Imagine sitting out in the sun, reading a digital screen as thin as paper, but seeing the same image quality as if you were indoors. Thanks to research from Chalmers University of Technology, Sweden, it could soon be a reality. A new type of reflective screen – an electronic paper – offers optimal color display, while using ambient light to keep energy consumption to a minimum. Tradi­tional digital screens use a backlight to illu­minate the text or images displayed upon them. This is fine indoors, but we've all experienced the difficulties of viewing such screens in bright sunshine. Reflective screens, however, attempt to use the ambient light, mimicking the way our eyes respond to natural paper.

“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. That will be the real break­through. Our research now shows how the techno­logy can be optimised, making it attractive for commer­cial use,” says Marika Gugole, Doctoral Student at the Department of Chemistry and Chemical Engineering at Chalmers University of Technology. The researchers had already previously succeeded in deve­loping an ultra-thin, flexible material that reproduces all the colors an LED screen can display, while requiring only a tenth of the energy that a standard tablet consumes.

But in the earlier design the colors on the reflec­tive screen did not display with optimal quality. Now, using a previously researched, porous and nano­structured material, containing tungsten trioxide, gold and platinum, they tried a new tactic – inverting the design in such a way as to allow the colors to appear much more accurately on the screen. The inversion of the design represents a great step forward. They placed the component which makes the material electrically conductive underneath the pixelated nano­structure that reproduces the colors – instead of above it, as was previously the case. This new design means you look directly at the pixelated surface, therefore seeing the colors much more clearly. 

In addition to the minimal energy consump­tion, reflective screens have other advantages. For example, they are much less tiring for the eyes compared to looking at a regular screen. To make these reflective screens, certain rare metals are required - such as the gold and platinum but because the final product is so thin, the amounts needed are very small. The researchers have high hopes that eventually, it will be possible to signi­ficantly reduce the quantities needed for production. “Our main goal when developing these reflective screens, or electronic paper as it is sometimes termed, is to find sus­tainable, energy-saving solutions. And in this case, energy consumption is almost zero because we simply use the ambient light of the surroundings,” explains research leader Andreas Dahlin, Professor at the Department of Chemistry and Chemical Engi­neering at Chalmers.

Reflective screens are already available in some tablets today, but they only display the colors black and white well, which limits their use. “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,” says Andreas Dahlin, who envisions a number of further appli­cations. In addition to smart phones and tablets, it could also be useful for outdoor advertising, offering energy and resource savings compared with both printed posters or moving digital screens. (Source: Chalmers U.)

Reference: M. Gugole et al.: Electrochromic Inorganic Nanostructures with High Chromaticity and Superior Brightness, Nano Lett. 21, 4343 (2021); DOI: 10.1021/acs.nanolett.1c00904

Link: Dept. of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden