Thin-film Flexural Ultrasonic Transducers for Air-coupled Measurement

The flexural ultrasonic transducer (FUT) is composed of a circular metallic plate bonded to a piezoelectric ceramic disc and attached to a cylindrical support. The ceramic’s vibrations stimulate resonant modes in the plate, generating ultrasound waves in the medium in front. FUTs are utilised for proximity measurement, but with an increasing focus on using lead-free piezoceramic elements. Also, it is challenging to accurately distribute epoxy resin between the ceramic and the plate. Through thin films, the epoxy bond layer can be removed, allowing for FUT geometry to be readily controlled, with the potential for thicker films for transmitter and thinner films for receiver FUTs, enabling tailored responses. This will enable high-frequency FUTs, above 60 kHz, at which commercial FUTs struggle to operate efficiently.