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From Dilute to Dense Suspensions of Active Colloids
Diffusiophoresis is an interfacially driven transport phenomenon, leading to the motion of macro-molecules under solute gradients. It is an efficient but rather unexplored mean to drive and manipulate particles. This energy transduction mechanism can also be used to device self-propelled particles. In this talk I will present our experiments on suspensions of active colloids, and describe their behavior at low and intermediate densities as well as their non-equilibrium equation of state, that is profoundly affected by self-propulsion. Finally I will present our results on another kind of active particles, magnetotactic bacteria, when their active swimming motion is put in competition with a steady Poiseuille flow, in certain regimes we observe a striking pearling instability.