A device that can treat hearing loss without batteries

Some people are born with hearing loss, others acquire it with age, infections or long-term exposure to noise. In many cases, the tiny hair cells in the inner ear that allow the brain to recognize electrical impulses as sound are damaged. As a step toward an advanced artificial cochlea, the researchers report a conductive membrane that converts sound waves into corresponding electrical signals without the need for external power when implanted in a model ear.

Some people are born with hearing loss, others acquire it with age, infections or long-term exposure to noise. In many cases, the tiny hair cells in the inner ear that allow the brain to recognize electrical impulses as sound are damaged. As a step toward an advanced artificial cochlea, researchers at ACS Nano report a conductive membrane that converts sound waves into corresponding electrical signals without needing external power when implanted in a model ear.

Once the hair cells in the inner ear stop working, there is no way to reverse the damage. Currently, treatment is limited to hearing aids or cochlear implants. However, these devices require external power sources and may have difficulty amplifying speech properly for the user to understand. One possible solution is to simulate healthy cochlear hairs, converting noise into electrical signals processed by the brain as recognizable sounds.

To do this, previous researchers have tried self-propelled piezoelectric materials, which charge when compressed by the pressure that accompanies sound waves, and triboelectric materials, which produce friction and static electricity when moved by these waves. However, the devices are not easy to manufacture and do not generate enough signal at the frequencies involved in human speech. So Yunming Wang and colleagues wanted a simple way to fabricate a material that uses both compression and friction for an acoustic sensing device with high efficiency and sensitivity over a wide range of audio frequencies.

To create the piezo-triboelectric material, the researchers mixed silica-coated barium titanate nanoparticles into a conductive polymer, which they dried into a thin, flexible film. They then removed the silica shells with an alkaline solution. This step left behind a sponge-like membrane with spaces around the nanoparticles, allowing them to compress when hit by sound waves. In tests, the researchers showed that contact between the nanoparticles and the polymer increased the electrical performance of the membrane by 55% compared to the original polymer.

When they inserted the membrane between two thin metal grids, the acoustic sensing device produced a peak electrical signal at 170 hertz, a frequency in the range of most adults' voices. Finally, the researchers implanted the device in the model's ear and played a music file. They recorded the electrical output and converted it into a new audio file that bore a striking resemblance to the original version. The researchers say their self-powered device is sensitive to the wide acoustic range needed to hear most sounds and voices.

It will be a great help for the deaf.

resources

Jiaqi Zheng, Zhaohan Yu, Yunming Wang, Yue Fu, Dan Chen, Huamin Zhou. Acoustic Core-Shell Resonance Harvester for Application of Artificial Cochlea Based on the Piezo-Triboelectric Effect. ACS Nano, 2021; DOI: 10.1021/acsnano.1c04242

American Chemical Society. "Flexible device could treat hearing loss without batteries." ScienceDaily. ScienceDaily, 27 October 2021.