Silica nanoparticles used to make mosquito-repellant clothing
By Ben Coxworth
June 7, 2012
For many of us, mosquitoes are an irritating pest that can ruin any number of outdoor activities. For many others, however, they are also spreaders of malaria – a disease which infected approximately 216 million people in 2010, according to an estimate by the World Health Organization. Repeatedly slathering on bug repellant is one way of dealing with the insects, although wearing clothing made from mosquito-repellant fabric sounds a lot more preferable. While existing mozzie-unfriendly garments have some limitations, Portuguese tech company Nanolabel has developed a new treatment process that it claims is far superior to traditional technology.
Known as NANOMOSKI, the process involves impregnating textiles with amorphous silica (silicon dioxide) nanoparticles. Immobilized in the pores of these particles is a “non-toxic active substance” that isn’t too popular with the mosquitoes. In tests performed at Lisbon’s Institute of Hygiene and Tropical Medicine, that substance repelled 81 percent of Anopheles gambiae mosquitoes, while keeping 89 percent of them from feeding. By contrast, textiles treated with microencapsulated DEET (which is definitely not non-toxic) had a repellency index of 40 percent, and a feeding inhibition of 65 percent.
While Nanolabel is keeping the identity of the active substance under wraps, the company claims that it has been in use for over 30 years, and “is proven biocompatible and is classified by EPA with the lowest degree of toxicity (grade IV) in all categories.”
The silicon dioxide is essentially just sand, and is environmentally innocuous. The particles are larger than 100 nanometers, which puts them well above the size of permeability of human skin – or that of other animals that have been tested.
In a conventional finishing process which can be conducted at regular fabric-dying facilities, the nanoparticles are reportedly deposited into the material, as opposed to just adhering to the outer surface of its fibers. In lab tests, this allowed the particles to remain in the material for up to 90 washes – although by that point, the repellant content was down to 35 percent. That said, according to the company, a maximum of 40 washes is presently considered "good" for conventional anti-mosquito-treated clothing.
Corporate buyers are currently being sought for the technology.