title: Brownian diffusion of a partially wetted colloid.
abstract: The dynamics of colloidal particles at interfaces between two fluids plays a central role in microrheology, encapsulation, emulsification, biofilm formation, water remediation and the interface-driven assembly of materials. Common intuition corroborated by hydrodynamic theories suggests that such dynamics is governed by a viscous force lower than that observed in the more viscous fluid. Here, we show experimentally that a particle straddling an air/water interface feels a large viscous drag that is unexpectedly larger than that measured in the bulk. We suggest that such a result arises from thermally activated fluctuations of the interface at the solid/air/liquid triple line and their coupling to the particle drag through the fluctuation-dissipation theorem. Our findings should inform approaches for improved control of the kinetically driven assembly of anisotropic particles with a large triple-line-length/particle-size ratio, and help to understand the formation and structure of such arrested materials.
authors.affiliation: Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, 34000 Montpellier, France.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boniello
authors.affiliation: Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, 34000 Montpellier, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Blanc
authors.affiliation: Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, 34000 Montpellier, France.
authors.forename: Denys
authors.initials: D
authors.lastname: Fedorenko
authors.affiliation: Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, 34000 Montpellier, France.
authors.forename: Mayssa
authors.initials: M
authors.lastname: Medfai
authors.affiliation: Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, 34000 Montpellier, France.
authors.forename: Nadia Ben
authors.initials: NB
authors.lastname: Mbarek
authors.affiliation: Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, 34000 Montpellier, France.
authors.forename: Martin
authors.initials: M
authors.lastname: In
authors.affiliation: Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, 34000 Montpellier, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Gross
authors.affiliation: Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, 34000 Montpellier, France.
authors.forename: Antonio
authors.initials: A
authors.lastname: Stocco
authors.affiliation: Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, 34000 Montpellier, France.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Nobili