Hybrid microcantilever sensors

• US 6,823,717 B2
• Filed: 06/03/2003
• Issued: 11/30/2004
• Est. Priority Date: 06/03/2002
• Status: Expired due to Fees

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: Clay Macomber, Michael P. Eastman, Timothy L. Porter
• Inventors: Eastman, Michael P., Porter, Timothy L., Macomber, Clay
• Primary Examiner(s): CYGAN, MICHAEL T
• Application Number:
  US10/454,344
• Publication Number:
  US 20040194534A1
• Time in Patent Office: 546 Days
• Field of Search: 73/240.1, 73/240.6, 73/310.5, 73/290.5, 73/310.1, 73/310.2, 73/310.3, 733/350.2, 733/350.3, 733/350.4, 733/350.5
• US Class Current: 73/31.05
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/2475 Embedded probes, i.e. probes incorporated in objects to be inspected
• CPC Class Codes: G01N 33/54386 Analytical elements

Abstract

An apparatus and method for sensing chemical and/or biological analytes in a gaseous or liquid medium by monitoring the changes in impedance and thickness of a sensing element in the presence of the analyte is provided. Detecting means are provided to measure the change in the physical property of the sensing material to determine the presence and/or the amount of analyte present. An array of hybrid sensors dedicated to detecting a particular analyte which may be included in the medium, is also provided.

Claims

1. A hybrid sensor for detecting at least one analyte comprising:

a sensing material having at least volumetric and impedance responses to the presence of at least one analyte;

at least one detector in electrical and physical contact with said sensing material for measuring the volumetric and impedance responses of the sensing material; and

an analyzer for correlating said volumetric and impedance responses into a single measurement to determine at least the identity of the at least one analyte.

2. The hybrid sensor as in claim 1, wherein said analyzer also determines the concentration of the at least one analyte.

3. The hybrid sensor as in claim 1, wherein said detector includes an signal analyzer for facilitating measurement of the impedance of said sensing material.

4. The hybrid sensor as in claim 1, wherein said detector includes a frequency analyzer for measuring the impedance of said sensing material.

5. The hybrid sensor as in claim 4, wherein the frequency analyzer detects the impedance by application of an alternating current to the sensing material.

6. The hybrid sensor as in claim 1, wherein the detector includes a microcantilever sensor having a deflectable arm which deflects in response to a change in the thickness of the sensing material.

7. The hybrid sensor as in claim 6, wherein the deflectable arm includes at least one measurable physical property which changes when said arm deflects and said detector is further capable of measuring a change in said at least one measurable physical property.

8. The hybrid sensor as in claim 6, in which said detector includes a transducer capable of transducing said deflection of said deflectable arm to a measurable electrical signal.

9. The hybrid sensor as in claim 6, in which said deflectable arm includes a piezoresistive member formed one of therein and thereon and said detector includes an electrical circuit capable of measuring a change in resistance of said piezoresistive member due to said deflection.

10. The hybrid sensor as in claim 9, wherein said piezoresistive member comprises barium titanate.

11. The hybrid sensor as in claim 1, in which said sensing material is disposed on a further substrate.

12. The hybrid sensor as in claim 6, wherein said sensing material is formed on a surface and said deflectable arm is in physical contact with said sensing material and disposed essentially parallel to said surface when in rest position.

13. The hybrid sensor as in claim 1, wherein said sensing material comprises a chemical sensor formed of a polymer which undergoes an impedance and volumetric change upon exposure to said at least one analyte.

14. The hybrid sensor as in claim 1, wherein the sensing material comprises a biological sensor formed of either layered biological molecules or composite materials containing biological molecules, the biological sensor being capable of adsorbing said at least one analyte and volumetrically and electrically changing as a result of said adsorption.

15. The hybrid sensor as in claim 14, in which said biological sensor comprises antibodies.

16. The hybrid sensor as in claim 14, in which said biological sensor comprises a functionalized DNA strand disposed on a substrate.

17. The hybrid sensor as in claim 16, in which said at least one analyte comprises the complementary DNA strand of double-stranded DNA.

18. The hybrid sensor as in claim 1, wherein said sensing material comprises at least one polymer matrix material selected from the group consisting of polyvinyl acetate (PVA), polyisobutylene (PIB), polyethylene vinyl acetate (PEVA), poly(4-vinylphenol), poly(styrene-co-allyl alcohol), poly(methylstyrene), poly(N-vinylpyrrolidone), poly(styrene), poly(sulfone), poly(methyl methacrylate), and poly(ethylene oxide).

19. The hybrid sensor as in claim 1, wherein said sensing material comprises at least one analyte sensitive dopant selected from the group consisting nickel acetate, Pd, Pt, and lithium perchlorate.

20. The hybrid sensor as in claim 1, in which said sensing material comprises a discrete deposit of material formed on a surface.

21. The hybrid sensor as in claim 6, in which said deflectable arm includes silicon nitride as a component thereof.

22. The hybrid sensor as in claim 1, in which said at least one analyte is included within one of a gaseous medium and a liquid medium.

23. The hybrid sensor as in claim 6, in which said deflectable arm includes a thickness ranging from 10 microns to 50 microns, a width ranging from 25 microns to 75 microns, and a length ranging from 100 microns to 200 microns.

24. The hybrid sensor as in claim 6, in which said detector is capable of measuring the extent of said deflection of said deflectable arm.

25. The hybrid sensor as in claim 1, wherein the detector measures the impedance of the sensing material at a frequency between 0.01 Hz and 65 kHz.

26. The hybrid sensor as in claim 1, wherein the detector measures the impedance of the sensing material at a frequency between 10 Hz and 178 Hz.

27. The hybrid sensor as in claim 1, wherein the detector measures the impedance of the sensing material at a voltage of between about 0.01 and 0.1 V.

28. The hybrid sensor as in claim 1, wherein the analyte is a volatile organic material.

29. An array of hybrid sensors for detecting analytes, comprising:

a plurality of discrete sensing materials formed on a surface, each sensing material undergoing a change in impedance and volume in the presence of at least one analyte;

a corresponding plurality of detectors each individual detector in electrical and physical contact with at least one of said discrete sensing materials for measuring the volumetric and impedance responses of the at least one discrete sensing material; and

an analyzer for correlating said volumetric and impedance responses into a single measurement to determine at least the identity of the at least one analyte.

30. The array of hybrid sensors as in claim 29, wherein each sensing material is different from the other sensing materials.

31. The array of hybrid sensors as in claim 29, in which said analyzer further determines the concentration of each of the analytes.

32. The array of hybrid sensors as in claim 29, wherein each sensing material undergoes a volumetric change in response to the presence of a different analyte.

33. The array of hybrid sensors as in claim 29, in which each of the detectors includes a microcantilever sensor including a deflectable arm, the deflectable arm being in physical contact with the sensing material.

34. The array of hybrid sensors as in claim 33, in which each of the microcantilever sensors includes a piezoresistive element in contact with said deflectable arm.

35. The array of hybrid sensors as in claim 34, in which each said piezoresistive element undergoes a change in resistance as a result of the deflection of the deflectable arm due to the volumetric change in said corresponding sensing material, each detector further including an electrical circuit for measuring the resistance of the piezoresistive element.

36. The array of hybrid sensors as in claim 33, in which each said deflectable arm includes at least one measurable physical property which changes when said arm deflects and said detector being capable of measuring the change in said at least one measurable physical property of each deflectable arm.

37. The array of hybrid sensors as in claim 29, in which each said deflectable arm responds measurably differently to a different analyte.

38. A method for detecting an analyte within a medium, comprising:

forming a sensing material which undergoes at least a volumetric and impedance response in the presence of said analyte;

providing at least one detector in electrical and physical contact with said sensing material for measuring the volumetric and impedance responses of the sensing material;

introducing a medium containing said analyte to said sensing material, said medium being one of a liquid and a vapor;

measuring said volumetric and impedance responses with said at least one detector; and

correlating said volumetric and impedance responses into a single measurement to determine at least the identity of the at least one analyte.

39. The method as in claim 38, wherein said detector includes a deflectable microcantilever arm in physical contact with said sensing material the deflectable microcantilever arm having at least one measurable physical property which changes when said microcantilever arm deflects;

and

wherein said measuring said volumetric response comprises measuring a change in said at least one measurable physical property.

40. The method as in claim 39, wherein said microcantilever arm includes a piezoresistive member one of therein and thereon, and said measuring comprises measuring a resistance change of said piezoresistive member as a result of one of said deflection.

41. The method as in claim 39, in which said microcantilever arm includes two conductive leads coupled to said piezoresistive member and said measuring includes measuring resistance across said two conductive leads.

42. The method as in claim 38, in which said measuring includes measuring resistance of said sensing material to determine the impedance change of said sensing material each of before and after said step of introducing.

43. The method as in claim 38, wherein said detector includes a signal analyzer in signal communication with said sensing material for measuring the impedance of said sensing material.

44. The method as in claim 38, wherein the analyzing includes determining the concentration of the analyte.