Saturday, 3 November 2012

Clothes for a cleaner future

One thing that all seven billion people possess is clothing. If this could be made to perform some function which helps the environment it could significantly compensate for the damage we do as human beings.
Moves in this direction are currently underway and not too far from the shops.

Denim which absorbs Nox

Nitrogen mono-oxide and nitrogen dioxide are atmospheric pollutants produced by traffic and factories. Generically they are known as NOx and they damage both health (nausea, irritated eyes, respiratory problems) and the environment (acid rain, global warming, inhibition of plant growth). They can also react with aerosols from cans in a harmful way.

 Since over half the world population live in cities it is becoming increasingly important to remove them from the air.

The natural world provides us with the means: titanium dioxide, which is found mainly in two kinds of ore – ilmenite and rutile – and is used in catalytic converters to remove NOx from engine exhaust gases, as well as in paving stones, glass and sun cream. A small company in the UK called Catalytic Clothing discovered that by spraying nanometric titanium dioxide particles onto denim they had invented a form of clothing which absorbs NOx from the air. The more the clothing is subjected to movement while being worn the more NOx is absorbed and converted into harmless water soluble nitrates. Presumably, someone jogging in titanium oxide coated denim clothes would extract more NOx the faster they jogged.

The most encouraging thing about this development is that it is not far from market. ‘Field of Jeans’ has just been exhibited at the Manchester Science Festival, UK (27 Oct – 4 November, 2012).

As well as making new clothes with the specially coated denim (and other materials?) the same company is working with the detergent company Ecover to produce a washing powder additive called CatClo. If this became universally available and could work on other fabrics as well as denim the benefit to city air quality could be considerable and in the near future.

Converting pressure, heat and sunlight into electricity

These products could be on the market within 2-3 years. If they took off it might speed up the manufacture and marketing of piezoelectric clothing and shoes. A lot of research is going on in this area. The idea is to utilise the piezoelectric effect by which pressure on a material is converted into electricity. When a person moves it causes pressure to build up in parts of the clothes worn and this pressure can be used to power small electronic devices such as mobile phones or batteries. Pressure in the soles of shoes can also be used to generate electrical power as the person walks. See, for example,

This would indirectly benefit the environment by reducing the need to make batteries, a very energy intensive process which generates waste and global warming emissions.  The pioezoelectric effect is already being incorporated into fashion designs.

The thermoelectric effect could also be used. This is the conversion of differences in temperature across the interface between two different materials into an electric voltage. E.g. the inside of a shoe being worn is hotter than the outside. The same principle of deriving electricity from heat  could be used wherever otherwise wasted heat is available - a hot water pipe for instance. The solar voltaic effect – by which sunlight is converted into electricity, is another possibility.

Hydrophobic clothing

There have been startling developments in spray-on technology to make fabric able to completely repel water. The same method can be used to make all sorts of equipment fully water proof e.g. by applying hydrophobic coatings to the outside and inside of a mobile phone it will still work underwater as long as the signal is strong enough. Hydrophic clothes  help the environment by reducing, if not eliminating, the need to clean them.

author of  the novel 2077 AD which is now being revised and expanded
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