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Fart neutraliser!

What makes a material smart?

Well, they can’t play computer games, that’s for sure!

Why are they smart then?

In short: ‘A smart material is any material that can significantly change one of its properties in response to an external factor’.

Sounds complicated right? So what does it mean? OK, how about a material that can spring back to its original shape even if you twist it out of shape, hit it or even sit on it?

Well, sitting on your glasses is no longer such a problem! Nitinol, memory metal, is probably the most well-known smart material. Making glasses out of this material can be very useful. For example, if you sit on your glasses all you have to do is warm them up by holding them under the hot tap, and they twist themselves back into their original shape. This saves quite a few quid on specs!

And clotted arteries? No problem!

Stent

Nitinol is really good for surgical stents too.

A surgical what?

A surgical stent is a fine tube of wire mesh used to open narrow arteries. The cooled stent is placed inside the narrow artery. As the blood flows back into the artery the stent is warmed up. As it warms up the stent changes its shape to form a small, strong mesh tube that stops the artery from becoming blocked.

Can they make fire?

Well kind of. Some materials, like crystals and some ceramics, can produce an electric voltage. This is how a piezoelectric gas lighter works. When you press the trigger a small spring-loaded hammer whacks the crystal. This produces a big enough voltage to make a spark that will light a gas ring.

What have smart materials go to do with UFOs?

Nothing really, but bust before big earthquakes there are often many sightings of lights in the sky. Some people think these lights are UFOs. Scientists now think the lights may be the result of piezoelectric crystals in the rocks being squashed and producing big discharges of lightening!

Lights earthquake

Can we use these materials to our advantage?

Yes! We use piezoelectric materials in all sorts of things:

Piezoelectrics

Piezoelectric microphones

Piezoelectric microphones work in just the same way. Sound is a series of pressure waves. In a microphone the pressure changes are picked up by thin foil which vibrates in time with the sound waves and in turn squashes a tiny piezoelectric crystal. This produces electricity in time with the sound waves. Brilliant and very simple!

Piezoelectric loudspeakers

The piezoelectric effect also works the other way round. This means if you put a voltage across the crystal it will change its size. This is how a piezoelectric loudspeaker works. The beeping sound produced by the alarm on a digital watch will be produced when an ac voltage is placed across the crystal. It grows and shrinks in time with the AC. This produces a vibration that we hear as a beep. It’s most important use is in ultrasound scan machines, where tiny piezo loudspeakers are used to produce the sound and piezo microphones are used to receive it.

Forget the sound equipment, and the specs, what about smart glass?

Smart Glass

Smart glass is really clever stuff. Placing a voltage across it completely changes the way it lets light through. One minute it can be perfectly clear, like window glass, the next it is completely frosted so you can’t see though it. This could be really useful in so many places: imagine being able to press a button to turn the sun down!

Windows to mirrors!

Wouldn’t it be interesting if you could turn any window into a mirror at the touch of a button? Well, you can if you use transition metal glass. Billions are spent keeping buildings cool using air conditioning, but it would be better to stop the building overheating in the first place.

Switchable mirrors can do just that. What’s more the latest materials can selectively switch different wavelengths. This means you can press the button and switch the windows to reflect the long wavelength infra red light that gets the building hot, but still let visible light though so you don’t have to pay lighting bills. Now that really is smart! If you want to see this technology in action just put ‘Transition Metal Switchable Mirror’ into ‘YouTube’.

No sweat, Starfleet style!

The last time you bought a jumper or jacket you probably looked at the cut, colour and price. Soon you’ll be making a lot more choices than that! Material technologists around the world are making fabrics that can keep us warm, cool, dry, moisturised and even bacteria free!

Think back to Star Trek. Have you ever noticed that the crew only ever wear their Starfleet issue tee-shirts no matter where they end up? Their tee-shirts are smart indeed: they can keep their temperature even on freezing or tropical planets! And, they never get sweaty! Only the Klingons get body odour!

The oldest smart material

Wax Jacket

The oldest smart material was a waxed jacket. As it gets hot, paraffin wax melts and allows heat to escape. As it gets colder it solidifies and keeps some of the heat in. New polymers are being developed that do the same trick, but are much more effective. These can change from being good insulators at low temperatures to being conductors at high temperatures.

Electric socks

By attaching a small power supply you can keep your toes at a snugglesome 30oC. This would be really useful if you are a mountaineer or polar explorer where frostbite nibbles off toes.

Smell, no farts!

Smart fabrics aren’t just good at keeping us toasty; they can be treated with chemicals that can kill bacteria. No more nasty niffs! A company in the USA even sell fart-neutralising underpants. It has a strategically-placed carbon triangle that filters out offensive gases as they pass through. Mmmm….handy Christmas presents!

Old underwear

Oobleck’s. Ooh what! – Non Newtonian fluids

Most fluids are Newtonian. This means that they always ‘flow’ when they are at a temperature between their melting point and their boiling point. Water is a good example: it freezes and boils at extreme temperatures but is a liquid between these temperatures.

Some liquids are non Newton. They are often called Ooblecks after the goopy stuff in an old Dr.Seuss book called Bartholomew and the Oobleck. This means that they sometimes flow but sometimes don’t, depending on what you do to them. The classic Oobleck behaves like a liquid if you treat it gently, but a solid if you hit it hard. A simple Oobleck is really easy to make.

Oobleck recipe

Mix 1 part water with 1.5 to 2 parts cornstarch (custard powder!).

Start with one cup of water and one and a half cups of cornstarch, then work in more cornstarch if you want a more 'solid' oobleck. It takes about 10 minutes to get a really good Oobleck.

Put Oobleck into ‘u tube’ to see home-made Ooblecks in action. It really is worth making one as they are a lot weirder to handle than you would expect!

Walk across a swimming pool!

Walk across lake

The classic experiment is to fill a small swimming pool with Oobleck and challenge people to get across it. The trick is to run. If you feet hit the Oobleck hard it will support your weight. If you are tentative or slow it behaves like a liquid and you sink.

Bullet-proof vests?

Definitely! One of the things Ooblecks may be useful for is making bullet-proof vests. Traditional bullet-proof vests are heavy and very rigid. This has always made them difficult to wear. Imagine a vest with a layer of Oobleck. It would be soft and flexible to wear, but would turn into an impenetrable solid when struck by a bullet. Not a bad idea.

Can you think of any other applications for Ooblecks?

My own personal ‘must have’ Oobleck, speaking as a cricketer, would be Oobleck lined underpants.

Project

Can you make a device that uses a smart material? What about an automatic light or a temperature sensitive switch?

The big questions:

What makes a material ‘smart’?

Why are smart materials important?

Are there different types of smart material?

Can plastics, metals or even liquids be smart?

What is an Oobleck and how can you make one?