JP5187824B2 - Microfluidic device, fuel cell and manufacturing method thereof - Google Patents

Description

  The present invention relates to a microfluidic device, a fuel cell, and a manufacturing method thereof, and more particularly, to a microfluidic device that handles a minute flow rate, a fuel cell that applies the structure, and a manufacturing method thereof.

  A fuel cell is a power generator that generates power when fuel and an oxidant are supplied. Normally, air can be used as the oxidizer, so that it is possible to continuously generate power by changing the fuel. For this reason, fuel cells are attracting a great deal of attention not only as stationary power sources but also as portable power sources.

  Usually, in a stationary fuel cell or the like, hydrogen or a gas containing hydrogen is used as a fuel. However, as a portable power source, it is advantageous that power can be generated for a long time with fuel stored in a container of the same size. . Therefore, a liquid fuel having a high energy density per volume is more advantageous as the fuel.

  Although it is possible to generate hydrogen from liquid fuel and use it for power generation with a reformer, the entire fuel cell system becomes complicated, so it is considered easier to directly supply liquid fuel for miniaturization. ing.

  Japanese Unexamined Patent Publication No. 11-510311 (Patent Document 1) discloses a fuel cell that supplies liquid fuel directly to the fuel electrode. This fuel cell is a direct methanol fuel cell that uses a mixture of methanol and water as fuel.

A typical direct methanol fuel cell will be described with reference to FIG.
FIG. 11 is a diagram schematically showing a direct methanol fuel cell 100A including a fuel electrode 102A, an oxidant electrode 103A, and an electrolyte membrane 104A in a housing 101A. A fuel in which methanol and water are mixed by the fuel pump 106A is supplied from the fuel tank 105A to the anode chamber 107A. The fuel supplied into the fuel electrode chamber 107A permeates into the fuel electrode 102A and reacts to generate protons (hydrogen ions), electrons, and carbon dioxide.

  Usually, a porous material is used for the fuel electrode 102A, and the reaction at the fuel electrode 102A occurs in a layer in which a catalyst is supported in the vicinity of the interface with the electrolyte membrane 104A. Protons generated at the fuel electrode 102A pass through the electrolyte membrane 104A and move to the oxidant electrode 103A, and electrons flow from the fuel electrode 102A to the oxidant electrode 103A via an external circuit (not shown). These electrons are used as the output of the fuel cell.

  Carbon dioxide is discharged from the fuel electrode 102A to the fuel electrode chamber 107A, and is discharged from the outlet port 112A together with unreacted fuel. The carbon dioxide discharged from the outlet port 112A and unreacted fuel are collected in the fuel tank 105A, and the carbon dioxide is discharged from a discharge port 108A provided in the fuel tank 105A.

  On the other hand, on the oxidant electrode 103A side, oxygen is supplied to the oxidant electrode chamber 110A by the compressor 109A. This oxygen diffuses from the oxidant electrode chamber 110A into the oxidant electrode 103A. In the oxidant electrode 103A, oxygen reacts with protons diffused from the fuel electrode 102A to generate water. The generated water becomes water vapor and is discharged from the oxidant chamber 110A together with unreacted oxygen from the outlet port 111A. In the example shown in FIG. 11, oxygen is used as the oxidizing agent. In addition, although oxygen concentration becomes low, air can also be used as an oxidizing agent.

  In the conventional direct methanol fuel cell, as shown in FIG. 11, a mixture of fuel methanol and water is supplied to the fuel electrode chamber 107A and permeates from the fuel electrode chamber 107A into the diffusion layer of the fuel electrode 102A, and the electrolyte membrane. It reacts in the layer containing the catalyst in the vicinity of the interface with 104A. Carbon dioxide, which is a reaction product, is discharged into the fuel electrode chamber 107A, merges with the supplied fuel, and discharged from the outlet port 112A together with unreacted fuel. In order to perform highly efficient and stable power generation in a fuel cell, it is necessary to efficiently and stably supply fuel and discharge carbon dioxide as a reaction product.

  By the way, the main flow of fuel supplied by the fuel pump 106A is sent to the fuel electrode chamber 107A and then discharged from the outlet port 112A provided in the fuel electrode chamber 107A. For this reason, the flow in the porous material of the fuel electrode 102A that directly contributes to the reaction of the fuel electrode 102A deviates from the main flow of fuel in the fuel electrode chamber 107A. Furthermore, although the capillary action works in the porous material of the fuel electrode 102A, it is difficult to supply the fuel into the fuel electrode 102A efficiently and stably because of restrictions on the shape and direction. This has made it difficult to improve the output as a fuel cell and to generate power for a long time with high efficiency. In addition, when a pump that pumps fuel at high pressure is used, the power supply device is increased in size, so that it is particularly difficult to employ it as a power source for portable devices and the like.

  By the way, in Japanese Patent Application Laid-Open No. 2002-175817 (Patent Document 2), a fuel permeation member that permeates fuel is arranged in a fuel flow path to which fuel is supplied to promote fuel supply to the fuel electrode. .

However, in the fuel cell described in Patent Document 2, the fuel is supplied to the fuel electrode by the permeation by the fuel permeation member, so that the reaction efficiency of the fuel at the fuel electrode is insufficient and the output is insufficient. It was.
Japanese National Patent Publication No. 11-510311 JP 2002-175817 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to stably supply a fluid (mainly liquid) in a very small amount as efficiently as possible to a wide range of reaction fields and to provide a wide range. In addition to providing a microfluidic device capable of efficiently and stably discharging reaction products generated from the reaction field, and by applying the structure of this microfluidic device, the reaction efficiency of the fuel at the fuel electrode and An object of the present invention is to provide a fuel cell that increases the efficiency of discharge of reaction products and can obtain a high output even if it is downsized.

A microfluidic device according to the present invention includes a flow path plate having a flow path groove, a diffusion member that is disposed to face the flow path plate and diffuses a supply substance supplied from the flow path groove, and a flow path plate. An interposition member interposed between the diffusion member and the flow path groove, a first flow path for supplying the supply material to the diffusion member, and a second for discharging the discharge material from the diffusion member. And the first channel and the second channel are separated from each other, and the interposition member is formed in the non-channel region on the main surface where the channel groove of the channel plate is formed. A first portion that opposes, a second portion that opposes the first flow path, and a third portion that opposes the second flow path ; And a diffusion preventing structure that suppresses the diffusion of exhaust substances.

  According to the above configuration, the supply substance can be supplied almost uniformly little by little through the interposition member from the channel facing the diffusion member. Furthermore, the lower part of the wall that becomes the non-flow channel region is configured so that the supply substance is not discharged from the first flow path side to the second flow path side without passing through the diffusion member by the diffusion prevention structure. It is possible to suppress the unreacted discharge from the second flow path and to efficiently react the supplied feed substance. That is, the reaction amount per area of the supply area can be further improved.

In the microfluidic device, the interposition member has a structure in which the supply substance is less likely to permeate in the plane direction as compared to the film thickness direction.

Accordingly, even if the diffusion preventing structure corresponding to the pattern of the first flow path and the second flow path is not formed on the interposition member, the portion facing the first flow path is in the film thickness direction, that is, the first flow path. It is easy to permeate in the direction from the first flow path to the diffusion member, and in the lower part of the wall, it is possible to form a diffusion preventing structure that is difficult to permeate from the planar direction, that is, from the first flow path side to the second flow path side. The manufacturing process is also simplified.

  In one embodiment, in the microfluidic device, the interposition member has a structure in which the discharged substance is less likely to permeate in the plane direction as compared with the film thickness direction.

  According to this embodiment, the exhausted substance faces the second flow path without forming a diffusion preventing structure in accordance with the pattern of the first flow path and the second flow path on the interposed member. The portion is easy to permeate in the film thickness direction, that is, in the direction from the diffusing member to the second flow path, and in the lower part of the wall, a diffusion preventing structure that is difficult to permeate from the plane direction, that is, from the second flow path side to the first flow path side. Therefore, the manufacturing process is also simplified.

  In one embodiment, in the microfluidic device, the diffusion preventing structure is a structure in which a substance that suppresses the diffusion of the supply substance is contained in the interposed member.

  According to this embodiment, it is possible to more reliably prevent the supply substance from passing through the lower part of the wall from the first flow path or through the interposition member into the second flow path.

  In one embodiment, in the microfluidic device, the diffusion preventing structure is a structure in which a substance that suppresses the diffusion of the discharged substance is contained in the interposed member.

  According to this embodiment, it is possible to more reliably prevent the discharged substance from passing through the second flow path through the lower part of the wall or through the inside of the interposition member into the first flow path.

  In one embodiment, in the microfluidic device described above, in a state where the supply substance is supplied to the first flow path, the portion where the discharge substance faces the first flow path in the interposition member is The pressure required to permeate the one flow path side is equal to or higher than the discharge pressure of the discharged substance from the diffusion member.

  According to this embodiment, it is possible to prevent the discharge material from flowing back to the first flow path from the diffusion member through the portion facing the first flow path of the interposition member and inhibiting the supply of the mixture.

  In one embodiment, in the microfluidic device described above, in a state where the supply substance is supplied to the diffusion member, the portion where the supply substance faces the second flow path in the interposition member is changed from the diffusion member side to the second flow. The pressure required to permeate to the road side is equal to or higher than the discharge pressure of the supply substance from the diffusion member.

  According to this embodiment, when the thin film heater is turned off and the reforming reaction is stopped, or when the thin film heater is turned off and the diffusion member is lowered below a predetermined temperature, Even when the mixture of methanol and water as the supply substance is liquefied, the liquefied mixture can be prevented from being discharged to the second flow path.

The fuel cell according to the present invention is disposed so as to face the fuel electrode, a fuel electrode that supplies liquid fuel and generates cations and electrons from the liquid fuel, and allows the cations from the fuel electrode to pass therethrough. The electrolyte membrane is disposed so as to face the electrolyte membrane while being supplied with the oxidant, and is disposed so as to face the fuel electrode and the oxidizer electrode that reacts the cation and the oxidant that has permeated through the electrolyte membrane. And a flow path plate having flow path grooves. The flow channel groove forms a first flow channel for supplying liquid fuel to the fuel electrode and a second flow channel for discharging exhaust gas from the fuel electrode, and the first flow channel and the second flow channel. The fuel electrode has an electrode layer on the electrolyte membrane side containing the catalyst and a diffusion layer on the flow path plate side. The fuel cell further includes an interposition member interposed between the flow path plate and the diffusion layer. The intervening member includes a first portion facing the non-flow channel region on the main surface where the flow channel grooves of the flow channel plate are formed, a second portion facing the first flow channel, and a second flow channel. The first portion has a diffusion preventing structure that suppresses the diffusion of the liquid fuel and the exhaust gas in the planar direction of the interposition member.

  According to the above configuration, the liquid fuel can be supplied almost uniformly little by little from the flow path facing the diffusion layer through the interposition member. At this time, the lower part of the wall is configured so that the liquid fuel is not discharged from the first flow path side to the second flow path side without passing through the diffusion layer by the diffusion prevention structure, so that compared with the case without the diffusion prevention structure Thus, it is possible to suppress the unreacted discharge of the fuel and to efficiently react the supplied fuel. That is, it is possible to improve the utilization efficiency of the fuel for generating power per area of the supply area of the first flow path. Further, when the exhaust gas generated at the fuel electrode is discharged from the diffusion layer to the second flow path, the exhaust gas diffuses in the interposition member from the second flow path side to the first flow path side by the diffusion prevention structure. Thus, it is possible to suppress the discharge to the first flow path side and to prevent the supply of fuel from the first flow path from being hindered. Therefore, according to this embodiment, the fuel utilization efficiency can be very high, and high output can be easily obtained even if the size is reduced.

In the fuel cell, the interposition member has a structure in which liquid fuel is less likely to permeate in the plane direction as compared to the film thickness direction.

Thus, even if the diffusion preventing structure corresponding to the pattern of the first flow path and the second flow path is not formed on the interposition member, the portion facing the first flow path is in the film thickness direction, that is, the first flow path. It is easy to permeate in the direction from the first flow path to the diffusion layer, and at the lower part of the wall, it is possible to form a diffusion prevention structure that is difficult to permeate from the planar direction, that is, from the first flow path side to the second flow path side. The manufacturing process is also simplified.

  In one embodiment, in the fuel cell, the interposition member has a structure in which the exhaust gas is less likely to permeate in the plane direction as compared with the film thickness direction.

  According to this embodiment, this allows the interfacing member to face the second flow path without forming a diffusion prevention structure that matches the pattern of the first flow path and the second flow path. Is easy to permeate in the film thickness direction, that is, the direction from the diffusion layer to the second flow path, and forms a diffusion prevention structure that hardly permeates from the plane direction, that is, from the second flow path side to the first flow path side at the lower part of the wall. Therefore, the manufacturing process is also simplified.

  In one embodiment, in the fuel cell, the diffusion preventing structure is a structure in which a substance that suppresses the diffusion of the liquid fuel is contained in the interposed member.

  According to this embodiment, liquid fuel can be more reliably prevented from passing through the lower part of the wall from the first flow path or through the inside of the interposed member to the second flow path.

  In one embodiment, in the fuel cell, the diffusion preventing structure is a structure in which a substance that suppresses the diffusion of exhaust gas is contained in the interposed member.

  According to this embodiment, the exhaust gas from the diffusion layer can be more reliably prevented from passing through the lower part of the wall from the second flow path side or through the interior of the interposition member to the first flow path side. Can do.

  In one embodiment, in the fuel cell, in a state where the liquid fuel is supplied to the first flow path, a portion of the interposing member where the exhaust gas faces the first flow path is defined as the first from the diffusion layer side. The pressure required to permeate to the flow path side is equal to or higher than the exhaust gas discharge pressure from the diffusion layer.

  According to this embodiment, it is possible to prevent the exhaust gas from flowing backward from the diffusion layer through the portion of the interposition member that faces the first flow path and inhibiting the supply of the mixture.

  In one embodiment, in the fuel cell, in a state where the liquid fuel is supplied to the diffusion layer, the portion where the liquid fuel faces the second flow path in the interposition member is changed from the diffusion layer side to the second flow path side. The pressure required to permeate the liquid is greater than or equal to the discharge pressure of the liquid fuel from the diffusion layer.

  According to this embodiment, it is possible to prevent liquid fuel from being discharged into the second flow path not only during power generation but also when the fuel cell is OFF, that is, when the current output to be taken out is zero.

  The method of manufacturing a microfluidic device and the method of manufacturing a fuel cell according to the present invention are the above-described microfluidic device and fuel cell manufacturing method, in which a flow path plate in which a flow path groove is formed is applied on a substrate. Pressing the applied filler-containing material layer, transferring the filler-containing material to the convex portion of the flow path plate, and placing the flow path plate on which the filler-containing material has been transferred on the interposition member, A step of impregnating the interposition member with a material containing a filler by annealing and bonding the flow path plate and the interposition member.

  According to the above method, it is possible to manufacture the diffusion preventing structure impregnated with the substance that suppresses the diffusion of the supply substance and the discharge substance while the flow path plate and the interposition member can be reliably bonded together without a gap.

  In one embodiment, in the manufacturing method of the microfluidic device and the manufacturing method of the fuel cell, the unevenness that promotes the transfer of the material containing the filler on the convex surface of the flow path plate to which the material containing the filler is transferred. A structure is provided.

  According to this embodiment, the adhesive strength of the material including the flow path plate and the filler can be increased, and the bonding strength between the flow path plate and the interposition member can be increased.

According to the microfluidic device according to the present invention, a fluid (mainly liquid) can be stably supplied to a wide range of reaction fields in a very small amount as efficiently as possible, and reaction products generated from the wide range of reaction fields can be efficiently supplied. According to the fuel cell of the present invention, which can be discharged stably, by applying the structure of the microfluidic device described above, the reaction efficiency of the fuel and the discharge efficiency of the reaction product at the fuel electrode can be increased and the size can be reduced. Even high output can be obtained.

  Embodiments of the present invention will be described below. Note that the same or corresponding portions are denoted by the same reference numerals, and the description thereof may not be repeated.

  Note that in the embodiments described below, when referring to the number, amount, and the like, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. In the following embodiments, each component is not necessarily essential for the present invention unless otherwise specified. In addition, when there are a plurality of embodiments below, it is planned from the beginning to appropriately combine the configurations of the embodiments unless otherwise specified.

(Embodiment 1)
FIG. 1 is a plan view showing a microfluidic device according to Embodiment 1 of the present invention, and FIG. 2 is a sectional view taken along line II-II in FIG.

  Referring to FIGS. 1 and 2, in microfluidic device 1 according to the present embodiment, flow path plate 10 having flow path grooves 11 and 12 and the fluid supplied from flow path grooves 11 and 12 diffuse. The diffusion member 20 disposed so as to oppose the flow path plate 10 and the diffusion amount of the fluid that is sandwiched between the flow path plate 10 and the diffusion member 20 and is supplied from the flow path grooves 11 and 12 to the diffusion member 20 And a supply suppressing member 50 to be suppressed. The supply suppressing member 50 is opposed to a region where the flow channel grooves 11 and 12 are not formed in the flow channel plate 10, and is opposed to the first portion 51 serving as a fluid diffusion preventing structure and the flow channel grooves 11 and 12, respectively. A second portion 52 and a third portion 53 are included.

  The flow path plate 10 has ports 30 and 40 that serve as fluid inlets and outlets. The channel grooves 11 and 12 extend so as to branch from the ports 30 and 40, respectively. The channel groove 11 and the channel groove 12 are separated by a wall 13 having a predetermined thickness. The wall 13 is in contact with the supply suppressing member 50. Therefore, the channel 11 </ b> A formed by the channel groove 11 and the supply suppressing member 50 and the channel 12 </ b> A formed by the channel groove 12 and the supply suppressing member 50 are separated by the wall 13. A heater 60 is attached to the diffusing member 20. The diffusion member 20 and the heater 60 are covered with the housing 70 and are sandwiched between the flow path plate 10 and the supply suppressing member 50 and the housing 70.

  According to the microfluidic device 1, hydrogen gas can be generated from a mixture of methanol and water by causing a steam reforming reaction represented by the following formula (1). The steam reforming reaction represented by the formula (1) is usually promoted at a temperature of about 200 ° C to 300 ° C.

CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ (1)
A mixture (fluid) of methanol and water is introduced into the channel 11A from the port 30 at a predetermined pressure. Since the flow path 11A is not in direct communication with the flow path 12A, and the diffusion of the mixture in the flow path 11A to the diffusion member 20 is suppressed by the supply suppression member 50, the mixture is in the flow path 11A. To charge. Then, the mixture is gradually supplied from the channel 11 </ b> A to the entire area of the diffusing member 20 little by little through the supply suppressing member 50. If the supply suppressing member 50 is not provided, the diffusion of the mixture introduced into the flow channel 11A into the diffusion member 20 is not suppressed, so that the mixture cannot be filled up to the end of the flow channel 11A. The supply of the mixture to 20 tends to be extremely uneven.

  The diffusion member 20 is heated by the thin film heater 60, and the reforming reaction of the mixture is promoted when passing through the diffusion member 20. Hydrogen and carbon dioxide generated in the diffusion member 20 are discharged to the flow path 12A having a lower pressure than the flow path 11A. Here, since the diffusing member 20 is composed of a large number of fine holes and has a large surface area, the mixture is subdivided into a minute amount and efficiently heated. Thereby, the reforming reaction amount per area of the channel region of the channel 11A, that is, the amount of hydrogen generated can be increased. Further, at this time, the lower portion of the wall 13 that becomes the non-flow channel region is formed by the first portion 51 as the diffusion preventing structure so that the mixture of methanol and water can flow from the flow channel 11A side to the flow channel 12A without passing through the diffusion member 20. Since the mixture is configured not to be discharged to the side, it is possible to suppress the mixture from being unreacted and discharged to the flow path 12A and to react the supplied mixture efficiently. That is, the amount of hydrogen generated per area of the supply region of the flow path 11A can be further improved.

  In the present embodiment, as the flow path plate 10, any substrate can be used as long as it is a substrate having no permeability to the mixture, such as a metal, a silicon substrate, and a glass substrate. In a typical example of the present embodiment, a silicon substrate that has been subjected to microfabrication is used. Further, the width of the flow paths 11A, 12A opening to the supply suppressing member 50 side is, for example, about 2 μm to 200 μm, and the depth of the flow paths 11A, 12A is about 2 μm to 200 μm. Since the sizes of the passages 11A and 12A are relatively determined by the diffusion speed and thickness of the diffusion member 20, the size is not particularly limited to this, and the widths and depths of both flow paths are not necessarily the same. It does not have to be.

  Further, as the diffusion member 20, for example, a porous material having chemical resistance such as porous silicon, carbon paper, a sintered body of carbon, a sintered metal such as nickel, a foam metal, etc. can be used. As long as the pore diameter of the porous material can draw the fluid from the flow path 11A into the diffusion member 20 and has heat resistance capable of withstanding the temperature rise due to reaction heat or the like, the diffusion member is particularly limited to these. It is not a thing. In a typical example in the present embodiment, a porous carbon sintered body in which holes having a pore diameter of about several μm to several tens of μm are formed as the diffusing member 20.

  A reforming catalyst may be formed on the surface of the porous diffusion member 20. The reforming catalyst has an action of promoting a chemical reaction with respect to methanol and water, and has a function of generating hydrogen and carbon dioxide from methanol and water.

  The supply suppressing member 50 may be any material that is less permeable to the mixture than the diffusion member 20. For example, metal, silicon substrate, glass substrate, heat-resistant resin material such as polyimide, etc. with fine holes and fine slits processed or porous material can be used, but local flow rate varies. Less porous material is preferred. The pore diameter of the porous material is relatively determined according to the film thickness and the pore diameter of the diffusion member 20, and is not particularly limited. For example, the film thickness is about 1 μm to 30 μm, and the pore diameter of the porous material is 0.01 μm. To about 1 μm can be used. The permeation speed of the supply suppressing member 50 is preferably a numerical value lower than the permeation speed of the diffusion member 20 by about one to two digits when the air permeability is measured by the Gurley tester method, for example.

  The first part 51 constituting the diffusion preventing structure is such that the mixture diffused from the flow path 11 </ b> A to the supply suppressing member 50 does not permeate the diffusion member 20 side and passes through the lower part of the wall 13 or the supply suppressing member 50. Any structure that suppresses permeation to the adjacent flow path 12A may be used. For example, the first portion 51 is made porous only by the second portion 52 and the third portion 53 facing the flow paths 11A and 12A in the supply suppressing member 50 made of metal, a silicon substrate, a glass substrate, polyimide, or the like, Alternatively, it can be formed by providing fine holes or fine slits. In addition, the first portion 51 which is a diffusion preventing structure is configured such that the second portion 52 facing the flow channel 11A and the third portion 53 facing the flow channel 12A are closed, and the flow from the flow channel 11A to the diffusion member 20 is blocked. The first portion 51 may be formed so as to protrude from the wall 13 to the flow channel groove side, or the first portion 51 narrower than the width of the wall 13 may be used as long as the flow from the diffusion member 20 to the flow channel 12A is not hindered. The portion 51 may be formed.

  It is preferable that the supply suppressing member 50 has a structure in which the supply substance (mixture) is less likely to permeate in the plane direction as compared with the film thickness direction. The first portion 51 as the diffusion preventing structure is a structure in which the mixture diffused from the flow path 11A to the supply suppressing member 50 is difficult to permeate in a direction deviating from the flow direction from the flow path 11A toward the diffusion member 20. Since the structure is such that the supply substance does not easily permeate in the plane direction as compared with the film thickness direction as described above, the first portion matched to the pattern of the flow paths 11A and 11B is provided in the supply suppression member 50. Even if 51 is not formed, the second portion 52 facing the flow path 11A can easily pass through in the film thickness direction, that is, the direction from the flow path 11A toward the diffusion member 20, and in the lower part of the wall 13, the planar direction, that is, the flow path A diffusion preventing structure that hardly permeates from the 11A side to the flow path 12A side can be formed. By doing so, the manufacturing process of the microfluidic device is simplified.

  Further, it is preferable that the supply suppressing member 50 has a structure in which the discharged substance from the diffusion member 20 is less likely to permeate in the plane direction as compared with the film thickness direction. Thereby, it is possible to suppress the emission material that has permeated from the diffusion member 20 to the supply suppressing member 50 from permeating in a direction deviating from the direction of the flow from the diffusion member 20 toward the flow path 12A. Therefore, it is possible to prevent the discharged substance from the diffusion member 20 from flowing backward from the flow path 12A through the lower portion of the wall 13 or through the inside of the supply suppressing member to the flow path 11A. Further, even if the supply suppressing member 50 is not formed with a diffusion prevention structure that matches the pattern of the flow paths 11A and 12A, it is difficult for light to permeate from the plane direction, that is, from the flow path 12A side to the flow path 11A side at the lower portion of the wall 13. Since the diffusion preventing structure can be formed, the manufacturing process of the micro and fluidic devices is simplified.

  The supply suppression member 50 as described above, for example, forms micropores or microslits only in the film thickness direction in the supply suppression member 50, and makes the diameter of the microholes or the length of the microslits smaller than the width of the wall 13. Can be produced. Further, since the porous material can be made difficult to allow fluid to permeate in a plane direction orthogonal to the stretching direction by stretching, when the porous material is used for the supply suppressing member 50, the porous material is By adjusting the extending direction to the flow direction of the flow paths 11A and 12A, it is possible to suppress the mixture from passing through the flow path 11A through the lower portion of the wall 13 or the inside of the supply suppressing member 50 to the flow path 12A. At the same time, it is possible to prevent the discharged substance from passing from the flow path 12A to the flow path 11A through the lower portion of the wall 13 or the inside of the supply suppressing member 50.

  The first portion 51, which is a diffusion preventing structure, preferably has a structure in which a substance that suppresses the diffusion of the supplied substance is contained in the supply suppressing member 50. Thereby, it can prevent more reliably that a mixture permeate | transmits to the flow path 12A from the flow path 11A through the lower part of the wall 13, or the supply suppression member 50 inside.

  If a fine hole or the like remains in the supply suppressing member 50 below the wall 13, leakage of the supply substance (mixture) and the discharged substance at the joining interface between the wall 13 and the supply suppression member 50 is likely to occur. Further, when a porous material is used for the supply suppressing member 50, the transmission in the planar direction in the supply suppressing member 50 cannot be completely eliminated. However, by containing a substance that suppresses the diffusion of the mixture in the supply suppressing member 50, it is possible to suppress leakage at the bonding interface with the wall 13 and suppress transmission in the planar direction in the supply suppressing member 50. it can. As a substance to be contained in the supply suppressing member 50, an acrylic resin or a polyimide resin can be used.

  Moreover, it is preferable that the 1st part 51 which is a spreading | diffusion prevention structure is a structure which made the supply suppression member 50 contain the substance which suppresses the spreading | diffusion of discharge | emission substance. Thereby, it is possible to more reliably prevent the discharged substance from the diffusion member 20 from passing through the flow path 12A through the lower portion of the wall 13 or the inside of the supply suppressing member 50 to the flow path 11A.

  Next, a manufacturing method of a structure in which the supply suppressing member 50 contains a substance that suppresses the diffusion of the supply substance and the discharged substance will be described with reference to FIG. First, as shown in FIG. 3A, a flow path plate 10 in which flow path grooves are formed and a substrate 511B on which a layer of a material 511A containing a filler that becomes a diffusion suppressing substance is formed are prepared. Next, as shown in FIG. 3B, the flow path plate 10 is placed on the substrate 511B on which the layer of the material 511A is formed, and the convex region 10A in which the flow path groove is not formed is made of a material containing a filler. Bond to 511A. Thereafter, as shown in FIG. 3C, when the substrate 511 </ b> B is peeled off from the flow path plate 10, the material 51 </ b> A containing the filler is transferred to the area 10 </ b> A where the flow path grooves of the flow path plate 10 are not formed. Next, as shown in FIGS. 3D and 3E, the flow path plate 10 to which the material 51A is transferred is bonded to the supply suppressing member 50 and annealed, so that the filler is supplied to the supply suppressing member. A region (first portion 51) that is diffused into 50 and impregnated with the filler is formed. Thereby, the flow path plate 10 and the supply suppressing member 50 can be reliably bonded together without any gap, and the diffusion preventing structure (first portion 51) impregnated with the substance that suppresses the diffusion of the supply substance and the discharge substance is formed. can do.

  As the flow path plate 10, as described above, any substrate that is not permeable to a mixture such as a metal, a silicon substrate, or a glass substrate can be used. However, here, a glass substrate is used as the flow path plate 10. Describe the conditions at the time. As the material 511A including the filler, an acrylic resin dissolved in a solvent so as to be easily applied was used. The film thickness is about 50 μm. Since the film thickness of the material 511 </ b> A varies depending on the film thickness of the supply suppressing member 50, the thickness is not limited to the above value, but is preferably about 1 to 3 times the film thickness of the supply suppressing member 50. If the film thickness is too small, the supply suppressing member 50 cannot be sufficiently filled. Conversely, if the film thickness is too large, the filled region (first portion 51) is too wide in the plane direction to fill the channel groove. The region without the material (the second portion 52 and the third portion 53) is made too narrow.

  The substrate 511B is not particularly limited in material, but it is preferable to use a flexible and highly flat substrate. Here, a PET (polyethylene terephthalate) film was used. Since PET has flexibility, it can be easily peeled off from the flow path plate 10 and has high flatness, so that the material 511A containing the filler is easily peeled off from the PET film. For this reason, the film thickness of the material 511A transferred to the flow path plate 10 can be sufficiently ensured. In addition, as for annealing when the flow path plate 10 and the supply suppressing member 50 are bonded together, in the case of acrylic resin, annealing is performed for about 10 minutes to 60 minutes at a temperature of about 80 ° C. to 120 ° C. And the flow path plate 10 and the supply suppressing member 50 can be bonded together. The annealing temperature and annealing time are not limited to this, but under this condition, the supply of the filler is suppressed because the solvent used for applying the material including the filler is not sufficiently evaporated at 80 ° C. or lower. There is a possibility that the fixing in the member 50 becomes insufficient. Further, at a temperature of 120 ° C. or higher, the material containing the filler is rapidly diffused in the supply suppressing member 50, which may make it difficult to apply to a fine flow path pattern. In order to suppress the diffusion of the filler and securely fix it in the supply suppressing member, it is preferable to gradually increase the temperature over about 30 minutes and anneal at a temperature of 100 ° C. or more for about 10 minutes.

  It is preferable to provide a concavo-convex structure capable of taking in or impregnating the material containing the filler into the convex region 10A where the channel groove of the channel plate 10 to which the material 511A containing the filler is transferred is not formed. . Thereby, the adhesive strength between the flow path plate 10 and the material 511A containing the filler is increased, and the bonding strength between the flow path plate 10 and the supply suppressing member 50 can be increased. FIG. 4 shows an example of such a structure. By forming grooves in the convex region 10A (FIG. 4 (a)), increasing the surface roughness (FIG. 4 (b)), or reducing the surface flatness (FIG. 4 (c)), the flow is improved. It is possible to increase the adhesive strength between the road plate 10 and the material 511A.

  In a state where the supply substance (mixture of methanol and water) is supplied to the flow path 11A, the discharged substance permeates from the diffusion member 20 side of the second portion 52 facing the flow path 11A to the flow path 11A. The necessary pressure is equal to or higher than the discharge pressure of the discharged material from the diffusion member 20. Accordingly, it is possible to prevent the discharge material from flowing back to the flow path 11A through the second portion 52 facing the flow path 11A of the supply suppressing member 50 from the diffusion member 20 and inhibiting the supply of the mixture.

  Usually, when a mixture of methanol and water is supplied from the flow path 11A, the pressure of the mixture is higher on the flow path 11A side than the diffusion member 20 side with the second portion 52 of the supply suppressing member 50 interposed therebetween. As shown in chemical reaction formula (1), hydrogen and carbon dioxide are generated in the diffusion member 20 when the reforming reaction of the mixture proceeds in the diffusion member 20 maintained at a predetermined temperature. When the pressure of the discharged substance rises and exceeds the pressure necessary for the discharged substance to permeate from the diffusion member 20 to the flow path 11A side in the state where the supply substance (mixture of methanol and water) is supplied to the flow path 11A The exhaust material flows backward to the flow channel 11A side, but since the pressure on the downstream flow channel 12A side is lower than that on the diffusion member 20 side, the exhaust material is always supplied from the diffusion member 20 side toward the flow channel 11A. The discharge pressure of the discharged material can be kept below the pressure required to permeate the gas. Thereby, it is possible to prevent the discharged substance from flowing backward into the flow path 11A and hindering the supply of the mixture from the flow path 11A.

  In a state where the mixture is supplied to the diffusing member 20, the pressure necessary for the mixture to permeate from the diffusing member 20 side of the third portion 53 facing the channel 12 </ b> A to the channel 12 </ b> A side is from the diffusing member 20. Above the discharge pressure of the mixture. As a result, when the heater 60 is turned off and the reforming reaction is stopped, or when the heater 60 is turned off and the diffusion member 20 is lowered below a predetermined temperature, the mixture in the diffusion member 20 is removed. When liquefied as a mixture of methanol and water, the liquefied mixture can be prevented from being discharged to the flow path 12A.

  Here, the pressure required for the mixture in the liquid state to pass through the supply suppressing member 50 from the diffusion member 20 to the flow path 12A side will be described. When the mixture (liquid) on the diffusion member 20 side tries to permeate the supply suppression member 50, the meniscus formed at the interface between the mixture (liquid) in the micropores of the supply suppression member 50 and the gas on the flow path 12A side. The formula showing the balance of force is expressed as the following formula.

P ₁ = σ · cos (π−α) / d + P _g (2)
Here, P ₁ is the pressure of the mixture, P _g is the pressure of the gas on the flow path 12A side, σ is the surface tension of the mixture, α is the angle between the meniscus and the inner wall of the fine hole, and d is the inner diameter of the fine hole of the supply suppressing member 50. is there. That is, when the discharge pressure of the mixture is P ₁ , the mixture can enter the micropores up to the value of the micropore inner diameter d, and the discharge pressure of the mixture when the micropore inner diameter d is the minimum. (2) when equation above values of P _1, it is possible to mixture diffusing member 20 side into the channel 12A side passes through the supply suppressing member 50. Therefore, when the discharge pressure of the mixture from the diffusion member 20 is smaller than P _{1 at} this time, the balance position of the meniscus cannot enter the position where the inner diameter of the micropore is minimum, and the mixture flows. It is possible to prevent discharge to the path 12A.

  Next, an example in which the microfluidic device according to the present embodiment is used in a fuel reformer of a fuel cell using hydrogen as a fuel will be described with reference to FIG.

  As shown in FIG. 5, the fuel cell 100 is configured to include a fuel electrode 102, an oxidant electrode 103, and an electrolyte membrane 104 in a housing 101 as a basic configuration. A mixture of methanol and water is supplied to the microfluidic device 1 from the fuel tank 105 (methanol tank). Hydrogen generated by the steam reforming reaction of methanol is supplied to the fuel electrode chamber 107. Hydrogen supplied to the fuel electrode chamber 107 reacts at the fuel electrode 102 to generate protons (hydrogen ions) and electrons. Protons generated at the fuel electrode 102 pass through the electrolyte membrane 104 and move to the oxidant electrode 103, and electrons flow from the fuel electrode 102 to the oxidant electrode 103 via an external circuit (not shown). These electrons are used as the output of the fuel cell. Unreacted hydrogen is discharged from the fuel electrode 102 to the fuel electrode chamber 107.

  On the other hand, in the oxidant electrode 103, oxygen is supplied to the oxidant electrode chamber 110 by the compressor 109. This oxygen diffuses from the oxidant electrode chamber 110 into the oxidant electrode 103. In the oxidizer electrode 103, oxygen reacts with protons diffused from the fuel electrode 102 to generate water. The generated water becomes steam and is discharged from the oxidant electrode chamber 110 through the outlet port 111 together with unreacted oxygen. In the example shown in FIG. 5, oxygen is used as the oxidant, but air can also be used as the oxidant.

  The contents described above are summarized as follows. That is, the microfluidic device according to the present embodiment is a microfluidic device that can be used, for example, as a fuel reformer of the fuel cell shown in FIG. A diffusion member 20 that is disposed so as to face the flow path plate 10 and diffuses the supply substance supplied from the flow path groove 11, and an “interposition member” interposed between the flow path plate 10 and the diffusion member 20. And a supply suppressing member 50. The channel grooves 11, 12 are a channel 11 </ b> A as a “first channel” for supplying a supply substance to the diffusion member 20, and a “second channel” for discharging the discharge substance from the diffusion member 20. As a flow path 12A. The flow paths 11A and 12A are separated from each other, and the supply suppressing member 50 is a portion facing the non-flow area (convex area 10A) on the main surface where the flow grooves 11 and 12 of the flow path plate 10 are formed. The first portion 51 as a “diffusion prevention structure” that suppresses the diffusion of the supply substance and the discharge substance in the planar direction of the supply suppression member 50.

  According to the microfluidic device according to the present embodiment, the supply substance can be supplied almost uniformly little by little from the flow path 11 </ b> A facing the diffusion member 20 through the supply suppression member 50. Further, the lower portion of the wall 13 that becomes the non-flow channel region is configured so that the supply substance is not discharged from the flow channel 11A side to the flow channel 12A side without passing through the diffusion member 20 by the first portion 51 of the supply suppression member 50. Therefore, it is possible to suppress the supply substance from being unreacted and discharged from the flow path 12A, and to efficiently react the supplied supply substance. That is, the reaction amount per area of the supply area can be further improved.

(Embodiment 2)
6 is a plan view showing a configuration of a fuel cell according to Embodiment 2 of the present invention, and FIGS. 7 and 8 are a VII-VII sectional view and a VIII-VIII sectional view in FIG. 6, respectively.

  Referring to FIGS. 6 and 7, the fuel cell according to the present embodiment includes a flow path plate 10, ports 30 and 40, a supply suppressing member 50, a heater 60, a housing 70, and a lid 80. It is comprised including.

  As shown in FIG. 7, the fuel cell according to the present embodiment has a fuel electrode 102, an electrolyte membrane 104 disposed so as to face the fuel electrode 102, and the electrolyte membrane 104 opposite to the fuel electrode 102. And an oxidant electrode 103 arranged so as to be included. The fuel electrode 102, the electrolyte membrane 104, and the oxidizer electrode 103 are accommodated in the housing 70 with the electrolyte membrane 104 sandwiched between the fuel electrode 102 and the oxidizer electrode 103. One edge (upper surface) of the housing 70 is joined and attached to the edge of the flow path plate 10 disposed so as to face the fuel electrode 102.

  As shown in FIG. 6, the flow path plate 10 has a through-hole (port 30) that forms a supply port for liquid fuel, a through-port (port 40) that forms a discharge port for exhaust gas, and a comb-tooth shape from the supply port. It has a channel groove 11 that extends and a channel groove 12 that extends in a comb-tooth shape from the discharge port.

  The channel groove 11 and the channel groove 12 are separated by a wall 13 having a predetermined thickness. The wall 13 of the flow path plate 10 is in contact with the fuel electrode 102. Therefore, the channel 11 A formed by the channel groove 11 and the fuel electrode 102 and the channel 12 A formed by the channel groove 12 and the fuel electrode 102 are separated by the wall 13. As the flow path plate 10, a substrate that is not permeable to liquid fuel, such as a metal, a silicon substrate, a glass substrate, or a resin substrate, can be used, but here, a nickel plate that has been subjected to microfabrication is used.

  When the flow path plate 10 is made of an insulating material such as a non-conductive glass substrate, a conductive wiring layer may be inserted between the flow path plate 10 and the supply suppressing member 50. As the wiring layer, for example, a gold thin film formed by electroless plating can be used. A supply suppressing member 50 that suppresses the supply of liquid fuel from the flow path 11A to the diffusion layer 20A is provided between the flow path plate 10 and the diffusion layer 20A of the fuel electrode 102. The supply suppressing member 50 includes a first portion 51 provided in a portion facing the non-flow-path region of the surface having the flow-path grooves 11 and 12 of the flow-path plate 10, and second portions located on both sides of the first portion 51. 52 and a third portion 53. The first portion 51 constitutes a liquid fuel diffusion prevention structure.

  The supply suppressing member 50 may be any material that is less permeable to fuel than the diffusion layer 20A. Metals, silicon substrates, glass substrates, resin materials such as polyimide and polytetrafluoroethylene (PTFE) processed with fine holes and fine slits, or porous materials can be used. A porous material with little variation is preferred. The pore diameter of the porous material is relatively determined according to the film thickness and the pore diameter of the diffusion layer 20A, and is not particularly limited. For example, the film thickness is about 1 μm to 30 μm, and the pore diameter of the porous material is 0.01 μm. About 1 μm can be used. The permeation rate of the supply suppressing member 50 is preferably a numerical value that is lower by one to two digits than the permeation rate of the diffusion layer 20A, for example, when the air permeability is measured by the Gurley tester method. The supply suppressing member 50 is not limited to a porous material as long as the fuel permeation rate is lower by about one to two digits than the permeation rate of the diffusion layer 20A, and may not have micropores.

  The first portion 51, which is a diffusion preventing structure, does not allow the liquid fuel that has diffused from the flow path 11A to the supply suppression member 50 to pass through the lower part of the wall 13 or the supply suppression member 50 without passing through the diffusion layer 20A. Any structure that suppresses permeation to the adjacent flow path 12A may be used, and the second portion 52 facing the flow path 11A and the third portion 53 facing the flow path 12A of the supply suppressing member 50 made of polyimide, PTFE, or the like. Can be formed by making it porous or forming a region in which fine holes or fine slits are formed. Further, the first portion 51, which is a diffusion preventing structure, is closed by the second portion 52 facing the flow channel 11A and the third portion 53 facing the flow channel 12A, and the flow from the flow channel 11A to the diffusion layer 20A The flow from the diffusion layer 20 </ b> A to the flow path 12 </ b> A is not obstructed and may be formed so as to protrude from the wall 13 toward the flow path grooves 11, 12, or may be formed narrower than the width of the wall 13.

  The material of the electrolyte membrane 104 may be, for example, an organic material or an inorganic material as long as it is a proton-conductive heat-resistant and acid-resistant material. Here, the electrolyte membrane 104 contains a sulfonic acid group containing an organic fluorine-containing polymer as a skeleton. Perfluorocarbon (Nafion 117 (registered trademark) manufactured by DuPont) is used. Further, the electrolyte membrane 104 only needs to have a proton-conducting function, and may be one in which the electrolyte membrane is embedded in another base material.

  As shown in FIG. 7, the fuel electrode 102 includes an electrode layer 1041 on the electrolyte membrane 104 side and a diffusion layer 20A on the flow path plate 10 side. As the diffusion layer 20A of the fuel electrode 102, a porous material such as carbon paper, a sintered body of carbon, a sintered metal such as nickel, or a foam metal can be used. The electrode layer 1041 is formed using a resin layer containing a metal catalyst. As this metal catalyst, for example, a platinum-ruthenium alloy is used, but other alloys such as platinum and gold, platinum and osmium, platinum and rhodium can be used. In addition, as the resin layer of the electrode layer 1041, for example, a perfluoroalkylsulfonic acid resin is used.

  In the fuel electrode 102, the electrode layer 1041 and the diffusion layer 20A are formed by pressing the diffusion layer 20A to the electrode layer 1041 by hot pressing or the like, or when the electrode layer 1041 is a resin, the material of the electrode layer 1041 is applied to the diffusion layer 20A. It can be laminated by impregnating a resin to be heat treated.

  On the other hand, the oxidant electrode 103 is covered with a lid part 80 extending from the other surface (lower surface) of the housing 70, and the lid part 80 is provided with an oxidant introduction port 80A to which, for example, air is supplied as an oxidant. And an exhaust port 80B for exhausting the exhaust gas. A flow path (oxidant electrode chamber 110) on the oxidant electrode side is formed between the lid 80 and the oxidant electrode 103.

  The oxidant electrode 103 has an electrode layer 1042 on the electrolyte membrane 104 side and a diffusion layer 20B on the lid 80 side. Similar to the electrode layer 1041 of the fuel electrode 102, the electrode layer 1042 is made of a resin layer containing a metal catalyst. As the diffusion layer 20B, a porous material such as carbon paper, a sintered body of carbon, a sintered metal such as nickel, and a foamed metal can be used as in the diffusion layer 20A of the fuel electrode 102. The present invention does not depend on the type or supply direction of the oxidant, and oxygen may be used instead of air. Further, the oxidant electrode chamber 110 is not formed, and a fan or a blower pump is used. An oxidant may be directly supplied to the exposed surface of the oxidant electrode 103 using a simple air blowing mechanism.

  The oxidant electrode 103 can be manufactured by a conventionally known method. For example, the oxidant electrode 103 can be manufactured using the method described for the method of laminating the electrode layer 1041 of the fuel electrode 102 and the diffusion layer 20A.

  The housing 70 may be made of a material used as a casing of a conventionally known fuel cell. Examples of the resin constituting the housing 70 include a carbon resin, or a resin such as a glass substrate, acrylic, and PDMS as in the case of the flow path plate 10.

  The membrane electrode assembly including the electrolyte membrane 104, the fuel electrode 102, and the oxidant electrode 103 of the fuel cell according to the present embodiment can be obtained by a conventionally known method, for example, the electrolyte obtained as described above. It can be manufactured by bonding the fuel electrode 102 and the oxidant electrode 103 to the membrane 104 by hot pressing. Then, the supply suppressing member 50 and the membrane electrode assembly are laminated on the flow path plate 10 and covered with the housing 70 integrated with the oxidant chamber manufactured as described above, and the flow path plate 10 and the housing 70 are covered. The fuel cell is manufactured by bonding.

  In the fuel cell according to the present embodiment, when a flexible resin material such as PDMS is used for the flow path plate 10 and the housing 70, the flow plate 10 and the housing 70 are bent even when the flow path plate 10 and the housing 70 are bent. The road plate 10 and the diffusion layer 20A can be stably connected with low electrical resistance.

  In the fuel cell according to the present embodiment, a mixture of methanol and water can be used as a liquid fuel. However, as conventionally known, hydrocarbon-based organic materials such as ethanol, dimethyl ether, propanol, and ethylene glycol are used instead of methanol. Fuel can be used.

  This liquid fuel is introduced into the flow path 11A from the port 30 which is a fuel supply port, and is supplied from the flow path 11A to the diffusion layer 20A of the fuel electrode 102 through the second portion 52 facing the flow path 11A in the supply suppressing member 50. Then, it diffuses / penetrates into the diffusion layer 20A and reaches the electrode layer 1041 to react. Thereby, positive ions (H +), electrons, and carbon dioxide as exhaust gas are generated. The cation (H +) reaches the electrode layer 1042 of the oxidant electrode 103 via the electrolyte membrane 104. On the other hand, the electrons are guided from the electrode layer 1041 to the electrode layer 1042 of the oxidant electrode 103 via an external circuit (not shown). Further, the exhaust gas such as carbon dioxide generated in the electrode layer 1041 of the fuel electrode 102 diffuses in the diffusion layer 20A and reaches the flow path 12A through the third portion 53 facing the flow path 12A in the supply suppressing member 50. The fluid is discharged from the port 40 which is a discharge port through the flow path 12A.

  On the other hand, the air as an example of the oxidant introduced from the introduction port 80A of the lid 80 is diffused into the diffusion layer 20B of the oxidant electrode 103, and the positive electrode from the fuel electrode 102 is formed in the electrode layer 1042 of the oxidant electrode 103. Reacts with ions (H +) and electrons. Thereby, water vapor | steam produces | generates and this water vapor | steam passes through a flow path (oxidant electrode chamber 110), and is discharged | emitted from the discharge port 80B.

  In the fuel cell according to the present embodiment, the flow path 11A is not directly connected to the flow path 12A, and the diffusion of the fuel electrode 102 to the diffusion layer 20A is suppressed by the supply suppression member 50, so that the liquid fuel Is filled in the flow channel 11A and is gradually and gradually supplied from the flow channel 11A facing the diffusion layer 20A through the supply suppressing member 50 to the entire diffusion layer 20A. At this time, the lower part of the wall 13 is configured so that the liquid fuel is not discharged from the flow path 11A side to the flow path 12A side without passing through the diffusion layer 20A by the diffusion prevention structure 50. Compared with the case where there is no portion 51, it is possible to suppress the unreacted discharge of the fuel and to efficiently react the supplied fuel. That is, it is possible to further improve the utilization efficiency of the fuel per area of the flow path area of the flow path 11A for power generation.

  Further, when the exhaust gas generated in the fuel electrode 102 is discharged from the diffusion layer 20A to the flow path 12B, the exhaust gas is supplied from the flow path 12A side to the flow path 11A side by the first portion 51 as a diffusion preventing structure. It is possible to prevent the exhaust gas from being discharged to the flow path 11A side by diffusing inside the suppressing member 50 and preventing the supply of fuel from the flow path 11A from being hindered.

FIG. 9 shows the result of measurement of the amount of fuel supplied when the fuel cell according to the present embodiment is used for power generation and the fuel use efficiency with respect to the amount supplied (◆: fuel supply amount / ■: fuel use efficiency) ). The fuel utilization efficiency indicates the ratio of the fuel used for the reaction to the supplied fuel. The output current of the fuel cell is constant at 40 mA / cm ² . In the results shown in FIG. 9, the fuel supply pressure is low at 10 ³ Pa or less (300 to 500 Pa) (the differential pressure between the supply pressure to the flow path 11A and the pressure of the flow path 12A), and 2 to 6 microliters / cm. It shows that power generation of 40 mA / cm ² can be performed with a small amount of fuel supply of about ² / min. In the fuel cell according to the present embodiment, the fuel supply amount can be suppressed to half or less as compared with the fuel cell without the diffusion suppression structure. Further, since the fuel discharge to the flow path 12A is suppressed, the fuel use efficiency can be very high, and the fuel use efficiency can be improved more than twice compared to a fuel cell without a diffusion suppression structure. I was able to.

FIG. 10 shows the relationship between the current output and the fuel supply amount when power is generated using the fuel cell according to the present embodiment. Here, the fuel supply pressure (the differential pressure between the supply pressure to the flow path 11A and the pressure of the flow path 12A) is constant at 10 ³ Pa. When the setting of the output current is changed, it can be seen that the fuel supply amount changes accordingly. This is because the fuel filled in the flow path 11A is supplied by capillary action so as to suppress the discharge of the fuel to the flow path 12A and replenish the fuel consumed in the reaction. This is because the fuel supply amount is automatically adjusted. Therefore, it can be seen that the fuel cell according to the present embodiment can self-adjust the fuel supply amount efficiently without adjusting the supply amount with a pump or the like, and can easily obtain a high output even if it is downsized.

  The supply suppressing member 50 preferably has a structure in which the liquid fuel is less likely to permeate in the plane direction as compared to the film thickness direction. The first portion 51, which is a diffusion preventing structure, may have a structure in which the liquid fuel diffused from the flow path 11A to the supply suppressing member 50 does not easily permeate in a direction deviating from the flow direction from the flow path 11A toward the diffusion layer 20A. That's fine. By making the diffusion suppressing member 50 a structure in which the liquid fuel is less likely to permeate in the plane direction compared to the film thickness direction, the diffusion suppressing member 50 is matched to the flow path 11A and the second passage 12A as in the case of the diffusion prevention structure. Even if the anti-diffusion structure is not formed in the supply suppressing member 50, the second portion 52 facing the flow path 11A can easily transmit in the film thickness direction, that is, the direction from the flow path 11A toward the diffusion layer 20A. In the lower part, the first portion 51 as a diffusion preventing structure that hardly permeates in the planar direction, that is, from the channel 11A side to the channel 12A side can be formed, and the manufacturing process is simplified.

  The supply suppressing member 50 preferably has a structure in which the exhaust gas is less likely to permeate in the plane direction than in the film thickness direction. The first part 51 is a structure that prevents diffusion, and the first part 51 is configured such that the exhaust gas diffused from the diffusion layer 20A to the supply suppressing member 50 is difficult to permeate in a direction deviating from the direction of flow from the diffusion layer 20A toward the flow path 12A. That's fine. A diffusion cap structure adapted to the flow paths 11A and 12A as in the case of the above diffusion prevention structure by making the diffusion suppressing member 50 a structure in which the exhaust gas is less likely to permeate in the plane direction as compared with the film thickness direction. Even if the supply suppressing member 50 is not formed, the third portion 53 facing the flow path 12A can easily transmit in the film thickness direction, that is, the direction from the diffusion layer 20A toward the flow path 12A. The first portion 51 can be formed as a diffusion preventing structure that is difficult to transmit in the direction, that is, from the flow path 12A side to the flow path 11A side, and the manufacturing process is also simplified.

  The supply suppression member 50 as described above, for example, forms micropores or microslits only in the film thickness direction in the supply suppression member 50, and makes the diameter of the microholes or the length of the microslits smaller than the width of the wall 13. Can be produced. Further, since the porous material can be made difficult to allow fluid to permeate in a plane direction orthogonal to the stretching direction by stretching, when the porous material is used for the supply suppressing member 50, the porous material is By adjusting the extending direction to the flow direction of the flow paths 11A and 12A, the liquid fuel can be prevented from penetrating from the flow path 11A to the flow path 12A through the lower portion of the wall 13 or the inside of the supply suppressing member 50. In addition, it is possible to prevent the discharged substance from permeating from the flow path 12A to the flow path 11A through the lower portion of the wall 13 or the inside of the supply suppressing member 50.

  The first portion 51 as the diffusion preventing structure may be a structure in which a substance that suppresses the diffusion of the liquid fuel is contained in the supply suppressing member 50. Thereby, it can prevent more reliably that liquid fuel permeate | transmits to the flow path 12A from the flow path 11A through the lower part of the wall 13, or the supply suppression member 50 inside.

  The first portion 51 as the diffusion preventing structure may be a structure in which a substance that suppresses the diffusion of exhaust gas is contained in the supply suppressing member 50. Thereby, it is possible to more reliably prevent the exhaust gas from the diffusion layer 20A from passing through the lower part of the wall 13 from the flow channel 12A side or through the inside of the supply suppressing member 50 to the flow channel 11A side.

  If a fine hole or the like remains in the supply suppressing member below the wall 13, liquid fuel or exhaust gas leaks easily at the joining interface between the wall 13 and the supply suppressing member 50. Further, when a porous material is used for the supply suppressing member 50, the permeation of the liquid fuel and the exhaust gas in the planar direction in the supply suppressing member 50 cannot be completely eliminated. However, by containing a substance that suppresses the diffusion of liquid fuel or exhaust gas in the supply suppressing member 50, leakage at the joint interface with the wall 13 is suppressed, and transmission in the planar direction in the supply suppressing member 50 is suppressed. Can be suppressed. As a substance to be contained in the supply suppressing member 50, an acrylic resin or a polyimide resin can be used. About the structure which contains the substance which suppresses the spreading | diffusion of liquid fuel and exhaust gas in the supply suppression member 50, it can manufacture by the method similar to Embodiment 1 demonstrated using FIG.

  In a state where the liquid fuel is supplied to the flow channel 11A, the pressure necessary for the exhaust gas to permeate from the diffusion layer 20A side of the second portion 52 facing the flow channel 11A to the flow channel 11A side is the diffusion layer 20A. It is preferable that it is more than the discharge pressure of the said exhaust gas from. Accordingly, it is possible to prevent the exhaust gas from flowing backward from the diffusion layer 20A through the second portion 52 facing the flow path 51 of the supply suppressing member 50 and obstructing the supply of the liquid fuel.

  Normally, when liquid fuel is supplied from the flow path 11A, the pressure of the liquid fuel is higher on the flow path 11A side than the diffusion layer 20A side with the second portion 52 of the supply suppressing member 50 interposed therebetween. When the reaction of the liquid fuel proceeds at the fuel electrode 102, carbon dioxide is generated in the diffusion layer 20A, so that the pressure of the generated exhaust gas rises and the diffusion layer 20A in a state where the liquid fuel is supplied to the flow path 11A. When the pressure required for the exhaust gas to permeate to the flow path 11A is exceeded, the exhaust gas flows backward to the flow path 11A, but the downstream flow path 12A side is always lower in pressure than the diffusion layer 20A side, so The pressure of the exhaust gas can be kept below the pressure necessary for the exhaust gas to permeate. As a result, it is possible to prevent the exhaust gas from flowing backward into the flow path 11A and hindering the supply of liquid fuel from the flow path 11A.

  In the state where the liquid fuel is supplied to the diffusion layer 20A, the pressure required for the liquid fuel to permeate from the diffusion layer 20A side of the third portion 53 facing the flow channel 12A to the flow channel 12A side is diffused. It is higher than the discharge pressure of the liquid fuel from the layer 20A. As a result, it is possible to prevent liquid fuel from being discharged into the flow path 12A not only during power generation but also when the fuel cell is OFF, that is, when the current output to be taken out is zero.

  Here, the pressure required for the mixture in the liquid state to pass through the supply suppressing member 50 from the diffusion layer 20A to the flow path 12A side will be described. When the liquid fuel on the diffusion layer 20A side tries to penetrate into the supply suppressing member 50, the balance of the force of the meniscus formed at the interface between the liquid fuel in the micropores of the supply suppressing member 50 and the gas on the flow path 12A side is obtained. The formula shown is expressed as:

P _f = σ · cos (π−α) / d + P _g (3)
Here, P _f is the pressure of the liquid fuel, P _g is the pressure of the gas on the flow path 12A side, σ is the surface tension of the mixture, α is the angle between the meniscus and the inner wall of the fine hole, and d is the inner diameter of the fine hole of the supply suppressing member 50. It is. In other words, when the discharge pressure of the liquid fuel is P _f , the mixture can enter the micro holes up to the value of the inner diameter of the micro holes d, and the discharge pressure of the mixture is the minimum of the micro hole inner diameter d. When the value is equal to or greater than the value of P _{f in} the expression (3), the mixture can pass through the supply suppressing member 50 from the diffusion layer 20A side to the flow path 12A side. Therefore, when the discharge pressure of the mixture from the diffusion layer 20A is smaller than P _{f at} this time, the balance position of the meniscus cannot enter the position where the inner diameter of the micropores is the smallest, and the liquid fuel does not enter. It is possible to prevent discharge to the flow path 12A.

In general, the liquid fuel necessary for the reaction at the fuel electrode 102 is, for example, about several μl / min per unit area assuming a power generation of about 150 mW / cm ^{2 in a} fuel cell using methanol and water as fuel. is there. Therefore, even if more fuel is supplied, this excess fuel is used to push out the fuel filled in the diffusion layer 20A, or diffuses through the electrolyte membrane 104 and causes a decrease in output. The utilization efficiency of will be further reduced. That is, the reaction of the fuel electrode 102 is not rate-determined by the amount of fuel supplied, and the reaction proceeds in a reaction-limited state. Therefore, as in the fuel cell according to the present embodiment, by providing the supply suppressing member 50 and the diffusion prevention structure (first portion 51) formed on the member, it is necessary for the reaction with the minimum necessary supply. The reaction can be continued by efficiently supplying the fuel.

  The above contents are summarized as follows. That is, the fuel cell according to the present embodiment is disposed so as to face the fuel electrode 102 and the fuel electrode 102 that is supplied with liquid fuel and generates cations and electrons from the liquid fuel. An electrolyte membrane 104 through which the cation passes, and an oxidizer electrode 103 that is provided so as to face the electrolyte membrane 104 while being supplied with the oxidizer and reacts the cation that has passed through the electrolyte membrane 104 with the oxidant, And a flow path plate 10 having flow path grooves 11 and 12 disposed so as to face the fuel electrode 102. The channel grooves 11 and 12 serve as a “first channel” that supplies liquid fuel to the fuel electrode 102 and a “second channel” that discharges exhaust gas from the fuel electrode 102. A flow path 12A is formed. The flow paths 11A and 12A are separated from each other. The fuel electrode 102 includes an electrode layer 1041 on the electrolyte membrane 104 side containing a catalyst and a diffusion layer 20A on the flow path plate 10 side. The fuel cell further includes a supply suppression member 50 as an “interposition member” interposed between the flow path plate 10 and the diffusion layer 20A. The supply suppressing member 50 diffuses the liquid fuel and the exhaust gas in the planar direction of the supply suppressing member 50 in a portion facing the non-flow path region on the main surface where the flow path grooves 11 and 12 of the flow path plate 10 are formed. It has the 1st part 51 as a "diffusion prevention structure" to suppress.

  According to the fuel cell according to the present embodiment, the liquid fuel can be supplied almost uniformly little by little through the supply suppressing member 50 from the flow path 11A facing the diffusion layer 20A. At this time, the lower portion of the wall 13 is configured so that the liquid fuel is not discharged from the flow path 11A side to the flow path 12A side by the first portion 51 of the supply suppressing member 50 without passing through the diffusion layer 20A. Compared with the case where there is no one portion 51, it is possible to suppress the unreacted discharge of the fuel and to efficiently react the supplied fuel. That is, the utilization efficiency of the fuel per area of the supply area of the flow path 11A for power generation can be improved. Further, when the exhaust gas generated at the fuel electrode 102 is discharged from the diffusion layer 20A to the flow path 12A, the exhaust gas is supplied from the flow path 12A side to the flow path 11A side by the first portion 51 of the supply suppressing member 50. It is possible to suppress the diffusion inside the suppressing member 50 and discharge to the flow path 11A side, and prevent the supply of fuel from the flow path 11A from being hindered. Therefore, according to this embodiment, the fuel utilization efficiency can be very high, and high output can be easily obtained even if the size is reduced.

  In the above-described embodiment, the flow path grooves 11 and 12 of the flow path plate 10 are extended in a comb-tooth shape. However, the extension pattern of the flow path grooves 11 and 12 is not limited to a comb-tooth shape. Thus, it may extend in a bent crank shape, or may extend in a curved shape or a spiral shape.

  Although the embodiments of the present invention have been described above, the embodiments disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a top view which shows the microfluidic device which concerns on Embodiment 1 of this invention. It is II-II sectional drawing in FIG. It is a figure for demonstrating the manufacturing process of the microfluidic device shown by FIG. 1, FIG. FIG. 5 is a partially enlarged view for explaining a manufacturing process of a modification of the microfluidic device shown in FIGS. 1 and 2. It is a figure which shows the structure of the fuel cell to which the microfluidic device which concerns on Embodiment 1 of this invention is applied. It is a top view which shows the fuel cell which concerns on Embodiment 2 of this invention. It is VII-VII sectional drawing in FIG. It is VIII-VIII sectional drawing in FIG. It is a graph (the 1) which shows the performance of the fuel cell which concerns on Embodiment 2 of this invention. It is a graph (the 2) which shows the performance of the fuel cell which concerns on Embodiment 2 of this invention. It is a figure which shows the structure of the conventional fuel cell.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Microfluidic device, 10 Channel plate, 10A Convex area, 11, 12 Channel groove, 13 Wall, 20 Diffusion member, 20A, 20B Diffusion layer, 30, 40 Port, 50 Supply suppression member, 51 1st part, 51A material, 52 second part, 53 third part, 60 heater, 70 housing, 80 lid, 80A oxidant inlet, 80B outlet, 100, 100A fuel cell, 101, 101A housing, 102, 102A fuel electrode, 103, 103A Oxidant electrode, 104, 104A Electrolyte membrane, 105, 105A Fuel tank, 106A Fuel pump, 107, 107A Fuel electrode chamber, 108A Release port, 109, 109A Compressor, 110, 110A Oxidant electrode chamber, 111, 112, 111A, 112A Outlet port, 511A material, 511B substrate 1041, 1042 Electrode layer.

Claims (16)

A channel plate having a channel groove;
A diffusion member that is disposed so as to face the flow path plate and diffuses the supply substance supplied from the flow path groove;
An interposition member interposed between the flow path plate and the diffusion member, and having a structure in which the supply substance is less likely to permeate in a plane direction as compared with a film thickness direction ,
The flow path groove forms a first flow path for supplying the supply substance to the diffusion member and a second flow path for discharging the discharge substance from the diffusion member,
The first flow path and the second flow path are separated;
The interposed member includes a first portion facing a non-flow channel region on a main surface of the flow channel plate where the flow channel is formed, a second portion facing the first flow channel, A microfluidic device including a third portion facing the two flow paths, and having a diffusion prevention structure that suppresses diffusion of the supply substance and the discharge substance in the planar direction of the intervention member in the first part .   The microfluidic device according to claim 1, wherein the interposed member has a structure in which the discharged substance is less likely to permeate in a planar direction as compared with a film thickness direction.   The microfluidic device according to claim 1, wherein the diffusion preventing structure is a structure in which a substance that suppresses diffusion of the supply substance is contained in the interposition member.   The microfluidic device according to claim 1, wherein the diffusion preventing structure is a structure in which a substance that suppresses diffusion of the discharged substance is contained in the interposition member.   In a state where the supply substance is supplied to the first flow path, a portion of the interposition member where the discharge material faces the first flow path is moved from the diffusion member side to the first flow path side. The microfluidic device according to claim 1, wherein a pressure required to permeate is equal to or higher than a discharge pressure of the discharge material from the diffusion member.   In a state where the supply substance is supplied to the diffusion member, the supply substance permeates from the diffusion member side to the second flow path side through the portion of the interposition member that faces the second flow path. 2. The microfluidic device according to claim 1, wherein a pressure required for the liquid is equal to or higher than a discharge pressure of the supply substance from the diffusion member. A fuel electrode that is supplied with liquid fuel and generates cations and electrons from the liquid fuel;
An electrolyte membrane disposed so as to face the fuel electrode and permeable to cations from the fuel electrode;
An oxidant electrode that is disposed so as to face the electrolyte membrane while being supplied with the oxidant, and reacts the cation that has permeated through the electrolyte membrane with the oxidant;
A flow path plate arranged to face the fuel electrode and having a flow path groove,
The flow path groove forms a first flow path for supplying the liquid fuel to the fuel electrode and a second flow path for discharging exhaust gas from the fuel electrode,
The first flow path and the second flow path are separated;
The fuel electrode has an electrode layer on the electrolyte membrane side containing a catalyst, and a diffusion layer on the flow path plate side,
Further comprising an interposed member interposed between the flow path plate and the diffusion layer and having a structure in which the liquid fuel is less likely to permeate in a plane direction as compared to a film thickness direction ;
The interposed member includes a first portion facing a non-flow channel region on a main surface of the flow channel plate where the flow channel is formed, a second portion facing the first flow channel, And a third portion facing the second flow path, and the first portion has a diffusion prevention structure that suppresses diffusion of the liquid fuel and the exhaust gas in the planar direction of the interposition member. The fuel cell according to claim 7 , wherein the interposition member has a structure in which the exhaust gas is less likely to permeate in a planar direction than in a film thickness direction. The fuel cell according to claim 7 , wherein the diffusion preventing structure is a structure in which a substance that suppresses diffusion of the liquid fuel is contained in the interposition member. The fuel cell according to claim 7 , wherein the diffusion preventing structure is a structure in which a substance that suppresses diffusion of the exhaust gas is contained in the interposition member. In a state where the liquid fuel is supplied to the first flow path, a portion of the interposition member where the exhaust gas faces the first flow path is moved from the diffusion layer side to the first flow path side. The fuel cell according to claim 7 , wherein a pressure necessary for permeation is equal to or higher than a discharge pressure of the exhaust gas from the diffusion layer. In a state where the liquid fuel is supplied to the diffusion layer, the liquid fuel permeates from the diffusion layer side to the second flow channel side through a portion of the interposition member that faces the second flow channel. The fuel cell according to claim 7 , wherein a pressure required for the fuel cell is equal to or higher than a discharge pressure of the liquid fuel from the diffusion layer. A method of manufacturing a microfluidic device according to any one of claims 1 to 6 ,
Pressing the flow path plate in which the flow path grooves are formed against a material layer including a filler formed on the substrate, and transferring the material including the filler to the convex portion of the flow path plate;
The flow path plate on which the material containing the filler is transferred is placed on the interposed member, and the material containing the filler is impregnated into the interposed member by annealing, and the flow path plate and the intermediate A method for manufacturing a microfluidic device, comprising a step of bonding a packaging member together. The method of manufacturing a microfluidic device according to claim 13 , wherein a concavo-convex structure that promotes transfer of the material including the filler is provided on a convex surface of the flow path plate to which the material including the filler is transferred. A method of manufacturing a fuel cell according to any one of claims 7 to 12 ,
Pressing the flow path plate in which the flow path grooves are formed against a material layer including a filler formed on the substrate, and transferring the material including the filler to the convex portion of the flow path plate;
The flow path plate on which the material containing the filler is transferred is placed on the interposed member, and the material containing the filler is impregnated into the interposed member by annealing, and the flow path plate and the intermediate The manufacturing method of a fuel cell provided with the process of bonding together a mounting member. The method of manufacturing a fuel cell according to claim 15 , wherein a concavo-convex structure that promotes transfer of the material including the filler is provided on a convex surface of the flow path plate to which the material including the filler is transferred.

Images