Stress percolation criticality of glass to fluid transition in active cell layers

TL;DR

This study models the transition of active cell layers from solid-like to fluid-like states as a critical percolation phenomenon, linking mechanical stress patterns to phase transition universality classes with biological implications.

Contribution

It unifies two pathways of phase transition in active cell layers and demonstrates their criticality within the 2D site percolation universality class.

Findings

Transition is a critical phenomenon in stress development.

Transition belongs to the 2D site percolation universality class.

Provides insights into biological processes like wound healing.

Abstract

Using three-dimensional representation of confluent cell layers, we map the amorphous solid to fluid phase transition in active cell layers onto the two-dimensional (2D) site percolation universality class. Importantly, we unify two distinct, predominant, pathways associated with this transition; namely (i) cell-cell adhesion and (ii) active traction forces. For each pathway, we independently vary the corresponding control parameter and focus on the emergent mechanical stress patterns as the monolayer transitions from a glassy- to a fluid-like state. Through finite-size scaling analyses, our results lead us to establish the glassy- to fluid-like transition as a critical phenomena in terms of stress development in the cell layer and show that the associated criticality belongs to the 2D site percolation universality class. Our findings offer a fresh perspective on solid (glass-like) to fluid phase transition in active cell layers and can bridge our understanding of glassy behaviors in active matter with potential implications in biological processes such as wound healing, development, and cancer progression.