WO1999026061A1 - Capteur de gaz - Google Patents

Capteur de gaz Download PDF

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Publication number
WO1999026061A1
WO1999026061A1 PCT/GB1998/003356 GB9803356W WO9926061A1 WO 1999026061 A1 WO1999026061 A1 WO 1999026061A1 GB 9803356 W GB9803356 W GB 9803356W WO 9926061 A1 WO9926061 A1 WO 9926061A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrodes
array
interrogation means
gas sensor
pair
Prior art date
Application number
PCT/GB1998/003356
Other languages
English (en)
Inventor
Peter Alfred Payne
Original Assignee
Osmetech 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 Osmetech Plc filed Critical Osmetech Plc
Publication of WO1999026061A1 publication Critical patent/WO1999026061A1/fr

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Classifications

    • 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
    • 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

Definitions

  • This invention relates to gas sensors and methods for the manufacture of same, with particular reference to gas sensors which employ conducting organic polymers as the active gas sensing medium.
  • COPs conducting organic polymers
  • Polypyrrole and substituted derivatives thereof are well known (see, for example, International Publications WO 96/00384, WO 96/00383, and K C Persaud and P Pelosi in "Sensors and Sensory Systems for an Electronic Nose", pp 237-256, eds J W Gardner and P N Bartlett, 1992, Kluwer Academic Publishers, Netherlands, and references therein).
  • a single gas sensor is produced by depositing a layer of COP between a pair of electrodes, the sensor being operated as a chemiresistor, i.e.
  • the presence of a gas is detected by measuring variations in the dc resistance of the COP, these variations being caused by adsorption of the gas onto the COP.
  • a plurality of sensors it is common for a plurality of sensors to be incorporated into a single gas sensing device. Each sensor has a different COP and/or a different dopant anion, and thus each sensor displays different response characteristics.
  • the use of such arrays of COP sensors allows gases, vapours and odours to be recognised by the response "fingerprint" - the pattern of sensor responses across the array. In this manner, an impressive range of gases can be detected and identified - either individually or as components of mixtures - with good sensitivity.
  • the spacing between the electrodes is relatively large - preferably 100 ⁇ m or greater. This is because larger electrode spacings permit a greater surface area of COP to be presented to a gas, resulting in a higher threshold for saturation of the response of the sensor.
  • International Publication WO 93/03355 discloses gas sensors having COP deposited on and between a pair of electrodes having a spacing in the range 7 to 25 ⁇ m.
  • the present invention overcomes the aforementioned problems and disadvantages by providing a COP gas sensor which may be manufactured by a single electrodeposition step, but which permits large gaps to be bridged by COP.
  • a method for fabricating a gas sensor comprising the steps of : providing a number of spaced apart electrodes disposed on a substrate, the number of electrodes being three or greater; electrochemically depositing at least one COP on and between said number of electrodes so that the electrodes are electrically connected to one another by the deposited at least one COP; providing sensor interrogation means for measuring one or more electrical properties of the at least one polymer; and connecting said sensor interrogation means to a single pair of electrodes.
  • the interrogation means may be connected to the first and last electrodes in the array.
  • the spacings between adjacent electrodes may be less than 25 ⁇ m, preferably in the range 1 to 15 ⁇ m.
  • the pair of electrodes connected to the interrogation means may be separated by greater than 100 ⁇ m, preferably greater than 200 ⁇ m.
  • the number of electrodes in the array may be ten or greater, preferably twenty or greater.
  • the spacings between adjacent electrodes summed between the pair of electrodes connected to the interrogation means may be greater than 50 ⁇ m, preferably greater than 100 ⁇ m, most preferably greater than 200 ⁇ m.
  • the interrogation means may measure the dc resistance between the pair- of electrodes.
  • a gas sensor comprising : an array of spaced apart electrodes disposed on a substrate, the number of electrodes in the array being three or greater; at least one COP deposited on and between said number of electrodes so that the electrodes are electrically connected to one another; and sensor interrogation means for measuring one or more electrical properties of the at least one COP, the interrogation means being connected to a single pair of electrodes.
  • the interrogation means may be connected to the first and last electrodes in the array.
  • the spacings between adjacent electrodes may be less than 25 ⁇ m, preferably in the range 1 to 15 ⁇ m.
  • the pair of electrodes connected to the interrogation means may be separated by greater than 100 ⁇ m, preferably greater than 200 ⁇ m.
  • the number of electrodes in the array may be ten or greater, preferably twenty or greater.
  • the spacings between adjacent electrodes summed between the pair of electrodes connected to the interrogation means may be greater than 50 ⁇ m, preferably greater than 100 ⁇ m, most preferably greater than 200 ⁇ m.
  • the interrogation means may comprise means adapted to measure the dc resistance between the pair of electrodes.
  • a gas sensor according to the second aspect of the invention in the detection of gases.
  • Figure 1 shows a diagrammatic view of (a) an electrode array configured for deposition of COP and (b) the gas sensor produced by deposition of the COP;
  • Figure 2 shows a diagrammatic plan view of (a) an electrode array configured in an alternative way for deposition of COP and (b) the electrode array after deposition of the COP.
  • Figures 1 and lb depict stages in a method for fabricating a gas sensor comprising the steps of : providing an array 10 of spaced apart electrodes 12 disposed on a substrate 14, the number of electrodes 12 in the array being three or greater; electrochemically depositing at least one COP 16 on and between said electrodes 12 so that the electrodes are electrically connected to one another by the deposited COP 16; providing sensor interrogation means 18 for measuring one or more electrical properties of the COP; and connecting said sensor interrogation means 18 to a single pair of electrodes 12a, 12b.
  • a gas sensor may be produced having a large spacing between the two electrodes interrogated by the sensor interrogation means ⁇ 18.
  • the gas sensor is fabricated by a single electrode deposition step (if a single layer of COP is employed in the sensor).
  • the invention solves the problem discussed previously, namely that it is usually not possible to produce useful gas sensors by electrochemically depositing COP between electrodes having spacings in excess of ca. 20 ⁇ m.
  • the solution is to provide an array of electrodes in which adjacent electrodes are spaced apart by a distance commensurate with the properties of the COP to be deposited, and to electrochemically deposit COP on and between the electrodes in the array.
  • the electrochemical deposition is most conveniently performed whilst holding some or all of the electrodes in the array at the same potential, by providing suitable conductive tracks 20 which electrically connect to electrodes 12. Alternatively, it is possible to hold the electrodes at a constant current level. After the electrodeposition step is performed, most of the conductive tracks 20 are removed, so that the electrodes 12 in the array 10 are only electrically connected by the COP 16.
  • interrogation means is connected to the first 12a and last 12b electrodes in the array, as shown in Figure lb, thereby maximising the spacing between the pair of electrodes.
  • Slater et al discloses a gas sensor in which COP is deposited over eight microband electrodes of 5 ⁇ m width and 5 ⁇ m separation. After electrodeposition of COP, connection is made to the first five electrodes with a multiplexer, enabling measurement to be made between selected pairs of electrodes, i.e. in selected zones of the sensor. Indeed, the purpose of the device of Slater et al is that a matrix of responses of different pairs of electrodes is compiled as a function of response time, in order to improve discrimination between gases. There is no indication in Slater et al that measurements between a single pair of electrodes might be advantageously obtained.
  • the maximum gap between the interrogated electrodes in Slater et al is 35 ⁇ m, of which 20 ⁇ m is COP and 15 ⁇ m comprises "intermediate" electrodes.
  • the spacings between adjacent electrodes are usually less than 25 ⁇ m, preferably in the range 1 to 15 ⁇ m.
  • the actual spacing employed depends on the particular COP used - the purpose is to use an electrode spacing across which the COP in question can be conveniently and usefully deposited.
  • the pair of electrodes connected to the interrogation means are typically separated by greater than 100 ⁇ m, preferably greater than 200 ⁇ m. This implies that the number of electrodes in the array is ten or greater, preferably twenty or greater. In terms of sensor response, a more meaningful quantity than the separation between the pair of electrodes connected to the interrogation means may be obtained by subtracting the sum of the widths of the intermediate electrodes from the separation between the pair of electrodes connected to the interrogation means. This approach provides the length of COP between the interrogated electrodes which is not supported by an electrode.
  • an array comprising ten electrodes of width 10 ⁇ m, the separation between adjacent electrodes being 20 ⁇ m, and the first and the tenth electrode being connected to the interrogation means.
  • the separation between the interrogated pair of electrodes of 260 ⁇ m, whilst the spacings between adjacent electrodes, summed between the pair of electrodes connected to the interrogation means, is 180 ⁇ m.
  • the spacings between adjacent electrodes, summed between the pair of electrodes connected to the interrogation means may be greater than 50 ⁇ m, preferably greater than 100 ⁇ m, most preferably greater than 200 ⁇ m.
  • the electrochemical deposition of COP is performed using techniques well known in the art. In Figure la, the array of electrodes is connected for electrochemical deposition in an interdigitated fashion.
  • a counter electrode is required, although it is possible to hold the two sets of electrodes in the interdigitated array at different potentials with respect to the counter electrode (see, for example, J. Phys. Chem 95 (1991) 9042). It is possible in addition to use a reference electrode.
  • Figure 2a Another embodiment is shown in Figure 2a, where the conductive tracks 20 are deposited so as to electrically connect all electrodes 12 in the array. The array functions as a working electrode during electrode position of COP. Suitable auxiliary electrodes (not shown) are employed, and again it is possible to use a reference electrode.
  • substrates include silicon, glass and ceramic materials.
  • the fabrication of the electrodes and conductive tracks is conveniently performed using photolithographic techniques.
  • the interrogation means comprises means adapted to measure the dc resistance between the pair of electrodes. It is also possible to employ interrogation means which apply and measure quantities related to a time varying electrical signal, such as an ac signal or a pseudo random binary signal (see EP 0 286 307 and International Publications WO 97/19349 and WO 97/18467).

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Pathology (AREA)
  • Immunology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Biochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Combustion & Propulsion (AREA)
  • Medicinal Chemistry (AREA)
  • Food Science & Technology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

L'invention se rapporte à un procédé de fabrication d'un capteur de gaz consistant à utiliser un réseau d'électrodes disposées à distance les unes des autres sur un substrat, le nombre de ces électrodes étant supérieur ou égal à trois; à déposer par processus électrochimique au moins un polymère organique conducteur sur et entre les électrodes de sorte que celles-ci soient reliées électriquement les unes aux autres par ledit polymère organique conducteur; à équiper le capteur d'un organe d'interrogation pour mesurer une ou plusieurs caractéristiques électriques dudit polymère et à relier ledit organe d'interrogation du capteur à une unique paire d'électrodes.
PCT/GB1998/003356 1997-11-13 1998-11-10 Capteur de gaz WO1999026061A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9723845.5 1997-11-13
GBGB9723845.5A GB9723845D0 (en) 1997-11-13 1997-11-13 6568471001

Publications (1)

Publication Number Publication Date
WO1999026061A1 true WO1999026061A1 (fr) 1999-05-27

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1998/003356 WO1999026061A1 (fr) 1997-11-13 1998-11-10 Capteur de gaz

Country Status (2)

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GB (1) GB9723845D0 (fr)
WO (1) WO1999026061A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1700103A2 (fr) * 2003-12-11 2006-09-13 The Aerospace Corporation Capteurs a nanofibres polymeres conductrices
CN104792847A (zh) * 2015-03-31 2015-07-22 广西智通节能环保科技有限公司 一种碳纳米管金属复合物气体传感器

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4761710A (en) * 1987-06-23 1988-08-02 Industrial Technology Research Institute Polyimide capacitive humidity sensing element
WO1993003355A1 (fr) * 1991-07-29 1993-02-18 Neotronics Limited Dispositif de detection de produits volatils
WO1996000383A1 (fr) * 1994-06-23 1996-01-04 Aromascan Plc Polymeres organiques semi-conducteurs pour des detecteurs de gaz

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4761710A (en) * 1987-06-23 1988-08-02 Industrial Technology Research Institute Polyimide capacitive humidity sensing element
WO1993003355A1 (fr) * 1991-07-29 1993-02-18 Neotronics Limited Dispositif de detection de produits volatils
WO1996000383A1 (fr) * 1994-06-23 1996-01-04 Aromascan Plc Polymeres organiques semi-conducteurs pour des detecteurs de gaz

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1700103A2 (fr) * 2003-12-11 2006-09-13 The Aerospace Corporation Capteurs a nanofibres polymeres conductrices
EP1700103A4 (fr) * 2003-12-11 2007-04-18 Aerospace Corp Capteurs a nanofibres polymeres conductrices
CN104792847A (zh) * 2015-03-31 2015-07-22 广西智通节能环保科技有限公司 一种碳纳米管金属复合物气体传感器

Also Published As

Publication number Publication date
GB9723845D0 (en) 1998-01-07

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