A team of chemists at the University of California, Riverside has developed a new type of ‘paper’ that can be written on, erased and then rewritten on up to 20 times without affecting the quality of the print.
Currently in prototype form, this innovation gains its rewritable properties from commercially available redox dyes, which have colour-changing properties. The dyes are applied one time only to the top layer of the material. A photomask template of the desired text or image is laid on top and then everything is exposed to ultraviolet light. The uncovered portions are photobleached away, leaving the print behind. To erase the print, the material is heated to 115°C, reversing the process.
‘The printed letters remain legible with high resolution at ambient conditions for more than three days – long enough for practical applications such as reading newspapers,’ says Dr. Yadong Yin, Professor of Chemistry and the research lab leader. ‘Better still, our rewritable paper is simple to make, has low production cost, low toxicity and low energy consumption.’ And while 115°C seems like a high temperature, Dr. Yin explains that in conventional laser printers, cellulose-based paper is already heated to about 200°C.
For now, this paper is actually a very thin plastic, but the team are hoping to develop the concept with a thin cellulose-based paper. Furthermore, they are hoping to increase the duration of prints for more than three days and increase the number of times the paper can be rewritten to 100. They are also looking at the introduction of multi-coloured printing.
You can watch a video of this material in action here.
Source: Yin Lab, UC Riverside