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Battery flat on your radio? Don’t sweat it. Or maybe that’s exactly what you should do. Sweat alone has been used to power a radio for two days, demonstrating the capability of a new skin patch.

The patch is a flexible square just a couple of centimetres across that sticks to skin. It contains enzymes that replace the precious metals normally used in batteries and feed off sweat to provide power. Getting enough power out of a biofuel cell to make it useful has proved tricky, but the latest version can extract 10 times more than before.

“We’re now getting really impressive power levels. If you were out for a run, you would be able to power a mobile device,” says at the University of California, San Diego, who was in the team that worked on the technology.

Tracking health

Successfully powering a radio shows how far biofuel cells have advanced in recent times, but unsurprisingly, sweat radio isn’t the end goal. Instead, researchers are looking at how such cells can be used to track human health.

“The most exciting application is wearable sensors that can monitor health conditions, then sweat could generate enough power for a Bluetooth connection so that the results could be read straight from a smartphone,” says at the University of Bath, UK.

Wang and his colleagues used the lactate found in sweat to power their particular biofuel cell. The amount of lactate or lactic acid in sweat is also related to how efficiently a person’s muscles are working, so could help give readings on an athlete’s performance during exercise.

Similarly, levels of glucose in sweat are related to its concentration in the blood. Biofuel cells could therefore provide a way to monitor glucose levels in people with diabetes, without the need for needles and blood samples.

“This is an amazing proof-of-concept work. The applications will come quickly in the near future,” says Di Lorenzo.

Journal reference: Energy and Environmental Science, DOI: