C. Cottin-Bizonne

Suspensions of Active Particles

We study the behaviour of dense active suspensions of self-propelled colloids. At intermediate densities we observe the formation of clusters, resulting from a permanent dynamical merging and separation of active colloids. We have characterised in depth their kinetics of formation and their dynamics which shows vivid translational and rotational motions. These experimental results are discussed in the framework of a simple statistical model that captures quantitatively the measured dynamics. This sheds some new light on the internal organisation of the clusters and on the mechanisms underlying their formation.

In the dense regime, characterizing the dynamics as a function of the activity we have evidenced an unexpected