Method of making a distributed activator for a two-dimensional shape memory alloy

• US 6,278,084 B1
• Filed: 04/12/2000
• Issued: 08/21/2001
• Est. Priority Date: 09/05/1996
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Maynard, Ronald S.
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): FUQUA, SHAWNTINA T
• Application Number:
  US09/547,982
• Time in Patent Office: 496 Days
• Field of Search: 604/95, 604/53, 604/93, 604/114, 604/281, 128/657, 128/658, 128/786, 219/209, 219/201, 219/522, 219/528, 219/533, 219/534, 219/548, 219/552, 219/549, 219/553
• US Class Current: 219/209
• CPC Class Codes: A61B 1/0058 using shape-memory elements
• CPC Class Codes: A61F 2/848 having means for fixation to the vessel wall, e.g. barbs
• CPC Class Codes: A61F 2/92 Stents in the form of a rolled-up sheet expanding after insertion into the vessel , e.g. with a spiral shape in cross-section
• CPC Class Codes: A61F 2210/0076 multilayered, e.g. laminated structures
• CPC Class Codes: A61M 25/0158 with magnetic or electrical means, e.g. by using piezo materials, electroactive polymers, magnetic materials or by heating of shape memory materials
• CPC Class Codes: F03G 7/065 using a shape memory element

Abstract

A distributed activation system for a unitary sheet of electrically conductive or insulative shape memory alloy having a sufficiently small section to limit the lateral flow of heat including at least one heating element disposed on the shape memory alloy sheet for locally heating an adjacent portion of the sheet such that the adjacent portion assumes a predetermined shape when activated to its threshold temperature. The activation system may be configured for shape memory alloy apparatus and related methods in combination with a control system for selectively activating discrete-shape memory alloy portions with various combinations of at least one heating element that receive an adjustable current such that the resultant local heating causes the sheet to assume a desired overall shape. Methods of forming and selectively activating two-dimensional sheets of electrically conducive and insulative shape memory alloy are further provided.

Claims

1. A method of making a distributed actuator array having a two-dimensional SMA sheet, the method comprising the methods of:

a.) providing an insulating layer over the two-dimensional SMA sheet;

b.) providing a distributed array of heaters over the insulating layer, each to selectively heat a respective portion of the two-dimensional SMA sheet;

c.) providing electrically isolated feed lines for supplying current to each respective heater of the array;

d.) providing an array of sensors for deriving angular deflection states of local portions of the two-dimensional SMA sheet;

e.) providing a control unit;

f.) providing a storage device to store a set of the angular deflection states for the local portions of the two-dimensional SMA sheet;

g.) storing in the storage device electrical current values respectively associated with the angular deflection states; and

h.) providing selected ones of the current values to the control unit to selectably enable the flow of electrical current through ones of the feed lines to achieve an associated one of the angular deflection states.

2. The method of claim 1, and further including the method of training the two-dimensional SMA sheet to a desired shape prior to providing the insulating layer.

3. The method of claim 1, and further including the methods of:

providing an array of temperature sensors over the two-dimensional SMA sheet such that each of the temperature sensors derives a local temperature state of a respective portion of the two-dimensional SMA sheet;

utilizing the derived temperature states to further control the flow of the electric current such that a selected angular deflection state may be achieved.

4. The method according to claim 1, and further including the method of training the two-dimensional SMA sheet to assume a desired shape subsequent to providing electrically isolated feed lines.

5. A method of making a distributed actuator array comprising a two-dimensional SMA sheet, comprising the methods of:

a.) providing an insulating layer over the two-dimensional SMA sheet;

b.) providing a distributed array of heaters over the insulating layer for selective local heating of a portion of the two-dimensional SMA sheet adjacent to each heater of the distributed array;

c.) providing electrically isolated feed lines for supplying current to each respective heater of the array;

d.) providing a control unit to control the flow of current to each respective heater of the array; and

e.) providing an array of transistors such that each transistor is disposed to receive a signal from the control unit, and in response thereto, to drive an associated one of the heaters with a selected current.

6. A method according to claim 5, wherein the array of transistors is an array of power transistors, each power transistor having an output lead connected to a corresponding one of the heaters for driving the heater element to an activation threshold in response to the signal received from the control unit.

7. A method of making a distributed actuator array comprising the methods of:

a.) providing a two-dimensional sheet of an electrically insulative shape memory alloy;

b.) using VLSI techniques to form an electrical insulative layer on the two-dimensional sheet; and

c.) positioning at least one heating element over the two-dimensional sheet to selectively heat an associated portion of the two-dimensional sheet.

8. A method of making a distributed actuator array comprising the methods of:

a.) providing a two-dimensional sheet of an electrically insulative shape memory alloy;

b.) forming an electrical insulative layer on the two-dimensional sheet;

c.) positioning at least one heating element over the two-dimensional sheet to selectively heat an associated portion of the two-dimensional sheet;

d.) providing at least one cooling element in proximity to the two-dimensional sheet to increase thermal transfer performance, the cooling element being provided by a substrate layer formed in proximity to the two-dimensional sheet, the at least one cooling element to include a set of ducts for transporting a thermal coolant.

9. A method of making a distributed actuator array comprising the methods of:

a.) providing a two-dimensional sheet of an electrically insulative shape memory alloy having a sufficiently small thickness to limit the lateral flow of heat through the two-dimensional sheet;

b.) forming an electrical insulative layer on the two-dimensional sheet; and

c.) positioning at least one heating element over the two-dimensional sheet to selectively heat an associated portion of the two-dimensional sheet.

10. The method of claim 9, wherein method c.) includes the method of providing a distributed array of heating elements.

11. The method of claim 10, and further including the method of providing a current source to supply electrical current to selectable ones of the heating elements to thereby allow the selectable ones of the heating elements to generate heat.

12. The method of claim 11, and further including the method of providing a control unit to control the flow of the electrical current from the current source to the selectable ones of the heating elements.

13. The method of claim 12, and including the method of providing a storage device to store position mappings of the two-dimensional sheet.

14. The method of claim 13, and further including the method of storing in the storage device electrical current values to be selectably provided by the control unit to selectable ones of the heating elements to achieve a resultant shape of the two-dimensional sheet.

15. The method of claim 9, wherein the method b.) is performed according to VLSI techniques.

16. The method of claim 9, and further including the method of mounting at least one deflection sensor on the two-dimensional sheet to detect a change in shape of the two-dimensional sheet.

17. The method of claim 9, and further including the method of depositing additional protective layers on the two-dimensional sheet.

18. The method of claim 9, and further including the method of providing at least one cooling element in proximity to the two-dimensional sheet to increase thermal transfer performance.

19. The method of claim 18, wherein the at least one cooling element is provided by a substrate layer formed in proximity to the two-dimensional sheet that includes a set of ducts for transporting a thermal coolant.

20. The method of claim 9, and further including the method of training the two-dimensional sheet to assume a desired shape.

21. A method of manufacturing a distributed actuator array, comprising the methods of:

a.) providing a two-dimensional SMA sheet;

b.) providing multiple heaters to heat selected portions of the two-dimensional SMA sheet;

c.) providing a current supply to selectively supply current to the multiple heaters;

d.) providing a storage device to store electrical current values associated with angular deflection states of the two-dimensional SMA sheet; and

e.) providing selected ones of the electrical current values stored in the storage device to the current supply to activate ones of the multiple heaters, and to thereby enable the two-dimensional SMA sheet to assume an associated one of the angular deflection states.

22. The method of claim 21, and including the method of providing an insulating layer over the two-dimensional SMA sheet.

23. The method of claim 22, and further including the method of training the two-dimensional SMA sheet to a desired shape prior to providing the insulating layer.

24. The method of claim 21, and further including the methods of:

providing an array of temperature sensors over the two-dimensional SMA sheet, each to derive a local temperature state of a respective portion of the two-dimensional SMA sheet; and

utilizing the derived temperature states to control activation of the two-dimensional SMA sheet.

25. The method according to claim 21, and further including the method of training the two-dimensional SMA sheet to assume a desired shape subsequent to providing electrically isolated feed lines.

26. The method according to claim 21, and further including the methods of:

providing an array of sensors for deriving angular deflection states of local portions of the two-dimensional SMA sheet;

providing a control unit;

providing the derived deflection states to the control unit for active control of the angular deflection state of the two-dimensional SMA sheet.

27. The method according to claim 21, wherein method e.) includes the method of providing an array of transistors to provide current to the multiple heaters.

28. The method according to claim 27, wherein the array of transistors is an array of power transistors, each power transistor having an output lead connected to a corresponding heater to drive one or more of the heaters to an activation threshold.

29. The method of claim 21, and further including the method of providing at least one cooling element in close proximity to the two-dimensional SMA sheet.

30. The method of claim 21, wherein the at least one cooling element is provided by a substrate layer formed in proximity to the two-dimensional sheet that includes a set of ducts for transporting a thermal coolant.

31. The method of claim 21, wherein method b.) is performed according to VLSI techniques.

32. The method of claim 21, and further including the method of mounting at least one deflection sensor on the two-dimensional sheet to detect a change in shape of the two-dimensional sheet.

33. The method of claim 21, and further including the method of depositing additional protective layers on the two-dimensional sheet.

34. The method of claim 21, wherein method a.) is performed to provide the two-dimensional SMA sheet with a sufficiently small thickness to limit the lateral flow of heat through the two-dimensional SMA sheet.

35. The method of claim 21, and further including the method of storing intermediate angular deflection states in the storage device.

36. The method of claim 35, wherein the method of storing intermediate angular deflection states in the storage device further includes the method of storing one or more respective current values associated with each of the intermediate angular deflection states.