Science Interviews


Sun, 26th Feb 2006

Stamping Out Stinky Socks With Nanoparticles

Neal Morgan, Cambridge University

Part of the show The Science of Nanotechnology

Chris - Now you've all been waiting for this! The nanotechnology behind smelly feet! But there's a serious side behind this too isn't there Neal?

Neal - There is. This is basically to do with nanoparticles and more importantly, functional nanoparticles. A group in ETH Zurich University in Switzerland came up with idea of mass producing lots of silver oxide nanoparticles. These are basically very tiny particles of silver oxide.

Chris - How tiny?

Neal - We're talking anything from a few molecules up to a few thousand nanometres. So basically we're talking a billionth of the size of the coffee cup in front of you there. The purpose of these particles being so small is that their surface area to volume is incredibly high, which makes them incredibly reactive. Silver itself is very good at killing bacteria, so the idea of this spin - off company was to mass produce silver nanoparticles which would then be put into socks. When you put your socks on, the bacteria which would cause the nasty smells would be killed off and hopefully you won't have smelly feet.

Chris - A few foot facts for you: the average person sheds about 40 000 skin cells every single minute, which over a lifetime will weigh about three or four stone in dead skin. The sweat glands in your feet squirt about a litre and a half of sweat into each of your shoes on a roughly daily basis. So if you put the two together, you get a pretty stinky combo. It's interesting about silver. Do you know why it has this profound antibacterial effect?

Neal - I'm afraid I don't specifically know why, but I know that lots of companies are investigating this and I believe one of the big plaster manufacturers has started to put silver into their plasters for specifically that purpose. This makes specific antibacterial plasters for cuts and grazes.

Chris - It['s easy to think of this as a new technology, but it's not though is it? There's evidence that the ancient Egyptians knew about this because they used to put silver into some of their drinking water because they knew it killed bugs. Of course, water-borne illnesses cause a hell of a lot of problems where you've got sun, people and pollution all coming together to give people food poisoning. So tell us about these socks a bit more. How do you actually attach the particles onto the fabric so that when you put the socks through the wash, they don't all fall off?

Neal - The particles themselves are then incorporated into the dyes so you'd mix them up with the dye products and they become suspensions of these particles. When you spray that onto the fibres they become intertwined with the cotton and that's why they don't just fall out and give you piles of silver nanoparticles in the bottom of your shoes.

Chris - One other spin-off from that is that someone said that they were going to make paint which could tackle smoke problems. So if you had a pub and lots of people smoke in there, you can have this paint which mops up and neutralises tobacco smells. Someone else suggested that a sports bag could also be treated in the same way as the socks.

Neal - And there was research I was reading on the BBC science website the other day where an Australian group has developed a new form of titanium nanoparticles which are doped with another chemical, which I think was vanadium. You may have heard about self-cleaning glass. The way it works is that you have a very thin layer of titanium dioxide on the surface of the glass. This can oxidise chemicals very rapidly under the presence of UV light. Now that's all very well and good for window panes which are exposed to natural sunlight. But this Australian group has shortened what is known as the band gap, which is basically what frequency of light makes these particles active. They have been able to reduce it down to light frequencies very similar to the natural lighting in your bathroom. So for instance, if they can develop this technology further, you basically get paints and tiles in your bathroom that are self-cleaning under your bathroom lights.

Chris - Well wouldn't that be fabulous! My wife would be delighted.


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