A device for delivering fluid to a patient, comprising: an exit port assembly a reservoir including a side wall extending towards an outlet connected to the exit port assembly a lead screw received at least partly in the reservoir and longitudinally extending towards the outlet a plunger secured to the lead screw and having an outer periphery linearly slideable along the side wall of the reservoir, such that linear movement of the lead screw towards the outlet of the reservoir forces fluid within the reservoir through the outlet to the exit port assembly a sensor detecting linear movement of the lead screw an elongated shape memory element having a changeable length decreasing from an uncharged length to a charged length when at least one charge is applied to the shape memory element, wherein the shape memory element is operatively connected to the lead screw such that the changeable length of the shape memory element decreasing from an uncharged length to a charged length causes linear movement of the lead screw towards the outlet of the reservoir and a processor connected to the shape memory element and the sensor detecting linear movement of the lead screw, and programmed to apply a charge to the shape memory element and remove the charge upon receiving a signal from the sensor indicative of linear movement of the lead screw.
