Observation and interpretation of SAW-induced regular and chaotic dynamics of droplet shape

The following four types of phenomena in the dynamical behavior of liquid drops placed on YZ-lithium niobate 15-MHz surface-acoustic-wave (SAW) delay line are observed and recorded as short movies. (i) Progressive acoustic transport of a drop. (ii) Vortex acoustic streaming inside a drop. (iii) The formation of quasi-stationary smoothed peak on the drop surface under the action of counter-propagating SAWs and its chaotic dynamics during evaporation on acetone drop. (iv) Self-sustained oscillation of such a peak on the drop surface in the case when the substrate has a slight slope with respect to the horizontal. The two last mentioned phenomena are new, to the best of the authors' knowledge. Various interpretations of the peak appearance on the drop surface in the filed of counter-propagating waves are discussed.