Nonlinear acoustic-structure interaction in high intensity focused ultrasound power transfer systems

Abstract

Ultrasound power transfer (UPT) has emerged as one of the most promising technique to wirelessly transfer power. The mechanism of UPT involves vibration-induced generation of acoustic waves from a piezoelectric transmitter which propagate in a medium to interact with a piezoelectric receiver, and generate vibrations-induced electrical response in the receiver. In this work, a novel technique of using a high intensity focused ultrasound (HIFU) is proposed to enhance the power transfer efficiency as compared to current UPT systems. HIFU concentrates the entire transmitted energy at a focal spot where the piezoelectric receiver is placed, thus dramatically reducing the input energy required, as compared to unfocused UPT systems. The physics of the HIFU-UPT system consists of a nonlinear acoustic wave propagating in a medium to induce a nonlinear structural response in the receiver. Implementing the HIFU-UPT phenomena in an experimentally validated finite-element based model shows that the nonlinear acoustic field can induce disproportionately high responses in a receiver if the harmonics in the acoustic wave coincide with the structural resonant frequencies of the receiver. This research aims to provide a comprehensive framework for designing UPT systems operating in nonlinear acoustic fields with a finite size receiver.