Criticality of isotropic stress percolation during glass to fluid transition in active cell layers

The transition between solid-like to fluid-like states in cellular systems is of relevance to a range of biological processes, including cancer metastasis, wound healing and tissue morphogenesis. However, our fundamental understanding of how cells collectively switch between these two states remains limited. Using a three-dimensional phase-field based 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. To achieve this, we use two distinct and independent paths to model this transition based on increasing (1) cell-cell adhesion and (2) active traction forces. Our findings provide a new perspective on the fundamental mechanical mechanisms associated with the solid-like to fluid-like transition in active cell layers.