequency transducers is presented. 1-3 composites for interventional transmitter design were analyzed by the Krimholtz-Leedom-Matthaei (KLM) model and finite element analysis (FEA). The dual frequency transducer prototype with a 2 MHz 1-3 composite transmitter and a 14 MHz receiver was fabricated and characterized, followed by microbubble detection tests. The transmitter showed the peak negative pressure (PNP) of -1.5 MPa. The -6 dB pulse echo fractional bandwidth for the transmitter and receiver were 61 % and 45 %, respectively. The prototyped dual frequency transducer was used to successfully excite microbubbles and to detect super harmonic responses from microbubbles. The measured harmonic signal showed a 12 dB contrast-to-noise ratio (CNR).}, journal={2014 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS)}, author={Kim, Jinwook and Li, Sibo and Jiang, Xiaoning and Kasoji, Sandeep and Dayton, Paul A.}, year={2014}, pages={679–682} }
 @misc{martin_lindsey_ma_lee_li_foster_jiang_dayton_2014, title={Dual-Frequency Piezoelectric Transducers for Contrast Enhanced Ultrasound Imaging}, volume={14}, ISSN={["1424-8220"]}, DOI={10.3390/s141120825}, abstractNote={For many years, ultrasound has provided clinicians with an affordable and effective imaging tool for applications ranging from cardiology to obstetrics. Development of microbubble contrast agents over the past several decades has enabled ultrasound to distinguish between blood flow and surrounding tissue. Current clinical practices using microbubble contrast agents rely heavily on user training to evaluate degree of localized perfusion. Advances in separating the signals produced from contrast agents versus surrounding tissue backscatter provide unique opportunities for specialized sensors designed to image microbubbles with higher signal to noise and resolution than previously possible. In this review article, we describe the background principles and recent developments of ultrasound transducer technology for receiving signals produced by contrast agents while rejecting signals arising from soft tissue. This approach relies on transmitting at a low-frequency and receiving microbubble harmonic signals at frequencies many times higher than the transmitted frequency. Design and fabrication of dual-frequency transducers and the extension of recent developments in transducer technology for dual-frequency harmonic imaging are discussed.}, number={11}, journal={SENSORS}, author={Martin, K. Heath and Lindsey, Brooks D. and Ma, Jianguo and Lee, Mike and Li, Sibo and Foster, F. Stuart and Jiang, Xiaoning and Dayton, Paul A.}, year={2014}, month={Nov}, pages={20825–20842} }
 @article{wang_li_jiang_liu_geng_2013, title={Design, fabrication and characterization of a bi-frequency co-linear array (7.5MHz/15MHz)}, ISSN={["1948-5719"]}, DOI={10.1109/ultsym.2013.0131}, abstractNote={Ultrasound imaging with high resolution and large field of depth is important in disease diagnosis, surgery guidance and post-surgery assessment. Conventional ultrasound imaging arrays work at a particular frequency, with -6dB fractional bandwidth of <; 100%, limiting the resolution or field of depth in many ultrasound imaging cases. This paper presented design of a 7.5 MHz / 15 MHz bi-frequency co-linear array prototype with a wide bandwidth of 5MHz-20 MHz, which can be significant in a broad range of biomedical ultrasound imaging applications. To demonstrate the concept, a 32-element 1-D linear sub-array was fabricated, followed by element characterization and beamforming tests using a Verasonics system. Beam steering at +/- 40 degree was achieved without obvious side lobes. The initial results suggest great potential of this bi-frequency co-linear array for medical imaging with high resolution and large field of depth.}, journal={2013 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS)}, author={Wang, Zhuochen and Li, Sibo and Jiang, Xiaoning and Liu, Ruibin and Geng, Xuecang}, year={2013}, pages={504–507} }
 @inproceedings{li_huang_jiang_jian_cui, title={A dual-layer micromachined PMN-PT 1-3 composite transducer for broadband ultrasound imaging}, booktitle={2013 ieee international ultrasonics symposium (ius)}, author={Li, S. B. and Huang, W. B. and Jiang, X. N. and Jian, X. H. and Cui, Y. Y.}, pages={773–776} }