Core-Shell Particles that are Unresponsive to Acoustic Radiation Force

Abstract

Common sense dictates that particles in an ultrasonic standing wave should experience a nonzero radiation force, and be moved. However, the authors predict that layered particles can be engineered to ignore this force---akin to ``invisibility cloaking'' for sound. Establishing how to choose the material and thickness of the coating for an acoustically neutral object, this study opens possibilities for acoustophoretic methods of particle trapping, separation, and sorting in microfluidic devices.