Purcell effect of phase-transitioning nanodroplets enhanced acoustic radiation and scattering
Date: 2026/06/03 – 2026/06/03
Academic Seminar: Purcell effect of phase-transitioning nanodroplets enhanced acoustic radiation and scattering
Speaker: Chengzhi Shi, Associate Professor at University of Michigan
Time: 9:00 p.m., June 3, 2026 (Beijing Time)
Location: Online
Abstract
Microscale ultrasound devices are increasingly important for medical diagnostics and targeted therapies, yet achieving strong acoustic output at small scales remains challenging. Conventional strategies, including transducer arrays and MEMS components, often fail to satisfy the stringent requirements of compactness, flexibility, and power efficiency necessary for wearable applications. These challenges arise from fundamental trade-offs between miniaturization, acoustic intensity, and biological safety. We present a new strategy that leverages the acoustic Purcell effect, enabled through specially engineered perfluorocarbon nanodroplets (PFCnDs) designed to boost ultrasound emission. A theoretical framework for nanodroplet-enhanced Purcell effect is developed and experimentally confirmed through ultrasound emission measurements—the first demonstration of its kind. By tailoring the acoustic environment around the droplets, we achieve an acoustic Purcell factor normalized by droplet diameter (APF/D) of 1.6×10⁵ ± 2.6×10² m⁻¹, surpassing previous acoustic Purcell designs by two orders of magnitude. Furthermore, tunable droplet size and concentration allow precise control over Purcell-enhanced pressure radiation, mediated by the acoustic density of states. In B-mode imaging, PFCnDs operating in the Purcell-enhanced regime deliver 42 ± 1.4 dB contrast gain relative to conventional ultrasound, arising from enhanced acoustic scattering. This work establishes a nanoscale acoustic Purcell framework for efficient ultrasound emission and marks a key advance toward integrating nanophononic design with high-contrast, ultrasound-based biomedical diagnostics and therapeutic platforms.
Biography
Dr. Chengzhi Shi is an Associate Professor in the Department of Mechanical Engineering at the University of Michigan. Before joining the University of Michigan, he was an Assistant Professor in the GWW School of Mechanical Engineering at Georgia Tech. Dr. Shi earned his Ph.D. degree from the University of California, Berkeley in 2018 and his M.S. and B.S. degrees from Shanghai Jiao Tong University in 2013 and 2010. His research interests include physical acoustics, wave propagation, metamaterials, ultrasound imaging, and therapeutic ultrasound. He has published many highly cited papers in renowned journals including Science, PNAS, and Nature Communications. Dr. Shi has also won prestigious awards including the NSF CAREER and the ONR YIP awards.