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Basic Designs of Piezoelectric Positioning Elements
Basics
The piezoelectric effect is often encountered in daily life. For example, in small butane cigarette or gas grill lighters, a lever applies pressure to a piezoelectric crystal creating an electric field strong enough to produce a spark to ignite the gas. Furthermore, alarm clocks often use a piezoelectric element. When AC voltage is applied, the piezoelectric material moves at the frequency of the applied voltage and the resulting sound is loud enough to wake even the strongest sleeper.The word "piezo" is derived from the Greek word for pressure. In 1880, Jacques and Pierre Curie discovered that pressure applied to a quartz crystal creates an electrical charge in the crystal; they called this phenomena the piezo effect. Later they also verified that an electrical field applied to the crystal would lead to a deformation of the material. This effect is referred to as the inverse piezo effect. After the discovery it took several decades to utilize the piezoelectric phenomenon. The first commercial applications were ultrasonic submarine detectors developed during World War I and in the 1940’s scientists discovered that barium titanate ceramics could be made piezoelectric in an electric field.
As stated above, piezoelectric materials can be used to convert electrical energy into mechanical energy and vice versa. For nanopositioning, the precise motion which results when an electric field is applied to a piezoelectric material is of great value. Actuators using this effect first became available around 20 years ago and have changed the world of precision positioning.
Piezoelectric actuators (PZTs) offer the user several benefits and advantages over other motion techniques:
- Repeatable nanometer and sub-nanometer sized steps at high frequency can be achieved with PZTs because they derive their motion through solid state crystal effects. There are no moving parts (no "stick-slip" effect).
- PZTs can be designed to move heavy loads (several tons) or can be made to move lighter loads at frequencies of several 10 kHz.
- PZTs act as capacitive loads and require very little power in static operation, simplifying power supply needs.
- PZTs require no maintenance because they are solid state and their motion is based on molecular effects within the ferroelectric crystals.
For more detailed information see "Fundamentals of Piezoelectricity and Piezo Actuators", click here
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