Novel continuous particle sorting in microfluidic chip utilizing cascaded squeeze effect

This article presents a novel technique for the continuous sorting and collection of microparticles in a microfluidic chip using a cascaded squeeze effect. In the proposed approach, microparticles of different sizes are separated from the sample stream using sheath flows and are then directed to specific side channels for collection. The sheath flows required to separate the particles are generated using a single high voltage supply integrated with a series of variable resistors designed to create electric fields of different intensities at different points of the microchip. Numerical simulations are performed to analyze the electrical potential contours and flow streamlines within the microchannel. Experimental trials show that the microchip is capable of continuously separating microparticles with diameters of 5, 10 and 20 mu m, respectively. To further evaluate the performance of the microchip, a sample composed of yeast cells and polystyrene beads is sorted and collected. The results indicate that the microchip achieves a recovery ratio of 87.7% and a yield ratio of 94.1% for the yeast cells and therefore attains a comparable performance to that of a large-scale commercial flow cytometer. Importantly, the high performance of the microchip is achieved without the need for a complex control system or for sophisticated actuation mechanisms such as embedded microelectrodes, ultrasonic generators, or micropumps, and so forth.