Researchers create pixels a million times smaller than those on smartphone screens

The smallest pixels ever created, a million times smaller than those in smartphones, made by trapping light particles under tiny gold rocks, could be used for new types of large-scale flexible displays, large enough to cover entire buildings.

The colored pixels, developed by a team of scientists led by the University of Cambridge, are compatible with roll-to-roll manufacture on flexible plastic films, which drastically reduces production costs. The results are reported in Science Advances magazine.

It has long been a dream to imitate the iridescent skin of an octopus or squid, allowing people or objects to disappear into the natural background, but making large flexible display screens is still prohibitive because they are built with high precision on multiple levels.

At the center of the pixels developed by Cambridge scientists is a tiny golden particle a few billionths of a meter. The grain lies above a reflective surface, trapping light in the intermediate space. Surrounding each grain is a thin, sticky coating that changes chemically when electrically switched, causing the pixel to change color across the spectrum.

The team of scientists from different disciplines made the pixels by coating tubs of golden grains with an active polymer called polyaniline and spraying them on flexible mirror-coated plastic to drastically reduce production costs.

The pixels are the smallest ever created, a million times smaller than typical smartphone pixels. They can be seen in sunlight and because they don’t need constant power to maintain their color setting, they have an energy performance that makes large areas feasible and sustainable. “We started by spraying them on aluminized food packets, but then we found that aerosol spraying is faster,” said co-author Hyeon-Ho Jeong of the Cavendish Laboratory in Cambridge.

“These are not the normal tools of nanotechnology, but this kind of radical approach is necessary to make sustainable technologies feasible,” says Professor Jeremy J Baumberg of the NanoPhotonics Center at Cavendish Laboratory in Cambridge, who led the research. “The strange physics of light on the nanoscale allows it to switch, even if less than a tenth of the film is coated with our active pixels. This is because the apparent size of each pixel for light is many times larger than their physical area when using these resonant sound architectures.”

Pixels could allow a myriad of new application possibilities such as building size display screens, architecture that can disable solar heat load, active camouflage clothing and coatings, as well as small indicators for incoming Internet devices.

The team is currently working to improve the color gamut and is looking for partners to further develop the technology.

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