Spider silk is well-known for its unusual combination of being both lightweight and extremely strong—in some cases, stronger than steel. Due to these properties, researchers have been developing spider-silk-inspired materials for potential applications such as durable yet lightweight clothing, bullet-proof vests, and parachutes.
But so far, the acoustic properties of spider webs have not yet been explored. Now in a new study, a team of researchers from Italy, France and the UK has designed an acoustic metamaterial (which is a material made of periodically repeating structures) influenced by the intricate spider web architecture of the golden silk orb-weaver, also called the Nephila spider.
“There has been much work in the field of metamaterials in recent years to find the most efficient configurations for wave attenuation and manipulation,” coauthor Federico Bosia, a physicist at the University of Torino in Italy, told Phys.org. “We have found that the spider web architecture, combined with the variable elastic properties of radial and circumferential silk, is capable of attenuating and absorbing vibrations in wide frequency ranges, despite being lightweight.”
By modeling different versions of the new spider-web-inspired acoustic metamaterial, the researchers demonstrated that the new design is more efficient at inhibiting low-frequency sound and is more easily tuned to different frequencies than other sound-controlling materials. Combined with the stiffening mechanical properties and the heterogeneity of spider silk, the tunable acoustic properties demonstrated here suggest that spider-web-inspired metamaterials could lead to a new class of applications for controlling vibrations. Possibilities include earthquake protection for suspended bridges and buildings, noise reduction, sub-wavelength imaging, and acoustic cloaking.
The acoustic advantages of the spider web arise, at least in part, from the concentric circles, or “rings,” of the web. These rings resonate at a particular frequency when exposed to vibrations. Based on this natural architecture, the researchers designed the acoustic metamaterial to have square units containing resonating rings with supporting ligaments that radiate outward from the center of the rings. The design could be incorporated into many diverse man-made structures.