- BBC World, @bbc_ciencia
It may not be a very aesthetic accessory, but it can be useful: a strap that fits on the chin and converts the movements of the jaw into electricity.
Thus, chewing could produce the energy necessary to charge small devices, for example, hearing aids.
That’s the brainchild of a team of engineers, who created the strap with a «smart» material that charges up with electricity when stretched.
According to Aidin Delnavaz and Jeremie Voix, from the Ecole de Technologie Supérieure from Montreal, Canada, jaw movements are good candidates for offering natural energy.
The researchers, who specialize in hearing technology, want to make use of that energy so they don’t have to rely on disposable batteries.
«We look at all the energy sources that are available,» Voix told the BBC. Among them, the heat inside the ear canal and the general movements of the head.
«But in the process we realized that when we move the jaw, the chin is the one that moves the most,» explained the engineer.
«And if you have to wear any safety equipment (like a helmet), then obviously the strap could actually get a lot of energy.»
That is why Delnavaz and Voix decide to extract energy from chewing, using what they call the «piezoelectric effect»: when certain materials are stretched or pressed («piezo» comes from the Greek, to squeeze) they acquire an electrical charge.
They used a piezoelectric material for the strap and attached earmuffs to make their prototype, which they tested on Delnavaz’s jawbone.
Thus, by chewing gum for 60 seconds, he obtained 18 microwatts of electricity.
This may not be much: to power something as small as an ear, 20 of these straps would be missing.
But engineers say this could be fixed by adding more layers of the material to the strap.
With 20 layers, Delnavaz says, «and a total thickness of 6mm, it could power a 200 microwatt smart headset.»
The strap would still be comfortable, according to its creators.
Delnavaz used the prototype for several hours to test it, and at no time did he feel that it bothered him to chew or speak.
«We showed in this study that the strap does not need to be highly configured,» he explained. «Let go is enough to get energy.»
The results of the experiment are published in the specialized magazine Smart materials and structuresof the international organization Institute of Physics.
«You could load cochlear implants and things like that,» said Steve Beeby, another scientist at the University of Southampton, UK, who was not involved in this work.
«But it won’t be useful for recharging a mobile phone or anything like that.»
In this, Voix agrees. Based on what she has envisioned, it will be useful in situations where people are already wearing a strap and can plug in a small, essential device to it.
For example, those who work with heavy machinery and must wear hard hats and hearing protection headphones.
The scientist also suggests military applications, such as helmets and communication headsets for soldiers.
However, these possibilities are still remote, although there are already accompanied by new forms of recharging for ears with technology of Bluetooth.