Effect of Charge Density on the Taylor Cone in Electrospinning (original) (raw)
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Electrospinning Studies: Jet Forming Force
In electrospinning, the electric forces are the main factor responsible for the jet stretching and the mass transport between the spinning and collector electrodes. A theoretical description of the force acting on the Taylor cone and the polymer jet in the roller electrospinning process is presented in the paper. Relations between the force, the thickness of solution layer on the roller surface, volume flow rate through a jet and the fluid viscosity are described based on the Navier-Stokes equation. Simultaneously, possible limits for the validity of obtained formulas are discussed.
Journal of Applied Polymer Science, 2009
Poly(vinyl alcohol) (PVOH) was electrospun using different methods to charge the polymer solution. A positive high voltage relative to the collecting electrode significantly increased the fiber deposition rate. Electron microscopy showed that approximately half of the increase in fiber mass was due to thicker fibers being deposited. The current flowing from the grounded electrode was measured to determine the charge carried on the PVOH jet. This showed that for a positive voltage charging condition there is a much larger current and hence more charge carriers generated in the PVOH solution. As a result, more mass is ejected from the Taylor cone, implying that a positive voltage also produces longer fiber for a given time period. We also tested whether different substrate materials caused any variation when the charging conditions were changed. Statistically significant variation between substrates was only found when the substrate was an insulator and was expected to support a high-deposition rate. This confirms the view that the PVOH fiber arrives at the collecting electrode carrying a charge that must be neutralized, otherwise a repulsive charge will form where the fiber is deposited and some fiber will be lost to any alternative earth. In electrospraying, charge carriers are generated using associated redox reactions. Thus, for electrospinning a lack of symmetry in these reactions may result in the generation of different quantities of charge carriers in the PVOH solution and changes in the mass deposition rate of electrospun fiber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Investigation of the Optimum Electric Field for a Stable Electrospinning Process
IEEE Transactions on Industry Applications, 2012
Electrospinning is an easy and inexpensive process that produces continuous nanofibers through an electrically charged jet of polymer solution consisting of sufficiently long chain molecules. As reported in the literature, the entire electrospinning process is governed by the external electric field caused by the applied voltage between the electrodes and the induced electric field caused by free and induced charges on the fluid surface. Therefore, the electric field is the most critical parameter in electrospinning. In this work, a comprehensive analysis was carried out to investigate the effects of external and induced electric fields on the electrospinning process, which include the Taylor cone formation, the straight jet portion, and the unstable or whipping jet region. It was observed that all regions are highly influenced by the applied and induced electric fields, which results in a considerable variation in the morphology of the nanofibers.
Electrospinning has become a widely implemented technique for the generation of nonwoven mats that are useful in tissue engineering and filter applications. The overriding factor that has contributed to the popularity of this method is the ease with which fibers with submicron diameters can be produced. Fibers on that size scale are comparable to protein filaments that are observed in the extracellular matrix. The apparatus and procedures for conducting electrospinning experiments are ostensibly simple. While it is rarely reported in the literature on this topic, any experience with this method of fiber spinning reveals substantial ambiguities in how the process can be controlled to generate reproducible results. The simplicity of the procedure belies the complexity of the physical processes that determine the electrospinning process dynamics. In this article, three process domains and the physical domain of charge interaction are identified as important in electrospinning: (a) creation of charge carriers, (b) charge transport, (c) residual charge. The initial event that enables electrospinning is the generation of region of excess charge in the fluid that is to be electrospun. The electrostatic forces that develop on this region of charged fluid in the presence of a high potential result in the ejection of a fluid jet that solidifies into the resulting fiber. The transport of charge from the charge solution to the grounded collection device produces some of the current which is observed. That transport can occur by the fluid jet and through the atmosphere surrounding the electrospinning apparatus. Charges that are created in the fluid that are not dissipated remain in the solidified fiber as residual charges. The physics of each of these domains in the electrospinning process is summarized in terms of the current understanding, and possible sources of ambiguity in the implementation of this technique are indicated. Directions for future research to further articulate the behavior of the electrospinning process are suggested.
Polymer, 2007
The electrospinning process uses electrical force to produce nanofibers. A charged droplet acquires a conical shape known as the Taylor cone and then becomes unstable. A charged jet emerges from the vertex and develops a spiral path due to the electrically driven bending instability, which makes it possible, in a small space, for the jet to elongate by a large amount and produce nanofibers. Evaporation and the associated solidification were identified as important factors that affect the diameter of electrospun nanofibers. In this study, the evaporation rate and solidification of the charged jet were controlled by varying the relative humidity during electrospinning of poly(ethylene oxide) from aqueous solution. As the relative humidity increased, the solidification process became slower, allowing elongation of the charged jet to continue longer and thereby to form thinner fibers. As the relative humidity increased from 5.1% to 48.7%, the diameter of the solidified fiber decreased from 253 nm to 144 nm. As the relative humidity increased above 50%, beads formed on the thinner fibers, indicating that the capillary instability occurred before the jet solidified. The vapor concentration of solvent is an effective electrospinning process control parameter of fiber diameter that also produces a systematic change in the development of beads on the fibers.
Journal of Computational Science, 2022
Nanofibers made in the electrospinning process have a very interesting set of material properties that are beneficial for many applications. Despite many existing commercial solutions, there are still some problems that need to be solved to improve the quality of obtained materials as well as overall process performance. For example, an irregularity of the electric field intensity distribution along the collector surface, resulting in an irregular distribution of nanofibers decreases the efficiency of the electrospinning process. Moreover, it also leads to the generation of coarser nanofibers from the middle part of the cylinder surface in comparison to those produced at the cylinder ends. The numerical simulations of the electrospinning process applying infinite domains using the finite element method presented in this paper provide effective methods to improve the distribution of the electric field intensity on the collector, which has a direct impact on the obtained structure of nanofibers.
Effect of Polymer Concentration on Electrospinning System
In this study we tried to find effect of concentration on Needle Electrospinning Method. Firstly we solved PVB in isopropanol different concentrations as 6%, 7%, 8%, 9%, 10% PVB polymer. Later we compared fiber characteristics for each solution. We investigated that there is a non-linear relationship between solution concentration and fiber diameter.
Effects of electrostatic polarity and the types of electrical charging on electrospinning behavior
Journal of Applied Polymer Science, 2012
In this study, we examined the effect of applied electrostatic voltages and the types of electrical charging on jet movement, fiber productivity, fiber diameter and deposited configuration by two inverse polarity systems, termed as spinneret and collector charging systems. Jet movement parameters such as Taylor cone, straight jet length, whipping angle, and pitch of whipping loop are examined and compared. The results show that the electronegative collector charging system or the electropositive spinneret charging system is superior to their contrastive system in terms of smaller fiber diameter, compact fiber deposited configuration, and higher fiber productivity. Optimal applied voltage found was 25 kV for electronegative collector charging system and 30 kV for electropositive spinneret charging system and resulted in finest fiber diameter (209 nm for electronegative collector charging system and 247 nm for electropositive spinneret charging system). Polyvinyl acetate solution jet is easier to be ejected, stretched, and accelerated under electropositive charging. The spinning jet with electropositive charges can be achieved either in the spinneret charging system by using electropositive charger or in the collector charging system by using electronegative charger. This finding is an important guideline for the designing of electrospinning device. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 126: E89-E97, 2012
Journal of Applied Polymer Science, 2016
Electrospinning allows the production of ultrafine nanofibers through the stretching of a charged polymer jet with an external electrostatic field. In this study, we derived a simplified and accurate model relating the processing parameters, including the solution volumetric flow rate (Q), the applied electric field (E), and the polymer concentration, to the final fiber diameter. The model takes into consideration the jet behavior starting at the stable region and moving to the bending instability region. We validated the model experimentally by performing the electrospinning process with a polyacrylonitrile/N,N-dimethylformamide solution with different ranges of concentrations (8-11 wt %), Qs (900-1320 lL/h), and Es (88,889-113,889 V/m). The final fiber diameter was measured with scanning electron microscopy. The model predicted the fiber diameter with a relative error of less than 10%.