Smart materials are those that change in response to changing conditions in their surroundings or in the application of other directed influences - such as passing an electric charge through them.   Modern products increasingly use them as imaginative designers see the potential they offer.  Shirts that change colour with changes in temperature and thermometers that are in the from of printed strips use thermochromic inks whilst Photochromic inks respond to changes in light conditions.  Clothing also uses inks that have this characteristic and have patterns that change with altering light conditions.

Materials that respond to an electric current might be used as component parts of safety valves or as a part of a functional system that uses the change in shape with current to trigger some other process, 
These are 'shape memory alloys' (SMA)

Thermoelectric materials again use current but change temperature - in this way cooling or heating can take place and this effect is being used to design innovative