Why a spider hanging from a thread does not rotate

[C1ay]

The extraordinary properties of spider's thread are like a blessing for researchers working on polymers. However, the amazing twisting properties it displays are still not very well understood. How can one explain the fact that a spider suspended by a thread remains completely motionless, instead of rotating like a climber does at the end of a rope?

 

lefthttp://hypography.com/gallery/files/9/9/8/spider_thumb.jpg[/img]Researchers at the Laboratoire de physique des lasers (CNRS/University of Rennes) have described the exceptional properties of this material which still has some secrets to reveal. The results will be published in Nature on 30 March 2006.

 

Fasten an object to the end of a vertically suspended thread. Give it a slight twist and let go. You will observe that the object rotates for a certain length of time and with a certain amplitude, depending on the material of the thread. Now observe a spider suspended from its thread: It is stable, doesn't move, spins its thread in a perfectly straight line and always recovers its balance after environmental disturbances.

 

By experimenting with a torsion pendulum to which they attached a mass equivalent to a spider's weight, researchers at the Laboratoire de physique des lasers (CNRS/University of Rennes) compared the dynamic reactions of different types of thread to a 90. rotation. The results are revealing: a Kevlar filament (which is synthetic) behaves like an elastic, with reduced oscillations. A copper thread oscillates slightly but does not return to its original shape, and becomes more fragile as a result of these oscillations. Spider's thread, on the other hand, is very efficient at absorbing oscillations, regardless of air resistance, and retains its twisting properties during the experiments. It also returns to its exact original shape. Certain alloys, such as Nitinol, possess similar properties but must be heated to 90. to return to their original shape.

 

The amazing properties of spider's thread have been known for several years: its ductility, strength and hardness surpass those of the most complex synthetics fibers . It now also seems that through natural selection, spider's thread has evolved into a material with "self-shape memory effect" which allows it to return to its original configuration without outside stimulus. This complex dynamic process has recently been represented as a "stacked" model which the authors use to depict the relaxation of the different proteins in spider's thread.

 

Source: University of Rennes

[Racoon]

I love Spiders!

[IDMclean]

You know a difference I would note between a climber's rope and most any thread we make and a spiders thread might be in that our thread is monodirectional twist, and I would bet that a spider's thread is bidirectional twist or perhaps some kind of braid (of molecular composition, or perhaps the spinnerets weaving polymers efficiently).

[C1ay]

I suspect a spiders thread has no twists or braids, that it is simply an extrusion. There's some close up images here....

[IDMclean]

Well hence my conjecture on the nature of such a braid. It does not have to be a macroscopic braid.

 

It is possible that it opperates in similar manner as that of gecko's sticky appendages (nano-width "hairs" that use the tension between molecules to stick to practically any surface). In tht the molecules themselves, that make up the spider silk may form a latice such that it is either a bi-directional or multidirection twisted (or braided) strand. So that if we were to talk about it in the sense of "spin" or Chirality, it would both have right handed and left handed orientation, so as to remain resolute to change to the structure of the fiber.

 

Might go beyond simply the molecular to the atomic or subatomic scale. I wonder what Spider silk looks like under various MRI Scans.