Bi and tri-layer flows of blood of different cell concentration have been flowed through slits of high aspect ratio and heights on the order of 300 um. The effluent stream has been carefully sampled by extracting different fractions of the whole stream through side branches, allowing the estimation of cell distribution over the transverse section. Results for different initial hematocrit distributions, wall shear rates, and residence times will be presented and used to quantify the contributions of shear induced drift away from the slit wall and shear induced diffusion, which tends to mitigate the drift. Residence times required to reach equilibrium between these processes will be reported.

Results shed light on fundamental processes of cellular movement in microfluidic flows and provide new data to aid in the design of practical devices, including those that are therapeutically useful. These new devices include filters sized to separate plasma from cells and membranes deployed in microfluidic environments to effect very rapid extraction of solutes from blood.