8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Thu 811:10-14:00P7.95Spontaneous spreading of liquid films on surfacescontaining micropillar arraysCraig Priest, 1 Ciro Semprebon, 1 and Martin Brinkmann 21 University of South Australia, Mawson Lakes Bvd, 5095, Mawson Lakes, Australia2 Max Planck Institute for Dynamics and Self-Organization, Goettingen, GermanyIt is well-known that surface topographies have a major influence on surface wettability, rangingfrom superhydrophobicity to spontaneous film formation (superhydrophilicity). [1] While the transitionbetween these two extremes has received much attention, the mechanism of spontaneous filmformation on partially hydrophobic, discontinuous topographies remains unclear. [2] We have directlyobserved and theoretically calculated the meniscus morphology at individual rows of pillarsof varied separation, height, and wettability to determine the criteria for spontaneous spreading ofthin (microscopic) liquid films. We show that the onset of spontaneous spreading in pillar arrays isdetermined, in part, by pinning events that affect the meniscus shape on surface topography, ratherthan a pure consideration of the global minimisation of interfacial energy. The various pinningregimes and their transient effects on the liquid morphology are identified.[1] J. Bico, U. Thiele, D. Quéré, Colloids and Surfaces bf 206, 41 (2002).[2] C. Priest, P. S. H. Forsberg, R. Sedev, J. Ralston, Proceedings of the 2nd European Conferenceon Microfluidics, Toulouse, France, FLU10-44 (2010).95