Flexural bending resonance of acoustically levitated glycerol droplet

A levitated glycerol droplet supported by an acoustic standing wave, when subject to modulated field at frequency on the order of 150 Hz, behaves as a solid plate and exhibits flexural bending resonance rather than the conventional equatorial star-shape oscillations. Three oscillation modes are observed: seesaw, saddleback, and monkey saddle with the increasing energy levels. The finite element analysis generates droplet shapes consistent with the experimental observation and yields apparent plate flexural rigidity in terms of surface tension and aspect ratio of plate thickness to diameter. High viscosity leads to the plate-like behavior of the droplet.