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

Krpoun, Renato; Shea, Herbert

doi:10.1063/1.2981077

Cited by 45 publications

(23 citation statements)

References 18 publications

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“…Post-acceleration remains the preferred choice to increase the performance. From earlier simulations [26], we see that the key drivers to reduce V ext are the extractor electrode diameter and the extractor-emitter gap. The former is designed at 168 µm, enough to allow 40° beam half-angle clearance while the latter is kept at 50 µm.…”

Section: Electrode Designmentioning

confidence: 99%

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Microfabricated electrospray emitter arrays with integrated extractor and accelerator electrodes for the propulsion of small spacecraft

Dandavino¹,

Ataman²,

Ryan³

et al. 2014

J. Micromech. Microeng.

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Microfabricated electrospray thrusters could revolutionize the spacecraft industry by providing efficient propulsion capabilities to micro and nano satellites (1–100 kg). We present the modeling, design, fabrication and characterization of a new generation of devices, for the first time integrating in the fabrication process individual accelerator electrodes capable of focusing and accelerating the emitted sprays. Integrating these electrodes is a key milestone in the development of this technology; in addition to increasing the critical performance metrics of thrust, specific impulse and propulsive efficiency, the accelerators enable a number of new system features such as power tuning and thrust vectoring and balancing. Through microfabrication, we produced high density arrays (213 emitters cm−2) of capillary emitters, assembling them at wafer-level with an extractor/accelerator electrode pair separated by micro-sandblasted glass. Through IV measurements, we could confirm that acceleration could be decoupled from the extraction of the spray—an important element towards the flexibility of this technology. We present the largest reported internally fed microfabricated arrays operation, with 127 emitters spraying in parallel, for a total beam of 10–30 µA composed by 95% of ions. Effective beam focusing was also demonstrated, with plume half-angles being reduced from approximately 30° to 15° with 2000 V acceleration. Based on these results, we predict, with 3000 V acceleration, thrust per emitter of 38.4 nN, specific impulse of 1103 s and a propulsive efficiency of 22% with <1 mW/emitter power consumption.

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Section: Electrode Designmentioning

confidence: 99%

“…Modeling of the electrical field in the emission region was done using COMSOL, extending the model of Krpoun [26] to study the effect of the acceleration electrode on onset. The iterative procedure takes a 49.3° truncated cone topped by a spherical tip.…”

Section: Extraction Field and Electrospray Onsetmentioning

confidence: 99%

Microfabricated electrospray emitter arrays with integrated extractor and accelerator electrodes for the propulsion of small spacecraft

Dandavino¹,

Ataman²,

Ryan³

et al. 2014

J. Micromech. Microeng.

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“…Figure 7 shows the measured emitter spray current as a function of time during a voltage ramp for a single capillary emitter filled with 5 µm diameter silica beads for EMI-Tf 2 N. The current strongly depends on the voltage. There is no electrospray below a critical voltage that depends on device geometry and on the surface tension of the sprayed liquid [10].…”

Section: Testingmentioning

confidence: 99%

Microfabricated out-of-plane arrays of integrated capillary nano-electrospray emitters

Krpoun

Shea

2009

TRANSDUCERS 2009 - 2009 International Solid-State Sensors, Actuators and Microsystems Conference

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This paper presents the fabrication and operation of an integrated nano-electrospray thruster consisting of an array of microfabricated silicon capillary emitters and microfabricated silicon extractor electrodes. Based on previous work in which we showed operation of single microfabricated capillaries [1], the improved thruster presented here allows simultaneously operation of arrays of emitters. In addition, we control the hydraulic impedance of the capillaries by filling them with silica beads, thus tailoring the flow rate in order to spray either in droplet regime or in ionic regime for two ionic liquids. Operation in both modes is confirmed by mass spectrometry and retarding potential analysis. In ion regime, a specific impulse of 3500 s is obtained at 1.2 kV for the ionic liquid EMI-BF 4 .

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“…The dimensions of the microfabricated parts of the thruster are shown in figure 5, and have been optimized using a method allowing the calculation of the onset voltage and estimation of the crosstalk between capillaries [29]. The capillary standoff height is 70 μm, and its inner diameter is 24 μm.…”

Section: Thruster Layoutmentioning

confidence: 99%

Integrated out-of-plane nanoelectrospray thruster arrays for spacecraft propulsion

Krpoun

Shea

2009

J. Micromech. Microeng.

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Nanoelectrosprays, well known for their use in sample injection for the mass spectrometry of large biomolecules, can also be used in other applications such as spacecraft propulsion. The thrust generated by a single electrospray emitter is well below 1 μN, which is several orders of magnitude below the required thrust for planned formation flying missions. This paper presents the process flow and the microfabrication of large 2D arrays of out-of-plane nanoelectrospray capillary emitters with integrated extractor electrodes as well as electrospray results. The capillaries, 70 μm high and with 24 μm inner diameter, are etched from one silicon-on-insulator wafer. The extractor electrodes are from another silicon-on-insulator wafer. Both parts are passively aligned to within 2 μm, centering each capillary under one extractor electrode, thus ensuring highly uniform emitter characteristics over large arrays. Low hydraulic impedance has been a major problem in out-of-plane electrospray designs in the past, which is solved here by adding a post-processing step in which the capillaries are filled with 5 μm silica microspheres fixed in place by silanization. Finally, this paper reports on successful spray tests carried out under vacuum conditions with single and arrays of capillaries spraying the ionic liquid EMI-Tf 2 N demonstrating the operation of our nanoelectrospray thrusters in an ionic mode.

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

Cited by 45 publications

References 18 publications

Microfabricated electrospray emitter arrays with integrated extractor and accelerator electrodes for the propulsion of small spacecraft

Microfabricated electrospray emitter arrays with integrated extractor and accelerator electrodes for the propulsion of small spacecraft

Microfabricated out-of-plane arrays of integrated capillary nano-electrospray emitters

Integrated out-of-plane nanoelectrospray thruster arrays for spacecraft propulsion

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