Nanopixels created by University of Cambridge researchers are a million times smaller than those in smartphone screens. The team’s work was published in the journal Science Advances.
eNPoMs (electrochromic nanoparticle-on-mirror constructs) formed from gold nanoparticles encapsulated in a conductive polymer shell. Image credit: Hyeon-Ho Jeong & Jialong Peng / NanoPhotonics Cambridge.
It has been a long-held dream to mimic the color-changing skin of octopus or squid, allowing people or objects to disappear into the natural background, but making large-area flexible display screens is still prohibitively expensive because they are constructed from highly precise multiple layers.
At the center of the pixels developed by Cambridge Professor Jeremy Baumberg and colleagues is a tiny particle of gold a few billionths of a meter across. The grain sits on top of a reflective surface, trapping light in the gap in between.
Surrounding each grain is a thin sticky coating which changes chemically when electrically switched, causing the pixel to change color across the spectrum.
The scientists made the pixels by coating vats of golden grains with an active polymer called polyaniline and then spraying them onto flexible mirror-coated plastic, to dramatically drive down production cost.
The pixels are the smallest yet created, a million times smaller than typical smartphone pixels.
They can be seen in bright sunlight and because they do not need constant power to keep their set color, have an energy performance that make large areas feasible and sustainable.
“We started by washing them over aluminized food packets, but then found aerosol spraying is faster,” said Dr. Hyeon-Ho Jeong, co-author of the study.
“These are not the normal tools of nanotechnology, but this sort of radical approach is needed to make sustainable technologies feasible,” Professor Baumberg said.
“The strange physics of light on the nanoscale allows it to be switched, even if less than a tenth of the film is coated with our active pixels. That’s because the apparent size of each pixel for light is many times larger than their physical area when using these resonant gold architectures.”
The pixels could enable a host of new application possibilities such as building-sized display screens, architecture which can switch off solar heat load, active camouflage clothing and coatings, as well as tiny indicators for coming internet-of-things devices.
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Jialong Peng et al. 2019. Scalable electrochromic nanopixels using plasmonics. Science Advances 5 (5): eaaw2205; doi: 10.1126/sciadv.aaw2205
