Image: University of Oxford
We’re still not there yet, but we’re getting closer to flexible screens that bulge and bend rather than shattering when you drop them. Just this week LG announced the release of its rollable TV screen, but that looks positively clunky compared to a super-flexible display developed by materials scientists at Oxford University that’s just a few hundred nanometers thick.
The researchers made what they call “nano-pixels”—pixel-like devices that are just 300 by 300 nanometers across and could be incorporated into film-like materials for foldable flexibility. Think smart glasses, or even contact lenses.
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While the pictures above might not look super-high quality, bear in mind each is around 70 micrometers across, which is less than the width of a human hair. For the size, this is really high res. Sebastian Anthony at ExtremeTech compared the nano-pixels to the pixels you might get in a smartphone display and said that the nano-pixels are about 150 times smaller—which means they could make for super high-res images if you got enough together to make the same display size (and if you could find a good enough graphics card).
As outlined in a paper in Nature, the researchers made the images using a layer of “phase change” material—a material that can change properties in response to stimuli like heat or an electrical charge. In a statement, researcher Harish Bhaskaran explained they were playing around with a phase change material called GST (a germanium antimony tellurium alloy) to see how electrical properties affected optical properties, and found that when they sandwiched the material between transparent conductors and applied a current, it changed colour. That allowed them to draw the teensy-tiny pictures by electrically stimulating each pixel.
The phase change they used was a germanium antimony tellurium alloy, and the researchers found that the thinner the layer of material, the better the contrast in the image. Changing the thickness of the electrode layer made of indium tin oxide under the material allowed them to change the colour, and lead author Peiman Hosseini said they were able to create any colour they wanted.
They wrote in the paper that, “This optoelectronic framework using low-dimensional phase-change materials has many likely applications, such as ultrafast, entirely solid-state displays with nanometre-scale pixels, semi-transparent ‘smart’ glasses, ‘smart’ contact lenses and artificial retina devices.”
Bhaskaran told me that the artificial retina would effectively work in the opposite way to a display—i.e. the material could respond to different colour wavelengths electrically, and send that information to your optic nerve. That’s looking well into the future, but it shows that the potential applications of the technology reach beyond display screens. “Essentially what we’ve demonstrated is you can modulate the refractive index of this material quasi-permanently by an electrical signal,” he said. “If you can do that, you can do a whole lot of things.” Another example he gave would be light modulation through windows.
It would, Bhaskaran said, be a viable option for consumer electronics as it’s an inexpensive technique. But the work is nowhere near the stage of the bendy TV screen yet, and it’ll take further development to fulfill its applications. It’s early stages: for now the team has demonstrated that it works for still images like the above and have filed a patent for the tech. The researchers are building prototype displays like an e-reader-style screen, backlit screen and flexible screen this year and are most keen to showcase the high resolution.
And the idea offers more advantages than just being ultra-slim and bendy. Bhaskaran explained that a display using the technology inherently has a very low energy consumption because it’s very effective at scale.
“I don’t think it will replace your standard LCD screen overnight,” he said. “I think what you’ll see is it’ll probably start having applications in micro-projection displays where you need the super-high resolution. Then once the technology matures you could have large scale applications that become less expensive.”
