Scientists Create Transparent, Stretchy Speaker that Plays Music (Video)

Scientists have created some strange materials in the past, but this may be the strangest yet. They've developed a transparent speaker that's as clear as a window and as stretchy as rubber. While it plays music, though, it's not electronic. This new speaker is made out of saltwater gel and rubber.

The new speaker is called an ionic conductor. In order for it to work, a high-voltage signal runs across its surfaces and through its layers. This forces the rubber to rapidly contract and vibrate, producing sounds that span the entire audible spectrum--from 20 hertz to 20 kilohertz. In fact, this is the first demonstration that electrical charges carried by ions, rather than electrons, can be put to meaningful use in fast-moving, high-voltage devices.

So what do ionic conductors have that other electronic systems don't? They can be stretched to many times their normal area without an increase in resistivity, for one. This resistivity is a problem common in stretchable electronic devices. In addition, they can be transparent, which makes them well-suited for optical applications. Thirdly, the gels used as electrolytes are biocompatible, so it would be relatively easy to create ionic devices such as artificial muscles or skin.

"The big vision is soft machines," said Christoph Keplinger, co-lead author of the new paper, in a news release. "Engineered ionic systems can achieve a lot of functions that our body has: they can sense, they can conduct a signal and they can actuate movement. We're relaly approaching at ype of soft machine that biology has to offer."

The new audio speaker actually represents a robust proof of concept for ionic conductors. Why? Producing sounds across the entire audible spectrum requires both high voltage and high-speed actuation (to vibrate quickly). These criteria are both crucial for applications.

"We'd like to change people's attitudes about where ionics can be used," said Keplinger in a news release. "Our system doesn't need a lot of power, and you can integrate it anywhere you would need a soft, transparent layer that deforms in response to electrical stimuli--for example, on the screen of a TV, laptop or smartphone to generate sound or provide localized feedback--and people are even thinking about smart windows. You could potentially place this speaker on a window and achieve active noise cancellation, with complete silence inside."

Currently, researchers are still working on the engineering and chemistry of ionics. They plan to focus on identifying the best combination of materials for compatibility, long life and adhesion between the layers of the new device that they've created.

The findings are published in the journal Science.

Want to see the speaker in action? Check out the video below, courtesy of YouTube and Harvard.