Abstract

The spontaneous emergence of collective motion and large-scale coherent patterns is a distinct feature of soft active matter. Such systems, in which an immersed microstructure induces active stresses in the medium, range from bacterial swarms to reactive colloidal suspensions to shaken granular materials. Understanding how the local interactions between individual agents translate into collective dynamics is of great fundamental and applied interest.

Swimming particles in strongly confined liquids, such as bacterial colonies in a thin film, are subject to unique hydrodynamic interactions and represent a good candidate to study such dissipative non-equilibrium systems. This seminar will present results of numerical simulations based on a minimal model for swimmer dynamics and hydrodynamic interactions in a Hele-Shaw geometry. We show that two-dimensional dilute suspensions of fore-aft asymmetric swimmers can exhibit a rich variety of novel collective behaviours. We substantiate some of these phenomena using a linear stability analysis and a nonlinear traffic flow model.