Multiscale Design of Dual-Gradient Metamaterials Using Gel-Mediated 3D-Printed Graphene Aerogels for Broadband Electromagnetic Absorption

Three-dimensional (3D)-printed graphene aerogels hold promise for electromagnetic wave absorption (EWA) engineering due to its ultralow density, outstanding electromagnetic dissipation with the flexibility and precision of manufacturing strategies. However, their high conductivity causes severe impedance mismatch, limiting EWA performance. 3D printing requirements also constrain the dielectric properties of printable graphene inks, hindering the integration of high-performance absorbers with advanced manufacturing. This study proposes a polyacrylic acid (PAA) gel-mediated 3D porous graphene oxide (GO) aerogel multiscale regulation strategy. Precise gel content control enables dual-gradient tuning of the rheology (Benefiting direct ink writing (DIW)) and dielectric loss (Enhancing EWA) of GO/PAA composites and reduces aerogel density (6.9 mg cm^-3 from 28.2 mg cm^-3). Thermal reduction decomposes PAA into amorphous carbon nanoparticles anchored on reduced graphene oxide (rGO), enhancing impedance matching and absorption via synergistic 0D/2D interfacial polarization and conductive loss. The optimized rGO/PAA aerogel achieves a minimum reflection loss (RL) of -39.86 dB at 2.5 mm and an effective absorption bandwidth (EAB) of 8.36 GHz (9.64-18 GHz) at 3.2 mm. Combining DIW and this aerogel, we design a metamaterial absorber (MA) with dual material (dielectric loss) and structural gradients. This MA exhibits an ultrawide EAB of 14 GHz (4-18 GHz) with a total thickness of 7.8 mm. This work establishes a coupled design paradigm of "composition-structure-performance," providing an engineerable solution for developing lightweight, broadband EWA materials.