Smart - or shape memory - materials are an invention that has changed the world of engineering. There are two types: metal MlttWd and plastic polymers. The metal alloys were made first and they are usually an expensive mixture of titanium and nickel.
Shape memory materials are called 'smart' because they ^^J to changes in their j, for example:
environment
• plastics that return to their liWIuiiMIshape
when the temperature changes. One use is in
surgery where plastic threads 'remember' the
shape of a knot, react to the patient's body
temperature and make themselves into
stitches.
• metal alloys that have a 'memory' and can
return to their original shape. They are used in
medical 222E21S that are Q ^J so they
can be put inside the patient's body through a
small cut. The implant then ^3EHS Dack to its
original shape. More everyday uses are for
flexible spectacle frames and teeth braces.
• solids that darken in sunlight, like the lenses in
some sunglasses.
• liquid crystals that change shape and colour.
These have been used in climbing ropes that
change colour if there is too much strain and
weight on them.
The future of these materials and their possible uses is limited only by human |E22J|J223S One clever idea is that if cars were made of smart metal, a minor accident could be repaired by leaving the car in the sun!