Facile construction of intelligent flexible double layer honeycomb sandwich structure for tunable microwave absorption by 4D printing

The integration of structure and material can endow microwave absorbers with excellent performance and broad application fields. However, its integrative manufacturing is extremely challenging, especially for the integration of functional materials and intelligent structures. In this context, the liquid crystal display (LCD) 4D printing was used to construct a kind of intelligent flexible double layer honeycomb sandwich structure by integrating multifunctional MXene@flake carbonyl iron powder (FCIP) and shape memory polymers (SMPs) resin. By controlling the applied time of the magnetic field, the structure with shape memory effect (SME) will be recovered to different radius of curvature (R) and center angle (α), which can endow the device with different absorption strengths and effective absorption bandwidth (EAB). When the α and R of the structure are 65.2° and 16.7 cm, the minimum reflection loss (RL_min) measured by the bow method is −50.87 dB, and the EAB (RL < −10 dB) reaches 13.8 GHz covering the C, X, and Ku bands. In addition, the applicability of smart structure devices in stealth technology is further confirmed by radar cross section (RCS) simulation, which is consistent with the conclusion of the measured results. This work enables the potential for rapid manufacturing of an intelligent, flexible, and ultra-broadband strong microwave absorbing device with integrated structure and function by 4D printing, which can be used in smart anti electronic reconnaissance, flexible wearable devices, and stealth technology.