Phase Ordering in Binary Mixtures of Active Nematic Fluids

TL;DR

This paper investigates how mixtures of two active nematic fluids exhibit turbulent microphase separation driven by activity differences, with implications for biological systems like cell sorting and bacterial colonies.

Contribution

It introduces a continuum two-fluid model to analyze phase ordering in active nematic mixtures, highlighting the role of elastic alignment and substrate friction in domain dynamics.

Findings

Active mixtures show turbulent microphase separation.

Elastic alignment enhances phase separation effects.

Relative flows driven by active anchoring explain domain behavior.

Abstract

We use a continuum, two-fluid approach to study a mixture of two active nematic fluids. Even in the absence of thermodynamically-driven ordering, for mixtures of different activities we observe turbulent microphase separation, where domains form and disintegrate chaotically in an active turbulent background. This is a weak effect if there is no elastic nematic alignment between the two fluid components, but is greatly enhanced in the presence of an elastic alignment or substrate friction. We interpret the results in terms of relative flows between the two species which result from active anchoring at concentration gradients. Our results may have relevance in interpreting epithelial cell sorting and the dynamics of multi-species bacterial colonies.