Patent Publication Number: US-2021170398-A1

Title: Assay device

Description:
TECHNICAL FIELD 
     The present invention relates to an assay device configured to perform an assay using a liquid. 
     BACKGROUND ART 
     Primarily in the fields of biology, chemistry, and the like, assay devices including microflow passages have been employed for performing, for example, inspections, experiments, and assays using very small quantities of liquids such as reagents, processing agents, and the like on the order of a μl (1 microliter), that is to say, in the range from approximately 1 μl or more to less than approximately 1 ml. As such assay devices, an assay device of the lateral flow type, an assay device of the flow through type, and the like have recently been used for the purpose of reducing costs, improving operability, durability and liquid control performance, and the like. 
     In particular, the assay device of the lateral flow type is simply configured to move and operate the liquid using capillary phenomena of hydrophilic porous media, such as paper, cellulose membranes, and the like. The assay device of the lateral flow type may be produced at low cost, requiring no external mechanisms, such as pumps and the like, and no complicated operations, allowing improvement in durability. The assay device of the lateral flow type is employed for detecting or quantifying the concentration of antibodies or antigens contained in a sample through the ELISA (Enzyme-Linked Immuno Sorbent Assay) process, immunochromatography, and the like, in particular. 
     In an exemplary case of the assay device, the channel, and the assay region connected to the channel, are provided in a plurality of layered porous media. The channel and the assay region are defined by the barrier constituted by the photoresist polymer that has been absorbed over the entire region of the layered porous media in the thickness direction (for example, see Patent Document 1). 
     The inventor of the present invention has invented the assay device as another exemplary case. The assay device includes the microflow passage, the porous medium disposed at a distance from one end of the microflow passage, and the space between the one end of the microflow passage and the porous medium. In the assay device, the liquid flowing in the microflow passage, passes over the space to come in contact with the porous medium while being absorbed thereby, and the fluid is then separated by the space so as to be held in the microflow passage (for example, see Patent Document 2). 
     CITATION LIST 
     Patent Document 
     Patent Document 1: JP 2010-515877 A 
     Patent Document 2: JP 6037184 B 
     SUMMARY OF INVENTION 
     Technical Problem 
     In an exemplary case of the assay device, since the channel and the assay region are constituted by the porous medium, a large quantity of liquid, for example, a reagent must be continuously fed from the channel to the assay region so as to ensure fluidity. Since the flow rate of the reagent passing through the porous medium, is reduced, the time taken for determining the effect may be prolonged. As a result, flowability of the liquid may be deteriorated, and risk of non-specific adsorption in the channel or the assay region, may be increased. 
     In another exemplary case of the assay device, there may be a risk of non-specific adsorption of the specimen, reagent, impurities, or the like on the wall that defines the microflow passage. Viscosity, friction, and the like generated between the liquid flowing in the microflow passage, and the wall that defines the microflow passage, may cause a risk of deteriorating the liquid flow performance. In a case of using the pressure-sensitive adhesive, the adhesive, or the like for the wall that defines the microflow passage, a case of using the assay device provided with the layered structure including a plurality of layers for forming the microflow passage between those layers, or the like, viscosity of the pressure-sensitive adhesive, the adhesive, or the like, and variation in the interlayer distance for forming the microflow passage, may increase the risk of generating the non-specific adsorption, and may deteriorate liquid flow performance. 
     In exemplary cases of the assay device, the non-specific adsorption may cause the risk of reducing yields of assay, destabilizing background, and generating noise. In the foregoing circumstances, the detector configured to detect assay reactions by obtaining signals derived from the assay reactions, may fail to detect such signals accurately. Furthermore, an air gap may be generated in the liquid, and the air gap may reduce liquid flowability. 
     In another exemplary case of the assay device, the liquid in the porous medium is likely to evaporate earlier than the liquid in the microflow passage. The evaporation of the liquid in the porous medium may accelerate evaporation of the liquid in the microflow passage. Variation in the ventilation performance owing to individual differences in the porous medium and moisture level of the porous medium may cause unevenness in the air flow rate in the space. The reduced air flow rate owing to the unevenness may deteriorate the liquid exchange performance in the space, and therefore, meniscus tortuosity in one end of the microflow passage may be increased. As a result, residual liquid in the space may be generated. The residual liquid in the space is particularly undesirable in view of preventing contamination. 
     The liquid control performance may be deteriorated by the prolonged time taken for determining the effect as mentioned above, generation of the non-specific adsorption, deterioration in the liquid flow performance, deterioration in the liquid exchange performance, the residual liquid, or the like. In other words, the assay device is required to improve the liquid control performance. 
     Solution to Problem 
     To solve the problem, the assay device according to an aspect includes a microflow passage configured to allow liquid to flow, an absorbing porous medium disposed at a distance from one end of the microflow passage, the one end being positioned on one side in a flow direction of the liquid, and a separating space disposed between the one end of the microflow passage and the absorbing porous medium. The assay device further includes two sideways ventilation passages being adjacent to both sides of the microflow passage, respectively in a width direction orthogonal to the flow direction, the two sideways ventilation passages being communicated with the microflow passage to allow air circulation. 
     The assay device according to another aspect includes a microflow passage configured to allow liquid to flow, a porous medium disposed at a distance from one end of the microflow passage, the one end being positioned on one side in a flow direction of the liquid, and a separating space disposed between the one end of the microflow passage and the porous medium. The assay device further includes a housing space housing the absorbing porous medium, a separating space wall defining the separating space in cooperation with the absorbing porous medium, the separating space wall including a top portion and a bottom portion defining the separating space on both sides in a height direction orthogonal to the flow direction and the width direction, and a guide wall protruding to the one side in the flow direction from the top portion or the bottom portion of the separating space wall in the housing space, the guide wall abuts the absorbing porous medium in the height direction, and the top portion or the bottom portion of the separating space wall, and the guide wall are formed to separate from the microflow passage in the height direction toward the one side from the other side in the flow direction. 
     Advantageous Effects of Invention 
     In the assay device according to this aspect, the liquid control performance can be enhanced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic exploded perspective view showing an assay device according to a First Embodiment. 
         FIG. 2  is a schematic plan view showing the assay device according to the First Embodiment. 
         FIG. 3  is a sectional view taken along line A-A of  FIG. 2 . 
         FIG. 4  is a sectional view taken along line B-B of  FIG. 2 . 
         FIG. 5  is a sectional view taken along line C-C of  FIG. 2 . 
         FIGS. 6( a ) to 6( d )  are plan views showing states in which sequential flows of the first liquid is supplied to the assay device according to the First Embodiment. 
         FIGS. 7( a ) to 7( d )  are plan views showing states in which sequential flows of the second liquid is supplied to the assay device according to the First Embodiment subsequent to supply of the first liquid. 
         FIG. 8  is a schematic exploded perspective view showing an assay device according to a Second Embodiment. 
         FIG. 9  is a schematic plan view showing the assay device according to the Second Embodiment. 
         FIG. 10  is a sectional view taken along line D-D of  FIG. 9  in the state before supplying the liquid to an inlet of the assay device. 
         FIG. 11  is a sectional view taken along line D-D of  FIG. 9  in the state after supplying the liquid to the inlet of the assay device. 
         FIG. 12  is a schematic exploded perspective view showing an assay device according to a Third Embodiment. 
         FIG. 13  is a schematic plan view showing the assay device according to the Third Embodiment. 
         FIG. 14  is a sectional view taken along line E-E of  FIG. 13 . 
         FIG. 15  is a schematic plan view showing an assay system according to a Fourth Example. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Assay devices according to the First and the Second Embodiments will be described. Referring to  FIGS. 2, 8, 13 and 15 , an outer shape of the assay device is expressed by a virtual line (that is, two-dot chain line), and components inside the assay device are expressed by solid lines and phantom lines (that is, broken lines). Although not specifically shown, each direction to which the assay device is oriented as shown in  FIGS. 6( a ) to 6( d ) , and  FIGS. 7( a ) to 7( d ) , is the same as the direction to which the assay device is oriented as shown in  FIG. 2 . 
     The liquid applicable to the assay device according to the Embodiment, is not restricted specifically so long as it is allowed to flow in the assay device. The liquid may typically contain water as a solvent, that is, it may be an aqueous solution. The liquid applicable to the assay device, may not only be produced as chemically pure liquid but also produced by dissolving, dispersing, or suspending gas, another liquid, or solid in the liquid. 
     The liquid may be hydrophilic. Liquid samples derived from an organism, may be used as the hydrophilic liquid, for example, whole blood, serum, blood plasma, urine, diluted solution of feces, saliva, cerebrospinal fluid, and/or the like of humans or animals. The use of these samples allows the assay device to effectively diagnostically measure a specimen in the liquid sample for the purpose of testing for pregnancy, urine, feces, adult diseases, allergies, infectious diseases, drugs, cancer, and/or the like. Suspension of food, drinking water, river water, soil-derived suspended solid, and/or the like may be used as the hydrophilic liquid. The use of such liquid allows the assay device to measure pathogens contained in food and drinking water, or contaminants in the river water and the soil. 
     In the specification, the “lateral flow” denotes the flow of liquid moved by gravitational sedimentation as the drive force. The movement of liquid based on the lateral flow denotes the liquid movement dominantly (prevailingly) caused by the liquid drive force generated by gravitational sedimentation. The movement of the liquid based on capillary force (capillary phenomenon), denotes the liquid movement predominantly (prevailingly) caused by interfacial tension. The liquid movement based on lateral flow, differs from the liquid movement based on capillary force. 
     In the specification, the “specimen” denotes the chemical compound or composition to be detected or measured using the liquid. For example, the “specimen” may be saccharides (for example, glucose), proteins or peptides (for example, serum proteins, hormones, enzymes, immunoregulatory factors, lymphokines, monokines, cytokines, glycoproteins, vaccine antigens, antibodies, growth factors, or multiplication factors), fats, amino acids, nucleic acids, steroids, vitamins, pathogens or antigens thereto, natural substances or synthetic chemicals, contaminants, medicines for therapeutic purpose or illegal drugs, metabolites of these substances, or those containing antibodies. 
     In the specification, the “microflow passage” denotes the flow passage configured to allow the liquid flow in the assay device in order to detect or measure the specimen using a very small quantity of liquid on the order of a μl (microliter), that is, ranging from approximately 1 μl or more to less than approximately 1 ml (milliliter), or in order to weigh a small quantity of liquid. 
     In the specification, the “film” denotes the membranous substance with thickness of approximately 200 μm (micrometer) or less, and the “sheet” denotes the membranous substance or tabular substance with thickness in excess of approximately 200 μm. 
     In the specification, the “plastic” denotes the polymerized or shaped material to be produced using polymerizable or polymer material as an essential component. The plastic includes polymer alloys formed by combining two or more kinds of polymers. 
     In the specification, the “porous medium” denotes a member having many micropores, which allows absorption and passage of the liquid therethrough, for example, paper, cellulose membranes, non-woven fabric, plastics, and/or the like. The “porous medium” may exhibit a hydrophilic property corresponding to the hydrophilic liquid, and exhibit a hydrophobic property corresponding to the hydrophobic liquid. The “porous medium” may exhibit the hydrophilic property, and may be formed as the paper. Furthermore, the “porous medium” may be formed as any one selected from the cellulose, cellulose nitrate, cellulose acetate, filter paper, tissue paper, toilet paper, paper towel, fabric, or a hydrophilic porous polymer through which water can pass. 
     First Embodiment 
     An assay device according to a First Embodiment will be described. 
     Outline of the Structure of Assay Device 
     Referring to  FIGS. 1 to 5 , a schematic structure of the assay device according to this Embodiment will be described. The assay device includes a microflow passage  1  configured to allow liquid to flow. As described below, the direction along the liquid flow in the microflow passage  1  (as indicated by an arrow F), will be referred to as a “flow direction”. In the Embodiment, the liquid flows toward one side of the microflow passage  1  from the other side. The one side in the flow direction will be defined as a downstream side, and the other side in the flow direction will be defined as an upstream side. 
     The assay device includes a first absorbing porous medium  2  disposed at a distance from one end  1   a  of the microflow passage  1 , which is positioned at the one side (that is, downstream side) in the flow direction. The assay device includes a separating space  3  disposed between the one end  1   a  of the microflow passage  1  and the first absorbing porous medium  2 . The separating space  3  is in the form of a cavity in the assay device. The first absorbing porous medium  2  is configured to ensure absorption of the liquid from the one end  1   a  of the microflow passage  1 . The assay device includes a housing space  4  capable of housing the first absorbing porous medium  2 . The housing space  4  is formed to continue to the separating space  3  in the flow direction. 
     The assay device includes an inlet  5  disposed in the other end  1   b  of the microflow passage  1 , which is positioned at the other side (that is, upstream side) in the flow direction. The inlet  5  is configured to allow liquid to be supplied to the microflow passage  1 . In the microflow passage  1 , the liquid charged from the inlet  5 , flows from the other end  1   b  to the one end  1   a  via an intermediate section  1   c  between the one end  1   a  and the other end  1   b.    
     The assay device includes two adjacent sideways ventilation passages  6  at both sides of the microflow passage  1  in the width direction (indicated by an arrow W) substantially orthogonal to the flow direction. Each of the sideways ventilation passages  6  is configured to allow air circulation. The microflow passage  1  is communicated with the two sideways ventilation passages  6  in the width direction. The respective sideways ventilation passages  6  extend along the flow direction. In particular, the two sideways ventilation passages  6  may extend along both side edges  1   d  of the microflow passage  1  in the width direction. 
     The assay device further includes a connecting ventilation passage  7  which connects the two sideways ventilation passages  6  and extends around a circumference of the inlet  5 . The connecting ventilation passage  7  is also configured to allow air circulation. The air circulation occurs in the two sideways ventilation passages  6  and the connecting ventilation passage  7 , which are continuously connected to each other. Each of the other ends of the two sideways ventilation passages  6  at the other side in the flow direction, may be connected to the connecting ventilation passage  7 . The assay device may be configured to include no connecting ventilation passage. 
     The assay device includes a microflow passage wall  8  that defines the microflow passage  1 . The microflow passage wall  8  includes a top portion  8   a  at a top side and a bottom portion  8   b  at a bottom side in a height direction (indicated by an arrow H) substantially orthogonal to the flow direction and the width direction. The top portion  8   a  and the bottom portion  8   b  of the microflow passage wall  8  are held at a distance from each other in the height direction. The distance between the top portion  8   a  and the bottom portion  8   b  in the height direction, is determined to generate the interfacial tension of the liquid for preventing leakage of the liquid flowing in the microflow passage  1  to the sideways ventilation passages  6 . The microflow passage  1  opens to the two sideways ventilation passages  6  at both sides in the width direction. 
     The assay device includes a separating space wall  9  that defines the separating space  3  in cooperation with the first absorbing porous medium  2 . The separating space may be defined by further components in addition to the first absorbing porous medium and the separating space wall. The separating space wall  9  includes a top portion  9   a  and a bottom portion  9   b  which are positioned at the top side and the bottom side in the height direction, respectively. 
     The assay device includes a guide wall  10  protruding toward the one side in the flow direction in the housing space  4  from the bottom portion  9   b  of the separating space wall  9 . The guide wall  10  abuts the first absorbing porous medium  2  in the height direction. The bottom portion  9   b  of the separating space wall  9  and the guide wall  10 , and inclines to be apart from the microflow passage  1  in the height direction from the other side to the one side in the flow direction. Note that  FIGS. 3 and 11 , described later, do not clearly show the inclination of the bottom portion  9   b  of the separating space wall  9  as it tends to be less than that of the guide wall  10 . However, the guide wall may be formed to protrude from the top portion of the separating space wall to the one side in the flow direction in the housing space. In such a case, the top portion of the separating space wall and the guide wall may be separated from the microflow passage in the height direction toward the one side from the other side in the flow direction. 
     The assay device includes a housing space wall  11  that defines the housing space  4 . The assay device includes two sideways ventilation passage walls  12  that define the two sideways ventilation passages  6 , respectively. The assay device also includes a connecting ventilation passage wall  13  that defines the connecting ventilation passage  7 . 
     The assay device may be provided with a reaction porous medium  14  to be disposed in the intermediate section  1   c  of the microflow passage  1 . The reaction porous medium  14  is configured to be able to react with the liquid or the substance, such as the specimen and/or the like contained in the liquid. Accordingly, the reaction porous medium  14  may be configured to support the reaction reagent or the like to be used for the assay. In an example, the reaction porous medium  14  may be cellulose which supports the antibody and the antigen. However, it is not limited to the specific type of porous medium. In addition to the reaction porous medium  14 , at least one of the top portion and the bottom portion of the microflow passage wall may be configured to be able to react with the liquid or the substance, such as the specimen and/or the like contained in the liquid. The assay device may be configured not to include the reaction porous medium. In such a case, at least one of the top portion and the bottom portion of the microflow passage wall may be configured to be able to react with the liquid or the substance, such as the specimen and/or the like contained in the liquid, as described above. 
     Detailed Structure of Assay Device 
     Referring to  FIGS. 1 to 5 , detailed structures of the assay device according to the Embodiment will be described. Such an assay device may further be configured as follows. The assay device may be configured to have the height direction vertically directed in the usage state. In this case, the top portion and the bottom portion of the assay device are directed upward and downward in the vertical direction, respectively. 
     The microflow passage  1  is substantially linearly formed. In the present invention, the microflow passage may be formed into a curved or a bent shape. The other end  1   b  of the microflow passage  1  is defined by the other end  8   c  of the microflow passage wall  8 . The other end  8   c  of the microflow passage wall  8  is positioned between the microflow passage  1  and the connecting ventilation passage  7 . 
     The height of the microflow passage  1 , that is, the distance in the height direction between the top portion  8   a  and the bottom portion  8   b  of the microflow passage wall  8  may be in the range from approximately 1 μm to approximately 1000 μm (that is, approximately 1 mm (millimeter)) inclusive. The width d of the microflow passage  1  may be in the range from approximately 100 μm to approximately 10000 μm (that is, approximately 1 cm (centimeter)) inclusive. The length of the microflow passage  1  in the flow direction may be in the range from approximately 10 μm to approximately 10 cm inclusive. The capacity P of the microflow passage  1  may be in the range from approximately 0.1 μl to approximately 1000 μl inclusive. More preferably, it may be in the range from approximately 1 μl or more to less than approximately 500 The respective dimensions and the capacity of the microflow passage are not limited to the abovementioned values. 
     The first absorbing porous medium  2  has its height greater than that of the microflow passage  1 . The first absorbing porous medium  2  protrudes closer to the bottom side than the microflow passage  1  in the height direction. If the guide wall protrudes from the top portion of the separating space wall to the one side in the flow direction in the housing space, the first absorbing porous medium may protrude closer to the top side than the microflow passage in the height direction. 
     A downstream portion  3   a  of the separating space  3 , which is positioned at the downstream side in the flow direction is closed with the first absorbing porous medium  2 . The separating space  3  is communicated with the microflow passage  1  and the two sideways ventilation passages  6  in the flow direction. Specifically, an upstream portion  3   b  of the separating space  3 , which is positioned at the downstream side in the flow direction is communicated with the microflow passage  1  and the two sideways ventilation passages  6  in the flow direction. The top portion  9   a  of the separating space wall  9  is provided with two ventilation spaces  3   c.    
     The two ventilation spaces  3   c  are communicated with the two sideways ventilation passages  6 , respectively at the upstream side in the flow direction. The top portions  8   a ,  9   a  of the microflow passage wall  8  and the separating space wall  9  may linearly extend continuously along the flow direction. The ventilation space  3   c  allows air ventilation between the separating space  3  and the sideways ventilation passages  6 . The two ventilation spaces  3   c  are positioned outside the microflow passage  1  in the width direction. The distance between the two ventilation spaces  3   c  in the width direction may be substantially equivalent to the width of the microflow passage  1 . The two ventilation spaces  3   c  may be disposed corresponding to the two sideways ventilation passages  6  in the width direction, respectively. The two ventilation spaces  3   c  may be communicated with the housing space  4 . In particular, the two ventilation spaces  3   c  may extend to be communicated with the top portion of the housing space  4  in the height direction at the downstream side in the flow direction. 
     The capacity Q of the separating space  3  may be in a range from approximately 0.001 μl to approximately 10000 μl, inclusive. The ratio of the capacity Q of the separating space  3  to the capacity P of the microflow passage  1 , that is, Q/P may be approximately 0.01 or more. The capacity of the separating space, and the ratio of the capacity of the separating space to that of the microflow passage are not limited to the abovementioned values. The capacity Q of the separating space  3  may be more than the capacity P of the microflow passage  1 . However, it is possible to set the capacity of the separating space to be equal to or less than the capacity of the microflow passage. 
     Hydrophilization treatments may be applied to the respective surfaces of the microflow passage wall  8  and the separating space wall  9 , which come in contact with the liquid. The hydrophilization treatment may be the optical treatment using plasma, or the treatment using the blocking agent capable of preventing the non-specific conjugate contained in the liquid, if any, from being adsorbed by those surfaces, or may include at least one of the abovementioned treatments. It is possible to use commercial blocking agents, such as Block Ace, bovine serum albumin, casein, skimmed milk, gelatin, surfactants, polyvinyl alcohol, globulin, serum (for example, fetal bovine serum or normal rabbit serum), ethanol, MPC polymer and/or the like as the blocking agent. It is possible to use a single kind of blocking agent, or a mixture of two or more kinds of blocking agents. 
     The inlet  5  is formed to penetrate through the top portion  8   a  of the microflow passage wall  8  in the height direction. Each of the sideways ventilation passages  6  is formed to be recessed to the top side and the bottom side of the microflow passage  1  in the height direction. The connecting ventilation passage  7  is formed to be recessed to the bottom side of the microflow passage  1  in the height direction. A top portion  13   a  of a connecting ventilation passage wall  13  positioned on the top side in the height direction is disposed substantially corresponding to the top portion  8   a  of the microflow passage wall  8  in the height direction. The two sideways ventilation passages  6  and the connecting ventilation passage  7  may extend continuously to form a substantially U-like shape. 
     The guide wall  10  is disposed between the first absorbing porous medium  2  and a second absorbing porous medium  15 , described later, in the height direction. The guide wall  10  may be disposed to form a tapered shape toward the upstream side from the downstream side in the flow direction. The guide wall may be formed into any other shape in a non-restrictive manner. 
     The reaction porous medium  14  may be formed into a laterally extending narrow shape. The reaction porous medium  14  may be disposed to occupy the region across the entire width of the microflow passage  1 . The reaction porous medium  14  may be formed into any other shape, and be freely disposed in a non-restrictive manner. 
     The assay device includes the second absorbing porous medium  15  in addition to the first absorbing porous medium  2 . The second absorbing porous medium  15  is positioned closer to the bottom side than the first absorbing porous medium  2  in the height direction. If the guide wall protrudes toward the one side in the flow direction from the top portion of the separating space wall in the housing space, the second absorbing porous medium  15  may be positioned closer to the top side than the first absorbing porous medium in the height direction. The first and the second absorbing porous media  2 , 15  come in contact with each other in the height direction while having the guide wall  10  intervening therebetween. The liquid is fed to the second absorbing porous medium  15  via the first absorbing porous medium  2 . The housing space  4  is configured to house the second absorbing porous medium  15  in addition to the first absorbing porous medium  2 . 
     The assay device includes a ventilation passage vent hole  16  which communicates one of the two sideways ventilation passages  6  with the outside of the assay device. The ventilation passage vent hole  16  is formed to allow air circulation from the outside of the assay device to the sideways ventilation passage  6  defined by one of the two sideways ventilation passage walls  12 . In particular, the ventilation passage vent hole  16  may be formed to penetrate through a top portion  12   a  of one of the two sideways ventilation passage walls  12  positioned at the top side in the height direction. The ventilation passage vent hole, however, is not limited to the above-mentioned one. The ventilation passage vent holes may be formed in both of the two sideways ventilation passage walls. 
     The assay device includes a housing space vent hole  17  which communicates the housing space  4  with the outside of the assay device. The housing space vent hole  17  is formed to penetrate through the housing space wall  11 . The housing space vent hole  17  may be positioned at one side in the flow direction in the housing space  4 . 
     A flow passage top-side cavity  18  is formed at the top side of the top portion  8   a  of the microflow passage wall  8  in the height direction. A flow passage bottom-side cavity  19  is formed at the bottom side of the bottom portion  8   b  of the microflow passage wall  8  in the height direction. A separating space top-side cavity  20  is formed at the top side of the top portion  9   a  of the separating space wall  9  in the height direction. A housing space top-side cavity  21  is formed at the top side of a top portion  11   a  of the housing space wall  11  in the height direction. 
     One end of the flow passage top-side cavity  18  positioned at the one side in the flow direction is communicated with the separating space top-side cavity  20 . The other end of the flow passage top-side cavity  18  positioned at the other side in the flow direction is at a distance from the inlet  5 . The flow passage top-side cavity  18  is communicated with the two sideways ventilation passages  6  in the width direction. The flow passage bottom-side cavity  19  is formed corresponding to the microflow passage  1  when viewed in the height direction. The flow passage bottom-side cavity  19  is communicated with the two sideways ventilation passages  6  in the width direction. The flow passage bottom-side cavity  19  is also communicated with the connecting ventilation passage  7  in the flow direction. The separating space top-side cavity  20  is formed corresponding to the top portion  9   a  of the separating space wall  9  when seen from the height direction. The housing space top-side cavity  21  is disposed at a distance from the separating space top-side cavity  20  in the flow direction. The separating space top-side cavity  20  is communicated with the two ventilation spaces  3   c  in the width direction. The housing space top-side cavity  21  is communicated with the two ventilation spaces  3   c  in the height direction. 
     The assay device includes a window portion  22  configured to allow the reaction porous medium  14  in the microflow passage  1  to be visually observed from the outside of the assay device. The window portion  22  is transparent. The window portion  22  is positioned at the top side of the flow passage top-side cavity  18  in the height direction. The window portion  22  may be positioned corresponding to the intermediate section  1   c  of the microflow passage  1 , in particular, the reaction porous medium  14 . 
     Layered Structure of Assay Device 
     A layered structure of the assay device will be described referring to  FIG. 1 . In an example, the assay device according to the Embodiment may be formed using a layered structure as described below. Obviously, the assay device may be produced using a structure other than the layered structure. 
     The assay device includes a top-side casing layer S 1 , a top-side cavity layer S 2 , a top-side core layer S 3 , an intermediate core layer S 4 , a bottom-side core layer S 5 , a bottom-side cavity layer S 6 , an intermediate spacer layer S 7 , an intermediate adhesion layer S 8 , a bottom-side spacer layer S 9 , a bottom-side adhesion layer S 10 , and a bottom-side casing layer S 11 , which are sequentially arranged from the top to bottom of the assay device. Each of the top-side casing layer S 1 , the top-side core layer S 3 , the bottom-side core layer S 5 , the intermediate spacer layer S 7 , the bottom-side spacer layer S 9 , and the bottom-side casing layer S 11  is produced using the material which prevents permeation of the liquid. A contact angle between the top-side core layer S 3  and the bottom-side core layer S 5  may be less than 90°. The top-side core layer S 3  and the bottom-side core layer S 5  may be transparent. It is possible to make at least one of the top-side core layer and the bottom-side core layer translucent or opaque. At least one of the top-side core layer S 3  and the bottom-side core layer S 5  is elastically deformable under the liquid pressure upon passage of the liquid through the assay device. 
     The top-side casing layer S 1 , the top-side core layer S 3 , the bottom-side core layer S 5 , the intermediate spacer layer S 7 , the bottom-side spacer layer S 9 , and the bottom-side casing layer S 11  may be produced using plastics. Materials for forming the top-side casing layer S 1 , the top-side core layer S 3 , the bottom-side core layer S 5 , the intermediate spacer layer S 7 , the bottom-side spacer layer S 9 , and the bottom-side casing layer S 11  may be plastic sheets or plastic films. The plastic material includes polyolefins (PO) such as polyethylene (PE), high density polyethylene (HDPE), and polypropylene (PP), ABS resins (ABS), AS resins (SAN), polyvinylidene chloride (PVDC), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), nylon, polymethyl methacrylate (PMMA), cycloolefin copolymer (COC), cycloolefin polymer (COP), polycarbonate (PC), polydimethylsiloxane (PDMS), polyacrylonitrile (PAN), biodegradable plastics such as polylactic acid (PLA), other polymers, or combinations of them. If at least one of the top-side casing layer, the top-side core layer, the bottom-side core layer, the spacer layer, and the bottom-side casing layer is made of the material which does not allow fluid infiltration, it is possible to produce the layer using material other than plastics. The material other than plastics may be resin, glass, metal, and/or the like. It is possible to use either the same or different materials/ingredients for producing the top-side casing layer S 1 , the top-side core layer S 3 , the bottom-side core layer S 5 , the intermediate spacer layer S 7 , the bottom-side spacer layer S 9 , and the bottom-side casing layer S 11 . 
     Each of the top-side cavity layer S 2 , the intermediate core layer S 4 , the bottom-side cavity layer S 6 , the intermediate adhesion layer S 8 , and the bottom-side adhesion layer S 10  is in the form of a double-sided tape or the layer including the double-sided tape. The respective top and bottom surfaces of these layers S 2 , S 4 , S 6 , S 8 , S 10  exhibit adhesive properties. The top and bottom surfaces of the top-side cavity layer S 2  are bonded to the bottom surface of the top-side casing layer S 1 , and the top surface of the top-side core layer S 3 , respectively. The top and bottom surfaces of the intermediate core layer S 4  are bonded to the bottom surface of the top-side core layer S 3  and the top surface of the bottom-side core layer S 5 , respectively. The top and bottom surfaces of the bottom-side cavity layer S 6  are bonded to the bottom surface of the bottom-side core layer S 5  and the top surface of the intermediate spacer layer S 7 , respectively. The top and bottom surfaces of the intermediate adhesion layer S 8  are bonded to the bottom surface of the intermediate spacer layer S 7  and the top surface of the bottom-side spacer layer S 9 , respectively. The top and bottom surfaces of the bottom-side adhesion layer S 10  are bonded to the bottom surface of the bottom-side spacer layer S 9  and the top surface of the bottom-side casing layer S 11 , respectively. 
     At least one of the top-side cavity layer, the intermediate core layer, the bottom-side cavity layer, the intermediate adhesion layer, and the bottom-side adhesion layer may be produced using the materials or ingredients which may be used for producing the top-side casing layer, the top-side core layer, the bottom-side core layer, the spacer layer, the bottom-side spacer layer, and the bottom-side casing layer, as described above. In such a case, the adjacent layers may be bonded using bonding means such as the adhesive, the welding, and/or the like. The materials or ingredients to be used for producing at least one of the top-side cavity layer, the intermediate core layer, the bottom-side cavity layer, the intermediate adhesion layer, and the bottom-side adhesion layer may be the same as or different from those used for producing the adjacent layer. 
     Relationship between Components and Layered Structure of Assay Device 
     Referring to  FIGS. 1, and 3 to 5 , an explanation will be made with respect to the relationship between components and the layered structure of the assay device according to the Embodiment, which is produced using the abovementioned layered structure. The microflow passage  1  is formed to penetrate through the intermediate core layer S 4  in the height direction. The top-side core layer S 3  and the bottom side core layer S 5  include the top portion  8   a  and the bottom portion  8   b  of the microflow passage wall  8 , respectively. 
     The separating space  3  is formed to penetrate through the intermediate core layer S 4  in the height direction. The ventilation space  3   c  is formed to penetrate through the top-side core layer S 3  in the height direction. The top-side core layer S 3  includes the top portion  9   a  of the separating space wall  9 . The bottom-side core layer S 5  includes the bottom portion  9   b  of the separating space wall  9 . The housing space  4  includes seven through sections  4   a ,  4   b ,  4   c ,  4   d ,  4   e ,  4   f ,  4   g , which penetrate through the intermediate core layer S 4 , the bottom-side core layer S 5 , the bottom-side cavity layer S 6 , the intermediate spacer layer S 7 , the intermediate adhesion layer S 8 , the bottom-side spacer layer S 9 , and the bottom-side adhesion layer S 10  in the height direction, respectively. The top-side core layer S 3  and the bottom-side casing layer S 1   l  include the top portion  11   a  and the bottom portion  11   b  of the housing space wall  11 , respectively. 
     The four top-side through sections  4   a  to  4   d  of seven through sections  4   a  to  4   g  constituting the housing space  4 , are formed to ensure housing of the first absorbing porous medium  2 . The three bottom-side through sections  4   e  to  4   g  are formed to ensure housing of the second absorbing porous medium  15 . The second absorbing porous medium  15  may be greater than the first absorbing porous medium  2 . In particular, the length of the second absorbing porous medium  15  in the flow direction may be longer than that of the first absorbing porous medium  2 . 
     The inlet  5  is formed to include three through sections  5   a ,  5   b ,  5   c , which penetrate through the top-side casing layer S 1 , the top-side cavity layer S 2 , and the top-side core layer S 3  in the height direction, respectively. The bottom-side core layer S 5  includes the guide wall  10 . The sideways ventilation passage  6  is formed to include five through sections  6   a ,  6   b ,  6   c ,  6   d ,  6   e , which penetrate through the top-side cavity layer S 2 , the top-side core layer S 3 , the intermediate core layer S 4 , the bottom-side core layer S 5 , and the bottom-side cavity layer S 6  in the height direction, respectively. The top-side casing layer S 1  and the intermediate spacer layer S 7  include the top portion  12   a  and the bottom portion  12   b  of the sideways ventilation passage wall  12 , respectively. The connecting ventilation passage  7  is formed to include two through sections  7   a ,  7   b , which penetrate through the bottom-side core layer S 5  and the bottom-side cavity layer S 6  in the height direction, respectively. The intermediate core layer S 4  and the intermediate spacer layer S 7  include the top portion  13   a  and the bottom portion  13   b  of the connecting ventilation passage wall  13 , respectively. 
     The ventilation passage vent hole  16  is formed to penetrate through the top-side casing layer S 1  in the height direction, and to communicate one of the two sideways ventilation passage walls  12  with the outside of the assay device. The housing space vent hole  17  is formed to penetrate through the bottom-side casing layer S 11  in the height direction, and to communicate the housing space  4  with the outside of the assay device. 
     The flow passage top-side cavity  18 , the separating space top-side cavity  20 , and the housing space top-side cavity  21  are formed to penetrate through the top-side cavity layer S 2  in the height direction. The flow passage top-side cavity  18 , the separating space top-side cavity  20 , and the housing space top-side cavity  21  are positioned between the top-side casing layer S 1  and the top-side core layer S 3  in the height direction. The flow passage bottom-side cavity  19  is formed to penetrate through the bottom-side cavity layer S 6  in the height direction. The flow passage bottom-side cavity  19  is positioned between the bottom-side core layer S 5  and the intermediate spacer layer S 7  in the height direction. The top-side casing layer S 1  includes the window portion  22 . 
     Fluid Control in Assay Device 
     Referring to  FIGS. 6( a ) to 6( d ), and 7( a ) to 7( c ) , an explanation will be made with respect to fluid control executed in the assay device according to the Embodiment. Here, liquids applied to the assay device are referred to as first and second liquids L 1 , L 2 . In the explanation, the first and second liquids L 1 , L 2  will be supplied to the assay device in this order. The first liquid L 1  and the second liquid L 2  are different from each other. However, the first liquid and the second liquid may be the same. In  FIGS. 6( a ) to 6( d ), and 7( a ) to 7( d ) , solid lines are used, for the purpose of explanation, for indicating the microflow passage  1 , the absorbing porous medium  2 , the separating space  3 , the housing space  4 , the inlet  5 , the sideways ventilation passages  6 , the connecting ventilation passage  7 , and the reaction porous medium  14  as well as the first and the second liquids L 1 , L 2 . 
     Typically, each quantity of the liquids (each quantity of the first and the second liquids L 1 , L 2 ) supplied to the assay device may be equal to or greater than approximately 1 μl, and less than approximately 1 ml. Preferably, each quantity of the liquids is equal to or greater than approximately 1.5 μl, and more preferably, approximately 3.0 μl or more. The upper limit of each quantity of the liquids may be in the range from several μl to several hundreds of ill. Determination of each quantity of the liquids may stabilize detection sensitivity of the specimen and facilitate detection of the specimen and/or the like. In this case, each quantity of the liquids may be obtained by a drop of the liquid. Each quantity of the liquids may be greater than the capacity of the microflow passage  1 . In such a case, the liquid may be divided adequately by the separating space  3  into a part absorbed by the absorbing porous medium  2  and another part detained in the microflow passage  1 . Each quantity of the liquids may be made less than the capacity of the microflow passage, or substantially equivalent to that of the microflow passage. 
     First, the first liquid L 1  is supplied to the inlet  5  as shown in  FIG. 6( a ) . The first liquid L 1  then flows into the microflow passage  1 . The first liquid L 1  further flows in the microflow passage  1  from the upstream side to the downstream side in the flow direction. While the first liquid L 1  is flowing in the microflow passage  1 , an assay is performed by the reaction porous medium  14 . The two sideways ventilation passages  6  are disposed at both sides of the reaction porous medium  14  in the width direction. Air circulation in the two sideways ventilation passages  6  allows the first liquid L 1  to flow from the upstream side to the downstream side in the flow direction after passing through the reaction porous medium  14  in the microflow passage  1 . 
     In a case in which supply of the first liquid L 1  is continued, in particular, supply of the first liquid L 1  by quantity in excess of the capacity of the microflow passage  1 , the first liquid L 1  flowing in the microflow passage  1  reaches the separating space  3  as shown in  FIG. 6( b ) . The first liquid L 1  comes in contact with the absorbing porous medium  2  after passing through the separating space  3 . Thereafter, the flow of the first liquid L 1  extends from the one end  1   a  of the microflow passage  1  to the absorbing porous medium  2  in the separating space  3  along inner side edges of the two ventilation spaces  3   c  by interfacial tension of the first liquid L 1  and the air circulation in the two ventilation spaces  3   c . The first liquid L 1  is absorbed by the absorbing porous medium  2  in the abovementioned state until the supply of the liquid L 1  is stopped. When flowing into the separating space  3  from the one end  1   a  of the microflow passage  1 , the first liquid L 1  moves under the force toward the flow direction based on the lateral flow. The interfacial tension of the first liquid L 1  in the abovementioned state at the inner edges of the two ventilation spaces  3   c  becomes significantly greater than the force that directs the first liquid L 1  toward the two ventilation spaces  3   c  based on at least one of the lateral flow and the capillary force of the absorbing porous medium  2 . Consequently, the first liquid L 1  in the abovementioned state ensures prevention of leakage of the first liquid L 1  from the ventilation space  3   c.    
     After stopping supply of the first liquid L 1 , the flow of the first liquid L 1  is narrowed in the separating space  3  to be away from the inner edges of the two ventilation spaces  3   c  as being directed from the one end  1   a  of the microflow passage  1  and the absorbing porous medium  2  toward the center therebetween in the flow direction, as shown in  FIG. 6( c ) . The first liquid L 1  is then divided by the separating space  3  into a part absorbed through the capillary force of the absorbing porous medium  2 , and another part held in the microflow passage  1  as shown in  FIG. 6( d ) . 
     After stopping supply of the first liquid L 1 , the second liquid L 2  is further supplied to the inlet  5  as shown in  FIG. 7( a ) . Similar to the first liquid L 1 , the supplied second liquid L 2  flows in the microflow passage  1 . The second liquid L 2  extrudes the first liquid L 1  which has been preliminarily filled in the microflow passage  1  toward the separating space  3 . As a result, solution exchange occurs in the microflow passage  1  by replacing the first liquid L 1  with the second liquid L 2 . The assay is performed by the reaction porous medium  14  in the foregoing while the second liquid L 2  is flowing in the microflow passage  1 . 
     In a case in which supply of the second liquid L 2  is continued, in particular, supply of the second liquid L 2  by a quantity in excess of that of the first liquid L 1  which has been preliminarily filled in the microflow passage  1 , the first liquid L 1  extruded by the second liquid L 2  comes in contact with the absorbing porous medium  2  via the separating space  3  as shown in  FIG. 7( b ) . The flow of the first liquid L 1  extends to reach a convex portion  5  of the absorbing porous medium  2  from the one end  1   a  of the microflow passage  1  in the separating space  3  again. Thereafter, subsequent to the first liquid L 1 , the second liquid L 2  comes in contact with the absorbing porous medium  2  via the separating space  3 . Similar to the first liquid L 1 , the second liquid L 2  then flows as shown in  FIG. 7( c ) , and is divided by the separating space  3  into the part absorbed through the capillary force of the absorbing porous medium  2  and another part detained in the microflow passage  1  as shown in  FIG. 7( d ) . 
     The solution exchange allows the ELISA process or the like to easily generate multistage antigen-antibody reaction. The solution exchange may be securely executed, in particular, when making quantity of the second liquid L 2  supplied to the assay device substantially equal to or greater than that of the first liquid L 1  which has been filled in the microflow passage  1 . 
     In other words, in the assay device according to the Embodiment, when supplying multiple kinds of liquid to the inlet  5  sequentially, the microflow passage  1  is preliminarily filled with the preceding one of the multiple kinds of liquid, and supply of the preceding liquid is stopped. Subsequently, another one of the multiple kinds of liquid, which is subsequent to the preceding liquid, is supplied to the inlet  5  so that the preceding liquid can be replaced with the subsequent liquid in the microflow passage  1 . The solution exchange for replacing the preceding liquid with the subsequent liquid may be executed repeatedly. In such a case, typically, the preceding liquid is different from the subsequent liquid. The preceding liquid may be the same as the subsequent liquid. 
     The assay device according to the Embodiment includes the microflow passage  1  configured to allow liquid to flow, the absorbing porous medium  2  disposed at a distance from the one end  1   a  of the microflow passage  1 , and the separating space  3  disposed between the one end  1   a  of the microflow passage  1  and the absorbing porous medium  2 . It is further provided with the two sideways ventilation passages  6  which are adjacent to both sides of the microflow passage  1 , respectively in the width direction, and communicated with the microflow passage  1  to allow air circulation. 
     The liquid in the microflow passage  1  comes in contact with air in the sideways ventilation passage  6  in the width direction. This makes it possible to avoid the contact of the liquid with the wall that defines the microflow passage  1  in the width direction. This may reduce the probability of non-specific adsorption of samples, reagents, impurities and/or the like which adhere on the wall that defines the microflow passage  1 , and further reduces the risk of mixture of impurities from adhering to the wall that defines the microflow passage  1  with the liquid. This may avoid the influence of viscosity and friction between the liquid in the microflow passage  1  and the wall that defines the microflow passage  1  in the width direction. As the wall that defines the microflow passage  1  does not exist, it is possible to avoid the influence of intensity or non-uniformity of the force generated when packaging the microflow passage  1  on the flowability of the liquid flowing in the microflow passage  1 . It is possible to release an air gap generated in the liquid in the microflow passage  1  into the sideways ventilation passages  6 . It is also possible to efficiently supply such gas as nitrogen and oxygen in the sideways ventilation passages  6  to the liquid in the microflow passage  1 . As a result, the flowability of the liquid may be improved, resulting in enhanced liquid control performance. 
     The assay device according to the Embodiment further includes the inlet  5  disposed in the other end  1   b  of the microflow passage  1  to allow the liquid to be supplied to the microflow passage  1 , and the connecting ventilation passage  7  for connecting the two sideways ventilation passages  6  and extending around the inlet  5  to allow air circulation. 
     The two sideways ventilation passages  6  are connected with the connecting ventilation passage  7  so as to allow efficient air circulation to the two sideways ventilation passages  6  and the connecting ventilation passage  7 . Around the inlet  5 , it is also possible to reduce the probability of non-specific adsorption of samples, reagents, impurities and/or the like which adhere on the microflow passage wall  8  that defines the microflow passage  1 , and further avoid the influence of viscosity and friction between the liquid in the microflow passage  1  and the microflow passage wall  8 . This makes it possible to improve flowability of the liquid, resulting in enhanced liquid control performance. 
     In the assay device according to the Embodiment, the microflow passage wall  8  includes the top portion  8   a  and the bottom portion  8   b  for defining the microflow passage  1  in the height direction, and the top portion  8   a  and the bottom portion  8   b  of the microflow passage wall  8  are held at a distance from each other in the height direction. 
     The liquid supplied from the inlet  5  may be securely guided into the microflow passage  1  so as to allow the liquid to flow toward the downstream side from the upstream side in the flow direction in the microflow passage  1 . This makes it possible to improve flowability of the liquid, resulting in enhanced liquid control performance. 
     The assay device according to the Embodiment further includes the reaction porous medium  14  disposed in the microflow passage  1  to react with the liquid or the substance contained in the liquid. 
     Even if the reaction porous medium  14  is disposed in the microflow passage  1  for confirming the assay reaction, the air circulation in the sideways ventilation passages  6  ensures the liquid flow in the microflow passage  1  while allowing passage of the liquid through the reaction porous medium  14 , to makes it possible to enhance the liquid control performance. In addition to or instead of the reaction porous medium, at least one of the top portion and the bottom portion of the microflow passage wall is made able to react with the liquid or the substance, such as the specimen and/or the like contained in the liquid to provide similar functions and effects to those derived from the above-mentioned structure. 
     The assay device according to the Embodiment includes the housing space  4  for housing the absorbing porous medium  2 , the separating space wall  9  for defining the separating space  3  in cooperation with the absorbing porous medium  2 , which is provided with the top portion  9   a  and the bottom portion  9   b  for defining the separating space  3  at both sides in the height direction, and the guide wall  10  which protrudes to the one side in the flow direction from the bottom portion  9   b  of the separating space wall  9  in the housing space  4 . The guide wall  10  abuts on the absorbing porous medium  2  in the height direction. One of the top portion  9   a  and the bottom portion  9   b  of the separating space wall  9 , and the guide wall  10  are formed to separate from the microflow passage  1  in the height direction toward the one side from the other side in the flow direction. 
     As the height of the separating space  3  increases toward the downstream from the upstream of the liquid flow, the liquid may be securely divided by the separating space  3  into the part absorbed by the absorbing porous medium  2  and another part detained in the microflow passage  1 . This makes it possible to enhance the liquid control performance. 
     Second Embodiment 
     An explanation will be made with respect to an assay device according to a Second Embodiment. The assay device of the Embodiment is similar to that of the First Embodiment except the point to be described below. Explanations of structures of the assay device similar to those of the First Embodiment will be omitted. In this Embodiment, similar components to those of the First Embodiment will be designated with the same reference numerals. 
     Structure of Assay Device 
     Referring to  FIGS. 8 to 11 , an explanation will be made with respect to the structure of the assay device according to the Embodiment. The assay device according to the Embodiment includes a microflow passage  31  and a microflow passage wall  32  that defines the microflow passage  31 . The microflow passage  31  and the microflow passage wall  32  according to the Embodiment are similar to the microflow passage  1  and the microflow passage wall  8  according to the First Embodiment, respectively except the point to be described below. The microflow passage wall  32  includes a top portion  32   a  and a bottom portion  32   b  for defining the microflow passage  31  in the height direction. As the liquid is supplied from the inlet  5  to the microflow passage  31 , in the other end  31   b  of the microflow passage  31 , an abutment state of the top portion  32   a  and the bottom portion  32   b  of the microflow passage wall  32  in the height direction is made changeable into a state in which those portions are separated in the height direction. The two sideways ventilation passages  6  may extend along respective side edges  31   d  of the microflow passage  31  in the width direction. 
     A connecting ventilation passage  33  according to the Embodiment is similar to the connecting ventilation passage  7  according to the First Embodiment except the point to be described below. The connecting ventilation passage  33  communicates with the other end  31   b  of the microflow passage  31 . The connecting ventilation passage  33  is formed to be recessed to the top-side of the microflow passage  31  in the height direction. 
     A flow passage top-side cavity  35  according to the Embodiment is similar to the flow passage top-side cavity  18  of the First Embodiment except the point to be described below. The flow passage top-side cavity  35  communicates with the inlet  5 . The other end of the flow passage top-side cavity  35  communicates with the connecting ventilation passage  33 . 
     Relationship between Components and Layered Structure of Assay Device 
     Referring to  FIGS. 8, 10 and 11 , an explanation will be made with respect to a relationship between components and a layered structure of the assay device according to the Embodiment. The assay device according to the Embodiment includes a top-side cavity layer S 12 , a top-side core layer S 13 , and an intermediate core layer S 14 . The top-side cavity layer S 12 , the top-side core layer S 13 , and the intermediate core layer S 14  according to the Embodiment are similar to the top-side cavity layer S 2 , the top-side core layer S 3 , and the intermediate core layer S 4  according to the First Embodiment, respectively, except the point to be described below. 
     The connecting ventilation passage  33  is formed to include five through sections  33   a ,  33   b ,  33   c ,  33   d ,  33   e , which penetrate through the top-side cavity layer S 12 , the top-side core layer S 13 , the intermediate core layer S 14 , the bottom-side core layer S 5 , and the bottom-side cavity layer S 6 , respectively, in the height direction. In the connecting ventilation passage  33  according to the Embodiment, the sections  33   d ,  33   e  penetrating through the bottom-side core layer S 5  and the bottom-side cavity layer S 6  are similar to the sections  7   a ,  7   b  penetrating through the bottom-side core layer S 5  and the bottom-side cavity layer S 6  in the connecting ventilation passage  7  according to the First Embodiment. The top-side casing layer S 1  and the intermediate spacer layer S 7  include a top portion  34   a  and a bottom portion  34   b  of a connecting ventilation passage wall  34 , respectively. The top-side cavity layer S 12  does not include the housing space top-side cavity  21  according to the First Embodiment. 
     Fluid Control in Assay Device 
     Referring to  FIGS. 10 and 11 , an explanation will be made with respect to the fluid control in the assay device according to the Embodiment. The fluid control in the assay device according to the Embodiment is similar to the fluid control in the assay device according to the First Embodiment, except for the point described below. 
     The principle of flow of the liquid L in the microflow passage  31  of the assay device according to the Embodiment may have a theoretical basis as described below. The liquid L described herein may be replaced with the first liquid L 1  or the second liquid L 2  as abovementioned in the First Embodiment. Referring to  FIG. 10 , before supplying the liquid L, the top portion  32   a  and the bottom portion  32   b  of the microflow passage wall  32  are in a partial abutment state in the microflow passage  31 . In  FIG. 10 , as the reaction porous medium  14  is squeezed by the top portion  32   a  and the bottom portion  32   b  of the microflow passage wall  32  in an intermediate section  31   c  of the microflow passage  31 , it is expressed as an approximately linear part. 
     As  FIG. 11  shows, upon supply of the liquid L to the inlet  5  of the assay device in the abovementioned state, the top portion  32   a  and the bottom portion  32   b  of the microflow passage wall  32  are peeled from each other by the liquid L which flows based on the lateral flow. In the microflow passage  31 , peeling charge is generated in the top portions  32   a  and the bottom portion  32   b  of the microflow passage wall  32  to attract water molecules, resulting in the surface tension in the liquid L. This allows the liquid L to flow in the microflow passage  31  without reducing the flow rate. The foregoing principle of flow of the liquid L may be a theoretical basis as a possible conceivable example, which is not limited so long as the liquid L is allowed to flow in the microflow passage without reducing its flow rate. 
     The assay device according to the Embodiment provides similar effects to those derived from the assay device according to the First Embodiment except the effect obtained by maintaining the top portion  32   a  and the bottom portion  32   b  of the microflow passage wall  32  separated in the height direction. In the assay device according to the Embodiment, the liquid supplied from the inlet  5  to the microflow passage  31  makes the abutment state of the top portion  32   a  and the bottom portion  32   b  of the microflow passage wall  32  in the height direction at the other end  31   b  of the microflow passage  31  changeable into a state in which these portions are in a separated state in the height direction. This makes it possible to execute the fluid control in the assay device as mentioned above. The flowability of the liquid may be improved, resulting in enhanced liquid control performance. 
     Third Embodiment 
     An explanation will be made with respect to an assay device according to a Third Embodiment. The assay device according to this Embodiment is similar to the assay device according to the First Embodiment, except for the point described below. Explanations of similar structures to those of the assay device according to the First Embodiment will be omitted in the Embodiment. 
     Outline of Structure of Assay Device 
     Referring to  FIGS. 12 to 14 , an explanation will be made with respect to an outline of the structure of the assay device according to the Embodiment. The outline of the structure of the assay device according to the Embodiment may be defined similarly to the outline of the structure of the assay device according to the First Embodiment. 
     In the outline of the structure, a microflow passage  41  of the Embodiment may be defined similarly to the microflow passage  1  of the First Embodiment. One end  41   a , the other end  41   b , an intermediate section  41   c , and side edges  41   d  of the microflow passage  41  of the Embodiment may be defined similarly to the one end  1   a , the other end  1   b , the intermediate section  1   c , and the side edges  41   d  of the microflow passage  1  of the First Embodiment. 
     A first absorbing porous medium  42 , a separating space  43 , a housing space  44 , an inlet  45 , two sideways ventilation passages  46 , and a connecting ventilation passage  47  may be defined similarly to the first absorbing porous medium  2 , the separating space  3 , the housing space  4 , the inlet  5 , the two sideways ventilation passages  6 , and the connecting ventilation passage  47  of the First Embodiment, respectively. A microflow passage wall  48  of the Embodiment may be defined similarly to the microflow passage wall  8  of the First Embodiment. A top portion  48   a  and a bottom portion  48   b  of the microflow passage wall  48  of the Embodiment may be defined similarly to the top portion  8   a  and the bottom portion  8   b  of the microflow passage wall  8  of the First Embodiment, respectively. 
     A separating space wall  49  of the Embodiment may be defined similarly to the separating space wall  9  of the First Embodiment. A top portion  49   a  and a bottom portion  49   b  of the separating space wall  49  of the Embodiment may be defined similarly to the top portion  9   a  and the bottom portion  9   b  of the separating space wall  9  of the First Embodiment. A guide wall  50 , a housing space wall  51 , two sideways ventilation passage walls  52 , and a connecting ventilation passage wall  53  according to the Embodiment may be defined similarly to the guide wall  10 , the housing space wall  11 , the two sideways ventilation passage walls  12 , and the connecting ventilation passage wall  13  according to the First Embodiment. 
     Detailed Structure of Assay Device 
     Referring to  FIGS. 12 to 14 , an explanation will be made with respect to detailed structures of the assay device according to the Embodiment. The detailed structures of the assay device according to the Embodiment may be similar to those of the assay device according to the First Embodiment, except for the point described below. The microflow passage  41  is formed to have its width decreased toward one side from the other side in the flow direction. Each of the top portion  48   a  and the bottom portion  48   b  of the microflow passage wall  48  is also formed to have its width decreased toward the one side from the other side in the flow direction. The microflow passage  41  and the microflow passage wall  48  allow the liquid to be efficiently divided by the separating space  43  into the part absorbed through the capillary force of the absorbing porous medium  42 , and the other part detained in the microflow passage  41 . 
     A downstream portion  43   a , an upstream portion  43   b , and two ventilation spaces  43   c  of the separating space  43  of the Embodiment may be defined similarly to the downstream portion  3   a , the upstream portion  3   b , and the two ventilation spaces  3   c  of the separating space  3  of the First Embodiment, respectively. The connecting ventilation passage  47  includes a top portion  47   a  and a bottom portion  47   b  positioned at the top side and the bottom side of the microflow passage  41  in the height direction, respectively. The connecting ventilation passage  47  is positioned corresponding to the microflow passage  41  in the height direction, and includes a partition portion  47   c  as a partition between the top portion  47   a  and the bottom portion  47   b  in the height direction. The two sideways ventilation passages  46 , and the top portion  47   a  and the bottom portion  47   b  of the connecting ventilation passage  47  may extend continuously to form a substantially U-like shape. The assay device includes a reaction porous medium  54  defined similarly to the reaction porous medium  14  of the First Embodiment. Similar to the First Embodiment, in addition to the reaction porous medium  54 , at least one of the top portion and the bottom portion of the microflow passage wall may be made able to react with the liquid or the substance, such as the specimen and/or the like contained in the liquid. Similar to the First Embodiment, the assay device may be configured to have no reaction porous medium. In such a case, at least one of the top portion and the bottom portion of the microflow passage wall may be made able to react with the liquid or the substance, such as the specimen and/or the like contained in the liquid as in the First Embodiment. 
     The assay device includes a second absorbing porous medium  55  in addition to the first absorbing porous medium  42 . The second absorbing porous medium  55  is positioned closer to the bottom side than the first absorbing porous medium  42  in the height direction. The second absorbing porous medium  55  includes an upstream portion  55   a  and a downstream portion  55   b , which are layered in the height direction. The upstream portion  55   a  of the second absorbing porous medium  55  is positioned closer to the first absorbing porous medium  42  than the downstream portion  55   b  in the height direction. If the guide wall protrudes toward one side in the flow direction from the top portion of the separating space wall in the housing space, the second absorbing porous medium may be positioned closer to the top side than the first absorbing porous medium in the height direction. The first and the second absorbing porous media  42 ,  55  come in contact with each other in the height direction while having the guide wall  50  intervened therebetween. The liquid is designed to be fed to the second absorbing porous medium  55  via the first absorbing porous medium  42 . The housing space  44  is configured to house the second absorbing porous medium  55  in addition to the first absorbing porous medium  42 . 
     The assay device includes the reaction porous medium  54  and the second absorbing porous medium  55 , which are defined similarly to the reaction porous medium  14  and the second absorbing porous medium  15  according to the First Embodiment, respectively. The assay device also includes a vent hole/window portion  56  which allows the reaction porous medium  54  in the microflow passage  41  to be visually observed from the outside of the assay device. The vent hole/window portion  56  may be positioned corresponding to the intermediate section  41   c  of the microflow passage  41 , in particular, the reaction porous medium  54 . The vent hole/window portion  56  is formed to allow air circulation to the two sideways ventilation passages  46  from the outside of the assay device. In particular, the vent hole/window portion  56  may be formed to penetrate through top portions  52   a  of the two sideways ventilation passage walls  52  positioned at the top side in the height direction. The vent hole/window portion  56  is formed to bypass the top portion  48   a  of the microflow passage wall  48  which is deformed by the reaction porous medium  54  to protrude toward the top side in the height direction. The vent hole/window portion, however, is not limited to the abovementioned one. The vent hole/window portion may be formed to allow air circulation only to one of the two sideways ventilation passages from the outside of the assay device. 
     The assay device includes a housing space vent hole  57  which may be defined similarly to the housing space vent hole  17  according to the First Embodiment. The assay device includes a relief cavity  58  adjacent to the bottom side of the bottom portion  48   b  of the microflow passage wall  48  in the height direction. The relief cavity  58  is positioned corresponding to the vent hole/window portion  56 . The relief cavity  58  is formed to bypass the bottom portion  48   b  of the microflow passage wall  48  which is deformed by the reaction porous medium  54  to protrude toward the bottom side in the height direction. 
     The assay device includes two side holes  59  which communicate the two sideways ventilation passages  46  with the outside of the assay device, respectively. The two side holes  59  are formed to penetrate the two sideways ventilation passage walls  52  in the width direction, respectively. The respective side holes  59  are positioned corresponding to the microflow passage  41  in the height direction. The respective side holes  59  are configured to allow a shielding member (not shown) for shielding the liquid flow in the microflow passage  41  to be detachably inserted into the microflow passage  41  from the outside of the assay device. The two side holes  59  are positioned corresponding to each other in the flow direction. The respective side holes  59  are positioned in one side relative to the reaction porous medium  54  in the flow direction. The respective side holes  59  may be adjacent to the vent hole/window portion  56  in one side in the flow direction. However, the assay device may be configured to have one side hole which communicates only one of the two sideways ventilation passages with the outside of the assay device. 
     The assay device according to the Embodiment does not include cavities respectively corresponding to the flow passage top-side cavity  18 , the flow passage bottom-side cavity  19 , the separating space top-side cavity  20 , and the housing space top-side cavity  21  of the assay device according to the First Embodiment. However, the assay device according to the Embodiment may be configured to form a cavity corresponding to at least one of those cavities. 
     Layered Structure of Assay Device 
     Referring to  FIG. 12 , an explanation will be made with respect to the layered structure of the assay device. The assay device according to the Embodiment may be produced using the layered structure as an example to be described below. It is to be understood that the assay device may be produced using the structure other than the layered structure. 
     The assay device according to the Embodiment includes a top-side casing layer S 21 , a top-side cavity layer S 22 , a top-side core layer S 23 , an intermediate core layer S 24 , a bottom-side core layer S 25 , a bottom-side cavity layer S 26 , an intermediate spacer layer S 27 , an intermediate adhesion layer S 28 , a bottom-side spacer layer S 29 , a bottom-side adhesion layer S 30 , and a bottom-side casing layer S 31 , which are defined similarly to the top-side casing layer S 1 , the top-side cavity layer S 2 , the top-side core layer S 3 , the intermediate core layer S 4 , the bottom-side core layer S 5 , the bottom-side cavity layer S 6 , the intermediate spacer layer S 7 , the intermediate adhesion layer S 8 , the bottom-side spacer layer S 9 , the bottom-side adhesion layer S 10 , and the bottom-side casing layer S 1   l  of the assay device according to the First Embodiment, respectively. 
     Relationship Between Components and Layered Structure of Assay Device 
     Referring to  FIGS. 12 and 14 , an explanation will be made with respect to a relationship between components and the layered structure of the assay device according to the Embodiment in the case in which the assay device is produced using the layered structure as described above. The relationship between the components and the layered structure of the assay device according to the Embodiment is similar to the relationship between the components and the layered structure of the assay device according to the First Embodiment, except for the point described below. 
     The housing space  44  is formed to have six through sections  44   a ,  44   b ,  44   c ,  44   d ,  44   e ,  44   f , which penetrate the bottom-side core layer S 25 , the bottom-side cavity layer S 26 , the intermediate spacer layer S 27 , the intermediate adhesion layer S 28 , the bottom-side spacer layer S 29 , and the bottom-side adhesion layer S 30  in the height direction, respectively. The intermediate core layer S 24  and the bottom-side casing layer S 31  include a top portion  51   a  and a bottom portion  51   b  of the housing space wall  51 , respectively. 
     The two top-side through sections  44   a ,  44   b  of the six through sections  44   a  to  44   f  constituting the housing space  44  are formed to ensure housing of the first absorbing porous medium  42 . The four bottom-side through sections  44   c  to  44   f  are formed to ensure housing of the second absorbing porous medium  55 . The top-side through section  44   c  of those four through sections  44   c  to  44   f  is formed to ensure housing of the upstream portion  55   a  of the second absorbing porous medium  55 . The three bottom-side through sections  44   d  to  44   f  of those four through sections  44   c  to  44   f  are formed to ensure housing of the downstream portion  55   b  of the second absorbing porous medium  55 . 
     The second absorbing porous medium  55  may be greater than the first absorbing porous medium  42 . In particular, the length of the second absorbing porous medium  55  in the flow direction may be longer than that of the first absorbing porous medium  42 . The upstream portion  55   a  of the second absorbing porous medium  55  may have the length in the flow direction substantially the same as that of the first absorbing porous medium  42  in the flow direction, and the downstream portion  55   b  of the second absorbing porous medium  55  may have the length in the flow direction longer than that of the first absorbing porous medium  42  in the flow direction. 
     The inlet  45  is formed to include three through sections  45   a ,  45   b ,  45   c , which penetrate through the top-side casing layer S 21 , the top-side cavity layer S 22 , and the top-side core layer S 23  in the height direction, respectively. Each of the sideways ventilation passages  46  is formed to include three through sections  46   a ,  46   b ,  46   c , which penetrate through the top-side core layer S 23 , the intermediate core layer S 24 , and the bottom-side core layer S 25  in the height direction, respectively. 
     The top-side cavity layer S 22  and the bottom-side cavity layer S 26  include the top portions  52   a  and the bottom portions  52   b  of the sideways ventilation passage wall  52 , respectively. The top portion  47   a  and the bottom portion  47   b  of the connecting ventilation passage  47  penetrate through the top-side core layer S 23  and the bottom-side core layer S 25  in the height direction, respectively. The intermediate core layer S 24  includes the partition portion  47   c  of the connecting ventilation passage  47 . The top-side cavity layer S 22  and the bottom-side cavity layer S 26  include the top portion  53   a  and the bottom portion  53   b  of the connecting ventilation passage wall  53 , respectively. 
     The vent hole/window portion  56  includes two through sections  56   a ,  56   b  which penetrate through the top-side casing layer S 21  and the top-side cavity layer S 22  in the height direction, respectively. The housing space vent hole  57  is formed to penetrate through the bottom-side casing layer S 1   l  in the height direction, and communicates the housing space  44  with the outside of the assay device. The relief cavity  58  is formed to penetrate through the bottom-side cavity layer S 26  in the height direction. The respective side holes  59  are formed to include two through sections  59   a ,  59   b , which penetrate through the top-side core layer S 23  and the intermediate core layer S 24  in the height direction. The two side holes  59  communicate the two sideways ventilation passages  46  with the outside of the assay device, respectively. 
     The fluid may be controlled in the assay device according to the Embodiment similarly to the assay device according to the First Embodiment. The assay device of the Embodiment provides similar effects to those derived from the assay device according to the First Embodiment. 
     The assay device according to the Embodiment includes the side holes  59  which communicate at least one of the two sideways ventilation passages  46  with the outside of the assay device. The side holes  59  are positioned corresponding to the microflow passage  41  in the height direction. The side holes  59  allow the shielding member (not shown) for shielding the liquid flow in the microflow passage  41  to be detachably inserted into the microflow passage  41  from the outside of the assay device. 
     As the Embodiments according to the present invention have been described in the nonrestrictive manner, the present invention may be varied and modified based on the technical concept. 
     EXAMPLES 
     First Example 
     In a First Example, the assay device configured according to the First Embodiment as shown in  FIGS. 1 to 5  was used to perform solution exchange between blue-colored methylene blue dyeing liquid and transparent phosphate buffer solution. Specifically, operations of supplying the blue-colored methylene blue dyeing liquid, and then the transparent phosphate buffer solution to the inlet  5  of the assay device were performed repeatedly by 10 times. In a series of operations, fluidity of the liquid in the assay device, the liquid absorbing level of the convex portion  5  of the absorbing porous medium  2 , and the meniscus in the one end  1   a  of the microflow passage  1  in the assay device were confirmed. 
     In the First Example, it was confirmed with respect to secure flows of the methylene blue dyeing liquid and the phosphate buffer solution in the assay device, performance of the absorbing porous medium  2  to securely absorb the methylene blue dyeing liquid and the phosphate buffer solution, and suppression of the meniscus tortuosity in the one end  1   a  of the microflow passage  1  in the assay device. It was further confirmed with respect to reduction in the residual liquid in the separating space  3 . Consequently, it was confirmed that the solution exchange was securely performed between the methylene blue dyeing liquid and the phosphate buffer solution. 
     Second Example 
     In a Second Example, the same assay device as the abovementioned one in the First Example was used to perform the solution exchange among transparent phosphate buffer solution, red-colored eosin, and blue-colored methylene blue dyeing liquid. Specifically, first, the transparent phosphate buffer solution was supplied to the inlet  5  of the assay device. Upon passage of approximately 3 minutes after stopping supply of the phosphate buffer solution, the red-colored eosin was supplied to the inlet  5  of the assay device. Upon passage of approximately 3 minutes after stopping supply of the eosin, the transparent phosphate buffer solution was supplied to the inlet  5  of the assay device. Upon passage of approximately 3 minutes after stopping supply of the phosphate buffer solution, the blue-colored methylene blue dyeing liquid was supplied to the inlet  5  of the assay device. In a series of operations, fluidity of the liquid in the assay device, the liquid absorbing level of the absorbing porous medium  2 , and the meniscus in the one end  1   a  of the microflow passage  1  in the assay device were confirmed. 
     In the Second Example, it was confirmed with respect to secure flows of the phosphate buffer solution, the eosin, and the methylene blue dyeing liquid in the assay device, performance of the absorbing porous medium  2  to securely absorb the phosphate buffer solution, the eosin, and the methylene blue dyeing liquid, and suppression of the meniscus curvature in the one end  1   a  of the microflow passage  1  in the assay device. It was further confirmed with respect to reduction in the residual liquid in the separating space  3 . Consequently, it was confirmed that the solution exchange was securely performed among the phosphate buffer solution, the eosin, and the methylene blue dyeing liquid. 
     Third Example 
     In a Third Example, the same assay device as the abovementioned one in the First Example was used to perform the solution exchange among transparent HRP (horseradish peroxidase) labelled antibody solution, transparent phosphate buffer solution, and transparent TMB (3,3′,5,5′-tetramethylbenzidine) solution. The TMB solution is a coloring reagent using HRP as enzyme. Specifically, first, the transparent HRP labeled antibody solution was supplied to the inlet  5  of the assay device. Upon passage of approximately 3 minutes after stopping supply of the HRP labeled antibody solution, the transparent phosphate buffer solution was supplied to the inlet  5  of the assay device. Upon passage of approximately 3 minutes after stopping supply of the phosphate buffer solution, the transparent TMB solution was supplied to the inlet  5  of the assay device. In a series of operations, it was confirmed with respect to fluidity of the liquid in the assay device, the liquid absorbing level of the absorbing porous medium  2 , and the meniscus in the one end  1   a  of the microflow passage  1  in the assay device. 
     In the Third Example, it was confirmed with respect to secure flows of the HRP labeled antibody solution, the phosphate buffer solution, and the TMB solution in the assay device, performance of the absorbing porous medium  2  to securely absorb the HRP labeled antibody solution, the phosphate buffer solution, and the TMB solution, suppression of the meniscus curvature in the one end  1   a  of the microflow passage  1  in the assay device. It was further confirmed with respect to reduction in the residual liquid in the separating space  3 . Consequently, it was confirmed that the solution exchange was securely performed among the HRP labeled antibody solution, the phosphate buffer solution, and the TMB solution. 
     Fourth Example 
     In a Fourth Example, the solution exchange was performed in an assay system configured by laterally arranging and combining four assay devices according to the Third Embodiment, including a first assay device M 1 , a second assay device M 2 , a third assay device M 3 , and a fourth assay device M 4  as shown in  FIG. 15 . Referring to  FIG. 15 , the first to the fourth assay devices M 1  to M 4  were arranged in the width direction in this order. In the assay system, the first absorbing porous media  42  of the first to the fourth assay devices M 1  to M 4  were integrally connected in the width direction, and the second absorbing porous media  55  of the first to the fourth assay devices M 1  to M 4  were integrally connected in the width direction as well. 
     A pretreatment process was applied to the assay system before performing the solution exchange as described below. In the process of producing the assay system, before laminating the layers S 21  to S 31  for constituting the four assay devices M 1  to M 4 , approximately 20 μL of the antibody solution was prepared by containing the antiadiponectin antibody (GeneTex, Anti-Adiponectin, Mouse (B863M), No. GTX44473) in the phosphate buffer solution with density of approximately 20 μg/mL. The resultant antibody solution was applied to surfaces of the top portions  48   a  and the bottom portions  48   b  of the microflow passage walls  48  for defining the microflow passages  41 , and left overnight in a sealed condition. The antiadiponectin antibody was brought into the solid phase on the surfaces of the top portions  48   a  and the bottom portions  48   b  of the microflow passage walls  48 . 
     The layers S 21  to S 31  for constituting the first to the fourth assay devices M 1  to M 4  were laminated, and two droplet drops of approximately 30 μL of cleaning solution prepared by containing a surfactant (Tween20) in the phosphate buffer solution were supplied to each of the inlets  45  of the respective assay devices M 1  to M 4 . Furthermore, approximately 30 μL of stabilizing solution (Surmodics, StabilCoat) was supplied to each of the inlets  45  of the respective assay devices M 1  to M 4 . The devices were dried in the state in which the supernatant of the stabilizing solution was aspirated, and kept in the environment at the temperature of approximately 4° C. until the start of assay. 
     The solution exchange to be described below was performed in the pretreated assay system. The solution exchange was performed using adiponectin derived from the adiponectin kit (CircuLex Human Adiponectin ELISA Kit produced by Medical &amp; Biological Laboratories, Co., Ltd.), the HRP labeled antibody solution, and the TMB solution. 
     First, the two droplet drops of the cleaning solution were supplied to each of the inlets  45  of the respective assay devices M 1  to M 4 . Then the adiponectin was contained in the phosphate buffer solution to prepare approximately 30 μL of the first, the second, the third, and the fourth adiponectin solutions with densities of approximately 0 ng/mL, 40 ng/mL, 80 ng/mL, and 160 ng/mL, respectively. The first to the fourth adiponectin solutions were supplied to the inlets  45  of the first to the fourth assay devices M 1  to M 4 , respectively. Upon passage of approximately 10 minutes after stopping supply of the first to the fourth adiponectin solutions, three droplet drops of the cleaning solution were supplied to each of the inlets  45  of the respective assay devices M 1  to M 4 . 
     The HRP labeled antibody solution was supplied to each of the inlets  45  of the respective assay devices M 1  to M 4  by approximately 30 μL. Upon passage of approximately 7.5 minutes after stopping supply of the HRP labeled antibody solution, five droplet drops of the cleaning solution were supplied to each of the inlets  45  of the respective assay devices M 1  to M 4 . The TMB solution was supplied to each of the inlets  45  of the respective assay devices M 1  to M 4  by approximately 30 μL. Upon passage of approximately 10 minutes after stopping supply of the TMB solution, the state of the assay system was confirmed. 
     In the Fourth Example, it was confirmed with respect to secure flows of the cleaning solution, the adiponectin solution, the HRP labeled antibody solution, and the TMB solution in the assay system, performance of the first and the second absorbing porous media  42 , 55  to securely absorb the cleaning solution, the adiponectin solution, the HRP labeled antibody solution, and the TMB solution, darkening of each color of the first and the second absorbing porous media  42 , 55  toward the fourth assay device M 4  from the first assay device M 1  in the width direction, and suppression of each meniscus curvature in the one ends  41   a  of the microflow passages  41  in the respective assay devices M 1  to M 4 . It was further confirmed with respect to reduction in the residual liquid in each of the separating spaces  43 . Consequently, it was confirmed that the solution exchange was securely performed among the cleaning solution, the adiponectin solution, the HRP labeled antibody solution, and the TMB solution. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  31 ,  41  . . . Microflow passage 
           1   a ,  31   a ,  41   a  . . . One end 
           1   b ,  31   b ,  41   b  . . . The other end 
           2 ,  42  . . . First absorbing porous medium 
           3 ,  43  . . . Separating space 
           4 ,  44  . . . Housing space 
           5 ,  45  . . . Inlet 
           6 ,  46  . . . Sideways ventilation passage 
           7 ,  33 ,  47  . . . Connecting ventilation passage 
           8 ,  32 ,  48  . . . Microflow passage wall 
           8   a ,  32   a ,  48   a  . . . Top portion 
           8   b ,  32   b ,  48   b  . . . Bottom portion 
           9 ,  49  . . . Separating space wall 
           9   a ,  49   a  . . . Top portion 
           9   b ,  49   b  . . . Bottom portion 
           10 ,  50  . . . Guide wall 
           14 ,  54  . . . Reaction porous medium 
           59  . . . Side hole