Why do feet smell? How do chemists help to provide a solution to the problem? Why do modern washing practices make the smells worse than they used to be? What have bacteria got to do with it? In this activity you will find out how chemists are helping to solve an unpleasant problem and investigate for yourself how preventing smells is linked to acids, bases and neutralization, bonding, reversible reactions and nanotechnology.
Your clothes are next to your skin. Your skin produces oils and sweat, which end up on your clothes. On its own this mixture does not smell bad (in fact, scientists think that sweat contains chemicals called pheromones which help to attract members of the opposite sex). The smell arises when bacteria are present. Bacteria live on both your skin and your clothes and they thrive in these environments.
In low numbers these bacteria are not a problem as they are mostly harmless and unnoticeable. However, as the bacteria multiply they produce waste products and these can be substances which have an unpleasant smell. A bacterial population above about 105 (100 000) per gram of clothing will produce a noticeable smell. A population of 106 bacteria per gram causes a medium smell and above 10/8 per gram there will be a strong smell. Look at the picture below of T-shirt fibers.
Now look more closely:
If you look at the middle of the photograph above, you can see that there seems to be some damage to the fiber. This is not visible to the naked eye. Look at the fiber in close-up:
It is still hard to tell what the damage is caused by. The next photograph should help:
A colony of bacteria is living on the t-shirt fiber. The bacteria glue themselves to it and form a ‘bio-film.’ This bio-film is very difficult to remove and can remain even after washing.
Modern washing practices have not helped this problem. A few years ago it was common to wash many items on a hot wash (60 °C or above). Now, most clothing is washed on a cool cycle at 40 °C and many new fabrics cannot be washed above this temperature.
Scientists have been working on a solution to this problem for a number of years. They have designed silver nano particles that manufacturers can blend into the yarn to help prevent bacterial growth. This yarn was given the trade name Siltex. Siltex will continuously emit the silver ions to disintegrate the germs molecular structure eliminating by the same hydrogen in their DNA. It does not have the same effect on human cells so it is safe to use in contact with the skin.
Once the bacteria are dead they can no longer produce smelly chemicals and the fabrics smell fresh for longer. They still need to be washed, but perhaps not as often.
All DTMX funky odorless urban socks have antiseptic and deodorizing (anti-odor) effects resulting from the suppression of the growth of various bacteria and fungi. The antibacterial effect is permanent and can not be removed by washing.