Microchip for analyzing liquid sample
Patent Information
- Application Number
- JP2025540710
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Priority Date
- 2023-08-16
- Filing Date
- 2024-08-14
- Publication Date
- 2025-02-20
Abstract
Description
Microchip for liquid sample analysis
[0001] The present invention relates to a microchip for analyzing liquid samples.
[0002] It is known that a liquid sample such as blood is introduced into a flow channel in a microchip, and the components in the liquid sample are analyzed by reacting the sample with a reaction solution containing an antibody or the like in a reaction field provided in the middle of the flow channel. One known method for producing such a microchip is to bond a substrate having a groove formed on its surface that serves as the flow channel to a film or substrate with an adhesive.
[0003] Patent Document 1 discloses a microchip in which a reagent to be reacted with a liquid sample is previously placed in a recess and sealed with a film. However, this microchip is used by peeling off the film when in use, and is not used by passing a liquid while the liquid is retained within the film. Therefore, there has been a demand for a cheaper and easier method of producing a microchip that allows a liquid, such as a reagent, contained inside to be passed through a flow path with a simple operation and used.
[0004] JP 2009-168667 A
[0005] An object of the present invention is to provide a microchip that is made by bonding a substrate and a film together and has a flow path and a liquid storage section inside, and that can easily pass the liquid stored inside into the flow path by applying pressure during use.
[0006] The present inventors have conducted extensive research to solve the above problems. As a result, the inventors discovered a microchip for liquid sample analysis having a flow path and a liquid storage portion therein, the microchip being formed by bonding a substrate having a bonding surface with a groove that forms the flow path, a depression that is provided in part of the groove and serves as the liquid storage portion for storing the liquid, and a wall portion that is provided between the groove and the depression and blocks the outflow of the liquid from the liquid storage portion to the flow path, and a film that is attached to the bonding surface of the substrate and forms the flow path and the liquid storage portion by covering the groove, wherein, of the bonding portions between the substrate and the film, the bonding portion between the end face of the wall portion of the substrate and the film has a first bonding strength that allows peeling at a pressure of 30 kPa or more but less than 300 kPa, and the other bonding portions have a bonding strength that is stronger than the first bonding strength, thereby enabling a microchip that can stably retain liquid to be easily manufactured, and when using the obtained microchip, pressurization can be applied to the liquid stored inside to peel off the adhesion between the end face of the wall portion and the film, allowing liquid to easily pass through the flow path.
[0007] That is, the microchip of the present invention is a microchip for liquid sample analysis having a flow path and a liquid storage portion therein, comprising: a substrate having a bonding surface on which a groove forming the flow path, a depression provided in a part of the groove to serve as the liquid storage portion for storing the liquid, and a wall portion provided between the groove and the depression to block the outflow of the liquid from the liquid storage portion to the flow path, and a film attached to the bonding surface of the substrate and covering the groove to form the flow path and the liquid storage portion, wherein, of the bonding portions between the substrate and the film, the bonding portion between the end face of the wall portion of the substrate and the film has a first bonding strength that is strong enough to cause separation under a pressure of 30 kPa or more but less than 300 kPa, and the other bonding portions have a bonding strength stronger than the first bonding strength.
[0008] In one embodiment, the microchip may be such that the joint between the end face of the wall portion of the substrate and the film is joined with an adhesive having a gel fraction of 60% or more after hardening, and the other joints are joined with an adhesive having a gel fraction of 60% or more after hardening, after the joining surface of the substrate has been surface-treated so that the water contact angle is 10 to 40°.
[0009] In another aspect, the microchip may be such that the joints between the end faces of the wall portions of the substrate and the film are joined with an adhesive having a gel fraction of 60% or more after hardening, and the other joints are joined by welding. In another aspect, the microchip may be such that the joints between the end faces of the wall portions of the substrate and the film are joined with an adhesive having a gel fraction of 60% or more after hardening, after the end faces of the wall portions have been surface-treated so that they have a water contact angle of 110° or more, and the other joints are joined with an adhesive having a gel fraction of 60% or more after hardening.
[0010] In another embodiment, the microchip may be such that the joint between the end face of the wall portion of the substrate and the film is either surface-treated so that the end face of the wall portion has a water contact angle of 110° or more, or the joint other than the end face of the wall portion of the substrate has a water contact angle of 10 to 40°, and only a region of not more than half of the end face of the wall portion of the substrate downstream side is bonded with an adhesive having a gel fraction of 60% or more after hardening, and the other joints are bonded with an adhesive having a gel fraction of 60% or more after hardening.
[0011] According to the present invention, it is possible to provide a microchip that can stably hold a liquid inside during storage and can easily pass the liquid through the flow channel by applying pressure during use.
[0012] FIG. 1 is a diagram showing the substrate of a microchip before adhesive application; FIG. 2 is a diagram showing the substrate of a microchip after adhesive application; FIG. 3 is a diagram showing the completed microchip with a film attached to the substrate; FIG. 4 is a diagram showing a part of the A-A cross section of the microchip; FIG. 5 is a diagram showing the microchip in a state where the adhesive has been peeled off and liquid has been allowed to flow into the liquid storage section; FIG. 6 is a diagram showing a part of the B-B cross section of the microchip with liquid having been allowed to flow into the liquid storage section; FIG. 7 is a diagram showing the microchip in a state where the adhesive has been peeled off and liquid has been allowed to flow from the liquid storage section to the downstream flow path; FIG. 8 is a diagram showing the structure of the substrate of the microchip of Examples 1, 2 and 3.
[0013] The present invention relates to a microchip for analyzing liquid samples, having a flow path and a liquid storage portion therein, comprising: a substrate having a bonding surface on which a groove forming the flow path, a depression provided in part of the groove to serve as the liquid storage portion for storing the liquid, and a wall portion provided between the groove and the depression for blocking the outflow of the liquid from the liquid storage portion to the flow path; and a film attached to the bonding surface of the substrate and covering the groove to form the flow path, wherein of the bonding portions between the substrate and the film, the bonding portion between the end face of the wall portion of the substrate and the film has a first bonding strength that is strong enough to cause separation under a pressure of 30 kPa or more but less than 300 kPa, and the other bonding portions have a bonding strength stronger than the first bonding strength.
[0014] When the microchip is used to analyze specimens such as biological samples, the liquid stored in the liquid storage section is preferably a solution, suspension, or cleaning solution of a reagent (reactant) that reacts with the analyte contained in the specimen. Examples of reactions include biological reactions and chemical reactions, including binding reactions. Examples of reagents include, but are not limited to, antibodies, enzymes, proteins (including peptides) such as receptors, nucleic acids such as DNA and RNA, sugar chains, and low-molecular-weight compounds that bind to biological components. These substances may be labeled with fluorescent substances or immobilized on a carrier or carrier. Examples include substances such as antibodies that specifically bind to the target (detection target) substance in the specimen, enzyme proteins that use the target substance as a substrate, and blood coagulation factors such as PT reagents. When the target substance is nucleic acid, the reactant may be a nucleic acid probe or a polymerase (nucleic acid amplification enzyme) that amplifies the nucleic acid. When the microchip is used to culture or analyze cells or microorganisms, the liquid stored in the liquid storage section may be a culture medium for cells or microorganisms.
[0015] A recess that serves as a liquid storage area, which is an area for storing liquid, is formed in a portion of the groove that forms the flow path of the microchip substrate, and the liquid is stored in advance in the recess that will become the liquid storage area. Then, with the liquid stored in the recess, a film is bonded to form the flow path and the liquid storage area. A wall for blocking the outflow of liquid from the liquid storage area to the flow path is provided between the liquid storage area and the flow path, preferably at the connection between the liquid storage area and the flow path, and more preferably at the connection between the liquid storage area and the upstream flow path and the connection between the liquid storage area and the downstream flow path. By bonding the end face of the wall to the film, the liquid is retained within the liquid storage area and sealed so as not to flow into the flow path. If either the upstream flow path or the downstream flow path does not exist, the wall need only be the connection between the liquid storage area and the upstream flow path or the downstream flow path.
[0016] The bonded portion between the end face of the wall portion of the substrate and the film is bonded with a first bonding force sufficient to cause separation under pressure of 30 kPa or more but less than 300 kPa. Therefore, applying a pressure of 30 kPa or more but less than 300 kPa to the microchip causes the end face of the wall portion to separate from the film, allowing the liquid to pass from the liquid reservoir into the flow path. Meanwhile, the bonded portion of the substrate's bonding surface other than the end face of the wall portion (excluding the end face of the wall portion, the grooves that form the flow path, the depressions that form the liquid reservoir, and, if present, the through-holes that form the inlet, the through-holes that form the outlet, and the grooves that form the waste liquid reservoir) is bonded to the film with a bonding force stronger than the first bonding force. This allows selective separation of only the bonded portion between the end face of the wall portion and the film, thereby controlling the flow of liquid. If the pressure for separating the end face of the wall portion from the film is less than 30 kPa, there is a high risk of unexpected separation due to operations that are not intended for liquid flow or even a slight impact. If the pressure is 300 kPa or more, it becomes difficult to control the liquid immediately after the liquid has passed through. Furthermore, pressures of 300 kPa or higher increase the risk of damage to unexpected areas other than the wall end faces, making this unsuitable for practical use in microchips. For this reason, the pressure used to peel the wall end faces and the film should be between 30 kPa and 300 kPa.
[0017] The microchip for liquid sample analysis of the present invention and its manufacturing method will be described below with reference to the drawings. However, the following is merely an example, and the manufacturing method of the present invention and the microchip obtained thereby are not limited to the following aspects.
[0018] 1 shows a plan view of a substrate 110 in which grooves 111 forming flow paths 111 of a microchip 100 are dug in the surface. A depression is provided in part of the groove 111 to serve as a liquid storage section 116, which is a region for storing liquid. Walls 114a and 114b that block the outflow of liquid are provided on the upstream and downstream sides, respectively, between the liquid storage section 116 and the groove 111. Of the walls 114a and 114b, the surfaces facing the film 120 to be bonded are also referred to as (wall) end faces 114a and 114b. The surface in which the grooves 111 are dug is the surface to be bonded to the film 120, and is also referred to as a bonding surface 115.
[0019] A through-hole serving as an inlet 112 for pressurizing the liquid is provided at one end of the groove 111 upstream of the liquid storage section 116, and a through-hole serving as an outlet 113 (discharge port) for the outflow of the liquid or air is provided at the other end. Pressure is applied to the liquid stored in the liquid storage section 116 using, for example, a microsyringe or a pump. It is also possible to pressurize the liquid by blocking the inlet 112 with a finger or a simple pressurizing member.
[0020] Two or more flow paths 111 may be provided. The shape of the flow path 111 does not matter, and it may be straight or curved. Furthermore, the flow path 111 may have a branch. In this case, there may be two or more inlet ports 112, liquid storage portions 116, wall portions 114a and 114b, and / or outlet ports 113.
[0021] For example, a liquid sample is stored in a first liquid storage section provided in the first flow path, and a substrate reaction liquid (reactant) is stored in a second liquid storage section provided in the second flow path. When pressurized through the corresponding inlets (pressure ports), the liquid sample and the substrate reaction liquid are separated from the end face of the wall and the film, allowing the liquid to pass through the flow path beyond the liquid storage sections. The first and second flow paths merge beyond the first and second liquid storage sections. By providing a reaction field in the confluent region, the liquid sample reacts with the substrate reaction liquid. In this case, the outlet may be provided at the downstream end of the merged flow paths.
[0022] Furthermore, a washing liquid may be stored in a third liquid storage section provided in the third flow path, and after the reaction between the liquid sample and the reaction substrate liquid, the washing liquid may be passed through the flow path of the microchip 100. For example, the third flow path is formed so as to join the first liquid storage section and the second liquid storage section on the upstream side, and the washing liquid is passed through the first flow path and the second flow path by pressurization from an inlet (pressure port).
[0023] The inlet 112 and the outlet 113 may be provided on either the substrate 110 or the film 120. For example, a groove 111 that will become the flow path 111 may be provided on the substrate 110, and a film 120 having through-holes at positions overlapping both ends of the groove 111 may be prepared and attached to the substrate 110. Furthermore, one of the through-holes that will become the inlet 112 and the outlet 113 may be provided in the substrate 110, and the other may be provided in the film 120.
[0024] The cross-sectional shape of the groove 111 that becomes the flow path 111 can be any shape, such as a concave, U-shaped, or V-shaped. The depth of the groove 111 that becomes the flow path 111 is preferably 10 to 1000 μm. The width of the groove 111 is preferably 10 μm to 4 mm, and particularly preferably 50 μm to 4 mm. A width of less than 10 μm increases the risk of blockage due to the inflow of adhesive into the flow path, and welding techniques are not possible because the shape of the flow path would be deformed by high heat. Welding techniques are difficult for widths between 10 μm and 50 μm, but bonding can be achieved using adhesive. A width of 50 μm to 2 mm allows for good bonding with either method. On the other hand, a width greater than 4 mm increases the likelihood of rupture at unexpected locations other than the end surface 114a of the wall portion 114 when pressure is applied to penetrate the wall portion 114. This is because, as the area of the film 120 not bonded to the substrate 110 increases, a greater peel force is applied to the surface of the film not bonded to the substrate when pressure is applied to the flow channel to penetrate the end face of the wall. The length of the portion corresponding to the flow channel 111, including the thickness of the wall 114 (the longitudinal length of the flow channel 111), is, for example, 3 mm to 5 cm. The width of the groove 111 may be constant or may vary. The depth of the groove 111 may also be constant or may vary. Note that, in order to control the direction of the liquid flow, the groove 111 that becomes the flow channel 111 of the substrate 110, the portion of the film 120 covering the flow channel 111, the wall surfaces on both sides of the wall 114, etc. are hydrophilized. The hydrophilization treatment may also be applied to the depression that becomes the liquid storage portion 116 and the portion of the film 120 covering the liquid storage portion 116.
[0025] The width of the groove 111 (width of the flow path 111) may be narrower than the width of the walls 114a and 114b. By making the width of the walls 114a and 114b wider than the width of the flow path 111, the flow rate of the liquid passing through the gap between the end faces 114a and 114b of the walls 114a and 114b and the film 120 increases, making the liquid more likely to flow.
[0026] The depression that becomes the liquid storage section 116 may be large enough to store a desired amount of liquid, and its shape is not particularly limited, but may be cylindrical or prismatic, for example, and by increasing the area and depth, it is possible to store a larger amount of liquid. The area of the depression may be, for example, 0.1 to 50 mm ２ and in the case of a circular liquid storage portion 116, its diameter is, for example, 0.2 to 6 mm. However, the area may vary depending on the depth of the groove, and may be, for example, a cone-shaped depression. The depth of the depression is preferably greater than the depth of the groove that becomes the flow path, and is, for example, 20 μm to 3 mm. If the area of the depression, i.e., the area of the film 120 that is not bonded to the substrate 110, becomes large, there is a risk that the liquid storage portion will break at a pressure lower than that at which the wall portion 114 is penetrated. In order to prevent unexpected breakage of the liquid storage portion, for example, the area of the depression should be 4 mm ２ If the water contact angle exceeds this value, it is desirable that the joint between the end face of the wall of the substrate 110 and the film 120 be surface-treated so that the end face of the wall has a water contact angle of 110° or more, or that the joint portion other than the end face of the wall of the substrate be surface-treated so that the water contact angle is 10 to 40°, and then the end face of the wall of the substrate is bonded with an adhesive having a gel fraction of 60% or more after curing only in a region of less than half of the downstream side of the end face of the wall of the substrate. This method allows penetration only through the end face of the wall with a relatively low pressure of 30 to 80 kPa, preventing unexpected collapse of the liquid storage section. It is also possible to prevent collapse of the liquid storage section by bonding a plate material with a thickness of 0.5 mm or more only to the liquid storage section of the film surface, thereby physically suppressing deflection of the film when pressure is applied to the liquid storage section. As a means of physically suppressing deflection of the film, even without bonding a plate material to the liquid storage section of the film surface, mechanically pressing the same area can also prevent collapse of the liquid storage section.
[0027] The walls 114a and 114b are provided to prevent the liquid stored in the liquid storage section 116 from flowing into the flow path 111. The thickness of the walls 114a and 114b (the length in the longitudinal direction of the flow path 111) may be such that the pressurized liquid separates the end faces 114a and 114b of the walls 114a and 114b from the film 120 and passes from the liquid storage section 116 to the flow path 111, but is preferably 400 μm to 5 mm. Even if the thickness of the adhesive applied to the substrate 110 is a thin film of 5 to 10 μm, when the film 120 is pressed against the substrate 110, the edges of the applied adhesive will spread by approximately 100 to 200 μm, depending on the pressure. Therefore, if the length of the wall is less than 400 μm, it becomes difficult to apply the adhesive to only half or less of the wall end face. On the other hand, if the length of the wall portion exceeds 5 mm, the amount of liquid passing through the end face of the wall portion after penetration is small, making it unsuitable for practical use. The thickness of the wall portions 114a and 114b may be constant or may vary. The wall surfaces of the wall portions 114a and 114b may be inclined so that the thickness of the wall portions 114a and 114b becomes thinner as they approach the end faces 114a and 114b. By making the wall surfaces of the wall portions 114a and 114b inclined or stepped, and by configuring the liquid storage portion 116 so that the depth becomes shallower closer to the wall portions 114a and 114b, liquid can easily flow between the end faces 114a and 114b and the film 120, making it easier for the end faces 114a and 114b to peel off from the film 120. Specifically, by making the depth of the portions 1 to 4 mm from the wall portions 114a and 114b toward the pressure source shallower, it becomes easier to peel the wall portions 114a and 114b from the film 120. If the distance of the shallow portions from the wall portions is less than 1 mm, the area of the film 120 that bends when pressure is applied is small, making it difficult to achieve the effect of making peeling easier. On the other hand, if the distance exceeds 4 mm, the area of the film 120 that bends when pressure is applied is large, making it difficult to penetrate only the wall portions. The depth may be shallower than the groove 111, but a depth of 5 to 30 μm is more preferable. The height of the wall portions 114a and 114b may be formed to be approximately the same height as the joining surface 115, or may be formed to be lower than the joining surface 115.
[0028] The size of the through-hole that serves as the inlet 112 may be large enough to pressurize the liquid in the liquid storage section 116 using a microsyringe or a pump connected via an adapter. The size of the through-hole that serves as the inlet 112 is, for example, 0.2 to 3 mm in diameter. The size of the through-hole that serves as the outlet 113 is not particularly limited as long as it functions as an outlet for the liquid sample. The size of the through-hole that serves as the outlet 113 is, for example, 0.2 to 3 mm in diameter.
[0029] The material of the microchip 100 (substrate) can be metal, glass, plastic, silicone, etc., but from the viewpoint of detecting the reaction by light emission, color development, or visual observation, a transparent material is preferable, and transparent plastic is more preferable. Examples of the material of the microchip 100 include polyethylene, polypropylene, polystyrene, polymethyl methacrylate, cycloolefin polymer, cycloolefin copolymer, polyphenylene oxide, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyamide, polyimide, phenol resin, epoxy resin, polyvinylidene chloride, polyvinyl chloride, acrylonitrile-butadiene-styrene (ABS) resin, poly (2-methoxyethyl acrylate) (PMEA) resin, etc.
[0030] Grooves 111 and through-holes provided in substrate 110 of microchip 100 can be dug with a blade or a laser beam, but can also be formed by injection molding when microchip 100 is made of plastic. Formation by injection molding is preferable because microchip 100 can be produced efficiently with consistent quality.
[0031] The material of the film 120 is preferably a transparent plastic, and more preferably polyethylene terephthalate (PET) resin, cycloolefin polymer (COP) resin, cycloolefin copolymer (COC) resin, polystyrene (PS) resin, polycarbonate (PC) resin, or polymethyl methacrylate (PMMA) resin. Furthermore, using a moisture-proof film as the film is preferable because it can prevent the stored liquid from evaporating. The degree of moisture-proofness is, for example, a water vapor permeability of 1.5 g / m. 2- The water vapor permeability is 0.25 to 1.5 g / m or less. 2 ・It is preferable that the concentration is 0.25 to 0.5 g / m 2 It is more preferable that the thickness is 10 μm or more. The moisture-proof film may be polytetrafluoroethylene (PCTFE) alone, a multilayer film containing PCTFE, or a vapor-deposited film. Examples of multilayer films containing PCTFE include a four-layer film consisting of, from the outermost layer, PCTFE, maleic anhydride-modified polyethylene (MAPE), linear low-density polyethylene (LL), and cycloolefin polymer (COP) resin, and a five-layer film consisting of, from the outermost layer, PCTFE, MAPE, ethylene-vinyl alcohol copolymer resin (EVOH), MAPE, and COP. To achieve moisture resistance, the thickness of the PCTFE layer is preferably 10 μm or more, and more preferably 20 μm. Examples of vapor-deposited films include films of polyethylene terephthalate (PET) vapor-deposited with aluminum, alumina, silica, nylon, alumina, and silica. Aluminum may be used alone. The moisture-proof film is not limited to the above and may be a multilayer film containing one or more of films such as polytetrafluoroethylene (PTFE) and perfluoroalkoxyalkane (PFE). The total thickness of the film 120 is preferably 10 to 200 μm, more preferably 100 to 200 μm. The Young's modulus (tensile elastic modulus) of the film material is preferably 50 to 2800 MPa, more preferably 70 to 1000 MPa. Using a film with the above total thickness and Young's modulus makes it possible to specifically peel only the wall end surface 114a by applying pressure. Depending on the film material, if the total thickness of the film 120 exceeds 200 μm and the Young's modulus of the film exceeds 2800 MPa, the film will not deform even when pressure is applied, making it difficult to penetrate the wall 114.
[0032] With liquid stored in liquid storage section 116 of substrate 110, substrate 110 and film 120 are joined together to obtain microchip 100.
[0033] Among the joints between the substrate 110 and the film 116, the joints between the wall end surfaces 114a and 114b of the substrate 110 and the film 116 have a first bonding strength that causes separation when subjected to a pressure of 30 kPa or more but less than 300 kPa, while the other joints have a stronger bonding strength than the first bonding strength. A stronger bonding strength than the first bonding strength is not particularly problematic as long as it is stronger than the first bonding strength, but for example, it is a bonding strength that does not cause separation when subjected to a pressure of at least 300 kPa. That is, the joints between the wall end surfaces of the substrate and the film are subjected to a first bonding treatment, and the other joints are subjected to a second bonding treatment. Here, "other joints" refers to joints between the substrate and the film other than the joints between the wall end surfaces of the substrate and the film. Specifically, it refers to the joints between the film and the regions of the joint surface of the substrate excluding the grooves that form the flow paths, the depressions that form the liquid storage portions, the outflow ports and the through-holes that form the outflow ports, and the wall end surfaces (hereinafter also referred to as joint regions other than the wall end surfaces). If there is a depression that will serve as a waste liquid reservoir, this area is also excluded.
[0034] The first and second bonding treatments may both be treatments using an adhesive, or the first bonding treatment may be a treatment using an adhesive and the second bonding treatment may be a welding treatment. In the former case, in order to vary the adhesive strength between the bonded portion between the wall end surface of the substrate and the film and the other bonded portions, it is preferable to perform a surface treatment on either the wall end surface of the substrate or a bonding region other than the wall end surface. By performing the surface treatment and then applying an adhesive, the adhesive bonding strength can be varied.
[0035] As the adhesive, it is preferable to use an adhesive with a gel fraction of 60% or more after curing, and more preferably an adhesive with a gel fraction of 80% or more. By using an adhesive with a gel fraction of 60% or more after curing, it is possible to apply the pressure required to penetrate the wall 114 to the inside of the flow path. On the other hand, an adhesive with a gel fraction of less than 60% after curing has an insufficient degree of cross-linking, resulting in a structure that allows air to pass through. As a result, pressure is lost before the inside of the flow path reaches the pressure of 30 to 300 kPa required to penetrate the wall 114, and the wall 114 cannot be penetrated.
[0036] The gel fraction of the adhesive after curing can be measured, for example, by the following method. The adhesive is applied to a substrate to prepare a test piece of a certain area. The test piece is immersed in toluene at 23°C for 24 hours, then removed from the toluene and dried at 110°C for 1 hour. The weight of the dried test piece is measured, and the gel fraction is calculated using the following formula (1): Gel fraction (wt%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (1) (W ０ : Weight of substrate, W １ : weight of test piece before immersion, W ２ : weight of test piece after immersion and drying)
[0037] Adhesives with a gel fraction of 60% or more after curing, depending on the composition and curing conditions, include (meth)acrylic resin adhesives, natural rubber adhesives, urethane resin adhesives, ethylene-vinyl acetate resin emulsion adhesives, ethylene-vinyl acetate resin adhesives, epoxy resin adhesives, vinyl chloride resin solvent-based adhesives, chloroprene rubber adhesives, cyanoacrylate adhesives, silicone adhesives, styrene-butadiene rubber solvent-based adhesives, nitrile rubber adhesives, nitrocellulose adhesives, phenolic resin adhesives, modified silicone adhesives, polyester adhesives, polyamide adhesives, polyimide adhesives, olefin resin adhesives, vinyl acetate resin emulsion-based adhesives, polystyrene resin solvent-based adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone resin adhesives, polyvinyl butyral adhesives, polybenzimidazole adhesives, polymethacrylate resin solvent-based adhesives, melamine resin adhesives, urea resin adhesives, resorcinol adhesives, etc. Adhesives with a gel fraction of 60% or more after curing can be used alone or in combination of two or more.
[0038] Adhesives with a gel fraction of 60% or more after curing are preferably photocurable (either radically reactive or cationic polymerizable), and more preferably ultraviolet curable (UV curable). If a UV curable adhesive is used, the curing reaction can be initiated quickly by irradiating UV light after the application process, allowing bonding. Examples of UV-curable adhesives include UVX-8204 (manufactured by Denka Co., Ltd.), UVX-8400 (manufactured by Denka Co., Ltd.), SX-UV100A (manufactured by Cemedine Co., Ltd.), SX-UV200 (manufactured by Cemedine Co., Ltd.), BBX-UV300 (manufactured by Cemedine Co., Ltd.), U-1340 (Chemitech Co., Ltd.), U-1455B (Chemitech Co., Ltd.), U-1558B (Chemitech Co., Ltd.), Aronix UV-3000 (Toagosei Co., Ltd.), TB3094 (ThreeBond Co., Ltd.), and Hitaloid 7975D (Hitachi Chemical Co., Ltd.). Acrylic UV-curable adhesives exhibit good adhesion to a wide range of plastic materials and can rapidly develop strength after UV irradiation. The viscosity of the adhesive used to attach the film 120 to the substrate 110 is preferably, for example, 2,000 to 31,000 mPa·s.
[0039] When applying adhesive to the end face of the wall, more than half of the end face of the wall (the first half of the longitudinal direction of the flow path at the end face) may be left uncoated with adhesive, and pressure may be applied from the uncoated side. That is, adhesive may be applied only to the downstream half of the end face of the wall on the liquid storage section side (i.e., the latter half of the longitudinal (flow) direction of the flow path at the end face). Less than half (1 / 2) may be, for example, 1 / 2 to 1 / 5. That is, the substrate may be bonded to the film by applying adhesive to an area of 1 / 2 or less of the end face of the wall, which corresponds to the downstream side of the flow path. In this embodiment, applying pressure from the upstream side increases the peel angle between the end face and the film, thereby reducing the peel stress compared to when the peel angle is 0°.
[0040] In an embodiment in which the first joining treatment is a treatment using an adhesive and the second joining treatment is a welding treatment, the joint between the wall end surface of the substrate and the film is joined with an adhesive having a gel fraction of 60% or more after hardening, and the other joints are joined by welding.
[0041] Examples of welding methods include heat sealing (also called thermal welding), laser welding, and ultrasonic welding, with heat sealing being particularly preferred. Heat sealing allows for efficient welding using a simple device consisting of a pressure mechanism and a heater. In order to accurately heat-seal only the desired bonding area other than the wall end surface of the substrate 110, it is preferable to use a stainless steel or aluminum jig having the same convex shape as the desired bonding area. The film 120 is placed on the convex shape of the jig, and the substrate 110 is placed on top of it with the bonding surface 115 facing the film 120. A high-temperature heat treatment is then performed using a temperature-controllable press, thereby bonding only the convex-shaped area. The pressure can be applied from the film side, the substrate side, or both sides, and is not particularly limited. The pressure is not particularly limited as long as it is sufficient to bond the materials together and does not deform the flow path shape, but a pressure of 0.1 to 12.0 MPa is preferred. The temperature during bonding depends on the materials to be bonded, but can be set to ±10°C of the glass transition temperatures of the substrate 110 and the film 120. More preferably, the surface of the substrate 110 can be set to a temperature 1 to 10°C lower than the glass transition temperature of the substrate 110, and the surface of the film 120 can be set to a temperature 1 to 10°C higher than the glass transition temperature of the film 120. This makes it possible to heat seal the substrate 110 while maintaining the shape of the flow channel. Bonding is also possible by raising the surface of the substrate 110 above the glass transition temperature, but this is not practical because it would deform the shape of the flow channel. The time required for heat sealing depends on the materials to be bonded, and is not particularly limited as long as the bonding is achieved and the shape of the flow channel is not deformed; for example, 5 seconds to 2 hours is preferred.
[0042] Laser welding allows for stronger and more precise joining than heat sealing, and is therefore preferred when strength is required at joints other than the wall end faces. Highly transparent amorphous resins such as COP, polycarbonate, and PMMA can be used for good joining, but the materials are not particularly limited. The transparency of one of the resins required for laser welding requires, for example, a laser transmittance of 30% or more. A gray or black material with high light absorption can be used for the other resin, and a highly light-absorbent marking can be applied only to the laser-welded portion of the transparent material. A substrate 110 with a laser transmittance of 30% or more is placed on top, and a laser-absorbing film 120 is placed on the bottom so that it is aligned with the substrate 110. Laser welding of the substrate 110 and film 120 is possible by irradiating the film from above with a laser. When using a laser-absorbing substrate 110 and a film 120 with a laser transmittance of 30% or more, the laser can be irradiated from below, or the substrate 110 can be placed on the bottom and the film 120 on the top, and the laser can be irradiated from above; these methods can be modified as appropriate. The laser method is not particularly limited, but a heat sink-type laser resin welding method is particularly preferred. With the heat sink method, the substrate 110 and the film 120 can be joined even if they are made of the same transparent material, and the heat sink (heat dissipator) can prevent temperature increases on the surface and inside of the components, resulting in a highly accurate flow path.
[0043] Ultrasonic welding can bond thermoplastic resins even if they are colored or dirty, and can simultaneously bond multiple points in a short time. The duration of ultrasonic treatment is not particularly limited as long as bonding is achieved, but a period of 1 to 10 seconds is preferred. The operating frequency of the ultrasonic welder is preferably 15 kHz to 200 kHz.
[0044] The end surface of the wall of the substrate is bonded to the film with an adhesive that has a gel fraction of 60% or more after curing, so the bonded portion peels off at a pressure of 200 kPa or more but less than 300 kPa. On the other hand, the other bonded portions of the substrate are bonded using a welding technique such as heat sealing, so a pressure of approximately 1000 kPa or more is required for peeling, although this depends on the shape of the flow path, and peeling does not occur at a pressure of 200 kPa or more but less than 300 kPa. Therefore, the bonded portion between the end surface of the wall of the substrate and the film can be selectively peeled off at a pressure of 200 kPa or more but less than 300 kPa.
[0045] Next, an embodiment will be described in which the bonding strength is changed by performing a surface treatment on either the end face of the wall portion of the base material or a bonding region other than the end face of the wall portion, and then applying an adhesive thereto.
[0046] In one embodiment, the wall end faces of the substrates are not surface-treated, and the bonding regions other than the wall end faces of the substrates are surface-treated so that the bonding surfaces of the substrates have a water contact angle of 10 to 40°, and then bonded with an adhesive having a gel fraction of 60% or more after curing. Depending on the type of adhesive used, the water contact angle of the bonding surfaces of the substrates is preferably 10 to 40°. By achieving a water contact angle of 10 to 40° on the bonding surfaces of the substrates, the adhesive's wettability with the substrates is improved, allowing the adhesive to conform to the fine irregularities (10 nm or less) on the substrate surface. The adhesive solidifies while wet on the substrate surface, thereby achieving strong bonding strength. Even when the water contact angle of the substrate is less than 10°, strong bonding can be expected, but due to its high wettability, it becomes difficult to precisely apply the adhesive only to the desired positions, increasing the risk of the adhesive flowing into the flow channel, making it unsuitable for practical use. On the other hand, when the water contact angle exceeds 40°, the adhesive is less likely to wet the bonding surfaces of the substrates uniformly, and sufficient bonding strength cannot be expected.
[0047] Here, atmospheric pressure plasma treatment, vacuum plasma treatment, corona treatment, excimer treatment, etc. can be used as hydrophilic treatments to achieve a water contact angle of 10 to 40°. However, vacuum plasma is preferred because it can be performed at room temperature and does not cause deformation of the flow path shape. Gases that can be used for vacuum plasma treatment include oxygen, nitrogen, argon, etc., but air is particularly preferred. Specifically, plasma is used that consists of ordinary air, with a volumetric ratio of approximately 78% nitrogen, approximately 21% oxygen, and approximately 1% argon, and a lower percentage of carbon dioxide, under a medium vacuum of 100 to 0.1 Pa.
[0048] The wall end surfaces of the substrate are bonded to the film without surface treatment (the water contact angle of the substrate surface without surface treatment is usually 80 to 100°, depending on the type of substrate), using an adhesive with a gel fraction of 60% or more after curing, so the bonded portion peels off at a pressure of 200 kPa or more but less than 300 kPa. Meanwhile, the other bonded portions of the substrate are bonded with an adhesive with a gel fraction of 60% or more after curing, after the bonding surface of the substrate is surface treated so that the water contact angle is 10 to 40°, so a pressure of approximately 500 kPa is required for peeling, but peeling does not occur at a pressure of 200 kPa or more but less than 300 kPa. Therefore, the bonded portions between the wall end surfaces of the substrate and the film can be selectively peeled off at a pressure of 100 kPa or more but less than 200 kPa.
[0049] In another embodiment, the joint between the end face of the wall portion of the substrate and the film is formed by surface-treating the end face of the wall portion so that the water contact angle is 110° or more, and then bonding is performed with an adhesive having a gel fraction of 60% or more after hardening, and other joints are formed with an adhesive having a gel fraction of 60% or more after hardening.
[0050] By increasing the water contact angle of the bonding surface of the substrate 110 to 110° or greater, the wettability of the adhesive to the substrate 110 decreases, resulting in a lower bond strength. Examples of surface treatments (hydrophobic treatments) that achieve a water contact angle of 110° or greater include fluorine coating and silicone treatment. Examples of fluorine coating agents include Fluorosurf FS-1610C-4.0 (Fluorotechnology Co., Ltd.), water- and oil-repellent fluorine coating agent GF03 (Gust Japan Co., Ltd.), Guardsurf AZ-6000 (Harves Co., Ltd.), and fluorine coating agent INT series (Noda Screen Co., Ltd.). In this case, a fluorine-based resin concentration of 0.2 to 0.8% is preferred. Examples of silicone treatment agents include dimethyl silicone, methylphenyl silicone, methylhydrogen silicone, and modified silicones in which various organic groups have been introduced into some of the methyl groups. In this case, a spray type with a silicone concentration of 0.01 to 10% is preferred.
[0051] The wall edge of the substrate is surface-treated to have a water contact angle of 110° or more, and then bonded to the film with an adhesive that has a gel fraction of 60% or more after curing, so the bonded area peels off at a pressure of 80 to 150 kPa. Meanwhile, the other bonded areas of the substrate are bonded without surface treatment (the water contact angle of the substrate surface without surface treatment is typically 80 to 100°) with an adhesive that has a gel fraction of 60% or more after curing, so a pressure of approximately 200 to 300 kPa is required for peeling, and peeling does not occur at a pressure of 80 to 150 kPa. Therefore, the bonded areas between the wall edge of the substrate and the film can be selectively peeled off at a pressure of 80 to 150 kPa.
[0052] Referring to Figure 2, we will explain the adhesive application process in an embodiment in which a fluorine coating is applied only to the wall end surfaces, and then the substrate and film are bonded with an adhesive having a gel fraction of 60% or more after curing. However, the adhesive application process can be performed in a similar manner even in an embodiment in which the bonding area other than the wall end surfaces is plasma-treated and bonded with an adhesive having a gel fraction of 60% or more. First, a substrate 110 is prepared, which has two through-holes on its surface that serve as an inlet and outlet, a groove that serves as a flow path, a recess that serves as a liquid storage area, and a wall portion, and the end surface of the wall portion is fluorine-coated. The fluorine coating can be performed using, for example, Fluorosurf FS-1610C-4.0. Next, adhesive 117 is applied to bonding surface 115 by screen printing. Note that Figure 2 shows substrate 110 of microchip 100 after adhesive application.
[0053] In another embodiment, the joint between the wall and the film is surface-treated so that the end surface has a water contact angle of 110° or more, or the wall end surface of the substrate is not surface-treated but the joint area other than the wall end surface of the substrate is surface-treated so that the water contact angle is 10 to 40°, and only half or less of the downstream side of the wall end surface of the substrate is bonded with an adhesive having a gel fraction of 60% or more after curing, while the other joints are bonded with an adhesive having a gel fraction of 60% or more after curing. This allows the joint between the wall end surface of the substrate and the film to be selectively peeled with a pressure of 30 to 80 kPa. On the other hand, the other joints of the substrate are not surface-treated and are bonded with an adhesive having a gel fraction of 60% or more after curing, so a pressure of approximately 200 to 300 kPa is required for peeling, and peeling does not occur with a pressure of 30 to 80 kPa. Therefore, the joint between the wall end surface of the substrate and the film can be selectively peeled with a pressure of 30 to 80 kPa.
[0054] The adhesive 117 is applied to the bonding surface 115 of the substrate 110 in an area other than the groove 111, the liquid storage portion 116, the inlet 112, and the outlet 113. For accurate application, the adhesive 117 is preferably applied by a printing technique, and more preferably by screen printing. By using screen printing, even when the adhesive 117 is filled into a screen printing plate in an area that covers the entire surface of the substrate 110, the adhesive 117 is transferred to the application area that comes into contact with the screen printing plate, but the adhesive 117 is not transferred to the groove 111 and the recess that becomes the liquid storage portion 116 that do not come into contact. Therefore, the adhesive 117 can be accurately applied to the desired application area.
[0055] The thickness of the adhesive 117 applied to the substrate 110 is preferably 5 to 15 μm. To control the thickness of the adhesive 117, the number of meshes per inch of the screen is preferably, for example, 500 to 730. The opening rate of the mesh is preferably, for example, 39 to 47%. The thickness of the mesh is preferably, for example, 15 to 28 μm. As a result, the thickness of the applied adhesive 117 is preferably 5 to 15 μm.
[0056] Other methods for applying the adhesive 117 to the substrate 110 include inkjet printing, gravure printing, and a dispenser, which allow the adhesive to be precisely applied to the desired application area. With these application techniques, when the adhesive 117 is ejected into the grooves 111, the adhesive 117 applied inside the grooves 111 changes the shape of the flow paths 111. Therefore, the printing process and dispenser operation may be controlled by a program, by capturing an image of the positions of the grooves 111 in the substrate 110, or by fixing the positions of the printing stage and the substrate 110, so that the adhesive 117 is applied to the desired application area.
[0057] <Bonding Process> With reference to Fig. 3, a process of preparing film 120, storing liquid in the liquid storage portion, and then bonding film 120 to substrate 110 will be described. Fig. 3 is a diagram of a completed microchip in which film 120 is bonded to substrate 110. Fig. 3 shows a plan view of microchip 100 obtained by bonding film 120 to bonding surface 115 of substrate 110, in which grooves 111 and liquid storage portions 116 are dug. Channels 111 formed inside microchip 100 are indicated by dashed lines.
[0058] By laminating and bonding the film 120 onto the substrate 110, the groove 111 and the upper portion of the depression that will become the liquid storage portion 116 are covered with the film 120, forming the flow path 111 through which the liquid passes, and the liquid storage portion 116. The liquid is also retained within the liquid storage portion 116 by the walls 114a and 114b. The adhesive 117 hardens by UV irradiation to form an adhesive portion. By applying the adhesive to a predetermined application area by screen printing in this way, and then laminating and bonding the film 120 onto the substrate 110, it is possible to bond the substrate 110 and the film 120 and form a structure that blocks the outflow of liquid in the same process.
[0059] Furthermore, by laminating the film 120, the through-holes of the substrate 110 are sealed on the bonding surface 115 side, and only the surface opposite to the bonding surface 115 becomes an inlet. As a result, the through-holes of the substrate 110 function as an inlet 112 and an outlet 113.
[0060] 3 to 8, the flow of the liquid stored in the liquid storage portion 116 will be described below. Fig. 4 is a diagram showing a part of the cross section AA of the microchip 100 shown in Fig. 3.
[0061] For example, a solution of a reagent that reacts with a target substance in a liquid sample is stored in the liquid storage unit 116 (FIGS. 3 and 4). The reagent that reacts with the target substance in the liquid sample may be supported on a carrier such as beads and then stored in the liquid storage unit. The liquid storage unit may also store a stirrer for stirring the reagent that reacts with the target substance in the liquid sample or the carrier such as beads that supports the reagent.
[0062] A film 120 is attached to the substrate 110, and the end faces 114a, 114b of the wall portion and the film 120 are sealed by being joined with an adhesive or the like, so that the liquid in the liquid storage portion 116 does not flow into the flow path 111.
[0063] During use, a liquid sample is introduced under pressure from inlet 112 using a syringe or the like, causing the liquid sample to pass through the flow path and reach the wall just before the liquid reservoir. Here, pressure causes end surface 114a of wall 114 to peel away from the film, allowing the liquid sample to pass into the liquid reservoir and mix with the reaction liquid previously stored in the liquid reservoir (FIGS. 5 and 6). Note that the bond between the substrate and the film, except for the bond between the wall end surface and the film, is stronger than the bond between the wall end surface and the film. Therefore, the bond does not peel even when pressure is applied, allowing stable liquid flow control.
[0064] FIG. 6 shows a portion of the B-B cross section of microchip 100 shown in the figure, in which end surface 114a of wall portion 114 and film 120 have been peeled off, and the liquid sample has passed through flow channel 111 and into liquid storage portion 116.
[0065] A substance in a liquid sample reacts with a reactant (reagent) in a reaction solution, and the liquid sample can be analyzed by detecting this reaction. The target substance in the sample can be measured by observing or detecting the reaction. Examples of reactions include, but are not limited to, color reactions, luminescence reactions, amplification reactions, and agglutination reactions.
[0066] Examples of liquid samples include liquid samples obtained from living organisms such as blood and urine, or diluted solutions thereof, extracts from living organisms such as plants and animals, naturally occurring water such as rivers, oceans, and rainfall, cleaning solutions, wastewater, etc. The components in the sample (target substances to be measured) are also not particularly limited, and examples thereof include proteins, nucleic acids, low-molecular-weight compounds, and sugars.
[0067] After the reaction, further pressurization and liquid passage can peel off downstream wall 114b separating the liquid storage portion from the downstream flow path, allowing the liquid (mixed liquid) in the liquid storage portion to flow into the downstream flow path ( FIGS. 7 and 8 ). FIG. 8 is a diagram showing a portion of the A-A cross section of microchip 100 shown in FIG. 7 . Further pressurization and liquid introduction through inlet 112 causes the liquid in liquid storage portion 116 to peel off end surface 114b and film 120, passing through the gap between end surface 114b and film 120 and flowing downstream of flow path 111. The outflowing liquid passes through the downstream flow path and can be discharged from outlet 113. A waste liquid storage portion for storing the discharged liquid may be provided in part of the downstream flow path. If it is not necessary to discharge the liquid from the liquid storage portion, the downstream flow path and outlet may not be provided.
[0068] EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following embodiments.
[0069] <Microchip Fabrication 1> A substrate 310 (machined product made of COP resin) (size: 59.4 x 26.2 mm, thickness: 3.0 mm) shown in Figure 9 was prepared. In the substrate 310, the groove 311a forming the flow path was 47.4 mm long, 500 μm deep, and 500 μm wide at the inlet. The substrate had a crescent-shaped (upper half) reservoir 322 formed by cutting a 4 mm diameter circle in half, with the center located 37.55 mm from the inlet toward the outlet. The reservoir 323, which received the liquid from the reservoir 322, had a crescent-shaped (lower half) reservoir 323 formed by cutting a 4.5 mm diameter circle in half. A 2 mm wide wall 314 was provided between the reservoirs 322 and the flow path (between reservoirs 322 and 323). Furthermore, in the substrate, the holes serving as the inlet 312 and outlet 313 were through-holes with a circular cross section and an inner diameter of 2 mm.
[0070] The substrate 310 and the ZF14-100 film (manufactured by Zeon Corporation, COP) used for bonding were prepared as untreated and vacuum plasma surface treatments. Regarding the vacuum plasma surface treatment of the substrate 310, one in which the flat surface excluding the wall portion 314 was treated, and one in which the entire surface including the wall portion 314 was treated were prepared. When the wall portion 314 was not irradiated with vacuum plasma, the wall portion 314 was masked with stainless steel tape. The vacuum plasma conditions were a medium vacuum of 11 Pa, using ordinary air containing approximately 78% nitrogen, approximately 21% oxygen, approximately 1% argon, and a lower percentage of carbon dioxide, etc., and a voltage of 10 V supplied to the plasma power source for 10 seconds. As a result, the water contact angle of the treated surface was 25°. The water contact angle of the substrate surface without surface treatment was 85°.
[0071] An adhesive was used to bond the substrate 310 and the film. The adhesive used was a unique blend of TB3094, a solvent-free, radical-reactive acrylic UV-curable adhesive with a gel fraction of 90% or more, and a solvent-free, radical-reactive acrylic UV-curable adhesive with a gel fraction of 50%. The adhesive was applied by screen printing to the surface of the substrate 310 where the grooves 311a were formed. The screen used had a mesh count of 640, an opening ratio of 39%, and a coating thickness of approximately 7 μm.
[0072] The adhesive-coated surface of the substrate 310 was laminated with a film, and a UV-LED light source was used to irradiate ultraviolet light with a wavelength of 365 nm for 10-20 seconds to initiate the curing reaction of the adhesive, thereby bonding the film onto the substrate 310.
[0073] <Microchip Evaluation 1> We confirmed whether selective peeling of the wall 314 and the film was possible by selectively increasing the bonding strength of the substrate 310 at a location other than the wall 314 and then peeling it off. We also confirmed the gel fraction after curing of the adhesive that could maintain sufficient pressure in the flow path to penetrate the wall 314.
[0074] The inlet 312 was connected to a pressurizing syringe pump using a connector made of silicone tubing and ABS resin bushing. A pressure sensor was attached to the syringe pump, and the pressure at the moment the adhesive on the end surface 314a of the wall 314 peeled off was recorded using a peak hold function. When pressurized by the syringe pump, in a microchip where the surface treatment was performed on areas other than the wall 314 and the adhesive was bonded with TB3094 having a gel fraction of 90% or more, the adhesive on the end surface 314a of the wall 314 peeled off at 250 kPa, and distilled water introduced thereafter flowed into the flow path. On the other hand, in a microchip where the entire surface, including the wall 314, was uniformly surface-treated and the adhesive was bonded with TB3094 having a gel fraction of 90% or more, liquid leakage occurred around the wall 314 at 240 kPa. These results demonstrate that surface treatment can increase the adhesive strength of areas other than the wall 314 compared to the adhesive strength of the joint of the wall 314, thereby enabling selective peeling of the wall 314. With the uniquely formulated adhesive with a gel fraction of 50%, air leaked from the adhesive layer before the pressure required to penetrate the wall 314 was reached, regardless of whether the wall 314 was surface treated, and it was not possible to peel the end surface 314a of the wall 314. These results demonstrate that adhesives with a low gel fraction after curing and a porous appearance are not suitable for peeling the wall 314.
[0075] It was confirmed whether selective peeling of the wall 314 and the film was possible by selectively reducing the bonding strength of only the end face 314a of the wall 314 of the substrate 310 and peeling it off.
[0076] <Fabrication of Microchip 2> The substrate used in fabrication was the same substrate 310 as in Example 1. ZF14-100 was used as the film. TB3094 with a gel fraction of 90% or more was used as the adhesive.
[0077] Before bonding, the end surface 314a of the wall portion 314 of the substrate 310 was pretreated with a fluorine coating agent or a silicone coating agent. Fluorosurf FS-1610C-4.0 (Fluoro Technology Co., Ltd.) was applied as the fluorine coating agent, and KF96SP (Shin-Etsu Chemical Co., Ltd.) was applied as the silicone coating agent, and then dried. As a result of these treatments, the water contact angle of the end surface 314a became 110° or more. Other than this, the microchip was fabricated using the same procedure as in Example 1.
[0078] <Microchip Evaluation 2> Using a connector made of a silicone tube and an ABS resin bushing at the inlet 312, the pressure required to peel the end face 314a from the adhesive was measured using the same method as in Example 1. Pressure was applied through the through-hole on the reservoir 322 side. Experimental results showed that for microchips bonded after application of a fluorine coating agent, the adhesive on the end face 314a of the wall 314 peeled at 130 kPa. For microchips bonded after application of a silicone coating agent, the adhesive on the end face 314a of the wall 314 peeled at 125 kPa. In both microchips, distilled water introduced thereafter flowed into the preceding flow path. These results demonstrate that selective peeling of the wall 314 is possible by reducing the adhesive strength of the end face 314a of the wall 314.
[0079] <Fabrication of Microchip 3> As an example of a mode for selectively reducing the bonding strength of only the end face 314 a of the wall portion 314 of the substrate 310, it was confirmed whether the pressure required for selectively peeling the wall portion 314 and the film could be reduced by applying adhesive to only half of the area of the end face 314 a on the downstream side of the flow path (on the liquid storage portion 323 side).
[0080] The substrate used in the production was the same substrate 310 as in Example 1. The film used was ZF14-100. The adhesive used was TB3094 with a gel fraction of 90% or more.
[0081] Before bonding, the end surface 314a of the wall portion 314 of the base material 310 was coated with a fluorine coating agent, Fluorosurf FS-1610C-4.0 (Fluoro Technology Co., Ltd.), and then dried. As a result of these treatments, the water contact angle of the end surface 314a became 110° or more.
[0082] The adhesive TB3094 was applied by screen printing to the surface of the substrate 310 where the groove 311a was provided. At this time, a screen mask was provided so that approximately half of the area on the upstream side of the flow path (storage section 322 side) of the end face of the wall section 314 was left uncoated with adhesive (adhesive was applied to approximately half of the area on the downstream side (storage section 323 side)).
[0083] <Microchip Evaluation 3> Using a connector made of a silicone tube and an ABS resin bushing at the inlet 312, the pressure required to peel the end face 314a from the adhesive was measured using the same method as in Example 1. Pressure was applied through the through-hole on the reservoir 322 side. Experimental results showed that in a microchip in which a fluorine coating agent was applied and only half of the end face 314a was bonded with adhesive, the adhesive on the end face 314a of the wall 314 peeled off at 30 kPa, and distilled water introduced thereafter flowed into the flow path. Thus, by selectively reducing the bonding strength of only the end face 314a of the wall 314 of the substrate 310 and applying adhesive only to the half of the end face 314a downstream of the flow path (toward the reservoir 323), it was possible to reduce the pressure required to selectively peel the wall 314 from the film to 30 kPa.
[0084] DESCRIPTION OF SYMBOLS 100...microchip, 110...substrate, 111...channel, 111...groove, 112...inlet, 113...outlet, 114a, 114b...wall, 115...bonding surface, 116...liquid storage portion, 117...adhesive, 120...film, 310...substrate, 311a...groove, 312...inlet, 313...outlet, 314...wall, 314a, 314b, 314c...end surface, 317...adhesive, 320...film, 322...half-moon shaped storage portion obtained by cutting a circle with a diameter of 4 mm in half, 323...half-moon shaped storage portion obtained by cutting a circle with a diameter of 4.5 mm in half
Claims
1. A microchip for analyzing liquid samples having an internal flow path and a liquid storage portion, comprising: a substrate having a bonding surface on which a groove forming the flow path, a depression provided in part of the groove to serve as the liquid storage portion for storing the liquid, and a wall portion provided between the groove and the depression for blocking the outflow of the liquid from the liquid storage portion to the flow path; and a film bonded to the bonding surface of the substrate and covering the groove to form the flow path and the liquid storage portion, wherein of the bonding portions between the substrate and the film, the bonding portion between the end face of the wall portion of the substrate and the film has a first bonding strength sufficient to cause peeling under a pressure of 30 kPa or more but less than 300 kPa, and the other bonding portions have a bonding strength stronger than the first bonding strength.
2. The microchip according to claim 1, wherein the joints between the end faces of the wall of the base material and the film are joined with an adhesive having a gel fraction of 60% or more after hardening, and the other joints are joined with an adhesive having a gel fraction of 60% or more after the joining surfaces of the base material have been surface-treated so that the water contact angle is 10 to 40°.
3. The microchip according to claim 2, wherein the adhesive is applied to an area of the end face of the wall portion of the base material that corresponds to the downstream side of the flow path and that is not more than half the area, and the base material is joined to the film.
4. The microchip according to claim 2, wherein the surface treatment is an atmospheric plasma treatment, a vacuum plasma treatment, a corona treatment or an excimer treatment.
5. The microchip according to claim 1, wherein the joints between the end faces of the wall of the base material and the film are joined with an adhesive having a gel fraction of 60% or more after hardening, and the other joints are joined by welding.
6. The microchip according to claim 5, wherein the welding is heat sealing, laser welding or ultrasonic welding.
7. The microchip according to claim 1, wherein the joints between the end faces of the wall portions of the substrate and the film are joined with an adhesive having a gel fraction of 60% or more after hardening, after the end faces of the wall portions have been surface-treated so that they have a water contact angle of 110° or more, and the other joints are joined with an adhesive having a gel fraction of 60% or more after hardening.
8. The microchip according to claim 7, wherein the adhesive is applied to an area of the end face of the wall portion of the base material that is equal to or less than half the area of the end face of the wall portion that is downstream of the flow path, and the base material is joined to the film.
9. The microchip according to claim 7, wherein the surface treatment is a fluorine coating or a silicon coating.
10. The microchip according to any one of claims 1 to 9, wherein the substrate or the film has through holes serving as an inlet for pressurizing the liquid and an outlet for the liquid or air to flow out, at both ends of the flow path formed by bonding the substrate and the film together.
11. The microchip according to any one of claims 1 to 9, wherein the liquid stored in the liquid storage section is pressurized using a microsyringe or a pump through the inlet, or is pressurized by pressing with a finger.
12. The microchip according to any one of claims 1 to 9, wherein the substrate is made of any one of plastic, silicone, and glass.
13. The microchip according to any one of claims 1 to 9, wherein the film has a Young's modulus (tensile elastic modulus) of, for example, 50 to 2800 MPa.
14. The microchip according to claim 13, wherein the film is made of cycloolefin polymer (COP), cycloolefin copolymer (COC), polymethyl methacrylate (PMMA), polystyrene (PS), polycarbonate (PC) and polyethylene terephthalate (PET).