High-Efficiency Inductive Powering and Auto-Localization of CMOS Brain Implants by a Wearable Metasurface and Coupled Matching

We present a high-efficiency wireless powering architecture designed for subcortical medical implants. Conventional inductive links struggle to bridge the mid-field gap, where the power density decays rapidly with depth. To overcome this, we propose a 13.56 MHz system enhancing a coupled-matching topology with a passive hexagonal metasurface (MS) relay. This MS configuration boosts evanescent fields to create a magnetic funnel, while the matching network enables intrinsic implant auto-localization. Complementing the link, we report a 65-nm CMOS hybrid rectifier utilizing a bootstrapped scheme with a dynamic auxiliary biasing path to achieve >70\% efficiency. Experimental validation confirms a 1.7X power boost at 30-mm depth, delivering 250 uW, and improved misalignment tolerance, establishing a robust framework for batteryless deep-brain neuromodulation.