Optimal design of ultrasonic transducer based on multi-layer backing with adjustable impedance

Ultrasonic transducers, especially used in medical imaging, strike a balance between sensitivity and bandwidth to yield high-quality images. This challenge centers on the optimal transmission of acoustic energy across the layers of transducer. The backing layer stands as a critical component of transducers, orchestrating the conversion of acoustic impedance to enhance bandwidth. While traditional designs often utilize metal particle-polymer composites, issues arise from material limitations, complex fabrications, and deviations in sample properties. This study introduces an optimized multilayer backing (MLB) design using a metal-polymer structure. Implementing an equivalent circuit model, an MLB of epoxy-aluminum composite is designed. The ultrasonic transducer has an operating frequency of about 6 MHz, in which the backing layer is a stacking composite of 19.3 μm epoxy resin and 30 μm aluminum foil. Notably, this optimized design increased the -6dB bandwidth from 27.72 % to 33.44 % and verified its superior electro-acoustic performance based on ultrasonic imaging. Furthermore, this innovative design approach provides a wider range of acoustic impedance, improves the efficiency of ultrasonic energy transmission, and provides a streamlined approach to miniaturized transducer design.