Scalable Microfabrication of Multi-Emitter Arrays in Silicon for a Compact Microfluidic Electrospray Propulsion System.

The recent proliferation of SmallSats and their use in increasingly demanding applications require the development of onboard electric propulsion compatible with the power, mass, and volume constraints of these spacecraft. Electrospray propulsion is a promising technology for SmallSats due to its unique high efficiency and scalability across the wide power range of these platforms, for example, from a few watts available in a CubeSat to a few hundred watts in a MiniSat. The implementation of electrospray propulsion requires the use of microfabrication techniques to create compact arrays of thousands of electrospray emitters.

Energy barrier for ion field emission from a dielectric liquid sphere.

Ion field emission from the surface of a dielectric liquid is commonly modeled as a kinetic process with an energy barrier lowered by the strength of the electric field. Expressions for the energy barrier exist for simplified cases such as a planar surface and a conducting sphere. This article derives an analytical expression for the more general case of a dielectric sphere, which is the continuum model and geometry for most cases of interest.

Study of the electrostatic jet initiation in near-field electrospinning.

Hypothesis: The electrostatic initiation of a jet from the meniscus of a polymeric solution is a key step in near-field electrospinning (NFES), however this process is not sufficiently understood to determine a criterion for the critical emitter voltage triggering the jet, nor to optimize the electrodes. It is expected that the jet initiation in NFES is similar to that in cone-jet electrosprays, and can be described with a first principles model.

Experiments: The electrostatic jet initiation of an SU-8 polymeric solution is studied with two different electrode geometries to quantify the initiation parameters and illustrate the optimization of the electric field.

Pressure-induced amorphization in silicon caused by the impact of electrosprayed nanodroplets.

This Letter describes the shock-induced amorphization of single-crystal Si bombarded by nanodroplets. At impact velocities of several kilometers per second, the projectiles trigger strong compression pulses lasting tens of picoseconds. The phase transition, confirmed via transmission electron microscopy and electron backscatter diffraction, takes place when the projectile's stagnation pressure is approximately 15 GPa.

Retarding potential and induction charge detectors in tandem for measuring the charge and mass of nanodroplets.

The determination of the mass of a nanoparticle via time-of-flight typically requires a direct measurement of its charge. This can be done with a differential retarding potential analyzer and an induction charge detector operating in tandem. The spectrometer described in this article selects a particle with a specified retarding potential from a beam and directs it to an induction charge detector where both its velocity and charge are measured.

Induction charge detector with multiple sensing stages.

An induction charge detector yields the net charge and the time of flight of a particle. The unique ability to independently measure these two parameters sets apart this rather simple detection technique. The main shortcoming of this instrument is its high charge detection limit, resulting from the intrinsic noise of the detector electronics and the low signal associated with the charge to measure.

Tandem mobility mass spectrometry study of electrosprayed tetraheptyl ammonium bromide clusters.

Multiply charged electrospray ions from concentrated solutions of Heptyl4N+Br- (designated A+B- hereafter) in formamide are analyzed mass spectrometrically (MS) following mobility selection in ambient air in a differential mobility analyzer (DMA). Most of the sharp mobility peaks seen are identified as (AB)(n)A+ clusters, with 0 < or = n < ot = 5. One anomalously abundant and mobile ion is identified as NH4+(AB)4.

Electric-field-induced ion evaporation from dielectric liquid.

A direct proof of ion field evaporation from dielectric liquids is presented. The flux of sodium ions ejected from the surface of an electrospray of formamide is measured using time-of-flight and retarding potential techniques. The electric field at the emitting surface is varied through the electrospraying parameters.