Melting and solidification of acoustically levitated drops

A single axis acoustic levitator has been used to suspend a drop of commercial grade succinonitrile in air. The drop is subjected to thermal cycling in order to observe melting and solidification of the drop in the acoustically levitated state. Melting takes place over a temperature rise of a few degrees, which is typical for an impure material. Solidification initially progresses along the drop surface because of the temperature gradient developed in the drop. The resultant solid drop shows a dendritic surface feature with a cavity in some circumstances. An attempt is made to calculate the growth velocity of the dendrites.