Stick-Slip Contact Line Motion on Kelvin-Voigt Model Substrates

TL;DR

This paper presents the first numerical simulations of unsteady soft wetting on Kelvin-Voigt substrates, revealing three distinct regimes of contact line motion influenced by viscoelastic and liquid damping effects.

Contribution

It introduces a coupled numerical model for unsteady soft wetting, elucidating the mechanisms behind stick-slip instability and the transition between different wetting regimes.

Findings

Identifies three regimes: steady viscoelastic braking, stick-slip motion, and classical wetting.

Shows liquid damping suppresses stick-slip at higher speeds.

Provides insights into the interplay between solid viscoelasticity and liquid dissipation.

Abstract

The capillary traction of a liquid contact line causes highly localized deformations in soft solids, tremendously slowing down wetting and dewetting dynamics by viscoelastic braking. Enforcing nonetheless large velocities leads to the so-called stick-slip instability, during which the contact line periodically depins from its own wetting ridge. The mechanism of this periodic motion and, especially, the role of the dynamics in the fluid have remained elusive, partly because a theoretical description of the unsteady soft wetting problem is not available so far. Here we present the first numerical simulations of the full unsteady soft wetting problem, with a full coupling between the liquid and the solid dynamics. We observe three regimes of soft wetting dynamics: steady viscoelastic braking at slow speeds, stick-slip motion at intermediate speeds, followed by a region of viscoelastic braking where stick-slip is suppressed by liquid damping, which ultimately gives way to classical wetting dynamics, dominated by liquid dissipation.