Page 27 - IJB-10-6

International Journal of Bioprinting Bioprinting for wearable tech and robot

2. Bioprinting process pivotal element in the bioprinting process. The laser-
31
based approach utilizes a focused laser beam to locally cure
2.1. Bioprinting methods bioinks through a process known as laser-induced forward
Principal bioprinting methods include inkjet, extrusion, transfer (LIFT). Conversely, SLA typically involves the
32
laser, and stereolithography (SLA)-based approaches. use of a digital light projector or laser that scans across the
In this section, we categorize the various bioprinting surface of a photopolymer resin, curing it layer-by-layer to
methods based on the type of physical field used. For form the desired 3D structure. Compared with extrusion
33
example, extrusion and inkjet printing are classified as or inkjet bioprinting, the use of optics usually enables
force-controlled methods, whereas laser and SLA printing higher-resolution patterning, necessary for producing
are considered light-controlled methods. constructs with finely detailed architecture.

2.1.1. Extrusion and inkjet bioprinting Laser and SLA-based methods can be distinguished
Extrusion and inkjet bioprinting fundamentally share based on their requirements in printing materials and
several similarities. 21,22 The techniques involve the precise preservation of biological activity within the printed
deposition of bioinks, consisting of living cells and structures. Laser-based bioprinting requires bioinks that
biomaterials, through a computer-controlled delivery are suitable for accurate LIFT and enable rapid solidification
system. Recently, Yang et al. proposed a mechanical without compromising the viability of encapsulated cells.
extrusion-based bioprinting strategy to load cells into Afting et al. proposed a platform for minimally invasive
hollow hydrogel-based scaffolds (HHSs). The scaffolds had microimplant manufacturing based on one-photon
high mechanical responsiveness to load cells and provided photopolymerization and multi-photon 3D laser printing,
an efficient and promising way for cell-based therapy. displaying significant promise for engineering complex
23
Both extrusion and inkjet methods require careful tuning microarchitectures. SLA often requires selective curing
34
of printing parameters, including pressure, speed, and of the material within a container to develop the desired
resolution, to ensure high cell viability and precise control structure in a layer-by-layer manner. Nonetheless, the
over the mechanical and structural properties of the final SLA method surpasses the laser-based method in terms
construct. Another similarity of both approaches is their of printing efficiency by allowing multiple structures to be
capability to print a wide range of biomaterials, including printed in a single run without vat cleaning, which reduces
hydrogels, polymers, and ceramics, for fabricating various the printing time and increases productivity. Kam
35
tissue types. Buduo et al. utilized inkjet bioprinting to print et al. presented a thermal initiator for 3D printing that
silk fibroin, a natural protein derived from Bombyx mori enabled localized polymerization using near-infrared and
cocoons. The printed structure had viscoelastic, shear- visible light. The proof-of-concept successfully fabricated
thinning, thixotropic, and transparent features, and was hydrogel and polymeric objects using SLA and two-photon
employed as enzymatic sensors for quantitative analysis. 24 printing techniques, offering versatility and potential
There are also several differences between the two for new applications, especially in creating scaffolds
modalities. 25,26 Extrusion-based bioprinting utilizes a for bioprinting. 36
process where a continuous stream of biomaterials is Laser and SLA-based bioprinting offers high resolution
extruded through a nozzle and deposited in a predetermined and precision for fabricating intricate tissue structures. In
27
pattern. Conversely, inkjet printing utilizes the deposition contrast, extrusion and inkjet methods are more scalable
of small droplets of bioink. Inkjet printing features higher and versatile but may lack the level of detail and accuracy.
printing precision but may result in lower cell viability Additionally, electrospinning, magnetic, and acoustic
38
37
due to the forces exerted during droplet formation. In printing have also been used in bioprinting. These methods
28
39
contrast, extrusion-based printing offers better control incorporate diverse principles and techniques, including
over the printing process, enabling the printing of highly magnetic fields, ultrasonic vibrations, and electromagnetic
complex structures with high cell viability. Additionally, forces, for controlled deposition of cells and biomaterials.
extrusion-based bioprinting is known for its ability to The key criteria for selecting a bioprinting method include
print more complex biomaterials, such as thermoplastic features like accuracy, resolution, speed, capacity for
polymers and alginate gels, which may be challenging to creating complex structures, material biocompatibility,
deposit using inkjet printing. 29,30 and potential for scalability in manufacturing. 40
2.1.2. Laser and stereolithography-based bioprinting 2.2. Bioprinting materials
Laser and SLA-based bioprinting are two advanced The progress and innovation in bioprinting have
biofabrication techniques that conceptually emphasize fundamentally relied on advancements in material science.
light-initiated polymerization or crosslinking as the The development of materials with specific properties has

Volume 10 Issue 6 (2024) 19 doi: 10.36922/ijb.3590