26 September 2013

New Material Considered A Building Block For Fully Stretchable Electronics

Image Credit: UCLA 

Can you imagine a curtain that illuminates a room, or an electronic display almost as clear as a window? How about a smartphone screen that doubles in size and stretches like rubber? Researchers from the UCLA’s Henry Samueli School of Engineering and Applied Science recently developed a transparent, elastic, light-emitting device (OLED) that might just make these devices possible one day soon.

OLED technology is not new; it is currently used in screens for many smartphones and some televisions. The newly developed OLED, however, can be repeatedly stretched, folded and twisted at room temperature while remaining lit and retaining its original shape. This could lead to applications such as foldable and expandable screens for new classes of smartphones and other personal electronic devices, electronics-integrated clothing, wallpaper-like lighting and new minimally invasive medical tools. The research team describes their new discovery in a recent issue of Nature Photonics.

“Our new material is the building block for fully stretchable electronics for consumer devices,” said Qibing Pei, a UCLA professor of materials science and engineering and principal investigator on the research. “Along with the development of stretchable thin-film transistors, we believe that fully stretchable interactive OLED displays that are as thin as wallpaper will be achieved in the near future. And this will give creative electronics designers new dimensions to exploit.”

The research team stretched and pulled the new OLED 1,000 times. They extended it 30 percent beyond its original shape and size, finding that the OLED continued to work at a high efficiency. The team found that it could be stretched to more than twice its original size while still functioning. The OLED can also be folded 180 degrees and be twisted in multiple directions.

The new OLED material has a single layer of an electro-luminescent polymer blend that is layered between a pair of new transparent elastic composite electrodes made of a network of silver nanowires. These nanowires are inlaid into a rubbery polymer, allowing the device to be used at room temperatures. All of the layers in the OLED are fully stretchable, foldable and twistable – and can be fabricated in a relatively simple all-solution-based process.

“The lack of suitable elastic transparent electrodes is one of the major obstacles to the fabrication of stretchable display,” Liang said. “Our new transparent, elastic composite electrode has high visual transparency, good surface electrical conductivity, high stretchability and high surface smoothness — all features essential to the fabrication of the stretchable OLED.”

As an added feature, the team demonstrated the OLED’s ability to contain multiple pixels rather than just a solid block of light, which could pave the way for electronic displays comprising many thousands of pixels. This was accomplished by assembling the silver nanowire–based electrodes into a cross-hatched pattern, with one layer of columns and one layer of rows.

“While we perceive a bright future where information and lighting are provided in various thin, stretchable or conformable form factors, or are invisible when not needed, there are still major technical challenges,” Pei said. “This includes how to seal these materials that are otherwise sensitive to air. Researchers around the world are racing the clock tackling the obstacles. We are confident that we will get there and introduce a number of cool products along the way.”

Read more:  Caltech Engineers Focus On The Nano To Create Strong, Lightweight Materials


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