High intensity focused ultrasound array transducers using 2-2 stacked piezoelectric composite appropriate for sonochemistry application

High power ultrasound can be used as a catalysis to enhance the efficiency of chemical reactions. The generation of cavitation accelerates the reaction. The ultrasonic system in sonochemistry is typically based on single-frequency transducers, with some reactor designs incorporating multiple transducers operating at different frequencies. Currently, high intensity focused ultrasound (HIFU) is mainly used in clinical applications, such as prostate cancer surgery - high frequency ultrasound is utilized to provide accurate focusing and prevent cavitation. This paper considers the application of the HIFU technique in sonochemistry, in which an array transducer is used to generate cavitation through its steering ability. In this paper, the HIFU array transducer is based on a stacked, 2-2 connectivity piezoelectric composite and is configured as a 1-D linear array. As the goal is to produce cavitation in a liquid load, the operating frequency is below 500kHz. A 2-layer stacked structure, without backing, is adopted to increase the thickness of composite and reduce frequency. Due to the high acoustic impedance of the piezoceramic composite, a two matching layer system is applied to improve the coupling efficiency. The prototype array has been calibrated through experimental measurements of acoustic pressure field, impulse response and cavitating field.