The average American businessperson spends anywhere from $500 to $1,500 on dry cleaning each year. In addition to the economic costs, the Environmental Protection Agency has said that the most commonly used chemical, perchloroethylene (perc), can leech into our bodies, causing respiratory irritation and possibly cancer, and the air, depleting the ozone layer.
Over the past few years, some dry cleaners have begun using “green” or “organic” cleaning methods, many of which include replacing perc with carbon dioxide. But, Walid Daoud, a chemical engineer at City University of Hong Kong's School of Energy and Environment, has developed a method that would cancel out the need for dry cleaning altogether.
In his lab, Daoud has created fabric that cleans itself when it’s exposed to light.
The magic involves an invisible, light-reactive coating. Daoud’s team applies a nano-thin layer of photocatalysts (anatase titanium dioxide, to be precise) onto cashmere. When a coffee, red wine or tomato stain is present, researchers place the material under light for 24 hours. The light source incites a chemical reaction that creates oxidants, which in turn can break down any contaminants, including bacteria and soil.
Daoud has been experimenting with similar self-cleaning coatings for other fabrics, including cotton, since the early 2000s. Such fabrics could eliminate the need for energy-hungry washing machines, which consume some 40 gallons of water per load and account for 22 percent of the average household's water usage. But cashmere, which is fine wool spun from the soft undercoat of a particular type of goat, is trickier than sturdy cotton.
“Cashmere is a sensitive protein and can be easily damaged,” Daoud explained to the City University of Hong Kong news service. “It has poor resistance to oxidation, chemicals, and high temperatures.” So Daoud had to find a mix of chemicals that wouldn’t harm the fabric during oxidation.
Now that Daoud and his team have found the right chemical cocktail, they are developing methods to ensure that the coating will have no ill effects on the wearer or the environment.
“The project aims at delivering a set of testing systems and standard protocols, including a nano-coating emission chamber for testing stability, nanoparticle performance, and safety under simulated wear,” he said.
The team also plans to establish methods to test the durability and effectiveness of the coating next month. In the end, treated garments would only run at a 1 to 1.5 percent premium compared to untreated ones; so a $75 sweater would cost about $76.13.
Researchers have been demonstrating stain-resistant coatings for several years. For example, a team at Harvard has shown off a Slippery Liquid-Infused Porous Surface (SLIPS), which imbues cotton and polyester with omni-repellent properties. The U.S. Army has been testing similar dirt-wicking materials for uniforms. Earlier this year, Silic, a startup, completed a fully funded Kickstarter campaign to bring a repellent t-shirt to market; it’s currently up for preorder. And, last summer, Rust-Oleum released NeverWet, a spray treatment with similar, if not inferior, capabilities. Users apply two layers of NeverWet onto pretty much any surface and allow it to dry. Once set, the coating will repel water, oil, dirt and more from the surface. Rust-Oleum doesn’t recommend users apply NeverWet to clothes though—the treatment’s silicone base can be carcinogenic—and the treatment wears off in time and leaves a chalky residue.
But, Daoud’s coating is among the first to actively remove stains from fabric.
Unfortunately, consumers will have to either wait or make due with these interim solutions, because it could be years before self-cleaning cashmere makes its public debut.