Modeling of Electrospinning of Polymer Nanofibers:  Stability Analysis of a Single Jet

Alexander Spivak, Ph.D. Candidate
Department of  Engineering Mechanics
University of Nebraska - Lincoln
Advisor:  Yuris Dzenis

Date:  Tuesday, March 9, 1999
Time:  3:30 p.m.
Place:  W128 Nebraska Hall


Emerging technology of manufacturing of thin polymer fibers by electrospinning is addressed. This presentation shows results of analytical modeling of the electrospinning process. General three-dimensional electrohydrodynamic model of a weakly conductive viscous jet accelerated by an external electric field is formulated taking into account inertial, hydrostatic, viscous, electric, and surface tension forces. Nonlinear rheologic constitutive equation (Oswald-deWaele law) is used to describe polymer fluid. Kinetics of thermal fluctuations of the jet flow parameters is introduced by adding Langevin sources of stress and electric charge fluctuations in the electrohydrodynamic equations. One-dimensional differential equations for jet radius, flow rate and linear surface charge density are obtained by averaging the physical quantities over the jet cross-section. Variation of the jet radius with coordinate in the beginning of the jet and fluctuation level of the jet flow parameters are analyzed. Obtained expression for asymptotic decay of jet radius at large distances from the beginning of the jet is discussed. Level of thermal fluctuations of jet flow parameters is estimated using Fluctuation-Dissipation Relations (FDR). Derived equation for a correlation function of jet radius fluctuations is used for jet stability analysis. An expression for the critical initial jet radius is obtained and experimentally verified. Primary stages of electrospinning process are shown on video. The results show good agreement with experimental data. The analytical modeling provides better understanding of the electrospinning process. The derived equations can be used for the process optimization.