Engineers and scientists have an enduring fascination with spider webs. Similar to the typical worm silk that makes comfortable sheets, but much stronger, the material has inspired the invention of lighter and more breathable body armor and materials that can make aircraft components stronger without adding weight. Researchers are even using examples drawn from spider webs to design sensitive microphones that could one day be used to treat hearing loss and deafness and to improve other listening 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 sound from 10 feet away.
When you hear sound through your ear, what you’re really experiencing are changes in air pressure that cause your eardrum to vibrate. Here’s how microphones work: by mimicking 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 pressure wave like a stick hitting a drum head, they move with the displaced airflow. Air is a liquid medium “like copper,” said Ronald Miles, a professor of mechanical engineering at Binghamton. People move in this medium without noticing much resistance, but the silk fibers are jostled by the speed of the viscous forces in 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’re making devices that work like them.” But he wondered if he could create a device that looked more like a spider and sensed “the sound with the movement of the 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 webs. They presented their research Thursday at the 186th meeting of the Acoustical Society of America in Ottawa.
The researchers’ device consists of an extremely thin cantilever shaft (like a diving board) made of silicon that responds to small fluctuations in the airflow created by sound. To translate this into something humans can hear, a laser measures the shaft’s subtle movements, like a spider decoding its web.
A disadvantage of typical pressure-sensing microphones, Dr. Miles said, is that improving them often means making them bigger. Think of the bulky microphones you see in a recording studio compared to the thin headphones used by a motivational speaker. With a spider-inspired microphone that responds to airflow rather than pressure, Dr. Miles said, “you can make it quite a bit smaller without paying a price.”
Helping people hear may be the natural next step.
Somewhat counterintuitively, 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. This could help detect hearing problems in a baby’s ear earlier, for example, and “then they can start treatment for it,” Dr. Miles said.
Another advantage of measuring airflow instead of pressure for sound measurement is that it can be used to locate the source of the 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 web researcher at the Karolinska Institute in Sweden, who was not involved in the study, agreed that spider webs have potential medical applications. It’s known for its strength, she said, but it’s also “well tolerated when implanted and has been shown to allow peripheral nerve regeneration” in animal experiments.
Dr. Miles is excited about using a web-inspired microphone to detect infrasound, which is below the range of human hearing. This can be useful for tasks such as tornado tracking.
“Being able to localize sound at these very low frequencies is really difficult with pressure microphones,” he said. “With a speed sensor microphone, you can do it very easily.”
Spider-inspired microphones have a long way to go before they’re ready for the mainstream. But the team already has a patent, and Dr. Miles is advising a Canadian company that is creating new types of microphones.
And if the research bears fruit, perhaps humans will finally break free of the biases that lead to devices inspired by our bodies, giving way to more inventions derived from how spiders and other creatures perceive the world.
