Elastic tweezers for a vibrated granular bead

Optical tweezers are usually used to capture colloidal particles. In this talk, we will show that this method can be transferred in the realm of vibrated granular matter. It has been shown that the velocity distribution of mechanically vibrated beads is gaussian provided that a randomization of the collisions is achieved. This can be done via a rough surface, a layer of glued beads for instance. First we checked that a bead on top of a such rough surface undergoes a Brownian motion. Then we attached the bead to a flexible string and analyzed the fluctuations of motion. It revealed the drastic influence of the string elasticity, acting as a confining potential. This being equivalent to the harmonic potential achieved with optical tweezers. This new experimental setup paves the way to study stochastic behavior of small particles that should mimic colloidal suspension in 2D.