Europhys. Lett.
Volume 48, Number 3, November 1999
Page(s) 286 - 291
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 September 2002
DOI: 10.1209/epl/i1999-00479-1

Europhys. Lett, 48 (3), pp. 286-291 (1999)

Viscous drops rolling on a tilted non-wettable solid

D. Richard and D. Quéré

Laboratoire de Physique de la Matière Condensée, URA 792 du CNRS, Collège de France
75231 Paris Cedex 05, France

(received 10 May 1999; accepted in final form 3 September 1999)

PACS. 68.10$\rm -m$ - Fluid surfaces and fluid-fluid interfaces.
PACS. 68.15$\rm +e$ - Liquid thin films.


A viscous liquid drop sliding down an inclined solid that it partially wets runs all the faster since it is large. Here we examine what happens in the limit of very high contact angles, on a so-called super-hydrophobic surface. It is shown that a droplet rolls instead of sliding, which leads to a surprising law for the velocity as a function of the drop radius: the smaller the droplet, the larger the running velocity. A recent model of Mahadevan and Pomeau allows us to propose an explanation for this paradoxical behaviour.


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