Sensing systems utilizing acoustic wave devices

• US 7,608,978 B2
• Filed: 06/21/2007
• Issued: 10/27/2009
• Est. Priority Date: 06/21/2007
• Status: Active Grant

• Current Assignee: P.J. Edmonson Ltd.
• Original Assignee: P.J. Edmonson Ltd.
• Inventors: Edmonson, Peter J., Hunt, William D.
• Primary Examiner(s): SAN MARTIN, JAYDI A
• Application Number:
  US11/812,687
• Publication Number:
  US 20080315718A1
• Time in Patent Office: 859 Days
• Field of Search: 310/336, 310/332.21
• US Class Current: 310/313.00R
• CPC Class Codes: G01N 2291/02466 Biological material, e.g. blood
• 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 29/024 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: H10N 30/302 Sensors

Abstract

A sensing system includes an acoustic wave device comprising a body of piezoelectric material, and a first electrode assembly mounted on the piezoelectric body whereby an appropriate input applied to the electrode assembly produces an acoustic wave in the piezoelectric body and a first frequency response. The acoustic wave device also has a second electrode assembly to produce a second frequency response, the second electrode assembly being in contact with an area sensitive to a supplied stimulus to cause a characteristic of the sensitive area to change when a supplied stimulus is sensed to thereby change the second frequency response. The acoustic wave device has an output connected to the input of an amplifier, the amplifier having an output connected to the input of a coupling device. The coupling device is connected to the input of the acoustic wave device and has an output connected to a detector. The acoustic wave device, the amplifier and the coupling device are configured to be in an “off” condition when no supplied stimulus is sensed by the sensitive area of the acoustic wave device and to be in an “on” condition when a supplied stimulus is sensed by the sensitive area. The coupling device is configured to send a change signal to the detector when a change from the “off” condition to the “on” condition occurs.

Claims

1. A sensing system including a detector and an oscillating circuit comprising a coupling device, an amplifier, and a plurality of resonators, wherein:

each resonator comprises;

(i) a body of piezoelectric material;

(ii) an input electrode assembly mounted on the body of piezoelectric material whereby the input electrode assembly when activated produces an acoustic wave across the body of piezoelectric material; and

(iii) an output electrode assembly mounted on the body of piezoelectric material and being in contact with a sensitive area that is sensitive to a supplied stimulus so that the acoustic velocity of the acoustic wave across the sensitive area is modified when a supplied stimulus binds to the sensitive area in sufficient quantity, whereby the output electrode assembly receives the acoustic wave after the acoustic wave has passed across the sensitive area; and

wherein for each resonator, when the input electrode assembly is activated, the input electrode assembly and the output electrode assembly cooperate to produce a frequency response representative of one of presence or absence of a sufficient quantity of the stimulus;

wherein the resonators are coupled in series from 1 to n;

and wherein;

the n^th resonator has an output connected to an amplifier input of the amplifier;

the amplifier has an amplifier output connected to a coupling device input of the coupling device;

the coupling device has a first coupling device output connected to an input of the first resonator;

the coupling device has a second coupling device output connected to the detector; and

the amplifier has a gain that is insufficient to cause the oscillator circuit to meet Barkhausen criteria when at least one of the n resonators produces a frequency response representative of absence of a sufficient quantity of its respective stimulus and that is sufficient to cause the oscillator circuit to meet Barkhausen criteria when all of the n resonators produce a frequency response representative of presence of a sufficient quantity of their respective stimulus, so that the detector emits a detection signal only when all of the n resonators produce a frequency response representative of presence of a sufficient quantity of their respective stimulus.

2. The sensing system of claim 1, wherein the n resonators are electrically connected in series.

3. The sensing system of claim 2, wherein each wave produced by each respective first electrode assembly is a surface acoustic wave.

4. The sensing system of claim 1, wherein the n resonators are acoustically coupled in series.

5. The sensing system of claim 4, wherein each wave produced by each respective first electrode assembly is a surface acoustic wave.

6. The sensing system of claim 1, wherein each sensitive area is sensitive to a different stimulus.

7. The sensing system of claim 6, wherein each wave produced by each respective first electrode assembly is a surface acoustic wave.

8. The sensing system of claim 1, wherein at least one sensitive area comprises molecular recognition elements.

9. The sensing system of claim 8, wherein each wave produced by each respective first electrode assembly is a surface acoustic wave.

10. The sensing system of claim 1, wherein at least one sensitive area comprises antibodies.

11. The sensing system of claim 10, wherein each wave produced by each respective first electrode assembly is a surface acoustic wave.

12. The sensing system of claim 1, wherein the resonators comprise respective first and second electrode assemblies mounted on a common body of piezoelectric material.

13. The sensing system of claim 12, wherein each wave produced by each respective first electrode assembly is a surface acoustic wave.

14. The sensing system of claim 1, wherein each resonator comprises first and second electrode assemblies mounted on a separate body of piezoelectric material.

15. The sensing system of claim 14, wherein each wave produced by each respective first electrode assembly is a surface acoustic wave.

16. The sensing system of claim 1, further comprising a reference resonator whose sensitive area is inactivated connected as a first resonator in the series.

17. The sensing system of claim 16, wherein each wave produced by each respective first electrode assembly is a surface acoustic wave.

18. The sensing system of claim 1, wherein each wave produced by each respective first electrode assembly is a surface acoustic wave.