Method and system for measuring physical parameters with a piezoelectric bimorph cantilever in a gaseous or liquid environment

• US 7,663,295 B2
• Filed: 12/14/2006
• Issued: 02/16/2010
• Est. Priority Date: 12/15/2005
• Status: Expired due to Fees

• Current Assignee: Universiteit Hasselt
• Original Assignee: IMEC International
• Inventors: Mortet, Vincent, Petersen, Rainer
• Primary Examiner(s): Benson; Walter
• Assistant Examiner(s): ROSENAU, DEREK JOHN
• Application Number:
  US11/610,976
• Publication Number:
  US 20070138909A1
• Time in Patent Office: 1,160 Days
• Field of Search: 310330-332, 310/338, 310/323.21, 310/336
• US Class Current: 310/338
• 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 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;

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 frequencies 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, each based on a combination of the resonant frequencies.

2. The sensor of claim 1, 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).

3. The sensor of claim 1, 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).

4. The sensor of claim 1, 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).

5. The sensor of claim 1, further comprising an adhesion layer positioned between the electrode material and at least one of the first layer and the piezoelectric material.

6. The sensor of claim 5, wherein the adhesion layer comprises titanium (Ti).

7. The sensor of claim 1, wherein the piezoelectric bimorph cantilever further comprises a layer for binding at least one of a biological species and a chemical species.

8. The sensor of claim 1, wherein means for vibrating the piezoelectric bimorph cantilever comprises an AC voltage source.

9. The sensor of claim 1, wherein means for measuring the output signal of the electrodes comprises an impedance analyzer.

10. The sensor of claim 1, wherein means for determining the resonant frequencies comprises a frequency-selective network.

11. The sensor of claim 10, wherein the frequency-selective network is mounted on a support on which the piezoelectric bimorph cantilever is mounted.

12. The sensor of claim 1, further comprising a protective housing disposed about the piezoelectric bimorph cantilever.