The Itsy Bitsy Spider inspired a microphone

Engineers and scientists have an enduring fascination with spider silk. Similar to typical worm silk that makes for comfortable sheets, but much sturdier, the material has inspired the invention of lighter and more breathable body armor and materials that can make aircraft parts stronger without adding weight. Researchers are even using samples from spider webs to design sensitive microphones that could one day be used to treat hearing loss and deafness and improve other listening devices.

Spiders use their webs as enormous external eardrums. A team of scientists from Binghamton University and Cornell University reported in 2022 that arachnids can detect sound from 10 feet away.

When you hear a sound through your ear, you are actually experiencing changes in air pressure that cause your eardrum to vibrate. This is 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 drumhead, they move with the flow of air being displaced. Air is a liquid medium “like honey,” says Ronald Miles, a professor of mechanical engineering at Binghamton. People navigate this environment without noticing much resistance, but silk fibers are tossed back and forth by the speed of the viscous forces in the air.

Dr. Miles wondered whether this principle could lead to a new kind of microphone.

“Humans are quite arrogant animals,” he said. “They make devices that work like them.” But he wondered if he could build a device that would look more like a spider and “could perceive 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 silk. 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, cantilevered shaft (like a diving board) made of silicon that responds to tiny fluctuations in airflow caused by sound. To convert that into something people can hear, a laser measures the subtle movements of the shaft, the way a spider decodes its web.

One drawback to typical pressure-sensing microphones, says Dr. Miles, is that making them better often means making them bigger. Think of the chunky microphones you see in a recording studio compared to the spindly headphones used by a motivational speaker. Featuring a spider-inspired microphone that responds to airflow instead of pressure, Dr. Miles: “You can make it a lot smaller without paying a price.”

Helping people hear could be the logical next step.

Somewhat counterintuitive, our ears emit sounds when they vibrate in response to pressure. With funding from the National Institutes of Health, Dr. Miles to develop a probe that measures these very quiet otoacoustic emissions. That could, for example, help detect hearing problems in a baby’s ear earlier, and “then they can start treatments for it,” said Dr. Miles.

Another advantage of measuring airflow instead of pressure to measure sound is that it can be used to locate the sound source. This could improve hearing aids designed to pick up sounds coming from a specific place in a noisy environment, added Dr. Miles to it.

Anna Rising, a spider silk researcher at the Karolinska Institutet in Sweden who was not involved in the study, agreed that spider silk has potential medical applications. It is known for its robustness, she said, but it is also “well tolerated when implanted and has been shown to facilitate peripheral nerve regeneration in animal studies.”

Dr. Miles is excited about using a web-inspired microphone to detect infrasound, which is beyond human hearing range. That can be useful for tasks like tracking tornadoes.

“It’s very difficult to localize the sound of those very low frequencies with pressure microphones,” he said. “With a velocity-sensitive microphone you could do it very easily.”

Spider-inspired microphones still have a long way to go before they’re ready for the mainstream. But the team already has a patent and Dr. Miles advises a Canadian company on building new types of microphones.

And if the research bears fruit, humans may finally be able to break away from the biases that lead to devices inspired by our bodies, making way for more inventions to emerge from the way spiders and other creatures perceive the world.

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