Powering Implants by Galvanic Coupling: A Validated Analytical Model Predicts Powers Above 1 mW in Injectable Implants

Abstract

While galvanic coupling for intrabody communications has been proposed lately by different research groups, its use for powering active implantable medical devices remains almost non-existent. Here it is presented a simple analytical model able to estimate the attainable power by galvanic coupling based on the delivery of high frequency (>1 MHz) electric fields applied as short bursts. The results obtained with the analytical model, which is in vitro validated in the present study, indicate that time-averaged powers above 1 mW can be readily obtained in very thin (diameter < 1 mm) and short (length < 20 mm) elongated implants when fields which comply with safety standards (SAR < 10 W/kg) are present in the tissues where the implants are located. Remarkably, the model indicates that, for a given SAR, the attainable power is independent of the tissue conductivity and of the duration and repetition frequency of the bursts. This study reveals that galvanic coupling is a safe option to power very thin active implants, avoiding bulky components such as coils and batteries.