Microfluidic cell counter/sorter utilizing multiple particle tracing technique and optically switching approach

This paper proposes a novel microfluidic system based on a computer controlled digital image processing (DIP) technique and optical tweezers for automatic cell/microparticle recognition, counting and sorting in a continuous flow environment. In the proposed system, the cells/microparticles are focused electrokinetically into a narrow sample stream and are then driven through the region of interest (ROI), where they are recognized and traced in real time using a proprietary DIP system. Synchronized control signals generated by the DIP system are then used to actuate a focused IR laser beam to displace the target cells from the main sample stream into a neighboring sheath flow, which carries them to a downstream collection channel where they are automatically counted. Experimental trials show that the microchip is capable of continuously sorting and counting microparticles with diameters of 5 and 10 mum. In addition, a sample composed of yeast cells and polystyrene (PS) beads is successfully sorted and collected with a 100% of yield ratio and 91.9% of recovery ratio. The proposed system provides a simple, low-cost, high-performance solution for cell manipulation in microfluidic devices.