Pre-stressed piezoelectric unimorphs are widely used in many engineering field due to their good actuation performances. They are manufactured by using stress mismatch of adjacent layers, which results in the domed shape and internal stress profile of the piezoelectric layer. The internal stress of the piezoelectric layer can affect the actuation performance of the pre-stressed piezoelectric unimorph significantly. This paper investigates the effect of mechanical pre-stress on the piezoelectric actuation characteristics, and evaluated the actuation performance of a new pre-stressed actuator developed by the present authors, PUMPS, considering the internal stress effects.

This paper proposes a new fabrication method for a curved shape piezoelectric actuator. Instead of using thermal coefficient mismatch, which has been used for conventional processes for curved shape actuators, we used pre-stressed substrates and the room temperature adhesion process. First, a substrate material is strained in the longitudinal direction, and then a piezoelectric material is attached on the substrate. A difference of the mechanical strains between the substrate and the piezoelectric layer makes the final manufactured actuator get curved. Using this method, the curved shape actuator can be easily fabricated at room temperature. Several performance tests of the proposed unimorph actuators were accomplished and the test results showed the proposed actuator got comparable actuation capability compared with conventional curved shape actuators.