Microfluidics or lab-on-a-chip technology has shown great potential for the separation of target particles/cells from heterogeneous solutions. Among current separation methods, vortex sorting of particles/cells in microcavities is a highly effective method for trapping and isolating rare target cells, such as circulating tumor cells, from flowing samples. By utilizing fluid forces and inertial particle effects, this passive method offers advantages such as label-free operation, high throughput, and high concentration. This paper reviews the fundamental research on the mechanisms of focusing, trapping, and holding of particles in this method, designs of novel microcavities, as well as its applications. We also summarize the challenges and prospects of this technique with the hope to promote its applications in medical and biological research.
