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International Journal of Bioprinting Coronary and peripheral artery disease. State of the art.

main limitation of this technique regarding copper, chromium, cobalt chromium, stainless
tissue engineering and bioprinting of artificial steel, and super-alloys should be mentioned. After
tissues or medicines is the high temperatures of the deposition of a thin, uniform layer of powder,
the majority of thermoplastic polymers, which the laser scans the desired shape to induce melting
are incompatible with the stability of drugs, cells and fusion of the material, thus binding the
and a wide variety of biological ingredients [48-50] . powder particles to create the 3D construct [55-57] .
Nonetheless, owing to the required properties This 3DP technique is usually associated to rough
and features of VS, FDM allows the production surfaces in the final 3D constructs, which is
of tough and resistant 3D constructs, thus undesirable when it comes to VS [37] . Therefore, the
accomplishing the optimal mechanical properties use of PBF necessitates post-processing techniques
of these medical devices. (such electrochemical polishing) to smoothen the
construct’s surface.
(ii) Vat photopolymerization (VPP) embodies all
the techniques in which a “liquid photopolymer (v) Binder jetting (BJT) 3DP is also known as “drop-
in a vat is selectively cured by light-activated on-solid deposition,” “drop-on-powder,” “drop-on-
polymerization” (ISO/ASTM 59000:2021). In bed sedimentation,” “binder jetting,” or “plaster
the field of 3DP, digital light processing (DLP) printing” . BJT is a non-contact 3DP technique based
[50]
and stereolithography (SLA) (Figure 4) can be on the spreading of a solid material (often powder)
differentiated. Both of them use laser-based liquid followed by a liquid linker or binder (Figure 4). The
resin polymerization technology, differing in the liquid binder, deposited in the required areas, binds
light source and the curing methodology employed: the powder and increases its consistency layer-by-
SLA utilizes a mobile UV laser beam while DLP layer, thus creating the 3D structure.
works with UV light from a static projector. In DLP,
the UV light remains stationary, and the entire liquid Solvent-casting 3DP (SC-3DP) is midway between
receives light with a single projection of the structure PBF and MEX 3DP techniques. Depending on the type
to be printed; in SLA, the laser beam moves while the materials used, they can be classified as extrusion-
tracing the geometry layer-by-layer . Therefore, based 3DP or as powder-solidification 3DP. In SC-3DP,
[50]
DLP is faster than SLA, though the precision and the solid material and its proper binder are mixed in the
accuracy can be compromised for too complicated same cartridge, that is, the powdery material (either metal
structures. Another remarkable difference to bear or polymer) is mixed with its proper binder system (i.e.,
in mind, especially when it comes to scale-ups, is polymers, volatile solvents, etc.) and extruded through
the production costs, since SLA printers are more a nozzle. Post-processing steps such as debinding and
[58]
expensive than DLP. sintering techniques are needed afterward . Debinding
refers to the elimination of unnecessary additives (such as
(iii) Material jetting (MJT) 3DP technique is also binding polymers). Sometimes, this step consists of solvent
known as “drop-on-drop deposition,” “droplet- evaporation in an open environment. A sintering process
based 3DP” or “inkjet 3DP” (Figure 4). It is a is the binding or “coalescence” of a solid mass by means of
non-contact printing technique that reproduces heating or compression, and a post-processing step, which
the 3D design by selectively depositing droplets can be overlooked for most polymers, is usually necessary
of the so-called “ink.” These droplets can be for strong materials such as metals.
created by different techniques such as thermal,
piezoelectric or electrostatic actuators. MJT 3DP 4. 3D printing for vascular stents
can also be divided into continuous or drop-on-
demand, depending on the frequency of ink drop Although all 3DP techniques are based on the same
ejection [19,52-54] . principle, there are significant differences between them
that significantly affect the employed materials, the
(iv) Powder bed fusion (PBF) 3DP is also known as printing procedure and the final properties of the 3D
selective laser melting or selective laser sintering construct. In other words, not all the 3DP techniques are
(Figure 4). It consists on fusing metallic powders suitable for the production of every VS, and not every
by melting them with a high power-density laser. material is compatible with all the 3DP processes. In view
PBF enables the generation of 3D scaffolds with of this, it seems logical to address the available studies in
superior geometrical freedom in comparison to view of the 3DP technique used in each case so as to gain a
other 3DP techniques. Among the most used more comprehensible understanding about the strong and
materials for this technique, aluminum, titanium, weak points of each technique.

Volume 9 Issue 2 (2023) 231 https://doi.org/10.18063/ijb.v9i2.664