The Electromagnetic-Core-First Paradigm: A Mechatronic Co-Design Framework for High-Density Implantable Systems

The miniaturization of implantable mechatronic systems is fundamentally limited by a pervasive design conflict: within a rigid spatial envelope, the requirements for high electromagnetic power density, physiological fluid pathways, and perfect biocompatibility compete irreconcilably. To resolve this, we propose a paradigm shift--the Electromagnetic Core-First (ECF) co-design framework. Unlike traditional sequential approaches that force performance compromise, ECF establishes a maximized electromagnetic core (via NSGA-III optimization under manufacturing constraints) as the immutable foundation. Fluid and thermal structures are then co-optimized in parallel within this fixed boundary, achieving global system synergy. Demonstrating its efficacy, we realized a fully magnetically levitated Fontan blood pump (O38.2 mm). The ECF-designed prototype, featuring a novel nested magnet topology, achieves: (1) 57.4% higher air-gap flux density vs. baseline designs and an 18.4 N static suspension force at only 4 W; (2) physiological flow matching (8.8 mmHg at 3.2 L/min); and (3) exceptional biocompatibility, with a hemolysis index of 0.0061 g/100 L and surface temperature rise <1.9{degrees}C. This work transcends the presentation of a single device; it establishes a systematic, physics-driven design paradigm that transforms extreme miniaturization from a constraint into a catalyst for performance, applicable to next-generation implantable mechatronic systems.