Capillary number effect on the depletion of leucocytes of blood in microfiltration chips for the isolation of circulating tumor cells

To increase the purity of isolated circulating tumor cells (CTCs) in microfiltration chips, the depletion of leucocytes in human blood was systematically studied as a function of two dimensionless parameters, Capillary number Ca and the normalized leucocyte diameter. An optimized Ca* of 0.038 was identified to differentiate the capturing of cancer cells and leucocytes. Such Ca effect can be applied as a guideline for designing an optimized microfiltration system with both high capture efficiency and purity for isolating CTCs from human blood.