Imagine having an ultra high-resolution display built directly into a pair of contact lenses. This could be the future of digital displays thanks to scientists at Oxford University, who have adapted a material currently used to store data on DVDs and transformed it into a radical new display technology.
Writing in Nature today, they say the material could usher in a new generation of displays that are thinner, lighter, with higher resolution and lower power consumption than any existing technology.
They could even be mounted on flexible or transparent surfaces, raising the possibility of applications beyond just e-readers and smartphones to things such as car windshields and contact lenses.
The development relies on the same process that turns water into ice cubes in your freezer. Many substances undergo changes in structure when they change temperature, such as going from solid to liquid, or crystalline to non-crystalline. These phase-change materials are currently used for a wide range of applications, from computer memory and rewritable DVDs to advanced forms of home insulation.
The team, led by Professor Harish Bhaskaran, was exploring other uses of phase-change materials like germanium antimony tellurium (GST), when they realized they might be able to use them to produce a colour display.
They took a single layer of GST just nanometers thick and sandwiched it between two ultra-thin layers of a transparent conductor, and stuck that on top of a mirrored surface.
The researchers predicted that by varying the thickness of one of the transparent layers, they could change the color of light that was reflected back, and by changing the phase of the GST they could switch it from one color to another. They then built a prototype to see if the material could change from grey to blue when it was heated.
"We couldn't believe it. It worked on the first attempt. So we tried it with a few other colors and it worked well," says Bhaskaran. "I've been an experimentalist for a long time, and I've never seen things work this well at the first attempt."
The researchers then used the head of an atomic force microscope to draw a monochromatic image on the surface.