Condensation on Soft Substrates: A Mesoscopic Perspective

Abstract

We consider the condensation and evaporation of a volatile partially wetting liquid on a soft substrate in contact with a homogeneously saturated gas phase. Recent experiments demonstrated a strong dependence of nucleation density on the substrate softness. Motivated by these experiments, we approach the problem considering both macroscale and mesoscale models. On the macroscale, we employ thermodynamic considerations to determine the critical nuclei energies and the resulting nucleation probabilities in the limits of rigid and liquid substrates. On the mesoscale, we use a gradient dynamics model for a drop of volatile liquid on a soft substrate with Kelvin-Voigt viscoelasticity in Winkler-foundation form. The governing energy functional incorporates elastic and interface energies as well as bulk liquid energy. We show that nucleation probabilities obtained with the two models agree for small supersaturation, but display differences when drop nuclei are small. Finally, we use the mesoscopic model to investigate the condensation and evaporation dynamics of drops in the intermediate elastic regime and relate the results to the experimental findings.