Spark-generated microbubble cell sorter for microfluidic flow cytometry.

High-speed and accurate cell sorting is of great significance for cell analysis regarding both bioresearch and clinical application. Different from the jet-in-air sorting of commercial flow cytometers, sorting in fully enclosed and disposal microfluidic chips can avoid aerosols and crosscontamination, thus contributing to the improvement of biosafety and test accuracy. However, current microfluidic sorters usually require complicated structures, or otherwise cannot attain high throughput. In this article, a sorting mechanism for microfluidics is proposed for the first time based on the jet flow induced by the spark-generated cavitation microbubble that can be easily realized by a pair of electrodes. The sorter was integrated into a microfluidic chip based on three-dimensional (3D) hydrodynamic focusing and a binary optical element (BOE) for laser illumination. Besides, several aspects of the sorting mechanism were studied to optimize the device. It achieved a switching time of 250 μs at the sample flow velocity of 5 m/s and performed the continuous operation at 200 Hz. Both the stability of fluorescence signals and the viability of cells were basically maintained. To conclude, this work explores a new on-chip sorting mechanism which possesses the merits of simple structure, easy control, and fast switching.