If These Walls Could Talk
Your walls soon could get a voice of their own. A new technology has the potential to turn just about any surface, including your walls, into a speaker. Microphones and speakers use piezoelectric materials that move in response to voltage, or create voltage from movement. But common piezoelectric materials are expensive, heavy and brittle.
Now materials scientist Michael Yu at Johns Hopkins University in Baltimore and colleagues say they have made a rubbery plastic-based material that could help place piezoelectric devices in previously impractical areas.
Andrew Medley, one of the first ground breakers in flat speaker technology, sees the technology being used for minute hearing aids and replacing bulky speakers in cars.
The team’s invention is based on a polypropylene foam with piezoelectric properties that was discovered in 2004. The plastic is flexible and has entirely different mechanical properties to most other, often crystalline or ceramic, piezoelectric materials.
By adding silicone rubber to that material, Yu and colleagues have made it possible to separately control the material’s piezoelectric mechanical properties.
Until now changing the flexibility, say, of a piezoelectric material would always impact its electrical properties. That made it near-impossible to design materials with certain combinations of physical and piezoelectric properties.
Combined with the ease with which polymers can be processed, the new material should open up novel applications: wallpaper that functions as speakers, lightweight devices to scavenge movement energy, and foldable speakers, are just some of their ideas.