Résumé:

At the interface, as in the bulk, the Brownian motion rules the diffusion of colloids. The motor of the motion is the thermal energy kT; and the friction coefficient accounts for viscous dissipations at the interface. These physical conditions constrain the colloid to move following random walk trajectories. To observe directional trajectories, overcoming the limitation of Brownian motion, we have investigated Janus Silica-Platinum active colloids. The catalytic motor of the motion in our case is provided by the Platinum face, on which H2O2 (the fuel) decomposes into oxygen gas and water. To study the motion at the interface we have used a particle-tracking video-microscopy method. We start presenting the results on the motion of Silica colloids (Radius = 1 µm) at air-water interface. Then we describe the fabrication of Janus Silica-Platinum colloids. Presenting the results on the active motion, we discuss the effect of H2O2 fuel concentration and the competition between directional and Brownian motion.