A fluid infusion device is provided with a cannula spring which functions as an introducer needle, a retraction return spring, and a fluid path. A hollow cannula tubing is wound, bent and sharpened into a shape which allows it to operate as an introducer needle, retraction spring and fluid path in an infusion device. A button is used to insert the introducer needle portion of the cannula spring and a soft catheter, and once the introducer needle portion and catheter have been fully inserted, an engagement between the button and post of the base of the infusion device releases the cannula spring such that the introducer needle portion of the cannula spring automatically retracts, leaving the catheter in the body. An end of the introducer needle portion of the cannula spring remains in fluid communication with the catheter in the body to provide an uninterrupted fluid path.
