Metamaterial-based Compact and Efficient Wireless Power Transfer System for Biomedical Implants

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We have developed a metasurface of low magnetic losses and employed it to design a a compact WPT system to biomedical implants. We have also proposed the design theory of a low inductance value to overcome the problem of frequency shifting and misalignment. We verified the proposed design by conducting experiments using chicken meat bought at an ordinary grocery shop. The performance of the proposed system was satisfactory as expected.This brief presents a compact and efficient resonance-shift insensitive wireless power transfer (WPT) system. This is possible by using a small electrical length defected ground structure (DGS) resonator, which is found effective against the resonance-shift phenomenon resulted from the higher permittivity of the tissue. Tissue has two undesired effects on a WPT system: (i) reduced coupled quality factor, and (ii) self-resonance shifting that leads to mismatch loss. So, the efficiency of a WPT system degrades in a tissue environment. Then, using the small electrical length DGS, we build a WPT transmitter (TX) using three cooperative DGS resonators to mitigate both issues. The fabricated prototype operates at 49 MHz in the air and tissue. This shows no change in operating frequency when the same receiver (Rx) is kept in the air or embedded inside tissues, which proves the effectiveness of the proposed cooperative DGS-WPT system against the resonance shift. The measured efficiency is 62% when the RX is embedded inside the tissue and is 68% in the air.