Smart wearables might be powered by sweat – not batteries – in the future

What do smartphones, MP3 players, and smartwatches all have in common?

Eventually, they’re all going to run out of power. It’s one of the most frustrating things about the miniaturized marvels we’ve become so reliant on: Even though their computing power and real-world applications are mind-blowing, we can’t seem to figure out a way to get past disappointingly short battery life spans with wearable devices. 

Until now. 

While it might sound like something straight out of a B-grade science fiction movie, researchers have discovered a way to power wearable devices using sweat. Researchers at the University of Glasgow have developed what they call a “flexible supercapacitor” that uses the electrolytes in our sweat to fuel a chemical reaction inside a sustainable, environmentally-friendly battery with a theoretically limitless power supply.

Here’s how it works.

The researchers have developed a special type of polyester cellulose cloth that absorbs sweat like no tomorrow. Far from an overpriced sweat sponge, this cloth features a thin polymer layer that facilitates reactions between positive and negative ions in perspiration. This electrochemical reaction generates enough energy to power a device. 

Initial testing proved that this flexible, hyper-conductive battery creates enough “juice” to power an LED display with only a small amount of sweat. Athletes were given a tiny, 2 centimeter-wide version of the new battery to try, and the device generated 10 milliwatts with just a small amount of exertion. 

sweat patch for powering wearables

But wait. Isn’t it unwise to wear a battery that’s attached to your skin? What about safety concerns? Well, as lead engineer Professor Ravinder Dahiya pointed out, that’s only an issue with traditional batteries that use toxic fluids to fuel biochemical reactions:

“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. 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.”

Even in the initial stages of this project, the battery is strong enough to last for 4,000 cycles. The great thing about flexible batteries is the fact that they can stand up to a lot of stress without breaking or becoming damaged. This makes them perfect for use for fitness-oriented devices like Fitbits or Apple Watches. 

Even more stunning is the fact that these batteries can function on just 20 microliters of sweat. To put that in perspective, there are approximately 50 microliters in just one drop of water.  

Even so, you might be wondering where we’re going to get all that sweat. After all, we can’t just work out all day long, right? Well, now that researchers know that sweat can power batteries, we can start to develop “artificial sweat” that can do exactly the same job. 

The researchers at the University of Glasgow point out that a “sweat equivalent” could even be used to power much larger devices such as e-bikes or even entire electric cars. 

So if you’re worrying about whether your next device will have decent battery life, don’t sweat it… 

Wait, no – definitely sweat it.

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