Page 330 - IJB-10-2

International Journal of Bioprinting Continuous gradient TPMS bone scaffold

Figure 10. Comparison of mechanical properties of different TPMS structures: (a) elastic modulus and (b) ultimate strength.

with an increase in the periodic parameter ω, and there is 4. Optimization of Gyroid bone-like
no extreme value, making it challenging to determine the scaffold structure
range of the periodic parameters.
Through the analysis of mechanical properties and
3.3. Permeability of continuous gradient permeability of various continuous gradient TPMS
TPMS structure structures, the results indicate that the G-type gradient
To identify a more suitable bone scaffold structure for structure exhibits favorable mechanical properties and
the human body, the study focused on investigating the permeability, making it more suitable for constructing
permeability of TPMS porous structures with various bone-like structures and promoting bone tissue repair.
continuous gradients. Figure 11 displays the flow velocity However, further optimization design is required to ensure
of different structures and the fluid streamlines from the a better fit between the continuous gradient TPMS structure
side of each bracket and the outlet. These streamlines and the structure of the human femur. The structure of the
effectively highlight the trajectory of cells or nutrient fluids human femur is depicted in Figure 13, which shows the
passing through the bone implant, enabling the analysis continuous change in radial porosity, gradually increasing
of the interaction between the bone implant structure and from the outside to the inside. Additionally, the main force
cells and nutrient fluids that facilitate bone regeneration. acting on the femur is longitudinal. To achieve a continuous
From the figure, it is evident that the streamline trajectory gradient TPMS structure with good permeability and
in the G gradient structure follows a spiral path, whereas mechanical properties, a function can be assigned to the
the streamline trajectory in the P gradient structure is periodic parameter ω, with a restriction of floating around
almost linear. The spiral trajectory facilitates full contact ω = 3. This enables the realization of parametric control
between cells or nutrient solutions and the bone scaffold, over the continuous gradient TPMS bone-like structure.
which is beneficial for bone repair. Figure 12 exhibits the To achieve a radial increase in porosity while
permeability of different structural models. The highest maintaining a constant relative density, the cell size can
permeability is observed in G_II, measuring 2.80 × 10 -8 be adjusted. This involves changing the parameters of the
mm , while the lowest permeability is found in P_III, control period to establish a specific functional relationship.
2
measuring 5.20 × 10 mm .
-9
2
The new functional relation is denoted as Equation XII:
Based on the analysis of permeability, it is evident
that the permeability of G gradient porous structure first (, x yz,) x
x

increases and then decreases with the increase of periodic (, x yz,) y (XII)
y
parameters. As for the P gradient porous structure, its z
permeability gradually decreases. In comparison, G_II z (, x yz,)
and P_III possess similar mechanical properties, but In order to create a continuous gradient TPMS
G_II boasts the best permeability, aligning well with the structure, the following conditions must be met:
characteristics of bone. Consequently, it holds immense (XIII)
potential for practical applications. d d d z
y
x
Volume 10 Issue 2 (2024) 322 doi: 10.36922/ijb.2306