A fabric behaves like a fluid, says professor Yoel Fink from the Massachusetts Institute of Technology, which explains perhaps why designers often even refer to the “flow” of a garment.
“The fabrics that we're wearing have small waves going through them,” said Fink, a professor of Materials Science at MIT. “We don't see them because they're just too small.”
Fink and a team from multiple universities, including Rhode Island School of Design, have made a material that catches those tiny waves.
The functional, piezoelectric fiber, once bent, produces a voltage that enables signal processing and an output of valuable data. Information from the sensing material could someday support wearable hearing aids, clothes that communicate, and garments that track vital signs.
“Having a few functional fibers allows an entire fabric to take on a new meaning,” Fink told Tech Briefs.
How to Make a Fabric-Based Microphone
The material begins as a preform rectangular “block” – about the size of a thick marker. Once you heat the preform, you can pull it, taffy-style, into long strips.
Fink and a group of researchers tested the fiber’s sound sensitivity by attaching the sensor to a suspended mylar sheet. With lasers, the engineers measured the vibration of the sheet — and by extension, the fiber — in response to sounds played through a nearby speaker.
Test sounds included a range of environments, from quiet libraries to noisy roads. The fiber vibrated and generated an electric current proportional to the sound played.
Next, the team wove the fiber with conventional yarns to produce panels of drapable, machine-washable fabric.
“It feels almost like a lightweight jacket — lighter than denim, but heavier than a dress shirt,” said researcher Elizabeth Meiklejohn from the Rhode Island School of Design (RISD) , who wove the fabric using a standard loom.
Meiklejohn worked with a team that included lead author Wei Yan, who helped develop the fiber as an MIT postdoc, Prof. Fink, and a number of additional students and researchers at MIT, Case Western Reserve University, University of Wisconsin at Madison, and the U.S. Army Research Institute of Environmental Medicine.
“The dedication of our students, postdocs, and staff to advancing research, which has always marveled me is especially relevant to this work, which was carried out during the pandemic,” said Fink.
In a short Q&A below, Fink explains why he thinks the future is in fabrics and the days of “computers in a glass box” are numbered.
Tech Briefs: My sense is that smart clothing hasn't necessarily caught on, so why do you think that is?
Prof. Yoel Fink: I don't think it exists yet, which is why it hasn't caught on!
Folks refer to this field as wearables, and I'll just point out that wearables is a word for things we don't wear. The technology, the engineering, and even the science of how to get fabrics — true fabrics and fibers — to do special things is only now emerging. That future is happening now.
The idea that you're going to put on watches or trinkets and all that stuff, I think, has met adoption hurdles, which limit the horizon of the so-called wearables.
Tech Briefs: So, what do you consider to be the shortcomings of those wearables?
Prof. Yoel Fink: Number one has to do with convenience. I think we prefer to walk around with the least amount of stuff that we can. Number two has to do with aesthetics. They’re not very aesthetic. Number three is in terms of value proposition. They're not really capable of delivering, for example, the health benefits that we think eventually fabrics will. On those three counts there is room for improvement.
Tech Briefs: What does it feel like to wear your functional fibers?
Prof. Yoel Fink: The key is to interfere to the least amount with the fabric itself — to make it look and feel just like a normal fabric. In that respect, the technology is essentially imperceptible or transparent. So, you would not be able to look at this shirt and say, “OK, this shirt is a microphone, or this shirt has memory, or this shirt is capable of doing computations,” because the technology is really at the fiber level.
I think the important thing to realize is that what we're talking about here is changing, among other things, the aesthetics of technology. You would never come in and say, “Oh, the microphone is this object of beauty.” There are no museums that host microphones, right? Those are fairly unattractive objects, but if I showed you a fabric microphone, you'd say, “Oh my God, this could be really aesthetic.” It doesn't look like technology, but it actually is.
Tech Briefs: So, how do you display the fiber’s “report” in a way that's helpful to the wearer?
Prof. Yoel Fink: Where we are now: We connect this fiber to a circuit. The circuit grabs the information and converts it to a digital format and enables signal processing. A year ago, we published a paper that talked about a digital fiber . That fiber could take signals that are analog and convert them basically to allow you to store digital information; it has memory and has a computer program. So, now you're taking a fiber that could measure something, and you have another fiber that could store and analyze it. You put these things together, and you start seeing how a fabric is going to become a computer. And that's what we're aiming for. We're not quite there now, but we're not too far away.
Tech Briefs: What kinds of early applications do you envision for a fabric microphone?
Prof. Yoel Fink: Our fibers or fabrics capture, in some ways, the soundtrack of our lives. Every time your heart beats, every time you take a breath, every time you bend your arm, every time you walk, every time a joint moves, every time blood flows, there’s sound. The fabrics capture all of that. All that sound gets into a fabric and is lost during the day.
So, what we're trying to do here is say, “Could we make that soundtrack of our lives accessible to us?” We can listen to our heart. This is not listening to the electrical signal of the heart. This is listening to the heart itself. The heart is a pump, and we’re listening to the valves and the operation of that pump. Electrical signals don't tell the whole story.
A second piece: Now there's some fraction of the population that has heart issues. There's a much larger fraction of the population that becomes pregnant at some point in their lives. And one of the things that we're talking about is how to monitor the unborn and listen to the way the unborn communicate — through their sounds and through their movement and also through their heart. Being able to listen to the heart of the unborn is going to give us tremendous information about their health and well-being.
Last but not least: The groups that have hearing deficiencies, which is all of us. We all will eventually have hearing deficiencies. Hearing aids work in quiet environments, not noisy environments.
The reason we have two ears and two eyes is because it allows us to get a sense of depth and of directionality. For hearing, that allows us to sit in a bar to listen to the person we're talking to even though the bar is much louder. By having multiple fibers in a fabric, we show in the paper that we could discern the direction of sound. We think that could really be transformative to people who have hearing aids and that want to impart a directional capability to those hearing aids.
Tech Briefs: What’s next?
Prof. Yoel Fink: It’s called Fabric Computing!
Now I'm teaching a course at MIT called Computing Fabrics where we're showing how the world of computation and the world of fabrics are converging, and I think that will have tremendous implications for the future of all of us. The days of the computer or phone in a glass box in our pocket or pocketbook are numbered. The future of computing is in fabrics.
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