Morphology and stability of droplets sliding on soft viscoelastic substrates

TL;DR

This study investigates how energy dissipation in liquids and soft viscoelastic substrates influences droplet shape and stability, revealing conditions for contact angle hysteresis and slip effects, with implications for wetting dynamics on soft materials.

Contribution

It introduces a non-linear model explaining droplet behavior on viscoelastic gels, highlighting the role of energy dissipation partition and slip in contact line dynamics.

Findings

Equal energy dissipation leads to rigid-like droplet behavior.

Selective dissipation causes contact angle hysteresis.

Model predictions match experimental data.

Abstract

We show that energy dissipation partition between a liquid and a solid controls the shape and stability of droplets sliding on viscoelastic gels. When both phases dissipate energy equally, droplet dynamics is similar to that on rigid solids. When only the solid dissipate, we observe an apparent contact angle hysteresis, of viscoelastic origin. We find excellent agreement between our data and a non-linear model of the wetting of gels of our own that also indicates the presence of significant slip. Our work opens general questions on the dynamics of curved contact lines on compliant substrates.