Fruit of the Nano-Loom

New textiles tap polymer science to both trap and kill toxins – all while wicking away sweat.

By exploiting chemistry and nanotechnology, researchers are creating a new generation of clothes that do more than look fashionable and keep the wearer warm. Already, stores are selling pants that resist stains thanks to coatings made of “nanowhiskers,” and odor-eating socks that trap microbes using nanoparticles.

Now, scientists are developing clothing for military and medical applications that seem to do it all: block toxins, kill bacteria on the surface, and breathe sufficiently to allow perspiration to escape.

The latest advance, a collaboration between researchers at Cornell University and the University of California, Davis, stitches together porous membranes and bacteria-killing polymer molecules. The results could provide enhanced performance for situations where resistance to liquid or vapor is needed, such as for medical personnel or soldiers exposed to pathogens. The researchers plan to test their new fabric on medical and military staff this year, and to commercialize the fabric by 2008.

“There has been a lot of work in textiles to come up with combinations of materials that give high functional properties,” says Kay Obendorf, a textiles chemistry professor at Cornell who specializes in the surface chemistry of fibers. “We need a material that will be a barrier to bacteria while changing its toxicity level.”

The latest work had its genesis in 2000, when Gang Sun, a professor of textiles and clothing at the University of California, Davis, invented a method for attaching chlorine-containing polymer molecules, called halamides, to textile fibers. These molecules kill bacteria almost instantly on contact. “Halamides are chemically the same as the disinfectant used in swimming pools,” Sun says. “They are safe for contact with the skin, kill bacteria, and absorb odor.”

With this technology, Sun created prototype “odor-free” socks in 2000, and showed that bacteria-battling halamides could be re-activated by simply adding some household bleach to the wash. In 2001, he licensed the technology to Vanson HaloSource, a Redmond, WA-based bioscience company that uses halamide-based technology for commercial applications. Vanson HaloSource has successfully developed anti-bacterial bed sheets and cotton pads for medical use, and it has also given Sun nearly $400,000 to continue his research.

Sun said he knew that the military had already developed protective clothing using porous membranes to stop the penetration of biological agents like bacteria. But some agents would still be stuck on the outside surface of the uniform, which could lead to a contamination threat. By teaming up with Obendorf in 2005, Sun built on this existing technology by attaching halamide molecules to porous membranes. These hybrid materials will now be applied as a coating to fabric, thereby trapping and killing deadly agents such as anthrax.

Here’s how they did it: They started with porous membranes made of polyurethane, a substance that has strength and elasticity – useful properties in fabrics such as spandex. Then they grafted on a layer of halamide molecules, forming a permanent chemical bond between the two dissimilar materials. The attached halamide layer has an affinity for liquid. When a liquid hits the hybrid material, this layer swells, absorbing toxins that might be in the liquid. “This will give the ultimate protection,” said Sun. “We can absorb, trap, and kill the bacteria.”

Sun and Obendorf also optimized the pore size of the membrane to allow perspiration to pass through, while blocking bacteria, which are much larger. Perspiration forms vapor droplets less than a nanometer in diameter – the equivalent of a few pairs of atoms lined up in a row. An anthrax bacterium, for example, is about one micrometer in size.

“Gang Sun’s pioneering work represents one of the major successes of National Textile Center-sponsored research,” said Martin Jacobs, executive director of the National Textile Center, a federally funded research consortium of eight U.S. universities. The NTC granted Sun and Obendorf $300,000 to create these materials. “He has generated both commercial and U.S. Air Force interest.”

Ultimately, Sun said, these garments could safeguard soldiers, medical workers, and civilians from harm. He and Obendorf are also working with the National Textile Center to develop fabrics for agricultural workers exposed to pesticides in an environment with high temperatures and high humidity, and hope to bring their textiles to market for all applications in two years. “If there is a potential risk,” said Sun, “these technologies can provide the best protection.”

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