Design and High-Resolution Characterization of Silicon Wafer-like Omniphobic Liquid Layers Applicable to Any Substrate

Abstract

Liquid fouling can reduce the functionality of critical engineering surfaces. Recent studies have shown that minimizing contact angle hysteresis is a promising strategy for achieving omniphobic (all-liquid repellent) properties, thereby inhibiting fouling. Prior omniphobic films can repel a broad range of liquids, but the applicability of these coatings has always been limited to silicon wafers or smooth glass. Here we develop a facile procedure to generate an omniphobic coating on any surface, including metals, paper, ceramics, etc. The coating involves depositing an ultrasmooth, silicon wafer-like silica layer and then treating this layer with a highly reactive chlorosilane, which grafts polydimethylsiloxane chains onto the surface. Negligible contact angle hysteresis (≤1°) for various liquids, including ultralow surface tension oils, alcohols, and fluoro-solvents, was achieved on many different substrates regardless of their initial roughness or chemistry. In fact, the contact angle hysteresis was so low we were forced to propose an alternate measurement technique, using tilt angles, that reduced the inherent errors associated with traditional contact angle goniometry. The coating's durability was characterized and, when it was damaged, could be repeatedly repaired, fully restoring the omniphobic properties to their initial state.