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Thermal actuation of artificial microswimmers

Thomas Bickel <I>Laboratoire Ondes et Matière d’Aquitaine (LOMA), Université de Bordeaux

The design of artificial micro- and nanoswimmers that propel themselves in a viscous fluid in the absence of mechanical forces is a challenging issue in nanotechnology. In recent years, self-propulsion has been achieved using metal-capped Janus colloids under illumination by a laser beam. Janus colloids have two sides that differ in their physical or chemical properties. Heat absorption by the metal cap generates a temperature gradient which in turn gives rise to a flow in the surrounding fluid and thus causes self-propulsion. In this talk, I will first discuss the mechanism responsible for the thermo-osmotic flow. I will then focus on the temperature profile and the resulting flow pattern in the vicinity of a single Janus particle. Collective phenomena will be addressed next. In particular, I will show that active colloids experience a viscous torque due to thermal interactions in the nonuniform local field of their neighbors. This torque tends to align the particles with the temperature gradient and affects significantly the collective behavior at large Péclet number. Finally, I will also present preliminary results regarding thermal actuation of interfacial colloids.