WO1999040397A1 - Device at piezoelectric crystal oscillator - Google Patents

Device at piezoelectric crystal oscillator Download PDF

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Publication number
WO1999040397A1
WO1999040397A1 PCT/SE1999/000051 SE9900051W WO9940397A1 WO 1999040397 A1 WO1999040397 A1 WO 1999040397A1 SE 9900051 W SE9900051 W SE 9900051W WO 9940397 A1 WO9940397 A1 WO 9940397A1
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WO
WIPO (PCT)
Prior art keywords
oscillators
crystal
piezoelectric
frequency
oscillator
Prior art date
Application number
PCT/SE1999/000051
Other languages
French (fr)
Swedish (sv)
Inventor
Michael Rodahl
Bengt Kasemo
Anatol Krozer
Original Assignee
Q-Sense Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Q-Sense Ab filed Critical Q-Sense Ab
Priority to AU24449/99A priority Critical patent/AU2444999A/en
Publication of WO1999040397A1 publication Critical patent/WO1999040397A1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B06GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06BMETHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0644Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01GWEIGHING
    • G01G3/00Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
    • G01G3/12Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
    • G01G3/13Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing having piezoelectric or piezoresistive properties
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N5/00Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid

Abstract

The present invention offers a monolithic, piezoelectric crystal device which simultaneously (i) has several oscillators on the same crystal, the resonance frequencies of which can be selected in a flexible way; (ii) does not show any problem with regard to acoustic superhearing between the oscillators, and (iii) facilitates a simple addressing of the single oscillators.

Description

1
TITLE
DEVICE AT PIEZOELECTRIC CRYSTAL OSCILLATOR
DESCRIPTION Technical field
The present invention intends to offer a monolithitc, piezoelectric crystal device which simultaneously (i) has several oscillators on the same crystal, the resonance frequency of which can be chosen in a flexible way, (ii) do not show any problems related to acoustical overhearing between the oscillators, and (iii) facilitate a simple addressing of the individual oscillators.
Background of the invention
It is previously known to use crystal micro balancing means at the weighing of small amounts of material. Such micro balancing units are based upon a so called piezoelectric effect of the sensor material (cf below). Consequently all materials which possess piezoelectric properties can be used as sensoric material. Example of suitable sensoric materials are quartz, lithium niobate, and gallium arsenide. In the following we will briefly describe the function of a micro balancing unit and present our invention starting from quartz as sensoric material. However, the following description is generally due for piezoelectric materials.
The quartz crystal micro balancing unit, QCM, (from the English Quartz Crystal Microbalance) is an extremely sensitive balance intended to weigh small amounts of material, often in the form of a film, which is added to or removed from the electrodes of the QCM. For details, cf the references (Guilbaut 1980; Alder and McCallum 1983; Czanderna and Lu 1984; Lu 1984; Buttry 1991). The QCM consists of a disc of a single crystal of a piezoelectric material, usually quartz. As an example we choose a so called AT-cut quartz crystal. Such a crystal oscillates in shearing mode with an amplitude of 1-10 rim and a basic frequency of /= constant f1 (1)
where t is the thickness of the crystal. Having a t = 0.17 mm f is - 10 MHz. The crystal will 2 start to oscillate when an AC field is applied perpendicular to the surface of the crystal. The frequency of the AC field shall be centred around the intrinsic frequency of the crystal. The more far away the frequency of the AC field is from the intrinsic frequencies of the crystal (a crystal can have more than one intrinsic frequency) the less will the oscillation amplitude of the crystal will become. If one draws the oscillation amplitude of the crystal as a function of the driving frequency one will obtain a peak at the resonance frequency of the crystal.
In practise the AC filed will be applied over electrode pairs of metals, one on each side of the crystal, which electrodes have been deposited by means of evaporation of in any other suitable manner. The pair of electrodes are then brought into electrical contact with an external oscillation circuit or device that can generate a frequency close to the intrinsic frequency of the oscillator, e.g., an frequency generator, and which can excite the oscillator. Such a device can manage to measure very small mass changes on the electrodes of the quartz crystal, in the size of 1 ng/cm2, or less under advantageous conditions.
Under ideal conditions the shift in resonance frequency, Δf, is proportional to the change of mass, Δm, i.e., Δ/= -constant -Δm (2).
The size of the constant will depend on the type of crystal material used, the resonance frequency, and the crystallographic cut of a given material.
An oscillator is hereby defined as that part of a piezoelectric crystal which can be brought into resonance at a certain frequency. The lowest frequency as the oscillator can be brought into resonance (into a desired mode of oscillation) is defined as the basic resonance frequency. In a conventional piezoelectric crystal oscillator the physical extension of the oscillation is substantially (but not exact, cf. e.g., Rodahl and Kasemo, 1997) the overlap of the electrodes of the underside and the overside.
There are several situations when it is desirable/necessary to be able to obtain more information at the time of determination. Below two examples of determination situations are described where the present invention can be used to increase the information determined and significantly improve the measurement.
Case 1 : Viscoelastic systems
Equation 2 presumes that the mass, represented by Δm, is fixedly attached to the electrode, and accompanies the oscillation of the QCM without any dissipative losses. Equation 2 does not work when the mass applied is a liquid drop or consists of a viscous material which is not rigidly attached to the crystal and/or is deformed elastically or plastically during the oscillation movement. In such cases the mass-frequency relation becomes more complex. Then it is important to obtain more information of the properties of the film applied in order to correct characterize the film.
Some of this information can be obtained by measuring the response of the film at several different frequencies. Then it is important to be able to choose these frequencies in a flexible way starting from the conditions as the film requests. It is, using common technology, possible to excite a QCM in its harmonics, but these are situated in a great and fixed distance from each other. (The frequencies of the harmonics run as 3f0, 5f_ etc., wherein^is the basic frequency). The present invention facilitates excitation/measurement of the film applied at many more frequencies which can be chosen in a flexible manner.
Case 2: Multiple sensors
All sensors give undesired responses due to variations in the measuring conditions. QCM is no exception: small variations in, e.g., the surrounding pressure and/or temperature can seriously affect the measurement in a unpredictable way, if they are not controlled. One way of reducing the consequences of variations in temperature etc. is to use two independent oscillators: one used as an active sensor, and one used as a reference sensor. Both oscillators are then made subject to the same conditions of e.g., temperature and pressure, but only the active oscillator interacts with that one is interested of measuring on. If the oscillators react in the same way on changes of temperature etc. the difference signal between the oscillators then depends only on what one wants to measure. In this situation it is important that: * the active oscillator is matched against the reference oscillator so that it reacts in the same way on changes in temperature etc. E.g., a very small deviation of the cutting angle or quality between the crystals can provide great differences in the temperature response 4
* to design the measurement in such a way that both oscillators are made subject to exactly the same conditions. The more far away the oscillators are placed from each other the more difficult it is to keep the conditions exactly the same, i.e. gradients in the surrounding conditions cause faults in the measurement.
If the two oscillators should be placed on one and the same crystal plate their properties will become practically the same, e.g., with reference to the quality of the crystal. It is then desirable to place the oscillators as close as possible on the crystal plate. The closer the oscillators are situated to each other, the more like can their measurement conditions be made. Less material consumption and size are two further important advantages by placing the oscillators close together.
The number of oscillators per crystal can be more than two. For example an array of oscillators can be placed upon a crystal. If the surface chemistry or another property of the different oscillators can be made different so that they will react differently on different substances in a sample several parameters can be registered simultaneously and/or pattern recognition can be utilized to identify a substance which does not react specifically with any of the oscillators but provides different (unspecific) signals for each oscillator. Even in such application it is desirable to place the oscillators as close as possible to each other so that the sample volume will become as small as possible and so that the registration conditions for the different oscillators will become as similar as possible.
In order to be able to utilize a multi-oscillator each individual oscillator has to be able to be addressed (registered) individually. Using conventional technique it is required either a series of drive and monitoring electronics for each oscillator which is connected directly to each oscillator or a system of multiplexing which sequentially connects the oscillators to drive and monitoring electronics by means of one or more relays (or the similar device).
A strongly restriction factor for how close the oscillators can be placed to each other is acoustic superhearing (acoustic connection). The piezoelectric oscillation is excited by the electrical field between a pair of electrodes but the oscillation is not fully restricted to the overlap between the electrodes but is damped approximately in an exponential fashion 5 outside the electrode overlap (Rodahl and Kasemo, 1997). This "oscillation tail" can connect to another oscillator if it is situated too close (Kaushik, Chattopadhyaya et al. 1981). The oscillators will then not become independent but joined, and the whole idea using multiple oscillators on one crystal will fall apart.
There are several publications (e.g. US-A-5,495,135, 3,898,489, 5,032,755 and 4,894,577) concerning different embodiments to reduce undesired resonance modes (spurious modes) in piezoelectric crystals using one or more oscillators but these do not discuss acoustic connection between the resonance desired in QCM application. J Vig has patented (US-A- 5,686,779) a design of a temperature sensor using a matrix of piezoelectric oscillators on one and the same crystal. He describes how these can be disconnected thermally but in the present case a good thermal conductivity between the oscillators is desired so that they will have the same temperature. Many previous works (Kaushik, Chattopadhyaya et al. 1981) which relates to undesired acoustic connection between multiple oscillators on the same piezoelectric crystal have only proposed, as a counteraction to this connection, to place the pairs of electrodes far enough from each other in that no connection occurs. A work (PCT/JP96/ 02125) discusses ways of reducing acoustic connection by building barriers between oscillators. This work only discusses filter applications and does not solve the problem described in case 1 above or the addressing of the different oscillators.
In view of what has been said above the object of the present invention is to offer a monolithic, piezoelectric crystal device which simultaneously (i) has several oscillators on the same crystal, the resonance frequencies of which can be selected in a flexible way, (ii) does not show any problem with regard to acoustic superhearing between the oscillators, and (iii) facilitates a simple addressing of the single oscillators.
Short description of the figures
Figure I (lateral view, cross-section A-A in Figure 2) and Figure 2 (shall not be interpreted as a cross-section but is a top planar view) show an example of an embodiment of the present invention.
Figures 3 to 5 illustrate schematically other examples of embodiment of the present invention where the crystal has been cut from the side (as in Figure 1).
Common to Figures 1 to 5 is that they are not scale proportional in order better to illustrate the art of the invention. Further, common to the figures is that all figures show three independent oscillators but this number can of course be varied both up and down.
Figure 6 shows the registration of the frequency spectrum from a crystal manufactured in accordance with the embodiment shown in Figure 5.
Detailed description of the invention
In the following examples of embodiments of the invention are presented which shall be interpreted within the frame work of the accompanying claims. In the following examples of embodiments of the invention three oscillators per crystal is shown but this number can be varied up and down.
In a first embodiment of the present invention shown in Figures 1 and 2, there is piezoelectric crystal (5) on its upper side designed with staircase like pattern provided with a number of electrodes (1, 2, 3). The electrodes of the upper side (1, 2, 3) are provided with contact means using electrode wings (11, 12, 13). In this embodiment there is only one electrode (71) which advantageously can be connected to earth, on its under side functions as counter electrode to all electrodes (X) on the upper side.
The manufacture of the piezoelectric crystal (5) can be done by known technique, such as by means of wet etching, dry etching, (reactive ion etching) MITE (micro machining by iron track etching), abrasion and/or other technique suitable for the purpose.
The arrangement using only one counter electrode (71) on the under side of the crystal is advantageous i.a. when the crystal is used as a QCM in liquid phase registrations where one side of the crystal is brought into contact with a liquid. In order to avoid that the conductivity of the liquid influences the resonance properties of the QCM that part of the crystal which is brought into contact with the liquid should be completely covered by an electrode (Rodahl, Hook et al. 1996). Furthermore, there is only one wire needed to bring the counter electrode into contact..
When using the invention as a sensor in liquid phase registration it is in many cases an advantage if that part of the sensor which is brought into contact with the liquid is smooth. This will be of no problem in the present invention as one side can be kept smooth (as shown in the Figures). If this restriction does not apply, it is possible to structure both sides of the crystal if this should be an advantage.
The basic tone frequency of the oscillators depends of the thickness of the oscillator in accordance with equation 1. By choosing a suitable thickness of the crystal for each oscillator one can thereby determine the basic tone frequencies of the oscillators. In the present invention the resonance frequencies of the oscillators in such away that they will not have any overlapping frequency peaks which drastically reduces the acoustic superhearing which means that the oscillators can be placed closer than would have been possible in a conventional crystal with several oscillators. Two resonance peaks are overlapping if a drive frequency can bring both oscillators into a significant oscillation, and if that is not the case, then the resonance peaks are not overlapping.
Figure 3 shows another example of an embodiment of the present invention where the resonance frequency of each oscillator have been adjusted by coating the crystal with films (31, 32, 33) of varying thickness in connection to each electrode on the upper side of the crystal. The thickness of the film and the density thereof will then determine how much the resonance frequency will be changed in relation to the areas where no film has been applied, (cf equation 2). If the thickness of the crystal corresponds with a desired resonance frequency of one of the oscillators, no film is needed for one oscillator.
In order to obtain a good resonance for each oscillator it is of importance that the film has good mechanical properties so that the oscillation of the oscillator will not become too much damped and that the film has a good adhesion to both the crystal and the electrode. It is, e.g., possible to use the same material in the film as in the electrode. Common electrode materials are gold and silver. Chromium and titan are common material in order to improve the adhesion between electrode and crystal. 8
Figure 4 shows an embodiment of the present invention where the oscillators are lowered into the crystal. The cavity can be made using already known technique such as by means of wet etching, dry etching, (reactive ion etching) MITE (micro machining by iron track etching), abrasion and/or other technique suitable for the purpose. The electrodes (1, 2,3) are placed in the cavities (41 , 42, 43). In the same way as above the resonance frequency of each oscillator can be changed by altering the depth of the cavity. If all cavities are made to the same depth the resonance frequency can be changed by coating the cavities with films of different mass in a similar way as in the foregoing example.
Figure 5 shows an example of the embodiment of the present invention which has only two electrodes (51, 71) but in other respects the same as in Figure 4. When the oscillators of the crystal has non-overlapping resonance frequencies they can be driven/registered by addressing each oscillator at its resonance frequency. Example of equipment which can address each oscillator in the latter way is e.g., a net work analyser or the drive electronics described in the Swedish patent SE-C-504 199. It is of course possible to drive/register on the oscillators by individual wires in a conventional way (as described above).
The possibility of addressing the oscillators at their resonance frequencies is not restricted to crystals having cavities therein but can also be used in all embodiments given above.
Example
Figure 6 shows a frequency spectrum of a quartz crystal having three lowered oscillators and only two electrodes, of the type as shown in Figure 5. The sample was manufactured from a 5 MHZ AT-cut crystal having a diameter of 25 mm. The cavities made by etching using MITE, were approximately 36, 52, and 68 μm deep and had a diameter of 6 mm with a separation of about 1.5 mm. As evident each oscillator gives raise to its own unique resonance frequency, well separated from the others. In this case a film/sample which had been placed upon one of the electrodes (preferably the electrode which covers the smooth side of the crystal) is excited and registered at 5.75 MHZ, 6.05 MHZ, and 6.45 MHZ. Using traditional QCM technique this will not be possible but one should have needed three separate crystals. This means that there is needed three identical films/samples which have to be applied on each their crystal in an identical way. This problem (which can be very great) is avoided using the present invention.
99/40397
10
REFERENCES
Alder, J. F. and J. MeCallum (1983). "Piezoelectric crystals for mass and chemical measurements." The Analyst 108(1291).
Buttry, D. A. (1991). Applications of the quartz crystal microbalance to electrochemistry. Electroanalytical Chemistry. A. J. Bard. New York, Marcel Dekker, Inc. 17: 1-86.
Czanderna, A. W. and Lu (1984). Introduction, history, and overview of applications of piezoelectric quartz crystal microbalances. Applications of piezoelectric guartz crystal microbalances. C. Lu and A. W. Czanderna. Amsterdam, Elsevier. 7: 1-18.
Guilbaut, G. G. (1980). "Uses of the piezoelectric crystal detector in analytical chemistry." Ion Selective Electrode Review 2: 3-16.
Kaushik, D., et al. (1981). "Thin film thickness monitoring using a doubly oscillating quartz crystal and measurement of growth rate." Journal of Physics E: Scientific Instruments 14: 345-348.
Lu, C. (1 984). Theory and practice of the quartz crystal microbalance. Applications of piezoelectric quartz crystal microbalance. C. Lu and A. W. Czanderna. Amsterdam, Elsevier. 7: 19-61.
Rodahl, M., et al. (1 996). "QCM operation in liquids: An explanation of measured variations in frequency and Q factor with liquid conductivity." Analytical Chemistry 68(13): 2219-2227.
Rodahl, M. and Kasemo (1997). "QCM frequency and dissipation factor response to localized liquid deposits." Sensors & Actuators B 37: 111-116.

Claims

11CLAIMS
1. A piezoelectric oscillator comprising a piezoelectric part having at least one main surface and at least a pair of exciting electrodes which can drive two or more oscillators of said piezoelectric crystal to resonance, characterized in that at least two of said oscillators have no overlapping resonance frequency peaks.
2. Device according to claim 1, characterized in that the piezoelectric part has an electrode on each side of the crystal which covers more than one oscillators to drive more than one or more oscillators.
3. Device according to claim 1, characterized in that the piezoelectric part consists of different types piezoelectric materials, such as quartz, and different crystallographic cuts, such as AT- and BT- crystallographic cuts.
4. Device according to claim 1, characterized in that the piezoelectric part is structured on one side only.
5. Device according to claim 1, characterized in that the piezoelectric part is used in gas.
6. Device according to claim 1, characterized in that the piezoelectric part is used in vacuo.
7. Device according to claim 1, characterized in that the piezoelectric part (5, 55, 75, 85, 95) is used in liquid phase. 12
8. Device according to one or more of the preceding claims, characterized in that at least one of the resonance frequency of the oscillators and/or dissipation factor is registered.
9. Device according to one or more of the preceding claims, characterized in that at least two of the resonance frequency (-ies) and/or dissipation factors of the oscillators are utilized to identify one or more substances of a sample by means of pattern recognition.
10. Device according to one or more of the preceding claims, characterized in that at least two of the oscillators have a surface treatment differing from the other.
11. Device according to one or more of the preceding claims, characterized in that one registration utilizes basic tone frequency as well as harmonics and/or different oscillation amplitude(-s) of at least one of the oscillators to register properties of a sample which is frequency dependent and/or amplitude dependent.
PCT/SE1999/000051 1998-01-23 1999-01-15 Device at piezoelectric crystal oscillator WO1999040397A1 (en)

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Application Number Priority Date Filing Date Title
AU24449/99A AU2444999A (en) 1998-01-23 1999-01-15 Device at piezoelectric crystal oscillator

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SE9800189A SE9800189L (en) 1998-01-23 1998-01-23 Device at a piezoelectric crystal oscillator
SE9800189-4 1998-01-23

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2410645A (en) * 2004-01-30 2005-08-03 Smiths Group Plc Multi resonant frequency transducer for acoustic level gauging
WO2011029593A1 (en) 2009-09-09 2011-03-17 Andreas Hettich Gmbh & Co. Kg Device for testing for hemostasis
WO2011033285A1 (en) 2009-09-18 2011-03-24 Cambridge Enterprise Limited Apparatus and method for detecting target species in an analyte
WO2012076827A1 (en) 2010-12-10 2012-06-14 Universite De Technologie De Troyes System and method for detecting biological or chemical species involving a qcm transducer

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2100950A (en) * 1981-06-23 1983-01-06 Standard Telephones Cables Ltd Crystal filter
US4547748A (en) * 1984-08-13 1985-10-15 The United States Of America As Represented By The Secretary Of The Army Frequency synthesizer using a matrix of selectable piezoelectric resonators
US4596697A (en) * 1984-09-04 1986-06-24 The United States Of America As Represented By The Secretary Of The Army Chemical sensor matrix
US4760351A (en) * 1986-08-22 1988-07-26 Northern Illinois University Multiple oscillator device having plural quartz resonators in a common quartz substrate
US4991151A (en) * 1987-04-28 1991-02-05 Edap International Elastic pulse generator having a desired predetermined wave form
US4999284A (en) * 1988-04-06 1991-03-12 E. I. Du Pont De Nemours And Company Enzymatically amplified piezoelectric specific binding assay
US5112342A (en) * 1989-03-09 1992-05-12 U.S. Philips Corp. Depilator
US5200714A (en) * 1990-07-07 1993-04-06 Asahi Dempa Co., Ltd. Crystal oscillator with quartz vibrator having temperature detecting faculty, quartz vibrator for use therein, and method of measuring temperature using quartz vibrator
WO1996035103A1 (en) * 1995-05-04 1996-11-07 Michael Rodahl A piezoelectric crystal microbalance device
EP0783205A1 (en) * 1995-07-27 1997-07-09 Daishinku Corporation Multiple-mode piezoelectric filter

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2100950A (en) * 1981-06-23 1983-01-06 Standard Telephones Cables Ltd Crystal filter
US4547748A (en) * 1984-08-13 1985-10-15 The United States Of America As Represented By The Secretary Of The Army Frequency synthesizer using a matrix of selectable piezoelectric resonators
US4596697A (en) * 1984-09-04 1986-06-24 The United States Of America As Represented By The Secretary Of The Army Chemical sensor matrix
US4760351A (en) * 1986-08-22 1988-07-26 Northern Illinois University Multiple oscillator device having plural quartz resonators in a common quartz substrate
US4991151A (en) * 1987-04-28 1991-02-05 Edap International Elastic pulse generator having a desired predetermined wave form
US4999284A (en) * 1988-04-06 1991-03-12 E. I. Du Pont De Nemours And Company Enzymatically amplified piezoelectric specific binding assay
US5112342A (en) * 1989-03-09 1992-05-12 U.S. Philips Corp. Depilator
US5200714A (en) * 1990-07-07 1993-04-06 Asahi Dempa Co., Ltd. Crystal oscillator with quartz vibrator having temperature detecting faculty, quartz vibrator for use therein, and method of measuring temperature using quartz vibrator
WO1996035103A1 (en) * 1995-05-04 1996-11-07 Michael Rodahl A piezoelectric crystal microbalance device
EP0783205A1 (en) * 1995-07-27 1997-07-09 Daishinku Corporation Multiple-mode piezoelectric filter

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2410645A (en) * 2004-01-30 2005-08-03 Smiths Group Plc Multi resonant frequency transducer for acoustic level gauging
WO2011029593A1 (en) 2009-09-09 2011-03-17 Andreas Hettich Gmbh & Co. Kg Device for testing for hemostasis
DE102009040880A1 (en) 2009-09-09 2011-03-31 Andreas Hettich Gmbh & Co. Kg Apparatus for performing hemostasis tests
WO2011033285A1 (en) 2009-09-18 2011-03-24 Cambridge Enterprise Limited Apparatus and method for detecting target species in an analyte
WO2012076827A1 (en) 2010-12-10 2012-06-14 Universite De Technologie De Troyes System and method for detecting biological or chemical species involving a qcm transducer

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SE9800189L (en) 1999-07-24
SE9800189D0 (en) 1998-01-23

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