Page 430 - IJB-10-1

International Journal of Bioprinting Mechanically biomimicking 3D bone model

Figure 3. Simulation results showing strain distributions of local-implant and entire-surface compression (A-i and B-i, respectively) in the comparison
between infill-uniform and infill-varied structures. Experimental initial-state deformation of infill-varied structures under local-implant and entire-
surface compression (A-ii and B-ii, respectively).

ratio were referenced from the material data provided relationship between the design parameters (D , D , vol )
S
S
H
by 3D printing filament manufacturer. The material and the correlated mechanical properties based on the
properties and boundary conditions for the simulation are sequential deformation behavior. Figure 4 shows cross-
provided in Figure S2 and Table S1 in the Supplementary sectional images of six different specimens where the
File. For the entire-surface compression, the strain was design parameters of infill were varied, which allowed a
evenly distributed throughout the part for the infill- comparison of their compressive properties. Specimens
uniform structure but was concentrated in the central soft (i), (ii), and (iii) had the same D and vol , but different D
S
H
S
part for the infill-varied structure (Figure 3B-i and B-ii). values of 45%, 35%, and 25%, respectively, and specimens
By contrast, the local-implant compression caused the (iv) and (iii) had the same D and vol , but different D
S
S
H
strain distribution to be concentrated near the surficial values of 20% and 15%, respectively. Specimens (iv), (v),
regions for both infill-uniform and infill-varied structures. and (vi) had the same D and D , but different vol values
S
H
S
The simulation results support that the infill density of 33%, 50%, and 67%, respectively. These infill conditions
of the surficial part dominates the initial deformation of each specimen from (i) to (vi) were compared, as shown
behavior and the correlated mechanical stiffness in the in Table S2 (Supplementary File). The stiffness and failure
case of implant compression in the bone model, regardless load of these six specimens were compared to determine
of the infill variation. Furthermore, the experimental the relationship between the structural design parameters
results revealed that the implant locally compressed the and mechanical properties.
infill-varied structure as the surficial indentation without The compressive properties of specimens (i), (ii), and
buckling of the soft part (Figure 3A-ii).
(iii) were compared in Figure 5A, revealing that while the
3.3. Tunable mechanical properties of infill-varied failure load remained constant, the stiffness increased as
structure D increased. This was due to the increased resistance for
H
In the previous section, we confirmed that the compressive local compression caused by the higher infill density in the
deformation of infill-varied structure occurred surficial hard region. However, the local compression did
sequentially based on the dominant force acting on not affect the outer wall, where the infill-varied structure
the surficial or central part. We next investigated the buckled, causing a similar level of failure load. Therefore,

Volume 10 Issue 1 (2024) 422 https://doi.org/10.36922/ijb.1067