Hydrodynamic blood cell separation using fishbone shaped microchannel for circulating tumor cells enrichment

Cancer patients have a range of from 1 to 1000 circulating tumor cells (CTCs) with 5 × 109 erythrocytes in 1 ml volume of their peripheral blood. Due to this rarity of CTCs, a pre-process for the enrichment of CTCs in blood sample is required. For a fast and passive CTCs enrichment process, we developed a fishbone shape microchannel, which has geometry of 50 repeated 45° angled expansion and contraction channels. The enrichment process can be achieved from the differences between the dominant forces with respect to the diameter of each type of cell. For the feasibility test, we used three different sizes of microparticles of 2 μm, 6 μm, and 13 μm dia. to mimic platelet, erythrocytes, and leukocyte or human breast cancer cells, respectively. The results show that the smaller particles (2 μm or 6 μm dia.) laterally move to both side wall directions by dominant inertial lift force, whereas the larger particle (13 μm dia.) focused on the centerline of the channel by dominant momentum change-induced inertial force under appropriate fluid flow velocity. We also performed a cell separation experiment using MCF-7 and a human erythrocyte mixture. The recovery efficiency of MCF-7 is over 98% at the detection window with a high throughput (250 μl/min).