JP7541864B2 - Method for manufacturing a microfluidic device - Google Patents

Description

The present invention relates to a method for manufacturing a device that forms a microchannel inside a porous substrate.

In recent years, the development of microchannel devices that utilize micro-sized fine channels to perform biochemical analysis efficiently (microscopic, rapid, and simple) within a single chip has attracted attention in a wide range of fields, including biochemical research, medicine, drug discovery, healthcare, the environment, and food. Among these, paper-based paper microanalysis chips have the advantages of being lighter and less expensive than conventional devices, not requiring a power source, and being easily disposable. For this reason, they are expected to be used in medical activities in developing countries and remote areas where medical facilities are not well-equipped, as well as at disaster sites, and as testing devices at airports and other locations where the spread of infectious diseases must be stopped at the border. In addition, because they are inexpensive and easy to use, they are attracting attention as healthcare devices that can manage and monitor one's own health condition.

In the early 1990s, photolithography and molds were used to form micron-sized fine flow channels on glass or silicon, and microanalysis chips were developed that could perform sample pretreatment, stirring, mixing, reaction, and detection on a single chip. As a result, it was possible to miniaturize testing systems, perform rapid analysis, and reduce specimens, reagents, and waste liquids. However, while the micro flow channels created using these photolithography techniques are highly accurate, they are expensive to manufacture and difficult to incinerate, making them difficult to dispose of. In addition, because additional equipment such as syringe pumps is required to send the test liquid into the flow channel, they are limited to use in well-equipped environments and have been used mainly in biochemistry research institutions.

In response to these issues, paper microanalysis chips use inexpensive materials such as paper and cloth as a base material, and by utilizing the capillary phenomenon of the material itself, they can drive samples and test solutions, making them low-cost and usable in non-electrical environments. They are also easy to carry (distribute) and dispose of (just burn it). Furthermore, since no maintenance is required for the device, anyone (even ignorant elderly people or children) can easily perform POC (point of care) diagnosis at low cost, anywhere (regardless of location, even in places without power). Therefore, research and development of paper microanalysis chips for various infectious diseases, specific diseases, and healthcare (chronic disease management, health management) is currently being conducted at research institutes around the world.

Various methods have been proposed for actually creating flow paths on paper, including photolithography and screen printing. As mentioned above, forming flow paths using photolithography is expensive due to the many process steps required, such as mask exposure and etching, and printing does not offer the same on-demand capabilities, so in recent years, a method has been proposed in which flow paths are formed using an inkjet printer.

Patent Literature 1 proposes a method of creating a flow path inside a filter paper using a commercially available inkjet printer. However, this method involves coating the entire surface of the filter paper with polystyrene or the like, and then forming the flow path using a solvent such as chloroform, which may compromise safety for users and may also cause contamination of the flow path itself by the solvent.
Therefore, recently, a method has been proposed in which a flow path is formed by using a UV-curable resin in the ink, as described in Patent Document 2. This method allows the flow path to be designed freely and enables the formation of a flow path with high rigidity and solvent resistance. However, this method requires the UV resin impregnated inside the paper to be cured, which requires irradiation with high-energy ultraviolet rays and a longer-than-usual curing time, making it a disadvantageous flow path formation method in terms of productivity and cost.

In addition, since inkjet printers use a piezo or thermal method to eject ink from nozzles to form flow path patterns, the viscosity of the resin to be ejected must be kept low to a certain extent. In that case, the low-viscosity UV resin ejected onto the paper may diffuse during the process of penetrating into the paper, which may affect the accuracy of the completed flow path. For example, the actual flow path width may be several hundred μm narrower than the target flow path width, so there is a problem with dimensional accuracy in forming complex flow paths or high-definition flow paths. In addition, with low-viscosity resin, it is difficult to place a large amount of resin on paper in one ejection. Therefore, in order to place a large amount of resin on paper, it is necessary to eject multiple times or increase the size of the head, which leaves issues such as reduced productivity and resolution.
Another method is to use a printer that can eject high-viscosity ink and form highly precise dots. However, this method is known to be extremely slow in forming flow path patterns, resulting in a significant drop in flow path productivity.

Patent Document 3 proposes a method of creating flow paths inside a substrate by using an inkjet printer that uses solid ink (wax ink) to soak filter paper with wax ink. However, this method uses a technique in which solid wax is melted and ejected to draw a flow path pattern, so the actual resolution is low and the edge accuracy of the flow path pattern is low. In addition, because the main component of the material that forms the flow paths is wax, the heat resistance and solvent resistance are low, which may limit the robustness and use of the created flow paths.

Furthermore, Patent Document 4 proposes a method of forming flow paths by using a thermal transfer printer to infiltrate a porous member with a thermoplastic material. This method is said to be effective in reducing bleeding and non-infiltrated areas because it is possible to use a thermoplastic material with a relatively high melt viscosity compared to the inkjet method, but when a large amount of thermoplastic material is transferred to paper, the resolution may decrease due to thermal diffusion. Therefore, there are still some shortcomings in forming highly accurate flow path walls. There are still some shortcomings in forming highly accurate flow path walls.

For the above reasons, there is a demand for a method for fabricating paper microanalysis chips that can form flow paths that are highly hydrophobic, highly solvent resistant, and resistant to heat and damage, on demand, with high precision (less bleeding inside the paper), and that can form the flow paths at low cost while maintaining high productivity.
In view of the above, the present invention proposes a method for forming a flow path inside a substrate such as filter paper using an electrophotographic method, thereby satisfying the above demands.
However, in general, in electrophotographic image formation, in order to maintain image quality, resins are designed to prevent toner from soaking into the paper as much as possible, so it is difficult to create flow paths inside the paper using general toner. Furthermore, although general toner has a certain degree of hydrophobicity, it is not sufficient, and it also does not have high solvent resistance, so it cannot be used as is to form flow path walls, taking into account seepage, etc.
Based on these findings, we propose a method for manufacturing a microchannel device that uses an electrophotographic method to form highly accurate flow channels, and a method for manufacturing a microchannel device that uses a resin that can be rapidly permeated into the substrate by heating and melting, and that can form highly accurate flow channels.

JP 2015-52584 A Patent No. 5935153 US Patent Application Publication No. 2012/0198684 JP 2015-131257 A

The present invention aims to provide a method for manufacturing microchannel devices at low cost and with high productivity, by forming highly hydrophobic, solvent-resistant, and heat- and damage-resistant channels on demand with high precision.

According to one aspect of the present invention, there is provided a method for producing a microchannel device having a channel sandwiched between channel walls formed inside a porous substrate, comprising the steps of:
A step of placing a first hydrophobic resin on the surface of the porous substrate by electrophotography to form a flow path pattern on the surface of the porous substrate; and a step of melting the first hydrophobic resin by heat to cause the first hydrophobic resin to penetrate into the porous substrate to form a flow path wall inside the porous substrate.
A method for manufacturing a microfluidic device having the above structure is provided.

According to another aspect of the present invention, there is provided a method for producing a microchannel device having a channel sandwiched between channel walls formed inside a porous substrate, comprising the steps of:
A step of placing a first hydrophobic resin on the surface of the porous substrate to form a flow path pattern on the surface of the porous substrate; and a step of melting the first hydrophobic resin by heat to cause the first hydrophobic resin to penetrate into the porous substrate to form a flow path wall inside the porous substrate.
having
The present invention provides a method for manufacturing a microchannel device, wherein in the step of forming the channel wall, the first hydrophobic resin is infiltrated at a temperature at which the storage modulus G ' of the first hydrophobic resin is 14 Pa or less and the loss modulus G'' of the first hydrophobic resin is 10 Pa or more.

According to one aspect of the present invention, it is possible to provide a method for manufacturing microchannels that are highly hydrophobic, highly resistant to solvents, and resistant to heat and damage, on demand, with high productivity and at low cost, using a high-viscosity material.
According to another aspect of the present invention, a method for forming a highly accurate flow path pattern in a porous substrate with suppressed bleeding can be provided.

3 is a configuration diagram of a flow path pattern forming unit in the first embodiment. FIG. FIG. 2 is a diagram illustrating a configuration of a process cartridge P in the first embodiment. 4 is a block diagram showing a schematic control mode of a flow path pattern forming unit in the first embodiment. FIG. FIG. 2 is a flow path pattern diagram in the first embodiment. 1 is a cross-sectional view of a porous substrate S1 on which a flow path pattern was formed in Example 1. FIG. 1 is a graph showing the temperature dependence of storage modulus and loss modulus of resin particles A, B, and C. 1 is a graph showing the temperature dependence of storage modulus and loss modulus of resin particles using VYLON 200 (registered trademark). 1 is a graph showing the temperature dependence of storage modulus and loss modulus of resin particles D. FIG. 13 is a configuration diagram of a flow path pattern forming unit 200 in a fourth embodiment. 13 is a cross-sectional view of a porous substrate S2 on which a flow path pattern was formed in Example 4. FIG. 13A to 13C are explanatory diagrams illustrating a flow path formation process in the fifth embodiment. 13 is an explanatory diagram illustrating a flow path formation process in the sixth embodiment. FIG. 13 is an explanatory diagram illustrating a flow path formation process in the seventh embodiment. FIG. 13 is an explanatory diagram illustrating a flow path formation process in the eighth embodiment. FIG. FIG. 13 is a configuration diagram of a flow path pattern forming unit in a ninth embodiment. FIG. 13 is a configuration diagram of a fixing device unit in a ninth embodiment. 23 is an explanatory diagram illustrating a flow path formation process in Example 10. FIG. FIG. 13 is a diagram of a microchannel device provided with a cover layer and a protective layer in Example 11.

Below, exemplary embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are merely examples, and the present invention is not limited to the contents of the embodiments. Also, in each of the following figures, components that are not necessary for explaining the embodiments are omitted from the figures.

In the present invention, first, a flow path pattern is formed on a porous substrate using a hydrophobic resin by electrophotography. Next, the flow path pattern is melted by heat and allowed to penetrate into the porous substrate. In this way, a flow path is formed inside the porous substrate. Each component is described below.

<Flow path pattern forming unit>
The overall configuration of the flow path pattern forming unit will be described with reference to Figures 1, 2 and 3. Figure 1 is a cross-sectional view showing the schematic configuration of a flow path pattern forming unit according to an embodiment of the present invention, and each component is shown in a simplified manner. Figure 2 is a schematic cross-sectional view of a process cartridge P according to an embodiment of the present invention. Figure 3 is a block diagram showing the schematic control mode of the main parts of the flow path pattern forming unit.

First, the configuration of the flow path pattern forming unit, the flow path pattern forming process, and each member will be described. Each member involved in the flow path pattern forming process will be described in accordance with the order of the flow path pattern forming process with reference to Figs.
The flow path pattern forming unit can accommodate the process cartridge P, and the process cartridge can be replaced for easy maintenance and convenience. The process cartridge P has a photosensitive drum 11 as an image carrier. Around the photosensitive drum 11, a charging roller 12, a developing device 20, and a cleaning member 14 are provided. The charging roller 12 is a roller-shaped charging member for charging the surface of the photosensitive drum 11. The developing device 20 develops the electrostatic latent image formed on the surface of the photosensitive drum 11 with a developer (resin particles). The cleaning member 14 cleans the surface of the photosensitive drum 11. The voltages required for forming the flow path pattern can be applied by a charging high voltage power supply 71, a developing high voltage power supply 72, and a transfer high voltage power supply 74, and are controlled by a control unit 202 (FIG. 3). In addition, the flow path pattern forming unit can drive the photosensitive drum 11 of the process cartridge P by a motor M1 (not shown), and drive the developing device 20 of the process cartridge P by a motor M2 (not shown).

When the flow path pattern formation starts, the photosensitive drum 11 is rotated in the direction of the arrow A in Fig. 2 by the drive of the motor M1, and the charging roller 12 is rotated in the direction of the arrow B in Fig. 2 following the rotation of the photosensitive drum 11. In the examples described later, the process speed of the photosensitive drum 11 is set to 150 mm/sec.
The photosensitive drum 11 is constructed by providing a photosensitive material such as OPC, amorphous selenium, amorphous silicon, etc., on a cylindrical drum base made of aluminum, nickel, etc. In the embodiment described later, the outer diameter is 20 mm, and the thickness of the photosensitive material is 13 μm.

The charging roller 12, which is a charging member, can be a single-layer roller made of a conductive shaft body (conductive core metal) and a conductive rubber layer. A voltage is applied to the charging roller 12 by a charging high-voltage power source 71, which is a voltage application unit. Next, the charging roller to which the voltage has been applied is brought into contact with the photosensitive drum 11 to uniformly charge the surface of the photosensitive drum 11. A DC (direct current) voltage is applied to the charging roller 12, and the photosensitive drum 11 is uniformly charged to a charging potential Vd by discharging. In the examples described later, a single-layer roller with an outer diameter of 7.5 mm and a volume resistance of 10 ³ to 10 ⁶ Ω·cm is used as the charging roller 12, and a DC voltage is applied. The surface of the photosensitive drum is uniformly charged to −460 V (Vd: dark potential).

After the surface of the photosensitive drum 11 is charged by the charging roller 12, the surface of the photosensitive drum 11 is irradiated with laser light 9 from the exposure unit 73. The surface potential of the photosensitive drum 11 irradiated with the laser light 9 changes to Vl, which is the light area potential, and an electrostatic latent image is formed. In the embodiment described later, Vl is set to -100V. As shown in FIG. 3, the exposure unit 73 receives a time-series electric digital pixel signal of the image (flow path pattern) information that is input from the controller 200 to the control unit 202 via the interface 201 and image-processed. The exposure unit 73 has a laser output unit that outputs the laser light 9 modulated in response to the input time-series electric digital pixel signal, a rotating polygon mirror, an fθ lens, a reflecting mirror, etc., and exposes the surface of the photosensitive drum 11 in the main scanning direction with the laser light 9. This main scanning exposure and the sub-scanning caused by the rotation of the photosensitive drum 11 form an electrostatic latent image corresponding to the image (flow path pattern) information on the photosensitive drum 11.

<Flow path pattern formation process>
The flow path pattern forming unit has a contact/separation unit 75 that controls the position of the developing device 20, and can control the position of the developing device 20 to be different when the flow path pattern is formed and when the flow path pattern is not formed. The operation of the contact/separation unit 75 is controlled by the control unit 202 shown in FIG.
After the photosensitive drum 11 starts to rotate, the developing device 20 moves the developing roller 23 serving as a developer carrier, which has been spaced apart from the photosensitive drum 11 , by the contact/separation unit 75 so that the developing roller 23 comes into contact with the photosensitive drum 11 .

Then, the developing roller 23 starts to rotate in the direction of the arrow C in FIG. 2, and the resin particle supply roller 24 as a resin particle supply member starts to rotate in the direction of the arrow D in FIG. 2 by driving the motor M2 connected to each. Then, a voltage of -300V is applied from the high-voltage development power supply 72 for the developing roller 23 to the developing roller 23 as a developing voltage, and the electrostatic latent image (Vl portion above) formed on the photosensitive drum 11 is supplied with developer (resin particles) by the developing roller 23 to be developed. The ratio of the moving speed of the surface of the photosensitive drum 11 to the moving speed of the surface of the developing roller 23 at this time (moving speed of the surface of the developing roller 23/moving speed of the surface of the photosensitive drum 11) is called the developing peripheral speed ratio. By controlling this developing peripheral speed ratio, the amount of developer developed on the photosensitive drum 11 can be controlled. For example, if the development speed ratio is 2.5, when all the developer on the development roller 23 is developed onto the photosensitive drum 11, the amount of developer per unit area on the surface of the photosensitive drum 11 will be 2.5 times the amount of developer per unit area on the surface of the development roller 23. In the embodiment described below, the development speed ratio is controlled by the speed of the motor M2 so that an amount of developer suitable for forming a microchannel wall inside the porous substrate S1 can be supplied to the photosensitive drum.

The developer image (resin particle image) is transferred to a porous substrate S1 as a recording medium by a potential difference with a transfer roller 4 to which a transfer voltage is applied by a transfer high-voltage power supply 74. The porous substrate S1 is a sheet-like medium made of porous material, as described later.
In the examples described later, a roller having a conductive core and an elastic layer of semiconductive sponge whose main component is NBR hydrin rubber as an elastic body and whose resistance is adjusted using an ionic conductive material was used as the transfer roller 4. The outer diameter of the transfer roller 4 was 12.5 mm, the outer diameter of the conductive core was 6 mm, and a transfer voltage of +2000 V was applied. The resistance value of the transfer roller used in the examples was as follows when +2000 V was applied.
Under normal temperature and humidity conditions of 23°C and 50% relative humidity: 1.0 x 10 ⁸ Ω to 3.0 x 10 ⁸ Ω
Under high temperature and humidity environment of 32°C and 80% relative humidity: 0.5 x 10 ⁸ Ω
Under low temperature and low humidity environment of temperature 15° C./relative humidity 10%: 8.0×10 ⁸ Ω

The porous substrate S1 onto which the developer image has been transferred is discharged to the outside of the flow path pattern forming unit with the developer image facing upward in the direction of gravity. After passing the transfer roller 4, the photosensitive drum 11 has the developer that has not been transferred scraped off by the cleaning member 14 in contact with it. Thereafter, the process from charging by the charging roller 12 is repeated again, thereby continuously forming flow path patterns.
After the flow path pattern formation is completed, the developing roller 23 is separated from the photosensitive drum 11 by the contact/separation unit 75, and a post-rotation operation is performed to reset the state inside the flow path pattern forming unit, so that the next time flow path pattern formation is performed, printing can be performed quickly. After the developing roller 23 is separated from the photosensitive drum 11 by the contact/separation unit 75, the drive of the motor M2 is turned off, so that deterioration of the developer can be suppressed.

Next, the operation control of the flow path pattern forming unit will be described with reference to FIG. 3. The control unit 202 controls the operation of the flow path pattern forming unit and transmits and receives various electrical information signals. It also processes electrical information signals input from various process devices and sensors, and processes command signals to various process devices. The controller 200 transmits and receives various electrical information to and from the host device, and controls the flow path pattern forming operation of the flow path pattern forming unit in accordance with a predetermined control program and reference table via the interface 201 by the control unit 202. The control unit 202 is configured with a CPU 155, which is a central element that performs various arithmetic processing, and a memory 15 such as a ROM and RAM, which are storage elements. The RAM stores the detection results of the sensor, the count results of the counter, and the results of calculation, and the ROM stores the control program, a data table obtained in advance by experiments, and the like. The control unit 202 is connected to each control target, sensor, counter, and the like in the flow path pattern forming unit. The control unit 202 controls the transmission and reception of various electrical information signals, the timing of driving each part, and the like, to control a predetermined flow path pattern forming sequence. The control unit 202 controls, for example, the charging high-voltage power supply 71, the developing high-voltage power supply 72, the exposure unit 73, the transfer high-voltage power supply 74, and the developing peripheral speed change unit 76, and adjusts the applied voltage, the exposure amount, etc.

In the flow path pattern forming unit of FIG. 1, the connection from the control unit 202 to the charging high voltage power supply 71, the developing high voltage power supply 72, the exposure unit 73, and the transfer high voltage power supply 74 is not shown. However, in reality, the charging high voltage power supply 71, the developing high voltage power supply 72, the exposure unit 73, and the transfer high voltage power supply 74 are connected to the control unit 202, and the control unit 202 controls each of them. Then, this flow path pattern forming unit forms a flow path pattern in the porous substrate S1 based on an electrical flow path pattern signal input from a host device to the controller 200. Examples of the host device include an image reader, a personal computer (hereinafter also referred to as a PC), a facsimile, and a smartphone.

<Developing device>
Next, the configuration of the developing device 20 according to the present invention, which is related to the developing process, will be described in detail with reference to FIG.
The developing device 20 includes a developing container 21 having an opening facing the photosensitive drum 11, and resin particles are stored in place of the developer (toner) used in normal electrophotographic devices in the developing container 21. The developing device 20 also includes a developing roller 23 and a resin particle supply roller 24.
The developing roller 23 carries and transports the resin particles to the electrostatic latent image on the photosensitive drum 11. The developing roller 23 may be a roller having a surface layer with roughening particles dispersed on the surface of an elastic layer. The transportability of the resin particles can be adjusted by the surface roughness of the developing roller 23. In the examples described below, a roller having a surface layer with 10 μm diameter particles dispersed with urethane rubber as a binder on the surface of an elastic layer made of silicone rubber was used. The surface roughness Ra was about 3.5 μm.

The resin particle supply roller 24 has a foam layer that rubs against the surface of the developing roller 23, and serves to supply the resin particles in the developing container 21 to the developing roller 23. The resin particle supply roller 24 is electrically connected to the developing roller 23 to equalize the potential. The developing device 20 also includes a developing blade 25 that is a resin particle regulating member that regulates the resin particles supplied to the developing roller 23.
The developing device 20 also includes a developing blade 25, which is a resin particle regulating member that regulates the coating amount of resin particles supplied to the developing roller 23. The developing blade 25 may be, for example, a thin stainless steel (SUS) plate supported by a supporting metal plate. The developing blade 25 is electrically connected to the developing roller 23, and the potentials of the two are equalized.
In the examples described below, a developing blade 25 was used in which a stainless steel (SUS) plate with a thickness of 80 μm was supported by a supporting metal plate with a thickness of 1 mm. The tip of the SUS plate of the developing blade 25 was brought into contact with the developing roller 23 with a pressure of 25 to 35 g/cm. The direction of contact was the counter direction in which the tip of the free end side with respect to the contact portion was located upstream in the rotation direction of the developing roller 23. With the above configuration, the surface of the developing roller 23 after passing the developing blade 25 is coated with resin particles at, for example, 0.50 mg/ ^cm2 per unit area.

<Flow path pattern>
In Example 1 described later, a flow path pattern 80 shown in Fig. 4(a) was formed by placing resin particles on the porous substrate S1 using a flow path pattern forming unit to form a resin particle image. The symbols in Fig. 4(a) are as follows. Resin particle image 81, reagent section 83 to which a reagent is attached, test liquid section 84 to which a test liquid is attached, and flow path 82 connecting reagent section 83 and test liquid section 84. However, the shape and size of the flow path pattern are not limited to these, and may be a combination of straight lines and curves, a shape using branches, and the width of the flow path may be changed.
When forming the flow path pattern of FIG. 4A in an embodiment described later, the width L1 of the resin particle images 81 sandwiching the flow path 82 was set to 4 mm, and the width L2 of the flow path 82 was set to 1.5 mm.

An example of a flow path pattern having curves and branches is shown in FIG. 4(b). In this example, reagent sections 85b, 85c, and 85d for applying reagents and test liquid section 85a for applying test liquid are connected by flow path 85e.

<Heating process>
The porous substrate S1 on which the flow path pattern 80 is formed undergoes a heating process using a heating unit, whereby the resin particles melt and permeate into the porous substrate S1, forming a micro-flow path device having a flow path surrounded by hydrophobic walls.
Therefore, the heating temperature must be a temperature at which the resin particles melt and the molten resin penetrates the porous substrate S1. The physical properties of the resin particles will be described later, but in the configuration of the example described later, the resin particles melted and penetrated the porous substrate S1 at 140°C or higher.

The heating time needs to be long enough for the molten resin to completely penetrate the porous substrate S1 in the thickness direction, but if the heating time is too long, the resin will diffuse more than necessary, and the flow paths 82 after the heating process may become narrower than the flow path pattern that was formed. Although it depends on the heating temperature, a heating time of 1 to 10 minutes can form an appropriate flow path wall.
In view of the above, the heating conditions in the examples described below were set to 2 minutes in an environment of 200 ° C. As the heating unit, an oven (Yamato Scientific Co., Ltd. constant temperature incubator DN610H) was used. However, the heating method is not limited to this, and a far-infrared heater or a hot plate may be used, and the heating conditions should be selected according to the physical properties of the resin particles and the porous substrate S1.

The heating process under the above conditions will be described with reference to FIGS.
As a diagram showing the resin particles before and after heating, a schematic cross-sectional view taken along the dashed line 80a in Fig. 4 is shown in Fig. 5. Fig. 5(a) is the cross-sectional view before heating, and Fig. 5(b) is the cross-sectional view after heating.
As shown in Fig. 5(a) , the resin particles before heating are merely attached to the surface of the porous substrate S1. The resin particles are melted by subsequent heating, and the molten resin penetrates into the porous substrate S1 by capillary action.
After heating at 200°C for 2 minutes, as shown in Figure 5 (b), the hydrophobic resin penetrates into the porous substrate S1 in the thickness direction, and a flow path 82 sandwiched between the molten resin is formed in the porous substrate S1.
As described above, by using the flow channel pattern forming unit and the heating unit, a micro flow channel device having a flow channel surrounded by a flow channel wall in the porous substrate S1 can be manufactured.
When using a microfluidic device created based on the flow channel pattern of FIG. 4(a), for example, a chemical that exhibits a color reaction is applied to the reagent section 83, and then the test liquid is applied to the test liquid section 84. The applied test liquid diffuses through the flow channel 82 to the reagent section 83. The test device or the examiner can check the color reaction that occurs at that time. For example, in the case of a blood glucose level test, the test liquid can be blood, and the reagent can be a mixture of oxidase, peroxidase, and potassium iodide, and in the case of a uric acid level test, the test liquid can be blood, and the reagent can be a mixture of uricase, peroxidase, and 4-aminoantipyrine.
An example of use of the microchannel device created based on the flow channel pattern of FIG. 4B will be described. After attaching reagent b to reagent portion 85b, reagent c to reagent portion 85c, and reagent d to reagent portion 85d, the test liquid is attached to the test liquid portion 85a. The test liquid attached to the test liquid portion 85a then permeates the flow channel 85e, but by branching on the way, it reacts only with reagent b in reagent portion 85b, only with reagent c in reagent portion 85c, and only with reagent d in reagent portion 85d. By using the branched flow channel, it is possible to simultaneously test the reaction to multiple reagents. In addition, by making the flow channel curved, like the flow channel toward 85d, it is possible to eliminate or reduce the accumulation of the test liquid at the edge portion.

<Developer>
In producing a microchannel device by the above process, preferred developer properties will be described.

The resin constituting the channel walls of the microchannel device is required to have a certain degree of hydrophobicity since it is required not to expand due to moisture in the air. Therefore, resin particles composed of hydrophobic resin are used as the developer. The hydrophobicity of the resin particles is preferably about 1% or less in terms of water absorption. Furthermore, the lower the water absorption, the more the test liquid can be suppressed from seeping out of the channel, and the less the impact on the test can be reduced, so the water absorption is more preferably 0.1% or less.
The developer must have both the property suitable for the flow path pattern forming process described above and the property of melting in a heating process and quickly penetrating into the porous substrate without bleeding due to capillary action.
Specifically, resin particles containing a resin as a main component that has the property of melting in a heating process and quickly penetrating into the porous substrate S1 without bleeding due to capillary action may be used. In order to provide properties suitable for the flow path pattern forming process, a charge control agent or the like may be added as necessary.

Inkjet printers require the ink to have a viscosity of about 0.15 Pa·s when ejecting the ink from the head. Thermal transfer printers also require materials with a viscosity of 1.6 Pa·s or less. On the other hand, electrophotographic printers can use materials with a melt viscosity of 1000 Pa·s or more at 100° C., allowing a wide range of material choices, and electrophotographic printers are preferred from this viewpoint as well.
When the melt viscosity is low, the resin particles can easily penetrate into the porous substrate, but the bleeding becomes large. Conversely, when the melt viscosity is high, the bleeding during penetration is thought to be small, but the resin particles cannot easily penetrate into the porous substrate. However, it has been found that by appropriately controlling the storage modulus G' and loss modulus G'' of the resin particles, it is possible to satisfactorily achieve both the penetration property and the suppression of bleeding.

An example of a resin that can achieve both high permeability and low bleeding is cycloolefin copolymer, hereinafter referred to as "COC."
Regarding COC, the characteristics in the flow path pattern forming process will be described first. COC not only has a negative chargeability with respect to the developing blade 25 and the developing roller 23, but also has low water absorption, so that it has high charge stability in the flow path pattern forming process and has high storage stability. In addition, because it has high mechanical strength, it is unlikely to crack or deform even when it is repeatedly rubbed between the developing roller 23 and the regulating blade 25. As described above, COC is suitable for the flow path pattern forming process using the electrophotographic method. The ratio of COC in the resin particles containing COC is preferably 50% by mass or more.

Microfluidic devices may require solvent resistance. COC resin is highly hydrophobic and also highly solvent resistant, meaning it will not dissolve in a variety of test liquids and can be used to form flow channels that allow testing without leakage from the flow channels. Furthermore, as mentioned above, COC resin also has high mechanical strength and is resistant to heat and damage, making it possible to create microfluidic devices that are easy to handle.

Resin particles A used in Example 1 described later were produced as follows.
(i) Pellets of COC (TM grade, specific gravity: 1.02, manufactured by Polyplastics Co., Ltd.) are finely pulverized.
(ii) The finely pulverized material is classified to have a volume average particle size of 6 μm.
(iii) The classified particles are subjected to a thermal spheronization treatment to obtain COC particles.
(iv) 1.6% by mass of hydrophobic silica particles having a number-average particle size of 10 nm are externally added to the thermally spheronized COC particles as an external additive.
By coating the resin particle surface with an external additive, negative charging performance and flowability can be improved. Note that the silica particles used as the external additive have been hydrophobized and the amount of external additive is small, so that it does not affect the flow path when finally used as a micro-channel device. However, the amount of external additive and the substance to be externally added are not limited to these, and may be appropriately selected depending on the configuration of the developing device, such as the developer carrier and developer regulating member used.

Generally, COC has a melt viscosity of about 1000 Pa·s even at 100° C., so it is difficult to use it in ink-jet systems, thermal transfer systems, and the like.
When the flow path pattern is formed by electrophotography, the resin particles are required to have the same size and shape as those of a general toner for electrophotography, and therefore the size and shape of the resin particles may be similar to those of a general toner for electrophotography.

<Porous substrate>
As the porous substrate, those that show a suitable porosity and hydrophilicity are suitable. As the porous structure, those with open cells and mesh (nanofibers, etc.) structures are suitable, and examples thereof include filter paper, plain paper, wood-free paper, watercolor paper, Kent paper, synthetic paper, synthetic resin porous film, fabric, textile products, etc. Among these, filter paper is preferred because of its high porosity and good hydrophilicity.
The porosity can be appropriately selected depending on the purpose, but is preferably 20% to 90%. Within this range, the strength as a base material is sufficient, while sufficient characteristics regarding the permeability of the sample liquid are obtained.
Hydrophilicity is a necessary property for allowing a biological fluid containing water, such as blood, urine, or saliva, as a sample liquid, to diffuse into the substrate.
The average thickness of the porous substrate is generally 0.01 mm to 0.3 mm. If the average thickness is 0.01 mm or more, the substrate has adequate strength. If the average thickness is 0.3 mm or less, the COC can easily penetrate and the flow path wall can be easily formed. However, the average thickness may be selected according to the application, and a thicker thickness of about 0.6 mm may be used.

Since the resin is permeated into the pores of the porous substrate and filled with the resin to form a flow path wall (hydrophobic wall), it is necessary to sufficiently fill the pores of the porous substrate with resin particles in order to form a flow path that is suppressed from leaking or seeping out. On the other hand, if too much resin is permeated, the excess resin will spread over the surface of the porous substrate or seep out to the back side. Therefore, the amount of resin particles must be adjusted according to the porosity and thickness of the porous substrate. In the electrophotographic method, the amount of resin particles placed on the porous substrate can be easily adjusted when forming a flow path pattern, and a larger amount of resin particles can be placed at one time compared to other methods. Therefore, it is easy to form a reliable flow path, and from this viewpoint it is a preferable method.

The amount of resin particles on the porous substrate can be appropriately adjusted by changing the amount of resin particles per unit area (g/ ^cm2 ) on the developing roller 23, the development peripheral speed ratio of the flow path pattern forming unit, and the transfer voltage for transferring the resin particles on the surface of the photosensitive drum 11. In addition, it is not necessarily necessary to place an amount of resin particles that completely fills the pores in the porous substrate, as long as the amount is sufficient to function as a flow path.

For example, three types of filter paper made of cellulose fibers having a thickness of 20 μm and different basis weights, S1-1, S1-2, and S1-3, can be used as the porous substrate.
The apparent density (g/cm ³ ) of the porous substrates S1-1, S1-2, and S1-3 can be calculated as (basis weight/thickness×1000), and the porosity (%) can be calculated as ((true density−apparent density)/true density×100) (see Table 1).

<Viscoelastic properties of resin particles>
The storage modulus G' represents the elasticity of an object, and a low storage modulus G' represents a large deformation for a certain load. In other words, when the storage modulus G' of the resin fine particles is low, the resin fine particles are more likely to permeate the porous substrate S1 when a permeation force due to capillary action acts on the porous substrate S1.

The loss modulus G'' represents the viscosity of an object, and a high loss modulus G'' of resin microparticles represents high viscosity. High viscosity means that when the speed of a fluid differs at each point in the flow, there is a strong tendency to smooth out the speed to make it uniform. In other words, when the loss modulus G'' of resin microparticles is high, the resin particles try to move at the same speed as the surroundings when penetrating into the porous substrate, so that the unevenness of penetration within the pores S is reduced and bleeding is suppressed. Unevenness in the temperature of the porous substrate or unevenness in the size of the pores in the porous substrate can cause uneven capillary forces, which can cause bleeding of the flow path pattern. For this reason, resin particles that have high viscosity and are less likely to bleed at the temperature of the heat fixing process are preferable.

In other words, in order to form a good flow path, it is important to carry out the heating process at a temperature that exhibits melting characteristics such as a low storage modulus G' and a high loss modulus G'', and to penetrate the resin particles.
Here, the viscoelastic properties required for the resin particles to penetrate into the porous substrate quickly and without bleeding during the heating process will be explained using a graph of the elastic modulus of resin particles A ( FIG. 6A(a) ). In FIG. 6 , the notation "1E+3" means "1×10 ³ ." The solid line in FIG. 6A(a) shows the value of the storage elastic modulus G' of resin particles A when the temperature is changed, and the dotted line in FIG. 6A(a) shows the value of the loss elastic modulus G'' of resin particles A when the temperature is changed. The detailed physical properties of resin particles A will be described later, but resin particles A have a low storage elastic modulus G' of 0.4 Pa and a high loss elastic modulus G'' of 10 Pa at 200° C.

In measuring the elastic modulus, first, the resin particles were set in a pellet molding die having a diameter of 20 mm, a load of 15 tons was applied with a pressurizer, and the amount of the resin particles was adjusted so that the pellet thickness after pressing was 1 mm, to prepare a pellet. Next, the prepared pellet (diameter 20 mm, thickness 1 mm) was fixed between the lower plate and the upper plate of a rotational viscoelasticity measuring device AR-G2 (manufactured by TA Instruments). A shear stress of 10 Pa was applied from the upper plate at a period of 1 Hz, and the storage elastic modulus G' and the loss elastic modulus G'' were calculated from the phase difference with the shear stress as a response at that time. The above measurements were performed between 70°C and 200°C while changing the temperature between the plates at a rate of 2°C/min.

First, looking at the storage modulus G' shown by the solid line in FIG. 6A(a), as the temperature rises, the storage modulus G' rapidly decreases, falling below 14 Pa at 130°C and reaching 0.4 Pa at 200°C. If the storage modulus G' is 14 Pa or less, the resin particles will quickly penetrate into the porous substrate S1 due to the capillary phenomenon caused by the porous substrate S1, as described above. In this example, the resin particles penetrated into the porous substrate at 130°C or more, at which the storage modulus G' becomes 14 Pa or less, so the temperature in the heating process must be at least 130°C or more.

On the other hand, the loss modulus G″ shown by the dotted line in FIG. 6A(a) also decreases with increasing temperature, but even at 200° C., the viscosity remains high at approximately 10 Pa. If the loss modulus G″ is 10 Pa or more, bleeding can be sufficiently suppressed to a small extent, and therefore, from the viewpoint of the loss modulus G″, the temperature in the heating process is preferably 200° C. or less.
That is, in the case of resin particles A, the heating temperature at which the resin particles A can rapidly permeate the porous substrate without bleeding is 130° C. or higher and 200° C. or lower.

(Examples 1 and 2, Comparative Example 1)
Using the device shown in FIGS. 1 and 2 and the above-mentioned resin particles A, the flow path pattern shown in FIG. 4(a) was formed on the above-mentioned porous substrate S1-2.
The results when the heating temperature in the heating process was 200° C. (Example 1), 130° C. (Example 2), and 120° C. (Comparative Example 1) are shown in Table 2. At a heating temperature of 120° C., the storage modulus G′ was 32 Pa, and penetration into the porous substrate was insufficient.

At 200°C, resin particles A containing COC have a ratio of storage modulus G' to loss modulus G'', tan δ (= G''/G'), of approximately 26, which is considerably larger than the tan δ of most resin materials, which is approximately 0.1 to 1.0. Due to this property, resin particles A can penetrate into the porous substrate S1-2 due to their low storage modulus G', while maintaining viscosity due to their high loss modulus G'', and form flow paths without bleeding. In other words, resin particles using COC can precisely penetrate the flow path pattern formed on the porous substrate into the interior of the porous substrate to form flow path walls. Therefore, flow paths corresponding to the flow path pattern can be precisely formed.

<Comparative Example 2>
As Comparative Example 2, a case where resin particles B having viscoelasticity shown in Fig. 6A(b) was used will be described. Resin particles B are particles having a volume average particle size of 6 μm made of a copolymer of styrene and butyl acrylate, not COC, to which silica particles are externally added in the same manner as resin particles A. As shown in Fig. 6A(b), the storage modulus G' and loss modulus G'' of resin particles B tend to decrease with increasing temperature, but both stop decreasing between 1 x ¹⁰² Pa and 1 x ¹⁰³ Pa. Therefore, there is no temperature region in resin particles B where the storage modulus G' is 14 Pa or less.
In fact, even when resin particles B were placed on a porous substrate and subjected to a heating process at a heating temperature of 200°C, the resin particles B simply melted and spread on the surface of the porous substrate, and no sign of the resin particles B penetrating into the interior of the porous substrate S1 was observed.

<Comparative Example 3>
In addition, as Comparative Example 3, a case where resin particles C having the viscoelasticity shown in FIG. 6A (c) are used will be described. At 200° C., the resin particles C have a storage modulus G' of 0.4 Pa and a loss modulus G'' of 0.1 Pa, and at 125° C., the storage modulus G' is 12 Pa and the loss modulus G'' is 5 Pa. That is, the resin particles C are resin particles with low storage modulus G' and loss modulus G'', and there is no temperature region where the storage modulus G' is 14 Pa or less and the loss modulus G'' is 10 Pa or more. Therefore, in the formation of the flow path wall using the resin particles C, although the resin particles C quickly penetrate into the porous substrate by heating, when penetrating into the porous substrate, the penetration proceeds intensively in the places where it is easy to penetrate, causing bleeding. When the flow path wall was actually formed at a heating temperature of 125° C., bleeding occurred.

Example 3
Instead of the COC (TM grade, manufactured by Polyplastics Co., Ltd.) used in resin particles A, COC (8007F-600 grade, manufactured by Polyplastics Co., Ltd.) was used. Furthermore, 50 parts by mass of a plastic component (paraffin wax HNP-51 (Nippon Seiro Co., Ltd.)) was kneaded with 100 parts by mass of COC to obtain a kneaded resin. Resin particles D were obtained in the same manner as resin particles A, except that this kneaded resin was used.

When COC (8007F-600 grade, manufactured by Polyplastics Co., Ltd.) is used alone, there is no temperature range up to 300°C where the storage modulus G' is 14 Pa or less. However, by mixing paraffin wax as a plastic component, a temperature range where the storage modulus G' is 14 Pa or less comes into existence. Specifically, resin particle D had the viscoelasticity shown in Figure 6C (e). In this case, in the range of 195°C to 300°C, the storage modulus G' was 14 Pa or less and the loss modulus G'' was 10 Pa or more.

In general, materials with similar solubility parameters (hereinafter referred to as SP values) have high affinity and mix well. By using a plastic component whose SP value difference with respect to COC is 3.5 or less, viscoelasticity can be controlled appropriately. The SP value can be determined by the Fedors method. In the combination of this example, the SP value difference is 1.56.

When flow path walls were formed in the same manner as in Example 1 using resin particles D and a heating temperature of 200° C. in the heating process, flow paths corresponding to the flow path pattern could be formed with high precision.
In addition, when the COC is used in combination with a plastic component, the flow path wall exhibits a characteristic of being less likely to crack. Therefore, the flow path wall formed using the resin particles D is less likely to crack even when deformed. As the COC used in combination with a plastic component, a COC that softens at a relatively high temperature is used compared to when the COC is used alone. Since such a COC generally has a large deformation rate (breaking elongation rate) until it breaks, it is considered that the flow path wall formed by using the COC in combination with a plastic component is less likely to crack. As the plastic component, waxes such as hydrocarbon wax, ester wax, and alcohol wax; crystalline resins such as crystalline polyester, and other silicone oils can be used.

<Durability evaluation>
The durability of the microfluidic device was evaluated with a focus on crack resistance.
The flow path pattern prepared in Example 3 was wound around a metal cylinder having a predetermined diameter, and then both ends were pulled with a force of 4.9 N to observe whether cracks occurred in the flow path pattern. The diameter of the cylinder was gradually reduced, and the evaluation was repeated until cracks were observed in the flow path pattern.

In a 0.08 mm thick microchannel device made using resin particles D, no cracks were observed until it was wrapped around a 4 mm diameter cylinder, and cracks were first observed when it was wrapped around a 3 mm diameter cylinder. In a microchannel device similarly made using resin particles A used in Example 1, cracks were observed when it was wrapped around a 12 mm diameter cylinder. The breaking elongation of the COC used in resin particles A was 1.3, and the breaking elongation of the COC used in resin particles D was 4.5.

The results of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 2.
Resin particles A had a low storage modulus G' and a high loss modulus G'' at a heating temperature of 200°C or 130°C, and resin particles D had a high storage modulus G'' at a heating temperature of 200°C, so they could penetrate into the porous substrate quickly and without bleeding.
At a heating temperature of 200° C., resin particles B did not penetrate into the porous substrate because of their high storage modulus G′.
Resin particles C had a low storage modulus G' at a heating temperature of 125° C. and quickly penetrated into the porous substrate, but also had a low loss modulus G'' and therefore caused bleeding during penetration.

In summary, the viscoelasticity of the resin particles must be such that the storage modulus G' is 14 Pa or less and the loss modulus G'' is 10 Pa or more when they are heated to melt and penetrate into the porous substrate. In this case, it was possible to form flow paths with high precision according to the flow path pattern.

In this embodiment, COC was used as the resin having a storage modulus of 14 Pa or less and a loss modulus of 10 Pa or more, but other known materials may be used as long as they satisfy the storage modulus and loss modulus requirements.
For example, when VYLON (registered trademark) 200 (manufactured by Toyobo Co., Ltd.), which is a polyester resin, was used instead of COC, the resin particles had the viscoelasticity shown in FIG. 6B (d). In this case, in the range of 210 ° C. to 300 ° C., the storage modulus is 14 Pa or less and the loss modulus is 10 Pa or more. The resin particles were transferred to the porous substrate S1 by the flow path pattern forming unit 100 and heated for 2 minutes in an oven set at 230 ° C., and the resin particles could be permeated into the porous substrate S1 without bleeding.

As described above, by using the electrophotographic method, it is possible to form a flow path pattern even with a highly viscous material that is difficult to eject using the inkjet method, and the freedom of material selection is increased. This makes it possible to form a flow path pattern using highly viscous resin particles that have melting properties that allow the resin particles to quickly penetrate into the substrate in the heating section. In addition, because it is an electrophotographic method, it is possible to form a flow path pattern on demand with high productivity, low cost, and high accuracy.
Furthermore, by heating at a temperature where the storage modulus G' of the resin particles is low enough to penetrate the porous substrate S1 (14 Pa or less) and the loss modulus G'' is high (10 Pa or more), it is possible to form flow paths corresponding to the flow path pattern with high accuracy without bleeding. If a micro flow path is formed under these conditions, the formation of the flow path pattern is not limited to the electrophotographic method.

Example 4
A case where an apparatus having a plurality of flow path pattern forming units as shown in FIG. 7 is used will be described.
Regarding the flow path pattern forming unit 200 in this embodiment, only the differences from the flow path pattern forming unit in the first embodiment will be described, the same members will be given the same reference numerals, and the description of the similar parts will be omitted. In the first embodiment, a filter paper having a thickness of 80 μm was used as the porous substrate, but it is possible that a porous substrate having different physical properties is required depending on the application. For example, when a porous substrate having a high porosity or a porous substrate having a larger thickness is used, more toner is required to fill the voids. In other words, it is necessary to form a thicker resin particle image on the porous substrate.

In the flow path pattern forming unit described in Example 1, possible methods for forming a thicker resin particle A image on the porous substrate include increasing the surface roughness of the developing roller 23 and changing the contact state (position or pressure) between the developing roller 23 and the developing blade 25. This increases the amount of resin particles A transported by the developing roller 23, and as a result, the thickness of the resin particle A image formed on the porous substrate also increases.
In addition, by increasing the peripheral speed ratio of the developing roller 23 to the photosensitive drum 11, the amount of resin particles A developed onto the photosensitive drum 11 can be increased without changing the amount of resin particles A on the developing roller 23, and the thickness of the resin particle A image formed on the porous substrate can be increased.
However, it is difficult to continuously form a stable flow path pattern while increasing the thickness of the resin particle A image formed on the porous substrate by several times by these methods alone. This is because if the amount of resin particles A conveyed by the developing roller 23 is increased too much, so-called fogging, in which insufficiently charged resin particles adhere to the part that should originally be the flow path wall, is likely to occur. In addition, if the peripheral speed ratio is increased too much, streaky development unevenness (so-called banding) is likely to occur in the formed flow path pattern due to uneven driving speed.

By using a device having multiple flow path pattern forming units, it becomes possible to stably form a resin particle A image on the porous substrate that is several times thicker than a device having only one flow path pattern forming unit. Since the electrophotographic method uses resin particles to form the flow path pattern, it is possible to stably form a thick material layer on the porous substrate. In inkjet and thermal transfer methods that form images using a material with a relatively low viscosity, if a large amount of material is placed on the porous substrate, the low viscosity may cause the material to spread or bleed. Another method is to repeatedly supply small amounts of material to the porous substrate at time intervals, but this significantly reduces productivity.

<Flow path pattern forming unit>
The overall configuration of the flow path pattern forming unit will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view showing a schematic configuration of a flow path pattern forming unit 200 according to an embodiment of the present invention, and each component is shown in a simplified manner.
In the flow path pattern forming unit 200, four process cartridges P (P1, P2, P3, P4) are arranged horizontally: a first process cartridge P1, a second process cartridge P2, a third process cartridge P3, and a fourth process cartridge P4. This is convenient because maintenance can be performed on each process cartridge. Each of the process cartridges P1, P2, P3, and P4 has the same configuration as the process cartridge P in FIG. 1.

<Flow path pattern formation process>
The operation of the process cartridge in the flow path pattern formation is the same as that of the flow path pattern forming unit in the first embodiment. The developer image developed on the photosensitive drum 11 is primarily transferred to the intermediate transfer body 5 in contact with the primary transfer roller 6 due to the potential difference with the primary transfer roller 6. The primary transfer roller 6 is connected to a transfer high voltage power source 74, and +300 V is applied by dividing the voltage applied to the secondary transfer roller 7 described later. This process is performed sequentially for the process cartridge P1, process cartridge P2, process cartridge P3, and process cartridge P4, and all the developer images are superimposed on the intermediate transfer body 5. The superimposed developer images are transferred to a porous substrate as a recording medium in a secondary transfer section where the intermediate transfer medium 5 and the transfer roller 7 are arranged in close proximity due to the potential difference with the secondary transfer roller 7 to which +2000 V is applied by the transfer high voltage power source 74. The secondary transfer roller 7 uses a member similar to the transfer roller 4 in FIG. 1.
The porous substrate onto which the developer image has been transferred is discharged to the outside of the flow path pattern forming unit 200 with the developer image facing upward in the direction of gravity. After passing through the intermediate transfer body 5, the photosensitive drum 11 has the developer that has not been transferred scraped off by the cleaning member 14 in contact with it, and the process from charging by the charging roller 12 is repeated again, thereby continuously forming images.

The flow path pattern forming unit 200 has mainly four development modes (printing modes) according to the actual porosity and thickness of the porous substrate used.
The development mode 1 is a mode in which a resin particle A image is formed on a porous substrate using resin particles A only from the process cartridge P1. That is, in the flow path pattern forming process, the process cartridge P1 irradiates the photosensitive drum 11 with a laser beam 9 to develop the resin particles A, but the process cartridges P2, P3, and P4 do not irradiate the photosensitive drum 11 with the laser beam 9 and do not develop the resin particles A. In the development mode 1, a resin particle A image of 1.25 mg/ ^cm2 per unit area can be formed on the porous substrate surface, similar to the flow path pattern forming unit 100 in FIG.

In the development mode 2, a resin particle A image is formed on the porous substrate using the resin particles A of the process cartridges P1 and P2. That is, in the flow path pattern forming process, the process cartridges P1 and P2 are irradiated with the laser light 9, but the process cartridges P3 and P4 are not irradiated with the laser light 9. This allows an image of the resin particles A of 2.5 mg/ ^cm2 per unit area to be formed on the surface of the porous substrate S2.

In the development mode 3, an image of resin particles A is formed on the porous substrate using resin particles A in the process cartridges P1, P2, and P3. That is, in the flow path pattern forming process, the process cartridges P1, P2, and P3 are irradiated with laser light 9, but the process cartridge P4 is not irradiated with laser light 9. This allows a resin particle A image of 3.75 mg/ ^cm2 per unit area to be formed on the surface of the porous substrate.

In the development mode 4, a resin particle A image is formed on the porous substrate using the resin particles A of all the process cartridges P1, P2, P3, and P4. That is, in the flow path pattern forming process, the laser 9 light is irradiated onto all the process cartridges P1, P2, P3, and P4. This allows a resin particle A image of 5.0 mg/ ^cm2 per unit area to be formed on the surface of the porous substrate.

<Selecting the development mode>
Since the flow path pattern forming unit 200 has the above-mentioned multiple development modes, the user can select the development mode from, for example, a personal computer as a host device according to the conditions of the porous substrate S2 to be printed. Which development mode is appropriate is determined by the thickness and substantial porosity of the porous substrate S2. If the amount of resin particles placed on the voids of the porous substrate S2 is small, the voids of the porous substrate S2 cannot be filled completely, and leakage occurs in the flow path as a micro-channel device. In addition, if the amount of resin particles placed on the voids of the porous substrate S2 is too large, the excess resin particles may diffuse into the porous substrate S2 beyond the range of the flow path pattern relative to the amount of resin particles that fills the voids, narrowing the flow path. Therefore, it is preferable to select a development mode that fills at least the voids of the porous substrate S2 and has an amount of resin particles that is as close to filling as possible.

As an example of development mode selection, consider the case where filter paper with only a different thickness is used for the porous substrate shown in the embodiment. When using a porous substrate S2 with a thickness of 80 μm, if 1.0 mg/cm ² or more of resin particles are required on the porous substrate S2, the maximum filter paper thickness that can form a good flow path according to the amount of resin particles per unit area can be calculated as follows. That is, the maximum filter paper thickness for each development mode that can form a good flow path = 80 (μm) × the amount of resin particles (mg/cm ² ) on the porous substrate surface for each development mode / 1.0 (mg/cm ² ). Table 3 shows the maximum filter paper thickness that can form a good flow path without leakage in each development mode.

Based on these conditions, it is recommended to select the following development mode according to the thickness of the filter paper from Table 3.
Filter paper with a thickness of 100 μm or less: Development mode 1
Filter paper with a thickness of 100 μm to 200 μm: Development mode 2
Filter paper with a thickness of 200 μm to 300 μm: Development mode 3
Filter paper with a thickness of 300 μm to 400 μm: Development mode 4
A combination of development mode and filter paper thickness is shown as an example, but the amount of resin particles required also varies depending on the porosity of the filter paper, so the development mode is changed depending on the porosity of the filter paper.

<Double-sided printing>
Note that the above shows the maximum filter paper thickness achieved by placing resin particles on one side of a porous substrate and then heating to cause the resin particles to penetrate into the porous substrate. However, by using double-sided printing, it is possible to form good flow paths without leakage even in thicker porous substrates.
As an example of double-sided printing, a method of double-sided printing on a porous substrate S2 having a thickness of 600 μm, which differs from the porous substrate only in thickness, will be described with reference to FIG.
8(a), 8(b), 8(c), and 8(d) are cross-sectional views of the locations where resin particles A are placed in each process of double-sided printing. In the following, the surface on which the resin particles A are placed first is referred to as the front side of the porous substrate S2, and the surface on which the resin particles A are placed later is referred to as the back side of the porous substrate S2.

First, since the thickness of the porous substrate S2 is 600 μm, double-sided printing using development mode 3 was selected from Table 3. Figure 8 (a) shows the state after the flow path pattern formation process using development mode 3. At this time, the resin particles A are simply attached to the front side of the porous substrate S2.

Next, the state after the heating process is shown in FIG. 8(b). The resin particles A attached to the front side of the porous substrate S2 have penetrated into the interior of the porous substrate S2 due to heating. However, at this time, because the amount of resin particles A is small compared to the thickness of the porous substrate S2, the molten resin does not reach the back side of the porous substrate S2, and no flow path surrounded by the molten resin is formed.

Then, the porous substrate S2 is turned over and the flow path pattern formation process is carried out again in development mode 3, as shown in FIG. 8(c). By the second development, resin particles A are placed on the back side of the area that was previously infiltrated with the molten resin on the front side.

The state after the heating process is then performed again is shown in FIG. 8(d). By performing the heating process again, the resin containing the molten resin particles A also permeates from the back side of the porous substrate S2, and connects with the resin that has already permeated from the front side, forming a flow path 82 surrounded by the resin containing the molten resin particles A.

As described above, even in porous substrates of a thickness where it is difficult to form good flow paths without leakage by printing only on the front side, good flow paths without leakage can be formed by infiltrating the resin made of molten resin particles A from both the front and back sides of the paper. In other words, in the configuration of this embodiment, good flow paths without leakage can be formed in porous substrates up to 800 μm thick, which is twice as thick as in development mode 4. In addition, by using a flow path pattern forming unit equipped with five or more process cartridges P, it is also possible to form flow paths in porous substrates with a higher porosity and thickness.

<Fine adjustment of resin particle amount>
In this embodiment, the amount of resin particles placed on the porous substrate in each development mode is a discrete value, but it is also possible to place an amount of resin particles that is a value between each development mode. For example, by changing the development circumferential speed ratio, the amount of resin particles developed in each process cartridge P changes, so the amount of resin particles placed on the porous substrate may be adjusted by the development circumferential speed ratio. In addition, by weakening the intensity of the laser light 9, the ratio of resin particles developed from the developing roller 23 to the photosensitive drum 11 (so-called development efficiency) can be reduced, so the amount of resin particles placed on the porous substrate may be adjusted by the intensity of the laser light. By optimizing the amount of resin particles placed on the porous substrate, it is possible to reduce the amount of excess resin particles compared to filling the voids in the porous substrate, making it possible to create a microchannel device with higher accuracy.

<Summary>
As described above, by appropriately selecting the development mode, single-sided printing/double-sided printing, development speed ratio/laser light intensity, it is possible to easily and stably form a resin particle image on a porous substrate with an appropriately adjusted thickness according to various porous substrates. This is achieved by using an electrophotographic method that can easily and accurately adjust the amount of resin particles placed on the porous substrate over a wide range.

Example 5
In Example 5, a microchannel device is manufactured in which a protective layer is provided to cover one surface side of the formed channel. By forming the protective layer, the channel can be made into a closed system, and the sample liquid can be prevented from drying out and from sticking to hands, improving safety.
In this embodiment, the material forming the flow channel wall and the material forming the protective layer are the same material. In this case, the adhesion between the flow channel wall and the protective layer is improved, resulting in a flow channel device with high sealing performance. When making a micro flow channel device having a flow channel wall and a protective layer using the same material, the processes of forming the protective layer and the flow channel wall are performed separately.

In this example, a porous substrate S1-2 was used in which a polyethylene terephthalate (PET) film (Toray Industries, Inc., Lumirror S10, thickness 50 μm) was attached to one side as a cover film B. By attaching the cover film B, it is possible to suppress drying and contamination on the attached side. The average thickness of the cover film is preferably 0.01 mm or more and 0.5 mm or less from the viewpoint of achieving both strength and flexibility.
The material of the cover film is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include the following: polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate, polyimide resin (PI), polyamide, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, styrene-acrylonitrile copolymer, cellulose acetate, etc. These may be used alone or in combination of two or more. Among these, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are particularly preferred.

First, resin particles A were placed on the surface of the porous substrate S1-2 to which the PET film B was not attached, in the same manner as in Example 1. The resin particles were then melted and allowed to permeate the porous substrate, forming flow path walls so as to form the flow path pattern of FIG. 4(a) (FIGS. 9(a) to (b)).
Next, resin particles A were placed through a flow path pattern forming process at a position covering the flow path 82 in Fig. 4(a) (Fig. 9(c)). At this time, the resin particles were placed so as to overlap the flow path walls on both sides of the flow path by 2.25 mm each.
Next, as a second heating process, heating was performed at 120°C for 2 minutes. At this temperature, the COC placed on the surface of the porous substrate melts on the surface and does not penetrate into the porous substrate, so the flow path formed inside the porous substrate S1-2 is maintained. As a result, a protective layer is formed to cover the flow path (Figure 9(d)).

In this embodiment, a cover film was adhered to one side of the porous substrate, but a protective layer may be formed using COC instead of a cover film, resulting in a microchannel device having protective layers on both sides of the porous substrate.
In the present embodiment, the resin forming the flow path wall and the resin forming the protective layer are the same resin, but they may be different resins. In the case where different resins are used, it is preferable to use a hydrophobic resin in order to prevent the influence of water.
For comparison, the heating temperature in the second heating process was changed to 130° C. to form a protective layer, but the resin particles penetrated and blocked the flow path. When the protective layer was formed by adjusting the temperature to a temperature at which the storage modulus G' was 20 Pa, the resin particles did not penetrate and a good protective layer was formed.
From the above results, the heating temperature of the second heating process for forming the protective layer is
The temperature is equal to or lower than a temperature at which the storage modulus G' (14 Pa or more, preferably 20 Pa or more) at which the resin particles do not penetrate into the porous substrate can be maintained, and
To be able to form a protective layer, the temperature must be equal to or higher than the melting point (softening point) of the resin particles.

Example 6
In Example 5, a protective layer was formed on the surface of the porous substrate to cover the flow path, but a protective layer can also be formed on the surface side of the flow path inside the porous substrate. In this example, such a microchannel device is manufactured. The porous substrate S1 has a backing material B such as a laminate on the back side.
First, in the same manner as in Example 1, resin particles A were placed on the porous substrate S1, and then the resin particles were allowed to penetrate into the porous substrate, forming flow path walls so as to form the flow path pattern of FIG. 4(a) (FIGS. 10(a)-(b)).

Next, resin particles A were placed in the flow path 82 in FIG. 4(a) (FIG. 10(c)).
Next, heating was performed at 120°C for 30 seconds. Since sufficient penetration does not occur during this heating time, a protective layer covering the upper part of the flow path is formed (Figure 10 (d)). Under these conditions, penetration of about 0.04 mm occurs, so when a porous substrate with a thickness of 0.08 mm is used, a flow path height of about 0.04 mm can be ensured. The heating time can be appropriately adjusted according to the material used and the thickness of the protective layer to be formed.

Example 7
In Example 6, the heating time was changed to form the protective layer, but the amount of COC particles placed on the flow channel was reduced to reduce the amount of resin that penetrates, forming a similar protective layer. In this example, such a micro flow channel device is manufactured. In this manufacturing method, a protective layer can be easily formed without using multiple materials and without performing the heating process twice.
In this embodiment, when forming a flow path pattern in the flow path pattern forming process, resin particles A are placed on both the region that becomes the flow path wall and the region that becomes the flow path. A smaller amount of resin particles A is placed on the surface of the part that becomes the flow path of the porous substrate S1 than the amount of resin particles A placed on the surface of the part that becomes the flow path wall (FIG. 11(a)). The amount of resin particles A is preferably about 25 to 75 mass % of the part that forms the flow path wall.
Next, a heating process is performed. The heating conditions are the same as in Example 1, at 200 ° C. for 2 minutes. Through the heating process, the resin particles in the flow path wall part permeate to form a flow path wall. On the other hand, since the amount of resin particles in the flow path part is small, they remain in a state of slightly permeating into the porous substrate (FIG. 11 (b)). The degree of permeation at this time increases as the storage modulus G' at the heating temperature decreases, so it is required that the storage modulus G' is not too low. When resin particles with a storage modulus G' of 0.2 Pa at 200 ° C. were used, the flow path height was as low as 0.02 mm, so the storage modulus G' is preferably 0.2 Pa or more. More preferably, the storage modulus G' is 0.4 Pa or more. The flow path height is the thickness of the paper minus the permeated distance, and is preferably 0.02 mm or more.

Example 8
In Example 8, another example is shown in which a protective layer is provided so as to cover the flow path. In Example 8, the flow path pattern forming unit of Fig. 7 is used to form the protective layer while controlling the storage modulus G' by changing the materials of the protective layer and the flow wall.
7 is as described above, and in this embodiment, COC (manufactured by Polyplastics Co., Ltd., 8007 grade) is placed in process cartridge P1, and COC (manufactured by Polyplastics Co., Ltd., TM grade) is placed in process cartridge P2. The other process cartridges are empty.
First, a protective layer pattern is formed on the intermediate transfer body 5 using the process cartridge P1, and then a flow path wall pattern is superimposed on the protective layer pattern using the process cartridge P2 (FIG. 12(a)).
The superimposed patterns are then transferred from the intermediate transfer member onto the porous substrate (FIG. 12(b)).
The porous substrate onto which this pattern has been transferred is heated in a heating process at 200° C. for 2 minutes to obtain a microchannel device with a protective layer provided on the channel (FIG. 12(c)).
Considering the results of Example 5, the resin particles used to form the protective layer preferably have a storage modulus G' of 20 Pa or more at the temperature in the heating process.
In the above embodiment, the flow path and the protective layer were formed using only two cartridges, but it is also possible to form an additional protective layer using another resin using an empty cartridge.

<Example 9>
In Examples 1 to 8, an oven was used as the heating unit in the heating process, but in this example, a heating and pressurizing unit is used.
The overall configuration of the flow path pattern forming unit will be described with reference to Fig. 13. Fig. 13 is a cross-sectional view showing the schematic configuration of the flow path pattern forming unit 500, and each component is shown in a simplified manner.
In the flow path pattern forming unit 500, a first process cartridge P1 having a fixing separation developer TB described later and a second process cartridge P2 having resin particles A are arranged horizontally, and a fixing unit 550 is also provided.
First, a fixing/separating developer layer is formed in the same shape as the flow path wall pattern on the intermediate transfer body 5 using a process cartridge P1. Next, the flow path wall pattern is superimposed on the formed fixing/separating toner layer using a process cartridge P2. After that, the formed pattern is transferred from the intermediate transfer body onto a porous substrate.

The flow path pattern formed on the porous substrate undergoes a heating and pressurizing process by the fixing unit 550, whereby the resin particles A penetrate into the porous substrate, forming a micro-flow path device having flow paths surrounded by hydrophobic walls. The fixing separation developer layer is a layer for preventing the molten resin particles A from adhering to the fixing member, and the amount of the developer applied may be as small as about 0.1 mg/ ^cm2 .
The fixing unit may be any unit capable of raising the temperature of the resin particles to a temperature range where the permeation is favorable, and may be any unit generally used in electrophotographic image forming apparatuses. In particular, from the viewpoint of not disturbing the flow path, it is preferable that the fixing is performed at a low pressure, and a film-type fixing unit as shown in FIG. 14 is suitable.

The fixing unit shown in Fig. 14 will be briefly described. A heating rotor 552 is pressed against a pressure roller 551 via a heating film 554. The heating film 554, which is sandwiched between the pressure roller 551, a support holder 555, and a plate-shaped heating element 553, rotates around the support holder 555 and a fixing stay (not shown) relative to the pressure roller 551. The pressure roller 551 is formed of an aluminum or iron core metal 556, an elastic layer 557 on the outside thereof, and a release layer 558 that covers the surface of the elastic layer 557.
The fixing/separating developer may be any developer that is generally used as a toner for an electrophotographic image forming apparatus, and preferably contains a thermoplastic resin as a binder resin and a release agent, but does not need to contain a colorant that is generally contained in a toner.
In addition, a composite heating process may be performed, for example, by performing a heating process using a heating and pressurizing unit as a preheating process and then performing a main heating process using an oven.

Example 10
In Example 10, the technique of forming a protective layer using a developer with a different storage modulus G' in Example 8 and the technique of forming a protective layer by changing the amount of the protective layer in Example 7 were used in combination. Then, while a protective layer was placed on the surface of the porous substrate, a protective layer was also formed on the surface side inside the porous substrate (FIGS. 15(a)-(b)). By forming such protective layers from both sides, a microchannel device in which the channels are strongly protected can be obtained (FIGS. 15(c)-(d)).

Example 11
In this example, a microchannel device is manufactured in which a cover layer with a reduced printing rate is provided on the surface of the test liquid section. The protective layer was formed as a solid image with a printing rate of 100%, but when a cover layer is provided on the surface of the test liquid section, the printing rate is appropriately adjusted within the range of 10 to 90%. By providing a cover layer on the surface of the test liquid section, the amount of test liquid flowing into the test liquid section can be controlled. If it is desired to greatly reduce the amount of test liquid flowing in, the printing rate of the cover layer should be increased, and if it is desired to reduce it slightly, the printing rate of the cover layer should be decreased.
A specific example of a method for manufacturing a microchannel device in which a cover layer is provided on the test liquid section will be described below.
First, in the same manner as in Example 1, resin particles A were placed on the porous substrate and melted and impregnated to form flow path walls so as to form the flow path pattern shown in FIG. 4(b).

Next, the following steps were carried out in the same manner as in the step of forming the protective layer in Example 5 to complete the microchannel device shown in Fig. 16. In Fig. 16, 310a denotes a reagent portion, and 310e denotes a channel.
A necessary amount of COC particles (resin particles A) is placed to form a protective layer 320 with a printing rate of 100% so as to cover the flow path.
A necessary amount of COC particles (resin particles A) is placed on the test liquid portion 310c to form a cover layer 311c with a printing rate of 50%.
A necessary amount of COC particles (resin particles A) was placed on the test liquid portion 310b to form a cover layer 311b with a printing rate of 80%.
Thereafter, heating was performed at 120° C. for 2 minutes to form a protective layer 320 and cover layers 311b-c on the surface of the porous substrate.

This microfluidic device is
When a large amount of test liquid is required, the test liquid is applied from the test liquid portion 310d.
On the other hand, if it is desired to reduce the amount of test liquid to flow in, for example, to about half the amount, the test liquid is applied from the test liquid portion 310c,
If an even smaller amount is desired, the test liquid can be applied from the test liquid portion 310b.
If the pattern of the cover layer 311c printed on the test liquid portion 310c has a printing rate of 50%, the amount of test liquid flowing into the test liquid portion 310c will be about half the amount of the test liquid dropped.
Furthermore, if the pattern of the cover layer 311b printed on the test liquid portion 310b has a printing rate of 80%, the amount of test liquid flowing into the test liquid portion 310b will be about 20% of the amount of test liquid dropped.

4. Transfer roller 5. Intermediate transfer body 6. Primary transfer roller 7. Secondary transfer roller P. Process cartridge 11. Photosensitive drum 12. Charging roller 14. Cleaning blade 15. Memory 20. Developing device 21. Development container 23. Development roller 24. Resin particle supply roller 25. Development blade T. Developer 71. High voltage charging power source 72. High voltage development power source 73. Exposure unit 74. High voltage transfer power source 75. Contact unit 80. Flow path pattern 81. Resin particle image 82. Flow path 83. Reagent section 84. Test liquid section 200. Flow path pattern forming unit

Claims (13)

A method for manufacturing a microchannel device in which a channel sandwiched between channel walls is formed inside a porous substrate, comprising the steps of:
A step of placing a first hydrophobic resin on the surface of the porous substrate to form a flow path pattern on the surface of the porous substrate; and a step of melting the first hydrophobic resin by heat to cause the first hydrophobic resin to penetrate into the porous substrate to form a flow path wall inside the porous substrate.
having
A method for manufacturing a microchannel device, characterized in that in the step of forming the channel wall, the first hydrophobic resin is infiltrated at a temperature at which the storage modulus G ' of the first hydrophobic resin is 14 Pa or less and the loss modulus G'' of the first hydrophobic resin is 10 Pa or more. The method for manufacturing a microchannel device according to claim 1, wherein the first hydrophobic resin is allowed to penetrate into the porous substrate at a temperature at which the storage modulus G' of the first hydrophobic resin is 14 Pa or less and the loss modulus G'' of the first hydrophobic resin is 10 Pa or more. The method for manufacturing a microchannel device according to claim 1 or 2, wherein the first hydrophobic resin has a water absorption rate of 1% or less. The method for manufacturing a microchannel device according to claim 3, wherein the water absorption rate of the first hydrophobic resin is 0.1% or less. The method for manufacturing a microchannel device according to any one of claims 1 to 4, wherein the melt viscosity of the first hydrophobic resin at 100°C is 1000 Pa·s or more. The method for manufacturing a microchannel device according to any one of claims 1 to 5, wherein the first hydrophobic resin is a cyclic olefin copolymer. The method for manufacturing a microchannel device according to claim 6, wherein the first hydrophobic resin further contains a plasticizing component. The method for manufacturing a microchannel device according to any one of claims 1 to 7, wherein a protective layer is formed on the surface of the porous substrate so as to cover the channel, or a protective layer is formed so as to block the surface side of the channel. In the flow path pattern, the first hydrophobic resin is present in both a region that becomes a flow path wall and a region that becomes a flow path, and the amount of the first hydrophobic resin in the region that becomes the flow path wall is made greater than the amount of the first hydrophobic resin in the region that becomes the flow path,
9. The method for manufacturing a microchannel device according to claim 8, wherein the first hydrophobic resin is melted to form a channel wall inside the porous substrate and to form a protective layer to block the surface side of the channel. The method for manufacturing a microchannel device according to claim 9, wherein the amount of the first hydrophobic resin in the region that will become the channel is 25 to 75% by mass of the amount of the first hydrophobic resin in the region that will become the channel wall. In the flow path pattern, a second hydrophobic resin having a storage modulus of 20 Pa or more at a temperature in a process of forming a flow path wall is present in a region that becomes a flow path,
9. The method for manufacturing a microchannel device according to claim 8, wherein the first hydrophobic resin and the second hydrophobic resin are melted to form a channel wall composed of a first hydrophobic resin inside the porous substrate, and a protective layer composed of the second hydrophobic resin is formed to cover the channel. The method for manufacturing a microchannel device according to claim 8, further comprising the steps of forming a channel wall inside the porous substrate using the first hydrophobic resin, placing a hydrophobic resin that is the same as or different from the first hydrophobic resin on the surface of the porous substrate, and melting the hydrophobic resin to form a protective layer to cover the surface of the channel, or to block the surface side of the channel. The method for manufacturing a microchannel device according to any one of claims 1 to 12, wherein the step of placing a first hydrophobic resin on the surface of the porous substrate and forming a channel pattern on the surface of the porous substrate is performed by an electrophotographic method.

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