Novel Techniques For The Fabrication Of Cyclic Olefin Copolymer Microfluidic Chips And Chip Electrophoresis With Amperometric Detection

Microfluidic chips electrophoresis is a novel high performace separation and detection technique established in recently years that has attracted more and more atterntion. Amperometric detection, which with the advantages such as high sensitivity, high selectivity, simple equipment and easy miniaturization etc., is one of the most widely used detection methods in capillary and chip electrophoresis. The aim of the project described in this thesis is to establish a platform of chip electrophoresis with micro-chips made of a new thermoplastic material, cyclic olefin copolymer (COC), and amperometirc detection. The reseach includes the fabrication techniques of COC chips, formation of hydrogel plugs in the microchannels and several aspects with regard to the ampermetric detection. The thesis contains four chapters:1. Introduction:The status and progress of the microfluidic chip based electrophoresis of the recent years has been reviewed, with the emphasis on the chip materials, fabrication methods, and the principle and application of amperometric detection in microchip format.2. Fabrication of COC microchip:To reduce the cost of the microchip based analysis, the fabrication methods have to meet the requirments of simple, fast and acceptable quality in mass production. A modified wire embossing technique was established for fabrication of micro channels with circular cross-section. A method that using photosensitive dry film as the mold for embossing complicated patterns of microchannel networks was established. The influence of different base materials, copper clad laminates and microscope slides, was examined. The factors including solvent composition, temperature, pressure and sealing time were systematically investigated and the optimum condition was selected. The proposed method is simple and has the capability to fabricate complicated microchannel networks.3. Hydrogel grafting inside channels:Localized hydrogel plugs inside microchannel has the potential to be used for sample preconcentration, separation field decoupling in amperometric detection etc., but it is very difficult to be fabricated with normal chemical methods. In this work, a photochemical method was used with high intensity UV lamp as the light source, benzophennone as the initiator, N,N'-Methylenebisacrylamide as the crosslinker to form poly (β-Hydroxyethyl methacrylate) hydrogel at predetermined segments of the microchannels. Influence of variuous parameters on the quality of the hydrogel was investigated and the optimum condition was obtained.4. Amperometric detection in microchips:With lab-built miniaturized virtul potentiaostat and proper software that writen in Labview, the influence of microchannel configuration, separation medium and electrode arrangement was investigated using pencil lead as the working electrode. The alignment of the working electrode was performed by a guiding channel fabricated at the end of the separation channel. Adopting separation channel with smaller diameter and adding sheath flow were both used for eliminating the influence of separation voltage. Dopamine was successfully detected on the COC microchips with end-column amperometric detection, and acceptable peak shape was obtained.