Sensor arrays for detecting analytes in fluids

• US 5,891,398 A
• Filed: 09/16/1998
• Issued: 04/06/1999
• 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:
  US09/154,604
• Time in Patent Office: 202 Days
• Field of Search: 422/82.01, 422/82.02, 422/68, 422/69, 422/98, 436/150, 436/149, 204/406, 204/415, 204/418, 73/23.31, 73/23.2, 73/23.34, 73/335.05, 324/691, 324/693, 338/13, 338/14, 338/7
• US Class Current: 422/82.02
• 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 electrochemical electrode arrays G01N27/27
• 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 method of manufacturing a chemically sensitive sensor, comprising the steps of:

providing a first nonconductive organic material, a second nonconductive organic material, a conductive material, a solvent, a substrate, and an electrical measuring apparatus having first and second conductive leads;

mixing the first and second nonconductive organic materials, the conductive material and the solvent to form a mixture;

contacting the substrate with the mixture;

allowing the solvent to substantially evaporate leaving a sensor film; and

connecting the first and second conductive leads to the sensor film.

2. The method of claim 1, wherein the step of mixing includes mechanical mixing.

3. The method of claim 2, wherein the step of mechanical mixing includes ball-milling.

4. The method of claim 2, wherein the step of mechanical mixing further comprises heating.

5. The method of claim 1, wherein the first and second nonconductive organic materials and the conductive material are soluble in the solvent, and wherein the step of mixing includes dissolving.

6. The method of claim 1, wherein at least one of the materials is insoluble in the solvent, and wherein the step of mixing further comprises the steps of:

dissolving the soluble material(s) in the solvent to form a solution; and

suspending the insoluble material(s) in the solution to form a suspension.

7. The method of claim 6, wherein the insoluble material is selected from the group consisting of carbon black and colloidal metal.

8. The method of claim 7, wherein the colloidal metal is colloidal silver.

9. The method of claim 6, wherein the step of suspending the insoluble material in the solution includes vigorous mixing.

10. The method of claim 6, wherein the step of suspending the insoluble material in the solution further comprises sonication.

11. The method of claim 6, wherein the solvent is a polar solvent.

12. The method of claim 11, wherein the polar solvent is selected from the group consisting of tetrahydrofuran, acetonitrile and water.

13. The method of claim 6, wherein the solvent is a nonpolar solvent.

14. The method of claim 1, wherein the step of contacting is selected from the group consisting of spinning, spraying and dip coating.

15. The method of claim 1, wherein the substrate is an inert, nonconductive substrate.

16. The method of claim 15, wherein the inert, nonconductive substrate is selected from the group consisting of glass and ceramic.

17. The method of claim 1, wherein the substrate is a conductive substrate.

18. The method of claim 1, wherein the substrate is a semiconductive substrate.

19. The method of claim 18, wherein the semiconductive substrate is selected from the group consisting of Si, GaAs, InP, MoS₂, and TiO₂.

20. The method of claim 1, wherein the substrate is an integrated circuit.

21. The method of claim 1, wherein the first nonconductive organic material is a nonconductive organic polymer.

22. The method of claim 1, wherein the second nonconductive organic material is a nonconductive organic polymer.

23. The method of claim 1, wherein the conductive material is selected from the group consisting of organic conductors, inorganic conductors and mixed inorganic/organic conductors.

24. The method of claim 1, wherein after the step of allowing the solvent to substantially evaporate, the method further comprises the step of removing the sensor film from the substrate.

25. The method of claim 24, wherein the first nonconductive organic material is a nonconductive polymer and following the step of contacting the substrate with the mixture, the method further comprises the step of cross-linking the polymer to enhance the structural rigidity of the sensor.

26. The method of claim 25, wherein the step cross-linking is chemical cross-linking.

27. The method of claim 26, wherein the nonconductive polymer is rubber and the chemical cross-linking is sulfur cross-linking.

28. The method of claim 26, wherein the chemical cross-linking is dicumyl peroxide radical cross-linking.

29. The method of claim 25, wherein the method of cross-linking is radiation cross-linking.

30. The method of claim 29, wherein the first nonconductive polymer is a polyolefin and the cross-linking is UV-radiation cross-linking.

31. The method of claim 29, wherein the first nonconductive polymer is Nylon, and the radiation cross-linking is e-beam cross-linking.

32. The method of claim 24, wherein the mixture further comprises an additive to enhance sensor rigidity.

33. The method of claim 32, wherein the additive is a polymer.

34. The method of claim 33, wherein the additive polymer is a high molecular weight, high transition metal polymer.

35. The method of claim 32, wherein the additive is clay.

36. The method of claim 32, wherein the additive is montmorillonite.

37. The method of claim 1, wherein the first nonconductive organic material is a reaction precursor of a nonconductive organic polymer, and the step of solvent evaporation causes polymerization of the reaction precursor.

38. The method of claim 1, wherein the conductive material is formed from a reaction precursor of the conductive material, the precursor soluble in the solvent, the method further comprising the step of applying an activating agent to cause the soluble precursor to react and form the conductive material.

39. The method of claim 38, wherein the activating agent is selected from the group consisting of chemical, doping agent, thermal treatment and thermal treatment under vacuum.

40. A method of manufacturing a chemically sensitive sensor, comprising the steps of:

providing a first solution of a first nonconductive organic material and a conductive material dissolved in a solvent, a second solution of a second nonconductive organic material dissolved in a solvent, a substrate having a pre-selected region, first and second conducting leads each coupled to an electrical measuring apparatus and an inkjet device;

delivering the first solution to the inkjet device;

ejecting the first solution from the inkjet device onto the pre-selected region of the substrate;

delivering the second solution to the inkjet device;

ejecting the second solution from the inkjet device onto the pre-selected region of the substrate; and

connecting the first and second conductive leads to the pre-selected region of the substrate.

41. The method of claim 40, wherein the substrate is an integrated circuit having conductive leads in the pre-selected region of the substrate.

42. The method of claim 40, wherein the first solution is miscible in the second solution.