Dual output acoustic wave sensor for molecular identification

• US 5,076,094 A
• Filed: 10/03/1990
• Issued: 12/31/1991
• Est. Priority Date: 10/03/1990
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.), United States Department of Energy (Government of the United States of America), Sandia Corporation (Martin Marietta Corporation)
• Original Assignee: United States Department of Energy (Government of the United States of America)
• Inventors: Martin, Stephen J., Frye, Gregory C.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US07/592,383
• Time in Patent Office: 454 Days
• Field of Search: 73/19.03, 73/24.01, 73/24.03, 73/24.06, 73/24.04, 73/61 R, 73/61.1 R, 73/590, 73/597, 73/599, 73/602, 73/643, 310/313 R, 310/313 D, 310/313 B
• US Class Current: 73/19.03
• 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 2291/0423 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

Abstract

A method of identification and quantification of absorbed chemical species by measuring changes in both the velocity and the attenuation of an acoustic wave traveling through a thin film into which the chemical species is sorbed. The dual output response provides two independent sensor responses from a single sensing device thereby providing twice as much information as a single output sensor. This dual output technique and analysis allows a single sensor to provide both the concentration and the identity of a chemical species or permits the number of sensors required for mixtures to be reduced by a factor of two.

Claims

1. A method for the identification and quantification of sorbed chemical species onto a coating of a device capable of generating and receiving an acoustic wave, comprising:

(a) measuring the changes in the velocity of the acoustic wave resulting from the sorption of the chemical species into the coating as the wave travels through the coating;

(b) measuring the changes in the attenuation of an acoustic wave resulting from the sorption of the chemical species into the coating as the wave travels through the coating;

(c) correlating the magnitudes of the changes of velocity with respect to changes of the attenuation of the acoustic wave to identify the sorbed chemical species.

2. The method of claim 1, further comprising:

(d) correlating the absolute magnitude of the velocity changes to the concentration of the identified chemical species.

3. The method of claim 1, further comprising:

(d) correlating the absolute magnitude of the attenuation changes to the concentration of the identified chemical species.

4. The method of claim 2 or 3, wherein the chemical species is in a gas phase.

5. The method of claim 2 or 3, wherein the chemical species is in a liquid phase.

6. The method of claim 2 or 3, wherein the chemical species is derived from a solid phase.

7. An apparatus for detecting and identifying at least one unknown chemical species, comprising:

(a) an acoustic wave device capable of generating, transmitting and receiving an acoustic wave, said device coated with a material, said material having properties which change upon sorption of a chemical species;

(b) means for measuring the velocity of an acoustic wave travelling through said material;

(c) means for simultaneously measuring the attenuation of the acoustic wave traveling through said coating material;

(d) sampling means to contact said acoustic wave device to said unknown chemical species for sorption of said unknown chemical species into said coating material;

(e) means for determining the changes in both the attenuation and velocity values of said acoustic wave upon sorption of said unknown chemical species into said coating material; and

(f) means for correlating the magnitudes of the changes of velocity with respect to the changes of the attenuations of the acoustic wave; and

(g) means for comparing the values of the velocity and attenuation changes to known values of velocity and attenuation of known chemical species in order to identify said unknown sorbed chemical species.

8. The apparatus of claim 7, further comprising:

(g) means for comparing the magnitude of the changes in the velocity response to known values of known chemical species in order to determine the concentration of said unknown sorbed chemical species.

9. The apparatus of claim 7, further comprising:

(g) means for comparing the magnitude of the changes in the attenuation response to known values of known chemical species in order to determine the concentration of said unknown sorbed chemical species.

10. The apparatus of claims 8 or 9, wherein said acoustic wave device comprises a piezoelectric substrate having two interdigitated transducers at opposing ends of said substrate, one of said transducers to generate an acoustic wave, and the other of said transducers to receive an acoustic wave as said wave is transmitted through said piezoelectric substrate and generate a signal having a frequency of said acoustic wave in response thereto.

11. The apparatus of claims 8 or 9, wherein said acoustic wave device comprises a substrate having two interdigitated transducers at opposing ends of said substrate and a piezoelectric coating material on one face of each transducer, one of said transducers to generate an acoustic wave, and the other of said transducers to receive an acoustic wave as said wave is transmitted through said substrate and generate a signal having a frequency of said acoustic wave in response thereto.

12. The apparatus of claim 11, wherein said piezoelectric coating material is aluminum nitride.

13. The apparatus of claim 10 wherein said interdigitated transducers are lithographically patterned from a metallized aluminum layer cast onto the substrate.

14. The apparatus of claim 11 wherein said interdigitated transducers are lithographically patterned from a metallized layer cast onto the substrate.

15. The apparatus of claim 14 wherein said metallized layer is aluminum.

16. The apparatus of claim 14 wherein said metallized layer is gold-on-chrome composite.

17. The apparatus of claims 8 or 9, wherein said acoustic wave is a surface acoustic wave.

18. The apparatus of claims 8 or 9, wherein said acoustic wave is an acoustic plate mode.

19. The apparatus of claims 8 or 9, wherein said acoustic wave is a Lamb wave.

20. The apparatus of claims 8 or 9, wherein said acoustic wave is a Love wave.

21. The apparatus of claim 7 wherein one of said properties of said material which change upon sorption of a chemical species is mass of said material.

22. The apparatus of claim 7 wherein one of said properties of said material which change upon sorption of a chemical species is the viscoelasticity of said material.

23. The apparatus of claim 10, wherein said means for measuring the velocity of an acoustic wave traveling through said material further comprises an oscillator loop comprising:

(a) a first coupler electrically connected to said acoustic wave device to direct a fraction of said signal'"'"'s power into a first and second path;

(b) a RF amplifier electrically connected along said first path to said first coupler to amplify said signal;

(c) a directional coupler electrically connected to said first path to direct a portion of said signal along said first path and along a third path;

(d) a frequency counter electrically connected along said third path to said directional coupler, said frequency counter to measure a frequency shift (Δ

f) of said signal which is related to the velocity shift (Δ

v) of said wave as it travels through said material by Δ

f/f_o =KΔ

v/v_o where K is the fraction of the acoustic wave path covered by said material sorbing said unknown chemical species and v_o and f_o are the unperturbed velocity and frequency, respectively;

(e) a second coupler electrically connected along said first path to said directional coupler to direct a portion of said signal along said first path into said acoustic wave device and along a fourth path;

(f) means for measuring power of said wave electrically connected between said first and second couplers along said second and fourth paths respectively.

24. The apparatus of claim 23, wherein said means for measuring power is a vector voltmeter.

25. The apparatus of claim 23, further comprising:

(g) two impedance matching networks, one of said networks electrically connected to said input transducer and the other of said networks electrically connected to said output transducer;

(h) a variable attenuator electrically connected along said first path between said directional coupler and said second coupler, to reduce the power of the signal;

(i) a phase shifter electrically connected along said first path between said RF amplifier and said directional coupler; and

(j) a bandpass filter electrically connected along said first path between said phase shifter and said RF amplifier, to filter the signal.

26. The apparatus of claim 10, further comprising:

(a) means for generating an input signal into said input transducer to launch an acoustic wave external, but electrically connected along a first path, to said acoustic wave device;

(b) a first coupler electrically connected to said signal generating means along said first path between said generating means and said input transducer, said first coupler to direct a portion of said signal along a second path means for measuring the phase of said signal;

(c) a second coupler electrically connected to said output transducer to receive an output signal, said second coupler to direct a portion of said output signal along a third path;

(d) means for measuring the phase shift and the attenation shift of said signal electrically interconnected between said first and second couplers along said second and third paths, respectively.

27. The apparatus of claim 10, further comprising:

(a) means for generating an input signal into said input transducer to launch an acoustic wave external, but electrically connected along a first path, to said acoustic wave device, and the frequency of said input signal from said signal generating means is maintained at a constant phase value;

(b) a first coupler electrically connected to said signal generating means along said first path between said generating means and said input transducer, said first coupler to direct a portion of said signal along a second path means for measuring the power of said signal;

(c) a second coupler electrically connected to said output transducer to receive an output signal, said second coupler to direct a portion of said output signal along a third path;

(d) means for monitoring the frequency shift of said output signal, where the velocity shift (Δ

v) of said acoustic wave is determined from the frequency shift (Δ

f) using Δ

f/f_o =KΔ

v/v_o where K is a fraction of said acoustic wave path covered by said coating material sorbing said unknown chemical species and v_o and f_o are the unperturbed velocity and frequency of said wave and signal, respectively.

28. The apparatus of claim 23, wherein said means for measuring the attenuation of said acoustic wave traveling through said material is measured using said first and second couplers to divide a portion of said signal at the input and output transducers, respectively, and to measure power level of said signal by means for measuring power.

29. The apparatus of claim 28, wherein said means for measuring power is a vector voltmeter.

30. The apparatus of claim 28, wherein said means for measuring power is a power meter.

31. The apparatus of claim 26, wherein said means for measuring the attenuation of said acoustic wave traveling through said material is measured using said first and second couplers to divide a portion of said signal at the input and output transducers, respectively, and to measure power level of said signal by means for measuring power.

32. The apparatus of claim 31, wherein said means for measuring power is a vector voltmeter.

33. The apparatus of claim 27, wherein said means for measuring the attenuation of said acoustic wave traveling through said material is measured using said first and second couplers to divide a portion of said signal at the input and output transducers, respectively, and to measure power level of said signal by means for measuring power.

34. The apparatus of claim 33, wherein said means for measuring power is a vector voltmeter.

35. The apparatus of claim 11, wherein said means for measuring the velocity of an acoustic wave traveling through said material further comprises an oscillator loop comprising:

(a) a first coupler electrically connected to said acoustic wave device to direct a fraction of said signal'"'"'s power into a first and second path;

(b) a RF amplifier electrically connected along said first path to said first coupler to amplify said signal;

(c) a directional coupler electrically connected to said first path to direct a portion of said signal along said first path and along a third path;

(d) a frequency counter electrically connected along said third path to said directional coupler, said frequency counter to measure a frequency shift (Δ

f) of said signal which is related to the velocity shift (Δ

v) of said wave as it travels through said material by Δ

f/f_o =KΔ

v/v_o where K is the fraction of the acoustic wave path covered by said material sorbing said unknown chemical species and v_o and f_o are the unperturbed velocity and frequency, respectively;

(e) a second coupler electrically connected along said first path to said directional coupler to direct a portion of said signal along said first path into said acoustic wave device and along a fourth path;

(f) means for measuring power of said wave electrically connected between said first and second couplers along said second and fourth paths respectively.

36. The apparatus of claim 35, wherein said means for measuring power is a vector voltmeter.

37. The apparatus of claim 35, further comprising:

(g) two impedance matching networks, one of said networks electrically connected to said input transducer and the other of said networks electrically connected to said output transducer;

(h) a variable attenuator electrically connected along said first path between said directional coupler and said second coupler, to reduce the power of the signal;

(i) a phase shifter electrically connected along said first path between said RF amplifier and said directional coupler; and

(j) a bandpass filter electrically connected along said first path between said phase shifter and said RF amplifier, to filter the signal.

38. The apparatus of claim 11, further comprising:

(a) means for generating an input signal into said input transducer to launch an acoustic wave external, but electrically connected along a first path, to said acoustic wave device;

(b) a first coupler electrically connected to said signal generating means along said first path between said generating means and said acoustic wave device, said first coupler to direct a portion of said signal along a second path means for measuring the phase shift of said signal;

(c) a second coupler electrically connected to said acoustic wave device along said first path to receive an output signal from said acoustic wave device, said second coupler to direct a portion of said output signal along a third path for measuring the phase shift and the velocity shift of said output signal; and

(d) means for measuring phase and monitoring the frequency shift of said signal electrically interconnected between said first and second couplers along said second and third paths, respectively.

39. The apparatus of claim 11, further comprising:

(a) means for generating an input signal into said input transducer to launch an acoustic wave external, but electrically connected along a first path, to said acoustic wave device, and the frequency of said input signal from said signal generating means is maintained at a constant phase value;

(b) a first coupler electrically connected to said signal generating means along said first path between said generating means and said input transducer, said first coupler to direct a portion of said signal along a second path means for measuring the power of said signal;

(c) a second coupler electrically connected to said output transducer to receive an output signal, said second coupler to direct a portion of said output signal along a third path;

(d) means for monitoring frequency shift where the velocity shift (Δ

v) of said acoustic wave is determined from the frequency shift (Δ

f) using Δ

f/f_o =KΔ

v/v_o where K is a fraction of said acoustic wave path covered by said coating material sorbing said unknown chemical species and v_o and f_o are the unperturbed velocity and frequency of said wave and signal, respectively.

40. The apparatus of claim 35, wherein said means for measuring the attenuation of said acoustic wave traveling through said material is measured using said first and second couplers to divide a portion of said signal at the input and output transducers, respectively, and to measure power level of said signal by means for measuring power.

41. The apparatus of claim 40, wherein said means for measuring power is a vector voltmeter.

42. The apparatus of claim 38, wherein said means for measuring the attenuation of said acoustic wave traveling through said material is measured using said first and second couplers to divide a portion of said signal at the input and output transducers, respectively, and to measure power level of said signal by a vector voltmeter.

43. The apparatus of claim 39, wherein said means for measuring the attenuation of said acoustic wave traveling through said material is measured using said first and second couplers to divide a portion of said signal at the input and output transducers, respectively, and to measure power level of said signal by a vector voltmeter.

44. The apparatus of claim 7, wherein said sampling means further comprises a semipermeable membrane surrounding said acoustic wave device which permits said unknown chemical species in a liquid solution to be transported across said membrane into a gas phase to be contacted with said acoustic wave device.

45. An array comprising a plurality of the apparatus of claim 7, each apparatus electrically interconnected for the purpose of detecting multiple chemical species.

46. The array of claim 45, further comprising a pattern recognition means interconnected to said array, said pattern recognitions means to identify and quantify said multiple chemical species based on a plurality of correlated velocity and attenuation changes, each of said correlated velocity and attenuation changes associated with one of said sensors, said plurality of correlated changes analyzed by said pattern recognition menus.

47. An apparatus for detecting and identifying at least one unknown chemical species, comprising:

(a) at least one acoustic wave device, wherein said acoustic wave device comprises a piezoelectric substrate having two interdigitated transducers at opposing ends of said substrate, one of said transducers to generate an acoustic wave, and the other of said transducers to receive an acoustic wave as said wave is transmitted through said piezoelectric substrate and to generate a signal having a frequency of said acoustic wave in response thereto, said substrate coated with a material, said material having properties which change upon sorption of a chemical species;

(b) an oscillator loop to measure the velocity of an acoustic wave traveling through said material, said loop further comprising a first coupler electrically connected to said acoustic wave device to direct a fraction of said signal'"'"'s power into a first and second path, a RF amplifier electrically connected along said first path to said first coupler to amplify said signal, a directional coupler electrically connected to said first path to direct a portion of said signal along said first path and along a third path, a frequency counter electrically connected along said third path to said directional coupler, said frequency counter to measure a frequency shift (Δ

f) of said signal which is related to the velocity shift (Δ

v) of said wave as it travels through said material by Δ

f/f_o =KΔ

v/v_o where K is the fraction of the acoustic wave path covered by said material sorbing said unknown chemical species and v_o and f_o are the unperturbed velocity and frequency, respectively, a second coupler electrically connected along said first path to said directional coupler to direct a portion of said signal along said first path into said acoustic wave device and along a fourth path, and a bandpass filter electrically connected along said first path between said directional coupler and said RF amplifier, to filter the signal

(c) a vector voltmeter electrically connected between said first and second couplers along said second and fourth paths to divide said signal at said output transducer and to divide said signal at said input transducer, respectively, for measuring the power level of said signal which power level is proportional to the attenuation of power of said wave traveling through said material;

(d) sampling means to contact said acoustic wave device to said unknown chemical species for sorption of said unknown chemical species into said coating material;

(e) microprocessing means for acquiring data indicating changes in and storing the values of said changes of both the attenuation and velocity values of said acoustic wave upon sorption of said unknown chemical species;

(f) a microprocessing analysis means for comparing the values of the velocity and attenuation changes to known values of known chemical species in order to identify said unknown sorbed chemical species; and

(g) microprocessing comparing means for comparing the absolute value of the changes in the velocity response to known values of known chemical species in order to determine the concentration of said unknown sorbed chemical species.

48. A method for the identification and quantification of sorbed chemical species into a coating of a device capable of generating, transmitting and receiving an acoustic wave, comprising:

(a) measuring the changes in the velocity of the acoustic wave resulting from the sorption of the chemical species into the coating as the wave travels through the coating;

(b) measuring the changes in the attenuation of an acoustic wave resulting from the sorption of the chemical species into the coating as the wave travels through the coating;

(c) correlating the magnitudes of the changes of velocity with respect to changes of the attenuation of the acoustic wave to identify the sorbed chemical species.

(d) correlating the absolute magnitude of the velocity changes to the concentration of the identified chemical species.