Page 45 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

ELECTROSPINNING POLY(Ε-CAPROLACTONE) UNDER CONTROLLED ENVIRONMENTAL CONDITIONS
Table 2.1 PCL fibers dimensions. The calculated mean and standard deviation refers to all the samples spun from one of the solutions studied, under the whole explored range of environmental conditions
15 wt% PCL in CHCl3/THF 100/0 wt
7 ± 0.6 μm
15 wt% PCL in CHCl3/THF 90/10 wt
8 ± 0.7 μm
20 wt% PCL in CHCl3/THF 50/50 wt
6 ± 0.7 μm
20 wt% PCL in CHCl3/THF 10/90 wt
7 ± 1 μm
20 wt% PCL in CHCl3/THF 0/100 wt
6 ± 0.6 μm 2
With our selected systems the jet instability is close to the target, leading to thicker fibers compared to the above-mentioned research. Hence there is much less fiber surface exposed to the environment within a shorter time and, therefore, also less influence of the environmental conditions. Additionally we used a coaxial gas shield around the spinning nozzle. This stabilizes the Taylor cone and environmental changes cannot a ect the cone. Without this shield, the Taylor cone would be destabilized at a humidity higher than 70%, mostly because of precipitation due to the water, hence the fiber diameter range would increase.
2.4.2
Surface morphology
SEM micrographs in Figure 2.1 show the e ect on fiber surface morphology of relative humidity and temperature for 15 wt% in CHCl3 solution. A 10% increase in relative humidity or a 5°C increase in temperature can make a di erence until 30°C for the whole range of RHs explored, while from 35°C on, the morphology tends to be pore-less until the highest relative humidity. At 40°C, the highest temperature we investigated, the fiber surface is totally smooth until 70% of relative humidity. The solvent system, more specifically its water miscibility, influences the surface morphology of electrospun fibers too. Figure 2.2 shows fibers spun from solutions with di erent CHCl3/THF ratios at 20°C.
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