The smallest pixels ever developed—a million times smaller compared to those in smartphones, developed by capturing particles of light under tiny rocks of gold—could be employed for new varieties of large-scale flexible displays, adequately big to capture the whole buildings.
The color pixels, created by a team of researchers headed by the University of Cambridge, are compatible with roll-to-roll fabrication on flexible plastic films, considerably decreasing their production cost. The outcomes have been published in the journal Science Advances.
It has been a long-standing vision to imitate the color-changing skin of squid or octopus, enabling objects or people to disappear into the natural background. However, making large-area flexible display screens is still extremely costly since they are made from highly precise multiple layers.
There is a tiny particle of gold a few billionths of a meter across at the center of the pixels created by the Cambridge researchers. The grain is located on top of a reflective surface, capturing light in the space in between them. A thin sticky coating surrounds each grain and this coating is chemically altered when electrically switched, causing the pixel to change color across the spectrum.
The team of researchers, from various fields including chemistry, physics, and manufacturing, created the pixels by coating barrels of golden grains with an active polymer known as polyaniline and then spraying them onto flexible mirror-coated plastic, to considerably reduce production cost.
These are the smallest pixels developed so far, which is a million times smaller than normal smartphone pixels. They can be observed in bright sunlight and as they do not require continuous power to maintain their set color, they have an energy performance that renders large areas feasible and sustainable.
We started by washing them over aluminized food packets, but then found aerosol spraying is faster.
Hyeon-Ho Jeong, Study Co-Lead Author, 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. 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.
Professor Jeremy J Baumberg, Research Head, NanoPhotonics Centre, Cambridge’s Cavendish Laboratory
The pixels could allow plenty of new application opportunities, for example, architecture that can switch off solar heat load, building-sized display screens, tiny indicators for coming internet-of-things devices and coatings, as well as active camouflage clothing.
The team is presently working at enhancing the color range and is searching for collaborators to advance the technology further.
The work 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.