Models of 3D confluent tissue as under-constrained glasses

TL;DR

This study demonstrates that 3D models of under-constrained confluent tissues exhibit tunable glassy dynamics, including sub-Arrhenius behavior, suggesting such phenomena are generic across dimensions in disordered materials.

Contribution

We extend the 2D Voronoi model to 3D, showing that under-constrained tissue models can exhibit a range of glassy dynamics, including sub-Arrhenius behavior, confirming the generality across dimensions.

Findings

3D Voronoi model shows tunable Arrhenius and sub-Arrhenius dynamics.

Structural and mechanical properties align with 2D model trends.

Sub-Arrhenius glassy behavior is a generic feature of under-constrained materials.

Abstract

The dynamics of glassy materials slows down upon cooling, typically showing either Arrhenius or super-Arrhenius behavior. However, it was recently shown that 2D cell-based models for biological tissues can be continuously tuned between Arrhenius and sub-Arrhenius dynamics. In previous work, using the 2D Voronoi model, we proposed that such atypical dynamical behavior could be a generic feature of the broad class of mechanically under-constrained materials. Our earlier study had left two important points open: (1) many 2D systems are affected by long-wavelength fluctuations and the 2D melting scenario, and (2) the 2D Voronoi model sits exactly at the isostatic point, making it a marginal case rather than a strictly under-constrained one. Both points complicate the interpretation of our 2D Voronoi model results and their generalization to other systems; to remedy this, here we use large-scale simulations to study the glassy behavior of the 3D extension of the Voronoi model. We first show that the structural relaxation time $\tau_\alpha$ of the 3D Voronoi model can be tuned between sub-Arrhenius and Arrhenius behavior, like the 2D Voronoi model. We then establish that the four-point susceptibility, the structure factor, and the model's mechanical properties all display trends consistent with the 2D Voronoi model. These results provide strong evidence that sub-Arrhenius glassy dynamics are a generic feature of under-constrained materials across dimensions. Our work thus broadens the class of disordered materials known to have highly unusual glassy phenomenology.