Microfluidic device to separate micro-beads with various fluorescence intensities

This article presents a new microfluidic device for separating fluorescence-activated beads depending on fluorescence intensity. Our system is composed of three parts: focusing, detection, and separation. Fluorescent polystyrene beads were introduced into the microfluidic device and focused 12.8 μm to the center of the microfluidic channel by the hydrodynamic sheath flow that was eight times greater than the inlet flow. The beads were then excited by a 532 nm laser at 30 μW and simultaneously detected using a photomultiplier tube (PMT). Also, beads were separated into three outlets by a dielectrophoretic (DEP) force induced by microelectrodes at 10 V and a 500 kHz frequency, depending on their fluorescence intensities. The detection and separation processes were automated using 50% of each bead's relative intensity signal as threshold of different intensities. Using this system, we successfully manipulated and separated three different intensities of beads; in the future, genetically engineered cells will be separated depending on the expression levels of the fluorescent proteins.