Volume 79, Number 5, September 2007
Article Number 56005
Number of page(s) 5
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 08 August 2007
EPL, 79 (2007) 56005
DOI: 10.1209/0295-5075/79/56005

Wicking within forests of micropillars

C. Ishino1, 2, M. Reyssat1, E. Reyssat1, K. Okumura2 and D. Quéré1

1  Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, ESPCI - 10 rue Vauquelin, 75005 Paris, France
2  Department of Physics, Graduate School of Humanities and Sciences, Ochanomizu University Tokyo 112-8610, Japan

received 18 May 2007; accepted in final form 19 July 2007; published September 2007
published online 8 August 2007

We describe how a wetting liquid brought into contact with a forest of micropillars impregnates this forest. Both the driving and the viscous forces depend on the parameters of the texture (radius b and height h of the pillars, pitch p of the network) and it is found that two different limits characterize the dynamics of wicking. For small posts (h < p), the film progresses all the faster since the posts are high, allowing a simple control of this dynamics. For tall pillars (h > p), the speed of impregnation becomes independent of the pillar height, and becomes mainly fixed by the radius of the posts.

68.08.Bc - Wetting .
68.35.Md - Surface thermodynamics, surface energies .
85.40.Hp - Lithography, masks and pattern transfer .

© Europhysics Letters Association 2007