Wetting ridge dissipation at large deformations

TL;DR

This paper investigates the dissipation mechanisms in large deformations of soft substrates caused by sliding drops, revealing limitations of linear models and emphasizing the importance of accounting for large deformations in viscoelastic wetting.

Contribution

It provides the first explicit computation of dissipation under large deformations in viscoelastic substrates during wetting, extending beyond previous linear theories.

Findings

Linear theory becomes inaccurate for thin layers.

Large deformations significantly affect dissipation.

Results align with recent experimental observations.

Abstract

Liquid drops slide more slowly over soft, deformable substrates than over rigid solids. This phenomenon can be attributed to the viscoelastic dissipation induced by the moving wetting ridge, which inhibits a rapid motion, and is called "viscoelastic braking". Experiments on soft dynamical wetting have thus far been modelled using linear theory, assuming small deformations, which captures the essential scaling laws. Quantitatively, however, some important disparities have suggested the importance of large deformations induced by the sliding drops. Here we compute the dissipation occurring below a contact line moving at constant velocity over a viscoelastic substrate, for the first time explicitly accounting for large deformations. It is found that linear theory becomes inaccurate especially for thin layers, and we discuss our findings in the light of recent experiments.