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The kinetics of electrochemical reactions is controlled by diffusion processes of charge carriers across a boundary layer between the electrode and the electrolyte, which result in a shielding of the electric field inside the electrolyte and a concentration gradient across this boundary layer. In accumulators the diffusion rate determines the rather long time needed for charging, which is a major drawback for electric mobility. This diffusion boundary can be removed by acoustic streaming in the electrolyte induced by surface acoustic waves propagating of the electrode, which results in an increase of the charging current and thus in a reduction of the time needed for charging. For a quantitative study of the influence of acoustic streaming on the charge transport an electropolishing cell with vertically oriented copper electrodes and diluted H 3 PO 4 -Propanol electrolytes were used. Lamb waves with various excitation frequencies were exited on the anode with different piezoelectric transducers, which induced acoustic streaming in the overlaying electrolytic liquid. An increase of the polishing current of up to approximately 100 % has been obtained with such a set-up.

With an acoustic levitator small particles can be aggregated near the nodes of a standing pressure field. Furthermore it is possible to atomize liquids on a vibrating surface. We used a combination of both mechanisms and atomized several liquids simultaneously, consecutively and emulsified in the ultrasonic field. Using a high-speed camera we observed the coagulation of the spray droplets into single large levitated droplets resolved in space and time. In case of subsequent atomization of two components the spray droplets of the second component were deposited on the surface of the previously coagulated droplet of the first component without mixing.