A Microfluidic Capillary Electrophoresis Fluorescence Detection System Based On Liquid-core Waveguide Requiring No Filters

Microfluidic chip-based capillary electrophoresis (CE) has been widely used in chemical and biological analysis because of its several advantages:high efficiency, fast speed, low consumption of sample, as well as its integration. Fluorescence detector is currently employed most broadly in microfluidic chip-based CE systems, owing to its high sensitivity and noninvasiveness. Liquid-core waveguide (LCW) tubes are capable of guiding propagation of light and serving as fluid conduits, which are used in a variety of spectroscopic applications to simplify optical configurations, replace optical components, and improve the integration. In this paper, quartz capillary tubes coated externally with gold have been developed. Based on the wavelength-selection of Au-coated LCW capillaries, a simple and miniaturized microfluidic CE fluorescence detection system was established, which discarded optical components such as filters.In chapter1, the recent progress in microfluidic capillary electrophoresis detection systems was reviewed, and the types and optical configurations of fluorescence detector were introduced in detail. The working principle of LCW and different claddings such as air, nonmetals and metals with low refractive index, were introduced respectively. Their application in the optical detection systems was summarized. Finally, the purpose and design of this work were proposed.In chapter2, Au-coated liquid-core waveguide capillary with filtering function was developed, and a microfluidic CE fluorescence detection system based on liquid-core waveguide requiring no filters was established. Gold film was prepared by electroless deposition, and the micrometer-size excitation window on it was made by photolithography and etching techniques. The effects of deposition time, excitation window width and LCW capillary length on sensitivity were investigated respectively. Fluorescence collection efficiency, waveguide ability and effective filter length of Au-coated LCW capillary were investigated theoretically and practically. With a532-nm semiconductor laser serving as excitation light source, the detection limitation for rhodamine6G was2.3×10-13mol/L (S/N=3), which was at the similar sensitivity of the system based on Teflon AF1600-coated LCW capillary. With a457-nm light-emitting diode (LED) serving as excitation light source and no filters being employed, the detection limitation of the system was2.0μmol/L (S/N=3), which was at the similar sensitivity of the system using filters. The Au-coated LCW capillary can function as sampling probe, separation channel, fluorescence propagation and filter, and this detection system just consists of a LED, an Au-coated LCW capillary and a PMT.In chapter3, the microfluidic CE fluorescence detection system based on liquid-core waveguide requiring no filters was summarized and its prospective application was discussed.