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Some special electronic equipment not only need to avoid the interference of external electromagnetic waves (EMWs), but also need to transmit effective signals. Therefore, the development of directional electromagnetic interference (EMI) shielding materials has a great prospect. The asymmetric structure, consisting of the porous magentic rGF (reduced graphene oxide and Fe 3 O 4) layer and the dense electrical conductivity rGM (reduced graphene oxide and MXene) layer, was constructed by dual-needle 3D printing technology. After encapsulation and curing with polydimethylsiloxane (PDMS), the rGF/rGM/PDMS composites were prepared. When the ratio of rGF and rGM layers is 6:4, the SE values of rGF-6/rGM-4/PDMS composites are 38.75 dB and 30.79 dB respectively when EMWs are incident on the rGF layer and rGM layer respectively, and the ΔSE of which is about 8 dB. The results showed that the asymmetric structure composed of porous magnetic layer and dense deeply electric conductive layer could generate a special process of "weak reflection-absorption-strong reflection-reabsorption" for incident EMW. At the same time, the simulation results of the waveguide method validated the experimental results, and further explained the directional EMI shielding mechanism of asymmetric structure. For the first time, this work designs an asymmetric structure based on the double needle 3D printing technology, which provides useful inspiration for the structural design and potential application of directional EMI shielding materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon-based (e.g. carbon fibers or carbon nanotube (CNT)) polymer composite materials, due to the high specific strength, and good chemical stability features, is a promising structural material for energy-efficient applications in aerospace and civil infrastructures. However, the difficulty of viscosity-related infusing and curing of polymer limits composite mechanical performance and manufacturing efficiency. Here we overcome these difficulties and report an electrothermal-triggered flooded thermoset curing to enable rapid and energy-efficient manufacturing of carbon/polymer composite. The underlying concept is based on the two-step localized in- situ infusion and curing in flooded polymer by Joule heating of carbon-based materials to facilitate the flow of polymer into the microstructure in low current, followed by curing of polymer resin in high current. The viscosity adjustment and defoaming process in the infusing process and the curing properties (degree of cure and strength) of the composites were used to prove the effectiveness of this curing strategy in composite fabrication. This electrothermal-triggered curing approach provides a rapid, energy-efficient, scalable, and volumetric composite manufacturing technique. Image 1 • An energy-efficient and scalable electrothermal-triggered thermoset curing approach. • The curing approach exhibits the ability to control the viscosity of the polymer. • Electrothermal preforms can facilitate the flow of polymer into the microstructure. • The preparation process of carbon fibers and CNTs composites was demonstrated. [ABSTRACT FROM AUTHOR]