Fluid adsorption at a non-planar wall: roughness induced first-order wetting

TL;DR

This paper investigates how surface roughness affects fluid wetting transitions at non-planar walls, revealing that roughness can induce a first-order transition even when the planar case exhibits second-order wetting.

Contribution

It develops a linear response theory linking non-planar free energy to planar correlation functions and derives analytical expressions for phase boundary shifts due to roughness.

Findings

Surface roughness can convert second-order wetting into first-order transition.

Analytical expressions quantify the phase boundary shift caused by roughness.

Roughness influences wetting behavior even with small deviations from a flat surface.

Abstract

We study the problem of fluid adsorption at a non-planar wall with a view to understanding the influence of surface roughness on the wetting transition. Starting from an appropriate Landau-type free energy functional we develop a linear response theory relating the free energy of the non-planar system to the correlation functions in its planar counterpart. We generalize the well known graphical construction method used to study the planar surface phase diagram and derive analytical expressions for the shift in the phase boundary for first and second-order wetting transitions. Of particular interest is the influence of surface roughness on a second order wetting transition which is driven first order, even for small deviations from the plane.