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

Sheng Sun,Jianyuan Wang,Menglun Zhang,Yuan Ning

doi:10.1063/10.0009632

Abstract

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.

Highlights

When an alternating voltage is applied to a piezoelectric micromachined ultrasonic transducer (PMUT), the piezoelectric micromachined ultrasonic transducers (PMUTs) produces an ultrasound wave owing to the reverse piezoelectric effect of the material from which it is constructed
It is found that the resonant frequency of the PMUT array is 508 kHz, which coincides with the design frequency
By self-transmit and self-receive, the PMUT array can test within a distance of 17.5 cm, with the slight errors being attributed to effects such as slight deviations of the sound speed in air

Summary

INTRODUCTION

For many high-speed or high-precision facilities, such as satellites, high-speed railways, and solar panels, testing of surface cleanliness is crucial. Existing stain detection methods include touch inspection and optics.. Existing stain detection methods include touch inspection and optics.2 The former is inefficient and potentially dangerous. Most of the existing ultrasonic testing methods use ultrasonic probes, but these are generally large and have high power consumption. PMUTs do not require a DC bias, and they are simple to fabricate, with additional advantages of low power consumption, small size, low cost, and high sensitivity.. PMUTs do not require a DC bias, and they are simple to fabricate, with additional advantages of low power consumption, small size, low cost, and high sensitivity.3,4 These advantages enable PMUTs to replace traditional transducers in various applications, such as fingerprint recognition, ranging, and portable imaging.. Mechanical scanning imaging of stains on metal blocks is performed using the PMUT array, and its successful application to stain detection is demonstrated

WORKING PRINCIPLE

DEVICE DESIGN AND FABRICATION

PMUT array characterization

Pulse echo characterization

Imaging and detection of stain

CONCLUSION