Page 470 - IJB-9-4

International Journal of Bioprinting β-Ti21S auxetic FGPs produced by laser powder bed fusion

In light of the elastic modulus of the two bulk materials Funding
(E = 52GPa for Ti-21S, E = 110GPa for Ti-6Al-4V), a
reduction of around 53% is observed by using the novel This work is part of the project N. 2020.0042 - ID 50430,
β-Ti alloy to produce the FGPSs. “Produzione additiva di protesi ortopediche a struttura
trabecolare in Ti-beta” funded by Fondazione Cariverona.
4. Conclusion
Conflict of interest
2D and 3D metrological characterizations were carried out
on two different auxetic FGPSs with aspect ratio equal to The authors declare that they have no know financial
1.5 and angle θ of 15° and 25°, corresponding to relative interests or personal relationships that could have appeared
to influence the work reported in this paper.
density gradients of 0.34 – 0.49 – 0.66 and of 0.40 – 0.58 –
0.75, respectively. Quasi-static and cyclic compression tests Author contributions
were performed to evaluate quasi-elastic modulus, yield
stress and cyclic Young’s modulus. Simulation analyses Conceptualization: Lorena Emanuelli
based on the homogenization method were conducted, and Investigation: Lorena Emanuelli, Alireza Jam, Raffaele De
the results obtained were compared with the experimental Biasi, Carlo Lora
values. The main results of the study may be summarized Methodology: Lorena Emanuelli, Raffaele De Biasi, Anton
as follows: du Plessis, Matteo Benedetti, Massimo Pellizzari
Resources: Lorena Emanuelli, Raffaele De Biasi
(i). 2D metrological characterization by SEM highlights Writing – original draft: Lorena Emanuelli, Raffaele De
a subdimension of the strut and an oversizing of the Biasi, Anton du Plessis, Matteo Benedetti, Massimo
pore size due to laser printing process in both auxetic Pellizzari
FGPSs with the exception for the auxetic θ = 25° high Writing – review & editing: All authors
density level, where the loss of the auxetic geometry
affects the analysis. Ethics approval and consent to participate
(ii). 3D metrological characterization by X-ray µ-CT
imaging shows an undersizing of both the pore size Not applicable.
and strut thickness because of the surface irregularity Consent for publication
and unmelted powders on the strut surface with
higher accumulation at the corners of the auxetic Not applicable.
geometry. The excess of material at the corners
increased by increasing the θ angle, and the results Availability of data
were not affected by the different relative density level. No additional data are available to the public.
(iii). The 3D metrological characterization, by means of
µ-CT imaging, permits a more holistic method to References
evaluate the printability of the auxetic FGPSs thanks 1. Geetha M, Singh AK, Asokamani R, et al., 2009, Ti based
to the analysis of the entire volume. biomaterials, the ultimate choice for orthopaedic implants-a
(iv). A good correlation between calculated and review. Prog Mater Sci, 54: 397–425.
experimental mechanical properties is obtained. https://doi.org/10.1016/j.pmatsci.2008.06.004
A refined analysis using real strut thickness leads to
an elastic modulus very close to the experimental 2. Gepreel MA, Niinomi M, 2013, Biocompatibility of Ti-alloys
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modulus. On the other hand, for the auxetic structure 3. Kumar A, Nune KC, Misra RD, 2016, Biological functionality
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the experimental one. This highlights the excess ornamented three dimensional Ti-6Al-4V mesh scaffolds.
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case of too high density level where the loss of auxetic https://doi.org/10.1002/jbm.a.35809
structure occurs.
4. Wang X, Xu S, Zhou S, et al., 2016, Topological design
Acknowledgments and additive manufacturing of porous metals for bone
scaffolds and orthopaedic implants: A review. Biomaterials,
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Volume 9 Issue 4 (2023) 462 https://doi.org/10.18063/ijb.728