CHIN STRAP HARVESTS ENERGY FROM CHEWING
A chin strap that can
harvest energy from jaw movements has been created by a group of researchers in
Canada.
It is hoped that the
device can generate electricity from eating, chewing and talking, and power a
number of small-scale implantable or wearable electronic devices, such as
hearing aids, cochlear implants, electronic hearing protectors and
communication devices.
The first results of
the device's performance have been published today, 17 September, in IOP
Publishing's journal Smart Materials and Structures.
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 mW of power could be generated from chewing during meals alone.
To harvest this
energy, the study's researchers, from Sonomax-ÉTS Industrial Research Chair in
In-ear Technologies (CRITIAS) at École de technologie supérieure (ÉTS) 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 µW, but
taking into account the optimum set-up for the head-mounted device, the power
output was around 10 µW.
Co-author of the study
Aidin Delnavaz said: "Given that the average power available from chewing
is around 7 mW, we still have a long way to go before we perfect the
performance of the device.
"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 µW intelligent hearing protector."
One additional
motivation for pursuing this area of research is the desire to curb the current
dependency on batteries, which are not only expensive to replace but also
extremely damaging to the environment if they are not disposed of properly.
"The only
expensive part of the energy harvesting device is the single PFC layer, which
costs around $20. Considering the price and short lifetime of batteries, we
estimate that a self-powered hearing protector based on the proposed chin strap
energy harvesting device will start to pay back the investment after three
years of use," continued Delnavaz.
"Additionally,
the device could substantially decrease the environmental impact of batteries
and bring more comfort to users.
"We will now look
at ways to increase the number of piezoelectric elements in the chin strap to
supply the power that small electronic devices demand, and also develop an
appropriate power management circuit so that a tiny, rechargeable battery can
be integrated into the device."
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