A new hearing aid does not need batteries: it uses energy from movement

While hearing aids make people's lives easier, they do have their limitations—namely, battery life. To

to solve the problem, scientists are creating a prototype of a device that charges on its own. 

Scientists from Huazhong University of Science and TechnologyA new type of hearing aid is being developed in China. To create the prototype, the researchers used a sponge material that has both piezoelectric and triboelectric properties.

Piezoelectric materials are producedelectric current when subjected to mechanical stress. In triboelectric devices, however, electrical charges appear in the material due to friction. The triboelectric effect itself is a type of contact electrification in which some materials become electrically charged after they come into frictional contact with another material.

Adapted fromACS Nano2021; DOI: 10.1021/acsnano.1c04242

Chinese scientists have created a piezo-triboelectrichearing aid material by coating barium titanate nanoparticles with silica. They then mixed them with a liquid conductive polymer, and then dried the mixture in the form of a thin, flexible membrane. The scientists then used an alkaline solution to dissolve the silica shells of the nanoparticles, leaving the particles themselves free inside the holes in the polymer matrix.

After the membrane has been clamped between twothin metal gratings, it was affected by sound waves. They made the entire membrane vibrate back and forth, creating an electric current due to the piezoelectric effect. In addition, when the nanoparticles bounced off the walls of the hollow polymer chambers, a triboelectric charge was generated. It increased the overall electrical power of the membrane.

The team tested the device by installing itinto a scale model of the human ear and turning on music. When the electrical signals generated by the prototype were converted  into a digital audio file, the result was very similar to the original music. Further testing showed that the device was sensitive to a wide acoustic range.

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