William Uspal (University of Hawaii at Manoa): Clustering, flocking, and emergent hyperuniformity by breaking microswimmer shape and actuation symmetries

Flow-mediated hydrodynamic interactions driven by particle activity are ubiquitous in active mater systems. Although these interactions are strongly influenced by the interfacial actuation mechanism and geometry of the swimming particles, theoretical understanding of how these microscopic design parameters govern collective dynamics remains limited. Here, we develop a multiscale theoretical framework to study self-organization in systems of microswimmers. We demonstrate that breaking symmetries in the particle shape and interfacial actuation can lead to various collective behaviors. For instance, under certain conditions, discoidal swimmers with non-axisymmetric (but achiral) actuation spontaneously form immotile n-particle clusters. At larger time and length scales, the clustering drives a transition to a dynamically arrested absorbing state characterized by a disordered class I hyperuniform distribution of clusters. Under other conditions, the particles form a globally aligned flocking state. Our analysis highlights the essential role of particle-sourced long-range flows in establishing these behaviors. As an outlook on current research, we consider the impact of introducing chirality in these systems in the form of particle spinning and circle-swimming. Overall, our findings reveal purely hydrodynamic mechanisms for spontaneous order in active colloidal systems.

Zoom Information:

https://us02web.zoom.us/j/2022111100

(Meeting code: 2022111100 Password: skcm2)