Electrospray emitters are an obvious choice for miniaturized thrusters for a variety of applications on small satellites (e. g., CubeSats), as well as for other micropropulsion purposes. They are inherently small and require a relatively low electric power for operation, and therefore, they fulfill the requirements imposed due to the small volume of CubeSats. Electrospray emitters of the internally wetted capillary type were fabricated by 3D microlithography in the SU-8 photopolymer down to capillary diameters of about 10 μm. Thus, the emitters are an order of magnitude smaller in lateral dimensions than those fabricated by advanced 3D printing methods and still half an order of magnitude smaller than those made by planar photolithography in SU-8. Fabrication methods and process parameters are presented. Furthermore, the preliminary results of the electric characterization of the emission behavior are shown. The experiments show promising results regarding the fabrication quality and extraction behavior.

An internally wetted capillary-type electrospray thruster design is presented. The capillary emitters are optimized for fabrication using 3D micro lithography and can achieve sub 10-micrometer capillary diameters with an aspect ratio of over 20. Also provided is a design for a completely modular integrated extraction electrode that comprises an electrode carrier produced by 3D micro lithography and a thin metal film. The electrode orifices, distance to emitters, and size are all customizable thanks to the modularity of the design, which is compatible with any electrospray thruster type. The design provides alignment precision within 5 micrometers of the emitter tip and electrode orifice. While our new electrode achieved reproducible extraction, instability is still present. The data on emission from these emitter-electrode stacks is presented, as well as in situ microscopic optical observation of individual emitters. The images demonstrate emission in multiple extraction modes, microfluidic behaviour of the capillaries in space-like conditions, and interactions of the emission modes with the integrated electrode.