Reflective screens designed to display brilliant colours
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. This could soon be a reality, with a new type of reflective screen, developed by Swedish researchers, offering optimal colour 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 on them. This is fine indoors, but difficult to view in bright sunshine. Reflective screens attempt to use the ambient light, mimicking the way our eyes respond to natural paper. Reflective screens are already available in some tablets today, but they only display the colours black and white well, which limits their use.
“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 Marika Gugole, a doctoral student at Chalmers University of Technology. “Our research now shows how the technology can be optimised, making it attractive for commercial use.”
Chalmers researchers had previously succeeded in developing an ultrathin, flexible material that reproduces all the colours an LED screen can display, while requiring only a tenth of the energy that a standard tablet consumes. But in the earlier design the colours on the reflective screen did not display with optimal quality. The team’s latest study, conducted with Linköping University and published in the journal Nano Letters, takes the material one step further.
Using a previously researched, porous and nanostructured material, containing tungsten trioxide, gold and platinum, the researchers tried a new tactic — inverting the design in such a way as to allow the colours to appear much more accurately on the screen. They placed the component which makes the material electrically conductive underneath the pixelated nanostructure that reproduces the colours — instead of above it, as was previously the case. This new design means you look directly at the pixelated surface, therefore seeing the colours much more clearly.
In addition to the minimal energy consumption, reflective screens are much less tiring for the eyes compared to looking at a regular screen. Furthermore, while the screens require the use of rare metals such as gold and platinum, the amounts needed are very small as the final product is so thin. 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,” said Chalmers Professor Andreas Dahlin, research leader on the project. “And in this case, energy consumption is almost zero because we simply use the ambient light of the surroundings.”
Prof Dahlin envisions a number of applications for the technology in addition to smartphones and tablets — such as outdoor advertising, offering energy and resource savings compared with printed posters or moving digital screens. He concluded, “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.”
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