Abstract

The mechanical behaviour of amorphous solids, from molecular glasses, soft materials, to granular matter, is of interest in diverse contexts – from biological assemblies to geophysical structures – with the response to repeated, or cyclic, deformation being of particular importance. The nature of plasticity and internal structure change, leading to eventual failure, is more elusive in amorphous solids than their crystalline counterparts. The transition to the yielded state exhibits several striking features, including a divergence of the number of cycles to failure, and a non-monotonic approach to failure. Failure times, although broadly distributed, can be remarkably well predicted from measures of plasticity and dissipated work. A remarkable analogy holds between yielding in amorphous solids and the fluidization of “active solids”, composed of self-propelled particles. The interplay of finite persistence times of active forces, and confinement—both relevant in the case of sub-cellular biological assemblies—has rich implications for the fluidization behaviour. We use the insights from these investigations to formulate an approach to understanding mechanically induced cell state transitions through coarse-grained models. Investigations through computer simulations, and theoretical models that reproduce and rationalize these observations will be described. 1) Maity, S., Bhaumik, H., Athani, S. et al. Fatigue failure in glasses under cyclic shear deformation. Nat. Phys. (2026). https://doi.org/10.1038/s41567-026-03174-x 2) Goswami, Y., Shivashankar, G.V. & Sastry, S. Yielding behaviour of active particles in bulk and in confinement. Nat. Phys. 21, 817–824 (2025).