3D Printing of Periodic Porous Metamaterials for Tunable Electromagnetic Shielding Across Broad Frequencies

Abstract

The new-generation electronic components require a balance between electromagnetic interference shielding efficiency and open structure factors such as ventilation and heat dissipation. In addition, realizing the tunable shielding of porous shields over a wide range of wavelengths is even more challenging. In this study, the well-prepared thermoplastic polyurethane/carbon nanotubes composites were used to fabricate the novel periodic porous flexible metamaterials using fused deposition modeling 3D printing. Particularly, the investigation focuses on optimization of pore geometry, size, dislocation configuration and material thickness, thus establishing a clear correlation between structural parameters and shielding property. Both experimental and simulation results have validated the superior shielding performance of hexagon derived honeycomb structure over other designs, and proposed the failure shielding size (D_f ≈λ/8 - λ/5) and critical inclined angle (θ_f ≈43° - 48°), which could be used as new benchmarks for tunable electromagnetic shielding. In addition, the proper regulation of the material thickness could remarkably enhance the maximum shielding capability (85 - 95 dB) and absorption coefficient A (over 0.83). The final innovative design of the porous shielding box also exhibits good shielding effectiveness across a broad frequency range (over 2.4 GHz), opening up novel pathways for individualized and diversified shielding solutions.

Keywords: 3D printing; Honeycomb pore structure; Periodic porous metamaterials; Polymeric component; Tunable electromagnetic shielding.

Fig. 1

a Schematic diagram for preparation of TPU/CNTs printing filaments and the 3D printing process. The characterization of CNTs and TPU/CNTs suspension, including b Zeta potential, c particle size distribution and d UV–Vis-NIR spectrum; e CNTs stability characterization by using UV–Vis-NIR spectrum at 500 nm wavelength; f EMI SE of TPU/CNTs composite filament, g compressive strength versus strain curves and h the compression deformation rate of L-n composites with different CNTs content

Fig. 2

a FDM printing models and the optical images of printed parts (dimensions of 22.9 × 10.2 × 2.0 mm³) with different periodic pore units; b Optimal images of the printed different periodic pore structure units (assembled in circular porous part with diameter 12 mm and thickness 2 mm) with different inscribed circle diameter (D_in); c SEM images of 0.8 mm D_in size samples with different pore units

Fig. 3

EMI SE of printed samples with various pore structure unit at different D_in including a straight, b triangle, c square and d honeycomb; e EMI SE versus pore factor c of corresponding printed samples; the simulation results of f electric-field distribution and g power loss density of 2 mm D_in sample with different pore structure unit; h schematic representation of the corresponding shielding mechanism

Fig. 4

a Optical images of honeycomb sample, b schematic comparison of parameters D_in, D_out and D^*. c Optical images of honeycomb structural units with different D^* dimensions. d Average electromagnetic parameters (SE_T, SE_A, and SE_R), e absorption coefficient A, reflection coefficient R (at L = 2 mm thickness) and f overall EMI SE effectiveness in the X-band for printed samples of different D^* sizes. g EMI SE at 8.5, 10, 12, and 15 GHz for printed honeycomb samples with different size of D^* and h schematic representation of the corresponding shielding mechanism

Fig. 5

a FDM printing models, optical images of printed samples with different thickness. The EMI SE at b 8.5, c 10, d 12 GHz and the e absorption coefficient A and reflection coefficient R of printed samples with different thickness. f Schematic representation of the corresponding shielding mechanism

Fig. 6

a Optical image of the misaligned structure and a schematic diagram of its front view cross section (YZ plane); b top view (XY plane) of the FDM printing models and optical images; c SE_T and d SE_R of printed samples with different misaligned structure; e schematic diagrams and values of different inclined angles θ; f SE_T and g SE_R of printed samples with different inclined angles θ; h schematic representation of the corresponding shielding mechanism

Fig. 7

a Schematic diagram for various transmission form of electromagnetic waves in different scenarios; b–b2 digital photographs of the printed shielding boxes with different D^* size and the compression test with a 15 kg load done on a D^* = 2 mm shielding box; c schematic diagram for placing earphone as EMWs field source inside the printed shielding box and d EMWs radiation intensity value received outside; e schematic diagram of using a microwave oven (300 W working power) as EMWs field source for microwave treatment of a printed shielding box with chocolate filled in, f the corresponding thermal imaging picture, g the extracted specific temperature values and h the digital photographs of the filled chocolate with microwave treatment; i the thermal imaging pictures of the naked chocolate and the filled chocolate in the printed D^* = 15 mm shielding box under irradiation of microwave oven with 1000 W power