After the fibers made by cassette tape played by moving a tape head over the fabric, here it is fibers that can hear and sing by themselves.

To Yoel Fink, an associate professor of materials science and principal investigator at MIT’s Research Lab of Electronics, the threads used in textiles and even optical fibers are much too passive. For the past decade, his lab has been working to develop fibers with ever more sophisticated properties, to  enable fabrics that can interact with their environment.

In the August issue of Nature Materials, Fink and his collaborators announce a new milestone on the path to functional fibers: fibers that can detect and produce sound. Applications could include clothes that are themselves sensitive microphones, for capturing speech or monitoring bodily functions, and tiny filaments that could measure blood flow in capillaries or pressure in the brain.

Despite the delicate balance required by the manufacturing process, the researchers were able to build functioning fibers in the lab. “You can actually hear them, these fibers,” says Chocat, a graduate student in the materials science department. “If you connected them to a power supply and applied a sinusoidal current” — an alternating current whose period is very regular — “then it would vibrate. And if you make it vibrate at audible frequencies and put it close to your ear, you could actually hear different notes or sounds coming out of it.”

In addition to wearable microphones and biological sensors, applications of the fibers could include loose nets that monitor the flow of water in the ocean and large-area sonar imaging systems with much higher resolutions: A fabric woven from acoustic fibers would provide the equivalent of millions of tiny acoustic sensors.

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