Abstract: The development of high-performance electromagnetic wave (EMW) absorbing materials with both strong attenuation capability and favorable biocompatibility is increasingly important for emerging applications in wearable electronics, implantable devices, and portable medical equipment. In this study, we present a class of hollow magnetic carbon nanofibers (Ni/HCNFs) with precisely controlled curvature, fabricated via electrospinning combined with sacrificial template method and subsequent high-temperature carbonization. By tuning the diameter of SiO₂ nanospheres, the internal cavity size and geometric curvature of the nanofibers are systematically regulated. The optimized Ni/HCNFs with 300 nm cavities exhibit an outstanding minimum reflection loss of -58.7 dB and an effective absorption bandwidth of 5.28 GHz. The enhanced EMW absorption is attributed to the synergistic effects of impedance matching optimization, multiple reflections within hollow cavities, and intensified interfacial/dipolar polarization losses originating from curvature-induced lattice strain gradients and surface stress fields, as verified by density functional theory calculations and finite element simulations. Furthermore, preliminary biocompatibility assessments indicate that the Ni/HCNFs exhibit low cytotoxicity and good cell viability when co-cultured with fibroblast cells, suggesting their potential as safe and efficient EMW absorbers for future bio-integrated electronic systems. This work not only provides a robust strategy for designing lightweight and high-performance EMW absorbing materials but also opens a new avenue for their application in biocompatible, targeting microwave hyperthermia carrier and environmentally adaptive scenarios.

Key words: Hollow carbon nanofibers, Curvature engineering, Electromagnetic wave absorption, Lattice strain gradient, Biocompatibility