Flexible ultrasonic transducers

TLDR

The flexible transducer is built on a thin stainless‑steel foil serving as substrate and bottom electrode, with a porous PZT/PZT piezoelectric composite film (40–70 µm thick) fabricated by sol‑gel spray and a silver‑paste top electrode, and its performance versus foil thickness was modeled numerically. The flexible UTs successfully performed pulse‑echo nondestructive testing on flat and curved surfaces at room temperature and 160 °C, delivering signal strengths comparable to a commercial broad‑band transducer, with simulation results matching experimental measurements.

Abstract

Flexible ultrasonic transducers (UTs) consisting of a metal foil, a piezoelectric ceramic film, and a top electrode have been developed. The flexibility is realized owing to the porosity of piezoelectric film and the thinness of metal foil. In this paper, the stainless steel (SS), lead-zirconate-titanate (PZT)/PZT composite and silver paste were chosen as metal foil, piezoelectric film, and top electrode materials, respectively. The SS foil serves as both substrate and bottom electrode. The PZT/PZT piezoelectric composite film is made by the sol-gel spray technique. PZT/PZT films of thicknesses from 40 to 70 microm were fabricated onto SS foils. The capability of these flexible sensors operated in the pulse-echo mode for nondestructive testing on flat and curved surfaces of different materials at room temperature and 160 degrees C has been demonstrated. Numerical simulations of the effects of the metal foil thickness on the ultrasonic performance of flexible UTs also were carried out, and the results are in reasonable agreement with experimental data. In addition, a PZT/PZT flexible transducer showed a signal strength comparable with that obtained by a commercial room temperature broad bandwidth transducer.