Additively manufactured electrohydrodynamic ionic liquid pure-ion sources for nanosatellite propulsion

© 2020 The AuthorsThis study reports the design, fabrication, and characterization of novel, low-cost, additively manufactured, miniaturized, multiplexed electrospray sources with zinc oxide nanowire (ZnONW)-based nanofluidics that produce, in both polarities, pure ions from ionic liquids. The devices comprise an emitting electrode with a monolithic array of emitters and an extractor electrode that triggers the electrohydrodynamic emission of ions from the emitter tips. The emitters are solid cones coated with a nanoporous, hydrothermally grown ZnONW forest that transports ionic liquid to the emitter tips. The emitting electrodes are 3D-printed using either SS 316L via binder jetting or FunToDo Industrial Blend resin via vat polymerization. The extractor electrode is 3D-printed using SS 316L via binder jetting. Experimental characterization of the devices in vacuum using an external collector electrode and the ionic liquid EMI-BF4 shows bipolar pure-ion emission with maximum per-emitter current on the order of microamperes, maximum per-emitter thrust on the order of a fraction of a micronewton, and an average of ~95% beam transmission, resulting in 100% polydispersive efficiency and a significantly higher specific impulse for a given bias voltage compared to state-of-the-art devices. This development is of great interest for miniaturized spacecraft propulsion and focused ion beam applications.