Séminaire général : Active Matter and Active Interfaces, par Cécile COTTIN-BIZONNE

visioconférence : https://cnrs.zoom.us/j/95332727697?pwd=4C990Uof15JHbBlyHGCHVs1FLbZJHm.1

résumé : The observation of flocks of birds, schools of fish, and swarms of bees reveals captivating examples of collective behavior in nature. Over the past decade, physicists have unveiled intriguing features in the dynamics of such active systems, leading to the emergence of active matter as a new field of Physics. Since then, nearly all entities of soft matter have been made active and capable of self-propulsion. These systems have given rise to both spectacular phenomena and fundamental questions. In this presentation, we will describe the case of dense self-propelled Janus colloids sedimenting under the effect of gravity. At low volume fraction, they behave like a perfect hot gas, but at intermediate fractions, new non-trivial collective phenomena emerge, such as cluster formation. This raises the question of whether interactions similar to “wetting-type effects” occur in such active fluids. We will explore an analogy with the classical capillary rise effect within the realm of active matter, examining how a non-phase-separated sediment of self-propelled Janus colloids behaves when in contact with a vertical wall.

biographie : Cécile Cottin-Bizonne is a CNRS Research Director at the Institut Lumière Matière in Lyon, within the Liquids and Interfaces team. Her research activities broadly focus on the dynamics of liquids and particles at interfaces, as well as the potential coupling mechanisms between surface properties and dynamics. The fundamental understanding of these effects and the ability to harness them to create systems with novel properties, such as active matter, are the primary motivations behind her research topics.