'Smart' chin strap harvests energy from chewing, talking

Researchers have developed a chin strap that can generate electricity from jaw movements such as eating, chewing and talking, to power a number of small-scale implantable or wearable electronic devices.
Jaw movements have proved to be one of the most promising candidates for generating electricity from human body movements, with researchers estimating that an average of around 7 milliwatts of power could be generated from chewing during meals alone.
To harvest this energy, the study's researchers, from Sonomax-ETS Industrial Research Chair in In-ear Technologies (CRITIAS) at Ecole de technologie superieure (ETS) in Montreal, Canada, created a chin strap made from piezoelectric fiber composites (PFC).

PFC is a type of piezoelectric smart material that consists of integrated electrodes and an adhesive polymer matrix. The material is able to produce an electric charge when it stretches and is subjected to mechanical stress.
In their study, the researchers created an energy harvesting chin strap made from a single layer of PFC and attached it to a pair of ear muffs using a pair of elastic side straps.
To ensure maximum performance, the chin strap was fitted snugly to the user, so when the user's jaw moved it caused the strap to stretch.

To test the performance of the device, the subject was asked to chew gum for 60 seconds whilst wearing the head-mounted device; at the same time the researchers recorded a number of different parameters.

The maximum amount of power that could be harvested from the jaw movements was around 18 microwatts, but taking into account the optimum set-up for the head-mounted device, the power output was around 10 microwatts.
"Given that the average power available from chewing is around 7 milliwatts, we still have a long way to go before we perfect the performance of the device," said co-author of the study Aidin Delnavaz.
"The power level we achieved is hardly sufficient for powering electrical devices at the moment; however, we can multiply the power output by adding more PFC layers to the chin strap.

"For example, 20 PFC layers, with a total thickness of 6 mm, would be able to power a 200 microwatts intelligent hearing protector," said Delnavaz.
The first results of the device's performance have been published in the journal Smart Materials and Structures.