Acoustically Driven Fluid and Particle Motion in Confined and Leaky Systems

Acoustic manipulation of fluids and particles garners increasing interest for use in medicine and biotechnology. One approach is based on actuation of confined, acoustically ``leaky'' systems, but finding accurate physical models for them has been stymied by a lack of relevant empirical data. To advance the field, the authors provide experimental benchmark results for particle trajectories in three dimensions, and describe them with a minimal numerical model. They reveal that a pseudo-standing wave drives acoustic streaming and the acoustic radiation force on suspended particles---important insight for developing clinical applications.