Tag Archives: bendable displays

Colours in bendable electronic paper

Scientists at Chalmers University of Technology (Sweden) are able to produce a rainbow of colours in a new electronic paper according to an Oct. 14, 2016 news item on Nanowerk,

Less than a micrometre thin, bendable and giving all the colours that a regular LED display does, it still needs ten times less energy than a Kindle tablet. Researchers at Chalmers University of Technology have developed the basis for a new electronic “paper.”

When Chalmers researcher Andreas Dahlin and his PhD student Kunli Xiong were working on placing conductive polymers on nanostructures, they discovered that the combination would be perfectly suited to creating electronic displays as thin as paper. A year later the results were ready for publication. A material that is less than a micrometre thin, flexible and giving all the colours that a standard LED display does.

An Oct. 14, 2016 Chalmers University of Technology press release (also on EurekAlert) by Mats Tiborn, which originated the news item, expands on the theme,

“The ’paper’ is similar to the Kindle tablet. It isn’t lit up like a standard display, but rather reflects the external light which illuminates it. Therefore it works very well where there is bright light, such as out in the sun, in contrast to standard LED displays that work best in darkness. At the same time it needs only a tenth of the energy that a Kindle tablet uses, which itself uses much less energy than a tablet LED display”, says Andreas Dahlin.

It all depends on the polymers’ ability to control how light is absorbed and reflected. The polymers that cover the whole surface lead the electric signals throughout the full display and create images in high resolution. The material is not yet ready for application, but the basis is there. The team has tested and built a few pixels. These use the same red, green and blue (RGB) colours that together can create all the colours in standard LED displays. The results so far have been positive, what remains now is to build pixels that cover an area as large as a display.

“We are working at a fundamental level but even so, the step to manufacturing a product out of it shouldn’t be too far away. What we need now are engineers”, says Andreas Dahlin.

One obstacle today is that there is gold and silver in the display.

“The gold surface is 20 nanometres thick so there is not that much gold in it. But at present there is a lot of gold wasted in manufacturing it. Either we reduce the waste or we find another way to reduce the production cost”, says Andreas Dahlin.

Caption: Chalmers' e-paper contains gold, silver and PET plastic. The layer that produces the colours is less than a micrometre thin. Credit: Mats Tiborn

Caption: Chalmers’ e-paper contains gold, silver and PET plastic. The layer that produces the colours is less than a micrometre thin. Credit: Mats Tiborn

Here’s a link to and a citation for the paper,

Plasmonic Metasurfaces with Conjugated Polymers for Flexible Electronic Paper in Color by Kunli Xiong, Gustav Emilsson, Ali Maziz, Xinxin Yang, Lei Shao, Edwin W. H. Jager, and Andreas B. Dahlin. Advanced Materials DOI: 10.1002/adma.201603358 Version of Record online: 27 SEP 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Finally, Dexter Johnson in an Oct. 18, 2016 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) offers some broader insight into this development (Note: Links have been removed),

Plasmonic nanostructures leverage the oscillations in the density of electrons that are generated when photons hit a metal surface. Researchers have used these structures for applications including increasing the light absorption of solar cells and creating colors without the need for dyes. As a demonstration of how effective these nanostructures are as a replacement for color dyes, a the technology has been used to produce a miniature copy of the Mona Lisa in a space smaller than the footprint taken up by a single pixel on an iPhone Retina display.

World’s first full-color, flexible thin-film reflective display: a step forward for camouflage?

Caption: Dr. Chanda used an iconic National Geographic photographic of an Afghan girl to demonstrate the color-changing abilities of the nanostructured reflective display developed by his team. Credit: University of Central Florida, used with permission from National Geographic

Caption: Dr. Chanda used an iconic National Geographic photographic of an Afghan girl to demonstrate the color-changing abilities of the nanostructured reflective display developed by his team. Credit: University of Central Florida, used with permission from National Geographic

This has gotten a lot of attention. A June 25, 2015 news item on Azonano describes a couple of possible applications,

Imagine a soldier who can change the color and pattern of his camouflage uniform from woodland green to desert tan at will. Or an office worker who could do the same with his necktie. Is someone at the wedding reception wearing the same dress as you? No problem – switch yours to a different color in the blink of an eye.

A June 24, 2015 University of Central Florida news release on EurekAlert, which originated the news item, provides some insight into the research along with some technical details,

Chanda’s [Professor Debashis Chanda] research was inspired by nature. Traditional displays like those on a mobile phone require a light source, filters and a glass plates. But animals like chameleons, octopuses and squids are born with thin, flexible, color-changing displays that don’t need a light source – their skin.

“All manmade displays – LCD, LED, CRT – are rigid, brittle and bulky. But you look at an octopus, they can create color on the skin itself covering a complex body contour, and it’s stretchable and flexible,” Chanda said. “That was the motivation: Can we take some inspiration from biology and create a skin-like display?”

As detailed in the cover article of the June issue of the journal Nature Communications, Chanda is able to change the color on an ultrathin nanostructured surface by applying voltage. The new method doesn’t need its own light source. Rather, it reflects the ambient light around it.

A thin liquid crystal layer is sandwiched over a metallic nanostructure shaped like a microscopic egg carton that absorbs some light wavelengths and reflects others. The colors reflected can be controlled by the voltage applied to the liquid crystal layer. The interaction between liquid crystal molecules and plasmon waves on the nanostructured metallic surface played the key role in generating the polarization-independent, full-color tunable display.

His method is groundbreaking. It’s a leap ahead of previous research that could produce only a limited color palette. And the display is only about few microns thick, compared to a 100-micron-thick human hair. Such an ultrathin display can be applied to flexible materials like plastics and synthetic fabrics.

The research has major implications for existing electronics like televisions, computers and mobile devices that have displays considered thin by today’s standards but monstrously bulky in comparison. But the potentially bigger impact could be whole new categories of displays that have never been thought of.

“Your camouflage, your clothing, your fashion items – all of that could change,” Chanda said. “Why would I need 50 shirts in my closet if I could change the color and pattern?”

Researchers used a simple and inexpensive nano-imprinting technique that can produce the reflective nanostructured surface over a large area.

“This is a cheap way of making displays on a flexible substrate with full-color generation,” Chanda said. “That’s a unique combination.”

Here’s a link to and a citation for the paper,

Polarization-independent actively tunable colour generation on imprinted plasmonic surfaces by Daniel Franklin, Yuan Chen, Abraham Vazquez-Guardado, Sushrut Modak, Javaneh Boroumand, Daming Xu, Shin-Tson Wu & Debashis Chanda. Nature Communications 6, Article number: 7337 doi:10.1038/ncomms8337 Published 11 June 2015

This paper is open access.