On the measured current in electrospinning

Bhattacharjee, Pradipto K.; Schneider, Tobias; Brenner, Michael P.; McKinley, Gareth H.; Rutledge, Gregory C.

doi:10.1063/1.3277018

Cited by 49 publications

(38 citation statements)

References 24 publications

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“…4 , where K is the conductivity of the polymer solution [43]. All of these works were certainly developed with the conventional Accepted for publication in Chemical Engineering Journal, Dec 2011 spinneret-based configuration in mind, but the physics behind the induction of surface charge in the presence of an electric field and consequent generation of electrical stresses should be roughly transferable to jets emitted from free liquid surfaces as well.…”

Section: Electrospinningmentioning

confidence: 99%

Free surface electrospinning from a wire electrode

Forward

Rutledge

2012

Chemical Engineering Journal

145

110

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Electrostatic jetting from a free liquid surface offers an alternative to conventional electrospinning in which jets are emitted from spinnerets. In this work we analyze a system in which a wire electrode is swept (in a rotary motion) through a bath containing a polymeric solution in contact with a high voltage, resulting in entrainment of the fluid, the formation of liquid droplets on the wire and electrostatic jetting from each liquid droplet. Solutions of polyvinylpyrrolidone in ethanol were used as test systems to evaluate each stage of the process.The volume of individual droplets on the wire were measured by photographic methods and correlated with the viscosity, density and surface tension of the liquid, and with system parameters such as electrode rotation rate and wire diameter. The local electric field in the absence of liquid entrainment was modeled using conventional electrostatics, and jet initiation was found to occur consistently at the angular position where the electric field exceeds a critical value of 34 kV/cm, regardless of rotation rate. Two operating regimes were identified. The first is an entrainment-limited regime, in which all of the entrained liquid is jetted from the wire electrode. The second regime is field-limited, in which the residence time of the wire electrode in an electric field in excess of the critical value is too short to deplete the fluid on the wire. The productivity of the system was measured and compared to the theoretical values of liquid entrainment. As expected, highest productivity occurred at high applied potentials and high rotation rates.

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Section: Electrospinningmentioning

confidence: 99%

Free surface electrospinning from a wire electrode

Forward

Rutledge

2012

Chemical Engineering Journal

145

110

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“…The solution parameters and properties as well as process param-eters that control the fiber diameter and morphology are numerous and have been extensively investigated. [20][21][22] Parameters such as polymer concentration, molecular weight and its distribution, [23][24][25] solvent quality and volatility 26,28,29 (coupled with environmental conditions as solvent saturation 24,30,31 ), surface tension, 32 conductivity, 33 viscosity, 34,35 viscoelasticity, flow rate, distance between the electrodes (and their configuration) as well as the applied potential difference 36 (that we indicate schematically indicate in Figure 1) form a complex set of interactions. The parameters that can be controlled can generally be divided into two groups, parameters that determine the solution properties and the experimental parameters that characterise the process.…”

Section: Introductionmentioning

confidence: 99%

Dispersity and spinnability: Why highly polydisperse polymer solutions are desirable for electrospinning

Palangetic

Reddy

Srinivasan

et al. 2014

Polymer

116

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We develop new criteria that describe the minimum concentration limits controlling the spinnability of dilute and semi-dilute flexible polymer solutions with high molecular weight and varying polydispersity. By asserting that the finite and bounded extensional viscosity of the solution is the key material property determining the stability of a filament during spinning, we propose a new scaling relating the minimum necessary concentration of a polymer c spin to its molecular weight M and the quality of the solvent (through the excluded volume exponent n) of the form c spin ⇠ M (n+1) . This new scaling differs from the classical interpretation of the coil overlap concentration c ⇤ or entanglement concentration c e as the minimum concentration required to increase the viscosity of the spinning dope, and rationalizes the surprising spinnability of high molecular weight polymers at concentrations much lower than c e .Furthermore, we introduce the concept of an extensibility average molecular weight M L as the appropriate average for the description of polydisperse solutions undergoing an extensiondominated spinning process. In particular it is shown that this extensibility average measure, and thus the solution spinnability, is primarily determined by the extensibility of the highest molecular weight fractions. For highly polydisperse systems this leads to an effective lowering of the minimum required concentration for successful fiber spinning (in comparison to narrowly distributed polymer solutions of similar weight average molecular weights). These predictions are validated with experimental observations of the electrospinnablity of monoand polydisperse poly(methyl methacrylate) (PMMA) solutions as well as a model bimodal blend, and through comparison to published literature data on the minimum spinnable polymer concentration for a variety of flexible long chain polymers over a range of molecular weights.

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“…In conjunction with this effect, thicker proto-fibers are more resistant to bending in general, and so generally due to both effects, thicker jets increase the length of the linear region. The other dominant effect on the whipping instability is the charge on the proto-fiber which is the drives the instability: both the applied voltage level and the fluid conductivity [97] are positively correlated with the surface charge density. Thus the total charge on the fluid surface in the high conductivity case is expected to be at least 3.4Â larger (at 55 kV) than for a moderate conductivity fluid (at 16 kV).…”

Section: Enhanced Whipping Regionmentioning

confidence: 98%