Biomedical Engineering Reference
In-Depth Information
scaffoldstomakethescaffoldsosteoconductive.Anumberofgroups
chose PCL as the matrix polymer due to its good biocompatibility.
51
Other biodegradable polymers, such as polyvinyl alcohol (PVA),
PLLA, and PLGA (LA:GA=95:5), and their composites were also suc-
cessfully processed into scaffolds by using the SLS technique.
47
,
52
Generally, dry-blending was used to mix polymer granules with bio-
ceramicpowders.Themixtureswerethensinteredtoformscaffolds
accordingtorespectivescaffolddesigns.Usingdry-blendingtomake
raw materials for RP techniques has advantages and disadvantages,
and one obvious disadvantage is the inhomogeneous distribution of
fine bioceramicparticles in RP-produced scaffolds.
A new strategy for making good-quality composite scaffolds
via SLS is to use composite microspheres instead of dry-blended
bioceramic-polymer mixtures. Our previous investigations demon-
strated the feasibility of this strategy by forming, via SLS, carbon-
ated hydroxyapatite (CHAp)/PLLA composite scaffolds, which are
osteoconductive and partially biodegradable, through the use of
CHAp/PLLA nanocomposite microspheres, which were fabricated
in a solid-in-oil-in-water (S/O/W) emulsion solvent evaporation
process.
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For obtaining osteoconductive and totally biodegradable
composite scaffolds, microspheres composed of osteoconductive
and totally resorbable Ca-P nanoparticles and a natural biodegrad-
ablepolymer PHBV can be used.
45.3 Design of Scaffolds and the Nanocomposite Strategy
During the SLS process, the raw material in the particulate form is
first loaded in the powder tanks (both left and right) of the SLS
machine, and after preheating of the powder, the laser beam scans
over the cross-section on the powder surface following the cross-
sectional profiles of the design to heat up the powder to a preset
temperature, causing the particles to fuse together to form a solid
mass. When one layer of the cross-section is sintered, the piston
in the left (or right) powder tank moves up and the piston in the
build part moves down. Subsequently, the roller spreads another
layer of powder over the previously sintered part. Relatively large
quantitiesofpowderedmaterialswithappropriateparticlesizesare
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