Inkless rewritable paper enabled by a scalable photochromic membrane

Rewritable paper has attracted wide research attention in the field of environment-friendly information transmission owing to its potential to promote sustainable society development. Traditional organic dye-based rewritable paper may cause emission of pollution. To solve this problem, this study presents a flexible inorganic photochromic membrane by in situ growth of highly dispersed Cu-doped WO₃ nanoparticles in a polymethyl methacrylate matrix. Obvious discoloration of the as-prepared membrane can be repeated more than 200 times under alternating UV irradiation/heating based on an oxidation-reduction process between W⁶⁺ and W⁵⁺. The proof of concept for rewritable paper and encryption algorithm is demonstrated herein. The results of this study are of great significance for the design and fabrication of a novel type of rewritable colorful paper.