Broadband mechanical metamaterial absorber enabled by fused filament fabrication 3D printing

Rationally designed porous structures are promising as broadband electromagnetic (EM) wave absorbers for counteracting military radar signal or reducing EM interference between electronic components. However, their poor mechanical properties associated with low density limit the scalability. Here, we report a three-dimensional printed, broadband mechanical metamaterial absorber (BMMA) that implements a dual-function of EM wave absorption and reinforced relative stiffness. Based on tuning the lattice unit-cells and comprising materials, the proposed BMMAs feature a multilayered design comprising geometrically optimized octet-truss structures composed of carbon black-based backbone composites. Three-dimensionally printed BMMAs achieve > 90% absorbance (-98.66% on average) for frequencies spanning 5.8-18 GHz, while maintaining nearly constant stiffness per unit mass density of 1.37 at a low density (-200 kg/m3). This design strategy will inspire versatile metamaterials that offer multi-functions enabled by adjusting unit-cell parameters via a single structure.