A new technology for producing light-printable paper could be cost-competitive with conventional paper. The paper, which can be erased and rewritten more than 80 times, could offer environmental and economic benefits.

The research from by Wenshou Wang (University of California-Riverside) and colleagues follows up on the team’s earlier progress on light-printable paper, introducing a class of solid-state photoreversible color switching system that mimics the feel and appearance of conventional paper. The nanoparticle-based coating reportedly improves on previous efforts in several areas, including reversibility and stability.

Prussian blue.The coating contains equal parts of Prussian blue and titanium dioxide (TiO₂) nanoparticles, mixed and applied to paper. Prussian blue, a nontoxic pigment, switches from blue to colorless when it gains electrons. Titanium dioxide acts as a photocatalyst, accelerating chemical reactions when exposed to UV light.

To print blue text on a colorless background, the background is light-printed. The TiO₂ releases electrons, which the Prussian blue nanoparticles pick up, turning clear in the process. For clear text on blue paper, the particles that define the text or image change to clear.

The paper retains printing for about five days before turning back to solid blue. Heating the paper for about 10 minutes erases the page faster.

Because paper is a major component of landfills—40%, according to the researchers—a viable rewritable paper product can reduce waste in landfills and save on paper costs. Applications could include everything from newspapers to oxygen sensors.

The team’s next project is constructing a laser printer that uses the paper product. They are also exploring methods for full-color printing.