The direct piezoelectric effect, that is, conversion of stress/strain into surface charges, has been widely used in sensor devices with new applications in piezoelectric energy harvesters [6-8] whereas the

inverse piezoelectric effect could be used for actuator devices [9-11].

Piezomotors are devices in which mechanical movement is achieved due to the

inverse piezoelectric effect. The materials that form the basis of such drives are called piezoelectrics.

Owing to the

inverse piezoelectric effect of the piezoelectric materials, a force applied to the fundamental structure will be induced by the voltage on piezo-patch, and the force is proportional to the voltage.

Piezoelectric elements are integrated into the main structure, the inverse piezoelectric effect is utilized, and piezoelectric elements are deformed via an external voltage, which is passed on to the main structure, thus realizing active control of structural shape.

Under the condition that the mechanical load remains constant, because of the inverse piezoelectric effect, the displacement of the structure under control can be changed by changing the driving element input voltage changes.

When considering the direct and inverse piezoelectric effect, the [PHI] generated by the mechanical effect can be given as follows according to (59):

The direct and inverse piezoelectric effects are considered for the sensors and actuators.

The Curies also realised that these same materials deformed when exposed to an electrical field, now known as the

inverse piezoelectric effect.

In actuator applications, the

inverse piezoelectric effect is used.

Piezoelectricity refers to the coupling between a mechanical stress and an electrical charge displacement (direct piezoelectric effect) or between an applied electric field and the resulting mechanical strain (inverse piezoelectric effect) (1).

This generates the corresponding direct or inverse piezoelectric effect.

It can also be defined as the strain and electrical field ratio in the case of

inverse piezoelectric effect according to the following relationship: