Towards a Conformal Metasurface Transmitter for Programmable Near-Field Power Transfer to Miniaturized Bioelectronics

The emergence of contactless and battery-free powering for bio-electronics, such as wearable devices and implants, has sparked significant interest in wireless power transfer (WPT) and energy harvesting technologies. This paper presents the first active metasurface array for microwave Wireless Power Transfer (WPT) systems, allowing near-field programming of the electromagnetic fields. We introduce a conformal vertically-stacked multi-layer power transmitter composed of beamformer Integrated Circuits (ICs). Thanks to per-element phase/amplitude control, the metasurface array breaks the dependency between Electric and Magnetic fields dictated by the geometry of the transmitter in single-element power transmitters. To increase the maximum deliverable power to miniaturized bio-electronics under the Specific Absorption Rate (SAR) safety limit, we leverage the near-field programming to suppress SAR distribution while adjusting the intensity of the Magnetic (Electric) field at the receiver's location. We evaluate the performance of this approach through electromagnetic-circuit co-design and simulation and define a new Figure of Merit (FoM) to quantify the maximum deliverable power.