Huazhong University of Science and Technology researchers are currently hard at work improving their initial design of a “battery-free” set of hearing aids. The original design and proof-of-concept work, published in the journal ACS Nano, made use of piezoelectric and triboelectric properties of a custom material of their own making, which consisted of a “spongy” network of conducting polymer with barium titanate (BaTiO3) nanoparticles nestled within its “pores.”
The new study was led by Huazhong researcher Yunming Wang, who worked with a team of scientists to develop the potential new technology. The study aims to address the current issue of present hearing aids with respect to their limited battery life. In designing their new technology, Wang and team managed to avoid the issue by skipping batteries entirely.
In order to construct the conductive membrane, Wang and team coated barium titanate nanoparticles in silicon dioxide (SiO2) shells, which were then mixed into a liquid conductive polymer. The polymer mixture was then dried and formed into a flexible thin film, then treated with an alkaline solution; the solution selectively dissolved the silicon dioxide shells of the nanoparticles, leaving the nanoparticles loose inside the newly-created “pores” of the flexible polymer film.
The whole setup was sandwiched between two metal grids; whenever the entire setup vibrated—like, say, when it vibrates in the presence of sound waves—the barium titanate nanoparticles clash against the walls of the “pores” they’re trapped in; this generates electricity via the triboelectric effect, where the separation of two surfaces caused the generation of charge, as discussed in an earlier news piece regarding “nanogenerator” wooden floorings.
At the same time, as the entire system vibrated, the compression of the polymer film created charges via the piezoelectric effect, where the application of mechanical stress causes the generation of charge.
The combination of both piezoelectric and triboelectric performance on the setup boosted its electrical output by as much as 55%, compared to its output via piezoelectric performance alone; this means that the material is vastly better at creating electricity with the barium titanate beads inside it compared to if they weren’t there. And with the two effects now providing charge to the setup simply by being exposed to vibrations, the entire mechanism now requires no external power from batteries, making them “battery-free.”
To test the performance of the model with respect to sound detection, the team mounted a prototype to a model ear, which was then exposed to sound waves from a piece of music. After receiving the electrical signal produced by the device then restructuring the data into another music file, Wang and team found the new file to resemble the original music played.
Further testing of the device’s range of detection found it sensitive to a wide acoustic range, implying potentially good performance when used with respect to the usual range of sounds perceived by human hearing.
References
- ACS Nano. (2021, October 27). Flexible device could treat hearing loss without batteries. American Chemical Society. https://www.acs.org/content/acs/en/pressroom/presspacs/2021/acs-presspac-october-27-2021/flexible-device-could-treat-hearing-loss-without-batteries.html
- Coxworth, B. (2021, October 27). Battery-free hearing aid generates its own electricity. New Atlas. https://newatlas.com/science/battery-free-hearing-aid/
- Zheng, J., Yu, Z., Wang, Y., Fu, Y., Chen, D., & Zhou, H. (2021). Acoustic core–shell resonance harvester for application of artificial cochlea based on the piezo-triboelectric effect. ACS Nano. https://doi.org/10.1021/acsnano.1c04242
