Effect of criticality on wetting layers: A Monte-Carlo simulation study

A solid substrate, when exposed to a vapour, can interact with it in such a way that sufficiently close to liquid-vapour coexistence a macroscopically thick liquid wetting layer is formed on the substrate surface. If such a wetting transition occurs for a binary fluid mixture in the vicinity of the critical end point of demixing transitions, critical fluctuations lead to additional long-ranged interactions (Casimir forces) within the wetting layer, changing its equilibrium thickness. We demonstrate this effect by Monte-Carlo simulations of wetting layers of a symmetrical Lennard-Jones binary fluid mixture near its critical end point. The results suggest that the effect should also be detectable in corresponding wetting experiments.