Fabrication And Modification Of Cyclic Olefin Copolymer Microfluidic Chips

Polymeric microfluidic chips have increasingly attracted attention because of their advantages including low cost, easily machining, versatility for surface modification and good biocompatibility. As a new engineering thermoplastic, cyclic olefin copolymer (COC) takes more and more attention in recent years. COC is a low cost polymer with some unique properties, such as high chemical resistance, excellent transparency and low background fluorescence. However, the surface of COC microchannel is hydrophobic like most plastics. As a result of hydrophobic interaction, the surface of the channel can adsorb molecules like proteins, leading to poor reproducibility and analyte loss. This hydrophobic property makes the further application of COC chips very challenging. This work described in this thesis mainly focuses on COC microfluidic chip-based capillary electrophoresis, which is listed as follows.1. Based on wire hot-embossing method, a facial way towards mass-production of COC microfluidic chips had been established. In this work, small-diameter copper wires were used as masters to imprint channels with the aid of binder clips. After hot-imprinting, the copper wires were etched away by nitric acid easily. Cylindrical and smooth channels were fabricated through optimizing conditions of temprature and heating time. A mixture of four amino acids including arginine, glycin, leucine and glutamic acid labeled with FITC was successfully separated in a thus prepared COC microchip using electrophoresis with laser-induced fluorescence (LIF) detection. The FITC-labeled amino acids were baseline resolved within 80 s.2. Surface modification of COC microchip by sulfonation with chlorosulfonic acid as sulfonating agent was carried out. The modified polymer surfaces were found to be more hydrophilic in comparison to their unmodified counterparts. The contact angle of prinstine COC surfaces was found to be 82°, while the contact angle of sulfonated COC surfaces was 41°. More efficient seperation of a mixture of amino acids on the modified COC microchips were achieved comparing with the native COC microchips. The modified chips were further employed in the analysis of tea and red wine by microchip based capillary electrophoresis.3. Surface bromination of COC was carried out by UV irradiation of bromine solution in contact with chip surface. Surfaces with-OH or-NH2 groups were obtained through nucleophilic substitution by soaked the bromined COC in sodium hydroxide or ethylenediamine solutions. The performance of modification was characterized by contact angle and dyeing with sodium fluorescein. The results clearly showed that the surfaces of modified COC were more hydrophilic. The wall of microchannels of COC chip were modified, and the chips were used in chip based electrophoresis and the protein adsorption tests. The chips with-NH2 fuctional group were found to be effective on elimination of protein adsorption. The analytical performance of chips with-OH fuctional group was characterized by electrophoresis of sodium fluorescein and animo acids. A theoretical plate number of 4.7×105/m was attained for sodium fluorescein.