Jet diameter of the first coil in the electrospinning whipping region: the role of fluid viscosity

Abstract

In solution electrospinning, the ultrafine fiber is derived from the dramatic stretching of the whipping fluid jet. The first coil of the whipping fluid jet with the highest stretch rate plays a vital role in determining the microstructure and physical property of electrospun submicron/micron fibers. However, it still remains challenging to control precisely the stretching and jet diameter of the first coil of the whipping fluid jet. Herein, a comprehensive model for the jet diameter of the first coil of the whipping fluid jet is established, indicating that the jet diameter is a consequence of the balance between viscous and electrostatic forces, and is a function of the fluid viscosity, electric current, and flow rate. Furthermore, the stretch rate of the first coil of the whipping fluid jet is predicted, which decays as a scaling law with an exponent −1/2 along the axial direction. The theoretical predictions agree well with the experimental results. This work compensates for the deficiency of previous diameter models and enriches the mechanism of jet stretching, which can provide a valuable theoretical guide for the structural and functional design of submicron/micron fibers.