@article{garcia_kim_vinod_kim_fang_jiang_2023, title={A Bi-In-Sn eutectic multi-layer high temperature ultrasound transmitter with candle-soot nanoparticles for improved photoacoustic efficiency}, volume={12487}, ISBN={["978-1-5106-6081-6"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.2658480}, abstractNote={There is a growing need for non-invasive structural health monitoring in extreme environments. For nuclear power plants, pressure and temperature sensing under hazardous environment plays an important role for coolant system safety and stability management. Current sensing methods are intrusive, and suffer from degradation in the plant environment, limited life cycle, and complicated repair and replacement procedures. In this paper, we present an advanced Bi-In-Sn liquid metal (LM) transducer with the addition of candle-soot nanoparticles (CSNP) for improved photoacoustic efficiency and a metallic stencil for control of the liquid metal layer thickness. The sensitivity of the liquid metal candle-soot nanoparticle (LM-CSNP) ultrasound transmitter was characterized under 2 mJ/cm<sup>2</sup> at 65 °C, and 6 mJ/cm2 at 100 °C —300 °C. Compared with existing LM transmitter, the newly presented transmitter showed a sensitivity 6.6 times stronger than previously reported LM only transmitter.}, journal={NONDESTRUCTIVE CHARACTERIZATION AND MONITORING OF ADVANCED MATERIALS, AEROSPACE, CIVIL INFRASTRUCTURE, AND TRANSPORTATION XVII}, author={Garcia, Nicholas and Kim, Ho-Wuk and Vinod, Kaushik and Kim, Taeyang and Fang, Tiegang and Jiang, Xiaoning}, year={2023} }
 @article{kim_wu_chen_dai_zhou_jiang_2023, title={Intravascular Sono-Ablation for In-Stent Restenosis Relief: Transducer Development and the In-Vitro Demonstration}, volume={70}, ISSN={["1558-2531"]}, DOI={10.1109/TBME.2023.3238679}, abstractNote={This study aimed to propose a new clinical modality for the relief of in-stent restenosis (ISR) using focused ultrasound (FUS) ablation. In the first research stage, a miniaturized FUS device was developed for the sonification of the remaining plaque after stenting, known as one of the causes of ISR.This study presents a miniaturized (<2.8 mm) intravascular FUS transducer for ISR treatment. The performance of the transducer was predicted through a structural-acoustic simulation, followed by fabrication of the prototype device. Using the prototype FUS transducer, we demonstrated tissue ablation with bio-tissues over metallic stents, mimicking in-stent tissue ablation. Next, we conducted a safety test by detecting the existence of thermal damage to the arterial tissue upon sonication with a controlled dose.The prototype device successfully delivered sufficient acoustic intensity (>30 W/cm2) to a bio tissue (chicken breast) through a metallic stent. The ablation volume was approximately 3.9 × 7.8 × 2.6 mm3. Furthermore, 1.5 min sonication was sufficient to obtain an ablating depth of approximately 1.0 mm, not thermally damaging the underlying artery vessel.We demonstrated in-stent tissue sonoablation, suggesting it could be as a future ISR treatment modality.Comprehensive test results provide a key understanding of FUS applications using metallic stents. Furthermore, the developed device can be used for sonoablation of the remaining plaque, providing a novel approach to the treatment of ISR.}, number={7}, journal={IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING}, author={Kim, Howuk and Wu, Huaiyu and Chen, Mengyue and Dai, Xuming and Zhou, Ruihai and Jiang, Xiaoning}, year={2023}, month={Jul}, pages={2172–2180} }
 @article{wu_hossain_kim_gallippi_jiang_2021, title={A 1.5-D Array for Acoustic Radiation Force (ARF)-Induced Peak Displacement-Based Tissue Anisotropy Assessment With a Row-Column Excitation Method}, volume={68}, ISSN={["1525-8955"]}, url={https://doi.org/10.1109/TUFFC.2020.3030040}, DOI={10.1109/TUFFC.2020.3030040}, abstractNote={Many biological tissues, including muscle or kidney, are mechanically anisotropic, and the degree of anisotropy (DoA) in mechanical properties is diagnostically relevant. DoA can be assessed either using the ratio of shear wave velocities (SWVs) or acoustic radio forced impulse (ARFI)-induced peak displacements (PD) measured longitudinal over transverse orientations. Whether using SWV or PD as a basis, DoA expressed as the ratio of values requires 90° transducer rotation when a linear array is employed. This large rotation angle is prone to misalignment errors. One solution is the use of a fully sampled matrix array for electronic rotation of point spread function (PSF). However, the challenges of matrix array are its high fabrication cost and complicated fabrication procedures. The cheaper and simpler alternative of matrix array is the use of a row-column array. A 3×64 elements 1.5-D array with a row-column excitation mode is proposed to assess DoA in mechanical properties using the PD ratio. Different numbers of elements in elevational and lateral directions were selected to have orthogonal ARFI excitation beams without rotating the transducer. A custom-designed flex circuit was used to fabricate the array with a simpler electrode connection than a fully sampled matrix array. The performance of the array was evaluated in Field II simulation and experiment. The output pressure was 0.57-MPa output under a 40- [Formula: see text] excitation with a -6-dB point spread dimension of 14×4 mm2 in orthogonal directions. The PD was measured to be [Formula: see text] in an isotropic elastic phantom with Young's modulus of 5.4 kPa. These results suggest that the array is capable of assessing DoA using PD ratio without physical rotation of the transducer. The array has the potential to reduce the misalignment errors for DoA assessment.}, number={4}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Wu, Huaiyu and Hossain, Md Murad and Kim, Howuk and Gallippi, Caterina M. and Jiang, Xiaoning}, year={2021}, month={Apr}, pages={1278–1287} }
 @article{kim_kim_wu_zhang_dayton_jiang_2021, title={A multi-pillar piezoelectric stack transducer for nanodroplet mediated intravascular sonothrombolysis}, volume={116}, ISSN={["1874-9968"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85110135734&partnerID=MN8TOARS}, DOI={10.1016/j.ultras.2021.106520}, abstractNote={• Multiple pillar piezoelectric stack design for intravascular sono-thrombolysis. • High (>3MPa) acoustic pressure output and long (>2.2 wavelengths) focal distance. • Fast lysis rate (3.8–5.0 mg/min) through cavitation effect of infused nanodroplets. • In-vitro validation of the therapeutic efficacy through a flow model. We aim to develop a nanodroplet (ND)-mediated intravascular ultrasound (US) transducer for deep vein thrombosis treatments. The US device, having an efficient forward directivity of the acoustic beam, is capable of expediting the clot dissolution rate by activating cavitation of NDs injected onto a thrombus. We designed and prototyped a multi-pillar piezoelectric stack (MPPS) transducer composed of four piezoelectric stacks. Each stack was made of five layers of PZT-4 plates, having a dimension of 0.85 × 0.85 × 0.2 mm 3 . The transducer was characterized by measuring the electrical impedance and acoustic pressure, compared to simulation results. Next, in-vitro tests were conducted in a blood flow mimicking system using the transducer equipped with an ND injecting tube. The miniaturized transducer, having an aperture size of 2.8 mm, provided a high mechanical index of 1.52 and a relatively wide focal zone of 3.4 mm at 80 V pp , 0.96 MHz electric input. The mass-reduction rate of the proposed method (NDs + US) was assessed to be 4.1 and 4.6 mg/min with and without the flow model, respectively. The rate was higher than that (1.3–2.7 mg/min) of other intravascular ultrasound modalities using micron-sized bubble agents. The ND-mediated intravascular sonothrombolysis using MPPS transducers was demonstrated with an unprecedented lysis rate, which may offer a new clinical option for DVT treatments. The MPPS transducer generated a high acoustic pressure (~3.1 MPa) at a distance of approximately 2.2 wavelengths from the small aperture, providing synergistic efficacy with nanodroplets for thrombolysis without thrombolytic agents.}, journal={ULTRASONICS}, author={Kim, Howuk and Kim, Jinwook and Wu, Huaiyu and Zhang, Bohua and Dayton, Paul A. and Jiang, Xiaoning}, year={2021}, month={Sep} }
 @article{kim_kerrigan_bourham_jiang_2021, title={AlN Single Crystal Accelerometer for Nuclear Power Plants}, volume={68}, ISSN={["1557-9948"]}, url={https://doi.org/10.1109/TIE.2020.2992002}, DOI={10.1109/TIE.2020.2992002}, abstractNote={Reliable vibration sensing is essential to the immediate detection of unusual vibrations, ensuring the safety of nuclear power plant structures. For nuclear power plant applications, the sensor element must endure the harsh environment while retaining reliable performance. Aluminum nitride (AlN) single crystal is considered a promising candidate for the sensing unit due to its robustness to high temperature (HT) and irradiation conditions. However, there are few efforts in developing industrial accelerometers using AlN bulk-machined materials. This article aims to develop a shear-type accelerometer with AlN single crystal plates. The accelerometer's design is based on the numerical simulation results, followed by the fabrication of the sensor and the extensive validation under HT (~1000 °C). The sensitivity of the accelerometer was about 9.2 pC/g. The prototype sensor showed stable performance at varying temperatures from room temperature to 1000 °C. Furthermore, the sensitivity of the accelerometer was successfully sustained for 10 h under HT exposure of 1000 °C, and no obvious mechanical damage was detected after the test. After gamma irradiation for 1 month, the sensor performed stably, without any significant change in sensitivity. The developed AlN accelerometer can be a promising option to monitor the structural integrity of nuclear power plant structures.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Kim, Howuk and Kerrigan, Sean and Bourham, Mohamed and Jiang, Xiaoning}, year={2021}, month={Jun}, pages={5346–5354} }
 @article{wu_goel_kim_zhang_kim_dayton_xu_jiang_2021, title={Dual-Frequency Intravascular Sonothrombolysis: An In Vitro Study}, volume={68}, ISSN={["1525-8955"]}, url={https://doi.org/10.1109/TUFFC.2021.3103409}, DOI={10.1109/TUFFC.2021.3103409}, abstractNote={Thrombo-occlusive disease is one of the leading causes of death worldwide. There has been active research on safe and effective thrombolysis in preclinical and clinical studies. Recently, the dual-frequency transcutaneous sonothrombolysis with contrast agents [microbubbles (MBs)] has been reported to be more efficient in trigging the acoustic cavitation, which leads to a higher lysis rate. Therefore, there is increasing interest in applying dual-frequency technique for more significant efficacy improvement in intravascular sonothrombolysis since a miniaturized intravascular ultrasound transducer typically has a limited power output to fully harness cavitation effects. In this work, we demonstrated this efficacy enhancement by developing a new broadband intravascular transducer and testing dual-frequency sonothromblysis in vitro. A broadband intravascular transducer with a center frequency of 750 kHz and a footprint size of 1.4 mm was designed, fabricated, and characterized. The measured -6-dB fractional bandwidth is 68.1%, and the peak negative pressure is 1.5 MPa under the driving voltage of 80 Vpp. By keeping one frequency component at 750 kHz, the second frequency component was selected from 450 to 650 kHz with an interval of 50 kHz. The in vitro sonothrombolysis tests were conducted with a flow model and the results indicated that the MB-mediated, dual-frequency (750+500 kHz) sonothrombolysis yields an 85% higher lysis rate compared with the single-frequency treatment, and the lysis rate of dual-frequency sonothrombolysis increases with the difference between the two frequency components. These findings suggest a dual-frequency excitation technique for more efficient intravascular sonothrombolysis than conventional single-frequency excitation.}, number={12}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Wu, Huaiyu and Goel, Leela D. and Kim, Howuk and Zhang, Bohua and Kim, Jinwook and Dayton, Paul A. and Xu, Zhen and Jiang, Xiaoning}, year={2021}, month={Dec}, pages={3599–3607} }
 @article{wu_kim_zhang_kim_dayton_xu_jiang_2021, title={Intravascular Dual-frequency Ultrasound Transducer Using a Stack Composite}, ISSN={["1948-5719"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85122850530&partnerID=MN8TOARS}, DOI={10.1109/IUS52206.2021.9593424}, abstractNote={Intravascular sonothrombolysis has attracted much attention due to the safe and effective treatment potential compared to other conventional mechanical thrombectomy and high-dose medication. Meanwhile, multiple frequency sonothrombolysis is known to be more efficient to activate cavitation of micro or nano size contrast agents. Yet, the multiple frequency effects combined with an intravascular device have rarely been studied in the past due to technical limitations in transmitting acoustic pressure output with multiple frequencies from a single small aperture. Therefore, in this study, an intravascular ultrasound transducer with a composite structure is reported, which can operate with the dual-frequency condition for enhancing the cavitation effect of infused contrast agents. Compared with single frequency excitation, the in-vitro test results showed a 34% improvement in the lysis rate when the dual-frequency excitation was applied with the nanodroplets infusion.}, journal={INTERNATIONAL ULTRASONICS SYMPOSIUM (IEEE IUS 2021)}, author={Wu, Huaiyu and Kim, Howuk and Zhang, Bohua and Kim, Jinwook and Dayton, Paul and Xu, Zhen and Jiang, Xiaoning}, year={2021} }
 @article{kim_kim_jiang_2021, title={Laser ultrasonic defect localization using an omni-arrayed candle soot nanoparticle patch}, volume={60}, ISSN={["1347-4065"]}, DOI={10.35848/1347-4065/ac2012}, abstractNote={The generation of ultrasonic surface waves with lasers has become a useful noncontact NDT&E tool. This laser ultrasound technique provides a very flexible and simple method for noncontact and remote generation of ultrasonic surface waves, and has the advantage that various wave shapes can be easily produced by changing the shape of the beam that is illuminating the target. In this work, a laser ultrasound NDT&E method is proposed for defect localization by incorporating an omni-arrayed patterned candle soot nanoparticles-polydimethylsiloxane (CSNP-PDMS) patch. The omni-arrayed CSNP-PDMS patch generates a surface wave with a selective range of frequency, and an omni-directional signal with high amplitude, which surpasses the limitation of the line-arrayed patch. Further, the arrival time algorithm was adopted to validate the effectiveness of the omni-directional patch for 2D damage detection, which in turn the maximum magnitude of contour mapping from calculation agrees well with the true defect location.}, number={10}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Kim, Taeyang and Kim, Howuk and Jiang, Xiaoning}, year={2021}, month={Oct} }
 @article{kim_kim_garcia_fang_jiang_2021, title={Liquid metallic laser ultrasound transducer for high-temperature applications}, volume={118}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0046052}, DOI={10.1063/5.0046052}, abstractNote={This study aims to investigate a laser ultrasound (LUS) transducer for high-temperature (>100 °C) applications. For decades, many researchers have investigated efficient LUS transducers, yet studies on laser ultrasound transducers capable of performing at the high-temperature condition are rarely found in the literature. Most current LUS transducers still utilize a polymer-based composite material, that is, not stable at varying temperature conditions. This study introduces a liquid metallic (LM) LUS transducer that utilizes field's metal, which has a high thermal expansion (∼3 × 10−4 K−1). We hypothesized that such a high thermal expansion of the liquid metal can effectively produce laser-generated ultrasound waves, substituting for conventional polymer-based transducers. A numerical simulation predicted that the LM LUS transducer would produce higher LUS intensity (∼22 dB) than that without the LUS transducer. Experiment results confirmed that the LM transducer effectively intensifies the ultrasound wave signals, obtaining a signal-to-noise gain over 30 dB. Moreover, the transducer was found capable of transmitting detectable wave packets in relatively high-temperature conditions (∼400 °C), while conventional candle soot nanoparticle-polydimethylsiloxane could not perform stably at these elevated temperatures. The investigations introduced in this article are scientifically significant since we demonstrated the engineering feasibility of liquid metallic materials for LUS transducers.}, number={18}, journal={APPLIED PHYSICS LETTERS}, author={Kim, Howuk and Kim, Kyunghoon and Garcia, Nicholas and Fang, Tiegang and Jiang, Xiaoning}, year={2021}, month={May} }
 @article{zhang_wu_goel_kim_peng_kim_dayton_gao_jiang_2021, title={Magneto-sonothrombolysis with combination of magnetic microbubbles and nanodroplets}, volume={116}, ISSN={["1874-9968"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85107639068&partnerID=MN8TOARS}, DOI={10.1016/j.ultras.2021.106487}, abstractNote={This paper reports a novel technique using the rotational magnetic field oscillation and low-intensity sub-megahertz ultrasound stimulation of magnetic microbubbles (MMBs) to promote the nanodroplets (NDs) phase transition and improve the permeation of NDs into the blood clot fibrin network to enhance the sonothrombolysis efficiency. In this study, the influence of different treatment methods with a combination of MMBs and NDs on the thrombolysis rate of both unretracted and retracted clots were investigated, including the stable and inertial cavitation, tPA effects, MMBs/NDs concentration ratio, sonication factors (input voltage, duty cycle) and rotational magnetic field factors (flux density, frequency). We demonstrated that tPA-mediated magneto-sonothrombolysis in combining NDs with MMBs could significantly enhance in vitro lysis of both unretracted clots (85 ± 8.3%) and retracted clots (57 ± 6.5%) in a flow model with 30 min treatment. The results showed that the combination of MMBs and NDs substantially improves in vitro lysis of blood clots with an unprecedented lysis rate.}, journal={ULTRASONICS}, author={Zhang, Bohua and Wu, Huaiyu and Goel, Leela and Kim, Howuk and Peng, Chang and Kim, Jinwook and Dayton, Paul A. and Gao, Yu and Jiang, Xiaoning}, year={2021}, month={Sep} }
 @article{kim_yuan_2020, title={Adaptive signal decomposition and dispersion removal based on the matching pursuit algorithm using dispersion-based dictionary for enhancing damage imaging}, volume={103}, ISSN={["1874-9968"]}, DOI={10.1016/j.ultras.2020.106087}, abstractNote={This paper aims to develop a method for high-resolution damage imaging for a sparsely distributed sensor network on a plate-like structure. Techniques for dispersion removal and signal decomposition are indispensable to accurate damage localization. By combining the dispersion-removed wave packets with the damage-imaging algorithm, a point-like damage can be precisely localized. In this article, a matching pursuit algorithm was utilized to decompose overlapping wave packets and then recompress the dispersion. The matching pursuit dictionary was constructed based on an asymptotic solution of the dispersion relation for Lamb waves in toneburst wave packets. The dispersion-based Hanning-window dictionary provided the parametric information for the extracted wave packets, such as propagation time-delay, dispersion extent, and phase. The parameters were leveraged for the dispersion-removal algorithm. Results of the simulation indicate that the proposed algorithm is capable of recompressing multiple dispersive wave packets with the different modes. Finally, the proposed approach was validated by the results of the experiment using a sparse array of piezoelectric wafers on an aluminum plate. Extracting the parameters of individual wave packets and removing the dispersion through matching pursuit, the algorithm for minimum-variance imaging produced a high-quality image with a fine spatial resolution. The image artifacts were significantly suppressed, and the accuracy was improved by 62.1% compared to conventional minimum-variance imaging.}, journal={ULTRASONICS}, author={Kim, Howuk and Yuan, Fuh-Gwo}, year={2020}, month={Apr} }
 @article{yu_kim_kim_barange_jiang_so_2020, title={Direct Acoustic Imaging Using a Piezoelectric Organic Light-Emitting Diode}, volume={12}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.0c05615}, abstractNote={Conventional ultrasonic imaging requires acoustic scanning over a target object using a piezoelectric transducer array, followed by signal processing to reconstruct the image. Here, we report a novel ultrasonic imaging device that can optically display an acoustic signal on the surface of a piezoelectric transducer. By fabricating an organic light-emitting diode (OLED) on top of a piezoelectric crystal, lead zirconate titanate (PZT), an acousto-optical piezoelectric OLED (p-OLED) transducer is realized, converting an acoustic wave profile directly to an optical image. Because of the integrated device architecture, the resulting p-OLED features a high acousto-optic conversion efficiency at the resonance frequency, providing a piezoelectric field to drive the OLED. By incorporating an electrode array in the p-OLED, we demonstrate a novel tomographic ultrasound imaging device that is operated without a need for conventional signal processing.}, number={32}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Yu, Hyeonggeun and Kim, Jinwook and Kim, Howuk and Barange, Nilesh and Jiang, Xiaoning and So, Franky}, year={2020}, month={Aug}, pages={36409–36416} }
 @article{goel_wu_kim_zhang_kim_dayton_xu_jiang_2020, title={EXAMINING THE INFLUENCE OF LOW-DOSE TISSUE PLASMINOGEN ACTIVATOR ON MICROBUBBLE-MEDIATED FORWARD-VIEWING INTRAVASCULAR SONOTHROMBOLYSIS}, volume={46}, ISSN={["1879-291X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85086524519&partnerID=MN8TOARS}, DOI={10.1016/j.ultrasmedbio.2020.03.012}, abstractNote={Previous work revealed that a forward-viewing intravascular (FVI) transducer can be used for microbubble (MB)-mediated sonothrombolysis and that the clot lysis was dependent on MB concentration. This study examined the effects of combining tissue plasminogen activator (tPA) with MB-mediated FVI sonothrombolysis. In vitro clot lysis and passive cavitation experiments were conducted to study the effect of low-dose tPA in FVI sonothrombolysis with varying MB concentrations. Enhanced FVI sonothrombolysis was observed in cases in which ultrasound (US) was combined with tPA or MBs compared with control, tPA alone or US alone. The lysis rate of US + tPA + MBs was improved by up to 130%, 31% and 8% for MB concentrations of 106, 107 and 108 MBs/mL, respectively, compared with MBs + US alone. Changes in stable and inertial cavitation doses were observed, corresponding to changes in clot lysis in MB-mediated FVI sonothrombolysis with and without tPA.}, number={7}, journal={ULTRASOUND IN MEDICINE AND BIOLOGY}, author={Goel, Leela and Wu, Huaiyu and Kim, Howuk and Zhang, Bohua and Kim, Jinwook and Dayton, Paul A. and Xu, Zhen and Jiang, Xiaoning}, year={2020}, month={Jul}, pages={1698–1706} }
 @article{kim_cui_chang_kim_zhu_jiang_2020, title={Flexible 1–3 Composite Ultrasound Transducers With Silver-Nanowire-Based Stretchable Electrodes}, volume={67}, url={https://doi.org/10.1109/TIE.2019.2937063}, DOI={10.1109/TIE.2019.2937063}, abstractNote={In this article, a flexible piezo-composite transducer composed of the active piezoelectric material (PZT-5H) and passive polymer matrix [polydimethylsiloxane (PDMS)] is developed to achieve excellent flexibility, sensitivity, and bandwidth for biomedical and industrial applications. The flexible electrodes [silver nanowires (AgNWs) mixed with PDMS] are deposited on the transducers using a spray coating method, providing a sufficient conductivity of an electrode through repeated bending tests. The flexible 1–3 composite transducer exhibits robust mechanical flexibility (curved radius <5 mm) without failure due to the stretchable mechanical properties of PDMS and AgNWs network, which indicates that the AgNW/PDMS electrode is a promising alternative to conventional metal-type electrodes, such as Au film. The acoustic characterization suggests that the −6 dB fractional bandwidth (∼49%) and transmitting sensitivity (∼107 mV/V) of the prototyped transducer are promising for nondestructive testing, biomedical imaging, and therapy.}, number={8}, journal={IEEE Transactions on Industrial Electronics}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Kim, Taeyang and Cui, Zheng and Chang, Wei-Yi and Kim, Howuk and Zhu, Yong and Jiang, Xiaoning}, year={2020}, month={Aug}, pages={6955–6962} }
 @article{kim_wu_cho_zhong_mahmood_lyerly_jiang_2020, title={Miniaturized Intracavitary Forward-Looking Ultrasound Transducer for Tissue Ablation}, url={https://doi.org/10.1109/TBME.2019.2954524}, DOI={10.1109/TBME.2019.2954524}, abstractNote={Objective: This paper aims to develop a miniaturized forward-looking ultrasound transducer for intracavitary tissue ablation, which can be used through an endoscopic device. The internal ultrasound (US) delivery is capable of directly interacting with the target tumor, resolving adverse issues of currently available US devices, such as unintended tissue damage and insufficient delivery of acoustic power. Methods: To transmit a high acoustic pressure from a small aperture (<; 3 mm), a double layer transducer (1.3 MHz) was designed and fabricated based on numerical simulations. The electric impedance and the acoustic pressure of the actual device was characterized with an impedance analyzer and a hydrophone. Ex vivo tissue ablation tests and temperature monitoring were then conducted with porcine livers. Results: The acoustic intensity of the transducer was 37.1 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> under 250 Vpp and 20% duty cycle. The tissue temperature was elevated to 51.8 °C with a 67 Hz pulse-repetition frequency. The temperature profile in the tissue indicated that ultrasound energy was effectively absorbed inside the tissue. During a 5-min sonification, an approximate tissue volume of 2.5 × 2.5 × 1.0 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> was ablated, resulting in an irreversible lesion. Conclusion: This miniaturized US transducer is a promising medical option for the precise tissue ablation, which can reduce the risk of unintended tissue damage found in noninvasive US treatments. Significance: Having a small aperture (2 mm), the intracavitary device is capable of ablating a bio tissue in 5 min with a relatively low electric power (<; 17 W).}, journal={IEEE Transactions on Biomedical Engineering}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Kim, Howuk and Wu, Huaiyu and Cho, Namwoo and Zhong, Pei and Mahmood, Kamran and Lyerly, Herbert Kim and Jiang, Xiaoning}, year={2020}, month={Jul}, pages={1–1} }
 @article{kim_kim_morrow_jiang_2020, title={Stress Measurement of a Pressurized Vessel Using Ultrasonic Subsurface Longitudinal Wave With 1-3 Composite Transducers}, volume={67}, ISSN={["1525-8955"]}, url={https://doi.org/10.1109/TUFFC.2019.2941133}, DOI={10.1109/TUFFC.2019.2941133}, abstractNote={This article aims to develop a stress-sensing method for a pressurized vessel based on subsurface longitudinal (SSL) waves confined in a specific waveform by using 1-3 composite transducers. Although ultrasonic SSL waves have been commonly utilized for stress sensing, wave excitation under the predefined function using the composite-type transmitter is not well studied. In this article, composite-type transducers having a wide frequency bandwidth (> 60%) and a predominant thickness mode are utilized to enhance the signal intensity of the SSL wave and the accuracy of the sensor by incorporating a specific toneburst waveform. Finite element analysis demonstrates that the signal intensity of the composite-type transducer is up to 45.3% higher than that of a single-phase transducer. Pulse-echo tests reveal that the frequency bandwidth of the developed transducer reaches up to 60.7% and is, therefore, sufficient (> 57.0%) to transmit and receive Hanning-windowed toneburst signals. Results of stress sensing affirm a linear relationship between the time delay of SSL wave and the mechanical stress of a pressurized vessel (0.335 ns/MPa). Accordingly, the regression model is constructed via principal component regression (PCR) under temperature-varying condition. PCR has a less significant degree of error (0.62 MPa) compared to that of a typical least square regression (9.49 MPa).}, number={1}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Kim, Howuk and Kim, Taeyang and Morrow, Daniel and Jiang, Xiaoning}, year={2020}, month={Jan}, pages={158–166} }
 @article{kim_chang_kim_jiang_2020, title={Stress-Sensing Method via Laser-Generated Ultrasound Wave Using Candle Soot Nanoparticle Composite}, volume={67}, url={https://doi.org/10.1109/TUFFC.2020.2989035}, DOI={10.1109/TUFFC.2020.2989035}, abstractNote={This article aims to develop a semi-noncontact stress-sensing system using a laser-generated ultrasound (LGU) wave assisted by candle soot nanoparticle (CSNP) composite. While the acoustoelastic effect is commonly targeted to measure the stress level, efforts to combine it with the LGU wave signal have been lacking due to weak signal intensity. In this study, the CSNP-based transducer is designed to potentiate the photoacoustic energy conversion. To demonstrate the wave propagation with the designed parameters, a numerical simulation was first conducted. The experimental results showed that a laser intensity of 6.5 mJ/cm2 was enough to generate the subsurface longitudinal (SSL) wave from the CSNP composite transducer. The normal beam projection is the most effective wave-generation method, exhibiting the highest signal magnitude compared with inclined projection cases. Finally, the laser-assisted stress-sensing system was assessed by increasing the internal pressure of an air tank. The sensitivity of the developed sensor system was estimated to be 0.296 ns/MPa, showing a correlation of 0.983 with the theoretical prediction. The proposed sensing system can be used to monitor the structural integrity of nuclear power plants.}, number={9}, journal={IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Kim, Howuk and Chang, Wei-Yi and Kim, Taeyang and Jiang, Xiaoning}, year={2020}, month={Sep}, pages={1867–1876} }
 @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{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{zhang_kim_wu_gao_jiang_2019, title={Sonothrombolysis with magnetic microbubbles under a rotational magnetic field}, volume={98}, ISSN={["1874-9968"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85067191804&partnerID=MN8TOARS}, DOI={10.1016/j.ultras.2019.06.004}, abstractNote={Thrombosis is an extremely critical clinical condition where a clot forms inside a blood vessel which blocks the blood flow through the cardiovascular system. Previous sonothrombolysis methods using ultrasound and microbubbles (MBs) often have a relatively low lysis rate due to the low microbubbles concentration at clot region caused by blood flow in the vessel. To solve this problem, the magnetic microbubbles (MMBs) that can be retained by an outer magnetic field against blood flow are used in this study. Here we report the development of a new method using the rotational magnetic field to trap and vibrate magnetic microbubbles at target clot region and then using an intravascular forward-looking ultrasound transducer to activate them acoustically. In this study, we investigated the influence of different blood flow conditions, vessel occlusion conditions (partial and fully occluded), clot ages (fresh, retracted), ultrasound parameters (input voltage, duty cycle) and rotational magnetic field parameters (amplitude, frequency) on the thrombolysis rate. The results showed that the additional use of magnetic microbubbles significantly enhances in vitro lysis of blood clot.}, journal={ULTRASONICS}, author={Zhang, Bohua and Kim, Howuk and Wu, Huaiyu and Gao, Yu and Jiang, Xiaoning}, year={2019}, month={Sep}, pages={62–71} }
 @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{kim_yuan_2018, title={Enhanced damage imaging of a metallic plate using matching pursuit algorithm with multiple wavepaths}, volume={89}, ISSN={["1874-9968"]}, DOI={10.1016/j.ultras.2018.01.014}, abstractNote={Waveforms received by sensors resulting from multiple wavepaths overlap and are hard to interpret. Because of this difficulty, they are usually intentionally ignored, thereby only the first arrival of wave mode being used for damage localization. This article proposes an imaging algorithm for damage localization by incorporating multiple wavepaths using piezoelectric wafers affixed on a metallic plate. Matching pursuit (MP) algorithm to enhance image quality is adopted for separating each wave packet individually. MP algorithm is an adaptive time-frequency signal decomposition technique that matches the best-fit elementary atom functions from an overcomplete dictionary. This study proposes a new dictionary composed of atom functions that constitute possible wave packets propagated by an excitation of Hann-windowed toneburst. The proposed dictionary converges faster and separates individual wave packets more accurately than typical Gaussian based dictionaries. Simulated studies first confirm the performance of MP algorithm with the proposed dictionary in comparison with those using conventional non-adaptive time-frequency analysis as well as MP with heuristic Gaussian-based dictionaries. The results of this study validate the proposed algorithm that multiple wavepaths can localize the damage with three to four piezoelectric wafers versus typical approaches employing only primary scattered waves.}, journal={ULTRASONICS}, author={Kim, Ho-Wuk and Yuan, Fuh-Gwo}, year={2018}, month={Sep}, pages={84–101} }
 @article{kim_yuan_2017, title={Damage Imaging of an Isotropic Plate Using Matching Pursuit Algorithm}, volume={10168}, ISSN={["1996-756X"]}, DOI={10.1117/12.2258691}, abstractNote={A matching pursuit (MP) algorithm is effective tool to decompose the overlapped wave packets in a signal so that each wave mode can be identified. For the successful separations of the wave packets, an atom function should be properly designed, that can well resemble the physical features of the signal of interest. In this paper, a novel atom function for the MP algorithm is proposed based on the wave propagating model due to an excitation of a Hann-windowed toneburst signal, which performs very accurately compared to the MP algorithm with the existing Gaussian-type atom functions. The decomposed wave packets, including the directly scattered wave from damage as well as the reverberant waves from the free edges of the plate, via the MP method are employed in the damage imaging algorithm, highlighting the damaged location with higher intensity than the conventional algorithm utilizing only a direct reflected wave. The proposed approach is verified from the experiment where four piezoelectric wafers can accurately identify the damage location in a plate.}, journal={SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2017}, author={Kim, H. W. and Yuan, F. G.}, year={2017} }