A system for controlling fluid flow in a catheter assembly is disclosed herein. An intravenous catheter assembly has a catheter adapter and a needle hub, and the catheter adapter has an inner lumen. A septum is disposed within a portion of the inner lumen, and a slit is formed through the septum. A Parylene coating is disposed within the slit of the septum, the Parylene coating has a thickness of between approximately 0.00005 to 0.0005 millimeters. An introducer needle has a first end coupled to the needle hub and the second end extending through the inner lumen of the catheter adapter. A middle portion of the introducer needle is positioned within a portion of the septum.
