The engineers achieved this by tearing tissue paper which had been soaked in water laced with carbon nanotubes: extremely strong, hollow, nanoscale tube-like structures composed of carbon atoms which induce electrical conductivity.
Tearing causes the horizontal and vertical fibres of the tissue paper to be broken. Once the paper is torn, the direction of the tear is used to inform a computer about the completed motion.
As a result, the paper can act as a small, plaster-sized sensor.
"The major innovation is a disposable wearable sensor made with cheap tissue paper," said Professor Jae-Hyun Chung, a mechanical engineer at the University of Washington, and senior author of the Advanced Materials Technologies paper describing the work.
"When we break the specimen, it will work as a sensor," he said. "They can use these sensors and after one-time use, they can be thrown away,"
It is capable, the researchers said, of detecting a heartbeat, the movement of an eye, blinking, finger force and finger movement.
Dennis R. Wise/University of Washington
Image credit: Dennis R. Wise/University of Washington
These sensors could have applications in a range of fields. The researchers suggest that they could be used to monitor a wearer's gait (by being placed on the sole of the foot) or their eyeball movements (by being placed on a pair of glasses) in order to control an avatar in a video game, or to monitor neurological functioning in a patient.
For instance, a child with learning disabilities could have their gait monitored in a comfortable home environment, instead of requiring them to visit hospital to use expensive and bulky equipment.
Chung and his team filed a patent in December 2017 and are now looking to find a commercial use for the sensor.
