Wireless-Powered Flexible Bioelectronic Implants with Deformation-Aware Optimization

Wireless power transfer (WPT) enables stable energy delivery to implantable medical devices without batteries, but optimizing flexible and deformable receiving coils for biological environments remains a critical challenge. This study introduces a deformation-aware optimization framework for implantable WPT systems, integrating mechanical deformation, electromagnetic coupling, and biological tissue isolation. A field uniform planar PCB Tx coil is used to mitigate misalignment sensitivity. Guided by this framework, a dual-layer planar Rx coil is designed and analyzed under self-resonant-frequency (SRF) constraints, with key geometric parameters (turn number and width-to-spacing ratio) evaluated across three representative coil shapes (circular, square, and elliptical). The framework quantifies how bending-induced changes in coil inductance/resistance and coupling affect link performance and enables deformation-aware compensation to improve robustness. Experimental results demonstrate that the 8-turn circular Rx coil (w:s = 2:1) achieves the best overall performance, with deformation-aware optimization maintaining high efficiency and reduced efficiency variance across 0°-90° bending under 20 mm tissue isolation. The proposed approach is further validated through simulations, ex vivo measurements with tissue isolation, and an in vivo rat implantation study in which stable device positioning and integration are confirmed by magnetic resonance imaging. These results establish a practical and experimentally validated pathway for designing mechanically robust and electromagnetically efficient flexible Rx coils for deformation-tolerant implantable inductive WPT links.