Improving power transfer efficiency in bio-telemetry systems using negative permeability metamaterials

Summary form only given. Wireless power transfer over short distances is increasingly used to power implanted biomedical devices. A typical power transfer system consists of an external coil outside the body and an internal coil on the implanted device. The efficiency of the wireless power transfer depends on the Q of the constituent coils as well as the coupling. Coupling between the coils is severely limited by the distance between the coils. It was shown by Pendry [1] that negative refractive index materials (a very unique class of metamaterials) can produce a perfect image by focusing propagating waves and enhancing the evanescent waves that dominate in the near field. Since wireless power transfer is achieved by near field magnetic field coupling, using metamaterials can enhance this coupling and thereby increase the range of operation. A theoretical analysis using the point dipole approximation for resonating coils showed that power transfer efficiency increased when an anisotropic negative permeability material was placed between the primary and secondary coils [2].