Overview of the ‘Rare cell sorter’ for isolating and recovering single rare cells from whole blood samples.

<p>(a) External view of the ‘Rare cell sorter’. (b) Fabricated open-channel microfluidic chip. The opaque area is the main pattern with micropillars. (c) Scanning electron microscope image of the main pattern. (d) Concept of the open-channel microfluidic chip for CTC isolation and recovery. The blood sample is introduced between the supply unit and the open-channel microfluidic chip. Because of gravitational potential energy, the remaining sample gathers along a side, which has a small gap between the supply unit and microfluidic chip. Isolated CTCs can be recovered by micropipette manipulation. (e) Schematic illustration of the forces acting on the CTCs during the isolation process. The results of finite element analysis of fluid dynamics in the blood sample show that CTCs move toward the meniscus of the air–liquid interface along the black lines, which represent streamlines resulting from the drag force (<i>Fd</i>). The CTCs are then subjected to capillary force (<i>Fc</i>) associated with the meniscus of the air–liquid interface. As a result, CTCs are trapped on the microfluidic chip due to the total force (<i>F</i>), comprising <i>Fd</i> and <i>Fc</i>. (f) CTCs drift toward the meniscus of the air–liquid interface and are trapped on the microfluidic chip. Small cells, such as red blood cells (RBCs), pass through the gaps between pillars, while CTCs and some white blood cells (WBCs) remain trapped due to their larger size.