Electromagnetic Functional Properties of Flexible Picosecond Laser-Induced Graphene Films Modified with Silver Nanoparticles

With the rapid development of flexible and highly integrated electronic devices, flexible electromagnetic shielding and absorption materials have attracted increasing attention in the field of electromagnetic compatibility. However, picosecond laser-induced graphene (ps-LIG) still suffers from limited microstructural continuity and restricted tunability of sheet resistance when constructing flexible conductive networks. In this work, a flexible multilayer metamaterial absorber based on silver-nanoparticle-modified ps-LIG films is designed and developed. The formation mechanism of ps-LIG on polyimide substrates is systematically investigated, and a clear correlation among laser processing parameters, microstructural evolution, and electrical resistance is established, enabling broad and trend-governed tuning of the sheet resistance over a wide range of 10-1200 Ω/sq. Subsequently, silver nanoparticles are introduced via laser-assisted in situ reduction, forming a flexible LIG/Ag composite conductive network while preserving the intrinsic porous architecture. Owing to the enhanced electron transport continuity and interfacial polarization effects, the electromagnetic shielding effectiveness is significantly improved from approximately 19.5 dB for unmodified ps-LIG to about 30 dB while maintaining ∼83% of its initial performance after 500 bending cycles. Furthermore, absorption measurements demonstrate that broadband and efficient electromagnetic absorption with a bandwidth of 12.9 GHz is achieved over the frequency range of 5.1-18 GHz by exploiting the tunable sheet resistance and patterning capability of ps-LIG. This work provides a unified and scalable material platform for flexible EMI shielding and broadband electromagnetic absorption devices.