Energy and Matter Supply for Active Droplets

TL;DR

This paper investigates how active droplets, models for cell-like systems, can sustain non-equilibrium states, undergo division, and exhibit life-like behaviors through energy and matter exchange driven by boundary or bulk chemical energy.

Contribution

It introduces a comprehensive analysis of non-equilibrium active droplets, demonstrating their stability, division, and potential for life-like processes in simple physical systems.

Findings

Droplet division occurs generally in active droplet systems.

Active droplets can maintain non-equilibrium steady states.

Metabolism and division emerge from phase separation and chemical reactions.

Abstract

Chemically active droplets provide simple models for cell-like systems that can grow and divide. Such active droplet systems are driven away from thermodynamic equilibrium and turn over chemically, which corresponds to a simple metabolism. We consider two scenarios of non-equilibrium driving. First, droplets are driven via the system boundaries by external reservoirs that supply nutrient and remove waste (boundary-driven). Second, droplets are driven by a chemical energy provided by a fuel in the bulk (bulk-driven). For both scenarios, we discuss the conservation of energy and matter as well as the balance of entropy. We use conserved and non-conserved fields to analyze the non-equilibrium steady states of active droplets. Using an effective droplet model, we explore droplet stability and instabilities leading to droplet division. Our work reveals that droplet division occurs quite generally in active droplet systems. Our results suggest that life-like processes such as metabolism and division can emerge in simple non-equilibrium systems that combine the physics of phase separation and chemical reactions.