Fabrication of nano-capillary emitter arrays for ionic liquid electrospray thrusters

In this study, we fabricated nano-capillary emitter arrays for stable ion emission of ionic liquid electrospray thrusters, employing the fabrication of field emitter arrays or gated nano electron sources. A nano-capillary emitter was successfully fabricated with a 100–300 nm capillary diameter, which prevented ionic liquid leakage by significantly increasing the fluidic impedance of the ionic liquid compared to a previously proposed emitter. An ion emission experiment was conducted with 1-ethyl-3-methylimidazolium dicyanamide as the propellant. Ion emission started at a low voltage of 61 V owing to a small gap of approximately 1 μm between the emitter and extractor electrode. The maximum current density was 43 mA cm−2 on the positive side and −13 mA cm−2 on the negative side without leakage of the ionic liquid, which was more than 100 times higher than that of conventional electrospray thrusters. Moreover, we obtained continuous ion emission without current intercepted by the extractor.