Characterization of acousto-electric drop arrays with application to evaporation studies

Abstract

An acousto-electric levitator has been developed to study liquid drop and solid particle clusters and arrays. This device uses both an acoustic standing wave and a high dc electric field simultaneously to form and levitate several charged drops in a two-dimensional array in air. A 2-D theoretical model is employed to study the profile of the acoustic field and the forces that hold the arrays at the center of the levitator. A study of the evaporation of alkane drops and arrays has been performed. It is shown that when a minimal acoustic field is used to levitate drops (by compensating with an electric field), the evaporation rate in the acousto-electric levitator is almost the same as that of drops suspended by a glass fiber. The experimental results for an isolated drop are compared with the theory of a quasi-steady model. The point source method is used to calculate theoretically the results for array evaporation. Both single and multiple component drops are studied. [Work supported by NASA (NAG3-2147) and by NSF (CTS-9870015).]