Spreading of colloid clusters in a quasi-one-dimensional channel.

The effect of hydrodynamic interactions on the spreading of clusters of colloid particles in a quasi-one-dimensional channel is analyzed both experimentally and theoretically. An n-particle cluster spreading diffusion coefficient is defined, in terms of the displacement Δx(t) in time t, by Dn≡<[∑i=1nΔxi(t)]2>/2nt, where the average is taken over all groups of n adjacent particles. Our study focuses on the n-dependence of Dn with some attention to the dependence of Dn on colloid packing fraction. We find that the ratio of Dn to the infinite dilution self-diffusion coefficient DS0 increases as n increases, eventually saturating for large n. The observed dependence of Dn on n is in satisfactory agreement with the predictions obtained from both Stokesian dynamics simulations and hydrodynamic calculations using the method of reflections. [ABSTRACT FROM AUTHOR]