Pinning of a drop by a junction on an incline

TL;DR

This paper investigates the equilibrium shapes and stability of drops pinned at a junction on an inclined plane, considering different contact line scenarios and supported by molecular dynamics simulations.

Contribution

It introduces a theoretical framework for drop pinning at a junction on an incline, analyzing different contact line configurations and their stability.

Findings

Three distinct equilibrium scenarios depending on contact line behavior.

The wetted length of the junction line significantly influences retention force.

Molecular dynamics simulations support the theoretical predictions.

Abstract

The shape of a drop pinned in a local equilibrium on an incline is a long-standing problem. The substrate can be homogeneous or heterogeneous and we herewith consider a drop pinned on an incline at the junction between a hydrophilic half-plane (the top half) and a hydropho-bic one (the bottom half). Relying on the equilibrium equations deriving from the balance of forces, we exhibit three scenarii depending on the way the contact line of the drop on the substrate either simply leans against the junction or overfills (partly or fully) the hydrophobic side. We draw some conclusions on the geometry of the overlap and the stability of these tentative equilibrium states. In the corresponding retention force factor, we find that a major role is played by the wetted length of the junction line. The predictions of the theory are illustrated and supported by extensive molecular dynamics simulations.