Disinfecting cap for open female luer devices

A cap configured for removable attachment to an open female luer device, the open female luer device having an open distal end with a contacting surface, and the cap comprising:

• a body comprising an opening configured to receive the female luer device, a bottom, and a chamber defined between the opening and the bottom, the chamber configured to hold a liquid disinfectant;
• a male post in the chamber and dimensioned to receive the female luer device, the male post projecting from the bottom towards the opening of the body and comprising a taper corresponding to a taper of the female luer device;
• a wall of the chamber comprising a thread originating proximate the opening and extending into the chamber, a least a portion of the thread having a height that increases as a function of increasing distance from the opening;
• and
• a movable piston positioned about the male post, the movable piston comprising:
• a central opening dimensioned to provide an interference fit with the male post;
• a top region comprising a sealing surface configured to form a seal with an inner surface of the open distal end of the female luer device;
• and
• a flexible circumferential skirt dimensioned to contact the wall of the chamber.