Gradient‐Engineered Liquid‐Metal Magnetic Hollow Microspheres for Flexible and Broadband Microwave Absorption

ABSTRACT The development of high‐performance flexible microwave absorption materials (MAMs) is crucial for next‐generation wearable stealth and electromagnetic protection, yet it remains challenging to integrate ultra‐wideband absorption, lightweight, and mechanical robustness in a single material. Here, a novel collision‐mediated energy transfer strategy coupled with a pH‐regulated deposition process is proposed to fabricate liquid‐metal magnetic hollow microspheres with a compositional‐gradient structure. This hierarchical architecture enables efficient impedance matching and multi‐mode energy dissipation. As a result, the material achieves an effective absorption bandwidth (EAB) of 9.0 GHz at a thickness of 2.39 mm. In addition, a reflection loss below −20 dB is obtained at 1.46 GHz, indicating highly competitive performance among hollow‐microsphere‐based MAMs. Importantly, the absorption performance remains stable under mechanical deformation. The material maintains an EAB of 8.0 GHz even after 100% tensile strain, demonstrating its potential for flexible applications. Multiscale quantitative analyses reveal synergistic magnetic‐dielectric coupling loss mechanisms. Practical radar cross‐section simulations corroborate the exceptional stealth capability, with only 0.16% of incident energy reflected. This work provides a viable strategy for designing flexible and broadband microwave absorption materials.