No ink required to print on this paper — yet look how readable the type is. (Photo: University of California, Riverside/YouTube)
by BRYAN NELSON
As much as 40 percent of our landfills consist of paper and cardboard, and a major source of that material comes from office supplies. Just think of all the paper that gets used and discarded on a daily basis through the printer in your office alone. Even if that paper gets recycled, it still presents a different sort of problem due to pollution associated with the ink removal process.
Then there’s the concern about deforestation. In the United States, about one-third of all harvested trees are used for paper and cardboard production.
Paper and printing is a problem, to be sure. But now, thanks to a breakthrough from a team of scientists at Shandong University in China, the University of California, Riverside, and Lawrence Berkeley National Laboratory, it might be a problem with a solution.
The researchers have invented a new type of rewritable paper that can be printed with light — no ink required. The paper feels like normal paper to the touch, but it’s coated in color-changing nanoparticles that react to UV light. The technology works simply enough: a UV light printer zaps the paper everywhere except where the text is meant to be. The text then boldly stands out against the clear, light-zapped background.
“The greatest significance of our work is the development of a new class of solid-state photoreversible color-switching system to produce an ink-free light-printable rewritable paper that has the same feel and appearance as conventional paper, but can be printed and erased repeatedly without the need for additional ink,” explained Yadong Yin, chemistry professor at the University of California, Riverside. “Our work is believed to have enormous economic and environmental merits to modern society.”
The researchers published a paper on their work in the journal Nano Letters.
The nanoparticles return to their original background state if left untreated for five days, so the text will disappear naturally. (It certainly beats a paper shredder.) But if you wanted to erase and rewrite onto the same paper sooner than that, it will also revert back if heated for only about 10 minutes at 250 degrees Fahrenheit. It’s kind of like a hardcopy version of Snapchat, assuming you’ve got the proper equipment on hand to erase a message after it’s been read.
“We believe the rewritable paper has many practical applications involving temporary information recording and reading, such as newspapers, magazines, posters, notepads, writing easels, product life indicators, oxygen sensors, and rewritable labels for various applications,” said Yin.
Aside from producing little waste, the technology is also inexpensive. The coating materials are so cheap that they add almost nothing to the cost of a sheet of paper. Meanwhile, the printing technology ought to be cheaper than traditional inkjet printers simply because no ink is required. (Imagine never having to change out your ink cartridge again!)
And of course, because the paper can be re-used more than 80 times before the effect is dulled, the technology saves on the cost of paper as well.
“Our immediate next step is to construct a laser printer to work with this rewritable paper to enable fast printing,” said Yin. “We will also look into effective methods for realizing full-color printing.”