@article{kim_zhang_wang_wu_xu_liu_moon_yamashita_ryu_liu_et al._2024, title={Electrical de-poling and re-poling of relaxor-PbTiO<sub>3</sub> piezoelectric single crystals without heat treatment}, volume={15}, ISSN={["2041-1723"]}, url={https://doi.org/10.1038/s41467-024-50847-3}, DOI={10.1038/s41467-024-50847-3}, abstractNote={Re-poling of unexpected partially depoled piezoelectric materials conventionally needs to be first fully depoled through annealing above their Curie temperature to revive piezoelectric performances. Here, we investigated de-poling and re-poling of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals under electric fields at room temperature. We found that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to successfully depolarize poled crystals at room temperature. We also demonstrated a reversible polarization switching process with a relaxor-PbTiO3 single crystal ultrasound transducer without device performance degradations. This experimental observation is supported by phase-field simulation, showing that alternating current electric fields can readily induce de-poling at room temperature, while direct current electric fields induce a transient depoled state only within an uncontrollable short period of time. The findings suggest new strategies for unprecedented in-device tailoring of the polarization states of ferroelectric materials. The authors find that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to depolarize poled relaxor-PbTiO3 single crystals at room temperature, without conventional heat treatment.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Kim, Hwang-Pill and Zhang, Mao-Hua and Wang, Bo and Wu, Huaiyu and Xu, Zhengze and Liu, Sipan and Moon, Sunho and Yamashita, Yohachi and Ryu, Jong Eun and Liu, Jun and et al.}, year={2024}, month={Jul} }
 @article{kreager_wu_chang_moon_mitchell_peng_huang_muller_tian_jiang_2024, title={High-Performance PMN-PT Single-Crystal-Based 1-3 Composite Transducer Integrated with a Biopsy Needle}, volume={14}, ISSN={["2079-6374"]}, url={https://www.mdpi.com/2079-6374/14/2/74}, DOI={10.3390/bios14020074}, abstractNote={To address the need for high-resolution imaging in lung nodule detection and overcome the limitations of the shallow imaging depth associated with high-frequency ultrasound and the complex structure of lung tissue, we successfully integrated 50 MHz ultrasound transducers with 18-gauge biopsy needles. Featuring a miniaturized size of 0.6 × 0.5 × 0.5 mm3, the 50 MHz micromachined 1-3 composite transducer was tested to perform mechanical scanning of a nodule within a lung-tissue-mimicking phantom in vitro. The high-frequency transducer demonstrated the ability to achieve imaging with an axial resolution of 30 μm for measuring nodule edges. Moreover, the integrated biopsy needle prototype exhibited high accuracy (1.74% discrepancy) in estimating nodule area compared to actual dimensions in vitro. These results underscore the promising potential of biopsy-needle-integrated transducers in enhancing the accuracy of endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNA) for clinical applications.}, number={2}, journal={BIOSENSORS-BASEL}, author={Kreager, Benjamin C. and Wu, Huaiyu and Chang, Wei-Yi and Moon, Sunho and Mitchell, Josh and Peng, Chang and Huang, Chih-Chung and Muller, Marie and Tian, Jian and Jiang, Xiaoning}, year={2024}, month={Feb} }
 @article{moon_xue_ganesh_shukla_kreager_cai_wu_zhu_sharma_jiang_2024, title={Ultrasound-Compatible Electrode for Functional Electrical Stimulation}, volume={12}, ISSN={["2227-9059"]}, url={https://doi.org/10.3390/biomedicines12081741}, DOI={10.3390/biomedicines12081741}, abstractNote={Functional electrical stimulation (FES) is a vital method in neurorehabilitation used to reanimate paralyzed muscles, enhance the size and strength of atrophied muscles, and reduce spasticity. FES often leads to increased muscle fatigue, necessitating careful monitoring of the patient's response. Ultrasound (US) imaging has been utilized to provide valuable insights into FES-induced fatigue by assessing changes in muscle thickness, stiffness, and strain. Current commercial FES electrodes lack sufficient US transparency, hindering the observation of muscle activity beneath the skin where the electrodes are placed. US-compatible electrodes are essential for accurate imaging and optimal FES performance, especially given the spatial constraints of conventional US probes and the need to monitor muscle areas directly beneath the electrodes. This study introduces specially designed body-conforming US-compatible FES (US-FES) electrodes constructed with a silver nanowire/polydimethylsiloxane (AgNW/PDMS) composite. We compared the performance of our body-conforming US-FES electrode with a commercial hydrogel electrode. The findings revealed that our US-FES electrode exhibited comparable conductivity and performance to the commercial one. Furthermore, US compatibility was investigated through phantom and in vivo tests, showing significant compatibility even during FES, unlike the commercial electrode. The results indicated that US-FES electrodes hold significant promise for the real-time monitoring of muscle activity during FES in clinical rehabilitative applications.}, number={8}, journal={BIOMEDICINES}, author={Moon, Sunho and Xue, Xiangming and Ganesh, Vidisha and Shukla, Darpan and Kreager, Benjamin C. and Cai, Qianqian and Wu, Huaiyu and Zhu, Yong and Sharma, Nitin and Jiang, Xiaoning}, year={2024}, month={Aug} }
 @article{xue_zhang_moon_xu_huang_sharma_jiang_2023, title={Development of a Wearable Ultrasound Transducer for Sensing Muscle Activities in Assistive Robotics Applications}, volume={13}, ISSN={["2079-6374"]}, url={https://doi.org/10.3390/bios13010134}, DOI={10.3390/bios13010134}, abstractNote={Robotic prostheses and powered exoskeletons are novel assistive robotic devices for modern medicine. Muscle activity sensing plays an important role in controlling assistive robotics devices. Most devices measure the surface electromyography (sEMG) signal for myoelectric control. However, sEMG is an integrated signal from muscle activities. It is difficult to sense muscle movements in specific small regions, particularly at different depths. Alternatively, traditional ultrasound imaging has recently been proposed to monitor muscle activity due to its ability to directly visualize superficial and at-depth muscles. Despite their advantages, traditional ultrasound probes lack wearability. In this paper, a wearable ultrasound (US) transducer, based on lead zirconate titanate (PZT) and a polyimide substrate, was developed for a muscle activity sensing demonstration. The fabricated PZT-5A elements were arranged into a 4 × 4 array and then packaged in polydimethylsiloxane (PDMS). In vitro porcine tissue experiments were carried out by generating the muscle activities artificially, and the muscle movements were detected by the proposed wearable US transducer via muscle movement imaging. Experimental results showed that all 16 elements had very similar acoustic behaviors: the averaged central frequency, −6 dB bandwidth, and electrical impedance in water were 10.59 MHz, 37.69%, and 78.41 Ω, respectively. The in vitro study successfully demonstrated the capability of monitoring local muscle activity using the prototyped wearable transducer. The findings indicate that ultrasonic sensing may be an alternative to standardize myoelectric control for assistive robotics applications.}, number={1}, journal={BIOSENSORS-BASEL}, author={Xue, Xiangming and Zhang, Bohua and Moon, Sunho and Xu, Guo-Xuan and Huang, Chih-Chung and Sharma, Nitin and Jiang, Xiaoning}, year={2023}, month={Jan} }
 @article{xue_wu_cai_chen_moon_huang_kim_peng_feng_sharma_et al._2024, title={Flexible Ultrasonic Transducers for Wearable Biomedical Applications: A Review on Advanced Materials, Structural Designs, and Future Prospects}, volume={71}, ISSN={["1525-8955"]}, url={https://doi.org/10.1109/TUFFC.2023.3333318}, DOI={10.1109/TUFFC.2023.3333318}, abstractNote={Due to the rapid developments in materials science and fabrication techniques, wearable devices have recently received increased attention for biomedical applications, particularly in medical ultrasound imaging, sensing, and therapy. Ultrasound is ubiquitous in biomedical applications because of its non-invasive nature, nonionic radiating, high precision, and real-time capabilities. While conventional ultrasound transducers are rigid and bulky, flexible transducers can be conformed to curved body areas for continuous sensing without restricting tissue movement or transducer shifting. This article comprehensively reviews the application of flexible ultrasound transducers in the field of biomedical imaging, sensing, and therapy. First, we review the background of flexible ultrasound transducers. Following that, we discuss advanced materials and fabrication techniques for flexible ultrasound transducers and their enabling technology status. Lastly, we highlight and summarize some promising preliminary data with recent applications of flexible ultrasound transducers in biomedical imaging, sensing, and therapy. We also provide technical barriers, challenges, and future perspectives for further research and development.}, number={7}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Xue, Xiangming and Wu, Huaiyu and Cai, Qianqian and Chen, Mengyue and Moon, Sunho and Huang, Ziping and Kim, Taeyang and Peng, Chang and Feng, Wuwei and Sharma, Nitin and et al.}, year={2024}, month={Jul}, pages={786–810} }
 @article{kreager_moon_mitchell_wu_peng_muller_huang_jiang_2023, title={Lung nodule biopsy guided using a 30 MHz ultrasound transducer: in vitro study}, volume={12488}, ISBN={["978-1-5106-6083-0"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.2658585}, abstractNote={Ultrasound is often favored in biopsy guidance since it is non-ionizing, inexpensive, portable, and has a high frame rate. However, imaging probes that operate at a low frequency may not be able to differentiate between tiny targets and surrounding tissues clearly, and at a high frequency, it suffers from tissue scattering and signals attenuation, which is hard to image deeper targets such as lung tissues. In this study, we developed a biopsy needle (with a size of 18 G) integrated with a 30 MHz high-frequency ultrasound transducer (axial resolution: ~ 100 µm) for the lung nodule biopsy in vitro test. To mimic contrasting biological tissues, a melamine foam-gelatin phantom was developed. With an advancing step of 0.5 mm, the distance from the biopsy needle to the gelatin-foam boundary was estimated by the speed of sound in gelatin and the time-of-flight of the echo signal. The results showed that the 30 MHz ultrasound transducer can map the geometry of the gelatin-foam boundary, indicating the capability of distinguishing tumor and healthy lung tissue with this ultrasound-guided biopsy technique.}, journal={HEALTH MONITORING OF STRUCTURAL AND BIOLOGICAL SYSTEMS XVII}, author={Kreager, Ben and Moon, Sunho and Mitchell, Josh and Wu, Huaiyu and Peng, Chang and Muller, Marie and Huang, Chih-Chung and Jiang, Xiaoning}, year={2023} }
 @article{moon_wu_zhang_kim_dayton_xu_jiang_2022, title={A Dual-Frequency Intravascular Ultrasound Transducer for Amplified Nanodroplet Vaporization Effects in Cavitation-Enhanced Sonothrombolysis}, ISSN={["1948-5719"]}, DOI={10.1109/IUS54386.2022.9958578}, abstractNote={Thromboembolism often leads to stroke, myocardial infarction, and other severe complications. There remains a need for new technologies for clinical thrombosis treatment. Sonothrombolysis mediated with cavitation-enhancing agents has shown promise in the treatment of thromboembolism in preclinical studies and clinical trials. Recent works have emphasized specifically efficient sonothrombolysis using phase-change nanodroplets, likely due to their generation of cavitation within the clot matrix. Yet, it has also been reported that nanodroplets might vaporize more effectively under high-frequency excitation and generate more cavitation with low-frequency excitation. Therefore, in this work, a dual-frequency (10 MHz/500 kHz) intravascular transducer intended for nanodroplet-specific sonothrombolysis was developed to improve clot mass reduction rate while retaining lower acoustic pressures than the typical nanodroplet vaporization threshold at sub-megahertz excitation (> 5 MPa). It results in a 34 % improvement of thrombolysis efficiency compared to a single low-frequency excitation.}, journal={2022 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IEEE IUS)}, author={Moon, Sunho and Wu, Huaiyu and Zhang, Bohua and Kim, Jinwook and Dayton, Paul A. and Xu, Zhen and Jiang, Xiaoning}, year={2022} }
 @article{xue_zhang_moon_xu_huang_sharma_jiang_2022, title={Development of a wearable ultrasound transducer for sensing muscle activities in assistive robotics applications: In vivo study}, ISSN={["1948-5719"]}, DOI={10.1109/IUS54386.2022.9958535}, abstractNote={People who suffer from the amputation of limbs or with mobility impairment due to methodological disorder sometimes require assistive robotics (AR), such as robotic prostheses and exoskeletons, to function satisfactorily and productively in daily life. Dynamic measurements of muscle voluntary activities are widely used to control AR, and sensors used to control AR should be non-invasive, effective, and wearable. Ultrasound (US) imaging is an effective method for measuring muscle activity. Nevertheless, conventional US transducers are cumbersome and inflexible, making them inconvenient for continuous monitoring of muscle activity for AR control. In light of no report available about using a flexible transducer for detecting muscle activities for AR, this work aims to develop a novel wearable US device for detecting muscle activities. In specific, a 16-element 10 MHz flexible sparse array was designed, fabricated, and characterized. The feasibility of monitoring muscle activity in different regions was demonstrated by an in vivo human experiment.}, journal={2022 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IEEE IUS)}, author={Xue, Xiangming and Zhang, Bohua and Moon, Sunho and Xu, Guo-Xuan and Huang, Chih-Chung and Sharma, Nitin and Jiang, Xiaoning}, year={2022} }