title: Sedimentation and effective temperature of active colloidal suspensions.
abstract: In this Letter, we investigate experimentally the nonequilibrium steady state of an active colloidal suspension under gravity field. The active particles are made of chemically powered colloids, showing self propulsion in the presence of an added fuel, here hydrogen peroxide. The active suspension is studied in a dedicated microfluidic device, made of permeable gel microstructures. Both the microdynamics of individual colloids and the global stationary state of the suspension under gravity are measured with optical microscopy. This yields a direct measurement of the effective temperature of the active system as a function of the particle activity, on the basis of the fluctuation-dissipation relationship. Our work is a first step in the experimental exploration of the out-of-equilibrium properties of active colloidal systems.
authors.affiliation: LPMCN, Université de Lyon, Université Lyon 1 and CNRS, UMR 5586, F-69622 Villeurbanne, France.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Palacci
authors.forename: Cécile
authors.initials: C
authors.lastname: Cottin-Bizonne
authors.forename: Christophe
authors.initials: C
authors.lastname: Ybert
authors.forename: Lydéric
authors.initials: L
authors.lastname: Bocquet
mesh_terms: D003102:Colloids; D006112:Gravitation; D007840:Latex / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D010984:Platinum / Q000737:chemistry; D013535:Suspensions / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics
chemical_list: D003102:Colloids; D007840:Latex; D013535:Suspensions; D010984:Platinum