Energy Harvesting

The actuator employs a novel geometry, which produces very large movement from simple and compact structure. The actuator comprises two arms formed a single metal substrate and two piezoelectric ceramic plates. The planar disposition of the two ceramic plates mean that, unlike a conventional bimorph structure, high fields can be applied with danger of repolarising the ceramic. The first arm of the actuator produces a downward movement which provides an angle for rthe movement amplification of the second arm. The total movement is slightly less than could be obtained from a single beam of twice the length. However, the stiffness of a single beam has cubic relationship to the length, so only very low forces could be obtained this way. A key advantage of the planar bimorph structure is that it forms an effective pivot point approximately half way along the length of the actuator.

The piezoelectric ceramic is a commercial grade lead zirconate titanate. It is selected for its high d31 coefficient to achieve a large displacement in a bending actuator. The formed and compacted ceramic is sinterted, the machineed size to size. This forms a dense grain structure with typical grain sizes of 15 micrometers diameter. A metallic electrode is then applied to the ceramic. The ceramic plates are bonded to the metal substrate and electrical connections made to complete the assembled actuator.