No ink required: printing paper with light

Yadong Yin and his colleagues at the the University of California at Riverside have invented the groundbreaking paper that does not require ink.

This is important as it will help to reduce the carbon emissions generated by paper production. Currently 1% of annual carbon emissions can be attributed to paper production, despite the emphasis on recycling. The aim with creating this paper was to reduce the impacts of deforestation.

Paper makes up 40% of landfill sites and the recycling process contributes to pollution because the ink has to be removed first.

The paper can be printed using UV light and can be erased by heating to temperatures of 120°C.

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The technology behind this lies in a colour-changing chemical that can be a applied to conventional paper, turning it into a re-usable, light-printable version.

It uses nanoparticles with the dye Prussian blue and titanium oxide. The mixture is then applied to normal paper.

When the coating is exposed to ultraviolet light, electrons from titanium oxide move to the dye in the nanoparticle.

This addition of electrons makes the blue dye turn white. By focusing the ultraviolet light into shapes, you can print white words on a blue background—or blue words on a white background.

The words will then disappear naturally in 5 days, or within ten minutes if heated to 120°C.

Professor Yadong Yin, a chemistry professor at the University of California, Riverside and a co-author of the study, said: ‘The greatest significance of our work is the development of a new class of solid-state photo reversible colour-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.’

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‘Our work is believed to have enormous economic and environmental merits to modern society.’

‘The light-printable paper is indeed cost-competitive with conventional paper,’ said Yin.

‘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.’

The next stage is to develop a cost effective laser printer to work alongside the paper.

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Nick Ismail

Nick Ismail is a former editor for Information Age (from 2018 to 2022) before moving on to become Global Head of Brand Journalism at HCLTech. He has a particular interest in smart technologies, AI and...

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