A Low-Frequency Versatile Wireless Power Transfer Technology for Biomedical Implants

TLDR

Implantable biomedical sensors and actuators are highly desired, yet their power source size and performance are limited by RF wireless power transfer, which poses radiation hazards, tissue absorption, and requires sensitive impedance matching. The authors propose a novel low‑frequency wireless power transfer system using rotating rare‑earth permanent magnets to avoid RF hazards and achieve load‑independent efficiency. The LF‑WPTT employs rotating permanent magnets to generate a low‑frequency magnetic field that inductively couples to a receiving coil, delivering power without the need for complex impedance matching. The system delivers 2.967 W at ~180 Hz over 1 cm with 50 % efficiency, and shows minimal loss even when the coil is enclosed in non‑magnetic stainless steel, outperforming recent high‑frequency designs.

Abstract

Implantable biomedical sensors and actuators are highly desired in modern medicine. In many cases, the implant's electrical power source profoundly determines its overall size and performance . The inductively coupled coil pair operating at the radio-frequency (RF) has been the primary method for wirelessly delivering electrical power to implants for the last three decades . Recent designs significantly improve the power delivery efficiency by optimizing the operating frequency, coil size and coil distance . However, RF radiation hazard and tissue absorption are the concerns in the RF wireless power transfer technology (RF-WPTT) , . Also, it requires an accurate impedance matching network that is sensitive to operating environments between the receiving coil and the load for efficient power delivery . In this paper, a novel low-frequency wireless power transfer technology (LF-WPTT) using rotating rare-earth permanent magnets is demonstrated. The LF-WPTT is able to deliver 2.967 W power at ∼ 180 Hz to an 117.1 Ω resistor over 1 cm distance with 50% overall efficiency. Because of the low operating frequency, RF radiation hazard and tissue absorption are largely avoided, and the power delivery efficiency from the receiving coil to the load is independent of the operating environment. Also, there is little power loss observed in the LF-WPTT when the receiving coil is enclosed by non-magnetic implant-grade stainless steel.