Air-coupled piezoelectric micromachined ultrasonic transducers for surface stain detection and imaging

This paper proposes an air-coupled piezoelectric micromachined ultrasonic transducer (PMUT) for detection and imaging of surface stains. A 508 kHz PMUT array is designed, fabricated, and characterized in terms of its electrical and acoustic properties, and it is used in a pulse echo validation test. Imaging of stains on metal blocks is successfully demonstrated. Compared with existing optical methods for stain detection, the proposed approach can work in a dark environment without color requirements. This work provides a new and promising route for the development of miniaturized stain detection systems.