title: Stochastic interactions of two Brownian hard spheres in the presence of depletants.
abstract: A quantitative analysis is presented for the stochastic interactions of a pair of Brownian hard spheres in non-adsorbing polymer solutions. The hard spheres are hypothetically trapped by optical tweezers and allowed for random motion near the trapped positions. The investigation focuses on the long-time correlated Brownian motion. The mobility tensor altered by the polymer depletion effect is computed by the boundary integral method, and the corresponding random displacement is determined by the fluctuation-dissipation theorem. From our computations it follows that the presence of depletion layers around the hard spheres has a significant effect on the hydrodynamic interactions and particle dynamics as compared to pure solvent and uniform polymer solution cases. The probability distribution functions of random walks of the two interacting hard spheres that are trapped clearly shift due to the polymer depletion effect. The results show that the reduction of the viscosity in the depletion layers around the spheres and the entropic force due to the overlapping of depletion zones have a significant influence on the correlated Brownian interactions.
authors.affiliation: Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut 06269-3139, USA.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Karzar-Jeddi
authors.affiliation: Vant Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Department of Chemistry, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
authors.forename: Remco
authors.initials: R
authors.lastname: Tuinier
authors.affiliation: Graduate School of Engineering, Kyoto University Katsura Campus, Nishikyo-ku, Kyoto 615-8510, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut 06269-3139, USA.
authors.forename: Tai-Hsi
authors.initials: TH
authors.lastname: Fan