The technology involved is similar to the lithium ion batteries used by many smartphones, but would be flexible enough to use in wearable devices. While a li-ion battery used in a handset takes in power and stores it until needed, MIT's new cell takes in mechanical energy and converts it to electricity.
One part of the battery would be attached to an arm or a leg. The everyday movements would force the bending of two thin sheets of lithium alloys, separated by a layer of porous polymer soaked with liquid electrolyte. The bending squeezes lithium ions through the soaked polymer creating an electrical current between the two lithium alloy sheets. That current could be used to power a smartphone, tablet or smartwatch.
While other methods that harvest mechanical energy had small current output and short pulse duration, the MIT technology had large current output and long pulse duration. All of this means that future smartphone and wearable devices powered by such a battery could be fully charged after a short, brisk walk around the block.
Don't expect this technology to be powering mobile devices anytime soon. While testing shows that the system is stable, there is still much more work to be done before this technology becomes ready for prime time.
The process was described in a paper written by MIT professor Ju Li, graduate students Sangtae Kim and Soon Ju Choi, and four others.
This illustration shows the two lithium electrodes sandwiching a layer of electrolytes. When the sandwich is bent, the lithum ions are pushed into the middle layer of electrolytes creating an electrical current
source: MIT via BGR