From waste to wideband: achieving ultra-broadband absorption with bio-inspired, machine learning-optimized metamaterials

The development of high-performance electromagnetic wave-absorbing materials that combine cost efficiency and environmental sustainability remains a critical challenge in the fields of functional materials and stealth technology. Although the magnetoelectric coupling strategy has emerged as an important approach for designing high-performance absorbers by introducing magnetic loss and improving impedance matching, its ability to enhance absorption bandwidth remains limited, thereby restricting its application in scenarios requiring broadband absorption. To address this issue, this study proposes an innovative strategy for fabricating a hierarchical composite absorber derived from waste-based activated carbon spheres (ACSs). Inspired by natural biological structures, a sweet potato leaf-inspired electromagnetic wave absorber (SPL) has been designed. Leveraging electromagnetic wave localization theory and machine learning-assisted structural optimization, the resulting SPL successfully maximizes the localization of electromagnetic waves within the material distribution region. This leads to exceptional electromagnetic wave absorption performance, achieving a reflectivity below -10 dB across the entire 3–50 GHz frequency range at a matching thickness of only 10 mm. Simultaneously, owing to the inherent absorption characteristics of the activated carbon base, the composite retains its excellent capacity for adsorbing harmful gases. This work not only provides a high-performance, low-cost, and multifunctional electromagnetic wave absorber but also offers valuable insights into the value-added reuse of waste resources and the rational design of bio-inspired structures for advanced electromagnetic protection applications in both military and civilian architectural domains.