Passive particles diffusion in active systems.

GASTÓN L. MIÑO; THOMAS E. MALLOUK; MAURICIO HOYOS; JEREMI DAUCHET; DAVID GRIER; YANG WANG; ANNIE ROUSSELET; ERIC CLÉMENT

Paris

Workshop; Les Rencontres de la Montagne Sainte Geneviève; 2010

Fondation Pierre-Gilles de Gennes

We focus on two systems of active swimmers, one being a living population of wild-type E-coli, the other being an assembly self-propelled Au-Pt rods mimicking bacterial swimming close to a surface. In both situations we are interested in the momentum transfer picture due to the activation of the fluid around passive tracers. We monitor the particle diffusivity and relate the diffusion values to the swimming behaviour of the active particle. In particular, we are able to characterize two types of motion (diffusive/convective). We study in detail the relation between active swimmer densities, their motion characteristics and the activation of the fluid inducing enhanced tracer diffusivity larger than the expected standard Brownian picture.