We demonstrate that colloidal spheres can be arrayed on an azobenzene-containing polymer film, which has been patterned such that it forms a template, and that in a subsequent step, the spheres can be selectively photoimmobilized on the film. The steps were made possible by utilizing two photoresponsive properties of the polymer. The first is photoinduced surface deformation, which provides a patterned indented template. The spheres were organized on the surface in accordance with the template structure. The second is photoinduced immobilization, where small objects on the film are immobilized after irradiation. The area-selective immobilized patterns were obtained after washing.
A photoimprint-based immobilization process is presented for cylindrical viruses on the surface of an azobenzene-bearing acrylate polymer by using atomic force microscopy (AFM). Tobacco mosaic virus (TMV), 18 nm in diameter and ca. 300 nm in length, was employed as a model virus. First, a droplet of an aqueous solution containing TMV was placed on the acrylate polymer surface. After drying the droplet, the polymer surface was irradiated with light at a wavelength of 470 nm from blue-light-emitting diodes. Finally, the surface was washed by aqueous solution with detergents. The polymer surface was observed at each step by AFM. TMV was shown to embed itself gradually on the polymer surface during photoirradiation in a time scale of tens of minutes because of the formation of the surface groove complementary to the shape of TMV. Analysis of immobilization efficiency of TMV on the polymer surface by the immunological enzyme luminescence indicated that efficiency increased proportional to the photoirradiation time. In these experimental conditions, the absorption band of the azobenzene moiety remained constant before and after the photoirradiation. These results show that TMV is physically held on the complementary groove formed on the polymer surface by the photoirradiation.
SUMMARYDeformation of an organic photosensitive azopolymer by near-field light generated by an optical fiber probe with a very small aperture diameter of about 50 nm is studied. The azopolymer is deformed in response to the polarization state of the light incident on the probe. If the probe aperture diameter is made smaller, the mark shape can be made smaller but the probe must be moved closer to the material. However, the mark width is about 6 times the probe aperture diameter.
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