Integration of CTC enrichment methods. (a) Two-stage microfluidic chip consisting of a focusing region, geometrically activated surface interaction (GASI) region, and magnetic-activated cell sorter (MACS) to selectively separate CTCs depending on EpCAM expression level. Magnets in the first stage chip separate CTCs and WBCs bound with CD-45 antibody-coated magnetic particles. CTCs pass through the focusing region and move into EpCAM antibody-coated GASI region. EpCAM (+) CTCs are captured in the surface of the GASI region and EpCAM (−) CTCs are separated; (b) The monolithic chip integrates with deterministic lateral displacement (DLD), inertial focusing, and MACS to split purified CTCs from blood cells. Blood cells injected the monolithic chip and red blood cell (RBC) and platelets are removed in DLD region. CTCs and WBCs are aligned in the inertial focusing channel and two cells are separated in the MACS channel. Pure CTCs are collected after passing through the 2nd inertial focusing and MACS channel. Reproduced from ref. [36,39] with permission from 2015 ELSEVIER and 2017 Nature Publishing Group.