Biomedical Engineering Reference
In-Depth Information
deposition manufacturing (LDM) and two-photon polymerization
(TPP), have recently been investigated, developed, and commercial-
ized for the fabrication of tissue engineering scaffolds utilizing dif-
ferent biomaterials, especially natural biodegradable polymers, as
raw materials.
SLA is based on the use of an electromagnetic radiation source,
typically ultraviolet (UV) radiation, to initiate photopolymerization
of photopolymerizable resins. With the investigation and develop-
ment of photopolymerizable biomaterials, SLA becomes increas-
ingly popular for scaffold fabrication.
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With the development of
materialscience,somehydrophilicpolymerscanbemodifiedbythe
addition of a photolabile group and thus become photolabile and
cross-linkable. For example, some photoreactive and cross-linkable
groups such as acrylates or methacrylates can be easily attached to
poly(ethylene glycol) (PEG) and then cross-linked into a PEG hydro-
gel for use in tissue engineering and even for encapsulating cells in
thepresenceofacytocompatiblephotoinitiator.
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Poly(propylene
fumarate) (PPF), an unsaturated linear polyester that can be cross-
linked by UV light and degraded by simple hydrolysis of the ester
bonds into nontoxic products, is suitable for SLA and is a promising
biodegradable material for bonetissueengineering.
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FDM developed by Stratasys Inc., USA, utilizes a temperature-
controlled head to extrude thermoplastic materials to build solid
objects layer by layer. FDM is constrained by the use of thermo-
plastic materials with good melt viscosity properties, and cells
cannot be encapsulated into scaffolds during the FDM process
due to the high temperatures applied. In the past, only a few
non-resorbable polymeric materials, such as polyamide, acryloni-
trile butadiene styrene (ABS), and other resins, could be used for
FDM. Recently, poly(
ε
-caprolactone) (PCL) filaments were fabri-
cated from PCL pellets, with a consistent filament diameter fitting
for the FDM system for building fibrous PCL scaffolds.
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Further-
more,biodegradablebioceramic-polymercompositescaffoldsbased
on calcium phosphate/PCL were fabricated through FDM for bone
tissue engineering.
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3D printing was first developed at the Massachusetts Institute
of Technology (MIT) and has become perhaps one of the most
widely investigated RP techniques for scaffold fabrication.
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During
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