Yoel Fink, a materials-science professor at MIT, has invented a new type of fiber that can detect and produce sound–potentially opening the way for shirts that are also microphones or voice recorders, or tiny fibers which could measure your vitals.
Fink has long thought that we should be able to demand a lot more from the fibers in our clothes. So for a decade, his lab has been developing fibers that can interact with their environment. His newest creation, with Shunji Egusa, Noémie Chocat, and Zheng Wang, will be published in next month’s Nature Materials.
The secret of the new acoustic fibers is that they’re piezoelectric.
Their piezoelectric properties come from engineering at the atomic level: Each strand of fiber has fluorine atoms only on one side, and hydrogen atoms on the other. The different in charge held by those atoms creates a “lopsided” electric field across the fiber itself.
Thus, when an electric field is applied to the fibers, they flex and change shape. And also vice versa: When the fibers change shape–due to a sound wave, for example–they emit an electric signal. (Piezoelectric materials are what lie behind all those schemes to have floors that produce electricity when a person walks across them.)
“You can actually hear them, these fibers,” says Chocat, one of the fiber’s co-creators. If connected to an AC current, the fabric actually vibrates–and you can hear notes coming off of it, if the current is right.
The researchers believe the fibers could be used in wearable microphones (at last!) or–more practically–in tiny sensor filaments that could measure the blood pressure in a capillary or in the brain. The fibers could also be woven into massive sonar detectors. Or, more fantastically, you could pair the acoustic fibers with others that Zink’s lab has developed, to create fabrics that when stretched give off electricity and light.
[Research Laboratory of Electronics at MIT/Greg Hren]