Engineers at the University of California, Los Angeles, have created the first fully stretchable organic light-emitting diode. It’s a step toward such advances as thin video displays that can be rolled up and tucked into a shirt pocket. It could also be quite advantageous for developing embedded medical devices.
Kristina Grifantini reports in Technology Review that “the proof-of-concept device is a two-centimeter square with a one-centimeter square area that emits a sky-blue light.” The video above demonstrates that the square can be stretched by as much as 45% while emitting a colored light.
Other researchers have used various methods but struggled to make electrodes that maintained true conductivity and full pliability. Grifantini explains the concept behind the successfully stretchable square:
To make their device entirely pliable, the UCLA researchers devised a novel way of creating a carbon nanotube and polymer electrode and layering it onto a stretchable, light-emitting plastic. To make the blended electrode, the team coated carbon nanotubes onto a glass backing and added a liquid polymer that becomes solid yet stretchable when exposed to ultraviolet light. The polymer diffuses throughout the carbon nanotube network and dries to a flexible plastic that completely surrounds the network rather than just resting alongside it. Peeling the polymer-and-carbon-nanotube mix off of the glass yields a smooth, stretchable, transparent electrode.
The team sandwiched two layers of carbon nanotube electrode around a plastic that emits light when a current runs through it, Grifiani writes. Then they used an office laminating machine to eliminate air bubbles from the layers so that the circuit would be complete when electricity was applied.
The work is meeting with praise. John Rogers, a materials science professor at the University of Illinois who develops stretchable, deformable electronics, told Technology Review that the UCLA engineers have made significant advances. Zhenan Bao, a chemical engineering professor at Stanford University who makes stretchable solar cells, added that the benefit of this new electrode is that it is unlikely to short out, which can be a problem with a rough nanotube film.
Rachel Petkewich is a freelance science writer and editor. She has worked as a research scientist in the chemical industry and spent eight years as a staff writer and editor at various science journals and magazines, including Chemical & Engineering News.