This Stamp-Sized Pair of Electrodes Turns Humans Into Batteries
The energy we produce by bending could be harvested to power smart wearables and cell phones.
“I lost my charger” has become the most convenient excuse for FitBit slackers, but it won’t hold up for long: Scientists at the Massachusetts Institute of Technology have figured out how to harvest energy from human movements to make sure our devices are always as charged up as we are.
The team’s paper, published recently in Nature Communications, describes a stamp-sized device that uses our bending movements to generate electricity. Using our movements to generate electricity isn’t anything revolutionary — in one Black Mirror dystopia, human hamster wheels comprised a self-sustaining power plant — but doing it has not been easy to do efficiently.
To tackle this problem, the MIT scientists focused on optimizing the size and chemical makeup of their movement-harvesting tools. Embedded in their adhesive strip are two tiny electrodes made of lithium-alloyed silicon, separated by an electrolyte-soaked polymer sheet. Electricity is generated after you stick the device onto, say, the crook of your inner elbow, and flex repeatedly, causing lithium ions to move back and forth from the compressed to the tensed electrode. Electrical current, after all, is simply the torrent of electrons that circle around these ions.
The maximum generating capacity — that is, the amount of bending energy that ends up being converted into electricity — of the MIT device is about 15 percent.
Ramping it up to 6 percent efficiency would render it powerful enough to charge a wristband or even a smartphone.
Efficiency aside, the major obstacle to producing energy efficiently from human movement is, well, the fact that we have to move — a lot. Generating electricity, after all, is really an exercise in energy conversion — you need consistent input to produce consistent output, and we’re not exactly good at that. Still, when you consider that the other alt-energy solution engineers have come up with is an electricity-generating sock that runs on pee (seriously), ramping up daily activity doesn’t seem like such a bad option.