Fluctuation Amplitude of a Trapped Rigid Sphere Immersed in a Near-Critical Binary Fluid Mixture within the Regime of the Gaussian Model

Abstract

The position of a colloidal particle trapped in an external field thermally fluctuates at equilibrium. As is well known, the ambient fluid is not a simple heat bath and the particle mass appears to increase, which influences the mean square velocity of the particle. In this study, we suppose that the particle is surrounded by a binary fluid mixture in the homogeneous phase near, but not too close to, the critical point. Usually, one component is preferably attracted by the particle surface, and the resultant adsorption layer becomes significant because of the near-criticality. When the particle fluctuates in this situation, its mean square displacement should also be influenced by the ambient fluid because the adsorption layer does not follow the particle motion totally. We calculate the influence in a simple case, where a rigid spherical particle fluctuates with a small amplitude and its surface attracts one component weakly. We utilize the hydrodynamics in the limit of no dissipation to examine the contribution from the ambient mixture to the equal-time correlation, which is shown to be reduced by an additional stress, including osmotic pressure.

13 pages, 4 figures

References in corpus (4)

• Nonequilibrium critical Casimir interactions in binary fluids
• High-resolution detection of Brownian motion for quantitative Optical Tweezers experiments
• Attractive interaction and bridging transition between neutral colloidal particles due to preferential adsorption in a near-critical binary mixture
• Undulation Amplitude of a Fluid Membrane Surrounded by Near-Critical Binary Fluid Mixtures

Cited by in corpus (8)

• Drag Coefficient of a Rigid Spherical Particle in a Near-Critical Binary Fluid Mixture beyond the Regime of the Gaussian Model
• Tracer particle in a confined correlated medium: an adiabatic elimination method
• Dynamics and steady states of a tracer particle in a confined critical fluid
• Undulation Amplitude of a Fluid Membrane in a Near-Critical Binary Fluid Mixture Calculated beyond the Gaussian Model Supposing Weak Preferential Attraction
• Inducing oscillations of trapped particles in a near-critical Gaussian field
• Drag Coefficient of a Circular Inclusion in a Near-Critical Binary Fluid Membrane
• Fluctuations of the critical Casimir force
• Nonequilibrium relaxation of a trapped particle in a near-critical Gaussian field