Metasurface-based radiative near-field wireless power transfer system for implantable medical devices

This article presents a novel approach to improve the efficiency of a radiative near-field wireless power transfer (WPT) system by using metasurface. The WPT system is designed particularly for implantable applications, which operate at the industrial, scientific, and medical (ISM) 2.40-2.48 GHz band. To construct the WPT link, a patch antenna is used as the transmitting element whereas a small planar loop antenna is considered as the receiving element. The receiving antenna is implanted under the skin tissue model operating at 2.45 GHz. The metasurface with a high refractive index is placed above the surface of the skin layer to improve the power transfer efficiency. Regarding the motion of the human body, different misalignment tolerances between the transmitter and the implant receiver are discussed. Also, the effect in the change of the skin property and placement depth of the Rx antenna inside the skin tissue model is studied. Furthermore, the study of specific absorption rate for the proposed configuration is performed. Finally, the proposed WPT system is designed and experimentally verified with and without metasurface. The experimental result confirms a significant amount of improvement in power transfer efficiency due to the integration of metasurface.