Soft wetting with (a)symmetric Shuttleworth effect

TL;DR

This paper investigates how the Shuttleworth effect influences wetting on soft substrates, presenting two models to analyze equilibrium states and deformation behaviors, with implications for understanding experimental observations.

Contribution

It introduces two models for soft wetting with a strong Shuttleworth effect, one macroscopic and one mesoscopic, enabling comparison and deeper insight into substrate deformations.

Findings

Symmetry of Shuttleworth effect affects substrate deformation

Models predict robust features of soft wetting behavior

Comparison aligns with recent experimental results

Abstract

The wetting of soft polymer substrates brings in multiple complexities as compared to the wetting on rigid substrates. The contact angle of the liquid is no longer governed by Young's law, but is affected by the substrate's bulk and surface deformations. On top of that, elastic interfaces exhibit a surface energy that depends on how much they are stretched -- a feature known as the Shuttleworth effect (or as surface-elasticity). Here we present two models by which we explore the wetting of drops in the presence of a strong Shuttleworth effect. The first model is macroscopic in character and consistently accounts for large deformations via a neo-Hookean elasticity. The second model is based on a mesoscopic description of wetting, using a reduced description of the substrate's elasticity. While the second model is more empirical in terms of the elasticity, it enables a gradient dynamics formulation for soft wetting dynamics. We provide a detailed comparison between the equilibrium states predicted by the two models, from which we deduce robust features of soft wetting in the presence of a strong Shuttleworth effect. Specifically, we show that the (a)symmetry of the Shuttleworth effect between the "dry" and "wet" states governs horizontal deformations in the substrate. Our results are discussed in the light of recent experiments on the wettability of stretched substrates.