Cavitation controls droplet sizes in elastic media

TL;DR

This paper presents a theoretical model explaining how cavitation in elastic media influences droplet sizes and arrangements, aligning with experimental observations in synthetic and biological systems.

Contribution

The study introduces a cavitation-based model that predicts droplet size distribution and spatial correlation in elastic matrices, advancing understanding of droplet formation in complex environments.

Findings

Large droplets form via cavitation events breaking the matrix

Small droplet sizes are stabilized by the energy barrier of cavitation

Droplet density increases with faster cooling

Abstract

Biological cells use droplets to separate components and spatially control their interior. Experiments demonstrate that the complex, crowded cellular environment affects the droplet arrangement and their sizes. To understand this behavior, we here construct a theoretical description of droplets growing in an elastic matrix, which is motivated by experiments in synthetic systems where monodisperse emulsions form during a temperature decrease. We show that large droplets only form when they break the surrounding matrix in a cavitation event. The energy barrier associated with cavitation stabilizes small droplets on the order of the mesh size and diminishes the stochastic effects of nucleation. Consequently, the cavitated droplets have similar sizes and highly correlated positions. In particular, we predict the density of cavitated droplets, which increases with faster cooling, as in the experiments. Our model also suggests how adjusting the cooling protocol and the density of nucleation sites affects the droplet size distribution. In summary, our theory explains how elastic matrices affect droplets in the synthetic system and it provides a framework for understanding the biological case.