pH and CO2 sensing device and method of making the same

Claim 1

A CO 2 gas sensor comprising: an electrically nonconductive substrate; a metal/metal oxide junction type active electrode including an active electrode metal, the active electrode metal being applied to the substrate by one of thick film and thin film techniques, and the active metal being then subjected to electro-oxidizing conditions for a period of time sufficient to oxidize a portion of the applied active electrode metal, the applied active electrode metal being made cathodic prior to discontinuance of the electro-oxidizing conditions; a silver/silver halide junction type reference electrode, adheringly applied to the substrate; an insulating, dielectric coating applied over at least portions of the substrate and electrodes; and a polymeric membrane comprising a laminate of a hydrophobic polymeric material atop a hydrophilic membrane material applied over at least those portions of the electrodes not having the insulating dielectric coating applied thereto, the polymeric membrane being capable of relatively rapidly transmitting CO 2 thereacross, and the polymeric material including a liquid electrolyte bound by the polymeric membrane.

Claim 3

A method for making a solid state pH sensor comprising the steps of: selecting an electrically nonconducting substrate formed from a material selected from a group consisting essentially of ceramics, refractories, thermoplastics, and thermosetting resins; applying an active electrode metal to the substrate by one of thick and thin film techniques to form an electrode of desired physical configuration adhered to the substrate; adheringly applying to the substrate a silver/silver halide junction type reference electrode; oxidizing a portion of the active electrode metal by subjecting the active electrode metal to electro-oxidizing conditions for a period of time necessary to form a desired quantity of an oxide of the metal, the active electrode metal being made cathodic at least immediately prior to terminating the electro-oxidizing conditions; and applying to at least portions of the electrodes and the substrate an insulating dielectric coating.

Claim 4

A method for making a solid state pH sensor comprising the steps of: selecting an electrically nonconducting substrate formed from a material selected from a group consisting essentially of ceramics, refractories, thermoplastics, and thermosetting resins; applying an active electrode metal to the substrate by one of thick and thin film techniques to form an electrode of desired physical configuration adhered to the substrate; adheringly applying to the substrate a silver/silver halide junction type reference electrode; oxidizing a portion of the active electrode metal by subjecting the active electrode metal to electro-oxidizing conditions for a period of time necessary to form a desired quantity of an oxide of the metal, the active electrode metal being made cathodic at least immediately prior to terminating the electro-oxidizing conditions; and applying to at least portions of the electrodes and the substrate an insulating dielectric coating.

Claim 9

A method for making a CO 2 gas sensor comprising the steps: selecting an electrically nonconducting substrate formed from a material selected from a group consisting essentially of ceramics, refractories, thermoplastics, and thermosetting resins; applying an active electrode metal to the substrate by one of thick and thin film techniques to form an electrode of desired physical configuration adhered to the substrate; adheringly applying to the substrate a silver/silver halide junction type reference electrode; applying to at least portions of the electrodes and the substrate an insulating dielectric coating; oxidizing a portion of the active electrode metal by subjecting the active electrode metal to electro-oxidizing conditions for a period of time necessary to form a desired quantity of an oxide of the active electrode metal, the active electrode metal being made cathodic prior to terminating the electro-oxidizing conditions; and applying to at least those portions of the resulting sensor not having an applied coating of an insulating dielectric a polymeric membrane comprising a laminate of a hydrophobic polymeric material atop a hydrophilic membrane material capable of binding a liquid electrolyte within the polymeric membrane, electro-oxidation being accomplished by making the active electrode metal anodic within a fused salt electrolyte consisting of NaNO 3 and LiCl salts under an impressed current of between about 0.1 milliamperes and 20.0 milliamperes per square centimeter of active electrode metal surface, followed by making the now active electrode cathodic prior to removing the active electrode from the fused salt electrolyte.

Claim 10

A method for making a CO 2 gas sensor comprising the steps: selecting an electrically nonconducting substrate formed from a material selected from a group consisting essentially of ceramics, refractories, thermoplastics, and thermosetting resins; applying an active electrode metal to the substrate by one of thick and thin film techniques to form an electrode of desired physical configuration adhered to the substrate; adheringly applying to the substrate a silver/silver halide junction type reference electrode; applying to at least portions of the electrodes and the substrate an insulating dielectric coating; oxidizing a portion of the active electrode metal by subjecting the active electrode metal to electro-oxidizing conditions for a period of time necessary to form a desired quantity of an oxide of the active electrode metal, the active electrode metal being made cathodic prior to terminating the electro-oxidizing conditions; and applying to at least those portions of the resulting sensor not having an applied coating of an insulating dielectric a polymeric membrane comprising a laminate of a hydrophobic polymeric material atop a hydrophilic membrane material capable of binding a liquid electrolyte within the polymeric membrane, electro-oxidation being accomplished by making the active electrode metal anodic within a fused salt electrolyte consisting of NaNO 3 and LiCl salts under an impressed current of between about 0.1 milliamperes and 20.0 milliamperes per square centimeter of active electrode metal surface, followed by making the now active electrode cathodic prior to removing the active electrode from the fused salt electrolyte.

Claim 11

A method for making a transcutaneous blood CO 2 gas sensor comprising the steps: selecting an electrically nonconducting substrate formed from alumina; applying an active electrode metal to the substrate by one of thick and thin film techniques to form an electrode of desired physical configuration adhered to the substrate; adheringly applying to the substrate a silver/silver halide junction type reference electrode; applying to at least portions of the electrodes and the substrate an insulating dielectric coating; oxidizing a portion of the active electrode metal by subjecting the active electrode metal to electro-oxidizing conditions for a period of time necessary to form a desired quantity of an oxide of the active electrode metal, the active electrode metal being made cathodic prior to terminating the electro-oxidizing conditions; and applying to at least those portions of the resulting sensor not having an applied coating of an insulating dielectric a polymeric membrane comprising a laminate of a hydrophobic polymer material atop a hydrophilic membrane material capable of binding a liquid electrolyte within the polymeric membrane, and wherein electro-oxidation is accomplished by making the active electrode anodic within a fused salt electrolyte consisting of NaNO 3 and LiCl salts under an impressed current of between about 0.1 milliamperes and 20.0 milliamperes per square centimeter of active electrode metal surface, followed by making the now active electrode cathodic prior to removing the active electrode from the fused salt electrolyte.

Claim 12

A method for making a transcutaneous blood CO 2 gas sensor comprising the steps: selecting an electrically nonconducting substrate formed from alumina; applying an active electrode metal to the substrate by one of thick and thin film techniques to form an electrode of desired physical configuration adhered to the substrate; adheringly applying to the substrate a silver/silver halide junction type reference electrode; applying to at least portions of the electrodes and the substrate an insulating dielectric coating; oxidizing a portion of the active electrode metal by subjecting the active electrode metal to electro-oxidizing conditions for a period of time necessary to form a desired quantity of an oxide of the active electrode metal, the active electrode metal being made cathodic prior to terminating the electro-oxidizing conditions; and applying to at least those portions of the resulting sensor not having an applied coating of an insulating dielectric a polymeric membrane comprising a laminate of a hydrophobic polymer material atop a hydrophilic membrane material capable of binding a liquid electrolyte within the polymeric membrane, and wherein electro-oxidation is accomplished by making the active electrode anodic within a fused salt electrolyte consisting of NaNO 3 and LiCl salts under an impressed current of between about 0.1 milliamperes and 20.0 milliamperes per square centimeter of active electrode metal surface, followed by making the now active electrode cathodic prior to removing the active electrode from the fused salt electrolyte.

Claim 14

A method for making a precious metal/precious metal oxide junction type electrode comprising the steps of: selecting a precious metal electrode precursor the metal being selected from a group consisting of palladium, iridium, rhodium, ruthenium and osmium; immersing at least a portion of the electrical precursor in a molten salt electrolyte; making the electrode precursor anodic at an electrical current not exceeding about 20 milliamperes per square centimeter of immersed electrode precursor to form a desired quantity of the precious metal oxide; and at least once making the electrode precursor cathodic prior to removal from the molten salt electrolyte at an electrical current not exceeding the current density while anodic.

Claim 15

A method for making a precious metal/precious metal oxide junction type electrode comprising the steps of: selecting a precious metal electrode precursor the metal being selected from a group consisting of palladium, iridium, rhodium, ruthenium and osmium; immersing at least a portion of the electrical precursor in a molten salt electrolyte; making the electrode precursor anodic at an electrical current not exceeding about 20 milliamperes per square centimeter of immersed electrode precursor to form a desired quantity of the precious metal oxide; and at least once making the electrode precursor cathodic prior to removal from the molten salt electrolyte at an electrical current not exceeding the current density while anodic.