Hydrodynamic activation and sorting of white blood cells in a microfabricated lattice

We demonstrate a novel hydrodynamic shear activation of leucocyte adhesion, using physiological flow conditions and a microfabricated array of channels with length scales similar to those of human capillaries. Vital chromosome stains and cell specific fluorochrome labeled antibodies reveal that the eventual adhesion of the leukocytes to the silicon array displays a strong dependence on cell type and nuclear morphology, with granulocytes activating more rapidly with distance and penetrating a smaller distance than lymphocytes. Further, the granulocytes interact with the lymphocytes in a self-exclusionary manner under shearing flow with the eventual separation of the two cell types in the array. Such arrays of microfabricated obstacles thus have an interesting potential for sorting white blood cells by type from a 10 microliter drop of whole blood.