| At the beginning of the thesis, special consideration has been given to the basic parameters of the e-spinning technique. Fibers and patches were prepared from a solution of Poly (ε-caprolactone) (PCL) in selected solvent systems (N, N dimethylformamide (DMF)/chloroform or acetic acid/pyridine). In order to study the influence of the instrumental parameters (applied electric potential, distance between tip and counter electrode) and the solution properties on the fiber morphology (polymer concentration, electrical conductivity...), scanning electron microscopy (SEM), viscosity and electrical conductivity measurements were used.With the increase of polymer concentration, the fiber diameter increases. But after reaching a maximum value, the diameter starts to decrease. We suggest that because of the viscosity, the fiber diameter increase with the increasing of polymer concentration at first. When the viscosity is too high, we suggest that multi-jets are formed at the end of capillary or the flow rate is becomes too small due to the very viscous liquid.. So the flow rate of the PCL solution decreases.The solvent of acetic acid including a small amount (40μg) of pyridine has a much higher electrical conductivity than the solvent mixture of DMF and chloroform. So, fibers prepared from the solution of Poly (ε-caprolactone) (PCL) in acetic acid with a small amount (40μg) of pyridine have much thinner fiber diameter. If the solution of Poly (ε-caprolactone) (PCL) in acetic acid is without pyridine, beads are formed. Pyridine can enhance the electrical conductivity.With the increase of DMF in the PCL solutions, the fiber diameter decreases. DMF could help to reduce the surface tension of the polymer solutions and increase the electrical conductivity. That means the solvent molecules are distributed more averagely over the entangled polymer molecules in the solution of lower surface tension, the molecule chains are straighter, they are more fully stretched by charge, so, the thinner fibers could be obtained.The fiber diameter decreased slightly with the increasing of applied voltage and remained constant with further increase. Beads formation was observed at very high applied voltages. When the applied voltage is too low, the jet can't emerge from the droplet of the capillary tip as the surface tension can not be overcome. And, the increased in beads density due to the increased voltage may be the result of increased stability of the jet as the Taylor Cone recedes into the syringe needle.One important point and still an open question are the mechanical property of single e-spun fiber and whole patch properties. Therefore, the elastic properties of nano- and micron-scaled fibers using three-point bending tests by atomic force microscopy (AFM) were used. Two kinds of fibers, pure PCL fibers and collagen fibers with different fiber diameter were investigated. The crystallinity of pure PCL fibers was measured by differential scanning calorimetry (DSC). E-modulus of pure PCL fiber determined at ambient conditions decreases from 15.1 to 0.005 GPa with increasing fiber diameter from 50 nm to 2500 nm. The dependence shows exponential behavior.E-modulus of several collagen fibers determined at ambient conditions with diameters ranging from 45 nm to 170 nm decreases from 53 to 3 GPa. The dependence shows exponential behavior as well.For this phenomenon, there may be two explanations: the crystallinity and the orientation of the molecular chains. After DSC measurements, it seems that the crystallinity decreases a little with the decreasing of the E-modulus. The orientation of the molecular chains measured by wide-angle X-ray diffraction (WAXD) will be performed in further studies and might explain the relationship of fiber diameter and their elastic properties.The research in this thesis carried out some new directions of e-spinning. Investigation of the orientation of molecular chains will hopefully explain the three-point bending result.
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