The Piezoelectric Effect
Piezoelectric materials have unique atomic structures that enable them to generate an electrical charge when mechanical stress or vibration is applied to it. This is known as Direct Piezoelectric Effect. The materials can also change in size or shape when an electric field is applied, which is known as the Converse Piezoelectric Effect.
Piezoelectric materials can be naturally occurring, like quartz, or they can be synthetically manufactured like Lead Zirconate Titanate or PZT. Synthetic piezoelectric materials exceed the properties of those found in nature. Many piezoelectric devices are made of the same ceramic materials as capacitor dielectrics.