Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1997-09-23
1999-03-02
Bell, Bruce F.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204412, 204424, 204403, 204431, 205782, 205784, 2057855, 205789, 205792, 2057925, G01N 2726
Patent
active
058765778
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB95/02299 filed Sep. 28, 1995.
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 from a multiplicity of components in the form of a reusable Clark cell. Clark sensors are expensive to construct and require frequent 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 comprising an electrode and a conductor 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.
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 laminar 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 enumerations, 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 coating methods for example dipping, spraying, spin coating and dosing may also be employed. Distortion printing can be employed if physical deforming is used to construct the wells or receptacles. Conventional flexible printed circuit board techniques
REFERENCES:
patent: 4225401 (1980-09-01), Pace
patent: 4407907 (1983-10-01), Takamura et al.
patent: 4957615 (1990-09-01), Ushizawa et al.
patent: 5120421 (1992-06-01), Glass et al.
Ackland Martin
McAleer Jerry
Bell Bruce F.
Cranfield Biotechnology Ltd.
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