3D metamaterial broadband microwave absorber covered by structural topology-based pixelated color-changing layer

With rapid advancement in ISR (intelligence, surveillance, and reconnaissance), the demand for multispectral stealth technology has become urgent. In the field of radar stealth, 3D metamaterial absorbers have garnered significant attention due to their ultra-wideband microwave absorption. However, they face the challenge of restricted multispectral-compatible stealth capabilities, elevating the risk of being detected under ISR technology. In this study, we propose a solution by covering the absorber with a structural topology-based pixelated color-changing layer (STPCL), providing environmental camouflage and enhancing absorption intensity. Multiwall carbon nanotubes/spherical carbonyl iron/silicone rubber composites and thermochromic capsules/polydimethylsiloxane composites are used to fabricate the absorber and the STPCL, respectively. The STPCL not only provides adaptive camouflage in grassland and desert environments but also increases the characteristic dimensions to tune the absorption peaks and incorporates a grading circuit with stepped impedance to enhance impedance matching. As a result, the absorption bandwidth is slightly extended from 3.28-40 to 2.87-40 GHz, while the average reflection loss is improved from −13.55 to −16.83 dB. This approach demonstrates the potential to enhance the functionality and adaptability of metamaterial microwave absorbers in diverse operational environments.