Vertical vibration of liquid drops on nano-structured surfaces

This paper reports on both ion track etching induced nano-structured surfaces with high hydrophobicity and the fundamental vibration modes of submillimeter drops supported by such surfaces. A drastic reduction in the hysteresis of the contact angles (Delta theta <= 6 degrees) substantially increases the mobility of the supported drop, which acquires a quasifree behaviour. The dependence of the oscillating modes on drop volume established experimentally is confronted to predictions of classical models dealing with free oscillations of droplets without gravity. (C) 2008 Elsevier B.V. All rights reserved.