title: Direct measurement of anisotropic near-wall hindered diffusion using total internal reflection velocimetry.
abstract: By applying the three-dimensional total internal reflection velocimetry (3D-TIRV) technique to freely suspended micron-sized fluorescent particles, we are able to simultaneously observe the three-dimensional anisotropic hindered diffusion for values of the gap-size-to-radius ratio much less than one. We demonstrate that the 3D-TIRV can be used to accurately track freely suspended 1.5-mum radius particles. The displacement measurements reveal that the hindered diffusion coefficients are in close agreement with the theoretical values predicted by the asymptotic solutions of Brenner [Chem. Eng. Sci. 16, 242 (1961)] and Goldman [Chem. Eng. Sci. 22, 637 (1967)] for gap-size-to-radius ratio much less than one, while hindered diffusion anisotropicity is simultaneously observed in all data sets.
authors.affiliation: Division of Engineering, Brown University, Providence, Rhode Island 02912, USA. peter.huang@tufts.edu
authors.forename: Peter
authors.initials: P
authors.lastname: Huang
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Breuer