Washington: Chemists have finally developed a rewritable paper that can be erased and written on more than 20 times with no significant loss in contrast or resolution, which can help the environment.
Chemists at the University of California, Riverside have now fabricated in the lab just such novel rewritable paper, one that is based on the color switching property of commercial chemicals called redox dyes.
The dye forms the imaging layer of the paper and printing is achieved by using ultraviolet light to photobleach the dye, except the portions that constitute the text on the paper.
Yadong Yin, a professor of chemistry, said that this rewritable paper does not require additional inks for printing, making it both economically and environmentally viable and it represents an attractive alternative to regular paper in meeting the increasing global needs for sustainability and environmental conservation.
The paper comes in three primary colors: blue, red and green, produced by using the commercial redox dyes methylene blue, neutral red and acid green, respectively. Included in the dye are titania nanocrystals (these serve as catalysts) and the thickening agent hydrogen cellulose (HEC). The combination of the dye, catalysts and HEC lends high reversibility and repeatability to the film.
During the writing phase, ultraviolet light reduces the dye to its colorless state. During the erasing phase, re-oxidation of the reduced dye recovers the original color; that is, the imaging material recovers its original color by reacting with ambient oxygen. Heating at 115 C can speed up the reaction so that the erasing process is often completed in less than 10 minutes.
The study was published online in Nature Communications.