Experimental characterization of electrospinning: the electrically forced jet and instabilities

In the electrospinning process, polymer fibers with submicron-scale diameters are formed by subjecting a fluid jet to a high electric field. We report an experimental investigation of the electrically forced jet and its instabilities. The results are interpreted within the framework of a recently developed theory for electrified fluid jets. We find that the process can be described by a small set of operating parameters and summarized through the use of operating diagrams of electric field versus flow rate. In addition, the jet current is related to the net charge density and found to depend on the fluid properties, the applied electric field and the equipment configuration. The net charge density appears to be relatively insensitive to the flow rate, at least for high flow rates. The experiments reveal that a key process in the formation of submicron-scale solid fibers is a convective instability, the rapidly whipping jet. The dependence of this instability on electric field and flow rate, and the exponential nature of its growth rate are in accord with the theory.