Soft particles at a fluid interface

TL;DR

This paper investigates the shapes of soft elastic particles at fluid interfaces using molecular dynamics and continuum elasticity, revealing how wetting properties and material stiffness influence particle conformation.

Contribution

It combines molecular dynamics simulations with continuum elasticity theory to analyze how wetting and elasticity affect soft particle shapes at interfaces, highlighting the limits of linear theory.

Findings

Molecular simulations accurately match continuum theory for partially wetting gels.

Complete wetting causes deviations from linear elasticity predictions due to molecular effects.

Particle shape depends on Young's modulus and wetting state.

Abstract

Particles added to a fluid interface can be used as a surface stabilizer in the food, oil and cosmetic industries. As an alternative to rigid particles, it is promising to consider highly deformable particles that can adapt their conformation at the interface. In this study we compute the shapes of soft elastic particles using molecular dynamics simulations of a cross-linked polymer gel, complemented by continuum calculations based on linear elasticity. It is shown that the particle shape is not only affected by the Young's modulus of the particle, but also strongly depends on whether the gel is partially or completely wetting the fluid interface. We find that the molecular simulations for the partially wetting case are very accurately described by the continuum theory. By contrast, when the gel is completely wetting the fluid interface the linear theory breaks down and we reveal that molecular details have a strong influence on the equilibrium shape.