Scientists in California have created rewritable paper, using light instead of ink.

Despite the rise of e-readers and smartphones, the United States still uses 70 million tons of paper each year. The chemists at the University of California, Riverside, hope their new paper, which can be erased and reused up to 80 times, can help cut down that amount.

At the heart of the new technology are nanoparticles, materials thousands of times smaller than the width of a human hair.

The writing fades in five days, as oxygen in the air takes electrons from the dye nanoparticles and turns them back to their original colour.

The process can be accelerated by heating the paper, making it reusable in a matter of minutes.