Photoresponsive Gel: Self-repairing of Surface Damages
Discovering scratches on your parked car… Have you ever had such a sad experience? However, if you can easily repair scratches by light irradiation, it would be wonderful!
AIST has developed photoresponsive gels which turn from a solid-like gel into a fluidic sol by irradiation with UV light to repair such damages, and then return to a gel state by irradiation with visible light.
AIST has developed optically healable gels which are novel liquid-crystalline materials consisting of particle/liquid-crystal composite systems, in which polymeric particles are mixed with liquid crystals and photoresponsive compounds such as azobenzene derivatives. The gel state is brought about by the formation of three-dimensional network structures with the particles in the liquid-crystal matrices. The gel-sol transition of the materials can be reversibly induced by controlling the network structures using photochemical reactions of the photoresponsive compounds.
Here the surface of the gel material is scratched with the depth of approximately 2 mm. When the scratched area is irradiated with UV light, the transformation from a gel state to a sol state of the material occurs in the irradiated area. Because the fluidity of the sol state is much higher than that of the gel state, the scratch is filled up with the sol material. The photoinduced sol state returns to the gel state by the irradiation with visible light.
Although the material surface becomes a darker color upon irradiation with UV light, the color can be restored by leaving the material in a dark place for one night after gelation.
As the next stage, we are trying to develop hard and tough materials which can be used as paints, coatings and others.