Wednesday, April 02, 2008

Self Cleaning Clothes - What to Wear This Summer?

Whether you're extremely environmentally conscious or just plain lazy, self-cleaning clothes are a good thing for everyone. Except those of us that gain comfort and confidence from the intense sanitizing power of the traditional washer-dryer. No one can tell me I don't smell pine fresh if I know my clothes have just gone through the wash cycle. Self cleaning clothes leave things a bit more debatable; but it is true that self-cleaning material would benefit energy guzzling humans in more than one way.

Researchers announced in a February 2008 issue of the journal Chemistry of Materials that they have now found a way to coat wool with nanoparticles of titanium dioxide, making the fabrics essentially self-cleaning. The technology was developed in 2004, but could only be bound to cotton. Next on the way will hopefully be silk and hemp.

This particular type of self cleaning is achieved by leaving the fabrics in the sun. The titanium dioxide is a photocatalyst - so exposure to UV light causes it to burn organic materials, like food and bacteria. The burning occurs at room temperature, so no damage comes to the wearer or the material. In fact, the researchers say the particles may actually make the materials stronger, so they last longer when they are washed traditionally.

The images represent wool with three different degrees of saturation in the nanoparticles. The bottom three images shows the wool fully coated and modified to be self-cleaning, with a red wine stain initially (left), after 8 hours (center) and 20 hours (right). The top is without nanoparticles, and the middle is with nanoparticles unmodified.

The key question remaining is how the titanium oxide burns organic materials like food and wine, but not organic materials like wool, cotton, or skin. Any ideas would be great.

Because of the anti-bacterial nature of the newly coated fabrics, it's likely that the self cleaners will first make their way into hospitals. But I imagine there will be difficulty trying to convince the health board that hospital workers should not wash their clothes. Assuming they still wash the hospital wear, that kind of defeats the enviro-friendly aspect of the clothes. However, it it might make a difference in stopping the spread of bacteria in hospitals.

LiveScience reported in January 2007 that killing bacteria was the driving force behind another self cleaning method, now used by soldiers to protect against bacterial infections. The Air Force developers went straight for the gut when the created underwear that doesn't need washing. Serious consumer marketers should probably consider ties first.

Apparently the Air Force's approach is working well. Jeff Owens, one of the researchers who developed the technique said "During Desert Storm, most casualties were from bacterial infections-not accidents or friendly fire. We treated underwear for soldiers who tested them for several weeks and found they remained hygienic. They also helped clear up some skin complaints."

The article doesn't specifically mention how this particular method is achieved. What it does say is that nanoparticles are attached to the fabric using microwaves. Then bacteria-, dirt-, and oil-repelling chemicals are bound to the nanoparticles. What chemicals they use, or exactly how they then make the material self-cleaning is left to be guessed. Other reports said the technology would be introduced into sports wear, but I haven’t heard anything about it since.

But wait! It gets weirder! Rather than eradicating your clothes of bacteria, how about implanting them with it? Researchers have experimented with planting a harmless strain of E. coli in clothing fibers, giving the bacteria the chance to feed on whatever falls on the clothes. Right now, they're still figuring out whether or not the bacteria could survive on the irregular diet, and how long it would take them to clean up an average stain, and how they are ever going to market this to anyone. I shouldn't judge - as the researchers point out, we are actually crawling with microorganisms and bacteria even after a shower and an old-school clothes wash. As long as I couldn't feel the shirt moving, I suppose I'd give it a try. Then again - there's always the slight possibility than an underfed shirt could start to feed off of its wearer.

But one often overlooked aspect of our daily energy consumption is in the water and heat used by the washer and dryer. You can buy more ecologically friendly washers and dryers, but there's also the waste product to consider. Suds from most types of detergent don't mesh well with natural ecosystems. So maybe self-cleaning clothes represent a step into the future - and particularly, a future where technology actually leads to lower energy consumption.


1 - Courtesy of New Scientist:

2- Self-Cleaning Keratins
Walid A. Daoud, S. K. Leung, W. S. Tung, J. H. Xin, K. Cheuk, and K. Qi
Chem. Mater.; 2008; 20(4) pp 1242 - 1244;

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