Size limit for particle-stabilized emulsion droplets under gravity

TL;DR

This study identifies a size limit for particle-stabilized emulsion droplets under gravity, showing that stability depends on the balance between particle weight and interfacial forces, with droplet curvature influencing particle ejection.

Contribution

It provides a quantitative criterion for droplet stability based on particle weight and interfacial forces, incorporating the effect of droplet curvature.

Findings

Droplets become unstable beyond a size threshold set by gravity.

Particle ejection occurs near the droplet base and decreases over time.

Stability is achieved when particle weight is less than interfacial binding force.

Abstract

We demonstrate that emulsion droplets stabilized by interfacial particles become unstable beyond a size threshold set by gravity. This holds not only for colloids but supra-colloidal glass beads, using which we directly observe the ejection of particles near the droplet base. The number of particles acting together in these ejection events decreases with time until a stable acorn-like configuration is reached. Stability occurs when the weight of all remaining particles is less than the interfacial binding force of one particle. We also show the importance of the curvature of the droplet surface in promoting particle ejection.