Local composition controls pattern formation in conserved active emulsions

TL;DR

This paper introduces a mechanism for controlling droplet size in active emulsions by leveraging chemical interconversion and differential diffusivity, which stabilizes structures without needing interaction asymmetries.

Contribution

It reveals a universal stabilization mechanism for droplet coarsening in active emulsions through composition-dependent transport effects.

Findings

Enrichment of faster-diffusing species inside droplets opposes growth.

Composition gradients can arrest coarsening without interaction asymmetries.

The mechanism is supported by theory and simulations.

Abstract

Phase separation in passive systems leads to uncontrolled droplet growth, limiting structural control in soft materials and cells. We identify a generic mechanism to arrest coarsening based on chemical interconversion between molecular species with different diffusivities. Sharp-interface theory and simulations show that when the faster-diffusing species becomes enriched inside droplets, composition gradients emerge that oppose mass influx. This transport asymmetry stabilizes droplet sizes even without interaction asymmetries, offering a minimal route to regulate structure formation in active emulsions.