Biomedical Engineering Reference
In-Depth Information
scaffold above. The prepared PCL scaffold was further treated by
a thermal fibril-bonding process for strengthening of mechanical
properties; the scaffold was heat-treated nearby the PCL melting
temperature (59
◦
C, 1 hr) to bond accumulated PCL fibrils to each
other.
30.3 Characterization of Pore-Size-Gradient Scaffolds
30.3.1
Measurements of Pore Sizes and Porosity
Surface morphologies of the prepared cylindrical alginate, chitosan,
and PCL scaffold sections (thickness 5 mm) along the longitudi-
naldirectionwereobservedbyscanningelectronmicroscopy(SEM;
Model S-3000N, Hitachi, Japan) operated at an accelerating volt-
age of 15 kV. Before morphology observations, the specimens were
coatedwithplatinumusingasputtercoater(SC7680,QuorumTech-
nologies,UK)underanargonatmosphere.Theaverageporesizesof
the scaffold section surfaces were measured using an image analy-
sis program (i-solution, IMT, Korea) from the SEM photographs.
The porosity of the scaffold sections was measured using a spe-
cific gravity bottle (Hubbard, Hanil, Korea) based on Archimedes'
principle.
26
Briefly, the porosity of the scaffold was determined as
follows:
Porosity (%)
=
[(
W
2
−
W
3
−
W
s
)
/ρ
e
]
/
[(
W
1
−
W
3
)
/ρ
e
]
×
100
where,
W
1
=
specific gravity bottle weightfilled withethanol;
W
2
=
specific gravity bottle weight including ethanol and scaffold;
W
3
=
specific gravity bottle weight taken out ethanol-saturated scaffold
from
W
2
;
W
s
=
scaffold weight;
ρ
e
=
density of ethanol; and
thus (
W
1
-
W
3
)/
ρ
e
=
total volume of the scaffold including pores,
(
W
2
-
W
3
-
W
s
)/
ρ
e
=
pore volumein the scaffold.
Figure 30.3 shows the sectional morphologies of the cylin-
drical alginate, chitosan, and PCL scaffolds fabricated by the
centrifugation method. It was observed that the pore size and
porosity of the scaffolds gradually increased along the cylindri-
cal axis, regardless of polymer types used, owing to the grad-
ual increment of the centrifugal force along the longitudinal axis
in the cylindrical mold containing fibril-like polymers during the
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