Scientists and engineers love spider silk. The unique material is a major target for efforts to mimic nature’s inventiveness because it is so strong, lightweight, biologically compatible and disposable — all properties that make it attractive for creating smart materials that could be used to make bullet-proof clothing, strong rope, bandages, artificial tendons and more. We’ve created goats that secrete spider silk in their milk and listened in to the messages encoded in vibrating webs.
Now researchers from Oxford University have investigated spider webs’ stickiness. In a paper published in Biology Letters, they looked at a strategy employed by a spider found in British garden centers (it's able to survive in hot, humid greenhouses) that differs a bit from most spiders' method of snagging prey.
Sticky webs spun by the more common orb weavers, for example, are studded with a glue-like substance created in glands on the spider’s belly. Typically, spiders also create silk that is several micrometers thick, but the garden center spider, also called the feather-legged lace weaver and Uloborus plumipes, spins silk threads so fine they are measured on the nano-scale. Still, these filaments are very sticky.
The spider creates this unique silk in an organ called the cribellum, which consists of "one or two plates densely covered in tiny silk outlet nozzles," according to a press statement. The organ funnels raw silk through very long, narrow ducts before spitting them out the tiny nozzles. Then, using special hairs growing on its hind legs, the spider combs the newly formed silk threads. The combing and a "violent pulling," or hackling, on the many gossamer filaments emerging from the nozzles actually adds an electrostatic charge to the threads and creates "regularly spaced, wool-like 'puffs' covering the capture threads," one of the study’s authors, Fritz Vollrath, says in the statement. The thinness of the silk and the electric charge culminate to make the puffs very sticky.
The micrographs and close-up photographs of the spider’s silk-generating structures and the silk itself are stunning.
The discovery points toward a new way of making polymers, reports Arielle Duhaime-Ross for the Verge. "It might even help scientists come up with their own version of the super sticky nano-scale threads," she writes. It’s yet another spider secret we’ve learned and a step closer to those sci-fi sounding applications we hope to achieve with super strong, sticky silk.