Fire-Ant-Inspired Magnetic Swarms with Stable Flotation for Programmable Shape Morphing and Cooperative Multitasking

Inspired by the remarkable buoyancy and collective adaptability of fire ant rafts, this study presents magnetic composite micro-floaters (MCMs) capable of stable flotation at air-water interfaces-a key advancement for magnetic microrobotic swarms in fluid environments. The system overcomes the intrinsic sinking tendency of high-density NdFeB microparticles through bioinspired surface engineering. MCMS are fabricated via a solvent-exchange phase inversion process, encapsulating NdFeB cores with hydrophobic polycaprolactone (PCL) and engineered surface roughness. This design emulates the hydrophobic cuticle and air-trapping strategies of fire ants, conferring exceptional resistance to vertical magnetic fields (up to 0.5 T) without submersion. Unlike conventional approaches, this eliminates reliance on restrictive parallel-field configurations. When subjected to programmable magnetic fields, MCM swarms exhibit dynamic self-assembly, reconfiguration into complex structures, and stable navigation through wave-disturbed environments while preserving swarm cohesion. Their multifunctional performance includes cargo transport at 70 times their weight, guided oil spill remediation via controlled aggregation, and precise manipulation of droplets (200 times their volume) for merging, stirring, and maze navigation-all achieved at the air-water interface. By synergizing fire ant-inspired flotation stability with magnetic reconfigurability, this work establishes a versatile platform for surface-based microrobotics, unlocking new opportunities in environmental remediation, microfluidics, and programmable matter.