Impalement of fakir dropsM. Reyssat1, J. M. Yeomans2 and D. Quéré1
1 Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, ESPCI - 75005 Paris, France
2 The Rudolf Peierls Centre for Theoretical Physics, University of Oxford - 1 Keble Road, Oxford OX1 3NP, UK
received 7 September 2007; accepted in final form 19 November 2007; published January 2008
published online 20 December 2007
Water drops deposited on hydrophobic materials decorated with dilute micro-posts generally form pearls. Owing to the hydrophobicity of the material, the drop sits on the top of the posts. However, this "fakir state" is often metastable: if the drop impales inside the texture, its surface energy is lowered. Here we discuss the transition between these two states, considering the drop size as a parameter for inducing this transition: remarkably, it is found that a drop impales when it becomes small, which is interpreted by considering its curvature. This interpretation allows us to propose different recipes for avoiding this detrimental effect.
68.08.-p - Liquid-solid interfaces.
68.08.Bc - Wetting.
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