Gas Sensor

• US 20100050735A1
• Filed: 07/20/2007
• Published: 03/04/2010
• Est. Priority Date: 07/21/2006
• Status: Abandoned Application

• Current Assignee: Anaxsys Technology Limited
• Original Assignee: Anaxsys Technology Limited
• Inventors: Varney, Mark, Garrett, Michael
• Application Number:
  US12/374,661
• Publication Number:
  US 20100050735A1
• Time in Patent Office: Days
• US Class Current: 73/23.300
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: G01N 27/121 for determining moisture content, e.g. humidity, of the fluid moisture content of the tested material G01N27/048
• CPC Class Codes: G01N 27/4045 for gases other than oxygen
• CPC Class Codes: G01N 27/407 for investigating or analysing gases G01N27/411 takes precedence
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

A sensor for sensing a target substance in a gas stream is provided, the sensor comprising: a sensing element disposed to be exposed to the gas stream, the sensing element comprising: a working electrode; a counter electrode; and a layer of ion exchange material extending between the working electrode and the counter electrode; whereby contact of the ion exchange layer with the gas stream forms an electrical contact between the working and counter electrodes.

Claims

1. A sensor for sensing a target substance in a gas stream, the sensor comprising:

a sensing element disposed to be exposed to the gas stream, the sensing element comprising;

a working electrode;

a counter electrode; and

a layer of ion exchange material extending between the working electrode and the counter electrode;

whereby contact of the ion exchange layer with the gas stream forms an electrical contact between the working and counter electrodes.

2. The sensor according to claim 1, wherein the ion exchange material is selected from the group consisting of an ionomer and a sulphonated tetrafluoroethylene copolymer.

3. The sensor according to claim 1, wherein the ion exchange layer comprises a mesoporous material.

4. The sensor according to claim 3, wherein the mesoporous material is selected from the group consisting of zeolite, zeolite 13, zeolite 4A and a mixture of zeolite 13 and zeolite 4A.

5. The sensor according to claim 3, wherein the mesoporous material is distributed as a fine dispersion.

6. The sensor according to claim 1, wherein the ion exchange material is selected from the group consisting of water and condensed water vapour.

7. The sensor according to claim 1, wherein the target substance is selected from the group consisting of an acidic substance, carbon dioxide and water.

8. The sensor according to claim 1, further comprising a conduit through which the gas stream is channeled to impinge upon the sensing element.

9. The sensor according to claim 8, wherein the conduit comprises a mouthpiece into which a patient may exhale.

10. The sensor according to claim 1, wherein the working electrode and counter electrode are in a form selected from the group consisting of a point, a line, rings and flat planar surfaces.

11. The sensor according to claim 1, wherein one or both of the working electrode and the counter electrode comprises a plurality of electrode portions.

12. The sensor according to claim 11, wherein both the working electrode and the counter electrode comprise a plurality of electrode portions arranged in an interlocking pattern.

13. The sensor according to claim 11, wherein the electrode portions are arranged in a concentric pattern.

14. The sensor according to claim 1, wherein the surface area of the counter electrode is greater than the surface area of the working electrode.

15. The sensor according to claim 14, wherein the ratio of the surface area of the counter electrode to the working electrode is at least 2:

1.

16. The sensor according to claim 14, wherein the ratio of the surface area of the counter electrode to the working electrode is at least 5:

1.

17. The sensor according to claim 1, wherein the electrodes are supported on an inert substrate.

18. The sensor according to claim 1, wherein each electrode comprises a metal selected from the group consisting of Group VIII of the Periodic Table of the Elements, copper, silver, gold and platinum.

19. The sensor according to claim 1, further comprising a layer of insulating material disposed over a portion of each electrode, the insulating layer being so shaped as to leave a portion of each electrode exposed for direct contact with a gas stream.

20. The sensor according to claim 1, further comprising a reference electrode.

21. The sensor according to claim 1, wherein the electrodes are mounted on a substrate, the electrodes being applied to the substrate by a method selected from the group consisting of thick film screen printing, spin/sputter coating and visible/ultraviolet/laser photolithography.

22. The sensor according to claim 1, wherein one or more electrodes is comprised of a plurality of layers, the outer layer being a layer of pure metal applied by electrochemical plating.

23. The sensor according to claim 1, further comprising a heater to heat the gas stream directly impinging upon the electrodes.

24. A method of sensing a target substance in a gas stream, the gas stream comprising water vapour, the method comprising:

causing the gas stream to impinge on a layer of ion exchange material extending between a working electrode and a counter electrode;

applying an electric potential across the working electrode and counter electrode;

measuring the current flowing between the working electrode and counter electrode as a result of the applied potential; and

determining from the measured current flow an indication of the concentration of the target substance in the gas stream.

25. The method of claim 24, wherein the target substance is selected from the group consisting of an acidic substance, carbon dioxide, water vapour and a combination thereof.

26. The method of claim 24, wherein a constant voltage is applied across the working electrode and the counter electrode.

27. The method of claim 24, wherein a variable voltage is applied across the working electrode and the counter electrode.

28. The method of claim 27, wherein the variable voltage alternates between a rest potential and a potential above the reaction threshold potential.

29. The method of claim 28, wherein the voltage is pulsed at a frequency of from 0.1 Hz to 20 kHz.

30. A method of measuring the concentration of a target substance in the exhaled breath of a patient, the method comprising:

causing the exhaled breath to impinge on a layer of ion exchange material extending between a working electrode and a counter electrode;

applying an electric potential across the working electrode and counter electrode;

measuring the current flowing between the working electrode and counter electrode as a result of the applied potential; and

determining from the measured current flow an indication of the concentration of a target substance in the exhaled breath stream.

31. The method of claim 30, wherein the target substance is selected from the group consisting of water, carbon dioxide and a combination of water and carbon dioxide.

32. The method of claim 30, wherein the method is applied to determine the lung function of a patient.

33. The method of claim 30, wherein the method is applied to determine the lung function of a patient suffering from asthma, COPD or ARDS.

34. The method of claim 31, wherein the tidal breathing of a patient is monitored.

35. A system for monitoring the composition of a gas stream comprising:

a sensor wherein the sensor comprises;

a sensing element disposed to be exposed to the gas stream, the sensing element comprising;

a working electrode;

a counter electrode; and

a layer of ion exchange material extending between the working electrode and the counter electrode;

whereby contact of the ion exchange layer with the gas stream forms an electrical contact between the working and counter electrodes;

a microcontroller for receiving an output from the sensor; and

a display;

wherein the microcontroller is programmed to generate a continuous image of the concentration of a target substance in a gas stream being analysed on the display.

36. The system of claim 35, wherein the sensor is adapted to be exposed to the breath of a patient.

37. The system of claim 35, wherein the target substance is selected from the group consisting of water, carbon dioxide and a combination of water and carbon dioxide.