Vendredi 22 mars à 11h00 ; salle des séminaires IRPHE
Abstract: Microrollers are colloidal particles that spin close to interfaces without touching them. As they rotate, they move forward, generating large advective flows over long distances. We have found that these flows induce remarkable collective effects such as the formation of unstable fronts and stable motile structures, composed of thousands of particles, which can be used for guided particle transport or fluid pumping at the microscale. Combining experiments, simulations and theory, we will detail the mechanisms of the instability, the parameters that condition the existence of these motile structures, and we will also explore the effect of the nature of the underlying interface on these collective phenomena. We will conclude with an intriguing phenomenon we have recently uncovered: microrollers can be hydrodynamically trapped by obstacles, but only when subjected to Brownian motion. While noise is generally necessary to escape sinks in dynamical systems, we will show that it is the only way to reach this hydrodynamic attractor.
Blaise Delmotte / LadHyX, CNRS, École Polytechnique, Institut Polytechnique de Paris