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Zolfagharian, et al.
contribute to landfills. The PLA is used in this study method, the material is added in the areas in which
as it has been found to be feasible for the production of the estimation of the strain energy is too high .
[39]
scaffolds with different architectures and controlled
porosities which are tailored for use as temporary 2.4 Finite element analysis (FEA) and mesh
fixtures in biomedical applications [33,34] . In addition, convergence
polyvinyl alcohol used as support materials, which TO with the minimum compliance criteria was
is a water-soluble, biodegradable polymer under coupled with a structural analysis module in
both aerobic and anaerobic conditions . ANSYS 2019 R2 to evaluate varying splint
[35]
2.3 TO designs. Since, the mechanical properties of the
3D printed parts are affected by the 3D printing
TO is utilized here to create a series of splints parameters, for example, layer thickness and
optimized for the loading conditions. The original raster width, Young’s modulus and Poisson’s ratio
splint will be compared with the topology- of PLA were obtained according to Type I ASTM
optimized splints in mechanical performance and in D638 test standard. PLA with a density of m ,
3
thermal qualities that will affect the users’ comfort Young’s modulus of 2850 MPa, and Poisson’s ratio
experience. With these processes, splints can be of 0.25 were defined for the material properties of
produced with much better mechanical properties the splint. The maximum pressure exerted was
requiring less material, for more breathability and estimated to be 64×10 Pa applied at the rim of the
4
comfort, while having equal strength. In this study, splint, and the base was assumed to fix (Figure 5).
a splint is developed based on TO in which the The domains of 100%, 79.49%, 71.13%, and
algorithm starts from a solid model of the material. 62.51% mass were discretized by unistructural
Distributed loading and boundary conditions are tetrahedral elements with 394,439, 140,904,
defined based on the specifications of the splint 104,634, and 104,026 elements, respectively, as
finger, as shown in Figure 5. The main objective shown in Figure 6, where higher mesh density was
here is to remove the maximum material while selected for the region of interest and local mesh
preserving the volume fraction and maximum refinement was conducted to achieve high mesh
stiffness of the 3D-printed splint [36,37] . quality. Note that mesh independence studies were
The theory of the optimality criteria (OC)
is used in ANSYS Workbench. The OC method A B
uses an estimation of the optimality conditions
to update the design variables of each point .
[38]
The designs are updated independently using this

C D

Figure 6. Domains discretization with tetrahedral
Figure 5. Schematic view of boundary conditions elements for (A) 100%, (B) 79.49%, (C) 71.13%,
on a sample splint design. and (D) 62.51% mass.

International Journal of Bioprinting (2020)–Volume 6, Issue 2 21