A smart material actuator comprising a mechanical amplifier with a fixed supporting member, at least one mountable actuating arm, and mechanical web having at least one compliant member attached to the mountable arm and a movable supporting member. A piezoelectric stack is affixed between a first mounting surface on the fixed supporting member and a second mounting surface on the movable supporting member. With the fixed supporting member being substantially rigid, and the piezoelectric stack being affixed between the first mounting surface and the second mounting surface, which are substantially parallel, applying an appropriate electric potential to the piezoelectric stack will cause it to expand substantially without angular movement. The expansion urges the second mounting surface away from the first, thereby causing the compliant members of the mechanical web to flex, thereby moving the mountable actuating arm. The configuration of the web and the length of the mountable arm cause the actuating end of the arm to move across a distance greater than the expansion of the piezoelectric stack. In this way, the expansion of the stack is effectively amplified by the mechanical amplifier. Actuators of this type may be used both to create mechanical motion from electrical energy and to harvest electrical energy from mechanical motion, or sense the degree of such motion. A number of arm designs and means of attachment to external components are disclosed, in addition to methods of generating electricity from mechanical motion and generating vibration using such actuators and methods of tuning the resonant frequency and increasing the efficiency of energy harvesting through resonant operation.