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Date:  Fri, February 21, 2020
Time:  10:30am - 11:30am
Location:  Holmes Hall 389
Speaker:  Li Quan, candidate for PhD, University of Texas at Austin

Abstract
Sound waves are ubiquitous in our daily life, from communications with our neighbors to sophisticated surface acoustic wave technology in our electronic gadgets. Strong interactions between matter and sound waves not only provide an important degree of freedom to manipulate sound waves, but they also offer a useful tool to extract information from unknown bodies. Typical applications are ultrasound imaging, ultrasonic drug delivery, non-destructive testing, etc. However, the precise control of sound propagation is still a big challenge. Advanced functional materials and metamaterials have been providing new opportunities in acoustics, enabling scientists and engineers to explore new ways to tailor and control sound-matter interactions in ways not available in nature. In this talk, I will address some of the basic open questions in the exploration of acoustic metamaterials. First, I will discuss the powerful opportunities of acoustic metamaterials in controlling sound radiation and scattering. Low-frequency sound waves travel with similar properties in all directions, hence we are typically able to hear another person’s voice or the sound emitted from a small source no matter whether we stand in front, left or right of the speaker. By locally engineering the acoustic impedance of a metasurface, we can overcome these limitations and collimate sound wave radiation. Endowing this platform with nonlocal phenomena opens even more exciting opportunities, such as wavefront steering towards extreme angles with large efficiency, asymmetrical reflection, nonreciprocal and hyperbolic sound propagation. In my talk, I will discuss the basic phenomena underlying this unusual control of sound propagation, the opportunities for technology, and my vision for the future development of this field, with applications in quantum systems, cancer therapy, and medical phenotyping.

Bio
Li Quan is currently a Ph.D. candidate in the Department of Electrical and Computer Engineering at the University of Texas at Austin. He received his B.S. and M.S. degree in acoustics from Nanjing University in 2011 and 2014, respectively. After one year working as a cellphone audio engineer, in 2015, he joined the Metamaterials & Plasmonics Research Laboratory at the University of Texas at Austin. His research mainly aims to understand the physical mechanisms of interactions between waves and matters, especially in the scope of acoustics, design novel devices, and seek their possible biomedical and industrial applications. Li Quan's research span over a broad scope of acoustics, such as acoustic metamaterials, ultrasound non-destructive testing, the physical model of MEMS microphones, etc. To date, he has authored and/or co-authored 14 journal papers, 16 conference papers and 4 patents, among which are published in highly selective journals, including 2 Nature Communications and 3 Physical Review Letters. He is also a reviewer for 18 international peer-review journals.