Confined active particles: patterns and self-organisation. - Albane Théry (University of Pennsylvania)

Active particles, often move in confined environments, where interactions with boundaries shape their ability to propel efficiently and form collective structures. We will discuss our recent results on the boundary-mediated propulsion of microswimmers at both the individual and collective levels. We highlight in particular how different theoretical and numerical approaches can be used depending on the nature of the interaction - hydrodynamic vs steric -, the complexity of the surrounding fluid as well as the geometry of the environment -plane walls or spheres. These theoretical results are compared with recent experimental findings, demonstrating how boundaries shape single swimmer propulsion and enable the emergence of collective organisation for example in bacterial and molecular motors suspensions.