HK1178598B - Electrochemical cell and method of making an electrochemical cell - Google Patents

Description

Electrochemical cell and method for producing an electrochemical cell

This application is a divisional application of a PCT application with application number 200580024249.5 (international filing date: 2005-05-20), entitled "electrochemical cell and method of producing an electrochemical cell", entering the national phase.

The parent application for this application claims the benefit of US provisional application serial No. 60/521555, filed 3/21/2004, which is incorporated herein by reference.

Background of the invention

The present invention relates to electrochemical cells and methods of producing electrochemical cells for detecting the presence, measuring the amount and/or monitoring the level of one or more components present in a liquid sample. These cells perform electrochemical measurements by evaluating electrochemical parameters (i.e., potential, current, resistance, etc.) between two or more electrodes in contact with the sample. Electrode sensors typically include a working electrode and a counter or reference/counter ("reference") electrode.

Electrochemical cells are particularly valuable in biological research and control technologies when the invention is implemented in the chemical industry, particularly when complex mixtures are encountered (e.g. in the food industry or in biochemical engineering). More particularly it is suitable for animal or human medicine, and is particularly suitable for ex vivo measurement or monitoring of components in body fluids. For convenience, the invention will be described in terms of one such method, the in vivo glucose assay method.

To perform the determination of glucose in the human body, a blood sample is taken from a test subject and the sample is mixed with a reagent that typically contains an enzyme and a redox mediator. The chemistry employed in such a measurement method is typically:

glucose + GOD_ox- - - > gluconolactone + GOD_red

GOD_red+2 ferricyanide- - - - > GOD_ox+2 ferrocyanide

In the formula GOD_oxIs the enzyme glucose oxidase in an oxidized state, and GOD_redIs enzyme glucose oxidase in reduced state. Ferricyanide ([ Fe (CN))₆]^3-) Is oxidized GOD_redOxidizing medium ofIt may therefore also oxidize the glucose molecules. Ferrocyanide ([ Fe (CN))₆]^4-) Is the reduced form of the mediator, which transfers electrons to the electrode (thereby regenerating ferricyanide). Thus, the generated ferrocyanide (measured electrochemically) indicates the glucose concentration in the sample. Other enzymes, such as glucose dehydrogenase, have also been used.

Since glucose monitoring for diabetics is preferably performed several times a day and since each test uses a common household instrument, which requires blood or interstitial fluid to be available from the fingertips, the pressure developed has become a more convenient and less expensive instrument for the user. As a result, electrochemical cells have been disclosed in which the test sample has a small volume. See, for example, US patents 6576101, 6551494, 6129823 and 5437999. As the size of the sample cell becomes smaller, the percentage change in electrode area and cell volume caused by small tolerances in manufacturing becomes larger. This is important because the signal magnitude may depend on the electrode area and the cell volume. Therefore, more stringent production controls may be required to achieve the necessary cell dimensional accuracy, but these more stringent production controls are not consistent with the goal of reducing costs.

Brief description of the invention

In a first aspect, the present invention provides a simple method of producing an electrochemical cell which is particularly applicable to the production of cells having small and consistent sample volumes and electrode areas. The resulting electrochemical cell includes opposing first and second electrodes separated by a resistive sheet. This method comprises the steps of:

(a) forming a first restriction hole in the resistive sheet, thereby forming a punched resistive sheet;

(b) attaching the punched electrically resistive sheet to a first electrically conductive sheet to form a composite sheet, wherein a first electrically conductive surface portion of the first electrically conductive sheet is exposed through the first restraining aperture and a second electrically conductive surface portion of the electrically conductive sheet is exposed either through a second restraining aperture in the electrically resistive sheet or as an extension beyond an edge of the electrically resistive sheet;

(c) punching a notch hole through the electrically resistive sheet and the first electrically conductive sheet of the composite sheet, wherein the notch hole intersects the first restriction hole in the electrically resistive sheet, thereby transforming the first restriction hole into a notch in the electrically resistive sheet, and punching a first contact area visible through the second exposed partially open opening of the electrically conductive sheet to form a first electrical contact, thereby forming a punched composite sheet;

(d) punching the second electrically conductive sheet with one or more punches to form an electrically conductive sheet having a cutout hole corresponding to the cutout hole of the punched composite sheet and a second contact area in the second electrically conductive sheet to form a counter electrode sheet;

(e) attaching the counter electrode sheet to the resistive sheet portion of the punched composite sheet with the conductive surface facing the resistive sheet, said counter electrode sheet being attached such that the notch hole corresponding to the notch hole in the composite sheet is aligned with the notch hole in the composite sheet and the second contact region is aligned with the second confinement hole to form an electrochemical sheet, and

(f) the electrochemical sheet is divided to form a waste electrochemical sheet and a free electrochemical cell having a sample space for receiving a sample, the sample space being defined by the first and second electrically conductive sheets and the gap in the electrically resistive sheet, and first and second contact areas in electrically conductive contact with the electrode portions of the first and second electrically conductive sheets exposed in the sample space for connection of said first and second electrode portions to a meter.

If appropriate to make a test strip, reagents may be added during construction of a test strip as described previously.

In a preferred embodiment, both ends of the first major open area are cut in step (c) to form a sample space open at both ends and bounded by these sides. One aperture of the sample space is at the outer edge of the sample collection tip of the device, while the other aperture is adjacent to an aperture formed near the tip of the device.

The method of constructing an electrochemical cell of the present invention has a number of advantages over the prior art. First, this method uses only a limited number of sheets of material, which may be the same size but significantly larger than the final battery. Second, the method of the present invention does not require any printing or lithographic techniques to determine the sample volume and electrode area, or to form electrode leads and connections. Third, the accuracy and precision of this production method is good when using macroscopic methods, since very large device sizes can be determined using punching or similar punching operations. This allows the production of electrochemical cells using very small sample volumes without a significant increase in production costs. Fourth, electrochemical cells produced using the method of the present invention have reduced electrode "edge" effects which reduce cell accuracy. The electrochemical cells of the method of the invention are therefore cost-impressive and therefore usable (single use), demonstrating a significant measurement accuracy of such cells when only a minimum of sample is required.

The implementation of this method results in a simple structure of the electrochemical cell. Thus, in another aspect of the invention there is provided an electrochemical cell having a sample receiving end and a connector end, comprising in order:

(a) a first substrate having a layer of unpatterned conductive material applied to a first surface thereof;

(b) a resistive intermediate layer, and

(c) a second substrate having a layer of unpatterned conductive material applied to a first surface thereof;

wherein the first surface of the first substrate and the first surface of the second substrate are attached to the resistive intermediate layer;

wherein the cell is provided with an aperture near the sample receiving end but at a distance from the free edge of the device, said aperture passing through the first substrate, the resistive intermediate layer and the second substrate,

wherein the cell has a sample space which passes through the resistive intermediate layer and is bounded on opposite sides by the unpatterned conductive material of the first substrate and the unpatterned conductive material of the second substrate, said sample space extending from the free edge of the device to the aperture and being open at both ends. Suitable for the production of such a cell, the electrochemical cell may further comprise a reagent in the sample space.

Brief description of the drawings

Fig. 1A and B show isometric views of an electrochemical cell produced by the method of the present invention.

Fig. 2A and B show a sample receiving end and sample space of another embodiment of an electrochemical cell produced according to the present invention.

Figures 3A-D show top views of specific embodiments of sample receiving ends.

Fig. 4A-C show various embodiments of electrochemical cell connector ends produced according to the present invention.

FIG. 5 shows a schematic diagram of the steps of the present invention.

Fig. 6A and B show a specific embodiment of a resistive sheet with restricted apertures.

Figure 7 shows a detailed view of a composite punched sheet formed in the method of the present invention.

Fig. 8 shows a detailed view of a punched second conductive sheet formed in the method of the present invention.

Figure 9 shows a detailed view of a punched composite sheet used in the method of the invention.

Figure 10 shows a view of a segment electrode formed using the method of the present invention.

FIG. 11 illustrates the composition of a multi-test device using the method of the present invention.

Fig. 12A and B show a cross section through a multi-test device constructed as in fig. 11.

FIG. 13 illustrates the construction of another embodiment of a multiple test device using the method of the present invention.

FIG. 14 shows an additional multi-test device.

FIG. 15 shows an additional multi-test device.

Detailed description of the invention

According to a particular embodiment of the present invention, there is provided a method of producing an electrochemical cell, the method comprising the steps of:

(a) punching one or more restrictive holes in the electrically resistive sheet, thereby forming a punched electrically resistive sheet, the one or more restrictive holes defining first and second major hole regions,

(b) attaching a punched electrically resistive sheet to a first electrically conductive sheet, thereby forming a composite sheet, wherein an electrically conductive surface of the first electrically conductive sheet is visible through one or more holes in the punched electrically resistive sheet,

(c) punching a notch hole through the resistive sheet and the first conductive sheet of the composite sheet, wherein the notch hole intersects the first major area in the resistive sheet to transform the first major open area into a notch of the resistive sheet, and punching a first contact area through the portion of the conductive sheet that is open to view through the second major open area of the resistive sheet to form a first electrical contact to form a punched composite sheet;

(d) punching the second electrically conductive sheet with one or more punches to form an electrically conductive sheet having a cutout hole corresponding to the cutout hole of the punched composite sheet and a second contact area in the second electrically conductive sheet to form a counter electrode sheet;

(e) attaching the counter electrode sheet to the resistive sheet portion of the punched composite sheet with the conductive surface facing the resistive sheet, said counter electrode sheet being attached such that the notch hole corresponding to the notch hole in the composite sheet is aligned with the notch hole in the composite sheet and the second contact region is aligned with the second confinement hole to form an electrochemical sheet, and

(f) the electrochemical sheet is divided to form a waste electrochemical sheet and a free electrochemical cell having a sample space for receiving a sample, the sample space being defined by the first and second electrically conductive sheets and the gap in the electrically resistive sheet, and first and second contact areas in electrically conductive contact with the electrode portions of the first and second electrically conductive sheets exposed in the sample space for connection of said first and second electrode portions to a meter.

Definition of

Numerical values in the specification and claims of this application should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement techniques of the type described in the present application to measure the value.

As used in the specification and claims of this application, the following terms should be understood as follows:

the term "analyte" as used in the specification and claims of this application denotes a component of a sample to be measured. Non-limiting examples of specific analytes include glucose, hemoglobin, cholesterol, and vitamin C.

The term "redox mediator" as used in the specification and claims of this application means a chemical species other than an analyte that is oxidized and/or reduced in a multi-step process of transferring electrons to or from an electrochemical cell electrode. Non-limiting examples of media include:

ferricyanide

·[FeIII(CN)5(ImH)]^2-

·[FeIII(CN)5(Im)]^3-

·[RuIII(NH3)5(ImH)]³⁺

·[RuIII(NH3)5(Im)]²⁺

·[FeII(CN)5(ImH)]^3-

·[RuII(NH3)5(Im)H]²⁺

·[(NC)5FeII(Im)RuIII(NH3)5]^-

·[(NC)5FeIII(Im)RuIII(NH3)5]⁰

·[(NC)5FeII(Im)RuII(NH3)5]^2-

Ferrocene (Fc) and its derivatives, including but not limited to:

ferrocene monosulfonate

Ferrocene disulfonate

·FcCO₂H

·FcCH2CO₂H

·FcCH:CHCO₂H

·Fc(CH₂)₃CO₂H

·Fc(CH₂)₄CO₂H

·FcCH₂CH(NH₂)CO₂H

·FcCH₂SCH₂CH(NH₂)CO₂H

·FcCH₂CONH₂

·Fc(CH₂)₂CONH₂

·Fc(CH₂)₃CONH₂

·Fc(CH₂)₄CONH₂

·FcOH

·FcCH₂OH

·Fc(CH₂)₂OH

·FcCH(Me)OH

·FcCH₂O(CH₂)₂OH

·1，1′-Fc(CH₂OH)₂

·1，2-Fc(CH₂OH)₂

·FcNH₂

·FcCH₂NH₂

·Fc(CH₂)₂NH₂

·Fc(CH₂)₃NH₂

·1，1′-Me₂FcCH₂NH₂

·FcCH₂NMe₂

·(R)-FcCH(Me)NMe₂

·(S)-FcCH(Me)NMe₂

·1，2-Me₃SiFcCH₂NMe₂

·FcCH₂NMe₃

·FcCH₂NH(CH₂)₂NH₂

·1，1′-Me₂FcCH(OH)CH₂NH₂

·FcCH(OH)CH₂NH₂

·FcCH:CHCH(OH)CH₂NH₂

·Fc(CH₂)₂CH(OH)CH₂NH₂

·FcCH₂CH(NH₂)CH₂OH

·FcCH₂CH(CH₂NH₂)CH₂OH

·FcCH₂NH(CH₂)₂OH

·1，1′-Me₂FcCHOCONHCH₂

·FcCH(OH)(CH₂)₂NH₂

·1，1′-Me₂FcCH(OH)CH₂NHAc

·FcB(OH)₃

·FcC₆H₄OPO₃Na₂

Osmium II and osmium III tris (phenanthroline) (i.e., Os-phen) complexes,

including but not limited to:

·Os(4，7-dmphen)₃

·Os(3，4，7，8-tmphen)₃

·Os(5，6-dmphen)₃

·Os(bpy)₃Cl₂

·Os(5-mphen)₃

·Os(5-Cl-phen)₃

·Os-(5-NO₂-phen)₃

·Os(5-phphen)₃

·Os(2，9-dm-4，7-dpphen)₃

and homostructural ruthenium complexes including, but not limited to:

·Ru(4，7-dmphen)₃

·Ru(3，4，7，8-tmphen)₃

·Ru(5-mphen)₃

·Ru(5，6-dmphen)₃

·Ru(phen)₃

·[Ru(4，4′-diNH₂-bipy)3]²⁺

osmium II and osmium III tris (bipyridyl) complexes (i.e., Os- (bpy)₃)，

Including but not limited to:

·Os(bpy)₃

·Os(dmbpy)₃

and related ruthenium complexes, for example:

·Ru(bpy)₃

·Ru(4，4’-diNH₂-bpy)₃

·Ru(4，4’-diCO₂Etbpy)₃

osmium II and osmium III bis (bipyridyl) (i.e., Os- (bpy)₂) Complexes

With other ligands, including but not limited to:

·Os(bpy)₂dmbpy

·Os(bpy)₂(HIm)₂

·Os(bpy)₂(2MeHIm)₂

·Os(bpy)₂(4MeHIm)₂

·Os(dmbpy)₂(HIm)₂

·Os(bpy)₂Cl(HIm)

·Os(bpy)₂Cl(1-MeIm)

·Os(dmbpy)₂Cl(HIm)

·Os(dmbpy)₂Cl(1-MeIm)

and related ruthenium complexes, for example:

·Ru(bpy)₂(5，5′diNH₂-bpy)

·Ru(bpy)₂(5，5′diCO₂Etbpy)

·Ru(bpy)₂(4，4′diCO₂Etbpy)

·

where Et is ethyl, bpy is bipyridyl, dmbpy is dimethylbipyridyl, MeIm is N-methylimidazole, MeHIm is methylimidazole, Him is imidazole, phen is phenanthroline, mphen is methylphenantholine, dmphen is dimethylphenanthroline, tmphen is tetramethylphenanthroline, dmdpphen is dimethyldiphenylphenanthroline, phen is phenylphenanthroline. In addition, it should be understood that reduced or oxidized forms of these mediators can be used, either alone or in combination with each other.

Patents relating to particular media include US 4318784, 4526661, 4545382, 4711245, 5589326, 5846702, 6262264, 6352824, 6294062, 4942127, 5410059, [54] 5378628, 5710011 and 6605201, which are incorporated herein by reference.

The term "port having a rectilinear cross-section" as used in the specification and claims of this application is a port having four straight sides. A straight reference edge is simply an edge that is not significantly curved when viewed and does not imply a perfect linearity threshold for the punching process. Non-limiting examples of rectilinear cross-section ports are trapezoids, parallelograms, squares, and rectangles. The corners of the rectilinear port are ideally rounded. Such a shaped mouth is preferred because the cutting error of such straight edges is small, while rounded corners are not easily torn.

The term "restricted opening" refers to an opening surrounded by the electrical resistance sheet material, wherein the opening is free of any connection to the periphery of the electrical resistance sheet. As described in more detail below, the restrictive orifice may have a single main open area, such as an orifice having a straight cross-section, or it may have more than one main open area connected by a generally narrower connecting portion.

The term "primary open area" refers to the portion of the constricting orifice that will form the sample space or connector of an electrochemical cell.

The term "opposed electrodes" refers to electrodes that are placed on different substrates used to construct the sample cell such that they are placed in different planes on the top and bottom (or on both sides) of the cell such that charge carriers move in a direction generally perpendicular to the plane of the electrodes. "opposed electrodes" are thus distinguished from parallel electrodes in which the electrode pairs are placed on a common surface in a common plane and charge carrier movement is generally parallel to the plane of the two electrodes.

The term "punched hole" as used in the description and claims of this application refers to a cut through a sheet of material in a direction substantially perpendicular to the major surface. The term "substantially" in this context should recognize that there may be slight process deviations from absolute perpendicularity, but these deviations should be minimized to avoid creating top-to-bottom inconsistencies in the port dimensions. Punching devices or other devices that physically cut the layers into the desired shape may be used to punch the holes. Laser cutting may also be used, where there is no concern about heat generation and/or volatiles evolution. Chemical etching through these materials can also be employed.

The term "unpatterned layer of conductive material" refers to a layer of conductive material deposited on a surface of a material, for example, by painting, sputtering, evaporation, screen printing, chemical vapor deposition, or chemical deposition, without any patterned decoration defining regions of the electrode. The pattern decoration may be used for contact pads or connector tracks, however, all conductive elements may use the entire unpatterned layer, and this is preferred since few production steps are involved. The unpatterned or entire unpatterned layer is desirably a uniform coating, although any scratches, scars, or other defects may occur because the processing or production process does not impart a pattern decoration to the conductive material.

Electrochemical cell

The method of the invention is used to produce electrochemical cells. Fig. 1A shows such a cell schematically represented. The cell is comprised of a bottom layer 130, a top layer 131 and an intermediate layer 132. At least on the surface facing the intermediate layer 132, the top and bottom layers are electrically conductive. In a preferred substrate embodiment, the top and bottom layers 130, 131 are insulating substrates that have been coated with a conductive layer. As shown more clearly in fig. 1B, in which the top layer 131 has been removed, the intermediate layer 132 has a notch 133 formed in the edge. The gap 133, and the top and bottom layers 130, 131 together define a space for receiving a sample during use of the electrochemical cell. The volume of this space is therefore determined by the thickness of the intermediate layer 132 and the size of the gap. The electrochemical cell also has contact areas 134 and 135 that are connectable to a meter that provides an electrical connection between the meter and the portions of the top and bottom layers 130, 131 that contact in the sample receiving space.

The middle layer 132 is a resistive material that insulates the conductive layer and prevents conductivity between the conductive top and bottom layers 130, 131 unless they are connected by a sample placed in the sample-receiving space. Non-limiting examples of suitable materials for use as this layer include polyimide, polyester, polyethylene terephthalate (PET), polycarbonate, glass, fiberglass, or other non-conductive material that provides the desired support. The intermediate layer 132 is suitably 500-50 μm thick. Thicker materials may be used when larger sample volumes are acceptable. Thinner materials may be used but may present a number of difficulties in handling and also increase the difficulty in adding the sample to the finished cell, as this thickness determines one dimension of the sample space. In a preferred embodiment of the invention, the sample space volume is less than 5. mu.l, more preferably less than 1. mu.l. In particular embodiments of the invention, the sample space volume is 500, 300, 200, 100 or 50 nl.

The conductive portions of the top and bottom layers 130, 131 are selected to be consistent with the particular analyte that the electrochemical cell is intended to detect. Specific examples of suitable conductive electrode materials include gold, carbon, silver, palladium, and platinum. The conductive materials used for the top and bottom layers 130, 131 may be the same, or they may be different from each other. In a preferred embodiment of the invention, the conductive material is gold. The conductive portions of the top and bottom layers are suitably thin coatings on one surface of a sheet of insulating substrate. The material used for the intermediate layer 132 may also be used as a thin substrate.

Depending on the analyte to be detected, such an electrochemical cell may include a reagent composition disposed in the space for receiving the sample. In the case of an electrochemical cell for the detection of glucose, such a reagent composition suitably comprises an enzyme effective to oxidize glucose, such as glucose oxidase, and a redox mediator, such as ferricyanide. Reagent compositions for this purpose are known in the art, for example, U.S. Pat. No. 4711245 to Higgins et al and U.S. Pat. No. 3, 5437999 to Diebold et al, which are incorporated herein by reference. Particular embodiments of the reagent contain glucose oxidase and ferricyanide.

In addition to its electrochemical function, the reagent composition, if present, may help to overcome the hydrophobicity of the sample space so that blood or other aqueous samples may be added to the space due to the hydrophilicity of the reagent. It can be noted that when no reagent is used, the sample volume is surface treated with Triton or other surfactant to reduce hydrophobicity and facilitate sample addition.

Figures 2A-B show sample receiving ends and sample spaces of additional embodiments of electrochemical cells produced according to the present invention. In fig. 2A, the device is fully assembled. The sample space 22 extends from the device tip 23 to the aperture 24. The sample chamber length is about 1mm, for example 1.5mm to 0.5mm, although longer lengths may be used to make the volume of the sample space larger. Fig. 2B shows the tip portion of fig. 2A with the top layer removed. The conductive surface 25 of the bottom layer 26 is visible in the sample space bottom 22. The sample space 22 is defined at the bottom by the conductive surface 25 of the sheet 26 and at the sides by the resistive sheet 27. The end of the sample space is open at the end of the device and opposite the aperture 24.

Figure 3A shows a top view of a variation of the sample receiving tip portion of figure 2A. In this case, at least the end portion (i.e., the portion facing the tip) of the aperture 34 is complementary in shape to the tip. The term "complementary" means that the profile of the leading portion of the strip 36 is the same as the profile of the leading portion of the aperture 38, the former moving from the latter in the direction of the sample space or the length of the channel 22. This configuration is ideal for maintaining a stable volume of sample space and a stable area of electrodes, even if the sample space is not well aligned with the rest of the device (fig. 3B). This configuration also allows for multiple sample spaces at the tip of the device with the same benefits, as shown in fig. 3C and 3D.

Fig. 4A-C show various embodiments of electrochemical cell connector ends produced according to the present invention. In fig. 4A, a connector tab 41 extends from the device end with a first conductive layer 42 having a conductive surface facing downward in the direction shown. Connector tab 43 extends from the end of the device as a second conductive layer 42 having a conductive surface facing upwardly in the direction shown. A resistive layer 45 is shown between the conductive layers 42, 44. Fig. 4B shows an alternative embodiment in which two edge-located protrusions 141, 141' extend from the top conductive layer and a central protrusion 46 extends from the bottom conductive layer. Fig. 4C shows another alternative embodiment, in which two edge-located protrusions 141, 141 'extend from the top conductive layer and two center-located protrusions 146, 146' extend from the bottom conductive layer.

Method of the invention

In accordance with the method of the present invention, an electrochemical cell as described above is formed by punching one or more restriction holes into an electrically resistive sheet, thereby forming a punched electrically resistive sheet having at least one restriction opening. These constraining holes are preferred in the method of the invention because the dimensional stability of such holes is higher than that of the notch cut to the edge of the sheet and therefore the production variation in the spatial dimensions of the received sample is not large. In a particular embodiment of the invention, the constraining pores in the resistive sheet are "rectilinear sections".

Attaching a punched electrically resistive sheet to the first electrically conductive sheet to form a composite sheet, wherein the electrically conductive surface of the first electrically conductive sheet is visible through the first and second holes in the punched electrically resistive sheet. The particular material used to achieve this attachment is not critical, although a thick adhesive layer that can help to vary the dimensions of the space in which the sample is received is not desirable. A preferred example of an adhesive coated electrically resistive sheet is a pressure sensitive acrylic adhesive coated electrically resistive sheet such as the ARCARE 7841 manufactured by Adhesives Research. Other examples of commercially available adhesives that are applied to the polyester substrate are adhesives produced by 3M: 3M #444, 3M #443, and 3M # 1512. The selection of the adhesive product is derived at least in part by the desired height of the sample space, said height being determined by the substrate plus the adhesive coating. Such adhesives are suitable for coating over the entire resistive layer to form a uniform coating, as obtained in commercial double-sided "tape". Heat sealing may also be used as a technique that may be employed, such as ultrasonic welding.

The next step is to punch a notch through the resistive sheet and the first conductive sheet of the composite sheet. This notch intersects the first restriction hole in the resistive material laterally, i.e. it is cut through two sides, preferably two opposite sides, in the straight first restriction hole of the first restriction hole, thereby transforming the first restriction hole into a notch in the resistive sheet. This results in the formation of a first electrode area defined by the composite sheet notch punch and by the notch in the resistive sheet. In addition, a first electrical contact is formed by punching a portion of the electrically conductive sheet visible through the second aperture of the electrically resistive sheet to form the first electrical contact, thereby forming a punched composite sheet. In a preferred embodiment, a single punching step is used to form both the notch and the first electrical contact.

The second conductive sheet is punched using a punch or punches to form a conductive sheet having a notch hole corresponding to the notch hole of the punched composite sheet, thereby forming an opposed electrode sheet having a second electrode region and a second contact region in the second conductive sheet. As used in the specification and claims of this application, the second electrically conductive sheet is attached to the punched composite sheet such that the electrically conductive sheet having a cutout hole corresponding to the cutout hole of the punched composite sheet is one in which the hole in the resulting opposed electrode sheet should be substantially aligned with the hole and the cutout of the punched composite sheet. Indeed, for ease of production, the same punch or punches (i.e. the same physical unit, or units having the same dimensions) may be used to form the opposed electrode sheets for forming the punched composite sheet. However, the invention does not exclude embodiments in which the opposed electrode plates are intentionally differently sized to provide differently sized working and counter electrodes.

An optional step of adding reagents may be performed. To facilitate production, the required reagents may be added to the punched composite sheet, with the indentations in the resistive material serving as reservoirs for the added reagents. Alternatively, such an agent may be added to the first or second conductive material or both before and after punching. In another embodiment, no reagents are added during the production of the electrochemical cell. In such a case, if a reagent is desired, the reagent may be added directly to the sample in the electrochemical cell, or may be added directly to the sample before the sample is added to the cell.

If desired, the two opposing electrodes may be administered with different agents. Because the electrodes are separated by a small distance, reagent diffusion is rapid in the presence of the sample, but this approach allows the two reagents to be stored separately until the sample is added. For example, if the presence of an enzyme inhibitor is determined by the loss of enzyme activity, it would be undesirable to have a single reagent containing the enzyme and a substrate that are capable of reacting during the deposition process. In particular, phosphatases, such as alkali metal phosphates, can be used to decompose phosphate matrices to produce products (e.g., p-aminophenol) whose electrical activity is detectable. This reaction was inhibited by excess phosphate, arsenate and conchotoxin, making it useful in a variety of analyte-specific devices. It is also possible to separate the enzyme from the buffer by deposition using a separation reagent, so that the enzyme reacts only after the sample and these reagents have been added and used at a suitable pH.

After forming the corresponding holes and second electrical contacts in the second electrically conductive sheet, the resulting counter electrode sheet is attached to the resistive sheet portion of the punched composite sheet having the electrically conductive surface facing the resistive sheet. The counter electrode sheet is attached such that the punched hole in the counter electrode sheet corresponding to the composite sheet notch hole is aligned with the notch hole in the composite sheet and the second contact area is aligned with the composite sheet second restraining hole. This results in the formation of an electrochemical sheet in which the second electrode area is defined on the opposed electrode sheet by the resistive sheet cut-outs and the second electrically conductive sheet punched holes.

Finally, the electrochemical sheet is split apart from the surrounding material to form a waste electrochemical sheet, and a free electrochemical cell having a sample-receiving space defined by the first and second electrodes and the gaps in the resistive material, and first and second electrically conductive contact areas in electrical contact with the first and second electrodes for connection of the first and second electrodes to a meter. This step may be performed on one cell at a time, on one sheet of cells at a time, or on multiple cells or sheets in a consolidation operation.

It will be appreciated that from each sheet of material, a plurality of cells may be formed by forming a plurality of sets of punched holes adjacent to one another. It will also be appreciated that multiple cells may be formed in close proximity to one another so that they are separated without leaving any excess material between them. Multiple strips may also be formed from a single sheet in such an arrangement as "nose to tail" or "nose to nose and tail to tail" such that punching of a single restriction creates a nose of one strip and a tail of the immediately next strip, or a nose and nose, or a tail and tail.

In a particular embodiment of the invention, the sample is added to the electrochemical cell due to the hydrophilic nature of the dry, soluble reagent. To prevent air lock-up that would prevent filling, vent holes are often required to vent the cell gases when samples are added to the cell. For such a case, the punched composite sheet may further comprise vent holes through the resistive sheet and the first conductive sheet, wherein the vent holes are aligned with the resistive sheet notches to form air channels that are connected to the interior of the sample receiving space.

Optionally, the vent hole may be punched through the second conductive sheet of the composite sheet, wherein the vent hole is aligned with the notch of the resistive sheet in the assembled cell to form an air channel that is connected to the interior of the sample receiving space. In another embodiment, two rows of air holes may be punched. The sample may be added to the sample area through a vent hole or through a hole between the conductive sheets.

In a preferred embodiment of the invention as illustrated in fig. 2A, 2B and 3, vent holes 24, 34 are formed such that a transverse cut is made through the notch and thereby defines the proximal (i.e., inward) end of sample space 22. In this case, it will be appreciated that the closest "vent" may actually function as the point of sample addition and the end port functions as the vent. Such venting holes may be formed through the entire device (i.e., through the first conductive sheet, the resistive sheet, and the second conductive sheet), or through only one of the conductive sheets and the resistive sheet.

Figure 5 shows a specific embodiment of the method of the present invention. The following steps illustrate the methods of producing two electrochemical cells. However, it will be appreciated that the method may be varied at some time to produce one cell, or that the entire production operation may be carried out using the same steps to produce more than two electrochemical cells.

The method comprises the following steps: a resistive sheet is provided. The electrical resistance sheet 51 is coated with an adhesive on both major surfaces thereof.

Step two: as shown in detail in fig. 6A, two registration holes 61 for production alignment are prepared for the first-step resistive sheet 51, which will not be part of the final device. The resistive sheet 51 is placed in a mold (not shown) that is aligned with the resistive sheet through two registration holes. The sheet 51 is then punched to form a punched sheet 52 having two large and two small holes therethrough. The large hole 62 is a hole through which an electrical connector is to be formed. The small hole 63 is a hole over which a notch hole and a vent hole defining a sample space are to be formed. Fig. 6B shows an alternative configuration in which the conductive layer extends beyond the edge of the resistive layer and connectors are formed in this extension. Thus, only one restriction port is needed that is involved in forming the sample space.

Step three: the punched resistive sheet 52 is then attached to the first conductive sheet 53, thus forming a composite sheet 54. The conductive sheet has at least one conductor (e.g., gold) coated surface facing the punched resistive sheet 52 and it also includes two locating holes aligned with the locating holes of the resistive sheet 52. Once the composite sheet 54 is formed, the conductive surface of the first conductive sheet 53 is visible through the holes punched through the resistive sheet 52.

Step four: the composite sheet 54 is punched to form a punched composite sheet 55. Fig. 7 shows such a punched composite sheet 55 in more detail. The punched composite sheet 55 is cut such that the nearest and farthest ends of the rectangular hole 63 are cut, leaving a starting point for a generally rectangular/square sample space 71. The punching of step four also defines a first electrical connector 72 by which the electrodes formed by the first conductive sheet can be electrically connected to the measurement device.

Step five: reagent 513 is added to the punched composite sheet 55 over the sample space 71 to form a reagent sheet 56. For a glucose sensor, the reagent added to punched composite sheet 55 suitably contains glucose oxidase and a ferricyanide-containing redox mediator. Preferably, the medium is added to the liquid carrier in a volume sufficient to fill at least 50%, more preferably a larger portion of the sample space. This results in the medium coated on the walls of the sample space being higher and thus closer to the second electrode. This reduces the time for the medium to reach the second electrode during use, thus improving the response time of the device.

Step six: the second sheet 57 of conductive material is provided with two locating holes. These two alignment holes are used for production alignment and do not become part of the final device. The conductive sheet 57 is put into a die (not shown) and punched out, thereby forming the opposite electrode sheet 58. A top electrode with punched holes defining the sample space has been used. Thus, as shown in FIG. 8, the punched holes 81 define device tips 82 and vent holes 83, which are the same shape as those in the punched composite sheet 55. This punching also defines a second connector area 84 for connecting an electrode formed from a sheet of a second electrically conductive material. The punch outs 84 forming the second connector areas need not be identical to the punch outs 72 forming the connector areas. It is desirable that the basic principle of the two sets of accessible contact points is not to make contact with each other.

The second conductive sheet 57 is suitably of the same material and construction as the first conductive sheet 53, although it may be made of a different material or include a marker.

Step seven: the counter electrode sheet 58 is attached to the reagent sheet 56 of step five to form an electrochemical sheet 59 with the registration holes of the counter electrode sheet aligned with the registration holes of the reagent sheet. The conductive portion of the counter electrode sheet 58 is in contact with the resistive sheet of the reagent sheet 6. This step results in the sample space being bounded by two conductive sheets on the top and bottom and a resistive sheet on the sides, with a hole at each end of the sample space.

Step eight: the electrochemical sheet 59 of step seven is separated, thereby forming a waste electrochemical sheet 510 and two free electrochemical cells 511 and 512. It will be appreciated how the steps of this particular embodiment may be varied to provide a method of producing more or less than two electrochemical cells.

Fig. 9 shows a mechanism for dividing the conductive coating in the sample space without forming the electrode surface, forming two legs. The stylus 91 is drawn along the conductive surface 92 of the gold 58 to form a non-conductive line or gap 93 which divides the conductive surface from the vent hole 94 to the end of the strip of the connector 95. Using these locating holes as guides to ensure proper positioning of the scribed lines, such non-conductive lines or gaps 93 may be formed after or before the connectors and vent holes are identified by punching. In the latter case, the scribed line may extend to where it will be removed by punching. The electrically resistive sheet should form the non-conductive lines of the first sheet before it is attached to the first electrically conductive sheet (step 3). Other methods of forming such non-conductive lines or gaps 93, other than by dragging a stylus across the surface, include the use of a cutoff wheel that can pass through the entire conductive layer, laser ablation, and chemical etching.

Punching a hole in one or both conductive sheets in this manner results in a battery as illustrated in fig. 10 that can be easily subjected to a power continuity test as part of the quality control method. If the punch pattern and the scribed lines are used as shown in fig. 9, fig. 10 shows just the electrode layers of the cell. The position of the sample space 122 is indicated by a dashed line. If the electrical connection between connectors 101 and 102 is evaluated (e.g. by conductivity measurements), a good connection can be determined if the conductive sheet extending through the entire path of the electrode layer legs or ring-shaped portion is not damaged at all. For example, the detection scratch 103 or 104 should be a fail, and the detection scratch (e.g., 105) should not be a fail. Since the connection between the electrode portion on sample space 122 and connector 101 or 102 is sufficient to obtain valid test results, this provides an easily accessible form of non-destructive quality control which is in fact more stringent than the requirements for handling the device. Drawing a middle line along the length of this surface as shown in fig. 9 may also form two middle connector projections without cutting into projection shapes.

The method of the present invention may also be used to produce multi-cell devices. Fig. 11 illustrates a first method of achieving this result, where two test cells are stacked. In this method, two punched composite sheets 1101 and 1102 are formed as previously described. Reagents are added to each of the punched composite sheets 1101, 1102 in accordance with the analyte to be tested. The reagents applied to sheets 1101 and 1102 may be the same, or they may be different, for testing both analytes simultaneously. Punched composite sheets 1101 and 1102 each have an adhesive inner face 1103, 1103' and are attached by this face to an intermediate punched sheet 1104, and punched sheet 1104 is made of an electrically insulating material coated on both sides with electrically conductive layers. After removal of the cell from the sheet, the result was a test device with two stacked test cells. Fig. 12A shows a cross-sectional view through a multi-cell device at a point away from the sample space and vent holes. Fig. 12B shows a cross-sectional view through a multi-cell device at the point where the sample spaces 1222, 1222' intersect the vent 1224. In each figure, these conductive surfaces are represented by wavy lines. Because of the small size of the test cells and the proximity of these wells, samples can be easily added in parallel.

Figure 13 illustrates an alternative embodiment of a method of producing a multi-test cell device. In this embodiment, two or more adjacent sample spaces are formed. As depicted in fig. 13, two holes were formed instead of the single first restriction hole for determining the sample space in the above-described embodiment. In the particular embodiment shown in fig. 13A, two co-linear holes 1301, 1302 are formed in the resistive sheet perpendicular to the long axis of the device. The composite strip is punched along the dashed lines to form device nose 1304 and vent 1305, separating the ends of the two holes, creating two sample spaces. In this structure, the sample spaces are appropriately filled from the vent hole. In this conductive sheet, the two sample spaces are electrically isolated by cutting or scribing along dashed lines 1306 prior to assembly. It will be appreciated that the same result may be achieved using an elongated hole that merges holes 1301 and 1302 and extends across the vent hole between them. In addition, it will be appreciated that the relative specific locations of the wells in this particular embodiment are not critical, and it will also be appreciated that they need not be co-linear (e.g., fig. 3C) as long as separate electrical connections to each sample space can be achieved.

In another embodiment of the method of the present invention, multiple test devices can be produced using a combination of the method illustrated in FIGS. 11 and 12 and the method illustrated in FIG. 13. In this particular embodiment, the resulting device may have one or more cells at each stacking level.

In a further embodiment of the invention of the cell of fig. 13, two sample spaces can be formed by moving the wells 1301, 1302 and providing separate vent holes in such a way that only one sample space is fillable by the outer edge and the other sample space is fillable by the inner edge only. Without the cut 1306, there is no problem of filling the sample space. This provides more convenience to the user since the sample collection point (by means of the belt) does not affect its results. Filling two spaces may be different from filling only one space based on determining the effective electrode area, as described, for example, in US patent publication US 2005-0069892a1 and US patent application No. 10/907813, filed 4/15 2005, which are incorporated herein by reference.

Fig. 14 and 15 show two other embodiments of a multi-cell test device. In fig. 14, four sample spaces 1401 are formed, all of which enter through a common surface. This configuration reduces the need to align a particular portion of the device tip with the blood/fluid drop 1402, since filling (or partially filling) any or all of these sample spaces is sufficient to enable measurements. In fig. 15, six sample spaces 1501 are aligned in a ring around a hexagonal multiband and extend from the ring outside to the exhaust space 1502. The devices are separated by score lines 15-3 which have connector tabs 1504 facing the central axis. In fig. 15, only one conductive layer and spacer layer is shown. The top layer with the conductive surface should complete the device with the other electrodes and their associated connector protrusion or protrusions.

Thus, it can be seen that the method of the present invention provides flexibility in forming electrochemical test cells having multiple sample spaces. These sample spaces may be coplanar, in which case they may be arranged in parallel, may be arranged end-to-end, like a spoke, in a wheel or any other desired configuration. The sample space may also occupy multiple planes.

Claims (13)

1. An electrochemical device having a sample receiving end and a connector end, comprising, in order:

(a) a first substrate having a layer of conductive material applied to a first surface thereof;

(b) a resistive intermediate layer, and

(c) a second substrate having a layer of conductive material applied to a first surface thereof; wherein the content of the first and second substances,

the first surface of the first substrate and the first surface of the second substrate are attached to the resistive intermediate layer;

the device has a first sample space, which passes through the resistive intermediate layer and is bounded on opposite sides by a portion of the conductive material of the first substrate forming the unpatterned first electrode and a portion of the conductive material of the second substrate forming the unpatterned second electrode,

the connector end comprising first and second connectors, the first connector having two separate connector tabs for connection to a meter and extending from a first substrate, the second connector having at least one connector tab for connection to a meter and extending from a second substrate,

the connector projections of the second connector are visible between the connector projections of the first connector when the tape is viewed in a plan view, and

the resistive intermediate layer extends between the first and second substrates to a location where the connector tab of the first connector extends from the first substrate.

2. The device of claim 1, further comprising a reagent disposed within the sample space.

3. The device of claim 2, wherein the reagent comprises an enzyme and a redox mediator.

4. The device according to claim 3, wherein the enzyme is glucose oxidase.

5. The device of any of claims 1-4, wherein the conductive material on the first substrate comprises palladium.

6. A device according to any of claims 1 to 4, wherein the conductive material on the second substrate comprises palladium.

7. The device according to any of claims 1-4, wherein the thickness of the intermediate layer is 50-500 μm.

8. The device according to any of claims 1-4, wherein the volume of the sample space is less than 1 μ l.

9. The device of any one of claims 1-4, further comprising a second sample space formed in a stacked configuration with respect to the first sample space.

10. The device of any one of claims 1-4, further comprising an additional sample space formed in a coplanar orientation with respect to the first sample space.

11. The device according to any of claims 1-4, wherein the volume of the sample space is less than 500 nl.

12. The device according to any of claims 1-4, wherein the volume of the sample space is 100 and 300 nl.

13. The device according to any of claims 1-4, wherein the sample space has a width dimension determined by opposite sides of a punched-out opening in the resistive intermediate layer, wherein the opposite sides are substantially straight and parallel to each other.