November 1, 2009
- One of a kind: More than a million spiders were silked to create this tapestry. Picture from the American Museum of Natural History in New York.
How To Silk A Spider
During the rainy seasons of the past four years, scores of workers in Madagascar spent their days collecting more than a million female GOLDEN ORB SPIDERS (Nephila madagascariensis) from telephone and electrical wires. The collectors passed the arachnids to handlers, who placed them into harnesses and then drew out their silk on hand-cranked devices—all while trying not to get bitten by the maple-leaf-sized web weavers.
At this point, humans took over the weaving, making individual threads by twining together somewhere between 96 and 960 spider-silk filaments. From these emerged a beautifully patterned hand-woven 11- by 4-foot cloth that now stands as the world’s largest single textile made of spider silk.
On loan from textile expert Simon Peers and fashion designer Nicholas Godley, the partners who spearheaded the project, the golden cloth is now on display at the American Museum of Natural History, in New York City.
“The tapestry is a really great example of the interface between art and science,” says Todd A. Blackledge, a spider-silk expert at the University of Akron. “Society has long been fascinated with the incredible strength and toughness of spider silk.”
Because spider silk is stronger than steel by weight but is also stretchable, scientists have been trying to synthesize their own versions of the biomaterial for years. Producing the gossamer fibers artificially is especially desirable because spiders are cannibalistic and cannot be raised in captivity. “Scientists are getting closer every day” to a synthetic material, Blackledge tells C&EN, “but figuring out how the spiders spin liquid silk proteins into such high-quality fibers” remains a challenge.
Spiders use their spinnerets to create the right conditions—an optimal concentration gradient, pH, and pressure—to organize the liquid proteins into silk. This process has been difficult to replicate in the lab. “The major hurdle is still making the fibers highly consistent, both batch to batch but within batches as well,” says Randolph V. Lewis, a molecular biology professor at the University of Wyoming.
Until the kinks get worked out, those Malagasy spiders will have to keep working overtime.
Another team of scientists—this one at NASA’s Goddard Space Flight Center (GSFC), in Greenbelt, Md.—has also been ensnared by the technological wonders of nature. Inspired by the way LOTUS PLANTS shed water and dirt from their leaves, GSFC researchers are developing a transparent coating based on the surface architecture of the lotus to protect equipment from space dust.
“Lunar dust is electrostatically charged and has jagged edges, which makes it extremely difficult to remove from surfaces,” says Wanda C. Peters, who heads Goddard’s Coatings Engineering Group. It could also cause respiratory illness in astronauts and damage to spacecraft surfaces.
To alleviate these problems, the GSFC team partnered with Atlanta-based nanomaterials producer nGimat and Linthicum, Md.-based Northrop Grumman Electronics Systems to produce the lotus-based films. Although they might need to be modified according to what type of surface they are adhering to, “the coatings can be composed of silica, zinc oxide, or other oxides,” Peters tells C&EN. In addition, fluorinated silanes can be added to enhance the repellant nature of the films, Peters adds.
And just as a lotus plant uses spiky wax-based microstructures on its leaves to clean itself, GSFC’s coatings, which are nanotextured, shed dust particles “by reducing the surface energy and the amount of surface area needed for attachment,” Peters explains. Currently, her team is working to modify the coatings to withstand the UV radiation, solar wind, and temperature extremes of space.
Lauren K. Wolf wrote this week’s column. Please send comments and suggestions to newscripts@acs.org.
