Ultrathin Asymmetric Porous PLA Bilayers with Electrical-Magnetic Synergy for Absorption-Dominated EMI Shielding

Absorption-dominated electromagnetic interference (EMI) shielding materials are urgently needed to mitigate secondary electromagnetic pollution, yet achieving high absorption in ultrathin, sustainable polymer composites remains challenging. Herein, we propose an eco-friendly strategy combining electrical-magnetic synergistic fillers and an asymmetric porous bilayer architecture to achieve high absorption-dominated EMI shielding in poly(lactic acid) (PLA)-based composites. Graphene@copper-nickel ferrite (GNP@CuNiFe₂O₄) hybrid fillers, synthesized via sol-gel auto-combustion, are incorporated into a PLA/silver-decorated multi-walled carbon nanotubes (MWCNTs@Ag) matrix, yielding an EMI shielding effectiveness (SE) of 26.34   dB with an absorption coefficient of 0.38. To further enhance absorption, we design an ultrathin (135 ± 8 μm) asymmetric bilayer structure: a dense PLA/MWCNTs@Ag/GNP@CuNiFe₂O₄ layer provides impedance matching through electrical-magnetic dual networks, while a porous PLA/silver nanowires layer fabricated via green NaCl-templated leaching serves as a reflective layer. This architecture establishes a unique “absorption-reflection-reabsorption” mechanism, achieving an exceptional EMI SE of 34.00   dB with a high absorption coefficient of 0.54. This work provides a viable strategy for designing ultrathin, absorption-dominant EMI shields for next-generation eco-friendly electronics.