Exploring the Future of Hydrogels in Rapid Prototyping: A Review on Current Trends and Limitations - Biologically Responsive Biomaterials for Tissue Engineering - page 203

Rapid Prototyping techniques
with biomedical applications

Laser-based systems Nozzle-based systems Printer-based systems

FDM
PED
PEM
MJS
3D fiber deposition
PAM
LDM
MDM
3D-Bioplotter™
RPBOD
Robocasting

SLS
SLA 3DP™

TheriForm™
Inkjet printing

-SLA
SGC
2 photon-polymerization

µ

Fig. 9.2 Classification of RP techniques with biomedical applications into laser-, nozzle-, and
printer-based systems

resolution. Every technique is subdued to a lower technical limit size of the smallest
details producible. This so-called lower limit shows a clear relationship with the
feasible scale of the object: the higher the resolution of the smallest details, the smaller
will be its maximum object size [ 131 ] . However, since not all RP techniques are appli-
cable for the processing of hydrogel materials, some more than others, the amount
of RP technologies is further diluted. Figure 9.2 classi fi es the different RP techniques
with biomedical applications. The fabrication of hydrogel scaffolds requires mild
processing conditions. Some of the techniques mentioned in Fig. 9.2 are not able to meet
those constraints due to rather harsh processing conditions. Explaining those is not the
purpose of this review. Only the hydrogel-compatible systems are explained in detail.

9.3.1 Laser-Based Systems

9.3.1.1 Working Principles and Recent Trends of Laser-Based Systems

With the exception of selective laser sintering (SLS), all of the laser-based systems
are suitable for hydrogel processing. Unlike the nozzle- and printer-based systems
that sequentially deposit material, this subclass sequentially deposits light energy in
specific predefined patterns. This directly implies that only photocrosslinkable pre-
polymers can be employed to finally obtain a crosslinked hydrogel network.

Stereolithography (SLA) . SLA is considered to be the first commercially available
SFF technique, developed by 3D systems in 1986 [ 131 ]. An SLA apparatus (Fig. 9.3 )
consists of a reservoir to be filled with a liquid photocurable resin, a laser source