Thin Film and Droplet Patterns Shaped by Surface Forces

Abstract

We consider structure and dynamics of thin films and droplets dominated by interaction with the substrate. Droplet velocities are computed analytically in lubrication approximation using an integral solvability condition. This allows us to describe slow motion and rearrangement of droplet patterns due to interactions mediated by the substrate or precursor layer. A droplet may exhibit self-propelled motion by modifying wetting properties of the substrate, resulting in asymmetry in the contact angles. Long-time dynamics in particular systems may lead, depending on relative time scales of motion and substrate modification, to coarsening, pattern formation or persistent wandering of droplets. Similar techniques are applied to describe coexistence of film domains of different thickness and instabilities of domain boundaries in an evaporating liquid film.