Basic Designs of Piezoelectric Positioning Elements: Benders, Bimorph, Disks

Bender Type Actuators (Bimorph and Multimorph Design)

A Piezo bimorph operates similarly to a bimetallic strip in a thermostat. When the ceramic is energized the metal substrate is deflected with a motion proportional to the applied volt-age. Bimorph actuators providing motion up to 1000 µm are available and greater travel range is possible. Apart from the classical strip form, bimorph disk actuators are available, where the center arches when a voltage is supplied.

Instead of a Piezo/metal combination Piezo/Piezo combinations are possible where individual Piezo layers are operated in opposite mode (contraction/expan-sion). Two basic versions are available: the two electrode bimorph (serial bimorph) and the three electrode bimorph (parallel bimorph). In the serial type, one of the two ceramic plates is always operated opposite to the direction of polarization. To avoid depo-larization the maximum electric field is limited to a few hundred volts per millimeter. Serial bimorph benders are widely used as force sensors. Instead of two plates, monolithic, multi-layer type Piezo benders are available, too. 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
P-803 Multilayer bender actuators