Non-reciprocal interactions between condensates in chemically active mixtures

TL;DR

This paper investigates chemically active droplets in multi-component mixtures, revealing non-reciprocal interactions that lead to cluster formation and self-propulsion, highlighting mechanisms of out-of-equilibrium behavior in active matter.

Contribution

It analytically and numerically characterizes the state diagram of active droplets, discovering non-reciprocal interactions causing novel clustering and self-propulsion phenomena.

Findings

Non-reciprocal, chemically-mediated interactions between droplets

Formation of stable and meta-stable droplet clusters

Clusters can exhibit self-propulsion even with attractive interactions

Abstract

We study the behaviour of catalytically active droplets in multi-component conserved mixtures affected by noise. Working in the thin interface limit, we analytically determine the state diagram of the system, characterized by multiple dynamical regimes, and verify our findings using numerical simulations. In particular, we show the emergence of a non-reciprocal, chemically-mediated interaction between the droplets, which leads to the formation of (meta-)stable clusters of droplets of different species. We find that the clusters can display self-propulsion in a large part of the parameter space, including regions where the non-reciprocal interactions between the droplets are purely attractive. This surprising feature arises from the non-local nature of the chemical interactions, and points to locality violations as a general mechanism for energy dissipation and emergence of out-of-equilibrium steady states in active matter.