Page 91 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

TAILORING THE VOID SPACE AND MECHANICAL PROPERTIES IN ELECTROSPUN SCAFFOLDS
Figure 4.8 Comparison of the Tangent modulus of the conv. vs. LTE spun sca olds including the di erent fiber diameter. All sca olds where 4 spun for 60 min on a 50 mm long target drum.
The Tangent modulus of a LTE PCL sca old decreases below 100 kPa, compared to the ~4.5 MPa for the corresponding conventionally electrospun PCL sca old (Figure 4.8). A similar decrease in the Tangent modulus from ~6 to 15 MPa for conventionally to ~200 kPa for LTE spun sca old can be seen for the by nature sti er PLA sca olds.
Interesting to note is that the PCL LTE spun sca olds show a Tangent modulus of less than 100 kPa, a sti ness value comparable to a gel. The approximately 100-fold drop between the moduli of LTEandconventionalspunsca oldscanbeexplained by the increased porosity and the structural changes induced by the LTE spinning. Fibers in a conventional
spun sca old are closely packed, have many entanglements and are also partially fused together. LTE spun sca olds demonstrate the opposite, as they have a lower packing density and, therefore, much less entanglements and fused fibers. The structure of LTE spun sca olds may be best described as cotton- candy like. During elongation, the fibers have a high degree of mobility, and the individual fibers are only stretched once the fibers have re-oriented and the applied strain is su iciently large.
The low mechanical strength makes the handling of LTE and sca olds more challenging as opposed to the quite robust conventional spun ones. Nevertheless, even if the sca old gets squeezed
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