Properties of Spider Silk

Orb-spinning spiders use different kinds of silk in their webs.

Spiders have effective mechanisms for producing silk, with glands in their bodies that produce different kinds of silk for different uses. Scientists studying spider silk and impressed with its properties are working on producing artificial silks with its characteristics. These artificial silks have possible applications in the lives of humans.

Production

Spiders make silk from liquid proteins in their abdomens. Openings at the ends of glands, called spinnerets, dispense the liquid, which solidifies into silk just before leaving the spinnerets.

Thickness

Spider silk serves as a dragline to keep spiders from falling. The dragline of an orb-spinning spider is approximately 0.00032 inches in diameter; for a garden spider, it's 0.00012 inches. The thinnest draglines measure about 0.0000008 inches in diameter, writes author-photographer Rod Preston-Mafham in the book, "Spiders."

Strength and Flexibility

Spider silk ranks as the strongest natural fiber, according to an article in the June 17, 2006, issue of "New Scientist" magazine. Protein crystals -- corrugated sheets of protein -- give spider silk its strength, surrounded by chains of amino acids that make it flexible. One measure of the strength of spider silk is how much force it takes to break it apart along its length. When controlling for weight, spider silk proves more difficult to pull apart than tendon, bone, rubber or cellulose, says "Biology of Spiders" author Rainer F. Foelix, who also notes that spider silk is half as strong as steel.

Uses By Spiders

Some spiders use silk from the aciniform gland to "wrap" prey captured in webs. As flexible aciniform silk stretch to 200 percent of its length, it works perfectly to prevent struggling captives from breaking the thread and escaping.

Spiders that make orb webs, which have concentric structures called spirals, use silk from the pyriform glands to anchor and begin building the web, and silk from the flagelliform glands to make the spirals. Silk from the aggregate glands produces the sticky, prey-snaring substance that goes on the spirals.

Potential

Sutures and better bandages might result from ongoing research. The possibility of growing tendons, ligaments and cartilage on a frame of artificial spider silk shows promise, too. Nerve cells called Schwann cells readily adhere to and grow on threads of spider silk, and researchers hope to use artificial silk to grow and regenerate nerve cells, Foelix reports. Possible nonmedical applications for spider silk include stronger lightweight clothing and improving airbags, seat belts, parachutes and ropes, which need to be tear-resistant. Before the promise of duplicating spider silk can be realized, Foelix notes, researchers must find a way to produce it in large quantities.

References

• "Biology of Spiders"; Rainer Foelix; 2011
• "Arachnids"; Jan Beccaloni; 2009
• "New Scientist"; Spider Silk Gets An Upgrade; June 17, 2006
• "Spiders"; Rod-Preston Mafham; 2007
• "Advanced Materials & Processes"; Scientists Produce Artificial Spider Silk; November-December 2010