Smart Materials

Smart materials have properties that change depending on external conditions like temperature, light and electricity. Some smart materials that are already being used include:

Shape Memory Alloys

Viscoelastic Compounds

Piezoelectric Materials

Quantum Tunnelling Composites

Colour Change Materials

Most materials have a limited memory because of their elasticity. When they are stretched they go back to their old shape, however when they are stretched or bent further they stay in the shape they have been moulded to. If a part is made of SMA and it is bent out of shape it must be heated to above its transition temperature it returns to its original shape. The transition temperature is the temperature at which it changes from rubbery condition to a hard one. This cycle can be repeated many times. SMAs can be formed into most shapes, the most common one being an allow of nickel and titanium which has a transition temperature of 70 degrees, reaching this temperature can be reached by passing an electric current through the material or by directly heating it.

Viscoelastic Compounds are a type of smart liquid which is normally soft and mouldable although if they are suddenly hit or impacted they act like rubber and become bouncy. They are used to make toys like silly putty, they can also be used to change the way vehicle suspension systems respond to sudden movements.

Piezoelectric Materials do not conduct electricity but when squeezed quickly they create electricity for a moment. If electricity is put across the material there is a slight change in change. An example of this material is quartz. There are many Piezoelectric Materials that have been created including polymers and thin-film ceramics. They can be used for microphones, loudspeakers, electrical generators and sensors in alarms.

QTC is a flexible polymer that contaisn tiny metal particles. It is an insulator but when squeezed it becomes a conductor that can pass high currents. It can be used to make membrane switches (a switch that turns an electrical circuit on and off) in mobile phones, pressure sensors and speed controllers.

Thermochromic material are materials that change colour when the temperature changes. The colour changes occur because of liquid crystal technology. This can be used for plastic strips that indicate temperature, test strips on the side of batteries, packaging materials that show you when the food has been cooked to the right temperature and colour indicators on cups to show whether the contents are hot. Photochromic materials change colour depending UV light and are used for things liek nail varnish, jewellery, security markers and mobile phone cases.