Embedded piezoelectric microcantilever sensors

• US 6,854,317 B2
• Filed: 06/03/2003
• Issued: 02/15/2005
• Est. Priority Date: 06/03/2002
• Status: Expired due to Fees

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: Arizona Board of Regents (University of Arizona)
• Inventors: Eastman, Michael P., Porter, Timothy L.
• Primary Examiner(s): CYGAN, MICHAEL T
• Application Number:
  US10/454,346
• Publication Number:
  US 20040211243A1
• Time in Patent Office: 623 Days
• Field of Search: 73/232, 73/240.6, 73/290.5, 73/310.1, 73/310.5
• 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 includes a deflectable arm of a microcantilever at least partially embedded within a sensing element. A gaseous or liquid medium which may include the analyte being detected is introduced to the sensing element. The sensing element undergoes volumetric expansion or contraction in the presence of the analyte sought to be detected, typically by adsorbing the analyte. The volumetric change of the sensing element causes the deflectable arm to deflect. The deflectable arm includes at least one measurable physical property which changes when the arm deflects. Detecting means are provided to measure the change in the physical property to determine the presence and amount of analyte present. An array of microcantilevers in which each microcantilever is dedicated to detecting a particular analyte which may be included in the medium, is also provided.

Claims

1. An embedded microcantilever for detecting at least one analyte comprising:

a deflectable arm having a first end fixedly coupled to a substrate, and a second end at least partially embedded within a solid-phase sensing material deposit, wherein the solid-phase sensing material deposit is capable of producing a volumetric change based on the contact of the at least one analyte with the solid-phase sensing material, and said arm being capable of deflecting responsive to the volumetric change of the solid-phase sensing material deposit; and

detecting means capable of measuring the deflection of said arm.

2. The embedded microcantilever as in claim 1, wherein said arm includes at least one measurable physical property which changes when said arm deflects and said detecting means is capable of measuring a change in said at least one measurable physical property.

3. The embedded microcantilever as in claim 1, in which said detecting means includes an electric circuit for facilitating measurement of said deflection of said arm.

4. The embedded microcantilever as in claim 1, in which said detecting means includes a transducer capable of transducing said deflection of said arm to a measurable electrical signal.

5. The embedded microcantilever as in claim 1, in which said arm includes a piezoresistive member formed one of therein and thereon and said detecting means includes an electrical circuit capable of measuring a change in resistance of said piezoresistive member due to said deflection.

6. The embedded microcantilever as in claim 5, wherein said piezoresistive member comprises barium titanate.

7. The embedded microcantilever as in claim 1, in which said sensing material deposit is disposed on a further substrate.

8. The embedded microcantilever as in claim 1, wherein said sensing material deposit is formed on a surface and said deflectable arm is embedded within said sensing material deposit and disposed essentially parallel to said surface when in rest position.

9. The embedded microcantilever as in claim 1, wherein said sensing material deposit comprises a chemical sensor formed of a polymer and which undergoes a volumetric change in a vertical direction upon exposure to said at least one analyte.

10. The embedded microcantilever as in claim 1, wherein the sensing material deposit comprises a biological sensor formed of one of either layered biological molecules and composite materials, capable of adsorbing said at least one analyte and volumetrically changing in a vertical direction as a result of said adsorption.

11. The embedded microcantilever as in claim 10, in which said biological sensor comprises one of either antibodies and a composite containing antibodies.

12. The embedded microcantilever as in claim 11, in which said at least one analyte comprises a virus attracted to said antibodies.

13. The embedded microcantilever as in claim 10, in which said biological sensor comprises a thiolated single strand DNA, which is one of either disposed on a gold substrate or contained within a composite material.

14. The embedded microcantilever as in claim 13, in which said at least one analyte comprises the complementary DNA strand of double-stranded DNA.

15. The embedded microcantilever as in claim 1, wherein said sensing material deposit 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).

16. The embedded microcantilever as in claim 1, wherein said sensing material deposit comprises at least one analyte sensitive dopant selected from the group consisting nickel acetate and lithium perchlorate.

17. The embedded microcantilever as in claim 1, in which said sensing material deposit comprises a discrete pad of material formed on a surface.

18. The embedded microcantilever as in claim 1, in which said deflectable arm includes silicon nitride as a component thereof.

19. The embedded microcantilever as in claim 1, in which said at least one analyte is included within one of a gaseous medium and a liquid medium.

20. The embedded microcantilever as in claim 1, 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.

21. The embedded microcantilever as in claim 1, in which said detecting means is capable of measuring the extent of said deflection of said arm.

22. An array of embedded microcantilevers for detecting analytes, comprising:

a plurality of discrete solid-phase sensing material deposits formed on a surface;

a corresponding plurality of deflectable arms, each having one end fixedly coupled to a substrate and an overhang portion at least partially embedded within a corresponding one of said solid-phase sensing material deposits, wherein each of the solid-phase sensing material deposits is capable of producing a volumetric change based on the contact of at least one analyte with the solid-phase sensing material, and each deflectable arm being capable of deflecting responsive to a volumetric change in said corresponding solid-phase sensing material deposit; and

detecting means capable of measuring the deflection of each deflectable arm.

23. The array of embedded microcantilevers as in claim 22, wherein each sensing material deposits is different from the other sensing material deposits.

24. The array of embedded microcantilevers as in claim 23, in which said deflectable arms each have one end fixedly coupled to a common substrate and said surface is formed on a further substrate situated adjacent said common substrate.

25. The array of embedded microcantilevers as in claim 22, wherein each sensing material deposit of said plurality of discrete sensing elements undergoes a volumetric change in response to the presence of a different analyte.

26. The array of embedded microcantilevers as in claim 22, in which each deflectable arm includes a piezoresistive element one of therein and thereon and said detecting means includes electrical circuitry for measuring a change in resistance of each piezoresistive element as a result of deflection due to volumetric change in said corresponding sensing material deposit.

27. The array of embedded microcantilevers as in claim 22, in which each said deflectable arm includes at least one measurable physical property which changes when said arm deflects and said detecting means is capable of measuring a change in said at least one measurable physical property of each deflectable arm.

28. The array of embedded microcantilevers as in claim 22, in which each said discrete sensing material deposit is designed to volumetrically change substantially differently to at least one analyte.

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

providing a deflectable microcantilever arm having a first end fixedly coupled to a substrate, said microcantilever arm disposed in a rest position;

forming a solid-phase sensing material deposit adjacent to said arm and at least partially embedding a second end of said arm into said solid-phase sensing material deposit, said solid-phase sensing material deposit capable of at least one of vertical swelling and vertical contraction responsive to the contact of said analyte with said solid-phase sensing material deposit, said vertical swelling causing said microcantilever arm upward deflection and said vertical contraction causing said microcantilever arm downward deflection;

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

measuring said deflection of said microcantilever arm.

30. The method as in claim 29, wherein said microcantilever arm includes at least one measurable physical property which changes when said microcantilever arm deflects and said measuring comprises measuring a change in said at least one measurable physical property.

31. The method as in claim 29, 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 upward deflection and said downward deflection.

32. The method as in claim 31, 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.

33. The method as in claim 31, in which said measuring includes measuring resistance of said piezoresistive member each of before and after said step of introducing.

34. An embedded microcantilever for detecting at least one analyte comprising:

a deflectable arm having a first end fixedly coupled to a substrate, and a second end at least partially embedded within a sensing material deposit, wherein the sensing material deposit is different from said at least one analyte and is capable of producing a volumetric change based on the contact of the at least one analyte with the sensing material, and said arm being capable of deflecting responsive to the volumetric change of the sensing material deposit; and

detecting means capable of measuring the deflection of said arm.

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

providing a deflectable microcantilever arm having a first end fixedly coupled to a substrate, said microcantilever arm disposed in a rest position;

forming a sensing material deposit compositionally different from said at least one analyte adjacent to said arm and at least partially embedding a second end of said arm into said sensing material deposit, said at least one analyte and said sensing material deposit being capable of at least one of vertical swelling and vertical contraction responsive to the contact of said analyte with said sensing material deposit, said vertical swelling causing said microcantilever arm upward deflection and said vertical contraction causing said microcantilever arm downward deflection;

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

measuring said deflection of said microcantilever arm.