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"Muscle Building" -- The Discovery Files

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Harvard University researchers have created a gel-based audio speaker that demonstrates the capabilities of ionic conductors, which were long thought to be limited in their application.

Credit: NSF/Karson Productions

Audio Transcript:

Clear winner

I'm Bob Karson with the discovery files--new advances in science and engineering from the National Science Foundation.

When it comes to this innovation from Harvard University, we can see right through it; really. It's two round layers of a saltwater gel; clear as glass; sandwiching a thin, transparent sheet of rubber. And it does this: (Sound effect: play music from clip) it plays music. The "speaker" is actually an artificial muscle. A high-voltage signal runs across and through it, and forces the rubber to rapidly contract and vibrate, producing sound. But it's much more than a see-through speaker. It's the first ever demonstration that electrical charges carried by ions, rather than electrons, can be meaningfully used in a fast-moving, high voltage device.

Normally, ionic materials burn up under high voltages. And, since ions are much larger and heavier than electrons, physically moving them through a circuit is typically slow. The Harvard system overcomes both of these problems, opening a wide range of potential applications for stretchy, transparent devices from noise-cancelling windows to eyeglasses that could shift from wide angle to telephoto to reading mode in the blink of an eye.

Signals carried by charged ions are the electricity of the human body, so ionic artificial muscles, limbs and organs might someday be able to be meshed with our biological systems.

It's definitely something to keep your "I-on."

"The discovery files" covers projects funded by the government's National Science Foundation. Federally sponsored research--brought to you, by you! Learn more at or on our podcast.

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