Dense active matter: topology in biology

Active materials such as bacteria, molecular motors and self- propelled colloids, are Nature's engines. They continuously transform chemical energy from their environment to mechanical work. Dense active matter shows mesoscale turbulence, the emergence of chaotic flow structures characterised by high vorticity and motile topological defects. I shall describe flow patterns in active matter in confinement and the transition to active turbulence in channels. In recent work we have been modelling cell layers as active systems, and I will give examples where topological defects may be of relevance to biological function.