Expanding plunger rods for syringes

A syringe assembly, comprising:

• a substantially cylindrical barrel having a plunger end and a connection end;
• a plunger seal disposed within the plunger end of the barrel;
• a needle seal disposed within the connection end of the barrel;
• a fluid compartment defined within the barrel between the plunger seal and the needle seal;
• and
• an expanding plunger rod comprising:
• a substantially cylindrical outer sleeve having a closed-off bottom end and an open upper end;
• an inner sleeve having a lower end and an upper end, the inner sleeve being slidably disposed coaxially within the outer sleeve;
• an inner rod having a lower end and an upper end, the inner rod being slidably disposed coaxially within the inner sleeve and including a top piece extending axially above the open upper end of the outer sleeve;
• and
• a biasing member disposed axially within a cavity defined by the inner rod between the top piece of the inner rod and the closed-off bottom end of the outer sleeve, the biasing member biasing the top piece and the closed-off bottom end axially away from one another;
• wherein, in the packaged configuration, the inner rod is nested within the outer sleeve, and in the expanded configuration, the inner rod is disposed substantially axially above the outer sleeve, and the inner rod is configured to lock axially in place so as to prevent transition from the expanded configuration to the packaged configuration;
• wherein, in the expanded configuration, the upper end of the inner sleeve and the lower end of the inner rod are both disposed axially above the open upper end of the outer sleeve;
• and
• wherein the biasing member is configured to automatically transition the expanding plunger rod from the packaged configuration to the expanded configuration.