A vapor-pressure driven micro pump system comprising an enclosure of a supporting structure; a first chamber having a first volatile material as a propellant with a plurality of exit nozzles; a second chamber have a second volatile material inside of a collapsible diaphragm which separates the first and the second chambers within said enclosure, wherein a vacuum at the plurality of exit nozzles causes vaporization of said propellant, which is compensated and displaced by vapor of said second volatile material at a substantially constant pressure by moving of said collapsible diaphragm. The vapor-pressure driven pump system is useful for various situations, especially in a gravity-free environment in space exploration.