We report the design, fabrication, and characterization of a novel miniature electron impact gas ionizer manufactured via silicon micromachining and high-resolution 3D printing. The ionizer uses an array of 2,500 gated silicon nano-sharp field emitters (20 μm emitter pitch) as cathode and a set of additively manufactured, finely featured polymer and metallic parts as three-dimensional ion-generating structure. Finite element simulation of a gated field emitter tip predicts a start-up bias

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... e equal to 64 V -close to the 62 V turn-on bias voltage estimated via experiments. The Si field emitter array emits 124.5 μA of electron current with ~60% gate transmission while operating at 200 V. The ionization efficiency of the gas ionizer is linear with pressure, reaching values as high as ~0.4% at 5×10 -4 Torr.