An apparatus for performing contactless ODEP for separation of CTCs comprises an ODEP device including a first conductive glass, a bio-compatible membrane, and a second conductive glass, the bio-compatible membrane includes a transverse main channel and a longitudinal micro channel perpendicular to the main channel and joining the main channel at a cell separation zone; the first conductive glass includes a first hole and a second hole aligned with two ends of the main channel respectively, and a third hole aligned with one end of the micro channel that is distal to the cell separation zone; a sample receiving member disposed on and aligned with the first hole; an exhaust discharge member disposed on and aligned with the second hole; a target collection member disposed on and aligned with the third hole; and a controller including an optical projection device and an image fetch device.