JP5279069B2 - Bio battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that a bio battery causes drop in power generation capacity by activity deterioration of enzymes, mediators, or the like immobilized on an electrode, and deterioration by oxidation reaction caused by dissolved oxygen when operated under natural environment or in vivo environment cannot be prevented, and cannot continue power generation for a long time. <P>SOLUTION: A biodegradable polymer whose decomposition rate is controllable is utilized. For example, by connecting two or more bio batteries in a state being separated from an electrolyte solution, contact of an electrolyte solution with an electrode successively occurs by decomposition of the polymer, power generation successively starts in every cell, and as a result, power generation can be continued for a long time. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a bio battery capable of generating power over a long period of time. In particular, the present invention has a structure in which two or more batteries separated from an electrolyte solution are connected using a biodegradable polymer, and the wetted liquid of each battery by polymer decomposition and power generation by wetted liquid However, the present invention relates to a battery, particularly a fuel cell, capable of generating electricity for a long time by automatically and sequentially starting with a time difference. In the present invention, the electrode part is isolated from the electrolyte solution using a biodegradable polymer, and when the biodegradable polymer is decomposed, the electrolyte solution is in contact with the electrode part to generate power. It also relates to a battery or power generation device characterized by having a starting structure.

  Attempts have been made to disperse and arrange ultra-small electronic devices equipped with a power supply in the natural environment or in-vivo environment, and to perform continuous, comprehensive measurement, diagnosis and treatment using this device. Because such distributed and small devices are difficult to charge, the life of the power supply often limits the design and practical form of the device, and there is a need to develop a small power supply that can maintain the power generation capacity for a long period of time. Yes.

As power sources for electronic devices that are used in a distributed environment in the natural environment or in the living body, a primary battery such as a manganese battery or a biofuel cell (Non-Patent Document 1) can be considered. In particular, a biofuel cell uses a biocatalyst (enzyme or microorganism) and can be composed of only environmentally friendly organic substances, and can be a disposable power source that does not place a burden on the environment or the living body. In addition, due to the high reaction specificity of the biocatalyst, there is a possibility that sugar existing in nature can be directly used as an energy source without purification. Since sugars contained in body fluids (blood, tissue fluid, etc.) can also serve as fuel, development of skin patch type and implantable medical micro fuel cells has been studied (Non-patent Document 2).
However, since the amount of electricity that the primary battery can output is defined by the amount of active material, it is impossible in principle to extend the usage period beyond that. In a biofuel cell, the power generation capacity is reduced mainly due to degradation of the activity of enzymes, mediators and the like immobilized on the electrode. Although research aimed at stabilizing enzymes and mediators continues, it is extremely difficult to completely prevent degradation due to oxidation reactions caused by dissolved oxygen when working exposed to the natural environment or in vivo.

The consumption and deterioration of the primary battery and the biofuel cell proceed while the electrode is in contact with the electrolyte solution (in the biofuel cell, the electrolyte solution containing fuel). The active material is not consumed when it is not in contact with the electrolyte solution. Seawater batteries that can be stored for a long time using this fact have been used for emergency lifeboats, lifejacket lamps, and the like. A seawater battery is a primary battery made of Mg and AgCl, stored in a dry state, and injecting an electrolyte solution such as seawater to start power generation during use, so there is no deterioration during storage. Recently, an Mg-AgCl battery that starts power generation using urine has been developed and is expected as a power source for a urine test chip (Non-patent Document 3). The same applies to biocells including biofuel cells. Electrodes with immobilized enzymes and mediators can be stored for a long period of time if they are dry and not in contact with the solution. Power generation is not possible until an electrolyte solution containing fuel is injected. Be started. However, these techniques are methods for long-term storage and do not extend the operation time to a long period.

A. Heller, Phys Chem. Chem. Phys., 6; 209, 2004. A. Heller, AIChE J., 51; 1054, 2005. K. B. Lee, J. Micromech. Microeng., 15; 5210, 2005.

  The present invention is a biodegradable polymer whose rate of degradation can be adjusted, and by connecting a plurality of batteries separately from the electrolyte solution, liquid contact between the electrolyte solution and the electrode due to polymer degradation occurs sequentially. Thus, it is intended to provide a battery, particularly a bio battery (including a power generation device) including a primary battery and a biofuel cell, in which power generation starts sequentially for each battery, and as a result, long-term power generation can be maintained.

According to the present invention, a biodegradable polymer such as polylactic acid (PLA), polyglycolic acid (PGA), a copolymer of lactic acid and glycolic acid (PLGA) is used, and the electrode part and the electrolyte solution are isolated, When the biodegradable polymer is decomposed, the electrolyte solution comes into contact with the electrode portion and power generation is started.
In addition, according to the present invention, by using a plurality of biocells isolated from the electrolyte solution by using biodegradable polymers having different time required for decomposition, power generation of each battery is sequentially started. Thus, a bio battery capable of maintaining power generation for a long time is obtained.
In addition, according to the present invention, until one of the batteries comes into contact with the liquid, the remaining biodegradable polymer separator does not come into contact with the liquid and is not subjected to the decomposition action by the electrolyte solution. Even if a kind of biodegradable polymer is used, power generation of each battery is started sequentially, and a bio battery capable of maintaining power generation for a long time can be obtained.
In the present invention, a battery having a structure in which an electrode portion isolated from an electrolyte solution by using a biodegradable polymer is brought into contact with the electrolyte solution to generate electricity by decomposing the biodegradable polymer and / or Or the electromotive device is also provided.
Furthermore, the present invention can be applied to a battery in which fuel can be supplied from the outside, for example, a battery in the form of a normal primary battery packaged at the time of manufacture in addition to a fuel cell.

Thus, the present invention provides the following.
(1) electrode portion has at least one of the batteries is isolated from the electrolyte solution, the battery is connected two or more, the electrolyte solution in the electrode portion is isolated from the electrolyte solution is power and wetted A biobattery characterized in that when it is started, it sequentially generates power with the two or more connected batteries.
(2) The biobattery according to the above (1), wherein the electrode part sequentially contacts the electrolyte solution by the decomposition of the biodegradable polymer.
(3) The biobattery according to (1) or (2), wherein the biodegradable polymer is used as a partition wall that separates the electrode part from the electrolyte solution .
(4) The biodegradable polymer is used as an adhesive for adhering a partition plate or lid between the container or compartment containing the electrode part and the electrolyte to the container or compartment. The bio battery according to (1) or (2), characterized in that it is characterized in that
(5) the electrolyte solution by the biodegradable polymer is decomposed by a structure sequentially generating power by liquid contact to the electrode portion is started, long-term power generation, characterized in that to maintain (2) - The biobattery according to any one of (4).
(6) the biodegradable polymer, said to be characterized by what is between the time of degradation varies with two or more types, can be maintained long term power by sequentially generating starts with the decomposition (2) - ( The biobattery as described in any one of 4).
(7) The biobattery according to (1), wherein the electrode unit is in contact with the electrolyte solution sequentially by a mechanical switch.

(8) The biodegradable polymer includes polylactic acid, polyglycolic acid, a copolymer of lactic acid and glycolic acid, or a derivative thereof, as described in any one of ( 2 ) to (6) above The bio battery as described.
(9) The bio battery is a battery that generates electricity using an enzyme as an electrode catalyst and a fuel selected from the group consisting of sugar, lactic acid, and alcohol. The bio battery according to any one of the above.
(10) Any one of (1) to (8), wherein the biobattery is a battery that uses a microorganism to generate electricity using a fuel selected from the group consisting of sugar, lactic acid, and alcohol. The bio battery according to 1.
(11) The bio battery according to any one of (1) to (10), wherein the bio battery has a sheet-like shape in which two or more micro batteries of millimeter order or less are arranged in a plane. battery.
(12) The biobattery according to any one of (1) to (11), wherein all parts including an electrode and a structural material are made of an organic substance.
(13) A structure in which the electrode part is isolated from the electrolyte solution using the biodegradable polymer, and power generation is started by the electrolyte solution coming into contact with the electrode part by decomposing the biodegradable polymer. A battery or a power generation device comprising:

According to the present invention, the following effects can be obtained.
If a biodegradable polymer such as PLGA is used and a battery with a stable storage state can be provided by isolating the electrode of the bio battery from the electrolyte solution, there is a time difference by connecting a plurality of such batteries. Power generation is automatically started sequentially and power generation can be maintained for a long time. If the power generation of a bio battery can be maintained for a long period of time, it is effective to disperse small sensors equipped with this battery and collect environmental information, or to make an implantable diagnostic / treatment device self-supporting. Furthermore, a biobattery is an extremely safe power generation device that can be configured only with organic substances, has high affinity for the environment and living organisms, and can generate power for a long time according to the present invention. There is a possibility that it can be used as a disposable power source that does not place a burden on the environment or in vivo environment. According to the present invention, a battery that has been isolated from an electrolyte solution and has secured a stable storage state in an isolated environment such as a living body can be started by utilizing the phenomenon that a biodegradable polymer is decomposed. A technique for controlling the power start time is provided.
Other objects, features, excellence and aspects of the present invention will be apparent to those skilled in the art from the following description. However, it is understood that the description of the present specification, including the following description and the description of specific examples and the like, show preferred embodiments of the present invention and are presented only for explanation. I want. Various changes and / or modifications (or modifications) within the spirit and scope of the present invention disclosed herein will occur to those skilled in the art based on the following description and knowledge from other parts of the present specification. Will be readily apparent. All patent documents and references cited herein are cited for illustrative purposes and are not to be construed as a part of this specification. is there.

Embodiments of the present invention will be described below.
In this specification, “battery” refers to a power device that directly converts energy into direct current power, and includes, for example, an electromotive device / power generation device that uses energy generated by a chemical reaction. In particular, the invention includes a bio battery and a bio power generation device. For example, in addition to a fuel cell capable of supplying fuel from the outside, a battery in the form of a normal primary battery packaged at the time of manufacture is also included.
In the present specification, examples of the biofuel cell include a fuel cell that generates electricity using an enzyme as an electrode catalyst and glucose or alcohol as a fuel, or a fuel cell that generates electricity using glucose or alcohol as a fuel using a microorganism.
The present invention is a battery that can maintain power generation for a long time as a whole even if the life of each bio battery is short, by connecting two or more connected bio batteries to start power generation sequentially with a time difference. It is a feature. Specifically, two or more batteries isolated from the electrolyte solution using biodegradable polymers with different decomposition rates are manufactured and connected to automatically start power generation sequentially. It is a bio battery that can supply a certain amount of power over a certain amount. Or, even when isolated with the same type of biodegradable polymer, it is a battery that can supply a certain amount of power over a long period of time by adopting a structure in which the decomposition reaction starts sequentially. .
In the present invention, the target biocell is preferably a fuel cell, that is, a biofuel cell. The type of biobattery is not particularly limited, and includes all batteries that utilize redox reactions of enzymes and microorganisms, particularly all fuel cells, and those that use electron mediators, that is, mediators.

First, components in a battery that utilizes an enzyme redox reaction will be described.
Typical examples of the enzyme immobilized on the anode electrode include a combination of diaphorase and glucose dehydrogenase and glucose oxidase. Other than this, it is preferable to select from enzymes such as fructose oxidase, fructose dehydrogenase, alcohol oxidase, alcohol dehydrogenase, lactate oxidase and lactate dehydrogenase. However, the enzyme that can be used for the anode electrode is not limited to these, and any enzyme that is useful for decomposing biomass fuels such as sugar and alcohol may be used.
As the cathode electrode, it is preferable to use a noble metal single electrode such as platinum, or an electrode in which an enzyme of multi-copper oxidase such as billibine oxidase or laccase is immobilized on carbon or the like. However, enzymes that can be used for the cathode electrode are not limited to these, and any enzyme that is useful for oxygen reduction may be used.

The fuel in the fuel cell is preferably selected from glucose (glucose), fructose (fructose), alcohols such as methanol / ethanol, lactic acid, sucrose (sucrose), and the like. However, usable fuels are not limited to these, and any fuel may be used as long as it is useful for the anode electrode enzyme and the cathode electrode enzyme.
Next, in a battery using a redox reaction of microorganisms, when it is a fuel cell, all fuels used as biomass fuels such as sugar and alcohol, as well as nutrients that are assimilated for microorganisms, etc. The present invention can be applied to all of them.

In the present invention, the biodegradable polymer used to coat the biobattery or as an adhesive or the like is a synthetic polymer or a natural polymer, and has a function of preventing the electrolyte solution from coming into contact with the electrode part. However, it is hydrolyzed or decomposed into low molecular weight compounds by the action of enzymes and microorganisms, thereby allowing the electrolyte solution to enter and starting power generation. For example, specific examples include polylactic acid (PLA), polyglycolic acid (PGA), a copolymer of lactic acid and glycolic acid (PLGA), and derivatives thereof, which are biodegradable polymers based on synthetic polyester. It is preferred that Examples of the biodegradable polymer include 50/50 poly (D, L-lactide-co-glycolide) (50/50 DLPLG), 65/35 poly (D, L-lactide-co-glycolide) (65 / 35 DLPLG), 75/25 poly (D, L-lactide-co-glycolide) (75/25 DLPLG), 85/15 poly (D, L-lactide-co-glycolide) (85/15 DLPLG), poly (D, L-lactide) (DLPLA), poly (L-lactide) (LPLA), poly (glycolide) (PGA), poly (ε-caprolactone) (PCL), 25/75 poly (D, L-lactide- co-ε-caprolactone) (25/75 DLPLCL), 80/20 poly (D, L-lactide-co-ε-caprolactone) (80/20 DLPLCL) are known and approved by the FDA. However, usable biodegradable polymers are not limited to these, and any biodegradable polymers may be used as long as they can be hydrolyzed or decomposed into low molecular weight compounds by enzymes or microorganisms. The degradation rate can be adjusted by the average molecular weight and derivatization, and in particular for PLGA, it can be adjusted from several hours to one month depending on the copolymerization ratio. It is desirable that the decomposition rate can be set so that the next battery starts power generation immediately before the deterioration of battery performance becomes significant and it becomes difficult to maintain the function of the connected device.

Biodegradable polymers are materials that have been actively studied in recent years, and their main uses have been developed for agricultural films, food packaging, garbage bags, textiles, and the like. PLGA, one of biodegradable polymers, is known as a carrier material or coating material for drug particles as an application for adjusting the timing of drug administration in drug delivery technology (for example, JP-A-5-70363). , Special Table 2006-507036). In addition, a delivery device has been developed in which a drug is sealed in a hole made in a large number of holes in a silicon wafer, covered with PLGA, and the drug is released sequentially by decomposition of PLGA (ACRGrayson et al., Nature Materials, 2; 767 , 2003.
).
The form of the biodegradable polymer used in the present invention is not limited to simple substances such as PLA, PGA, PLGA, and derivatives thereof. For example, the biodegradable polymer may be used by mixing with a silicone resin having elasticity. Is possible. In addition, as a method of isolation from the electrolyte solution, a method of using as a partition plate between a container or compartment containing an electrode part and an electrolyte, a method of covering the electrode itself, a container or compartment containing an electrode part and an electrolyte. There is a method used as an adhesive for the partition plate. Furthermore, when a material having high chemical stability such as platinum is used as the electrode, it may not always be necessary to isolate it from the electrolyte solution.

  Although the present invention does not particularly limit the shape of the biobattery, it can be separated from the electrolyte solution by a biodegradable polymer, thereby preventing the electrolyte solution from contacting the electrode part and ensuring a stable storage state. Shapes that can be made are desirable. It is also important that the electrolyte solution quickly contacts the electrode part by degrading the biodegradable polymer, but if a cell-like shape on the order of millimeters or less is used, bubbles may hinder this. In this case, if the electrode portion is sealed with cotton or the like, the electrolyte solution can be relatively easily penetrated. Further, the isolated electrode part can be made hydrophilic or have a negative pressure or the like. Thus, if the isolation state is eliminated, it is possible to promptly bring the electrolyte solution and the electrode portion into contact with each other so that the electromotive phenomenon occurs sufficiently. In the present invention, two or more biocells are connected and there is no upper limit. It is desirable to connect more bio batteries and start power generation at an appropriate timing. For example, a large number of small batteries may be arranged on a flat plate, and each battery may be covered with a biodegradable polymer using a printing technique such as an inkjet printer.

Furthermore, the present invention can be applied to a battery in the form of a primary battery. For example, there is a primary battery in which Mg is a negative electrode and AgCl or PbCl ₂ is a positive electrode, but the type of applicable primary battery is not particularly limited.

The present invention provides a time difference type small power generation device. The power generation mechanism of the device is a power generation system in which electrodes that generate power one after another are switched and power can always be generated with new electrodes, and this is called “time difference type power generation”. Bioelectrodes such as enzyme electrodes that have been stored in a dry state that have not been exposed to electrolyte solutions such as fuel are considered to be relatively unlikely to suffer from performance degradation. The time difference type power generation enables the power generation with the electrode having high performance (not deteriorated) at all times, and the time difference type power generation can achieve this purpose.
The time difference power generation device of the present invention has at least the following mechanism:
(1) An electrolyte solution such as a fuel solution is introduced into a biocell, for example, a biofuel cell.
(2) Power generation by some anodes and cathodes begins. The other is in a storage state where the cover is shielded from the electrolyte solution such as fuel and does not cause a chemical reaction such as an enzyme reaction. (3) At the timing when the degradation of the performance of the bioelectrode such as the enzyme electrode generated in (2) becomes significant, a part of the bioelectrode such as the enzyme electrode that has been cut off from the electrolyte solution such as fuel is naturally or It is forcibly exposed to an electrolyte solution such as fuel. Bioelectrodes such as enzyme electrodes that have not yet been exposed to electrolyte solutions such as fuel are in storage.
(4) By continuing (2) and (3), new electrodes start generating power one after another with a time difference, and a nearly constant power generation amount can be obtained.

In one embodiment, the time difference power generation device can be constructed using biodegradable polymers having different degradation rates. The difference in the degradation rate of biodegradable polymers can be varied depending on, for example, the difference in monomer ratio and average molecular weight of the polymer. For example, PLGA (copolymer of polylactic acid and polyglycolic acid) Has been well studied. In a typical case, a biodegradable polymer thin film with different decay rates shuts off the enzyme electrode from the fuel, and a time-lag type small-scale power generation that automatically starts power generation with a time difference as the biodegradable polymer thin film collapses. Device.
In one embodiment, a biobattery having a configuration in which at least one battery in which an electrode portion is isolated from an electrolyte solution is included, two or more batteries are connected, and the batteries sequentially generate power can be given. In each battery, in order to generate power sequentially, for example, the electrodes may be in contact with each other sequentially by decomposition of the biodegradable polymer, or the electrodes may be sequentially in contact with the mechanical switch. Can be mentioned. In the above, what uses biodegradable polymer as a partition or an adhesive may be included. For example, a structure in which a plurality of batteries are attached to the side, and when the biodegradable polymer partition is disassembled, the electrode contacts the liquid sequentially, or the lid with a slow decomposition rate is bonded with the biodegradable polymer For example, the light and floating lid may be peeled off due to the decomposition of the biodegradable polymer of the adhesive, or the adhesive surface may be peeled off and the lid may be warped to open. The material of the lid may be a material different from the biodegradable polymer, or may be a material having a slow degradation rate, but is not limited thereto, and if the desired purpose can be achieved, Materials known in the field can be appropriately selected and used. For bonding with a biodegradable polymer, for example, CO ₂ bonding can be used. A typical configuration example is shown as a specific example in FIG.

In one embodiment, a plurality of biodegradable polymer isolation membranes for isolating the electrode portion from the electrolyte solution are provided, and the remaining biodegradable polymer is isolated until one of the plurality of isolation membranes contacts the liquid. The membrane does not come into contact with the liquid and is not subjected to the decomposition action by the electrolyte solution. Therefore, there are remaining electrodes in which the electrode portion is not in contact with the electrolyte solution, and the plurality of separation membranes are sequentially formed. There is a type in which the plurality of electrode portions are sequentially contacted with the electrolyte solution by being decomposed to enable time difference type power generation. In such an embodiment, the same biodegradable polymer can be used. In other words, (1) power generation and (2) the wall to the next battery (separated from electrolyte solution such as fuel solution) (composed of biodegradable polymer etc. or biodegradable polymer etc. as adhesive) Is a structure that proceeds simultaneously. In such a case, time difference type power generation can be realized with one kind of material. FIG. 12 shows a specific example of this configuration. Anything that exhibits these functions is within the scope of the present invention, and various structures other than those described above are possible.
In another aspect, when the output is weakened by a method such as pressing a button, the next battery may be activated (FIG. 13).
Hereinafter, the present invention will be specifically described with reference to the drawings. However, the examples are merely provided for the purpose of describing the present invention and for reference to specific embodiments thereof. is there. These exemplifications are for explaining specific specific embodiments of the present invention, but are not intended to limit or limit the scope of the invention disclosed in the present application. In the present invention, it should be understood that various embodiments based on the idea of the present specification are possible.
All examples were performed or can be performed using standard techniques, except as otherwise described in detail, and are well known and routine to those skilled in the art. . Here, in order to carry out the experiment in a short time, the difference in decomposition rate due to the average molecular weight of PLGA is used, and the battery has not deteriorated significantly, but the decomposition rate is controlled by the copolymerization ratio several times. It is known to be wide from several hours to several months, and it is possible to set the disassembly time corresponding to the battery life.

(Invasion of electrolyte solution by decomposition of biodegradable polymer)
As shown in FIG. 1 (a), cyclic voltammetry was performed using a potentiostat (HSV-100, Hokuto Denko). The solution is a phosphate buffered aqueous solution containing 1 mM ferrocenemethanol and maintained at 35 ° C. with a thermostat. A silver / silver chloride (Ag / AgCl) electrode was used for the reference electrode (R), platinum wire was used for the counter electrode (C), and three carbon electrodes (3 mm in diameter) as working electrodes were installed in a glass tube. . As shown in Fig. 1 (b), these glass tubes are attached with a lid with a 3mm diameter hole, one of the three glass tubes is used as it is, and the other two are average molecular weights. Were used after plugging the holes with different PLGA5005 (blending ratio 50:50, average molecular weight 5000) and PLGA5015 (blending ratio 50:50, average molecular weight 15000). PLGA was applied using 10 μl of a 1 g / ml PLGA solution dissolved in hexafluoro-2-propanol. FIG. 1 (c) is a cyclic voltammogram measured immediately after the start of the experiment, 15 minutes later and 40 minutes later. The redox current of ferrocenemethanol has doubled and tripled, the PLGA membrane has decomposed with a time difference, and the solution has flowed into the glass tube, so the area of the working electrode has doubled and tripled. Is reflected.

(Time difference power generation of biofuel cells)
The time difference type operation of the biofuel cell was performed with the experimental apparatus shown in FIG. The solution is a phosphate buffer aqueous solution containing 50 mM glucose (D (+)-Glucose, Mw: 180.16) and 1 mM NADH, and the temperature of the solution is kept at 35 ° C. A biofuel cell composed of an enzyme-immobilized anode and a Pt cathode was inserted into three glass tubes produced in the same manner as in Example 1, and the voltage generated at an external load of 100 kΩ was measured. The anode on which the enzyme was immobilized was prepared by laminating two kinds of enzymes. First, diaphorase, an enzyme that generates NAD ⁺ to oxidize NADH, immobilized by coating on a carbon electrode with poly -L- lysine and Ketchen black was modified vitamin K _3.
On top of that, a NAD ⁺ -dependent glucose dehydrogenase that oxidizes glucose was applied together with poly-L-lysine. As a result of the reaction of the two kinds of enzymes described above, an electrode having the ability to oxidize glucose and extract electrons is obtained. On the other hand, in the Pt cathode, a reduction reaction occurs in which these electrons are transferred to dissolved oxygen.

FIG. 2B shows the change in output voltage for 2000 seconds after the start of measurement. It can be seen that the output voltage suddenly increases at about 450 seconds and about 1600 seconds. This is a change caused by the collapse of the PLGA5005 and PLGA5015 membranes, and it can be said that the time difference power generation of the biofuel cell was successful. Since the three electrodes are connected in parallel, the output voltage does not exceed the electromotive force (voltage at open circuit) of the glucose fuel cell, but it can be said that it has become closer to the electromotive voltage as the electrode area increases. . This is because the power generation allowable value of the battery is increased, and the influence of the voltage drop due to the flow of current is relatively reduced. In this example, it was not possible to carry out experiments for a long time so that the performance of the battery was significantly deteriorated. I think that it can be made clear that the time difference operation is effective.

(Time difference type power generation of biofuel cells arranged on a flat plate)
As shown in FIG. 3 (a), a Pt electrode pattern (for cathode) and an Au electrode pattern (for anode) were formed on a glass plate by photolithography and sputtering. The enzyme was immobilized on the Au electrode in the same manner as in Example 2. Then, as shown in FIG. 3B, a PLA plate having a hole with a diameter of 3 mm on the upper surface and a diameter of 8 mm on the lower surface was attached. Similar to Example 1 and Example 2, the holes are closed by PLGA5005 and PLGA5015. The lead part of the electrode was insulated with polyimide. This plate battery was inserted into a phosphate buffer solution (35 ° C) containing 50 mM glucose (D (+)-Glucose, Mw: 180.16) and 1 mM NADH, and the output voltage was adjusted in the same way as in Fig. 2 (a). Changes were measured.

The output voltage measurement results were poorly reproducible and unstable. This was thought to be because the gas present in the electrode part did not escape and the electrolyte solution did not enter quickly even when PLGA was decomposed. Therefore, as shown in FIG. 3 (c), the electrode part was filled with cotton so that the electrolyte solution easily penetrated, and the result shown in FIG. 3 (d) was obtained. An increase in output voltage, which seems to correspond to the decomposition of PLGA, was confirmed. The reason that it takes longer than Example 2 is thought to be because there is no water pressure that promotes the collapse of the polymer when a glass tube is used.

  In Example 3, there are three sets of electrodes, but it is possible to arrange a larger number of batteries on the same substrate using a microfabrication technique, and each battery is covered with a biodegradable polymer by an inkjet printer or the like. By doing so, it is possible to produce a biofuel cell that is smaller and can generate power over a long period of time. In Example 3, a substrate is used, but it is also possible to produce a plastic sheet.

  Furthermore, since the cathode Pt electrode used in Example 3 has high chemical stability, it does not necessarily have to be coated with a biodegradable polymer, and only the anode on which a chemically unstable enzyme is immobilized is coated. A similar effect is achieved. Thereby, further miniaturization becomes possible. In order to increase the number of electrodes per volume, a structure in which a substrate or a sheet is laminated is also conceivable.

(Production of biofuel cell electrodes)
FIG. 4 shows a method for producing a biofuel cell in which all parts are made of organic materials. In FIG. 3, Au and Pt, which have no biodegradable function, are used as the anode and cathode electrodes, respectively, but an attempt was made to produce an electrode using only organic substances. First, a carbon electrode was produced on a Teflon (registered trademark) sheet using a printing method. Carbon here refers to carbon black and is treated as an organic substance. Next, a cylindrical PLA was placed on the carbon electrode, and the PLA was deformed into a plate by pressing with two pressing plates in the plate thickness direction. After pressurization, when the Teflon (registered trademark) sheet was removed, it was confirmed that the carbon electrode was transferred to the PLA side. The size of the PLA plate was 30mmx30mmx3mm. By installing an anode catalyst and a cathode catalyst on the carbon electrode, and further covering both electrodes with PLGA, a biofuel cell that starts power generation after a predetermined time difference is manufactured. The substrate must be a biodegradable material that has a longer degradation rate than the coating material. As the electrode, an organic substance having conductivity such as carbon can be used, and an electrode prepared by mixing carbon powder and a biodegradable substance can be used as long as the conductivity is not hindered. Here, PLA and PLGA are shown as biodegradable materials, but the materials are not limited to them, and any material can be used as a substrate material as long as it is a biodegradable material having a longer decomposition time than a coating material. Also good. The substrate mentioned here can be handled as a structural material constituting the fuel cell.

(Production of time difference type small power generation device)
(a) Preparation of PLGA thin film PLGA having a mixing ratio of lactic acid and glycolic acid of 1: 1 was used. PLGA5005 (Mw. 5000, Wako Chemical Industry) and PLGA5015 (Mw. 15000, Wako Chemical Industry) were used for PLGA. Since PLGA is very fragile when thin, it was made into a composite and increased in strength. The strength was improved by dispersing nanoclay (Cloisite30B, Southern Clay Products) in PLGA to make a composite.
Mix PLGA and nanoclay thoroughly in a weight ratio of 96: 4. The obtained mixture was dissolved in 1,1,1,3,3,3-Hexafluoro-2-propanol (hexafluoropropanol, Wako) at a concentration of 0.2 mg / mL. The obtained product is used as a PLGA solution, but nanoclay is not dissolved and is in a dispersed state. Therefore, a necessary amount was taken out after sufficiently dispersing using an ultrasonic cleaner immediately before use.

(b) Preparation of PDMS mold used for PLGA thin film production
In order to mold a PLGA thin film, PDMS having a thin film pattern was used as a mold. To produce a PDMS mold using microfabrication technology, SU-8, a thick film negative resist, was patterned into the desired thin film shape and transferred to PDMS. PLGA is suitable as a mold material because it can be easily peeled off from PDMS.
(1) The substrate was prepared as follows. Glass slide (MICRO SLIDE GLASS, Thickn
ess 0.8-1.0 mm, MATSUNAMI) was ultrasonically washed in an ethanol solution and dried. (2) The mask was manufactured as follows. The mask pattern was drawn with drawing software and printed on a commercially available OHP sheet in black. (3) Photolithography was performed as follows. (i) Spin coat (ACT-220D, Active) (4000rpm, 30sec) on substrate (AZ AD promoter, AZ Electronic Material Co., Ltd.) and use hot plate (TH-900, AS ONE) at 100 ° C Bake for 10 min. (ii) A photoresist (SU-8 2050, Kayaku Microchem Corporation) is spin coated (2000 rpm, 30 sec; thickness 70 μm). (iii) Raise the temperature gradually and bake at 95 ° C for 15 min. (iv) A mask is brought into close contact with the substrate and exposed for 33 seconds using an exposure apparatus (UIV-5100, USHIO). (v) Raise the temperature gradually and bake at 95 ° C for 9 min. (vi) The developer was developed in a developer (SU-8 developer, Kayaku Microchem Co., Ltd.) for 10 min, and rinsed with isopropanol for 1 min × 2 (FIG. 5 (a)). (4) Mix PDMS main agent (SILPOT 184, DOW CORNING TORAY) and curing agent (CATALYST SILPOT 184, DOW CORNING TORAY) at a weight ratio of 10: 1, stir well, and then thoroughly deaerate. Pour into the prepared SU-8 mold. (5) After baking in an oven and fully cured, it was removed from the SU-8 mold and the necessary part was cut out (Fig. 5 (b)
).

(c) Preparation of PLGA thin film
The procedure for forming a PLGA thin film using a PDMS mold was performed as follows. A flat PLGA thin film was obtained by embossing because a flat film was not obtained by simply drying the droplets. Using the glass microsyringe, 8 μl of the PLGA dispersion prepared in (a) above is dropped into the recess of the PDMS mold. Next, it is dried at room temperature for several hours. When the fluidity disappeared, it was dried for 2 days or more at 40 ° C. under reduced pressure in a vacuum oven (AVO-250N, AS ONE). Next, both surfaces were sandwiched between slide glasses, pressurized with hot embossing (AH-2003, AS ONE) heated to 120 ° C. (0.2 MPa), cooled, and then removed.

(d) Fabrication of electrode and PLGA thin film mounting frame An electrode substrate was fabricated using microfabrication technology. A frame for bonding the PLGA thin film to the electrode was prepared. The frame was manufactured as follows. First, the electrode substrate after lift-off was ultrasonically cleaned with ethanol and dried. Promoter (AZ AD Promoter, AZ Electronic Material Co., Ltd.) is spin-coated (ACT-220D, Active) (4000rpm, 30sec) on the substrate, and hot plate (TH-900, AS ONE) is used for 10 min at 100 ° C. I was Photoresist (SU-8 2050, Kayaku Microchem Co., Ltd.) is spin-coated (1000rpm 30sec), then gradually raised in temperature, baked at 95 ° C for 30min, aligned with the substrate and brought into close contact with the mask Then, exposure was performed for 60 seconds using an exposure apparatus (UIV-5100, USHIO). The temperature was raised gradually, the mixture was baked for 12 minutes, developed in a developer (SU-8 developer, Kayaku Microchem Co., Ltd.) for 15 minutes, and rinsed with isopropanol for 1 minute × 2 times. This electrode is shown in FIG. Hereinafter, the electrode with the SU-8 frame (height 150 μm) was used as a time difference device electrode.

(e) Adhesion of PLGA thin film In order to cut off the enzyme electrode from the fuel, it is necessary to adhere the prepared PLGA thin film to the upper surface of the enzyme electrode. Will be invited. Although the use of an adhesive is also conceivable, it is difficult to accurately apply a minute amount of the adhesive. Therefore, CO ₂ bonding was used as a method for bonding PLGA and the enzyme electrode. In this bonding method, the sample to be bonded is stuck in a pressure vessel at around 40 ° C, filled with CO ₂ gas, and the pressure is increased, so that the high density CO ₂ gas dissolves the PLGA surface. It can be glued. There are reports that cells can survive even in the CO ₂ gas used. In this example, the inside of the pressure vessel was made constant at 35 ° C. In CO ₂ bonding, it was suggested that CO ₂ gas was dissolved in the PLGA while diffusing in the PLGA from the outer periphery to the inside of the bonding surface. The time-difference type device electrode obtained in the above (d) and the PLGA thin film obtained in the above (c) were adhered. In CO ₂ bonding, the setting conditions of CO ₂ pressure and pressurizing time during processing can be changed depending on the bonding area (bonding distance), and for example, bonding can be performed with an applied pressure of 0.5 MPa and an applied time of 30 minutes.

(f) Time difference energization test using time difference type small power generation device By covering the electrode (prepared in (d) above) with the PLGA thin film obtained in (c) above, the electrode is cut off from the solution, and by the collapse of PLGA, It was examined whether it was possible to expose the electrode to the solution with a time difference.
A PLGA thin film manufactured using PLGA5005 and PLGA5015 was bonded to each electrode by CO ₂ bonding (0.5 MPa, 30 min). A 0.1 mM ferrocene methanol solution was fed into a PDMS channel (channel height 1 mm, channel width 5 mm) with a peristaltic pump at a flow rate of 0.5 mL / min (FIG. 7). Cyclic voltammetry (CV method, potential sweep rate 5mVs ^-1 ) measurement by potentiostat is started at the same time as the measurement solution passes through the upper surface of the PLGA thin film, and the same potential is measured every 3 minutes.
Repeatedly measured.
The current value at a potential of 0.3 V in the cyclic voltammogram was acquired according to the elapsed time. With the electrode covered with PLGA5005, the current was almost zero until 60 min after the introduction of the solution and with the electrode covered with PLGA5015 until 500 min, and the electrode was blocked from the solution by the PLGA thin film. In addition, with the electrode covered with a thin film using PLGA5005, the current value gradually increased, and we succeeded in making the electrode function with a time difference. We succeeded in making a time difference even with an electrode covered with a thin film electrode using PLGA5015. It was found that the disintegration processes of the two types of PLGA thin films were different.

(g) Time difference energization test using enzyme electrode
The time difference was verified using a glucose oxidation electrode covered with a PLGA thin film.
The PLGA thin film (PLGA5005) obtained in (c) above is bonded to the electrode prepared by enzyme modification on the substrate prepared in (d) above by CO ₂ bonding (0.5 MPa, 30 min). A fuel solution containing 1 mM NAD ⁺ , 10 mM glucose, and 0.1 M NaCl at a flow rate of 0.5 mL / min was fed into a PDMS channel (channel height 1 mm, channel width 5 mm) with a peristaltic pump (FIG. 7).
As soon as the measurement solution passed through the upper surface of the PLGA thin film, linear sweep voltammetry (LSV method, potential sweep rate 5 mV s ^-1 ) measurement using a potentiostat was started, and the same potential was repeatedly measured every 3 minutes.
FIG. 8 shows the result of plotting the current value of the potential 0 V of the obtained linear sweep voltammogram according to the elapsed time. In the electrode covered with the PLGA thin film from 0 min to 40 min into which the solution was introduced, no current was observed and the enzyme electrode was cut off from the fuel by the PLGA thin film. After that, an increase in current value was gradually obtained, and energization with a time difference was observed. However, a problem was observed in which the PLGA thin film remained on the enzyme electrode caused the fuel inflow rate through the PLGA thin film to be slower than the glucose consumption rate of the enzyme electrode.

(h) Electrode performance stability test of time difference type small power generation device Since it was confirmed that time difference glucose oxidation can be performed as described above, the stability of the time difference power generation biofuel cell was evaluated. A time difference power generation fuel cell in which enzyme electrodes are arrayed was constructed by using PLGA thin films having molecular weights different from Mw 5000 and Mw 15000 and having different decomposition rates.
The PLGA thin film (PLGA5005, 5015) obtained in (c) above is bonded to the electrode prepared by enzyme modification on the substrate prepared in (d) above by CO ₂ bonding (0.5 MPa, 30 min). Fuel containing 1 mM NAD ⁺ , 10 mM glucose and 0.1 M NaCl at a flow rate of 0.5 mL / min in a flow channel cell (Fig. 9) with PDMS flow channel (flow channel height 1 mm, flow channel width 5 mm) The solution was poured. At the same time as the measurement solution passed through the upper surface of the PLGA thin film, a constant voltage of 0 V was applied by a potentiostat to start measurement. For comparison, the measurement of one enzyme electrode not covered with a PLGA thin film was performed in the same manner.
A current-time curve is shown in FIG. Compared to the current value (a) with only one electrode, the performance declined more slowly and stability was improved. This is because the enzyme electrodes that were cut off from the fuel in PLGA5005 and 5015 started to wet into the solution with a time lag and the glucose oxidation started as the performance of the uncoated electrodes deteriorated with the passage of time. However, since the current value gradually increased, it is considered that the current value as a whole was improved. Table 1 shows the current value after elapse of time, with the maximum current value after the start of measurement being 100%.

As described in (g) above, regarding the enzyme electrode in which the fuel was blocked with the PLGA thin film, the amount of glucose supplied was not sufficient, so that a current value comparable to that of the electrode not covered with the PLGA thin film could not be obtained. After 8 hours, a slight recovery in performance was observed. This is thought to be because the PLGA thin film, which was easily perforated by decomposition, was greatly deformed by the influence of the fuel flow and the inflow of glucose increased.

According to the present invention, a bio battery can be operated in a time difference manner and a long-life battery can be provided. Therefore, a disposable battery, a battery using glucose as a fuel, a battery for an in-vivo medical device, and a battery for a skin patch medical device It can be applied to skin-applied cosmetic batteries (packs, etc.) and contributes to biodevice development including the medical field.
It will be apparent that the invention may be practiced otherwise than as particularly described in the foregoing description and examples. Many modifications and variations of the present invention are possible in light of the above teachings, and thus are within the scope of the claims appended hereto.

Activation of the electrode by penetration of the electrolyte solution by decomposition of the biodegradable polymer according to the invention. (A) Experimental configuration diagram. (B) A photograph of the glass tube used in the experiment. (C) Cyclic voltammograms measured immediately after the start of the experiment, after 15 minutes and after 40 minutes. The potential scanning speed is 50mV / s. Time difference power generation of a biofuel cell according to the present invention. (A) Experimental configuration diagram. (B) Change in output voltage with time at a load of 100 kΩ. Time difference power generation of a biofuel cell produced on a flat plate according to the present invention. (A) Photo of electrode prepared on glass plate (b) Photo of electrode substrate covered with PLGA. (C) Explanatory drawing that electrolyte solution becomes easy to penetrate | invade by packing cotton in an electrode part. (D) Change in output voltage with time at a load of 100 kΩ. A biofuel cell electrode according to the present invention. (A) Appearance photograph. (B) A method for manufacturing an electrode. The thin film pattern (a) and PDMS template (b) in preparation of the PDMS template used for PLGA thin film manufacture according to this invention are shown. 1 shows an electrode for a time difference device according to the present invention. The experimental block diagram in the time difference electricity test using the time difference type small power generation device according to this invention is shown. The graph which plotted the electric current value of the electric potential 0V of the linear sweep voltammogram obtained in Example 5 (g) according to elapsed time is shown. The experimental block diagram in the electrode performance stability test of the time difference type small power generation device according to this invention is shown. The current-time curve obtained in Example 5 (h) is shown. 1 shows a specific example in which a lid for isolating an electrode from a fuel solution is bonded with a biodegradable polymer in a time difference type small power generation device according to the present invention. A plurality of partition walls separating the electrodes from the fuel solution in the time difference type small power generation device according to the present invention are composed of the same biodegradable polymer, and the plurality of partition walls are sequentially brought into contact with the solution to be decomposed. A specific example is shown in which the electrodes are sequentially operated. A plurality of partition walls separating electrodes from a fuel solution in a time difference type small power generation device according to the present invention, wherein the plurality of partition walls are broken by a mechanical switch, and the plurality of electrodes are sequentially operated. A specific example is shown.

Claims (13)

The battery electrode portion that is isolated from the electrolyte solution has at least one battery is connected two or more, the electrolyte solution generator is started by wetted the electrode portion is isolated from the electrolyte solution Thus, a biobattery is characterized in that power generation is performed sequentially with the two or more connected batteries. The biobattery according to claim 1, wherein the electrode part is in contact with the electrolyte solution sequentially by decomposition of the biodegradable polymer. The biobattery according to claim 1 or 2 , wherein the biodegradable polymer is used as a partition wall that separates the electrode portion from the electrolyte solution . The biodegradable polymer is characterized in that a partition plate or lid between a container or compartment containing an electrode part and an electrolyte is used as an adhesive for adhering to the container or the compartment. The biobattery according to claim 1 or 2. By a structure wherein the biodegradable polymer electrolyte solution by being decomposed is started sequentially generates electricity by liquid contact to the electrode portion, claim 2-4, characterized in that the long-term power can be maintained The bio battery according to 1. Wherein the biodegradable polymer is used as the between disassembling least two different types, according to claim 2-4 either single, characterized in that the long-term power can be maintained by sequentially generating starts with the decomposition The bio battery according to 1. The biobattery according to claim 1, wherein the electrode part is in contact with the electrolyte solution sequentially by a mechanical switch. The biobattery according to any one of claims 2 to 6, wherein the biodegradable polymer includes polylactic acid, polyglycolic acid, a copolymer of lactic acid and glycolic acid, or a derivative thereof. The bio battery according to any one of claims 1 to 8, wherein the bio battery is a battery that generates electricity using an enzyme as an electrode catalyst and a fuel selected from the group consisting of sugar, lactic acid, and alcohol. battery. The biobattery according to any one of claims 1 to 8, wherein the biobattery is a battery that uses a microorganism to generate electricity using a fuel selected from the group consisting of sugar, lactic acid, and alcohol. . The biobattery according to any one of claims 1 to 10, wherein the biobattery has a sheet-like shape in which two or more micro batteries of millimeter order or less are arranged in a plane. The biobattery according to any one of claims 1 to 11, wherein all parts including an electrode and a structural material are made of an organic substance. The electrode part is isolated from the electrolyte solution using a biodegradable polymer, and the electrolyte solution is in contact with the electrode part when the biodegradable polymer is decomposed to generate power. A battery or a power generation device.