A Study of Wearable Wireless Power Transfer Systems on the Human Body

A study is performed to evaluate the performance of wearable Wireless Power Transfer (WPT) systems on various parts of the human body. Specifically, the effects of the human body on the Power Transfer Efficiency (PTE) of a Conformal Strongly Coupled Magnetic Resonance (CSCMR) WPT system is systematically examined. Two CSCMR systems are designed to operate at the 27.12 MHz Industrial, Scientific, and Medical (ISM) band, one on a 1.5 mm thick FR-4 substrate and one on a 1.5 mm thick ferrite sheet. Simulations and measurements of these two configurations are performed for 26 different placement locations on the human body. Considering our measured data on these 26 locations, it is found that when a CSCMR WPT system with a traditional substrate, such as FR-4, is placed directly on the skin of the human body, its PTE decreases on average by 7.2%. However, when the same system uses a ferromagnetic substrate instead of FR-4, its PTE decreases on average by only 1.6%. Additionally, a study of the Specific Absorption Rate (SAR) for the different placement locations is performed.