Medical device including an air evacuation system

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 a 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, wherein the distal end of the plunger rod includes a tapered neck shaped to form a releasable seal with the opening and the opening includes an undercut that is shaped to receive the tapered neck of the plunger rod;
• 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, an expandable portion adjacent to the proximal end comprising a bendable wall formed from an elastomeric material having a spring constant that expands a stopper cavity to create a vacuum within the stopper cavity, and a body extending from the distal face to the proximal end defining the stopper cavity, wherein the stopper is attached to the distal end of the plunger rod and the proximal end of the stopper includes an opening in fluid communication with the stopper cavity, wherein the distal end of the plunger rod is disposed within the stopper cavity and forms a releasable seal with the opening and is proximally and distally moveable within the stopper cavity;
• and
• a porous portion 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, wherein 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.