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Atomic Force Microscopes - Tutorial Page
Piezoelectric Ceramic Transducer
Mechanical motion is created from electrical energy with an electromechanical transducer.
Electrical motors such as are used in washing machines are the most common type of
electromechanical transducer. The electromechanical transducer most commonly used in
an atomic force microscope is the piezoelectric ceramic.
A piezoelectric material undergoes a change in geometry when it is placed in an electric
field. The amount of motion and direction of motion depends on the type of piezoelectric
material, the shape of the material, and the field strength. Figure 1 shows the motion
of a piezoelectric disk when exposed to an electric potential:
Figure 1: When a voltage is applied to the top and bottom surface of the
piezoelectric disc, the disc will expand.
A typical piezoelectric material will expand by about 1 nm per applied volt. Thus, to get
larger motions it is common to make piezoelectric transducers with hundreds of layers of
piezoelectric materials, illustrated in Figure 2.
Figure 2: Applying a voltage to the top and bottom surface of this stack of
piezoelectric disks causes the entire stack to expand. The amount of expansion depends on the applied voltage, piezo-material, and number of disks
By using one thousand layers of piezoelectric material it is possible to get motions as large as 1000 nm per volt. Thus with 100 volts it is possible to get 0.1 mm of motion with a multiple layer piezoelectric transducer.
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