Biomedical Engineering Reference
In-Depth Information
simultaneously, causing them to act as one photon of 400 nm, and thus starting the
polymerization reaction [
133
]. The non-linear excitation nature triggers polymer-
ization only in the focal point, while other regions remain unaffected. This
approach has potential solidification resolutions below the diffraction limit of the
applied light.
Moving the laser focus enables the fabrication of a direct “true” 3D object into
the volume of the photosensitive material. Creating reproducible micron-sized
objects with feature sizes of less than 100 nm [
146
] is attainable, thus being superior
to all other SFF techniques regarding accuracy and resolution.
9.3.1.2
Current Limitations and Hydrogel Feasibility
for Laser-Based Systems
SLA has already been frequently applied to develop porous hydrogel-based scaf-
folds (Table
9.1
). Yu et al. [
147
] have described the patterning of 2-hydroxyethyl
methacrylate (HEMA) followed by drying and subsequent rehydration to enable
cell adhesion. Initially, the procedure was applied to create single-layer structures;
however, at present, multiple layers can be superimposed to generate porous 3D
scaffolds. Liu et al. [
30
] selected poly(ethylene glycol)diacrylate (PEGDA) hydro-
gels to construct 3D scaffolds layer by layer using emulsion masks. In that study,
three hydrogel layers were fused at a resolution of several hundreds of microns.
Interestingly, the pores were interconnected enabling cell survival through convec-
tive flow of culture medium. However, this procedure is time consuming, requires a
great number of prefabricated masks depending on the required shape and is not
completely automated. Therefore, one can discuss whether this can be considered as
a genuine rapid prototyping technique. Lu et al. [
139,
148
] have adopted the above-
mentioned procedure to develop scaffolds possessing complex internal architectures
Table 9.1
Hydrogel materials explored in laser-based systems
Laser-based
systems
Hydrogel materials
Cell encapsulation
References
SLA
Gelatin-methacrylate/
gelatin-methacrylamide
×
[
70,
133,
159
]
Hyaluronic acid-methacrylate
√
[
154,
156
]
Cysteine-modi fi ed agarose
×
[
155
]
HEMA
×
[
147
]
PEG-D(M)A
√
[
30,
31,
132,
137,
139,
153
]
PEG-D(M)A
×
[
141,
149-
152
]
m -SLA
Alginate + acrylated TMC/TMP
√
[
135,
136,
157
]
Gelatin-methacrylamide
×
[
133
]
PEG-DA
×
[
158,
164
]
2PP
Gelatin-methacrylamide
×
[
133
]
PEG-DA
×
[
160,
161
]
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