Small Scale Acoustic Streaming near a Locally Excited Membrane

Experiments are described involving a membrane set into oscillatory motion (40 kc) by contact with a vibrating tip of small area. Small scale acoustic streaming is observed in a liquid above the membrane, especially near the area of contact; its character depends on the membrane tension. Loosely adhering films are removed from certain areas of the membrane. The cleared areas form a pattern, indicative of the surface stress distribution set up by the eddying liquid. The main features of the reported results are accounted for, at least, qualitatively, by application of acoustic streaming theory to idealized cases. Referring to the above results, the possibility is discussed of motion induced in biological cells by external vibrating bubbles.