Permeation Instabilities in Active, Polar Gels

TL;DR

This paper develops a theoretical model for active, polar gels that incorporates permeation and polarization effects, revealing novel instability mechanisms that could explain pattern formation in biological tissues.

Contribution

It introduces a two-fluid model for active, permeating, polar gels with new instability mechanisms driven by permeation-deformation and permeation-alignment couplings.

Findings

Identification of finite wave vector instabilities leading to periodic domains.

Prediction of conditions for multicellular migration patterns.

Analysis of stability influenced by permeation and polarization couplings.

Abstract

We present a theory of active, permeating, polar gels, based on a two-fluid model. An active relative force between the gel components creates a steady-state current. We analyze its stability, while considering two polar coupling terms to the relative current: a permeation-deformation term, which describes network deformation by the solvent flow, and a permeation-alignment term, which describes the alignment of the polarization field by the network deformation and flow. Novel instability mechanisms emerge at finite wave vectors, suggesting the formation of periodic domains and mesophases. Our results can be used to determine the physical conditions required for various types of multicellular migration across tissues.