A study of ejection modes for pulsed-DC electrohydrodynamic inkjet printing

Lee, M.W.; Kang, Daesung; Kim, N.Y.; Kim, H.Y.; James, Scott C.; Yoon, Sujung

doi:10.1016/j.jaerosci.2011.11.002

Cited by 67 publications

(39 citation statements)

References 19 publications

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“…More recent investigations of pulsating Taylor cones have been carried out by Marginean et al [30], Chen et al [31], and Choi et al [32], who proposed different scaling laws for the pulsation frequency and the masses delivered, while Marginean et al [33] introduced a classification of axial modes based on three periodic and stationary regimes interspersed with two chaotic regimes. Kim et al [34], Kang et al [35], and Lee et al [36] achieved improved control of the size and emission frequency of the droplets by using pulsed electric fields and partially classified the new dripping modes that appear in these conditions. Higuera et al [37] numerically analyzed the pulsating emission from a meniscus of an inviscid liquid of infinite electrical conductivity in a simplified configuration, qualitatively reproducing experimental results for constant and pulsed voltages.…”

Section: Introductionmentioning

confidence: 99%

Periodic emission of droplets from an oscillating electrified meniscus of a low-viscosity, highly conductive liquid

et al. 2015

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The generation of identical droplets of controllable size in the micrometer range is a problem of much interest owing to the numerous technological applications of such droplets. This work reports an investigation of the regime of periodic emission of droplets from an electrified oscillating meniscus of a liquid of low viscosity and high electrical conductivity attached to the end of a capillary tube, which may be used to produce droplets more than ten times smaller than the diameter of the tube. To attain this periodic microdripping regime, termed axial spray mode II by Juraschek and Röllgen [R. Juraschek and F. W. Röllgen, Int. J. Mass Spectrom. 177, 1 (1998)], liquid is continuously supplied through the tube at a given constant flow rate, while a dc voltage is applied between the tube and a nearby counter electrode. The resulting electric field induces a stress at the surface of the liquid that stretches the meniscus until, in certain ranges of voltage and flow rate, it develops a ligament that eventually detaches, forming a single droplet, in a process that repeats itself periodically. While it is being stretched, the ligament develops a conical tip that emits ultrafine droplets, but the total mass emitted is practically contained in the main droplet. In the parametrical domain studied, we find that the process depends on two main dimensionless parameters, the flow rate nondimensionalized with the diameter of the tube and the capillary time, q, and the electric Bond number B E , which is a nondimensional measure of the square of the applied voltage. The meniscus oscillation frequency made nondimensional with the capillary time, f , is of order unity for very small flow rates and tends to decrease as the inverse of the square root of q for larger values of this parameter. The product of the meniscus mean volume times the oscillation frequency is nearly constant. The characteristic length and width of the liquid ligament immediately before its detachment approximately scale as powers of the flow rate and depend only weakly on the applied voltage. The diameter of the main droplets nondimensionalized with the diameter of the tube satisfies d d ≈ (6/π ) 1/3 (q/f ) 1/3 , from mass conservation, while the electric charge of these droplets is about 1/4 of the Rayleigh charge. At the minimum flow rate compatible with the periodic regimen, the dimensionless diameter of the droplets is smaller than one-tenth, which presents a way to use electrohydrodynamic atomization to generate droplets of highly conducting liquids in the micron-size range, in marked contrast with the cone-jet electrospray whose typical droplet size is in the nanometric regime for these liquids. In contrast with other microdripping regimes where the mass is emitted upon the periodic formation of a narrow capillary jet, the present regime gives one single droplet per oscillation, except for the almost massless fine aerosol emitted in the form of an electrospray.

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Section: Introductionmentioning

confidence: 99%

Periodic emission of droplets from an oscillating electrified meniscus of a low-viscosity, highly conductive liquid

et al. 2015

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“…Droplet-to-nozzle diameter ratios down to about 1:5 and 1:15 have been reported by Chen et al (2006) (10 ^m droplets of an aqueous solution issuing from a 50 ^m i.d. nozzle) and by Lee et al (2012) (50 ^m droplets of diethylene glycol issuing from a 840 ^m i.d. nozzle), respectively.…”

Section: Introductionmentioning

confidence: 99%

“…The pulsating modes discussed above, which are obtained with a DC voltage, can be used for printing, sometimes giving uniform droplet volumes and velocities; see, e.g., Jayasinghe et al (2002), Wang et al (2005), , and Park et al (2007). However, Chen et al (2006), Mishra et al (2010) and Lee et al (2012), among others, find that these modes do not allow simultaneous control of the size of the deposited droplets and the printing frequency, and that they are sensitive to perturbations leading to inconsistent droplet array properties. Seeking more flexible control, Kim et al (2008) used a square wave pulsed voltage superimposed on a DC voltage bias, and showed that the frequency of droplet generation can be locked on to the frequency of the applied voltage when the latter is sufficiently small, while emission fails to occur in some cycles of the applied voltage when its frequency increases.…”

Section: Introductionmentioning

confidence: 99%

“…Seeking more flexible control, Kim et al (2008) used a square wave pulsed voltage superimposed on a DC voltage bias, and showed that the frequency of droplet generation can be locked on to the frequency of the applied voltage when the latter is sufficiently small, while emission fails to occur in some cycles of the applied voltage when its frequency increases. Although a quantitative model of the response of an electrospray to a time periodic applied voltage, or a classification of the functioning modes analogous to that mentioned above for a DC voltage, is not available, Kang et al (2011) and Lee et al (2012) identified four droplet ejection modes in their experiments with various voltage amplitudes and durations, and found that the mode that they term microdripping, in which one or a few individual droplets are ejected from the tip of the meniscus per cycle of the applied voltage, is best suited for printing applications. This mode, however, is obtained only at low voltage frequencies and in a narrow region of the amplitude-duration plane.…”

Section: Introductionmentioning

confidence: 99%

“…To leave out the viscosity of the liquid may be a reasonable approximation for experiments carried out with aqueous solutions, methanol, or ethanol (e.g. Chen et al, 2006;Choi et al, 2008;Juraschek & Rollgen, 1998;Kang et al, 2011;Mishra et al, 2010), though probably not for experiments with glycerol or ethylene glycol (Choi et al, 2008;Kim et al, 2008;Lee et al, 2012). The effect of the finite electrical conductivity of the liquid has been investigated by Kang et al (2011).…”

Section: Introductionmentioning

confidence: 99%

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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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Printing Technologies for Nanomaterials

Abbel

Meinders²

2017

Nanomaterials for 2D and 3D Printing

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A study of ejection modes for pulsed-DC electrohydrodynamic inkjet printing

Cited by 67 publications

References 19 publications

Periodic emission of droplets from an oscillating electrified meniscus of a low-viscosity, highly conductive liquid

Periodic emission of droplets from an oscillating electrified meniscus of a low-viscosity, highly conductive liquid

Pulsating emission of droplets from an electrified meniscus

Printing Technologies for Nanomaterials

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