March 4, 2008 -- Soap is so 20th century.
Scientists in Indiana, Wisconsin and Australia have developed nanotechnology-based coatings that clean themselves and could be used in everything from silk shirts to windshields. Besides the added convenience, the new materials could reduce the use of environmentally destructive cleaners while killing potentially deadly bacteria.
The three teams of scientists took different approaches to self-cleaning materials.
Clothes "with self-cleaning properties will become a standard feature of future textiles," said Walid Daoud, a scientist at the University of Monash in Australia, who coated silk and wool with anatase titanium dioxide, a common pigment already used in products.
The scientist then stained both nanotech treated fabrics and non-treated fabrics with red wine and exposed them to simulated sunlight.
After 20 hours, the stains on the nanotech-treated fabrics were almost completely gone, while the stains on conventional fabrics looked virtually the same. Sunlight reacts with the coating to break apart organic molecules like dyes, turning them into carbon dioxide and water at room temperature, noted study co-author Wing Sze.
While the researchers themselves don't wear nanotech treated fabrics, "we are currently collaborating with a famous textile company for doing mill-trials," said Sze. "We believe it won't be long before the product appears on the market."
The non-toxic fabrics retain the feel and look of wool and silk.
The team from the University of Wisconsin made another self-cleaning material, but one that would go on the outside of houses, car windshields, and other objects.
"You could use it on all kids of things: windshields, windows, airplane wings," said Tom Krupenkin, a professor at the University of Wisconsin and author of a study that describes the product. "There are lots of applications for this."
Their material is made of nanonails, so called because they look like a sheet of roofing nails driven partially in.
The nanonails stay dry and clean because the water molecules, held together by surface tension, can't slip between them. Not only does the material keep water out, but it also repels oils, solvents and other hydrocarbons. Either the next rainstorm or a quick flick of cloth would wipe the dirt away.
Eventually, the material, which can be made into a shrink wrap-like film, will get dirty. When that happens you can either wipe it clean with water or just replace it, said Krupenkin. All of the researchers noted that self-cleaning fabrics will be environmentally friendly, decreasing the use of heavy-duty detergents and solvents.
It will be a while before you see nanonail-coated windows, though.
"These applications are very demanding," said Krupenkin. "You want to make sure that the nanonails will be there for years to come."
Jeffrey Youngblood, a materials scientist at Purdue University, who is currently working on anti-fog coatings and a device that could be used to easily and safety clean up oil tanker spills, thinks self-cleaning materials will soon be ubiquitous.
"We are seeing the first self-cleaning technologies now," said Youngblood. "The next ten years will bring a huge array."
