Electro-hydrodynamic Stability Analysis of Bilayer Electrified Jet

A one-dimensional electrohydrodynamic model is developed for the electrified two-fluid jet's temporal instability analysis, considering electrospinning conditions where a high electric field is applied to fabricate nanofibers. The Leaky dielectric model is incorporated into the nonlinear governing equations for calculating electrical Maxwell stresses at jet interfaces in the current work. The stability of the compound jet is examined for the periodic axisymmetric disturbance to address the capillary breakup of the electrified jet. Complex dynamics of the fluid deformation is thoroughly analyzed for two distinct instability modes as illustrated by the external axial electric field according to its strength. A surface tension driven capillary mode with a short wavelength leads the critical instability for the weak electric field. For the high electric field, a conducting mode with a long wavelength is more dominant. Competition between the two modes is explained in terms of the flow rate, material properties and process parameters. In addition, the location of the interfacial boundary layer between two immiscible fluids is also the most influential factor regarding jet deformation. Study of the coelectrospinning jet stability behavior enables one to modify either the material properties or the processing conditions during co-electrospinning such that the axisymmetric instability is suppressed, leading to smooth nanofibers formation for various common to high-end applications.