Page 178 - v11i4

International Journal of Bioprinting Design of SLM-Ta artificial vertebral body

* d 2 1 2.2. Specimen fabrication
pl � (VIII) Spherical pure Ta powder was used to fabricate the lattice
ys l 2 cos 2 structure and AVB specimens. As shown in Figure 3, the
powder particle size distribution was D10 = 20.19 μm,
where σ is the yield strength of the parent material. D50 = 33.13 μm, and D90 = 52.37 μm. The chemical
ys
Overall, the design parameters of the struts, such as composition of the powder is listed in Table 2.
the ratio of strut diameter to length (d/Ɩ), the inclination An SLM metal three-dimensional 3D printer
angle of the strut (θ), and the number of struts (s), have (DiMetal-100 Pro; LASERADD, China) was employed to
significant effects on the elastic modulus and yield strength fabricate the Ta lattice structure and AVB specimens. The
of the lattice structures. In our previous study, compared to SLM printing parameters are provided in Table 3. Due to
the conventional body-centered cubic lattice structure, the the small strut diameter (0.34 mm) and wall thickness (1
imitation saddle surface (ISS) featured more slightly angled mm), the layer thickness was set to 0.03 mm to ensure
inclined struts, a greater number of struts and nodes, and high molding precision. The optimal process parameters
a higher strut diameter-to-length ratio. According to our of 350 W laser power, 650 mm/s scanning speed, and 0.08
previous results, the ISS lattice structure exhibited a mm hatch distance significantly improved the stability
53
higher yield-stress-to-elastic-modulus ratio than the body- and fluidity of the Ta molten pool, reduced the number of
centered cubic lattice, effectively reducing the risk of stress defects, and resulted in Ta specimens with densities greater
shielding. Therefore, the ISS lattice structure was selected than 99.9%. An interlayer rotation angle of 67° was used
to fill the interior of the AVB. to reduce anisotropy. The specimens were fabricated in a

Three lattice structures, named LS-1, LS-2, and LS-3, closed chamber under high-purity argon gas (99.9999%) to
were generated through Boolean operations. Their sidewall prevent oxidation. Post-processing included sandblasting
curvatures were 0.027, 0.014, and 0 mm , respectively. and ultrasonic cleaning to remove residual powder
−1
AVBs with the same corresponding sidewall curvatures particles from the printed Ta AVB specimens.
named AVB-1, AVB-2, and AVB-3 were obtained by 2.3. Morphological characterization
assembling topological thin-walled structures with lattice The dry weighing method was adopted to measure the
structures, as shown in Figure 2. Due to the small overall porosity of the specimens, as follows:
size of the AVB, a large sidewall curvature resulted in too
few unit cells in the central region. Therefore, the maximum m
sidewall curvature was set at 0.027 mm to ensure the p 1 d (IX)
−1
stability of the lattice structure during compression. t V a
Previous studies have indicated that bone implants with
porosities between 0.6 and 0.8 are favorable for cell and bone where m is the mass of the specimen, ρ is the theoretical
d
t
tissue growth. 32,33,54 The porosity of the lattice structures density of Ta, and V is the volume of the specimen.
a
(LS-1, LS-2, and LS-3) and the AVBs (AVB-1, AVB-2, and The surface morphology and feature size of the
AVB-3) were designed to be 74% and 70%, respectively. specimens were measured using an ultra-depth microscope
The design and actual parameters of the Ta AVB and lattice (VHX-6000; KEYENCE, Japan). As shown in Table 1, the
structure specimens are presented in Table 1. porosities of the AVB-1, AVB-2, and AVB-3 specimens

Table 1. Design and actual values of selective laser melting-tantalum AVB and LS
Specimens Porosity (%) Thin-walled thickness (mm) Lattice structure diameter (mm)
Design Actual Design Actual Design Actual
AVB-1 70 71 1 0.98 0.34 0.35
AVB-2 70 69 1 1.02 0.34 0.36
AVB-3 70 69 1 1.04 0.34 0.35
LS-1 74 75 / / 0.34 0.34
LS-2 74 75 / / 0.34 0.35
LS-3 74 74 / / 0.34 0.35
Abbreviations: LS: Lattice structure; AVB: Artificial vertebral body.

Volume 11 Issue 4 (2025) 170 doi: 10.36922/IJB025150133