Design and performance of a flexible broadband metamaterial absorbing structure fabricated based on the direct ink writing 3D printing

Abstract The method of three-dimensional (3D) printing significantly improves the design freedom of absorbing structures as these are fabricated under the layer-by-layer stacking mode. A four-layer gradient woodpile metamaterial absorbing structure (FGWMAS) based on the direct ink writing 3D printing (DIW3DP) is proposed. First, carbonyl iron powder/polydimethylsiloxane, which endows FGWMAS with outstanding flexibility, chemical and thermal stability, is prepared as the absorbing composites. The electromagnetic parameters are measured and used as inputs of the FGWMAS design. Additionally, the correlation is established between DIW3DP process parameters and the cross-sectional dimensions of the woodpile unit cell. Furthermore, the validity of the equivalent medium theory is verified, and it is utilised to realise the rapid design of FGWMAS. The thickness of each layer is optimised using genetic algorithms, and the optimised FGWMAS is obtained. The simulation results reveal that the maximum effective absorbing bandwidth of the proposed FGWMAS is up to 12.15 GHz (5.85–18 GHz) in the 1–18 GHz band range, and the minimum reflectivity is −37.91 dB at 10.95 GHz. This paper provides a new design and manufacturing method for metamaterial absorbing structures with micro unit cells. The DIW3DP flexible metamaterial absorbing structure has strong potential for conformal, low-cost, and customised application.