Hermetic implantable sensor

Abstract

At least one conductor is formed at a preselected location on a substrate made of a first insulating material having a high temperature resistance. The conductor is made from a solidified electrically conductive thick film material. A coating made of a second insulating material is formed over the substrate to hermetically seal at least a portion of the conductor. An exposed distal region of the conductor provides a detection electrode. The conductor has a reduced porosity that inhibits migration of fluid or constituents thereof through the conductor.

What is claimed is: 
     
         1 . A method of fabricating a sensor, comprising the steps of:
 providing a substrate made of a first insulating material having a high temperature resistance;   depositing an electrically conductive thick film material on the substrate to form at least one un-solidified conductor, said thick film material containing particles of a metal selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium and osmium;   heating the electrically conductive thick film material to a first predetermined temperature, below a second predetermined melting temperature thereof, which is sufficient to sinter a plurality of metal particles in the electrically conductive thick film material;   allowing the thick film material to cool to produce at least one solidified conductor having a porosity that is sufficiently low such that it may become hermetic when coated; and   coating a portion of the conductor with a second insulating material leaving at least one exposed region that provides a detection electrode.   
     
     
         2 . The method of  claim 1  wherein the first insulating material is selected from the group consisting of ceramic and glass/ceramic combinations. 
     
     
         3 . The method of  claim 2  wherein the ceramic is selected from the group consisting of oxides, carbides, borides, nitrides, and silicides of aluminum, zirconium, beryllium, silicon, titanium, yttrium, and zinc and mixtures thereof. 
     
     
         4 . The method of  claim 1  wherein the second insulating material is selected from the group consisting of glass, ceramic, glass/ceramic combinations, and polymers. 
     
     
         5 . The method of  claim 1  wherein the thick film material contains platinum particles and wherein the thick film material is heated to a peak temperature between about 1500 degrees C. and about 1700 degrees C. 
     
     
         6 . The method of  claim 5  wherein the thick film material is heated to the peak temperature for a dwell time between about ten minutes and about sixty minutes. 
     
     
         7 . The method of  claim 5  wherein the thick film material is heated to a temperature within a range that extends from below a melting point of a plurality of metal particles in the thick film material to approximately three hundred degrees C. below said melting point of a plurality of metal particles in the thick film material. 
     
     
         8 . A method of fabricating an electrochemical sensor, comprising the steps of:
 providing a substrate made of a first insulating material having a high temperature resistance;   depositing on the substrate an electrically conductive thick film material containing particles of a metal selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium and osmium to form at least one un-solidified conductor;   heating the electrically conductive thick film material to a first predetermined temperature m a range that extends from below a melting point of a plurality of metal particles in the thick film material to a temperature approximately 300 degrees C. below the melting point in order to sinter a plurality of metal particles in the electrically conductive thick film material;   allowing the thick film material to cool to produce at least one solidified conductor having a first porosity which is substantially less than a second porosity that would result from heating the electrically conductive thick film material to a temperature below the range; and   coating at least a portion of the at least one conductor with a second insulating material and leaving at least one exposed region thereof to provide a detection electrode.   
     
     
         9 . A method of fabricating a device implantable in living tissue for conveying electrical signals, comprising the steps of:
 providing a substrate made of a first biocompatible insulating material having a high temperature resistance;   depositing on the substrate an electrically conductive thick film material containing particles of a metal selected from the group consisting of platinum, palladium, rhodium ruthenium, iridium and osmium to form at least one un-solidified conductor;   heating the electrically conductive thick film material to a first predetermined temperature below a second predetermined melting temperature thereof which is sufficient to sinter a plurality of metal particles in the electrically conductive thick firm material;   allowing the thick film materials to cool to produce at least one solidified conductor having a porosity that is sufficiently low such that it may become hermetic when coated; and   coating at least a portion of the at least one solidified conductor with a second biocompatible insulating material.   
     
     
         10 . An antenna, comprising:
 a substrate made of a first insulating material having a high temperature resistance;   at least one conductor made of sintered metal particles and formed at a preselected location on the substrate and made from a solidified electrically conductive thick film material having metal particles sintered to provide reduced porosity in the conductor, said thick film material containing particles of a metal selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium and osmium;   a coating made of a second insulating material formed over the substrate in order to hermetically seal at least a portion of the conductor; and   the conductor having a predetermined geometry for transmitting or receiving RF signals at a predetermined frequency.   
     
     
         11 . The antenna of  claim 10  wherein the first insulating material is selected from the group consisting of ceramic and glass/ceramic combinations. 
     
     
         12 . The antenna of  claim 11  wherein the ceramic is selected from the group consisting of oxides, carbides, borides, nitrides, and silicides of aluminum, zirconium, beryllium, silicon, titanium, yttrium, and zinc and mixtures thereof. 
     
     
         13 . The antenna of  claim 11  wherein the second insulating material is selected from the group consisting of glass, ceramic, glass/ceramic combinations, and polymers. 
     
     
         14 . The antenna of  claim 10  wherein the substrate has a generally planar configuration. 
     
     
         15 . The antenna of  claim 10  and further comprising means extending through a hole in the substrate for providing an electrical connection to the conductor.