Static and dynamic high voltage limitation of series and parallel bimorph actuators

The series and parallel bimorph actuators were investigated to identify the limiting factors at high voltage operations. In the static condition, the series and parallel bimorph exhibit polarization-shaped and three-looped hysteresis curve, respectively. The parallel bimorph shows much larger magnitude of saturated and remnant polarization than the series bimorph. The series bimorph is mainly restricted by the breakdown voltage in contrast to the parallel bimorph, which is limited by the domain reorientation. In the dynamic condition, both types of actuators are mainly limited by the maximum stress and domain reorientation. The actuator tends to fracture at the location of maximum stress near the resonance when the voltage is increased to a certain degree. Further increasing the voltage, domain reorientation may happen at frequencies lower than the resonance. Comparatively, the series bimorph has higher resistance to the domain reorientation than the parallel bimorph.