Filling transition for a wedge

TL;DR

This paper investigates the filling transition of a liquid meniscus in a wedge, revealing conditions under which the meniscus height becomes macroscopically large and how this relates to wetting and prefilling phenomena.

Contribution

The study introduces an effective interface model to analyze the filling transition in wedges, distinguishing between continuous and discontinuous transitions and their relation to wetting behavior.

Findings

Filling transition occurs at a specific temperature $T_{\,phi}$ with a macroscopic meniscus height.

Transition can be continuous or discontinuous depending on fluid and substrate.

Discontinuous transition involves a prefilling line indicating a transition from small to large meniscus height.

Abstract

We study the formation and the shape of a liquid meniscus in a wedge with opening angle $2\phi$ which is exposed to a vapor phase. By applying a suitable effective interface model, at liquid-vapor coexistence and at a temperature $T_{\phi}$ we find a filling transition at which the height of the meniscus becomes macroscopically large while the planar walls of the wedge far away from its center remain nonwet up to the wetting transition occurring at $T_w>T_{\phi}$. Depending on the fluid and the substrate potential the filling transition can be either continuous or discontinuous. In the latter case it is accompanied by a prefilling line extending into the vapor phase of the bulk phase diagram and describing a transition from a small to a large, but finite, meniscus height. The filling and the prefilling transitions correspond to nonanalyticities in the surface and line contributions to the free energy of the fluid, respectively.