Investigation of flexible and ultrathin metasurface for wireless power transfer in implantable devices

A flexible and ultrathin (λ/26) metasurface to enhance wireless power transfer (WPT) efficiency for implantable medical devices (IMDs) operating in the 5.725–5.875 GHz ISM band is presented. By suppressing reflected waves at the air-skin interface through destructive interference, the metasurface achieves near-zero reflection, resulting in a 6.1 dB improvement in transmission coefficient. The metasurface employs a biocompatible PDMS substrate and a compact two-layer metallic configuration, allowing for conformal integration with the human skin. Simulation results demonstrate robust transmission enhancement under angular misalignment (up to 45°), lateral displacement, bending, and dielectric variation, while experiments confirm stability under bending and angular deviation. This approach offers good performance, reduced thickness, and enhanced flexibility, establishing a paradigm for high-frequency biomedical WPT interfaces.