Page 324 - IJB-10-2

International Journal of Bioprinting Continuous gradient TPMS bone scaffold

Figure 3. Three-dimensional model of continuous gradient porous structure.
follows: G_I (ω = 2), G_II (ω = 3), G_III (ω = 4), P_I (ω = 2), The morphology and manufacturing defects of the
P_II (ω = 3), and P_III (ω = 4). The thickness of the models samples were observed by means of scanning electron
is set to 0.4 mm. Figure 3 displays the 3D diagrams of the microscopy (SEM; Model FEI200, FEI, USA).
two sets of models and their specific parameters.
2.2.2. Mechanical properties test
The designed models were manufactured using a Static compression tests were conducted on a universal
metal 3D printing device (L-PBF system CR-PBFM250) testing machine (MTS 809, MTS Systems Corporation,
with Ti-6Al-4V material having a particle size of 15–45 Minnesota, USA) equipped with a 10 kN gravity sensor.
μm. The printing parameters were optimized prior to The loading rate used was 0.5 mm/min. The elastic
printing to ensure high-quality products. The laser power modulus of each sample was calculated from the slope of
used was 290 W, with a laser spot diameter of 85 μm. the linear phase observed at the beginning of each curve.
The scanning speed was set at 2000 mm/s, and the layer
thickness was 40 μm. The printing process was carried 2.3. Finite element analysis of continuous gradient
out under argon protection at a temperature of 26°C TPMS structure
to prevent oxidation. Two samples were made for each 2.3.1. Finite element analysis of mechanical properties
model, and the resulting samples were cleaned using To establish the initial model, Grasshopper was employed,
compressed air and ultrasound. and the generated STL file was imported into HyperMesh
software for topology processing in order to regenerate a
2.2. TPMS structure performance test refined mesh. The mesh model was then imported into
2.2.1. Porosity test ABAQUS software. The bottom of the Z-axis was fixed, and
The total porosity of the samples was determined using the a 40% strain was applied to the upper part of the Z-axis.
dry weighing method, and the calculation formula used The elastic modulus was set to 110 GPa and the Poisson’s
was as follows : ratio to 0.34. After the simulation, the stress distribution of
36
the TPMS structure was visualized.
Porosity (1 m / t V ) (VIII)
s
d
2.3.2. Finite element simulation of permeability
where m is the mass of each sample; ρ is the theoretical Six models with varying porosity were selected for
s
t
density of Ti-6Al-4V (4.42 g/cm ); and V is the volume set the study. These models underwent pretreatment in
3
d
for printing. HyperMesh software before being imported into COMSOL
Volume 10 Issue 2 (2024) 316 doi: 10.36922/ijb.2306