Acoustic angular momentum is a physical quantity characterizing the rotation of pressure and local particle velocity fields. The acoustic angular momentum was first observed in vortex waves and was found to have many interesting physics including pseudospin based topological effects, spin-momentum locking, and trapping potential for contactless particle manipulations. In this talk, Dr. Shi will focus on the discussion of the fundamentals and applications of the shear induced by the unique wave pattern of acoustic angular momentum in medical therapies. The induced shear stress drastically enhances fibrinolysis in blood clots that remarkably reduce the required treatment time with low risk of hemorrhage, especially in treating large, completely occluded, acute clots. Such capability makes the vortex ultrasound based endovascular sonothrombolysis a life-saving tool for severe cerebral venous sinus thrombosis, which has an increasing trend among young patients due to the COVID-19 pandemic. In addition, the induced shear flow deforms and merges bubbles during cavitation in fluids, which significantly enhances acoustic cavitation. In this case, the histotrpsy driven by acoustic angular momentum has a significantly lower cavitation threshold with a much higher ablation power for the treatment of liver cancer, which is the third leading cause of cancer-related deaths worldwide.

Bio: 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.