London, March 20 (HNA) – Having trouble hearing? Just turn up your shirt. That’s the idea behind a new “acoustic fabric” developed by engineers at the Massachusetts Institute of Technology (MIT) and collaborators at Rhode Island School of Design (RISD).
The team has designed a fabric that works as a microphone, converting sound first into mechanical vibrations, then into electrical signals, similar to how our ears hear.
All fabrics vibrate in response to audible sounds, though these vibrations are on the scale of nanometers — far too small to ordinarily be sensed. To capture these imperceptible signals, the researchers created a flexible fibre that, when woven into a fabric, bends with the fabric like seaweed on the ocean’s surface.
The fibre is designed from a “piezoelectric” material that produces an electrical signal when bent or mechanically deformed, providing a means for the fabric to convert sound vibrations into electrical signals.
The fabric can capture sounds ranging in decibel from a quiet library to heavy road traffic, and determine the precise direction of sudden sounds like handclaps. When woven into a shirt’s lining, the fabric can detect a wearer’s subtle heartbeat features. The fibres can also be made to generate sound, such as a recording of spoken words, that another fabric can detect.
A study detailing the team’s design appears in Nature. Lead author Wei Yan, who helped develop the fibre as an MIT postdoc, sees many uses for fabrics that hear.
“Wearing an acoustic garment, you might talk through it to answer phone calls and communicate with others,” says Yan, who is now an assistant professor at the Nanyang Technological University in Singapore. “In addition, this fabric can imperceptibly interface with the human skin, enabling wearers to monitor their heart and respiratory condition in a comfortable, continuous, real-time, and long-term manner.”
Yan’s co-authors include Grace Noel, Gabriel Loke, Tural Khudiyev, Juliette Marion, Juliana Cherston, Atharva Sahasrabudhe, Joao Wilbert, Irmandy Wicaksono, and professors John Joannopoulos and Yoel Fink at MIT, along with Anais Missakian and Elizabeth Meiklejohn from Rhode Island School of Design (RISD), Lei Zhu from Case Western Reserve University, Chu Ma from the University of Wisconsin at Madison, and Reed Hoyt of the U.S. Army Research Institute of Environmental Medicine.
“The long-standing collaboration between Yoel and me brings together a depth of knowledge and experience in our respective fields to support groundbreaking work in advanced fibres and textiles,” says RISD Professor Anais Missakian, Pevaroff-Cohn Family Endowed Chair in Textiles. “Fiber technology is an integral component, structurally and materially, of these woven and knit fabrics. Our work also supports student and alumni engagement at MIT and RISD, and I am truly grateful for the spaces that have opened up due to my work with Yoel and his team.”
The researchers tested the fibre’s sensitivity to sound by attaching it to a suspended sheet of mylar. They used a laser to measure the vibration of the sheet — and by extension, the fibre — in response to sound played through a nearby speaker. The sound varied in decibel between a quiet library and heavy road traffic. In response, the fibre vibrated and generated an electric current proportional to the sound played.
“This shows that the performance of the fibre on the membrane is comparable to a handheld microphone,” Noel says.
Next, the team wove the fibre with conventional yarns to produce panels of drapable, machine-washable fabric.