Chinese scientists are developing a prototype hearing aid that does not need a battery. The research results are published by ACS Nano.

While a hearing aid makes life easier for people, it has its limitations – namely, the battery capacity. To solve the problem, scientists are creating a prototype device that charges itself.

Scientists at Huazhong University of Science and Technology in China are developing a new type of hearing aid. To create a prototype, the researchers used a sponge material that has both piezoelectric and triboelectric properties.

Piezoelectric materials produce electrical current when subjected to mechanical stress. At the same time, in triboelectric devices, electric 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.

Chinese scientists have created a piezo-triboelectric hearing aid material by coating nanoparticles of barium titanate with silicon dioxide. 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 was sandwiched between two thin metal gratings, sound waves were applied to it. 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 placing it in a scale model of the human ear and playing 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 tests have shown that the device is sensitive to a wide acoustic range.