Optical waveguide sensor and method of making same

• US 4,889,407 A
• Filed: 12/02/1988
• Issued: 12/26/1989
• Est. Priority Date: 12/02/1988
• Status: Expired due to Term

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Biomedical Sensors Limited (Allegro Biodiesel Corp.)
• Inventors: Irvine, Michael P., Markle, David R., Crane, Barry C.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Healy, Brian M.
• Application Number:
  US07/279,384
• Time in Patent Office: 389 Days
• Field of Search: 350/96.10, 350/96.15, 350/96.29, 350/96.30, 350/96.32, 350/96.34, 350/320, 128/633, 128/634, 219/121.6, 219/121.61, 219/121.7, 219/121.71, 356/39, 356/432, 356/402, 250/227, 250/230, 250/231 R, 526/329.7
• US Class Current: 385/12
• CPC Class Codes: G01D 5/268 using optical fibres G01D5/28 - G01D5/38 take precedence
• CPC Class Codes: G01N 2021/174 either absorption-reflection or emission-fluorescence
• 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
• CPC Class Codes: G01N 21/80 Indicating pH value

Abstract

An optical waveguide sensor for determining an analyte in a medium, which sensor comprises an optical waveguide having a portion to be brought into contact with said medium, said portion having a plurality of cells arranged in an array which substantially covers the cross-sectional area of the waveguide, each of said cells containing an indicator sensitive to said analyte, and a method for the preparation of said sensor.

Claims

1. An optical waveguide sensor for determining an analyte in a medium, which sensor comprises an optical waveguide having a portion to be brought into contact with said medium, said portion having a plurality cells arranged in an aray which substantially covers the cross-sectional area containing an indicator sensitive to said analyte.

2. A sensor according to claim 1, in which the waveguide is an optical fiber.

3. A sensor according to claim 2, in which each of said cells is formed by ablating a hole in the optical fiber.

4. A sensor according to claim 3, in which said cell is ablated with a high energy laser.

5. A sensor according to claim 1, in which said array is a helical array.

6. A sensor according to claim 1, in which the analyte is the pH of the medium and the indicator is a pH-sensitive absorption indicator.

7. A sensor according to claim 6, in which the indicator is phenol red which is deposited in each cell in a gel.

8. A sensor according to claim 1, in which the waveguide is an optical fiber having a distal end and a reflective surface is bonded to said distal end.

9. A sensor according to claim 8, in which said reflective surface is a metal or a layer of reflective particles suspended in an epoxy resin.

10. A sensor according to claim 1, in which the optical fiber is made from polymethyl methacrylate.

11. A method for the preparation of an optical waveguide sensor for determining an analyte in a medium, which comprises selecting a portion of said waveguide, subjecting said portion to means for forming one or more cells within the waveguide, immersing said portion in a medium containing an indicator sensitive to said analyte and evacuating said one or more cells until each of said cells is filled with said indicator.

12. A method according to claim 11, in which said waveguide is an optical fiber.

13. A method according to claim 12, in which each of said cells is formed by ablating a hole in the optical fiber.

14. A method according to claim 13, in which said cell is ablated with a high energy laser.

15. A method according to claim 14, in which a plurality of cells is ablated in the optical fiber by ablating a first cell, then longitudinally moving and rotating the fiber and ablating a second cell and repeating the moving, rotating and ablating steps until the desired number of cells is formed, said cells being arranged in an array which substantially covers the cross-sectional area of the fiber.

16. A method according to claim 15, in which said array is a helical array.

17. A method according to claim 14, in which a plurality of cells arranged in an array which substantially covers the cross-sectional area of the fiber is ablated along said portion of the fiber by subjecting said portion to beams of radiation from a single laser wherein said beams are reflected by a series of reflectors, each of which is located around said portion at an angle which reflects its associated beam into said fiber at a site pre-selected to provide the relevant cell in the desired array.

18. A method according to claim 17, in which said array is a helical array.

19. A method for the preparation of an optical fiber pH sensor which comprises ablating a plurality of holes with an excimer laser to form cells in an array along a portion of an optical fiber, immersing said portion in a gel-forming solution of phenol red indicator and evacuating said cells so that the cells are filled with solution, removing the fiber from the solution and allowing an indicator-containing gel to form in each cell.

20. A method according to claim 19, in which a cross-linking agent is added to the solution to facilitate formation of said gel.

21. A method according to claim 19, in which said optical fiber has a distal end and a reflective surface is bonded to said distal end prior to or after said ablation step.

22. A method according to claim 21, in which said reflective surface is formed by suspending reflective particles in a liquid adhesive, immersing the distal end of said optical fiber in said liquid suspension, withdrawing said distal end from said liquid and curing said adhesive to provide a layer of said reflective particles on said distal end of the fiber.