Effects of capillary spacing on EHD spraying from an array of cone jets

Regele, Jonathan D.; Papac, Michael J.; Rickard, Matthew; Dunn‐Rankin, Derek

doi:10.1016/s0021-8502(02)00093-9

Cited by 61 publications

(46 citation statements)

References 15 publications

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“…One difficulty is the complex geometry surrounding the emitter and distorting the electric field around the liquid surface. Pioneering work on the effect of capillary spacing in arrays has been done by Regele et al 9 and Quang Tran Si et al 10 Both authors studied the influence of array pitch on the onset voltage and present an analytical model to calculate the onset voltage in their arrays which requires the experimental determination of a calibration factor. The objective of this paper is to present a method to quantitatively determine the onset voltage of a single or arrays of ES taking into account the real emitter-extractor geometry and the surface tension of the liquid.…”

Section: Introductionmentioning

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: Introductionmentioning

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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“…2 kV for a single emitter) and the non-linear behavior with number of emitters ( Figure S10), are well-characterized phenomena attributable to electrical shielding of emitters located in the central part of an array. [23,24] This shielding introduces some inefficiency into the surface reaction method in terms of surface coverage and reagent consumption.…”

Section: Methodsmentioning

confidence: 99%

Peptide Cross‐Linking at Ambient Surfaces by Reactions of Nanosprayed Molecular Cations

Badu‐Tawiah

Jjunju

et al. 2012

Angew Chem Int Ed

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The ability to control the chemical composition of surfaces is of fundamental interest and growing technological importance due to developments in nanotechnology, biotechnology, organic electronics, and functionalized materials.[1] The motivation behind this study is to generate new materials at surfaces, including new covalently bound surface coatings, by using molecular ions in the ambient environment as chemical reagents. In particular, we are interested in generating twoand three-dimensional peptidic macromolecular structures by cross-linking the linear peptide chains generated by conventional solid-phase synthesis [2] using suitable ambient ionic reagents. There is already a substantial literature on peptide cross-linking [3] but our approach is unique in that we use ionic reagents generated by mass spectrometry (MS) to effect rapid, small-scale derivatization. In pursuit of this larger aim, the present study focuses on cross-linking of oligolysines (K n , n = 3, 5) and on the model derivatization reaction of aromatic aldehydes with Girard T reagent. The results indicate that exposure of a nominally dry derivatizing agent (e.g., Girard T or an N-hydroxysuccinimide (NHS) ester reagent) present at a surface to a stream of charged microdroplets containing the analyte (e.g. an aldehyde or a peptide) is a rapid and efficient method of small-scale chemical synthesis.There is a growing interest in the study of the reactions of organic ions outside of the mass spectrometer, both at surfaces and in the gas phase. For example, [4] dry pyrylium ions react in air at surfaces bearing amines to give the pyridinium derivatives. This reactive scattering experiment at atmospheric pressure is the analog of typical vacuum-based ion/surface reactions performed with mass-selected ions at surfaces inside a mass spectrometer.[5] As examples of gasphase reactions, organic ions generated by electrospray ionization (ESI) and dried in a heated metal tube [6] undergo atmospheric pressure ionic reactions like the Fischer indole synthesis, the Borsche-Drechsel cyclization, and the pinacol rearrangement outside the mass spectrometer. Charged microdroplets are used to interrogate surfaces in desorption electrospray ionization (DESI), a method of ambient surface analysis. [7, 8] If a reagent is included in the primary spray solvent, then chemical reactions occur at greatly accelerated rates in the secondary droplets splashed [9] from the surface.For example, the rate of derivatization of ketones by the Girard T reagent is accelerated by two to three orders of magnitude in the droplet/surface process compared to conventional bulk solution. [10,11] The reactive DESI experiment also facilitates identification of reaction intermediates, [12] something also achieved with ESI.[13]Ambient peptide cross-linking was examined in two ways, in one experiment the cross-linking reagent was ionized and delivered in charged microdroplets to the peptide present on an ambient glass surface. In the other experiment, the reagents were interchanged and the pep...

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“…An increase in onset voltage is observed because the parasitic structure starts interfering with the emitter and one should note that the curve corresponds well with experimental results reported in literature. 4,5 Figures 8c and 8d finally show the influence of the sidewalls on the onset voltage as a function of extractor electrode distance and of standoff height of the capillaries. These results also allow to find a compromise between minimum capillary pitch and crosstalk.…”

Section: Influence Of Design Parameter Variationsmentioning

confidence: 98%

“…Recent studies have focused on the influence of interference effects on the onset voltage in an array of nozzles. 4,5 These models do not include the effect of surface tension and require a calibration coefficient which needs to be found experimentally. To determine the onset voltage of micromachined thrusters manufactured in our lab, 6 we have developed a method that combines analytical and finite-element modeling.…”

Section: Introductionmentioning

confidence: 99%