Design paradigm for strong-lightweight perfect microwave absorbers: The case of 3D printed gyroid shellular SiOC-based metamaterials

Research on microwave absorbing (MA) metamaterials with multifunctional coupling designs is a burgeoning topic. Reported here is a design paradigm for architecting mechanically robust all-dielectric MA metamaterials reaching perfect electromagnetic wave absorption. First, we generalized rules of optimal permittivities for nonmagnetic materials reaching theoretically ultimate reflection loss (RL) smaller than −150 dB, and proposed a facile criterion for evaluating MA performance based on the offset of dielectric Cole-Cole curves from theoretical optimal values. Subsequently, electromagnetic tunable polymer-derived SiOC ceramics with the highest reported printing accuracy of 20 μm were developed as metamaterials matrix, and the strong-lightweight gyroid shell-cellular (shellular) is introduced to optimize the MA performance while balancing mechanical properties. Finally, as-fabricated gyroid shellular MA metamaterials exhibit an unmatched MA performance coupled with unparalleled mechanical properties: the minimum RL achieves the ceiling value of −70.3 dB, the effective absorption bandwidth spans the whole X-band, and the specific compressive strength is as high as 63.0 MPa/(g/cm³) at 0.606 g/cm³ ultralow density. Besides, the theoretical framework was well-established for guiding structural optimization and practical manufacturing of inhomogeneous metamaterials. This research advanced an unambiguous theoretical direction for the development of structure-function integrated MA metamaterials through the synergistic interaction among theory, computation, and experiment.