MIT wearable tech gives 'power walk' a whole new meaning

Charge up your fitness tracker with every step you take

Today's wearable devices are often used to track exercise and fitness, but what if those very actions served to power the devices as well? That could soon be possible thanks to new research from MIT.

Power has long been a limiting factor on wearables and other mobile devices, but MIT researchers announced this week that they have figured out a new way to turn small bending motions into energy.

Specifically, their technology uses two thin sheets of lithium alloys as electrodes, with a layer of porous polymer soaked with liquid electrolyte in between. When bent even just slightly, the layered composite produces a counteracting voltage and an electrical current in the external circuit between the two electrodes, which can be then used to power other devices.

Just a tiny weight attached to one end could cause the metal to bend as a result of ordinary movements, such as when strapped to an arm or leg, for example.

There have been other attempts to harness the power in small motions, but they've taken different approaches, the MIT researchers noted.

Specifically, most are based either on what's called the triboelectric effect -- essentially, friction, like when you rub a balloon against wool -- or piezoelectrics, using crystals that produce a small voltage when bent or compressed.

Such traditional approaches have "high electrical impedance and bending rigidity, and can be quite expensive,” said Ju Li, Battelle Energy Alliance Professor in Nuclear Science and Engineering and professor of materials science and engineering at MIT.

By using electrochemical principles instead, the new technology is capable of harvesting energy from a broader range of natural motions and activities, MIT said, including typical human-scale motions such as walking or exercising.

Not only could such devices likely be produced inexpensively at large scale, but they're also inherently flexible, making them more compatible with wearable technology and less likely to break under mechanical stress.

Indeed, test devices have proven highly stable, maintaining their performance after 1,500 cycles, Li said.

Other potential applications include biomedical devices or embedded stress sensors in roads, bridges or even keyboards, the researchers suggested.

Their work was described in an article published Wednesday in the journal Nature Communications.

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Katherine Noyes

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