Device and Method Employing Shape Memory Alloy

• US 20100114028A1
• Filed: 11/02/2009
• Published: 05/06/2010
• Est. Priority Date: 10/09/2002
• Status: Abandoned Application

• Current Assignee: Abbott Diabetes Care Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Abbott Diabetes Care Incorporated (Abbott Laboratories Incorporated)
• Inventors: Reggiardo, Christopher V., Rush, Benjamin M.
• Application Number:
  US12/610,932
• Publication Number:
  US 20100114028A1
• Time in Patent Office: Days
• US Class Current: 604/151
• CPC Class Codes: A61M 2005/1726 the body parameters being measured at, or proximate to, the infusion site
• CPC Class Codes: A61M 2205/0288 Electro-rheological or magneto-rheological materials
• CPC Class Codes: A61M 2205/3317 Electromagnetic, inductive or dielectric measuring means
• CPC Class Codes: A61M 2205/3569 sublocal, e.g. between console and disposable
• CPC Class Codes: A61M 2205/3592 using telemetric means, e.g. radio or optical transmission
• CPC Class Codes: A61M 2205/702 automatically during use
• CPC Class Codes: A61M 5/14216 Reciprocating piston type
• CPC Class Codes: A61M 5/14244 adapted to be carried by the patient, e.g. portable on the body
• CPC Class Codes: A61M 5/16886 for measuring fluid flow rate, i.e. flowmeters
• CPC Class Codes: F04B 2205/09 Flow through the pump
• CPC Class Codes: F04B 43/043 Micropumps
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: F04B 51/00 Testing machines, pumps, or pumping installations
• CPC Class Codes: F05C 2251/08 Shape memory
• CPC Class Codes: G01F 1/64 by measuring electrical currents passing through the fluid flow; measuring electrical potential generated by the fluid flow, e.g. by electrochemical, contact or friction effects G01F1/58 takes precedence
• CPC Class Codes: G01F 1/708 Measuring the time taken to traverse a fixed distance
• CPC Class Codes: G01F 1/7088 using electrically charged particles as tracers
• CPC Class Codes: G01F 25/10 of flowmeters

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.

Claims

1. A medical device for pumping a fluid, comprising:

an inner tubular member coaxially aligned within an outer cylindrical shell, the inner tubular member defining a cavity and configured for axial movement relative to the outer shell;

a shape memory alloy wire having a shorter remembered shape associated with the inner tubular member to impart axial movement thereto;

a digital timing circuit for activating the shape memory alloy wire including a capacitor for providing electrical energy to the shape memory alloy wire to thermally transform the wire to the shorter remembered shape;

a biasing member biasing the inner tubular member away from the outer cylindrical shell increasing a size of the cavity;

a reservoir containing a fluid and being in fluid communication with the cavity; and

wherein as the shape memory alloy wire shortens and imparts axial movement to the inner tubular member, the size of the cavity is reduced thereby forcing fluid out of the cavity via an outlet, and as the biasing member restores the size of the cavity causing a vacuum therein, fluid is pulled from the reservoir into the cavity via an inlet.

2. The medical device for pumping a fluid of claim 1, wherein the cavity is shaped like a syringe barrel.

3. The medical device for pumping a fluid of claim 1, wherein the biasing member includes a longitudinal axis that is coaxially aligned with the inner tubular member and the outer cylindrical shell.

4. The medical device for pumping a fluid of claim 1, wherein the inner tubular member is slidable within the outer cylindrical shell and the relative sliding changes the size of the cavity.

5. The medical device for pumping a fluid of claim 1, wherein the shape memory alloy wire is connected to the inner tubular member and the outer cylindrical shell.

6. The medical device for pumping a fluid of claim 1, wherein the shape memory alloy wire includes a nickel-titanium alloy that has different phase transition temperatures.

7. The medical device for pumping a fluid of claim 1, wherein the inlet includes a one-way flow check valve in fluid communication with the cavity.

8. The medical device for pumping a fluid of claim 1, wherein the fluid is insulin.

9. The medical device for pumping a fluid of claim 1, wherein the inner tubular member coaxially aligned within the outer cylindrical shell is coaxially aligned with the cavity contained by the outer cylindrical shell, and the fluid flows through the inlet at one end of the inner tubular member into the cavity and then through the outlet at a second end of the outer cylindrical shell, and wherein the fluid flow is controlled by inlet and outlet check valves.

10. The medical device for pumping a fluid of claim 1, wherein the timing circuit is programmable.

11. The medical device for pumping a fluid of claim 1, wherein a rate of fluid delivery is controlled by varying the period of time between activating the shape memory alloy wire.

12. The medical device for pumping a fluid of claim 1, wherein at least a portion of the medical device is disposable with the exception of the timing circuit, capacitor, and the shape memory alloy wire.

13. The medical device for pumping a fluid of claim 1, wherein the fluid reservoir is collapsible.

14. The medical device for pumping a fluid of claim 1, wherein the digital timing circuit includes a replaceable battery.

15. The medical device for pumping a fluid of claim 14, wherein the battery is substantially electrically isolated from the shape memory alloy wire.

16. The medical device for pumping a fluid of claim 1, wherein the timing circuit includes a transistor switch and a battery, and wherein the battery and the capacitor are connected to each other in parallel and are connected to the shape memory alloy wire through the transistor switch.

17. The medical device for pumping a fluid of claim 1, wherein the fluid is insulin and when the size of the cavity is reduced, 0.1 microliter of insulin is pumped through the outlet.

18. The medical device for pumping a fluid of claim 1, wherein forcing the fluid out of the cavity and pulling the fluid into the cavity defines one cycle, and the medical device has an effective maximum of 3000 cycles.

19. The medical device for pumping a fluid of claim 1, wherein the timing circuit generates an electrical pulse duration lasting about 0.15 seconds.

20. A medical device for pumping a fluid, comprising:

an actuator being disposed adjacent a chamber, the chamber having a resilient tubing, the actuator being in contact with the resilient tubing;

a shape memory alloy wire attached to the actuator to impart movement to the actuator;

a digital timing circuit for activating the shape memory alloy wire including a capacitor for providing electrical energy to the shape memory alloy wire; and

a reservoir containing a fluid and being in fluid communication with the chamber so that as the shape memory wire imparts movement to the actuator, the resilient tubing reacts to the movement of the actuator to expand and thereby pull a predetermined volume of fluid from the reservoir into the chamber.

21. The medical device of claim 20, wherein the electrical energy heats the shape memory alloy wire to a transitional temperature thereby causing the wire to shorten.

22. The medical device of claim 21, wherein the actuator moves a predetermined amount corresponding to a maximum volume within the chamber.

23. The medical device of claim 21, wherein the shape memory alloy wire cools and a biasing spring associated with the wire moves the actuator a predetermined amount corresponding to the minimum volume within the chamber.

24. The medical device of claim 21, wherein the digital timing circuit is programmable.

25. The medical device of claim 20, wherein the capacitor is an electrochemical capacitor having a high capacitance and low-equivalent series resistance.

26. The medical device of claim 20, wherein the rate of fluid delivery is controlled by varying the period of time between actuations of the shape memory alloy wire.

27. The medical device of claim 20, wherein the pump is disposable with the exception of the electronics including the digital timing circuit and the shape memory alloy wire.

28. A medical device for pumping a fluid, comprising:

an inner tubular member coaxially aligned within an outer cylindrical shell, the inner tubular member defining a cavity and configured for axial movement relative to the outer shell;

a shape memory alloy wire associated with the inner tubular member to impart axial movement thereto;

a digital timing circuit for activating the shape memory alloy wire including a capacitor for providing electrical energy to the shape memory alloy wire;

a biasing spring connected to the inner tubular member and the outer cylindrical shell; and

a reservoir containing a fluid and being in fluid communication with the cavity so that as the shape memory wire imparts axial movement to the inner tubular member, the size of the cavity is increased thereby causing a vacuum which pulls fluid from the reservoir into the cavity, and a restoring force from the biasing spring reduces the size of the cavity pushing the fluid out via an outlet.

29. The medical device for pumping a fluid according to claim 28, wherein the fluid is insulin.

30. The medical device for pumping a fluid according to claim 28, wherein a digital timing circuit includes a programmable timing circuit, a battery, and a field effect transistor for switching and pulsing current flow, and wherein the battery and capacitor are connected in parallel.

31. The medical device for pumping a fluid according to claim 30, wherein the capacitor includes an electrochemical capacitor.

32. The medical device for pumping a fluid according to claim 30, wherein the battery includes a 200 milliamp-hour lithium/manganese dioxide battery.

33. The medical device for pumping a fluid according to claim 30, wherein the shape memory alloy wire includes a nickel-titanium alloy having a first transition temperature for a high temperature phase and a second transition temperature for a low temperature phase.