A medical device comprising: a syringe barrel including a side wall having an inside surface defining a chamber for retaining fluid, an open proximal end and a distal end including a distal wall with a tip extending distally therefrom having an open passageway in fluid communication with said chamber; a plunger rod comprising a proximal end, a distal end and body extending from the proximal end to the distal end, the plunger rod disposed within the chamber and moveable in the proximal and distal direction within the chamber; a stopper assembly disposed within the chamber and moveable in the proximal and distal direction within the chamber, the stopper assembly forming a fluid-tight seal with the inside surface of the syringe barrel, a stopper including a distal face, a proximal end and a body extending from the distal face to the proximal end wherein the body extending from the distal face to the proximal end defining a stopper cavity and wherein the stopper including an expandable portion adjacent to the proximal end comprising a bendable wall that expands the stopper cavity to create a vacuum within the stopper cavity; and a porous portion comprising a swellable polymer associated with the stopper to permit air to flow into the stopper cavity and to prevent liquid from entering the stopper cavity, the plunger rod and stopper configured to create a pressure differential between the stopper cavity and a portion of the chamber extending from the distal wall and the distal face of the stopper assembly, characterized in that the porous portion comprises a selective barrier that defines a liquid penetration pressure and an air penetration pressure that is less than the liquid penetration pressure. a syringe barrel including a side wall having an inside surface defining a chamber for retaining fluid, an open proximal end and a distal end including a distal wall with a tip extending distally therefrom having an open passageway in fluid communication with said chamber; a plunger rod comprising a proximal end, a distal end and body extending from the proximal end to the distal end, the plunger rod disposed within the chamber and moveable in the proximal and distal direction within the chamber; a stopper assembly disposed within the chamber and moveable in the proximal and distal direction within the chamber, the stopper assembly forming a fluid-tight seal with the inside surface of the syringe barrel, a stopper including a distal face, a proximal end and a body extending from the distal face to the proximal end wherein the body extending from the distal face to the proximal end defining a stopper cavity and wherein the stopper including an expandable portion adjacent to the proximal end comprising a bendable wall that expands the stopper cavity to create a vacuum within the stopper cavity; and a porous portion comprising a swellable polymer associated with the stopper to permit air to flow into the stopper cavity and to prevent liquid from entering the stopper cavity, the plunger rod and stopper configured to create a pressure differential between the stopper cavity and a portion of the chamber extending from the distal wall and the distal face of the stopper assembly,