Filter medium and method for analyzing object filtered out

Abstract

A filter medium according to the present disclosure comprises a film part which has a first main surface and a second main surface that is on the reverse side from the first main surface and through which a liquid containing an object to be filtered out is passed from the first main surface side and filtered. The film part has: a filter base part that defines a plurality of through-holes piercing from the first main surface to the second main surface; and one or more recesses provided to some of a portion surrounding each of the plurality of through-holes, on the first main surface side of the filter base part.

Description

Filtration filter and method for analyzing filtered material

[0001] The present disclosure relates to a filter and a method for analyzing an object to be filtered.

[0002] A known filtration filter for filtering a liquid containing a filtering target is, for example, that described in Patent Document 1. In the filtration filter described in Patent Document 1, a pair of protrusions protruding from a first main surface are provided at both widthwise ends of a filter base portion located between adjacent through holes, and a liquid reservoir portion for collecting a portion of the liquid is formed by the first main surface of the filter base portion and the pair of protrusions.

[0003] International Publication No. 2020 / 066578

[0004] The filtration filter described in Patent Document 1 can bring the captured object to be filtered into contact with a liquid, but has the problem that it cannot extract a small amount of cells and the liquid containing the cells without affecting the filtration efficiency, making it difficult to observe the cells filtered onto the filter.

[0005] A filtration filter according to one aspect of the present disclosure is a filtration filter having a first main surface and a second main surface opposite to the first main surface, and including a membrane portion that filters a liquid containing a substance to be filtered by passing it through from the first main surface side, wherein the membrane portion has: a filter base portion that defines a plurality of through holes that penetrate from the first main surface toward the second main surface; and one or more recesses provided on the first main surface side of the filter base portion in a portion around the plurality of through holes.

[0006] A method for analyzing a filtering target according to one aspect of the present disclosure is a method for filtering a liquid containing the filtering target and analyzing the captured filtering target, and includes the steps of: preparing a filtering filter according to the aspect described above; supplying the liquid to the first main surface of the filtering filter and capturing the filtering target in the recess; and analyzing the captured filtering target.

[0007] According to the present disclosure, it is possible to provide a filtration filter and a method for analyzing an object to be filtered that can bring the captured object to be filtered into contact with a liquid, extract a small amount of cells and a liquid containing the cells without affecting the filtration efficiency, and observe the cells filtered onto the filter.

[0008] 2A-B sectional view of FIG. 2B. Flowchart for explaining an example of a method for analyzing a filtering target. Schematic plan view of a membrane part of a filtration filter according to a first modified example of the first embodiment. Schematic sectional view of a membrane part of a filtration filter according to a second modified example of the first embodiment. Schematic sectional view of a membrane part of a filtration filter according to a third modified example of the first embodiment. Schematic sectional view of a membrane part of a filtration filter according to a fourth modified example of the first embodiment. Table showing the results of measuring the strength of the filtration filters of Example 1 and Comparative Example 1.

[0009] (Background to the present disclosure) After filtering a liquid containing filtration targets such as cells using a filtration filter, the filtration targets captured by the filtration filter may be observed. In the filtration filter described in Patent Document 1, a liquid reservoir for collecting the liquid is formed by a first main surface of the filter base and a pair of protrusions. The provision of the liquid reservoir allows the captured filtration targets to be immersed in the liquid stored in the liquid reservoir.

[0010] However, in the filtration filter described in Patent Document 1, groove-like liquid reservoirs are formed around the entire circumference of the base, which traps a large number of cells, resulting in poor filtration efficiency. Furthermore, protrusions are formed all over the filter base, which reduces the thickness of the filter base, resulting in poor strength against bending when liquid is passed through the filtration filter.

[0011] Therefore, the inventors have studied a filtration filter and a method for analyzing a filtration object that can bring the captured filtration object into contact with a liquid, extract a small amount of cells and a liquid containing the cells without affecting the filtration efficiency, and observe the cells filtered onto the filter, and have arrived at the following invention.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each drawing, elements are shown exaggerated for ease of explanation.

[0013] (First embodiment) [Overall configuration] Fig. 1 is a schematic plan view of a filtration filter 1 according to a first embodiment of the present disclosure. Fig. 2 is a schematic plan view showing a portion of the membrane part 2 of the filtration filter 1 of Fig. 1. Fig. 3 is an enlarged perspective view of a region R1 of Fig. 2. The X, Y, and Z directions in each figure indicate the vertical, horizontal, and thickness directions of the respective filtration filter 1.

[0014] The filtration filter 1 separates the material to be filtered from the liquid by passing the liquid containing the material to be filtered through the filtration filter 1 .

[0015] As shown in Fig. 1 , the filtration filter 1 according to the first embodiment includes a membrane 2 that captures a filtering target contained in a liquid. The membrane 2 is formed to a thickness of, for example, 10 µm or more and 50 µm or less. In the first embodiment, the filtration filter 1 also includes an annular frame 3 that is disposed so as to surround the outer periphery of the membrane 2. Note that, although the filtration filter 1 has a circular shape in a plan view in the example of Fig. 1 , the filtration filter 1 may have a shape other than a circle, such as a rectangle or another polygon.

[0016] In this specification, the term "filtering target" refers to a target to be filtered by the filtration filter 1. In the first embodiment, a biological substance is used as the filtering target.

[0017] Furthermore, in this specification, the term "biologically derived material" refers to a material derived from an organism, such as a cell (eukaryote), a bacterium (true bacterium), or a virus. Examples of cells (eukaryotes) include eggs, sperm, induced pluripotent stem cells (iPS cells), ES cells, stem cells, mesenchymal stem cells, mononuclear cells, single cells, cell clumps, floating cells, adherent cells, neurons, leukocytes, lymphocytes, cells for regenerative medicine, autologous cells, cancer cells, circulating cancer cells (CTCs), HL-60, HELA, and fungi. Examples of bacteria (true bacterium) include gram-positive bacteria, gram-negative bacteria, Escherichia coli, and Mycobacterium tuberculosis. Examples of viruses include DNA viruses, RNA viruses, rotaviruses, (avian) influenza viruses, yellow fever viruses, dengue fever viruses, encephalitis viruses, hemorrhagic fever viruses, and immunodeficiency viruses. In the first embodiment, the filtration filter 1 is particularly excellent at separating induced pluripotent stem cells (iPS cells), ES cells, stem cells, and circulating cancer cells (CTCs) from a liquid.

[0018] 2 and 3 , the membrane portion 2 of the filtration filter 1 has a filter base portion 5 that defines a plurality of through holes 4 that penetrate from the first main surface 10 a to the second main surface 10 b. In this embodiment, the filter base portion 5 includes a first filter base portion 51 that extends in a first direction (X direction) and a second filter base portion 52 that extends in a second direction (Y direction). The first filter base portion 51 and the second filter base portion 52 are arranged orthogonally to define the square through holes 4, and the plurality of through holes 4 are further arranged in a square lattice array.

[0019] The through-holes 4 are designed to have a side length L1 of, for example, 0.1 μm or more and 500 μm or less. The spacing L2 between adjacent through-holes 4, i.e., the width L2 of the filter base 5, can be, for example, 0.75 μm or more and 350 μm or less.

[0020] 2 and 3, the membrane portion 2 has a plurality of recesses 6 provided on the first main surface 10a side of the filter base portion 5, partially surrounding the plurality of through-holes 4. The recesses 6 are depressions provided in the filter base portion 5, without penetrating the membrane portion 2. By providing the recesses 6 on the first main surface 10a side of the filter base portion 5, the liquid can be captured in the recesses 6 when the liquid is passed through the membrane portion 2. This allows the filtration target captured on the first main surface 10a to come into contact with the liquid accumulated in the recesses 6, improving the survival rate of the captured filtration target. The recesses 6 can also capture the filtration target together with the liquid.

[0021] In this embodiment, the recess 6 has a diamond shape in a plan view seen from the Z direction. The shape of the recess 6 is not limited to a diamond shape and may be other shapes such as a polygon, a circle, or an ellipse. The length of one side L3 of the diamond shape of the recess 6 may be, for example, 1 μm or more and 20 μm or less, or may be smaller than the length L1 of one side of the through-hole 4. When the length L3 of one side of the diamond shape of the recess 6 is 20 μm or less, it is possible to capture a single filtering target in the recess 6. Furthermore, the length L3 of one side of the recess 6 may be set to 10 μm or less in accordance with the size of a single filtering target. Furthermore, when the filtering target is a bacterium, a virus, or the like, the length L3 of one side of the recess 6 may be set to 5 μm or less. Furthermore, when viewed from the Z direction, the opening area of ​​each of the multiple recesses 6 may be smaller than the opening area of ​​each of the multiple through-holes 4.

[0022] As shown in FIGS. 2 and 3 , the recesses 6 may be regularly arranged when viewed from the Z direction. In this embodiment, the recesses 6 are regularly arranged in the X and Y directions. Furthermore, in this embodiment, the recesses 6 are located at the intersections of the first filter base 51 and the second filter base 52. That is, in this embodiment, the recesses 6 are located in areas surrounded by four through holes 4 arranged in a square lattice pattern. In other words, each recess 6 is located in areas surrounded by four through holes 4a to 4d included in a unit lattice UL1, which is the smallest unit for forming a square lattice array. That is, each recess 6 is located at the center or center of gravity of the four through holes 4a to 4d in the unit lattice UL1. Alternatively, each recess 6 is located at the geometric center of a virtual figure connecting the geometric centers of the unit lattices UL.

[0023] FIG. 4A is a cross-sectional view taken along the line A-A in FIG. 2. FIG. 4B is a cross-sectional view taken along the line B-B in FIG. 2. As shown in FIGS. 4A and 4B, each of the plurality of recesses 6 is formed so that the dimension d1 at the first main surface 10a is larger than the dimension d2 at the bottom of the plurality of recesses 6. In other words, each of the plurality of recesses 6 is formed so that, when the membrane portion 2 is cut along a plane parallel to the first main surface 10a, the opening cross-sectional area of ​​the recess 6 decreases from the first main surface 10a toward the second main surface 10b. By forming the recess 6 so that the horizontal cross section decreases toward the bottom, the object to be filtered can be captured without being damaged. Furthermore, by forming the recess 6 so that the horizontal cross section decreases toward the bottom, the object to be filtered captured in the recess 6 can be easily recovered using a pipette or the like.

[0024] The depth d3 of each of the plurality of recesses 6 can be, for example, 1 μm or more and 20 μm or less. When the depth d3 of the recesses 6 is 5 μm or more and 15 μm or less, the recesses 6 can capture the object to be filtered while maintaining the strength of the filter base 5.

[0025] The first major surface 10a and the second major surface 10b of the membrane portion 2 may have different surface roughnesses. For example, in this embodiment, the surface roughness of the first major surface 10a is set to be greater than the surface roughness of the second major surface 10b. By making the surface roughness of the first major surface 10a greater than the surface roughness of the second major surface 10b, the wettability on the first major surface 10a side is increased, making it easier to introduce liquid into the membrane portion 2. On the other hand, the wettability on the second major surface 10b side is lower than that of the first major surface 10a, improving the drainage of liquid that has passed through the membrane portion 2. This makes it easier for liquid to pass through the membrane portion 2.

[0026] The filtration filter 1 can be formed, for example, from a resin. Examples of resins that can be used to form the filtration filter 1 include acrylic, polycarbonate, polyvinyl chloride, polyethylene, polypropylene, polystyrene, AS resin, and PET. The resin that can be used to form the filtration filter 1 may have a visible light transmittance of 80% or more. By forming the filtration filter 1 from a transparent resin, the object to be filtered captured in the recesses 6 can be observed with transmitted light while still being captured on the filtration filter 1. Observing with transmitted light enables spectral analysis of the object to be filtered.

[0027] [Manufacturing of Filtration Filter] The filtration filter 1 can be manufactured by, for example, an imprinting method. First, a resin that is the material for the filtration filter 1 is poured into a first mold in which portions corresponding to the through holes 4 are formed by plating. The first mold in which the resin has been poured is combined with a second mold in which portions corresponding to the recesses 6 are formed by plating, and the poured resin is cured, thereby manufacturing the filtration filter 1.

[0028] [Method for Analyzing a Filtering Target] A method for analyzing a filtering target using the filtration filter 1 will be described with reference to Fig. 5. Fig. 5 is a flowchart for explaining an example of a method for analyzing a filtering target.

[0029] In step S1, the above-described filtration filter 1 is prepared. For example, the filtration filter 1 held in a holder is attached to a container for collecting filtered liquid, such as a centrifuge tube. At this time, the filtration filter 1 is attached so that the first main surface 10a of the filtration filter 1 faces outward. Next, in step S2, liquid is supplied to the filtration filter 1 from the first main surface 10a side. When liquid is supplied to the filtration filter 1 from the first main surface 10a, the filtration target can be captured in the recesses 6 provided in the first main surface 10a of the filtration filter 1. Filter targets, such as cells, tend to come into contact with the filter. Therefore, some of the filtration target contained in the liquid adhere to the filter base 5 or the recesses 6 as the liquid passes through the filtration filter 1. At this time, the filtration target adheres precariously to the filter base 5 and is therefore prone to falling off when the filtration filter 1 is subjected to vibration or impact during observation work. On the other hand, due to the recessed shape of the recesses 6, the filtration target captured in the recesses 6 is less likely to fall off even when the filtration filter 1 is subjected to vibration or impact, and can be observed while retained in the filtration filter 1. Liquid not captured in the recesses 6 passes through the membrane unit 2 via the multiple through-holes 4. In step S2, filtration targets of various sizes, from smaller than the through-holes 4 to larger than the through-holes 4, can be captured in the recesses 6. For example, when the filtration target is larger than the through-holes 4, most of the filtration target is captured while trapped in the through-holes 4, while some of the filtration target is captured while trapped in the recesses 6 at the intersection of the first filter base 51 and the second filter base 52. Furthermore, when the filtration target is smaller than the through-holes, most of the filtration target passes through the through-holes 4, but some of the filtration target may adhere to the filter base 5. The intersection of the first filter base 51 and the second filter base 52, where the recesses 6 are provided, is the part of the filter base 5 where resistance to liquid flow is greatest. Therefore, the objects to be filtered are more likely to be captured at the intersection of the first filter base 51 and the second filter base 52 than at other parts of the filter base 5. Therefore, by providing the recess 6 at the intersection of the first filter base 51 and the second filter base 52, the objects to be filtered are more likely to be captured in the recess 6.Next, in step S3, the captured filtering object is analyzed. The analysis of the filtering object includes observing the color or shape of the filtering object using a microscope or the like, and performing analysis such as spectral analysis on the filtering object.

[0030] [Effects] The filtration filter 1 according to the first embodiment can provide the following effects.

[0031] The filtration filter 1 has a first main surface 10a and a second main surface 10b opposite to the first main surface 10a. The filtration filter 1 includes a membrane unit 2 that filters a liquid containing a filtration target by passing it through the first main surface 10a. The membrane unit 2 has a filter base unit 5 and a plurality of recesses 6. The filter base unit 5 defines a plurality of through holes 4 that penetrate from the first main surface 10a to the second main surface 10b. The plurality of recesses 6 are provided on the first main surface 10a side of the filter base unit 5, partially surrounding the plurality of through holes 4.

[0032] This configuration allows the captured filtration target to be brought into contact with a liquid, and allows a small amount of cells and cell-containing liquid to be extracted without affecting filtration efficiency, allowing the filtered cells to be observed. The recesses 6 allow a small amount of filtration target to be captured in the recesses 6 along with the liquid. Therefore, the filtration target for observation can be captured while in contact with the liquid without affecting filtration accuracy. The ability to bring the filtration target captured in the recesses 6 into contact with the liquid improves the survival rate of the captured filtration target. Furthermore, the recesses 6 in the filter base 5 reduce breakage when the filtration filter 1 is bent when a liquid is passed through it. Furthermore, the filtration filter 1 is resistant to bending and can be easily bent or rolled, improving the flexibility of the shape of the filtration filter 1. Furthermore, the recesses 6 in the filter base 5 increase the surface area of ​​the first main surface 10a, increasing frictional force and facilitating capture of the filtration target or liquid. Furthermore, the filtration target captured in the recesses 6 can be observed and analyzed together with the filtration filter 1 without being recovered from the filtration filter 1. By culturing the objects to be filtered, such as cells, while they are trapped in the recesses 6, secretions from the cells are more likely to accumulate in the recesses 6, making it possible to analyze the dynamics of the cells trapped in the recesses 6. By providing the recesses 6 in a portion of the periphery of the through-holes 4, turbulence that disrupts the flow of liquid can be generated near the recesses 6, and the turbulence can make it easier to peel off the objects to be filtered that have adhered to parts of the filter base 5 where the recesses 6 are not provided. By changing the shape, size, etc. of the recesses 6, the filtration filters 1 can be easily classified.

[0033] The filter base 5 includes a first filter base 51 extending in a first direction and a second filter base 52 extending in a second direction intersecting the first direction. The recesses 6 are located at the intersections of the first filter base 51 and the second filter base 52.

[0034] With this configuration, multiple recesses 6 can be arranged throughout the membrane portion 2, allowing for more efficient capture of the objects to be filtered. By forming the recesses 6 to match the size of the objects to be filtered, objects of the desired size can be efficiently captured. Furthermore, the provision of the recesses 6 makes it easier for the objects to be filtered to be captured at the intersection of the first filter base portion 51 and the second filter base portion 52. When the objects to be filtered are captured at the intersection of the filter base portion 51, the liquid flows away from the objects to be filtered, making it easier for the liquid to enter the through-holes 4, thereby improving filtration efficiency.

[0035] When viewed from a direction perpendicular to the first main surface 10a, the plurality of through holes are arranged in a square lattice pattern, with the recess 6 located at the center of a unit lattice, which is the smallest unit for forming the array.

[0036] With this configuration, a plurality of recesses 6 can be arranged over the entire membrane portion 2, and the material to be filtered can be efficiently captured.

[0037] When viewed in a direction perpendicular to the first main surface, each of the plurality of through holes 4 has a square shape, and each of the plurality of recesses 6 has a diamond shape.

[0038] This configuration allows more through holes 4 to be arranged in the membrane part 2, improving filtration efficiency. The diamond-shaped recesses 6 allow for efficient capture of filtration targets. Furthermore, the different shapes of the through holes 4 and the recesses 6 in plan view make it easy to find the filtration targets captured in the recesses 6. Furthermore, the diamond-shaped recesses 6 facilitate stress concentration at the intersection points of the first filter base part 51 and the second filter base part 52, allowing for partial detachment of the filter base part 5 where the recesses 6 are provided without destroying the through holes 4. Furthermore, the diamond-shaped recesses 6 allow for easy resizing of the filtration filter 1 itself to facilitate observation of the filtration targets.

[0039] When the membrane part 2 is cut along a plane parallel to the first main surface 10a, the opening cross-sectional area of ​​each of the plurality of recesses 6 decreases from the first main surface 10a toward the second main surface 10b.

[0040] This configuration reduces damage to the object to be filtered when capturing it, and also reduces surface tension, making it easier to catch the object to be filtered with a pipette or the like.

[0041] When viewed from a direction perpendicular to first main surface 10 a, the opening area of ​​each of the plurality of recesses 6 is smaller than the opening area of ​​each of the plurality of through holes 4 .

[0042] With this configuration, it is possible to capture objects to be filtered that are large enough to pass through the through holes 4.

[0043] When viewed from a direction intersecting the first main surface, the plurality of recesses 6 are arranged regularly.

[0044] With this configuration, it is possible to efficiently capture the objects to be filtered.

[0045] The filtration filter 1 is made of resin.

[0046] With this configuration, even if filtration filter 1 is bent due to the passage of liquid, damage can be suppressed.

[0047] The resin is permeable.

[0048] With this configuration, the object to be filtered can be captured in the recess 6 and further analyzed together with the filtration filter 1 .

[0049] A method for filtering a liquid containing a substance to be filtered and analyzing the captured substance to be filtered includes the steps of preparing the above-mentioned filtration filter 1, supplying a liquid to the first main surface 10a of the filtration filter 1 to capture the substance to be filtered, and analyzing the captured substance to be filtered.

[0050] With this configuration, the objects to be filtered can be captured and analyzed efficiently.

[0051] In the above-described embodiment, an example has been described in which the membrane part 2 has a plurality of recesses 6, but the number of recesses 6 may be one, or three or more.

[0052] In the above-described embodiment, the first filter base 51 and the second filter base 52 are perpendicular to each other, but the present invention is not limited to this. The first filter base 51 and the second filter base 52 may intersect at an angle other than 90 degrees.

[0053] In the above-described embodiment, the first filter base 51 and the second filter base 52 are formed in a straight line, but the present invention is not limited to this. The first filter base 51 and the second filter base 52 may have a curved shape, for example.

[0054] In the above-described embodiment, the plurality of through holes 4 are arranged in a square lattice pattern, but the present invention is not limited to this. The plurality of through holes 4 may be arranged in a lattice pattern such as an orthorhombic lattice, a hexagonal lattice, a rectangular lattice, a parallelepiped lattice, or a checkerboard pattern. Alternatively, the plurality of through holes 4 may be arranged irregularly.

[0055] In the above-described embodiment, the through holes 4 each have a square shape and the recesses 6 each have a diamond shape, but the present invention is not limited to this. The through holes 4 and the recesses 6 may have any shape, including polygonal, circular, elliptical, etc.

[0056] In the above-described embodiment, the surface roughness of the first main surface 10a and the surface roughness of the second main surface 10b are different from each other, but the present invention is not limited to this. The surface roughness of the first main surface 10a and the surface roughness of the second main surface 10b may be the same.

[0057] [Modification] Fig. 6 is a schematic plan view showing a membrane portion 2A of a filtration filter according to a first modification of the first embodiment. As shown in Fig. 6, the plurality of through holes 14 may have a circular shape. In the example of Fig. 6, the plurality of through holes 14 are arranged in a triangular lattice array. The recess 16 is located in the portion surrounded by three through holes 14a to 14c that constitute a unit lattice UL2, which is the smallest unit of the triangular lattice array, i.e., at the center of gravity of the unit lattice UL2.

[0058] 7 is a schematic cross-sectional view showing a membrane portion 2B of a filtration filter according to a second variation of the first embodiment. As shown in FIG. 7, each of the plurality of recesses 26 may be formed in a bowl shape. The bowl shape refers to, for example, a hemispherical recessed shape. With this configuration, the material to be filtered captured in the recesses 26 can be easily collected using a pipette or the like.

[0059] 8 is a schematic cross-sectional view showing a membrane portion 2C of a filtration filter according to a third modification of the first embodiment. As shown in FIG. 8, the size L3 of the openings of the plurality of through holes 34 on the first main surface 30a side may be smaller than the size L4 of the openings on the second main surface 30b side. By making the size L4 of the openings on the second main surface 30b side, through which the liquid is discharged, larger than the size L3 of the openings on the first main surface 30a side, the liquid that has passed through the membrane portion 2 is more easily discharged.

[0060] Fig. 9 is a schematic cross-sectional view showing a membrane portion 2D of a filtration filter according to Modification 4 of Embodiment 1. As shown in Fig. 9, in addition to the plurality of recesses 46 provided on the first main surface 40a of the filter base portion 45, a plurality of recesses 47 may also be provided on the second main surface 40b of the filter base portion 45.

[0061] [Examples] The strengths of the filtration filters of Example 1 and Comparative Example 1 were compared.

[0062] As Example 1, the filtration filter 1 described in Embodiment 1 was used. As Comparative Example 1, a filtration filter made of a material containing metal or metal oxide as a main component was used. The filtration filter of Comparative Example 1 is configured such that a pair of protrusions protruding from the first main surface are provided at both ends in the width direction of the filter base. In the filtration filter of Comparative Example 1, the first main surface of the filter base and the pair of protrusions form a liquid reservoir that collects a portion of the liquid containing the object to be filtered.

[0063] In Example 1, a filtration filter having square through-holes with a side length of 45 μm in plan view was used. The filtration filter of Example 1 had a thickness of 30 μm and a filter base width (width L2 in FIG. 2 ) of 30 μm. The filtration filter of Example 1 also had diamond-shaped recesses with a side length of 26 μm in plan view, and the recesses had a depth of 5 μm.

[0064] In Comparative Example 1, a filtration filter having a square through-hole with a side length of 20 μm in plan view was used. The filtration filter of Comparative Example 1 had a thickness of 5 μm and a width of 2 μm for the filter base. Furthermore, the filtration filter of Comparative Example 1 had protrusions with a height of 2 μm on both ends of the filter base. That is, the filtration filter of Comparative Example 1 had a shape in which walls with a height of 2 μm were provided on both ends of the filter base.

[0065] The strength comparison was carried out using a small tabletop tensile testing machine EZ Test manufactured by Shimadzu Corporation. The flexural modulus, maximum test force, and maximum displacement were evaluated at a tensile speed of 1 mm / min.

[0066] Fig. 10 is a table showing the results of measuring the strength of the filtration filters of Example 1 and Comparative Example 1. As shown in Fig. 10, it can be seen that Example 1 is superior in all of the items including the flexural modulus, the maximum point test force, and the maximum point displacement.

[0067] The filtration filter of Comparative Example 1 has a structure in which protrusions protrude from the filter base, making it vulnerable to bending, whereas the filtration filter of Example 1 has a structure in which recesses are formed by depressing the filter base, making it resistant to bending. Furthermore, by using recesses instead of protrusions, the filtration filter of Example 1 is resistant to deformation due to bending and tension, and it can be seen that the mechanical strength of the filtration filter of Example 1 is also improved.

[0068] (Summary of the embodiment) (1) The filtration filter of the present disclosure has a first main surface and a second main surface opposite to the first main surface, and is equipped with a membrane part that filters a liquid containing a substance to be filtered by passing it through from the first main surface side, and the membrane part has a filter base part that defines a plurality of through holes that penetrate from the first main surface toward the second main surface, and one or more recesses provided on the first main surface side of the filter base part in a portion around the plurality of through holes.

[0069] (2) In the filtration filter of (1), the filter base portion includes a first filter base portion extending in a first direction and a second filter base portion extending in a second direction intersecting the first direction, and the one or more recesses may be located at the intersection of the first filter base portion and the second filter base portion.

[0070] (3) In the filtration filter of (1) or (2), when viewed from a direction perpendicular to the first main surface, the plurality of through holes may be arranged in a lattice pattern including an orthorhombic lattice, a hexagonal lattice, a triangular lattice, a square lattice, a rectangular lattice, or a parallelepiped lattice, and the recess may be located at the center of a unit lattice, which is the smallest unit for constituting the arrangement.

[0071] (4) In the filtration filter of any one of (1) to (3), when viewed from a direction perpendicular to the first main surface, each of the plurality of through holes may have a square shape, and each of the one or more recesses may have a diamond shape.

[0072] (5) In the filtration filter of any one of (1) to (4), the opening cross-sectional area of ​​each of the one or more recesses may decrease from the first main surface toward the second main surface when the membrane portion is cut along a plane parallel to the first main surface.

[0073] (6) In the filtration filter of any one of (1) to (5), when viewed from a direction perpendicular to the first main surface, the opening area of ​​each of the one or more recesses may be smaller than the opening area of ​​each of the plurality of through holes.

[0074] (7) In the filtration filter of any one of (1) to (6), one or more recesses may be further provided on the second main surface side of the filter base.

[0075] (8) In the filtration filter of any one of (1) to (7), the first main surface may have a surface roughness different from that of the second main surface.

[0076] (9) In the filtration filter of (8), the surface roughness of the first main surface may be greater than the surface roughness of the second main surface.

[0077] (10) In the filtration filter of any one of (1) to (9), the size of the opening of the plurality of through holes on the first main surface side may be smaller than the size of the opening of the opening on the second main surface side.

[0078] (11) In the filtration filter of any one of (1) to (10), the plurality of recesses may be regularly arranged when viewed in a direction intersecting the first main surface.

[0079] (12) In the filtration filter of any one of (1) to (11), the filtration filter may be made of resin.

[0080] (13) In the filter of (12), the resin may be permeable.

[0081] (14) The method disclosed herein is a method for filtering a liquid containing a substance to be filtered and analyzing the captured substance to be filtered, and includes the steps of preparing a filtration filter according to any one of (1) to (13), supplying a liquid to a first main surface of the filtration filter and capturing the substance to be filtered in the recess, and analyzing the captured substance to be filtered.

[0082] The filtration filter of the present invention is useful, for example, for filtering cell suspensions.

[0083] REFERENCE SIGNS LIST 1 Filtration filter 2, 2A to 2D Membrane portion 4, 14, 24, 34 Through-hole 5, 45 Filter base portion 6, 16, 26, 46, 47 Recess 10a, 30a, 40a First main surface 10b, 30b, 40b Second main surface 45 Filter base portion 51 First filter base portion 52 Second filter base portion

Claims

1. A filtration filter comprising a membrane portion having a first main surface and a second main surface opposite to the first main surface, wherein a liquid containing the object to be filtered passes through from the side of the first main surface for filtration, The aforementioned membrane portion is A filter base portion defining a plurality of through holes penetrating from the first main surface toward the second main surface, On the first main surface side of the filter base portion, one or more recesses are provided in a part of the periphery of the plurality of through holes, It has, The filter base portion includes a first filter base portion extending in a first direction and a second filter base portion extending in a second direction intersecting the first direction. The one or more recesses are located only at the portion where the first filter base and the second filter base intersect. Filtration filter.

2. When viewed from a direction perpendicular to the first principal surface, The plurality of through holes are arranged in a grid pattern including a rhombic grid, a hexagonal grid, a triangular grid, a square grid, a rectangular grid, or a parallelepiped grid. The aforementioned recess is located in the center of the unit cell, which is the smallest unit for forming the arrangement. The filtration filter according to claim 1.

3. When viewed from a direction perpendicular to the first principal surface, Each of the aforementioned multiple through holes has a square shape, Each of the one or more recesses has a rhombus shape. The filtration filter according to claim 1.

4. The opening cross-sectional area of ​​each of the one or more recesses decreases from the first main surface toward the second main surface when the film portion is cut by a plane parallel to the first main surface. The filtration filter according to claim 1.

5. When viewed from a direction perpendicular to the first main surface, the opening area of ​​each of the one or more recesses is smaller than the opening area of ​​each of the plurality of through holes. The filtration filter according to claim 1.

6. The one or more recesses are further provided on the second main surface side of the filter base portion. The filtration filter according to claim 1.

7. The surface roughness of the first main surface and the surface roughness of the second main surface are different. The filtration filter according to claim 1.

8. The surface roughness of the first main surface is greater than the surface roughness of the second main surface. The filtration filter according to claim 1.

9. The plurality of through holes are such that the size of the opening on the first main surface side is smaller than the size of the opening on the second main surface side. The filtration filter according to claim 1.

10. When viewed from a direction intersecting the first main surface, the plurality of recesses are arranged regularly. The filtration filter according to claim 1.

11. The aforementioned filter is made of resin. The filtration filter according to claim 1.

12. The aforementioned resin is permeable, The filtration filter according to claim 11.

13. A method for filtering a liquid containing a substance to be filtered, and analyzing the captured substance to be filtered, A step of preparing a filter according to any one of claims 1 to 12, The steps include supplying the liquid to the first main surface of the filtration filter and capturing the object to be filtered in the recess, The steps include analyzing the captured material to be filtered, including, method.