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.