Tailor-Made and Biodegradable Vascular Scaffolds - Microsurgery: Advances, Simulations, and Applications - page 284

The experimental setup described in Fig. 8.6 was used to measure
Young's modulus. A commercial dip coater was modiied to be a
tensile tester by attaching a load cell. The load cell was connected
to a force gage, which was also connected to a laptop. The pull-up
motion of a dip coater was used to stretch specimens of PLCL sheet-
like scaffolds (pull-up speed: 0.1 mm/s). Time series variation of
tensile force was recorded in PC and was subsequently converted
into a stress-strain curve. Specimens were stretched until the tensile
force reached 5 N.

Evaluation of porosity
Porosity of the scaffold was also evaluated in a following way. The
apparent density ( S d ) of the scaffold was calculated from its dry
weight and volume. Here, S d was calculated as 0.34 g/cm 3 . The
porosity of the scaffold was determined according to the following
equation [4]:

S d )/ S PLCL × 100, (8.3)
where S PLCL was the density of nonporous PLCL polymer, which was
1.43 g/cm 3 at 26 ° C.
Four types of PLCL sheets were evaluated (PLCL nonporous
sheet, PLCL porous sheets cast from MSPs 1, MSPs 2, and MSPs 3).
Three samples were tested for each condition to consider SD. Figure
8.21 shows stress-strain curves of PLCL sheets obtained by tensile
test. All the curves had inverse J shape that is peculiar to typical
elastomers. Elastic (Young's) modulus of biodegradable elastomer
is generally estimated by the gradient of initial linear part. We
calculated Young's modulus from the strain range of 0 < F < 0.1. Figure
8.22 shows a quantitative data of Young's modulus and porosity
for nonporous PLCL sheet and three porous scaffolds cast from
MSPs. The Young's modulus of nonporous PLCL sheet was 5.2 MPa.
Regarding porous PLCL scaffolds, those cast from MSPs with larger
SD of diameter yielded higher Young's modulus and lower porosity.
Good correlation of higher porosity and lower Young's modulus
supports the credibility of this data. Table 8.2 shows precise values
of Young's modulus and porosity shown in Fig. 8.22. The elasticity of
the entire porous scaffold was quite close to the elastic modulus of
human artery (1-3 MPa).

Porosity(%) = ( S PLCL -