Taking internally wetted capillary electrospray emitters to the sub-ten-micrometer scale with 3D microlithography

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.