Nanofibrous aerogels with continuous conductivity gradient for ultrabroadband absorption-dominant electromagnetic interference shielding

Abstract

Electromagnetic interference (EMI) shields are limited by a severe impedance mismatch with free space, leading to strong reflections and secondary radiation. Here, we introduce ultralight all-polymer aerogels featuring a continuous through-thickness conductivity gradient (MCAs), fabricated in a single step via diffusion-driven oxidative polymerization of pyrrole within aramid nanofiber scaffolds. An exponentially decaying conductivity profile enables ultrabroadband, low-reflection performance in 5-mm-thick samples, achieving reflection power coefficient R < 0.1 across 10.2-40.0 GHz, while maintaining shielding effectiveness > 30 dB under low-conductivity face incidence. Waveguide measurements and simulations show that progressive impedance transition and internal field redistribution drive absorption-dominated ohmic loss rather than surface reflection. A gradient-stratified electromagnetic model delineates an optimal design window for key gradient parameter. Beyond EMI protection, this nanofibrous architecture provides mechanical robustness and facile processability, establishing a diffusion–reaction strategy for spatially programmed conductive networks relevant to electromagnetic, electronic, and energy systems. Electromagnetic interference shields can be limited by impedance mismatch with free space, leading to strong reflections and secondary radiation. Here, the authors introduce lightweight all-polymer aerogels with a continuous through-thickness conductivity gradient, fabricated in a single step via diffusion-driven oxidative polymerization of pyrrole within aramid-nanofiber scaffolds.