Monolithic electrodes and pH transducers

• US 20070138027A1
• Filed: 12/15/2005
• Published: 06/21/2007
• Est. Priority Date: 12/15/2005
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Receveur, Rogier, Mattes, Michael, Dinsmoor, David, Gupta, Arun
• Granted Patent: US 8,728,289 B2
• Time in Patent Office: Days
• US Class Current: 205/787.500
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence

Abstract

The disclosure provides monolithic electrodes including a substrate defining a walled cavity having a floor, an electrically conductive cathode layer overlaying the cavity floor, an electrically conductive contact pad overlaying the substrate, an electrically conductive via in electrical communication with the cathode layer and the contact pad, and a porous membrane layer overlaying the cavity and defining a chamber formed by the porous membrane layer, the walled cavity, and the cavity floor. The disclosure also provides pH transducers including monolithic indicator and reference electrodes, and methods of making and using monolithic pH electrodes and transducers.

Claims

1. An electrode comprising:

a substrate defining a floor of a walled cavity;

an electrically conductive cathode layer overlaying at least a portion of the cavity floor;

an electrically conductive contact pad overlaying at least a portion of the substrate;

an electrically conductive via in electrical communication with the cathode layer and the contact pad; and

a porous membrane layer overlaying the cavity to define a chamber formed by the porous membrane layer, the walled cavity, and the cavity floor.

2. The electrode of claim 1, wherein the cathode layer comprises one or more metals selected from the group consisting of silver, gold, platinum, palladium, rhenium and mercury.

3. The electrode of claim 1, wherein the cathode layer comprises a silver chloride layer overlaying a silver layer.

4. The electrode of claim 1, further comprising an electrolyte within the chamber.

5. The electrode of claim 4, wherein the electrolyte is selected from the group consisting of aqueous solutions of one or more of hydrogen chloride, potassium chloride, silver chloride, and sodium chloride.

6. The electrode of claim 1, wherein the cavity walls are formed by an electrically insulative layer overlaying the substrate.

7. The electrode of claim 1, wherein the cavity walls and the porous membrane layer are bonded together to provide a seal for the chamber.

8. The electrode of claim 1, wherein the contact pad is positioned on a surface of the substrate.

9. The electrode of claim 1, wherein the contact pad is positioned on a surface of the porous membrane layer.

10. The electrode of claim 1, wherein the substrate is selected from the group consisting of silicon, silicon on glass, and silicon on insulator.

11. The electrode of claim 1, wherein the porous membrane layer comprises a glass plate or a polymer.

12. The electrode of claim 11, wherein the porous membrane layer further comprises a glass frit extending between a top surface and a bottom surface of the glass plate.

13. The electrode of claim 11, wherein the porous membrane layer further defines an opening communicably extending to the chamber between a top surface and a bottom surface of the glass plate.

14. The electrode of claim 13, wherein the opening is sealed with a sealant bead positioned to occlude the opening.

15. The electrode of claim 1, wherein the electrode is a reference electrode and the porous membrane layer is permeable to an electrolyte within the chamber.

16. The electrode of claim 1, wherein the electrode is an indicator electrode and the porous membrane layer is selectively permeable to at least one of sodium ions or hydrogen ions.

17. A pH transducer comprising:

a substrate;

a pH indicator electrode formed on the substrate; and

a pH reference electrode formed on the substrate and electrically connected to the indicator electrode by way of circuitry.

18. The pH transducer of claim 17, wherein the substrate is selected from the group consisting of silicon, silicon on glass, and silicon on insulator.

19. The pH transducer of claim 17, wherein the indicator electrode is defined by:

a first walled cavity having a first floor defined by the substrate;

a first silver layer overlaying at least a portion of the first cavity floor;

a first silver chloride layer overlaying at least a portion of the first silver layer;

a first electrically conductive contact pad overlaying at least a portion of the substrate;

a first electrically conductive via in electrical communication with the first silver layer and the first contact pad; and

a first porous membrane layer overlaying the first cavity to define a first chamber formed by the first porous membrane layer, the first walled cavity, and the first cavity floor.

20. The pH transducer of claim 19, wherein the reference electrode is defined by:

a second walled cavity having a second floor defined by the substrate;

a second silver layer overlaying at least a portion of the second cavity floor;

a second silver chloride layer overlaying at least a portion of the second silver layer;

a second electrically conductive contact pad overlaying at least a portion of the substrate;

a second electrically conductive via in electrical communication with the second silver layer and the second contact pad; and

a second porous membrane layer overlaying the second cavity to define a second chamber formed by the second porous membrane layer, the second walled cavity, and the second cavity floor.

21. The pH transducer of claim 20, wherein one or both of the first and second cavity walls is formed by an electrically conductive layer overlaying the substrate.

22. The pH transducer of claim 20, further comprising a first electrolyte within the first chamber, and a second electrolyte within the second chamber.

23. The pH transducer of claim 22, wherein the second porous membrane layer is permeable to the electrolyte within the second chamber.

24. The pH transducer of claim 20, wherein the first and second electrolytes are compositionally different.

25. The pH transducer of claim 20, wherein the first and second electrolytes are selected from the group consisting of aqueous mixtures of one or more of hydrogen chloride, potassium chloride, silver chloride, and sodium chloride.

26. The pH transducer of claim 20, wherein one or both of the first and second contact pads is positioned on a surface of the substrate.

27. The pH transducer of claim 20, wherein the first contact pad is positioned on a surface of the first porous membrane layer, and the second contact pad is positioned on a surface of the second porous membrane layer.

28. The pH transducer of claim 20, wherein the first and second porous membrane layers comprise an integral glass sheet overlaying and bonded to each of the first and second walled cavities to provide a hermetic seal for the first and second chambers.

29. The pH transducer of claim 20, wherein the second porous membrane layer is permeable to an aqueous electrolyte.

30. The pH transducer of claim 20, wherein the second porous membrane layer further comprises a glass frit extending between a top surface and a bottom surface of the second porous membrane layer.

31. The pH transducer of claim 20, wherein the first porous membrane layer further defines a first opening communicably extending from an outer surface of the first porous membrane layer to the first chamber, and the second porous membrane layer further defines a second opening communicably extending from an outer surface of the second porous membrane layer to the second chamber.

32. The pH transducer of claim 31, wherein the first opening is sealed with a first sealant bead, and the second opening is sealed with a second sealant bead.

33. The pH transducer of claim 19, wherein the first porous membrane layer comprises sodium glass.

34. The pH transducer of claim 33, wherein the first porous membrane layer comprises inner and outer hydrated gel layers surrounding a layer of dry sodium glass.

35. A method for fabricating a monolithic pH electrode, comprising:

forming a cavity in a surface of a substrate, wherein the cavity has a floor defined by the substrate;

depositing a silver layer overlaying at least a portion of the cavity floor;

depositing a silver chloride layer overlaying at least a portion of the silver layer;

depositing an electrically conductive contact pad overlaying at least a portion of the substrate;

forming an electrically conductive via in electrical communication with the silver layer and the contact pad; and

applying a porous membrane layer overlaying the cavity to define a chamber formed by the porous membrane layer, the walled cavity, and the cavity floor.

36. The method of claim 35, further comprising forming a housing around the substrate to hold the substrate in a position that exposes an outer surface of the porous membrane layer.

37. The method of claim 35, further comprising forming an opening communicably extending to the chamber from an outer surface of the porous membrane layer to an inner surface of the porous membrane layer.

38. The method of claim 37, further comprising bonding the inner surface of the porous membrane layer to the cavity walls, adding an electrolyte to the chamber through the opening, and hermetically sealing the chamber.

39. A method for sensing pH within a body lumen, comprising:

inserting into a body lumen a monolithic pH transducer comprising a substrate, a pH indicator electrode formed on the substrate, a pH reference electrode formed on the substrate and electrically connected to the indicator electrode through a high impedence pH monitor formed on the substrate;

attaching the pH transducer to an inner wall of the body lumen; and

recording the pH within the body lumen as measured by the pH monitor and pH transducer.

40. The method of claim 39, wherein the body lumen is an esophagus, and the recorded pH is an intraesophageal pH.