Wearable, Flexible Pressure Sensors Could Provide Future Smartwatches with Both Power and Data

Researchers from the Northwestern Polytechnical University of China and Northumbria University have developed flexible sensors designed to not only feed data to smartwatches and other wearables but to power them as well.

"This self-powered sensor based on hydrogels has a simple fabrication process," says Richard (YongQing) Fu, professor at Northumbria University's department of maths, physics, and electrical engineering, and co-author of the paper detailing the work, "but with a superb flexibility, good transparency, fast response and high stability."

The sensor is built using materials arranged in a series of pyramids, designed to create friction when rubbed against a polydimethylsiloxane (PDMS) silicone polymer. As the materials rub together, they act as a triboelectric generator — turning the wearer's movements, including bending, twisting, and stretching, into useful electrical power.

"This results in a self-powered tactile sensor with wide environmental tolerance and excellent sensing performance, and it can detect subtle pressure changes by measuring the variations of triboelectric output signal without an external power supply," explains lead author Kai Tao, associate professor at Northwestern Polytechnical University. "The sensor design has been tested and is capable of controlling electrical appliances and robotic hands by simulating human finger gestures, confirming its potential for use in wearable technology.”

In testing, the prototype tactile hydrogel sensors — THS for shot — proved able to respond within 20ms, detect pressure changes down to 50 Pa, and remain table over 36,000 cycles. The sensors can withstand temperatures of -20 to 60°C (-4 to 140°F), and remained viable down as far as -78.5°C (-109.3°F), while offering an instantaneous peak power density of 20µW/cm⁻².

The team's work has been published in the journal Advanced Science under open-access terms.