POLYMER NANOFIBER-BASED ELECTRONIC NOSE

• US 20080150556A1
• Filed: 12/22/2006
• Published: 06/26/2008
• Est. Priority Date: 12/22/2006
• Status: Active Grant

• Current Assignee: Research Triangle Institute
• Original Assignee: Research Triangle Institute
• Inventors: Ensor, David S., Han, Li, Andrady, Anthony L.
• Granted Patent: US 8,052,932 B2
• Time in Patent Office: Days
• US Class Current: 324/693
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: G01N 27/127 comprising nanoparticles
• CPC Class Codes: Y10S 977/957 Of chemical property or presence

Abstract

A chemical sensor and a system and method for sensing a chemical species. The chemical sensor includes a plurality of nanofibers whose electrical impedance varies upon exposure to the chemical species, a substrate supporting and electrically isolating the fibers, and a set of electrodes connected to the plurality of fibers at spatially separated points to permit the electrical impedance of the plurality of fibers to be measured. The system includes the chemical sensor, an impedance measuring device coupled to the electrodes and configured to determine an electrical impedance of the plurality of fibers, and an analyzer configured to identify the chemical species based on a change in the electrical impedance. The method measures at least one change in an electrical impedance between spatially separated electrodes connected to a plurality of fibers upon exposure of the fibers to the chemical species, and identifies the chemical species based on the measured change in the electrical impedance.

Claims

1. A chemical sensor comprising:

a plurality of fibers whose electrical impedance varies upon exposure to a chemical species;

a substrate supporting and electrically isolating the fibers; and

a set of electrodes connected to the plurality of fibers at spatially separated points to permit the electrical impedance of the plurality of fibers to be measured.

2. The sensor of claim 1, wherein the fibers comprise nanofibers whose average fiber diameter is less than 500 nm.

3. The sensor of claim 1, wherein the fibers comprise nanofibers whose average fiber diameter is less than 100 nm.

4. The sensor of claim 1, wherein the fibers have an electrical impedance which changes due to at least one of an increase in volumetric size of the fibers by sorption of the chemical species or a change in electrical conduction by a chemical reaction of the chemical species with a material of the fiber.

5. The sensor of claim 1, wherein the fibers comprise conductive fibers.

6. The sensor of claim 5, wherein:

the conductive fibers comprise a non-conducting medium and a conducting additive dispersed in the non-conducting medium, and

the conducting medium has a density which permits electrical conduction by percolation of charge carriers through regions of the conducting medium in the conductive fibers.

7. The sensor of claim 6, wherein the conducting medium comprises a percentage of the conductive fibers ranging from 2% to 10%.

8. The sensor of claim 6, wherein the conducting medium comprises carbon tubes.

9. The sensor of claim 8, wherein the carbon tubes are disposed in a body of the fibers at a concentration that is within 10% of a conduction percolation threshold.

10. The sensor of claim 6, wherein the non-conducting medium comprises an organic polymer.

11. The sensor of claim 1, wherein the fibers comprises metallic particles included in the fibers to increase a fiber conductivity.

12. The sensor of claim 11, wherein the conducting particles include at least one of carbon black, carbon nanotubes, fullerenes and conducting metals, including at least one of Ag, Au, Cu, and Al.

13. The sensor of claim 1, wherein the plurality of fibers comprises aligned fibers.

14. The sensor of claim 1, further comprising:

plural sets of the electrodes to which respective groups of the fibers are connected at spatially separated points.

15. The sensor of claim 1, wherein the electrodes comprise electrodes printed on the plurality of fibers.

16. The sensor of claim 1, further comprising:

a preconcentrator disposed over the plurality of fibers to enhance sorption of the chemical species.

17. The sensor of claim 16, wherein the preconcentrator comprises a silicone layer.

18. A system for sensing a chemical species, comprising:

a chemical sensor including,

a plurality of fibers having a electrical impedance which varies upon exposure to the chemical species,

a substrate supporting and electrically isolating the fibers, and

a set of electrodes connected to the plurality of fibers at spatially separated points on the fibers;

an impedance measuring device coupled to the electrodes and configured to determine an electrical impedance of the plurality of fibers, and

an analyzer configured to identify the chemical species based on a change in the electrical impedance.

19. The system of claim 18, wherein the fibers comprise nanofibers having an average fiber diameter less than 500 nm.

20. The system of claim 18, wherein the fibers comprise nanofibers having an average fiber diameter less than 100 nm.

21. The system of claim 18, wherein the fibers have an electrical impedance which changes due to at least one of an increase in volumetric size of the fibers by sorption of the chemical species or a change in electrical conduction by a chemical reaction of the chemical species with a material of the fiber.

22. The system of claim 18, wherein the fibers comprise conductive fibers.

23. The system of claim 22, wherein:

the conductive fibers comprise a non-conducting medium and a conducting additive dispersed in the non-conducting medium, and

the conducting medium has a density which permits electrical conduction by percolation of charge carriers through regions of the conducting medium in the conductive fibers.

24. The system of claim 23, wherein the conducting medium comprises a percentage of the conductive fibers ranging from 2% to 10%.

25. The system of claim 23, wherein the conducting medium comprises carbon nanotubes.

26. The system of claim 25, wherein the carbon tubes are disposed in a body of the fibers at a concentration that is within 10% of a conduction percolation threshold.

27. The system of claim 23, wherein the fibers comprises metallic particles included in the fibers to increase a fiber conductivity.

28. The system of claim 27, wherein the conducting particles include at least one of carbon black, carbon nanotubes, fullerenes and conducting metals, including at least one of Ag, Au, Cu, and Al.

29. The system of claim 23, wherein the non-conducting medium comprises an organic polymer

30. The system of claim 18, wherein the plurality of fibers comprises aligned fibers.

31. The system of claim 18, further comprising:

plural sets of electrodes connected to plural respective groups of the fibers at spatially separated points.

32. The system of claim 18, further comprising a plurality of the chemical sensors forming a sensor network.

33. The system of claim 18, wherein the electrodes comprise electrodes printed on the plurality of fibers.

34. The system of claim 18, further comprising:

a preconcentrator disposed over the plurality of fibers to enhance sorption of the chemical species.

35. The system of claim 34, wherein the preconcentrator comprises a silicone layer.

36. A method for sensing a chemical species, comprising:

measuring at least one change in an electrical impedance between spatially separated electrodes connected to a plurality of fibers upon exposure of the fibers to the chemical species; and

identifying the chemical species based on the measured change in the electrical impedance of the plurality of fibers.

37. The method of claim 36, wherein measuring comprises:

measuring the change in electrical impedance of a plurality of nanofibers having an average fiber diameter less than 500 nm.

38. The method of claim 36, wherein measuring comprises:

measuring the change in electrical impedance of a plurality of nanofibers having an average fiber diameter less than 100 nm.

39. The method of claim 36, wherein measuring comprises:

measuring the change in electrical impedance of a plurality of conductive fibers.

40. The method of claim 36, wherein measuring comprises:

measuring the change in electrical impedance of a plurality of fiber having a non-conducting medium and a conducting medium dispersed in the non-conducting medium,

wherein the conducting medium has a density which permits electrical conduction by percolation of charge carriers through regions of the conducting medium in the conductive fibers.

41. The method of claim 36, wherein identifying the chemical species comprises:

comparing the measured change in electrical impedance to a library of changes for known concentrations of predetermined chemical species.

42. The method of claim 36, wherein identifying the chemical species comprises:

comparing measured changes in electrical impedance for respective groups of fibers to a library of changes for known concentrations of plural predetermined chemical species.

43. The method of claim 36, wherein measuring comprises measuring changes due to at least one of an increase in volumetric size of the fibers by sorption of the chemical species or a change in electrical conduction by a chemical reaction of the chemical species with a material of the fiber.