Condensation on Soft Substrates: A Mesoscopic Perspective

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