Biosafety Considerations of a Capacitive Link for Wireless Power Transfer to Biomedical Implants

This paper presents the design, modeling, and characterization of a capacitive link for wireless power transfer (WPT) to biomedical implants. The work specifically focuses on investigating the optimal range of link operation frequency, f
_op
, that maximizes the power transfer efficiency (PTE) and power delivered to the load (PDL) parameters under biosafety constraints imposed by specific absorption rate and electric-field strength in living tissue. A capacitive link, comprising two pairs of parallel plates (20mm × 20mm) coated with ~63.5μm-thick layer of Kapton and aligned around 3mm-thick muscle tissue, was set up in ANSYS HFSS™ for simulating PTE and biosafety-constrained PDL parameters over a wide range of f
_op
(0.2-20MHz), load resistance (0.01-10kΩ), and plates edge-to-edge distance, L (2-70cm). It is shown that for a wide range of L values, f
_op
in the range of ~5-10MHz allows PTE and biosafety-constrained PDL concurrently reach ~90% of their maximum achievable levels. Moreover, for large values of L (≥ 50cm), PDL levels of ~200mW can be achieved with PTE of ~60-70%.