The word piezo takes root from the Greek word ‘piezein’/’piezo’ which means, to press or apply pressure. Today, this word is often used to denote the piezoelectric effect-a phenomenon has been put to use by the industry since almost 100 years.
What is the piezoelectric effect?
This effect was discovered in the late 1800’s by the Curie Brothers during an experiment with quartz crystals. Jacques and Pierre were French physicists. They noted that when mechanical stress is applied to quartz crystals, an electric charge is created in the crystals. They termed this the ‘piezo effect’. Simply stated, piezoelectricity means electricity that is derived from pressure.
During subsequent experiments, they recorded that the reverse is also true, wherein applying an electric field to the quartz crystal causes an elastic deformation crystal. This was termed the ‘inverse piezo effect’. It was later discovered that the inverse piezoelectric effect could be used for producing ultrasonic waves. This discovery led to development of ultrasonic submarine detectors during WWI.
A common example of the use of the piezoelectric effect would be in a gas fireplace lighter. As the user presses the button, a spring-loaded hammer strikes an inbuilt piezoelectric material (that’s the clicking sound that we hear). The pressure produces a charge that is sufficient to produce a spark that ignites the gas. Other examples comprise gas butane grills, cigarette lighters, and piezoceramic igniters in furnaces.
The relevance of piezoelectricity in nanopositioning applications
As piezoelectric materials such as crystals and ceramics are capable of converting electrical energy into mechanical energy, and vice versa, the field of nanopositioning stands to benefit from the use of piezoelectric actuators. Piezoelectric actuators are capable of creating precise motion resulting from piezoelectric materials. Such precision positioning devices and systems have been in use for over several decades now, and continue to advance.
However, it needs to be noted here that naturally occurring piezoelectric materials demonstrate a very small piezoelectric effect. This brought up the need to develop polycrystalline ferroelectric ceramics such as Barium Titanate and Lead Zirconate Titanate that show improved piezoelectric properties. These materials are widely used in nanopositioning applications involving actuators or sensors. By stacking many layers of piezo material (multilayer actuator) more displacement can be produced at lower operating voltage. The latest multilayer actuator designs are ceramic encapsulated for exceptional reliability and lifetime and have been tested for 100 billion cycles.
Here are some qualities that make piezoelectric actuators the preferred choice in nanopositioning applications:
- They are capable of achieving high-frequency steps in the nanometer and sub-nanometer range. Since there are no mechanical parts adding to play and backlash, such actuators offer better repeatability.
- They are suitable for moving a range of weights, from a few pounds to several tons.
- Piezo electric actuators require very little power in static operation, thus reducing power supply requirements.
- They are maintenance free, and not susceptible to wear.
Flexure guiding mechanisms that are based on the principles of piezoelectricity are also used in multi-axis positioners and even in hexapod precision positioning systems. Piezoelectric hexapod platform positioners are decidedly superior to conventional hydraulic hexapods. Due to the high stiffness and fast response, they can be operated as both positioners and also vibration cancellation systems. Thus, hexapod precision positioning platforms also benefit from the use of piezoelectricity principles.
