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Smart Materials 2Resistant Materials
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Learning objectives
By the end of this unit, you will:
Know about some of the properties of different smart materials.
Be able to name different smart materials.
The key concepts covered are: Cultural understanding Creativity.
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Thermochromic materials
What applications can you think of for thermochromic materials?
Thermochromic materials react to changes in temperature.
Tiny capsules in thermochromic ink contain liquid crystals. As the temperature changes these crystals move. The reorientation of the crystals causes a change in colour at a specific temperature.
This sensitivity causes them to temporarily change colour when they are exposed to heat.
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Photochromic materials
What other applications can you think of for photochromic materials?
Photochromic materials are sensitive to exposure to light.This causes them to undergo a reversible change of colour when exposed to a certain amount of light.
Photochromic lenses become dark when they are exposed to UV radiation.Once the UV radiation is removed, the lenses gradually return to their normal state.They can be made of either glass or plastic.
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Thermo or photo?
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Shape memory alloys change shape at set temperatures.
Shape memory alloys
What applications can you think of for shape memory alloys?
One of the most common alloys is a combination of nickel and titanium. This shape memory alloy can be treated so that when it reaches a set temperature it contracts.When it cools it then returns to its original shape.
They become deformed once heated above the transformation temperature, but regain their shape as they cool.
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Shape memory alloy wire is called smart wire as it remembers its shape.
When a small electrical current passes through the wire it becomes smart.It remembers to change shape.The wire becomes shorter.This shortening can be used to control a robotic hand.
Shape memory alloys
In the future, this may help scientists produce artificial motion that is more similar to the range of human movement.
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Piezoelectric
What other applications can you think of for piezoelectric materials?
Piezoelectric materials have the ability to generate an electrical charge.
A mechanical stress is applied to the smart material.This causes a small electrical charge to be generated.In return, the shape of the solid changes by a small amount.
A car’s cigarette lighter is a good example of how piezoelectric materials are used in a every day application.
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Magnetorheological
What future applications do you think magnetorheological fluid will be used for?
Magnetorheological fluid is a type of smart material that has the ability to change state when placed in a magnetic field.
These fluids are composed of iron-like particles.In their normal state they are fluid.When placed in a magnetic field the particles are attracted to each other and join up to form a solid.
Currently, these materials are not widely used. It is thought of as a more futuristic smart material.
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Fill in the gaps
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Granules of polymorph become amorphous and mouldable, like plasticine, when put in hot water (at 62°C).
Polymorph is a smart material which is used for prototypes and models in technology.
Polymorph
It is an ideal material for using in vacuum moulding.
Polymorph can be reheated and reformed many times.
When it hardens (at 30°C) it becomes like polythene but stronger, stiffer and tougher.
Can you think of any more uses for polymorph?
