SUMMARY

Acoustic power transfer (APT) has received growing attention as a viable approach to deliver power remotely to small electronic devices. APT systems transfer electric power wirelessly by converting it into acoustic waves that travel through a medium to a receiving transducer that converts it back to electricity. The design of an efficient APT system requires coupled multiphysics modeling and analysis of individual components and their interactions to establish strategies toward maximizing the transferred energy. This work investigates different analytical and numerical models to analyze the performance of APT systems and to explore methods to increase the transferred power. Various electromechanical models are developed to represent the transducer (transmitter or receiver) dynamics for a broad range of aspect ratios, including Rayleigh and Bishop theories for moderate aspect ratios. Using these models, the effects of transducer shape and size, wave divergence, reflections, and medium absorption on the efficiency are investigated. Novel approaches using acoustic metamaterials/phononic crystals are introduced to enhance the efficiency in APT through wave focusing. Specifically, a 3D phononic crystal structure based on air inclusions in a 3D-printed polymer is introduced to manipulate acoustic waves in dense mediums such as water or similar impedance materials. A gradient-index lens is fabricated and experimentally characterized to focus underwater acoustic waves on a piezoelectric receiver, thereby significantly enhancing the power output. Ongoing efforts aim to use passive phononic crystals as well as active piezoelectric elements with shunt circuits to enable impedance matching for enhanced power transfer.