Energy Captured By Jaw-Powered Chinstrap

Eric Hopton for – Your Universe Online

Canadian scientists have developed a new method of harvesting energy from chin and jaw movements using a strap made from smart materials. The captured energy can be turned into electricity which is then used to recharge wearable or implanted devices such as hearing aids.

Whenever we eat, talk, chew, or even yawn we use up energy which until now has simply been wasted. Generating electrical charges from human body movements has clear attractions for commercial applications and this latest research has brought the achievement of that goal a little closer. The researchers from Montreal’s Sonomax-ÉTS Industrial Research Chair in In-ear Technologies, part of the École de Technologie Supériere (ÉTS), have just published their findings in the Institute of Physics’ Journal Smart Materials and Structures.

The Sonomax team made a chinstrap using commercially available materials known as piezoelectric fiber composites (PFC). This is a type of smart material made from a matrix of adhesive polymers with integrated electrodes which can produce an electrical charge when placed under mechanical stress or stretched – precisely the kind of movements that occur as a result of chin movements. The chinstrap contains a single layer of PFC material and is attached tightly but comfortably round the chin and connected to a set of earmuffs by means of elastic side straps.

Image Above: This is the experimental set up of an energy harvesting chin strap. Credit: Smart Materials and Structures/IOP Publishing

Doctor Aidin Delnavaz, a mechanical engineer at ÉTS, was the guinea pig for the chinstrap tests. Delnavaz and his colleague Doctor Jeremie Voix specialize in auditory technology research including cochlear implants and powered earmuffs. In initial trials of the prototype, a series of measurements was taken while Delnavaz chewed for 60 seconds wearing the smart chinstrap. The device was able to produce up to 18 microwatts of electrical power a minute. While this is too small a charge to be immediately viable in powering the kind of devices it is aimed at, the amount of electricity produced could, say the authors, be easily increased by bundling together additional layers of PFC material. Delnavaz estimates that around 20 layers of PFC material would be needed to power a small hearing aid. A 20 layer strap would still be a relatively thin 6mm in depth but would be powerful enough to drive a “200 microwatt intelligent hearing protector.” Delnavaz wore the prototype chinstrap for many hours during the tests and believes that even the much thicker 20 layer version would be perfectly comfortable, even in prolonged use.

Although jaw movements may be capable of producing as much as 580 joules of energy in a 24 hour period, this is only for applications with modest power requirements. In its current form this technology may never be powerful enough to drive even a mobile phone. Nevertheless, in the right situation, the strap could be highly beneficial by reducing the cost of battery replacement and the environmental damage caused by incorrect disposal of used batteries.

The developers see initial uses of the device being taken up mainly in situations where some kind of head-strap is already being worn and where a powered gadget like a Bluetooth dongle could be fitted. People wearing helmets or ear-sets as part of their job, such as the military, those working with noisy machinery, and even cyclists are good examples. This work is still at the “proof of concept” stage, but commercial interest is already there and BBC News reports that the team has already been approached by companies looking at new charging methods for Bluetooth devices.

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