Microswimmer collective dynamics in Brinkman flows

Tiny obstacles in a Brinkman fluid can dramatically alter how swimming microorganisms like bacteria or micro-algae coordinate their motion. The environmental resistance presented by the particulate delays and, at high enough levels, completely suppresses the collective instabilities that arise due to hydrodynamic interactions between the swimmers. By contrasting our results with those for homogeneous fluids, we highlight how the physical structure of a habitat can control and disrupt whether microorganisms swim in coordinated groups.