Smart – or shape memory – materials are an invention that has changed the world of engineering. there are two types: metal alloys 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 react to changes in their environment, for example: plastics that return to their original shape 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. перевод