Gibbs adsorption impact on a nanodroplet shape: modification of Young-Laplace equation

TL;DR

This paper presents a molecular dynamics study and a modified Young-Laplace equation to evaluate how Gibbs adsorption influences nanodroplet shape and volume, providing a quantitative approach to assess adsorption effects.

Contribution

It introduces a new analytical model linking Gibbs adsorption to nanodroplet volume changes, validated by molecular dynamics simulations.

Findings

Gibbs adsorption causes measurable nanodroplet volume contraction.

A threshold droplet size exists where adsorption effects become significant.

The approach enables quantification of adsorbed atoms per unit area.

Abstract

An efficient technique for the evaluation of the Gibbs adsorption of a liquid on a solid substrate is presented. The behavior of a water nanodroplet on a silicon surface is simulated with molecular dynamics. An external field with varying strength is applied on the system to tune the solid-liquid interfacial contact area. A linear dependence of droplet's volume on the contact area is observed. Our modified Young--Laplace equation is used to explain the influence of the Gibbs adsorption on the nanodroplet volume contraction. Fitting of the molecular dynamics results with these of an analytical approach allows us to evaluate the number of atoms per unit area adsorbed on the substrate, which quantifies the Gibbs adsorption. Thus, a threshold of a droplet size is obtained, for which the impact of the adsorption is crucial. Moreover, the presented results can be applied for the evaluation of the adsorption impact on the physical--chemical properties of systems with important surface-to-volume fraction.