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

NH (IZZK) peptide bioinks for bioprinting applications suction force-driven, high-velocity flow of the hydrogel
2
have been reported . These peptides have been rationally prepolymer that backs up the continuous replenishment
[17]
designed as ultrashort and self-assembling are considered to of the prepolymer solution below the curing part and
be an encouraging class of biomaterials as they address several the nonstop part growth. The process is unique for the
limitations that are affiliated with bioinks . Amphiphilic hydrogel prepolymer without externally supplemented
[18]
peptides are composed of 3 – 7 amino acids in length and oxygen. The rapid printing of centimeter-sized hydrogel
they self-assemble under physiological conditions to form models using FLOAT has exhibited a significant reduction
hydrogels from nanofibers that meticulously resemble fibers in deformation and cellular injury caused by prolonged
within the extracellular matrix. The characteristics previously exposure to environmental stresses in layer-by-layer-based
mentioned make ultrashort peptides a suitable biomaterial for printing methods.
regenerative medicine applications and tissue engineering .
[19]
Susapto et al. have demonstrated the excellent tunable Meanwhile, the additional degrees of freedom of robots
mechanical properties of their bioinks, thus making them have increased the capability, quality, and productivity of
[25]
suitable as robust bioinks for 3D bioprinting . These bioinks traditional 3D fabrication . One of the major issues in
[17]
avoid cell compromising abrasive conditions like chemical conventional additive manufacturing addressed by Bhatt
treatments or ultraviolet (UV) cross-linking during the printing et al. is that printing structural layers perpendicularly
[26]
process. Their peptide bioinks verified an instantly solidifying limits the types of geometry that can be printed . Robot-
cell-embedding 3D bioprinting process under physiological assisted additive manufacturing allows for change of
conditions at a low, cost-effective bioink concentration. These directions during 3D fabrication, thus making fabrication
[27]
peptide bioinks are capable of being considered superior of complex geometry feasible . A study by Song et al.
due to their biocompatible, body-like, synthetic nature, and concluded that printing in tilted orientations can help avoid
support of an automated cell printing process. the staircase effect that occurs due to the approximation of
planar layers for highly curved geometry . Moreover, a
[28]
The main classification of hydrogels is based on their 3D printing robot can decrease or eliminate, in some cases,
sources - natural, synthetic, and hybrid. Natural hydrogels the need for support structures due to its ability to orient
can be obtained from proteins (elastin, collagen, fibrin, silk the printing tool to reach the objects from different angles.
fibroin, and gelatin), polysaccharides, and decellularized In other words, the tool path of the deposition head can
tissues . Synthetic hydrogels display more versatile and be non-planar in space . This survey paper, Bhatt et al.,
[20]
[26]
easily controlled physical and chemical properties when also mentioned two other advantages of utilizing robots
compared to natural-origin hydrogels . Hybrid hydrogels, as 3D printers in manufacturing which are scalability and
[21]
on the other hand, are a mixture of natural and synthetic mobility of the printed structures . For instance, a recent
[26]
hydrogels, which incorporate structures with desirable study highlights the application of additive manufacturing
characteristics . Hydrogels can also be classified by their in the fabrication of lateral flow assays for the rapid in-field
[22]
structural integrity (durable and biodegradable). Durable detection of COVID-19 .
[29]
hydrogels are mostly synthetic and mechanically stronger
in comparison to hydrogels of natural origin, while In this study, we combined the advancing technologies
biodegradable hydrogels are natural polymers, commonly of additive manufacturing, 3D biofabrication, and
non-toxic, and demonstrate minimal adverse effects robotics to develop a hybrid fabrication approach for
compared to synthetic alternatives . For the hydrogels to high-quality printing of cellular bio-scaffolds with
[23]
function properly, they are expected to meet several design soft bioinks (Figure 1). We offer a multi-step method
criteria so that they can stimulate new tissue formation and involving SLA and extrusion-based printing technologies
induce minimal to no immune reaction from the recipient. to precisely engineer customizable mold support
The selection of these hydrogels depends primarily structures to improve printing resolution and mechanical
on their physical parameters (mechanical properties, fidelity. Our process is implemented by 3D bioprinting a
biodegradability or bioresorbability, porosity, and human ear model with peptide-based bioink embedded
swelling) and biological performance (biocompatibility, with MSCs and assessing the 3D scaffold for mechanical
cell adhesion, vascularization, and bioactivity) . fidelity and cell viability.
[20]
On the other hand, a fast hydrogel projection 2. Method
stereolithography (SLA) technology (FLOAT), which
allows the fabrication of centimeter-sized and multi- We proposed a hybrid fabrication approach to enable 3D
scale solid hydrogel models in minutes has been bioprinting using soft bioink materials, such as peptide
reported . This was achieved by precisely controlling hydrogels, for the printing of complex organ and tissue
[24]
the photopolymerization condition and establishing low structures. The hybrid approach involves a multi-step “3D

Volume 1 Issue 1 (2022) 3 https://doi.org/10.18063/msam.v1i1.7