A piezoelectric actuator is a type of electromechanical device that converts electrical energy into precise mechanical motion or displacement. It operates based on the principle of piezoelectricity, which refers to the property of certain materials to generate an electric charge in response to applied mechanical stress or conversely, to deform when an electric field is applied.
The basic principle of operation of a piezoelectric actuator involves three main steps:
Piezoelectric Material: The actuator is constructed using a piezoelectric material, typically a crystal or ceramic, that exhibits the piezoelectric effect. Common materials used include lead zirconate titanate (PZT) and certain types of quartz.
Applied Voltage: When an electric voltage is applied across the piezoelectric material, it undergoes a dimensional change due to the internal polarization of its atoms or molecules. This voltage-induced dimensional change is known as the direct piezoelectric effect. The degree of deformation depends on the magnitude of the applied voltage.
Mechanical Displacement: As the voltage is applied, the piezoelectric material either expands or contracts, depending on the polarity of the applied voltage. This mechanical displacement or deformation of the material is used to generate motion in the actuator.
Depending on the design and application, piezoelectric actuators can have different configurations, such as:
Stack Actuators: These actuators consist of multiple layers of piezoelectric material stacked together with electrodes in between. When a voltage is applied, the layers expand or contract in unison, resulting in a relatively large displacement.
Bimorph Actuators: Bimorph actuators consist of two piezoelectric layers bonded together with opposite polarization. When voltage is applied, one layer expands while the other contracts, causing the actuator to bend or deflect.
Tube Actuators: These actuators consist of a piezoelectric tube with electrodes on its inner and outer surfaces. Applying a voltage causes the tube to elongate or contract, producing axial motion.
Piezoelectric actuators find applications in various fields, such as precision positioning systems, nanopositioning in microscopy and lithography, valve control, microfluidics, and vibration control, among others. They are popular due to their rapid response, high precision, and ability to operate in a wide range of temperatures. However, they also have limitations, such as limited travel range and sensitivity to high mechanical loads, which need to be considered when selecting them for specific applications.