Physics of Active Emulsions

TL;DR

This paper reviews the physics of active emulsions, a class of non-equilibrium systems driven by external energy, highlighting their unique phenomena and potential applications in biology and engineering.

Contribution

It extends the physics of passive emulsions to active systems, discussing how external energy input leads to novel behaviors like droplet division and size control.

Findings

Active emulsions exhibit unique droplet behaviors not seen in passive systems.

External energy input enables spatial organization and size control of droplets.

Potential applications include biological organization and chemical engineering.

Abstract

Phase separating systems that are maintained away from thermodynamic equilibrium via molecular processes represent a class of active systems, which we call active emulsions. These systems are driven by external energy input for example provided by an external fuel reservoir. The external energy input gives rise to novel phenomena that are not present in passive systems. For instance, concentration gradients can spatially organise emulsions and cause novel droplet size distributions. Another example are active droplets that are subject to chemical reactions such that their nucleation and size can be controlled and they can spontaneously divide. In this review we discuss the physics of phase separation and emulsions and show how the concepts that governs such phenomena can be extended to capture the physics of active emulsions. This physics is relevant to the spatial organisation of the biochemistry in living cells, for the development novel applications in chemical engineering and models for the origin of life.