New Printing Technology Uses Light Instead of Ink

For so long, printing has hinged on the use of ink and paper. Now, scientists have invented a new way of writing with light so ink is no longer necessary and the paper could be re-used for up to 80 times.

Two nanoparticles behind light-printing technology

According to a report from Phys Org, researchers have developed light-printable paper by making use of the color-changing chemistry of nanoparticles.

"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," Yadong Yin, chemistry professor at the University of California, Riverside, explained. "Our work is believed to have enormous economic and environmental merits to modern society."

There are certain chemicals that are able to change colors upon exposure to light. Previous attempts to develop technology that takes advantage of these properties struggled with stability, toxicity, difficulties in applying the coating to regular paper and a number of other challenges.

The researchers were able to create a coating that has two different types of nanoparticles: a non-toxic blue pigment called Prussian blue that becomes colorless with the increase of electrons, and titanium dioxide, which is a photocatalytic material that reacts to UV light. These two are mixed to create the coating for paper, which appears blue.

In printing, this paper is exposed to UV light that creates a reaction in the titanium dioxide and releases electrons that is then sensed by the Prussian blue nanoparticles, turning the paper from blue to colorless. For blue text on a colorless background -- which is easier to read -- the background is actually the one being printed. Prussian blue analogs make other colors possible using this technology.

An ink-free, paper-conservative world

The main advantage of this new technology is gaining the ability to use the same piece of paper over and over again. The paper is expected to maintain the configuration for at least five days before it turns back into blue through oxidation. To fast-track the process, one simply has to heat the paper for several minutes.

Roughly 40 percent of landfills is discarded paper and about one-third of all trees that are cut down are used for paper production. Even recycling paper has a negative impact on the environment due to the pollution produced in ink removal. This new innovation has the potential to cut down these effects as the scientists say it can be used in the real world in a number of ways.

"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," Yin said.

The group of scientists from Handong University in China, the University of California, Riverside, and Lawrence Berkeley National Laboratory was behind the study, according to a report from Popular Mechanics.