Coarse-graining dense, deformable active particles

TL;DR

This paper develops a continuum model for dense, deformable active particles like epithelial cells, capturing their elongation, nematic order, and active turbulence, bridging particle-based and continuum approaches.

Contribution

It introduces a coarse-grained continuum framework for deformable active particles, incorporating active stresses and flow effects, aligning well with detailed multi-phase field simulations.

Findings

Contractile interactions induce particle elongation and nematic order.

Active stresses can generate turbulence in the particle assembly.

Model aligns with detailed multi-phase simulations of cell layers.

Abstract

We coarse-grain a model of closely-packed ellipses that can vary their aspect ratio to derive continuum equations for materials comprising confluent deformable particles such as epithelial cell layers. We show that contractile nearest neighbour interactions between ellipses can lead to their elongation and nematic ordering. Adding flows resulting from active hydrodynamic stresses produced by the particles also affects the aspect ratio and can result in active turbulence. Our results, which agree well with multi-phase field simulations of deformable isotropic cells, provide a bridge between models which explicitly resolve cells and continuum theories of active matter.