Line tension and wettability of nanodrops on curved surfaces

TL;DR

This study uses molecular dynamics simulations to analyze nanodrop behavior on curved surfaces, revealing that contact angles are unaffected by curvature and that line tension varies with surface shape and particle layering.

Contribution

It demonstrates that contact angles are independent of substrate curvature and provides a detailed analysis of line tension differences on convex and concave surfaces.

Findings

Contact angle remains unchanged with substrate curvature.

Line tension is higher on concave surfaces than convex.

Line tension peaks at zero curvature, linked to particle layering.

Abstract

In this paper we study the formation of nanodrops on curved surfaces (both convex and concave) by means of molecular dynamics simulations, where the particles interact via a Lennard-Jones potential. We find that the contact angle is not affected by the curvature of the substrate, in agreement with previous experimental findings. This means that the change in curvature of the drop in response to the change in curvature of the substrate can be predicted from simple geometrical considerations, under the assumption that the drop's shape is a spherical cap, and that the volume remains unchanged through the curvature. The resulting prediction is in perfect agreement with the simulation results, for both convex and concave substrates. In addition, we calculate the line tension, namely by fitting the contact angle for different size drops to the modified Young equation. We find that the line tension for concave surfaces is larger than for convex surfaces, while for zero curvature it has a clear maximum. This feature is found to be correlated with the number of particles in the first layer of the liquid on the surface.