"Dynamical clustering and phase separation in suspensions of self-propelled colloidal particles"

Dynamical clustering and phase separation in suspensions
of self-propelled colloidal particles

Ivo Buttinoni
Universität Stuttgart, Germany

Living active systems such as bacterial solutions or flocks of birds
show interesting collective phenomena which are only poorly
understood.In order to obtain some fundamental understanding, we try
to mimic similar processes in systems of artificial swimmers which
have been already shown to exhibit striking similarities with
biological systems. By means of a recently developed phoretic
swimmer-system whose propulsion can be controlled by the incident
light intensity, we study the complex dynamics of clustering which
occurs in dense suspensions of swimmers. At low densities we observe
the formation of small dynamic clusters, whose size and shape
continuously varies due to collisions and rotational diffusion. At
higher densities and large propulsion speeds the active suspension
undergoes a disorder-order phase transitionand separates into few big
clusters and a diluted gas phase. Numerical simulations suggest that
both the clustering and the phase separation can be explained by the
self-trapping of particles undergoing head-on collisions.


Date: February 13, 2013 (Wednesday)
Time: 15:40-16:40
Place: SA240