Electronic paper, from companies like E Ink, can display colour images now while minimising power usage. The trade-off is they look nowhere near as vibrant as display technologies like LCD and OLED, but new research out of Sweden could soon change that with an innovative type of reflective screen.
Over the past year, we’ve seen more e-reader and e-note devices adopting E Ink’s Kaleido colour e-paper display technology. Like an Amazon Kindle or Rakuten Kobo, the devices produce text and imagery that look like a printed page, but now in colour, although the quality of the colour reproduction pales in comparison to LCD and OLED displays. Even the LCD display in a cheap tablet or smartphone can reproduce over 16 million different colours, but E Ink’s Kaleido screens are limited to just 4,096 colours, and as a result, imagery tends to look desaturated on colour e-paper devices.
E Ink continues to improve its Kaleido e-paper technology, and there are already devices using Kaleido 2 screens, but researchers at Chalmers University of Technology in Sweden appear to have leaped well ahead of the colour e-paper currently available in consumer gadgets. In 2016, researchers at the school created a material, less than a micrometre thick, that was as flexible as paper and able to reproduce as many colours as an LCD display. But unlike LCDs, the material wasn’t illuminated and instead reflected ambient light in the same manner as the screens in e-readers. It not only has the appearance of paper (which can be easier on the eyes) but its creators also discovered the material could be used as a screen while requiring about one-tenth the amount of power a device like the Amazon Kindle needs.
Almost five years later, in a new study published in the journal Nano Letters, the researchers detail how they’ve improved the material with a relatively simple change: flipping its structure upside-down. The material is made up of multiple layers, including a “porous and nanostructured material, containing tungsten trioxide, gold and platinum” which produces different colours as it reflects light, and a layer that adds electrical conductivity so that like an LCD, colours can be continually refreshed and altered. Previously the conductive layer sat atop the colour nanostructure, but it’s now been relocated below it, improving the accuracy and fidelity of the colours as perceived by the human eye.
The researchers admit there are some challenges to mass-producing their potentially game-changing display technology. The ingredients in E Ink’s displays aren’t terribly expensive, meaning you can get an e-reader for less than $150. But with ingredients like gold and platinum needed to realise the new display technology — even at thicknesses of just 20 nanometres — manufacturing on a large scale could result in premium pricing for products incorporating them. It remains to be seen if the savings from the reduced power consumption would help offset the display costs, as it means tablets, smartphones, and e-readers could be shipped with much smaller batteries. Researchers could also eventually find a cheaper substitute for these rare materials.