Biomedical devices implanted inside the human body have a heavy demand on battery power. The internal batteries are charged wirelessly through two coils. The primary is placed outside the chest and is fed with an electromagnetic field, while the implanted secondary delivers current to the batteries. Increasing the number of turns in the internal secondary induces an increased amount of localized heat. A new approach proposed by the authors involves implanting a specifically designed multi-bundle concentric coil inside the body. It is shown that this newly proposed coil produces less localized heat. The total number of turns in the proposed coil is the same as that in the single-bundle coil except that it is divided into four equal bundles. Each bundle has a different diameter and is spatially concentric. Since the turns are divided into thinner bundles, they are easier to isolate with a biocompatible material and offer much better heat dissipation and fewer hotspots. Electromagnetic simulation using finite element analysis proved that the performance of the proposed coil is no lower than the single-bundle ordinary coil. Thermal simulation showed the improvement of temperature distribution using the multi-bundle coil, compared to the single-bundle coil.
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