What are smart materials?

A "smart material" is one having a molecular structure that responds in a particular and controlled way to influences upon it. These range from magnetically-changed materials, to "memory" molecules that return to their original form, to materials that generate an electric charge when pressed, twisted, or warped.

These materials can significantly change their mechanical properties (such as shape, stiffness, and viscosity), or their thermal, optical, or electromagnetic properties, in a predictable or controllable manner.

Some types of smart materials are piezoelectrics, electrostrictors, magnetostrictors, and shape-memory alloys.