Microscopic contact line dynamics dictate the emergent behaviors of particle rafts

TL;DR

This study uncovers how microscopic particle interactions govern the macroscopic behaviors of particle rafts at fluid interfaces, combining experiments and modeling to predict and control their failure modes.

Contribution

It introduces a theoretical framework linking particle-scale interactions to collective raft behaviors, enabling control over failure modes.

Findings

Phase diagram of collapse modes (folding vs. expulsion)

Control of failure mode through particle property tuning

Demonstration of collective dynamics from simple particle interactions

Abstract

Fluid-fluid interfaces laden with discrete particles behave curiously like continuous elastic sheets, leading to their applications in emulsion and foam stabilization. Although existing continuum models can qualitatively capture the elastic buckling of these particle-laden interfaces -- often referred to as particle rafts -- under compression, they fail to link their macroscopic collective properties to the microscopic behaviors of individual particles. Thus, phenomena such as particle expulsion from the compressed rafts remain unexplained. Here, by combining systematic experiments with first-principle modeling, we reveal how the macroscopic mechanical properties of particle rafts emerge from particle-scale interactions. We construct a phase diagram that delineates the conditions under which a particle raft collapses via collective folding versus single-particle expulsion. Guided by this theoretical framework, we demonstrate control over the raft's failure mode by tuning the physicochemical properties of individual particles. Our study highlights the previously overlooked dual nature of particle rafts and exemplifies how collective dynamics can arise from discrete components with simple interactions.