As per WWF, about 400 million tons of paper is being produced per year and this number is only rising. You would have thought that with all the technological advancement, the use of paper would reduce, so did we. However, check out this amazing take by chemists at the University of California, Riverside (UCR) for the purpose of saving paper. The team has created a re-writable paper that can be printed on, erased and used again.
At present, this paper is good for 20 cycles after which it has to be discarded. Comparing this with the conventional methods, we print on paper, eventually discarding the paper and also have to throw away the used printer cartridges. The UCR prototype rewritable paper is different since it makes use of the chemical properties associated with the commercial inks – redox dyes.
The dyes are applied onto the paper followed by the template being placed onto it. The combination is exposed to UV light which bleaches the uncovered area away, thus leaving us with only the print. To erase the image, the paper has to be subjected to a heat of 115 °C that makes the paper blank again.
Professor Yadong Yin, professor of Chemistry at UCR said, “Even for this kind of paper, heating to 115 °C poses no problem. In conventional laser printers, paper is already heated to 200 °C in order to get toner particles to bond to the paper surface. This rewritable paper does not require additional inks for printing, making it both economically and environmentally viable. It represents an attractive alternative to regular paper in meeting the increasing global needs for sustainability and environmental conservation.”
The UCR paper is, basically, a rewritable media that has been created from glass/plastic film and is capable of retaining the image that has been printed onto it for days before it is removed by heating it. Talking about the mix of dyes that is being used for printing, Professor Yin stated, “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. Better still, our rewritable paper is simple to make, has low production cost, low toxicity and low energy consumption.”
The team is experimenting on how to increase the print cycles and is aiming for 100-cycle life span. They are also working on how to increase the time period for which the print is retained. Professor Yin explained, “One way is to develop new photocatalyst nanoparticles that become highly reductive when irradiated by ultraviolet light. We are exploring, too, the possibility of multi-color printing. The design principle can be extended to various commercial redox dyes to produce rewritable paper capable of showing prints of different colors. All these efforts will help increase the practical applications of the technology.”
The research team along with Professor Yin includes Wenshou Wang, Ning Xie and Le He. The research was made possible through a grant from the US Department of Energy and has also filed a provisional patent. Check out the youtube video below for more details:
