Application of Low-Temperature Processed 0–3 Composite Piezoelectric Thick Films in Flexible, Nonplanar, High-Frequency Ultrasonic Devices

Low-temperature, flexible, 0–3 composite piezoelectric materials can decrease the size, cost, and complexity of high-frequency acoustic devices on temperature-sensitive substrates such as those in catheter-based ultrasonic devices and acousto-optic (AO) sensors. In this article, the application of low-temperature 0–3 connected composite thick films in flexible, nonplanar, high-frequency ultrasonic devices is reported. A flexible high-frequency ultrasound transducer and an AO radio frequency (RF) field sensor are demonstrated using PZT-based composite thick films. Flexible composite films have been fabricated with thicknesses between 20 and
$100 \mu \text{m}$
using screen-printing, stencil-printing, and dip-coating techniques. Composite films’ piezoelectric d33 coefficient is measured, with results between 35 and 43 pC/N. Ultrasonic transducers using these films demonstrate broadband acoustic response. A composite transducer is fabricated on flexible polyimide and wrapped around a 3-mm catheter. Pulse-echo experiments demonstrate the viability of these films both as an actuator and a sensor in flexible devices. The composite material is further dip-coated onto an optical fiber Bragg grating (FBG) to form a flexible AO RF field sensor. The sensor demonstrates RF field sensing in the 20–130-MHz range. The results from these experiments indicate significant potential for future flexible, high-frequency ultrasonic devices using low-temperature 0–3 composite piezoelectric materials on temperature-sensitive substrates.