Advanced High-Thrust Colloid Sources

Huberman, M. N.; Rosen, S.

doi:10.2514/3.62109

Cited by 36 publications

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“…We note, however, that earlier vacuum electrospray studies conducted with glycerol solutions observed a multitude of solvated ions including metastable ions and multiply charged species. 3,31,32,103 In general, the emitted cluster ions recorded in the MD simulations contain more nascent formamide molecules (that is, they are characterized by larger solvation numbers) than the clusters observed in the experiments where typical flight times (that is, the elapsed time between the instant of cluster generation and the moment of its detection) are of the order of 30 µs. The recorded occurrence of larger solvated ion clusters is likely to be correlated with the propensity of the solvent (formamide) to form hydrogen bonds (see Figures 11c-e).…”

Section: Discussionmentioning

confidence: 99%

“…Their physical characteristics (charge, mass, size, energies) are recorded when they cross two planes (which we refer to as "detection planes") located at (200 nm from the droplet center along the field direction (the z-axis). Properties of the recorded positively and negatively charged clusters are summarized in Figure 12 as a function of the cluster radii, R, estimated by using the equimolar radius defined by the cluster mass, m, the computed density of the NaI-formamide solution, F ∼ 1.32 g/cm 3 , and the relation m ) 4/3πR 3 F. Figure 12a displays the estimated surface electric field, E, of each cluster using Coulomb's law (eq 2). A change in the dependence of E on the cluster radius, R, is observed at R ≈ 1 nm, with clusters having radii R e 1 nm corresponding to single ions solvated by formamide molecules, whereas clusters with R g 1 nm are characterized as multi-ion droplets.…”

Section: Simulations Of 10 Nm Nai-formamide Dropletsmentioning

confidence: 99%

“…The associated phenomenology governs a number of venerable technological areas, most notably electrospray ionization 1 (see also the Nobel lecture by John Fenn titled "Electrospray Wings for Molecular Elephants" 2 ), electrospray propulsion, 3 electrospray painting, inkjet printing, 4 and electrospinning 5 of materials. In all of these applications, the electric field causes deformation and charging of the liquid surface, with consequent phenomena including generation of jets, charged-droplet formation, Coulomb fission, and ion-field evaporation (also referred to as field-induced ion desorption).…”

Section: Introductionmentioning

confidence: 99%

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Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

et al. 2008

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The energetics, interfacial properties, instabilities, and fragmentation patterns of electrosprays made from formamide salt solutions are investigated in a mass spectrometric vacuum electrospray experiment and using molecular dynamics (MD) simulations. The electrospray source is operated in a Taylor cone-jet mode, with the nanojet that forms being characterized by high surface-normal electric field strengths in the vicinity of 1 V/nm. Mass-to-charge ratios were determined for both positive and negative currents sprayed from NaI−formamide solutions with solute−solvent mole ratios of 1:8.4 and 1:36.9, and from KI−formamide solutions with mole ratios of 1:41 and 1:83. The molecular dynamics simulations were conducted on isolated 10 nm NaI−formamide droplets at mole ratios of 1:8 and 1:16. The droplet was subjected to a uniform electric field with strengths ranging between 0.5 and 1.5 V/nm. Both the experiments and simulations demonstrate a mixed charge emission regime where field-induced desorption of solvated ions and charged droplets occurs. The macroscopic parameters, such as average mass-to-charge ratio and maximum surface-normal field strengths deduced from the simulations are found to be in good agreement with the experimental work and consistent with electrohydrodynamic theory of cone-jets. The observed mass spectrometric Na+ and I− solvated ion distributions are consistent with a thermal evaporation process, and are correctly reproduced by the simulation after incorporation of the different flight times and unimolecular ion dissociation rates in the analysis. Alignment of formamide dipoles and field-induced reorganization of the positive and negative ionic charges in the interfacial region are both found to contribute to the surface-normal field near the points of charge emission. In the simulations the majority of cluster ions are found to be emitted from the tip of the jet rather than from the neck region next to the Taylor cone. This finding is consistent with the experimental energy distributions of the solvated ions which demonstrate that indeed most ions are emitted closer to the jet region, that is, beyond the cone-neck region where ohmic losses occur. This observation is also consistent with continuum electrohydrodynamic predictions of cluster-ion evaporation at surface regions of high curvature and therefore maximum surface electric field strengths, which may be the cone-neck region, the breakup region of the jet (usually near the tip of the jet), or the emitted charged droplets. In the nanoscale jets observed in this study, the regions of highest spatial curvature are at the ends of the jets where nascent drops either are forming or have just detached. The energetics, interfacial properties, instabilities, and fragmentation patterns of electrosprays made from formamide salt solutions are investigated in a mass spectrometric vacuum electrospray experiment and using molecular dynamics (MD) simulations. The electrospray source is operated in a Taylor cone-jet mode, with the nanojet that form...

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Section: Discussionmentioning

confidence: 99%

Section: Simulations Of 10 Nm Nai-formamide Dropletsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

et al. 2008

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“…Electric space propulsion was identified as one of many applications for electrosprays and it was actively pursued during the 1960-1980 period by several research groups [8][9][10][11]. Thrust is simply generated by ejecting charged particles at high speeds.…”

Section: Introductionmentioning

confidence: 99%

Electrospray emission from nonwetting flat dielectric surfaces

Lozano

Martı́nez-Sánchez

Lopez-Urdiales

2004

Journal of Colloid and Interface Science

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“…The mixed regime holds some interest by itself, since the mean mass velocity of the spray (ions + drops) can be tailored to yield a wide range of specific impulses (from a few hundred seconds to about 2,000 seconds, for the mixtures tested), although at the cost of incurring efficiency penalties due to the velocity dispersion. It must be noted that this mixed regime had already been used in the earlier generation of Colloid Thrusters [4,5,6], but only under very high voltage conditions where multiple Taylor cones are forced to coexist on one site; this so-called "Highly Stressed Regime" yields relatively high thrust per site, but with lower efficiency and wide spray angles. By contrast, we have tried to stay within the single-cone regime, that yields better collimated and more readily controlled sprays.…”

Section: Report Date (Dd-mm-yyyy)mentioning

confidence: 99%

Colloid Thrusters, Physics, Fabrication and Performance

Martı́nez-Sánchez¹,

Akinwande²

2005

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'ublic reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing in. tata needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other . SUPPLEMENTARY NOTES ABSTRACTThis document summarizes the results of 3 and 1/2 years of work by our team on the basic physics and technology required for the development of Colloid Thrusters (also called more recently Electrospray Thrusters). The research covered the basic physics of operation in the mixed ion-droplet mode, later extended to the newly discovered pure ionic mode, the microfabrication in Silicon of two types of arrays of colloid or electrospray emitters, and the development of a quantitative theory for the colloidal regime (no ions). This Executive Summary describes briefly the various achievements, with reference to our interim Reports and to our publications. Special emphasis is placed on the results that were obtained during the one-year extension (2004), which were not covered in our interim reports. The Theses, published papers and Conference papers for 2004 are enclosed in a companion CD disk; earlier Theses and publications were similarly attached to previous Reports. SUBJECT

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Advanced High-Thrust Colloid Sources

Cited by 36 publications

References 1 publication

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

Electrospray emission from nonwetting flat dielectric surfaces

Colloid Thrusters, Physics, Fabrication and Performance

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