Medical device assemblies capable of aspirating liquid into a syringe barrel or other medical devices while evacuating any air from the syringe are described. An exemplary medical device includes a syringe barrel (310), plunger rod (340) and stopper assembly (360) having an air permeable and liquid impermeable porous portion and structure for forming a vacuum within either the stopper or the plunger rod. Described is a medical device including a syringe barrel (310), plunger rod and stopper assembly having an air permeable and liquid impermeable porous portion and structure for forming a vacuum within chamber between the stopper and plunger rod wherein the plunger rod includes a sealing edge and is moveable relative to the stopper. Exemplary medical devices may include a vent for allowing air that permeates through the porous portion to escape to atmosphere.