Weatherability improvement of strain imaging sheet to use in real field for infrastructure inspection technology

We have been developing smart photonic coating for structural materials to visualize strain mapping on steel or aluminum and to detect cracks on concrete. In the technology, strain imaging sheet made of colloidal photonic crystal film coated on a polyethylene terephthalate sheet. The strain imaging sheets change structural color by mechanical deformation. Now we have been testing smart photonic coating for real concreate bridges One of the key issues is the durability of the sheet for long-term use at the outfield site. In outdoor exposure test and in laboratory accelerated exposure test, polystyrene particles in the colloidal photonic crystal film were damaged and lost the structural color. To protect the deteriorating, top coat layer containing ultraviolet absorber was effective to reduce the damage of the colloidal photonic crystal film.