Paper is a material that has been around for about 2000 years. And now, it is extremely important to us. But, the production of it having a significant environmental impact. It is a leading source of industrial pollution. And even after recycling, contributes to pollution due to the process of ink removal. So, in an effort to reduce these impacts, scientists have developed a light-printable paper.
Due to its color switching ability, the paper meets with some features that conventions paper did not. For example, stability, limited reversibility, high cost, toxicity, and difficulty in applying the coating to ordinary porous paper.
Professor Yadong Yin said, “The greatest significance of our work is the development of a new class of solid-state photoreversible color-switching system. It produces an ink-free light-printable rewritable paper that has the same feel and appearance as conventional paper. And it can print and erase repeatedly without the need for additional ink.”
This light-printable paper is printed via UV light and rewritten more than 80 times. Actually, its printing depends on a thin coating which applied on normal paper to transform it into the light-printable version.
The coating consists of two types of nanoparticles the Prussian blue and TiO2. These nanoparticles mixed and coated on the paper so that the plain unprinted paper appear solid blue. In the case of erasing, so, it will do by heating it to 120 °C. To erase the paper more quickly, the paper needs to be heated for about 10 minutes to return it to its solid blue state.
To print text or images, the paper needs to expose to UV light, which photoexcites the TiO2 nanoparticles. These nanoparticles then release electrons that were picked by the adjacent Prussian blue nanoparticles, which turn from blue to colorless.
Yin said, “The light-printable paper is indeed cost-competitive with conventional paper. The coating materials are inexpensive, and the production cost is also expected to be low as the coating can be applied to the surface of conventional paper by simple processes such as soaking or spraying. The printing process is also more cost-effective than the conventional one as no inks are needed. Most importantly, the light-printable paper can be reused over 80 times, which significantly reduces the overall cost.”
According to scientists, it has many possible applications involving temporary information recording and reading. For example, newspapers, magazines, posters, notepads, writing easels, product life indicators, oxygen sensors, and rewritable labels for various applications.
Yin said, “Our immediate next step is to construct a laser printer to work with this rewritable paper to enable fast printing. We will also look into effective methods for realizing full-color printing.“