Can a liquid drop on a substrate be in equilibrium with saturated vapor?

TL;DR

This paper demonstrates that a liquid drop on a substrate cannot be in equilibrium with saturated vapor due to evaporation caused by the Kelvin effect, which is independent of the modeling approach.

Contribution

It shows, using the diffuse-interface model and maximum-entropy principle, that liquid drops evaporate on substrates, challenging the assumption of equilibrium with saturated vapor.

Findings

Liquid drops on substrates evaporate due to the Kelvin effect.

Equilibrium with saturated vapor is impossible for convex liquid boundaries.

Evaporation occurs regardless of the specific modeling framework.

Abstract

It is well-known that liquid and saturated vapor, separated by a flat interface in an unbounded space, are in equilibrium. One would similarly expect a liquid drop, sitting on a flat substrate, to be in equilibrium with the vapor surrounding it. Yet, it is not: as shown in this work, the drop evaporates. Mathematically, this conclusion is deduced using the diffuse-interface model, but it can also be reformulated in terms of the maximum-entropy principle, suggesting model independence. Physically, evaporation of drops is due to the so-called Kelvin effect, which gives rise to a liquid-to-vapor mass flux in all cases where the boundary of the liquid phase is convex.