Surface Treated PDMS by UV-Vis Light Applied to Micro-fluidic Device
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1139-GG03-32
Surface Treated PDMS by UV-Vis Light Applied to Micro-fluidic Device Seisuke Kano1, Sohei Matsumoto1 and Naoki Ichikawa1 National Institute of Science and Technology (AIST), JAPAN
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ABSTRACT Hydrophobic property of PDMS surface was improved by the 400 W UV-Vis lamp light irradiation in the atmospheric condition for several ten minutes. As a result of this surface treatment, the surface became to hydrophilic character for one month long. This surface treatment technique applied to PDMS microfluidic device and verified valve-less switching. The UV-Vis light irradiated to PDMS micro fluidic pattern with partly covered by aluminum foil. Finally inlet and outlets were connected 0.5 mm diameter tubes. The syringe pumps injected the distilled water into the inlet of the PDMS micro channel at the flow rates of 0.5, 5.0, and 50 µl / min for the both width channel. As results of water injection water flowed only the UV-Vis treated channel at the flow rates of 0.5 and 5.0 µl / min. On the other hand, the water flowed for all channels at the flow rate of 50 µl / min. This result was observed from 5.0 µl/min flow again for both width devices which dried by air. These results were occurred by the difference of the flow conductance and wettability. The mechanism of this hyrophilicity of PDMS was reported to form Si-O in the surface by means of glassy surface. From the IR spectra, the Si-O-Si peak shifted to higher wave number for UV-Vis irradiated PDMS than the untreated PDMS comparing with the other IR peaks. This result showed that the Si-O-Si network bonding of PDMS changed to the O-Si-O bonding around the surface.
INTRODUCTION Polydimethyl siloxane, PDMS, has a highly potential as using to micro fluidic device, because of its economical, ecological, and flexible properties. However its surface showed hydrophobic property, therefore its application was limited. Lots of researchers try to surface treatments to control the wettability [1] by plasma irradiation [2-4], VUV light irradiation [5, 6], and so on. And also discussing the mechanism of hydrophilic surface of PDMS was reported as forming O-Si-O near the top surface by means of glassy surface. The problems of theses surface treatment were the hydrophilic property disappeared in a few hours. The reason was unknown yet but one of the possibilities the O-Si-O binding recover to Si-O network connection of PDMS origin. In many cases the treatments might be limited on the top surface of the PDMS by lower energy than that of concreting glassy O-Si-O bindings. The PDMS can store gas inside the body, that is, the body has channels connect to the surface. This structural property might be induced above recovery phenomena of the Si-O bindings. Therefore in our study the surface of PDMS was treated by irradiation of strong power light and changing the bindings inside the body. In our research, several types of UV lights including pulsed laser beam irradiated to the PDMS surface. It was succeeded to obtain long term hydrophilic surface of PDMS by the irradiation of high
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