Page 399 - IJB-10-4

International Journal of Bioprinting Design of biofixed metamaterial bone plates and fillers

(Bocheng, China) was used to observe and process volume ratio, can be designed as the non-load-bearing
the surface morphology of the parts and optimize the part of bone plates to stimulate bone tissue growth,
molding process. promote cell adhesion, and improve biocompatibility.
Nonetheless, analysis of the simulation results warrants
3. Results and discussion further experimental testing to validate the mechanical
performances of the different porous structures.
3.1. Selection of porous materials for the filler
3.1.2. Performance analysis of porous
3.1.1. Finite element analysis of the porous materials mixed-porous structures
The results of the finite element analysis of the porous Results from the finite element analysis suggested that
structures are displayed in Figure 2. From the stress diamond could be used to fill the extensive load-bearing
contour plots (Figure 2a, c, e, and g), it could be observed parts (i.e., cortical bone) of the bone plates to impart its
that under a pressure of 20 N, the maximum stress for the remarkable strength and biocompatibility. Likewise, Split
diamond, gyroid, Lidinoid, and Split P porous structures P could be used to fill the cancellous bone of bone plates
was 5.49e , 1.75e , 2.34e , and 2.50e MPa, respectively. The to enhance their biocompatibility. The contact interface
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diamond structure had the lowest stress concentration, between the different porous structures could directly
indicating relatively higher durability, while the Lidinoid affect the mechanical performance and biocompatibility
structure had a relatively higher stress concentration of the respective porous structures. Therefore, we designed
(i.e., lower durability) safety than the gyroid and Split P a mixed-porous structure using Boolean operations and
structures. The stress distribution of different curved implicit surface fusion methods and evaluated the smooth
porous structures was relatively uniform along the vertical transition effect of the interface using finite element
and horizontal directions, and there was minor stress analysis. The assessments are described as follows:
accumulation in the structures. The insignificant stress
accumulation could be associated with the intersectional (i) Design of the mixed-porous structure and transition
space between the porous curved structures, suggesting at the contact interface: The outer part of the mixed
that the curved surface structures would most likely structure was made of Split P (10 cm × 10 cm × 6
redistribute the stress through deformation. These findings cm), while the inner part was made of diamond (10
indicated that the curved porous structure could have a cm × 10 cm × 6 cm). The external porous structure
higher stability than non-porous structures. of the mixed-porous structure had dimensions of
10 cm × 10 cm × 12 cm, while the internal porous
From the displacement cloud diagrams (Figure 2b, d, f, structure had dimensions of 6 cm × 6 cm × 12 cm. A
and h), the displacement measured in the structures was in small pore size was used externally, and a large pore
descending order: Split P, Lidinoid, gyroid, and diamond size was used internally. Our results revealed that
structures corresponding to 2.69e , 2.38e , 2.07e , and the mixed-porous structure fused by the Boolean
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5.16e mm, respectively. The displacement of different operation displayed a clear boundary at the contact
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porous structures has a cumulative layerwise effect. This interface with sharp edges and evident transitional
indicates that the displacement of curved porous structures defects (Figure 3a). The mixed-porous structure
is more affected by the structure than by changes in fused by the implicit surface fusion method also
porosity. Further interpretation of the results suggests that displayed a clear boundary at the contact interface,
in diamonds, the displacement transfer was considered but the contact edge fusion effect was superior,
optimal, albeit with slight deformation at the bottom of the potentially improving the mechanical strength and
structure. This structural behavior correlated to the low biocompatibility of the bone plate (Figure 3b).
stress concentration in diamonds as aforementioned (i.e.,
stress is released through deformation). (ii) Tensile performance of the mixed-porous structure:
The tensile performance of the mixed structure at
Based on the stress analysis of the porous structure, the the interface was evaluated by tensile simulation.
diamond structure had a large porosity with considerable A tensile force of 20 N was applied to the upper
mechanical properties, while the Split P structure had a surface of the mixed structure, while the lower
large surface area-to-volume ratio and relatively moderate surface was fixed. The material was selected to be
stress concentration at the expense of a large displacement. the 316L stainless steel powder. The finite element
Therefore, the diamond structure can be designed as the analysis results of the tensile performance of the
load-bearing part in medical devices to improve their mixed-porous structure are displayed in Figure 4.
overall structural strength for practical applications. From the stress cloud maps at a tensile force of 20 N
Split P, due to its large displacement and surface area-to- (Figure 4a and c), the maximum stress of the mixed-

Volume 10 Issue 4 (2024) 391 doi: 10.36922/ijb.2388