Locker rooms and student dorms everywhere could soon be a little more fragrant, thanks to an invention by University of California, Davis, textile chemist Gang Sun: odorless sports socks. The same technology could be used to make everything from odor-free diapers to hospital gowns that repel bacteria and viruses.
"Textiles make great media for growing bacteria," says Sun. Bacteria and yeasts in clothing break down perspiration, which has little odor by itself, and cause the all too familiar rank smell.
Sun himself says he wore the socks for a couple of days, with no obvious smell. After use, the socks need only a machine wash with household chlorine bleach to recharge the bacteria-killing capacity, says Sun.
The technology works by attaching chlorine-containing molecules called halamines to textile fibers, using a method patented by Sun. Chlorine in the form of halamines has powerful bacteria-killing properties, used for example to disinfect swimming pools. Unlike chlorine gas, there are no adverse effects as toxic chlorinated carbon atoms are not generated.
By sticking halamines to the cellulose fibers in cotton, the bacteria-killing effect can be bonded to the material and used again and again. Eventually, the chlorine is used up and can be regenerated with a wash in chlorine bleach.
The key to this invention was finding a practical way to bind the halamines to the cotton. "Obviously, one limitation is that you can't destroy the fabric during manufacture," says Sun. The finished product has to be as robust as regular textile, and the process has to be economical. Ease of manufacture is another important factor. Most cotton mills use a durable press treatment, and halamine treatment can be added at this stage with minimal modification, according to Sun.
Commercial development of these bacteria-killing textiles into garments is licensed by the University of California to Seattle-based company HaloSource Corporation. The technology is being developed for a number of applications, according to Kent Foster, HaloSource director of marketing and business development. These include single-use products, such as diapers and incontinence pads, and products for multiple use such as sportswear, kitchen tools and microbe-resistant uniforms for hospital or prison staff.
One important application could be in hospital uniforms. Hospital infections are an increasing problem, and hospitals are trying to find ways to prevent infections spreading from patient to patient, says Sun. Medical worker uniforms might be important in spreading infection, by carrying microbes from one patient to another. Uniforms that could kill any bacteria or viruses landing on them might be a useful tool to prevent the spread of infection, he says.
Since the halamine treated fabrics kill microorganisms almost instantly on contact, Sun believes that these materials are best suited for medical uses such as uniforms, wipes, bedding and towels.
HaloSource is currently involved in technical evaluations, and discussions of product plans are under way with a number of manufacturers, says Foster. "HaloSource is working with some of the largest companies in consumer product areas, air filtration and uniforms," says Foster. "These companies have approached us as a result of publications by Sun," he says, adding that Sun has played a key role in developing relationships with manufacturers. "Sun is very practical in getting from the lab to a manufacturing environment," says Foster.
HaloSource is working with the grower-supported development and marketing company Cotton Incorporated on validation of halamine technology. "Cotton Inc. has made its pilot manufacturing facility in North Carolina available for prototyping and scale-up trials," says Foster. Sun was instrumental in bringing Cotton Inc. into contact with HaloSource, according to Foster.
The odor-free socks have been tested by volunteers, including the 51³Ô¹ÏºÚÁÏ Davis cross-country running squad. Coach Sue Williams says that the men and women of the squad tested the socks through one full workout, including an eight or nine mile run. "They had pretty hard use for a day," says Williams. "They were comfortable, not irritating, and smelt very mildly of chlorine before and after," she says. "After an eight- or nine-mile run, for socks not to smell of feet is a real bonus," she adds.
Sun began his work at China Textile University, Shanghai, where he taught polymer chemistry. He moved to Auburn University, Alabama, in 1989 to study for a Ph.D. in organic chemistry. While developing polymer disinfectants for self-cleaning air filters, he became interested in disinfectants and in ways of binding them to textile polymers. He has continued to collaborate with the Department of Textiles Engineering at Auburn University since coming to 51³Ô¹ÏºÚÁÏ Davis in 1994.