Hydrochromic molecular switches for water-jet rewritable paper

The days of rewritable paper are coming, printers of the future will use water-jet paper. Although several kinds of rewritable paper have been reported, practical usage of them is rare. Herein, a new rewritable paper for ink-free printing is proposed and demonstrated successfully by using water as the sole trigger to switch hydrochromic dyes on solid media. Water-jet prints with various colours are achieved with a commercial desktop printer based on these hydrochromic rewritable papers. The prints can be erased and rewritten dozens of times with no significant loss in colour quality. This rewritable paper is promising in that it can serve an eco-friendly information display to meet the increasing global needs for environmental protection. Office printing is popular around the world, but suffers from the relatively high cost of ink and excessive paper waste. Here the authors demonstrate an eco-friendly dye-impregnated rewritable paper that can be printed using water and erased by heating, thereby allowing simple, repeated recycling.