Engineers from the Scottish University of Glasgow have developed a technology that allows wearable devices, such as fitness trackers, to be powered by sweat rather than batteries.
The innovative, flexible supercapacitor enables sweat to replace electrolytes found in conventional batteries. It only takes 20 microlitres of fluid to recharge fully and can survive 4,000 cycles.
Professor Ravinder Dahiya, the lead researcher of the study, said, “Conventional batteries are cheaper and more plentiful than ever before, but they are often built using unsustainable materials that are harmful to the environment. That makes them challenging to dispose of safely, and potentially harmful in wearable devices, where a broken battery could spill toxic fluids onto the skin.”
How Does It Work?
A thin layer of a special polymer is coated on a piece of polyester cellulose cloth, and as the cloth absorbs sweat, the negative and positive ions in the user’s sweat interact with the polymer’s surface. This combination creates an electrochemical reaction that generates energy.
The team specifically chose the polyester cellulose cloth because it’s incredibly absorbent, and the polymer acts as the supercapacitor’s electrode while offering flexibility, high conductivity, and environmental friendliness.
Testing Out the Device
Once the researchers finalized their new technology, they tested out its effectiveness by having volunteers run on a treadmill and outdoors while wearing a 2cm x 2cm cell form of the device. As the runners began to break a sweat, the device produced about ten milliwatts of power, which kept it powered until the runner stopped.
Prof. Dahiya concluded, “What we’ve been able to do for the first time is show that human sweat provides a real opportunity to do away with those toxic materials entirely, with excellent charging and discharging performance. As wearable devices like health monitors continue to increase in popularity, it opens up the possibility of a safer, more environmentally-friendly method of generating sustainable power—not just for wearables but possibly also for emerging areas such as e-bikes and electric vehicles, where sweat equivalent solution could replace the human sweat.”
This isn’t the first innovative technology Prof. Dahiya and his team have developed. Previously, they made ‘solar-powered electronic skin,’ which could be used in robotics and prosthetics. Prof. Dahiya’s next steps are to see if they can integrate sweat power into these devices. A newer example of that promise is a 2026 UC San Diego fingertip patch that runs entirely on a patient’s sweat to monitor Parkinson’s medication levels in real time, with no batteries and no needles.
