The ultra-fine nature of spider silk has provided inspiration for scientists developing sensitive new types of microphones. Further down the track, these new devices could be put to use in advanced hearing aids and phones that pick up sounds at much lower frequencies, while doing a better job of filtering out background noise at the same time.
Spider silk is a wonder material that has drawn the interest of scientists in many fields, including those working in electronics, gene therapy, space exploration and medicine. Its tremendous strength and elasticity might even see it put to use as violin strings and car seats. But it is the silk's slenderness that caught the attention of a team of scientists from New York's Binghamton University.
Led by distinguished professor in mechanical engineering Ron Miles, the team was investigating the way insects differ from humans in how they detect sounds, and what we might be able to learn from them.
"We use our eardrums that pick up the direction of sound based on pressure, but most insects actually hear with their hairs," says Miles.
This is because instead of detecting pressure changes in the air, insects like mosquitos, flies and spiders detect the velocity of the air using very fine hairs on their bodies. It turns out that spider silk, too, is thin enough to be moved by the sound waves, even those at very low frequencies. The sensitivity is so great that the scientists liken it to hearing tectonic plates move in an earthquake.
"This can even happen with infrasound at frequencies as low as three hertz," Miles says of the movement of spider silk.
To turn this movement into something useful for their purposes, the scientists coated spider silk in gold and placed it inside a magnetic field. This allowed them to convert the movement created by the sound waves into an electronic signal, leaving them with a makeshift, highly sensitive microphone that detects a wider range of frequencies with better directional accuracy.
Because of these abilities, the team's microphone has the potential to pick up sounds that are too quiet for regular microphones and with better precision. So if worked into a hearing aid or smartphone microphone, for example, it could zero in on the sounds coming from a person's mouth while ignoring background noise.
"It"s actually a fairly simple way to make an extremely effective microphone that has better directional capabilities across a wide range of frequencies," says Miles.
The team's research was published in the journal Proceedings of the National Academy of Sciences.
Source: Binghamton University