WuXi AppTec Content Team Editor
Imagine this scenario: the clothes you wear not only identify the source of the sound for you in a noisy environment, but also record your every heartbeat. Such “long-eared” clothes sound quite sci-fi, but in a Nature paper this week, scientists from MIT and other institutions have made sci-fi a reality.
Actually, it is not surprising in theory to use clothes to “listen” to sounds. All fabrics, including the clothes you’re wearing, vibrate with sound. But the question is, how do we capture these imperceptible signals, since the amplitude of this vibration is only on the nanometer scale?
For the authors of this study, it was our ears that inspired them. When sound waves reach the human ear, there is a fibrous layer in the eardrum that converts the sound waves into mechanical vibrations; the mechanical vibrations then travel through the ossicular bone and into the inner ear, where the cochlea converts the vibrations into electrical signals that eventually pass through neurons into the brain.
Likewise, this research is about creating a fabric that ultimately converts sound waves into electrical signals. In their design, at the core of the fiber is a piezoelectric material: when bent or mechanically deformed, the piezoelectric material produces an electrical signal that converts sound vibrations into electrical signals.
▲Design idea of fabric “microphone”(Image source: Reference [1])
Specifically, the fibers consist of a piezoelectric polymer substrate and ceramic particles of barium titanate, a piezoelectric material. The research team then used the thermal drawing method, which elongates the entire fiber at high temperatures, giving the material its strongest piezoelectric properties.
From fiber to fabric, the research team did not need to weave these fibers directly into a complete fabric. They only needed to weave a piezoelectric fiber onto a common yarn to create a fabric sensitive enough to “hear” sound. This fabric captures a minimum volume of 40 decibels, the equivalent of a quiet library environment. In addition, the material is machine washable, has high drape, and is easy to mold, all of which set the stage for a wearable device.
▲Schematic diagram of creating a functional fabric (Photo credit: Fink Lab MIT/Elizabeth Meiklejohn RISD)
So what is the role of clothing made from this material? The team weaved the piezoelectric fabric into a layer of the shirt against the skin, so that when someone was clapping around, the shirt could tell where the sound was coming from. From 3 meters away, the fabric can detect the angle of the sound source to within 1°. Therefore, this technology is expected to help hearing-impaired people locate in a noisy environment, so as to listen more accurately.
Another amazing application of this fabric is that it creates clothing that monitors the user’s heartbeat in real time, as well as the slightest of first and second heart sounds. fluctuation. In addition, the material is expected to be used for monitoring of fetal heart rate in pregnant women.
▲One fiber and other materials make up a fabric (Photo credit: 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 garment allows you to make phone calls and communicate with others. The material is barely felt by the patient’s skin, so heartbeat and breathing conditions can be monitored in real-time comfortably over long periods of time.”
In addition to these scenarios, the researchers believe the material has broader applications. For example, implanted in space suits to listen to the location of space dust; embedded in buildings to detect cracks and the risk of stress fatigue.
“This research provides a whole new way for fabrics to listen to our bodies and their surroundings. “The corresponding author of the paper, MIT professor Yoel Fink said.
References:
[2] A fabric that “hears” your heartbeat. Retrieved Mar 17th, 2022 from https:https://www.eurekalert.org/news-releases/946234
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