FIBRE OPTIC SENSOR

• US 20090075321A1
• Filed: 03/13/2006
• Published: 03/19/2009
• Est. Priority Date: 03/11/2005
• Status: Active Grant

• Current Assignee: Andrew Obeid, Geoffrey Ward, Neville Davies, Suzanne Douglas, Trevor Duplooy
• Original Assignee: Andrew Obeid, Geoffrey Ward, Neville Davies, Suzanne Douglas, Trevor Duplooy
• Inventors: Davies, Neville, Obeid, Andrew, Ward, Geoffrey, Douglas, Suzanne, DuPlooy, Trevor
• Granted Patent: US 8,383,047 B2
• Time in Patent Office: Days
• US Class Current: 435/29
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/6848 Needles
• CPC Class Codes: G01N 2021/772 Tip coated light guide
• CPC Class Codes: G01N 2021/7786 Fluorescence
• CPC Class Codes: G01N 2021/7796 Special mountings, packaging of indicators
• CPC Class Codes: G01N 21/7703 using reagent-clad optical fibres or optical waveguides using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B

Abstract

A sensor for measuring the concentration of an assay substance, such as oxygen in tissue. The sensor comprises an optical fibre (2) which passes through, a gas isolation collar (11) into a cavity (15) defined by a needle tube (13) attached to the gas isolation collar. Both the optical fibre (2) and the needle tube (13) are bonded to the gas isolation collar (11) in gas-tight fashion. The cleaved end (8) of the optical fibre within the cavity is provided with an optically active substance (9) having optical properties, such as fluorescence, dependent on the concentration of the assay substance. The cavity (15) is filled with a polymer (16) which is permeable to the assay substance. Lateral flow passages (18) are provided for the assay substance to pass into the permeable polymer (16) and to the fluorophor (9). Light is supplied to the fluorophor via the optical fibre, and functions of its fluorescence are measured to calculate the concentration of the assay substance.

Claims

1. A sensor for measuring the concentration of an assay substance, the sensor comprising an optical fibre which extends longitudinally into a cavity defined by a surrounding wall, the optical fibre having an end portion within the cavity, the end portion terminating in a tip which is provided with an optically active substance which has optical properties which depend on the concentration of the assay substance;

wherein the cavity is filled with an encapsulating material which is permeable to the assay substance and which encapsulates the end portion of the optical fibre, and the surrounding wall is provided with at least one laterally directed flow path for communicating the cavity with a region to be sampled.

2. A sensor as claimed in claim 1, wherein the surrounding wall of the cavity is substantially impermeable and the or each flow path is provided by an aperture in the surrounding wall.

3. A sensor as claimed in claim 2, wherein the aperture is in the form of an elongate slot.

4. A sensor as claimed in claim 1, wherein the surrounding wall of the cavity is substantially impermeable and the or each flow path is provided by a permeable region in the surrounding wall.

5. A sensor as claimed in claim 1, wherein a plurality of flow paths are provided, spaced circumferentially around the surrounding wall.

6. A sensor as claimed in claim 1, wherein the surrounding wall of the cavity is substantially permeable so as to provide flow paths.

7. A sensor as claimed in claim 1, wherein the encapsulating material is a gas permeable polymer.

9. A sensor as claimed in claim 1, wherein the optical fibre passes through a gas isolation collar and into the cavity, the gas isolation collar being bonded to the optical fibre in substantially gas-tight fashion.

10. A sensor as claimed in claim 9, wherein the portion of the optical fibre which passes through the gas isolation collar is devoid of gas permeable components.

11. A sensor as claimed in claim 10, wherein the optical fibre comprises a glass fibre, a cladding layer and a buffer layer, and the buffer layer terminates short of the portion of the optical fibre that passes through the gas isolation collar.

12. A sensor as claimed in claim 9, wherein the cavity surrounding wall is defined by a tube which is connected to the gas isolation collar in substantially gas-tight fashion.

13. A sensor as claimed in claim 12, wherein the tube comprises separate proximal and distal portions which are bonded to the gas isolation collar and to each other in substantially gas-tight fashion.

14. A sensor as claimed in claim 9, wherein the gas isolation collar is elongate.

15. A sensor as claimed in claims 9, wherein the gas isolation collar is provided with a radially outwardly projecting shoulder.

16. A sensor as claimed in claim 9, wherein a fibre optic cable sheath is provided over the optical fibre and engages the gas isolation collar.

17. A sensor as claimed in claim 9, wherein the distal end of the cavity is open.

18. A sensor as claimed in claim 1, wherein the distal end of the cavity is closed.

19. A sensor as claimed in claim 1, wherein the cavity is substantially filled to capacity with the encapsulating material.

20. A sensor as claimed in claim 1, wherein the end portion of the fibre optic within the cavity is spaced from the surrounding wall of the cavity by encapsulating material.

21. A sensor as claimed in claim 1, adapted for use in measuring the concentration of oxygen in tissue.

22. A sensor as claimed in claim 1, wherein the optically active substance on the tip of the optical fibre is provided with a chemical barrier between the optically active substance and the encapsulating material.

23. A sensor as claimed in claim 1, wherein the optically active substance on the tip of the optical fibre is provided with a reflective optical barrier between the optically active substance and the encapsulating material.

24. A sensor as claimed in claim 1, wherein a plurality of optical fibres are provided, each with a tip on which is coated a different optically active substance for detecting a different assay substance.

25. A sensor as claimed in claim 1, wherein in addition to an optical fibre provided with a tip with an optically active substance, the sensor includes a different type of sensing element.

26. A sensor as claimed in claim 1, wherein the optically active substance exhibits fluorescent or phosphorescent activity which depends on the concentration of the assay substance.

27. A sensor as claimed in claim 1, wherein the optically active substance has colorimetric properties which depend on the concentration of the assay substance.

28. A sensor as claimed in claim 1, combination with apparatus for supplying light to the optical fibre, measuring properties of light emitted by the optically active substance, and calculating the concentration of the assay substance being analysed.

8. A sensor as claimed in claim 8, wherein the encapsulating material comprises permeable and impermeable components.

29. A method of measuring the concentration of an assay substance, the method comprising:

providing a sensor comprising an optical fibre which extends longitudinally into a cavity defined by a surrounding wall, the optical fibre having an end portion within the cavity, the end portion terminating in a tip which is provided with an optically active substance which has optical properties which depend on the concentration of the assay substance;

wherein the cavity is filled with an encapsulating material which is permeable to the assay substance and which encapsulates the end portion of the optical fibre, and the surrounding wall is provided with at least one laterally directed flow path for communicating the cavity with a region to be sampled,

providing an apparatus for supplying light to the optical fibre,

measuring properties of light emitted by the optically active substance, and

calculating the concentration of the assay substance being analyzed.

30. A method as claimed in claim 29, used for measuring oxygen concentration in tissue.

31. A sensor for measuring the concentration of an assay substance, the sensor comprising an optical fibre which extends longitudinally into an elongate cavity which is defined by a surrounding wall and has an open end remote from that through which the optical fibre passes, the optical fibre having an end portion within the cavity which is spaced a substantial distance from the open end, and the end portion including a tip which is provided with an optically active substance whose optical properties are dependent on the concentration of the assay substance, wherein the cavity is filled with an encapsulating material which is permeable to the assay substance.

32. A sensor for measuring the concentration of an assay substance, the sensor comprising an optical fibre which extends longitudinally through a base wall into a cavity which is defined by a surrounding wall, the optical fibre having an end portion enclosed within the cavity which includes a tip provided with an optically active substance having optical properties dependent on the concentration of the assay substance, wherein the optical fibre comprises a glass fibre, a cladding layer around the glass fibre and a buffer layer around the cladding layer, wherein the buffer layer is removed over an end region of the optical fibre, a gas isolation collar is bonded in sealing fashion to the cladding and/or glass fibre at a position remote from the remaining buffer layer, the gas isolation collar terminating short of the end portion of the optical fibre, and a tubular member is connected to the gas isolation collar, so that the end of the gas isolation collar provides the end wall of the cavity through which the end portion of the optical fibre passes in sealing fashion, and the tubular member provides the surrounding wall defining the cavity in which the end portion of the optical fibre is enclosed.

33. A sensor for measuring the concentration of an assay substance, the sensor comprising an optical fibre having an end region which extends longitudinally through a base wall into a cavity which is defined by a surrounding wall, the distal portion of the end region of the optical fibre which is enclosed within the cavity including a tip provided with an optically active substance whose optical properties are dependent on the concentration of the assay substance, wherein the end region of the optical fibre consists of material which is impermeable, a gas isolation collar is bonded in sealing fashion to a proximal portion of the end region, and a tubular member is bonded to the gas isolation collar, so that the end of the gas isolation collar provides the end wall of the cavity through which the end region of the optical fibre passes in sealing fashion, and the tubular member provides the surrounding wall defining the cavity in which the distal portion of the end region of the optical fibre is enclosed.

34. A method of manufacturing a sensor for measuring the concentration of an assay substance, comprising the steps of providing a length of optical fibre, applying to an end of the optical fibre a layer of an optically active substance whose optical properties are dependent on the concentration of the assay substance, bonding a tubular gas isolation collar to a region of the optical fibre adjacent the end of the optical fibre, the optical fibre passing through the collar in substantially gas-tight fashion and there being an end region, including the end with the optically active layer, projecting beyond the collar, providing an elongate needle tube connected to the gas isolation collar in gas-tight fashion, the needle tube providing a surrounding wall which defines a cavity in which the end region of the optical fibre is situated, and filling the cavity with an encapsulating material which surrounds the end region of the optical fibre.

35. A method as claimed in claim 34, wherein the optical fibre comprises a glass fibre, a cladding layer, and a buffer layer, and the buffer layer if removed from the end region of the optical fibre and the part of the optical fibre that passes through the gas isolation collar.