Battery-less hearing aid generates its own electricity

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Although hearing aids make life easier for many people, their limited autonomy can be problematic. Scientists set out to fill this gap by designing a hearing aid that requires no batteries.

Currently under development at Huazhong University of Science and Technology in China, the prototype device incorporates a spongy material with both piezoelectric and triboelectric qualities. Piezoelectric materials produce an electric current when subjected to mechanical stress, while triboelectric devices generate an electric charge in a material by allowing it to come in and out of contact with another material.

Scientists created their piezo-triboelectric material by coating barium titanate nanoparticles with silicon dioxide, mixing these particles in a liquid conductive polymer, and then drying the mixture in a thin flexible membrane. An alkaline solution was then used to dissolve the silicon dioxide envelopes of the nanoparticles, allowing these particles to sit freely in the holes in the polymer matrix.

After the membrane was sandwiched between two thin metal grids, it was subjected to sound waves. These waves vibrated the entire membrane back and forth, generating an electric current through the piezoelectric effect. In addition, when the nanoparticles bounced off the walls of their polymer hollow chambers, a triboelectric charge was generated – the latter increased the total electrical production of the membrane by 55%, compared to what would have been possible via the piezoelectricity alone.

The team tested the device by mounting it inside a model of a human ear, then playing music in that model. When the electrical signals produced by the prototype were converted into a digital audio file, the result was very close to the original music. Further testing indicated that the device is sensitive to a wide acoustic range, so it should be able to pick up most voices and other sounds in the human hearing range.

A research article, which is led by Yunming Wang, was recently published in the journal ACS Nano.

Source: American Chemical Society


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