Cross-scale magnetic catheter-magnetic swarm strategy for precise thrombus clearance

Thrombotic vascular occlusion presents a critical clinical emergency requiring rapid and precise intervention to restore blood flow and prevent tissue necrosis. Current therapies are constrained by poor accessibility to deeply seated thrombus and a lack of controlled navigation. Here, we propose a cross-scale thrombus removal strategy based on an integrated "magnetic catheter-magnetic swarm" system that couples a steerable magnetic catheter (macro-scale) with dynamically assembled Fe₃O₄@PDA swarm (micro-scale). Anisotropic Fe₃O₄@PDA nanoparticles were synthesized and magnetically actuated to form dynamic swarm under a rotating magnetic field. The swarm exhibited excellent maneuverability, deformation, and transport in complex and confined environments, while the magnetic catheter enabled precise macroscopic delivery. Driven by external magnetic fields, the swarm generated localized shear forces and hydrodynamic stresses to mechanically disrupt and loosen thrombus, promoting fragmentation and removal. The resulting debris, together with the swarm, was magnetically guided back to the catheter for retrieval, ensuring efficient clearance and minimizing embolism risk. This cross-scale system was validated in a cardiac vascular model, demonstrating safe, controllable, and minimally invasive thrombus removal in complex vascular structures. The proposed approach establishes a mechanics-driven platform for minimally invasive thrombus removal and offers a new paradigm for designing multifunctional micro/nanorobotic systems in biomedical applications.