A potentially simple and selective approach to isolate leukocytes from whole blood is microfiltration. Since RBCs can deform through openings (1–2 µm) much smaller than their diameter (~8 µm), while circulating leukocytes are spherical with diameters 6–8 μm22, microfilters consisting of pillars23, 24, weirs23, 25, 26, and membrane pores23, 27 have been developed to separate these leukocytes from RBCs. A key limitation in directly processing whole blood using microfiltration is the potential for cells to clog and foul the filter microstructures. Clogging of the filter matrix alters its hydrodynamic resistance and the filtration force on each cell, resulting in a significant reduction in selectivity within the filters. Cross flow filtration can be employed to divert trapped cells using a secondary flow tangential to the filter surface23, 28–31 but does not completely release the cells adsorbed within the filter microstructures and significantly reduces the overall selectivity as well as throughput.