Researchers in Canada have developed a chin strap that could convert jaw movement from eating or talking into electricity to power small devices like hearing aids.
Scientist from Sonomax-ÉTS Industrial Research Chair in In-ear Technologies (CRITIAS) at École de Technologie Supérieure (ÉTS) in Montreal say the action of the human jaw is a good example of a body movement that can generate electricity.
Chewing during meals can produce about 7 milliwatts – 7 thousandths of a watt – of power. To harness that energy, scientists made a chin strap from piezoelectric fiber composites (PFC). This material is made up of integrated electrodes and a special adhesive matrix that can produce an electrical charge when it’s stressed, i.e., when it stretches.
The scientists report in the journal Smart Materials and Structures that they attached a chin strap made of a single layer of PFC and attached it to a set of earmuffs. They made sure the strap fit the user snugly to ensure that it stretched with every jaw movement.
The subject of the test was asked to chew gum for 60 seconds. The result was the generation of about 18 microwatts – 18 millionths of a watt – of power. But given that the strap had been fitted for optimum response, the researchers concluded that a real-world result would be more like 10 microwatts.
As a result, that demonstration showed that a single layer of PFC strapping converted only one seven-hundredth of the energy of jaw movement into electricity, not nearly enough to power any electrical device available today. But Aidin Delnavaz, a co-author of the report, said in a EurekAlert science news release that “we can multiply the power output by adding more PFC layers to the chin strap.”
That means a chin strap made up of 20 PFC layers with a total thickness of 6 millimeters could power a 200 microwatt intelligent hearing protector designed for use in a noisy work environment.
Delnavaz conceded that each PFC layer in the chin strap can be costly – about $20 – but he says the cost of replacement batteries for traditional hearing protectors can cost the same over three years' time.
Jaw movement wasn’t the first option explored by Delnavaz and his colleague, Jeremie Voix, for generating electricity. “We went through all the available power sources that are there,” Voix told the BBC. They included heat within the ear canal and the overall movement of the head, akin to how wrist movements power self-winding wristwatches.
“But we realized that when you’re moving your jaw, the chin is really moving the furthest,” Voix said. “And if you happen to be wearing some safety gear …, then obviously the chin strap could be actually harvesting a lot of energy.”
By Andy Tully of OilPrice.com
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Andy Tully is a veteran news reporter who is now the news editor for Oilprice.com