ABSTRACT
There are plenty of fascinating materials in the world, and we still see many new materials invented almost every day-largely driven by the needs for new materials from a variety of engineering applications. One group of materials can respond accordingly to a particular stimulus by means of altering certain physical or chemical properties. The types of stimuli include heat (thermo-responsive); stress and/or pressure (mechano-responsive); electrical current and/or voltage (electro-responsive); magnetic želd (magneto-responsive); change of pH, solvent, or moisture level (chemoresponsive); light (photo-responsive); and other factors.
