Wireless Power Link Based on Inductive Coupling for Brain Implantable Medical Devices

An inductively powered brain implantable medical device (BIMD) in lieu of a battery-assisted BIMD has the ability to provide a reliable power supply and avoid surgical replacement of a discharged battery. In this letter, we propose a three-dimensional (3-D) bowtie implantable antenna embedded in the cerebral spinal fluid (CSF) coupled with an exterior loop antenna. The power transfer efficiency is maximized by designing a matching circuit for the exterior and implantable antennas to reduce the high intrinsic reactive part of the input impedance. To ensure safety for long-term implantation, a rigorous specific absorption rate simulation was conducted to abide with the safety standard. A liquid CSF phantom was developed to experimentally test the power transfer efficiency between the exterior and implantable antenna. Measurement of the fabricated 0.9 mm
³
implantable antenna prototype in the CSF phantom resulted in -30.12 dB wireless power link, which outperforms the current work in the literature in terms of the size and link efficiency for 3-D implantable antennas.