Piezoelectricity is applied to a wide array of smart sensors and devices, and has become a driving force behind many sensors and devices used in the smart products industry — and as a basis for many gadgets we use on a daily basis, from ear buds to cell phones. So it’s useful to take a closer look at how this effect occurs and the technology behind it.

What is piezo?

Piezo is an electromechanical device that converts mechanical movements into electrical signals, which increase according to the strength of mechanical movements. The word is derived from the Greek ‘piezein’, which means to squeeze or press — ‘piezo’ is Greek for the word ‘push’.

The technology behind it

Piezo sensors are created using non-conductive piezoelectric materials, crystals or ceramics. The most well-known piezoelectric material is quartz (SiO2), which is a naturally occurring  piezoelectric material. Piezoelectric materials can also be created artificially and are available in unlimited shapes and sizes. And when mechanical stress is applied to piezoelectric material it, generates a voltage that can be measured and processed, a phenomena called the Piezoelectric Effect.

One of the unique characteristics of this effect is that it is reversible, meaning that materials which exhibit the direct Piezoelectric Effect (the generation of electricity when stress is applied) also exhibit the converse effect. In this case the  voltage applied will change the shape of solid matter by a small amount (up to 4% change in volume).

piezoelectric ceramic features chart | Seebo IoT
Chart showing piezoelectric ceramic features . Image credit: nec-tokin

Applications of Piezoelectric sensors

Many commonly used devices utilize a piezoelectric sensor. Microphones and speakers are good examples, where  sound vibration is the mechanical stress that is  converted into, or converted from electrical signals, respectively.

Microphones: Some microphones (such as contact microphones for percussion instruments) use piezo materials to convert sound vibrations into an electrical signal (the direct effect).

Speakers: Speakers operate by converting electrical signals in order to to vibrate the speaker membrane and create sound (using the reverse effect). Piezoelectric speakers are featured in virtually every application that needs to efficiently produce sound from a small electronic gadget. These types of speakers are usually inexpensive and require little power to produce relatively large sound volumes.

These speakers can often be found in devices such as the following:

  • Cell phones
  • Ear buds
  • Sound-producing toys
  • Musical greeting cards
  • Musical balloons

The same technology forms the basis of many electrical devices, such as:

  • Motion detectors
  • Pressure sensors
  • Relays
  • Motors
  • Fast response solenoids
  • Ultrasonic sensors (as transducer)
  • Ultrasound imaging   

As the technology behind many smart sensors and devices that we use every day, it’s not surprising how this technology has come to influence our lives on a daily basis.

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