Fiber Structures & Effects of Different Experimental Parameters

**Each spacing on scale is 10 microns

Effect of distance

The fibers have a diameter of approximately 8-10 microns when electrospun under these conditions. Layers are molten into other layers when the distance was 10cm, and this is significantly less observed when the distances are 15cm and 18cm. Increasing the distance between the tip of the needle and the collecting plate promotes better three dimensionality in structure. At short distances, the electrospun fibers have less time to cool before they reach the collecting plate. Hence, they melt into other layers of the porous structure. On the other hand, when this distance is increased, the electrospun fibers have more time to cool before they reach the collecting plate. Hence, they do not melt into other existing layers and this promotes better three dimensionality.

Effect of applied voltage

When electrospun under a potential difference of 15kV, the fibers have a diameter of 9-1.2 microns. At 20kV, the fibers have a diameter of 8-10 microns. At higher voltages, the fibers are "pulled" harder, resulting in smaller diameters of fibers.

Effect of needle diameter

The fiber diameter ranges from 8 to 10 microns for a 1.2mm diameter needle whereas the fiber diameter ranges from 6 to 8 microns for a 0.9mm diameter needle. Smaller diameter needles result in thinner fiber threads.

Effect of molecular weight

The 20,000 molecular weight PEG shows better continuity. On the other hand, the 12,000 molecular weight PEG shows poor continuity as many cracks can be observed. Higher molecular weight PEG has better entanglement among the PEG chains and thus, is able to maintain continuity.

Effect of incorporating alumina particles

PEG with alumina particles incorporated has a limited elasticity, and many cracks are observed whereas pure PEG has very continuous fibers. PEG losses its memory when alumina particles are incorporated and it losses its ability to hold shape.