Implantable sensor electrodes and electronic circuitry

• US 7,525,298 B2
• Filed: 10/25/2004
• Issued: 04/28/2009
• Est. Priority Date: 10/23/2001
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Choy, David Yueh-Hua, Shah, Rajiv, Morgan, Wayne A., Gord, John
• Primary Examiner(s): Dole; Timothy J
• Application Number:
  US10/973,525
• Publication Number:
  US 20050056539A1
• Time in Patent Office: 1,646 Days
• Field of Search: 324/71.1, 324/658, 20440301-40315, 204/406, 204/412, 600/345, 600/347, 600/365
• US Class Current: 324/71.1
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61N 1/05 for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: G01R 27/14 Measuring resistance by measuring current or voltage obtained from a reference source G01R27/16, G01R27/20, G01R27/22 take precedence

Abstract

An electronic circuit for sensing an output of a sensor having at least one electrode pair and circuitry for obtaining and processing the sensor output. The electrode pair may be laid out such that one electrode is wrapped around the other electrode in a U-shaped fashion. The electronic circuitry may include, among other things, a line interface for interfacing with input/output lines, a rectifier in parallel with the line interface, a counter connected to the line interface and a data converter connected to the counter and the electrode pair. The data converter may be a current-to-frequency converter. In addition, the rectifier may derive power for the electronic circuit from communication pulses received on the input/output lines.

Claims

1. A sensor system comprising:

a catalytic agent;

a first electrode pair, comprising;

a first electrode; and

a second electrode that wraps at least partially around the first electrode;

a second electrode pair, comprising;

a third electrode; and

a fourth electrode that wraps at least partially around the third electrode; and

a spacer abutting the first electrode pair and the second electrode pair;

wherein the first electrode pair and the second electrode pair are for sensing parameters;

wherein the catalytic agent is located in a position to affect at least one parameter;

wherein the first electrode pair and the second electrode pair are positioned such that cross coupling between the second electrode and the third electrode and between the fourth electrode and the first electrode is reduced;

wherein the spacer is for cooperating with the catalytic agent, the first electrode pair and the second electrode pair such that the first electrode pair and the second electrode pair concurrently produce a first electrical value and a second electrical value, respectively, the second electrical value being different from the first electrical value; and

wherein the sensor system further comprises an electrical circuit to determine the at least one parameter based on the difference between the first electrical value and the second electrical value.

2. The sensor system of claim 1, wherein the catalytic agent comprises a biomolecule.

3. The sensor system of claim 2,

wherein the biomolecule comprises a glucose oxidase enzyme;

and

wherein if the second electrode pair and the glucose oxidase enzyme come into contact with blood having glucose, a reaction between the glucose oxidase enzyme and the glucose in the blood uses up oxygen so that there is less oxygen available for a reaction with the second electrode pair, which causes the value of at least one parameter to be different than it would be if the glucose oxidase enzyme were not present.

4. The sensor system of claim 3, wherein the at least one parameter is an amount of current flowing from the fourth electrode to the third electrode.

5. The sensor system of claim 1,

wherein the first electrode comprises a working electrode;

wherein the second electrode comprises a counter electrode;

wherein the third electrode comprises a working electrode; and

wherein the fourth electrode comprises a counter electrode.

6. The sensor system of claim 1, further comprising:

a substrate;

wherein the first electrode pair and the second electrode pair are formed on a first surface of the substrate.

7. The sensor system of claim 6, further comprising:

circuitry for processing the parameters sensed by the first and second electrode pairs.

8. The sensor system of claim 7,

wherein the circuitry is located on a second surface of the substrate;

and

wherein the circuitry is enclosed in a hermetically sealed casing.

9. The sensor system of claim 7, wherein the circuitry comprises a current-to-frequency converter and a measurement counter.

10. The sensor system of claim 7, wherein the circuitry comprises a temperature sensor for providing calibration based on temperature.

11. The sensor system of claim 1, further comprising:

a storage device; and

a power rectifier for receiving communication signals as input and for taking power from the communication signals and storing the power in the storage device.

12. The sensor system of claim 11, wherein the storage device comprises a capacitor.

13. The sensor system of claim 1, further comprising:

a line interface for interfacing with input/output lines;

wherein the line interface receives signals from a host device and sends signals to the host device by means of the input/output lines.

14. The sensor system of claim 13, wherein the line interface communicates with the host device using bipolar pulses.

15. The sensor system of claim 1, wherein the second electrode has generally a U-shaped configuration for wrapping around the first electrode.

16. The sensor system of claim 15, wherein the fourth electrode has generally a U-shaped configuration for wrapping around the third electrode.

17. The sensor system of claim 1, wherein the second electrode wraps around the first electrode by surrounding at least three sides of the first electrode.

18. The sensor system of claim 17, wherein the fourth electrode wraps around the third electrode by surrounding at least three sides of the third electrode.

19. The sensor system of claim 1, further comprising a reference electrode for setting a reference voltage for the first electrode pair and the second electrode pair,

wherein the reference electrode is shared by the first electrode pair and the second electrode pair.

20. A sensor system comprising:

a catalytic agent;

a first electrode pair, comprising;

a first electrode; and

a second electrode that wraps at least partially around the first electrode; and

a second electrode pair, comprising;

a third electrode; and

a fourth electrode that wraps at least partially around the third electrode;

wherein the first electrode pair and the second electrode pair are for sensing parameters;

wherein the catalytic agent is located in a position to affect at least one parameter;

wherein the first electrode pair and the second electrode pair are positioned such that cross coupling between the second electrode and the third electrode and between the fourth electrode and the first electrode is reduced;

wherein the sensor system further comprises a substrate;

wherein the first electrode pair and the second electrode pair are formed on a first surface of the substrate;

wherein the sensor system further comprises a spacer;

wherein the spacer is located on top of the first electrode pair and on top of the second electrode pair;

wherein there is an indentation in a portion of the spacer that is on top of the second electrode pair; and

wherein the catalytic agent is located in the indentation of the spacer.

21. The sensor system of claim 20, wherein the spacer is made of silicon.

22. A sensor system comprising:

a substrate;

a first electrode pair formed on a first surface of the substrate for sensing parameters, comprising;

a first electrode; and

a second electrode that wraps at least partially around the first electrode;

a second electrode pair formed on the first surface of the substrate for sensing parameters, comprising;

a third electrode; and

a fourth electrode that wraps at least partially around the third electrode;

circuitry located on a second surface of the substrate for processing the parameters sensed by the first and second electrode pairs; and

a spacer abutting the first electrode pair and the second electrode pair;

wherein the circuitry is enclosed in a hermetically sealed casing;

wherein the spacer is for cooperating with the first electrode pair and the second electrode pair such that the first electrode pair and the second electrode pair concurrently produce a first electrical value and a second electrical value, respectively, the second electrical value being different from the first electrical value; and

wherein the circuitry is for determining at least one parameter based on the difference between the first electrical value and the second electrical value.

23. The sensor system of claim 22,

wherein the first electrode pair senses a first parameter that is an amount of current flowing from the second electrode to the first electrode;

and

wherein the second electrode pair senses a second parameter that is an amount of current flowing from the fourth electrode to the third electrode.

24. The sensor system of claim 23, further comprising:

a catalytic agent;

wherein the catalytic agent is located in a position to affect the second parameter and to not affect the first parameter.

25. The sensor system of claim 22, wherein the circuitry comprises a current-to-frequency converter and a measurement counter.

26. The sensor system of claim 22, wherein the circuitry comprises a temperature sensor for providing calibration based on temperature.

27. The sensor system of claim 22, wherein the circuitry comprises:

a storage device; and

a power rectifier for receiving communication signals as input and for taking power from the communication signals and storing the power in the storage device.

28. A sensor system comprising:

a substrate;

a first electrode pair formed on a first surface of the substrate for sensing parameters, comprising;

a first electrode; and

a second electrode that wraps at least partially around the first electrode;

a second electrode pair formed on the first surface of the substrate for sensing parameters, comprising;

a third electrode; and

a fourth electrode that wraps at least partially around the third electrode; and

circuitry located on a second surface of the substrate for processing the parameters sensed by the first and second electrode pairs;

wherein the circuitry is enclosed in a hermetically sealed casing;

wherein the sensor system further comprises a spacer and a catalytic agent;

wherein the spacer is located on top of the first electrode pair and on top of the second electrode pair;

wherein there is an indentation in a portion of the spacer that is on top of the second electrode pair; and

wherein the catalytic agent is located in the indentation of the spacer.

29. A sensor system comprising:

a first electrode pair for sensing parameters, comprising;

a first electrode; and

a second electrode that wraps at least partially around the first electrode;

a second electrode pair for sensing parameters, comprising;

a third electrode; and

a fourth electrode that wraps at least partially around the third electrode; and

circuitry for processing the parameters sensed by the first and second electrode pairs;

wherein the first electrode pair and the second electrode pair are positioned such that cross coupling between the second electrode and the third electrode and between the fourth electrode and the first electrode is reduced;

wherein the sensor system further comprises a spacer abutting the first electrode pair and the second electrode pair;

wherein the spacer is for cooperating with the first electrode pair and the second electrode pair such that the first electrode pair and the second electrode pair concurrently produce a first electrical value and a second electrical value, respectively, the second electrical value being different from the first electrical value; and

wherein the circuitry is for determining at least one parameter based on the difference between the first electrical value and the second electrical value.

30. The sensor system of claim 29, further comprising:

a catalytic agent;

wherein the catalytic agent is located in a position to affect at least one parameter.

31. The sensor system of claim 29, wherein the circuitry is enclosed in a hermetically sealed casing.

32. The sensor system of claim 29, wherein the circuitry comprises a current-to-frequency converter and a measurement counter.

33. The sensor system of claim 29, wherein the circuitry comprises:

a line interface for interfacing with input/output lines;

wherein the line interface receives signals from a host device and sends signals to the host device by means of the input/output lines; and

wherein the line interface communicates with the host device using bipolar pulses.