The discovery that a common spider species can spin filaments of silk at the nano-scale could lead to technologies enabling commercial applications using artificially spun versions of such nano-fibers, researchers say.
Where most spiders spin silk threads that measure several micrometers thick, the "garden center spider" or "feather-legged lace weaver," a common spider in Britain, creates filaments just nanometers thick, and researchers at the University of Oxford say they're close to understanding just how the arachnids to it.
The scientists made videos of adult female Uloborus plumipes spiders as they spun their silk, then used microscopic techniques to look at their filament-spinning organs.
What they found is that the species possesses an organ not commonly found in most spiders, known as a cribellun, made up of two plates carrying silk spigots with diameters of just 50 nanometers.
Those spigots create filaments that don't rely on sticky globs of blue to capture prey -- seen in most spider webs -- but are instead dry, containing thousands of nano-scale threads believed to electrically charge to create puffed-up capture strands.
"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," says Oxford zoologist Katrin Kronenberger, first author of a study on the species appearing in the journal Biology Letters.
The spiders work on the filaments as they emerge to endow them with an "sticky" charge, says co-researcher Fritz Vollrath.
"The swath of gossamer, made of thousands of filaments, emerging from these spigots is actively combed out by the spider onto the capture thread's core fibers using specialist hairs on its hind legs," he says.
By this combing and pulling of the filaments, the spiders can impart an electrostatic charge that provides adhesion and created a form of super-sticky silk perfect for capturing prey.
Conventionally produced polymer fibers, artificial equivalents of spider silk produced by a process known as hot-melt extrusion, are difficult to make any thinner than around 10 micrometers, the researchers note.
A technology enabling the commercial production of filaments at the nano-scale by successfully mimicking the spider's ability would make it possible to manufacture stronger and longer fibers, they say.
"Studying this spider is giving us valuable insights into how it creates nano-scale filaments," Vollrath says. "If we could reproduce its neat trick of electro-spinning nano-fibers we could pave the way for a highly versatile and efficient new kind of polymer processing technology."
