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Our troops in Iraq could use uniforms that are lighter-weight, but won't wear out. That kind of new fabric would change life for the Army—and for a lot of civilians, too. As this ScienCentral News video reports, one nanotechnologist thinks synthetic spider silk could help make soldiers' uniforms rip-proof.
Spider silk is lightweight, flexible, waterproof— and one of the toughest materials in the world. It's also very difficult to imitate, but some materials scientists think that if they could do so, soldiers' uniforms would be lighter and much more durable. What exactly makes spider silk so surprisingly resilient?
"If you've ever sort of pushed aside a spider web, you've noted that it pulls before it breaks," says Paula Hammond, associate professor of chemical engineering, and director of laboratories and leader of the research team for chemical and biological protection at the Institute for Soldier Nanotechnologies at Massachusetts Institute of Technology. "Spider silk goes through this sort of stretching before it breaks, and in doing so, it absorbs a lot of energy. The energy that you're putting into pushing it or pulling it is actually being taken up by the stretching process. This energy-absorbing process is what makes the material so tough."
Spiders spin their silk by secreting a fluid, fibrous protein similar to keratin, the structural protein found in hair and horns. Spider silk protein hardens as it oozes, a process that scientists don't fully understand. But they do know that harvesting that protein is not easy or inexpensive, despite a variety of approaches. "You can't farm spiders the way you farm silkworms and create large amounts of these proteins spun by the animal naturally," explains Hammond. "Spiders are very cannibalistic. If you put two spiders together in a cage or any kind of enclosure, eventually one spider will eat the other."
Dr. Hammond's new fiber image: Boston Museum of Science
So Hammond is taking a synthetic approach, working on creating artificial fibers that work like spider silk. The structure of spider silk includes rigid regions that hold the silk together, soft regions that keep it flexible, and a third region within the soft parts that allows silk to stretch. To create artificial spider silk, Hammond's team starts with polyurethane, a type of plastic used to make synthetic packaging and fabrics. So far, the MIT researchers have succeeded in making fiber that's both soft and stretchy. Their next step will be to add nanoscale particles, each about the size of a single molecule, to help make the fiber stronger. Hammond says, "These nanoparticles will be designed to bind to a very specific region of the soft material, to reinforce it and make it stiffer. They'll also make the material resistant to tearing and cuts. That’s something that's of interest to the Army, and to people in general—clothing that’s not going to tear when, for example, you're climbing over a barbed wire fence."
Hammond thinks that police and emergency-care workers could benefit from uniforms made with artificial spider silk, too. "All of these people are physically active," she points out. "They sweat. So we're incorporating into the fiber another material that can absorb water and evaporate it. That allows the fiber to be breathable."
Spinning the new fiber into thread that can be woven into uniforms will require a special process, akin to the way the spider spins its silk. Hammond is collaborating with another MIT research group, headed by mechanical engineer Gareth McKinley to come up with a way to spin her new fiber into thread.