Surface Modification of Cyclic Olefinic Copolymers for Bio-Mems Microfluidic Devices
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SURFACE MODIFICATION OF CYCLIC OLEFINIC COPOLYMERS FOR BIO-MEMS MICROFLUIDIC DEVICES C. Ahn1, S. Kim1, H. Chao1, S. Murugesan2 and G. Beaucage2 1) Center for BioMEMS and Microchannels, University of Cincinnati, Cincinnati, Ohio, 45221. 2) Dept. of Materials Science, University of Cincinnati, Cincinnati, Ohio, 45221. Abstract Cyclic Olefin copolymers (COC) are a new class of polymers that may prove to be extremely useful in injection molding of micron scale fluidic devices. In microfluidic devices it is desirable to have a hydrophilic surface such as in flow driven by capillary action. However, such hydrophilic surfaces tend to display protein deposition when contacted with blood unlike hydrophobic surfaces. Alternatives to capillary action are then needed to control fluid flow for hydrophobic surfaces. Our goal in this research is to tune the slightly hydrophobic COC surfaces through simple surface modifications that are amenable to injection molding and other processing methods. In this study, the surface of an injection molded microfluidic component made from COC was modified in order to change the surface properties important to bio-fluidic devices. Some of the techniques used in this study were plasma treatments and ASG (aerosol gel) coating. Plasma treatments were conducted by using O2, CF4 and their combination gas. O2 treated surfaces became hydrophilic with increasing time of treatment. Combining O2 and CF4 made the surfaces more hydrophobic compared to CF4 only. The structural changes after the plasma treatments were examined by ATR (Attenuated Total Reflectance) spectroscopy. Titania and silica particles from the ASG process were synthesized from titanium iso-propoxide and tetraethoxysilane, respectively. Titania coated surfaces became more hydrophilic and the silica coated surfaces did not have much change in their surface characteristics. The hydrophobicity of the plastic surfaces was measured by their contact angle with water. The implication of these treatments on bio-fluidic devices and their adaptation to the injection molding process will also be discussed.
Introduction Water wettability (hydrophilicty and hydrophobicity) is important in many applications of polymeric materials, including fabrics, printing and biomedical uses1-2, 8. Various surface-modification techniques are available to make surfaces either more hydrophilic or phobic including attaching groups to the surfaces4-7 and thermal treatment3, 5. Contact angle is one of the easiest known ways to study the hydrophobicity and hydrophilicity of a surface. Fig. 1 shows the tendency of a water droplet to wet hydrophilic and hydrophobic surfaces and the corresponding contact angles.
Figure 1 Figure showing the wettability of a droplet on a hydrophobic and hydrophilic surface
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2 COC is made by first re
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