5.4.7.2 Piezoelectric Sensors

Here, typically pressure or force is used to create an electrical signal out of a piezoelectric material. For instance, in a microphone, sound waves can deform the piezoelectric element by bending it and thus giving a changing voltage. Similar principle can also be used for pickup guitars and microphones.

Other sensor applications are

• Detection and generation of sonar waves.

• To detect detonation in automotive engine by sampling the vibrations of the engine block

• To detect the precise moment of fuel injection in an automotive engine

• Detection of acoustic emissions in acoustic emission testing.

• Microbalances as very sensitive chemical and biological sensors.

• Strain gauges

• Medical applications using ultrasound waves

• Kidney stone treatment

In this application, electricity of high frequency is applied to the sample which gives rise to a change in the shape of the material. The shape change leads to emission of waves of frequencies in the ultrasound range.  These powerful ultrasound waves can be used to shatter pieces of materials inside the body such as kidney stone, which can then pass out through the urine.

5.4.7.3 Ultrasound Imaging Using Transduction Effect

Another application is its use in the ultrasound imaging of the fetus where piezoelectric acts as a transducer utilizing both direct and inverse effects. Since a high frequency field application to a piezoelectric can lead to emission of ultrasonic waves by direct effect, these waves, when they meet the tissues in the body, some of these waves get reflected. The reflected waves come back to piezoelectric exploit the inverse effect which leads to creation of charges from the piezoelectric which can then be modeled to generate an image of the fetus.