Biosensor and related manufacturing method

Abstract

The biosensor includes a first base member and a parallel second base member arranged in a parallel spaced apart relationship. At least one conductive layer is deposited on an opposing surface of each of the first and second base members in respective first and second conductive regions. The first conductive region includes at least one layer made from a first conductive material and the second conductive region includes at least one layer made from a second conductive material different from the first conductive material. The first conductive material is a noble metal, the first conductive regions of the biosensor define coplanar electrodes, and the second conductive layer is configured to electrically connect the coplanar electrodes to a test meter.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. patent application Ser. No. 17 / 749,759, entitled "BIOSENSOR AND RELATED METHOD OF MANUFACTURE," filed May 20, 2022, which is incorporated by reference in its entirety.

[0002] FIELD OF THEINVENTION This application relates generally to the field of biosensors, and more particularly to test strips and related methods for manufacturing test strips having one or more spaced apart layers of conductive material, wherein a coplanar electrode formed locally at one end of the test strip is made from a precious metal, and the remainder of the conductive layer of the test strip is made from another conductive material configured to enable electrical connection between the coplanar electrode and a test meter. [Background technology]

[0003] In the field of diabetes management, biosensors such as test strips onto which a blood sample can be applied are known. One end of the test strip is inserted into a test meter that applies at least one predetermined voltage to two or more electrodes formed on the test strip. The electrodes are made from a precious metal such as gold or palladium in addition to at least one reagent layer that is applied to one of the electrodes. Upon application of the at least one predetermined voltage, an electrochemical reaction occurs and the resulting current can be measured to determine the blood glucose concentration in the blood sample.

[0004] The inclusion of precious metals significantly impacts the manufacturing costs of the above-mentioned test strips, and therefore there is a widespread need in the field to reduce the amount of precious metals used in the manufacture of such biosensors without affecting their functionality or overall performance. Summary of the Invention

[0005] Thus, according to an aspect of the invention, a biosensor is provided that includes a first base member and a second base member made of insulating material facing each other in a spaced apart parallel relationship. At least one conductive layer is deposited on the facing surface of each of the first and second base members, more specifically on a first conductive region and a second conductive region adjacent the first conductive region. According to at least one version, the first conductive region includes a deposited layer of a first conductive material, the second conductive region includes at least a second conductive material different from the first conductive material, the first conductive material being a noble metal, and the first conductive regions form coplanar electrodes of the biosensor.

[0006] According to at least one embodiment, the noble metal disposed in the first conductive region of the biosensor can be at least one of gold and palladium. Alternatively, other noble metals from the group consisting of platinum, iridium, osmium, rhenium, ruthenium, and rhodium can be used to form the coplanar electrodes. The second conductive material can be made of any suitable conductive material, including but not limited to silver, copper, nickel, chromium, and / or alloys thereof, and the first and second conductive regions are electrically coupled to each other. According to one version, the first conductive region is defined by a single deposited layer of noble metal. In another version, the first conductive region is defined by a first deposited layer made of the second conductive material and a second deposited layer made of noble metal applied on the first deposited layer.

[0007] Preferably, the precious metal layer overlaps a portion of the non-precious metal layer. The biosensor may further include a spacer or spacer layer made of plastic or other insulating material introduced between the conductive material layers. The spacer layer includes a gap or space that serves as a functional area where an electrochemical reaction occurs in the presence of blood or other bodily fluid introduced into the biosensor. The biosensor further includes a contact pad defined in the second conductive region that is connectable to a test meter configured to provide at least one test voltage to the electrodes of the biosensor.

[0008] The opposing base members in the biosensor may be substrates or films made of electrically inactive materials. The noble metal layer may be applied by any suitable deposition process, including physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes. According to at least one embodiment, the noble metal layer is deposited with the second conductive region masked against the first conductive region. The second conductive metal layer may also be applied by any suitable deposition process.

[0009] According to another aspect, a method for manufacturing a biosensor is provided, the method comprising: Providing a first base member and a second base member; depositing at least one conductive layer on first and second conductive regions of each of the first and second base members; a first conductive material is deposited on each first conductive region and a second conductive material, different from the first conductive material, is deposited on each second conductive region adjacent the first conductive region, the first conductive material being a noble metal; The method includes disposing first conductive regions of the first and second base members in a spaced apart relationship to one another, such that the first conductive regions of the biosensor form a pair of coplanar electrodes.

[0010] In at least one version, a second conductive material is applied to the entire surface of each base member and then a first conductive material is deposited over the second conductive material, but only on the first conductive regions of the biosensor.

[0011] In another version, a first conductive material can be deposited on the first conductive region of each base member and a second conductive material can be deposited on the second conductive region. Preferably, a seam or other overlap is provided between the precious metal layer and the non-precious metal layer to maintain electrical connectivity between the defined electrodes and the test meter.

[0012] According to the present invention, non-precious metals can be incorporated into biosensors, more specifically electrochemical-based test strips with coplanar electrodes, in combination with precious metals by using a mask during the deposition process to apply a well-defined layer of precious metal to cover at least the working area of ​​the test strip (i.e., the area of ​​the test strip where the heterogeneous electrochemical reaction occurs). Advantageously, this design allows for the separation of the two functions of the test strip, namely the transmission of the electrical signal performed by the non-precious metal or alloy, and the surface chemical reaction performed on the precious metal portion of the substrate layer.

[0013] An advantage offered is that existing precious metal layers can be used in combination with non-precious metal materials for use in test strip production lines without affecting overall performance, thus realizing significant cost savings for the manufacture of biosensors.

[0014] Another advantage is that by using a precious metal stripe in combination with a non-precious metal or alloy layer, the chemistry of the test strip is not altered with respect to interaction with the existing precious metal surface.

[0015] Considerations such as surface energy, reagent adhesion, surface oxidation, and adsorption of contaminants to the electrode surface all remain substantially the same as with conventional known test strip designs.

[0016] Additionally, control of the thickness of the non-noble metal or alloy layer by the methods described herein allows the resistance value to be tailored to match that of a precious metal, thereby providing a conductive path or bridge for electrical signal transmission having a resistance comparable to that of precious metals (e.g., palladium and gold).

[0017] Additionally, the use of non-precious metals or alloys having a hardness greater than that of precious metals, especially gold, improves the robustness of the test strip's electrical contact with the test meter's connector.

[0018] These and other features and advantages will become readily apparent from the following detailed description which should be read in conjunction with the accompanying drawings. [Brief description of the drawings]

[0019] [Figure 1A] 1 is a top perspective view of a known test strip. [Figure 1B] 1B is an exploded top perspective view of the test strip of FIG. 1A. [Figure 1C] FIG. 1C is an enlarged perspective view of a distal portion of the test strip of FIGS. 1A and 1B. [Figure 1D] FIG. 2 is a side elevational view in cross section of a distal portion of the test strip of FIGS. 1A-1C. [Diagram 2] FIG. 2 is a schematic diagram of a test meter coupled to the test strip of FIGS. 1A-1D. [Diagram 3] 3 is an exemplary voltage waveform used in conjunction with the test meter of FIG. 2 for application to the test strip of FIGS. 1A-1D. [Figure 4] 1 is an exploded perspective view of a test strip made in accordance with an embodiment of the present invention. [Diagram 5] 5 is a top perspective view of the test strip of FIG. 4. [Figure 6(a)] 1 is a top view of a portion of a test strip made in accordance with an embodiment of the present invention. [Figure 6(b)] FIG. 6(b) is a side elevational view of a portion of the test strip of FIG. 6(a). [Figure 7] 1 is a side elevational view of a test strip shown in exploded form and made in accordance with an embodiment of the present invention. [Figure 8] 8 is a side elevational view of a portion of the test strip of FIG. 7. [Figure 9(a)] 9A and 9B are top and side elevational views, respectively, of a portion of the test strip of FIGS. 7 and 8, showing the overlap region. [Figure 9(b)] 9A and 9B are top and side elevational views, respectively, of a portion of the test strip of FIGS. 7 and 8, showing the overlap region. [Figure 10] 1 shows a side elevational view of another test strip made in accordance with an embodiment of the present invention. [Figure 11] 1 shows a side elevational view of another test strip made in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The following describes several embodiments of biosensors used to determine at least one analyte of interest (e.g., blood glucose), as well as related methods for fabricating the biosensors. More specifically, each of the biosensors and related fabrication methods described herein relate to a test strip having one or more opposing (coplanar) electrodes that define an electrochemical cell in which an electrical potential is driven in the presence of an enzyme or other reagent applied to at least one of the electrodes to cause an electrochemical reaction in the presence of a bodily fluid sample (e.g., whole blood). However, it will be understood that the invention disclosed herein may in principle be used with any type of electrochemical cell having spaced apart coplanar electrodes and a reagent layer. For example, the electrochemical cell may be in the form of a test strip. In one aspect, the test strip may include two opposing electrodes separated by a thin spacer layer, defining a sample-receiving chamber or zone with a reagent layer disposed on one of the opposing electrodes. Those skilled in the art will appreciate that other types of test strips, including configurations having two or more opposing electrodes, may also be used in accordance with the methods described herein.

[0021] Additionally, throughout the following description, certain terms are used to provide a proper frame of reference with respect to the accompanying drawings. These terms include "first," "second," "distal," "proximal," "upper," "lower," "top," "bottom," and the like, and are not intended to unduly narrow the scope of the present invention unless otherwise specified. Furthermore, the accompanying drawings are intended to adequately depict the salient features of the present invention. Thus, the drawings are not necessarily to scale and should not be used for scalar purposes.

[0022] For background, each of Figures 1A-1D illustrates a known biosensor in the form of a test strip 62 having a plurality of stacked layers, the test strip 62 being further defined by a distal end 80 and an opposing proximal end 82. The distal end 80 of the test strip 62 includes a sample receiving chamber 61 formed therein, and the proximal end 82 of the test strip 62 is configured to connect to a test meter, as shown diagrammatically in Figure 2. More specifically, the test strip 62 includes a pair of base or substrate members 64, 66, each of which is made from a suitable plastic material. When assembled, each of the base members 64, 66 is defined by an interior or inwardly facing surface and an opposing exterior or outwardly facing surface. Each of the inwardly facing surfaces of the base members 64, 66 is completely coated with a metallized film. More specifically, the inner surface of the upper base member 64 is coated with gold to form a metallized gold layer, and the inner surface of the lower base member 66 of the test strip 62 is coated with palladium to form a metallized palladium layer. Each of the precious metal layers covers the entire inwardly facing surface of the formed test strip 62, and the precious metal layers are applied to the base members 64, 66 using a sputtering process.

[0023] Sandwiched between the upper and lower precious metal layers is a spacer layer 60, also made from a suitable plastic. The spacer layer 60 includes a cut-out area 68 adjacent the distal end 80 of the test strip 62, which provides a predetermined spacing or gap between the metallized film layers and cooperates to form the sample receiving chamber 61. A reagent layer 72 including an enzyme / mediator is deposited on a portion of the surface of the metallized palladium layer at the distal end 80 of the test strip 62, forming coplanar electrodes of the test strip 62 separated by the spacer layer 60 which extends through the spacing 68. The test strip 62 further includes one or more electrode connection points or contact pads 67 formed at the proximal end 82 of the test strip 10, with the gold and palladium layers defining electrodes in the working area of ​​the test strip and electrode track connections to the contact pads 67, as shown in Figures 1A-1D.

[0024] The applied metallized film layers commonly provide upper and lower coplanar electrodes 166, 164, connecting tracks 76, 78, and contact pads 67, 63, with the connecting tracks 76, 78 of each metallized film layer electrically connecting the electrodes 166, 164 to the contact pads 63, 67 as shown in Figure 1B. The first electrode 166 is part of the applied metallized film layer immediately below the reagent layer 72 shown in Figure 1B. Similarly, the second electrode 164 is part of the remaining metallized film layer above the reagent layer 72.

[0025] The sample receiving chamber 61 is defined by a first electrode 166, a second electrode 164, and a spaced apart gap or cut-out area 68 formed in the spacer 60 near the distal end 80 of the test strip 62, as shown in Figures 1B and 1D. The first electrode 166 and the second electrode 164 define a bottom and a top of the sample receiving chamber 61. The cut-out area 68 of the spacer 60 defines the sidewalls of the sample receiving chamber 61. The sample receiving chamber 61 includes one or more ports 70 that provide sample inlet and / or vent. In the illustrated version, two ports 70 are provided, one port (see arrow 70) that allows for the entry of a fluid sample and the other port 70 that functions as a vent.

[0026] The sample receiving chamber 61 of the described test strip 62 has a small volume ranging from about 0.1 microliters to about 5 microliters, from about 0.2 microliters to about 3 microliters, or preferably from about 0.3 microliters to about 1 microliter. To provide the small sample volume, the cutout 154 is approximately 0.01 cm 2 ~ approx. 0.2cm 2 , about 0.02cm 2 ~about 0.15cm 2 , or preferably, about 0.03 cm 2 ~about 0.08cm 2In addition, the formed electrodes 166, 164 are spaced apart at intervals ranging from about 1 micron to about 500 microns, preferably between about 10 microns to about 400 microns, and more preferably between about 40 microns to about 200 microns. The relatively close spacing of the electrodes 166, 164 further allows for a redox cycle to occur, where an oxidized mediator produced at a first electrode can diffuse to a second electrode to be reduced, and then diffuse back to the first electrode to be reoxidized.

[0027] For reagent layer 60, examples of suitable mediators include ferricyanide, ferrocene, ferrocene derivatives, osmium bipyridyl complexes, and quinone derivatives. Examples of suitable enzymes include glucose oxidase, glucose dehydrogenase (GDH) using a pyrroloquinoline quinone (PQQ) cofactor, GDH using a nicotinamide adenine dinucleotide (NAD) cofactor, and GDH using a flavin adenine dinucleotide (FAD) cofactor [EC 1.1.99.10].

[0028] For operability, either the gold layer or the palladium layer can act as the working electrode of the test strip 62, depending on the magnitude and / or polarity of a test voltage applied from a test meter coupled to the test strip 62. The working electrode can measure a test-limiting current that is proportional to the reduced mediator concentration. For example, if the current-limiting species is a reduced mediator (e.g., ferrocyanide), it can be oxidized at the first electrode 166 as long as the test voltage is sufficiently more positive than the redox mediator potential relative to the second electrode 164. In such a situation, the first electrode 166 acts as the working electrode and the second electrode 164 acts as the counter / reference electrode.

[0029] Similarly, if the test voltage is sufficiently negative than the redox mediator potential, the reduced mediator may be oxidized at the second electrode 164 as the limiting current. In such a situation, the second electrode 164 acts as the working electrode and the first electrode 166 acts as the counter / reference electrode.

[0030] Initially, performing an analysis using a test strip 62 described herein involves introducing a volume of a fluid sample into the sample receiving chamber 61 through one of the ports 70. The port 70 and / or the sample receiving chamber 61 are configured to allow capillary action to cause the fluid sample to fill the sample receiving chamber 61. The first electrode 166 and / or the second electrode 164 may be coated with a hydrophilic reagent to promote capillary action in the sample receiving chamber 61.

[0031] FIG. 2 provides a simplified diagram showing a test meter 100 connecting with a first contact pad 67 and a second contact pad 63 of a test strip 62. The second contact pad 63 can be used to establish an electrical connection to the test meter 100 through a U-shaped notch 65 as shown in FIGS. 1A-1D. In one embodiment, the test meter 100 can include a second electrode connector 101, first electrode connectors 102a, 102b, a test voltage section 106, a current measurement section 107, a processor 212, a memory section 210, and a visual display 202 as shown generally in FIG. 2. The first contact pad 67 includes two prongs 67a, 67b. The first electrode connectors 102a, 102b connect separately to the prongs 67a, 67b, respectively. The second electrode connector 101 can be connected to the second contact pad 63. Test meter 100 is configured to measure the resistance or electrical continuity between prongs 67a, 67b to determine whether test strip 62 is electrically connected to test meter 100. Those skilled in the art will appreciate that test meter 100 may use a variety of sensors and circuitry to determine when test strip 62, or variations thereof, is properly positioned relative to test meter 100.

[0032] Test meter 100 is configured to apply a test voltage and / or current between first contact pad 67 and second contact pad 63. Once test meter 100 recognizes that test strip 62 has been inserted, test meter 100 turns on and initiates a fluid detection mode. In one embodiment, the fluid detection mode causes test meter 100 to apply a voltage such that a constant current of approximately 0.5 microamps flows between first electrode 166 and second electrode 164. Because test strip 62 is initially dry, test meter 100 measures a relatively large voltage, which may be limited by the maximum voltage that test meter 100 can supply. As the fluid sample fills the gap between first electrode 166 and second electrode 164 during the administration process, test meter 100 measures a decrease in the applied voltage, which, if it falls below a predetermined threshold, causes test meter 100 to automatically initiate a glucose test sequence.

[0033] In the version described herein in this context, test meter 100 can perform a glucose test by applying multiple test voltages over multiple predetermined intervals, as shown in FIG. 1 The first test voltage V applied to 1 , the second time interval T 2 The second test voltage V applied to 2 , and a third time interval T 3 The third test voltage V applied to 3 The glucose test time interval T G represents the amount of time to perform a glucose test (but not necessarily all of the calculations associated with the glucose test). The glucose test time interval T Gcan range from about 1 second to about 15 seconds or more, more preferably from about 1 second to about 5 seconds, as shown in FIG. 3. The multiple test current values ​​measured during the first, second, and third time intervals may be performed at a frequency ranging from about 1 measurement per nanosecond to about 1 measurement per 100 milliseconds. Although an embodiment is described that uses three test voltages in a serial manner, one skilled in the art will appreciate that the glucose test sequence may include a different number of open circuit voltages and test voltages. For example, in an alternative embodiment, the glucose test sequence may include an open circuit for a first time interval, a second test voltage for a second time interval, and a third test voltage for a third time interval. One skilled in the art will appreciate that the designations "first," "second," and "third" are chosen for convenience and do not necessarily reflect the order in which the test voltages are applied. For example, an embodiment may have a potential waveform in which a third test voltage may be applied prior to application of the first and second test voltages.

[0034] When a glucose assay is initiated, test meter 100 begins measuring a first time interval T 1 (e.g., for about 1 second) 1 (e.g., about −20 mV as shown in FIG. 3) may be applied during the first time interval T 1 can be in the range of about 0.1 seconds to about 3 seconds, preferably in the range of about 0.2 seconds to about 2 seconds, and most preferably in the range of about 0.3 seconds to about 1 second.

[0035] First time interval T 1 may be long enough so that sample-receiving chamber 61 may be completely filled with sample and so that reagent layer 72 may be at least partially dissolved or solvated. Reagent layer 160 has an area larger than the area of ​​the electrodes formed thereon, such that a portion of spacer layer 150 may overlap and contact reagent layer 160. In one embodiment, first test voltage V 1 can be a relatively low value so that a relatively small amount of reduction or oxidation current is measured. Typically, the second and third time intervals T 2 and T 3 A relatively small amount of current flows during the first time interval T1 For example, when ferricyanide and / or ferrocyanide are used as the mediator, the first test voltage V 1 can be in the range of about -100 mV to about -1 mV, preferably in the range of about -50 mV to about -5 mV, and most preferably in the range of about -30 mV to about -10 mV.

[0036] First test voltage V 1 After applying the second test voltage V, the test meter 100 applies a second test voltage V between the first electrode 166 and the second electrode 164. 2 (for example, about -0.3 volts as shown in Figure 3) for a second time interval T 2 (e.g., for about 3 seconds as shown in Figure 3). 2 may be a sufficiently negative value of the mediator redox potential such that an oxidation-limited current is measured at the second electrode 64. For example, when ferricyanide and / or ferrocyanide are used as the mediator, the second test voltage V 2 can be in the range of about -600 mV to about 0 mV, preferably in the range of about -600 mV to about -100 mV, more preferably about -300 mV.

[0037] The second time interval T 2 The second time interval T should be long enough so that the rate of production of the reduced mediator (e.g., ferrocyanide) can be monitored based on the magnitude of the oxidation-limiting current. The reduced mediator is produced by an enzymatic reaction with the reagent layer 72. 2 During this time, a limited amount of reduced mediator is oxidized at the second electrode 164 and a non-limited amount of oxidized mediator is reduced at the first electrode 166 to form a concentration gradient between the first electrode 166 and the second electrode 164. Further details regarding the manufacture and testing of test strips 62 are described in U.S. Patent Nos. 8,529,751 and 8,449,740, the contents of each of which are incorporated herein by reference in their entirety.

[0038] With the foregoing background, Figures 4 and 5 illustrate the basic configuration of a test strip 400 made in accordance with the present invention. More specifically, test strip 400 includes all of the structural components of test strip 62 described above in Figures 1A-1D, and is configured to connect to a test meter such as that shown in Figure 2 for application of a test waveform such as that shown in Figure 3. More specifically, test strips described herein in accordance with the present invention generally include respective upper and lower base members 404 and 408, and a spacer layer 420 sandwiched between upper and lower base members 404 and 408, the spacer layer 420 including a cutout region 428 adjacent a distal end 410 of test strip 100. However, unlike prior known versions, the precious metal layer is applied only to a localized portion of one or both of base members 404, 408, which is referred to herein as a first conductive region 440, located at the distal end 410 of test strip 400 and includes cutout region 428 of spacer layer 420. As previously mentioned, the upper base member 404 and the lower base member 408 are each made from a suitable insulating plastic material which may be provided as a rigid planar sheet or, alternatively, in film form.

[0039] 4 shows an exploded version of test strip 400 (reagent layer not shown in this view for clarity) showing a first conductive area 440 and an adjacent second conductive area 450, the second conductive area being essentially defined by the remaining portions of the opposing faces of upper base member 404 and lower base member 408, respectively. Only the first and second conductive areas 440, 450 of lower base member 408 are actually shown in FIG. 4, but it should be understood that the corresponding features of upper base member 404 are identical. First conductive area 440 includes cutout area 428 of spacer layer 420, which further defines a working area indicated by dark area 428 of test strip 400, as best seen in FIG. 5. A particular embodiment relating to the localized deposition of a metallized precious metal layer will now be described with reference to FIGS. 6(a)-11.

[0040] According to a first embodiment shown in FIG. 6(a) and FIG. 6(b), a first conductive material layer 460 is applied to the inner-facing surfaces of each of the upper and lower base members 404 and 408 of the test strip 400. Only the lower base member 408 is shown. For the purposes of the present invention, the first conductive material (e.g., non-precious metal) may include copper, silver, nickel, chromium, or alloys thereof (such as nichrome) and may be used as a material for electrical signal transmission. Literally any material having suitable electrical conductivity may be used for the first conductive layer 460. The first conductive material layer 460 may be applied by any suitable deposition technique, which may include a physical vapor deposition (PVD) process or a chemical vapor deposition (CVD) process, over the entire inner-facing surfaces of each of the upper and lower base members 404 and 408 according to this particular embodiment.

[0041] According to this first embodiment, adjacent the distal end 410 of the test strip 400, a second conductive material layer 470 is deposited directly on a portion of the first conductive layer 460 of each of the upper and lower base members 404 and 408. As shown in FIGS. 6(a) and 6(b), only the lower base member 408 is shown, but it will be understood that the upper base member 404 is similarly processed. More specifically, a strip of precious metal 470 is deposited directly on the first conductive material layer 460, but only in the first conductive region 440 located adjacent the distal end 410 of the test strip 400. According to this embodiment, a gold metallization layer (not shown) is deposited on the first conductive region of the upper base member 404, and a palladium metallization layer 470 is deposited on the first conductive region 440 of the lower base member 408. It will be understood that any noble metal may be selected for deposition, including those selected from the group consisting of platinum, iridium, rhenium, ruthenium, rhodium and osmium. The remaining portions of each first conductive material layer 460 are masked prior to depositing the noble metal layer 470, the latter of which may be deposited using any suitable deposition technique, but preferably using either a physical vapor deposition (PVD) or chemical vapor deposition (CVD) process. Furthermore, although this particular embodiment describes the use of two different noble metals (gold and palladium) on the electrodes facing each other, it will be understood that according to at least one other version, the same noble metal may be deposited on both of the defined electrodes. During manufacturing, the successive deposition of the film layers may be performed within the same material run or may be performed in separate runs.

[0042] According to another embodiment, referring to Figs. 7-9(b), another test strip 400A is provided. For clarity, like part numbers are given the same reference numerals herein. As previously mentioned, the test strip 400A includes an upper base member 404, a lower base member 408, a spacer layer 420 having a cut-out region 428 adjacent a distal end 410 of the test strip 400A, and a reagent layer 430 disposed in the cut-out region 428 directly above the lower base member 408. According to this embodiment, a first conductive material layer 460A is deposited on the opposing surfaces of the upper base member 104 and the lower base member 108, except for the first conductive region 440, which is masked. The first conductive layer 460A (i.e., non-precious metals) can include nickel, chromium, copper, and silver, and / or alloys such as nichrome can be used as materials for electrical signal transmission. As previously mentioned, literally any material having suitable electrical conductivity can be used for the first conductive material layer 460A. The first conductive material layer 460A, according to this particular embodiment, can be applied by any suitable deposition process over the entire inwardly facing surfaces of each of the upper and lower base members 404, 408. The first conductive area 440 at the distal end 410 of the test strip 400A is masked during deposition of the first conductive material (non-noble metal) layer 460A. A noble metal layer 470A is then deposited on each base member 404, 408, specifically directly on the first conductive area 440 of each of the upper and lower base members 404, 408, covering the area that will become the working area of ​​the test strip 400A. In this particular embodiment, gold or palladium is selected as the noble metal for the counter electrode, although it will be understood that other noble metals, including those previously mentioned, may be utilized. According to this embodiment, as best shown in Figures 8, 9(a) and 9(b), there is an overlap, indicated generally by reference numeral 480, of first and second conductive material layers 460A, 470A that extends over a distance compatible with the tolerances of the sputtering process.

[0043] If a difference in resistance exists (e.g., when using an alloy with a higher resistivity than that of the precious metal), the thickness of the sputtered layer can be increased or decreased for either the precious metal or non-precious metal layer to modify and match the electrical conductivity between the two layers to ensure that the conductivity of the non-precious metal or alloy layer is not signal limiting. For example, the thickness of the precious metal layer 470 in Figures 6(a) and 6(b) can be as thin as 5 nanometers, while in the spliced ​​adjacent version of Figures 7-9(b), the thickness of the precious metal layer 470A is thicker (e.g., at least 8 nanometers) due to the absence of an underlying metal layer.

[0044] It should be understood that other variations and modifications are possible. With reference to Figures 10 and 11, test strips 400B and 400C are shown in which a continuous precious metal layer 490 is disposed across the entire opposing surface of one of base members 404 (Figure 10) or base member 408 (Figure 11), and a "spliced" version using first and second conductive material layers 460A, 470A is applied to the other base member 408, 404. It should be understood that other suitable variations and configurations can be made in accordance with various aspects of the present invention.

[0045] In each of the embodiments described herein, the locally applied or deposited precious metal layers 470, 470A for each test strip define respective coplanar electrodes at the working area of ​​the test strip separated by cut-out areas 428 of the spacer layer 420. The overlapping portions of the non-precious metal material layers 460, 460A define electrode connection tracks that extend to contact pads provided at the opposing (proximal) end 414 of the test strip, thereby allowing connection to a test meter for application of appropriate test voltages in the manner previously described in Figures 2 and 3.

[0046] List of parts in Figures 1 to 11 60 Spacer layer 61 Sample receiving chamber 62 Test Strips 63 Contact Pad 64 Upper base member 65 U-shaped notch 66 Lower base member 67 Contact Pad 67a protrusion 67b Protrusion 68 Crop Area 70 Port 72 Reagent Layer 76 Electrode Track 78 Electrode Track 80 Distal end, test strip 82 Proximal end, test strip 100 Test and measurement equipment 101 second electrode connector 102a first electrode connector 102b first electrode connector 106 Test voltage section 107 Current measurement section 164 First Electrode 166 Second Electrode 202 Display 210 Memory section 212 processors 400 Test Strips 400A Test Strip 400B Test Strips 400C Test Strips 404 Upper base member 408 Lower base member 410 Distal end, test strip 414 Proximal end, test strip 420 Spacer layer 428 Cutout area, spacer layer 430 Reagent Layer 440 First conductive region 450 Second conductive area 460 First conductive material layer 460A first conductive material layer 470 Second conductive material layer 470A second conductive material layer 480 overlap (splice) 490 Continuous conductive material layer T 1 Time Interval T 2 Time Interval T 3 Time Interval T G Glucose test time (sequence)

[0047] It will be understood that only some exemplary embodiments have been described herein, and that several variations and modifications embodying the concepts of the present invention will become readily apparent to those skilled in the art upon reading this application and following the appended claims below.

Claims

1. 1. A biosensor comprising: A first base member; a second base member, the first base member and the second base member being fabricated from an insulating material, the first base member and the second base member opposing one another in a spaced apart parallel relationship; at least one conductive layer deposited on opposing surfaces of each of the first and second base members, each opposing surface including a first conductive region and a second conductive region adjacent to the first conductive region, the first conductive region including at least a first conductive material, the second conductive region including at least a second conductive material different from the first conductive material, the first conductive material being a noble metal, and the first conductive regions being coplanar electrodes of the biosensor.

2. 2. The biosensor of claim 1, wherein the precious metal is at least one of the group consisting of gold, palladium, platinum, osmium, rhodium, ruthenium, iridium, and rhenium.

3. 2. The biosensor of claim 1, wherein the first conductive region of the first base member comprises one of a first precious metal and the first conductive region of the second base member comprises a second precious metal different from the first precious metal.

4. 10. The biosensor of claim 1, wherein the first conductive region of the first base member and the second base member comprise the same precious metal.

5. 10. The biosensor of claim 1, wherein the second conductive material layer comprises at least one from the group consisting of nickel, chromium, copper, silver, and alloys thereof.

6. 2. The biosensor of claim 1, wherein the at least one conductive layer comprises a layer of the second conductive material deposited on at least one of the first conductive region and the second conductive region of the first base member and the second base member, and a layer of the precious metal deposited directly on the second conductive material layer in the first conductive region.

7. 2. The biosensor of claim 1, wherein the conductive layer includes a layer of the first conductive material applied to the first conductive region and a layer of the second conductive material applied to the second conductive region.

8. The biosensor of claim 6 , wherein the first conductive region and the second conductive region overlap one another.

9. The biosensor of claim 7 , wherein the first conductive region and the second conductive region overlap one another.

10. 2. The biosensor of claim 1, further comprising a spacer layer disposed between the conductive layers, the spacer layer including a separation area between the first conductive areas of the first base layer and the second base layer and defining a functional area of ​​the biosensor.

11. The biosensor of claim 1 , wherein the second conductive region includes at least one contact pad configured to couple to a test meter.

12. The biosensor of claim 1 , wherein the precious metal layer is applied by a physical vapor deposition (PVD) or chemical vapor deposition (CVD) process.

13. The biosensor of claim 1 , wherein the second conductive material is applied by a physical vapor deposition (PVD) or chemical vapor deposition (CVD) process.

14. 1. A method of manufacturing a biosensor, the method comprising: Providing a first base member and a second base member; depositing a conductive layer on a surface of each of the first base member and the second base member, each base member having a first conductive region and a second conductive region, a first conductive material being deposited on the first conductive region of the base member, a second conductive material different from the first conductive material being deposited on the second conductive region of the base member adjacent to the first conductive region, and the first conductive material being a noble metal; disposing the first conductive regions of the first base member and the second base member in a spaced apart relationship to one another, the first conductive regions forming a pair of coplanar electrodes.

15. 15. The method of claim 14, The method further comprising providing a spacer layer between the conductive layers, the spacer layer including a space formed between the first conductive regions.

16. Depositing the conductive layer comprises: depositing the layer of the second conductive material over the first and second conductive regions of the first and second base members; 15. The method of claim 14, further comprising: depositing the first layer of conductive material on the second layer of conductive material in the first conductive region.

17. Depositing the conductive layer comprises: depositing the first layer of conductive material over the first conductive region of the first base member and the second base member; 15. The method of claim 14, further comprising depositing the layer of the second conductive material over the second conductive region of the first base member and the second base member.

18. 17. The method of claim 16, The method further comprising forming an overlap between the first conductive material and the second conductive material between the first conductive region and the second conductive region.

19. 20. The method of claim 17, The method further comprising forming an overlap region between the first conductive material and the second conductive material in the first conductive region and the second conductive region.

20. 15. The method of claim 14, wherein the first conductive material is deposited by one of a physical vapor deposition (PVD) or chemical vapor deposition (CVD) process.

21. 15. The method of claim 14, wherein the second conductive material is deposited by one of a physical vapor deposition (PVD) or chemical vapor deposition (CVD) process.

22. The method of claim 14 , further comprising forming electrical contact pads on the second conductive region configured to engage a test meter.

23. The method of claim 14 further comprising providing a reagent layer over at least one of the first conductive area and over the precious metal.

24. 15. The method of claim 14, wherein the first conductive material deposited on the first conductive region of one of the first base member and the second base member is a first precious metal and the first conductive material deposited on the first conductive region of the other of the first base member and the second base member is a second precious metal, the second precious metal being different from the first precious metal.

25. 15. The method of claim 14, wherein the first conductive material deposited on the first conductive region of the first base member and the second base member is the same noble metal.

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