The researchers at the University of Michigan at Ann Arbor were able to trap narrow beams of light at different lengths, which ultimately reflects as colour on a device. The colours remained in place from different viewing angles, and the technology could be applied to e-readers in the future, the researchers said in a statement.
That could lead to a new generation of colour e-readers in which sunlight could be used as an ambient light source to display colour images, much like existing e-ink displays, the researchers said. The technology could also eliminate the need for backlighting typically found in LCD displays. That could improve battery life of a device, as an LCD is considered the most power-hungry component in an e-reader or tablet.
The researchers were able to display only static images in a demonstration, but are working toward the display of moving color images in the future. The researchers were not immediately available for comment on when the technology would become commercially viable.
The top e-readers from Amazon and Barnes & Noble today have e-ink screens with greyscale displays, and tablets largely have LCD screens. Technology for e-ink colour displays is available in only a handful of products like the Ectaco JetBook Color, but the refresh rates and resolution still don’t match LCD screens.
Qualcomm in 2011 introduced Mirasol colour display technology, which made it to the Kyobo e-reader. However, Kyobo has been discontinued and Mirasol has failed to find adopters.
Researchers drew inspiration from a peacock tail, which shows different colours when reflecting specific wavelengths of light at specific angles. Mimicking the peacock concept, the researchers applied specific measurements to create slits that would reflect colours.
A 40-nanometer-wide slit reflected cyan, a 60-nm slit reflected magenta, and a 90-nm slit reflected yellow. The light was trapped inside nanoscale metallic grooves and then redirected through the slits placed in different angles.
The researchers created a device to show the trapped light funneled through the slits. The grooves were fabricated and etched in a glass plate with a layer of silver. When light hit the surface, an electric field pulled in specific wavelengths of light and then funneled through the slits.
The research could lead to new reflective display screens that could show consistent colours from different viewing angles, the researchers said.
The research was published in Nature magazine.