Electrospray performance of microfabricated colloid thruster arrays

Microfabricated emitters have been produced by deep reactive ion etch technology. To demonstrate their suitability as components of integrated colloid thruster systems, we have evaluated the electrospray performance of individual and arrays of these microfabricated emitters and compared them to that of conventional stainless-steel emitters. We show that, after accounting for electrostatic differences caused by changes in physical geometry, the spray current dependence on flow rate for microemitters demonstrates similar scaling behavior to that of conventional single stainless-steel emitters. The spray current per nozzle is found to be independent of array size and the total spray current to depend simply on the number of nozzles in the emitter array. We have also found that in a triangular array of microemitters there is no significant geometry-induced shielding or field reduction between emitters. We report on the electrospray performance of the room-temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate with conventional emitters, which appears to be a promising new colloid thruster propellant.