In addition to
crystals, there are
ceramic compounds and
polymers that also exhibit piezoelectric behavior. There is an entire field of
industry dedicated to piezoelectric devices and products. Piezoelectricity isn't only
electricity generated in a material by motion, pressure, or stress, it is also motion induced in the material by the introduction of electricity.
The effect comes from the material in question changing its structure to either free or absorb electrons.
The primary consumer product applications are currently in motion and vibration damping, in things like skis, tennis racquets, and baseball bats. In these products, unwanted vibration is damped by being absorbed into piezoelectric material glued to the inside of or bonded into the fabric of the item, where it is converted into electrical energy. In more advanced products (skis mostly), the energy generated is then routed to parts of the item that need additional stiffening. They are also found in those sneakers that light up with every step.
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Piezoelectric materials are now starting to be seen in automotive suspensions, where their stiffness can be electronically controlled.
There are many industrial applications for piezoelectric devices, including:
Ultrasonic transducers
This is used to measure the physical characteristics of the object it is attached to by sending high-frequency sound waves into it and measuring the echo.
Shear transducers
These measure how close the object they are attached to, like a bolt or driveshaft, is to failure by registering how much stress they are under.
Pressure sensors
This measures pressure in whatever it is bonded to by measuring its distortion at the point of pressure.
Linear actuators
This is simply a piece of piezo material that extends and contracts under current to move a load.
Bending actuators
As above, only it bends to move the load when current is applied.
Future applications include
artificial muscles, "smart wing" flexible
wings that don't have traditional
flaps and
ailerons, and as a
power source for
smart textiles.