Engineers and scientists have a long-standing fascination with spider silk. Similar to the typical worm silk that makes sheets comfortable, but much stronger, the material has inspired the invention of lighter, more breathable garments. armor and materials which could strengthen the plane's components without adding weight. Researchers are even using samples taken from spider webs to design sensitive microphones that may one day be used to treat hearing loss and deafness and to improve other hearing devices.
Spiders use their webs as huge external eardrums. A team of scientists from Binghamton University and Cornell University reported in 2022 that webs allow arachnids to detect sounds from 10 feet away.
When you hear a sound through your ear, what you are really experiencing is changes in air pressure that make your eardrum vibrate. This is how microphones work: imitating the human ear and vibrating in response to pressure.
Spider webs serve a similar purpose but use a different mechanism.
Instead of vibrating when hit by a wave of pressure, like a stick hitting the head of a drum, they move with the flow of traveling air. Air is a fluid medium “like honey,” said Ronald Miles, a mechanical engineering professor at Binghamton. Humans navigate this environment without noticing much resistance, but the silk fibers are buffeted by the speed of the viscous forces of the air.
Dr. Miles couldn't help but wonder if this principle could lead to a new type of microphone.
“Humans are kind of arrogant animals,” he said. “They make devices that work like them.” But he wondered whether to build a device that looked more like a spider and sensed “sound with the movement of air.”
He and his colleagues, including Jian Zhou, also a professor of mechanical engineering at Binghamton, and Junpeng Lai, a postdoctoral researcher, designed and built a microphone inspired by the principles of natural spider silk. They presented their research on Thursday at the 186th meeting of the Acoustical Society of America in Ottawa.
The researchers' device is composed of an extremely thin cantilever shaft (like a trampoline) made of silicon that responds to small fluctuations in airflow created by sound. To turn that into something humans can hear, a laser measures the subtle movements of the shaft, like a spider decoding its web.
One downside to typical pressure-sensing microphones, Dr. Miles said, is that upgrading them often means making them larger. Think about the thick microphones you see in a recording studio, compared to the thin headphones a motivational speaker wears. With a spider-inspired microphone that responds to airflow rather than pressure, Dr. Miles said, “you can make it a little smaller without paying a price.”
Helping people hear might be the natural next step.
In a somewhat contradictory way, our ears make sounds when they vibrate in response to pressure. With funding from the National Institutes of Health, Dr. Miles' team will develop a probe that measures these very quiet otoacoustic emissions. That could help with earlier detection of hearing problems in a baby's ear, for example, and “then they can start treatments for it,” Dr. Miles said.
Another advantage of detecting airflow instead of pressure to measure sound is that it can be used to locate the source of a sound. This could improve hearing aids designed to pick up sounds coming from a specific location in a noisy environment, Dr. Miles added.
Anna Rising, a spider silk researcher of the Karolinska Institute in Sweden, who was not involved in the study, agreed that spider silk has potential medical applications. It is known for its harshness, he said, but is also “well tolerated when implanted and It has been shown to allow regeneration of peripheral nerves” in animal experiments.
Dr. Miles is excited about using a web-inspired microphone to detect infrasound, which is below the human hearing range. This could be useful for tasks such as tracking tornadoes.
“Being able to localize sound at those very low frequencies is really difficult with pressure microphones,” he said. “With a speed-sensing microphone, you could do it very easily.”
Spider-inspired microphones have a long way to go before they are ready for widespread use. But the team already has a patent and Dr. Miles is advising a canadian company Building new types of microphones.
And if the research bears fruit, perhaps humans can finally free themselves from prejudices that lead to devices inspired by our bodies, making way for more inventions based on how spiders and other creatures perceive the world.
