Micromachined bubble-jet cell sorter with multiple operation modes

We present a high-speed microfluidic cell sorter employing embedded heaters and nozzles to generate deflecting jets to change the movement of the cells. We simulated the transient flow fields to validate the concept and optimize the sorter design. The simulation demonstrates spatial switching windows corresponding to 1.1, 1.5, and 2.4 times the switching chamber length for push, pull, and combined operation modes, respectively. A single-jet sorter with one actuator and one nozzle is also demonstrated for binary sorting. Experimental verification was obtained using micromachined devices characterized by stroboscopic measurements. With a 4.9 μs working period for the 20 μm × 20 μm heaters that generate the deflecting jets, the sorter can potentially attain a working frequency of 50 kHz or higher. We built a scattered-light based optical system to detect moving particles and successfully performed sorting of 20 μm microspheres. This type of sorter is promising for micromanipulation of a variety of biological cells and inorganic particles.