Novel Low Voltage Piezoactuators for High Displacements

To improve the performance of piezoelectric actuators, new 3-D designs were developed to gain higher displacements or specific bending effects. Such 3-D actuators of e.g. helical structure have next to the standard actuator or sensor applications the potential to be used in Hi-Fi digital sound projectors. To lower the voltage of the power supply for these miniaturized devices, multilayer structures based on thin tapes must be used. Two processing routes to manufacture helical shaped multilayer PZT structures with specific electrode designs are tested. One route starts from tape cast PZT green tapes of 90 μ m or 50 μ m thickness, the other from extruded and stretched PZT filled thermoplastic films (Solufill™) of 9 μ m thickness. The properties of these two films are compared. The sheets are screen printed and laminated similar to standard planar multilayer processing. To manufacture helical three-dimensional multi-layers from these laminates new processing techniques are required. The most important difference compared to planar multilayer processing is the necessity to bend the laminated structures. The bending behavior depends on the layer thickness, the number of layers, the diameter of the helix and the flexibility of the tape. In addition, specific measures have to be taken to ensure that the bent multilayer keeps its shape and keeps the alignment of the electrode design during binder burnout and sintering. Finally, working products of super-helical structure suitable for miniaturized loudspeaker application are built and tested.