| Several novel microfluidic systems including integrated flow cytometors and miniaturized fluorescence detectors using organic light emitting diode as single point or two dimensional light sources were developed for cellular manipulation, apoptotic analysis and whole column imaging detection, respectively.A simple cross-channel microchip was employed for flow cytometry and single cell fluorescence detection, where cells were introduced into micro-channels and driven passing through the detector by combined effect of hydrodynamic and electric power. This miniaturized flow cytometor was applied to estimate the damage degree of HeLa cells exposed to ultraviolet (UV) radiation for 10, 20 and 40 min respectively by the number of cells determined and their fluorescence intensity.As cells were found damaged in electric field when electric force was employed for driving cells in flow cytometor, a novel microfluidic device based on gravity driving was developed for flow cytometry and cell sorting. In the experiments, cells flowed spontaneously under their own gravity in an upright-put microchip, passed through the detection point and then entered into the sorting electric field one by one at average velocity of 0.55 mm/s for cell sorting. In order to study the dynamical and kinematical characteristics of single cell in gravity and electric field, physical and numerical module based on Newton's Law of motion was established and optimized. This system was also applied to estimate necrotic and apoptotic effect of UV radiation on HeLa cells and results shown that UV radiation induced membrane damage contributed to apoptosis and necrosis of HeLa cells.However, a bulky laser induced fluorescence detection system was still an obstacle for further miniaturization of microfluidic systems. Therefore, a simply fabricated microfluidic device using a green organic light emitting diode (OLED) and thin film interference filter as integrated excitation source was then presented and applied to fluorescence detection of proteins. A layer-by-layer compact systemconsisting of glass/PDMS microchip, pinhole, excitation filter and OLED were designed and equipped with a coaxial optical fiber for fluorescence detection. A 300μm thick excitation filter was employed for eliminating nearly 95% of the unwanted light emitted by OLED which had overlaped with fluorescence spectrum of the dyes. The distance between OLED illuminant and microchannels was limited to 1mm for sensitive detection. This system was used for fluorescence detection of Rhodamine6G, Alexa532 and BSA conjugates in 4% linear polyacrymide (LPA) buffer (in 1×TBE, pH8.3) and 1.4 fmol of mass detection limit at 0.7nL injection volume for Alexa532 was obtained.Although sensitivity achieved by the above OLED induced fluorescence detection system was roughly six orders of magnitude poorer than good laser-induced fluorescence detection in capillary electrophoresis because of its low irradiance and purity, OLEDs have the potential to be used as a two dimensional light source for whole column imaging detection in isoelectric focusing (IEF) systems, which is problematic for lasers and high performance LEDs. So an integrated and simplified microfluidic device using OLED array as the two dimensional light source for single- and multi-channel whole column imaging detection was developed and used for IEF of R-phycoerythrin. The IEF conditions were optimized and the total analysis time was extremely reduced to 15s for 1cm long microchannels at 700V/cm of electric field strength without the presence of electroosmotic flow (EOF). The compression of pH gradient caused by electrolytes drawning into the microchannels was efficiently restrained when 1% of hydroxylpropylmethyl cellulose (HPMC) in 2% ampholyte was used as the carrier for IEF. Under optimized IEF conditions, the detection limit of this system was～2.5×10-99 mol/Lor 45 pg at 75nL per column injection of R-phycoerythrin.
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