Size control guidelines for chemically active droplets

TL;DR

This paper develops a theoretical framework to control the size of chemically active droplets in biological and synthetic systems by analyzing reaction-driven phase separation, providing guidelines for achieving desired droplet sizes.

Contribution

It introduces a binary fluid model driven by chemical reactions that classifies droplets into two size-controlled regimes and identifies parameters for maintaining specific droplet sizes.

Findings

Two classes of size-controlled droplets identified

Parameter regimes for small droplet formation determined

Guidelines for chemical reactions to control droplet size provided

Abstract

Biological cells and synthetic analogues use liquid-liquid phase separation to dynamically compartmentalize their environment for various applications. In many cases, multiple droplets need to coexist, and their size needs to be controlled, which is challenging because large droplets tend to grow at the expense of smaller ones. Chemical reactions can, in principle, control droplet sizes, but there are no clear guidelines on how to robustly achieve size control. To provide guidelines, we consider a binary fluid model driven out of equilibrium by chemical reactions. We reveal two different classes of size-controlled droplets, depending on the ratio of droplet radius to the reaction-diffusion length. Moreover, we determine parameter regimes in which droplets become small. Taken together, our theory allows us to separately predict the chemical reactions necessary for maintaining droplets of a given class or size.