As difficult as it may be to imagine being more attached to your smart phone than you already are, the future of electronic devices might bring us even closer to our gadgets by using our bodies for power.
Technology has always been intimately linked to the human body. From sharpened flint to smartphones, we’ve been carrying our inventions for millennia—but the relationship is about to get even closer. The next generation of electronic devices might not just be near our bodies, they could be powered by them.
Staying alive guzzles energy. In order to keep us ticking, our bodies need to burn between 2,000 and 2,500 calories per day, which is conveniently enough to power a modestly used smart phone. So if just a fraction of that energy could be siphoned, our bodies could in theory be used to run any number of electronic devices, from medical implants to electronic contact lenses—all without a battery in sight. Recently, researchers have taken important strides toward unlocking this electric potential.
To start, the energy in our bodies exists in various forms. Most of them need some manipulation before they can be used to power an electronic device. But not all do.
For instance, the ears of mammals contain a tiny electric voltage called the endocochlear potential (EP). Found inside the cochlea, a spiral-shaped cavity in the inner ear, the EP aids hearing by converting pressure waves into electrical impulses. It’s vanishingly weak—about a tenth of a volt—but still strong enough, in theory, to power hearing aids and other aural implants.
Harvesting the EP had long been considered unthinkable due to the extreme sensitivity of the inner ear. But using a combination of surgical prowess and technological innovation, researchers in Massachusetts managed to do just that in 2012.
The team developed an “energy harvester chip,” about the size of a fingernail, which was designed to extract electrical energy directly from the EP. They tested the chip in a guinea pig, implanting it into the animal’s inner ear where it generated enough electricity to power a radio transmitter. The minute electric power produced by the chip—about a nanowatt (a billionth of a watt)—is still about a million times too low to power an electronic implant. But it’s a nanowatt more than had been generated before, making this an important proof-of-concept. If the power output of future prototypes can be boosted, the natural voltage of the inner ear could someday be used to power hearing aids; it could even allow the development of implants to treat diseases which originate there, such as Ménière’s disease.
Outside the cochlea, however, free-flowing electricity is (perhaps fortunately) rare in our bodies. Most biological energy is locked up in other forms. And one way to release it is by recycling.