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 <2% difference yet differ by about ≈25 dB across the band, indicating a dominant orientation-driven contribution beyond material quantity, indicating that orientation also governs attenuation predominantly through increased propagation tortuosity and geometry-induced impedance modulation. Variant 2 provides the highest broadband shielding (≈50–70 dB), whereas Variant 3 yields the lowest (≈16–31 dB). Discrepancies between simulation and measurement are primarily associated with uncertainty in permittivity extraction and print-induced geometric deviations.