Figure 3.

Label-free CTC isolation method. (a) Illustration of microfluidic cell sorter. A physical barrier is located, as shown, to separate the cells by size difference. Small cells pass through the gap under the barrier and are collected at outlet 2, while the large cancer cells move along the barrier and are collected at another outlet. Reprinted with permission from the authors of [83]; (b) Schematic of the multi-obstacle architecture microfiltration chip for CTC separation. The size gradient filter chip has two filter gaps and the cells are captured between the two filter gaps. Reprinted with permission from the authors of [82]; (c) Schematic of acoustic tweezers for isolating circulating tumor cells from a blood sample. These yellow tilted transducers generate soundwaves to move the cells as they pass through the device. The tumor cells are separated from the blood cells based on the difference in size and compressibility. Reprinted with permission from the authors of [91]; (d) The principle of CTC enrichment by a spiral channel. The CTCs are focused near the inner wall because of the combination of the inertial lift force and the Dean force, while the white blood cells are focused closer to the outer wall. Reprinted with permission from the authors of [94]; (e) Illustration of VTX-1 CTC isolation platform. A blood sample flows through the microchannels and the laminar microscale vortices trap the cells based on their size, shape, and deformability. Reprinted with permission from the authors of [95].