Chemotactic self-caging in active emulsions

TL;DR

This paper investigates how chemically active droplets communicate via chemical footprints, leading to collective behaviors like transient caging, and provides insights into the dynamics of active emulsions through experiments and simulations.

Contribution

It introduces a physicochemical model of chemically active particles that self-modify their environment, revealing new collective behaviors such as self-caging due to chemorepulsive interactions.

Findings

Chemically active droplets exhibit transient caging behavior.

Chemical footprints influence individual and collective droplet dynamics.

The study combines experiments and simulations to understand active emulsion behavior.

Abstract

A common feature of biological self-organization is how active agents communicate with each other or their environment via chemical signaling. Such communications, mediated by self-generated chemical gradients, have consequences for both individual motility strategies and collective migration patterns. Here, in a purely physicochemical system, we use self-propelling droplets as a model for chemically active particles that modify their environment by leaving chemical footprints, which act as chemorepulsive signals to other droplets. We analyze this communication mechanism quantitatively both on the scale of individual agent-trail collisions as well as on the collective scale where droplets actively remodel their environment while adapting their dynamics to that evolving chemical landscape. We show in experiment and simulation how these interactions cause a transient dynamical arrest in active emulsions where swimmers are caged between each other's trails of secreted chemicals. Our findings provide new insight into the collective dynamics of chemically active particles and yield principles for predicting how negative autochemotaxis shapes their navigation strategy.