This piece first appeared on physics.org: http://www.physics.org/featuredetail.asp?id=57 this month (Oct 2010)…. its basically an extended version of my Intro to Nanotechnology
Nanotechnology. It’s one of those words you hear bandied about, sometimes in a slightly sinister context. But what exactly is it?
‘Nano’ comes from the Greek word for small. So, nanotechnology is just the science and engineering of the very small. But how small? Well, take an average human hair – it has a thickness of about a fifth of a millimetre. Imagine splitting that hair 100,000 times across its width. The piece of hair you’d have left would be about two nanometres (2 nm) thick. Any object between 1 and 100 nm can be called ‘nano’.
A nanometre is just a very small length measurement, and it’s that tiny size which makes nanotechnology interesting – on such a small scale, the laws of physics change, opening up new possibilities for science.
Nanotechnology is already all around us, in many of the products we buy every day. We’ve been studying it for years, so it’s not a futuristic as you might think. In many cases, Mother Nature got there first, with everything from self-cleaning surfaces to volcanic nanoparticles… We’re only just catching up!
Where might you find nanotechnology? Here are a few examples.
The sporting industry was an early adopter of nanotechnology – Rafael Nadal became Wimbledon Champion using a nano-enhanced racket. These rackets were reinforced with nanoscale Silicon Dioxide (SiO2) crystals, resulting in a lightweight frame that is incredibly stiff and strong.
Golfer Pádraig Harrington uses nano-enhanced clubs – the shaft is filled with plates of nanoceramic to increase its strength, carbon nanotubes reinforce the glue which hold the carbon fibres together. This same technology also has applications in skiing, along with other sports.
Nature has often been used as an inspiration for new materials. Lotus leaves are famously self-cleaning: their secret is that each leaf is covered in billions of nano-bumps. When water hits the leaf, it can’t penetrate between the nano-bumps, and instead, rolls off. Any dirt on the leaf is carried off in the water droplet. We’ve only just caught up – the roof of London’s St. Pancras Station is made from self-cleaning glass.
Silver’s antibacterial properties have been known for thousands of years, with the ancient Egyptians putting silver paste on wounds. These days, silver nanoparticles utilise the same property, but in a more cost-effective way. Cotton fibres can be soaked in a suspension of these nanoparticles. Their small size means that they don’t change the feel of the fabric but remain very effective in controlling the growth of bacteria. Could this be the end to smelly socks?
The beauty industry has often been accused of inventing pseudo-scientific terms to sell their products, but maybe surprisingly, the industry actually invests a huge amount of money in nanotechnology research. The active ingredient in many anti-wrinkle creams is simply vitamin A, just in nanoparticle form, which allows for faster absorption into the skin.
Almost all sunscreens are made from titanium dioxide (TiO2) or zinc oxide (ZnO), which are white in colour. Transparent sunscreens have exactly the same composition, but nanotechnology has been used to shrink the size of the particles, which changes their appearance.
Nanotechnology doesn’t just offer us luxurious lifestyle products. It can be used to make better power generation systems, so vital in our fossil-fuel dependent society.
More than 60% of the energy produced by a car engine is wasted, mostly in the form of heat. Thermoelectric materials can capture this heat and produce electricity, and by using nanotechnology, these materials can be made more efficient. Capturing wasted energy is just the beginning – batteries with nanowire-filled electrodes have been produced, and have ten times the capacity of today’s lithium-ion batteries.
What about grey goo?
One thing nanotechnology hasn’t managed to produce is the swarms of self-replicating nanobots, nicknamed ‘grey goo’, once predicted by critics. Scaling a mechanical robot down to that size is an immensely complex task, one we are far away from ever achieving. The simple truth is, in the nanoworld, friction behaves very differently – no nanobot could ever be created by accident.
Friction causes wear and eventually failure in mechanical systems, and its effect is always dependent on the contact area between surfaces. The huge surface areas and high roughness that exist on the nanoscale mean that friction may well be far higher than that predicted by classical theory. Any truly nanoscale device is therefore likely to be susceptible to incredibly high friction, meaning it won’t be long until it quite literally grinds to a halt.
You can’t talk about nanotechnology without talking about the risks involved. While grey goo scare stories may be unjustified, there are still many questions surrounding the use of nanotechnology, especially around its place in the beauty industry.
For example, as yet, there is very little known about the interaction of nano-objects and skin cells. Nanomaterials are treated as cautiously as any other class of chemicals, and so far, the results have been positive, but much more research is needed, especially on their long-term effects. UK labs are developing reliable measurement techniques for all classes of nano-objects… To paraphrase a quote by the great Lord Kelvin, only by measuring something do we truly understand it.
The moral of the story? Size really does matter, especially when it comes to physics.