The brown recluse spider’s method of spinning its uniquely strong silk suggests new ways to create strong materials for impact-absorbing structures.

Brown recluse spider. Credit: Joseph McClainSpider silk has long interested materials scientists, who are unraveling the secrets of the substance’s strength in order to apply this knowledge to synthetic materials. Unlike orb spiders — the ones that make the large octagonal webs to catch flying insects — the brown recluse constructs a messy-looking web near the ground, to catch crawling bugs.

Their silk is much stronger than that of other spider species, a characteristic that attracted the attention of a joint team from the College of William and Mary and the University of Oxford. One of the researchers described the brown recluse’s silk as “better than Kevlar™.”

The team discovered that brown recluse silk has a flat cross-section, like a ribbon, not round, as is the case with other spiders. The chief source of strength is the loops the spider spins into each strand. The spinneret produces about 500 microloops per inch of silk.

Materials scientists have long known that loops add strength to a material, but loops also cause the material to fray prematurely. The flat ribbon shape turns out to be the key that prevents the spider’s looped silk from this pitfall.

The researchers have demonstrated with computer simulations that fibers with lots of loops are considerably stronger than straight fibers, according to team member Fritz Vollrath of Oxford.

“This right away suggests possible applications. For example, carbon filaments could thus be made less brittle, to allow them to serve in novel impact-absorbing structures, for example in spider-like webs of carbon-filaments to capture the floating space debris that endangers astronauts’ lives and satellites’ integrity,” Vollrath explained.

The research team is enthusiastic about continuing their research. Challenges face further development of a synthetic based on the spider silk. No synthetic fiber exists that has the ribbon shape of the silk, and the composition of the silk itself has not been analyzed.