Analysis device sheet

Abstract

To provide an analysis device sheet that prevents a reduction in accuracy and performance due to deformation of a substrate and enables stable detection.SOLUTION: An analysis device sheet has a channel wall that is formed by impregnating hydrophobic resin in the entire area in a thickness direction of a porous base material, and a plurality of closed channels are formed by at least part of the channel wall. When projection is performed for the channel wall along a longitudinal direction of the analysis device sheet, and the projected image is superimposed on a reference straight line x along the longitudinal direction of the analysis device sheet, the reference straight line x and the projected image overlap each other at a ratio of 95% or more in terms of length. When projection is performed for the channel wall along a direction orthogonal to the longitudinal direction of the analysis device sheet, and the projected image is superimposed on a reference straight line y along the direction orthogonal to the longitudinal direction of the analysis device sheet, the reference straight line y and the projected image overlap each other at a ratio of 95% or more in terms of length.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an analytical device sheet in which electrodes are formed using flow paths in a porous substrate. [Background technology]

[0002] In recent years, the development of analytical devices that utilize micro-sized fine channels to perform efficient (trace-volume, rapid, and simple) biochemical analysis within a single device has attracted attention in a wide range of fields. These fields include not only biochemical research but also medicine, drug discovery, healthcare, the environment, and food. Among these, paper-based analytical devices offer many advantages over conventional devices, such as light weight, low cost, no need for a power source, and high disposability. Therefore, it is expected to be used as a screening device in medical activities in developing countries and depopulated areas that lack medical facilities, as well as at disaster sites, and at airports and other locations where the spread of infectious diseases must be stopped at the border.In addition, because it is inexpensive and easy to use, it is attracting attention as a healthcare device that can manage and monitor one's own health condition.

[0003] As an example of a paper analytical device, Patent Document 1 describes a configuration in which electrodes are formed on a porous substrate so as to straddle a wax-based hydrophobic flow path wall. In this configuration, one end of the electrode reacts with the sample in the flow path to form a predetermined potential, and the other end of the electrode is connected to a measuring device for measurement. The device is composed of two electrodes: a reference electrode that exhibits a fixed potential based on a reference solution, and an ion-selective electrode that exhibits a potential corresponding to the ion concentration of the sample. The ion concentration of the sample can be measured by measuring the potential difference between the two electrodes. An analytical device with this functionality can be made sufficiently large, even if it is approximately 20 mm square. Furthermore, paper substrates with sizes such as A4 (210 mm x 297 mm) are widely available. Therefore, a manufacturing method in which multiple analytical devices are arranged on the same substrate and then cut into individual devices after fabrication is effective for production efficiency. Patent Document 1 also describes a method for fabricating 28 devices on a 20 cm x 20 cm paper substrate.

[0004] Considering that analytical devices such as those described above will be used in, for example, point-of-care testing (POCT), the user will likely pick up the device by hand and place it in a measuring device, and having a margin around the measurement functional section will make it easier to handle. Furthermore, even in applications such as continuous measurements using an automated measuring device, having a margin as described above will facilitate handling in order to transport devices sequentially within the measuring device. In other words, a configuration in which each device contains functional sections, such as flow channels and electrodes involved in the measurement, as well as a margin used for handling the device, makes it easier to handle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2016 / 033438 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above-mentioned device manufacturing method, if the device is placed in a high-humidity environment during manufacturing, the margins may absorb moisture and swell, causing the paper substrate to deform. Deformation of the paper substrate can lead to a decrease in the positional accuracy of the electrodes and reagents formed on the flow path, as well as a decrease in the accuracy of the functional layer formed on the electrodes, which in turn can lead to a decrease in measurement performance. [Means for solving the problem]

[0007] The present invention provides an analytical device sheet in which a plurality of analytical devices each having a closed flow path are arranged on the same porous substrate, the analytical device sheet has flow path walls formed by impregnating the porous substrate with a hydrophobic resin over the entire thickness direction of the porous substrate; the closed flow path is formed by at least a portion of the flow path wall, When the channel wall is projected along the longitudinal direction of the analytical device sheet and the projected image is superimposed on a reference line x along the longitudinal direction of the analytical device sheet, the ratio of the length over which the reference line x and the projected image overlap is 95% or more based on the longitudinal length of the entire region in which the plurality of analytical devices are formed, When the channel wall is projected along a direction perpendicular to the longitudinal direction of the analytical device sheet and the projected image is superimposed on a reference line y extending along a direction perpendicular to the longitudinal direction of the analytical device sheet, the ratio of the length over which the reference line y and the projected image overlap is 95% or more, based on the length in a direction perpendicular to the longitudinal direction of the entire region in which the plurality of analytical devices are formed; The present invention relates to an analytical device sheet characterized by the above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an analytical device sheet that can suppress deterioration in accuracy and performance due to deformation of the substrate and obtain an analytical device that can perform stable detection. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 10 is a top view of the analytical device M1 after the flow channel 21 has been formed. [Figure 2] FIG. 10 is a top view of the analytical device M1 after the working electrode 31 has been formed. [Figure 3A] FIG. 10 is a top view of the analytical device M1 after the reference electrode and the electrolyte layer are formed. [Figure 3B] FIG. 2 is a cross-sectional view of the analytical device M1 taken along a dashed line D1. [Figure 4] FIG. 2 is a top view of an analytical device sheet A (analytical device group A). [Figure 5] FIG. 10 is a top view of an analytical device sheet B (analytical device group B). [Figure 6] FIG. 10 is a top view of the analytical device M2 after the flow channel 21 has been formed. [Figure 7]FIG. 10 is a top view of the analytical device M2 after electrode surface treatment has been performed. [Figure 8] FIG. 10 is a top view of an analytical device sheet C (analytical device group C). [Figure 9] FIG. 10 is a top view of an analytical device sheet D (analytical device group D). [Figure 10] FIG. 10 is a top view of an analytical device sheet E (analytical device group E). [Figure 11] FIG. 10 is a top view of an analytical device sheet F (analytical device group F). DETAILED DESCRIPTION OF THE INVENTION

[0010] The method of the present invention is characterized by producing a flow channel wall shape in which a straight line passing between closed flow channels passes through an area of ​​the flow channel wall K, thereby making it possible to suppress deformation due to swelling of the substrate. Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are merely examples, and the present invention is not limited to the contents of the embodiments. Furthermore, in the following drawings, components that are not necessary for explaining the embodiments are omitted from the drawings.

[0011] <Projection explanation> First, the concept of projection will be explained using Fig. 9. The configuration of the analysis device will be described later.

[0012] The analytical device sheet D shown in Fig. 9 is an arrangement of 96 analytical devices M1, similar to the analytical device sheet B in Fig. 5, except for the shape of the flow path walls. The flow path walls K2 in the analytical device sheet D are formed of 10 independent rectangles, K2a to K2j. K2a to K2j extend in the longitudinal direction (hereinafter referred to as the x-direction) of the A4-sized porous substrate S1, and are rectangular with a length of 73 mm and a width of 1 mm. K2a to K2c, K2d to K2g, and K2h to K2j are also spaced apart at 40 mm intervals in the lateral direction (hereinafter referred to as the y-direction), which is perpendicular to the longitudinal direction. When K2a to K2j are projected along the x-direction, they overlap with K2a to K2c to form a projection image K2Sa, K2d to K2g overlap with K2d to form a projection image K2Sd, and K2h to K2j overlap with K2h to form a projection image K2Sh, resulting in a total of three line segments. K2Sa, K2Sd, and K2Sh are combined to form the projection image K2S of the flow path wall K2. The total length of the projection image K2S is 219 mm, consisting of three 73 mm line segments. The flow path wall 11 in the analytical device M1 also exists as a flow path wall in the analytical device sheet D. When the flow path wall 11 is projected in the y-direction in the same way as the flow path wall K2, its projection image 11S becomes 12 independent line segments with a length H1 = 6 mm, but all of these are included in K2S when projected in the x-direction. That is, the total length of the projection images of all the flow path walls in the analytical device sheet D projected in the x direction is 219 mm.

[0013] <About the ratio of projected images> Next, the relationship between the total length of the projection image K2S and the length of the region where the analytical device is formed will be described.

[0014] The area of ​​the analytical device sheet D where the analytical devices M1 are formed has a length in the x direction indicated by the arrow D9, which is 229 mm. As described above, the total length of the projection image of the flow path walls in the analytical device sheet D projected along the x direction is 219 mm. Therefore, in the x-direction, with respect to the entire length of the region where a plurality of analysis devices are formed on the analysis device sheet D, the ratio (%) of the length where the image of the flow path wall overlaps with the straight line in the x-direction (reference straight line x) is represented by the following formula (2). 219÷229×100≒95.6 ··· Formula (2)

[0015] That is, when a straight line perpendicular to the x-direction of the porous substrate S1 is drawn on the analysis device sheet D, the flow path wall intersects in 95.6% of the region, which is the majority of the entire region where the plurality of analysis devices M1 are arranged. Therefore, due to the effect of the hydrophobic flow path wall, the analysis device sheet D can suppress the deformation associated with the moisture absorption of the porous substrate S1 in the x-direction.

[0016] Considering the deformation of the entire porous substrate S1, it is necessary to consider the projection of the flow path wall not only in the x-direction but also in the y-direction, which is the short side direction. A specific example will be shown and described below.

[0017] The analysis device sheet E shown in FIG. 10 has 96 analysis devices M1 arranged in the same manner as the analysis device sheet B in FIG. 5, and only the shape of the flow path wall is different. The flow path wall 11 included in the analysis device M1 is the same, but as other flow path walls, it has a flow path wall K3 composed of 7 rectangles of K3a to K3g and a flow path wall K4 composed of 8 rectangles of K4a to K4h. K3a to K3g extend in the x-direction and are rectangles with a length of 71 mm and a width of 1 mm. K4a to K4h extend in the y-direction and are rectangles with a length of 60 mm and a width of 1 mm.

[0018] <Projection along the x-direction> As described above, for the flow path wall K3 of the analysis device sheet E, first consider the projection along the x direction. At this time, since the projected images of the flow path wall 11 of the analysis device M1 and the flow path wall K4 are included in the projected image K3S of the flow path wall K3, only the projected image K3S is considered. Since the flow path wall K3 consists of a plurality of independent flow path walls, for example, there is a region without a flow path wall between K3c and K3d. However, when considering the projection along the x direction, this region is connected by the projected images of K3a and K3f. When considering the projected image of the entire flow path wall K3 with respect to the x direction, it becomes a line segment, the projected image K3S, and its length is 229 mm. Also, in the x direction, the length of the entire region where a plurality of analysis devices are formed is 229 mm indicated by D9. That is, when a straight line (reference straight line x) orthogonal to the x direction, which is the longitudinal direction of the porous base material S1, is drawn on the analysis device sheet E, it will intersect the flow path wall in all regions (100% of the regions) where the analysis devices M1 are arranged. Thereby, the analysis device sheet E can suppress deformation associated with moisture absorption of the porous base material S1 in the x direction.

[0019] <Projection along the y direction> Subsequently, consider the projection of the flow path wall of the analysis device sheet E in the y direction. In this case, since the projected images of the flow path wall 11 of the analysis device M1 and the flow path wall K3 are included in the projected image K4S of the flow path wall K4, only the projected image K4S is considered. And although the flow path wall K4 consists of a plurality of independent flow path walls, when considering the projection in the y direction, the gaps between the flow path walls are filled in the same way as in the x direction, so the projected image becomes a line segment, the projected image K4S, and its length is 154 mm. Also, in the y direction, the length of the entire region where a plurality of analysis devices are formed is 154 mm indicated by D11. That is, when a straight line (reference straight line y) orthogonal to the y direction, which is the short-side direction of the porous base material S1, is drawn on the analysis device sheet E, it will intersect the flow path wall in all regions (100% of the regions) where the analysis devices M1 are arranged. Thereby, the analysis device sheet E can suppress deformation associated with moisture absorption of the porous base material S1 in the y direction.

[0020] As explained above, in the analytical device sheet E, it can be said that within the range where the analytical devices are arranged, any straight line drawn in either the longitudinal or lateral direction of the porous substrate S1 will necessarily intersect with a flow path wall somewhere. In other words, by forming flow path walls such as flow path walls K3 and K4, deformation of the porous substrate S1 due to moisture absorption can be suppressed. Furthermore, compared to the analytical device sheet A shown in FIG. 4, it can be constructed using less channel wall material, which can contribute to reducing the environmental load and costs. [Example]

[0021] [Example 1] The present invention relates to an analytical device sheet having a configuration in which a plurality of analytical devices are arranged on the same substrate. First, we will explain the configuration for each device.

[0022] <Substrate / flow path wall> The substrate of the analytical device M1 and the flow path walls of the analytical device M1 will be described with reference to Fig. 1. Fig. 1 is a simplified top view of the analytical device M1 before various electrodes are formed.

[0023] In this example, filter paper was used as the porous substrate S1. It was made of cellulose, had a thickness of 100 μm, and a porosity of 50%. The minute gaps between the cellulose fibers facilitate capillary action, and the substrate also possesses excellent hydrophilicity, allowing it to function as a flow path through which liquids can smoothly penetrate. Naturally, the porous substrate S1 is not limited to filter paper as long as it functions as a flow path. It can also be made of paper such as plain paper, fine paper, watercolor paper, Kent paper, or synthetic paper, as well as synthetic resin porous films, fabrics, and textile products. A hydrophobic resin was impregnated into a portion of the entire thickness of the porous substrate S1 to form flow path walls 11 with a height H1 of 6 mm and a width L1 of 14 mm. The flow path walls 11 were formed by electrophotographically printing the hydrophobic resin as toner and then heating it to melt and penetrate the resin, according to the method described in Japanese Patent Application Laid-Open No. 2021-37612. However, the method is not limited to this, and other methods such as infiltrating wax using a wax printer or infiltrating resin by screen printing may also be used, and a combination of multiple methods may also be used.

[0024] Additionally, the area inside the channel wall 11 is a channel 21 (closed channel) that is not permeated with the hydrophobic resin that forms the channel wall. The channel 21 is a channel through which the sample permeates due to capillary action caused by the porosity of the porous substrate S1. The channel 21 is composed of a working electrode placement section S1b for placing a working electrode, a reference electrode placement section S1c for placing a reference electrode, a dispensing section S1d located between the working electrode placement section S1b and the reference electrode placement section S1c, and a 1.5 mm-wide channel connecting the dispensing section S1d to the working electrode placement section S1b and the reference electrode placement section S1c. The working electrode placement section S1b and the reference electrode placement section S1c are squares measuring 4 mm on each side, and the dispensing section S1d is a circle with a diameter of 2.3 mm. The size, shape, etc. of the flow path are not limited to this.

[0025] Hereinafter, the formation of electrodes of the analytical device M1 will be described with reference to FIG. FIG. 2 is a top view of the analytical device M1 after the working electrode 31 has been formed.

[0026] <Working electrode> The working electrode 31 has a shape consisting of a 3 mm square that fits within the working electrode placement section S1b and a 1 mm wide x 4.5 mm long rectangle that extends from the working electrode placement section S1b to the outer region of the flow path wall 11. Although Ag / AgCl was used as the material for the working electrode 31 as an electrode for detecting Cl ion concentration, the material is not limited to this and any material or configuration that functions as a working electrode may be used, and an ion-selective membrane may be formed in addition to the electrode.

[0027] The working electrode 31 was formed using a screen printing machine LS-35TVA manufactured by Newlong Co., Ltd. For printing, an Ag / AgCl paste (Ag:AgCl=6.4) was printed using a #200 plate, and dried at 80° C. for 10 minutes.

[0028] The working electrode 31 formed as described above is formed on the flow path, and therefore comes into contact with the sample permeating from the dispensing section S1d, and can exhibit a potential corresponding to the Cl ion concentration of the sample. To detect this potential, the electrode portion extending to the external region of the flow path wall 11 can be brought into contact with an external measuring device.

[0029] Hereinafter, the formation of the reference electrode and electrolyte layer of the analytical device M1 will be described with reference to FIGS. 3A and 3B. FIG. 3A is a top view of the analytical device M1 after the reference electrode and the electrolyte layer have been formed, and FIG. 3B shows a cross section taken along the dashed line D1-D1'.

[0030] <Reference electrode> The reference electrode 32 is a rectangle with a width of 1 mm and a length of 7.5 mm that extends from the reference electrode placement section S1c to the outer region of the flow path wall 11. Like the working electrode 31, it reacts with the sample that has permeated the flow path in the reference electrode placement section S1c. By making the width 1 mm, when an electrolyte layer 41 (described later) is applied, it is easy to place the electrolyte layer 41 in the flow path of the reference electrode placement section S1c, including the back side of the reference electrode 32.

[0031] Ag / AgCl was used as the material for the reference electrode 32. By using Ag / AgCl, an equilibrium reaction according to the following formula (1) occurs in the aqueous solution, and therefore a stable potential can be obtained when the Cl ion concentration around the reference electrode 32 is stable due to the electrolyte layer 41. [ka]

[0032] The reference electrode 32 was applied to the reference electrode placement portion S1c using a screen printing machine LS-35TVA manufactured by Newlong Co., Ltd. For printing, Ag / AgCl paste (Ag:AgCl=6:4) was printed using a #200 plate, and dried at 80°C for 10 minutes.

[0033] To detect the potential of the reference electrode 32 formed as described above, contact with an external measuring device can be made at the electrode portion extending to the external region of the flow path wall 11. Then, by measuring the potential difference between the reference electrode 32 and the working electrode 31, a potential difference corresponding to the Cl ion concentration of the sample can be obtained, and by preparing a calibration curve in advance, the Cl ion concentration of the sample can be calculated from the potential difference.

[0034] <Electrolyte layer> The role of the electrolyte layer 41 is to dissolve in the water content of the sample when the sample permeates the reference electrode placement area S1c, saturating the Cl ion concentration and thereby stabilizing the potential of the reference electrode 32. KCl was used as the material for this purpose. KCl was selected because it dissolves easily in water, the diffusion rates of K ions and Cl ions are approximately equal, and it is unlikely to generate a liquid junction potential. Naturally, the material for the electrolyte layer 41 is not limited to this, and any material that can stabilize the potential of the reference electrode 32 may be used, for example, NaCl.

[0035] The electrolyte layer 41 was applied using a Biospot (Microjet Corporation). The solution was prepared by dissolving KCl in pure water to a concentration of 16 wt%. The droplet size was 6 nL / droplet, the frequency was 10 Hz, and the vertical and horizontal pitch was 300 μm. The KCl amount was adjusted by applying three coats. The amount of KCl can be stabilized by adjusting the amount of KCl to saturate the KCl solution relative to the amount of analyte permeating the reference electrode placement area S1c. Therefore, the amount of KCl applied is not limited to this amount as long as it is sufficient to create saturated KCl. Note that when applied under the above conditions, the KCl aqueous solution attached to the porous substrate S1 diffuses within the porous substrate S1 before volatilizing, allowing KCl to be deposited on the backside of the reference electrode 32 as shown in Figure 3B. This stabilizes the Cl ion concentration around the reference electrode 32 when the analyte permeates, stabilizing the potential of the reference electrode 32. In other words, the reference electrode functions more stably.

[0036] Next, an actual analytical device sheet will be described with reference to FIG. FIG. 4 is a top view of an analytical device sheet A manufactured in a configuration in which a plurality of analytical devices are arranged on the same substrate. These plurality of analytical devices are collectively referred to as an analytical device group A.

[0037] <Analytical device sheet and method for producing same> The configuration of one analytical device M1 is as described above. However, for actual production, it is more efficient to manufacture multiple analytical devices in bulk by arranging them on a sheet of paper, such as A4 size (210 mm × 297 mm). In this example, eight analytical devices M1 were arranged at 20 mm intervals in the transverse direction (y direction) and 12 analytical devices M1 were arranged at 20 mm intervals in the longitudinal direction (x direction) on an A4 size porous substrate S1. The components that function for measurement within the analytical device are the flow path, working electrode, and reference electrode. Although one analytical device M1 can be contained within an area of ​​20 mm × 10 mm, a 20 mm × 20 mm area is reserved for each device to ensure a handle area for handling each device. The analytical device sheet A can be produced by performing the processes described above (forming the flow path wall, forming the working electrode, forming the reference electrode, and forming the electrolyte layer) in accordance with this arrangement.

[0038] In the analytical device sheet A, the analytical device group A forms a channel wall H that forms a closed channel for each analytical device M1. Furthermore, when forming the channel wall H, a grid-patterned channel wall K is formed at a 20 mm pitch so as to surround each individual analytical device M1 without overlapping it. The grid line width is 2.5 mm. The analytical device sheet A has hydrophobic regions impregnated with a hydrophobic resin as the channel wall, and hydrophilic regions that do not contain hydrophobic resin and exhibit the inherent hydrophilicity of the substrate. The hydrophilic regions absorb moisture and swell as the humidity of the environment in which the A4-sized porous substrate S1 is placed increases. On the other hand, the hydrophobic regions absorb very little moisture, making them less likely to swell. In addition, the rigidity of the impregnated hydrophobic resin also has the effect of suppressing deformation of the substrate. The degree of swelling / deformation of the entire A4-sized porous substrate S1 is determined by the balance between the hydrophilic and hydrophobic regions. In analytical device sheet A, the flow path area is approximately 65%, so the moisture absorption range is large, but between the closed flow paths there are hydrophobic regions due to the flow path walls K in a grid pattern in the longitudinal direction (x direction) and the lateral direction (y direction). In this analytical device sheet A, there are always straight lines D2 and D3 that pass between the flow path walls. That is, with the channel wall shape of the grid pattern of Example 1, when a straight line is drawn between adjacent closed channels in the x direction, a straight line A can be drawn that always overlaps with the channel wall to both ends in the y direction of the analytical device sheet A, and when a straight line is drawn between adjacent closed channels in the y direction, a straight line B can be drawn that always overlaps with the channel wall to both ends in the x direction of the analytical device sheet A. Therefore, deformation due to swelling of the substrate can be suppressed.

[0039] In this embodiment, the configuration is such that the above-mentioned straight lines A and B can be drawn for any adjacent closed flow paths, but it is also acceptable to have a configuration in which the above-mentioned straight lines A and B can be drawn for some adjacent closed flow paths.

[0040] In this analytical device sheet A, the percentage of the length where the projected image of the flow path wall overlaps with a straight line in the x direction (reference line x) is 100%, and the percentage of the length where the projected image of the flow path wall overlaps with a straight line in the y direction (reference line y) is also 100%, based on the length of the entire area where multiple analytical devices are formed.

[0041] <Comparative Example 1> As a comparative example to the analytical device sheet A, an analytical device sheet B having an analytical device group B will be described with reference to FIG.

[0042] FIG. 5 is a simplified top view of the analytical device sheet B. Like analytical device sheet A, analytical device sheet B is manufactured with a configuration in which 96 analytical devices M1 are arranged at 20 mm intervals on an A4-sized porous substrate S1, but differs in that it does not have a grid-patterned channel wall K. Because there is no grid-patterned channel wall K, hydrophilic regions exist over a wide area between the channels of adjacent analytical devices. For example, lines D4 and D5, which are lines passing between channels, do not pass through the channel wall, and the entire area above D4 and D5 is a hydrophilic region. This hydrophilic region is a continuous region extending from one end of the porous substrate to the other, and since there is no hydrophobic region along the way to suppress deformation, it is prone to swelling / deformation, for example, due to increased humidity. In this analytical device sheet B, the percentage of the length where the projected image of the flow path wall overlaps with a straight line in the x direction (reference line x) is less than 50%, and the percentage of the length where the projected image of the flow path wall overlaps with a straight line in the y direction (reference line y) is less than 80%, based on the total length of the area where multiple analytical devices are formed.

[0043] Here, we compared the shape changes of analytical device sheets A and B after the process of forming the channel walls / channels was completed and then left for 12 hours until they stabilized in a high-temperature / high-humidity environment. Specifically, we measured the expansion rate relative to the original length of the porous substrate S1 in the longitudinal direction and the change in the distance between the upper and lower end devices when the device was moved from a 23°C / 50% to a 30°C / 80% environment. The ideal distance between the upper and lower end devices is 220 mm (20 mm pitch x 11 devices = 220 mm), but this indicates how many mm the distance deviates from 220 mm. The expansion rate is the ratio of the change in the distance between the upper and lower end devices to 220 mm. The results are shown in Table 1.

[0044] [Table 1]

[0045] From Table 1, analytical device sheet B has a deformation of 0.83 mm between the devices at the top and bottom ends. For example, if this deformation occurs and the working electrode is formed later, aligning it with the upper channel will result in a 0.83 mm offset in its position relative to the lower channel. This offset occurs because the porous substrate S1 deforms due to factors such as humidity, but the mask shape of the screen printer used to form the electrodes is determined by the mold and always prints in a consistent shape. Because highly accurate flow channels are designed on the order of hundreds of micrometers, a 0.83 mm offset in the analytical device positioning accuracy can affect sample penetration through the channel and potentially lead to poor contact between the sample and the electrode, resulting in poor measurement accuracy. On the other hand, analytical device sheet A exhibits a 0.51 mm offset in the distance between the upper and lower devices, a reduction of approximately 40% compared to analytical device sheet B. As mentioned above, the grid-patterned channel walls K are thought to suppress moisture absorption and, due to their rigidity, to suppress deformation of the hydrophilic regions. To further enhance the deformation suppression effect, the line width of the lattice pattern flow path walls can be increased. However, since increasing the area for forming the flow path walls increases the amount of hydrophobic resin used and the associated cost, an appropriate analytical device sheet can be obtained by forming the flow path walls in a lattice pattern with the required line width according to the required accuracy.

[0046] In this embodiment, a grid patterned flow path wall K was formed to suppress deformation of the porous substrate S1, but the shape of the flow path wall is not limited to this, and any shape can be used as long as a pattern is used in which the overlapping length between the projected image of the flow path wall and the straight lines in the x and y directions is 95% or more, based on the total length of the area in which multiple analytical devices are formed.

[0047] [Example 2] Regarding the analytical device M2 of this embodiment, only the differences from the analytical device M1 of the first embodiment will be described, the same members will be given the same reference numerals, and the description of similar parts will be omitted.

[0048] The configuration of the analytical device M2 will be described with reference to Fig. 6. Fig. 6 is a top view of the analytical device M2 after the flow paths have been formed.

[0049] <Flow path> The analytical device M2 has a larger flow path wall than the analytical device M1, forming a flow path wall 12 with a height H2 of 20 mm and a width L2 of 20 mm. As will be described later, this is to expand the hydrophobic region and prevent the A4-sized porous substrate S1 from being deformed by the influence of moisture.

[0050] The electrode configuration of the analytical device M2 will be described below with reference to Fig. 7. Fig. 7 is a top view of the analytical device M2 after forming the working electrode 33 and the reference electrode 34 and then performing the electrode surface treatment described below.

[0051] <Working electrode / reference electrode> The working electrode 33 and the reference electrode 34 are similar to the working electrode 31 and the reference electrode 32 up to the point where they are formed by screen printing, but differ in that they are subsequently subjected to an electrode surface treatment.

[0052] <Electrode surface treatment> After screen printing, the working electrode 33 and reference electrode 34 have a Ag:AgCl ratio of 6:4. To further improve their electrode stability, surface treatment was performed to increase the AgCl ratio. Specifically, the porous substrate S1 was immersed for 10 minutes in an aqueous solution containing 100 mM each of 1,3-diaminopropanetetraacetic acid, iron, and ammonium (PDTA) and NaCl. The surface was oxidized. However, the material used in the treatment solution is not limited to this. Any material that increases the AgCl ratio as an oxidizing agent, such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), or potassium dichromate, can be used. The electrode surface treatment was performed on the electrode area formed on the flow channel 21 and on the electrode wall, adjacent to the flow channel, within a 1 mm area, as shown by 33a and 34a in Figure 7. The reason for not treating a portion of the flow channel wall is that the electrode region extending from the flow channel toward the flow channel wall is connected to an external measuring device for potential measurement, as mentioned above, and increasing the AgCl ratio could reduce the stability of the contact. Therefore, before performing the electrode surface treatment, the electrode region extending toward the outside of the flow channel wall is protected with tape (3M 851T) to prevent surface treatment, and then immersed in the surface treatment solution. This allows only the desired area to be surface treated. The electrode surface treatment process is then completed by rinsing with water and drying.

[0053] As described above, when the entire A4-sized porous substrate S1 is immersed in an aqueous liquid such as a surface treatment liquid or cleaning water, deformation may occur due to moisture adsorption and drying in the hydrophilic region, as in Example 1. In particular, since the moisture content changes more rapidly than the humidity change, the amount of deformation of the A4-sized porous substrate S1 may also increase. For this reason, the flow path wall 12 of the analytical device M2 in this example is made wide.

[0054] Figure 8 shows a configuration in which 96 analytical devices M2 described above are arranged at 20 mm intervals in the longitudinal and lateral directions of an A4-sized porous substrate S1, similar to the analytical device sheet A. As shown in Figure 8, a channel wall H is formed to form a closed channel for each analytical device M2. Furthermore, during the formation of the channel wall H, a channel wall K is formed to surround each individual analytical device M2 without overlapping it. As a result, the hydrophobic resin is impregnated into the entire space between adjacent channels, and the channel wall K and the channel wall H form a continuous, integrated channel wall. For example, lines D6 and D7 passing between channels always pass through the channel wall, which is a hydrophobic region. This is referred to as analytical device sheet C. In this analytical device sheet C, the percentage of the length where the projected image of the flow path wall overlaps with a straight line in the x direction (reference line x) is 100%, and the percentage of the length where the projected image of the flow path wall overlaps with a straight line in the y direction (reference line y) is also 100%, based on the length of the entire area where multiple analytical devices are formed.

[0055] Here, using analytical device sheet C, the expansion coefficient relative to the original length in the longitudinal direction of the A4-sized porous substrate S1 and the change in the distance between the upper and lower ends of the device were measured before and after the electrode surface treatment step, as in Example 1. Furthermore, to compare the effects of the flow path wall 12 of analytical device M2, the changes before and after the electrode surface treatment step were also measured for analytical device sheet A and analytical device sheet B. The expansion coefficient is the ratio of the change in the distance between the upper and lower ends of the device to the original length (220 mm) in the longitudinal direction of the A4-sized porous substrate S1. The results are shown in Table 2.

[0056] [Table 2]

[0057] From Table 2, it can be seen that the distance between the devices at the upper and lower ends of the analysis device sheet B has shrunk by 1.38 mm, and it is deformed more significantly than the humidity increase effect described in Example 1. Also, similar to Example 1, it can be seen that for the analysis device sheet A, the deformation of the A4-sized porous substrate S1 can be suppressed compared to the analysis device sheet B. And for the analysis device sheet C, it can be seen that the deformation of the A4-sized porous substrate S1 is further suppressed and hardly deformed. Thus, it was found that by controlling the area of the hydrophobic region, the deformation of the A4-sized porous substrate S1 can be suppressed even after undergoing a process that is extremely greatly affected by water moisture absorption. That is, not limited to the electrode surface treatment as in this example, this configuration is also effective when passing through a simple cleaning process or a pretreatment process with a predetermined solution.

[0058] [Example 4] In this example, the same reference numerals are given to the members already described in Examples 1 to 3, and the description of the same parts is omitted.

[0059] The analysis device sheet F shown in FIG. 11 is the same as the analysis device sheet B in FIG. 5, with 96 analysis devices M1 arranged side by side, and only the shape of the flow path wall is different. The analysis device sheet F fills the spaces between the analysis devices M1 with flow path walls, but the flow path wall regions are divided into two parts in each of the x and y directions. This is because in the process of manufacturing the analysis device, a region without forming a flow path wall is provided as a region that can be contacted when, for example, transporting paper.

[0060] The flow path wall of this analysis device sheet F can be divided into four regions, K5a, K5b, K5c, and K5d, as shown in FIG. 11, and the combined region of these is defined as the flow path wall K5. The space between K5a and K5b and the space between K5c and K5d are separated by a width of L3 = 6 mm. Also, the space between K5a and K5c and the space between K5b and K5d are separated by a width of H3 = 11 mm. The projected image when the flow path wall K5 is projected along the x and y directions will be described.

[0061] <x direction> When the flow path wall K5 is projected in the y direction, K5a and K5b overlap and form a projected image K5Sxa. Similarly, K5c and K5d overlap and form a projected image K5Sxd. The combined length of these two line segments, K5Sxa and K5Sxd, forms the projected image K5Sx of the flow path wall K5 in the x direction. The total length of K5Sx is 218 mm, which is 11 mm shorter than the length D9 = 229 mm of the entire region where the analysis device is formed in the x direction. Therefore, in the x direction of the analysis device sheet F, based on the length of the entire region where a plurality of analysis devices are formed, the ratio of the length where the projected image of the flow path wall overlaps with the straight line in the x direction is calculated in the same way as Equation (2) and is approximately 95.2%.

[0062] <y direction> Similarly, an explanation will be given for the y direction as well. When the flow path wall K5 is projected in the y direction, K5a and K5c overlap and form a projected image K5Sya. Similarly, K5b and K5d overlap and form a projected image K5Syd. The combined length of these two line segments, K5Sya and K5Syd, forms the projected image K5Sy of the flow path wall K5 in the y direction. The total length of K5Sy is 148 mm, which is 6 mm shorter than the length D11 = 154 mm of the entire region where the analysis device is formed in the y direction. Therefore, in the y direction of the analysis device sheet F, based on the length of the entire region where a plurality of analysis devices are formed, the ratio of the length where the projected image of the flow path wall overlaps with the straight line in the y direction is calculated in the same way as Equation (2) and is approximately 96.1%.

[0063] From the above, in the analysis device sheet F, within the range where the analysis devices are arranged, if a straight line is drawn at any location in the longitudinal and transverse directions of the porous substrate S1, the flow path wall intersects with most of the regions. That is, by forming the flow path wall like the flow path wall K5, deformation due to moisture absorption of the porous substrate S1 can be suppressed.

[0064] As explained above, in an analytical device sheet in which multiple analytical devices are arranged on the same porous substrate, deformation of the porous substrate due to the influence of moisture can be effectively suppressed by using a pattern in which the overlapping length of the projected image of the flow path wall with a line in the x direction (reference line x) and a line in the y direction (reference line y) is 95% or more, based on the entire length of the area in which multiple analytical devices are formed. Furthermore, by controlling the area of ​​the hydrophobic region formed by the flow path wall, the degree of suppression of deformation of the porous substrate can also be controlled. This makes it possible to provide an analytical device with high shape accuracy and capable of more stable detection. [Explanation of symbols]

[0065] M1: Analysis device M2: Analysis device H: Channel wall K: Channel wall S1…Porous base material S1b…Working electrode arrangement part S1c…Reference electrode arrangement part S1d...Dispensing section 11...Channel wall 12...Channel wall 21...Flow path 31...Working electrode 32...Reference electrode 33...Working electrode 34...Reference electrode

Claims

[Claim 1] An analytical device sheet in which a plurality of analytical devices each having a closed flow path are arranged on the same porous substrate, the analytical device sheet has flow path walls formed by impregnating the porous substrate with a hydrophobic resin over the entire thickness direction of the porous substrate; the closed flow path is formed by at least a portion of the flow path wall, When the channel wall is projected along the longitudinal direction of the analytical device sheet and the projected image is superimposed on a reference line x along the longitudinal direction of the analytical device sheet, the ratio of the length over which the reference line x and the projected image overlap is 95% or more based on the longitudinal length of the entire region in which the plurality of analytical devices are formed, When the flow path wall is projected along a direction perpendicular to the longitudinal direction of the analytical device sheet and the projected image is superimposed on a reference line y extending along a direction perpendicular to the longitudinal direction of the analytical device sheet, a ratio of the length of the reference line y overlapping the projected image to 95% or more based on the length of the entire region in which the plurality of analytical devices are formed in a direction perpendicular to the longitudinal direction; An analytical device sheet characterized by:

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