Lateral field excited acoustic wave sensor
First Claim
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1. An acoustic wave sensor comprising:
- a substrate formed from a piezoelectric crystal with a crystallographic orientation, said substrate having a sensing surface and a reference surface, said reference surface being opposite from said sensing surface, said sensing surface in contact with a fluid containing a measurand of interest; and
a pair of electrodes deposited upon said substrate reference surface, said electrodes separated by a gap and oriented upon said reference surface relative to said crystallographic orientation of said substrate such that, upon said electrodes generating a lateral electric field therebetween, said lateral electric field induces only a transverse shear mode acoustic wave within said substrate.
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Abstract
An acoustic wave sensor having a piezoelectric substrate shaped to generate lateral electric fields. The sensor has a pair of electrodes deposited upon a reference surface of the substrate. A sensing surface that is opposite from the reference surface is adapted to be immersed in an environment, such as a gas or a liquid.
34 Citations
27 Claims
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1. An acoustic wave sensor comprising:
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a substrate formed from a piezoelectric crystal with a crystallographic orientation, said substrate having a sensing surface and a reference surface, said reference surface being opposite from said sensing surface, said sensing surface in contact with a fluid containing a measurand of interest; and a pair of electrodes deposited upon said substrate reference surface, said electrodes separated by a gap and oriented upon said reference surface relative to said crystallographic orientation of said substrate such that, upon said electrodes generating a lateral electric field therebetween, said lateral electric field induces only a transverse shear mode acoustic wave within said substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for fabricating an acoustic wave sensor comprising the steps of:
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(a) providing a piezoelectric crystal; (b) forming the crystal into a substrate having a crystallographic orientation, the substrate including a reference surface and a sensing surface opposite from the reference surface, the sensing surface in contact with a fluid containing a measurand of interest; and (c) depositing a pair of electrodes upon the reference surface of the sensor substrate, the electrodes separated by a gap and oriented upon the reference surface relative to the crystallographic orientation of the substrate such that, upon the electrodes generating a lateral electric field therebetween, the lateral electric field induces only a transverse shear mode acoustic wave within the substrate. - View Dependent Claims (17, 18, 19, 20, 21)
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22. An apparatus for measuring a characteristic of an environment comprising;
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an acoustic wave sensor having a piezoelectric substrate formed from one of the group of quartz, langatate, langasite, langanite, lithium tantalate and lithium niobate, said substrate having a crystallographic orientation, the substrate also having a reference surface and a sensing surface opposite from said reference surface, said sensing surface in contact with a fluid that contains a measurand, and pair of electrodes deposited upon said reference surface of said substrate with said electrodes oriented relative to said crystallographic orientation of said substrate such that, upon said electrodes generating a lateral electric field therebetween, the lateral electric field induces only a transverse shear mode acoustic wave within said substrate; a variable voltage supply electrically connected to said sensor electrodes and operative to cause said electrodes to generate a lateral electric field therebetween that produces transverse shear mode acoustic waves within said substrate that extend into said environment, said variable voltage supply having a variable frequency and being operative to sweep through a predetermined frequency range; and a device electrically connected to said sensor and operative to detect the resonance frequency of the sensor, said device being further operative to detect shifts in the resonant frequency caused by said measurand deposited upon said sensing surface varies and to correlate said resonant frequency shift with said measurand. - View Dependent Claims (23, 24, 25, 26, 27)
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Specification