CA2201359A1 - Electrochemical oxygen sensor - Google Patents
Electrochemical oxygen sensorInfo
- Publication number
- CA2201359A1 CA2201359A1 CA002201359A CA2201359A CA2201359A1 CA 2201359 A1 CA2201359 A1 CA 2201359A1 CA 002201359 A CA002201359 A CA 002201359A CA 2201359 A CA2201359 A CA 2201359A CA 2201359 A1 CA2201359 A1 CA 2201359A1
- Authority
- CA
- Canada
- Prior art keywords
- sensor
- electrode
- oxygen
- layer
- substrate
- 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.)
- Abandoned
Links
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
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/404—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors
Abstract
An electrochemical oxygen sensor comprises an impermeable substrate and a plurality of conductive layers applied thereto by thick film deposition. At least one conductive layer comprises an electrode and a conductor connected to the electrode. The electrode may have a covering layer of an ion exchange polymer.
Description
~ W096/10174 - ~~ ~ PCTI~b951~2299 ~ 2 0 1 3 ~ 9 ELECTROCHEMICAL OXYGEN SENSOR
This invention relates to an electrochemical oxygen sensor adapted to detect gaseous or dissolved oxygen. The sensor may also detect other reducible chemical species. The invention also relates to manufacture of such sensors by thick layer deposition including printing techniques.
Conventional oxygen sensors are constructed ~rom a multiplicity of components in the form of a reusable Clark cell. Clark sensors are expensive to construct and require ~requent maintenance by skilled technicians. In particular the electrolyte gel and gas permeable membrane may need regular attention.
According to a first aspect of the present invention an electrochemical oxygen sensor comprises an impermeable substrate and a plurality of conductive layers applied thereto by thick film deposition, at least one conductive layer compriæing an electrode and a conduc~or connected to the electrode.
A sensor in accordance with this invention can be manufactured economically by screen printing or other lithographic techniques. Electrosensors may be disposable before maintenance becomes necessary. Miniaturisation of a sensor is facilitated. The sensors can be fabricated as micro-electrode arrays as disclosed in WO91/08474. The active area of the sensor may be manufactured by printing or ink jet methods and appropriate layers may be applied as described below so that the sensor can detect oxygen and reducible species in aqueous or other condensed phases. Coupling the oxygen sensor to other reagents that either consume or release oxygen, for example enzymes, allows detection of a wide range of analytes.
Sensors in accordance with the present invention have the advantage that it is not essential to provide a membrane as must be used in conventional Clark cells. This simplifies manufacture and enhances the sensitivity of the sensors.
WO96/10174 ~ 2 0 ~ 3 5 9 ~ ~b~S/02299 ~
This invention relates to an electrochemical oxygen sensor adapted to detect gaseous or dissolved oxygen. The sensor may also detect other reducible chemical species. The invention also relates to manufacture of such sensors by thick layer deposition including printing techniques.
Conventional oxygen sensors are constructed ~rom a multiplicity of components in the form of a reusable Clark cell. Clark sensors are expensive to construct and require ~requent maintenance by skilled technicians. In particular the electrolyte gel and gas permeable membrane may need regular attention.
According to a first aspect of the present invention an electrochemical oxygen sensor comprises an impermeable substrate and a plurality of conductive layers applied thereto by thick film deposition, at least one conductive layer compriæing an electrode and a conduc~or connected to the electrode.
A sensor in accordance with this invention can be manufactured economically by screen printing or other lithographic techniques. Electrosensors may be disposable before maintenance becomes necessary. Miniaturisation of a sensor is facilitated. The sensors can be fabricated as micro-electrode arrays as disclosed in WO91/08474. The active area of the sensor may be manufactured by printing or ink jet methods and appropriate layers may be applied as described below so that the sensor can detect oxygen and reducible species in aqueous or other condensed phases. Coupling the oxygen sensor to other reagents that either consume or release oxygen, for example enzymes, allows detection of a wide range of analytes.
Sensors in accordance with the present invention have the advantage that it is not essential to provide a membrane as must be used in conventional Clark cells. This simplifies manufacture and enhances the sensitivity of the sensors.
WO96/10174 ~ 2 0 ~ 3 5 9 ~ ~b~S/02299 ~
Furthermore the sensors have the surprising ability to detect and measure dissolved oxygen in biological fluids for example foodstuffs such as milk, food slurries or other food products and physiological specimens.
The impermeable substrate preferably provides a planar surface upon which the conductive components may be deposited.
A 1,7m; n~7~ substrate is preferred. Plastic substrates may be employed together with coatings of materials which do not require curing at high temperatures. Alternatively ceramic substrates can be used with high temperature resistant coatings.
According to a preferred aspect of the present invention an electrochemical oxygen sensor comprises an impermeable substrate and a plurality of conductive films disposed on the substrate and arranged to form a multiplicity of electrochemical electrodes in use.
The sensor preferably includes contacts for attachment to a detector circuit.
The electrodes can be applied to the substrate to form an array of individual sensors. The device can then be mechanically formed, for example by thermoforming or by bonding of a further layer which may overlie the conductive layers to define an array of wells or receptacles. Such an array can be used for a variety of simultaneous or successive analyses. For example microbial ~nl7merations, chemical and toxin determinations, antibiotic arrays and substrate determinations may be facilitated.
According to a second aspect of the present invention a method of manufacture of an electrochemical oxygen sensor comprises the steps of providing an impermeable substrate, forming a plurality of conductive layers by thick film deposition on the substrate, at least one conductive layer comprising a redox electrode and a conductor connected to the electrode.
A variety of techniques may be used to form the electrodes, including printing, for example screen printing, lithography, ink jet and flexographic printing. various _ WO96/10174 PCT/GB95/02299 2~01 359 coating methods for example dipping, spraying, spin coating and dosing may also be employed. Distortion printing can be employed i~ physical de~orming is used to construct the wells or receptacles. Conventional flexible printed circuit board techniques can be used in the construction of sensors in accordance with this invention.
According to a preferred aspect of the present invention an electrochemical oxygen sensor comprises an impermeable substrate layer, a plurality of electrode layers and a layer of active material overlaying one of said electrode layers wherein the electrodes and active layers comprise films deposited on an underlying surface. The underlying surface may comprise the substrate or a film deposited over the substrate.
The active material may comprise a polymer which is selectively perm.eable to cat_~ns and polar species but impermeable to anionic and non-polar compounds. Preferred active layers comprise ion exchange polymers especially perfluorinated ion exchange polymers for example Nafion or Promeon (Trade Marks). Use of a cationic polymer affords a sensor adapted to detect oxygen in liquid or other condensed analytes by prevention of the latter from contacting the electrode surface. Nafion is a copolymer of tetrafluoroethylene and perfluoro[2-(fluorosulphonyl ethoxy)propyl vinyl}ether manufactured by Dupont. Alternative sulphonated fluorocarbon polymers may be employed. Oxygen may be determined by direct electrochemical reduction or by means of its effect on oxygen reduction catalyst. Such an intermediate species is sensitive to oxygen. Especially preferred oxygen reduction catalysts include cobalt (II) porphyrin compounds for example cobalt (II) tetraaminophenyl porphyrin. Amine complexes of cobalt eg h~A~m; no cobalt (II) may also be employed.
Sensors in accordance with this invention have the advantage of ease of sterilisation. Individual electrodes or electrode arrays can be sealed into a bag, other container or packaging to facilitate thermal, chemical or radiation sterilisation. Such procedures cannot be used with a WO96/10174 P~l/~5~ 225g 22 01 ~59 _4_ conventional Clark electrode.
In a preferred embodiment of this invention sensor apparatus includes an oxygen sensor as previously described together with a detector circuit, the circuit being adapted to apply a potential to the electrode relative to a reference or counterelectrode and further adapted to measure the current after a period of equilibration.
In particularly preferred em.bodiments the control circuit is adapted to apply two or more potentials to the electrodes and to measure the respective currents at these potentials.
Measurement at two potentials can avoid false results due to reduction of cont~m;nAnt species. For example measurements may be carried out at -800mV at which cont~m;n~nts cau~ed by microbial metabolism are also reduced in addition to oxygen.
Oxygen is not reduced at -500mV. The making of two measurements at -500mv and -800mv allows the contribution due to the metabolites to be determined and the oxygen level measured. More than two potentials may be employed to differentiate various reducible cont~m;n~nts from oxygen.
A particular application of this invention is in the detection of spoilage, for example of an aseptically packaged product such as UHT milk or other food product. A simple electrode for example having no additional layers, can detect oxygen or other reducible species in the product contained in such packaging. The absence of additional layers allows rapid equilibration so that a test can be carried out within a few seconds. In such an assay the absence of reducible species can indicate that the growth of micro-organisms has taken place.
Conventional methods for testing such products include pH
measurement which has been shown to be a very poor indicator of spoilage and ATP measurement via bioluminescence which is expensive and suffers from interference by somatic ATP. In contrast oxygen determination using disposable electrodes in accordance with this invention is inexpensive, rapid and reliable. These factors allow for more statistically significant sampling procedures to be adopted than has been previously possible.
,~ WO 96/10174 PCT/GB95/02299 A further use of sensors in accordance with this invention is for determination of the oxygen content of gaseous media. There are many known solid state oxygen sensors, ~or example using yttria stabilised zirconia but these are ceramic devices which operate at high temperatures. Deposition of a polymer electrolyte onto an electrode in accordance with the present invention facilitates production of a disposable solid state amperometric oxygen sensor which may be operated at room temperature.
Formation of sensors in accordance with this invention into a tray defining a multiplicity of receptacles each including a sensor affords a convenient laboratory device for microbial enumeration, biological oxygen demand (BOD) and toxicity testing and determination of antibiotic activity.
There are many further applications for such an array. The receptacles of an array may contain media having different concentrations of an antibiotic substance inoculated with a micro~or~anism. Growth of the micro-organism can be detected by a reduction in the electrochemically determined oxygen level of the medium. A rapid and simple method of assessment of the sensitivity of an organism to an antibiotic is afforded.
Sensors in accordance with this invention may be used for determination of residual antibiotics, for example in food products such as milk.
The invention is further described by means of example but not in any limitative sense, with reference to the accompanying drawings of which:
Figure 1 is a plan view of a sensor in accordance with the present invention;
Figure 2 is a cross-section on X-X of the sensor shown in' Figure 1;
Figure 3 is a plan view of a printed sensor with additional layers;
Figure 4 shows cross-sectional views of sensors having additional layers;
Figure S illustrates a sensor having micro-electrodes in the sensing region;
WO96/10174 2 2 0 1 3 5 9 P~ b~_/02299 ~
Figure 6 is a cross-section of a sensor shown in Figure 5;
Figure 7 shows an array of printed electrodes formed to make a series of wells; and Figure 8 is a cross-section of a sensor shown in Figure 7.
The sensor shown in Figures 1 or 2 has an active layer 6 in the sensing region 7 directly exposed to the analyte. The planar substrate 1 is composed of a polymeric material, for example polyester or polycarbonate a cellulose material for example paper or card or a ceramic. Conductive films 2 and 3 are formed of any suitable conducting ink, for example carbon, silver, platinum or gold inks are disposed on the substrate.
The sensing region 7 comprises an active layer 6, counter electrode 3 and reference electrode 4. The counter electrode 3 and reference electrode 4 may be combined as shown or may be provided as separate electrodes. The reference electrode 4 may be formed from an ink containing silver and silver chloride.
Alternatively the silver chloride may be electrolytically deposited. The active layer 6 may comprise a surface on which oxygen can be reduced. Silver, gold, platinum, iridium or lead surfaces may be employed. Carbon may also be employed. An insulating layer 5 serves to shield the conductors from the analyte.
Figures 3 and 4 show a more complex construction wherein the active layer 6 is coated with a selective layer 8. The selective layer may be a multi-layer structure as shown in Figure 4b wherein four selective layers 8, 9, 10 and 11 are shown. Any number of selective layers may be employed. The selective layers 8 to 11 can be deposited by screen printing, ink jets, spray, airbrush dipping or dosing techniques.
Alternative techniques can be employed. The selective layers may have a variety of compositions.
Cationic polymer electrolytes, for example Nafion and Promeon (Trade Marks) may be employed to detect oxygen in the gaseous phase. A permeable cellulosic layer, for example cellulose acetate, ethyl hydroxy ethyl cellulose, etc may be g6/10174 2 2 0 1 3 ~ GB95/02299 used to ensure that ionic reducible and high molecular weight substances do not contact the underlying active layer.
Enzymes, for example glucose oxidase which consume oxygen when reacting with their specific substrate may be incorporated into a selective layer. The substrate may be measured by this means by detection of depletion of oxygen.
Organelles for example chloroplasts and mitochondria may be incorporated into a selective layer. Photosynthetic organisms may be used, the interruption of photosynthesis serving to indicate toxicity of the analyte. Micro-organisms may be incorporated into the selective layer and changes in microbial respiration can be used to indicate the presence of toxins, antibiotics and metabolisable substrates.
Manganese dioxide or other agents may be incorporated into a selective layer to allow determination of hydrogen peroxide or hydroperoxides.
Figures 5 and 6 show the use of microelectrodes 12 in an array 13. The microelectrodes can vary in size and diameter for example having a ~lmen.cion of 20 ~m. Such microelectrodes may be formed by laser ablation as disclosed in WO91/08474, the disclosure of which is incorporated into this specification by reference. Use of microelectrodes affords the benefit that the amount of reducible material consumed during the measurement is m;n;m; sed enabling continuous measurement without perturbation of equilibria in the analyte. The number and dimensions of the electrodes may be selected in accordance with the performance characteristics required. Microelectrodes 12 may extend through the insulating layer 5 to the active layer to form an array 13. A microelectrode array may be coated with overlayers of selected materials (not shown) as previously described.
The conductive layers 2 may be formed from printed carbon ink in a conventional manner. Manufacture by a laser ablation is facilitated by selection of an appropriate material for the insulating layer 5, for example, parylene.
Figures 7 and 8 illustrate an array of cells wherein each cell 14 has an electrode including an active layer 6 and a combined counter and reference electrode 3, 4. The electrodes WO96110174 2 2 0 1 3 5 9 PCT/GB9S102299 ~
3, 4 are connected to an edge connector 15 by means o~
conductors 16 and 17. In a preferred embodiment the conductors 16 and 17 are printed on the upper surface of a l~m;n~r t substrate which is subsequently deformed to provide the array of wells. Alternatively an additional layer comprising the well walls l9 may be ~secured to the substrate as a subsequent step. In this embodiment the conductors 16 and 17 are insulated from the environment by printing a dielectric layer so that the conductors are exposed only at the cell and connector ends. Alternatively the conductors 16 and 17 can be printed onto the underlayer of the substrate and the electrical connection can be made by means of holes 22. In a simple arrangement, the electrodes can have an integral common construction 17 to allow use of less complex contacts 23 and ancillary detector circuitry (not shown).
The impermeable substrate preferably provides a planar surface upon which the conductive components may be deposited.
A 1,7m; n~7~ substrate is preferred. Plastic substrates may be employed together with coatings of materials which do not require curing at high temperatures. Alternatively ceramic substrates can be used with high temperature resistant coatings.
According to a preferred aspect of the present invention an electrochemical oxygen sensor comprises an impermeable substrate and a plurality of conductive films disposed on the substrate and arranged to form a multiplicity of electrochemical electrodes in use.
The sensor preferably includes contacts for attachment to a detector circuit.
The electrodes can be applied to the substrate to form an array of individual sensors. The device can then be mechanically formed, for example by thermoforming or by bonding of a further layer which may overlie the conductive layers to define an array of wells or receptacles. Such an array can be used for a variety of simultaneous or successive analyses. For example microbial ~nl7merations, chemical and toxin determinations, antibiotic arrays and substrate determinations may be facilitated.
According to a second aspect of the present invention a method of manufacture of an electrochemical oxygen sensor comprises the steps of providing an impermeable substrate, forming a plurality of conductive layers by thick film deposition on the substrate, at least one conductive layer comprising a redox electrode and a conductor connected to the electrode.
A variety of techniques may be used to form the electrodes, including printing, for example screen printing, lithography, ink jet and flexographic printing. various _ WO96/10174 PCT/GB95/02299 2~01 359 coating methods for example dipping, spraying, spin coating and dosing may also be employed. Distortion printing can be employed i~ physical de~orming is used to construct the wells or receptacles. Conventional flexible printed circuit board techniques can be used in the construction of sensors in accordance with this invention.
According to a preferred aspect of the present invention an electrochemical oxygen sensor comprises an impermeable substrate layer, a plurality of electrode layers and a layer of active material overlaying one of said electrode layers wherein the electrodes and active layers comprise films deposited on an underlying surface. The underlying surface may comprise the substrate or a film deposited over the substrate.
The active material may comprise a polymer which is selectively perm.eable to cat_~ns and polar species but impermeable to anionic and non-polar compounds. Preferred active layers comprise ion exchange polymers especially perfluorinated ion exchange polymers for example Nafion or Promeon (Trade Marks). Use of a cationic polymer affords a sensor adapted to detect oxygen in liquid or other condensed analytes by prevention of the latter from contacting the electrode surface. Nafion is a copolymer of tetrafluoroethylene and perfluoro[2-(fluorosulphonyl ethoxy)propyl vinyl}ether manufactured by Dupont. Alternative sulphonated fluorocarbon polymers may be employed. Oxygen may be determined by direct electrochemical reduction or by means of its effect on oxygen reduction catalyst. Such an intermediate species is sensitive to oxygen. Especially preferred oxygen reduction catalysts include cobalt (II) porphyrin compounds for example cobalt (II) tetraaminophenyl porphyrin. Amine complexes of cobalt eg h~A~m; no cobalt (II) may also be employed.
Sensors in accordance with this invention have the advantage of ease of sterilisation. Individual electrodes or electrode arrays can be sealed into a bag, other container or packaging to facilitate thermal, chemical or radiation sterilisation. Such procedures cannot be used with a WO96/10174 P~l/~5~ 225g 22 01 ~59 _4_ conventional Clark electrode.
In a preferred embodiment of this invention sensor apparatus includes an oxygen sensor as previously described together with a detector circuit, the circuit being adapted to apply a potential to the electrode relative to a reference or counterelectrode and further adapted to measure the current after a period of equilibration.
In particularly preferred em.bodiments the control circuit is adapted to apply two or more potentials to the electrodes and to measure the respective currents at these potentials.
Measurement at two potentials can avoid false results due to reduction of cont~m;nAnt species. For example measurements may be carried out at -800mV at which cont~m;n~nts cau~ed by microbial metabolism are also reduced in addition to oxygen.
Oxygen is not reduced at -500mV. The making of two measurements at -500mv and -800mv allows the contribution due to the metabolites to be determined and the oxygen level measured. More than two potentials may be employed to differentiate various reducible cont~m;n~nts from oxygen.
A particular application of this invention is in the detection of spoilage, for example of an aseptically packaged product such as UHT milk or other food product. A simple electrode for example having no additional layers, can detect oxygen or other reducible species in the product contained in such packaging. The absence of additional layers allows rapid equilibration so that a test can be carried out within a few seconds. In such an assay the absence of reducible species can indicate that the growth of micro-organisms has taken place.
Conventional methods for testing such products include pH
measurement which has been shown to be a very poor indicator of spoilage and ATP measurement via bioluminescence which is expensive and suffers from interference by somatic ATP. In contrast oxygen determination using disposable electrodes in accordance with this invention is inexpensive, rapid and reliable. These factors allow for more statistically significant sampling procedures to be adopted than has been previously possible.
,~ WO 96/10174 PCT/GB95/02299 A further use of sensors in accordance with this invention is for determination of the oxygen content of gaseous media. There are many known solid state oxygen sensors, ~or example using yttria stabilised zirconia but these are ceramic devices which operate at high temperatures. Deposition of a polymer electrolyte onto an electrode in accordance with the present invention facilitates production of a disposable solid state amperometric oxygen sensor which may be operated at room temperature.
Formation of sensors in accordance with this invention into a tray defining a multiplicity of receptacles each including a sensor affords a convenient laboratory device for microbial enumeration, biological oxygen demand (BOD) and toxicity testing and determination of antibiotic activity.
There are many further applications for such an array. The receptacles of an array may contain media having different concentrations of an antibiotic substance inoculated with a micro~or~anism. Growth of the micro-organism can be detected by a reduction in the electrochemically determined oxygen level of the medium. A rapid and simple method of assessment of the sensitivity of an organism to an antibiotic is afforded.
Sensors in accordance with this invention may be used for determination of residual antibiotics, for example in food products such as milk.
The invention is further described by means of example but not in any limitative sense, with reference to the accompanying drawings of which:
Figure 1 is a plan view of a sensor in accordance with the present invention;
Figure 2 is a cross-section on X-X of the sensor shown in' Figure 1;
Figure 3 is a plan view of a printed sensor with additional layers;
Figure 4 shows cross-sectional views of sensors having additional layers;
Figure S illustrates a sensor having micro-electrodes in the sensing region;
WO96/10174 2 2 0 1 3 5 9 P~ b~_/02299 ~
Figure 6 is a cross-section of a sensor shown in Figure 5;
Figure 7 shows an array of printed electrodes formed to make a series of wells; and Figure 8 is a cross-section of a sensor shown in Figure 7.
The sensor shown in Figures 1 or 2 has an active layer 6 in the sensing region 7 directly exposed to the analyte. The planar substrate 1 is composed of a polymeric material, for example polyester or polycarbonate a cellulose material for example paper or card or a ceramic. Conductive films 2 and 3 are formed of any suitable conducting ink, for example carbon, silver, platinum or gold inks are disposed on the substrate.
The sensing region 7 comprises an active layer 6, counter electrode 3 and reference electrode 4. The counter electrode 3 and reference electrode 4 may be combined as shown or may be provided as separate electrodes. The reference electrode 4 may be formed from an ink containing silver and silver chloride.
Alternatively the silver chloride may be electrolytically deposited. The active layer 6 may comprise a surface on which oxygen can be reduced. Silver, gold, platinum, iridium or lead surfaces may be employed. Carbon may also be employed. An insulating layer 5 serves to shield the conductors from the analyte.
Figures 3 and 4 show a more complex construction wherein the active layer 6 is coated with a selective layer 8. The selective layer may be a multi-layer structure as shown in Figure 4b wherein four selective layers 8, 9, 10 and 11 are shown. Any number of selective layers may be employed. The selective layers 8 to 11 can be deposited by screen printing, ink jets, spray, airbrush dipping or dosing techniques.
Alternative techniques can be employed. The selective layers may have a variety of compositions.
Cationic polymer electrolytes, for example Nafion and Promeon (Trade Marks) may be employed to detect oxygen in the gaseous phase. A permeable cellulosic layer, for example cellulose acetate, ethyl hydroxy ethyl cellulose, etc may be g6/10174 2 2 0 1 3 ~ GB95/02299 used to ensure that ionic reducible and high molecular weight substances do not contact the underlying active layer.
Enzymes, for example glucose oxidase which consume oxygen when reacting with their specific substrate may be incorporated into a selective layer. The substrate may be measured by this means by detection of depletion of oxygen.
Organelles for example chloroplasts and mitochondria may be incorporated into a selective layer. Photosynthetic organisms may be used, the interruption of photosynthesis serving to indicate toxicity of the analyte. Micro-organisms may be incorporated into the selective layer and changes in microbial respiration can be used to indicate the presence of toxins, antibiotics and metabolisable substrates.
Manganese dioxide or other agents may be incorporated into a selective layer to allow determination of hydrogen peroxide or hydroperoxides.
Figures 5 and 6 show the use of microelectrodes 12 in an array 13. The microelectrodes can vary in size and diameter for example having a ~lmen.cion of 20 ~m. Such microelectrodes may be formed by laser ablation as disclosed in WO91/08474, the disclosure of which is incorporated into this specification by reference. Use of microelectrodes affords the benefit that the amount of reducible material consumed during the measurement is m;n;m; sed enabling continuous measurement without perturbation of equilibria in the analyte. The number and dimensions of the electrodes may be selected in accordance with the performance characteristics required. Microelectrodes 12 may extend through the insulating layer 5 to the active layer to form an array 13. A microelectrode array may be coated with overlayers of selected materials (not shown) as previously described.
The conductive layers 2 may be formed from printed carbon ink in a conventional manner. Manufacture by a laser ablation is facilitated by selection of an appropriate material for the insulating layer 5, for example, parylene.
Figures 7 and 8 illustrate an array of cells wherein each cell 14 has an electrode including an active layer 6 and a combined counter and reference electrode 3, 4. The electrodes WO96110174 2 2 0 1 3 5 9 PCT/GB9S102299 ~
3, 4 are connected to an edge connector 15 by means o~
conductors 16 and 17. In a preferred embodiment the conductors 16 and 17 are printed on the upper surface of a l~m;n~r t substrate which is subsequently deformed to provide the array of wells. Alternatively an additional layer comprising the well walls l9 may be ~secured to the substrate as a subsequent step. In this embodiment the conductors 16 and 17 are insulated from the environment by printing a dielectric layer so that the conductors are exposed only at the cell and connector ends. Alternatively the conductors 16 and 17 can be printed onto the underlayer of the substrate and the electrical connection can be made by means of holes 22. In a simple arrangement, the electrodes can have an integral common construction 17 to allow use of less complex contacts 23 and ancillary detector circuitry (not shown).
Claims (9)
1. An electrochemical oxygen sensor comprising an impermeable substrate and a plurality of conductive layers applied thereto by thick film deposition, at least one conductive layer comprising an electrode and a conductor connected to the electrode, the sensor further comprising a layer of active material overlaying said electrode, wherein the active material comprises an ion exchange polymer and wherein the active layer includes an oxygen reduction catalyst.
2. A sensor as claimed in claim 1, wherein a multiplicity of conductive films are disposed on the substrate and arranged to form a plurality of electrochemical electrodes.
3. A sensor as claimed in claim 1 or 2, wherein the oxygen reduction catalyst is cobalt (II) tetraaminophenyl porphyrin.
4. A sensor as claimed in claims 2 or 3, including a further layer defining an array of receptacles.
5. A sensor as claimed in any preceding claim wherein the conductor is carbon or silver.
6. A sensor as claimed in any preceding claim, wherein the sensor does not include a gas permeable membrane overlying the electrode.
7. A sensor as claimed in any preceding claim, including a detector circuit adapted to be connected in use to said conductor, the detector being arranged to detect electrochemical reduction at said electrode at two or more voltages.
8. Use of a detector as claimed in any preceding claim for measurement of dissolved oxygen in a biological fluid.
9. Use of a detector as claimed in claim 8, wherein the biological fluid is a foodstuff.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9419513.8 | 1994-09-28 | ||
| GB9419513A GB9419513D0 (en) | 1994-09-28 | 1994-09-28 | Electrochemical oxygen sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2201359A1 true CA2201359A1 (en) | 1996-04-04 |
Family
ID=10761997
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002201359A Abandoned CA2201359A1 (en) | 1994-09-28 | 1995-09-28 | Electrochemical oxygen sensor |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US5876577A (en) |
| EP (1) | EP0783687B1 (en) |
| AT (1) | ATE180055T1 (en) |
| AU (1) | AU688595B2 (en) |
| CA (1) | CA2201359A1 (en) |
| DE (1) | DE69509667D1 (en) |
| GB (1) | GB9419513D0 (en) |
| WO (1) | WO1996010174A1 (en) |
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|---|---|---|---|---|
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| DE69808749D1 (en) * | 1997-04-24 | 2002-11-21 | Daikin Ind Ltd | Comb-shaped sensor element with electrodes on the teeth and edge connections on the opposite side |
| JP4163383B2 (en) * | 1998-04-14 | 2008-10-08 | カリフォルニア・インスティテュート・オブ・テクノロジー | Method and system for determining analyte activity |
| JP2002526769A (en) | 1998-10-02 | 2002-08-20 | カリフォルニア インスティチュート オブ テクノロジー | Conductive organic sensors, arrays and methods of use |
| DE69941493D1 (en) * | 1998-11-16 | 2009-11-12 | California Inst Of Techn | Simultaneous determination of equilibrium and kinetic properties |
| DE60026309T2 (en) * | 1999-05-10 | 2006-12-14 | California Institute Of Technology, Pasadena | USE OF A SPATIAL-TIME REACTION BEHAVIOR IN SENSOR ARRAYS FOR THE DETECTION OF ANALYTES IN FLUIDS |
| US7122152B2 (en) * | 1999-05-10 | 2006-10-17 | University Of Florida | Spatiotemporal and geometric optimization of sensor arrays for detecting analytes fluids |
| US6631333B1 (en) * | 1999-05-10 | 2003-10-07 | California Institute Of Technology | Methods for remote characterization of an odor |
| US6724312B1 (en) | 1999-07-21 | 2004-04-20 | Daniel Barber | Pest control apparatus and methods |
| US7212112B2 (en) * | 1999-07-21 | 2007-05-01 | Dow Agrosciences Llc | Detection and control of pests |
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| US7348890B2 (en) * | 1999-07-21 | 2008-03-25 | Dow Agrosciences Llc | Pest control techniques |
| DE69924125D1 (en) * | 1999-07-21 | 2005-04-14 | Dow Agrosciences Llc | PEST CONTROL METHODS |
| US7262702B2 (en) * | 1999-07-21 | 2007-08-28 | Dow Agrosciences Llc | Pest control devices, systems, and methods |
| US6914529B2 (en) * | 1999-07-21 | 2005-07-05 | Dow Agrosciences Llc | Sensing devices, systems, and methods particularly for pest control |
| US6890715B1 (en) * | 1999-08-18 | 2005-05-10 | The California Institute Of Technology | Sensors of conducting and insulating composites |
| US6623620B2 (en) * | 1999-11-22 | 2003-09-23 | Hathaway Brown School | Method for detecting or monitoring sulfur dioxide with an electrochemical sensor |
| CA2764307C (en) * | 2001-06-29 | 2015-03-03 | Meso Scale Technologies, Llc. | Assay plates, reader systems and methods for luminescence test measurements |
| US20030228972A1 (en) * | 2002-06-05 | 2003-12-11 | Birss Viola | Oxygen reduction catalyst |
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| TWI478665B (en) | 2008-08-19 | 2015-04-01 | Dow Agrosciences Llc | Bait materials, pest monitoring devices and other pest control devices that include polyurethane foam |
| US20100168532A1 (en) * | 2008-10-24 | 2010-07-01 | The Trustees Of Columbia University In The City Of New York | Systems and methods for measuring brain activity |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3839178A (en) * | 1972-10-05 | 1974-10-01 | Gen Electric | Potentiometric oxygen sensor |
| DE2715285C2 (en) * | 1977-04-05 | 1983-08-25 | Vjačeslav Michajlovič Puškino Moskovskaja oblast' Krylov | Electrochemical cell for determining hydrogen and hydrogen-containing reducing agents |
| US4225401A (en) * | 1978-12-22 | 1980-09-30 | Kernforschungsanlage Julich Gesellschaft Mit Beschrankter Haftung | Method for generating hydrogen and oxygen |
| JPS57105970A (en) * | 1980-12-23 | 1982-07-01 | Toshiba Corp | Air electrode |
| JPS62180263A (en) * | 1986-02-04 | 1987-08-07 | Terumo Corp | Oxygen sensor |
| CA1333381C (en) * | 1986-02-20 | 1994-12-06 | Eric D. Nyberg | Method and articles employing ion exchange material |
| JPH01203964A (en) * | 1988-02-10 | 1989-08-16 | Toyota Motor Corp | Formation of electrode for oxygen concentration sensor |
| GB8927377D0 (en) * | 1989-12-04 | 1990-01-31 | Univ Edinburgh | Improvements in and relating to amperometric assays |
| US5120421A (en) * | 1990-08-31 | 1992-06-09 | The United States Of America As Represented By The United States Department Of Energy | Electrochemical sensor/detector system and method |
| DE4241206C2 (en) * | 1992-12-08 | 1996-07-11 | Inst Chemo Biosensorik | Thick film reference electrode |
-
1994
- 1994-09-28 GB GB9419513A patent/GB9419513D0/en active Pending
-
1995
- 1995-09-28 EP EP95932819A patent/EP0783687B1/en not_active Expired - Lifetime
- 1995-09-28 US US08/809,627 patent/US5876577A/en not_active Expired - Fee Related
- 1995-09-28 DE DE69509667T patent/DE69509667D1/en not_active Expired - Lifetime
- 1995-09-28 WO PCT/GB1995/002299 patent/WO1996010174A1/en active IP Right Grant
- 1995-09-28 AU AU35713/95A patent/AU688595B2/en not_active Ceased
- 1995-09-28 CA CA002201359A patent/CA2201359A1/en not_active Abandoned
- 1995-09-28 AT AT95932819T patent/ATE180055T1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE69509667D1 (en) | 1999-06-17 |
| EP0783687B1 (en) | 1999-05-12 |
| WO1996010174A1 (en) | 1996-04-04 |
| ATE180055T1 (en) | 1999-05-15 |
| EP0783687A1 (en) | 1997-07-16 |
| AU3571395A (en) | 1996-04-19 |
| GB9419513D0 (en) | 1994-11-16 |
| US5876577A (en) | 1999-03-02 |
| AU688595B2 (en) | 1998-03-12 |
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