(519j) Axial Dispersion of Brownian Colloids in Microfluidic Channels
We present a complete theoretical framework for the axial dispersion of a Brownian colloidal suspension confined in a parallel plate channel, extending the Taylor-Aris treatment to particles with diameters comparable to the channel width. The theoretical model incorporates the effects of confinement on the colloid distribution, corrections to the velocity profile due to the effects of colloid concentration on the suspension viscosity, and position-dependent anisotropic diffusivities. We test the theoretical model using explicit-solvent molecular dynamics simulations that fully incorporate hydrodynamic correlations and thermal fluctuations, and obtain good quantitative agreement between theory and simulations. We find that the non-uniform colloid structuring that arises in confinement due to excluded volume between the colloids and channel walls significantly impacts the transport properties of the suspension. The developed model should prove useful in many applications involving the axial dispersion of colloids, including extracting diffusion coefficients from microfluidic experiments and modeling the transport of colloids in geological fractures.