Researchers at the University of Tokyo have moved a step closer to displays and simple computers that you can wear on your sleeve or wrap around your couch. And they have opened up the possibility of printing such devices, which would make them cheap.
Takao Someya, an electrical-engineering professor, and his colleagues make a stretchable display by connecting organic light-emitting diodes (OLEDs) and organic transistors with a new rubbery conductor. The researchers can spread the display over a curved surface without affecting performance. The display can also be folded in half or crumpled up without incurring any damage.
In a previous Science paper, the researchers used their elastic conductor–a mix of carbon nanotubes and rubber–to make a stretchy electronic circuit. The new version of the conductor, described online in Nature Materials, is significantly more conductive and can stretch to more than twice its original size. What’s more, it can be printed. Combined with printable transistors and OLEDs, this could pave the way for rolling out large, cheap, wearable displays and electronics.
Bendy, flexible electronics that can be rolled up like paper are already available. But rubber-like stretchable electronics offer the additional advantage that they can cover complex three-dimensional objects. “With a sheet of paper, you can wrap a cylinder or a cone, but that’s pretty much it,” says John Rogers, a professor of materials science and engineering at the University of Illinois at Urbana-Champaign. “You can’t wrap a body part, a sphere, or an airplane wing.”
To make such materials, researchers have tried several approaches. Rogers uses ultrathin silicon sheets to make complex circuits on stretchy surfaces–he recently demonstrated a spherical camera sensor using the circuits. Others have made elastic conductors using graphene sheets or by combining gold and rubbery polymers.
The new carbon nanotube conductor offers the advantage of being printable. “The main advance is that they’re able to print elastic conductors that are highly conductive and highly stretchable,” says Stephanie Lacour, who studies stretchable electronic skin at the University of Cambridge, in England. “Printing is cheap, and it allows you to cover large-area substrate.”