Non-Equilibrium Gibbs' Criterion for Completely Wetting Volatile Liquids

TL;DR

This paper introduces a modified Gibbs' criterion accounting for evaporation effects, demonstrating a dynamic critical angle for depinning of volatile liquids that increases with evaporation rate, supported by experiments and theory.

Contribution

It presents the first experimental and theoretical evidence of a non-equilibrium depinning criterion for volatile liquids, extending Gibbs' criterion to include evaporation effects.

Findings

Depinning angle increases with evaporation rate.

Experimental and theoretical agreement on the modified criterion.

Depinning occurs at a dynamically produced critical angle.

Abstract

During the spreading of a liquid over a solid substrate, the contact line can stay pinned at sharp edges until the contact angle exceeds a critical value. At (or sufficiently near) equilibrium, this is known as Gibbs' criterion. Here, we show both experimentally and theoretically that for completely wetting volatile liquids there also exists a dynamically-produced critical angle for depinning, which increases with the evaporation rate. This suggests that one may introduce a simple modification of the Gibbs' criterion for (de)pinning, that accounts for the non-equilibrium effect of evaporation.