Sensor arrays for detecting analytes in fluids

• US 5,951,846 A
• Filed: 01/14/1998
• Issued: 09/14/1999
• Est. Priority Date: 03/27/1995
• Status: Expired due to Term

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Lewis, Nathan S., Freund, Michael S.
• Primary Examiner(s): Bell, Bruce F.
• Application Number:
  US09/006,142
• Time in Patent Office: 608 Days
• Field of Search: 205/787, 205/782.5, 205/775, 422/82.01, 422/82.02, 422/98, 422/68, 422/69, 436/150, 436/151, 204/406, 204/415, 204/418, 73/23.2, 73/23.31, 73/23.34, 73/335.05, 324/691, 324/693, 338/7, 338/13, 338/14
• US Class Current: 506/12
• CPC Class Codes: G01N 27/126 comprising organic polymers
• CPC Class Codes: G01N 33/0031 comprising two or more sensors, e.g. a sensor array
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

Chemical sensors for detecting analytes in fluids comprise first and second conductive elements (e.g. electrical leads) electrically coupled to and separated by a chemically sensitive resistor which provides an electrical path between the conductive elements. The resistor comprises a plurality of alternating nonconductive regions (comprising a nonconductive organic polymer) and conductive regions (comprising a conductive material) transverse to the electrical path. The resistor provides a difference in resistance between the conductive elements when contacted with a fluid comprising a chemical analyte at a first concentration, than when contacted with a fluid comprising the chemical analyte at a second different concentration. Arrays of such sensors are constructed with at least two sensors having different chemically sensitive resistors providing dissimilar such differences in resistance. Variability in chemical sensitivity from sensor to sensor is provided by qualitatively or quantitatively varying the composition of the conductive and/or nonconductive regions. An electronic nose for detecting an analyte in a fluid may be constructed by using such arrays in conjunction with an electrical measuring device electrically connected to the conductive elements of each sensor.

Claims

1. A sensor array for detecting an analyte in a fluid comprising first and second sensors electrically connected to an electrical measuring apparatus, each of said sensors comprising:

regions of nonconductive organic material and conductive material compositionally different than said nonconductive organic material; and

an electrical path through said regions of nonconductive organic material and said conductive material.

2. The sensor array of claim 1, wherein the sensors comprise chemically sensitive resistors.

3. The sensor array of claim 1, wherein the organic materials comprise organic polymers.

4. The sensor array of claim 3, wherein said nonconductive organic polymer of said first sensor is different from the nonconductive organic polymer of said second sensor.

5. The sensor array of claim 3, wherein the nonconductive material is selected from the group consisting of poly(styrene), poly(a-methyl styrene), poly(n-vinylpyrrolidone), poly(4-vinyl phenol), poly(vinyl butral), poly(vinyl acetate), poly(bis phenol A carbonate), poly(acrylonitral), poly(maleic anhydryde), and poly(allyl alcohol).

6. The sensor array of claim 3, wherein the nonconductive material is selected from the group consisting of main-chain carbon polymers, main-chain acyclic heteroatom polymers, and main-chain heterocyclic polymers.

7. The sensor array of claim 1, wherein each sensor exhibits a first electrical resistance when contacted with a first fluid comprising a chemical analyte at a first concentration, and a second electrical resistance when contacted with a second fluid comprising said chemical analyte at a second different concentration, wherein the difference between the first electrical resistance and the second electrical resistance of said first sensor being different from the difference between the first electrical resistance and the second electrical resistance of said second sensor under the same conditions.

8. The sensor array of claim 1, wherein said conductive material is an inorganic conductor.

9. The sensor array of claim 1, wherein the nonconductive region of the first sensor further comprises a first blend of a first nonconductive material and a second nonconductive material, and wherein the nonconductive region of the second sensor further comprises a second blend of a first nonconductive material and a second nonconductive material.

10. The sensor array of claim 9, wherein the first sensor has a first dynamic aggregate baseline resistance and a first dynamic aggregate resistance response to permeation by said analyte, and wherein the second sensor has a second dynamic aggregate baseline resistance and a second dynamic aggregate resistance response to permeation by said analyte, and wherein during use, the permeation of the first blend of nonconductive materials by the analyte in the first sensor produces said first dynamic aggregate resistance response which is different from said first dynamic aggregate baseline resistance, and the permeation of the second blend of nonconductive polymers by the analyte in the second sensor produces said second dynamic aggregate resistance response which is different from said second dynamic aggregate baseline resistance.

11. The sensor array of claim 10, wherein said first nonconductive material and said second nonconductive material of the first blend of the first sensor each has a baseline resistance, a baseline path length, and a resistance response to permeation by the analyte, and the first blend has a baseline resistance, a baseline path length, and a resistance response to permeation by the analyte that is different from the baseline resistance, baseline path length, and resistance response of the first nonconductive polymer and that is different from the baseline resistance, baseline path length, and resistance response of the second nonconductive material, and wherein during use, the baseline path length and baseline resistance of the first blend of nonconductive materials changes in a nonconstant fashion as the first blend is permeated by the analyte so that the first dynamic aggregate resistance response of the first sensor results from the resistance response of the first blend of nonconductive materials, and wherein said first nonconductive and said second nonconductive material of the second blend of the second sensor each has a baseline resistance, a baseline path length, and a resistance response to permeation by said analyte, and the second blend has a baseline resistance, a baseline path length, and a resistance response to permeation by the analyte that is different from the baseline resistance, baseline path length, and resistance response of the first nonconductive material and that is different from the baseline resistance, baseline path length, and resistance response of the second nonconductive polymer, and wherein, during use, the baseline path length and baseline resistance of the second blend of nonconductive polymers change in a nonconstant fashion as the second blend is permeated by the analyte so that the second dynamic aggregate resistance response of the second sensor results from the resistance response of the second blend of nonconductive materials.

12. The sensor array of claim 9, wherein the first nonconductive material in said first sensor is the same as said first nonconductive material in said second sensor.

13. The sensor array of claim 12, wherein the concentration of the first nonconductive material in the first blend of the first sensor is different from the concentration of the first nonconductive material in the second blend of the second sensor.

14. The sensor array of claim 9, wherein said second nonconductive material in the first sensor is the same as said second nonconductive material in the second sensor.

15. The sensor array of claim 1, wherein the conductive material is an organic inducting material.

16. The sensor array of claim 1, wherein the conductive material is a carbonaceous material.

17. The sensor array of claim 16, wherein the carbonaceous material is selected from the group consisting of carbon blacks, graphite, coke, and C₆₀.

18. The sensor array of claim 1, wherein the conductive material is an inorganic conductor.

19. The sensor array of claim 1, further comprising an information storage device coupled to the sensor array.

20. The sensor array of claim 1, wherein each sensor comprises a blend of nonconductive material and conductive material.

21. The sensor array of claim 1, wherein each sensor comprises a plurality of alternating nonconductive regions and conductive regions.

22. The sensor array of claim 1, wherein the nonconductive organic material of the first sensor is different from the nonconductive organic material of the second sensor.

23. The sensor array of claim 1, wherein the conductive material of the first sensor is different from the conductive material of the second sensor.

24. The sensor array of claim 1, wherein, on exposure to a fluid, the first sensor produces a resistance response which is different from the resistance response of the second sensor.

25. A method for detecting the presence of an analyte in a fluid, comprising the steps of:

providing a sensor array comprising first and second sensors, each sensor comprising regions of nonconductive organic material and conductive material compositionally different than said nonconductive material, and an electrical path through said regions of said nonconductive organic material and said conductive material;

exposing the first sensor and the second sensor to the fluid;

measuring a first resistance that occurs when the first sensor is permeated by the fluid;

measuring a second resistance that occurs when the second sensor is permeated by the fluid;

comparing the first measured resistance to the first resistance response to permeation by the analyte to generate a first indicator which indicates the presence or absence of the analyte in the fluid; and

comparing the second measured resistance to the second resistance response to the permeation by the analyte to generate a second indicator which indicates the presence or absence of the analyte in the fluid.

26. The method of claim 25, further comprising the step of comparing the first indicator and the second indicator to create a response pattern.

27. The method of claim 26, further comprising the step of using said response pattern to indicate the absence of a substance different from the analyte in the fluid.

28. The method of claim 25, further comprising the steps of:

providing an information storage device coupled to said electrical measuring apparatus; and

storing information in said information storage device.