I want ethylene gas from atmospheric water and carbon dioxide, in a counter-top sized reactor that is fed only electricity and draws the gas from the air. Then makes polyethylene feedstock for an attached 3D printer. Plus an attached shredder to recycle your polyethylene creations when you’re done with it.

If I’m Elon-rich and also SpaceX-Elon thinking about manufacturing plastic things on Mars to support local production, I’m all over this.