New in-ear technology can allow chewing to replace hearing aid batteries

Hearing aids are essential for people with hearing loss. But hearing aids have an Achilles’ heel: they are expensive to feed and unfavorable to the environment.

The good news is that researchers have discovered a renewable alternative energy source that can power hearing aids. Energy is produced inside the ear and is collected by an earplug built into sensors.

My doctoral project is to model the deformities of the ear canal created by the movements of the jaw. My results will contribute to a better estimate of the energy that can come from these deformations.

The problem with hearing aids

To understand the problem with hearing aids, think about the daily life of Clara, a 24-year-old architecture student who wears hearing aids from the age of eight. When the battery that powers her prosthesis runs out, Clara loses her hearing and is cut off from the world.

Part of her brain is constantly on the lookout to make sure she has a spare battery box on hand. In addition to this nuisance, the battery is an economic burden. Given battery consumption and the cost of the battery, Clara estimates that in 15 years, batteries cost more than buying a new hearing aid.

The same goes for environmental costs. The rare metals used in batteries are currently non-recyclable and many batteries end up in landfills.

Rechargeable batteries are already widely used for wireless headphones, which is surprising that hearing aids have not adopted this technology. It may sound strange to compare wireless headphones to hearing aids, but in terms of complexity, the only advantage of headphones over hearing aids is the audio amplifier, which makes it possible to increase the volume in the ear.

The big difference is the price. A hearing aid costs $ 1000-2000 compared to $ 100-300 for a pair of headphones. The business model, which includes manufacturers, health insurers, hearing care professionals and consumers, keeps the price high.

How our hearing system works.

In short, it is fair to say that Clara’s financial and environmental balance sheets are not positive. But the revolution is coming! She may soon be able to power her hearing aids with the movement of her jaw.

Our ear canals create energy

Here’s a little experiment: put your little finger in your ear, then open and close your mouth. Do you feel the change in pressure on your fingertip? The movement of the jaw presses the tissues around the ear canal, changing its shape. Researchers are proposing that this deformity in the ear be converted into electrical energy.

Several studies have evaluated the amount of energy that comes from this deformation and have obtained encouraging results. The latest study reports that up to 22% of the energy needed for daily hearing aid operation can be generated during a 10-minute lunch break.

In other words, the action of eating for 50 minutes would be enough to generate all the energy needed for daily use of the hearing aid. For this experiment, the researchers placed an earplug filled with water in the participants’ ears. They then measure the pressure in the earplug created by the movements of the jaw. Finally, they translated these pressure variations into ear canal deformities.

The human body still hides many surprises. On the one hand, it is a sustainable source of energy available at all times. Just as photovoltaic panels use solar energy, there are now technologies that collect energy from the human body. This is the case with automatic watches, which use the kinetic energy produced by the movements of the wrist.

When it comes to hearing aids, other studies have tried to convert heat near the ear or put a mini solar panel in the ear. But the greatest interest is in the conversion of energy from deformations of the ear canal.

In search of the perfect converter

One question remains unanswered: How can the collected energy be transformed and stored? Deformations in the ear canal are mechanical energy and energy can be stored in a battery only after it is transformed into electrical energy.

To solve this problem, researchers have placed strips of piezoelectric material around the perimeter of earplugs. These materials generate an electrical signal when deformed.

Hearing aids are used by many people with hearing loss, but their energy supply is a weak point in their design.
(Shutterstock)

Unfortunately, the prototypes tested so far still do not convert enough energy. Some devices are close to the target amount, but are not small enough to be integrated into a hearing aid. The development of flexible printed circuit boards that can be adapted to molds will make self-powered medical implants possible. With this progress, more efficient converters will begin to appear.

Will the hearing aid market be revolutionized soon?

If Clara’s earplugs could convert the deformities of her ear canal into electricity, Clara would be able to do her daily routine without worrying about recharging her devices. She will know that in the event of a power outage, all she has to do is chew gum or hum her favorite song.

This technology can also help reduce the cost of hearing aids, which would be of particular benefit to the 200,000 Canadians with hearing loss who do not use hearing aids due to their high cost.

What’s more, this technology can be extended to all technologies worn near or inside the ear, such as wireless headphones or earphones, digital hearing protectors, in-ear sensors or augmented reality glasses. It costs nothing to dream!

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