Study of the electrostatic jet initiation in near-field electrospinning

Hypothesis: The electrostatic initiation of a jet from the meniscus of a polymeric solution is a key step in near-field electrospinning (NFES), however this process is not sufficiently understood to determine a criterion for the critical emitter voltage triggering the jet, nor to optimize the electrodes. It is expected that the jet initiation in NFES is similar to that in cone-jet electrosprays, and can be described with a first principles model. Experiments: The electrostatic jet initiation of an SU-8 polymeric solution is studied with two different electrode geometries to quantify the initiation parameters and illustrate the optimization of the electric field. A first-principles model is developed to predict and analyze the initiation. Findings: Two jet emission mechanisms are identified: one in which the jet is ejected from a free-standing conical meniscus; and one resulting from the contact of the meniscus with the collector, as it evolves from a spherical to a conical shape. Both are triggered by a critical emitter potential. The former produces the thinnest jets with a diameter that depends on the properties of the fluid, while the latter is an alternative to existing mechanical initiation methods. The model reproduces well the experimental phenomena including the critical voltage. (C) 2019 Elsevier Inc. All rights reserved.