Materials science: Colour printing on rewritable paper

A new strategy to produce rewriteable paper that can print long-lasting yet erasable multi-colour images is demonstrated in Nature Communications this week.

Reusable paper holds environmental and cost benefits over its disposable counterpart, but its absence from the everyday marketplace stems from an existing inability to print multi-coloured, long-lasting images that are also erasable.

Qiang Zhao, Wei Huang and colleagues have designed a paper and ink combination that allows them to print multi-colour images that last for over six months, but that can also be erased on demand. The inks consist of metal salts dissolved in water, and the paper is modified to contain molecules that interact with these metals. Inkjet printing of a pattern or text causes the paper to change colour as a new compound forms. The colour adopted depends on the metal salts used, and as a broad range of these are available, a wide colour palette can be printed. Owing to the reversible nature of the chemical bonds, coating the paper with a specific substance will then break those bonds and erase the image.

The authors note that the paper can only be rewritten up to eight times before the colours will start to fade, but propose that their lost-cost strategy could bring us closer to realising commercially viable rewritable paper.