Reaching the thermodynamic limit of wicking on textured surfaces

Abstract

Wicking in a capillary tube could happen as long as the liquid contact angle is smaller than 90 degree, making it possible for weak hydrophilic liquids to spontaneously invade the tube. For textured surfaces, energy minimization argument predicts the same. However, wicking of weak hydrophilic liquids on textured surfaces has not been possible due to energy barriers induced by the textures. We demonstrate how these barriers could be avoided by adjusting the shape and arrangement of the pillars, thus the wettability required for wicking reaches the theoretical limit. An unprecedented wicking contact angle of 82 degree is reported. More surprisingly, wicking coefficients of such surfaces can be larger than that of rectangular grooves at the same porosity. These findings may significantly advance biomedical and thermal management technologies.