Anisotropic Shape Memory Composite for Dynamically Adjustable Electromagnetic Interference Shielding

Smart electromagnetic interference (EMI) shielding materialsthatenable dynamical adjustment of electromagnetic wave transmission arehighly desirable for various applications. Nevertheless, ordinarymaterials show nonadjustable EMI shielding performance after deployment.Herein, an anisotropic smart EMI shielding composite is presented,which shows tunable EMI shielding effectiveness by rotation, shapememory, and simple stacking. The composite possesses a sandwich structureconsisting of two graphene fibrous films (GFFs) with intermediateshape memory poly-(ethylene-co-vinyl acetate) (EVA).Owing to the aligned graphene fibers of GFF, the GFF/EVA compositeshowed anisotropic mechanical property, shape memory property, andshielding effectiveness. The composite shows high tensile strengthbut declined shape memory property in the axial direction (0 degrees)of the graphene fibers. In the 0 degrees direction of the GFF/EVA composite,a total shielding effectiveness (SE (T) )of >40.8 dB in the X-band is observed, which is much higher thanthatin the 90 degrees direction (vertical, <8.1 dB). The rotation-modulatedEMI shielding of GFF/EVA is achieved by the anisotropy-dependent EMIshielding performance. Moreover, tunable EMI shielding is demonstratedthrough the shape memory process of the composite and the average SET can be adjusted in the range from 43.2 to33.1 dB by fixing a tensile strain from 0 to 100%. Furthermore, theEMI shielding of the multilayered composite can be modulated by stackingindividual GFF/EVA composites at different angles. The smart GFF/EVAcomposite with tunable and function-switchable features is demonstrated,which will contribute to the development of smart EMI shielding materialsand devices for electromagnetic applications in various fields.