Device and method employing shape memory alloy

• US 7,959,606 B2
• Filed: 09/23/2009
• Issued: 06/14/2011
• Est. Priority Date: 10/09/2002
• Status: Expired due to Term

• 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.
• Primary Examiner(s): Lucchesi; Nicholas D
• Assistant Examiner(s): BERDICHEVSKY, AARTI
• Application Number:
  US12/565,130
• Publication Number:
  US 20100063449A1
• Time in Patent Office: 629 Days
• Field of Search: 604/65, 604/67, 604/122, 604/134, 604/154, 604/131, 604/151, 604/152
• US Class Current: 604/152
• 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 method of pumping a predetermined dose of insulin to a patient, comprising:

providing an insulin pump having a plunger configured for reciprocating movement in a displacement cavity;

providing an inlet conduit extending from an insulin reservoir to the displacement cavity for carrying insulin to the displacement cavity and an outlet conduit extending from the displacement cavity to the patient;

the inlet conduit being spaced apart from the plunger;

activating a shape memory alloy wire attached to the plunger;

shortening the shape memory alloy wire thereby pulling the plunger in the displacement cavity to a first limit associated with a maximum volume in the displacement cavity;

drawing insulin from the reservoir, through the inlet conduit, and into the displacement cavity as the plunger moves to the first limit;

deactivating the shape memory alloy wire; and

providing a biasing spring configured to move the plunger to a second limit associated with a minimum volume in the displacement cavity, thereby forcing insulin out of the cavity and into the patient.

2. The method of claim 1, wherein the shape memory alloy wire is activated by electrical energy from a pulse generating circuit.

3. The method of claim 2, wherein the electrical energy heats the shape memory alloy wire thereby inducing a phase transition and associated dimensional change shortening the wire.

4. The method of claim 3, wherein the electrical energy from the pulse generating circuit is switched off thereby allowing the shape memory alloy wire to cool to ambient temperature and wherein the biasing spring stretches the shape memory alloy wire until the plunger contacts the second limit.

5. The method of claim 4, wherein the pulse generating circuit includes a battery for providing electrical energy.

6. The method of claim 5, wherein the pulse generating circuit includes a capacitor for storing and discharging electrical energy.

7. The method of claim 6, wherein the battery charges the capacitor with electrical energy.

8. The method of claim 7, wherein the capacitor is a high-capacitance, low-equivalent series resistance electrochemical capacitor and is connected to the battery in parallel.

9. The method of claim 8, wherein the pulse generating circuit is programmable.

10. The method of claim 9, wherein the pulse generating circuit is programmed in accordance with the patient'"'"'s insulin dosage requirements.

11. The method of claim 10, the pulse generating circuit includes a transistor switch and wherein when the transistor switch is open, the battery maintains the capacitor fully charged with electrical energy, and when the transistor switch is closed, an electrical energy pulse is delivered from the capacitor to the shape memory alloy wire.

12. The method of claim 11, wherein the battery is substantially electrically isolated from the shape memory alloy wire.

13. The method of claim 11, wherein the electrical energy pulse duration is 0.15 seconds.

14. The method of claim 1, wherein the plunger completes one pump cycle when the plunger travels from the second limit to the first limit and back to the second limit.

15. The method of claim 14, wherein the battery has sufficient power for about 3000 to 4000 cycles.

16. The method of claim 14, wherein the insulin pump delivers consistent volumes of insulin to the patient over multiple cycles with an accuracy defined by a linear correlation coefficient of 0.999.

17. The method of claim 16, wherein the insulin pump delivers one microliter of insulin per each pump cycle.

18. The method of claim 16, wherein the insulin pump delivers a predetermined discrete dosage volume of insulin in the range of 0.5 to 5.0 microliters per each pump cycle.

19. The method of claim 16, wherein the insulin pump delivers a predetermined discrete dosage volume of insulin in the range of 1.0 to 3.0 microliters per each pump cycle.

20. The method of claim 1, wherein the reservoir is collapsible and gets smaller as insulin is withdrawn.

21. The method of claim 20, wherein the insulin reservoir is a balloon formed from a resilient material.

22. The method of claim 20, wherein the insulin reservoir includes a cylindrical bore with a movable piston.

23. The method of claim 1, wherein at least a portion of the insulin pump is disposable.

24. The method of claim 1, wherein the shape memory alloy wire is formed from nitinol.

25. A method of pumping a predetermined dose of insulin to a patient, comprising:

providing an insulin pump having a plunger configured for reciprocating movement in a displacement cavity;

providing an inlet conduit between an insulin reservoir and the displacement cavity, the inlet conduit being spaced apart from the plunger;

applying electrical energy to a shape memory alloy wire attached to the plunger;

heating the shape memory alloy wire thereby shortening the wire and pulling the plunger in the displacement cavity to a first limit associated with a maximum volume in the displacement cavity;

drawing insulin from the reservoir through the inlet conduit and into the displacement cavity as the plunger moves to the first limit;

deactivating the shape memory alloy wire; and

providing a biasing spring configured to move the plunger to a second limit associated with a minimum volume in the displacement cavity, thereby forcing insulin out of the cavity and into the patient.

26. The method of claim 25, wherein the shape memory alloy wire is activated by electrical energy from a pulse generating circuit.

27. The method of claim 26, wherein the electrical energy heats the shape memory alloy wire thereby inducing a phase transition and associated dimensional change shortening the wire.

28. The method of claim 27, wherein the electrical energy from the pulse generating circuit is switched off thereby allowing the shape memory alloy wire to cool to ambient temperature and wherein the biasing spring stretches the shape memory alloy wire until the plunger contacts the second limit.

29. The method of claim 28, wherein the pulse generating circuit includes a battery for providing electrical energy.

30. The method of claim 29, wherein the pulse generating circuit includes a capacitor for storing and discharging electrical energy.

31. The method of claim 30, wherein the battery charges the capacitor with electrical energy.

32. The method of claim 31, wherein the capacitor is a high-capacitance, low-equivalent series resistance electrochemical capacitor and is connected to the battery in parallel.

33. The method of claim 32, wherein the pulse generating circuit is programmable.

34. The method of claim 33, wherein the pulse generating circuit is programmed in accordance with the patient'"'"'s insulin dosage requirements.

35. The method of claim 34, the pulse generating circuit includes a transistor switch and wherein when the transistor switch is open, the battery maintains the capacitor fully charged with electrical energy, and when the transistor switch is closed, an electrical energy pulse is delivered from the capacitor to the shape memory alloy wire.

36. The method of claim 35, wherein the electrical energy pulse duration is 0.15 seconds.

37. The method of claim 25, wherein the plunger completes one pump cycle when the plunger travels from the second limit to the first limit and back to the second limit.

38. The method of claim 37, wherein the battery has sufficient power for about 3000 to 4000 cycles.

39. The method of claim 37, wherein the insulin pump delivers consistent volumes of insulin to the patient over multiple cycles with an accuracy defined by a linear correlation coefficient of 0.999.

40. The method of claim 39, wherein the insulin pump delivers one microliter of insulin per each pump cycle.

41. The method of claim 39, wherein the insulin pump delivers a predetermined discrete dosage volume of insulin in the range of 0.5 to 5.0 microliters per each pump cycle.

42. The method of claim 39, wherein the insulin pump delivers a predetermined discrete dosage volume of insulin in the range of 1.0 to 3.0 microliters per each pump cycle.

43. The method of claim 25, wherein the reservoir is collapsible and gets smaller as insulin is withdrawn.

44. The method of claim 43, wherein the insulin reservoir is a balloon formed from a resilient material.

45. The method of claim 43, wherein the insulin reservoir includes a cylindrical bore with a movable piston.

46. The method of claim 25, wherein at least a portion of the insulin pump is disposable.

47. The method of claim 25, wherein the shape memory alloy wire is formed from nitinol.