One of the many distinctions between the human genders is in the way we evaluate whether an item of clothing needs to be laundered. If a woman has worn the garment since it was last washed, it’s dirty. A man will smell it first, and if his eyes don’t water and his nose hairs don’t liquefy, it can be worn again. A process discovered and published by a team of chemists at the University of California, Davis could make that test unreliable.
The technique binds 2-anthraquinone carboxylic acid (2-AQC) to cotton fibers used to fabricate clothing. 2-AQC is photosensitive, meaning it reacts to light, in this case, sunlight or ultraviolet. When 2-AQC is exposed to light, it produces “reactive oxygen species” of oxygen, superoxide radicals and hydroxyl radicals, which combine with water to form hydrogen peroxide. Hydrogen peroxide (H2O2) is a commonly-used disinfectant, available at any drug store.
Here’s a warning: if you have a weak stomach or haven’t had lunch yet, you might want to switch over and see what the Police1 news page has to offer. This next part... well, ain’t pretty.
The Wearable Petri Dish
Sweat socks don’t stink solely from perspiration. Bacteria such as E. coli and S. aureus live on our skin and in other places you don’t want to think about, and slough off onto the fibers of our clothes. E. coli is the bug that makes you sick if it gets into your food; one variety of S. aureus causes necrotizing fasciitis and is better-known as “flesh-eating bacteria.”
Sweat produces the nice moist environment they like in order to propagate, and the oils from sebaceous glands and dead skin particles provide nourishment. Before long, you’ve got a wearable Petri dish of microbes sitting at the bottom of your gym bag. The smell comes from the metabolic byproducts of the bugs’ conversion of your leavings into more bugs—in essence, bacterial poop.
The chemists who developed the 2-AQC process saturated cotton fabric treated with 2-AQC and an untreated control sample with suspensions of actively growing E. coli and S. aureus, and then irradiated the fabric with UV light for an hour. The microcritters were fruitful and multiplied on the untreated control fabric, but were 99.99 percent eliminated on the treated sample. As a bonus, they also found that the treated fabric detoxified aldicarb, a commonly-used pesticide.
This development is of special interest to the military, since troops in combat can go for weeks having to wear the same uniforms, unable to wash themselves, much less their clothing. Reducing the bacterial load in the fabric will do more than just make everyone smell a little better. Major trauma is responsible for most battlefield casualties, but you’re just as dead if you succumb to an infection from a small cut or blister. All of us suffer from small wounds we get here and there, and anything that can reduce the likelihood of infection is a big plus.
It’s not likely we will ever get away from having to launder our clothing. Dirt that gets caught up in the fibers frays them and gradually wears away the fabric. Washing clears those contaminants and makes the garment last longer. Even if you don’t care how badly your “undies” stink, the people who have the adjacent lockers will.
References
Liu, N., Sun, G., and Zhu, J. Photo-induced self-cleaning functions on 2-anthraquinone carboxylic acid treated cotton fabrics. J. Mater. Chem., 2011, 21, 15383–15390.
