Biomedical Engineering Reference
In-Depth Information
5.3.2 M ECHANICAL T ESTING
Mechanical behavior is an important parameter in designing and developing new biomaterials.
Mechanical and structural integrity of the nanofi ber scaffolds are crucial to withstand in vitro
culture conditions and surgical manipulations. Tensile testing is often used as a method to determine
and compare mechanical properties of electrospun nanofi ber membranes. As shown in Figure 5.12,
composition of the nanofi ber mesh is an important parameter in determining its resulting mechani-
cal properties. Collagen incorporation (20% by weight) into the PCL matrix resulted in a mesh with
inferior modulus and stress at break although its elongation at break was slightly improved. Physical
and chemical interactions between PCL and collagen may have resulted in a weaker composite
material with different domains or phases in its structure.
Parameters and conditions at which the mechanical testing was performed may affect the result-
ing mechanical properties. Temperature and humidity are two factors that might affect a material's
behavior under observation. Thus it is imperative to simulate a testing environment, which is relevant
to the intended applications of the material. For instance, the tensile tests shown in Figure 5.12 were
done at 37°C with PBS immersion. As PCL is a thermoplastic with glass transition temperature of
about 60°C and a low melting point of around 60°C, it exists in a rubbery state at ambient tempera-
ture. Fluctuation in temperature may affect its mechanical characteristics. Furthermore the intended
application of the PCL and PCL/Col nanofi ber was for in vivo implantation. Hence, 37°C was chosen
with complete immersion in saline to better mimic the in vivo environment. Room temperature test-
ing may also be carried out in tandem in order to determine and compare ease of handling before the
implantation, ease of suturing, etc.
250
6
PCL
PCL collagen
PCL
5
187.11
200
PCL collagen
4.14
4
147.15
150
3
100
1.93
2
50
1
(a)
(b)
0
0
18
PCL
PCL collagen
16
14
12.35
12
10
8
6
4.59
4
2
(c)
0
FIGURE 5.12 Mechanical properties comparison of pure PCL and PCL/Col blend electrospun nanofi ber
membranes. Addition of collagen into the PCL structure resulted in a slight increase in elongation at break (a)
and decreases in stress at break and tensile modulus (b and c, respectively). The tensile test was carried out at
37ºC in phosphate-buffered saline (PBS) immersion.
 
 
Search WWH ::




Custom Search