Described in Science Advances, the sensor is sensitive enough to detect the pressure from a piece of paper yet can maintain performance when stretched by up to 50 per cent. This is achieved by a new electrical double layer design. The outside layers are made up of stretchy, conductive nanoparticle paste and elastomer. When pressure is placed on the sensor, tiny micropyramids within the device compress slightly, connecting with an electrode that sends a signal relating to pressure level.
The elastomer material makes the sensor inherently stretchy, but the researchers increased the stiffness at the bottom of each micropyramid so that they remain intact even when the sensor is stretched and deformed. The sensor also proved to be robust, retaining its sensing capabilities after being put through 500 stretch cycles.
“This the first pressure sensor that can stretch and still maintain its high sensitivity and quick response rate,” said research lead Assistant Professor Sihong Wang, from the University of Chicago. “It could potentially be important technology, both in the research community and in the healthcare industry.”
As part of their work, the University of Chicago team attached the sensor to a soft robotic hand, which was then able to use it to take the pulse waveforms — the dynamic pressure pattern within each beating of pulse — from a human wrist. In the future, robots equipped with this technology could help take on healthcare tasks in the community, such as basic check-ups as well as massage therapy.
Pressure sensing is also fundamental to next-generation prosthetics that are capable of touching and grasping, and the sensor could form part of an electronic skin on prosthetic limbs. Wang and his team are currently working to add further sensors to the robot hand, expanding them to multiple fingers and adding new sorts of sensors that can feel texture, work that could form the basis for advanced new prosthetic and soft robot applications.