title: Size dependence of tracer diffusion in a laponite colloidal gel.
abstract: Using a fluorescence recovery after photobleaching (FRAP) technique, we present measurements of probe diffusion in a colloidal glass-a Laponite suspension. By varying the probe size over 2 orders of magnitude, as well as the concentration of the colloidal glass, we evidence and quantify the deviations of the probe diffusivity from the bulk Stokes-Einstein expectations. These experiments suggest that the probe diffusion in the dynamically arrested Laponite structure is mainly controlled by the ratio between the probe size and the typical clay platelets interdistance. Comparing with a simple hindered diffusion mechanism, the reduction of tracer diffusion is discussed in terms of the hydrodynamic interaction of the probe with the Laponite structure. Finally, these results can be interpreted in terms of a scale dependent viscosity of the colloidal glass.
authors.affiliation: Laboratoire de Physique de la Matière Condensée et Nanostructures, Université de Lyon, Université Claude Bernard Lyon 1, CNRS, UMR 5586, Domaine Scientifique de la Doua, F-69622 Villeurbanne Cedex, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Petit
authors.forename: Catherine
authors.initials: C
authors.lastname: Barentin
authors.forename: Jean
authors.initials: J
authors.lastname: Colombani
authors.forename: Christophe
authors.initials: C
authors.lastname: Ybert
authors.forename: Lydéric
authors.initials: L
authors.lastname: Bocquet