Porous Copper-Flake-Based Polydimethylsiloxane Foams as Thermostable Electromagnetic Interference Shielding Materials for Soft Electronics

Wearable and soft electronics increasingly require lightweight materials that suppress electromagnetic interference (EMI) while remaining flexible and thermostable. Here, we use a simple, scalable sugar-templating strategy to fabricate porous polydimethylsiloxane foams loaded with copper nanoflakes (CuF). Sugar particles act as sacrificial porogens to control pore size, porosity, and CuF distribution in the cell walls, forming continuous conductive pathways in an elastic matrix. By systematically varying CuF content and sugar parameters, we establish structure–property relationships linking microstructure to mechanical and shielding performance. The optimized CuF30-Su40B foam exhibits a tensile strength of 0.31 MPa, an elongation at break of 112.55%, and a toughness of 0.61 MJ·m–3, while maintaining excellent bendability. In the X-band (8.2–12.4 GHz), the CuF40-Su40B foam achieves an average shielding effectiveness of 59.6 dB, corresponding to an attenuation of 99.9999% incident radiation. Scattering-parameter analysis indicates a reflection-dominated mechanism, with reflection coefficients up to 99.5% and negligible transmission, while residual fields are dissipated via conduction loss, interfacial polarization, and multiple internal reflections in the pores. These multifunctional foams thus act as soft, efficient EMI shields for next-generation flexible electronics, wearable sensors, and portable devices.