Analysis device sheet

Abstract

The present invention provides an analysis device sheet capable of performing stable detection by suppressing a deterioration in accuracy and performance due to deformation of a base material. This analysis device sheet has a flow passage wall formed by impregnating a porous substrate with a hydrophobic resin over the entirety thereof in a thickness direction, and is characterized in that: a plurality of closed flow passages are formed by at least a portion of the flow passage wall; if the flow passage wall is projected along the 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 proportion of the length over which the reference straight line x and the projected image overlap is 95% or more; and if the flow passage wall is projected 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 proportion of the length over which the reference straight line y and the projected image overlap is 95% or more.

Description

Analysis Device Sheet

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

[0002] In recent years, the development of analytical devices that utilize micro-sized fine channels to efficiently perform biochemical analysis (trace amounts, rapid, and simple) 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. 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, they are expected to be used in medical activities in developing countries and depopulated areas with limited medical facilities, as well as at disaster sites, and as testing devices in airports and other locations where the spread of infectious diseases must be prevented at the border. Furthermore, because they are inexpensive and easy to use, they are attracting attention as healthcare devices that can manage and monitor one's own health status.

[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 analyte 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 analyte's ion concentration. The analyte's ion concentration can be measured by measuring the potential difference between the two electrodes. An analytical device with this functionality can be sufficiently manufactured with a size of approximately 20 mm square. Furthermore, paper substrates with sizes such as A4 (210 mm x 297 mm) are widely available. Therefore, manufacturing multiple analytical devices on the same substrate and then cutting them into individual devices after manufacturing results in better 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 and place it in a measuring device, and having a margin around the measurement functional section to serve as a handle will make them 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.

[0005] US Patent Application Publication No. 2016 / 033438

[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.

[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 having flow path walls formed by impregnating the entire thickness of the porous substrate with a hydrophobic resin, the closed flow paths being formed by at least a portion of the flow path walls, when the flow path walls are 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 where the reference line x and the projected image overlap is 95% or more based on the longitudinal length of the entire area in which the plurality of analytical devices are formed, and when the flow path walls are 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 along the direction perpendicular to the longitudinal direction of the analytical device sheet, the ratio of the length where the reference line y and the projected image overlap is 95% or more based on the length in the direction perpendicular to the longitudinal direction of the entire area in which the plurality of analytical devices are formed. The present invention relates to an analytical device sheet characterized by the above.

[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.

[0009] 1 is a top view of an analytical device M1 after the flow path 21 has been formed. FIG. 2 is a top view of an analytical device M1 after the working electrode 31 has been formed. FIG. 3 is a top view of an analytical device M1 after the reference electrode and electrolyte layer have been formed. FIG. 4 is a cross-sectional view of the analytical device M1 at the dashed line portion D1. FIG. 5 is a top view of an analytical device sheet A (analytical device group A). ​​FIG. 6 is a top view of an analytical device sheet B (analytical device group B). FIG. 7 is a top view of an analytical device M2 after the flow path 21 has been formed. FIG. 8 is a top view of an analytical device M2 after electrode surface treatment has been performed. FIG. 9 is a top view of an analytical device sheet C (analytical device group C). FIG. 10 is a top view of an analytical device sheet D (analytical device group D). FIG. 11 is a top view of an analytical device sheet E (analytical device group E). FIG. 12 is a top view of an analytical device sheet F (analytical device group F).

[0010] The method of the present invention is characterized by manufacturing a channel wall shape in which a straight line passing through the closed channel passes through a region of the channel wall K, thereby making it possible to suppress deformation due to swelling of the substrate. Exemplary embodiments of the present invention will now 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.

[0011] <Explanation of Projection> 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 Figure 9 is an arrangement of 96 analytical devices M1, similar to the analytical device sheet B in Figure 5, with only the shape of the flow path wall being different. The flow path wall K2 in the analytical device sheet D is shaped like 10 independent rectangles, K2a to K2j. K2a to K2j extend in the longitudinal direction (hereinafter 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. Furthermore, K2a to K2c, K2d to K2g, and K2h to K2j are each spaced at 40 mm intervals in the lateral direction (hereinafter the y direction) perpendicular to the longitudinal direction. When K2a to K2j are projected along the x-direction, K2a to K2c overlap to form a projected image K2Sa, K2d to K2g overlap to form a projected image K2Sd, and K2h to K2j overlap to form a projected image K2Sh, resulting in a total of three line segments. K2Sa, K2Sd, and K2Sh are combined to form the projected image K2S of the flow path wall K2. The total length of the projected 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 projected 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] <Regarding the Proportion of Projected Images Included> Next, the relationship between the total length of the above-mentioned projected images K2S and the length of the region where the analytical device is formed will be described.

[0014] The region in 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 images of the flow path walls in the analytical device sheet D projected along the x direction is 219 mm. Therefore, in the analytical device sheet D, the percentage of the length where the projection images of the flow path walls overlap with the straight line in the x direction (reference line x) is expressed by the following formula (2), based on the entire length of the region in which multiple analytical devices are formed in the x direction: 219 ÷ 229 × 100 ≒ 95.6 ... formula (2)

[0015] In other words, when a line perpendicular to the x direction of the porous substrate S1 is drawn, the analytical device sheet D intersects with the flow path walls over 95.6% of the area where the analytical devices M1 are arranged, which is the majority of the area. Therefore, the analytical device sheet D can suppress deformation in the x direction due to moisture absorption of the porous substrate S1 due to the effect of the hydrophobic flow path walls.

[0016] When 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 described below.

[0017] The analytical device sheet E shown in Figure 10 is an arrangement of 96 analytical devices M1, similar to the analytical device sheet B in Figure 5, with the only difference being the shape of the flow path walls. The analytical device M1 includes the same flow path wall 11, but also includes a flow path wall K3 consisting of seven rectangular shapes K3a to K3g and a flow path wall K4 consisting of eight rectangular shapes K4a to K4h. K3a to K3g extend in the x direction and are rectangular shapes with a length of 71 mm and a width of 1 mm. K4a to K4h extend in the y direction and are rectangular shapes with a length of 60 mm and a width of 1 mm.

[0018] <Projection along the x-direction> As explained above, we first consider the projection along the x-direction of the flow path wall K3 of the analytical device sheet E. Here, the projection images of the flow path wall 11 of the analytical device M1 and the flow path wall K4 are included in the projection image K3S of the flow path wall K3, so only the projection image K3S is considered. Because the flow path wall K3 is composed of multiple independent flow path walls, there is an area without a flow path wall, for example, between K3c and K3d. However, when considering the projection along the x-direction, this area is connected by the projection images of K3a and K3f. Furthermore, when considering the projection image of the entire flow path wall K3 in the x-direction, the projection image K3S is a single line segment, and its length is 229 mm. Furthermore, the length of the entire area in which multiple analytical devices are formed in the x-direction is 229 mm, as indicated by D9. In other words, when a line (reference line x) perpendicular to the x-direction, which is the longitudinal direction of the porous substrate S1, is drawn on the analytical device sheet E, the line intersects with the flow path wall in the entire area (100% of the area) where the analytical devices M1 are arranged. This allows the analytical device sheet E to suppress deformation in the x-direction due to moisture absorption of the porous substrate S1.

[0019] <Projection along the y direction> Next, consider the projection in the y direction onto the flow path wall of the analytical device sheet E. In this case, the projection image of the flow path wall 11 of the analytical device M1 and the projection image of the flow path wall K3 are included in the projection image K4S of the flow path wall K4, so only the projection image K4S is considered. The flow path wall K4 is composed of multiple independent flow path walls, but when considering the projection in the y direction, the gaps between the flow path walls are filled in as in the x direction, so the projection image becomes a single line segment, the projection image K4S, and its length is 154 mm. In addition, in the y direction, the entire length of the area in which multiple analytical devices are formed is 154 mm, as indicated by D11. In other words, if a straight line (reference line y) perpendicular to the y direction, which is the short direction of the porous substrate S1, is drawn on the analytical device sheet E, it will intersect with the flow path wall in all areas (100% of the area) where the analytical devices M1 are arranged. This allows the analytical device sheet E to suppress deformation in the y direction due to moisture absorption of the porous substrate S1.

[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 channel wall somewhere. In other words, by forming channel walls like channel 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 environmental impact and costs.

[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, the configuration in units of one device will be described.

[0022] <Substrate / Flow Channel Wall> The substrate of the analytical device M1 and the flow channel wall 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. The material was cellulose, with a thickness of 100 μm and a porosity of 50%. The fine gaps between the cellulose fibers allow capillary action, and the substrate also has good hydrophilicity, functioning 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, and 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 direction of the porous substrate S1 to form a flow path wall 11 with a height H1 = 6 mm and a width L1 = 14 mm. The flow path wall 11 was formed by electrophotographically printing a hydrophobic resin as toner using the method described in JP 2021-37612 A, and then heating the resin to melt and penetrate it. 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 inner region of the channel wall 11 includes 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 includes 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 and shape of the channel are not limited to these.

[0025] The formation of the electrodes of the analytical device M1 will be described below with reference to Fig. 2. 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 formed by joining a 3 mm square that fits within the working electrode placement portion S1b and a 1 mm wide, 4.5 mm long rectangle that extends from the working electrode placement portion 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 printer 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.

[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] 3A and 3B, the formation of the reference electrode and electrolyte layer of the analytical device M1 will be described. Fig. 3A is a top view of the analytical device M1 after the reference electrode and 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 the electrolyte layer 41 described below is applied, it becomes easier to arrange 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.

[0032] The reference electrode 32 was applied to the reference electrode placement area S1c using a screen printer 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 is easily soluble in water, and the diffusion rates of K ions and Cl ions are approximately equal, making it less likely 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 manufactured by Microjet Co., Ltd. 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 entire reference electrode placement area S1c was printed at a 300 μm pitch in both the vertical and horizontal directions. The amount of KCl was adjusted by applying three coats. The amount of KCl can be stabilized by adjusting the amount of KCl to saturate the KCl 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 there is enough KCl 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 positioned on the back side 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, it functions more stably as a reference electrode.

[0036] Next, an actual analytical device sheet will be described with reference to Fig. 4. 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, and these plurality of analytical devices are collectively referred to as an analytical device group A.

[0037] <Analytical Device Sheet and Manufacturing Method Thereof> The configuration of one analytical device M1 is as described above. However, in actual production, production efficiency is improved by arranging multiple analytical devices together on a sheet of paper, such as A4 size (210 mm x 297 mm). In this example, an A4-sized porous substrate S1 was configured with eight analytical devices M1 arranged at 20 mm intervals in the transverse direction (y direction) and 12 analytical devices M1 arranged at 20 mm intervals in the longitudinal direction (x direction). The analytical device functions for measurement within the analytical device are the flow path, working electrode, and reference electrode. Although one analytical device M1 can be contained in an area of ​​20 mm x 10 mm, a 20 mm x 20 mm area is reserved for each device to ensure a handle area for handling each device. In accordance with this arrangement, 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).

[0038] In the analytical device sheet A, the analytical device group A forms a channel wall H that forms a closed channel for one analytical device M1. Furthermore, when the channel wall H is formed, 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 line width of the grid is 2.5 mm. The analytical device sheet A has a hydrophobic region impregnated with a hydrophobic resin as the channel wall, and a hydrophilic region that does not contain a hydrophobic resin and exhibits the hydrophilic properties of the substrate. The hydrophilic region absorbs moisture and swells as the humidity of the environment in which the A4-sized porous substrate S1 is placed increases. On the other hand, the hydrophobic region hardly adsorbs moisture, so swelling is unlikely to occur. In addition, the rigidity of the impregnated hydrophobic resin also has the effect of suppressing deformation of the substrate. The balance between the hydrophilic and hydrophobic regions determines the degree of swelling / deformation of the entire A4-sized porous substrate S1. In the analytical device sheet A, the flow path area is approximately 65%, so the moisture absorption range is large, but there are hydrophobic regions between the closed flow paths due to the grid-patterned flow path walls K in the longitudinal direction (x direction) and the lateral direction (y direction). In this analytical device sheet A, straight lines D2 and D3 always exist between the flow path walls. That is, with the grid-patterned flow path wall shape of Example 1, when a line is drawn between adjacent closed flow paths in the x direction, straight line A can be drawn that always overlaps with the flow path wall all the way to both ends of the analytical device sheet A in the y direction, and when a line is drawn between adjacent closed flow paths in the y direction, straight line B can be drawn that always overlaps with the flow path wall all the way to both ends of the analytical device sheet A in the x direction. 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 over which 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 over which 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 in which 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 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 are no grid-patterned channel walls K, hydrophilic regions exist over a wide area between the channels of adjacent analytical devices. For example, D4 ​​and D5, which are straight lines passing between the channels, do not pass through the channel walls, and all of D4 and D5 are hydrophilic regions. This hydrophilic region is a continuous region extending from one end of the porous substrate to the other, and since there is no deformation suppression force due to the hydrophobic region along the way, it is easily swollen / deformed, for example, by an increase in humidity. In this analytical device sheet B, the percentage of the length over which 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 over which 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 in which multiple analytical devices are formed.

[0043] Here, the analytical device sheet A and analytical device sheet B were compared for shape change when the process of forming the channel wall / channel was carried out and then left for 12 hours until stable in a high temperature / high humidity environment. Specifically, when moved from a 23 ° C / 50% to a 30 ° C / 80% environment, the expansion coefficient relative to the original length in the longitudinal direction of the porous substrate S1 and the change in the distance between the upper and lower end devices were measured. The distance between the upper and lower end devices is ideally 20 mm pitch x 11 devices = 220 mm, but this indicates how many mm it deviates from 220 mm. The expansion coefficient 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]

[0045] As shown in Table 1, the distance between the upper and lower devices of analytical device sheet B is deformed by 0.83 mm. For example, if the working electrode is formed in the subsequent process while this deformation has occurred, aligning the working electrode with the channel located at the upper end results in a 0.83 mm offset in position relative to the channel located at the lower end. 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. High-precision designed channels are designed in the hundreds of micrometers. Therefore, a 0.83 mm offset in the positional accuracy of the analytical device may affect, for example, the penetration of the sample into the channel. Furthermore, the deterioration of contact between the sample and the electrode may lead to a deterioration in measurement accuracy. On the other hand, the deformation of the distance between the upper and lower devices of analytical device sheet A is 0.51 mm, which is approximately 40% less than that of analytical device sheet B. As mentioned above, the grid-patterned channel walls K are thought to suppress moisture absorption and, due to the rigidity of the channel walls, 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 pattern 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 With regard to an analytical device M2 in this example, only the differences from the analytical device M1 in Example 1 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 12 than the analytical device M1, 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 of being formed by screen printing, but differ in that the electrode surface is subsequently subjected to an electrode surface treatment.

[0052] <Electrode Surface Treatment> After screen printing, the working electrode 33 and the reference electrode 34 have a Ag:AgCl ratio of 6:4. To further improve the electrode stability, a surface treatment was performed to increase the AgCl ratio. Specifically, the entire 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, to oxidize the surface. However, the material used for 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 area to be surface-treated was the electrode area formed on the flow path 21 and a 1 mm area of ​​the electrode formed on the flow path wall adjacent to the flow path, as shown by 33a and 34a in FIG. 7. The reason for not treating a portion of the flow path wall is that the electrode region extending from the flow path toward the flow path wall is connected to an external measuring device for potential measurement, as described 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 path wall is protected with tape (3M 851T) to prevent surface treatment, and then immersed in the surface treatment solution, allowing only the desired region 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 due to moisture adsorption and drying in the hydrophilic region may occur, 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 wider.

[0054] Figure 8 shows a configuration in which 96 analytical devices M2 described above are arranged at 20 mm pitches 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 one analytical device M2. Furthermore, when forming the channel wall H, a channel wall K is formed to surround each individual analytical device M2 without overlapping it. As a result, the space between adjacent channels is impregnated with hydrophobic resin, and the channel wall K and the channel wall H form a continuous, integrated channel wall. For example, D6 and D7, which are straight lines passing between the channels, always pass through the channel wall, which is a hydrophobic region. This is called analytical device sheet C. In this analytical device sheet C, the percentage of the length over which 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 over which 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 in which multiple analytical devices are formed.

[0055] Here, using the 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. In addition, to compare the effects of the flow path wall 12 of the analytical device M2, the changes before and after the electrode surface treatment step were also measured for the analytical device sheet A and the 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]

[0057] From Table 2, it can be seen that the distance between the upper and lower end devices of analytical device sheet B has shrunk by 1.38 mm, and that the deformation is even greater than the effect of increased humidity described in Example 1. Furthermore, it can be seen that analytical device sheet A, like Example 1, is able to suppress deformation of the A4-sized porous substrate S1 compared to analytical device sheet B. Furthermore, it can be seen that analytical device sheet C further suppresses deformation of the A4-sized porous substrate S1, with almost no deformation. In this way, it was found that by controlling the area of ​​the hydrophobic region, deformation of the A4-sized porous substrate S1 can be suppressed even after undergoing a process that is extremely affected by water absorption. In other words, this configuration is effective not only for electrode surface treatment as in this example, but also when undergoing simple cleaning processes or pretreatment processes using a predetermined solution.

[0058] [Embodiment 4] In this embodiment, the same reference numerals are used to designate the members already described in embodiments 1 to 3, and descriptions of similar parts will be omitted.

[0059] The analytical device sheet F shown in Fig. 11 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. In the analytical device sheet F, the spaces between the analytical devices M1 are filled with flow path walls, but the flow path wall area is divided into two in each of the x and y directions. This is because an area without flow path walls is provided as an area that can be contacted when, for example, paper is transported during the process of fabricating the analytical device.

[0060] The flow path wall of this analytical device sheet F can be divided into four regions, K5a, K5b, K5c, and K5d, as shown in Figure 11, and these regions together are referred to as flow path wall K5. K5a and K5b are separated by a width of L3 = 6 mm, and K5c and K5d are separated by a width of H3 = 11 mm. The projection images of this flow path wall K5 when 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, forming a projected image K5Sxa. Similarly, K5c and K5d overlap, forming a projected image K5Sxd. The sum of the 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 shorter than the overall length D9 (229 mm) of the area where the analytical devices are formed in the x direction by H3 = 11 mm. Therefore, in the analytical device sheet F, the percentage of the length where the projected image of the flow path wall overlaps with the straight line in the x direction, calculated in the same manner as in equation (2), is approximately 95.2% based on the overall length of the area where multiple analytical devices are formed.

[0062] <y Direction> The y direction will be described similarly. When the flow path wall K5 is projected in the y direction, K5a and K5c overlap, forming a projected image K5Sya. Similarly, K5b and K5d overlap, forming a projected image K5Syd. The combination of the 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, because it is shorter by L3 = 6 mm than the overall length D11 = 154 mm of the area where the analytical devices are formed in the y direction. Therefore, in the analytical device sheet F, the percentage of the length where the projected image of the flow path wall overlaps with the straight line in the y direction, calculated in the same manner as in equation (2), is approximately 96.1% based on the overall length of the area where multiple analytical devices are formed.

[0063] As described above, in the analytical device sheet F, in the range where the analytical devices are arranged, a straight line drawn in either the longitudinal direction or the lateral direction of the porous substrate S1 intersects with the flow path wall in most of the area. In other words, by forming a flow path wall like the flow path wall K5, deformation of the porous substrate S1 due to moisture absorption can be suppressed.

[0064] As described above, in an analytical device sheet in which multiple analytical devices are arranged on the same porous substrate, the pattern is such that the overlap length of the projected image of the flow path wall with the x-direction line (reference line x) and the y-direction line (reference line y) is 95% or more, based on the entire length of the area in which multiple analytical devices are formed. This can effectively suppress deformation of the porous substrate due to the influence of moisture. Furthermore, by controlling the area of ​​the hydrophobic region created 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.

[0065] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0066] This application claims priority based on Japanese Patent Application No. 2024-062889 filed on April 9, 2024 and Japanese Patent Application No. 2025-062596 filed on April 4, 2025, the entire contents of which are incorporated herein by reference.

[0067] M1...Analysis device M2...Analysis device H...Flow path wall K...Flow path wall S1...Porous substrate S1b...Working electrode placement section S1c...Reference electrode placement section S1d...Dispensing section 11...Flow path wall 12...Flow path wall 21...Flow path 31...Working electrode 32...Reference electrode 33...Working electrode 34...Reference electrode

Claims

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 having flow path walls formed by impregnating the entire thickness of the porous substrate with a hydrophobic resin, the closed flow path being formed by at least a portion of the flow path walls, when the flow path walls are 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 where the reference line x and the projected image overlap is 95% or more, based on the longitudinal length of the entire area in which the plurality of analytical devices are formed, and when the flow path walls are 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 along the direction perpendicular to the longitudinal direction of the analytical device sheet, the ratio of the length where the reference line y and the projected image overlap is 95% or more, based on the length in the direction perpendicular to the longitudinal direction of the entire area in which the plurality of analytical devices are formed. An analytical device sheet characterized by:

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