Essentially, a piezoelectric transducer is made by cementing thin sheets of crystal like quartz between thin metal plates. The metal plates are hooked up to electrodes to capture the electricity given off when the transducer is subjected to any kind of mechanical force or stress. These transducers were used in sonar, in microphones and in all sorts of applications including ultrasound.
They also could be used to generate electricity on our roadways. With the amount of heavy trucks rolling down the highway, piezoelectric transducers could be embedded in the pavement surfaces and every passing vehicle would generate electricity by it weight rolling over the transducers. This is an ideas whose time has come.
Young people get a real charge out of driving. It's an electric feeling. We should be collecting and monetizing that electricity.