Hydrodynamic interactions in quasi-two-dimensional colloidal suspensions -art. no. 038302

The effects of the hydrodynamic interactions on the short-time dynamics of colloidal, hard-sphere-like particles confined between two parallel walls a re measured by digital videomicroscopy. We find that such effects can be de scribed in terms of an effective two-dimensional hydrodynamic function H(k) , de fined as a straightforward adaptation to two dimensions of the corresp onding object describing collective dynamics for the three-dimensional (3D) suspensions. Interestingly, the behavior of H(k) is qualitatively similar to the hydrodynamic function of 3D suspensions of hard spheres. We also fou nd that for values of k where the static structure factor is 1, the dynamic s is determined only by self-diffusion.