Biomedical Engineering Reference
In-Depth Information
8.4
Evaluation of Wall Thickness and Young's
Modulus
8.4.1
Measurement of the Thickness of PLCL
Membranes aer Dip Coating
For simplicity, the models tested were straight cylinders (inner
diameter: 5 mm, outer diameter: 5.2 mm, length: 40 mm). During the
fabrication of PLCL scaffolds, dip coating of PLCL solution onto the
cylinder model was repeated three times in one direction and three
times in the opposite direction by setting the model upside down.
Besides the fabrication of carotid artery scaffolds, the thickness of
PLCL membrane was measured at dip coating by changing the pull-
up velocity of cylinder models (1 mm/s, 2 mm/s, 3 mm/s, 4 mm/s)
and the PLCL concentration in chloroform (3 w%, 5 w%, 10 w%).
The weight ratio of NaCl microparticles to PLCL was ixed for this
experiment (NaCl : PLCL = 4 : 6 at w%). After dip coating six times,
the thickness of the coated PLCL membrane at the middle of the
cylinder models was measured. Models were sliced into rings and
the thickness of PLCL membranes was observed using an inverted
optical microscope (IX71, Olympus Co. Ltd., Japan).
At each experimental condition, ive samples were measured to
calculate standard deviation (SD). Overall, 60 (4 × 3 × 5) samples
were tested. Figure 8.5 shows the relation between the thickness
of PLCL at dip coating and pull-up velocity and the concentration
of PLCL in chloroform ( n = 5 for each bar, vertical axis: logarithmic
scale). This graph indicates the following results: (i) PLCL thickness
was controllable from 40 μ m to 1200 μ m; (ii) a higher PLCL
concentration in chloroform yielded a thicker membrane; and (iii)
pull-up velocity during dip coating had little effect on the thickness,
but higher velocity yielded a thicker membrane.
8.4.2
Tensile Test
Sheet-like rectangular PLCL scaffolds at compositions listed in Table
8.1 were used as samples for the tensile test. The 15 types of polymer
solutions were dried on a glass dish followed by leaching of the
NaCl microparticles by DI water. The DI water was changed every 4
hours until no NaCl microparticles could be detected. The sheet-like
PLCL scaffolds obtained were stretched by a tensile testing machine
 
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