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Materials Science in Additive Manufacturing From 3D printed molds to bioprinted scaffolds

additive manufacturing by embedding the printed hydrogel with optimal parameters to allow the nozzle movement to
within a secondary thermo reversible hydrogel [33,34] . On the conform to the mold profile. In contrast to conventional
other hand, another strategy exploits the addition of self- mold casting, material extrusion into the mold is required
supporting nanoclay materials like laponite as an internal in this process to allow homogeneous layering of cells in
scaffold biomaterial for fabricating complex structures . the construct without negatively impacting viability. It also
[34]
In our approach, shape fidelity was considerably improved opens the door for the printing of multi-cellular scaffolds.
for peptide-based bioinks as compared to previous studies Based on the observations from this study, our method
regarding 3D bioprinting without support structures. is recommended as a supplementary approach for 3D
In experiments without support, it was only possible to bioprinting with soft bioinks to enhance mechanical
print the human ear model with basic outlined features, stability in fabrication without compromising cell viability.
yet geometries were not preserved in the construct. A valuable advantage of this approach is time efficiency
Hence, the method proved instrumental in maintaining and material conservation, as it removes the need for
essential geometries and print resolution. Moreover, our incorporating supports during printing. As the molds can
bioprinting approach is not temperature dependent, while be created in advance and easily be reused after cleaning
the bioprinted construct can be stored within the mold with ethanol, the printing process is not additionally
inside of an incubator and then removed, suggesting an lengthened, and cell viability is not jeopardized.
alternative strategy for the fabrication of complex 3D Alternative use of this method could be in the absence of
bioprinted structures. a 3D bioprinter, where 3D molds can be used to hold cell-
Fabrication of the mold went through several iterations laden soft bioink scaffolds and allow them to take shape
to achieve optimal results and appreciate the effectiveness over time. Due to the agile fabrication process, edits and
of the presented method. It was concluded that precise customization can be easily made and done repeatedly.
modification is essential before mold fabrication to ensure Our data also suggests that the Formlabs® elastic resin
accuracy and reusability of the support structure. FEA shows low cytotoxic effects when incubated with cells
analyses with the flexible material were crucial in creating overnight, since the number of live cells was considerably
an easy release technique for removing the construct after higher than dead cells (Figure 4B). This opens the possibility
printing. A further advantage could be taken of the mold’s for printing with softer materials that require a longer time
flexibility by reducing its border thickness. A decrease in to solidify and harden to maintain high shape fidelity.
thickness of 0.3 mm was found to make a considerable Molds could also be created from biodegradable materials
difference in the ease of removing the human ear construct. to disintegrate over time as cellular scaffolds take their own
It was also found that a 3-4 mm range is optimal for the shape. From this aspect, four-dimensional bioprinting and
thickness and flexibility to be maintained (Figure 3A and B). long-term shape fabrication can be further explored.
Using a commercially available SLA 3D printer with a
laser power of 250 mW facilitated the printing of small and 5. Conclusion
highly accurate support structures. In addition, the elastic The proposed “3D Printed Molds to Scaffolds” method is
resin material allowed the fabrication of a precise, highly a practical additive manufacturing approach to improve
flexible mold. Resolution and flexibility play an important biofabrication of soft material constructs. In the future,
role in making the method successful. Due to the non- traditional EBB methods will need to be paired with such
cytotoxicity of the material, the mold can be inserted in the techniques to make tissue and organ fabrication a wide-
incubator with cells to continue growing. Post-printing, scale reality. The hybrid approach enables the growth of
the cells can grow to the fine details of the mold. Further cells, which highlights its potential role in biofabrication.
modifications to the design can allow media and nutrition 3D bioprinted human ear scaffolds were observed to
to reach the cells to enhance the post-printing growth. maintain shape fidelity and cell viability. Automated time-
The automated pumping process for bioink extrusion dependent pumping of bioink and optimized g-code
allowed the construct to take shape during the print parameters were essential in achieving successful prints
without any clogging or disruption. It is worth mentioning with the mold. Moreover, the proposed method was
that printing tests done without automated pumping optimized and improved to achieve the intended goal.
produced constructs with looser infills, which made them
more fragile and difficult to remove from the mold without Funding
causing damage. G-code optimization requires a number The research reported in this publication was supported
of iterations to achieve free movement of the nozzle in the by funding from King Abdullah University of Science and
mold without collision. It is essential to slice the g-code Technology (KAUST).

Volume 1 Issue 1 (2022) 7 https://doi.org/10.18063/msam.v1i1.7