How Stain-Repellant Nanofabric is Made
The Fabric of Consumer Reality
ALAN ZEICHICK / Red Herring 1mar03
THE WORD nanotechnology brings to mind images of microscopic robots circulating in people's blood streams and tiny starships navigating the outer reaches of deep space. But nanometer-scale devices—those with dimensions in the range of one-billionth of a meter—don't exist exclusively in the realm of the exotic. Though the devices themselves might be high tech, the technology is appearing in commonplace products like tennis balls, suntan lotions, and textiles.
The economics of nanotechnology, particularly for consumer goods, requires that the products be competitive with more conventional offerings; that means the nano-scale components must be manufactured in bulk, using techniques similar to those employed in making larger-scale products. The building blocks of nano-scale devices are tiny fibers, hollow tubes, minute droplets, and other sub-miniature components that are often grown like crystals or dispersed through molecular-scale nozzles. These nano-components are then incorporated into ordinary materials, either during the original manufacturing process or through post-manufacturing treatments.
Nano-Tex is one company attracting attention for its engineered fabrics, which use tiny fibers to repel stains and wick moisture from sweaty athletes. Other companies, like DuPont and Corning, as well as research institutions, like Cornell University, the University of North Carolina at Charlotte, and the University of Texas at Austin, are exploring the use of nanotechnology to make fabrics more durable, lighter, and better able to absorb dyes and textures.
Nano-Care, the stain-repellent fabrics from Nano-Tex, incorporate billions of tiny fibers, each about to nanometers (that's 0.0000004 inches) long, that are embedded within traditional cotton or linen. The waterproof fibers, which Nano-Tex calls "nanowhiskers," make the fabric dense, increasing the surface tension so drops of liquid can't soak through—just like raindrops on a freshly waxed car. The company says this Nano-Care treatment will withstand 5o home launderings before its effectiveness is lost.
Nano-Care and other similar nano-tech treatments differ from fabric coatings like 3M's Scotchgard in that the nano-scale fibers are actually embedded into the products. In contrast, Scotchgard is applied to the finished goods, typically as a spray, and only protects what can be sprayed.
Nanotechnology can also be used in textiles to increase the ability of synthetic fabrics—like those made of the plastic polypropylene—to absorb dyes. Most polypropylenes resist dyeing, making them unsuitable for consumer goods like clothing, table cloths, or floor and window coverings. With one experimental technique, a special dye-friendly clay is ground into nanometer-size particles, which are given a light positive electrical charge to prevent them from clumping together. The clay is then mixed into raw polypropylene stock before it's extruded into threads, which are turned into fibers and woven into fabrics. The result is a composite material that can absorb a dye without weakening the fabric. And it doesn't even require nano-scale robots.
HOW STAIN-REPELLENT NANOTECH FABRIC IS MADE
Rolls of woven fabric from textile mills are immersed in liquids containing trillions of nanotech fibers.
The cotton, now permeated with the nanotech fibers, is dried in ovens, binding the tiny fibers to the comparatively much larger fabric threads.
The woven cotton, while appearing to be unchanged, now presents a nearly solid barrier to liquid. The nanotech fibers prevent the wine from soaking into the fabric.
ALAN ZEICHICK is principal technology analyst with Camden Associates and is editor in chief of BZ Media's SD Times. Write to firstname.lastname@example.org.