Method and apparatus for characterizing materials by using a mechanical resonator

• US 20020178787A1
• Filed: 07/23/2002
• Published: 12/05/2002
• Est. Priority Date: 10/08/1997
• Status: Active Grant

• Current Assignee: Meas France
• Original Assignee: Symyx Technologies Incorporated (Dassault Systemes SA)
• Inventors: Bennett, James, Matsiev, Leonid, McFarland, Eric
• Granted Patent: US 7,334,452 B2
• Time in Patent Office: Days
• US Class Current: 73/24.01
• CPC Class Codes: B01J 2219/00704 integrated with the reactor apparatus
• CPC Class Codes: G01H 13/00 Measuring resonant frequency
• CPC Class Codes: G01N 11/16 by measuring damping effect upon oscillatory body
• CPC Class Codes: G01N 2009/006 vibrating tube, tuning fork
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/0224 Mixtures of three or more liquids
• CPC Class Codes: G01N 2291/0255 (Bio)chemical reactions, e.g. on biosensors
• CPC Class Codes: G01N 2291/0256 Adsorption, desorption, surface mass change, e.g. on biosensors
• CPC Class Codes: G01N 2291/02818 Density, viscosity
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• 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 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/42 by frequency filtering or by tuning to resonant frequency
• CPC Class Codes: G01N 29/4418 with a model, e.g. best-fit, regression analysis
• CPC Class Codes: G01N 29/4427 with stored values, e.g. threshold values
• CPC Class Codes: G01N 29/4436 with a reference signal amplitude comparison G01N29/48
• CPC Class Codes: G01N 9/002 : using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis G01N9/34 takes precedence
• CPC Class Codes: G01N 9/34 : by using elements moving through the fluid, e.g. vane
• CPC Class Codes: G10K 11/02 : Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators

Abstract

A method and apparatus for measuring properties of a liquid composition includes a mechanical resonator, such as a thickness shear mode resonator or a tuning fork resonator, connected to a measurement circuit. The measurement circuit provides a variable frequency input signal to the tuning fork, causing the mechanical resonator to oscillate. To test the properties of a liquid composition, the mechanical resonator is placed inside a sample well containing a small amount of the liquid. The input signal is then sent to the mechanical resonator and swept over a selected frequency range, preferably less than 1 MHz to prevent the liquid being tested from exhibiting gel-like characteristics and causing false readings. The mechanical resonator'"'"'s response over the frequency range depends on various characteristics of the liquid being tested, such as the temperature, viscosity, and other physical properties. Particular mechanical resonators, such as tuning fork resonators, can also be used to measure a liquid composition'"'"'s electrical properties, such as the dielectric constant and conductivity, because the tuning fork'"'"'s structure allows a high degree of electrical coupling between the tuning fork and the surrounding liquid. The mechanical resonator can be covered with a coating to impart additional special detection properties to the resonator, and multiple resonators can be attached together as a single sensor to obtain multiple frequency responses. The invention is particularly suitable for combinatorial chemistry applications, which require rapid analysis of chemical properties for screening.

Claims

1. A method for measuring a property of a fluid composition using a tuning fork resonator, the method comprising:

placing the tuning fork resonator in the fluid composition such that at least a portion of the tuning fork resonator is surrounded by the fluid composition;

applying a variable frequency input signal to a measurement circuit coupled with the tuning fork resonator to oscillate the tuning fork resonator;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the tuning fork resonator; and

determining the property of the fluid composition based on the resonator response.

2. The method of claim 1, wherein the fluid composition is a liquid composition, wherein a plurality of liquid compositions are measured by a plurality of tuning fork resonators, and wherein said method further comprises:

providing an array of sample wells;

placing each of said plurality of liquid compositions in a separate sample well;

placing at least one of said plurality of tuning fork resonators in at least one sample well;

applying a variable frequency input signal to a measurement circuit coupled with each tuning fork resonator in said at least one sample wells to oscillate each tuning fork resonator associated with each of said at least one sample well;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of each tuning fork resonator associated with said at least one sample well; and

analyzing the resonator response of each tuning fork resonator associated with said at least one sample well to measure a property of each liquid composition in said at least one sample well.

3. The method of claim 2, wherein said method measures a physical property of each liquid composition in the array of sample wells.

4. The method of claim 2, wherein the physical property measured by said method is selected from the group consisting of specific weight, temperature and viscosity.

5. The method of claim 2, wherein said method measures an electrical property of each liquid composition in the array of sample wells.

6. The method of claim 5, wherein the electrical property measured by said method is selected from the group consisting of dielectric constant and conductivity.

7. The method of claim 2, wherein said method measures an electrical property and a physical property of each liquid composition in the array of sample wells simultaneously.

8. The method of claim 7, wherein the electrical properties and physical properties measured by said method are selected from the group consisting of specific weight, viscosity, temperature, dielectric constant and conductivity.

9. The method of claim 8, wherein said method simultaneously measures at least two properties selected from the group consisting of specific weight, viscosity, temperature, dielectric constant and conductivity of each liquid composition in the array of sample wells.

10. The method of claim 1, further comprising the step of coating the tuning fork resonator with a material that modifies the characteristics of the tuning fork resonator.

11. The method of claim 10, wherein the material used in said coating step is a functionality designed to change the resonator response of the tuning fork resonator if a selected substance is present in the fluid composition.

12. The method of claim 11, wherein said functionality used in the coating step contains receptor molecules for attracting molecules of the selected substance in the fluid composition to change the resonator response.

13. The method of claim 1, wherein the placing step includes placing a plurality of tuning fork resonators in the fluid composition.

14. The method of claim 13, wherein the varying step varies the frequency of the variable frequency input signal over a plurality of predetermined frequency ranges to obtain a plurality of frequency dependent resonator responses from the plurality of tuning fork resonators.

15. The method of claim 2, further comprising the step of coating at least one of said plurality of tuning fork resonators with a material that modifies the characteristics of said at least one tuning fork resonators.

16. The method of claim 15, wherein the material used in said coating step is a functionality designed to change the resonator response of said at least one tuning fork resonator of a selected substance is present in the liquid composition associated with said at least one tuning fork resonator.

17. The method of claim 16, wherein said functionality used in the coating step contains receptor molecules for attracting molecules of the selected substance in the liquid composition associated with said at least one tuning fork resonator.

19. The method of claim 18, the change monitored in the monitoring step is a physical change in the liquid composition.

20. The method of claim 19, wherein the physical change in the liquid composition is a liquid-to-solid state transformation of the liquid composition.

21. The method of claim 18, wherein the change monitored in the monitoring step is a chemical transformation of the liquid composition.

22. The method of claim 21, wherein the chemical transformation monitored in the monitoring step is a polymerization reaction.

23. The method of claim 18, wherein said method measures a property selected from the group consisting of specific weight, viscosity, temperature, dielectric constant and conductivity of the liquid composition and monitors said property over time.

24. The method of claim 23, wherein said method simultaneously measures at least two properties selected from the group consisting of specific weight, viscosity, temperature, dielectric constant and conductivity of the liquid composition and monitors said properties over time.

25. The method of claim 18, further comprising the step of coating the mechanical resonator with a material that modifies the characteristics of the mechanical resonators.

26. The method of claim 25, wherein the material used in said coating step is a functionality designed to change the resonator response of the mechanical resonator if a selected substance is present in the liquid composition.

27. The method of claim 26, wherein said functionality used in the coating step contains receptor molecules for attracting molecules of the selected substance in the liquid composition to change the resonator response.

28. The method of claim 18, wherein the placing step includes placing a plurality of mechanical resonators in the liquid composition.

29. The method of claim 28, wherein each of said plurality of mechanical resonators has a different resonator response characteristic, and wherein the varying step varies the frequency of the variable input signal over a plurality of frequency dependent resonator responses from the plurality of mechanical resonators.

30. The method of claim 18, wherein the mechanical resonator placed in the placing step is a multiple-mode resonator that can be operated in more than one mechanical mode, and wherein the varying step comprises varying the frequency of the variable frequency input signal to obtain a plurality of frequency-dependent resonator responses corresponding to said more than one mechanical mode.

18. A method for monitoring a change in a property of a liquid composition, the method comprising:

placing the mechanical resonator in the liquid composition such that at least a portion of the mechanical resonator is submerged in the liquid composition;

applying a variable frequency input signal to a measurement circuit coupled with the mechanical resonator to oscillate the mechanical resonator;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the mechanical resonator;

determining the property of the liquid based on the mechanical resonator response;

repeating the applying, varying, and determining steps over time; and

monitoring over time a change in the mechanical resonator response reflecting the change in property of the liquid composition.

31. An apparatus for measuring a property of a fluid composition, comprising:

a tuning fork resonator;

means for containing the fluid composition;

a measurement circuit coupled with said tuning fork resonator, said measurement circuit having a signal generator for generating a variable frequency input signal to cause said tuning fork to oscillate; and

a receiver coupled to the measurement circuit to output a frequency response of said tuning fork resonator.

32. The apparatus of claim 31, wherein the fluid composition is a liquid composition, the apparatus further comprising:

an array of tuning fork resonators; and

an array of sample wells for holding a plurality of liquid compositions, and wherein said measurement circuit and said receiver are coupled with said array of tuning fork resonators to obtain a frequency response associated with each of said plurality of liquid compositions.

33. The apparatus of claim 31, wherein the tuning fork comprises at least two tines, each tine including a quartz crystal center portion having at least two faces and an electrode on at least one of the two faces of said quartz crystal center portion.

34. The apparatus of claim 31, wherein said quartz crystal center portion of each tine has four faces and wherein four electrodes are connected to said quartz crystal center portion such that one electrode is coupled to each face.

35. The apparatus of claim 31, further comprising a coating material on said tuning fork resonator that modifies the characteristics of the tuning fork resonator.

36. The apparatus of claim 35, wherein said coating material is a functionality designed to change the resonator response of the tuning fork resonator if a selected substance is present in the fluid composition.

37. The apparatus of claim 36, wherein said functionality contains receptor molecules for attracting molecules of the selected substance in the fluid composition to change the resonator response.

38. The apparatus of claim 31, further comprising a plurality of tuning fork resonators, each tuning fork resonator having a different resonator response characteristic.

39. The apparatus of claim 38, wherein each tuning fork has a different functionality, each functionality designed to change the resonator response of its associated tuning fork resonator if a selected substance corresponding with the specific coating is present in the fluid composition.

40. A method for measuring a property of a plurality of liquid compositions using a plurality of mechanical resonators, the method comprising:

providing an array of sample wells;

placing each of said plurality of liquid compositions in a separate sample well;

placing at least one of said plurality of mechanical resonators into at least one of said sample wells such that at least a portion of the mechanical resonator is submerged in its associated liquid composition;

applying a variable frequency input signal to a measurement circuit coupled with at least one of said plurality of mechanical resonators to oscillate said at least one mechanical resonator in its associated liquid composition;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the at least one mechanical resonator; and

determining the property of the liquid based on the mechanical resonator response to measure a property of each liquid composition.

41. The method of claim 40, further comprising the step of distinguishing between at least two of said plurality of liquid compositions based on the mechanical resonator response.

42. The method of claim 40, wherein the mechanical resonator placed in the placing step is a thickness shear mode resonator.

43. The method of claim 40, wherein the mechanical resonator placed in the placing step is a tuning fork resonator.

44. The method of claim 40, further comprising placing a plurality of mechanical resonators in the placing step.

45. The method of claim 44, wherein the plurality of mechanical resonators placed in the placing step are selected from the group consisting of tridents, cantilevers, torsion bars, length extension resonators, bimorphs, unimorphs, membrane resonators, surface acoustic wave devices, thickness share mode resonators, and tuning fork resonators.

46. The method of claim 45, wherein each of the plurality of mechanical resonators placed in the placing step is a different type of mechanical resonator from the other mechanical resonators in the plurality of mechanical resonators.

47. The method of claim 40, wherein the mechanical resonator placed in the placing step is a multiple-mode resonator that can be operated in more than one mechanical mode, and wherein the varying step comprises varying the frequency of the variable frequency input signal to obtain a plurality of frequency-dependent resonator responses corresponding to said more than one mechanical mode.

48. The method of claim 40, wherein the mechanical resonator placed in the placing step is one selected from the group consisting of tridents, cantilevers, torsion bars, bimorphs, unimorphs, membrane resonators, and surface acoustic wave devices.

49. The method of claim 40, wherein said method measures a physical property of each liquid composition in the array of sample wells.

50. The method of claim 49, wherein the physical property measured by said method is selected from the group consisting of specific weight, temperature and viscosity.

51. The method of claim 40, wherein said method measures an electrical property of each liquid composition in the array of sample wells.

52. The method of claim 51, wherein the electrical property measured by said method is selected from the group consisting of dielectric constant and conductivity.

53. The method of claim 40, wherein said method measures an electrical property and a physical property of each liquid composition in the array of sample wells simultaneously.

54. The method of claim 53, wherein the electrical properties and physical properties measured by said method are selected from the group consisting of specific weight, viscosity, dielectric constant and conductivity.

55. The method of claim 54, wherein said method simultaneously measures at least two properties selected from the group consisting of specific weight, viscosity, temperature, dielectric constant and conductivity of each liquid composition in the array of sample wells.

56. The method of claim 40, further comprising the steps of:

calibrating each of said tuning fork resonators against a standard liquid having known properties to obtain calibration data; and

determining the property of each liquid composition based on the calibration data.

57. The method of claim 40, further comprising the step of coating at least one of said mechanical resonators with a material that modifies the characteristics of the mechanical resonator.

58. The method of claim 57, wherein the material used in the coating step is a functionality designed to change the resonator response of the mechanical resonator if a selected substance is present in the liquid composition.

59. The method of claim 58, wherein the functionality used in the coating step contains receptor molecules for attracting molecules of the selected substance in the liquid composition to change the resonator response.

60. A method for measuring a property of a liquid composition flowing through a conduit, the method comprising:

placing a mechanical resonator in the conduit such that at least a portion of the mechanical resonator will be surrounded by the fluid composition as the fluid composition flows through the conduit;

applying a variable frequency input signal to a measurement circuit coupled with the mechanical resonator to oscillate the tuning fork resonator;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the mechanical resonator; and

determining the property of the fluid composition based on the mechanical resonator'"'"'s response.

61. The method of claim 60, further comprising the steps of:

calibrating the mechanical resonator against a standard fluid having known properties to obtain calibration data; and

determining the property of the fluid composition based on the calibration data.

62. The method of claim 60, wherein the mechanical resonator placed in the placing step is a thickness shear mode resonator.

63. The method of claim 60, wherein the mechanical resonator placed in the placing step is a tuning fork resonator.

64. The method of claim 60, further comprising placing a plurality of mechanical resonators in the placing step.

65. The method of claim 64, wherein the plurality of mechanical resonators placed in the placing step are selected from the group consisting of tridents, cantilevers, torsion bars, length extension resonators, bimorphs, unimorphs, membrane resonators, surface acoustic wave devices, thickness share mode resonators, and tuning fork resonators.

66. The method of claim 65, wherein each of the plurality of mechanical resonators placed in the placing step is a different type of mechanical resonator from the other mechanical resonator in the plurality of mechanical resonators.

67. The method of claim 60, wherein the mechanical resonator placed in the placing step is a multiple-mode resonator that can be operated in more than one mechanical mode, and wherein the varying step comprises varying the frequency of the variable frequency input signal to obtain a plurality of frequency-dependent resonator responses corresponding to said more than one mechanical mode.

68. The method of claim 60, wherein the mechanical resonator placed in the placing step is one selected from the group consisting of tridents, cantilevers, torsion bars, length extension resonators, bimorphs, unimorphs, membrane resonators, and surface acoustic wave devices.

69. The method of claim 60, wherein said method measures a physical property of the fluid composition flowing through the conduit.

70. The method of claim 69, wherein the physical property measured by said method is selected from the group consisting of specific weight, temperature and viscosity.

71. The method of claim 60, wherein said method measures an electrical property of the fluid composition flowing through the conduit.

72. The method of claim 71, wherein the electrical property measured by said method is selected from the group consisting of dielectric constant and conductivity.

73. The method of claim 60, wherein said method measures simultaneously an electrical property and a physical property of the fluid composition flowing through the conduit.

74. The method of claim 73, wherein the electrical properties and physical properties measured by said method are selected from the group consisting of specific weight, viscosity, temperature, dielectric constant and conductivity.

75. The method of claim 74, wherein said method simultaneously measures at least two properties selected from the group consisting of specific weight, viscosity, temperature, dielectric constant and conductivity of the fluid composition flowing through the conduct.

76. The method of claim 60, further comprising the step of coating the mechanical resonator with a material to modify the characteristics of the mechanical resonators.

77. The method of claim 76, wherein the material used in said coating step is a functionality designed to change the resonator response of the mechanical resonator if a selected substance is present in the fluid composition to change the resonator response.

78. The method of claim 77, wherein said functionality used in the coating step contains receptor molecules for attracting molecules of the selected substance in the liquid composition.