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 mu m 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 mu W 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. (C) 2011 Elsevier B.V. All rights reserved.