Differential-activity driven instabilities in biphasic active matter

TL;DR

This paper develops a hydrodynamic theory for biphasic active matter, revealing how differential activity between phases induces instabilities and pattern formation, advancing understanding of active biological and synthetic systems.

Contribution

It introduces a generic model for biphasic active matter that explains activity-driven instabilities and characterizes the resulting pattern phase diagram.

Findings

Differential activity causes demixing instability.

Nonlinear evolution leads to diverse pattern formation.

The phase diagram maps different instability regimes.

Abstract

Active stresses can cause instabilities in contractile gels and living tissues. Here we describe a generic hydrodynamic theory that treats these systems as a mixture of two phases of varying activity and different mechanical properties. We find that differential activity between the phases provides a mechanism causing a demixing instability. We follow the nonlinear evolution of the instability and characterize a phase diagram of the resulting patterns. Our study complements other instability mechanisms in mixtures such as differential growth, shape, motion or adhesion.