Aloe leaf-inspired and machine learning-driven porous carbon/FeSiAl flake metamaterials for low-frequency...

Ultra-wideband, high-efficiency, and lightweight electromagnetic wave absorbers are crucial for communication, radar, and intelligent sensing systems. However, in the low-frequency band, the operating wavelength of incident waves far exceeds the characteristic dimensions of the material structure, hindering the generation of sufficient equivalent electromagnetic responses. This leads to poor impedance matching and inadequate energy dissipation, representing a significant bottleneck for achieving low-frequency ultra-wideband absorption. Herein, a bio-inspired aloe leaf-like electromagnetic metamaterial absorber is proposed. It utilizes porous carbon as a dielectric loss framework, with magnetic units periodically introduced on the upper and lower surfaces to construct a complementary dielectric-magnetic loss system. By synergizing intrinsic material losses with structural effects to regulate gradient impedance matching and multi-scale dielectric/magnetic losses, the absorber achieves electromagnetic wave localization and an "electromagnetic cage" effect. The absorber maintains a reflection loss below -10 dB across the 0.8-50 GHz range. At the lowest operating frequency of 0.8 GHz, it has a thickness of only 25.6 mm (approximately 1/15 of the wavelength) and an areal density of 0.18 g cm^-2. This study provides a new paradigm for the integrated material-structure design of ultra-wideband electromagnetic absorbers.