Write With Light, Erase With Heat, Repeat

Despite the digital revolution, people still use a lot of paper. Recent international surveys suggest that businesses retain 90% of all information on paper even though that paper is discarded after a single use. Chemists at the University of California, Riverside, hope that a rewritable paper alternative they’ve developed will someday lead to smaller piles of paper. Yadong Yin and colleagues created a solid composite film upon which they can write using ultraviolet light. The writing lasts for three days, or it can be erased by heating the material (Nat. Commun. 2014, DOI: 10.1038/ncomms6459). Writing and erasing on the film is accomplished via redox chemistry. In the current report, the researchers use photomasks to create dark images and letters with a colorless background. The film’s imaging layer is made of a redox dye, such as methylene blue; titanium dioxide nanocrystals, which in the presence of UV light catalyze the reduction of the dye to its colorless form; and hydroxyethyl cellulose, which slows down the oxidation of the dye molecules to their colored form. The writing and erasing process can be repeated up to 20 times without losing resolution.