Statistical properties of microphase and bubbly phase-separated active fluids

TL;DR

This paper investigates the statistical properties and phase behaviors of active fluids undergoing microphase and bubbly phase separation, revealing how domain size distributions depend on dynamic processes like coalescence and nucleation.

Contribution

It introduces a minimal field theory and an effective model to analyze the microphase separation and bubbly phases in active fluids, supported by large-scale simulations.

Findings

Bubbly phase consists of two macroscopic regions: homogeneous fluid and microphase-separated fluid.

Domain size distribution depends on the balance of Ostwald process, coalescence, and nucleation.

Results are validated through large-scale simulations and an effective domain-based model.

Abstract

In phase-separated active fluids, the Ostwald process can go into reverse leading to either microphase separation or bubbly phase separation. We show that the latter is formed of two macroscopic regions that are occupied by the homogeneous fluid and by the microphase separated one. Within the microphase separated fluid, the relative rate of the Ostwald process, coalescence, and nucleation determines whether the size distribution of mesoscopic domains is narrowly peaked or displays a broad range of sizes before attaining a cutoff independent of system-size. Our results are obtained via large-scale simulations of a minimal field theory for active phase separation and reproduced by an effective model in which the degrees of freedom are the locations and sizes of the microphase-separated domains.