Motion induced by a self-generated concentration gradient: Marangoni effect and diffusiophoresis/diffusioosmosis - Dolachai Boniface (Departament de Fisica de la Matèria Condensada, University of Barcelona)

Over the past 20 years, physicists have developed numerous millimetric/micrometric artificial self-moving objects. A motivation is to study the collective behaviours or to target medical applications such as drug delivery. A method to obtain autonomous particles is to make them release an "active" chemical product that alters surrounding environment properties and triggers interfacial phenomena. The Marangoni effect is privileged to create motion at a fluid interface, and diffusiophoresis/diffusioosmosis for objects evolving in the liquid bulk or close to a solid/liquid interface. In any case, symmetry breaking is necessary to obtain motion. I will present three autonomous systems releasing a chemical product: the camphor disk, the dichloromethane drop and the colloidal raft composed of a hematite surrounded by silica colloids. Despite their apparent intrinsic symmetry, all those objects display a motion. The objective is to comprehend the underlying mechanism.