Wicking within forests of micropillars

Abstract

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.