▎ WuXi AppTec content team editor
Imagine a scenario where the clothes you wear not only identify the source of sound in a noisy environment, but also record your every heartbeat. Such a "long-eared" outfit sounds quite sci-fi, but in a Nature paper this week, scientists from institutions like MIT made sci-fi come true.
In fact, it is not surprising in theory to "listen" to sounds with clothes. All fabrics, including the clothes you're wearing, vibrate with sound. But the question is, the amplitude of this vibration is only at the nanometer scale, how do we capture these imperceptible signals?
For the authors of this study, it was our ears that inspired them. When sound waves reach the human ear, there is a layer of fibers in the eardrum that converts the sound waves into mechanical vibrations; subsequently, mechanical vibrations enter the inner ear through the ossicle, where the cochlea converts the vibrations into electrical signals, which eventually enter the brain through neurons.
Similarly, the study was about creating a fabric that would eventually convert sound waves into electrical signals. In their design, the core of the fiber is a piezoelectric material: when bending or mechanical deformation occurs, the piezoelectric material can generate an electrical signal, which converts sound vibrations into electrical signals.
▲ The design idea of the fabric "microphone" (Image source: Reference[1])
Specifically, the fibers contain a piezoelectric polymer substrate and a piezoelectric material barium titanate ceramic particles. Subsequently, the research team used the hot drawing method to elongate the entire fiber at high temperatures, thus giving the material the strongest piezoelectric properties.
From fibers to weaving, the research team didn't need to weave these fibers directly into a complete fabric. They only need to weave a piezoelectric fiber into a normal yarn to make a fabric that is sensitive enough to "hear" sound. The minimum volume that this fabric can capture is 40 decibels, which is equivalent to a quiet library environment. In addition, the material is machine washable, highly draped and easy to form, all of which form the basis for a wearable device.
Schematic diagram of creating functional fabrics (Image: Fink Lab MIT/Elizabeth Meiklejohn RISD)
So, what is the role of clothes made from this material? The team woven this piezoelectric fabric into a layer of shirt against the skin so that when someone around them was clapping their hands, the shirt could discern the direction of the source of the sound. At a distance of 3 meters, the fabric can detect the angle of the sound source with an error of less than 1°. Therefore, this technology is expected to help people with hearing loss locate in noisy environments and thus listen more accurately.
Another amazing application of this fabric is that it creates clothes that monitor the user's heartbeat in real time, as well as slight fluctuations in the first and second hearts. In addition, this material is also expected to be used to monitor the fetal heart rate of pregnant women.
A fiber is made up of a fabric made up of other materials (Image: Fink Lab MIT/Elizabeth Meiklejohn RISD)
The first author of the paper, Professor Wei Yan, now at Nanyang Technological University in Singapore, said: "Wearing this acoustic costume, you can use it to make phone calls and communicate with others. In addition, the wearer's skin is hardly visible to the material, so heartbeat and breathing conditions can be monitored in real time in a comfortable way for a long time. ”
In addition to these scenarios, the researchers believe that this material has a broader application space. For example, implanted in spacesuits to listen to the location of space dust; embedded in buildings, detecting cracks and the risk of stress fatigue.
"This research offers a whole new way for fabrics to listen to our bodies and their surroundings." Corresponding author of the paper, MIT professor Yoel Fink, said.
Resources:
[2] A fabric that “hears” your heartbeat. Retrieved Mar 17th, 2022 from https://www.eurekalert.org/news-releases/946234
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