For application to synthetic resin parts and to the fabrication of microfluidic devices made of cyclo-olefin polymer (COP), an adhesiveless bonding technology was developed: photo-activation bonding. A Xe excimer lamp irradiating vacuum ultraviolet (VUV) light of 172 nm wavelength was used as a light source for COP surface modification. The surface modification procedure is extremely simple. A COP plate placed in air with atmospheric pressure is irradiated with the VUV light. Based on VUV photochemistry assisted with atmospheric oxygen, a modified layer including large amounts of polar functional groups (-OH, -CHO, -COOH, etc.) is formed on the COP plate. The VUV-modified COP plates were bonded at a low temperature through attractive interactions between the modified layers on the COP plates without deforming the plates' preformed microstructures. A strength test of bonding was conducted to elucidate the effects of surface modification and bonding conditions such as VUV-irradiation distance (d VUV ), VUV-irradiation time (t VUV ), bonding pressure (P B ), bonding temperature (T B ), and bonding time (t B ).
The anodic oxidation and cathodic reduction processes of the Cu/Cu 2 O multilayer film and pure Cu film in pH 8.4 borate buffer solution were analyzed by electrochemical quartz crystal microbalance (EQCM) for gravimetry and bending beam method (BBM) for stress measurement. The mass loss of the multilayer film during anodic oxidation at 0.8 V (SHE) in the passive region was less than that of the pure Cu film. The comparison between current transients and mass changes during anodic oxidation has succeeded in separating the anodic current density into two partial current densities of oxide film growth, . The compressive stress for the multilayer film was generated during anodic oxidation, while the tensile stress for the pure Cu film was generated.The mass loss of the multilayer film during cathodic reduction at a constant current density (i c = -20 µA cm -2 ) was significantly less than that estimated from coulometry, suggesting that H 2 O produced by cathodic reduction remained in the multilayer film.. The compressive stress was generated during cathodic reduction of the multilayer film, which was ascribed to H 2 O remained in the multilayer film.
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