Direct Ink Writing for High-Efficiency Microwave Attenuation with Nanofibers Alignment.

One-dimensional (1D) fibers have been widely used in composites reinforcement for microwave attenuation due to their outstanding mechanical and electromagnetic properties, especially in the axial direction. However, the precise control of fiber alignment in a polymer matrix remains a challenge. In this work, we successfully demonstrated the well-controlled alignment of silicon carbide nanowires (SiCNW) in a silicone matrix by using direct ink writing (DIW)-based 3D printing. It is proven that the printed multilayer material with fiber alignment could show a dramatic improvement in both reflection loss (RL) and effective attenuation bandwidth (EAB, RL < -10 dB). In particular, a uniaxial in-plane orientation is found to be the optimal alignment among other planar and also out-of-plane orientations. Benefiting from the optimized alignment, the 3D-printed SiC composite could show an EAB (∼6.4 GHz)1.6 times broader than that of the randomly mixed composite at the same thickness without alignment, associated with a minimum RL of -48 dB at 14.3 GHz. In addition, it is demonstrated that DIW could print different materials, such as SiCNW and multiwall carbon nanotube (MWCNT), in alternating layers for multiple-frequency-band attenuation benefiting from the distinct property of each material. Considering the one-step control of fiber alignment and material selectivity, DIW could play an important role in materials design for high-efficiency microwave attenuation.