Spider Spins Electrically Charged Silk

sciencehabit writes In their quest to make ultrastrong yet ultrasmall fibers, the polymer industry may soon take a lesson from Uloborus spiders. Uloborids are cribellate spiders, meaning that instead of spinning wet, sticky webs to catch their prey, they produce a fluffy, charged, wool-like silk. A paper published online today in Biology Letters details the process for the first time. It all starts with the silk-producing cribellar gland. In contrast with other spiders, whose silk comes out of the gland intact, scientists were surprised to discover that uloborids' silk is in a liquid state when it surfaces. As the spider yanks the silk from the duct, it solidifies into nanoscale filaments. This "violent hackling" has the effect of stretching and freezing the fibers into shape. It may even be responsible for increasing their strength, because filaments on the nanoscale become stronger as they are stretched. In order to endow the fibers with an electrostatic charge, the spider pulls them over a comblike plate located on its hind legs. The technique is not unlike the so-called hackling of flax stems over a metal brush in order to soften and prepare them for thread-spinning, but in the spider's case it also gives them a charge. The electrostatic fibers are thought to attract prey to the web in the same way a towel pulled from the dryer is able to attract stray socks.

Comments

I thought the point of the charge ...

[Ungrounded Lightning]

I thought the point of the charge was to make the "wooly" side-fibers of the strands wrap around the prey's limbs and/or the microscopic irregularities in the exoskeleton, tangling to it. "Tying" the fibers to the prey would have a similar binding effect to gluing them to it, without the need for glue, and lots of little fibers could make a very strong attachment.

(Stretching fibers made of long chains makes them stronger by aligning the chains along the direction of the stretch.)

Spider silk - amazing stuff

[Dutch Gun]

Spider silk is amazing stuff. Stronger than steel, tougher than kevlar, highly elastic, strong or light, sticky or dry as the need arises, instantly manufactured on demand, and even recyclable (some spiders eat their own webs to recycle the valuable proteins). An orb weaver typically has enough raw material in it's body to create three complete webs.

I recently saw a researcher demonstrating the property of a spitting spider's webs. The spitting spider, as it's name implies, actually spits a spray of sticky web at it's victim with silk-jets that vibrate back and forth at an astounding speed to create a wide spray pattern. As the web silk dries, it contracts as well, helping to bind the victim in a silk spray straightjacket.