Fluid contact angle on solid surfaces: role of multiscale surface roughness

TL;DR

This paper develops an analytical and numerical framework to understand how multiscale surface roughness influences the fluid contact angle on solid surfaces, revealing complex dependencies beyond simple slope distributions.

Contribution

It introduces a combined analytical and numerical approach to analyze the impact of multiscale roughness on contact angles, challenging previous simplified models.

Findings

Contact angle depends on roughness across multiple length scales.

Same slope distribution can lead to different contact angles.

No straightforward relation between slope distribution and contact angle.

Abstract

We present a simple analytical model and an exact numerical study which explain the role of roughness on different length scales for the fluid contact angle on rough solid surfaces. We show that there is no simple relation between the distribution of surface slopes and the fluid contact angle. In particular, surfaces with the same distribution of slopes may exhibit very different contact angles depending on the range of length-scales over which the surfaces have roughness.