Pulsation Modes and the Effect of Applied Voltage on Current and Flow Rate in Nanoelectrospray

Alexander, Matthew S.; Paine, Mark D.; Stark, John

doi:10.1021/ac0520036

Cited by 58 publications

(49 citation statements)

References 25 publications

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“…A very large increase in voltage will lead to unstable operation and multiple emission sites per capillary. Two research groups have studied pulsating ES with high speed cameras 13,14 and have defined four distinct modes of operation with a cycle duration around 500 s. During phase I the liquid accumulates at the tip of the capillary and is close to spherical shape. In phase II the Maxwell stress transforms the surface into a cone.…”

Section: A Liquid Surface Modelingmentioning

confidence: 99%

A method to determine the onset voltage of single and arrays of electrospray emitters

Krpoun

Shea

2008

Journal of Applied Physics

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This paper reports on an accurate and rapid method to compute the onset voltage of a single or an array of electrospray emitters with complex geometries and on the correlation of the simulation with experimental data. This method permits the exact determination of the onset voltage based only on the surface tension of the sprayed liquid and on the emitter geometry. The approach starts by determining the voltage at which electrostatic forces and surface tension forces are equal for a sharpening conic surface at the tip of a capillary as a function of the apex radius of the liquid. By tracing the curve of this computed equilibrium voltage as a function of the apex radius, the onset voltage for a liquid surface with the Taylor half-angle of 49.3°or larger can be determined. For smaller cone half-angles the method is only applicable to ionic sprays as an approximate knowledge of the critical field for ion emission is necessary. The combination of analytical models and finite element tools used to compute the necessary parameters is described. The method is validated on a complex microelectromechanical system emitter geometry as well as on a linear array of electrospray emitters. Finally an empirical model of the behavior of the electric field near the apex of a conic surface with asymptotes at a fixed half-angle is proposed, which allows establishing a simple method for onset voltage determination.

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Section: A Liquid Surface Modelingmentioning

confidence: 99%

A method to determine the onset voltage of single and arrays of electrospray emitters

Krpoun

Shea

2008

Journal of Applied Physics

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“…Thus, on the basis of a limited data set, Alexander et al (2006) reported only mode II for unforced electrosprays (electrosprays for which the flow rate is not imposed but determined by the electric suction at the liquid surface) when the applied voltage is increased past the onset of current oscillation. noted that not all the liquids show the same pulsation nature across the range of applied voltages wherein stable pulsating modes can be observed.…”

Section: Introductionmentioning

confidence: 99%

“…They found mode I in unforced electrosprays of low conductivity water and ethylene glycol solutions with large nozzles, but not with triethylene glycol solutions. Alexander et al (2006) also found a new mode that they termed as mode lib in which the variation of the time average current with voltage is different from that of mode II, and they noted that the evolution of the pulsation frequency and the pulse duration with voltage depends on the conductivity of the liquid and the diameter of the nozzle. concluded that mode lib can only be expected to occur in situations where increasing the voltage causes the liquid meniscus to retract.…”

Section: Introductionmentioning

confidence: 99%

Pulsating emission of droplets from an electrified meniscus

Higuera

Ibáñez

Hijano

et al. 2013

Journal of Aerosol Science

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A numerical description is given for the pulsating emission of droplets from an electrified meniscus of an inviscid liquid of infinite electrical conductivity which is injected at a constant flow rate into a region of uniform, continuous or time periodic, electric field. Under a continuous field, the meniscus attains a periodic regime in which bursts of tiny droplets are emitted from its tip. At low electric fields this regime consists of sequences of emission bursts interspersed with sequences of meniscus oscillations without droplet emission, while at higher fields the bursts occur periodically. These results are in qualitative agreement with experimental results in the literature. Under a time periodic electric field with square waveform, the electric stress that acts on the surface of the liquid while the field is on may generate a tip that emits tiny droplets or may accelerate part of the meniscus and lead to a second emission mode in which a few large droplets are emitted after the electric field is turned off. Conditions under which each emission mode or a combination of the two are realized are discussed for low frequency oscillatory fields. A simplified model is proposed for high electric field frequencies, of the order of the capillary frequency of the meniscus. This model allows computing the average emission rate as a function of the amplitude, duration and bias of the electric field square wave, and shows that droplet emission fails to follow the applied field above a certain frequency.

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“…And it is obvious that in solutions with lower KCl concentration due to less conductivity the surface charge diminishes [27]. Hence according to equation [1] in this phenomenon two main factors are interplaying: the first is electric field intensification and the other is surface charge density reduction. The observed behavior depicts the prevailing of electric field intensification factor.…”

Section: The Behavior Of Emanated Droplets and Effect Of Conductivitymentioning

confidence: 99%

“…Subsequently, they [7] reviewed electrospraying modes and clarified some ambiguous concepts of spraying modes which were arising from multiplicity of spraying functioning modes. Astable modes of spraying are other modes which attract growing interest in the recent years [1,2,19]. These modes of spraying occur in the transition between three axial modes of spraying (Dripping, Pulsating and cone-jet).…”

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confidence: 99%

Electrospray characteristics of aqueous KCl solutions with various electrical conductivities

Faraji¹,

Sadri²,

Hokmabad³

et al. 2018

Preprint

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Some of the authors of this publication are also working on these related projects: Enhancement of transport phenomena View projectDeveloping novel SCR catalysts for utilization in the reduction of the emissions such as mercury from coal-fired power plants. View Abstract In the present experimental study, the effects of electrical conductivity on electrospraying procedure are investigated. A metallic nozzle with 600 m ID as high voltage electrode and a stainless steel ring as a ground electrode were employed. Experiments were carried out in still room temperature. Four different aqueous KCl solutions were sprayed in various high voltages and flow rates. Results confirm that spraying modes changes with conductivity variation. For forming a cone shape, emerging from the nozzle, required applied electric field decreases with conductivity increasing. Results also revealed that conductivity of dispersed solution acts a main role on forming and elongation of the cones in electrospraying procedure. The size and velocity of emanated droplets are also investigated in order to gaining some insight to the electrospraying phenomenon. IntroductionElectrospraying of liquids is a well-established process for producing submicron particles. This spraying method (also known as electro hydrodynamic atomization) is a process in which high electric field is employed to disperse a liquid. High voltage is applied to a liquid supplied through an emitter (usually a metallic capillary). In electrospraying, the shear stress caused by the electric force applied to the surface of liquid, elongates the liquid meniscus formed at the tip of a capillary, to the form of a cone and/or a jet which then deforms and disrupts into droplets due to interplay of electrical and mechanical forces. In this method no additional purely mechanical energy is applied to spray the liquid. Electrohydrodynamic spraying (EHD spraying) has wide range of applications including fine resolution electrohydrodynamic printing [20,3], biomedical application especially drug delivery system [29,23], powder production [9, 11] and producing stable emulsions [13,16,21].Early works on the electrified surfaces has been done by Zeleny in 1917[24]. In 1969, Taylor conducted some experiments in electrified jets [22]. Cloupeau and Prunet-Foch introduced cone jet as one the modes which expects to have monodisperse produced droplets in 1989 [5]. Fernandez de la Mora and his coworkers investigated the droplets diameter and the current emitted from electrosprays in the well-known cone jet mode [8]. They also studied the effect of physical parameters like electrical conductivity, viscosity, liquid density and the feed rate on the electrospraying in cone jet mode [12]. Experimental observation of the dielectric constant effect on the cone jet mode spraying has also been investigated by D. R. Chen et al [4]. They proposed some scaling laws between produced droplets and dielectric constants.For other values of electric field and feed rates, some other regimes, different from cone jet mode...

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Pulsation Modes and the Effect of Applied Voltage on Current and Flow Rate in Nanoelectrospray

Cited by 58 publications

References 25 publications

A method to determine the onset voltage of single and arrays of electrospray emitters

A method to determine the onset voltage of single and arrays of electrospray emitters

Pulsating emission of droplets from an electrified meniscus

Electrospray characteristics of aqueous KCl solutions with various electrical conductivities

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