HIGH SENSITIVITY ACOUSTIC WAVE MICROSENSORS BASED ON STRESS EFFECTS

• US 20080163694A1
• Filed: 10/19/2007
• Published: 07/10/2008
• Est. Priority Date: 11/01/2006
• Status: Active Grant

• Current Assignee: Knowles Capital Formation, Inc. (Knowles Corporation)
• Original Assignee: Delaware Capital Formation Incorporated (Dover Corporation)
• Inventors: Andle, Jeffrey C., Haskell, Reichl B., Stevens, Daniel S.
• Granted Patent: US 7,886,575 B2
• Time in Patent Office: Days
• US Class Current: 73/652
• CPC Class Codes: G01N 2291/02491 Materials with nonlinear acoustic properties
• CPC Class Codes: G01N 2291/02827 Elastic parameters, strength or force
• 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 29/2412 using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18

Abstract

Acoustic sensing utilizing a bridge structure coupled about a portion of at least two sides of said bridge to a base substrate, wherein said bridge includes a piezoelectric section and has at least one active acoustic region proximate said bridge. A sensing material is disposed on at least a portion of at least one surface of the bridge, wherein the bridge produces stress effects measurable by an acoustic wave device located in the active acoustic region. According to one embodiment, the stress effects are measured by an acoustic wave device to sense a target matter. As target molecules accumulate on a sensing film affixed to at least a portion of the bridge, stress is produced in the bridge inducing a frequency change measured by an acoustic wave device.

Claims

1. A system for acoustic sensing, comprising:

a bridge structure coupled to a substrate about at least two sides of said bridge, wherein said bridge includes a piezoelectric section and has at least one acoustic wave device (AWD) proximate a portion of said bridge, said AWD includes an active acoustic region; and

wherein a perturbation of said bridge produces stress effects measurable by said AWD.

2. The system according to claim 1, further comprising a sensing material disposed on at least a portion of at least one surface of said bridge.

3. The system according to claim 2, wherein said sensing material is selected from at least one of the group consisting of:

metal, metal oxide, metal nitride, ceramic, carbide, polymer, magnetic material, magnetostrictive material, electrostrictive material, and biological material.

4. The system according to claim 1, wherein said active acoustic region is a thickness field excitation (TFE) structure formed by at least one positive electrode disposed on one side of said bridge and at least one ground electrode on an opposing side of said bridge, and wherein an electrical energy source is coupled to said at least one positive electrode and said at least one ground electrode.

5. The system according to claim 4, wherein said thickness field excitation (TFE) structure is a two port device wherein a first transducer is electrically coupled to said electrical energy source by a positive electrical connection and a negative electrical connection and a second transducer provides a response related to an input electrical signal from said electrical energy source to a second positive electrical connection and second negative electrical connection.

6. The system according to claim 1, wherein said active acoustic region is a lateral field excitation (LFE) structure formed by at least one positive electrode and at least one negative electrode electrically coupled on one side of said bridge and to an electrical energy source.

7. The system according to claim 1, wherein said active acoustic region is a surface generated acoustic wave (SGAW) structure formed by at least one transducer electrically coupled on one side of said bridge, wherein said at least one transducer is electrically coupled to an electrical energy source.

8. The system according to claim 7, further comprising a surface generated acoustic wave (SGAW) energy manipulating structure operatively coupled with said at least one transducer, wherein said SGAW energy manipulating structure is selected from the group consisting of:

reflective grating, delay line, metal trapping grating, multi-strip coupler, interdigital transducer, and thin film trapping layer.

9. The system according to claim 7, wherein said surface generated acoustic wave (SGAW) structure is a one port device wherein a single said transducer is electrically coupled to said electrical energy source by a positive electrical connection and a negative electrical connection.

10. The system according to claim 7, wherein said surface generated acoustic wave (SGAW) structure is a two port device wherein said at least one transducer comprises a first transducer and a second transducer, wherein said first transducer is electrically coupled to said electrical energy source by a positive electrical connection and a negative electrical connection and said second transducer provides a response related to an input signal from said electrical energy source to a second positive electrical connection and second negative electrical connection.

11. The system according to claim 1, wherein said bridge is a structure selected from at least one of the group consisting of:

full bridge bulk acoustic wave, full bridge bulk acoustic wave monolithic crystal filter (MCF), full bridge bulk acoustic wave lateral field excitation (LFE), full bridge surface generated acoustic wave, full bridge film bulk acoustic resonator (FBAR), isolation bridge bulk acoustic wave, isolation bridge bulk acoustic wave MCF, isolation bridge bulk acoustic wave LFE, isolation bridge surface generated acoustic wave, and isolation bridge bulk acoustic wave FBAR.

12. The system according to claim 1, wherein said bridge is coupled to said substrate by one of the group consisting of:

two supports and four supports.

13. The system according to claim 1, further comprising a measurement device coupled to said acoustic wave device (AWD) and measuring said stress effects.

14. A method for detecting a target substance, comprising:

forming a piezoelectric bridge having at least one acoustic wave device disposed proximate a portion of said bridge;

exposing said bridge to some environment;

causing a stress response of said bridge from said environment; and

detecting a response of said acoustic wave device to said bridge stress response.

15. The method according to claim 14, further comprising disposing a sensing material on at least one portion of said bridge and allowing adsorption/absorption of said target substance by said sensing material.

16. The method according to claim 14, further comprising aligning said acoustic wave device at an angle (ψ

) for a maximum change in frequency.

17. A sensing device for measuring stress effects, comprising:

a substrate having electrical connections disposed about said substrate and providing connectivity to an electrical energy source and a measurement device;

a bridge structure coupled to said substrate on a portion of at least two sides of said bridge comprising;

at least one acoustic wave device formed proximate a portion of said bridge,

said acoustic wave device comprising a piezoelectric section with at least two electrodes disposed thereon,

wherein a perturbation of said bridge causes a change in electrical properties of said acoustic wave device,

said change in electrical properties modifying a signal from said electrical energy source in a manner that is measurable by said measurement device.

18. The device according to claim 17, further comprising a sensing material disposed on at least a portion of at least one surface of said bridge causing said perturbation of said bridge.

19. The device according to claim 17, wherein said sensing device is selected from at least one of the group consisting of:

bulk acoustic (BAW) bridge gas sensors, BAW bridge magnetic sensors, BAW bridge torque sensors, surface acoustic wave (SAW) bridge gas sensors, SAW bridge magnetic sensors, SAW bridge gas sensors, monolithic crystal filter (MCF) bridge gas sensors, MCF bridge magnetic sensors, MCF bridge torque sensors, film bulk acoustic resonator (FBAR) bridge gas sensors, FBAR magnetic sensors, and FBAR torque sensors.

20. The device of claim 17, wherein said piezoelectric section is selected from the group consisting of quartz, lithium niobate, lithium tantalate, langasite, aluminum phosphate, gallium phosphate, calcium-niobium-gallium-silicate, calcium-tantalum-gallium-silicate, strontium-niobium-gallium-silicate, strontium-tantalum-gallium-silicate, zinc oxide, aluminum nitride, and compositions thereof.

21. A system for acoustic sensing, comprising:

a bridge structure coupled to a substrate about a portion of at least two sides of said bridge, wherein said bridge includes a piezoelectric section and having at least one acoustic wave device (AWD) proximate a portion of said bridge,

wherein said AWD includes an active acoustic region,

wherein boundaries of said active acoustic region are decoupled from boundaries of said bridge;

an electrical signal coupled to said bridge structure,

wherein stresses induced in said bridge produce force-frequency effects measurable by said AWD; and

wherein said force-frequency effects induce modulation of said electrical signal.

22. A sensing device for measuring physical parameters, comprising:

a substrate having electrical connections disposed about said substrate and providing connectivity to an electrical energy source and a measurement device;

a bridge coupled to said substrate on a portion of at least two sides of said bridge, said bridge comprising;

at least one acoustic wave device formed proximate a portion of said bridge, said acoustic wave device comprising a piezoelectric section with at least two electrodes disposed thereon, wherein said bridge is responsive to stresses induced by application of a point force to said bridge,

wherein said bridge stress response causes a change in electrical properties of said acoustic wave device, said change in electrical properties modifying a signal from said electrical energy source in a manner that is measurable by said measurement device.

23. The device according to claim 22, further comprising a diaphragm responsive to pressure disposed proximate said bridge, wherein said diaphragm transmits said point force.

24. The device according to claim 22, wherein magnetic fields acting upon a magnetic region proximate said bridge produce said point force.

25. The device according to claim 22, wherein an acceleration acting upon a proof mass proximate said bridge produces said point force.