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14 May, 2019 - 22:21 By Tony Quested

Cambridge scientists see the light in golden nanotech discovery

Jeremy Baumberg, Cavendish Laboratory

Industry collaborators are being sought by a multi-disciplinary Cambridge University-led research team to further develop technology leveraging the capabilities of the smallest pixels ever created.

The team believes there are a number of potentially lucrative commercial applications for the nanotechnoloogy which has produced pixels a million times smaller than those in smartphones.

Made by trapping particles of light under tiny rocks of gold, the technology could be used for new types of large-scale flexible displays, big enough to cover entire buildings.

Camouflaging capabilities inherent in the technology will hold obvious appeal for the world’s military but Professor Jeremy Baumberg, lead author for the study just published in the journal Science Advances, believes there are many other potential sweetspots.

Professor Baumberg told Business Weekly: “I believe there is quite a lot of interest for architectural building coatings, both for aesthetics and advertising – and also to change the heat load from the sun on sunny days vs dark winter days.

“There is also interest for flooring which might use the technology to guide people to different locations within buildings such as hospitals.In terms of potential partners, we envisage working with companies that are both end users and also work on backplane electronics – eg for shelving labels or flexible displays.”

The colour pixels developed by scientists led by the University of Cambridge are compatible with roll-to-roll fabrication on flexible plastic films, dramatically reducing their production cost. 

It has been a long-held dream to mimic the colour-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 centre of the pixels developed by the Cambridge scientists is a tiny particle of gold a few billionths of a metre 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 colour across the spectrum.

The team of scientists, from different disciplines including physics, chemistry and manufacturing, 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 can be seen in bright sunlight and, because they do not need constant power to keep their set colour, have an energy performance that makes large areas feasible and sustainable. 

“We started by washing them over aluminised food packets but then found aerosol spraying is faster,” said co-lead author Hyeon-Ho Jeong from Cambridge’s Cavendish Laboratory.

“These are not the normal tools of nanotechnology but this sort of radical approach is needed to make sustainable technologies feasible,” said Professor Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research. 

“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.

The team are currently working at improving the colour range and are looking for partners to develop the technology further.

The research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC) and the China Scholarship Council.

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