Manufactured spider silk could be used for artificial tendons and ligaments, sutures, parachutes and bulletproof vests. But engineers have not managed to do what spiders do effortlessly.
In a study published in the November issue of the Journal of Experimental Biology, Gareth H. McKinley, professor of mechanical engineering, and colleagues examined how spiders spin their native silk fibers, with hopes of ultimately reproducing the process artificially.
McKinley heads the Non-Newtonian Fluid Dynamics research group in MIT's Department of Mechanical Engineering. Non-Newtonian fluids behave in strange and unexpected ways because their viscosity, or consistency, changes with both the rate and the total amount of strain applied to them.
Spider silk is a protein solution that undergoes pronounced changes as part of the spinning process. Egg whites, another non-Newtonian fluid, change from a watery gel to a rubbery solid when heated. Spider silk, it turns out, undergoes similar irreversible physical changes.
Stickiness and Flow
McKinley and Nikola Kojic, a graduate student in the Harvard-MIT Division of Health Sciences and Technology, studied the silk of Nephila clavipes, the golden silk orb-weaving spider. One species of golden orb spider creates a web so strong it can catch small birds. In the South Pacific, people make fishing nets out of this web silk.
The researchers chose the golden silk spider because of the formidable strength of its web. But Kojic was taken aback when the first palm-sized spider crawled out of the box he received in the mail from an accommodating employee of Miami's MetroZoo. (She simply gathered some up from the grounds; the zoo does not exhibit golden orb spiders.)'"/>