A team of engineers from Harvard University have created a transparent speaker out of rubber and saltwater gel. A high-voltage signal runs across the surfaces and through the layers of the “ionic” speaker, forcing the rubber to contract and vibrate, which produces sounds spanning the entire audible spectrum (20 hertz to 20 kilohertz).
The speaker demonstrates that electrical charges carried by ions, rather than electrons, can be put to use in high-voltage devices. Ionic conductors can be stretched to many times their normal area without an increase in resistivity, they can be transparent, and the gels could be incorporated into biological systems.
The team plans to commercialize the technology by working with companies in a range of product categories, including smartphones, tablets, wearable electronics, consumer audio devices, and adaptive optics. In the future, they will focus on identifying the best combinations of materials for compatibility, long life, and adhesion between the layers. You can check out the transparent speaker in New Scientist‘s video below: