Effect of Charge Density on the Taylor Cone in Electrospinning

Abstract

A detailed understanding of charge density and its origins during the electrospinning process is desirable for developing new electrospinnable polymer-solvent systems and ensuring mathematical models of the process are accurate. In this work, two different approaches were taken to alter the charge density in order to measure its effect on the Taylor cone, mass deposition rate and initial jet diameter. It was found that an increase in charge density results in a decrease in the mass deposition rate and initial jet diameter. A theory is proposed for this behaviour in that an increase in charge density leads to the tip of the Taylor cone forming a smaller radius of curvature resulting in the concentration of electric stresses at the tip. This leads to the electrostatic forces drawing the initial jet from a smaller effective area or "virtual orifice".

Experimental investigation of the governing parameters of the electrostatic field–induced electrolyte jet micro electrical discharge machining on the silicon wafer

“…These experimental results support that it is the single micro discharge energy between the tip of the fine jet and the workpiece that determines the diameter of the crater after a single E-jet electrical discharge, which coincides with the conclusion in conventional EDM that the discharge energy mainly determines the crater size. 35,36…”

“…However, with the increase in voltage, the E-jet diameter will decrease. 35 This is because the increase in the voltage applied results in the increase in the electric field, leading to an increase in the charge density on the surface of Taylor cone. The charge density increases on the cone will cause a sharper angle at the tip part of the cone driven by the electrostatic field stress.…”

“…This also coincides with the description that the factors which determine the limits the miniaturization in µ-EDM may be the electrical discharge energy of each pulsating discharge. 35,36…”

“…The experiments in electrospinning have suggested that as the charge density increases, the cone will adopt a steeper angle caused by the electrostatic field stress. 35 With a steeper angle at the tip of the jet, there will be a smaller cross section near the tip of the fine jet. As a result, the increase in the concentration of the electrolyte results in the decrease in the cross section and the decrease in the diameter of the jet near the tip.…”

“…That the micro discharge energy affects the miniaturization in µ-EDM can explain the reasons why the crater size machined by the E-Jet after a single discharge increases with concentration of the electrolyte of the jet. 35,36…”