Variable volume, shape memory actuated insulin dispensing pump

A method of dispensing a liquid, comprising:

• drawing liquid into a pumping chamber by causing a shape memory material to contract and move a piston;
• expelling liquid from the pumping chamber by causing the shape memory material to relax and move the piston;
• monitoring the position of the piston;
• and
• controlling the position of the piston based upon the monitored position.

A hydraulic pump comprising:

• a chamber;
• a piston within the chamber;
• a shape memory element that drives the piston;
• a stroke length equal to the maximum distance of travel of a pumping surface of the piston;
• a position sensing mechanism that senses the position of the piston;
• and
• a positioning system including a linear feedback mechanism, wherein the positioning system moves the piston in increments less than the stroke length, resulting in a partial piston stroke.

A pump comprising:

• a reservoir having a maximum volume;
• an actuator comprising a shape memory alloy that moves a plunger, the plunger displacing liquid from the reservoir;
• and
• a control system that utilizes linear feedback to sense the position of the actuator and to manipulate the actuator to provide doses of variable volumes less than the maximum volume.

A pump comprising:

• a shape memory alloy;
• a piston connected to the shape memory alloy, said piston having a stroke length;
• means for sensing the precise position of the piston at any point of the piston stroke;
• and
• means for controlling the position of the piston by changing the length of the shape memory alloy, said means for controlling able to position the piston at any point of the piston stroke thereby enabling the pump to pump variable dosage sizes of a liquid.

A method of dispensing a liquid, comprising:

• providing a piston connected to a shape memory element;
• providing a potential to the shape memory element in order to change the length of the element,
• monitoring the position of the piston;
• and
• adjusting the potential applied to the shape memory element to move the piston and dispense liquid, based upon the monitored position.

A method of pumping a liquid, comprising:

• applying at least one electrical pulse to a shape memory alloy to move a piston;
• detecting a stressed state of the shape memory alloy;
• and
• modifying the at least one pulse if the stressed state is detected.

A pumping system comprising:

• a chamber;
• a first piston within the chamber;
• a shape memory element within the chamber that changes length when a current flows through the element,
• the element moving the first piston between a first and second physical limit, such that when the first piston is at the first limit the chamber is occupied with liquid and when the chamber is at the second limit the chamber is substantially discharged of liquid;
• and
• a second piston coupled to the shape memory element that moves to accommodate changes in the shape memory element and reduce stress on the pumping system.