Device and Method Employing Shape Memory Alloy

Abstract

A system for the metering and delivery of small discrete volumes of liquid is comprised of a small or minimal number of inexpensive components. One such component is a movable member, such as a miniature precision reciprocating displacement pump head, which is driven by an actuator that comprises a shape memory alloy material. The operating mechanism of the system is of little or minimal complexity. The system facilitates the precise metering and delivery of the small discrete volumes of liquid. Potential applications for the system include subcutaneous, long-term, automated drug delivery, for example, the delivery of insulin to a person with diabetes. In such an application, the small, simple and inexpensive nature of the invention would allow for its use as both a portable and a disposable system.

1 . A device for pumping a predetermined volume of fluid, comprising:
 a cavity operably associated with an inlet and an outlet, the inlet of a construction sufficient for operable communication with a source of fluid;   an inlet check valve operably associated with the inlet and an outlet check valve operably associated with the outlet;   a plunger operably associated with the cavity, the plunger disposed in a first position by way of a biasing force and moveable therefrom to a second position, the plunger sufficient to compress the resilient enclosure when in one of the first position and the second position, and sufficient to decompress the resilient enclosure when in a different one of the first position and the second position;   a biasing element operably associated with the plunger and of a construction sufficient to provide the biasing force;   an actuator including a shape memory alloy, the actuator operably associated with the plunger to move the plunger from the first position to the second position when the shape memory alloy partially undergoes a thermally induced transformation relative to an original condition thereof, and to move the plunger from the second position to the first position when the shape memory alloy returns toward the original condition; and   wherein the plunger draws fluid into the cavity when the plunger moves from the first position to the second position.   
     
     
         2 . The device of  claim 1 , wherein a phase transformation temperature of the shape memory alloy is about 70° C. above ambient temperature. 
     
     
         3 . A device for pumping a predetermined volume of fluid, comprising:
 a cavity operably associated with an inlet and an outlet, the inlet of a construction sufficient for operable communication with a source of fluid;   an inlet check valve operably associated with the inlet and an outlet check valve operably associated with the outlet;   a plunger operably associated with cavity, the plunger urged to a first position by a biasing force and moveable therefrom to a second position, wherein the plunger travels to compress the cavity when in the first position to fully decompress the cavity when in the second position;   a biasing element operably associated with the plunger to provide the biasing force;   an actuator including a NiTi alloy having a high first transition temperature and a low second transition temperature, wherein the actuator operably associated with the plunger moves the plunger from the first position to the second position when the NiTi alloy thermally transforms at the high first transition temperature, and moves the plunger from the second position to the first position when the NiTi alloy thermally transforms at the low second transition temperature and returns toward the original condition; and   wherein the plunger draws fluid into the cavity when the plunger moves from the first position to the second position.   
     
     
         4 . The device of  claim 3 , wherein the high first transition temperature is about 70° C. above ambient temperature. 
     
     
         5 . The device of  claim 3 , wherein the actuator includes a NiTi alloy wire that is partially heated on an end for a phase transformation in a portion of the wire proximate that end. 
     
     
         6 . A method of pumping a predetermined volume of fluid, comprising:
 providing a cavity operably associated with an inlet and an outlet;   providing an inlet check valve operably associated with inlet, and an outlet check valve operably associated with the outlet;   providing a plunger in a first position under bias via a biasing element;   providing a shape memory alloy having first and second transition temperatures, operably associated with the plunger;   providing at least one pulse of electricity to thermally transform the shape memory alloy at the first transition temperature to move the plunger to a second position; and   ceasing the providing of at least one pulse of electricity to the shape memory alloy for cooling to the second transition temperature to return the plunger to the first position under bias of the biasing element;   the cavity being compressed when the plunger is in one of the first position and the second position, and being decompressed when the plunger is in a different one of the first position and the second position; and   wherein the plunger draws fluid into the cavity when the plunger moves from the first position to the second position.   
     
     
         7 . The method of pumping a predetermined volume of fluid according to  claim 6 , wherein multiple pulses of electricity are applied to the shape memory alloy to thermally transform the shape memory alloy at least at the first transition temperature. 
     
     
         8 . The method of pumping a predetermined volume of fluid according to  claim 6 , wherein the first transition temperature is about 70° C. above ambient temperature. 
     
     
         9 . The method of pumping a predetermined volume of fluid according to  claim 6 , wherein the fluid includes insulin. 
     
     
         10 . The method of pumping a predetermined volume of fluid according to  claim 6 , wherein the method further comprises joining a fluid reservoir in communication with the cavity, wherein the fluid reservoir is contained in a collapsible, resilient enclosure. 
     
     
         11 . A device for pumping a predetermined volume of fluid, comprising:
 a fluid reservoir contained within an enclosure, wherein the enclosure is collapsible;   a displacement cavity in communication with the fluid reservoir;   a fluid inlet and a fluid outlet in communication with the displacement cavity;   a plunger acting on the cavity;   a shape memory actuator, having a first transition temperature to a high temperature phase with a remembered configuration and a second transition temperature to a low temperature phase with a malleable configuration, linked to the plunger;   a biasing element linked to the plunger; and   an electrical source providing a current to the shape memory actuator, wherein a current on state transforms the shape memory actuator to the high temperature phase and moves the plunger to a first position within the cavity, and a current off state allows the shape memory actuator to cool to the low temperature phase so that a biasing element moves the plunger to the second position within the cavity.   
     
     
         12 . A device for pumping a predetermined volume of fluid according to  claim 11 , wherein the shape memory actuator in the remembered configuration has a greater length than in the malleable configuration. 
     
     
         13 . A device for pumping a predetermined volume of fluid according to  claim 11 , wherein the shape memory actuator in the remembered configuration compresses the cavity in the first position and the biasing element decompresses the cavity in the second position. 
     
     
         14 . A device for pumping a predetermined volume of fluid according to  claim 11 , wherein the shape memory actuator in the high temperature phase has a shorter length than in the low temperature phase. 
     
     
         15 . A device for pumping a predetermined volume of fluid according to  claim 11 , wherein the shape memory actuator in the high temperature phase has a longer length than in the low temperature phase. 
     
     
         16 . A device for pumping a predetermined volume of fluid according to  claim 11 , wherein the shape memory actuator includes nitinol, and in the high temperature phase, has substantially transformed into the austentitic phase. 
     
     
         17 . A device for pumping a predetermined volume of fluid according to  claim 11 , wherein the shape memory actuator includes nitinol, and in the low temperature phase, has substantially transformed into the martensitic phase. 
     
     
         18 . A device for pumping a predetermined volume of fluid, comprising:
 a fluid reservoir contained within an enclosure;   a displacement cavity in communication with the fluid reservoir;   a fluid inlet and a fluid outlet in communication with the displacement cavity;   a plunger acting on the cavity;   a shape memory actuator, having a first transition temperature to a high temperature phase with a remembered configuration and a second transition temperature to a low temperature phase with a malleable configuration, linked to the plunger;   a biasing element linked to the plunger; and   an electrical source providing a current to the shape memory actuator, wherein a current on state transforms the shape memory actuator to the high temperature phase and moves the plunger to a first position within the cavity, and a current off state allows the shape memory actuator to cool to the low temperature phase so that a biasing element moves the plunger to the second position within the cavity;   and wherein at least the enclosure and displacement cavity are disposable and housed discrete from the plunger, actuator, biasing element, and electrical source.   
     
     
         19 . A device for pumping a predetermined volume of fluid according to  claim 18 , wherein the shape memory actuator includes a wire having a diameter of about 125 μm. 
     
     
         20 . A device for pumping a predetermined volume of fluid according to  claim 18 , wherein the shape memory actuator includes a wire having a length of about 40 mm.