| Co-Investigator(Kenkyū-buntansha) |
FURUKAWA Hiemitsu Tokyo University of Agriculture and Technology, Faculty of Technology, Assistant, 工学部, 助手 (50282827)
HORIE Kazuyuki Tokyo University of Agriculture and Technology, Faculty of Technology, Professor, 工学部, 教授 (10013690)
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| Research Abstract |
Sensitive deformation of polymer gels induced by various stimuli has been intensively investigated for over two decades. Using light as an external stimulus, space-selective laser is immediately applied to induce a minutely local deformation of the gels thereby expanding their potential applicability.
Here, we demonstrate for the first time that novel photoresponsive gels prepared from rigid poly(amide acid) chains having azobenzene moieties in main chains can undergo a macroscopic deformation induced by photoisomerization. A rod-shape gel can sharply and swiftly bend by blue laser irradiation and reversibly straighten when exposed to visible light. This implies that the trans-to-cis isomerization can successfully deform the rod gel macroscopically. Moreover, by using scanning microscopic light scattering, the reversible change in mesh-size between 2.1 nm and 0.83 nm was simultaneously observed.
On ultraviolet light irradiation by using He-Cd laser (442 nm, 20 mW), we bent a thin rod-shape gel at a selected position. Due to small diameter of laser light and high absorption coefficient, the network shrinking occurred within a small region very close to the surface. This local shrinking induces within several seconds the photoresponsive self-bending of the gel as a bi-metal. When the laser light is irradiated at a different position, the gel bends correspondingly at that position. Recovering to straight shape occurred in a few minutes on exposure to visible light by using a halogen lump with VY-50 filter. The response time of the reversible bending was measured. In good condition, photoresponsive bending' completely finishes within 10 seconds and photoresponsive recovering takes about 100 seconds. Thermal recovering was also observed to have taken about 20 minutes. By polymerizing poly(amide acid) gel in a tiny reactor fabricated by two-photon excitation, photo responsive nano-scale cantilever was fabricated.
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