Size dependent motion of nanodroplets on chemical steps

TL;DR

This paper investigates how nanodroplets move on chemically patterned surfaces, revealing size-dependent behaviors that can cause droplets to move contrary to macroscopic wettability expectations due to disjoining pressure effects.

Contribution

It provides a detailed analysis showing that nanodroplet motion can be driven by size-dependent sampling of disjoining pressure, even without lateral variations in the interface potential.

Findings

Nanodroplets can move towards less wettable regions contrary to macroscopic predictions.

Size-dependent effects influence droplet motion on chemical steps.

Disjoining pressure plays a key role in nanoscale droplet dynamics.

Abstract

Nanodroplets on chemically structured substrates move under the action of disjoining pressure induced forces. A detailed analysis of them shows that even in the absence of long-ranged lateral variations of the effective interface potential, already the fact, that due their small size nano-droplets do not sample the disjoining pressure at all distances from the substrate, can lead to droplet motion towards the less wettable part of the substrate, i.e., in the direction opposite to the one expected on the basis of macroscopic wettability considerations.