Brownian motion in quasibidimensional colloidal suspensions Article uri icon

abstract

  • Digital video microscopy is used to study the Brownian motion in quasibidimensional colloidal systems, consisting of spherical polystyrene particles suspended in water and confined between two glass plates. This technique allows the direct measurement of the lateral (two-dimensional) probability distribution function, [Formula Presented] of the random variable Δr (the particle displacement) at time [Formula Presented] and the mean squared displacement [Formula Presented] We studied the effect of confinement in highly diluted samples, where [Formula Presented] is found to be a linear function of time. The hydrodynamic interactions between the colloidal particles and the glass walls are found to be more important than predicted by approximate hydrodynamic theories. Keeping fixed the separation between the plates, we studied the effect of direct and hydrodynamic interactions between the particles by increasing the particle concentration. In this case, the short time dynamics is characterized by means of a theoretical approach that describes self-diffusion in terms of the static structure of the suspension. In all the samples studied, we found negligible deviations of [Formula Presented] from Gaussian behavior. © 1997 The American Physical Society.

publication date

  • 1997-01-01