The Latest Paper Trend: Re-Printable Paper?
OK, I’m going to talk about something completely different this week. Our son decided chemistry was for him in his undergraduate years, and is now pursuing a Ph.D. in physical chemistry at Temple University in Philadelphia. Coincidentally, he resides only a short distance from Printing Impressions’ office downtown. One of his tasks as a researcher is to stay informed on what state of the art means every month, so when we speak (which thankfully is often) he informs me of some really interesting developments he has run across.
And one that really piqued my interest a few weeks ago, was “re-writable paper.” Concerned about all of that paper we’re writing and printing on, the Yadong Yin research group at University California Riverside decided to come up with a substrate that could be “written” on, and subsequently erased, through a variety of methods. The writing step is achieved using UV light, while the off state can be achieved through an oxidation or heating step depending on the material.(1-2) In the process a commercially-available redox dye is introduced as the imaging layer.
Much of the current experiments were conducted using Prussian blue. Nanoparticles of this redox die were integrated with the photocatalytic activity of TiO2 (titanium oxide) particles to construct a new class of photo reversible color switching systems. Other colored dyes can also be used to introduce new ink colors.
This dye-based color switching system can be conveniently applied to the surface of conventional paper. This creates an ink-free, light-printable, rewritable paper that has the same look and feel as conventional paper.
A photo-mask is used to “write” to the paper using a UV lamp. It’s also possible that that direct printing could also be achieved with a scanning laser beam. This resembles an offset transfer process somewhat. High printing resolutions have been achieved. As for the “erasing,” that’s accomplished by heating the paper. We’re talking a limited life of the print at the moment, as oxidation (over a period of a week or so) will gradually erase the content. But the paper can be erased and re-written up to eighty times.
What kind of applications are we talking about here? The scientists have put forward a few such as newspapers, product life indicators, and various rewritable labels. So … here you are thinking inkjet is the very latest and greatest print technology to come down the pike? Think again! My thanks to our favorite scientist, Stefan Piontek.
Wang, Wenshou, Ning Xie, Le He, and Yadong Yin. “Photocatalytic Colour Switching of Redox Dyes for Ink-free Light-printable Rewritable Paper.” Nature Communications5 (2014): 5459.
Wang, Wenshou, Ji Feng, Yifan Ye, Fenglei Lyu, Yi-Sheng Liu, Jinghua Guo, and Yadong Yin. “Photocatalytic Color Switching of Transition Metal Hexacyanometalate Nanoparticles for High-Performance Light-Printable Rewritable Paper.” Nano Letters2 (2017): 755-61.