Ultrabroad-band and low-frequency microwave absorption based on activated waxberry metamaterial

Abstract Low-frequency yet ultrabroad band microwave absorption still remains a great challenge due to contradiction between impedance match and electromagnetic loss. The natural biomass with hierarchical structure provides new solution to address this issue. The electromagnetic (EM) metamaterials show frequency-designable advantage while its absorption band width is often limited. Here we report an alternative EM metamaterial based on activated waxberry with gradient impedance profile. Strong microwave absorptions at low frequencies were experimentally realized with our fabricated metamaterial, achieving