EP0830589A1 - Integrated sensor - Google Patents

Integrated sensor

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Publication number
EP0830589A1
EP0830589A1 EP96916244A EP96916244A EP0830589A1 EP 0830589 A1 EP0830589 A1 EP 0830589A1 EP 96916244 A EP96916244 A EP 96916244A EP 96916244 A EP96916244 A EP 96916244A EP 0830589 A1 EP0830589 A1 EP 0830589A1
Authority
EP
European Patent Office
Prior art keywords
sensing device
gas sensing
mass measurement
conductimetric
organic polymer
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP96916244A
Other languages
German (de)
French (fr)
Inventor
Peter Alfred Payne
Krishna Chandra Persaud
Richard Mark Dowdeswell
Mohammed El Hassan Amrani
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Osmetech PLC
Original Assignee
Aromascan PLC
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 Aromascan PLC filed Critical Aromascan PLC
Publication of EP0830589A1 publication Critical patent/EP0830589A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • G01N33/0031—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array
    • G01N33/0032—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array using two or more different physical functioning modes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
    • G01N27/126—Composition of the body, e.g. the composition of its sensitive layer comprising organic polymers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/02—Analysing fluids
    • G01N29/022—Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/025—Change of phase or condition
    • G01N2291/0256—Adsorption, desorption, surface mass change, e.g. on biosensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/02863—Electric or magnetic parameters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0423—Surface waves, e.g. Rayleigh waves, Love waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0426—Bulk waves, e.g. quartz crystal microbalance, torsional waves

Definitions

  • This invention relates to gas sensors, in particular to gas sensors which combine mass measurement and conductimetric detection facilities, thereby permitting two transduction techniques to be applied to a single sensor.
  • Quartz resonator sensors consist of a piezoelectric quartz crystal oscillator coated with a sensing membrane.
  • SAW devices consist of a piezoelectric substrate (such as quartz) having interdigitated electrodes fabricated thereon, and a thin film coating of a sensitive material.
  • a radio frequency voltage is applied across the electrodes which leads to the formation of a Rayleigh surface acoustic wave, the frequency of which is perturbed by the adsorption of gas due to the attendant increase in mass of the coating.
  • SAW devices can be operated at higher frequencies than quartz resonator devices resulting in improvements in sensitivity.
  • the selectivity of the sensor is determined by the coating material, which is typically a polymer that shows absorptive characteristics that are useful for the range of molecules to be detected.
  • the coating material typically a polymer that shows absorptive characteristics that are useful for the range of molecules to be detected.
  • Other materials have also been employed as coatings for quartz resonators, such as celluloses, gas chromatographic stationary phase materials and both natural and synthetic lipids.
  • Another type of gas sensor which is finding widespread application, involves the bridging of electrodes with semiconducting organic polymers (SOPs).
  • SOPs semiconducting organic polymers
  • the electrical properties of the polymer may be modified by the adsorption of gaseous species and therefore the presence of these species may be detected by monitoring the change in an electrical property accompanying the adsorption process.
  • the electrical property may be the dc resistance of the polymer (see, for example, K.C. Persaud and P. Pelosi, Gas sensors: towards an artificial nose, in "Sensors and Sensory Systems for Advanced Robots", NATO ASI Series: Series F: Computer and Systems Science, ed. P.
  • Sensors of this type offer a number of advantages including enhanced sensitivities compared to quartz resonator and SAW devices and rapid and reversible adsorption kinetics.
  • the "conductimetric" SOP based sensors and “mass measurement” sensors such as quartz resonators and SAWs may be regarded, to some extent, as complementary techniques. This is because the former, although possessing superior sensitivites, are only selective towards gases which adsorb onto the polymer and affect the electrical properties thereof. Such gases are generally polar molecules. The latter is selective toward all molecules which adsorb onto the active surface with an affinity which exceeds the inherent detection limit of the device.
  • the present invention provides an integrated sensor which combines both mass measurement and conductimetric transduction techniques in a single device.
  • the most relevant prior art in this regard appears to be constituted by a series of papers by JM Slater et al (see, for example, J.M. Slater, E.J. Watt, N.J. Freeman, I.P. May and D.J. Weir, Analyst, 117 (1992) 1265 and references therein) wherein a quartz resonator was coated with a SOP and mass measurements were made, augmented by conductimetric interrogation of a separate SOP sensor of the type described above.
  • gas sensing includes the detection of volatile species.
  • a gas sensing device comprising a mass measurement gas sensor coated with at least one layer of semiconducting organic polymer (SOP) and having both mass measurement and conductimetric transduction means.
  • SOP semiconducting organic polymer
  • the mass measurement gas sensor may be a quartz resonator device or a SAW device.
  • the conductimetric transduction means may comprise means for applying a dc electric signal across the layer or layers of SOP, and detection means for detecting changes in resistance.
  • the conductimetric transduction means may comprise means for applying an ac electric signal across the layer or layers of SOP, and detection means for detecting an impedance property.
  • the SOP may be deposited electrochemically, by oxidative chemical vapour deposition, or by spin or spray coating.
  • Figure 1 is a schematic diagram of the apparatus together with a view from above the SAW device.
  • Figure 2 is a view from below the SAW device.
  • Figures 1 and 2 depict a gas sensing device of the present invention comprising a mass measurement sensor 10 coated with a layer of SOP 12, and having both mass measurement transduction means 14 and conductimetric transduction means 16.
  • the mass measurement sensor 10 is a SAW device having interdigitated electrodes 18a, 18b fabricated onto a piezoelectric substrate 20 such as quartz.
  • the mass measurement transduction means 14 includes rf voltage applying means for applying said voltage across the elecrodes 18a, 18b.
  • the applied voltage produces a Rayleigh surface acoustic wave (i.e. a surface oscillation), the frequency of which is perturbed by changes in the mass of the sensor due to adsorption of gas onto the SOP coating.
  • This frequency shift produces a voltage phase shift which may be detected by phase sensitive detection means.
  • Said phase sensitive detection means may be part of the voltage applying means or a separate unit.
  • the sensor 10 may be connected to a reference sensor and the frequency difference measured.
  • the layer of SOP 12 bridges two electrodes 22a, 22b, and the conductimetric transduction means 16 includes means for applying an electric signal across these electrodes.
  • the electric signal may be a dc signal, in which instance the transduction means 16 also includes resistance measuring means (such as described in, for example, BA Gregory; "An Introduction to Electrical Instrumentation and Measurement Systems", 1982, MacMillen).
  • an ac electric signal may be applied, and an impedance property of the SOP layer 12, such as conductance, monitored.
  • a rf impedance analyser could serve as the conductimetric transduction means 16. In either instance the presence of a gas is detected by detecting the variation in the electrical property monitored caused by adsorption of the gas onto the polymer.
  • Data from both transduction techniques may be transmitted, via a suitable interface , to a computer 24 for display and analysis purposes.
  • the advantage of the present invention is that the complementary properties of two gas sensing methods are combined in one device; in particular this feature permits the detection of both polar and non-polar molecules.
  • the conductimetric method has relatively high sensitivity, but is only applicable to molecules which, in addition to being adsorbed onto the polymer, significantly affect the conductivity thereof. Generally speaking, such molecules are polar.
  • the mass measurement method requires only that there is significant adsorption, since the measured properties depend upon the mass of the adsorbed material, and therefore non-polar molecules - which are readily absorbed onto the surface of the SOP - may be detectable.
  • a single sensor may detect polar molecules at high sensitivities and, additionally, that hydrophobic interactions due to the adsorption of certain non-polar molecules will also be detectable by mass measurement techniques, even though the changes in SOP conductance associated therewith are of insufficient magnitude for detection by conventional SOP sensors.
  • the precise identity of molecules detectable by either method depends upon the nature of the SOP used. It should be noted that the results of the two transduction techniques - whether or not there is a significant response- can be used in combination to provide extra information on the nature of the gas detected.
  • the SOP layer may be deposited by any of the numerous techniques described in the literature, such as electrochemical or oxidative chemical vapour deposition, or by spin or spray coating. Numerous SOPs have previously been employed for gas sensing purposes, polypyrrole being perhaps the most commonly encountered example, and the present invention is not limited in scope in this respect.
  • the contact electrodes 22a, 22b may be bonded to the piezoelectric substrate - such is necessary if an electrochemical deposition is contemplated - or may be bonded or attached to the SOP itself.
  • a SOP coated quartz resonator device was produced by modification of a commercially available quartz resonator.
  • the resonator is a quartz wafer having a layer of aluminium of approximate thickness 0.02 ⁇ m deposited on both sides thereof. Aluminium of one face of the resonator was selectively removed by a hand painted etch comprising nitric, acetic and phosphoric acids. Polypyrrole was then deposited by an oxidative chemical vapour method over a substantial portion of the etched resonator surface.
  • the polypyrrole coating 36 extends for approximately 6mm, virtually from one side of the resonator 30 to another, and exhibits a resistance of ca. 10K ⁇ .
  • the resonator was then housed within a PTFE block and connected to a vapour rig of straightforward design.
  • the spring contact electrodes in contact with the aluminium coating 34 were connected to an impedance analyser and the reactance was measured around the resonant frequency (ca. 1845 KHz).
  • Figure 4 shows the effect of exposing the resonator to dry air 1, ethanol vapour 2 and toulene vapour 3 at a flow rate of 200 ml min "1 . Frequency shifts (with respect to the dry air valve) of -33.5 Hz ethanol and -18.5 Hz for toulene are observed.
  • Figure 5 shows the kinetic response of the resonator to a pulse of toulene vapour. A change of 1200% in the reactance (measured around 1844.91 KHz) is observed.
  • the frequency shift measurements are "mass measurements", because the observed perturbation of the resonant frequency is induced by the mass change due to adsorption of molecules with high affinity onto the polymer (although non-specific adsorption onto other regions of the resonator will likely play an as yet unquantified role).
  • Conductimetric measurements were also made by connecting the spring contact electrodes in contact with the polpyrrole coating 36 to a dc resistance measuring meter of conventional type.
  • the dc resistance of the resonator in a dry air atmosphere was 11.8 ⁇ , which rose to 13.1 ⁇ and 12.5 ⁇ on exposure to ethanol and toluene vapour respectively.
  • An improvement on the present arrangement would involve removal of part of the aluminium coating on one face of the resonator followed by patterning with a suitable gold electrode structure.
  • a polymer, or, if desired, an array of polymers could be deposited on and between the electrode structure.
  • Conventional wire bonding techniques could be used to connect to the electrode structure, whilst the spring loaded connection method would be retained for connection to the aluminium coatings.
  • arrays of quartz resonators or SAW devices, or combinations thereof, with different SOPs can be constructed. Patterns of responses from such arrays can be used to identify individual or complex mixtures of chemical species.

Abstract

There is disclosed a gas sensing device comprising a mass measurement gas sensor coated with at least one layer of semiconducting organic polymer and having both mass measurement and conductimetric transduction means.

Description

INTEGRATED SENSOR
This invention relates to gas sensors, in particular to gas sensors which combine mass measurement and conductimetric detection facilities, thereby permitting two transduction techniques to be applied to a single sensor.
The past decade has witnessed an upsurge of scientific and commercial interest in the development of sensors capable of detecting gases, vapours and odours. The result has been the emergence of a suite of detection techniques, possessing differing and often complementary characteristics.
Sensors based on quartz resonators and surface acoustic wave (SAW) devices may be referred to , broadly, as "mass measurement" techniques, since sensors of this kind are sensitive to, essentially, the mass of the gas adsorbed onto the active surface of the sensor. Quartz resonator sensors consist of a piezoelectric quartz crystal oscillator coated with a sensing membrane. In this instance, the increase in mass due to the adsorption of gaseous molecules onto the membrane results in a decrease in the resonant frequency : it is this frequency shift which is typically detected, although the response time constant may also be measured. SAW devices consist of a piezoelectric substrate (such as quartz) having interdigitated electrodes fabricated thereon, and a thin film coating of a sensitive material. A radio frequency voltage is applied across the electrodes which leads to the formation of a Rayleigh surface acoustic wave, the frequency of which is perturbed by the adsorption of gas due to the attendant increase in mass of the coating. SAW devices can be operated at higher frequencies than quartz resonator devices resulting in improvements in sensitivity.
In both instances the selectivity of the sensor is determined by the coating material, which is typically a polymer that shows absorptive characteristics that are useful for the range of molecules to be detected. Other materials have also been employed as coatings for quartz resonators, such as celluloses, gas chromatographic stationary phase materials and both natural and synthetic lipids.
Another type of gas sensor, which is finding widespread application, involves the bridging of electrodes with semiconducting organic polymers (SOPs). The electrical properties of the polymer may be modified by the adsorption of gaseous species and therefore the presence of these species may be detected by monitoring the change in an electrical property accompanying the adsorption process. The electrical property may be the dc resistance of the polymer (see, for example, K.C. Persaud and P. Pelosi, Gas sensors: towards an artificial nose, in "Sensors and Sensory Systems for Advanced Robots", NATO ASI Series: Series F: Computer and Systems Science, ed. P. Dario, Springer- Verlag, Berlin, 1988, pp 361-382 ) or an ac impedance property such as conductance (see, for example, UK Patent GB 2203553, assigned to the present applicants). Sensors of this type offer a number of advantages including enhanced sensitivities compared to quartz resonator and SAW devices and rapid and reversible adsorption kinetics.
The "conductimetric" SOP based sensors and "mass measurement" sensors such as quartz resonators and SAWs may be regarded, to some extent, as complementary techniques. This is because the former, although possessing superior sensitivites, are only selective towards gases which adsorb onto the polymer and affect the electrical properties thereof. Such gases are generally polar molecules. The latter is selective toward all molecules which adsorb onto the active surface with an affinity which exceeds the inherent detection limit of the device.
The present invention provides an integrated sensor which combines both mass measurement and conductimetric transduction techniques in a single device. The most relevant prior art in this regard appears to be constituted by a series of papers by JM Slater et al (see, for example, J.M. Slater, E.J. Watt, N.J. Freeman, I.P. May and D.J. Weir, Analyst, 117 (1992) 1265 and references therein) wherein a quartz resonator was coated with a SOP and mass measurements were made, augmented by conductimetric interrogation of a separate SOP sensor of the type described above.
It is understood that "gas sensing" includes the detection of volatile species.
According to the invention there is provided a gas sensing device comprising a mass measurement gas sensor coated with at least one layer of semiconducting organic polymer (SOP) and having both mass measurement and conductimetric transduction means.
The mass measurement gas sensor may be a quartz resonator device or a SAW device.
The conductimetric transduction means may comprise means for applying a dc electric signal across the layer or layers of SOP, and detection means for detecting changes in resistance.
Alternatively, the conductimetric transduction means may comprise means for applying an ac electric signal across the layer or layers of SOP, and detection means for detecting an impedance property.
The SOP may be deposited electrochemically, by oxidative chemical vapour deposition, or by spin or spray coating.
Contact electrodes may be bonded onto the SOP. Embodiments of the invention will now be described with reference to the accompanying drawings, in which:-
Figure 1 is a schematic diagram of the apparatus together with a view from above the SAW device; and
Figure 2 is a view from below the SAW device.
Figures 1 and 2 depict a gas sensing device of the present invention comprising a mass measurement sensor 10 coated with a layer of SOP 12, and having both mass measurement transduction means 14 and conductimetric transduction means 16.
In one embodiment the mass measurement sensor 10 is a SAW device having interdigitated electrodes 18a, 18b fabricated onto a piezoelectric substrate 20 such as quartz. The mass measurement transduction means 14 includes rf voltage applying means for applying said voltage across the elecrodes 18a, 18b. The applied voltage produces a Rayleigh surface acoustic wave (i.e. a surface oscillation), the frequency of which is perturbed by changes in the mass of the sensor due to adsorption of gas onto the SOP coating. This frequency shift produces a voltage phase shift which may be detected by phase sensitive detection means. Said phase sensitive detection means may be part of the voltage applying means or a separate unit. In order to compensate for, eg, temperature and pressure variations the sensor 10 may be connected to a reference sensor and the frequency difference measured.
The layer of SOP 12 bridges two electrodes 22a, 22b, and the conductimetric transduction means 16 includes means for applying an electric signal across these electrodes. The electric signal may be a dc signal, in which instance the transduction means 16 also includes resistance measuring means (such as described in, for example, BA Gregory; "An Introduction to Electrical Instrumentation and Measurement Systems", 1982, MacMillen). Alternatively, an ac electric signal may be applied, and an impedance property of the SOP layer 12, such as conductance, monitored. In this latter embodiment a rf impedance analyser could serve as the conductimetric transduction means 16. In either instance the presence of a gas is detected by detecting the variation in the electrical property monitored caused by adsorption of the gas onto the polymer.
Data from both transduction techniques may be transmitted, via a suitable interface , to a computer 24 for display and analysis purposes.
The advantage of the present invention is that the complementary properties of two gas sensing methods are combined in one device; in particular this feature permits the detection of both polar and non-polar molecules. The conductimetric method has relatively high sensitivity, but is only applicable to molecules which, in addition to being adsorbed onto the polymer, significantly affect the conductivity thereof. Generally speaking, such molecules are polar. The mass measurement method requires only that there is significant adsorption, since the measured properties depend upon the mass of the adsorbed material, and therefore non-polar molecules - which are readily absorbed onto the surface of the SOP - may be detectable. Thus it is contemplated that a single sensor may detect polar molecules at high sensitivities and, additionally, that hydrophobic interactions due to the adsorption of certain non-polar molecules will also be detectable by mass measurement techniques, even though the changes in SOP conductance associated therewith are of insufficient magnitude for detection by conventional SOP sensors. The precise identity of molecules detectable by either method depends upon the nature of the SOP used. It should be noted that the results of the two transduction techniques - whether or not there is a significant response- can be used in combination to provide extra information on the nature of the gas detected. It should also be noted that whilst the foregoing discussion focusses upon the detection of a single gaseous species, the detection of mixtures of gases, vapours and odours, by a single sensor or by a plurality of sensors, is within the scope of the invention.
The SOP layer may be deposited by any of the numerous techniques described in the literature, such as electrochemical or oxidative chemical vapour deposition, or by spin or spray coating. Numerous SOPs have previously been employed for gas sensing purposes, polypyrrole being perhaps the most commonly encountered example, and the present invention is not limited in scope in this respect.
The contact electrodes 22a, 22b may be bonded to the piezoelectric substrate - such is necessary if an electrochemical deposition is contemplated - or may be bonded or attached to the SOP itself.
In a second embodiment of the invention a SOP coated quartz resonator device was produced by modification of a commercially available quartz resonator. The resonator is a quartz wafer having a layer of aluminium of approximate thickness 0.02 μm deposited on both sides thereof. Aluminium of one face of the resonator was selectively removed by a hand painted etch comprising nitric, acetic and phosphoric acids. Polypyrrole was then deposited by an oxidative chemical vapour method over a substantial portion of the etched resonator surface. The resulting quartz resonator 30, shown in Figure 3, this comprises a quartz wafer 32, an aluminium coating 34 and a polypyrrole coating 36. The polypyrrole coating 36 extends for approximately 6mm, virtually from one side of the resonator 30 to another, and exhibits a resistance of ca. 10KΩ.
Electrical connections are made using commercially supplied spring contact electrodes (not shown). With such electrodes, the quartz wafer 32 is pressed between the windings of the spring contact. The contacts originally supplied with the resonator were positioned in contact with the aluminium coating 34 towards the corners of the upper wafer edge ("upper" being defined with respect to Figure 3). Identical contacts, cannibalised from another commercial quartz resonator device, were similarly placed on the lower wafer edge, in contact with the polypyrrole coating 36.
The resonator was then housed within a PTFE block and connected to a vapour rig of straightforward design. The spring contact electrodes in contact with the aluminium coating 34 were connected to an impedance analyser and the reactance was measured around the resonant frequency (ca. 1845 KHz). Figure 4 shows the effect of exposing the resonator to dry air 1, ethanol vapour 2 and toulene vapour 3 at a flow rate of 200 ml min"1. Frequency shifts (with respect to the dry air valve) of -33.5 Hz ethanol and -18.5 Hz for toulene are observed. Figure 5 shows the kinetic response of the resonator to a pulse of toulene vapour. A change of 1200% in the reactance (measured around 1844.91 KHz) is observed.
The frequency shift measurements are "mass measurements", because the observed perturbation of the resonant frequency is induced by the mass change due to adsorption of molecules with high affinity onto the polymer (although non-specific adsorption onto other regions of the resonator will likely play an as yet unquantified role). Conductimetric measurements were also made by connecting the spring contact electrodes in contact with the polpyrrole coating 36 to a dc resistance measuring meter of conventional type. The dc resistance of the resonator in a dry air atmosphere was 11.8Ω, which rose to 13.1 Ω and 12.5Ω on exposure to ethanol and toluene vapour respectively. Thus it is possible to extract responses from two complementary transduction techniques using a single quartz resonator.
An improvement on the present arrangement would involve removal of part of the aluminium coating on one face of the resonator followed by patterning with a suitable gold electrode structure. A polymer, or, if desired, an array of polymers could be deposited on and between the electrode structure. Conventional wire bonding techniques could be used to connect to the electrode structure, whilst the spring loaded connection method would be retained for connection to the aluminium coatings.
Similarly, arrays of quartz resonators or SAW devices, or combinations thereof, with different SOPs can be constructed. Patterns of responses from such arrays can be used to identify individual or complex mixtures of chemical species.

Claims

1. A gas sensing device comprising a mass measurement gas sensor coated with at least one layer of semiconducting organic polymer and having both mass measurement and conductimetric transduction means.
2. A gas sensing device according to claim 1 in which the mass measurement gas sensor is a quartz resonator device.
3. A gas sensing device according to claim 1 in which the mass measurement gas sensor is a SAW device.
4. A gas sensing device according to any one of claims 1 to 3 in which the conductimetric transduction means comprise means for applying a dc electric signal across the layer or layers of semiconducting organic polymer, and detection means for detecting changes in resistance.
5. A gas sensing device according to any one of claims 1 to 3 in which the conductimetric transduction means comprise means for applying an ac electric signal across the layer or layers of semiconducting organic polymer, and detection means for detecting an impedance property.
6. A gas sensing device according to any of the previous claims in which the semiconducting organic polymer is deposited electrochemically, by oxidative chemical vapour deposition, by spin coating or by spray coating.
7. A gas sensing device according to any of the previous claims in which contact electrodes are bonded onto the semiconducting organic polymer.
EP96916244A 1995-06-09 1996-06-06 Integrated sensor Withdrawn EP0830589A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GBGB9511734.7A GB9511734D0 (en) 1995-06-09 1995-06-09 Intergrated sensor
GB9511734 1995-06-09
PCT/GB1996/001339 WO1996042011A1 (en) 1995-06-09 1996-06-06 Integrated sensor

Publications (1)

Publication Number Publication Date
EP0830589A1 true EP0830589A1 (en) 1998-03-25

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AU (1) AU5906796A (en)
GB (1) GB9511734D0 (en)
WO (1) WO1996042011A1 (en)

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EP0935750B1 (en) 1996-11-01 2002-04-24 Bp Oil International Limited Testing device and method of use
DE19706486B4 (en) * 1997-02-19 2004-02-05 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Sensor device for determining the aging state of liquid media
GB9820009D0 (en) * 1998-09-14 1998-11-04 Mini Agriculture & Fisheries Artificial olfactory sensing system
US6881585B1 (en) 2000-03-06 2005-04-19 General Electric Company Method and apparatus for rapid screening of volatiles
WO2005052570A1 (en) * 2003-11-13 2005-06-09 Technische Universität Clausthal Sensor, sensor arrangement, and measuring method
WO2006006587A1 (en) * 2004-07-12 2006-01-19 Niigata University Gas detection method and gas sensor
KR101355371B1 (en) 2012-05-29 2014-01-27 포항공과대학교 산학협력단 Quartz Crystal Microbalance Sensors for Simultaneously Measurement of Electrical Properties and Mass Changes

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US4681855A (en) * 1985-08-05 1987-07-21 The United States Of America As Represented By The Secretary Of Commerce Humidity sensing and measurement employing halogenated organic polymer membranes
US4674320A (en) * 1985-09-30 1987-06-23 The United States Of America As Represented By The United States Department Of Energy Chemoresistive gas sensor
GB9116360D0 (en) * 1991-07-29 1991-09-11 Neotronics Ltd Device for sensing volatile materials
JP3139562B2 (en) * 1992-02-17 2001-03-05 日本電信電話株式会社 Odor quality sensing method

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AU5906796A (en) 1997-01-09
GB9511734D0 (en) 1995-08-02
WO1996042011A1 (en) 1996-12-27

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