Acoustic wave sensor with reduced condensation and recovery time

• US 20060032290A1
• Filed: 08/12/2004
• Published: 02/16/2006
• Est. Priority Date: 08/12/2004
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Liu, James Z.
• Granted Patent: US 7,134,319 B2
• Time in Patent Office: Days
• US Class Current: 73/29.20
• CPC Class Codes: G01N 2291/0256 Adsorption, desorption, surface mass change, e.g. on biosensors
• CPC Class Codes: G01N 2291/02845 Humidity, wetness
• 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 29/2462 Probes with waveguides, e.g. SAW devices
• CPC Class Codes: G01N 29/326 compensating for temperature variations

Abstract

An acoustic wave sensor apparatus is disclosed, which generally includes a piezoelectric substrate having a surface thereon. One or more interdigital transducers and a passivation layer can be formed upon the piezoelectric substrate. Additionally, an absorbent material can be formed upon the acoustic path (IDTs, electrodes, etc), such that the interdigital transducers respond to a plurality of acoustic waves propagating across the surface of the piezoelectric substrate, thereby providing data indicative of humidity in the vicinity of the piezoelectric substrate, along with the passivation layer and the interdigital transducers. Additionally, one or more heaters can be formed upon a side of the piezoelectric substrate opposite the side of the piezoelectric substrate upon which the interdigital transducers, the passivation and the absorbent material are located. The heater can be preferably configured from a material such as platinum.

Claims

1. An acoustic wave sensor apparatus, comprising:

a piezoelectric substrate having a surface thereon;

at least one interdigital transducer and a passivation layer formed upon said piezoelectric substrate; and

an absorbent material formed upon said passivation layer, wherein said at least on interdigital transducer responds to a plurality of acoustic waves propagating across said surface of said piezoelectric substrate, that provide data indicative of humidity in a vicinity of said piezoelectric substrate, said passivation layer and said at least on interdigital transducer.

2. The apparatus of claim 1 further comprising at least one heater formed upon a side of said piezoelectric substrate opposite a side upon which said at least one interdigital transducer, said passivation and said absorbent material are located.

3. The apparatus of claim 2 wherein said at least one heater comprises platinum.

4. The apparatus of claim 1 wherein said plurality of acoustic waves propagating across said surface of said piezoelectric substrate comprise multiple mode frequency outputs, such that at least one frequency mode thereof is optimized while all remaining frequency modes among said multiple mode frequency outputs are suppressed in order to generate particular data indicative of a monitored chemical species.

5. The apparatus of claim 4 wherein said piezoelectric substrate vibrates in said at least one frequency mode when condensation occurs in a vicinity of said piezoelectric substrate, such said condensation acts as a damping force thereon.

6. The apparatus of claim 5 wherein said piezoelectric substrate vibrates in a shear horizontal direction in order to lessen damping thereof.

7. The apparatus of claim 1 further comprising a plurality of oscillators associated with said at least one interdigital transducer, wherein each sensing components of said plurality of sensing components is located in a feedback loop with an oscillator of said plurality of oscillators to thereby provide a multiple mode acoustic wave sensor that provides multiple mode frequency outputs thereof.

8. The apparatus of claim 7 wherein said multiple modes frequency outputs comprise at least one of the following types of data:

flexural plate mode (FMP) data, acoustic plate mode data, and shear-horizontal acoustic plate mode (SH-APM) data.

9. The apparatus of claim 8 wherein said multiple mode frequency outputs further comprises at least one of the following types of data:

amplitude plate mode (APM) data, thickness shear mode (TSM) data, surface acoustic wave mode (SAW), and bulk acoustic wave mode (BAW) data.

10. The apparatus of claim 9 wherein said multiple mode frequency outputs further comprises at least one of the following types of data:

torsional mode data, love wave data, leaky surface acoustic wave mode (LSAW) data, and pseudo surface acoustic wave mode (PSAW) data, and at least one multiple mode acoustical vibration amplitude.

11. The apparatus of claim 10 wherein said multiple mode frequency outputs further comprises at least one of the following types of data:

transverse mode data, surface-skimming mode data, surface transverse mode data, harmonic mode data, and overtone mode data.

12. The apparatus of claim 11 wherein said at least one multiple mode acoustical vibration amplitude is controlled by said plurality of oscillators.

13. An acoustic wave sensor apparatus, comprising:

a piezoelectric substrate having a surface thereon;

at least one interdigital transducer and a passivation layer formed upon said piezoelectric substrate;

an absorbent material formed upon said passivation layer, wherein said at least on interdigital transducer responds to a plurality of acoustic waves propagating across said surface of said piezoelectric substrate, that provide data indicative of humidity in a vicinity of said piezoelectric substrate, said passivation layer and said at least on interdigital transducer;

at least one heater formed upon a side of said piezoelectric substrate opposite a side upon which said at least one interdigital transducer, said passivation and said absorbent material are located; and

a plurality of oscillators associated with said at least one interdigital transducer, wherein each sensing components of said plurality of sensing components is located in a feedback loop with an oscillator of said plurality of oscillators to thereby provide a multiple mode acoustic wave sensor that provides multiple mode frequency outputs thereof, wherein said at least one multiple mode acoustical vibration amplitude is controlled by said plurality of oscillators.

14. The apparatus of claim 13 wherein said plurality of acoustic waves propagating across said surface of said piezoelectric substrate comprise said multiple mode frequency outputs, such that at least one frequency mode thereof is optimized while all remaining frequency modes among said multiple mode frequency outputs are suppressed in order to generate particular data indicative of a monitored chemical species.

15. The apparatus of claim 13 wherein said piezoelectric substrate vibrates in at least one frequency mode among said multiple mode frequency outputs when condensation occurs in a vicinity of said piezoelectric substrate, such said condensation acts as a damping force thereon.

16. The apparatus of claim 15 wherein said piezoelectric substrate vibrates in a shear horizontal direction in order to lessen damping thereof.

17. A method for acoustic wave sensing, comprising the steps of:

providing a piezoelectric substrate having a surface thereon;

forming at least one interdigital transducer and a passivation layer upon said piezoelectric substrate; and

configuring an absorbent material upon said passivation layer, wherein said at least on interdigital transducer responds to a plurality of acoustic waves propagating across said surface of said piezoelectric substrate, that provide data indicative of humidity in a vicinity of said piezoelectric substrate, said passivation layer and said at least on interdigital transducer.

18. The method of claim 17 further comprising the step of forming at least one heater formed upon a side of said piezoelectric substrate opposite a side upon which said at least one interdigital transducer, said passivation and said absorbent material are located.

19. The method of claim 17 further comprising the step of configuring said piezoelectric substrate such that said plurality of acoustic waves propagating across said surface of said piezoelectric substrate comprise multiple mode frequency outputs, wherein at least one frequency mode thereof is optimized while all remaining frequency modes among said multiple mode frequency outputs are suppressed in order to generate particular data indicative of a monitored chemical species.

20. The method of claim 19 further comprising the step of configuring said piezoelectric substrate to vibrate in said at least one frequency mode when condensation occurs in a vicinity of said piezoelectric substrate, such said condensation acts as a damping force thereon.