Switching Direction of Liquid Flow by Amplification of Wetting Properties of Partilly Roughened Prism Array

Superhydrophilic and superhydrophobic surfaces inspired from nature have been developed for anti-fogging, anti-reflecting, water-repelling, anti-icing and self-cleaning films. The amplification of the hydrophilicity and hydrophobicity originates from surface roughness, particularly from their multiscale geometry. In this paper, we present a strategy to exploit the enhancement of wetting properties on roughened surfaces for switching the direction of unidirectional liquid flow on an opened microchannel. We exploit a unidirectional liquid spreading on a hierarchical two-face prism array, which have the symmetry in microscale while having the asymmetry in nanoscale. Based on the switching the direction of the lower critical angle, the transition of the surface chemistry results in the change of flow directions in an open channel.