Easily prepared and reusable film for fast-response rewritable light printing.

Paper, for hand-writing and printing, consumed a lot in the modern life. However, the production of conventional paper could cause many problems, such as deforestation and environmental pollution. Therefore, it is necessary and urgent to explore novel strategies to solve these problems. In this work, a polyoxometalate doped gelatin film with high strength, excellent transparency and fast photochromic properties is designed and prepared. The film can display different colors by using a variety of reagents, exhibiting its potential application as a paper medium. Its rapid photochromic properties allow complex high-resolution images to be displayed by UV light printing. It is found that the mechanical and photochromic properties could be regulated by the introduction of triethylene glycol, and the fading process could be controlled by changing temperature and humidity. Moreover, it is rewritable, self-repairable and recyclable, and can also achieve long-term preservation without fading. It is envisioned that the environmentally friendly film with low cost, easy-to-prepare and recycling advantages, have the potential to be an alternative of conventional paper for hand-writing and printing.