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"Nano-pixels" hold huge potential for flexible, low-power, high-res screens


July 10, 2014

Still images drawn with the "nano-pixel" technology that each measure around 70 micrometres across, which is smaller than the width of a human hair (Photo: Oxford University)

Still images drawn with the "nano-pixel" technology that each measure around 70 micrometres across, which is smaller than the width of a human hair (Photo: Oxford University)

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The Retina displays featured on Apple's iPhone 4 and 5 models pack a pixel density of 326 ppi, with individual pixels measuring 78 micrometers. That might seem plenty good enough given the average human eye is unable to differentiate between the individual pixels, but scientists in the UK have now developed technology that could lead to extremely high-resolution displays that put such pixel densities to shame.

Led by Oxford University scientists, a research team has created a prototype device that features pixels just 30 x 30 nanometers in size. The high resolution potential of the technology was discovered while the team was exploring the link between the electrical and optical properties of phase change materials (PCMs) that can switch from an amorphous to a crystalline state.

By sandwiching a seven-nanometer thick layer of the PCM Germanium-Antimony-Tellurium (Ge2Sb2Te5 or GST) between two layers of transparent electrodes made of indium tin oxide (ITO), the scientists discovered they could "draw" still images within the sandwich "stack" using an atomic force microscope. They then found that the "nano-pixels" could be switched on and off electronically, creating colored dots that could be used as the basis for an extremely high-resolution display.

"We didn't set out to invent a new kind of display," said Professor Harish Bhaskaran of Oxford University's Department of Materials, who led the research. "We were exploring the relationship between the electrical and optical properties of phase change materials and then had the idea of creating this GST 'sandwich' made up of layers just a few nanometers thick. We found that not only were we able to create images in the stack but, to our surprise, thinner layers of GST actually gave us better contrast. We also discovered that altering the size of the bottom electrode layer enabled us to change the color of the image."

But extremely high-resolution isn't the only impressive quality of the technology. The layers that make up the GST sandwich are created using a sputtering technique, which would allow them to be deposited as thin films on extremely thin and flexible substrates.

"We have already demonstrated that the technique works on flexible Mylar sheets around 200 nanometres thick," said Professor Bhaskaran. "This makes them potentially useful for 'smart' glasses, foldable screens, windshield displays, and even synthetic retinas that mimic the abilities of photoreceptor cells in the human eye."

Additionally, like the power-saving E-Ink displays used in eReaders, all the pixels don't need to be constantly refreshed, as is the case with LCD screens. This means that only those pixels that actually change would need to be refreshed, significantly lowering energy consumption.

Furthermore, the scientists believe displays based on the technology could switch between a color e-Reader mode that saves power by relying on reflected light, and a video display mode that makes use of a backlight.

The team believes displays made using the technology would be easy to manufacture from inexpensive materials, while also being reliable as they would be solid-state. Amongst the wide variety of potential applications, the team highlights the technology's benefits for use in smart glasses, where the nano-pixels would allow even images projected at a larger size would offer very high resolution.

"Along with many other researchers around the world, we have been looking into the use of these GST materials for memory applications for many years," says Professor David Wright from the Department of Engineering at the University of Exeter, who is co-author of a paper detailing the technology. "But no one before thought of combining their electrical and optical functionality to provide entirely new kinds of non-volatile, high-resolution, electronic color displays – so our work is a real breakthrough."

Although the work is still in its early stages, the team has filed a patent for the technology and is fielding discussions on the displays with companies and investors through Isis Innovation, Oxford University's technology commercialization company.

The team's paper appears in the journal Nature.

Source: Oxford University

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

My god, imagine Oculus Rift with such a display technology rather than OLED displays. Say bye bye to the screen door Effect.

Fredrik Pettersen

The world of tomorrow will be a very display-driven place. It already is, but even more so tomorrow. So many applications for this technology.

@Fredrik Pettersen - Hahaha... my thoughts exactly! The density is so great that if the field-of-view were completely immersive (no external world visible or blank at the peripheries), it would be very hard to distinguish visual virtual reality from visual reality. I suppose that's the ultimate goal. Talk about "presence". Wow!


Hellooo HD video contact lenses! Now if we can just get the power source and receiver to fit in that same space...

Dave Andrews

It seems to me that the basic technology could be used as a small photo imaging sensor with these very small pixels teamed in rows. Software defined scanning in the manner of an synthetic aperature radar could possibly achieve 3D with depth. Possibly this could make a colonoscopy pill camera but with far finer imaging than now. Maybe also laparoscopes could have far better, finer imaging along with space for surgical tools.


At 30nm pixel size, imagine using this to pattern photoresist for near 2014 state of the art semiconductors without million-dollar masks or ten million-dollar stepper machines.

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