Scientists hope to spin web without spiders

Last Updated: Tuesday, October 31, 2006 | 11:52 AM ET

CBC News

A team of engineers have identified key physical processes that give spider silk its strength and durability, bringing the idea of manufactured web silk one step closer to reality.

Scientists are hoping to tap into the strength of this natural fibre. Artificial spider silk could have a wide range of uses, from artificial tendons and ligaments to parachutes and bulletproof vests.

Researchers studied the golden silk spider, known for its incredibly strong silk. (Nikola Kojic, MIT)

In a study published in the November issue of the Journal of Experimental Biology, a team led by Gareth H. McKinley, professor of mechanical engineering from the Massachusetts Institute of Technology (MIT), looked at how spiders spin their native silk fibres, in an attempt to one day reproduce the process artificially.

McKinley and Nikola Kojic, a graduate student from the Harvard-MIT division of health sciences and technology, studied Nephila clavipes, the golden silk spider, known for the incredible strength of its web.

Spider silk is a protein solution that goes through irreversible physical changes in the so-called spinning process.

Spiders don't actually spin their webs. Instead, they squirt out a thick gel of silk solution. One teaspoonful of this can make 10,000 webs, according to researchers. Spiders then use their hind legs as well as their body weight and gravity to stretch the gel into a fine thread.

Researchers were able to extract a microscopic amount of the gel-like solution from the spider's silk-producing gland and test it for viscosity and stickiness.

The study's authors discovered the silk gains its strength as it flows out of the spider's gland, lengthens and dries.

Polymers and water 

The key to spider silk is polymers, according to researchers. The silk protein solution consists of 30 to 40 per cent polymers — the rest is water.

Polymers have been used in plastics, bulletproof vests and parts of the International Space Station. They are extremely strong, can be flexible or stiff, water-soluble or insoluble, and resistant to heat and chemicals.

Researchers found that the spider's silk-producing glands are capable of turning fibrous proteins into an insoluble fibre.

"The amazing thing nature has found is how to spin a material out of an aqueous solution and produce a fibre that doesn't re-dissolve," McKinley said in a news release.

Like a cooked egg white, dry spider silk doesn't revert to its former liquid state. What started out as a water-based solution becomes impervious to water.

As the liquid leaves the spider's abdomen, it takes on the characteristics of a liquid crystal. The silk as it stretches and dries forms tiny crystalline structures that act as reinforcing agents.

The researchers say they will try to replicate the silk process through polymer processing.

They will attempt to match the properties of the liquid artificial spinning material with those of the real thing "to successfully process novel synthetic materials with mechanical properties comparable to, or better than, those of natural spider silk," according to the study's authors.