Bonded body and bonding method thereof, microfluidic device and manufacturing method thereof

Abstract

To provide a method for joining a joining body of silicone molded bodies together firmly at the same time at multiple contact points between the silicone molded body and another silicone molded body, and a microfluidic device that can suppress sorption of samples in a microchannel even when using silicone as a material, and a method for manufacturing the same.SOLUTION: A first molded body and a second molded body are joined to each other by irradiating one or more contact points with ionizing radiation. A silicone molded body that forms a microchannel has reduced gas permeability due to a transmission of ionizing radiation, and sorption of gas into the silicone molded body can be suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for bonding a polyorganosiloxane (hereinafter also referred to as silicone) molded body and a silicone or glass molded body by irradiating them with ionizing radiation, a microfluidic device in which a silicone molded sheet and a silicone or glass molded sheet are laminated and bonded together by ionizing radiation with a microchannel formed therebetween, and a method for manufacturing the same. [Background technology]

[0002] Silicone, whose main component is polyorganosiloxane, is a material with excellent processability and properties such as heat resistance, insulation, weather resistance, low toxicity, and transparency. It is a resin material used in a variety of fields, including electrical and electronic parts, transportation machinery, building materials, daily necessities, and medical supplies. Therefore, there is a demand for the development of processing techniques for silicone molded bodies (hereafter simply referred to as silicone for the sake of convenience) and techniques for joining silicones together or silicone to glass.

[0003] Silicone itself has a certain degree of self-adsorption, but a bonding method for stronger bonding is known, as disclosed in Patent Documents 1 and 2, in which the surfaces of the silicone to be bonded are activated by irradiating them with atmospheric pressure plasma or excimer UV, and then the activated surfaces are bonded together. However, because surface modification by irradiation with atmospheric pressure plasma or the like is transient and short-lived, there is a restriction that the silicones must be bonded together immediately after surface modification.

[0004] Regarding the problem that surface modification is temporary, the inventors of the present application have developed a new silicone processing method in which the surface of silicone is irradiated with an electron beam with an absorbed dose of 2 MGy or more to form depressions, resulting in a surface layer thickness of 1 μm or more that maintains hydrophilicity for a long period of time more stable than the above-mentioned surface modification (Non-Patent Document 1).

[0005] In recent years, there has been an increasing demand for microfluidic devices used in applications such as sample mixing, reactions, synthesis, extraction, and analysis in the fields of regenerative medicine, drug discovery, and diagnostics. Silicone is commonly used as the substrate for microfluidic devices because of its excellent biocompatibility, chemical resistance, low autofluorescence, optical transparency, and mold release properties, as well as its low cost and disposability compared to glass. A typical microfluidic device has a base sheet made of silicone with fine microchannels recessed into its surface, measuring approximately 500 nm to 1 mm wide, laminated with a cover sheet made of silicone or glass that covers the microchannels. The laminated surfaces of the opposing base sheet and cover sheet are then bonded together to form an integrated structure.

[0006] When using an existing bonding method that uses an adhesive to bond a base sheet and a cover sheet, there is a concern that adhesive components (e.g., organic solvents) will leak from the bonding surface into the microchannel and affect the sample injected into the microchannel. Therefore, conventionally, when laminating a base sheet and a cover sheet, the opposing lamination surfaces are irradiated with atmospheric pressure plasma or excimer UV to modify the surface of the lamination surfaces, and then the two lamination surfaces are closely attached and left to stand for a certain period of time to bond them, as shown in Patent Document 1 and Patent Document 2. Patent Document 3 also discloses a method in which the laminated surfaces of a silicone base sheet and a cover sheet are irradiated with an electron beam to modify the surface of the lamination surfaces and then bonded.

[0007] Patent Document 4 also describes a photo-bonding method in which a glass substrate is placed on a silicone base, vacuum ultraviolet light is irradiated from the surface of the glass substrate, an oxide film of 10 nm or less is formed on the laminated surface of the silicone base facing the glass substrate, and the silicone base and glass substrate are bonded via the oxide film. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-154898 [Patent Document 2] Patent No. 3714338 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-21081 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-331731 [Non-Patent Document 1] TGOyama et al.,Applied Physics Letters,112,213704(2018) Summary of the Invention [Problem to be solved by the invention]

[0009] The bonding methods disclosed in Patent Documents 1 to 3 are techniques for bonding silicones by modifying the surface of the silicone in a range of several tens of nanometers deep from the surface, but it is difficult to modify the deeper parts of the silicone.

[0010] Furthermore, in bonding using the above-mentioned surface modification treatment, the bonding surfaces of the silicone to be bonded are irradiated in advance with atmospheric pressure plasma or excimer UV, so it is necessary to separate the silicone to be bonded. Furthermore, because the surface modification is temporary, there is a constraint in the bonding process that the bonding surfaces must be quickly brought into close contact after the surface modification treatment.

[0011] Even in the manufacturing methods described in Patent Documents 1 to 3, in which the laminated surfaces of a silicone base sheet and a cover sheet are surface-modified and then the base sheet and cover sheet are bonded together to form a microfluidic device in which the base sheet and cover sheet are laminated together, the manufacturing processes require complicated steps of modifying the laminated surfaces by plasma irradiation or vacuum ultraviolet irradiation, then positioning (aligning) the base sheet and cover sheet relative to each other, bringing the surface-modified laminated surfaces into close contact, and maintaining this close contact state for a predetermined period of time. Furthermore, the alignment process between the base sheet with recessed microchannels and the cover sheet covering the microchannels requires high precision, and once the laminated surfaces are brought into close contact, they cannot be reattached, resulting in low manufacturing yields.

[0012] According to the optical bonding method described in Patent Document 4, a glass cover sheet is laminated on a silicone base sheet, and then vacuum ultraviolet light is irradiated from the surface of the glass cover sheet to bond the base sheet and cover sheet together. However, the cover sheet must be made of glass that transmits vacuum ultraviolet light, and the base sheet and cover sheet are bonded together via an oxide film that is formed on the surface of the silicone base sheet by irradiation with vacuum ultraviolet light, which creates problems such as uneven bonding and insufficient bonding strength.

[0013] Furthermore, there is a demand for microfluidic devices that enable high-speed parallel processing by stacking multiple base sheets, each with a recessed microchannel, and injecting a sample into each of the multiple microchannels formed between the stacked surfaces of the multiple layers, and for microfluidic devices that form a three-dimensional microchannel by drilling through-holes in each of the base sheets stacked in multiple layers that connect the microchannels formed on both sides of the base sheets, but it is extremely difficult to manufacture these multi-layered microfluidic devices using the bonding methods described in Patent Documents 1 to 3, which require highly accurate positioning and adhesion of each of the stacked base sheets and cover sheets, or the optical bonding method described in Patent Document 4, which uses irradiation with vacuum ultraviolet light.

[0014] Furthermore, although silicone is suitable as a material for microfluidic devices as mentioned above, its porous structure with countless micropores of about 2-3 μm diameter means that it lacks gas barrier properties and sorbs low-molecular-weight compounds (i.e., absorbs them into the solid polymer). Therefore, when an aqueous solution of a sample is injected into a microchannel surrounded by silicone, its concentration drops significantly, making it unsuitable as a material for microfluidic devices used to culture and analyze water-soluble samples.

[0015] Furthermore, polydimethylsiloxane (hereinafter referred to as PDMS), a typical silicone, is hydrophobic with a contact angle of 105 degrees, so there was a risk that liquid samples would stagnate due to surface tension within the fine microchannels of microfluidic devices.

[0016] The present invention has been made in consideration of the above-mentioned conventional problems, and has as its object to provide a method for joining a joined body (a silicone joined body) that simultaneously and firmly joins a silicone molded body and another silicone or glass molded body at multiple contact points between the two molded bodies.

[0017] Another object of the present invention is to provide a method for bonding silicone molded articles that changes the physical properties of silicone molded articles within a certain range.

[0018] Another object of the present invention is to provide a microfluidic device and a method for manufacturing the same, in which a set of molded silicone sheets, which form a microchannel between the laminated surfaces, can be aligned and then firmly bonded together to laminate the set of molded sheets together.

[0019] Another object of the present invention is to provide a microfluidic device and a method for manufacturing the same, in which a microchannel is formed between each laminated surface, and multiple silicone molded sheets stacked in multiple layers can be aligned together, and then the laminated surfaces can be firmly bonded together to stack multiple molded sheets together in multiple layers.

[0020] Another object of the present invention is to provide a microfluidic device and a method for manufacturing the same that adds gas barrier properties to the silicone molded sheet that forms the microchannel, thereby suppressing sorption of samples injected into the microchannel.

[0021] Another object of the present invention is to provide a microfluidic device and a method for manufacturing the same, in which the silicone molded sheet that forms the microchannel is changed from hydrophobic to hydrophilic, so that the flow of the sample within the microchannel is not hindered. [Means for solving the problem]

[0022] In order to achieve the above-mentioned object, the bonding method for a bonded body according to claim 1 is a method for simultaneously bonding one or more first molded bodies mainly composed of polyorganosiloxane and one or more second molded bodies mainly composed of polyorganosiloxane or glass, While the first molded body and the second molded body are in contact with each other, one or more contact points where they are in contact are irradiated with ionizing radiation consisting of any one of electron beams, gamma rays, and X-rays, and the siloxane main chains of the first molded body and the siloxane main chains of the second molded body are covalently bonded at the interface of the contact points by ionizing radiation crosslinking caused by the ionizing radiation.

[0023] At the contact points present in the range through which ionizing radiation penetrates, the siloxane main chains of the first and second molded bodies at the interface of the contact points are covalently bonded together by ionizing radiation crosslinking, resulting in a strong bond.

[0024] The method for bonding a bonded body according to claim 2 is characterized in that the ionizing radiation is either an electron beam or a gamma ray, and the absorbed dose of the ionizing radiation at the contact point is 860 kGy or more.

[0025] The bond strength at the contact point between the first and second compacts depends on the absorbed dose of ionizing radiation at the contact point, and when the absorbed dose of ionizing radiation is 860 kGy or more, the contact point is firmly bonded.

[0026] The method for bonding a bonded body according to claim 3 is characterized in that the ionizing radiation is an electron beam, and the acceleration voltage of the electron beam is 500 keV or more.

[0027] The higher the acceleration voltage, the deeper the ionizing radiation can penetrate through the first and second molded bodies along the direction of incidence of the ionizing radiation. By using an electron beam with an acceleration voltage of 500 keV or higher, a thick material can be used as the first or second molded body that constitutes the silicone bonded body.

[0028] The microfluidic device described in claim 4 comprises a first molding sheet and a second molding sheet laminated on the first molding sheet, wherein the first lamination surface of the first molding sheet and the second lamination surface of the second molding sheet, which are in contact in the lamination direction, are joined together with a microchannel formed therebetween, and the first molding sheet and the second molding sheet are laminated together, wherein the first molding sheet is formed from polyorganosiloxane, and the second molding sheet is formed from polyorganosiloxane, glass, or an organic resin with a siloxane coating formed on the second lamination surface, and the first lamination surface and the second lamination surface, which are in contact in the lamination direction, are laminated together by ionizing radiation consisting of any one of electron beams, gamma rays, and X-rays, which passes through the first lamination surface and the second lamination surface, causing the siloxane main chains of the first lamination surface and the siloxane main chains of the second lamination surface to be covalently bonded by ionizing radiation crosslinking caused by the ionizing radiation, and the first molding sheet and the second molding sheet are laminated together.

[0029] At the interface between the first stacking surface formed from polyorganosiloxane and the second stacking surface on which a coating of polyorganosiloxane, glass, or siloxane is formed, which are opposed in the stacking direction, the siloxane main chains of the first stacking surface and the second stacking surface are covalently bonded by ionizing radiation crosslinking, resulting in a strong bond.

[0030] When ionizing radiation penetrates the first molded sheet, which has a microchannel formed between the first and second laminated surfaces, the hydrophobic side chains such as CH3 (methyl group) with low binding energy are lost due to the ionizing radiation, and the hydrophilic siloxane main chain with high binding energy is revealed. As a result, the microchannel is formed in the first molded sheet, which has changed from hydrophobic to hydrophilic.

[0031] Similarly, when ionizing radiation penetrates the first molded sheet having microchannels formed between the first and second laminated surfaces, the irregular flexible siloxane main chains are bound by covalent bonds with adjacent siloxane main chains at numerous locations, and the first molded sheet is transformed to have gas barrier properties. As a result, the microchannels are formed in the first molded sheet having gas barrier properties.

[0032] The microfluidic device described in claim 5 is characterized in that a stress relaxation portion consisting of a groove or a slit communicating with the side surfaces of the first molded sheet and the second molded sheet, which are laminated together, is formed on at least one of the first and second laminated surfaces excluding the portion where the microchannel is formed.

[0033] The stress relaxation portion formed on at least one of the first and second stacking surfaces absorbs the distortion caused by ionizing radiation penetrating the first or second molding sheet, so that even when the first and second stacking surfaces are joined, the first and second molding sheets, which are laminated together, do not bend due to uneven distortion.

[0034] When ionizing radiation passes through the first and second stacking surfaces, gas generated at the interface between the first and second stacking surfaces is released to the outside through the stress relief section from the sides of the first and second molded sheets that are stacked together.

[0035] The microfluidic device according to claim 6 is characterized in that the ionizing radiation is an electron beam.

[0036] The first and second stacking surfaces are bonded together using an electron beam, which has high directivity and allows easy control of irradiation timing.

[0037] A method for manufacturing a microfluidic device according to claim 7 includes laminating a first molded sheet and a second molded sheet, and bonding the first and second laminated surfaces excluding a portion where the microchannel is formed, in a state where a microchannel is formed between a first laminated surface of the first molded sheet and a second laminated surface of the second molded sheet that face each other in a lamination direction, and the first and second laminated surfaces are bonded together, the first and second laminated surfaces being bonded together except for a portion where the microchannel is formed, and the second molded sheet is made of polyorganosiloxane, and the second molded sheet is made of polyorganosiloxane, glass, or an organic resin having a siloxane coating formed on the second laminated surface. the first and second molded sheets are laminated together, the laminated first molded sheet and the second molded sheet are positioned relative to each other, and the first and / or second molded sheets that have been positioned relative to each other are irradiated with ionizing radiation consisting of any one of electron beams, gamma rays, and X-rays, so that at the contact surface where the first and second laminated surfaces come into contact with each other, the siloxane main chains of the first and second laminated surfaces are covalently bonded to each other by ionizing radiation crosslinking caused by the ionizing radiation, thereby joining the first and second laminated surfaces except for the portion where the microchannel is formed.

[0038] By irradiating the first molded sheet and / or the second molded sheet that are stacked in relative position with ionizing radiation, the siloxane main chains of the first and second laminated surfaces are covalently bonded by ionizing radiation crosslinking at the interface between the first laminated surface formed from polyorganosiloxane and the second laminated surface on which a coating of polyorganosiloxane, glass or siloxane is formed, which are opposite each other in the stacking direction, and are firmly bonded.

[0039] By irradiating the first molded sheet and / or the second molded sheet formed from polyorganosiloxane with ionizing radiation, hydrophobic side chains such as CH3 (methyl group) with low bond energy are removed by the ionizing radiation, and hydrophilic siloxane main chains with high bond energy are revealed. As a result, microchannels are formed in the first molded sheet and / or the second molded sheet that have changed from hydrophobic to hydrophilic.

[0040] Similarly, by irradiating the first molded sheet and / or the second molded sheet formed from polyorganosiloxane with ionizing radiation, the irregular flexible siloxane main chains are bound by covalent bonds with adjacent siloxane main chains at many points, and are changed to have gas barrier properties. As a result, microchannels are formed in the first molded sheet and / or the second molded sheet with gas barrier properties.

[0041] The method for manufacturing a microfluidic device described in claim 8 is characterized in that one or more of the first molded sheets and one or more of the second molded sheets are alternately stacked in multiple layers, all of the first molded sheets and all of the second molded sheets adjacent to each other in the stacking direction are positioned relative to each other, the first molded sheets and / or the second molded sheets stacked in multiple layers after being positioned relative to each other are irradiated with the ionizing radiation, and all of the first stacked surfaces and the second stacked surfaces except for the portions where the microchannels are formed are simultaneously bonded.

[0042] After the first and second molded sheets, which are alternately stacked in multiple layers, are positioned relative to each other, the first and second molded sheets, which are stacked in multiple layers, are simultaneously and firmly bonded to each other.

[0043] All of the first molded sheets and / or second molded sheets formed from polyorganosiloxane are simultaneously changed from hydrophobic to hydrophilic in a single step of irradiation with ionizing radiation, and are endowed with gas barrier properties.

[0044] The method for manufacturing a microfluidic device described in claim 9 is characterized in that all of the first molded sheets and second molded sheets adjacent to each other in the stacking direction are positioned relative to each other so that through holes passing through the first molded sheet and / or the second molded sheet in the stacking direction are connected to a microchannel formed between the first stacking surface and the second stacking surface.

[0045] After all adjacent first and second molded sheets in the stacking direction are positioned relative to each other so that the through holes that penetrate the first and / or second molded sheets in the stacking direction are connected to the microchannel, the first and second molded sheets stacked in multiple layers are simultaneously and firmly bonded together.

[0046] The method for manufacturing a microfluidic device described in claim 10 is characterized in that a stress relief portion consisting of a groove or a slit communicating with the side surface of the first molded sheet and the second molded sheet that are integrated by joining the first molded sheet and the second molded sheet is formed on at least one of the first and second laminated surfaces excluding the portion where the microchannel is formed.

[0047] The stress relaxation portion formed on at least one of the first and second stacking surfaces absorbs the distortion caused by ionizing radiation penetrating the first or second molded sheet, so even if the first and second molded sheets are stacked in multiple layers and bending displacements accumulate, the entire stack will not bend or warp significantly.

[0048] When a first molding sheet and / or a second molding sheet formed from polyorganosiloxane is irradiated with ionizing radiation, the gas generated inside the first molding sheet and / or the second molding sheet is released to the outside from the side of the first molding sheet and the second molding sheet that are joined together through a stress relief portion consisting of a groove or a slit.

[0049] The method for manufacturing a microfluidic device according to claim 11 is characterized in that the microchannel and the recessed groove have the same depth from the first stacking surface and the same depth from the second stacking surface.

[0050] A mold having protrusions of the same height for forming the microchannels and recessed grooves can be easily obtained by resist etching using photolithography or electroforming.

[0051] The method for manufacturing a microfluidic device described in claim 12 is characterized in that the entire surface of the first molded sheet and / or the second molded sheet, including the portion where the microchannel is formed, is irradiated with ionizing radiation along the stacking direction.

[0052] Since the entire surface of the first molded sheet and / or the second molded sheet including the portion where the microchannel is formed is irradiated with ionizing radiation, the inner surface of the microchannel formed from polyorganosiloxane becomes hydrophilic and has gas barrier properties.

[0053] The method for manufacturing a microfluidic device according to claim 13 is characterized in that the ionizing radiation is an electron beam.

[0054] All of the first and second stacking surfaces are bonded together using an electron beam, which has high directivity and allows easy control of irradiation timing. [Effects of the Invention]

[0055] According to the invention of claim 1, one or more contact points where the first molded body or the second molded body come into contact can be firmly joined at the same time.

[0056] Furthermore, the water contact angle can be reduced in the range from the surface to the contact point of the first molded article or the second molded article containing polyorganosiloxane as the main component.

[0057] According to the invention of claim 4, the first molded sheet and the second molded sheet are bonded together in a stacked state by irradiation with ionizing radiation, so that the first molded sheet and the second molded sheet can be aligned before the bonding process.

[0058] The first and second molded sheets, which have microchannels formed between their laminated surfaces, can be changed from hydrophobic to hydrophilic, so that aqueous solution samples injected into the microchannels do not become stagnant within the microchannels due to surface tension.

[0059] Furthermore, the first and second molded sheets, which have a microchannel formed between their laminated surfaces, have gas barrier properties, and even when silicone is used as a material for the microfluidic device, sorption of samples such as low molecular weight compounds injected into the microchannel can be suppressed.

[0060] According to the invention of claim 5, even when joined by ionizing radiation that penetrates the first and second stacking surfaces, the first and second stacking sheets that are laminated together maintain a flat surface without bending due to uneven distortion.

[0061] Furthermore, even if ionizing radiation passes through the first and second stacking surfaces, gas does not remain at the interface between the first and second stacking surfaces, and the generation of voids at the interface due to residual gas can be suppressed.

[0062] According to the invention of claim 6, the first and second stacking surfaces are bonded using an electron beam, which has high directionality and makes it easy to control the irradiation timing, thereby facilitating mass production of microfluidic devices in which the first and second molding sheets are stacked together.

[0063] According to the invention of claim 7, after the stacked first and second molded sheets are positioned relative to each other, the first and / or second molded sheets are irradiated with ionizing radiation and bonded to each other, so that the relative positioning of the first and second molded sheets can be repeatedly performed before bonding.

[0064] The first molded sheet and / or the second molded sheet, which have a microchannel formed between the laminated surfaces, can be changed from hydrophobic to hydrophilic, so that a liquid sample injected into the microchannel does not stagnate within the microchannel due to surface tension.

[0065] Furthermore, since gas barrier properties can be imparted to the first molded sheet and / or the second molded sheet having a microchannel formed between the laminated surfaces, even when silicone is used as a material for a microfluidic device, sorption of samples such as low molecular weight compounds injected into the microchannel can be suppressed.

[0066] According to the invention of claim 8, all of the first and second molded sheets stacked alternately in multiple layers can be positioned relative to each other with microchannels formed therebetween, and then all of the first and second molded sheets adjacent in the stacking direction can be firmly bonded together at the same time, making it possible to easily manufacture microfluidic devices in which a large number of microchannels are formed in parallel or in which microchannels are formed in a three-dimensional shape.

[0067] All of the microchannels formed between the first and second stacking surfaces can be formed in the first molded sheet and / or the second molded sheet made of polyorganosiloxane and made hydrophilic.

[0068] Furthermore, even if the first molded sheet and / or the second molded sheet in which a microchannel is formed between the laminated surfaces is a molded sheet formed from polyorganosiloxane, gas barrier properties can be imparted to the molded sheet.

[0069] According to the invention of claim 9, after all of the first and second molded sheets stacked alternately in multiple layers are positioned relative to one another so that the through holes passing through the first and / or second molded sheets in the stacking direction are connected to the microchannel, all of the first and second molded sheets adjacent in the stacking direction can be firmly bonded together at the same time, thereby making it possible to easily manufacture a microfluidic device in which a microchannel is formed in a three-dimensional shape.

[0070] According to the invention of claim 10, in the step of irradiating ionizing radiation to first and / or second molded sheets stacked in multiple layers and bonding the first and second stacked surfaces, even if distortion occurs in part of the bonding surface, the distortion does not extend beyond the stress relaxation portion formed on the bonding surface, and each of the bonded first and second molded sheets can be maintained flat. Therefore, even if the first and second molded sheets are alternately stacked together in multiple layers, the microchannels formed between the first and second stacked surfaces do not become partially inclined or change in inner diameter, and the entire multi-layer stack does not bend or warp significantly.

[0071] When ionizing radiation is applied to the first and / or second molded sheets stacked in multiple layers, even if gas is generated inside the first and / or second molded sheets formed from polyorganosiloxane, the gas is released to the outside through the micropores in the polyorganosiloxane and the stress relaxation parts formed on the bonding surfaces, thereby suppressing voids that would otherwise occur in the first and second molded sheets due to residual gas.

[0072] According to the invention of claim 11, the microchannel and the recessed grooves of the stress relaxation section can be formed using an electroforming mold that allows high-precision molding or a resist etching mold using photolithography technology.

[0073] According to the invention of claim 12, the inner surface of the microchannel is made hydrophilic, so that the aqueous solution sample injected into the microchannel does not stagnate within the microchannel, and sorption of the sample, such as a low molecular weight compound, injected into the microchannel can be suppressed.

[0074] Moreover, since ionizing radiation penetrates all the microchannels, the inside of the microchannels is sterilized.

[0075] According to the invention of claim 13, all of the first and second stacking surfaces are bonded using an electron beam, which has high directionality and makes it easy to control the irradiation timing, making it easy to mass-produce microfluidic devices in which the first and second molding sheets are stacked together. [Brief explanation of the drawings]

[0076] [Figure 1] 1A and 1B are side views showing a manufacturing process of a silicone bonded body 1 according to a first embodiment of the present invention, in which FIG. 1A is a temporarily bonded body 1′, FIG. 1B is a step of irradiating the temporarily bonded body 1′ with ionizing radiation, and FIG. 1C is a side view showing the silicone bonded body 1 in which a first molded body 2 and a second molded body 3 are bonded together by irradiating the first molded body 2 with ionizing radiation. [Figure 2] FIG. 10 is an explanatory diagram illustrating a method for comparing the bonding strength of two PDMS films 5A and 5B bonded together by irradiating them with gamma rays. [Figure 3]10 is a graph showing a bondable range when a bonded body is obtained by irradiating PDMS with electron beams having different acceleration voltages. [Figure 4] This is a photograph taken from the flat side of a silicone bonded assembly in which ten PDMS films were bonded together using electron beam irradiation. [Figure 5] 5 is a photograph of the silicone bonded body of FIG. 4 taken from the side. [Figure 6] FIG. 10 is an exploded perspective view of a microfluidic device 10 according to a second embodiment. [Figure 7] FIG. 1 is a longitudinal cross-sectional view of a microfluidic device 10. DETAILED DESCRIPTION OF THE INVENTION

[0077] A silicone bonded body 1 according to a first embodiment of the present invention and a method for manufacturing the silicone bonded body 1 will be described below with reference to Fig. 1. In Fig. 1, the bonded body 1 is composed of three first molded bodies 2 (2a, 2b, 2c) and three second molded bodies 3 (3a, 3b, 3c), which are bonded to each other at contact regions 4a to 4h by covalent bonds, which will be described later.

[0078] <Method for producing silicone bonded body> The method for producing the silicone bonded body 1 includes a step of irradiating ionizing radiation to the contact points where one or more first molded bodies 2 and one or more second molded bodies 3 are in contact with each other. This ionizing radiation irradiation step involves irradiating the first molded body 2 and the second molded body 3 in a state where they are in contact with each other with ionizing radiation. In other words, this step includes a step of irradiating ionizing radiation to a temporarily joined body in which the first molded body 2 and the second molded body 3 are in contact with each other. By this irradiation of ionizing radiation, the first molded body 2 and the second molded body 3 are bonded at the contact points where they are in contact with each other.

[0079] 1(a) shows the temporarily joined body before being irradiated with ionizing radiation. As shown in the figure, the first molded body 2 and the second molded body 3 are temporarily held to maintain contact at all of their contact areas 4a to 4h, forming a temporarily joined body 1'. The contact state of the molded bodies in this temporarily joined body 1' may be maintained by a jig (not shown) or by utilizing the self-adhesive properties of silicone.

[0080] The first molded body 2 may contain other substances as long as it is mainly composed of polyorganosiloxane. Here, "main component" refers to a material having a polyorganosiloxane content of 50% by mass or more. Preferably, it contains 80% by mass or more, more preferably 90% by mass or more, and even more preferably 98% by mass or more of polyorganosiloxane. For example, it may be formed from an organic resin such as cycloolefin polymer (COP) with a siloxane coating formed on the surface where it is laminated with another molded body. Furthermore, "mainly composed of polyorganosiloxane" includes a material that is essentially made of polyorganosiloxane.

[0081] The second molded body 3 is formed of a material mainly composed of polyorganosiloxane or glass mainly composed of SiO2 (glass). Here, "mainly composed of SiO2 (glass)" means that the SiO2 content is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 98% by mass or more of SiO2.

[0082] Here, the polyorganosiloxane includes polydimethylsiloxane (PDMS). Hereinafter, the bonded body and the method for manufacturing the bonded body will be described using an example in which the polyorganosiloxane is PDMS. In the embodiment shown in FIG. 1(a), the first molded body 2 and the second molded body 3 are both made of polyorganosiloxane and are each formed into a desired shape.

[0083] In this first embodiment, the first molded bodies 2a, 2b, and 2c and the second molded bodies 3a, 3b, and 3c may have any shape, such as a film or a sphere, and each of the contact regions 4a to 4h or each of the interiors may have a hollow portion, or may have a recessed or protruding portion. Furthermore, the first molded body 2 and the second molded body 3 may have a positioning mechanism to facilitate contact at a desired position.

[0084] Next, the temporary fastener 1' is irradiated with ionizing radiation. This irradiation of ionizing radiation bonds the first compact 2 and the second compact 3 at contact points or contact areas within a range of a depth D penetrated by the ionizing radiation. In the embodiment shown in FIG. 1(b), ionizing radiation is irradiated vertically from above to below, bonding contact areas 4a to 4h of the temporary fastener 1'.

[0085] In the present embodiment, conventionally known ionizing radiation can be used, such as electron beams, gamma rays, and X-rays. One or more of these ionizing radiations may be used in combination for irradiation.

[0086] When the ionizing radiation is an electron beam, the depth D to which the electron beam penetrates the temporary fastener 1' varies depending on the acceleration voltage of the electron beam; the higher the acceleration voltage, the longer D. For example, when PDMS with a density of 0.965 g / cm3 is irradiated from one direction with a 500 keV electron beam, D is approximately 1.5 mm, and if there is a hollow region in between, D becomes even longer. Therefore, when the length from the surface of the first molded body 2a of the temporary fastener 1' made of PDMS to the contact region 4d along the direction of incidence of the ionizing radiation is 1.5 mm, an electron beam with an acceleration voltage of 500 keV is irradiated.

[0087] When the ionizing radiation is gamma rays from cobalt 60, the depth D to which the gamma rays penetrate into the temporary fixing body 1' made of PDMS is approximately 300 mm, and if there is a hollow area therebetween, D becomes even longer.

[0088] Any number of contact points or contact areas 4 can be bonded at one time by irradiation with ionizing radiation, as long as they are within the range of ionizing radiation penetration D. For example, if five 100 μm thick film-like silicone molded bodies or glass molded bodies are stacked, all of the molded bodies can be bonded at once by irradiating them with ionizing radiation that penetrates to a depth of 500 μm or more from the surface.

[0089] The irradiation conditions for the ionizing radiation are not particularly limited, but for example, when an electron beam is used, 10 keV or more is preferable, 30 keV or more is more preferable, and 500 keV or more is even more preferable. The acceleration voltage may be set appropriately depending on the thickness of the objects to be joined. As mentioned above, the higher the acceleration voltage of the electron beam, the greater the penetration depth D of the electron beam. The upper limit of the acceleration voltage of the electron beam is not particularly limited, but may be set to, for example, 10 MeV or less, for example, 5 MeV or less.

[0090] Furthermore, the absorbed dose of ionizing radiation (e.g., electron beams or gamma rays) in each of the contact regions 4a-4h is preferably 200 kGy or more, more preferably 500 kGy or more, and even more preferably 860 kGy or more, to ensure strong bonding in each of the contact regions 4a-4h. The greater the absorbed dose, the more covalent bonds, as described below, are formed. However, if the absorbed dose is too high, the mechanical strength of the first or second molded body will decrease, so it is preferably 40 MGy or less, and more preferably 20 MGy or less.

[0091] Furthermore, the size of the irradiation spot of the ionizing radiation may be any size as long as the joining contact point or contact area 4 is included in the range through which the ionizing radiation passes, and may be either fixed irradiation in which the irradiation spot does not move, or scanning irradiation in which the irradiation spot moves.

[0092] The irradiation of ionizing radiation may be performed once or in a combination of multiple steps, and the bonded body (temporarily bonded body) may be irradiated with ionizing radiation from one direction or from different directions. Furthermore, the bonding of each contact region 4a to 4h may be performed by combining the irradiation of ionizing radiation with an existing bonding method such as surface modification of the contact surface by plasma treatment or the like or using an adhesive.

[0093] When the temporary fixing body 1' is irradiated with ionizing radiation, the ionizing radiation penetrates the first molded bodies 2a, 2b, and 2c made of polyorganosiloxane (for example, PDMS) and the second molded bodies 3a, 3b, and 3c, as shown by the dashed lines in FIG. 1(b). When the polyorganosiloxane (for example, PDMS) is exposed to ionizing radiation, side chains such as CH3 (methyl group) are cleaved and scattered as gas. Therefore, the siloxane main chains are (1 set) [ka] (2 sets) [ka] (3 types) [ka] (In formula 1, formula 2, and formula 3, R represents an organic group, and may be the same or different from each other) and are bonded by a covalent bond based on a siloxane bond (-Si-O-Si-) shown in any one of the structural formulas.

[0094] In the above formulas 1, 2, and 3, R is not particularly limited as long as it is an organic group, such as an alkyl group (e.g., methyl, ethyl, propyl, or butyl), an aryl group (e.g., phenyl or naphthyl), or a hydrogen atom, and is preferably a methyl group.

[0095] The ionizing radiation also penetrates each contact area 4a-4h (i.e., contact points) where the first molded bodies 2a, 2b, and 2c come into contact with the second molded bodies 3a, 3b, and 3c. The polyorganosiloxane (e.g., PDMS) facing these contact areas 4a-4h is similarly exposed to the ionizing radiation, and side chains such as CH3 (methyl groups) are cleaved. At the interfaces of each contact area 4a-4h, the PDMS having (-Si-O-) groups is covalently bonded to the PDMS or glass through siloxane bonds consisting of (-Si-O-Si-) structures shown in formulas (1) to (3).

[0096] That is, along the incident direction (vertical direction) of the ionizing radiation, the first molded bodies 2a, 2b, 2c and the second molded bodies 3a, 3b, 3c are simultaneously and firmly bonded to each other at all contact regions 4a to 4h (i.e., contact points) within the range of depth D that the ionizing radiation penetrates from the surface of the temporary joint body 1' (the surface of the first molded body 2a or the surface of the second molded body 3a), resulting in an integrated silicone bonded body 1 as shown in FIG. 1(c).

[0097] Furthermore, when the first molded body 2a, 2b, 2c or the second molded body 3a, 3b, 3c is primarily composed of polyorganosiloxane (e.g., PDMS), the polyorganosiloxane (e.g., PDMS) constituting the first molded body and the second molded body within the range through which the ionizing radiation penetrates along the direction of incidence of the ionizing radiation (the range from the ionizing radiation irradiated surface to a depth D) is exposed to the ionizing radiation and covalently bonds between the siloxane main chains with siloxane bonds consisting of (-Si-O-Si-) having the structures shown in formulas (1) to (3). That is, covalent bonds having the structures shown in formulas (1) to (3) are formed at the junction between the first molded body and the second molded body within the range through which the ionizing radiation penetrates and in a region 500 nm or more away from the junction of the first molded body or the second molded body.

[0098] When a first or second molded article primarily composed of polyorganosiloxane (e.g., PDMS) is irradiated with the ionizing radiation, hydrophobic side chains such as CH3 (methyl groups) are lost due to the ionizing radiation, revealing the hydrophilic siloxane main chain. As a result, the water contact angle of the molded article decreases in the range from the surface (the surface irradiated with ionizing radiation) of the polyorganosiloxane-based molded article to the point of contact. That is, the water contact angle can be reduced in the range from the surface of the first or second molded article primarily composed of polyorganosiloxane to the point where the ionizing radiation penetrates. For example, if the first or second molded article is primarily composed of PDMS, the water contact angle before irradiation with ionizing radiation is approximately 105 degrees, but after irradiation with ionizing radiation, the water contact angle can be reduced to 100 degrees or less, preferably 90 degrees or less, and more preferably 80 degrees or less.

[0099] Furthermore, when a first or second molded article primarily composed of polyorganosiloxane (e.g., PDMS) is irradiated with the ionizing radiation, covalent bonds having the structures shown in formulas (1) to (3) are formed in the ionizing radiation transmission area of ​​the molded article. That is, in the area from the surface (the surface irradiated with ionizing radiation) of the molded article primarily composed of polyorganosiloxane to the area through which the ionizing radiation passes, the irregularly flexible siloxane main chains are covalently bonded to adjacent siloxane main chains at numerous locations and are constrained, thereby imparting gas barrier properties. For example, compared to the gas barrier property before ionizing radiation irradiation, the gas permeability is reduced to 90% or less, preferably 80% or less, and more preferably 70% or less. In other words, the ionizing radiation transmission area of ​​the bonded article has reduced gas permeability compared to the ionizing radiation non-transmission area, and the gas permeability of the ionizing radiation transmission area is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less of the ionizing radiation non-transmission area.

[0100] The gas barrier properties (gas permeability) of the bonded structure can be evaluated using oxygen permeability and / or water vapor permeability as indicators. Oxygen permeability can be evaluated in accordance with JIS K7126-1 Appendix 2, and water vapor permeability can be evaluated in accordance with JIS K7129-1 Method A.

[0101] Whether the structures of the first molded bodies 2a, 2b, 2c and the second molded bodies 3a, 3b, 3c have changed to the above structures can be confirmed using an X-ray photoelectron spectrometer or Fourier transform infrared spectroscopy, as the amount of carbon or carbon-containing structures (such as methyl groups) decreases by 3% or more compared to before irradiation with ionizing radiation.

[0102] <Silicone bonded body> The silicone bonded body 1 disclosed in this specification is a bonded body formed by bonding one or more first molded bodies whose main component is polyorganosiloxane to one or more second molded bodies whose main component is polyorganosiloxane or glass, with the first molded bodies and the second molded bodies being bonded at one or more bonding points. The first molded body and the second molded body may be appropriately selected from those described in the manufacturing method for the silicone bonded body 1 above. A detailed description thereof will be omitted here.

[0103] In the silicone bonded body 1, the first and second molded bodies are bonded at the interface where they are joined by siloxane bonds consisting of (—Si—O—Si—) structures shown in formulas (1) to (3).

[0104] The silicone bonded body 1 is a molded body primarily composed of polyorganosiloxane, and in regions where ionizing radiation penetrated during the manufacturing process, the siloxane main chains of the polyorganosiloxane are bonded by siloxane bonds having the (-Si-O-Si-) structures shown in formulas (1) to (3). In other words, in at least one of the first molded body or the second molded body, the siloxane main chains are bonded by siloxane bonds having the (-Si-O-Si-) structures shown in formulas (1) to (3) at a depth of 500 nm or more from the bonding point. The depth at which siloxane bonds formed within the first molded body or the second molded body can be confirmed depends on the thickness of the molded body, but can be confirmed in a region at least 500 nm, preferably 800 nm or more, and more preferably 1000 nm or more away from the bonding point.

[0105] The presence of siloxane bonds consisting of (-Si-O-Si-) in the structures shown in formulas (1) to (3) can be confirmed by the above structural changes using an X-ray photoelectron spectrometer or Fourier transform infrared spectroscopy.

[0106] Furthermore, in the above structure, hydrophobic side chains such as CH3 (methyl group) are scattered by exposure to ionizing radiation, revealing the hydrophilic siloxane main chain, and therefore the contact angle with water of the first molded bodies 2a, 2b, 2c and the second molded bodies 3a, 3b, 3c, which have been penetrated by ionizing radiation, also decreases.

[0107] Furthermore, the irregular flexible siloxane main chains of PDMS in the first molded bodies 2a, 2b, and 2c and the second molded bodies 3a, 3b, and 3c are constrained by covalent bonds with adjacent siloxane main chains at numerous locations, changing them to have gas barrier properties, and reducing gas permeability by 3% or more compared to before irradiation with ionizing radiation. The change in gas permeability can be evaluated by measuring the amount of oxygen or water vapor that permeates the test piece using a pressure sensor or gas chromatograph.

[0108] Furthermore, the first molded bodies 2a, 2b, and 2c and the second molded bodies 3a, 3b, and 3c, which have been irradiated with ionizing radiation, shrink depending on the absorbed dose of ionizing radiation, and their compressive modulus increases by 5% or more compared to before irradiation with ionizing radiation. For example, by appropriately setting the absorbed dose of ionizing radiation, a bonded body can be obtained whose modulus of elasticity is increased by preferably 8% or more, more preferably 10% or more, compared to before irradiation with ionizing radiation. In other words, the ionizing radiation-transmitting region of the bonded body has a modulus of elasticity increased by 5% or more compared to the ionizing radiation-nontransmitting region, and a bonded body can be obtained whose modulus of elasticity is increased by preferably 8% or more, more preferably 10% or more, compared to the ionizing radiation-nontransmitting region. Note that the upper limit of the modulus of elasticity is not particularly limited, but if the modulus is too high, mechanical strength tends to decrease. For this reason, the modulus of elasticity is preferably 50 MPa or less. Changes in the modulus of elasticity can be confirmed using a scanning probe microscope or a compression test.

[0109] Example 1 (Bonding between PDMS films using gamma rays) Two PDMS films 5A and 5B, each 1 mm thick, 1.5 cm wide, and 2 cm long, were placed horizontally with a 1 cm overlap and irradiated with gamma rays (cobalt-60) at four different absorbed doses: 700 kGy, 860 kGy, 1000 kGy, and 1640 kGy. Then, as shown in Figure 2, the two PDMS films 5A and 5B were pulled in opposite longitudinal directions, as indicated by the arrows, and the bonding strength between the PDMS films 5A and 5B was compared.

[0110] As a result, as shown in Table 1, when the absorbed dose was 700 kGy or less, the PDMS films 5A and 5B peeled off before material failure occurred. When the absorbed dose was 860 kGy or more, the PDMS films 5A and 5B were firmly bonded together to the extent that material failure occurred before peeling.

[0111] [Table 1]

[0112] Example 2 (Electron beam bonding of molded sheets constituting a multi-stage microfluidic device) Eleven PDMS molded sheets were stacked with microchannels formed between each layer, and an electron beam was irradiated along the stacking direction to confirm the bonding state between the eleven molded sheets.

[0113] The molded sheets are 0.5 mm thick PDMS sheets with microchannels microfabricated on the lamination surface, and the total thickness of 11 molded sheets stacked and temporarily joined together is 5.5 mm. The acceleration voltage and irradiation energy (absorbed dose) of the electron beam for bonding the 11 molded sheets together are selected from the results of simulation. For example, Figure 3 shows the penetration depth of the electron beam when PDMS is irradiated with electron beams at different acceleration voltages, i.e., the bondable range (D), calculated using a Monte Carlo simulation code. It shows that the bondable range D expands depending on the acceleration voltage.

[0114] Based on the results of this simulation, a stack of 11 0.5 mm thick PDMS molded sheets was temporarily bonded together and irradiated with an electron beam at an accelerating voltage of 2 MeV until the average absorbed dose of the stack reached 2.2 MGy. This resulted in a microfluidic device in which the 11 PDMS molded sheets were completely bonded together.

[0115] Example 3 (Bonding of PDMS films using electron beams) Ten square PDMS films, each 0.5 mm thick and 20 mm long on each side, were temporarily stacked and irradiated with an electron beam at an accelerating voltage of 2 MeV until the average absorbed dose of the stack reached 2 MGy.

[0116] As a result, a silicone bonded structure was obtained in which ten PDMS films were completely bonded between their respective laminated surfaces, as shown in Figures 4 and 5. This silicone bonded structure maintained high transparency, as shown in Figure 4.

[0117] Example 4 (Gas permeability evaluation) A 1 mm thick, 15 cm square PDMS sheet was irradiated with approximately 2.2 MGy of 1 MeV electron beams, and the oxygen permeability and water vapor permeability were compared with those of an unirradiated PDMS sheet. Oxygen permeability was evaluated in accordance with JIS K7126-1 Appendix 2, and water vapor permeability was evaluated in accordance with JIS K7129-1 Method A. The results are shown in Table 2 below. Both the oxygen permeability and water vapor permeability of PDMS decreased after irradiation, demonstrating that the present invention reduces gas permeability and improves gas barrier properties.

[0118] [Table 2]

[0119] Example 5 (Hardness evaluation) A sample consisting of three 500 μm-thick, 10 mm x 20 mm PDMS films was irradiated with 1.6 MGy of gamma rays (cobalt-60) and bonded. The compressive modulus of the sample before and after irradiation, i.e., before and after bonding, was evaluated using a creep meter (RE2-3305B, Yamaden) under a load of 20 N. It was found that the Young's modulus, which was approximately 3 MPa before irradiation, increased to approximately 5.5 MPa after irradiation. This result demonstrates that the compressive modulus of PDMS is increased by the present invention.

[0120] Next, a microfluidic device 10 according to a second embodiment of the present invention and a method for manufacturing the same will be described with reference to Figures 6 and 7. This microfluidic device 10 is configured by alternately stacking two cover sheets 11a, 11b and two base sheets 12a, 12b in four layers, and is used for injecting a trace amount of sample such as an organic compound or a biological sample into a microchannel 15 formed between a stacking surface 13 of the cover sheet 11 and a stacking surface 14 of the base sheet 12, which are opposed in the stacking direction, and mixing, reacting, synthesizing, extracting, separating, or analyzing the sample injected into the microchannel 15.

[0121] 7, the third cover sheet 11b from the top also serves as a base sheet having recesses 15a that form microchannels 15 on its upper stacking surface 13a facing the base sheet 12a above it, and the second base sheet 12a also serves as a cover sheet that covers the recesses 15a that are recessed on the upper stacking surface 13a of the cover sheet 11b. As a result, three stages of microchannels 15 are formed in parallel between the stacking surfaces 13, 14 of the four stacked cover sheets 11 and base sheets 12.

[0122] Silicone (PDMS) is a material for the microfluidic device 10, and is biocompatible, chemical-resistant, low in autofluorescence, optically transparent, and easy to release. It is also less expensive and disposable than glass, and therefore, here, both the cover sheet 11 and the base sheet 12 are formed from PDMS, a type of polyorganosiloxane. However, they may also be formed from an organic resin such as cycloolefin polymer (COP) with a siloxane coating formed on the lamination surfaces 13 and 14. Furthermore, if neither the cover sheet 11 nor the base sheet 12, whose lamination surfaces 13 and 14 face each other in the lamination direction, are formed from glass, then either the cover sheet 11 or the base sheet 12 may be formed from glass whose main component is SiO2.

[0123] The cover sheet 11 and the base sheet 12 are each formed into a flat plate with a thickness of 1.5 mm by injection molding using an electroformed mold, using PDMS as the molding material, and the surfaces (upper stacking surfaces 13a, 14a) of the second to fourth cover sheets 11b and base sheets 12a, 12b are formed with recesses 15a that form microchannels 15 with a width and depth of 500 nm to 1 mm, and numerous grooves 16 that serve as stress relief sections with the same depth as the recesses 15a.

[0124] The recesses 15a forming the microchannels 15 can be designed in any length, shape, and number depending on the application of the microfluidic device 10, and one end of the recesses 15a is cylindrical with an inner diameter longer than the width of the recesses 15a, as shown in Fig. 6, so that the microchannels 15 can communicate with injection holes 18 and discharge holes 19, which will be described later. The microchannels 15 formed in parallel in three stages between the lamination surfaces 13 and 14 of the cover sheet 11 and the base sheet 12 communicate with each other via through-holes 17 that penetrate the second to fourth stages of the cover sheet 11b and the base sheets 12a and 12b, respectively.

[0125] Furthermore, the numerous recessed grooves 16 that serve as stress relief sections are formed in two orthogonal directions, intersecting and evenly in a grid pattern over the entire area of ​​the upper layer surface 13a of the cover sheet 11b and the upper layer surfaces 14a of the base sheets 12a and 12b, excluding the areas where recesses 15a that form the microchannels 15 are formed. The recessed grooves 16 are formed continuously up to the end faces of the cover sheet 11b and the base sheets 12a and 12b, and therefore communicate with the outside at the side surfaces of the microfluidic device 10 in which the cover sheets 11a and 11b and the base sheets 12a and 12b are alternately stacked in four layers.

[0126] According to this embodiment, the recesses 15a forming the microchannels 15 recessed into the surfaces (upper stacking surfaces 13a, 14a) of the cover sheet 11b and the base sheets 12a, 12b and the grooves 16 serving as stress relief sections are made to have the same depth, and therefore the recesses 15a and grooves 16 forming the fine microchannels 15 can be formed by injection molding using an electroforming mold that can be formed with high precision.

[0127] The top cover sheet 11a is provided with an injection hole 18 for injecting a sample into the microchannel 15 and a discharge hole 19 for discharging the sample from the microchannel 15 at positions that communicate with the microchannel 15 formed between the top cover sheet 11a and the second base sheet 12a.

[0128] As mentioned above, both the base sheet 12 and the cover sheet 11 are molded by injection molding, but if they can be molded using a mold to enable mass production, they can be molded using various molding methods such as transfer molding and compression molding, as appropriate, depending on the flow rate, type of PDMS, and shape of the base sheet 12 and cover sheet 11.

[0129] The two cover sheets 11a, 11b and the two base sheets 12a, 12b configured as described above are bonded together by irradiating an electron beam between the stacking surfaces 13, 14 facing each other in the stacking direction, as shown in Figure 7, to form a microfluidic device 10 in which microchannels 15 are formed in parallel in three stages between the stacking surfaces 13, 14.

[0130] The following describes a method for manufacturing this microfluidic device 10. First, two cover sheets 11a, 11b and two base sheets 12a, 12b, which have been formed by injection molding as described above, are stacked in order from the bottom base sheet 12b to the top cover sheet 11a, while positioning the top sheets relative to the bottom sheets. That is, the lower lamination surface 13b of the cover sheet 11b is bonded to the upper lamination surface 14a of the base sheet 12b so that the through-holes 17 drilled in the third-layer cover sheet 11b are aligned with the recesses 15a forming the microchannels recessed in the upper lamination surface 14a of the fourth-layer base sheet 12b; then, the lower lamination surface 14b of the base sheet 12a is bonded to the upper lamination surface 13a of the cover sheet 11b so that the through-holes 17 drilled in the second-layer base sheet 12a are aligned with the recesses 15a forming the microchannels recessed in the upper lamination surface 13a of the cover sheet 11b; and then, the lower lamination surface 13b of the cover sheet 11a is bonded to the upper lamination surface 14a of the base sheet 12a so that the injection hole 18 and the discharge hole 19 drilled in the first-layer cover sheet 11a are aligned with each end of the cylindrical recesses 15a forming the microchannels recessed in the upper lamination surface 14a of the second-layer base sheet 12a.

[0131] In the alignment process described above, the upper and lower stacking surfaces 13 and 14, which face each other in the stacking direction, are bonded together while the cover sheet 11 and the base sheet 12 are positioned relative to each other, but the stacking surfaces 13 and 14 are not joined, so they can be peeled off and reattached multiple times until they are accurately positioned. Furthermore, because PDMS has a certain degree of self-adhesiveness, the two cover sheets 11a and 11b and the two base sheets 12a and 12b, which are positioned relative to each other and stacked alternately, can be temporarily held in a stacked state without using a specific jig or the like.

[0132] Next, the laminate formed by stacking four sheets 11a, 11b, 12a, and 12b is irradiated with ionizing radiation to simultaneously bond the stacking surfaces 13 of all cover sheets 11 and the stacking surfaces 14 of all base sheets 12 that face each other in the stacking direction. However, since the thickness of the laminate formed by stacking four PDMS sheets is 6 mm, an electron beam with an acceleration voltage of 2 MeV is irradiated, referring to the simulation results shown in Figure 3.

[0133] The electron beam is irradiated evenly onto the entire plane of the top cover sheet 11a along the stacking direction (vertical direction) of the laminate, thereby simultaneously firmly bonding the stacking surfaces 13 of all cover sheets 11 and the stacking surfaces 14 of all base sheets 12 that face each other in the stacking direction, thereby producing a microfluidic device 10 in which two cover sheets 11a, 11b and two base sheets 12a, 12b are alternately stacked together.

[0134] As shown by the broken line in FIG. 7, in this microfluidic device 10, the upper and lower microchannels 15 communicate with each other via through-holes 17, so that the desired microchannels 15 can be designed in a three-dimensional shape.

[0135] In the step of irradiating the electron beam, the electron beam penetrates the entire area of ​​the two cover sheets 11a and 11b and the two base sheets 12a and 12b, including the area where the microchannel 15 is formed. Therefore, the contact angle of the inner wall surface of the microchannel 15 with water decreases, and the aqueous solution injected into the microchannel 15 does not stagnate within the microchannel 15 due to surface tension.

[0136] Similarly, in the step of irradiating with electron beams, the electron beams penetrate the entire area of ​​the two cover sheets 11a and 11b and the two base sheets 12a and 12b, including the area where the microchannel 15 is formed, and therefore the gas permeability of the cover sheets 11a and 11b and the two base sheets 12a and 12b made of PDMS decreases, thereby suppressing sorption of the sample injected into the microchannel 15 into the cover sheets 11a and 11b and the base sheets 12a and 12b.

[0137] Furthermore, an electron beam passes through the microchannel 15 between the stacking surfaces 13 and 14 while being shielded from the outside, thereby sterilizing the inside of the microchannel 15 before the sample is injected.

[0138] Furthermore, although the cover sheets 11a, 11b and the two base sheets 12a, 12b shrink when an electron beam penetrates them, the shrinkage strain is absorbed by the stress relief grooves 16, so the cover sheets 11a, 11b and the two base sheets 12a, 12b can be maintained flat. As a result, even if the cover sheets 11 and base sheets 12 are stacked in multiple layers, the entire microfluidic device 10 does not bend or flex significantly.

[0139] Furthermore, when an electron beam penetrates the cover sheet 11 or base sheet 12 made of PDMS, side chains such as CH3 (methyl group) turn into gas and are generated within the cover sheet 11 or base sheet 12. However, this gas is released to the outside through the micropores in the PDMS and the grooves 16, which are stress relief sections, so there is no risk of voids being generated within the cover sheet 11 or base sheet 12 or on their laminated surfaces 13 and 14.

[0140] In this second embodiment, the alternately stacked cover sheets 11 and base sheets 12 are bonded together by irradiating them with electron beams, but they may also be bonded together by irradiating them with other ionizing radiation such as gamma rays or X-rays.

[0141] In addition, in the above embodiment, the cover sheet 11 and the base sheet 12 stacked in four layers were bonded by irradiating them with ionizing radiation, but the present invention can also be applied to a microfluidic device 10 in which the cover sheet 11 and the base sheet 12 are stacked in multiple layers, as long as ionizing radiation reaches between all of the bonded layers of the temporarily bonded laminate.

[0142] Furthermore, the direction of irradiation with ionizing radiation is not limited to the vertical direction described above, and if it is not necessary to join the entire surface of the laminated surface 13 of the cover sheet 11 and the entire surface of the laminated surface 14 of the base sheet 12, the electron beam may be irradiated onto a portion of the surface of the temporarily held laminate. [Industrial Applicability]

[0143] The present invention is suitable for a silicone bonded body that is produced by bonding silicone molded bodies together at multiple locations. [Explanation of symbols]

[0144] 1 Silicone bonded body 2(2a, 2b, 2c) First molded body 3(3a, 3b, 3c) Second molded body 4a~4h contact area 10 Microfluidic Devices 11a, 11b: Cover sheet (first molding sheet) 12a, 12b: base sheet (second molding sheet) 13 Lamination surface (first molding surface) 14 Laminated surface (second laminated surface) 15 Microchannel 16 Groove (stress relief section)

Claims

1. A method for joining a plurality of joined bodies simultaneously, wherein one or more first molded bodies each mainly composed of polyorganosiloxane and one or more second molded bodies each mainly composed of polyorganosiloxane or glass are joined, A bonding method characterized by irradiating one or more contact points where the first molded body and the second molded body are in contact with each other with ionizing radiation consisting of any one of electron beams, gamma rays, and X-rays, and covalently bonding the siloxane main chains of the first molded body and the siloxane main chains of the second molded body at the interface of the contact points by ionizing radiation crosslinking caused by the ionizing radiation.

2. 2. The bonding method according to claim 1, wherein the ionizing radiation is either an electron beam or a gamma ray, and the absorbed dose of the ionizing radiation at the contact point is 860 kGy or more.

3. 2. The bonding method according to claim 1, wherein the ionizing radiation is an electron beam, and the accelerating voltage of the electron beam is 500 keV or more.

4. A first molded sheet; a second molded sheet laminated on the first molded sheet, a microfluidic device in which a first lamination surface of the first molded sheet and a second lamination surface of the second molded sheet that are in contact with each other in a lamination direction are joined together with a microchannel formed therebetween, and the first molded sheet and the second molded sheet are laminated together, The first molded sheet is formed from polyorganosiloxane, The second molded sheet is formed from polyorganosiloxane, glass, or an organic resin having a siloxane coating formed on the second lamination surface, A microfluidic device characterized in that the first and second stacking surfaces, which are in contact in the stacking direction, are exposed to ionizing radiation consisting of any one of electron beams, gamma rays, and X-rays that passes through the first and second stacking surfaces, causing the siloxane main chains of the first and second stacking surfaces to be covalently bonded by ionizing radiation crosslinking caused by the ionizing radiation, thereby stacking the first and second molded sheets together.

5. The microfluidic device according to claim 4, characterized in that a stress relaxation portion consisting of a groove or a slit communicating with the side surfaces of the first molded sheet and the second molded sheet laminated together is formed on at least one of the first and second laminated surfaces excluding the portion where the microchannel is formed.

6. 6. The microfluidic device according to claim 4, wherein the ionizing radiation is an electron beam.

7. The first molded sheet and the second molded sheet are laminated together, A method for manufacturing a microfluidic device, comprising bonding a first lamination surface of the first molded sheet and a second lamination surface of the second molded sheet, the first lamination surface and the second lamination surface being opposed to each other in a lamination direction, excluding a portion where the microchannel is formed, the method comprising: The first molded sheet made of polyorganosiloxane and the second molded sheet made of polyorganosiloxane, glass, or an organic resin having a siloxane coating formed on the second lamination surface are laminated together, The stacked first molded sheet and the second molded sheet are positioned relative to each other, the first molded sheet and / or the second molded sheet, which are positioned relative to one another and stacked, are irradiated with ionizing radiation consisting of any one of electron beams, gamma rays, and X-rays, and at the contact surface where the first stacking surface and the second stacking surface come into contact, the siloxane main chains of the first stacking surface and the siloxane main chains of the second stacking surface are covalently bonded by ionizing radiation crosslinking caused by the ionizing radiation; A method for manufacturing a microfluidic device, comprising bonding the first and second stacking surfaces together except for a portion where the microchannel is to be formed.

8. One or more of the first molded sheets and one or more of the second molded sheets are alternately stacked in multiple layers, All of the first molded sheets and the second molded sheets adjacent to each other in the stacking direction are positioned relative to each other, Irradiating the first molded sheet and / or the second molded sheet, which are positioned relative to each other and stacked in multiple layers, with the ionizing radiation; 8. The method for manufacturing a microfluidic device according to claim 7, wherein the first and second stacking surfaces are simultaneously bonded to each other in all areas except for the area where the microchannel is formed.

9. 9. A method for manufacturing a microfluidic device as described in claim 8, characterized in that all of the first molded sheets and the second molded sheets adjacent to each other in the stacking direction are positioned relative to each other so that through holes passing through the first molded sheet and / or the second molded sheet in the stacking direction are connected to the microchannel formed between the first stacking surface and the second stacking surface.

10. 10. The method for manufacturing a microfluidic device according to claim 7, wherein a stress relaxation portion consisting of a groove or a slit communicating with a side surface of the first molded sheet and the second molded sheet that are integrated by joining the first molded sheet surface and the second molded sheet is formed on at least one of the first and second laminated surfaces excluding the portion where the microchannel is formed.

11. The method for manufacturing a microfluidic device according to claim 10, wherein the microchannel and the recessed groove have the same depth from the first stacking surface and the same depth from the second stacking surface.

12. 10. The method for manufacturing a microfluidic device according to claim 7, wherein the ionizing radiation is irradiated along the stacking direction onto the entire surface of the first molded sheet and / or the second molded sheet, including the portion where the microchannel is formed.

13. 10. The method for manufacturing a microfluidic device according to claim 7, wherein the ionizing radiation is an electron beam.

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