Stochastic interactions of two Brownian hard spheres in the presence of depletants

Abstract

Brownian dynamics simulation of the motion of a rigid sphere in a viscous fluid very near a wall J. Chem. Phys. 113, 9268 (2000) 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 longtime 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. © 2014 AIP Publishing LLC. [http://dx

The second law of thermodynamics is riddled with (in percentage terms extremely rare) exceptions

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