Shear-induced platelet margination in a microchannel

The lateral migration of platelets in amicrochannel is studied numerically where the hydrodynamic interactions between red cells, platelets, and vessel walls are resolved by the Stokes flow boundary integral equations. The simulations provide a clear physical description of the expulsion of the platelets by the velocity fluctuations in the core cellular flow toward the cell-depleted layer near the wall. The lateral migration is shown to be diffusional, and we further demonstrate, in agreement with previous experiments, that the diffusivity scales sublinearly with the shear rate if the relevant capillary number, Ca < 1, as a result of its intrinsic dependence on the deformation of red cells.