Abstract
Flow cytometry is a popular technique for counting and sorting of individual cells. This study presents a new chip-based flow cytometer capable of cell injection, counting and switching in an automatic format. The new microfluidic system is also capable of multi-wavelength detection of fluorescence-labeled cells by integrating multiple buried optical fibers within the chip. Instead of using large-scale syringe pumps, this study integrates micro-pumps and micro-valves to automate the entire cell injection and sorting process. By using pneumatic serpentine-shape (S-shape) micro-pumps to drive sample and sheath flows, the developed chip can generate hydrodynamic focusing to allow cells to pass detection regions in sequence. Two pairs of optical fibers are buried and aligned with the microchannels, which can transmit laser light sources with different wavelengths and can collect induced fluorescence signals. The cells labeled with different fluorescent dyes can be excited by the corresponding light source at different wavelengths. The fluorescence signals are then collected by avalanche photodiode (APD) sensors. Finally, a flow switching device composed of three pneumatic micro-valves is used for cell sorting function. Experimental data show that the developed flow cytometer can distinguish specific cells with different dye-labeling from mixed cell samples in one single process. The target cell samples can be also switched into appropriate outlet channels utilizing the proposed microvalve device. The developed microfluidic system is promising for miniature cell-based biomedical applications. © 2007 The Japan Society of Applied Physics.