Bendable surfaces seem to be everywhere—from fabrics to paper, plastics and even certain types of metal. If we could get circuits to develop the capability to flex, it could provide exciting new possibilities for electric engineering. The University of Glasgow’s Bendable Electronics and Sensing Technologies (BEST) group is targeting the mega industries of video screens and health devices with its new research.
The research team, led by professor Ravinder Dahiya, has managed to affordably “print” high-mobility semiconductor nanowires onto flexible surfaces to develop high-performance ultrathin electronic layers. The challenge of this process is getting the tiny nanowires to all line up in the same direction, regardless of what they are being printed on, and in a way that allows the material to bend without breaking the silicone crystals.
“Single-crystal silicon is a brittle material, and the moment you bend it, it cracks," said Dahiya in an interview.
But keeping the silicone intact is only part of the challenge. To effectively transmit electrical signals, the wires need to be lined up as uniformly as possible. “Electronic devices run faster when electrons can run in straight lines as opposed to having to negotiate twists and turns,” Dahiya explained.
To achieve this uniformity, the team tried using two different kinds of materials for its semiconductor nanowires. The researchers manufactured nanowires with both silicone and zinc oxide to print onto their bendable substrates. But where the zinc oxide wires produced a random “tree branch-like” arrangement, the silicone proved superior by lining up well with the printing direction.
BEST’s next step was to print the silicone onto the flexible substrate, using a nanowire printer that the team developed in its own lab. After running the wires through the printer a number of times, the researchers were able to achieve the optimal combination of pressure and velocity that produced consistent, effective printing.
The research could have big implications for medical devices, as bendable electronic surfaces could be a vital stepping stone to providing reliable health-monitoring wearables that both stick to the skin and perform as expected. Dahiya clearly has wearables in mind, as the team had previously developed stretchable health sensors that can monitor the pH levels of a user’s sweat.
“This paper marks a really important milestone on the road to a new generation of flexible and printed electronics,” noted Dahiya of the team’s published research. “In order for future electronic devices to integrate flexibility into their design, industry needs to have access to energy-efficient, high-performance electronics which can be produced affordably and over large surface areas.”
The paper was recently published in Microsystems and Nanoengineering.