METHOD AND SYSTEM FOR MEASURING PHYSICAL PARAMETERS WITH A PIEZOELECTRIC BIMORPH CANTILEVER IN A GASEOUS OR LIQUID ENVIRONMENT

• US 20070138909A1
• Filed: 12/14/2006
• Published: 06/21/2007
• Est. Priority Date: 12/15/2005
• Status: Active Grant

• Current Assignee: Universiteit Hasselt
• Original Assignee: Interuniversitair Micro-Electronica Centrum VZW (IMEC International), Universiteit Hasselt
• Inventors: Mortet, Vincent, Petersen, Rainer
• Granted Patent: US 7,663,295 B2
• Time in Patent Office: Days
• US Class Current: 310/318
• 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 2291/0427 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 29/245 Ceramic probes, e.g. lead zirconate titanate [PZT] probes
• CPC Class Codes: Y10T 436/143333 Saccharide [e.g., DNA, etc.]

Abstract

A piezoelectric bimorph cantilever is used for determining physical parameters in a gaseous or liquid environment. The sensor works as a driven and damped oscillator. Contrary to common cantilever sensor systems, the piezoelectric film of the bimorph cantilever acts as both a sensor and an actuator. Using at least two resonance mode of the bimorph cantilever, at least two physical parameters can be measured simultaneously in a gas or a liquid. An optimized piezoelectric cantilever and a method to produce the cantilever are also described.

Claims

1. A method for measuring at least two physical parameters in an environment comprising at least one of a gas and a liquid, the method comprising:

providing a piezoelectric bimorph cantilever comprising at least a first layer, a piezoelectric layer, and two electrodes;

placing the piezoelectric bimorph cantilever in the environment;

vibrating the piezoelectric bimorph cantilever;

determining the resonant frequency of at least two resonance modes of the piezoelectric bimorph cantilever; and

determining at least two physical parameters of the environment based on the at least two resonance modes.

2. The method of claim 1, wherein providing the piezoelectric bimorph cantilever comprises fabricating the piezoelectric bimorph cantilever by a process comprising:

providing a first layer;

depositing a first electrode material on a portion of the base material;

depositing a piezoelectric material on a portion of the first layer;

depositing a second electrode material on a portion of the piezoelectric material; and

patterning the first layer and the piezoelectric material in a cantilever shape.

3. The method of claim 2, wherein the process further comprises coating the piezoelectric bimorph cantilever with a layer that is configured to bind at least one of a biological species and a chemical species.

4. The method of claim 1, wherein placing the piezoelectric bimorph cantilever in the environment comprises mounting the piezoelectric bimorph cantilever on a support, optionally in a protective housing, and coupling the electrodes to at least one of an analysis tool and an electronic network.

5. The method of claim 1, wherein vibrating the piezoelectric bimorph cantilever comprises applying an AC voltage across the at least two electrodes.

6. The method of claim 5, wherein applying the AC voltage across the at least two electrodes and determining the resonant frequency of the at least two resonance modes of the piezoelectric bimorph cantilever is achieved with an impedance analyzer.

7. The method of claim 1, wherein determining the resonant frequency of the at least two resonance modes of the piezoelectric bimorph cantilever comprises using a frequency-selective network.

8. The method of claim 7, wherein the frequency-selective network is mounted on a support comprising the piezoelectric bimorph cantilever.

9. The method of claim 1, wherein determining the at least two physical parameters of the environment based on the at least two resonance modes comprises comparing the at least two resonance modes with calibration curves.

10. The method of claim 9, wherein comparing the at least two resonance modes with the calibration curves comprises using integrating electronics on a support comprising the piezoelectric bimorph cantilever.

11. The method of claim 1, wherein determining the at least two physical parameters of the environment comprises determining pressure and temperature of the environment.

12. The method of claim 1, wherein determining the at least two physical parameters of the environment comprises detecting a change in weight of the piezoelectric bimorph cantilever and determining a concentration of at least one of a chemical species and a biological species.

13. A sensor for measuring at least two physical parameters in an environment comprising at least one of a gas and a liquid, comprising:

a piezoelectric bimorph cantilever comprising at least a first layer, a piezoelectric layer, and two electrodes;

a support on which the piezoelectric bimorph cantilever is mounted;

optionally protective housing comprising the piezoelectric bimorph cantilever;

electrical connections to the electrodes of the piezoelectric bimorph cantilever;

means for vibrating the piezoelectric bimorph cantilever with the electrodes;

means for measuring an output signal of the electrodes;

means for determining the resonant frequency of at least two resonance modes based on the output signal of the electrodes; and

means for determining at least two physical parameters of the environment based on the resonance frequencies.

14. The sensor of claim 13, wherein the first layer of the piezoelectric bimorph cantilever is selected from the group consisting of silicon (Si), silicon nitride (SiN), silicon carbide (SiC), diamond, and silicon oxide (SiO₂).

15. The sensor of claim 13, wherein the piezoelectric layer of the piezoelectric bimorph cantilever comprises a material selected from the group consisting of Lead Zirconate Titanate (PZT), zinc oxide (ZnO), aluminum nitride (AlN), and barium titanium oxide (BaTiO₃).

16. The sensor of claim 13, wherein the electrodes of the piezoelectric bimorph cantilever comprise a material selected from the group consisting of gold (Au), aluminum (Al), platinum (Pt), and titanium nitride (TiN).

17. The sensor of claim 13, further comprising an adhesion layer positioned between the electrode material and at least one of the first layer and the piezoelectric material.

18. The sensor of claim 17, wherein the adhesion layer comprises titanium (Ti).

19. The sensor of claim 13, wherein the piezoelectric bimorph cantilever further comprises a layer for binding at least one of a biological species and a chemical species.

20. The sensor of claim 13, wherein means for vibrating the piezoelectric bimorph cantilever comprises an AC voltage source.

21. The sensor of claim 13, wherein means for measuring the output signal of the electrodes comprises an impedance analyzer.

22. The sensor of claim 13, wherein means for determining the resonant frequencies comprises a frequency-selective network.

23. The sensor of claim 22, wherein the frequency-selective network is mounted on a support comprising the piezoelectric bimorph cantilever.