Biomedical Engineering Reference
In-Depth Information
SLSparametershaveonscaffolddesign.Despitethisproofofprinci-
ple, work has been done with SLS, demonstrating its potential to be
used to create an effective cell-seeded bone tissue engineering scaf-
fold from image data of a defect site that will support osteogenesis
of the seeded cells.
6
25.5 Fused Deposition Modeling
25.5.1
Scaffold-Manufacturing Process
FDM utilizes an extrusion-based technique to form 3D scaffolds. An
FDM machine consists of a building platform and an extrusion noz-
zle,inwhichafilamentofthescaffoldmaterialisfed(Fig.25.4).The
extrusion nozzle heats the scaffold material to just above its melt-
ing point and deposits the material on the building platform, where
it immediately solidifies. The extrusion nozzle then moves horizon-
tally to deposit a layer of the scaffold. After the layer is complete the
building platform is lowered by a layer thickness and subsequent
layers are built on top of the existing layer to create the 3D scaf-
fold. Materials used in FDM must be thermoplastics as the mater-
ial needs to be readily melted and solidified.
20
Materials commonly
used for bone tissue engineering purposes in FDM include PCL and
polypropylene(PP),aswellascompositescaffoldsofthesepolymers
withHA and TCP (Table25.4).
7
,
8
,
73
-
78
Scaffolds developed via FDM from PCL were shown to support
growthofosteoblast-likecells.Thesescaffoldshadaminimumchan-
nel size of 160
μ
m and porosity as high as 77%.
8
,
77
FDM is able
to achieve higher porosity and a smaller pore size than 3DP and
SLS without trapping particles within the pores since the scaffold
isbuiltfromanextrudedpolymerratherthanaparticlebed.PP-TCP
composite scaffolds manufactured using FDM were also developed
for bonetissue engineeringapplications. Samples were formed hav-
ing a pore size of 160
μ
m and porosity of 36% to 52%. The failure
strength was shown to be comparable to that of cancellous bone.
74
Limitations of FDM primarily result from the limited amount of
scaffold materials that can be used and the elevated temperatures
associated with the melting process.
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