Common Spider Spins Silk Fibers Only a Few Nanometers Thick with Electric Charge

How do spiders spin incredibly long and strong fibers just a few nanometers thick? It may have to do with electric charge. Scientists have taken a closer look at the common feather-legged lace weaver spider, Uloborus plumipes, in order to learn from its web-spinning technique.

Most spiders spin silk threads that are several micrometers thick. In the case of the feather-legged lace weaver, though, it has the ability to spin nano-scale filaments. Learning exactly how this is done could help researchers develop new technologies to enable the commercial spinning of nano-scale filaments in the future.

That's why scientists decided to look a bit closer at these spiders. They collected adult female lace weavers from garden centers in the UK. Then, they took photographs and videos of the spiders' spinning action and used three different microscopy techniques to examine the spiders' silk-generating organs. Of particular interest was the cribellum, which is an ancient spinning organ not found in many spiders and consisting of one or two plates densely covered in tiny silk outlet nozzles.

"Uloborus has unique cribellar glands, amongst the smallest silk glands of any spider, and it's these that yield the ultra-fine 'catching wool' of its prey capture thread," said Katrin Kronenberger, the first author of the new study, in a news release. "The raw material, silk dope, is funneled through exceptionally narrow and long ducts into tiny spinning nozzles or spigots. Importantly, the silk seems to form only just before it emerges at the uniquely-shaped spigots of this spider."

The silk that emerges from these spigots is made out of thousands of filaments, and is activtely combed out by the spider onto the capture thread's core fibers using hairs on its hind legs. The combing actually charges the fibers, and the electrostatic causes regularly spaced, wool-like "puffs" that cover capture threads. This makes the material incredibly sticky.

"Studying this spider is giving us valuable insights into how it creates nano-scale filaments," said Fritz Vollrath, co-author of the new study. "If we could reproduce its neat trick of electro-spinning nano-fibers we could pave the wave for a highly versatile and efficient new kind of polymer processing technology."

The findings are published in the journal Biology Letters.

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