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International Journal of Photoenergy
Volume 2012 (2012), Article ID 574124, 6 pages
http://dx.doi.org/10.1155/2012/574124
Research Article

Photomechanical Energy Conversion of Photoresponsive Fibers Exhibiting Bending Behavior

1Photocatalyst Group, Kanagawa Academy of Science and Technology, KSP Building East 412, 3-2-1 Sakado, Takatsu-ku, Kanagawa, Kawasaki 213-0012, Japan
2Division of Energy and Environment Photocatalyst, Research Institute for Science and Technology, Tokyo University of Science, 1-3 Kagurazaka, Tokyo, Shinjuku-ku 162-8601, Japan
3Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, Noda 278-8510, Japan

Received 12 June 2012; Revised 13 August 2012; Accepted 14 August 2012

Academic Editor: Vincenzo Augugliaro

Copyright © 2012 Kazuya Nakata et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Photoresponsive fibers based on poly(acrylamide) (PAA) with methylene blue (MB) dye were prepared. All semicircular fibers show bending towards the direction of the flat surface of the fiber when illuminated. The fibers recover their initial shape when the illumination stops. The fiber is heated upon illumination and cooled to room temperature once the illumination is stopped. The fiber also is sensitive to humidity, showing bending behavior towards the direction of the flat surface of the fiber upon changing the humidity. The mechanical energy of the PAA/MB fiber is approximately 0.6 mN for the bending direction when it is illuminated. A possible mechanism for the bending behavior is as follow: (1) the fiber is heated upon illumination because of the photothermal effect, (2) the fiber loses water molecules, (3) the fiber shrinks; bending towards the direction of the flat surface of the fiber occurs because of a difference in the shrinkage for the flat surface and the other side of the fiber. Finally, we demonstrated that a PP ball (1.5 mg) can be moved by the mechanical energy produced by the changing shape of the fiber upon illumination.