JP7810364B2 - Bonded body and bonding method thereof, microfluidic device and manufacturing method thereof - Google Patents

Description

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, and to 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 between them, and a method for manufacturing the same.

Silicone, whose main component is polyorganosiloxane, is a highly processable material with heat resistance, insulating properties, weather resistance, low toxicity, transparency, and other properties. It is a resin material used in a variety of fields, including electrical and electronic components, transportation machinery, building materials, household goods, and medical products. Therefore, there is a demand for the development of processing techniques for silicone molded products (hereafter simply referred to as silicone for the sake of convenience) and techniques for bonding silicone to other silicones or silicone to glass.

Silicone itself has a certain degree of self-adhesiveness, but a method for achieving stronger bonding is known, as disclosed in Patent Documents 1 and 2, for example, 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 temporary and not sustainable, there is a restriction that the silicone must be bonded together immediately after surface modification.

To address the issue of surface modification being temporary, the inventors of this application have developed a new silicone processing method in which the surface of the silicone is irradiated with an electron beam with an absorbed dose of 2 MGy or more to form depressions, resulting in a surface layer of 1 μm or more that remains hydrophilic for a long period of time, compared to the above-mentioned surface modification (Non-Patent Document 1).

In recent years, there has been growing demand in the fields of regenerative medicine, drug discovery, and diagnostics for microfluidic devices used in applications such as mixing, reacting, synthesizing, extracting, and analyzing samples. Silicone is commonly used as the base material for microfluidic devices because it is biocompatible, chemical-resistant, low intrinsic autofluorescence, optically transparent, and easy to release, and is less expensive and disposable than glass. A typical microfluidic device has a base sheet made of silicone with fine microchannels approximately 500 nm to 1 mm wide recessed into its surface, on which a cover sheet made of silicone or glass that covers the microchannels is laminated. The opposing surfaces of the base sheet and cover sheet are then bonded together to form an integrated structure.

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

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, and an oxide film of 10 nm or less is formed on the laminated surface of the silicone base facing the glass substrate, bonding the silicone base and glass substrate via the oxide film.

Japanese Patent Application Laid-Open No. 2004-154898 Patent No. 3714338 JP 2014-21081 A Japanese Patent Application Laid-Open No. 2004-331731 T. G. Oyama et al. , Applied Physics Letters, 112, 213704 (2018)

The bonding methods disclosed in Patent Documents 1 to 3 involve modifying the surface of the silicone within a range of several tens of nanometers from the surface to bond silicone to silicone, but modifying the deeper portions of the silicone is difficult.

In addition, when bonding using the above-mentioned surface modification treatment, atmospheric pressure plasma or excimer UV is irradiated onto the bonding surfaces of the silicone to be bonded beforehand, 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 requires the surfaces to be quickly brought into close contact after the surface modification treatment.

Even in the manufacturing methods described in Patent Documents 1 to 3, which involve modifying the surface of the laminated silicone base sheet and cover sheet, bonding the base sheet and cover sheet together, and creating a microfluidic device in which the base sheet and cover sheet are laminated together, these methods require a complex manufacturing process of modifying the surface of the laminated surface by plasma irradiation or vacuum ultraviolet light 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 for a predetermined period of time. Furthermore, the alignment process between the base sheet with recessed microchannels and the cover sheet that covers the microchannels requires high precision, and once the laminated surfaces are brought into close contact, they cannot be reattached, resulting in low manufacturing yields.

The optical bonding method described in Patent Document 4 allows a silicone base sheet to be laminated with a glass cover sheet and then irradiated with vacuum ultraviolet light 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 forms on the surface of the silicone base sheet when irradiated with vacuum ultraviolet light, which can result in uneven bonding and insufficient bonding strength.

In addition, 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 samples into the multiple microchannels formed between the layers of each layer, as well as microfluidic devices in which holes are drilled through each base sheet to connect the microchannels formed on both sides, forming a three-dimensional microchannel. However, it is extremely difficult to manufacture these multi-stage microfluidic devices using the bonding methods described in Patent Documents 1 to 3, which require highly accurate positioning and adhesion of each base sheet and cover sheet to be stacked, or the optical bonding method described in Patent Document 4, which uses irradiation with vacuum ultraviolet light.

Furthermore, as mentioned above, silicone is suitable as a material for microfluidic devices, but because it has a porous structure with countless micropores of about 2-3 μm in size, it lacks gas barrier properties and sorbs low-molecular-weight compounds (sorption, absorption into solid polymers). As a result, when an aqueous solution of a sample is injected into a microchannel surrounded by silicone, its concentration drops significantly, and it has been thought to be unsuitable as a material for microfluidic devices used to culture and analyze water-soluble samples.

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

The present invention was made in consideration of these conventional problems, and aims to provide a method for joining a bonded body (a silicone bonded body) that simultaneously and firmly bonds a silicone molded body to another silicone or glass molded body at multiple contact points between the two bodies.

Another object is to provide a method for joining silicone joined bodies that changes the physical properties of silicone molded bodies within a certain range.

Another objective of the present invention is to provide a microfluidic device and a method for manufacturing the same that can firmly bond a set of molded silicone sheets, each having a microchannel formed between the laminated surfaces, after aligning the surfaces together, thereby laminating the set of molded sheets together.

Another objective of the present invention is to provide a microfluidic device and a method for manufacturing the same, in which multiple molded silicone sheets, each with a microchannel formed between each layer, can be aligned together and then firmly bonded together to form multiple layers of molded sheets.

Another objective 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.

Another objective is to provide a microfluidic device and a manufacturing method for the same, in which the silicone molded sheet that forms the microchannel is changed from hydrophobic to hydrophilic, so that the flow of samples within the microchannel is not impeded.

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.

At contact points within the range penetrated by ionizing radiation, 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.

The method for joining a bonded body described in 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.

The bond strength at the contact point between the first and second molded bodies 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, a strong bond is formed at the contact point.

The method for bonding a bonded body described in 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.

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.

The microfluidic device described in claim 4 comprises a first molded sheet and a second molded sheet laminated on the first molded sheet. The first and second laminated surfaces of the first and second molded sheets, which are in contact in the stacking 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, and the second molded sheet is formed from polyorganosiloxane, glass, or an organic resin with a siloxane coating formed on the second laminated surface. The first and second laminated surfaces, which are in contact in the stacking direction, are exposed to ionizing radiation, consisting of one of electron beams, gamma rays, and X-rays, which penetrates the first and second laminated surfaces, and the siloxane main chains on the first and second laminated surfaces are covalently bonded to each other through ionizing radiation crosslinking caused by the ionizing radiation, thereby laminating the first and second molded sheets together.

At the interface between the first laminated surface formed from polyorganosiloxane and the second laminated surface formed with a polyorganosiloxane, glass, or siloxane coating, which are opposed in the lamination direction, the siloxane main chains of the first and second laminated surfaces are covalently bonded by ionizing radiation crosslinking, resulting in a strong bond.

When ionizing radiation penetrates the first molded sheet having the microchannel formed between the first and second laminated surfaces, hydrophobic side chains such as _CH3 (methyl group) with low binding energy are removed by the ionizing radiation, and hydrophilic siloxane main chains with high binding energy are revealed. As a result, the microchannel is formed in the first molded sheet that has changed from hydrophobic to hydrophilic.

Similarly, when ionizing radiation penetrates the first molded sheet, which has microchannels formed between the first and second laminated surfaces, the irregularly flexible siloxane main chains are covalently bonded to adjacent siloxane main chains at numerous locations and are constrained, resulting in the sheet being modified to have gas barrier properties. As a result, the microchannels are formed in the first molded sheet, which has gas barrier properties.

The microfluidic device described in claim 5 is characterized in that a stress relief portion consisting of a recessed groove or slit communicating with the side surfaces of the integrally laminated first molded sheet and the second molded sheet is formed on at least one of the first and second laminated surfaces, excluding the area where the microchannel is formed.

The stress relief section formed on at least one of the first and second lamination surfaces absorbs distortion caused by ionizing radiation penetrating the first or second molded sheet, so that even when the first and second lamination surfaces are joined, the integrally laminated first and second molded sheets do not flex due to uneven distortion.

When ionizing radiation passes through the first and second laminated surfaces, gas is generated at the interface between the first and second laminated surfaces and is released to the outside from the side of the first and second molded sheets, which are laminated together, through the stress relief section.

The microfluidic device described in claim 6 is characterized in that the ionizing radiation is an electron beam.

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.

The method for manufacturing a microfluidic device described in claim 7 includes laminating a first molded sheet and a second molded sheet, forming a microchannel between a first laminated surface of the first molded sheet and a second laminated surface of the second molded sheet, and bonding the first laminated surface and the second laminated surface except for the portion where the microchannel is formed. The method further includes bonding 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 laminated surface. The method is characterized in that the first and second molded sheets are laminated together, the laminated first and second molded sheets 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 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, 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 excluding the area where the microchannel is formed.

By irradiating the first and/or second molded sheets, which have been positioned relative to one another and stacked, with ionizing radiation, the siloxane main chains of the first and second laminated surfaces, which face each other in the stacking direction and are formed from polyorganosiloxane, and the second laminated surface, which is formed with a coating of polyorganosiloxane, glass, or siloxane, are covalently bonded by ionizing radiation crosslinking at the interface between the surfaces, resulting in a strong bond.

By irradiating the first molded sheet and/or the second molded sheet formed from polyorganosiloxane with ionizing radiation, hydrophobic side chains such as CH ₃ (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, the microchannel is formed in the first molded sheet and/or the second molded sheet that has changed from hydrophobic to hydrophilic.

Similarly, by irradiating the first molded sheet and/or the second molded sheet formed from polyorganosiloxane with ionizing radiation, the irregularly flexible siloxane main chains are covalently bonded to adjacent siloxane main chains at numerous locations and are constrained, thereby changing the structure to have gas barrier properties. As a result, microchannels are formed in the first molded sheet and/or the second molded sheet, which have gas barrier properties.

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 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.

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

All first and/or second molded sheets formed from polyorganosiloxane are simultaneously transformed from hydrophobic to hydrophilic in a single process of exposure to ionizing radiation, thereby imparting gas barrier properties.

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

All adjacent first and second molded sheets in the stacking direction are positioned relative to one another so that the through-holes that penetrate the first and/or second molded sheets in the stacking direction are connected to the microchannel, and then the multi-layered first and second molded sheets are firmly bonded together at the same time.

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

The stress relief section formed on at least one of the first and second lamination surfaces absorbs the strain caused by ionizing radiation penetrating the first or second molded sheet. Therefore, even if the first and second molded sheets are stacked in multiple layers and bending displacement accumulates, the entire stack will not bend or warp significantly.

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

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

By using resist etching with photolithography technology or electroforming, a mold with protrusions of the same height that form the microchannels and recessed grooves can be easily obtained.

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.

By irradiating the entire surface of the first molded sheet and/or the second molded sheet, including the area where the microchannel is formed, with ionizing radiation, the inner surface of the microchannel formed from polyorganosiloxane becomes hydrophilic and has gas barrier properties.

The method for manufacturing a microfluidic device described in claim 13 is characterized in that the ionizing radiation is an electron beam.

All first and second stacking surfaces are bonded using an electron beam, which has high directionality and makes it easy to control the irradiation timing.

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 simultaneously.

In addition, the water contact angle can be reduced in the range from the surface of the first or second molded body, which is primarily composed of polyorganosiloxane, to the contact point.

According to the invention of claim 4, the first molded sheet and the second molded sheet are bonded 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.

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.

In addition, the first and second molded sheets, which have microchannels 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 microchannels can be suppressed.

According to the invention of claim 5, even when bonded by ionizing radiation that penetrates the first and second laminated surfaces, the integrally laminated first and second molded sheets maintain their flatness without warping due to uneven distortion.

In addition, 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, preventing the generation of voids at the interface due to residual gas.

According to the invention of claim 6, the first and second stacking surfaces are bonded using an electron beam, which has high directionality and allows easy control of irradiation timing, facilitating mass production of microfluidic devices in which the first and second molded sheets are integrally stacked.

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 together, so that the relative positioning of the first and second molded sheets can be repeatedly performed before bonding.

The first molded sheet and/or the second molded sheet, which have microchannels formed between their laminated surfaces, can be changed from hydrophobic to hydrophilic, so that liquid samples injected into the microchannels do not stagnate within the microchannels due to surface tension.

In addition, gas barrier properties can be imparted to the first molded sheet and/or the second molded sheet, which have microchannels formed between their laminated surfaces, so even when silicone is used as a material for a microfluidic device, sorption of samples such as low-molecular-weight compounds injected into the microchannels can be suppressed.

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 one another with microchannels formed therebetween, and then all of the first and second molded sheets adjacent in the stacking direction can be firmly bonded simultaneously. This makes it possible to easily manufacture microfluidic devices in which multiple microchannels are formed in parallel or in which microchannels are formed in a three-dimensional shape.

All microchannels formed between the first and second laminated surfaces can be formed in the first molded sheet and/or the second molded sheet, which are made from polyorganosiloxane and have been made hydrophilic.

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.

According to the invention of claim 9, all of the first and second molded sheets stacked alternately in multiple layers are positioned relative to one another so that the through-holes that penetrate the first and/or second molded sheets in the stacking direction communicate with the microchannel. Then, all of the first and second molded sheets that are adjacent in the stacking direction can be firmly bonded together simultaneously, thereby facilitating the manufacture of a microfluidic device in which a microchannel is formed in a three-dimensional shape.

According to the invention of claim 10, in the process of irradiating ionizing radiation to first and/or second molded sheets stacked in multiple layers and bonding the first and second laminated surfaces, even if distortion occurs in a portion of the bonding surface, the distortion does not extend beyond the stress relief 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 laminated surfaces do not tilt in part or change in inner diameter, and the entire multi-layer stack does not bend or warp significantly.

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 relief portions formed on the bonding surfaces, thereby preventing voids from forming in the first and second molded sheets due to residual gas.

According to the invention of claim 11, the microchannel and the grooves of the stress relief section can be formed using an electroforming mold or a resist etching mold using photolithography technology, which allows for high-precision molding.

According to the invention of claim 12, the inner surface of the microchannel becomes hydrophilic, preventing aqueous solution samples injected into the microchannel from stagnating within the microchannel and suppressing sorption of samples such as low-molecular-weight compounds injected into the microchannel.

In addition, ionizing radiation penetrates all microchannels, sterilizing the inside of the microchannels.

According to the invention of claim 13, all first and second stacking surfaces are bonded using an electron beam, which has high directionality and allows easy control of irradiation timing, facilitating mass production of microfluidic devices in which first and second molded sheets are integrally stacked.

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. 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. 10 is a graph showing a bondable range when a bonded body is obtained by irradiating PDMS with electron beams having different acceleration voltages. This is a photograph taken from the flat side of a silicone bonded body in which ten PDMS films were bonded together by irradiation with an electron beam. 5 is a photograph of the silicone bonded body of FIG. 4 taken from the side. FIG. 10 is an exploded perspective view of a microfluidic device 10 according to a second embodiment. FIG. 1 is a longitudinal cross-sectional view of a microfluidic device 10.

The following describes a silicone bonded body 1 according to a first embodiment of the present invention and a method for manufacturing the silicone bonded body 1, using Figure 1. In Figure 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, as described below.

<Method for producing silicone bonded body>
The method for producing the silicone bonded body 1 includes a step of irradiating ionizing radiation to contact points between one or more first molded bodies 2 and one or more second molded bodies 3. The 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. In other words, the method 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. The irradiation of ionizing radiation bonds the first molded body 2 and the second molded body 3 at their contact points.

Figure 1(a) shows the temporarily joined body before irradiation with ionizing radiation. As shown, the first molded body 2 and the second molded body 3 are temporarily held together to maintain contact at all contact areas 4a-4h where they come into contact, forming a temporarily joined body 1'. The contact state of the individual molded bodies in this temporarily joined body 1' may be maintained using a jig (not shown), or the self-adhesive properties of silicone may be utilized to maintain the contact state of the individual molded bodies.

The first molded body 2 may contain other substances as long as it is primarily composed of polyorganosiloxane. Here, "primary component" refers to a component with 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 lamination surface with another molded body. Furthermore, "composed primarily of polyorganosiloxane" includes a component that is essentially made of polyorganosiloxane.

The second molded body 3 is formed of a material mainly composed of polyorganosiloxane or glass mainly composed of SiO ₂ (glass). Here, "mainly composed of SiO ₂ (glass)" means a material having an SiO ₂ content of 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 SiO ₂ .

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), a first molded body 2 and a second molded body 3 are both made of polyorganosiloxane and are each formed into a desired shape.

In this first embodiment, the first molded bodies 2a, 2b, and 2c and the second molded bodies 3a, 3b, and 3c can each have any shape, such as a film or a sphere. Each contact area 4a-4h or each interior area may have a hollow, 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 the desired position.

Next, the temporary fastener 1' is irradiated with ionizing radiation. This irradiation of ionizing radiation bonds the first molded body 2 and the second molded body 3 at contact points or contact areas within the range of the depth D through which the ionizing radiation penetrates. In the embodiment shown in Figure 1(b), ionizing radiation is irradiated vertically from above to below, bonding contact areas 4a-4h of the temporary fastener 1'.

In this embodiment, conventionally known ionizing radiation can be used, such as electron beams, gamma rays, and X-rays. Irradiation may be carried out using one or a combination of multiple types of such ionizing radiation.

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 area in between, D becomes even longer. Therefore, if the length along the direction of incidence of the ionizing radiation from the surface of the first molded body 2a of the temporary fastener 1' made of PDMS to the contact area 4d is 1.5 mm, an electron beam with an acceleration voltage of 500 keV is irradiated.

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 between them, D will be even longer.

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 D through which ionizing radiation penetrates. 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.

The irradiation conditions for the ionizing radiation are not particularly limited, but for example, when using an electron beam, 10 keV or higher is preferable, 30 keV or higher is more preferable, and 500 keV or higher is even more preferable. The acceleration voltage can 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 it can be set to, for example, 10 MeV or lower, e.g., 5 MeV or lower.

Furthermore, the absorbed dose of ionizing radiation (e.g., electron beams or gamma rays) in each contact region 4a-4h is preferably 200 kGy or more to ensure strong bonding in each contact region 4a-4h, more preferably 500 kGy or more, and even more preferably 860 kGy or more. 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 molded body or the second molded body will decrease, so it is preferably 40 MGy or less, and more preferably 20 MGy or less, for example.

Furthermore, the size of the ionizing radiation irradiation spot can 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 it can be either fixed irradiation in which the irradiation spot does not move, or scanning irradiation in which the irradiation spot moves.

The above-mentioned irradiation with ionizing radiation may be performed in a single step or in a combination of multiple steps. Furthermore, the bonded body (temporarily bonded body) may be irradiated with ionizing radiation from one direction, or the irradiation direction may be changed. Furthermore, bonding of each contact region 4a-4h may be achieved by combining the above-mentioned irradiation with ionizing radiation with existing bonding methods such as surface modification of the contact surface by plasma treatment or the use of adhesives.

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 (e.g., PDMS) and the second molded bodies 3a, 3b, and 3c, as shown by the dashed lines in Fig. 1(b). When polyorganosiloxane (e.g., PDMS) is exposed to ionizing radiation, side chains such as _CH3 (methyl group) are cleaved and scattered as gas or the like. Therefore, the siloxane main chains are
(1 set)
(2 sets)
(3 types)
(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—).

In the above formulas 1, 2, and 3, R is not particularly limited as long as it is an organic group. Examples include alkyl groups (methyl, ethyl, propyl, butyl, etc.), aryl groups (phenyl, naphthyl, etc.), and hydrogen atoms, with a methyl group being preferred.

The ionizing radiation also penetrates each of the contact regions 4a to 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 regions 4a to 4h is similarly exposed to the ionizing radiation, and side chains such as _CH3 (methyl groups) are cleaved. At the interfaces of each of the contact regions 4a to 4h, the PDMS having (-Si-O-) groups and the PDMS or glass are covalently bonded by siloxane bonds consisting of (-Si-O-Si-) structures shown in formulas (1) to (3).

In other words, 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 together at all contact areas 4a-4h (i.e., contact points) within the range of depth D that the ionizing radiation penetrates from the surface of the temporary bonded body 1' (the surface of the first molded body 2a or the surface of the second molded body 3a), resulting in the integral silicone bonded body 1 shown in Figure 1(c).

Furthermore, when the first molded bodies 2a, 2b, 2c or the second molded bodies 3a, 3b, 3c are 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 depth D) is exposed to ionizing radiation and covalently bonds between the siloxane main chains through siloxane bonds (-Si-O-Si-) having the structures shown in formulas (1) to (3). In other words, 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 areas 500 nm or more away from the junction of the first molded body or the second molded body.

When the first or second molded body mainly composed of polyorganosiloxane (e.g., PDMS) is irradiated with the ionizing radiation, hydrophobic side chains such as CH ₃ (methyl groups) are exposed to the ionizing radiation and disappear, revealing the hydrophilic siloxane main chain. As a result, the contact angle of the molded body with water decreases in the range from the surface (ionizing radiation irradiated surface) of the molded body mainly composed of polyorganosiloxane to the contact point. That is, the water contact angle can be reduced in the range from the surface of the first or second molded body mainly composed of polyorganosiloxane to the point where the ionizing radiation penetrates. For example, when the first or second molded body is mainly composed of PDMS, the water contact angle before irradiation with ionizing radiation is about 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.

Furthermore, when the first or second molded body 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 body. That is, in the area from the surface (the ionizing radiation-irradiated surface) of the polyorganosiloxane-based molded body 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-transmitting area of the bonded body has reduced gas permeability compared to the ionizing radiation-non-transmitting area, and the gas permeability of the ionizing radiation-transmitting area is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less, of the ionizing radiation-non-transmitting area.

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.

Whether the structures of the first compacts 2a, 2b, 2c and the second compacts 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) will decrease by 3% or more compared to before irradiation with ionizing radiation.

<Silicone bonded body>
The silicone bonded body 1 disclosed in this specification is a bonded body in which one or more first molded bodies, each having a polyorganosiloxane as the main component, are bonded to one or more second molded bodies, each having a polyorganosiloxane or glass as the main component, and the first molded bodies and the second molded bodies are 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 of the silicone bonded body 1 above. A detailed description thereof will be omitted here.

The silicone bonded body 1 is formed by bonding the first and second molded bodies at the interface where they are joined together via siloxane bonds (-Si-O-Si-) with structures shown in formulas (1) to (3).

The silicone bonded body 1 is a molded body primarily composed of polyorganosiloxane, in which the siloxane main chains of the polyorganosiloxane are bonded by siloxane bonds having the (-Si-O-Si-) structure shown in formulas (1) to (3) in the region where ionizing radiation penetrated during the manufacturing process of the bonded body. 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-) structure shown in formulas (1) to (3) at a depth of 500 nm or more from the bonded 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 or more, preferably 800 nm or more, and more preferably 1000 nm or more away from the bonded point.

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.

Furthermore, in the above structure, hydrophobic side chains such as _CH3 (methyl group) are scattered by exposure to ionizing radiation, and the hydrophilic siloxane main chain is revealed, so that 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.

In addition, the irregularly flexible siloxane main chains of the PDMS in the first molded bodies 2a, 2b, and 2c and the second molded bodies 3a, 3b, and 3c are bound by covalent bonds with adjacent siloxane main chains at numerous locations, changing the material 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 passes through the test piece using a pressure sensor or gas chromatograph.

Furthermore, the first molded bodies 2a, 2b, and 2c and the second molded bodies 3a, 3b, and 3c, which have been penetrated by ionizing radiation, shrink in accordance with the absorbed dose of ionizing radiation, and the compressive modulus increases by 5% or more compared to the modulus 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, and more preferably 10% or more, compared to the modulus 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-non-transmitting region, and a bonded body can be obtained whose modulus of elasticity is increased by preferably 8% or more, and more preferably 10% or more, compared to the ionizing radiation-non-transmitting region. Note that there is no particular upper limit to the modulus of elasticity, but if the modulus is too high, mechanical strength tends to decrease. For this reason, it is preferable that the modulus of elasticity be 50 MPa or less. Changes in the modulus of elasticity can be confirmed using a scanning probe microscope or compression testing.

Example 1
(Bonding between PDMS films by gamma rays)
Two PDMS films 5A and 5B, each 1 mm thick, 1.5 cm wide, and 2 cm long, were placed horizontally, overlapping by 1 cm, and irradiated with gamma rays (cobalt 60) at four different absorbed doses of 700 kGy, 860 kGy, 1000 kGy, and 1640 kGy. Thereafter, as shown in FIG. 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.

As a result, as shown in Table 1, when the absorbed dose was 700 kGy or less, peeling occurred before material failure occurred. Furthermore, 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 occurred.

Example 2
(Electron beam bonding between molded sheets constituting a multi-stage microfluidic device)
Eleven molded sheets made of PDMS, each stacked with a microchannel formed between each laminated surface, were irradiated with an electron beam along the stacking direction, and the bonding state between the eleven molded sheets was confirmed.

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 fixed is 5.5 mm. The acceleration voltage and irradiation energy (absorbed dose) of the electron beam used to bond the 11 molded sheets together are selected from simulation results. For example, Figure 3 shows the penetration depth of the electron beam when PDMS is irradiated with electron beams of 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.

Based on these simulation results, a stack of 11 0.5 mm thick PDMS molded sheets was temporarily bonded together and irradiated with an electron beam at an acceleration 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.

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

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.

Example 4
(Evaluation of gas permeability)
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. As 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.

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.

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 constructed by alternately stacking two cover sheets 11a, 11b and two base sheets 12a, 12b in four layers. A minute amount of sample, such as an organic compound or a biological sample, is injected into a microchannel 15 formed between the stacking surface 13 of the cover sheet 11 and the stacking surface 14 of the base sheet 12, which face each other in the stacking direction. The device is used for mixing, reacting, synthesizing, extracting, separating, or analyzing the sample injected into the microchannel 15.

As shown in Figure 7, the third cover sheet 11b from the top doubles as a base sheet with recesses 15a that form microchannels 15 recessed into its upper stacking surface 13a facing the base sheet 12a above it, and the second base sheet 12a from the top doubles as a cover sheet that covers the recesses 15a recessed into its upper stacking surface 13a. As a result, three tiers of microchannels 15 are formed in parallel between the stacking surfaces 13, 14 of the four stacked cover sheets 11 and base sheets 12.

As a material for the microfluidic device 10, silicone (PDMS) has excellent biocompatibility, chemical resistance, low autofluorescence, optical transparency, and mold releasability. It is also less expensive and disposable than glass. 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 the cover sheet 11 and the base sheet 12, whose lamination surfaces 13 and 14 face each other in the lamination direction, are not both formed from glass, then either the cover sheet 11 or the base sheet 12 may be formed from glass whose main component is SiO2.

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

The recesses 15a that form the microchannels 15 can be designed in any length, shape, and number depending on the application of the microfluidic device 10. One end of the recesses 15a is cylindrical with an inner diameter longer than its width, as shown in Figure 6, to connect the microchannels 15 to the injection holes 18 and discharge holes 19 described below. The microchannels 15, formed in three parallel rows between the lamination surfaces 13, 14 of the cover sheet 11 and base sheet 12, are connected via through-holes 17 that penetrate the second to fourth cover sheets 11b and base sheets 12a, 12b, respectively.

The numerous grooves 16 that serve as stress relief sections are formed in two perpendicular directions, intersecting and evenly in a grid pattern across the entire 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 the recesses 15a that form the microchannels 15 are formed. Because the grooves 16 are formed continuously to the end faces of the cover sheet 11b and the base sheets 12a and 12b, they communicate with the outside at the side 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.

In this embodiment, the recesses 15a that form the microchannels 15 recessed into the surfaces (upper layer surfaces 13a, 14a) of the cover sheet 11b and base sheets 12a, 12b, and the grooves 16 that serve as stress relief sections, are made to the same depth. This allows the recesses 15a and grooves 16 that form the fine microchannels 15 to be formed by injection molding using an electroformed mold that can be molded with high precision.

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 connect to the microchannel 15 formed between it and the second base sheet 12a.

As mentioned above, both the base sheet 12 and the cover sheet 11 are formed by injection molding, but as long as they can be mass-produced using a mold, they can be formed using various molding methods such as transfer molding and compression molding, depending on the flow rate, type of PDMS, and shape of the base sheet 12 and cover sheet 11.

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

The method for manufacturing this microfluidic device 10 is described below. 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, with the top sheets positioned relative to the bottom sheets. That is, the lower layer surface 13b of the cover sheet 11b is bonded to the upper layer surface 14a of the base sheet 12b so that the through-holes 17 formed in the third layer of cover sheet 11b are aligned with the recesses 15a forming the microchannels recessed in the upper layer surface 14a of the fourth layer of base sheet 12b; then, the lower layer surface 14b of the base sheet 12a is bonded to the upper layer surface 13a of the cover sheet 11b so that the through-holes 17 formed in the second layer of base sheet 12a are aligned with the recesses 15a forming the microchannels recessed in the upper layer surface 13a of the cover sheet 11b; and then, the lower layer surface 13b of the cover sheet 11a is bonded to the upper layer surface 14a of the base sheet 12a so that the injection hole 18 and discharge hole 19 formed in the first layer of cover sheet 11a are aligned with each end of the cylindrical recesses 15a forming the microchannels recessed in the upper layer surface 14a of the second layer of base sheet 12a.

In the above alignment process, which involves bonding the upper and lower stacking surfaces 13, 14 that face each other in the stacking direction while positioning the cover sheet 11 and base sheet 12 relative to each other, the stacking surfaces 13, 14 are not bonded together, 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, 11b and the two base sheets 12a, 12b that have been positioned relative to each other and stacked alternately can be temporarily held in a stacked state without the use of a specific jig or the like.

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

The electron beam is irradiated evenly across the entire plane of the top cover sheet 11a along the stacking direction (vertical direction) of the laminate, thereby simultaneously and 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, producing a microfluidic device 10 in which two cover sheets 11a, 11b and two base sheets 12a, 12b are alternately stacked together.

As shown by the dashed lines in Figure 7, this microfluidic device 10 connects the upper and lower microchannels 15 via through-holes 17, allowing the desired microchannels 15 to be designed in a three-dimensional shape.

During the electron beam irradiation process, the electron beam penetrates the entire area of the two cover sheets 11a, 11b and the two base sheets 12a, 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.

Similarly, during the electron beam irradiation process, the electron beam penetrates the entire area of the two cover sheets 11a, 11b and the two base sheets 12a, 12b, including the area where the microchannel 15 is formed, thereby reducing the gas permeability of the PDMS cover sheets 11a, 11b and the two base sheets 12a, 12b. As a result, sorption of the sample injected into the microchannel 15 into the cover sheets 11a, 11b and base sheets 12a, 12b can be suppressed.

Furthermore, electron beams pass 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.

Furthermore, the cover sheets 11a, 11b and the two base sheets 12a, 12b shrink when electron beams penetrate them, but the shrinkage strain is absorbed by the stress relief grooves 16, allowing the cover sheets 11a, 11b and the two base sheets 12a, 12b to remain flat. As a result, even when the cover sheets 11 and base sheets 12 are stacked in multiple layers, the entire microfluidic device 10 does not bend or flex significantly.

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.

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.

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

Furthermore, the direction of irradiation with ionizing radiation is not limited to the vertical direction described above. Furthermore, if it is not necessary to bond 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 only a portion of the surface of the temporarily held laminate.

The present invention is suitable for silicone bonded bodies manufactured by bonding silicone molded bodies together at multiple locations.

REFERENCE SIGNS LIST 1 Silicone bonded body 2 (2a, 2b, 2c) First molded body 3 (3a, 3b, 3c) Second molded body 4a to 4h Contact area 10 Microfluidic device 11a, 11b Cover sheet (first molded 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 relaxation portion)

Claims (13)

A method for joining a plurality of joined bodies, in which one or more first molded bodies mainly composed of polyorganosiloxane and one or more second molded bodies mainly composed of polyorganosiloxane or glass are simultaneously 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. The joining method described in claim 1, 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. The bonding method described in claim 1, characterized in that the ionizing radiation is an electron beam, and the acceleration voltage of the electron beam is 500 keV or more. 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. The microfluidic device described in claim 4, characterized in that a stress relief portion consisting of a recessed groove or 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 area where the microchannel is formed. A microfluidic device according to any one of claims 4 and 5, characterized in that the ionizing radiation is an electron beam. 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. 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 their entirety except for the portion where the microchannel is formed. 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 in the stacking direction are positioned relative to each other so that through holes penetrating the first molded sheet and/or the second molded sheet in the stacking direction communicate with the microchannel formed between the first stacking surface and the second stacking surface. A method for manufacturing a microfluidic device according to any one of claims 7 to 9, characterized in that a stress relief portion consisting of a recessed groove or slit communicating with the side surfaces of the first molded sheet and the second molded sheet that are integrated by bonding the first molded sheet and the second molded sheet is formed on at least one of the first and second molded sheet surfaces, excluding the area where the microchannel is formed. The method for manufacturing a microfluidic device described in claim 10, characterized in that the microchannel and the recessed groove have the same depth from the first stacking surface and the second stacking surface. A method for manufacturing a microfluidic device according to any one of claims 7 to 9, characterized in that 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. A method for manufacturing a microfluidic device according to any one of claims 7 to 9, wherein the ionizing radiation is an electron beam.