4D printing of hierarchically porous carbon-supported high-entropy ceramic metamaterial for tunable microwave...

Broadband-tunable electromagnetic wave absorption materials are critical for dynamic scenarios, such as those in wireless communication and radar systems. However, conventional absorbers are limited by narrow bandwidth and fixed postfabrication geometries. Herein, we propose a four-dimensional (4D)-printed pyramidal metamaterial comprising a hierarchically porous carbon-supported high-entropy ceramic and a shape memory elastomer. By synergizing macroscopic cavity resonances with microscopic defect-induced polarizations, the metamaterial delivers an absorption bandwidth of 14.16 gigahertz (≥90% absorption), representing a 98.88% enhancement over its bulk counterpart. In addition, it enables spatial reconfiguration via a moderate thermal stimulus (120°C), achieving tunable absorption across 5.24 to 18 gigahertz while maintaining reflection loss below -20 decibels (≥99% absorption). The base material's adaptability to complicated configurations is demonstrated by helical, origami-inspired, and load-bearing architectures. This work paves the way for metamaterial absorbers with multiple configurations and shape reversibility, advancing their applications in multispectral and intelligent adaptive systems.