What is the piezoelectric effect?
Piezoelectricity is the ability of certain crystalline materials to convert mechanical energy into electrical energy and vice versa.
The direct piezoelectric effect is that these materials, when subjected to mechanical stress, generate an electric charge proportional to that stress. An example of the use of the direct effect is found in gas lighters. Piezoelectric sensors, like acceleration sensors and pressure sensors, also exploit the direct piezoelectric effect.
The inverse piezoelectric effect is that the same materials become strained when an electric field is applied, the strain again being proportional to the applied field. An example of the use of the inverse effect is found in buzzers. Piezoelectric actuators, which can be used for micro-positioning, also rely on the inverse piezoelectric effect.