Back in December, researchers from Michigan State University (MSU) demonstrated their ferroelectret nanogenerator (FENG), a paper-thin device that can generate energy from motion. Now they've added a new trick to FENG's repertoire, turning it into a thin, flexible microphone and loudspeaker.

The core function of the MSU team's device is that it uses layers of charged ions to convert mechanical energy into electrical energy, and vice versa. In previous tests, that meant it could turn a swipe or tap of a finger into electrical signals to power a keyboard, touchscreen or LED lights, but the researchers soon realized the system was sensitive enough to pick up the vibrations caused by sound, making it a pretty effective microphone.

To test its mettle, the team turned it into a "security patch." The FENG material was hooked up to a computer and used as a voice recognition lock, which the researchers found was precise enough to distinguish between users. Since it can also convert electrical energy into mechanical energy, the system can operate as a speaker, too. Embedding the material into a flag and hooking it up to an iPad and amplifier, FENG could effectively belt out the tunes.

"The flag itself became the loudspeaker," says Nelson Sepulveda, lead researcher on the project. "So we could use it in the future by taking traditional speakers, which are big, bulky and use a lot of power, and replacing them with this very flexible, thin, small device. Or imagine a newspaper where the sheets are microphones and loudspeakers. You could essentially have a voice-activated newspaper that talks back to you."

While we're not sure newspapers are the way of the future, the researchers also claim the device could find use in portable lightweight speakers, noise-cancelling sheets, and voice-protected wearables.

The research was published in the journal Nature Communications and the team demonstrates the system in the video below.

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