Meta material unit-cell design and orientation effects in conductive fused filament formed polymer for EMI shielding effectiveness

Electromagnetic shielding performance in additively manufactured conductive polymers is strongly dependent on geometry; however, the influence of unit-cell orientation remains insufficiently quantified under waveguide-relevant conditions. A polyhedral metamaterial unit cell is designed using conductive PLA–Carbon Black and fabricated as WR-90-compatible shielding inserts via periodic tiling in four orientations (Variants 1–4). Shielding effectiveness is measured experimentally across 8.2–12.4 GHz and benchmarked against full-wave electromagnetic simulations. The four variants exhibit markedly different responses (≈20–70 dB) despite comparable external dimensions. Notably, Variants 1 and 2 have nearly identical mass with