Ag Nanoparticle-Coated Polystyrene Microspheres for Electromagnetic Interference Shielding Films with Low Metal Content

The fabrication of thin composite films incorporating metal-based fillers with a delicate structure to achieve high electromagnetic interference shielding effectiveness (EMI SE) at low metal content remains a great challenge. In this work, benefiting from the excellent electrical conductivity of Ag nanoparticles, Ag nanoparticle-coated polystyrene (PS@Ag) microspheres with a large PS core were selected as electrically conductive fillers, and the volume exclusion effect guaranteed the construction of an electrically conductive network with low silver loading. A spontaneous process to construct a segregated laminar structure with a three-dimensional electrically conductive network happened with the assistance of a gravity-driven effect. The flexible thin films with a low amount of silver exhibited outstanding EMI SE per unit thickness (SE/d). To further investigate the effect of the structure on the EMI SE efficiency, it is found that the alternate interfaces play a critical role in enhancing shielding performance by stacking multiple films compared to the bulk films obtained by casting. The EMI SE for an only 0.3 mm triple-piece stacking film with 6.3 wt % Ag loading could reach 55.3 dB compared to 37.2 dB for the triple-thickness casting film. Using the stacking process results in easy accessibility for tailored composites with the desired EMI SE, which supplies a new strategy for the design of shielding materials in the next-generation electronics.