Structure and manufacturing method of disposable electrochemical sensor strip

A disposable electrochemical sensor strip is provided. The sensor strip includes an isolating sheet having at least a through hole, at least a conductive raw material mounted in the through hole, a metal film covered on the conductive raw material to form an electrode which comprises an electrode working surface for processing an electrode action, and an electrode connecting surface, at least a printed conductive film mounted on the isolating sheet and having a connecting terminal for being electrically connected to the electrode connecting surface, and a signal output terminal for outputting a measured signal produced by the electrode action.

The present invention is relevant to U.S. application Ser. No. 10/354,684 filed on Jan. 30, 2003.

FIELD OF THE INVENTION

The present invention relates to a disposable electrochemical sensor strip, and more particular to a structure and manufacturing method of a sheet type strip which is suitable for examining an analyte in a fluid sample, for example, the concentration of glucose in human blood, and the concentration of a uric acid.

BACKGROUND OF THE INVENTION

Generally, a utilization of a noble metal as an electrode material for an electrochemical sensor can achieve a high stability and a high reproducibility of detection and is ready a well-known technique in the field of electrochemistry. But, in the sensor, the only demand of the noble metal is a surface of an electrode, and other surfaces of the noble metal are unnecessary. Especially, for a disposable strip, the noble metal surfaces rather than the electrode are all squanders. The main purpose of the present invention is to provide a structure and a manufacturing method of a low-price metal electrode in a disposable electrochemical sensor strip for significantly reducing the demand of the noble metal and further reducing the cost.

The metal electrode according to the present invention also can be applied in various metal-catalyzed electrodes (not only noble metals) with a direct catalysis, besides in a noble electrode without chemical interference. The disposable electrode and the sensor according to the present invention can be suitable for all kinds of electrochemical detection electrodes, biosensors, fluid biochemical sensor (e.g., sewage, insecticide concentration, and heavy metal sensor strips), domestic medical application (e.g., blood glucose, uric acid, and cholesterol sensor strip).

The principle of electrochemical sensor has been developed and applied in detecting all kinds of fluid biochemical ingredient. An electrochemical sensor may have different configurations for conforming to different functions. Please refer toFIG. 1.FIG. 1shows that a basic framework of an electrochemical detecting device10includes the following components:

1. A container12for containing a fluid sample to be an electrochemical measure region13.

2. A chemical reagent14for chemically reacting with an analyte contained in the fluid sample11and generating an output signal with an electric parameter, wherein the electric parameter is corresponding to a biochemical ingredient of the analyte contained in the fluid sample11. For example, if the fluid sample11is human blood and the analyte is glucose, the chemical reagent14is basically a glucose oxidase and a complex thereof.

3. Plural testing electrodes, as shown inFIG. 1, a counter electrode15, a working electrode16, and a reference electrode17, for transmitting a working voltage for an electrochemical reaction from an electrochemical meter18to the container12and again transmitting the electric parameter to the electrochemical meter18after the analyte contained in the fluid sample11undergoes an electrochemical reaction so that the electrochemical meter18can process a numerical analysis and then display the result thereon.

4. An electrochemical meter18for providing the working voltage (or current) needed by the electrochemical reaction and measuring the electric parameter (output voltage or current) produced by the electrochemical reaction to record, process the numerical analysis and display the testing data.

Meanwhile, plural testing electrodes can only include the counter electrode and the working electrode or further include a reference electrode. Moreover, a detecting electrode could be included as a fourth electrode. The number of the plural testing electrodes is varied according to the requirement of the electrochemical reaction.

The electrodes of different functions are made of different materials. In the laboratory, the counter electrode15is made of any conductive material, however the lower the conductive resistance the better the effect, such as a copper, a silver, a nickel, a graphite, a carbon, a gold, a platinum or other conductive materials, or can be a conductive membrane electrode formed by printing a carbon paste or a silver paste. The most common structure of the reference electrode17is a modified electrode171produced by means of printing or electroplating an Ag/AgCl film. Because the electric potential of the Ag/AgCl film is quite stable, it is extensively used as the reference electrode.

The selection of the working electrode16is more complex and can be sorted as two types, one is an electron-transfer mediator modified working electrode and the other is a metal-catalyzed electrode. The electron-transfer mediator modified working electrode has a chemical reagent immobilized thereon, wherein the chemical reagent includes an enzyme (such as a glucose oxidase) and a redox mediator (such as a potassium ferricyanide which is extensively used in the glucose testing piece). The enzyme and the analyte will react with each other to produce a new chemical compound (such as H2O2), the electrons generated from the redox reaction between the mediator and H2O2is utilized to produce an electric signal, and through the electrode, the electric parameter can be output. The main purpose of this kind of electrode is only simply a conductor and is not involved in chemical catalysis. However, the material of the electrode should be selected specifically to avoid a chemical reaction with the fluid sample11or the chemical reagent14thereby interfering with the result.

The electrode without the chemical interference should be made of an inert conductive material, which is generally a noble metal (such as a gold, a platinum, a palladium, or a rhodium), or a carbon containing material (such as a carbon base screen printing electrode or a graphite bar). Furthermore, because carbon and the noble metal have no chemical reactivity in a low temperature, the chemical interference would not happen. However, because the noble metal is more expensive, the carbon made electrode is usually applied as the electron-transfer mediator modified working electrode.

As to the metal-catalyzed electrode, it is made of a material which will directly electrochemically react with the chemical reagent, the analyte, or the derivatives thereof, and has an ability of direct catalysis or a function of a single selectivity for the analyte. Thus, the mediator is not needed to add into the chemical reagent. This kind of electrode, not only needs to be made of a chemically inactive metal, but also is generally made of a material that must have an ability to catalyze the reaction. Therefore, the material thereof should not be limited to be a noble metal but matched with the analyte, such as a copper, a titanium, a nickel, a gold, a platinum, a palladium, or a rhodium . . . etc., (for example, a rhodium electrode has an excellent ability to directly catalyze H2O2).

The two types of metal electrodes described above both have a high cost of the material and the processes when being formed under a conventional manufacturing method, especially the noble metal. Consequently, although the noble metal has a better stability, it still cannot be the mainstream of the disposable medical treatment testing in family. Nowadays, the biggest requirement of the biosensor is the medical treatment in family for a blood glucose, a uric acid or a cholesterol . . . etc. And, the electrode used by these biosensors mostly belongs to the electron-transfer mediator modified working electrode, and thus the disposable testing sheet of the biosensor can has the carbon base screen printing electrode printed thereon for reducing the cost, as described in U.S. Pat. No. 5,985,116, which is a typical example.

Please refer toFIG. 2which shows the example described in U.S. Pat. No. 5,997,817. In this patent, two conductive metal tracks201and202both coated by a palladium are fixed on an insulative backing203with an identical size for being the metal electrode of the sensor. A working electrode204and a counter electrode205, electrode leads206and207, and signal output terminals208and209are all integrally formed by palladium. However, the positions that must be formed by palladium are only two tiny sections of the working electrode204and the counter electrode205, and the other portions can only be formed by materials having a conductive characteristic rather than noble metal-palladium.

Further refer toFIG. 3in which shows the example described in EP 1 098 000 and is another manufacturing method for the metal electrode. In this patent, an insulation sheet301previously injection molded has positions of a pattern302surrounded by recesses and islands306, an electrode lead303, and output terminals304and305. Then, metallic deposit proceeds to deposit a metal layer on the surface of plastic insulation sheet. Due to all the surface of the insulation sheet being covered by deposited metal, an additional process has to be proceeded for removal of metal layer on the islands and remaining the patterns, the electrode leads and the output terminals. Thus, this method has a high cost and is only suitable for the electrode only formed by one kind of metal.

According to the technical defects described above, for reducing the manufacturing cost of the metal electrode in the disposable sensor strip and overcoming the problem of wasting the noble metal, the applicant devoted himself to develop a “structure and manufacturing method of disposable electrochemical sensor strip” through a series of experiments, tests and researches. In addition to effectively solve the wasting problem of the noble metal in prior arts, the electrodes according to the present invention can be formed or modified in advance respectively in different electroplating containers in a great quantity, and then be assembled to an insulation sheet for reducing manufacturing time thereof.

Furthermore, in addition to be employed as the noble metal electrode requiring no chemical interference, the metal electrode according to the present invention can also be employed as the metal-catalyzed electrode which has a direct catalyzing function. And, the disposable electrode and the sensor according to the present invention can be applied to all kinds of electrochemical testing electrodes, biosensors, biochemical analyte sensors for fluid (e.g., testing strips for a sewage, a pesticide content, a heavy metal ingredient etc.), all kinds of domestically medical treatment testing strips (e.g., testing strips for a blood glucose, a uric acid, and a cholesterol).

SUMMARY OF THE INVENTION

It is an object of the present invention to form a metal film on a conductive raw material for reducing the amount of noble metal applied in the metal electrode of a disposable sensor strip.

It is another object of the present invention to provide metal electrodes which can be formed and modified respectively in different electroplating containers in a great quantity in advance and then be assembled to an insulation sheet for reducing the manufacturing time thereof

It is a further object of the present invention to provide a metal electrode which can be mounted in a through hole of an insulation sheet, wherein an area of the through hole is an area of a working surface of the metal electrode. Additionally, the accurate area of the through hole can be achieved easily from the massive productivity of relevant industrial methods, and a stable working surface of the metal electrode was acquired simultaneously. And, because the testing signal produced by the sensor is in proportion to the electrode area, the present invention can therefore substantially increase the accuracy of reproducibility of the electrochemical sensor.

It is an additional object of the present invention to employ a tenon on an insulation sheet for being fixed in a notch of a measuring device.

In accordance with an aspect of the present invention, a disposable electrochemical sensor strip includes an insulation sheet having at least a through hole, at least a conductive raw material mounted in the through hole, a metal film covered on the conductive raw material to form an electrode which comprises an electrode working surface for processing an electrode action, and an electrode connecting surface, at least a printed conductive film mounted on the insulation sheet and having a connecting terminal for being electrically connected to the electrode connecting surface, and a signal output terminal for outputting a measured signal produced by the electrode action.

Preferably, the conductive raw material of the sensor strip is metallic so as to form a metallic electrode with the metal film.

Preferably, the conductive raw material has a material selected from a group consisting of a copper, a brass, an oxygen-free copper, a bronze, a phosphorized copper, a nickel silver copper and a beryllium copper.

Preferably, the sensor strip further includes a chemical reagent mounted on the electrode working surface for detecting an analyte through reacting with the analyte contained in a fluid sample so as to produce the measured signal which is then output through the signal output terminal.

Preferably, the electrode forms an electrode area in the through hole whose area is an area of the working surface for processing the electrode action and transmitting the measured signal.

Preferably, the printed conductive film is formed by printing a conductive paste on the insulation sheet so as to form the signal output terminal and the connecting terminal which is covered on the electrode connecting surface for electrically connecting with the electrode.

Preferably, the conductive paste is a conductive adhesive containing a material selected from a group consisting of a carbon, a silver, a copper, a nickel, an aluminum, a gold, a stainless steel and a combination mixture thereof.

Preferably, the strip further includes an insulating layer covered on the printed conductive film.

Preferably, the metal film is made of a material selected from a group consisting of a gold, a platinum, a rhodium, a ruthenium, an iridium, a silver, a copper, a nickel, a titanium, a chromium, an iron and an aluminum.

Preferably, the conductive raw material of the sensor strip is one of a carbon-including conductive plastic compound, a metal-including conductive plastic compound and a plastic material undergone with a conductive coating treatment.

Preferably, the conductive raw material of the sensor strip is modified with the metal film through a device selected from a group consisting of an electroplating device, an immersion plating device (chemical plating without electrifying), a metal deposition device, a printing device, a metal spraying device.

Preferably, the electroplating device holds an electroplating liquid containing a metal ion for coating the metal film on the conductive raw material.

Preferably, the conductive raw material is pre-modified with the metal film to form the electrode and then put in the through hole of the insulation sheet.

Preferably, the conductive raw material is first put in the through hole of the insulation sheet and then modified with the metal film through one of the electroplating device, the immersion plating device, the metal deposition device, the printing device, and the metal spraying device so as to form the electrode in the through hole.

Preferably, the metal film has a thickness ranged from 0.025˜20 μm.

Preferably, the through hole and the conductive raw material respectively have a shape selected from a group consisting of a circular form, a rectangular figure and an annular shape and are engaged with each other.

Preferably, the insulation sheet has two through holes whose bottoms are joined together to form a U-shaped recess for engaging with the conductive raw material having a U-shaped cross section, the metal film is coated on the conductive raw material in the U-shaped recess for forming the electrode with the electrode working surface in one leg of the U-shaped recess and the electrode connecting surface in another leg of the U-shaped recess, which are at the same side with respect to the insulation piece, so that the electrode working surface, the electrode connecting surface and the printed conductive film are formed at the same side of the insulation sheet.

Preferably, the through hole is a first through hole, the conductive raw material is a first conductive raw material, the printed conductive film is a first printed conductive film, the metal film is a first metal film, and the electrode is a first electrode to serve as a working electrode.

Preferably, the sensor strip further includes a second conductive raw material mounted in a second through hole of the insulation sheet, a second metal film modified on the second conductive raw material to form a second electrode which comprises a second electrode working surface which serves as a counter electrode and a second electrode connecting surface, and a second printed conductive film mounted on the insulation sheet and having a second connecting terminal which is electrically connected with the second electrode connecting surface, and a second signal output terminal.

Preferably, the sensor strip further includes a third conductive raw material mounted in a third through hole of the insulation sheet, a third metal film modified on the third conductive raw material to form a third electrode which comprises a third electrode working surface which serves as a reference electrode and a third electrode connecting surface, and a third printed conductive film mounted on the insulation sheet and having a third connecting terminal which is electrically connected with the third electrode connecting surface, and a third signal output terminal.

Preferably, the third metal film is a silver metal film, which is immersion plated in a chemical solution, electroplated in a chemical solution or printed by an AgCl paste thereon through a printing device so that the silver metal film is modified into an Ag/AgCl reference electrode.

Preferably, the insulation sheet has a flowing recess located at an edge portion above the electrodes for providing a fluid sample a space to flow therein, the flowing recess has a fluid inlet located at a side of the insulation sheet, the fluid inlet, the flowing recess and the through holes are integrally formed, a covering layer is covered on the flowing recess of the insulation sheet for forming a capillary channel and a measuring section by cooperating with the fluid inlet and the flowing recess, and the flowing recess further comprises a capillary vent for forming the capillary channel by cooperating with the fluid inlet.

Preferably, the counter electrode and the working electrode form an electrode assembly and a space above the electrode assembly and under the measure region is provided to position therein a chemical reagent with an even thickness.

Preferably, the insulation sheet has a protruding spacer for raising the covering layer and separating the fluid sample from an adhesive on the covering layer.

Preferably, the counter electrode and the reference electrode are both printed electrodes on the insulation sheet, and the working electrode is a metal electrode which is modified from the conductive raw material and mounted in the through hole of the insulation sheet.

Preferably, the first electrode further comprises a modified layer immobilized thereon for forming a modified electrode.

In accordance with another aspect of the present invention, a disposable electrochemical sensor includes an insulation piece having at least a through hole, at least a conductive raw material mounted in the through hole, and a metal film coated on the conductive raw material for forming an electrode which comprises an electrode working surface for processing an electrode action, and a signal output terminal for outputting a measured signal.

Preferably, the sensor further includes a chemical reagent mounted on the electrode working surface for detecting an analyte in a fluid sample through reacting with the analyte so as to generate the measured signal which is then output through the signal output terminal.

Preferably, the insulation piece comprises a tenon which is fixed in a notch of a measuring device for placing the sensor on an exact testing position of the measuring device.

Preferably, the electrode comprises a signal output point for being connected to a signal connecting point of the measuring device, the insulation piece has a measuring recess located at a portion above the electrode for measuring a fluid sample, the measuring recess and the through hole are integrally formed, a meshed piece is mounted on the measuring recess for filtering an impurity in the fluid sample, the electrode and the chemical reagent are positioned under the meshed piece for forming a measuring region, a covering layer is covered on the meshed piece and adhered to the insulation piece for avoiding the meshed piece from escaping from the measuring recess, and the covering layer comprises an opening for dropping therein the fluid sample.

Preferably, the signal output terminal of the electrode has a rivet joint, the sensor strip further comprises a metallic thin strip mounted on the insulation piece and having an output terminal and an electrode connecting hole electrically retaining therein the rivet joint.

In accordance with a further aspect of the present invention, a disposable electrochemical sensor strip includes an insulation sheet having at least a recess, at least a metal electrode mounted in the recess and having an electrode working surface for processing an electrode action and a signal output terminal for outputting a measuring signal produced by the electrode action.

Preferably, the sensor strip further includes a metal film integrally formed with the metal electrode.

Preferably, the sensor strip further includes a conductive raw material which is integrally formed with the metal film and the metal electrode.

In accordance with a further another aspect of the present invention, a disposable electrochemical sensor includes an insulation piece having at least a through hole, at least a metal electrode mounted in the through hole and having an electrode working surface and an electrode connecting surface so as to process an electrode action through the electrode action, and at least a printed conductive film mounted on the insulation piece and having a conductive connecting surface electrically contacting with the electrode connecting surface and a signal output terminal outputting a measured signal produced by the electrode action.

Preferably, the metal electrode is a copper electrode.

In accordance with a further another aspect of the present invention, a disposable electrochemical sensor strip includes an insulation sheet having at least a through hole, and at least a metal electrode mounted in the through hole and having an electrode working surface for processing an electrode action and a signal output terminal for outputting a measured signal produced by the electrode action.

Preferably, the insulation sheet comprises a tenon fixed in a notch of a measuring device for positioning the strip on the measuring device.

In accordance with an additional aspect of the present invention, a method for manufacturing a disposable electrochemical sensor strip includes steps of providing an insulation piece having at least two recesses, preparing a conductive raw material assembly comprising a first and a second conductive raw material, forming a modified electrode through modifying the first conductive raw material, and forming the disposable electrochemical sensor strip through positioning the modified electrode and the second conductive raw material in the at least two recesses.

Preferably, the method further includes an electroplating procedure for modifying the first conductive raw material to form a metal film and obtain the modified electrode.

Preferably, the method further includes a printing procedure for forming at least a signal output terminal through printing at least a conductive film on the insulation piece to be electrically connected to an output signal of the electrode.

Preferably, the method further includes a chemical reagent immobilizing procedure for modifying the electrode to obtain an enzyme electrode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Please refer toFIGS. 4(a)˜(c) which illustrate the structure of a disposable electrochemical sensor strip having one single electrode according to the present invention. The strip includes an insulation sheet401(so called an insulating substrate) having a through hole402. At least a conductive raw material403is mounted in the through hole402and is coated by a metal film404so as to form an electrode411, wherein the electrode411includes an electrode working surface409and an electrode connecting surface408. The electrode working surface409is employed to process an electrode action (namely to be an electrode). Moreover, at least a printed conductive film410whose thickness is ranged from 1.0 μm to 20 μm having a connecting terminal405and a signal output terminal406is printed on the insulation sheet401, wherein the connecting terminal405is electrically connected to the electrode connecting surface408and the signal output terminal406is employed to output a measured signal generated by the electrode action. Meanwhile, the conductive raw material403of the sensor strip can be made of a metal and then be coated by the metal film404to form a metal electrode411.

Furthermore, the sensor strip includes a chemical reagent414mounted on the electrode working surface409of the metal electrode411so as to form an enzyme electrode413for examining an analyte in a fluid sample. The chemical reagent414reacts with the analyte to generate a measured signal that is then output through the signal output terminal406. Moreover, the electrode411of the sensor strip will form an electrode area412in the through hole402for transmitting the measured signal. Namely, the insulation sheet401includes at least a through hole402, the metal electrode411is formed by coating the metal film404on the conductive raw material403and tightly mounted in the through hole402, the metal electrode411is peripherally mounted by the insulation sheet401for only revealing the electrode working surface409and the electrode connecting surface408, and the electrode working surface is employed to process the electrode action.

Meanwhile, a conductive film410having a connecting terminal405and a signal output terminal406is printed on the insulation sheet401, wherein the connecting terminal405is electrically connected to the electrode connecting surface408and the signal output terminal406is employed to output a measured signal generated by the electrode action. An insulating layer407is covered on a reverse side of the insulation sheet401so as to reveal only the signal output terminal406of the printed conductive film410. Therefore, the conductive areas except the electrode working surface409can be isolated by the insulating layer407and will not contact with the fluid sample in order to avoid an examining accuracy from being influenced.

In this embodiment, the electrode material that really works is the metal film404made of a gold, a platinum, a palladium, a rhodium, a ruthenium, an iridium, a silver, a copper, a nickel, a titanium, a chromium, an iron and an aluminum. As to the conductive raw material403, it should be made of a conductive material which can tightly combine with the metal film404, so that the material can be any conductive metal, any carbon-including conductive plastic compound, any metal-including conductive plastic compound, or a plastic material undergone with a conductive coating treatment.

The methods for covering the metal film404on the conductive raw material403include an electroplating, an immersion plating, a metal deposition, a metal spraying. The conductive raw material403can be previously put in the through hole402and then be modified by the metal film404, or, oppositely, the conductive raw material403can firstly be modified by the metal film404and then be put in the through hole402. The best procedures of this embodiment are firstly plating a noble metal film404on the conductive raw material403through a mass plating method (namely putting many conductive raw materials403in one plating container) and then putting the coated conductive raw material into the through hole402. The conductive raw material403can be made of a copper and an alloy thereof, such as a brass, an oxygen-free copper, a bronze, a phosphorized copper, a nickel silver copper and a beryllium copper. Because the copper and the alloy thereof are easily to form all kinds of electrode shapes and are conductive which is suitable for being modified by the metal film404through the plating process. The conductive raw material403can be made of the carbon-including conductive plastic compound by means of an injection-molding process. And, the carbon-including conductive plastic compound is conductive and suitable for being modified by the metal film through the plating process.

Nowadays, “plastic electroplating” has become a mature technology, which employs an injection-molding process to form the shape of the non-conductive plastic material403and further coats a conductive layer on the plastic material403for sequentially plating the metal film404thereon. Generally, a nickel layer will be previously coated on the plastic material, and then a needed metal film404is coated thereon.

The material of the printed conductive paste for forming the printed conductive film410can be a conductive adhesive containing a carbon, a silver, a copper, a nickel, an aluminum, a gold, a stainless steel and a combination mixture thereof, and the thickness of the printed film is ranged from 1.0 to 20.0 μm. The material of the insulation sheet401can adopt a polyvinyl chloride (PVC), a polypropylene (PP), a polycarbonate (PC), a polybutylene terephthalate (PBT), a polyethylene terephthalate (PET), a modified polyphenylene oxide (PPO) or an acrylonitrile butadiene styrene (ABS).

The thickness of the insulation sheet401is ranged from 0.2 mm to 3.0 mm. The conductive raw material403can be a circular form, a rectangular figure and an annular shape and has a thickness less than that of the insulation sheet401ranged from 0.00 mm to 0.15 mm, for example, the thickness of the insulation sheet is 0.60 mm, the through hole is circular with a diameter of 1.00 mm, and the raw material is a cylindrical copper plate with a thickness of 0.50 mm and a diameter of 1.02 mm. As the design described above, the diameter of the raw material is lightly larger than that of the through hole so as to ensure that they can tightly engage with each other. The metal film404covered on the electrode411can be a gold, a silver, a platinum, a rhodium, and a palladium, wherein when the metal film404of the electrode411is a silver, a silver chloride can be modified thereon for forming an Ag/AgCl reference electrode. Certainly, the conductive raw material403can be a copper and simultaneously the metal film404also can be a copper, namely the electrode411is a pure copper electrode.

The through hole402on the insulation sheet401can be formed through an injection-molding device, a punch press device, or a computerized drilling machine, and each of these mass producing methods can easily achieve an accurate dimension of the through hole over 99.5% reproducibility. If the electrode411is mounted in the through hole402, it can firstly form the insulation sheet401having the through hole402through injection- molding, punch pressing, or the drilling and then put the electrode411in the through hole through a mechanical processing device so that they can tightly engage with each other, or it can put the electrode in a injection-molding device and inject a plastic material therein for forming the insulation sheet and simultaneously engage the electrode in the through hole.

Please refer toFIGS. 5(a)˜(b) which illustrate another sensor strip having one single electrode. The sensor strip include an insulation sheet501having a through hole502, and a conductive raw material503is put in the through hole502so that they can tightly engaged with each other, wherein the top509of the conductive raw material503is further coated by a metal film50450as to form a metal electrode (meanwhile, the conductive raw material503is a metal or a carbon-including conductive plastic compound). The metal electrode includes an electrode working surface504and an electrode connecting surface508, wherein the electrode working surface is employed to process an electrode action. Moreover, a conductive film510having a connecting terminal505and a signal output terminal506is printed on the insulation sheet501, wherein the connecting terminal505is electrically connected to the electrode connecting surface508and the signal output terminal506is employed to output a measured signal generated by the electrode action. As to number507, it represents an insulating layer. The metal film504can be covered on the conductive raw material503by an electroplating, an immersion plating, a metal deposition, a metal spraying, or a metal printing.

According to another aspect of the present invention, the printed conductive film410can be replaced. Please refer toFIGS. 6(a)˜(c) which illustrate another sensor strip having one single electrode. In this embodiment, a metallic thin strip606is employed to replace the printed conductive film410inFIG. 4. The metal thin strip606has a signal output terminal608and a connecting hole607, wherein the connecting hole607is electrically connected to a rivet joint604on a metal electrode603for outputting a measured signal generated by the electrode. As to number605, it represents the electrode working surface. In this embodiment, the electrode can be a pure nickel electrode and also a pure iron electrode.

Furthermore, the conductive raw material403inFIG. 4can be replaced by an integral metal so that an integral metal electrode is formed and the insulation sheet has to further form a recess for containing the metal strip, as shown inFIGS. 7(a)˜(b). An integrally formed metal strip703is employed to replace the metallic thin strip606and the metal electrode603inFIG. 6. The metal strip703includes an electrode working surface704, an electrode lead705, and a signal output terminal706, wherein the metal strip703can be integrally formed the electrode working surface704, the electrode lead705and the signal output terminal706by an injection-molding or a punch pressing which is different from the printed conductive film410inFIG. 4. The insulation sheet701includes a through hole702and a recess707for mounting the metal strip703so as to engage with each other. Regarding to the process of covering a metal film on the metal strip703(not shown inFIG. 7), it can be achieved by firstly covering the metal film on the metal strip703and then putting thereof in the through hole702, or previously putting the metal strip703in the through hole702of the insulation sheet701and then covering the metal film thereon.

Please referFIGS. 8(a)˜(b) which illustrate a schematic view of a modified electrode. The metal electrodes inFIGS. 4˜7can be a working electrode or a counter electrode after properly selecting the conductive raw material and the metal film. For applying the electrochemical sensor, a modified layer801can be immobilized on the electrode802through a specific procedure so that the pure electrode802will be modified to be a modified electrode. For example, electrochemically immersing the metal electrode802which is coated by a silver film into a potassium chloride solution or printing the chlorine which will chemically react with the silver layer so as to form an Ag/AgCl reference electrode, or immobilizing or coating a chemical reagent414on the metal electrode411inFIG. 4so as to form an enzyme electrode413, wherein the chemical reagent can be a complex including at least a chemical material selected from a group consisting of an enzyme, a pH buffer, a surfactant/surface active agent, a redox mediator, a hydrophilic ploymer compound, or a hydrophilic filtering mesh.

The chemical reagent414on the enzyme electrode413is employed to react with an analyte in a fluid sample so as to generate an electric measuring signal which will be output by the electrode411to a meter, such as the electrochemical measuring device18inFIG. 9, for being calculated to obtain the concentration of the analyte. When the chemical reagent414of the enzyme electrode413described above contains a redox mediator, the electrode will be an electro-transfer mediator modified working electrode. When the electrode413is modified by a proper metal film, the electrode will be a metal-catalyzed electrode, such as a platinum catalyzed electrode, a palladium catalyzed electrode, a gold catalyzed electrode, a rhodium catalyzed electrode, or a copper catalyzed electrode. When the enzyme contained in the chemical reagent414of the enzyme electrode413is glucose oxidase for examining human whole blood, the analyzing result of the fluid sample will be a blood glucose concentration of human blood. When the enzyme contained in the chemical reagent414is an uricase for testing human whole blood, the analyzing result of the fluid sample will be a uric acid concentration in human blood. When the enzyme contained in the chemical reagent414is a cholesterol oxidase for testing human whole blood, the analyzing result of the fluid sample will be a cholesterol concentration in human blood.

Please referFIG. 9which illustrates an application of replacing the traditional electrode inFIG. 1through three disposable testing strips according to the present invention. The conductive raw material of each electrode can be made of any conductive material and modified by a metal film to form a specific electrode. For example, employing three disposable sensor strips of a gold film counter electrode409, an Ag/AgCl reference electrode formed by a silver film reference electrode802and an Ag/AgCl modified layer801, and an enzyme working electrode413which is modified from a platinum film electrode for replacing the traditional electrode inFIG. 1. A container900contains the three electrodes.

According to another aspect of the present invention, the recess707inFIG. 7can be altered to receive only the through hole and not the metal conductive strip, as shown inFIGS. 10(a)˜(b).FIGS. 10(a)˜(b) illustrate a sensor strip having two electrodes in a preferable embodiment according to the present invention. The sensor strip includes an insulation sheet1001having a rectangular through hole1002and an annular through hole1003and a rectangular working electrode1004and an annular counter electrode1006are respectively mounted in the through holes1002and1003so as to engage with each other. Two connecting terminals1007of the conductive films are printed below the insulation sheet1001and two signal output terminals1008thereof are electrically connected to the metal electrodes1004and1006for outputting the measured signal generated by the electrode action. A chemical reagent1005is immobilized on the working electrode1004for reacting with an analyte in a fluid sample so as to produce an electric signal which is then output to a device, such as the electrochemical measuring device18inFIG. 1, through two electrode1004,1006, connecting terminals1007and output terminals1008.

Please refer toFIGS. 11(a)˜(b) which illustrate a sensor testing strip having three electrodes in a preferable embodiment according to the present invention. The sensor strip includes an insulation sheet1101having three though holes1102, and a counter electrode1105, a working electrode1103and a reference electrode1104are respectively mounted in three through holes110250as to engage with each other. Three conductive films1108are printed below the insulation sheet1101, and the three printed conductive films include signal output terminals1109which are respectively connected to the metal electrodes1103,1104and1105for outputting the measured signal generated by the electrode action. An AgCl modified layer1107is coated on the reference electrode1104for modifying the electrode1104into an Ag/AgCl reference electrode. A chemical reagent1106is immobilized on the working electrode1103for reacting with the analyte in a fluid sample so as to generate an electric signal which will be output to a device18through the electrode1103, the output terminal1109.

Please referFIG. 12which illustrates an application of replacing the traditional electrode inFIG. 1through a disposable testing strip having three electrodes according to the embodiment inFIG. 11. A container1201contains the disposal test strip having a working electrode1103, a reference electrode1104and a counter electrode1105on a isolation sheet1101. An AgCl modified layer1107is coated on the reference electrode1104for modifying the electrode1104into an Ag/AgCl reference electrode. A chemical reagent1106is immobilized on the working electrode1103for reacting with the analyte in a fluid sample so as to generate an electric signal which will be output to a device18through the electrode1103.

The embodiments shown inFIGS. 4˜12are suitable for testing medium to large amount samples. As to small amount samples (for example, the disposable sensor strip for human blood only uses blood of several μL), the sensor strip therefor generally additionally has a structure for adsorbing the small amount sample in order to fully spread the sample over all electrodes. And, if the electrodes are not fully covered by the fluid sample, a testing error might be caused. Please refer toFIGS. 13(a)˜(c) which illustrate an application employing a three electrodes sensor strip having capillary channels according to the present invention. As shown inFIGS. 13(a)˜(c), an adsorbing structure generally includes a capillary channel inlet1308, a capillary channel1314, and a capillary vent1309, wherein the capillary channel1314is generally a measuring section for the fluid sample.

When the fluid sample attaches the capillary channel inlet1308, because the capillarity, the fluid will be automatically adsorbed by the capillary channel1314until the measuring section is fully by the fluid.FIGS. 13˜18all are embodiments of sensor strips suitable for small amount samples. Firstly,FIG. 13shows a three electrodes sensor strip having a capillary channel for examining the small amount sample. The sensor strip includes an insulation sheet1301having a fluid measuring recess1314(namely the capillary channel1314), and the bottom of the fluid measuring recess1314is a chemical reagent placing recess1306for placing a chemical reagent1307so as to have a uniform distribution thereof. Three through holes1302are positioned under the placing recess1306for respectively receiving a working electrode1303, a counter electrode1305and a reference electrode1304.

The three electrodes1303,1304and1305are engaged with the through holes1302and are respectively covered by a metal film1315(as shown inFIG. 13(d), to form a metal electrode1303,1304and1305. Each of the electrodes1303,1304and1305includes an electrode working surface and an electrode connecting surface and the electrode connecting surface is utilized to process an electrode action. Meanwhile, three printed conductive films1311are positioned under the insulation sheet1301and each of which includes a connecting terminal and a signal output terminal1312. The connecting terminal of each printed conductive film1311is respectively and electrically connected to the electrode connecting surface of each electrode so as to output a measured signal through the signal output terminal1312. Moreover, the fluid measuring recess1314further includes a fluid inlet1308and the capillary vent1309, and a covering layer1310is positioned on the recess1314so as to compose a completed capillary adsorbing structure. Furthermore, the insulation sheet1301has two protruding spacers1316and1317for raising the covering layer1310and separating the fluid sample from an adhesive on the covering layer1310.

The chemical reagent1307is positioned on the top of three electrodes1303,1304and1305for reacting with an analyte in the fluid sample so as to generate an electric signal which is then output to a device18through the electrodes1303,1304,1305and the signal output terminal1312, wherein the electric signal is proportional to a concentration of the analyte and utilized to calculate a parameter of the analyte. The conductive raw material1313of each electrode1303,1304and1305can be made of any conductive material. The metal film1315for covering the working electrode1303can be a gold, the metal film1315for covering the reference electrode1304can be a silver which can be coated by a silver chloride layer to form an Ag/AgCl reference electrode, and the metal film1315for covering the counter electrode1305can be a platinum.

Certainly, the metal film1315for covering the working electrode1303can be a rhodium, a palladium, a ruthenium and a copper, and when the metal film is a copper, the metal substrate1313can also be a copper, namely the electrode is integrally formed by a copper.

According to the embodiment described above, the present invention also provides a method for manufacturing a disposable electrochemical sensor strip. The method includes providing an insulation sheet1301having at least two recesses (through holes)1302, preparing a conductive raw material assembly including a first and a second conductive raw materials (namely the conductive raw material1313), modifying the first conductive raw material to form a modified electrode1315(which can be electroplated by a platinum to be a working electrode or be electroplated by an Ag/AgCl layer to be reference electrode), and forming the disposable electrochemical sensor strip through positioning the modified electrode and the second conductive raw material in two recesses1302. The method further includes an electroplating procedure for covering a metal film on the first conductive raw material to form the modified electrode1315, and a step of immobilizing a chemical reagent for obtaining an enzyme electrode.

Please refer toFIG. 14which illustrates a combination of embodiments of the sensor strips inFIGS. 13˜17and a device. An electrochemical device1401includes an inlet1402which is employed to guide an electrochemical sensor strip1301thereinto and the fluid sample will be adsorbed by the capillary channel inlet1308. The device1401provides a sufficient working potential needed by an electrochemical reaction to each electrode and receives the measured signal output by the electrode and displays an information after calculating the measured signal.

Please refer toFIGS. 15(a)˜(c) which illustrate another applying embodiment of a three electrodes sensor strip having the capillary channel according to the present invention. This sensor strip includes an insulation sheet1501having a first through hole1503for an electrode working surface and a second through hole1504for an electrode connecting surface, wherein the bottoms of the first and the second through holes are joined together to form a U-shaped recess1502for engaging with an electrode having a U-shaped cross section. The U-shaped electrode1505includes an electrode working surface1506and an electrode connecting surface1507, and both of which are located at the same side with respect to the insulation sheet1501. The electrode working surface1506is utilized to process an electrode action.

Furthermore, a first printed conductive film1508, a second printed conductive film1514and a third printed conductive film1511are simultaneously printed on the insulation sheet1501. The first printed conductive film1508having a connecting terminal1509and a working electrode output terminal1510is printed on the insulation sheet1501and covered on the electrode connecting surface1507, wherein the connecting terminal1509is electrically connected to the electrode connecting surface1507for outputting the measured signal to the output terminal1510. The second printed conductive film1514having a counter electrode output terminal1516and a second electrode terminal1515to be a counter electrode1515, and the third printed conductive film1511having a reference electrode output terminal1513and a third electrode terminal1512to be a reference electrode1512, wherein the reference electrode1512can be modified by a silver chloride layer1518to form an Ag/AgCl reference electrode.

Meanwhile, an insulating layer1519having a C-shaped opening1520is covered on the top of three conductive strips1508,1511, and1514except the electrode working surface1506and the electrode output terminal1510. Then, a covering layer1521having a capillary vent1522thereon is covered on the C-shaped opening1520for forming a completed capillary adsorbing structure. Because of the cooperation between the U-shaped recess1502and the U-shaped electrode1505in this structure, the first conductive film1508for connecting the working electrode1505can be printed on the insulation sheet1501together with the second conductive film1514(with the counter electrode1515) and the third conductive film1511(with the reference electrode1512) at the same time. Therefore, one printing procedure can be abridged.

Besides, a chemical reagent1517is positioned on the top of the working electrode1505for reacting with an analyte in a fluid sample so as to generate an electric signal which is then output to the working electrode output terminal1510through the electrode1505. Additionally, three printed conductive films1508,1511and1514can be made of a carbon-including conductive paste or a silver paste. As to number1523, it represents a fluid inlet.

In the embodiment described above, the working electrode1505is covered by the metal film according to the present invention to form a working electrode having a good performance, and the electrode working surface1506formed in the first through hole1503can be exactly obtained so as to significantly increase the qualitative reproducibility of the sensor. Regarding to the counter electrode1515and the reference electrode1512, because the material and working surface thereof do not need to be as exact as the working electrode, they can be formed by the traditional printing method for reducing the cost.

Please refer toFIGS. 16(a)˜(c) which illustrate further another applying embodiment of a three electrodes sensor strip having the capillary channel according to the present invention. And, this embodiment is actually an alternation of the embodiment inFIG. 10through replacing the printed conductive film1006by an integrally formed conductive strip or abridging it. In this embodiment, three conductive strips whose thickness are ranged from 0.05 mm to 1.00 mm respectively includes an electrode working terminal, an electrode lead and an electrode output terminal and all are integrally formed. The sensor strip includes an insulation sheet1601having a first plane1602and a second plane1603, wherein the second plane1603includes a first recess1604and a through hole1605thereon, as shown inFIG. 16(c), and, the through hole1605has another opening on the first plane1602. Then, a first conductive strip1606which is integrally formed is mounted in the first recess1604so as to engage with each other, and the first conductive strip1606includes a first electrode output terminal1608and a first electrode terminal to be a working electrode1607.

Moreover, the first plane1602of the insulation sheet1601includes a second recess1611and a third recess1610thereon for respectively receiving a second conductive strip1616and a third conductive strip1612mounted therein and engaged with each other. The second conductive strip1616which is integrally formed includes a second signal output terminal1618and a second electrode terminal to be a counter electrode1617, and the third conductive strip1612which is integrally formed includes a third signal output terminal1614and a third electrode terminal to be a reference electrode1613, wherein the reference electrode1613can be modified by a silver chloride modified layer1615SO as to form an Ag/AgCl reference electrode. An insulating layer1619having a C-shaped opening1620is covered on the top of two conductive strips1614and1618except the working electrode1607and the electrode output terminal1608.

Then, a covering layer1621having a capillary vent1622thereon is covered on the C-shaped opening1620for forming a completed capillary adsorbing structure. Besides, a chemical reagent1609is positioned on the top of the working electrode1607for reacting with an analyte in a fluid sample so as to generate an electric signal which is then output to the working electrode output terminal1608through the electrode1607. As to number1623, it represents a fluid inlet.

In addition, the embodiment inFIG. 16can be altered through replacing the counter electrode1617and the reference electrode1613by traditional printed conductive films printed on the insulating layer1619, as shown inFIGS. 17(a)˜(b).FIGS. 17(a)˜(b) illustrate another applying embodiment of a three electrodes sensor strip having the capillary channel according to the present invention. The sensor strip includes an insulation sheet1701having a fluid measuring recess1702thereon, and the a chemical reagent placing recess1703is positioned at the bottom of the measuring recess1702for placing a chemical reagent1708. Then, a through hole1704is position under the placing recess1703for receiving a first electrode1707, namely a metal electrode, which is formed by covering a metal film on a conductive raw material. The first electrode1707includes a first electrode terminal to be working electrode1707and a first electrode connecting surface.

Moreover, a first printed conductive film1718is located below the insulation sheet1701and includes a connecting terminal1719and a signal output terminal1720, wherein the connecting terminal1719is electrically connected to the first electrode connecting surface for outputting a measured signal through the signal output terminal1720. And, a capillary vent1706is located above the measuring recess1702and the number1705represents a fluid inlet. A covering layer1716is positioned on the fluid measuring recess1702for forming a completed capillary adsorbing structure. Furthermore, a second conductive film1709and a third conductive film1713are printed on the covering layer1716, wherein the second conductive film1709includes a counter electrode output terminal1711and a second electrode terminal to be a counter electrode1710, and the third conductive film1713includes a reference electrode output terminal1715and a third electrode terminal to be a reference electrode1714which can be modified by a silver chloride modified layer1712so as to form an Ag/AgCl reference electrode.

Besides, a chemical reagent1708is positioned on the top of the working electrode1707for reacting with an analyte in a fluid sample so as to generate an electric signal which is then output to the signal output terminal1720through the electrode1707. As to number1717, it represents a C-shaped opening.

In this embodiment described above, the counter electrode1710and the reference electrode1714are printed on the covering layer1716for avoiding the working electrode from being polluted when modifying the reference electrode. And, because the insulation sheet1701and the covering layer1716are separated when modifying, the working electrode will not be contaminated.

Please refer toFIGS. 18(a)˜(c) which illustrate another embodiment for applying a three electrodes sensor strip according to the present invention. In this embodiment, the signal output terminals in back of the metal electrodes are directly connected to the input connecting points on a measuring device. The sensor strip includes an insulation sheet1801having a fluid measuring recess1802and three through holes1803,1804and1805are located at the bottom of the measuring recess1802for respectively receiving three electrodes1808,1809and1810mounted therein and engaged with each other. Each of the electrodes1808,1809and1810includes a signal output terminal1813and an electrode working surface1811which is employed to process an electrode action.

A chemical reagent1814is positioned on the top of the electrode working surface1811, a meshed piece1815is positioned on the top of the chemical reagent1814for protecting the chemical reagent1814and filtering an impurity in a fluid sample and a covering layer1816having an opening1817is covered on the meshed piece1815and connected to the insulation sheet1801, wherein the opening1817serves as a fluid sample inlet.

Besides, the insulation sheet1801further includes two tenons1806and1807at two sides thereof so that the sheet1801can be slid into two notches1821of a measuring device1820(as shown inFIG. 18(d)) so as to be fixed therein. After the sheet1801is slid into the notches1821, the signal output points1813of the sensor strip will be directly connected with the signal connecting points1822of the measuring device1820so as to complete the signal transmission. Thus, in this embodiment, the printed conductive films on the insulation sheet are no more needed. As to the number1818, it represents a backside of the sheet1801.

If the metal electrode of a disposable sensor strip according to the present invention servers as a working electrode, it can be the first type: “electron-transfer mediator modified working electrode” and the second type: “metal-catalyzed electrode”. If the metal electrode according to the present invention serves as the first type electrode, it only needs to employ the noble metal which has no chemical interference and does not need to be limited as a specific kind, for example, all of gold, platinum, palladium, and rhodium can be employed. This kind of metal electrode according to the present invention utilizes a noble metal film to cover a conductive raw material for forming a metal electrode which is then mounted in a through hole of an insulation sheet. Through this configuration, the used amount of the noble metal can be reduced and the time for manufacturing the metal electrode also can be shortened. Furthermore, the sensor strip can therefore provide a good performance in the detecting reproducibility because the electrode area thereof can be exactly obtained. If the metal electrode according to the present invention serves as the second type electrode, the material of the working electrode should directly participate in the electrochemical catalysis (namely it doesn't need to add additional electron-transfer mediator therein). Thus, the material should be chemically matched with the chemical reagent and the analyte in the fluid sample. For responding to different chemical reactions, the metal material will not be limited to be the noble metal and can be any kind of metal, for example, a copper electrode can serve as a working electrode for detecting H2O2. When the material selected is not expensive, the conductive raw material and the metal electrode can be the same for saving the coating procedure of the metal film. Hence, the time for manufacturing the metal electrode still can be shortened, and the sensor strip can therefore provide a good performance in the detecting reproducibility because the electrode area thereof can be exactly obtained. Consequently, through the electrode structure and the manufacturing processes according to the present invention, the disposable sensor strip can significantly reform the defects in the prior arts.

The main principle for designing the structure and manufacturing method in the present invention is how to economize the noble metal material. Therefore, the present invention provides a cheap conductive raw material (such as a cylinder copper having a diameter of 1.0 mm and a thickness of 0.5 mm) for being further electroplated by a noble metal film (such as a rhodium film having a thickness of 0.025˜0.075 μm for forming a noble metal electrode. Then, the electrode is mounted in the through hole of an insulation sheet so as to engage with each other and reveals only an electrode working surface and an electrode connecting surface. The electrode working surface can process an electrode action and a conductive film is further printed to connect to the electrode connecting surface for being a lead and an output terminal of the electrode. In this structure, the noble metal material is only used for the metal film which is further limited to only the electrode area in the through hole. Thus, the amount of the noble metal can be reduced to be minimum. In addition, if millions of raw materials of electrodes are electroplated at a same time and then put into the trough holes of an insulation sheet via a mechanical process, not only the noble metal material but also the manufacturing cost can also be significantly reduced.

Besides, the electrode according to the present invention is mounted in the through hole of an insulation sheet, and, through the engagement from the insulation sheet, only an electrode working surface and an electrode connecting surface are revealed. Then, a conductive film is further printed to connect to the electrode connecting surface for being a lead and an output terminal of the electrode. Therefore, the electrode working surface is not directly contacted with the conductive film so that the electrode surface is completed independent and decided by the through hole only so as to obtain an extremely accurate electrode area. Because the measured current is proportional to the electrode area, the present invention can greatly improve the reproducibility of the electrochemical sensor strip.

Furthermore, the insulation sheet having the through hole thereon can be formed by an injection-molding method in the present invention. The same as above, the injection-molding process can also integrally form other structures, such as the fluid sample inlet, the capillary channel recess, the capillary convecting vent, the chemical reagent, placing recess and the protruding spacer. Therefore, not only the number of the assembling elements can be decreased to reduce the cost, but also the assembling error for many elements can also be cut down.

In view of the aforesaid, the present invention provides a novel manner which utilizes a metal film to cover on a conductive raw material for reduce the used amount of noble metal. Furthermore, the metal electrode is mounted in the through hole of the insulation sheet so that the time for manufacturing the disposable sensor strip according to the present invention can be significantly reduced. Therefore, the present invention is extremely suitable for being used in industrial production.