Anisotropic Shape Memory Composite for Dynamically Adjustable Electromagnetic Interference Shielding

Abstract

Smart electromagnetic interference (EMI) shielding materials that enable dynamical adjustment of electromagnetic wave transmission are highly desirable for various applications. Nevertheless, ordinary materials show nonadjustable EMI shielding performance after deployment. Herein, an anisotropic smart EMI shielding composite is presented, which shows tunable EMI shielding effectiveness by rotation, shape memory, and simple stacking. The composite possesses a sandwich structure consisting of two graphene fibrous films (GFFs) with intermediate shape memory poly(ethylene-co-vinyl acetate) (EVA). Owing to the aligned graphene fibers of GFF, the GFF/EVA composite showed anisotropic mechanical property, shape memory property, and shielding effectiveness. The composite shows high tensile strength but declined shape memory property in the axial direction (0°) of the graphene fibers. In the 0°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 than that in the 90°direction (vertical, <8.1 dB). The rotation-modulated EMI shielding of GFF/ EVA is achieved by the anisotropy-dependent EMI shielding performance. Moreover, tunable EMI shielding is demonstrated through the shape memory process of the composite and the average SE T can be adjusted in the range from 43.2 to 33.1 dB by fixing a tensile strain from 0 to 100%. Furthermore, the EMI shielding of the multilayered composite can be modulated by stacking individual GFF/EVA composites at different angles. The smart GFF/EVA composite with tunable and function-switchable features is demonstrated, which will contribute to the development of smart EMI shielding materials and devices for electromagnetic applications in various fields.

A Smart Amorphous Wire Composite with Tunable Electromagnetic Shielding

“…Sample Preparation: Co 68.15 Fe 4.35 Si 12.5 B 12 Cr 3 (at%) AWs were fabricated by an in-rotating water spinning method. [50] Experiments were conducted using a high-speed wheel with a sharp edge to contact the [4,9,10,38,49,[53][54][55][56][57][58][59][60][61][62] surface of a cobalt-based molten alloy, and then rapidly extracting and cooling the molten layer to instantaneously extract nearly circular wires. Compared to other traditional EMI shielding materials, Co-based AW has better EMI shielding performance (Figure S7, Supporting Information).…”

“…d) EMI shielding mechanism of AWC-D. e) The phase change of the reflected wave on the upper surface and the reflected wave on the lower surface. f ) Comparison of the SE tuning range of the AW composites with other composites [4,9,10,38,49,[53][54][55][56][57][58][59][60][61][62].…”