טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentStephanus Theron
SubjectInvestigation into Nanofiber Assembly during Electrospinning
DepartmentDepartment of Mechanical Engineering
Supervisor Full Professor Zussman Eyal


Abstract

The rigorous pursuit of further miniaturization in the nanotechnology field has resulted in the development of new materials and new applications. However, these nano-materials are discontinuous objects, and this leads to difficulties with their alignment, assembly and processing in applications.

Electrospinning is a unique yet straightforward method which is able to produce continuous and uniform fibers with diameters of the order of 100nm. In this process, a droplet of polymer solutions is subjected to electric field. When the electric force acting on the induced charges in the solution overcomes the surface tension of the fluid, a charged polymer jet is pulled out of the droplet and accelerated away from the droplet. It undergoes bending and elongation and dry nanofibers are deposited on a collecting plate as a non-woven fibrous mat. This process offers unique potential for cost-effective, electromechanical control of nanofiber assembly.

This thesis deals with 1) a systematic experimental study of the process parameters involved in the electrospinning process; 2) the modeling of experimental single and multi-jet configurations used in this work, and 3) improved control of the polymer jet path in the electrospinning process that will allow the assembly of electrospun nanofibers into three-dimensional nano-structures.

The process characterization studied the influence of different parameters on the volume charge density of the polymer jet. In the modeling, realistic configurations of the external electric field were employed. In addition the Upper-Convected Maxwell model was used to describe the viscoelastic behavior of the jets. In the study of nanofiber assembly, a technique has been developed to manipulate nanofibers. Parallel nanofiber arrays were collected that can be used for different applications in tissue engineering and nano-electronics and composite materials.