Parametric design analyzed the helical metamaterial's unit structure. The integrated, symmetrical design allows direct 3D printing without assembly, providing a precise fabrication solution.
Currently, traditional electromagnetic wave-absorbing materials struggle to meet practical application demands due to their simplistic loss mechanisms and narrow absorption bandwidth. Inspired by the unique helical microstructure of spirulina, a research team led by Professor Wang Zhi and Lecturer Yin Lixian from North University of China, in collaboration with Professor Tian Xiaoyong's team from Xi'an Jiaotong University, has designed and fabricated a helical metamaterial wave absorber using 3D printing technology. By employing a carbon nanotube-doped acrylonitrile butadiene styrene composite, the team constructed a helical structure with exceptional dielectric loss capabilities and distinctive electromagnetic response, achieving an ultra-wide effective absorption bandwidth of 33.7 GHz (covering 3.5–5.1 GHz and 7.9–40 GHz, with reflection loss RL ≤ -10 dB). The related research has been published in Composites Part B under the title "A bioinspired helical metamaterial for broadband electromagnetic wave absorption."
The preparation and 3D printing process of carbon nanotube/ABS (CNT/ABS) composite filaments were investigated using microfluidic chip technology combined with scanning electron microscopy (SEM). The results revealed that the addition of a toughening agent promoted a more uniform dispersion of CNTs within the ABS matrix. The 3D-printed helical structures exhibited homogeneous micron-scale surface protrusions, confirming the effectiveness of the material preparation process.
Using electromagnetic simulation software (such as CST), a parametric sweep method was employed to study the effects of parameters such as tube diameter, helical diameter, and structural thickness on reflection loss. The results indicate that when the tube diameter is 5 mm, the helical diameter is 14 mm, and the thickness is 10 mm, the absorption bandwidth can reach 34.6 GHz, validating the critical role of structural parameter optimization in wave absorption performance.
The reflection loss differences of helical structures made of three materials—ABS, copper, and CNT/ABS—as well as the differences between the helical and planar structures of CNT/ABS material were investigated through a combined approach of simulation and experimental testing. The results demonstrate that the helical structure made of CNT/ABS achieves a peak reflection loss of -35.1 dB and a bandwidth of 34.6 GHz, significantly outperforming other combinations. Moreover, the helical structure enhances wave absorption capability by modulating impedance matching.
The current direction and amplitude distribution in the helical structure at the 14.8 GHz absorption peak were investigated by monitoring the current density and phase changes using electromagnetic field simulation tools. The results indicate the presence of periodically rotating eddy currents on the helical surface, with the distribution becoming denser as the frequency increases, confirming that eddy current loss is one of the key mechanisms for wave absorption.
The direction and amplitude distributions of electric and magnetic fields within the helical structure unit were investigated using three-dimensional field simulation. The results reveal that closed loops of electric and magnetic fields form on the cross-section, with the resonance region shifting from the bottom to the top of the structure as the frequency increases, indicating that local electromagnetic resonance enhances the energy absorption efficiency.
The standing wave effect within the helical structure was investigated by simulating electric field waveforms under different phases and frequencies. The results indicate that a distinct standing wave forms at 14.8 GHz, where the distribution of nodes and antinodes prolongs the propagation path of electromagnetic waves and enhances energy dissipation, with the standing wave effect being more pronounced in the lower frequency band.
Based on material characterization and structural analysis, the absorption mechanism of the helical metamaterial was investigated. The results indicate that its absorption performance stems from the synergistic effects of material-related dielectric loss (including conduction loss and dipole polarization loss) and structural effects (such as eddy current loss, electromagnetic resonance, and standing wave effects), which collectively enhance the electromagnetic wave energy conversion efficiency.
The measured reflection loss of the optimized helical metamaterial was investigated using an arched frame reflection method combined with a vector network analyzer, and compared with traditional absorbers. The results demonstrate a measured bandwidth of 33.7 GHz (covering 3.5–5.1 GHz and 7.9–40 GHz), a peak reflection loss of -31.5 dB, and a thickness of only 10 mm. Its performance surpasses that of most conventional absorbers, validating the practicality of the design.
Conclusion
This study proposes a spirulina-inspired helical metamaterial absorber that achieves ultra-broadband electromagnetic wave absorption through the synergistic integration of material and structure. After systematically optimizing the geometric parameters of the CNT/ABS composite metamaterial, experimental measurements recorded an absorption bandwidth of 33.7 GHz (covering 3.5–5.1 GHz and 7.9–40 GHz; reflection loss ≤ -10 dB) and a peak reflection loss of -35.1 dB. This helical metamaterial addresses limitations of metallic helices (weak loss capability) and magnetic metamaterials (high mass density, poor physicochemical stability), demonstrating exceptional performance while maintaining structural compactness. It provides a novel solution for next-generation stealth technology and electromagnetic pollution mitigation.
Source:
https://doi.org/10.1016/j.compositesb.2025.112685
Morphology of the Fabricated Material and Its Preparation Process 
The effect of parameter variation on reflection loss. 
Comparison of Electromagnetic Properties for Different Materials and Structures 
Current and Field Distributions 
Field Direction and Amplitude Distribution 
Distribution of the Vertical Electric Field 
Schematic Diagram of the Absorption Mechanism 
Measurement Results and Performance Characterization 