January 28, 2013
Scientists Want To Know Why Spider Silk Is So Strong
Lee Rannals for redOrbit.com — Your Universe Online
Scientists are unraveling the mysteries of what makes the fiber that spiders spin five times as strong as piano wire.
A team from Arizona State University found a way to obtain a wide variety of elastic properties of the silk from several spiders' webs using non-invasive laser light scattering techniques.
"Spider silk has a unique combination of mechanical strength and elasticity that make it one of the toughest materials we know," Professor Jeffery Yarger of ASU's Department of Chemistry and Biochemistry, and lead researcher of the study, said in a statement. "This work represents the most complete understanding we have of the underlying mechanical properties of spider silks."
Spider silk is very complex and the team is studying its molecular structure so they can produce materials ranging from bulletproof vests to artificial tendons.
The array of elastic and mechanical properties of spider silks obtained by the team is the first of its kind and will facilitate future modeling efforts aimed at understanding the interplay of the mechanical properties and the molecular structure of silk used to produce spider webs.
"This information should help provide a blueprint for structural engineering of an abundant array of bio-inspired materials, such as precise materials engineering of synthetic fibers to create stronger, stretchier, and more elastic materials," according to Yarger.
The technique used during the research involved a low power laser, less than 3.5 milliwatts, which is less than the average laser pointer. This non-invasive, non-contact measurement produced findings that hosted variations among discrete fibers, junctions and glue spots.
The spider webs studied included: a Nephila clavipes web; a gilded silver face web; a western black widow web; and a green lynx spider's silk. The green lynx spider is the only spider included in the study that does not cast a web, but still produces silk to catch its prey.
The group also investigated one of the most studied aspects of orb-weaving dragline spider silk, which is a property unique to silk. Spider silk takes up water when exposed to high humidity and the absorbed water leads to shrinkage in an unrestrained fiber, with up to 50 percent shrinkage in 100 percent humidity.
The team's results are consistent with the hypothesis that super contraction helps the spider tailor the properties of the silk during spinning. This behavior is inspirational from a bio-inspired mechanical structure perspective.
"This study is unique in that we can extract all the elastic properties of spider silk that cannot and have not been measured with conventional testing," concluded Yarger.
The team wrote about their findings in a paper entitled "Non-invasive determination of the complete elastic moduli of spider silks," which was published in the journal Nature Materials.