June 14, 2004
Dirty Clothes To Be Cleaned By The Sun

"But Mom, its not my fault I'm dirty. Its cloudy today."

Scientists have invented an efficient way to coat cotton cloth with tiny particles of titanium dioxide. These nanoparticles are catalysts that help to break down carbon-based molecules, and require only sunlight to trigger the reaction. The inventors believe that these fabrics could be made into self-cleaning clothes that tackle dirt, environmental pollutants and harmful microorganisms.

Hong Kong Polytechnic University researchers Walid Daoud and John Xin baked 20 nanometer titanium dioxide particles into clothes for 15 minutes to create cloth that can be cleaned by standing in the sunlight. I like efforts to achieve better living through materials science. Not sure if this approach is wise though.

The first potential problem here is that when hit by photons the materials generate oxygen free radicals. Well, do you want to wear clothing that generates oxygen free radicals? It might accelerate the aging of your skin. Also, some of the oxygen radicals may react with O2 to form O3 ozone gas. It would be like walking around in a microenvironment that is like Los Angeles on a bad day (or Bakersfield or Fresno even more often). You wouldn't want to stand still too long since in order to avoid clothing pollution.

The other problem with this approach is that the oxygen radicals would probably damage the cotton fibers. Cotton is made from cellulose which is a polymer of glucose sugar. That polymer can be damaged by free radicals. So the clothing might wear out faster.

Self-cleaning clothes will be developed eventually. Though it is not clear that this approach is the one that will ultimately succeed.

Share |      Randall Parker, 2004 June 14 12:17 PM  Materials Advances

TangoMan said at June 14, 2004 1:29 PM:

That polymer can be damaged by free radicals. So the clothing might wear out faster.

Planned obsolesence - just what any capitalist desires in a product. They can charge a premium for the cloth because of the convenience factor and quantity sales will increase per person :) as the cloth wears out.

TangoMan said at June 14, 2004 2:07 PM:

Randall, your post on solar energy cleaning fired off a few synapses in my head and I remembered a post I made to a group about this guy in India who doesn't eat food and lives off of the sun and that NASA was studying his technique.

Totally bizarre and the skeptic in me is asking what's going on and why is NASA devoting money to this. I never followed it up to see how the hoax was debunked (sure solar might provide caloric energy in some fashion but where would he get nutrients?), so here are the source articles. Enjoy!

sammy said at June 14, 2004 2:35 PM:

there's a self-cleaning window that uses the same idea--titanium oxide nano-coating. it's called "pilkington aktiv"


it seems to make more sense for windows rather than clothes.

gmoke said at June 14, 2004 8:31 PM:

Sounds like Alec Guinness in The Man in the White Suit. I've heard that titanium dioxide is white and Alec Guinness' attempt at a self-cleaning, indestructible suit in that movie is blinding white. As the mob of workers afraid his invention is going to put them out of work and the mill owners who want to quash his invention to keep their factories worth something reach for poor Alec cornered in an alley, the material of the suit comes apart in their hands - accelerated wear, just as predicted.

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