Droplet spreading and pinning on heterogeneous substrates

TL;DR

This paper investigates how droplets spread and become pinned on heterogeneous surfaces by analyzing the statistical dynamics of the contact line, revealing dependencies on disorder, droplet volume, and surface features.

Contribution

It introduces a novel analysis of contact line depinning transitions considering non-local elasticity and surface heterogeneity effects.

Findings

Final droplet radius and contact angle depend on disorder strength and surface details.

Deviations from classical wetting models occur for small droplets and contact angles.

Pinning-depinning dynamics are characterized by statistical properties influenced by surface heterogeneity.

Abstract

The contact angle of a fluid droplet on an heterogeneous surface is analysed using the statistical dynamics of the spreading contact line. The statistical properties of the final droplet radius and contact angle are obtained through applications of depinning transitions of contact lines with non-local elasticity and features of pinning-depinning dynamics. Such properties not only depend on disorder strength and surface details, but also on the droplet volume and disorder correlation length. Deviations from Wenzel or Cassie/Baxter behaviour are particularly apparent in the case of small droplet volumes and small contact angles.