Ultrasound transducer optimization for wireless battery charging in subcutaneous implantable device

Wireless power transfer (WPT) is a promising way to power active implantable medical devices (AIMDs) which are increasingly used in modern life to monitor and/or treat diseases such as cardiovascular diseases which are the cause of about 1/3 of global deaths according to the WHO. In the last decade, among WPT technologies like optical, radio frequency or inductive coupling, acoustic power transfer (APT) has received great interest thank to its advantages in terms of efficiency, miniaturization, deep propagation, and electromagnetic compatibility. Designing an efficient implantable ultrasound (US) receiver requires appropriate material selection considerations. This study presents for the first time a benchmark of piezoelectric materials and their important parameters in the aim of optimizing the performance of US receiver for wireless battery charging in subcutaneous implantable device. Simulation and experimental results reveal that hard ceramics with high mechanical quality factor are the most suitable for making an efficient US receiver. APT measurement demonstrates that the US receiver provided a maximum of 3.7 mA charging current at a depth of 20 mm through silicone medium from an ultrasound beam with an acoustic intensity of 81 mW/cm2.