Worm-like instability of a vibrated sessile drop

¹ Université de Strasbourg, Institut Charles Sadron, CNRS - 23 Rue du Loess, BP 84047, F-67034 Strasbourg Cedex 2, France
² ENS de Lyon, Laboratoire de Physique, UMR CNRS 5672 - 46, allée d'Italie, F-69007 Lyon, France

Received: 28 May 2015
Accepted: 10 July 2015

Abstract

We study the effects of vertical sinusoidal vibrations on a liquid droplet with a low surface tension (ethanol) deposited on a solid substrate. In a precise range of amplitudes and frequencies, the drop exhibits a dramatic worm-like shape instability with a strong symmetry breaking, comparable to the one observed by Pucci et al. (Phys. Rev. Lett., 106 (2011) 024503) on a vibrated floating lens. However, the geometry of our system is much simpler since it does not involve the oscillation and deformation of a liquid-liquid-air contact line. We show that the Faraday waves appearing on the surface of the droplet control its shape and we draw a systematic phase diagram of the instability. A simple theoretical model allows us to derive a relation between the elongation of the droplet and the amplitude of the Faraday wave, in good agreement with measurements of both quantities.