Hearing loss can have a wide variety of causes. Many of us experience it gradually over an extended period of time as we age (presbycusis). Some people are born with it; others may get it through infection or sustained noise exposure.

One thing that most cases of hearing loss have in common though is damage to the microscopic hairs in our inner ear. Scientists have developed a solution in the form of a conductive membrane capable of translating incoming soundwaves into electrical signals. One of its remarkable features is that it doesn't require batteries by virtue of a clever trick.

*Image Credit: Mike_shots via Shutterstock*

Irreversible damage to inner ear hair cells

If damage to hair cells inside the cochlea is so severe that they stop working, nothing can be done to repair them.

Hearing aids or cochlear implants are currently the only options for treatment. However, these gadgets need outside power sources and often have problems accurately amplifying voices so that the user can comprehend them.

Simulating functional hair cells

Scientists have come up with a solution by simulating healthy cochlear hairs, chancing sound into electrical signals, which can then be converted to perceptible sound within the brain.

Damaged hair cells that stopped working cannot be restored - *Image Credit: Axel_Kock via Shutterstock*

In the past, researchers have attempted to use self-powered piezoelectric materials that charge via compression resulting from sound wave pressure and triboelectric materials that generate friction when they get displaced by these waves.

Sadly such devices are difficult to produce and don't generate enough signal in the sound frequencies associated with human speech. So now, scientists looked for a relatively easy way to manufacture a material that utilizes both friction and compression for an acoustic sensing device with high sensitivity and effectiveness through a wider array of sound frequencies.

Creating the right material

The researchers put barium titanate nanoparticles covered with silicon dioxide into a conductive polymer, which then dried into a thin, flexible film to make a piezo-triboelectric material.

The silicon dioxide shells were then removed using an alkaline solution.

This procedure left a sponge-like membrane surrounding the nanoparticles, allowing them to jiggle about when sound waves struck them.

Test results

The scientists found that contacting the nanoparticles with the polymer enhanced the membrane's electrical output by 55% when compared to the pure polymer in experiments. The acoustic detecting device produced a maximum electrical signal at 170 hertz, a frequency within the range of most adult voices when the membrane was placed between two thin metal grids.

The membrane inserted in a model ear. It simulates hair cells by changing sound waves into electrical pulses. The prototype is wired to a device that picks up the the output current signal.

Finally, the scientists implanted the gadget into a mock ear and played a music file. They captured the electrical output and transformed it into a new audio file that was strikingly close to the original.

The team claims that their self-powered gadget has a wide acoustic range, which is required to comprehend speech. If further development of this technology is successful, we may expect a major leap forward in the quality of life for people suffering from hearing loss!

The findings have been published in the peer-reviewed journal ACS Nano, listed below.

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