Strip electrode with conductive nano tube printing

Abstract

A sensor system that detects a current representative of a compound in a liquid mixture features a multi or three electrode strip adapted for releasable attachment to signal readout circuitry. The strip comprises an elongated support which is preferably flat adapted for releasable attachment to the readout circuitry; a first conductor and a second and a third conductor each extend along the support and comprise means for connection to the circuitry. The circuit is formed with single-walled or multi walled nanotubes conductive traces and may be formed from multiple layers or dispersions containing, carbon nanotubes, carbon nanotubes/antimony tin oxide, carbon nanotubes/platinum, or carbon nanotubes/silver or carbon nanotubes/silver-chloride. An active electrode formed from a separate conductive carbon nanotubes layer or suitable dispersion, positioned to contact the liquid mixture and the first conductor, comprises a deposit of an enzyme capable of catalyzing a reaction involving the compound and preferably an electron mediator, capable of transferring electrons between the enzyme-catalyzed reaction and the first conductor. A reference electrode also formed from a conductive carbon nanotube layer or suitable dispersion is positioned to contact the mixture and the second conductor. The system includes circuitry adapted to provide an electrical signal representative of the current which is formed from printing conductive inks made with nano size particles such as conductive carbon or carbon/platinum or carbon/silver, or carbon nanotubes/antimony tin oxide to form a conductive carbon nanotube layers. The multiple-electrode strip is manufactured, by then applying the enzyme and preferably the mediator onto the electrode. Alternatively the electrode can have a carbon nanotubes/antimony tin oxide, carbon nanotubes/platinum, or carbon nanotubes/silver or carbon nanotubes/silver-chloride surface and or a conductive carbon or silver ink surface connecting leg. The carbon nanotube solution is first coated and patterned into electro shapes and the conductive carbon nanotubes, carbon or silver ink can be attached by printing the ink to interface with the carbon nanotube electro surface. A platinum electrode test strip is also disclosed that is formed from either nano platinum distributed in the carbon nanotube layer or by application or incorporation of platinum to the carbon nanotube conductive ink.

1 . An electrochemical test device for determining the presence or concentration of an analyte in an aqueous fluid sample, the electrochemical test device comprising: 
 (a) one or more substrates comprising a non-conductive surface;    (b) a working electrode disposed on the surface of one of the one or more substrates and including a first electrode area comprising a conductive electrochemical reaction surface including a plurality of carbon nanotubes;    (c) a counter electrode disposed on the surface of one of the one or more substrates and including a second electrode area comprising a conductive film;    (d) a reference electrode disposed on the surface of one of the one or more substrates and including a second electrode area comprising a conductive film, and wherein at least a portion of the third electrode area comprises a reference material; and    (e) a reagent capable of reacting with the analyte to produce a measurable electrical effect which can be correlated to the presence or concentration of the analyte in the fluid sample, the reagent disposed in operative association with the first electrode area of the working electrode.    
     
     
         2 . The device of  claim 1 , wherein the conductive film of the electrode area of at least one of the counter electrode and the reference electrode comprises a conductive material with a size greater than 20 nm.  
     
     
         3 . The device of  claim 1 , wherein the conductive film of the working electrode comprises one or both of a second conductive material or a non-conductive material.  
     
     
         4 . The device of  claim 1 , wherein the conductive film of the first electrode area of the working electrode comprises a conductive material including essentially only carbon nanotubes.  
     
     
         5 . The device of  claim 1 , wherein the reference material comprises silver/silver-chloride.  
     
     
         6 . The device of  claim 1 , wherein the reagent includes an enzyme capable of reacting with the analyte, and enzyme is included in the conductive film.  
     
     
         7 . The device of  claim 6 , wherein the enzyme includes one or both of glucose oxidase and glucose dehydrogenase.  
     
     
         8 . The device of  claim 1 , wherein the conductive film of the first electrode area of the working electrode further includes a catalyst comprising a transition metal.  
     
     
         9 . The device of  claim 8 , wherein the catalyst comprises platinum.  
     
     
         10 . The device of  claim 1 , wherein the reagent includes a redox mediator.  
     
     
         11 . The device of  claim 10 , wherein redox mediator is included in the conductive film of the first electrode area of the working electrode.  
     
     
         12 . The device of  claim 10 , wherein the redox mediator is selected from the group consisting of imidazole osmium; potassium ferricyanide; 1,1.cent.-dimethyl ferrocene; methylene blue; p-benzoquinone; thionine; 2,6-dichloroindophenol; gallocyanine, indophenol; polyviologen; osmium bis (2,2.cent.-bipyridine) dihydrochloride; riboflavin-5.cent.-phosphate ester; and tetracyanoquinodimethane).  
     
     
         13 . An electrochemical test device for determining the presence or concentration of an analyte in an aqueous fluid sample, the electrochemical test device comprising: 
 (a) at least one substrate, the substrate comprising a non-conductive surface;    (b) a working electrode comprising a conductive film affixed to the non-conductive substrate surface, the working electrode having a first electrode area made by coating a liquid dispersion containing carbon nanotubes with a size greater than 20 nm with a surface morphology less than 0.33 microns RMS, a first lead and a first contact pad;    (c) a counter electrode comprising a conductive film affixed to the non-conductive substrate surface, the counter electrode having a second electrode area, a second lead and a second contact pad;    (d) a reagent capable of reacting with the analyte to produce a measurable electrical effect which can be correlated to the presence or concentration of the analyte in the fluid sample, the reagent disposed in association with at least a portion of the first electrode area of the working electrode; and    wherein the conductive film of at least one of the working electrode and the counter electrode includes a first conductive material comprising a plurality of carbon nanotubes less than 20 nm in diameter; and wherein at least one of the conductive films includes platinum.    
     
     
         14 . An electrochemical test device for determining the presence or concentration of an analyte in an aqueous fluid sample, the electrochemical test device comprising: 
 (a) at least one substrate, the substrate comprising a non-conductive surface;    (b) a working electrode comprising a conductive film affixed to the non-conductive substrate surface, the working electrode having a first electrode area made by coating a liquid dispersion containing carbon nanotubes with a size greater than 20 nm with a surface morphology less than 0.33 microns RMS with a surface morphology less than 0.33 microns RMS, a first lead and a first contact pad;    (c) a counter electrode comprising a conductive film affixed to the non-conductive substrate surface, the counter electrode having a second electrode area, a second lead and a second contact pad;    (d) a reagent capable of reacting with the analyte to produce a measurable electrical effect which can be correlated to the presence or concentration of the analyte in the fluid sample, the reagent disposed in association with at least a portion of the first electrode area of the working electrode; and    wherein the conductive film of at least one of the working electrode and the counter electrode includes a first conductive material comprising a plurality of carbon nanotubes; and wherein the leads of at least one of the working electrode and the counter electrode are formed from a second conductive material which includes a coarse solid conductive material.    
     
     
         15 . An electrochemical test device for determining the presence or concentration of an analyte in an aqueous fluid sample, the determination occurring in operative association with measurement circuitry including a metering device; the electrochemical test device comprising: 
 (a) one or more substrates, each substrate comprising a non-conductive surface;    (b) a working electrode disposed over at least the surface of one of the one or more substrates, the working electrode including: 
 (i) a first electrode portion including a conductive layer comprising a dispersion of a plurality of carbon nanotubes, the layer configured to provide effective transfer of charge in an electrochemical reaction in a communicating aqueous fluid sample;  
 (ii) a first conductive lead portion contacting and extending from the first electrode portion and configured to contact the measurement circuitry so as to communicate an electrical signal between the first electrode portion and the metering device,  
   (c) a counter electrode disposed over at least the surface of one of the one or more substrates, the counter electrode including a conductive second electrode portion and a second conductive lead portion extending from the second electrode portion, the second lead portion configured to contact the measurement circuitry so as to communicate an electrical signal between the second electrode portion and the metering device; and    (d) a reagent material disposed in association with the working electrode, the reagent material capable of reacting with the analyte to produce a measurable electrochemical effect which can be correlated to the presence or concentration of the analyte in the fluid sample; and    wherein the working electrode, the counter electrode and the one or more substrates are collectively arranged to form a region configured to position the aqueous fluid sample in communication with the reagent material, the working electrode and the counter electrode.    
     
     
         16 . The device of  claim 15 , wherein the electrochemical reaction surface of the conductive layer of the first electrode portion is formed by coating a liquid dispersion including carbon nanotubes with a size greater than 20 nm; and wherein the electrochemical reaction surface has a surface morphology less than 33 microns RMS.  
     
     
         17 . The device of  claim 15 , further comprising a reference electrode disposed over at least the surface of one of the one or more substrates, the reference electrode including a third electrode portion and a third conductive lead portion extending from the third electrode portion, the third conductive lead portion configured to contact the measurement circuitry so as to communicate an electrical signal between the third electrode portion and the metering device, and wherein at least a portion of the third electrode area comprises a reference material.  
     
     
         18 . The device of  claim 17 , wherein the reference material comprises silver/silver-chloride.  
     
     
         19 . The device of  claim 15 , wherein the conductive second electrode portion of the counter electrode comprises a reference material.  
     
     
         20 . The device of  claim 19 , wherein the reference material comprises silver/silver-chloride.  
     
     
         21 . The device of  claim 19 , wherein the second electrode area and the first electrode area are disposed closely space-apart from one another on the same substrate surface.  
     
     
         22 . The device of  claim 15 , wherein the conductive lead portion of at least one of the working electrode and the counter electrode comprises a coarse solid conductive material.  
     
     
         23 . The device of  claim 15 , wherein first electrode portion of the working electrode further comprises a polymeric binder material disposed in association with the dispersion of carbon nanotubes.  
     
     
         24 . The device of  claim 23 , wherein sufficient carbon nanotubes of the dispersion interconnect with one another to provide a overall conductive layer, and wherein the polymeric binder material is configured to permit effective charge transfer between nanotubes of the dispersion and a communicating aqueous fluid sample.  
     
     
         25 . The device of  claim 15 , wherein the reagent includes an enzyme capable of reacting with the analyte, and enzyme is included in the conductive film.  
     
     
         26 . The device of  claim 25 , wherein the enzyme includes one or both of glucose oxidase and glucose dehydrogenase.  
     
     
         27 . The device of  claim 15 , wherein the conductive film of the first electrode area of the working electrode further includes a catalyst comprising a transition metal.  
     
     
         28 . The device of  claim 27 , wherein the catalyst comprises platinum.  
     
     
         29 . The device of  claim 15 , wherein the reagent includes at least one redox mediator.  
     
     
         30 . The device of  claim 29 , wherein the redox mediator is selected from the group consisting of imidazole osmium; potassium ferricyanide; 1,1.cent.-dimethyl ferrocene; methylene blue; p-benzoquinone; thionine; 2,6-dichloroindophenol; gallocyanine, indophenol; polyviologen; osmium bis (2,2.cent.-bipyridine) dihydrochloride; riboflavin-5.cent.-phosphate ester; and tetracyanoquinodimethane).  
     
     
         31 . An electrochemical electrode structure for a test device for measuring the concentration of an analyte in a fluid sample, comprising: a plurality of layers disposed upon a substrate having a non-conductive substrate surface, each successive layer being at least partially superimposed upon at least one under-disposed layer, including: 
 (a) an elongate trace layer comprising a first conductive material, configured to provide a conduction path permitting transmission of an electrical signal along the conduction path;    (b) an active electrode layer comprising a dispersion of conductive carbon nanotubes, the active electrode layer including an electrochemical reaction surface configured to provide effective transfer of charge through the carbon nanotubes of the dispersion in an electrochemical reaction in communication with the fluid sample; and    (c) an reagent layer comprising at least one enzyme capable of reacting with the analyte to produce an electrochemically measurable electrical effect which can be correlated to the presence or concentration of the analyte in the fluid sample.    
     
     
         32 . The device of  claim 31 , wherein the electrochemical reaction surface of the active electrode layer if formed by coating a liquid dispersion including carbon nanotubes with a size greater than 20 nm; and wherein the electrochemical reaction surface has a surface morphology less than 33 microns RMS.  
     
     
         33 . The device of  claim 31 , wherein the active electrode layer further comprises at least one non-conductive material.  
     
     
         34 . The device of  claim 31 , wherein the active electrode layer further comprises a polymeric binder material.  
     
     
         35 . The device of  claim 31 , further comprising a binder layer configured to stabilize at least a portion of the active electrode layer.  
     
     
         36 . The device of  claim 31 , further comprising a mediator layer including a redox mediator, selected to enhance an electrical effect of a reaction of the enzyme with the analyte.  
     
     
         37 . The device of  claim 31 , further comprising a buffer layer including a buffer material selected to promote activity of the enzyme with the analyte.  
     
     
         38 . The device of  claim 31 , wherein the reagent layer further comprises at least one of (i) a redox mediator, selected to enhance an electrical effect of a reaction of the enzyme with the analyte; and (ii) a buffer material selected to promote activity of the enzyme with the analyte.  
     
     
         39 . The device of  claim 31 , wherein the reagent layer is disposed over at least a portion of the active electrode layer.  
     
     
         40 . The device of  claim 31 , wherein the trace layer lies on the substrate surface.  
     
     
         41 . The device of  claim 31 , wherein first conductive material of the trace layer comprises a metallic ink material.  
     
     
         42 . The device of  claim 31 , wherein first conductive material of the trace layer comprises a carbon-containing ink material.  
     
     
         43 . The device of  claim 31 , wherein at least one of the trace layer and the reagent layer is at least partially integrated with the active electrode layer.  
     
     
         44 . The device of  claim 15 , wherein the conductive second electrode portion of the counter electrode includes a conductive layer comprising a dispersion of carbon nanotubes, the layer configured to provide effective transfer of charge in an electrochemical reaction in a communicating aqueous fluid sample.  
     
     
         45 . The device of  claim 31 , wherein the active electrode layer further comprises at least one conductive material in addition to carbon nanotubes.