Academic Awards 2024 booklet

79 Glassy Dynamics in Dense Active Matter Glasses constitute a fascinating class of materials due to their ability to rapidly switch from liquid-like to solid-like behavior while preserving their dense disordered structure (Figure 1). Interestingly, living cells can also exhibit many features of glass-forming materials, and it is becoming increasingly clear that this glass- like cellular behavior plays a vital role in processes such as embryonic development, cancer metastasis, and cytoplasmic transport. However, the physics of these ‘living glasses’ is still poorly understood, and new theoretical tools must be developed to capture the unique complexities of this important class of materials. This work has sought to bridge the gap between the theoretical physics of glass formation and the non- equilibrium realm of active (self-propelled) and living systems. By focusing on a minimal model of biological glassy fluids (Figure 2), it was discovered that the added complexity of active motion can yield unique fluidization and solidification mechanisms, while at the same time revealing previously unknown universal principles which govern the dynamics of dense active matter. Our insights serve as a basis for more realistic bio-inspired and living materials, potentially opening pathways for physical theories to aid in the process of understanding biological processes and even inspire medical treatment. Figure 2: In a minimal model setup, one tries to reduce a complex system to its essential physical building blocks to extract fundamental insights. For instance, a cell layer can, from a physical perspective, be represented by a dense collection of self-propelling particles, i.e. an active glassy fluid. Key features are then the confluency of the cell layer (high density) and each cell’s ability to autonomously locomote (self-propelled motion).