Aging mechanism in tunable Pickering emulsion

TL;DR

This study investigates the stability mechanisms of tunable Pickering emulsions using microfluidics, revealing a new stability regime where surface coverage increases over time without droplet coalescence.

Contribution

It introduces a novel regime of Pickering emulsion stability where surface coverage grows over time, challenging previous limited coalescence models.

Findings

Surface coverage as low as 23% stabilizes emulsions.

Identified a new stability regime with increasing surface coverage.

Challenged existing models of droplet size control.

Abstract

We study the stability of a model Pickering emulsion system. A special counter-flow microfluidics set-up was used to prepare monodisperse Pickering emulsions, with oil droplets in water. The wettability of the monodisperse silica nanoparticles (NPs) could be tuned by surface grafting and the surface coverage of the droplets was controlled using the microfluidics setup. A surface coverage as low as 23$\%$ is enough to stabilize the emulsions and we evidence a new regime of Pickering emulsion stability where the surface coverage of emulsion droplets of constant size increases in time, in coexistence with a large amount of dispersed phase. Our results demonstrate that the previously observed limited coalescence regime where surface coverage tends to control the average size of the final droplets must be put in a broader perspective.