Lightweight and Highly Compressible Expandable Polymer Microsphere/Silver Nanowire Composites for Wideband Electromagnetic Interference Shielding

The exploration of lightweight and compressible electromagnetic interference (EMI) shielding materials with outstanding shielding effectiveness (SE) is still a tremendous challenge in the elimination of electromagnetic pollution. Lightweight and highly compressible expandable polymer microsphere/silver nanowire (EPM/AgNW) composites with micron-sized closed pores and an interfacial AgNW conductive network are fabricated via a facile thermal expansion process in an enclosed space. The EPM/AgNW composites with AgNW loading of 0.127 vol % show low density (0.061 g/cm³), high compressibility and compression strength (4.25 MPa at 92.6% of compressive strain), and high EMI SE (over 40 dB, 1 mm) at a wideband of 8-40 GHz. Their EMI SE can be improved to a record 111.5 dB by increasing the AgNW content to 0.340 vol %, which corresponds to the surface-specific SE (SSE/d; SE divided by density and thickness) up to 13433 dB·cm²/g. The EMI shielding mechanism is further discussed using the finite-element analysis software COMSOL Multiphysics, and the application of the EPM/AgNW composites is visually demonstrated via near-field shielding in a practical antenna radiation. The overall properties of light weight, high elasticity, excellent mechanical strength, and outstanding EMI shielding performance suggest that the as-prepared EPM/AgNW composites have a great potential for applications in modern electronics.