Electrochemical test paper containing coding electrode

Abstract

The utility model belongs to the technical field of biosensing, and discloses an electrochemical test paper containing a coding electrode, which comprises a substrate, a coding electrode and a detection electrode, the coding electrode and the detection electrode are arranged on the substrate, and the coding electrode and the detection electrode are positioned on the same side of the substrate, the coding electrode comprises at least three first electrode blocks and a connecting wire for electrically connecting two adjacent first electrode blocks in the at least three first electrode blocks; and the detection electrode is electrically connected with the coding electrode. According to the electrochemical test paper disclosed by the utility model, the detection electrodes are fully utilized while a large amount of coding information is provided, so that the production procedures are reduced, the production resources are saved, the production process difficulty is also reduced, the mass production of the test paper is facilitated, and the electrochemical test paper has a very good application prospect.

Description

Technical Field

[0001] The utility model belongs to the technical field of biosensing, and particularly relates to an electrochemical test strip comprising a coded electrode. Background Art

[0002] Biosensors based on electrochemical principles have been widely used in POCT (point-of-care testing) rapid diagnosis. Such biosensors use an insulating substrate (PET substrate) as a carrier, print biosensor electrodes on the insulating substrate, then assist enzyme solution in the reaction area of the substrate, and utilize the electrochemical oxidation-reduction reaction between the enzyme and the target to generate current, and detect the target through the strength of the current. For example, blood glucose test strips and blood ketone test strips for the auxiliary diagnosis and treatment of diabetes, and uric acid test strips for the diagnosis and treatment of gout and ketosis. However, such test strip biosensors are susceptible to production processes, batch differences in raw materials, production environments, etc. during the production process, resulting in deviations in the test results of test strips produced in different batches. In order to reduce the detection deviation, parameter calibration is required for each batch of test strips during use.

[0003] Chinese Patent CN219675901U discloses an electrochemical test strip with a coded electrode, in which the coded electrode and the detection electrode are located on different sides of the substrate. The coded electrode includes at least three first electrode points and at least one connecting band, and at least one connecting band electrically connects two of the at least three first electrode points. To increase the coded information, at least one second electrode point is also provided and is connected to the at least three first electrode points in one-to-one correspondence. The disadvantages of this solution are as follows: First, setting the coded electrode and the detection electrode on both sides of the substrate increases the complexity and difficulty of the manufacturing process; second, when a large amount of calibration information needs to be pre-stored, storing the information by adding multiple second electrode points on the sensor not only occupies space, but also increases the production process and manufacturing cost. At the same time, the corresponding detection instrument also needs to add corresponding contacts, further increasing the cost of the product. Summary of the Utility Model

[0004] To solve the above problems, the utility model provides an electrochemical test strip comprising a coded electrode. The test strip sets the detection electrode and the coded electrode on the same side of the substrate, and can store more coded information by the independent operation of the coded electrode or the electrical connection with the detection electrode.

[0005] To achieve the above object, the utility model adopts the following technical solutions:

[0006] The utility model provides an electrochemical test strip comprising a coded electrode, including a substrate, a coded electrode and a detection electrode arranged on the substrate. The coded electrode and the detection electrode are located on the same side of the substrate, wherein,

[0007] The encoding electrode includes at least three first electrode blocks and connection lines for electrically connecting two adjacent first electrode blocks among the at least three first electrode blocks;

[0008] The detection electrode is electrically connected to the encoding electrode.

[0009] In a preferred embodiment, the number of first electrode blocks of the encoding electrode does not exceed eight.

[0010] In a preferred embodiment, the encoding electrode is located below the detection electrode, and the first electrode blocks of the encoding electrode are arranged in a row as rectangles.

[0011] In a preferred embodiment, the detection electrode includes a target detection working electrode and a target detection counter electrode. The target detection working electrode and the target detection counter electrode form a target detection circuit. The encoding electrode and the detection electrode are on the same horizontal plane, and a connection line is provided therebetween for electrical connection through the connection line.

[0012] In a preferred embodiment, the target detection counter electrode includes a second electrode block, and any one of the first electrode blocks of the encoding electrode is electrically connected to the second electrode block of the target detection counter electrode.

[0013] In a preferred embodiment, the detection electrode further includes an impedance detection working electrode, an impedance detection counter electrode, and a sample injection detection electrode. The impedance detection working electrode and the impedance detection counter electrode form an impedance detection circuit, and the sample injection detection electrode and the target detection working electrode form a sample injection detection circuit.

[0014] In a preferred embodiment, the target detection counter electrode, the impedance detection counter electrode, and the sample injection detection electrode each include a second electrode block, and at least one first electrode block of the encoding electrode is electrically connected to at least one second electrode block in a one-to-one manner.

[0015] In a preferred embodiment, both the first electrode block and the second electrode block are one or a combination of carbon electrodes, silver electrodes, and gold electrodes.

[0016] In a preferred embodiment, the material of the connection line is one of carbon, silver, gold, platinum, and palladium, and a break point is provided on the connection line.

[0017] Compared with the prior art, the present utility model has the following beneficial effects:

[0018] (1) In the present utility model, the coding electrode and the detection electrode are printed on the same side of the substrate and on the same horizontal plane. While retaining the coding information, the production process is simplified. Compared with the coding electrode printed on the reverse side, printing on the same side as the detection electrode can save the time required for one printing process and avoid the production process difficulties faced in printing both sides, which is beneficial to the mass production of test strips.

[0019] (2) When the number of coding information needs to be increased, in addition to increasing the number of the first electrode blocks of the coding electrode, the present utility model can also be connected to the detection electrode, so as to make full use of the detection electrode, reduce the number of additionally added electrode blocks, and thus save production resources and the time required for the printing process, and save production costs.

[0020] (3) In the present utility model, the number of the first electrode blocks of the coding electrode can be flexibly adjusted according to the number of coding information required, and the detection device only needs several corresponding contacts to realize the recognition of coding information, avoiding the waste of production resources and further reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic structural diagram of an electrochemical test strip including a coding electrode shown in Embodiment 1;

[0022] Figure 2 Schematic structural diagram of the coding electrode shown in Embodiment 2;

[0023] Figure 3 Schematic structural diagram of the coding electrode shown in Embodiment 3;

[0024] Figure 4 Schematic structural diagram of the coding electrode shown in Embodiment 4;

[0025] Figure 5 Schematic structural diagram of a connection between a coding electrode and a detection electrode shown in Embodiment 4;

[0026] Figure 6 Schematic structural diagram of another connection between a coding electrode and a detection electrode described in Embodiment 4;

[0027] Figure 7 Schematic structural diagram of the coding electrode shown in Embodiment 5;

[0028] Figure 8 Schematic diagram of automatic coding realized by a coding electrode structure shown in Embodiment 6. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to make the objectives, technical solutions and advantages of the present utility model more clear and understandable, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0030] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present utility model; relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0031] In the description of the present utility model, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, an integral connection, or a detachable connection; it can be the communication inside two elements; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0032] Embodiment 1

[0033] As Figure 1 shown, this embodiment discloses the structure of an electrochemical test strip including a coded electrode, which includes a substrate 1, a coded electrode 3 and a detection electrode 2 provided on the substrate 1. Among them, the coded electrode 3 and the detection electrode 2 are located on the same side of the substrate 1 and are on the same horizontal plane.

[0034] Specifically, the substrate 1 is used for printing the coded electrode 3 and the detection electrode 2, and it has insulation properties. The material can be glass fiber (FR-4), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polypropylene (PP), etc.

[0035] The detection electrode 2 includes a working electrode for detecting the target substance and a counter electrode for detecting the target substance. The two form a detection circuit for the target substance. A bioactive substance reaction layer, such as an enzyme layer, covers the surface of the detection electrode 2. The concentration of the target substance is measured by generating a current signal through the electrochemical reaction between the bioactive substance and the detected target substance. In this embodiment, the detection electrode 2 further includes an impedance detection working electrode, an impedance detection counter electrode, and a sample injection detection electrode. Among them, the impedance detection working electrode and the impedance detection counter electrode form an impedance detection circuit, which can calibrate the test values of the hematocrit in different samples to make the test results more accurate; the sample injection detection electrode and the target substance detection working electrode form a sample injection detection circuit for judging whether the injection of the target substance is sufficient. Preferably, the detection electrode 2 is a combination of one or more of a carbon electrode, a silver electrode, and a gold electrode.

[0036] Further, as Figure 1 shown, the coding electrode 3 is located below the detection electrode 2. It includes a plurality of first electrode blocks 31 with the same structure, and a connecting wire 32 for electrically connecting two adjacent first electrode blocks 31. The coding electrode 3 is used to provide a variety of coding information. It can obtain different electrical parameters through independent operation, and after being recognized by the detection device, the corresponding coding information is determined. Then, the detection device provides the corresponding calibration parameters to make the detection result more accurate. It should be noted that the electrical parameter can be the connection or disconnection between two adjacent first electrode blocks 31; the electrical parameter can also be the current intensity relationship obtained after applying a voltage between two adjacent first electrode blocks 31. It should be understood that the disconnection between the first electrode blocks 31 includes not setting a connecting wire 32 between two adjacent first electrode blocks 31, or the set connecting wire 32 being cut off, and there is a break point on the connecting wire 32, which can be cut off by laser cutting or mechanical scribing.

[0037] In this embodiment, the number of the first electrode blocks 31 is 5. By increasing the number of the first electrode blocks 31, the coding information can be increased. Therefore, the number of the first electrode blocks 31 can be flexibly adjusted according to needs, preferably 3 - 8. When it is less than 3, the number of provided coding information is too small; when it is more than 8, due to the limited space of the test strip, the arrangement of the electrode blocks will be too dense, increasing the difficulty of laser or mechanical cutting of the connecting wire 32 and easily resulting in inaccurate coding information.

[0038] In order to obtain more coding information, in addition to increasing the number of the first electrode blocks 31, the coding electrode 3 can also be electrically connected to the detection electrode 2. As Figure 1As shown in the figure, second electrode blocks 21 are respectively formed at the ends of the extension lines of the electrodes of the detection electrode 2 close to the coding electrode 3. The first electrode block 31 and the second electrode block 21 are conductively connected through a connecting wire 32, so that more electrical parameters can be obtained. It should be understood that any one of the first electrode blocks 31 of the coding electrode 3 can be electrically connected to the second electrode block 21 of one of the electrodes of the detection electrode 2, or multiple first electrode blocks 31 of the coding electrode 3 can be connected one-to-one with multiple second electrode blocks 21 of the same number of the detection electrode 2. It should be noted that the electrodes corresponding to the second electrode blocks 21 connected to the coding electrode 3 cannot be the electrodes that need to provide a voltage difference. In this embodiment, the first second electrode block 211 and the second second electrode block 212 do not participate in the connection with the first electrode block 31 because the electrodes connected to these two electrode blocks are the target detection working electrode and the impedance detection working electrode in the detection electrode 2 respectively, and a voltage difference needs to be provided during actual operation.

[0039] It should be noted that in this embodiment, the first electrode blocks 31 and the second electrode blocks 21 are respectively arranged in a row, and the shape of the electrode blocks is rectangular, and it can also be other shapes and sizes in the prior art, without special limitation. Preferably, both the first electrode blocks 31 and the second electrode blocks 21 are one or a combination of carbon electrodes, silver electrodes, and gold electrodes, and the material of the connecting wire 32 is one of carbon, silver, gold, platinum, and palladium, preferably silver.

[0040] It should be understood that when the obtained electrical parameter is the connection or disconnection between electrode blocks, the principle of forming coding information is as follows: Since a connecting wire 32 can be provided between every two adjacent electrode blocks, there are a total of n - 1 connecting wires 32 between n electrode blocks. Based on the fact that the connecting wire 32 can conduct adjacent electrode blocks or cut off the breakpoints on the connecting wire 32 by laser or mechanical cutting to disconnect adjacent electrode blocks, each connecting wire 32 has 2 states, so n - 1 connecting wires 32 can form 2 n-1 types of coding information.

[0041] Taking this embodiment as an example, as Figure 1 shown, the number of the first electrode blocks 31 is 5, which are respectively marked as the first first electrode block 311, the first second electrode block 312, the first third electrode block 313, the first fourth electrode block 314, and the first fifth electrode block 315. The number of the second electrode blocks 21 is also 5, which are respectively marked as the first second electrode block 211, the second second electrode block 212, the second third electrode block 213, the second fourth electrode block 214, and the second fifth electrode block 215. In this embodiment, every two adjacent first electrode blocks 31 are connected through a connecting wire 32, and the first third electrode block 313 and the second third electrode block 213 are also connected through a connecting wire 32. Therefore, there are a total of 5 connecting wires 32, which can form 2 5= 32 kinds of encoded information. And at corresponding positions of the detection device, there are 6 contacts respectively corresponding to and cooperating with the first electrode block 31 and the second electrode block 21. When the biosensor test strip is inserted into the detection device, the 6 contacts are respectively connected to the 5 first electrode blocks 31 and the second electrode block 213 correspondingly. By judging whether there is a conductive connection between every two adjacent electrode blocks in the first electrode block 31 and whether there is a conductive connection between the first electrode block 313 and the second electrode block 213, the corresponding encoded information (i.e., code) can be determined. Furthermore, the detection device calls the calibration parameters matching the code for calibration to ensure the accuracy of subsequent detection results.

[0042] When the obtained electrical parameter is the current intensity relationship between adjacent electrode blocks, the principle of forming the encoded information is as follows: Taking this embodiment as an example, as Figure 1As shown in the figure, there are 5 first electrode blocks 31, namely the first electrode block 1 311, the first electrode block 2 312, the first electrode block 3 313, the first electrode block 4 314, and the first electrode block 5 315. There are also 5 second electrode blocks 21, namely the second electrode block 1 211, the second electrode block 2 212, the second electrode block 3 213, the second electrode block 4 214, and the second electrode block 5 215. In this embodiment, every two adjacent first electrode blocks 31 are connected by a connecting wire 32, and the first electrode block 3 313 and the second electrode block 3 213 are connected by a connecting wire 32. At corresponding positions of the detection device, 6 contacts are provided, which respectively cooperate with the 5 first electrode blocks 31 and the second electrode block 3 213. When the biosensor test strip is inserted into the detection device, the 6 contacts are respectively connected to the 5 first electrode blocks 31 and the second electrode block 3 213 to form an electrical circuit. The detection device is controlled to apply voltages to every two adjacent first electrode blocks 31 and between the first electrode block 3 313 and the second electrode block 3 213 in sequence according to the order of increasing or decreasing voltage values. Based on the fact that the resistances of the connecting wires 32 between the electrode blocks are basically the same, different current intensities between every two adjacent electrode blocks can be obtained. Based on the differences in their current intensities, corresponding coding information can be determined. For example, when the voltage value is applied in the order of increasing, the current intensity I1 between the first electrode block 1 311 and the first electrode block 2 312 is less than the current intensity I2 between the first electrode block 2 312 and the first electrode block 3 313, and I2 is less than the current intensity I3 between the first electrode block 3 313 and the first electrode block 4 314, and I3 is less than the current intensity I4 between the first electrode block 4 314 and the first electrode block 5 315, and I4 is less than the current intensity I5 between the first electrode block 3 313 and the second electrode block 3 213 (i.e., I1 < I2 < I3 < I4 < I5), it can be recorded as code1. It should be understood that when the connecting wire 32 between two adjacent electrode blocks is cut off, the resistance between them will be infinitely large, and the current intensity will be infinitely small, so that the relationship of the current intensity can be changed to obtain more coding information.

[0043] Embodiment 2

[0044] Figure 2 A structural schematic diagram of a coding electrode is disclosed. In this embodiment, the coding electrode 3 works independently. The number of its first electrode blocks 31 is 3, arranged in a row, and there are 2 cuttable connecting wires 32 in the middle. When the on-off of adjacent electrode blocks is used as the electrical parameter, the structure of the coding electrode 3 can provide various coding information. For example, the on and off of the first electrode block 1 311 and the first electrode block 2 312 can generate two kinds of coding information. Similarly, the on and off of the first electrode block 2 312 and the first electrode block 3 313 can also form two kinds of coding information. Therefore, when there are 3 first electrode blocks 31 of the coding electrode 3, a total of 22 = Four kinds of encoded electrode information.

[0045] Example 3

[0046] When the number of the first electrode blocks 31 of the encoding electrode 3 increases, the cutting methods of the connecting lines 32 also increase, and the encoded information also increases. As Figure 3 shown, in this embodiment, the number of the first electrode blocks 31 is 4, and there are 3 connectable lines 32 in the middle. The total number of encoded information formed is: 2 3 = 8 kinds.

[0047] Example 4

[0048] When the number of the first electrode blocks 31 of the encoding electrode 3 increases, the cutting methods of the connecting lines 32 also increase, and the encoded information also increases. As Figure 4 shown, in this embodiment, the number of the first electrode blocks 31 is 5, and there are 4 connectable lines 32 in the middle. The total number of encoded information formed is: 2 4 = 16 kinds.

[0049] It should be noted that, in addition to increasing the number of the first electrode blocks 31, the encoding information can also be increased by connecting the encoding electrode 3 and the detection electrode 2 through the connecting line 32. As Figure 1 shown, after the first electrode block three 313 is connected to the second electrode block three 213, there are a total of 5 connectable lines 32 in the middle, and the encoded information increases from the previous 2 4 = 16 kinds to 2 5 = 32 kinds. Multiple first electrode blocks 31 can also be connected to multiple second electrode blocks 21, and the second electrode blocks 21 corresponding to the electrodes that need to provide the voltage difference do not participate in the connection. As Figure 5 shown, in this embodiment, the first electrode block one 211 and the second electrode block two 212 do not participate in the connection. The first electrode block three 313 and the first electrode block five 315 are respectively connected to the second electrode block three 213 and the second electrode block five 215 one by one. At this time, there are a total of 6 connectable lines 32 in the middle, and the encoded information increases to 2 6 = 64 kinds; as Figure 6 shown, the first electrode block three 313, the first electrode block four 314, and the first electrode block five 315 are respectively connected to the second electrode block three 213, the second electrode block four 214, and the second electrode block five 215 one by one. At this time, there are a total of 7 connectable lines 32 in the middle, and the encoded information increases to 2 7= 128 types. It should be noted that the connection method and quantity can be flexibly selected according to the required coding information. The position and method of connecting the coding electrode 3 to the detection electrode 2 are not fixed. It can be the connection between the first electrode block three 313 and the second electrode block three 213, or the connection between the second electrode block three 213 and the first electrode block four 314. In addition, when the quantity of the first electrode blocks 31 for coding is 3, 4, 6, 7, or 8 respectively, the above connection method is also applicable, and no schematic diagram is drawn here for further illustration.

[0050] Example 5

[0051] When the quantity of the first electrode blocks 31 of the coding electrode 3 is 6, as Figure 7 shown, in this embodiment, the quantity of the connection lines 32 that can be cut is 5, and the total number of the formed coding information is: 2 5 = 32 types.

[0052] When the quantity of the first electrode blocks 31 of the coding electrode 3 is further increased, such as increased to 7 or 8, the formed coding information will be further increased, and no schematic diagram is drawn here for further illustration. When the quantity of the first electrode blocks 31 of the coding electrode 3 is 7, there are 6 connection lines 32 that can be cut in total, and the total number of the formed coding information is: 2 6 = 64 types. When the quantity of the first electrode blocks 31 of the coding electrode 3 is 8, there are 7 connection lines 32 that can be cut in total, and the total number of the formed coding information that can be formed is: 2 7 = 128 types. Considering the actual width of the electrochemical test strip, when the quantity of the first electrode blocks 31 of the coding electrode 3 is 7 or 8, it will be less in the actual use process, but it is still within the protection scope of this patent.

[0053] Example 6

[0054] This embodiment discloses the specific method for the coding electrode structure shown in Example 2 to achieve various coding information. It should be noted that the coding information in this embodiment is realized by cutting the connection lines 32 to control the connection or disconnection between adjacent first electrode blocks 31. As Figure 8As shown, when the connecting lines 32 between the first electrode block one 311 and the first electrode block two 312 and between the first electrode block two 312 and the first electrode block three 313 are not cut, the encoded information formed at this time is Code1. When the connecting line 32 between the first electrode block one 311 and the first electrode block two 312 is cut, while the connecting line 32 between the first electrode block two 312 and the first electrode block three 313 is not cut, the encoded information formed at this time is Code 2. When the connecting line 32 between the first electrode block one 311 and the first electrode block two 312 is not cut, while the connecting line 32 between the first electrode block two 312 and the first electrode block three 313 is cut, the encoded information formed at this time is Code 3. When the connecting line between the first electrode block one 311 and the first electrode block two 312 is cut and the connecting line 32 between the first electrode block two 312 and the first electrode block three 313 is also cut, the encoded information formed at this time is Code 4.

[0055] The connecting line 32 between the electrode blocks can be cut by laser or mechanically, and there can be various cutting methods.

[0056] Similarly, when the number of the first electrode blocks 31 is 4 - 8, or when the first electrode blocks 31 and the second electrode blocks 21 are connected by the connecting lines 32, the method of obtaining electrical parameters through on - off to form encoded information is also as Figure 6 shown. Different from this, the information of the encoding electrode 3 will be richer, and the number of electrode blocks can be flexibly increased according to actual needs.

Claims

1. An electrochemical test paper comprising a coding electrode, comprising a substrate (1), a coding electrode (3) arranged on the substrate (1), and a detection electrode (2), characterized in that: The encoding electrode (3) and the detection electrode (2) are located on the same side of the substrate (1), wherein: The encoding electrode (3) comprises at least three first electrode blocks (31) and a connecting line (32) for electrically connecting two adjacent first electrode blocks (31) among the at least three first electrode blocks (31); The detection electrode (2) is electrically connected to the encoding electrode (3).

2. The electrochemical test paper according to claim 1, characterized in that: The number of the first electrode blocks (31) of the encoding electrode (3) does not exceed eight.

3. The electrochemical test paper according to claim 2, characterized in that: The encoding electrode (3) is located below the detection electrode (2), and the first electrode blocks (31) of the encoding electrode (3) are arranged in a rectangular shape and in a row.

4. The electrochemical test paper according to claim 1, characterized in that: The detection electrode (2) comprises a target object detection working electrode and a target object detection counter electrode, the target object detection working electrode and the target object detection counter electrode constitute a target object detection circuit, the encoding electrode (3) and the detection electrode (2) are located at the same horizontal plane, a connecting line (32) is provided between the two, and the two are electrically connected via the connecting line (32).

5. The electrochemical test paper according to claim 4, characterized in that: The target object detection pair of electrodes comprises a second electrode block (21), and any one of the first electrode blocks (31) of the encoding electrode (3) is electrically connected to the second electrode block (21) of the target object detection pair of electrodes.

6. The electrochemical test paper according to claim 4, characterized in that: The detection electrode (2) further comprises an impedance detection working electrode, an impedance detection counter electrode and a sample injection detection electrode. The impedance detection working electrode and the impedance detection counter electrode form an impedance detection loop, and the sample injection detection electrode and the target object detection working electrode form a sample injection detection loop.

7. The electrochemical test paper according to claim 6, characterized in that: The target detection counter electrode, the impedance detection counter electrode and the sample injection detection electrode respectively comprise a second electrode block (21), and at least one first electrode block (31) of the encoding electrode (3) is electrically connected to at least one second electrode block (21) in a one-to-one manner.

8. The electrochemical test paper according to claim 5 or 7, characterized in that: The first electrode block (31) and the second electrode block (21) are both carbon electrodes, silver electrodes and gold electrodes, or a combination of multiple thereof.

9. The electrochemical test paper according to claim 1 or 4, characterized in that: The material of the connecting wire (32) is one of carbon, silver, gold, platinum and palladium, and a breakpoint is provided on the connecting wire (32).

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