Two types of high-speed particle and biomolecule sheath flow sorters were realized using thermosensitive hydrogel. One is all hydrogel sheath flow and the other is two-phase sheath flow that consists of a water flow including samples and two hydrogel carrier flows; these have been utilized instead of the air and water droplet two-phase flow used in the conventional commercialized cell sorting system. Flow switching is performed by the sol-gel transfer of the thermosensitive hydrogel generated by focused infrared (IR) laser irradiation. High-speed sorting less than 5.0 ms and no error sorting (120 000 counts) in the all hydrogel sheath flow system while 20 ms in the two-phase sheath flow was realized. Since sorting was performed in simple PDMS-glass microchannels without any electric stimulation and mechanical valve structures, the proposed system is suitable for many biochemical applications.
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