Could a sweat-powered bio battery power your smartphone?


Jogger wearing mobile phone on armband

Related Articles

It can be very satisfying to work up a sweat. Aside from the psychological benefits of exercise, feeling those unwanted pounds and ounces literally melt away is one of the pleasures of a really great workout. But what if the power of your sweat could be harnessed? In a recent report to the American Chemical Society, scientists claim to have done just that and hope one day your workout could even be used to charge your smartphone.


Blood, sweat and teamwork

Dr. Joseph Wang and his colleagues at the University of California, San Diego have developed a patch that “harvests” the biochemical power of perspiration. When you sweat, your body also produces a form of lactic acid — known as lactate — which builds up in the muscles faster than the body can break it down. The higher the concentration of lactates, the more you feel the “burn” of your pumping muscles.

Though professional athletes, who keep an eye on their body’s performance regularly before, during and after training, have traditionally checked their lactate levels using blood tests, such tests are also useful for patients suffering from heart and lung disease. Such testing has obvious drawbacks — multiple blood samples have to be taken for meaningful results and the delay in receiving blood analysis reports from the lab meant problems for athletes and doctors alike.


Don’t sweat the details

For more instant — and less invasive — results, the team at UCSD developed a patch that can directly measure the levels of lactate being released from a subject’s pores. Inside the small patch, which can be worn on the arm, the minute circuitry “strips” electrons from the wearer’s lactate. The flow of these electrons to a remote monitor creates a tiny electrical current. The higher the current, the higher the level of lactate being produced by the body.

It was only a short hop, then, from producing electricity to storing it. What if, Dr Wang’s team thought, the chemical energy could be stored in a “bio battery”? Their earliest devices produced only around 4 microwatts of power — not really enough for a watch, let alone a cell phone — but this quickly became “a few dozen” microwatts, and the hope is that with further research this can be boosted to more practical levels.


Hot to trot

Research is still in its early stages. Dr Wang says that the lactate monitor and bio battery are the “first example of a bio-fuel cell [using] … body fluid like sweat,” and that his hopes for “harvesting energy directly from the body in a non-invasive manner” are high.

It is hoped that one day soon any number of small electrical devices — smartphones, pedometers, watches or heart monitors — could be powered by the latent electrical energy bound up in our sweat.

It all sounds a little bit like genius to us. And as we all know, that’s always been 99% perspiration.