Not all electric devices need external power.
Key to the device is a microporous membrane relying on piezoelectric and triboelectric effects, meaning it generates current when under pressure and an electrical charge upon frictional contact.
Tiny nanoparticles are housed within the cavities of the finished polymer membrane. Wedged between two metal grids, the membrane was mounted inside a model ear for testing.
When music was played, not only did the membrane vibrate but the particles inside were, following the rhythm, pressed against the membrane wall, creating electric charges.
These signals, in turn, were converted into a digital audio file, which closely matched the original.