Building on previous work, the team from Chalmers University of Technology in Gothenburg built a reflective screen that relies on ambient light rather than a backlight, mimicking the way human eyes interact with real paper. Monochrome versions of the technology are already available in commercial e-readers, but replicating the array of colours produced by today’s screens has proved more difficult.
"For reflective screens to compete with the energy-intensive digital screens that we use today, images and colours must be reproduced with the same high quality,” said says Marika Gugole, a doctoral student at Chalmers’ Department of Chemistry and Chemical Engineering. “That will be the real breakthrough. Our research now shows how the technology can be optimised, making it attractive for commercial use."
While the team had already produced electronic paper capable of delivering colour, the fidelity of that colour was sub-optimal. The latest study, published in Nano Letters, describes how a tweak in the design process resulted in an ultra-thin, flexible material capable of reproducing the same colours as an LED screen.
Using a porous, nanostructured material containing tungsten trioxide, gold and platinum, the Chalmers engineers inverted the electrically conductive component so that it sits beneath the material rather than above it. This means the viewer looks directly at the pixelated surface, seeing the colours with much more clarity than before. As well as being much less energy intensive than traditional screens, the electronic paper is also significantly less taxing on the eyes.
"Our main goal when developing these reflective screens, or 'electronic paper' as it is sometimes termed, is to find sustainable, energy-saving solutions,” said research lead Andreas Dahlin, a Professor at the Department of Chemistry. “And in this case, energy consumption is almost zero because we simply use the ambient light of the surroundings."
In addition to smart phones and tablets, the technology could also have applications in outdoor advertising, providing energy and resource savings compared with printed posters or moving digital screens.
"A large industrial player with the right technical competence could, in principle, start developing a product with the new technology within a couple of months," said Dahlin.