Simple-to-Apply Wetting Model to Predict Thermodynamically Stable and Metastable Contact Angles on Textured/Rough/Patterned Surfaces

Abstract

Rough/patterned/textured surfaces with nano/microcavities that broaden below the surface—known as “re-entrants”—can be omniphobic (macroscopic contact angle greater than 90° for both water and oils). The existing theoretical models that explain the effects of texture on wetting are complex and do not provide a simple procedure for predicting the thermodynamically stable and metastable states and their corresponding contact angles (for example, wetting states that involve partially filled cavities). Here, we develop a simple-to-apply wetting model that allows for (1) predicting a priori the wetting state (partially or fully filled) of the cavities both under and outside the liquid droplet and the corresponding macroscopic contact angles on any type of textured surface; (2) determining the conditions under which metastable states exist; and (3) engineering specific nano/microtextures that yield any desired macroscopic contact angle, θt, for a given intrinsic contact angle θ0. Subsequently, we experimentally...