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Electric and Buckling Instabilities Effects on the Dynamics and Geometry of the Fibers in Electrospinning

Shariatpanahi, Peyman | 2011

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42721 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Iraji Zad, Azam; Ejtehadi, Mohammad Reza
  7. Abstract:
  8. Since previous models can not give a complete description for electrospinning electrical instability, using polymer solutions with diifferent properties, the aim of the existing thesis is to propose a new model that covers a range of materials from non-conducting to conducting and from viscous to elastic and also the initial jet’s tension. In addition, since the previous models have used large wave length approxiamtions, using accurate calculations we showed that the new model has better results for small wavelengths of about two times the jet’s radii. To compare the model to experimental results, we designed and made a proper setup to record the electrospinning process for a PEO solution with a fast camera which helped us to measure the instability wave lengths for voltages 7 to 15 KV. We showed that the experimental data fit the model with and without initial tension for comparatively small and large voltages. Then adding a conducting polymer, PAMPS, we observed that the fibers on the collector become helical. Taking into account that the conductivity affects this phenomenon, we proposed a model based on electrical instability for the helices’ formation. Then we showed that the experimental results best fit the elastic model. In addition using direct electrospnning we could produce micro and nano 3D helical PS fibers in water. Consequently we measured the buckling frequencis and showed that the results fits the proposed model by Habibi et. al. in the inertial regime. One of the experimental problems in electrospinning is that the dynamics occur in times of micro to milli seconds. We introduced the variable voltage electrospinning method by which in addition to investigate the buckling dynamic, we showed that it can also be used to produce new periodic micro structures. Finally, as an example for electrospinning applications, we applied electrospinning to produce TiO2 fibers. Heating electrospun fibers ,produced from PVP and TiP which contains Titanium, TiO2 fibers were made and we showed that the fiber diameters and crystal structure of the fibers can be controlled by the solution concentration and heating atmosphere comparatively
  9. Keywords:
  10. Electrospinning ; Electrical Bending ; Buckling ; Photocatalytic Property ; Nanofiber

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