Lab Chip 12, 1378–1383 (2012)

Credit: © 2012 RCS

One of the major applications of flow cytometry is separating cells according to subtype for further biological studies. Current cell-sorting techniques are limited in their purity and throughput, and the ability to sort mixed populations of live cells has yet to be demonstrated. Pei-Yu Chiou and co-workers in the USA have now developed a high-speed, high-purity laser-triggered fluorescence-activated cell sorter. Their device is capable of sorting up to 20,000 mammalian cells per second with a purity of 37%, or 1,500 cells per second with a purity of more than 90%. The device achieves fast switching (30 μs) in a small volume (around 90 pl) by using 532 nm focused pulses from a Q-switched Nd:YVO4 laser to produce vapour bubbles in a microfluidic circuit made from PDMS. The laser-induced bubbles create a liquid jet that temporarily switches the flow of cells from the main channel to a second (collection) channel. The volume and location of the fluid flow can be precisely controlled by the laser pulse energy and focus position, thus allowing multiple cell types to be sorted in any biological liquid. The researchers say that shorter switching times should be possible by utilizing smaller bubbles and a modified channel design.