| Based on the optimization of SU-8 photolithography, the design and fabrication of photomask and a new-type sealing technology, a kind of polymer-based (SU-8, EA51, PMMA, BOPP, etc.) microfluidic reactor with simple and fast process as well as low cost was achieved. Instead of traditional hot-press sealing technology, we adopted surface photografting polymerization of photo-crosslinked oligomer (EA51) to create a seal cover with considerable transparency, with UV transmittance (365nm) reaching 78%. Therefore the reactor facilitates both the observation of chemical reaction and photo-induced chemical reaction. In order to enhance the application scope of the microfluidic reactor, the substrate PMMA and micro-channels were modified for being further chemically-resistant and hydrophilic, respectively. So the reactor is adapted to both water-phase reaction and harsh chemicals. The main work is stated as the following:1. The optimization of SU-8 process parameters was carried out in combination with conditions of current lab facilities. The experiment results showed that soft-bake, exposure and post-bake are of most importance for definition of microfluidic pattern. For 50μm SU-8, the optimized parameters are: (1) Soft-bake: 5 minutes at 65℃, and gradually (6℃/min) increased to 95℃for 15 minutes; (2) Exposure: 120mJ/cm~2, with least exposure time; (3) Post-bake: 2 minutes at 65℃, and gradually (6℃/min) increased to 95℃for 4 minutes; (4) Developing: 8-10 minutes in SU-8 developer (oscillation at 40℃, 150rpm/min). Specific conditions for steps above were finely tuned according to the thickness of SU-8. In this work, precise photolithography of SU-8 microfluidic pattern was accomplished, with thickness of ranging from 20 to 300μm, characteristic size (channel width) of 40μm, and aspect ratio up to 6.2. Chemical reaction-oriented photomask was prepared and thus the micro-reactors fabricated. For higher degree of UV transmittance and lower cost, EA51 -coated (containing single-functional monomer and photoinitiators) BOPP (40μm, high UV transmittance) was used as sealing cover for micro-reactors, after EA51 coating become a kind of semi-solid adhesive under suitable pre-exposure. Experiments showed that UV transmittance (365nm) of EA51 coating was 78%, higher than that (50%) of SU-8 coating of the same thickness (60μm). The hydroxylation of BOPP is crucial for form of uniform EA51 coating and strong bond between BOPP and EA51. The flexible sealing process did not leak EA51, nor were there traces of blockage at sealed channels.3. The substrate of micro-reactor (PMMA) was made further chemically-resistant through surface modification with EA51. EA51 coating firmly formed on PMMA will protect PMMA from contacting with harsh chemicals. Robust bond also existed between EA51 and SU-8 microfluidic structures, because of the similar "Epoxy" structure. As construction materials of microfluidic channels, EA51 and SU-8 were hydroxylated and thus lower water-contact angles gained for the both. Flowing rate of water in channels driven by gravity was remarkably increased after hydroxylation modification.
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