Page 137 - MSAM-4-3

Materials Science in Additive Manufacturing Sunflower-inspired microwave-absorbing metastructure

A C

B

Figure 1. Modeling process for the sunflower-inspired metastructure. (A) Schematic representation of the spiral arrangement of seeds in a sunflower head,
serving as the structural inspiration for the metastructure. (B) Outline of a single constant-velocity spiral. (C) Construction of mirrored and concentric
spiral contours

where R represents the polar radius, θ is the polar angle, A
i
i
and k is the coefficient defining the spiral expansion rate.
i
Figure 1C illustrates the modeling process of a sunflower-
inspired spiral. Initially, the outermost spiral radius R is
1
determined by the periodic unit length L (equal to 2R).
Subsequent spirals are generated by performing mirror
reflections (along the polar radius) and ring-array rotations
(around the coordinate origin), progressively determining
inner spiral intersections. This iterative process results B
in a gradient arrangement of spiral radii along the
z-axis, producing a sunflower-like three-dimensional
spiral structure in both clockwise and counterclockwise
orientations.
A periodic array of these metastructure units is formed
along the x and y directions (Figure 2A). Specific geometric
parameters of the unit are detailed in Figure 2B. To achieve
optimal electromagnetic performance, multiple spiral
layers with distinct spiral coefficients (k , k , k , and k ) are Figure 2. Structural characteristics of the sunflower-inspired
metastructure. (A) Periodic array arrangement along the x and y axes.
2
1
3
4
stacked vertically, creating a gradient distribution. Each (B) A single metastructure unit cell illustrating key geometric parameters
spiral layer possesses an identical thickness (h =h =h =h ).
1
4
3
2
Electromagnetic simulations, including RL analysis and and polymer matrix PLA powder (4032D) (Dongguan
evaluations of electric, magnetic, and power loss field Huachuang Plastic Technology Co. Ltd., China). The
distributions, were performed using CST Studio Suite sunflower-inspired metastructure was fabricated using
software (Dassault Systèmes, France). FDM 3D printing (Figure 3). Before printing, CB-CIP/
PLA composite filaments were prepared. First, CB and PLA
2.2. Materials and fabrication were dried at 80°C for 6 h to remove residual moisture.
The raw materials used in this study included CB powder Subsequently, PLA was mixed with 1.5 wt.% aluminate
(surface area 55 – 70 m²/g, resistivity 2.5 Ω·m) (Tianjin coupling agent, followed by the addition of 20 wt.% CB
Zhengyuan Technology Co. Ltd., China), CIP powder and 30 wt.% CIP. Note that the weight percentages here
(Hebei Lebo Metal Material Technology Co. Ltd., China), are relative to the PLA matrix mass. This mixture was
Volume 4 Issue 3 (2025) 3 doi: 10.36922/MSAM025220048