Electrowetting-induced photochemical surface modificaton onto fluorocarbon
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Electrowetting-induced photochemical surface modificaton onto fluorocarbon
Hiroyuki Anai1 , Yuji Sato2 , and Masataka Murahara2 1 Department of Electrical and Electronics Engineering, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa, 259-1292, JAPAN 2 Entropia Laser Initiative, Tokyo Institute of Technology 2-12-1 O-okayama, Meguro-ku, Tokyo, 152-8552, ABSTRACT A plasma treatment method is widely used for polymer surface modification, but the hydrophilic property generated by this method deteriorates soon. Previously, we reported that an ArF excimer laser light was applied on a sample surface in the presence of water to substitute hydrophilic groups, which was modified to have a long-lasting hydrophilic property. This method, however, needed more than 10000 shots, and it is less economical compared with the plasma processing, which requires only one-minute irradiation. Thus, we demonstrated the surface modification of poly-tetrafluoroethylene [PTFE] to have a stable hydrophilic property with only 100 shots, by irradiating the ArF excimer laser on the sample at the moment when wettability was temporarily increased by the electro-wetting method.
INTRODUCTION When plastic is used as a biomedical material, it is necessary to control interactions between the material and living body at the interface, i.e., cell adhesion, cell growth, cell differentiation, and rejection symptoms. Suzuki et al. developed a synthetic dural substitute by Ne+ ion implantation into expanded polytetra-fluoroethylene (ePTFE) to give cellular adhesiveness [1]. Yasuda et al. modified polymethylmethacrylate [PMMA] and silicone rubber surfaces into hydrophilic by methane plasma treatment in order to improve the wettability and biocompatibility of contact lenses [2-3]. A plasma treatment and ion beam treatment methods are effective for modifying a large area into hydrophilic in a short time. However, these methods damage the sample surface physically, and the original characteristics of the sample material are not exercised. On other hand, Vallet et al. confirmed the electrowetting method, which placed water on a polyethylene terephalate [PET] film surface and applied a voltage of 200V between the water and the rear electrode under the PET film to decrease the contact angle by more than 30 degrees [4]. The Royal Philips Electronics (Netherlandsis) developing an electronic paper, on which video images appear, by using the electrowetting effect [5]. The electrowetting method decreases the contact angle of water temporarily when a high voltage is applied between the water and the sample, but the contact angle is restored to its original position when the voltage
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application stops [6-7]. We, therefore, modified the PTFE surface to have a stable hydrophilic by irradiating the ArF excimer laser on the sample at the moment when the wettability was increased temporarily by the electrowetting method. In our previous study, hydrophilic groups were incorporated on the PTFE surface by ultraviolet photon-induced photochemic
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