Microfluidic Electrophoresis Chip Channel Quality And Band Broadening

Electrophoresis separation on glass chip is an essential aspect in the development of microfluidic system. The aim of this study is to improve the separation efficiency of chip-based CE. Channel quality of the glass microchip and band broadening in chip-based CE were studied.In the first chapter, the literatures about properties of glass, the fabrication technology for production of glass microfludic chips, the methods for measuring diffusion coefficient and parameters effecting the separation efficiency and band broadening in chip-based CE system are reviewed.In the second chapter, the eching solution has been optimized for improving the microfluidic channel quality. The diffusion variances, the sum of the injection and detection variances and the dynamic diffusion coefficients for fluorescein sodium and rhodamine 123 have been measured in microfluidic chips. Experiment showed that the diffusion variances and variances from detection speed were the key factors for band broadening in chip-based capillary electrophoresis due to the short separation channel length, high electric field strength and high separation speed.Microfluidic channel quality were improved by wet etching in the solution of 1:0.5:0.75 mol/L HF/NH4F/HNO3 at 40℃. Experiment showed that the separation efficiency in glossily channel for fluorescein sodium was 4.8 x105 per meter, under the electric field 200 V/cm and the separation length 3.5 cm, 17% higher than in rough channel.Diffusion coefficient can be easily measured on microfluidic CE by changing separation length. The diffusion coefficient for fluorescein sodium obtained by this method was 3.4±0.2 X 10~-6cm2/s, agree well with the value in literature.Band broadening during injection and separation were investigate by microscope photograph and sample separation experiment. Experiment showed that the variance from detection speed is the main part of the detection variances, if the respond time of detection system is not fast enough. Higher electric field applied and higher mobility of component increased influence from variances from detection speed. By experiment and calculation, the respond time of our detection system was found to be 0.35 second, which limited to increasing the separation efficiency and resolution by using high electric field. Detector with fast respond can result in both fast and efficient separation.