PPE

Fiber developed in the United States to emit and detect sound waves

for hundreds of years, man-made fiber refers to the raw materials of clothes and ropes. 1n the information age, the meaning of fiber has become the glass filament carrying data in the communication network. But for Yul Fink, an associate professor at M1T’s electronics research lab, the fibers used in textiles or fiber optics are too passive. Over the past ten years, his laboratory has been working on developing more advanced fibers to enable fabric to interact with its surroundings. Br / >
in the latest issue of nature materials, Fink and his collaborators announced a landmark new functional fiber: a fiber that can detect and produce sound. The application of this fiber includes: it can be made into clothes used as microphone, which can capture voice or monitor body function; Or it can be made into a tiny monofilament that can measure blood flow in capillaries or brain pressure

new fiber contains asymmetric molecular plastic

ordinary optical fiber is made of “preform”, which is a large cylindrical single material that can be heated, drawn and cooled. 1n contrast, the fibers developed by Fink laboratories are geometrically arranged so that they remain intact during heating and stretching

the core of the new acoustic fiber is a kind of plastic commonly used in microphones. The fluorine content in the plastic allows researchers to ensure that its molecules are in an unbalanced state, with fluorine and hydrogen atoms on one side, even during heating and stretching. This molecular asymmetry gives the plastic a “piezoelectricity,” meaning that when an electric field is applied to it, it changes shape

in traditional piezoelectric microphone, the electric field is generated by metal electrode. However, in a fiber microphone, the stretching process causes the metal electrodes to lose their shape. So instead, researchers use conductive plastics that contain graphite. Conductive plastics produce a dense liquid when heated, thus maintaining a higher viscosity than metal electrodes. This not only prevents the material from mixing, but also makes the fiber have a normal thickness

after the fiber is stretched, researchers need to arrange all piezoelectric molecules in the same direction. At this point, we need a strong electric field (20 times stronger than the electric field that causes lightning in thunderstorms) to be applied to it. Because anywhere in the fiber is very narrow, this creates a tiny lightning ball that destroys the surrounding material

vocal fibers are widely used

although this delicate balance is needed in the manufacturing process, researchers are still able to make such functional fibers in the laboratory. 1f you connect them to a power source and apply a sinusoidal current (alternating current with a very stable period), the fibers vibrate. 1f you make it vibrate on the audio frequency and put it close to the ear, you can hear the different notes or sounds it makes. 1n the paper “nature materials”, researchers measured the acoustic properties of fibers more strictly. Because water conducts sound better than air, they put the fiber in a water tank opposite to a standard sound energy converter, which alternately emits sound waves that the fiber can detect, as well as the sound waves emitted by the fiber

researchers hope to integrate the properties of these experimental fibers into a single fiber. For example, strong vibration can change the optical properties of the reflective fiber, so that the fiber fabric can carry out optical communication. 1n addition to wearable microphones and biosensors, the fiber’s applications include a web that can monitor water flow in the ocean and a high-resolution large-area sonar imaging system. The fabric made of this acoustic fiber is equivalent to millions of tiny acoustic sensors. Using the same mechanism, piezoelectric elements, in turn, can turn electricity into motion, the researchers say

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