Deeply implanted biomedical devices (DIBDs) are a challenging application of wireless power transfer because of the requirement for miniaturisation whilst minimising patient exposure to tissue heating. This work proposes a capacitively-coupled conductive power transfer method for DIBDs, which allows for the safe transfer of power into the body whilst using minimum implant volume. The method uses parallel insulated capacitive electrodes to couple uniform current flow into the tissue and implants. Analytical analyses are presented, which result in a two-port network that describes circuit operation. The two-port network is further simplified for typical DIBD applications where coupling to the external electrodes is low. This results in a simple circuit model of power transfer for which the parameters are easily obtained by experimental measurements. The proposed circuit model has been validated using circuit coupled finite element analysis (COMSOL) and benchtop experiments using a tissue phantom. In addition, the safety aspect of the method has been evaluated via COMSOL simulation of the specific absorption rate (SAR) for various implanted receiver dimensions and implantation depths. Finally, a completed power supply, unaffected by the implantation depth, running at 6.78 MHz, delivering 10 mW deep into the body whilst meeting the IEEE C95.1 basic restriction is presented.

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