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Piezoelectric micromachined ultrasonic transducers for human-machine interfaces and biometric sensing

Improvements in thin-film piezoelectric materials such as AlN and PZT enable piezoelectric micromachined transducers that are superior to existing capacitive transducers. This paper presents the basic design equations, equivalent circuit model, and fabrication processes for piezoelectric micromachined ultrasonic transducers (PMUTs) operating in fluid or air. Relative to conventional ultrasonic transducers, PMUTs have the advantages of small size, low cost, low power consumption, and compatibility with integrated circuit manufacturing methods. These advantages enable PMUTs to be used in new applications such as human-machine interfaces and ultrasonic fingerprint sensors.