Biological and artificial swimmers often move in confined environments, such as the human body, soil, or foam, and in fluids that are rich in (bio)polymers. Understanding and controlling their behavior in their natural surroundings therefore requires experiments and models that reproduce these realistic conditions. This poses particular challenges as boundaries promote accumulation and self-organization through steric and hydrodynamic interactions, while non-Newtonian fluids break linearity and can make local effects dominant.

Thery, from the University of Pennsylvania, discussed both general and specific approaches to building minimal models for single microswimmers or suspensions, in some systems ranging from bacterial contamination in biological fluids to plankton trapped in foams.