Properties of Piezo Actuators

Unlimited Resolution
Piezo actuators convert electrical energy directly into mechanical energy and vice versa and allow for motions in the subnanometer range. There are no friction elements that limit resolution.

Stiffness, Load Capacity, Force Generation
To a first approximation, a piezo actuator is a spring-and-mass system. The stiffness of the actuator depends on the elasticity module of the ceramic (approx. 25% of that of steel), the cross section and length of the active material, and other nonlinear parameters. Typical actuators have stiffnesses between 1 and 2,000 N/μm and compressive limits between 10 and 100,000 N. For tensile stresses, a casing with integrated preload or an external preload spring is required. Adequate measures must be taken to protect the piezo ceramic from shear and bending forces and from torque.

No Wear and Tear
A piezo actuator has no moving parts, like gears or bearings. Its displacement is based on crystalline solid-state dynamics and shows no wear and tear. PI piezo actuators have gone through several billion cycles in endurance tests without measurable changes in their behavior.

Operation at Cryogenic Temperatures
The piezo effect continues to operate even at very low temperatures close to 0 Kelvin.

Vacuum and Clean Room Compatible
Piezo actuators neither cause abrasion nor do they require lubrications. The all-ceramic insulated PICMA® actuators have no polymer coating and are thus ideal for ultrahigh vacuum applications.

Operating Voltage
Two types of piezo actuators have become established:
Monolithic-sintered PICMA® multilayer actuators (low-voltage actuators) operate at voltages up to about 130 V and are made of ceramic layers from 20 to 100 μm in thickness.
Classical high-voltage actuators (PICA high-power actuators) are made from ceramic layers of 0.5 to 1 mm thickness and operate at voltages of up to 1000 V. PICA actuators can be manufactured with larger cross sections, making them suitable for larger loads than the more compact monolithic multilayer piezo actuators.

Low Energy Consumption
Static operation, even holding heavy loads for long periods, consumes virtually no power. A piezo actuator behaves very much like an electrical capacitor. When at rest, no heat is generated.

Rapid Response
Piezo actuators allow response times of a few microseconds. Acceleration rates of more than 10,000 g can be obtained.

High Force Generation
High-load piezo actuators capable of moving loads of several tons are available. They can cover travel ranges to 300 μm with resolutions in the subnanometer range.

Position Resolution
The piezo ceramic itself works free of friction and theoretically has unlimited resolution. In practice, the resolution actually attainable is limited by electrical and mechanical factors:
a) Sensor and servo-control electronics, amplifiers: Amplifier noise and sensitivity to electromagnetic interferences (EMI) affect positional stability.
b) Mechanical parameters: Design and mounting precision issues concerning the actuator, preload and sensor can induce microscopic friction which limits resolution and accuracy. Piezo actuators reach subnanometer resolution and stability.

No Magnetic Fields
The piezoelectric effect is related to electric fields, piezo actuators do not produce magnetic fields nor are they affected by them.

Travel Range
The travel ranges of piezo actuators are typically in between a few 10 to a few 100 μm for linear actuators. Bending actuators can achieve a few millimeters.