טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMekler Sabina
SubjectInvestigation of Transport Properties of Electrospun
Fibrous Bed
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Eyal Zussman
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Electrospinning is a process capable to produce polymeric fibres of nanometric dimensions, from a variety of polymeric solutions, by applying a high electrostatic field on a pendant solution droplet. The nanofibers collected on the collector electrode and form a non-woven porous structure with very high surface area to volume ratio. The electrospinning process became a topic of great interest because of the potential of the produced porous structure as a Tissue Engineering scaffold.

Transport properties, such as, porosity, permeability and pore size are among the most important properties while designing scaffold for tissue engineering.  In order to support three-dimensional tissue formation, scaffold should allow cells proliferation, migration, penetration into the porous structure and well connection between the cells.  The pores should also allow diffusion of nutrients, oxygen, grow factors and removal of metabolic waste. Additionally, the scaffolds should exhibit adequate microporosity in order to allow capillary ingrowth.

In the present work we focus on characterization of transport properties for nanofiber scaffold produced by electrospinning. We have also investigated the influence of the governing parameters in the electrospinning process on the transport properties. The parameters which have been investigated are: rehology of the polymer solution, the flow rate of the solution, the electric conductivity of the solution and the gradient of the electrostatic field in the process.

The permeability of the electrospun scaffolds was determined by applying air flow of known flow rate through the sample, measuring the pressure drop across it and using Darcy's law. The Knudsen number in those experiments varied at range of Kn ~ 0.002÷ 0. 02 and the Reynolds number was, Re<<1. The permeability values which were measured, normalized by square of the fiber diameter, varied from 0.05 to 15.  The porosity of the electrospun scaffolds was evaluated both by density method and mercury intrusion porosimetery. The highest porosity which measured in the experiments was 93%.

From the experiment results it was found that the porosity of the scaffold can be increased by reducing the flow rate in the electrospinning process.  The results also show that the permeability and the mean pore size of the scaffold can be increased by increasing the electric conductivity and the viscosity of the polymer solution. In generally it was obtained, that process parameters which contributed to larger fiber diameter mostly caused to higher permeability and large pore size but lower porosity.