KR20100074537A - Microfluidic fuel cell using photosensitive ceramic sheet and manufacturing method of the same - Google Patents

Abstract

PURPOSE: A microfluidic fuel cell is provided to be manufactured without an electrolyte separator according to laminar flow which is generated in a microchannel, to obtain excellent thermal stability and chemical resistance, and to secure chemical stability to an organic solvent which is used as a fuel. CONSTITUTION: A method for manufacturing a microfluidic fuel cell using a photosensitive ceramic sheet comprises: a step(S10) of fabricating a low temperature co-fired ceramic substrate; a step(S11) of manufacturing one or more photosensitive ceramic sheets; a step(S17) of forming a microchannel on the photosensitive ceramic sheet to make a fuel and a oxidizing agent flow into the microchannel; a step of (S19) of forming a unit cell to control the conversion of the fuel and the flow of electrons and of laminating the sheet which is composed of the unit cell and sintering the laminate.

Description

Microfluidic fuel cell using photosensitive ceramic sheet and manufacturing method of the same}

The present invention relates to a microfluidic fuel cell device using a photosensitive ceramic sheet and a method for manufacturing the same. More particularly, the present invention can be implemented without an electrolyte separator according to the formation of a laminar flow occurring in a microchannel, and stacked in series and in parallel. The present invention relates to a method for manufacturing a microfluidic fuel cell device using a photosensitive ceramic sheet having improved output density.

Currently, batteries commonly used in mobile phones and laptops are lithium-based secondary batteries. Such lithium batteries can be supplied in mass production at low cost, but have a disadvantage in that the use time is not long.

Compared with the disadvantages of the lithium battery, the portable fuel cell has a long time, and is easy to carry and easy to replace fuel because of its convenient operation. Therefore, the development of a technology related to a portable fuel cell as a power supply device for portable electronic devices has been actively made.

The portable fuel cell is a direct methanol fuel cell (DMFC) that uses methanol instead of hydrogen as a direct fuel, and a storage hydrogen fuel cell (H-) that stores electricity in a high pressure tank and combines with oxygen to generate electricity. Reformer Polymer Electolyte Fuel Cell (R-PEFC) and Micro Oxide Solid Fuel Cell ), And active research is being conducted for commercialization of such a portable fuel cell system.

Among the components of the portable fuel cell, the polymer electrolyte membrane, which plays a key role, determines the performance and life of the fuel cell. The polymer membrane should have excellent hydrogen conductivity but little permeation and diffusion of methanol or water other than hydrogen, and high physical shape, chemical stability, and mechanical strength.

Currently, Nafion membranes are the most widely used because of their excellent ion conductivity and low water mobility, but the development of new membranes and composite membranes has emerged as an indispensable task due to the high permeation rate of methanol, which leads to a decrease in performance. to be.

In addition, the portable fuel cell has a problem that the output density is relatively low compared to other fuel cells.

Accordingly, an object of the present invention is to provide a method for manufacturing a microfluidic fuel cell device using a photosensitive ceramic sheet which does not require a polymer separator by forming a laminar flow in which two or more fluids do not mix with each other in the manufacture of a portable fuel cell.

Another object of the present invention is to provide a method for manufacturing a microfluidic fuel cell device having excellent durability with thermal stability and chemical resistance by using a ceramic substrate and a sheet.

In addition, another object of the present invention is to incorporate a functional device in the photosensitive ceramic sheet using LTCC (Low temperature co-fired ceramic) method, which is easy to laminate and internalize the device, and in series and parallel combination It is possible to provide a method of manufacturing a microfluidic fuel cell using a photosensitive ceramic sheet that overcomes the low power density, which is a disadvantage of the microfluidic fuel cell, since the dimensional lamination is possible.

Further, another object of the present invention is to unify the fuel inlet or the oxidant inlet and simplify the structure of the fuel cell by allowing the adjacent fuel channels or the oxidant channels of the unit cells to be combined in parallel with each other.

According to the present invention, the above object is to produce a low temperature co-fired ceramic (LTCC) substrate; Fabricating at least one photosensitive ceramic sheet; Forming a fine channel to allow fuel and an oxidant to flow into the photosensitive ceramic sheet; Forming a unit cell by forming an electrode to control conversion of the fuel and flow of electrons; And laminating sheets formed of the unit cells.

Forming the electrode is preferably selected from a screen printing method or a lithography method.

In the stacking of the unit cells, it is preferable to stack the unit cells horizontally and in series to increase the output density.

In the stacking of the sheet formed of the unit cells, it is preferable to further laminate the photosensitive ceramic sheet in which the functional element is embedded.

It is preferable that the said functional element is any one or more of a micro heater and a pump.

The present invention also provides a microfluidic fuel cell device in which at least one unit cell and a fuel or oxidant channel of an adjacent unit cell in one layer are combined in parallel, and the layers having the parallel combined channel are connected in series. .

Preferably, the parallel fuel channel or oxidant channel has a fuel inlet for injecting fuel or an oxidant inlet for injecting oxidant into a single unit for each combination unit.

Preferably, the fuel channel and the oxidant channel are arranged symmetrically with each other.

In the present invention, since two or more fluids form a laminar flow that does not mix with each other in a channel, a polymer membrane is not required, and thus the life limitation of the fuel cell by the polymer membrane does not occur.

In addition, since the polymer electrolyte separator is not required, not only the simplification of the manufacturing process but also the performance degradation and short lifespan generated in the polymer electrolyte can be solved.

In addition, it is possible to secure chemical stability and improve efficiency for organic solvents used as fuel, compared to PDMS (Polydimethylsiloxane), which is a basic polymer material used in the fabrication of microfluidic devices, by manufacturing devices using ceramic materials and processes. It can be used stably in the required driving temperature range.

In addition, in the manufacture of a microfluidic fuel cell device, by using a ceramic substrate and a sheet, there is an effect of excellent durability due to thermal stability and chemical resistance due to the characteristics of the ceramic material.

In addition, the LTCC method, which is easy to stack and embed devices, enables the functional density to be embedded in the photosensitive ceramic sheet, and the three-dimensional stacking can be performed in a combination of series and parallel.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and embodiments.

1 is a flowchart illustrating a method for manufacturing a microfluidic fuel cell using a photosensitive ceramic sheet, which is divided and described according to each process as follows.

1. Fabrication of the substrate

First, a low temperature co-fired ceramic (LTCC) substrate is manufactured (S10). Since the LTCC process is based on the present invention, various functional devices can be added and embedded therein, and even a structure having more than 40 layers can be obtained in one firing process, thereby enabling three-dimensional stacking.

In manufacturing such a substrate, the material used and its content are shown in Table 1 below.

Material used Mineral bookbinder Dispersant menstruum Amorphous cordierite PVB BYK-111 Toluene: Ethanol
= 6: 4 Content (g) 100 12.00 1.00 Toluene: 57.25
Ethanol: 34.74 purpose of use Device
Configuration Of sheet
Strength Uniformity of inorganic material inside slurry Slurry Preparation by Wet Mixing

The manufacturing process for manufacturing the substrate using the material thus prepared is shown in Figure 2, the process sequence is primary mixing (S21), PVB melting (S23), PVB and slurry mixing (S25) and filtering, defoaming And a process of aging (S27).

The primary mixing (S21) process is performed for the purpose of dispersion. The inorganic material, the dispersant and the solvent (1/2) are mixed and dispersed for 24 hours or more using a ball mill. The remaining 1/2 solvent is used to dissolve the binder PVB.

PVB dissolution (S23) process is used for dispersing and adding PVB to the remaining solvent is dissolved using a stirrer. In this process, if heat is applied for rapid dissolution, the internal structure of PVB may be broken, so do it without heating.

The PVB and slurry mixing (S25) process is performed by mixing the dissolved inorganic PVB and the dissolved PVB in the slurry state in which the primary mixing (S21) process is completed, followed by secondary mixing for 24 hours or more using a grinder.

Filtering, degassing and aging (S27) process is performed by filtering the slurry after the secondary mixing into a net of a predetermined size to filter large particles in the slurry and degassing under vacuum. After defoaming, the RPM (rpm) of the pulverizer is maintained at 15 or less, aged for about 12 hours, and degassed, followed by a process of promoting the reaction between the components in the slurry.

2. Fabrication of Photosensitive Ceramic Sheet

Next, a photosensitive ceramic sheet is produced (S11). The microfluidic fuel cell of the present invention requires at least one photosensitive ceramic sheet because the photosensitive ceramic sheets are stacked in series and in parallel.

The manufacturing process for manufacturing the photosensitive sheet is as shown in FIG. 3, and is composed of solid dispersion (S31), photosensitive organic material addition (S33), defoaming and aging (S35), and tape casting (S37).

First, the material used in the solid dispersion (S31) process and its content (based on 50g of solid) are as shown in [Table 2] below.

Material used Mineral Dispersant menstruum Amorphous cordierite BYK-111 Toluene: Ethanol
= 6: 4 Content (g) 50.00 0.50 Toluene: 17.70
Ethanol: 10.77 purpose of use Device
Configuration Uniformity of inorganic material inside slurry Slurry Preparation by Wet Mixing

As described above, only half of the solvent was used to prepare the substrate, but in the process of manufacturing the photosensitive sheet, the total amount of the solvent was added. In the first mixing, the slurry mixed with the inorganic material, the dispersant, and the solvent is dispersed for 24 hours using a grinder.

Next, to add a photosensitive organic material (S33), the material used and its content (based on 50g solvent) are shown in Table 3 below.

Material used content purpose of use 2656 3.33 Acrylic polymer is added to maintain the initial strength of the sheet and the shape of the pattern during curing by exposure. 2648 6.67 DBP 4.00 (DPB) dibutylphtalate: An additive or plasticizer that helps to maintain the ductility of a sheet TPA 330 5.00 A photosensitive monomer (monomer) that polymerizes when cured by ultraviolet rays to maintain the shape of the pattern BT 3.50 Photo sensitizer: Additive to promote the reactivity of photoinitiator and photo monomer SudanIV 0.20 Organic dyes: Red dyes that are added to maximize the absorption of ultraviolet light in the wavelength range of light. IR 369 2.00 Photo initiator: Free radicals are generated in response to UV, and the radicals are polymerized by reacting with monomers. Additives that generate chain radicals in this reaction and start the reaction Flownon sp 0.40 Anti-setting agent: A substance added to prevent sedimentation due to the difference in density between mixtures of minerals.

Thereafter, the materials prepared in Table 3 above are added to the slurry in which dispersion is completed, and secondary mixing is performed using a grinder for 24 hours. Since curing occurs due to ultraviolet rays, the process is performed by completely blocking a clean room without ultraviolet rays or a container containing materials from light.

Next, defoaming and aging (S35) is performed, and this step is a process of removing air bubbles present in the slurry after the filtering process of filtering the inorganic material that is not composed of small particles in the same process as the manufacturing process of the substrate. In this way, bubbles can be suppressed from being generated on the sheet during tape casting. After defoaming, in order to promote the reaction of each additive, the mill RPM is set to 15 or less and aging is performed.

Next, a hand caster is used in a clean room, but in a space where ultraviolet rays are blocked, a tape casting S37 is performed using a casting machine. The initial set thickness is carried out to 140㎛, the cast slurry is dried at room temperature and when the drying is complete it takes the form of a sheet.

3. Electrode Formation

Next, an electrode is formed on the photosensitive ceramic sheet (S13), and the shape of the formed electrode will be described with reference to FIG. 4. 4 is a shape of the electrode formed by the present invention, it is prepared by a lithography method using a screen printing or photosensitive paste using a conductive paste. The shape of the electrode may show a difference depending on the shape of the device to be manufactured.

First, the screen printing method using the common electrode is performed for the purpose of inducing ionization by applying electricity to fuel and oxide injected into the device. In the method of forming such an electrode, a conductive paste containing silver, nickel, copper, or the like, commercialized using a screen mask having an electrode shape, is printed on a substrate with a predetermined thickness. The printed electrode is pressurized using a hot press to reduce the height difference between the substrate and the electrode to reduce the unevenness caused by the electrode in the lamination process.

Next, a lithography method using a photosensitive paste, which is performed by using a conductive paste containing a photosensitive material, is performed using a rectangular screen mask having a size that can include the entire area of the electrode. After printing the conductive paste reacting with ultraviolet rays to a square mesh frame having the size of the electrode on the substrate, the drying is carried out.

The dried sample is exposed to light under an ultraviolet light intensity of 450 W and an exposure time of 60 seconds using an exposure machine, and the shape of the electrode is obtained through development. Into 1 liter of ultrapure water (DI water) was added 7.88g of 98.5% of diethanolamine (Diethanolamin) and completely dissolved by stirring to prepare a developer. The time required for development varies depending on the composition of the conductive paste and the shape of the electrode used, and the concentration of the developer used is fixed to the above-described composition.

4. Exposure and development

Next, an exposure and development step (S15) is carried out. The process for exposure (S51) according to FIG. 5 is as follows. First, lamination is carried out to secure the required depth of the pattern, and then carried out at a pressure of 1000 psi for 30 seconds using a hot press equipment.

At this time, the pressure may be in the range of 1000 psi or more, and the pressurization time may be in the range of 20 to 40 seconds.

If the pressing time is 20 seconds or less, the bonding force between the laminated sheets is weakened, and when the pressure time is 40 seconds or more, deformation of the pattern may occur. In addition, in the case of using a plurality of sheets, it is necessary to increase the depth of penetration by using a higher intensity than in the case of using a single sheet in consideration of the depth through which ultraviolet rays can be transmitted, thereby making the circuit irregularities appear clearly. need.

In the case of exposing a single sheet (1 sheet), using an exposure machine, the UV intensity is 280 to 320 W and the exposure time is performed under conditions of 40 to 80 seconds. The intensity is 320 ~ 380W exposure time is carried out under the conditions of 40 ~ 80 seconds. Since the exposure time and intensity adjustment are necessary depending on the sheet, it is obvious that suitable conditions must be found through experiments before exposing the pattern, but it does not deviate greatly from the range of the conditions described above. The exposed sheet is dried using an oven, which is carried out at a temperature of 80 ° C. for 10 minutes to prevent swelling and bubbling which may occur during development. In the case of a one-stage pattern (T-type 2), it is preferable to perform post-lamination exposure on a substrate, and in the case of a two-stage pattern, perform a post-lamination exposure on the first stage and a post-exposure lamination process on the second and subsequent stages.

Thereafter, the development (S53) is performed. For developing, 7.88 g of 98.5% of diethanolamine (Diethanolamin) was added to 1 L of ultrapure water, and then completely dissolved through stirring to prepare a developer. The pattern is shown by spraying the prepared developing solution to the sheet which completed exposure and drying using a spray. The developed sheet with the developer is washed with ultrapure water (DI water) to remove the developer from the surface of the sheet and dried with air.

5. Formation of Microchannels

The microchannels are formed to allow the fuel and the oxidant to flow through the exposure and development (S15) as described above (S17). Fuel and oxidant in the formed channel forms a laminar flow that does not mix with each other has the advantage that the polymer membrane is not required.

6. Fabrication, lamination and sintering of electrode unit

In the present invention, the methanol used as the fuel is converted, and an electrode is formed to control the flow of electrons to form a unit cell, and the sheets formed of the unit cells are stacked (S19), followed by sintering.

Here, the substrate and the channel layer on which the electrode is formed are fabricated into cells through lamination. In the lamination step, each layer is placed on the prepared substrate, and lamination is performed at 120 to 180 psi at a temperature of 40 to 60 ° C. using a WIP apparatus. The lamination temperature and pressure indicated above are found at a temperature below the Tg of the sheet, and the shape of the p-pattern may collapse upon pressurization with excessive pressure at a temperature higher than this. If the temperature and pressure are below the above range, the lamination process itself does not proceed.

FIG. 6 is a schematic diagram and operation diagram of a cell formed through the lamination, and has a channel for allowing fuel and oxygen or hydrogen or oxidant to be injected through each inlet to be mixed with each other. It can be seen that it does not appear to form a laminar flow.

The fuel used was methanol and hydrogen was used as the oxidant. Methanol flows from the anode and hydrogen flows from the cathode, whereby hydrogen ions move from the anode to the cathode, producing a current density. As shown, in the laminar flow, the liquids do not mix without physical barriers and membranes and are physically connected and flowed side by side. Because of the strong viscosity, they do not mix unless forced to mix.

Thereafter, a plurality of cell stacks are used to make a cell combination of a certain size. A small amount of power generated in one unit cell can be matched to a required power condition through a series or parallel combination. 7 is a schematic diagram illustrating such a lamination method. In FIG. 7, it can be seen that the layers in which the channels are formed and the layers of holes through which the injected fluid flows coincide with each other are stacked. This is a multi-layered structure in which the injected fluid is injected into each layer, rather than a single shape injected into one cell, thereby generating electric power in such a manner that electrons generated in each cell are moved by a pre-formed electrode.

Here, the difference between the conventional microfluidic fuel cell and the microfluidic fuel cell according to the present invention will be described. First, in the case of a conventional microfluidic fuel cell, a fuel inlet is formed by using a catalytic reaction inside the cell. However, in the present invention, the injection of fuel and oxide used for electricity production is injected into the respective passages, and the ions of the respective injections generated at the interface using laminar flow among the flow characteristics of the fluid generated in the microspace. It is a method of producing electrical energy by exchange, which can induce a direct reaction rather than a conventional stepwise chemical reaction.

In addition, by using methanol as the main fuel, which excludes the use of chemicals used as other catalysts, it may have an advantage of making it more commercially available. 7 shows an embodiment according to the present invention, in which four cells are configured in parallel in one layer. In this case, four fuel inlets are used, but an inlet through which oxidants are injected. By symmetrically arranging fuel and oxidant channels for use in two, the manufacturing process and components have been simplified. In addition, when the cells of each layer are arranged in series, the entire device configuration is achieved by arranging and arranging the cells so that the cells of each layer may be supplied to the cells of each layer by one injection of fuel and oxidant at the lower end.

Here, by combining the fuel channels in parallel, two fuel inlets and four oxidant inlets can be provided.

In addition, the anode formed in the fuel channel and the cathode formed in the oxidant channel were also intended to be arranged to be interconnected through via hole processing.

Looking at the temperature of each material used in the present invention, the sintering temperature of the ceramic sheet is a material having a range of 780 ~ 810 ℃, sintering the electrode when forming an electrode using silver paste (Ag paste) in such a ceramic material When the difference between the temperature and the sintering temperature of the ceramic sheet shows a difference in shrinkage between the electrode and the ceramic substrate after sintering, peeling of the electrode or deformation of the substrate occurs.

In the case of the silver paste used in the present invention, the sintering temperature range as a material that can be used for LTCC can be controlled by the size of the added silver particles and the content of other inorganic materials. In the present invention, in order to have a temperature range of 780 ~ 810 ℃ sintering temperature range of the ceramic material used in the prior art was used a silver paste that proceeds sintering around 800 ℃.

The rate of temperature rise at the sintering temperature is directly related to the morphological deformation of the device. If the temperature increase rate is high, there is a problem that the deformation of the shape due to the separation phenomenon of each layer or the irregular shrinkage of the entire device can be brought. The sintering temperature mentioned in this process was determined based on the results of experiments for each condition. The optimum sintering temperature is 780 ~ 810 ℃ and the temperature increase rate is 1 ~ 3 ℃ / min. As a result of the experiment, in the case of the abrupt temperature increase, partial deformation of the ceramic sheet and the substrate or separation of each layer occurs during the burn out of the organic material. At the sintering temperature lower than the sintering conditions, the sintering of the silver electrode layer is not performed completely, so that electrical conductivity as an electrode is not realized. In addition, liquid phase sintering of the silver paste proceeds at a sintering temperature higher than the sintering conditions.

Therefore, the appropriate sintering temperature conditions were set in the range from the temperature to start the sintering to the sub-sintering region, this temperature can be changed depending on the type of ceramic material used, the composition and content of the added inorganic material.

According to the present invention, it is possible to fabricate a functional element such as a micro heater and a pump in a photosensitive ceramic sheet. In this case, a sheet formed of a unit cell and a sheet containing the functional element are stacked in step S19.

The dimension of the device used in the present invention preferably has a channel width of 10 ~ 1000 ㎛, channel depth of 10 ~ 1000 ㎛, channel length of at least 0.5 ~ 5.0 cm, four or more channels are configured on one substrate It is desirable to have the shape of a cell. In addition, the cell of one layer includes all of the microchannels, electrodes, and fuel inlets.

1 is a flow chart for a method of manufacturing a microfluidic fuel cell using the photosensitive ceramic sheet according to the present invention;

2 is a flow chart for manufacturing a substrate according to the present invention,

3 is a flow chart for producing a photosensitive ceramic sheet according to the present invention,

4 is a view showing the shape of the electrode formed by the present invention,

5 is a flow chart for the exposure and development process according to the present invention,

Figure 6 is a schematic diagram and operation of the cell formed through the lamination process according to the present invention,

7 is a schematic diagram of a process of manufacturing a cell combination of a predetermined size through a plurality of cell stacks according to the present invention.

Claims (8)

Fabricating a low temperature co-fired ceramic (LTCC) substrate; Fabricating at least one photosensitive ceramic sheet; Forming fine channels to allow fuel and oxidant to flow into the photosensitive ceramic sheet; Forming a unit cell by forming an electrode to control conversion of the fuel and flow of electrons; And Stacking and sintering the sheet formed of the unit cells; a method of manufacturing a microfluidic fuel cell device using a photosensitive ceramic sheet, characterized in that it comprises a. The method of claim 1, Forming the electrode, A method of manufacturing a microfluidic fuel cell device, characterized in that it is selected from a screen printing method or a lithography method. The method of claim 1, Stacking the unit cells, A method of manufacturing a microfluidic fuel cell device using a photosensitive ceramic sheet, wherein the unit cells are stacked in parallel and in series to increase an output density. The method of claim 1, Laminating the sheet formed of the unit cell, A method of manufacturing a microfluidic fuel cell device using a photosensitive ceramic sheet, wherein the photosensitive ceramic sheet further includes a laminated photosensitive ceramic sheet. The method of claim 4, wherein The functional element, A method of manufacturing a microfluidic fuel cell device using a photosensitive ceramic sheet, characterized in that at least one of a micro heater and a pump. Prepared by the method of claim 1, And a fuel channel or an oxidant channel of at least one unit cell and an adjacent unit cell in one layer in parallel with each other, and the layers having the parallel combined channel are connected in series with each other. The method of claim 6, And a fuel injection hole for injecting fuel or an oxidant injection hole for injecting an oxidant in the parallel combined fuel channel or oxidant channel for each combination unit. The method of claim 6, And the fuel channel and the oxidant channel are symmetrically arranged to each other.

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