Bender Type Actuators (Bimorph and Multimorph Design)
A PZT bimorph operates similarly to the bimetallic strip in a thermostat (see Fig. 45). When the ceramic is energized it contracts or expands proportional to the applied voltage. Since the metal substrate does not change its length, a deflection proportional to the applied voltage occurs. Bimorph actuators providing motion up to 1000 µm and more are available. In addition to the classical strip form, bimorph disk actuators where the center arches when a voltage is applied, are offered.
PZT/PZT combinations, where individual PZT layers are operated in opposite modes (contraction/expansion), are also available.
Two basic versions exist: the two-electrode bimorph (serial bimorph) and the three-electrode bimorph (parallel bimorph), see Fig. 46. In the serial type, one of the two ceramic plates is always operated opposite to the direction of polarization. To avoid depolarization, the maximum electric field is limited to a few hundred volts per millimeter. Serial bimorph benders are widely used as force sensors.
Monolithic multilayer-type PZT benders are also available. Similar to multilayer stack actuators, they run on a low operating voltage (60 to 100 V).
Bender type actuators provide large motion in a small package at the expense of stiffness, force and speed.
Example:
P-286 - 289 disk translators
PL122 multilayer bender actuators
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