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Updated: Oct 16, 2025

Measuring the Interaction Force Between a Droplet and a Super-hydrophobic Substrate by the Optical Lever Method
Published on: June 14, 2019
Can a liquid drop on a substrate be in equilibrium with saturated vapor?
1Department of Mathematics and Statistics, University of Limerick, Limerick V94 T9PX, Ireland.
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 is also 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 if the boundary of the liquid phase is convex.
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