Spontaneous dewetting of a hydrophobic micro-structured surface

Inspired by recent experimental observations and natural phenomena that spontaneous dewetting transition occurs on a hydrophobic micro-structured surface, a thermodynamic model of a condensed water droplet on a micro-pillar arrayed surface is established in order to disclose the mechanical mechanism. Based on a general model of an arbitrary-shaped micro-structured surface, surfaces with conical, rectangular and parabolic micro-pillars are investigated. A critical water droplet volume is found, beyond which dewetting transition can be realized. The effect of the micro-pillar's size and intrinsic contact angle on the free energy difference and critical water droplet volume are further studied. The theoretical model may provide a possible explanation for the abnormal Wenzel wetting state of condensed water droplets on lotus leaves and the anti-fogging behavior of a mosquito's compound eyes. The present results should be very useful for the biomimetic design of functional dewetting surfaces in practical applications.