Self-driving biosensors, wearable devices

Abstract

The objective is to obtain a self-driving biosensor that has power generation and monitoring functions on its own, without the use of external devices. [Solution] The self-driving biosensor according to this disclosure comprises a biofuel cell that generates electricity by the oxidation of fuel, and a display that shows visual changes according to the concentration of the fuel.

Description

[Technical Field]

[0001] This disclosure relates to a self-driving biosensor equipped with a biofuel cell, which has both a power generation function and a monitoring function on its own. [Background technology]

[0002] A biofuel cell is a battery that uses enzymes as electrode catalysts and generates electricity using sugars, alcohols, and other biomass resources as fuel. For example, a lactic acid biofuel cell generates electricity by utilizing the oxidation reaction of lactic acid at the anode and the reduction reaction of oxygen at the cathode. By fabricating the electrodes of the biofuel cell on a paper substrate or the like using screen printing, a small, safe, and highly biocompatible battery has been obtained, and research into its application to wearable sensors and the like is currently underway (for example, Patent Document 1, Non-Patent Document 1).

[0003] Since lactic acid is found in human sweat and is used to monitor health status, its use in wearable sensors is expected to enable monitoring of health status during exercise. Non-patent document 1 discloses a self-powered wearable lactic acid sensing device that is capable of wireless communication and uses lactic acid from sweat as fuel. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6994184 [Non-patent literature]

[0005] [Non-Patent Document 1] Isao Shitada, et al., "Development of a Self-Driven Biosensor Capable of Generating Electricity from Bodily Fluids and its Application to Health Monitoring," Surface Technology, Japan Surface Technology Association, January 2023, Vol. 74, No. 1, pp. 38-42. [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the sensing device described in Non-Patent Document 1 requires an external device such as a smartphone as a wireless communication receiver for operation verification. Therefore, the present disclosure aims to provide a self-driving biosensor that has power generation and monitoring functions on its own without using an external device such as a smartphone. [Means for solving the problem]

[0007] The embodiments for solving the above problems include the following embodiments. [1] Biofuel cells that generate electricity through the oxidation of fuel, The system includes a display that shows visual changes according to the concentration of the fuel, Self-propelled biosensor. [2] The display includes a material whose absorbance changes in response to changes in the concentration of the fuel in the wavelength range of 350 nm to 850 nm. The self-driving biosensor described in [1] above. [3] The display changes color tone according to the concentration of the fuel. The self-driving biosensor described in [1] or [2] above. [4] The aforementioned display includes an electrochromic material, A self-driving biosensor according to any one of the above [1] to [3]. [5] The aforementioned display includes PEDOT:PSS, A self-driving biosensor as described in any one of the above [1] to [4]. [6] A self-driving biosensor according to any one of the above [1] to [5], It comprises an adhesive member for attaching to the wearer's skin, Wearable devices. [Effects of the Invention]

[0008] According to the present disclosure, a self-powered biosensor having a power generation function and a monitoring function as a single unit can be obtained without using an external device. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] [Figure 1] It is a schematic diagram showing the power generation principle of a lactic acid biofuel cell. [Figure 2] It is a schematic diagram comparing the operation of wearable devices. [Figure 3] It is a schematic diagram of a BFC produced by screen printing. [Figure 4] It is a graph showing an LSV curve of a lactic acid biofuel cell. [Figure 5] It is a graph showing the results of a cyclic voltammogram of PEDOT:PSS. [Figure 6] It is a photograph showing the change in color tone of PEDOT:PSS. [Figure 7] It is a graph showing the change in absorbance of PEDOT:PSS due to a change in voltage. [Figure 8] It is a schematic diagram of an apparatus used for absorbance measurement of PEDOT:PSS for each lactic acid concentration. [Figure 9] It is a graph showing the change in absorbance of PEDOT:PSS for each lactic acid concentration. [Figure 10] (A) and (B) are diagrams illustrating the design of a self-powered biosensor. [Figure 11] (A) and (B) are diagrams illustrating the stacking order of the self-powered biosensor. MODE FOR CARRYING OUT THE INVENTION

[0010] Embodiments of the present invention will be described below with reference to the drawings. In each drawing, identical or corresponding parts are denoted by the same or similar reference numerals, and redundant explanations are omitted. Furthermore, the present invention is not limited to the following embodiments. In addition, in this specification, numerical ranges indicated using "~" include the numbers before and after "~" as the minimum and maximum values, respectively.

[0011] [Self-propelled biosensor] A self-driving biosensor according to the first embodiment of this disclosure comprises a biofuel cell that generates electricity by the oxidation of a fuel, and a display that shows a visual change according to the concentration of the fuel. Hereafter, the biofuel cell may be referred to as "BFC".

[0012] [Biofuel cell] Biofuel cells (BFCs) generally have electrodes, with the anode containing an enzyme that promotes the oxidation of the fuel. Electrons extracted by the oxidation of the fuel at the anode (for example, the conversion of glucose to gluconolactone) move to the cathode, where they are used to reduce oxygen and produce water (H2O). The electron transfer resulting from this process is used to generate electricity. By using enzymes as catalysts, biofuel cells can carry out the reaction under very mild conditions (room temperature and in a neutral solution).

[0013] For example, the biofuel cell of this disclosure comprises a substrate, electrodes (anode and cathode) formed on the substrate, a catalyst (enzyme) immobilized on each electrode, and a mediator immobilized on the electrodes as needed. The biofuel cell of this disclosure is configured such that fuel is supplied from an external source, and the fuel that reaches the anode undergoes an oxidation reaction at the anode.

[0014] As an example, let's explain the case of using lactic acid as fuel in a biofuel cell. A lactic acid biofuel cell generates electricity by oxidizing lactic acid, a biological substance. In a lactic acid biofuel cell, lactate oxidase (LOx) is used as a catalyst to promote the reaction of extracting electrons from lactic acid (oxidation). When LOx is placed on an electrode and electrons extracted from lactic acid are transferred to the electrode, an electric current flows. The higher the concentration of lactic acid, the more electrons are transferred to the electrode, and therefore the greater the current that flows. Thus, the current value of a lactic acid biofuel cell depends on the lactic acid concentration.

[0015] Figure 1 shows a schematic diagram of the power generation principle of a lactic acid biofuel cell. When LOx is fixed on the electrode, electrons are extracted to the electrode by oxidation (Ox) of lactic acid (L-lactate), producing pyruvate. In other words, the electrode functions as an anode. When an enzyme that catalyzes the oxygen reduction reaction (e.g., bilirubin oxidase, BOD) is fixed to the electrode that becomes the cathode, a reaction occurs in which electrons are transferred to oxygen to form water (reduction, Red). In addition, an electron transfer substance (a mediator that facilitates the transfer of electrons from the enzyme to the electrode) may also be fixed to the anode.

[0016] Although lactic acid was used as an example, the type of fuel used in the biofuel cell of this disclosure is not particularly limited as long as it is a substance whose oxidation is promoted by enzymes. For example, in addition to lactic acid, it may be sugars, alcohols, aldehydes, amino acids, amines, uric acid, etc. The fuel may be one type or two or more types. Furthermore, the fuel may be oxidizable in its original state by enzymes contained in the anode, or it may become oxidizable through hydrolysis, etc. (for example, starch that becomes glucose through hydrolysis). For example, these fuels may be components of body fluids (glucose, lactic acid, uric acid, etc.). For example, lactic acid is present in the sweat of healthy individuals at a concentration of approximately 5-40 mM, and if lactic acid in sweat is used as fuel, it can be monitored non-invasively as a real-time vital sign.

[0017] When using biofuel cells as wearable devices, disposable devices, etc., the fuel may contain sugars from the viewpoint of safety, biocompatibility, output stability, and ease of handling. The type of sugar is not particularly limited and includes monosaccharides (e.g., glucose), disaccharides, oligosaccharides, polysaccharides, sugar alcohols, etc.

[0018] In biofuel cells, the anode preferably contains an enzyme that promotes the oxidation of the fuel. The type of enzyme that promotes fuel oxidation is not particularly limited and can be selected according to the type of fuel to be oxidized. The anode may contain only one type of enzyme or two or more types. Alternatively, a combination of a catalyst, such as an enzyme that makes the fuel oxidizable through hydrolysis, and an enzyme that promotes oxidation may be used.

[0019] When the fuel is sugar, the enzymes used are specifically glucose oxidase and glucose dehydrogenase when the fuel is glucose, fructose oxidase and fructose dehydrogenase when the fuel is fructose, a combination of invertase and glucose dehydrogenase when the fuel is sucrose, and a combination of amylase and glucose dehydrogenase when the fuel is starch. When the fuel is a substance other than sugar, for example lactic acid, the enzyme used is the aforementioned lactate oxidase.

[0020] In a biofuel cell, the cathode preferably contains a catalyst that promotes oxygen reduction. The type of catalyst is not particularly limited and may be organic or inorganic. From the viewpoint of disposability and biocompatibility, organic materials are preferred. Examples of organic materials include enzymes that promote oxygen reduction, such as bilirubin oxidase and laccase. Examples of inorganic materials include metal catalysts such as platinum. The cathode may contain only one type of catalyst or two or more types.

[0021] The type of mediator is not particularly limited; any commonly used mediator can be used. Examples include thionine, tetrathiafulvalene, 1,2-naphthoquinone, 1,4-naphthoquinone, osmium complexes, ferrocene analogs, potassium ferricyanide, potassium ferrocyanide, benzoquinone analogs, methylene blue, methylene green, dopamine, azur A, or high molecular weight polymers thereof.

[0022] The material of the substrate in a biofuel cell is not particularly limited and may be a natural or synthetic material. From the viewpoint of environmental and biocompatibility, paper, nonwoven fabric, cloth, etc., made from natural or biodegradable materials are preferred. From the viewpoint of preventing short circuits between the anode and cathode caused by the liquid containing the fuel supplied to the biofuel cell (e.g., sweat), a water-repellent substrate or a substrate made of a material that does not absorb liquid may be used. The thickness of the substrate is not particularly limited and can be selected according to the shape of the biofuel cell. For example, the substrate may be ITO glass, paper, cloth, nonwoven fabric, transfer sheet, or other flexible substrates. ITO glass is preferred because ITO is chemically stable and can withstand oxidation and reduction reactions well. Paper is preferred because it is inexpensive, lightweight and easy to carry, has good storage properties, and can be incinerated or disposed of after use. Furthermore, paper has high biocompatibility, can fix chemical substances, and can allow liquid to penetrate into its hydrophilic fibers through capillary action. In addition, by using printing technology, small biofuel cells can be manufactured on the substrate inexpensively and in large quantities.

[0023] The material of the electrodes (also called anodes or cathodes) in a biofuel cell is not particularly limited as long as it contains a conductive material. Examples of conductive materials include carbon materials and metals, and carbon materials are preferred from the viewpoint of disposability and biocompatibility. Examples of carbon materials include graphite, carbon black (Ketjenblack, acetylene black, etc.), mesoporous carbon produced by a molding method such as MgO-based carbon (preferably porous carbon with meso / macropore size of 10 nm to 150 nm and particle size of 0.5 μm to 10 μm), and carbon nanomaterials. One type of carbon material may be used, or two or more types may be used in combination.

[0024] The position in which the enzyme or catalyst is placed on the electrode is not particularly limited. From the viewpoint of efficiently obtaining the oxidation or reduction promoting effect of the enzyme or catalyst, it is preferable to place it on the surface of the electrode that is in contact with the fuel or oxygen. As a method to increase the surface area of ​​the electrode in contact with the fuel or oxygen and improve power generation efficiency, one method is to form an electrode with pores and place the enzyme or catalyst inside the pores. From the viewpoint of forming an electrode with pores, it is preferable to use a particulate material as the conductive material, and more preferable to use a particulate material with pores. Examples of particulate materials with pores include mesoporous carbon produced by a template method such as MgO template carbon.

[0025] The position of electrodes in a biofuel cell is not particularly limited. From the viewpoint of making the biofuel cell thinner, it is preferable that the electrode material be applied to a substrate by screen printing or the like. In this case, the anode and cathode may be formed on the same substrate, or they may be formed on different substrates.

[0026] Leads may be formed on the substrate to electrically connect the electrodes. These leads can be formed using commonly available conductive materials. The leads may have through-holes in the portion in contact with the cathode to increase the oxygen supply to the cathode.

[0027] The shape of the electrodes in a biofuel cell is not particularly limited. From the viewpoint of improving power generation efficiency, they may be in a patterned shape with multiple anodes or cathodes connected together.

[0028] A biofuel cell may have other components besides electrodes, if necessary. For example, protective materials to protect the biofuel cell from the outside air.

[0029] [display] The self-driving biosensor relating to this disclosure includes a display that shows visual changes. The display that shows visual changes may be an electrochromic display (hereinafter sometimes referred to as "ECD"). In this disclosure, since it is possible to combine the above-mentioned biofuel cell (BFC) with an electrochromic display (ECD), the electrochromic material of the ECD can be made to produce visual changes in accordance with the amount of electricity of the biofuel cell (i.e., the concentration of the fuel).

[0030] An electrochromic display is a display element that utilizes the electrochromic phenomenon, in which the color of a substance reversibly changes through an electrochemical oxidation-reduction reaction, making it a device capable of displaying information as a visual change. However, conventional electrochromic display devices required an external circuit to control the color tone. From a practical standpoint, the presence of an external circuit increased manufacturing costs and prevented the device from being disposable as a simple, portable device. Therefore, through trial and error, we developed an electrochromic display that could be constructed simply by printing ink onto the entire surface of paper or elastomer-based materials, thereby reducing costs and realizing a disposable electrochromic display. By combining this electrochromic display with a biofuel cell, it became possible to visually confirm the operation of the biofuel cell with a standalone device.

[0031] For example, an electrochromic display may be formed on the same substrate as the biofuel cell by screen printing or the like, and lead portions may be arranged to electrically connect the electrochromic display to the electrodes (anode and cathode) of the biofuel cell. The shape and size of the electrochromic display are not particularly limited. It is sufficient if the shape and size allow the wearer to confirm the change in color when the self-driving biosensor of this disclosure is attached. The thickness is also not particularly limited and can be selected according to the shape of the self-driving biosensor, etc. Configurations combining a biofuel cell and an electrochromic display will be described in more detail in the embodiments described later.

[0032] The electrochromic display of this disclosure comprises at least a substrate and electrodes (anode and cathode) formed on the substrate, and an electrolyte arranged between the electrodes such that an electrochemical reaction proceeds. At least one of the electrodes contains an electrochromic material. The substrate and electrodes may be those described in the biofuel cell section. Examples of electrolytes include phosphoric acid, phosphate, sodium sulfate, sodium chloride, potassium chloride, and the like.

[0033] Electrochromic materials are not particularly limited in type, as long as they are substances that exhibit electrochromic properties. They may be metal oxides or organic compounds. Examples include oxide nanowires (tungsten oxide, molybdenum oxide, etc.), conjugated organic compounds (PEDOT:PSS, PRODOT, NPBDF, etc.), metal ions (silver, iron, etc.), and metal complexes in general.

[0034] As an example, PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid)) is a conductive polymer whose color intensity changes with oxidation-reduction reactions. PEDOT:PSS has a structure in which PEDOT, a π-conjugated polymer, is doped with PSS as an acceptor. As PEDOT is reduced, cations in the solution are doped into the PSS polymer. The oxidation-reduction reaction of PEDOT:PSS is as shown in equation (1) below. PEDOT n+ PSS m- +ne - +nC + ⇔PEDOT 0 (C + ) n PSS m- (1) (C + cations in solution)

[0035] As described above, the "self-powered biosensor" of the present disclosure functions by, for example, reacting fuel in body fluid with an enzyme of a biofuel cell to extract electric power, and causing the electrochromic material to undergo a redox reaction by using this electric power, thereby serving both as a power source and a monitoring sensor. Since the amount of electric power generated by the biofuel cell depends on the concentration of the fuel, a redox reaction occurs in the electrochromic display according to the amount of electric power corresponding to the fuel concentration, and as a result, a visual change corresponding to the fuel concentration is exhibited.

[0036] [Wearable device] A wearable device according to a second embodiment of the present disclosure comprises the self-powered biosensor according to the first embodiment, and an affixing member for affixing to the skin of a wearer. With this configuration, the self-powered biosensor can be directly fixed to the skin of the wearer. The affixing member may be an adhesive tape member. For example, the tape member may be one in which an adhesive is applied to both surfaces of a base material made of nonwoven fabric. That is, a double-sided tape can be used as the tape member. One adhesive surface of the double-sided tape may be affixed to the wearer's skin. The other adhesive surface may be affixed to a substrate of the self-powered biosensor. Furthermore, an opening may be formed in the tape member to serve as a flow path for a fuel-containing solution (e.g., sweat).

[0037] If the substrate of the self-driving biosensor is made of paper, the self-driving biosensor may be placed on the skin so that the side of the substrate without electrodes is in contact with the skin, and then secured to the skin with transparent surgical tape to cover the self-driving biosensor. In other words, the surgical tape functions as an adhesive material. With this configuration, a fuel-containing solution (e.g., sweat) secreted from the skin is absorbed by the paper substrate, and oxidation of the fuel (e.g., lactic acid) occurs at the anode of the biofuel cell. Electrons generated by the oxidation of the fuel move from the anode to the electrochromic display and then to the cathode of the biofuel cell, and the electrons that have moved to the cathode reduce oxygen supplied from the outside air. Through this process, power is generated, and at the same time, the electrochromic display displays a color tone corresponding to the fuel concentration. The wearable device of this disclosure can be used as a new healthcare tool that can diagnose exercise efficiency, fatigue level, etc., simply by being attached to the body.

[0038] As described above, by combining a biofuel cell with a color-changing electrochromic display, it is possible to enable, for example, simpler monitoring of exercise status. Refer to Figure 2 to compare a conventional wearable device with the wearable device of this disclosure. Figure 2(A) illustrates a conventional wearable device. A biofuel cell (BFC) is connected to a wireless transmission device (WTD), and when the wireless transmission device is driven by the power generated by the biofuel cell, the time at that time is displayed on the screen of an external device such as a smartphone. Figure 2(B) illustrates the wearable device according to this disclosure. In the wearable device of this disclosure, the color tone of the electrochromic material in the electrochromic display (ECD) changes depending on the amount of power of the biofuel cell (BFC). Therefore, the wearer can visually check the fuel concentration (e.g., lactic acid concentration) in the solution (e.g., sweat) on the spot. Since the lactic acid concentration in sweat can be an important indicator of exercise and metabolic status, the wearable device of this disclosure is useful, for example, for managing the condition of athletes. [Examples]

[0039] Examples are shown below to further specifically describe the present disclosure. However, the present disclosure is not limited to these examples, and can be implemented in various modes with various modifications and improvements based on the common knowledge of those skilled in the art. In the following examples, lactic acid is used as a fuel and PEDOT:PSS is used as an electrochromic material, but it is understood that the self-powered biosensor of the present disclosure is not limited to these.

[0040] [Evaluation of Paper-Substrate Lactic Acid Biofuel Cell] First, a biofuel cell was fabricated and its characteristics were evaluated. As shown in FIG. 3, in the biofuel cell 10, an electrode was fabricated by laminating a conductive carbon layer 12 and a GMgOC layer 13 by screen printing on water-repellent Japanese paper (Gasenshi "Shoun", manufactured by Togawa Paper Co., Ltd.) serving as the substrate 11. Note that the carbon layer 12 of the cathode may have through holes to increase the amount of oxygen supplied to the cathode. This electrode was modified with lactic acid oxidase (LOx) added with thionine and a crosslinking agent at the anode. Bilirubin oxidase (BOD) was modified at the cathode. When linear sweep voltammetry (LSV) was performed using this electrode under the following conditions, as shown in FIG. 4, a maximum power density of 128 μW / cm 2 was obtained. <LSV Measurement Conditions> • Anode: anode added with thionine, LOx, and PEG • Cathode: cathode added with BOD • Test solution: phosphate buffer solution (pH 7.0) containing 100 mM lactic acid • Start potential: -0.71 V (from OCP measurement result) • Potential step: 1 mV • Scan rate: 1 mV / s

[0041] Note that MgOC is mesoporous carbon using magnesium oxide (MgO) fine particles as a template, and GMgOC is mesoporous carbon obtained by graft-polymerizing a polymer having a glycidyl group on the surface of MgOC.

[0042] [Redox reaction of PEDOT:PSS] Next, characteristic evaluation of an electrochromic display was performed. PEDOT:PSS, which is used as an electrochromic material, is a conductive polymer that reversibly changes color shade accompanying a redox reaction. The cyclic voltammogram shown in Figure 5 was obtained by cyclic voltammetry performed for electrochemical evaluation.

[0043] In PEDOT:PSS, the structure of PEDOT changes through oxidation, which narrows the band gap between the conduction band and the valence band and reduces energy. As a result, the absorption wavelength shifts to the longer wavelength side, leading to infrared absorption and thus a lighter color. The color tone change of PEDOT:PSS is shown in the photograph of Figure 6. In Figure 6, PEDOT:PSS is formed into a film on ITO glass. As shown in Figure 6, the color tone change of PEDOT:PSS ((A) deep blue ⇔ (B) nearly transparent) was confirmed visually.

[0044] [Change in absorbance of PEDOT:PSS] In addition to visual evaluation, absorbance measurement was also performed. As shown in Figure 7, the change in absorbance depending on the applied potential could be confirmed. <CA Measurement Conditions> · Working electrode: ITO glass electrode coated with PEDOT:PSS · Reference electrode: Silver-silver chloride electrode · Counter electrode: Platinum electrode · Measurement solution: 0.2 M aqueous sodium sulfate solution · Constant potential: -0.8, -0.7, -0.6, -0.5, -0.4, -0.3, -0.2, -0.1 V <Spectrophotometer Measurement Conditions> · Device: UV1900, manufactured by Shimadzu Corporation · Start time: 5 minutes after application of each voltage · Scan range: 850.0~350.0 nm · Data interval: 1.0 nm

[0045] [Absorbance Measurement of PEDOT:PSS for Each Lactic Acid Concentration (Example 1)] As shown in Fig. 8, PEDOT:PSS 22 deposited on ITO glass 21 was immersed in a test solution and connected to a biofuel cell (BFC). The PEDOT:PSS portion was set in a spectrophotometer, and absorbance was measured while dropwise adding phosphate buffer solutions containing lactic acid at different concentrations ranging from 0 M to 100 mM to the biofuel cell. <Composition of PEDOT:PSS 22> ·1 mL of PH1000 (PEDOT:PSS, manufactured by H.C. Stark Co., Ltd.) ·10 μL of FS30 (PEDOT:PSS, manufactured by FUJIFILM Wako Pure Chemical Corporation) ·100 μL of DMSO <bfc> • Anode: Anode with thionine, LOx, and PEG added. • Cathode: BOD-added cathode • Test solution: Phosphate buffer solution (pH 7.0) containing 0, 1, 5, 10, 25, 50, and 100 mM lactic acid. <ecd> • Electrode: PEDOT:PSS22 deposited on ITO glass 21 by spin coater. • Test solution: 0.2M sodium sulfate aqueous solution <Spectrophotometer measurement conditions> • Equipment: UV1900, manufactured by Shimadzu Corporation • Start time: 5 minutes after each voltage is applied • Scan range: 850.0~350.0nm • Scan speed: Very slow • Data interval: 1.0 nm

[0046] As shown in Figure 9, we confirmed that the absorbance changes with the change in lactic acid concentration. In particular, the absorbance value increased with increasing lactic acid concentration from 1 to 25 mM. This measurement allowed us to confirm the operation of a lactic acid biofuel cell when PEDOT:PSS, which was deposited on ITO glass, was immersed in the solution and connected to it.

[0047] [Manufacturing method for a device combining BFC and ECD] As an example, a device design combining a biofuel cell and an electrochromic display with PEDOT:PSS was created, as shown in Figure 10, and two types of screen printing plates were fabricated, as shown in Figures 11(A) and (B). A transparent resist 37 was printed as a protective layer on parts other than the biofuel cell (anode and cathode). The dimensions (in mm) in Figure 10 include the resist.

[0048] As shown in Figure 11, using the fabricated stencil, a carbon layer 32a was first laminated on the Japanese paper 31 as the electrode for the BFC side, and a carbon layer 32b was laminated as the electrode for the ECD side. The carbon layer 32a, which serves as the cathode for the BFC, has through-holes to increase the oxygen supply to the cathode. Next, a stretchable Ag layer 33 was laminated to electrically connect the BFC electrode and the ECD electrode. Then, a PEDOT:PSS layer 34 was laminated on the ECD side. Finally, a GMgOC layer 35 was laminated on the carbon layer 32a of the BFC to obtain the device shown in Figure 10. The carbon layer 32b of the ECD and the PEDOT:PSS 34 are electrically connected by the electrolyte 36 shown in Figure 10. In this way, a device combining a biofuel cell and an electrochromic display can be fabricated by screen printing using the fabricated stencil. Note that Figures 10(A) and 10(B) show an example of a device design, and the device design is not limited to this. Furthermore, the Japanese paper 31 used as the substrate was water-repellent treated Japanese paper, similar to the substrate used for the biofuel cell described above. In addition, the electrolyte 36 of the ECD may be a conductive solution or a gel. <Printing and drying conditions for the carbon layer> • Ink: Carbon • Squeegee angle: 75° • Clearance: 1.8mm • Workpiece thickness: 0.13mm • Coating thickness: 65mm • Print volume: 125mm • Coating speed: 120 mm / s • Print speed: 150mm / s ·Drying temperature and time: 120℃, 15min <Printing and drying conditions for the stretchable Ag layer> • Ink: Stretchable silver • Squeegee angle: 70° • Clearance: 1.00mm • Workpiece thickness: 0.13mm • Coating thickness: 65mm • Print volume: 125mm • Coating speed: 20mm / s • Print speed: 20mm / s ·Drying temperature and time: 120°C, 30 min <Printing and drying conditions for PEDOT:PSS layer> ·Ink: PEDOT / PSS 5.0 wt.% conductive screenprintable ink OrgaconEL-P-5015 (manufactured by Sigma-Aldrich), Clevios TM S V4 STAB ·Squeegee angle: 75° ·Clearance: 1.80 mm ·Work thickness: 0.13 mm ·Coating amount: 65 mm ·Printing amount: 125 mm ·Coating speed: 20 mm / s ·Printing speed: 20 mm / s ·Drying temperature and time: 150°C, 30 min <Printing and drying conditions for GMgOC layer> ·Ink: GMgOC ·Squeegee angle: 70° ·Clearance: 2.00 mm ·Work thickness: 0.20 mm ·Coating amount: 65 mm ·Printing amount: 135 mm ·Coating speed: 30 mm / s ·Printing speed: 100 mm / s ·Drying temperature and time: 60°C, 24 h Description of Reference Numerals

[0049] BFC Biofuel Cell ECD Electrochromic Display WTD Wireless Transmission Device 10 Biofuel Cell 11 Substrate 12 Carbon Layer 13 GMgOC Layer 21 ITO Glass 22 PEDOT:PSS 31 Japanese Paper 32a, 32b carbon layer 33 Stretchable Ag layer 34 PEDOT:PSS layer 35 GMgOC layer 36 Electrolytes 37 Resist< / ecd> < / bfc>

Claims

1. Biofuel cells that generate electricity through the oxidation of fuel, The system includes a display that shows visual changes according to the concentration of the fuel, Self-propelled biosensor.

2. The display includes a material whose absorbance changes in response to changes in the concentration of the fuel in the wavelength range of 350 nm to 850 nm. The self-driving biosensor according to claim 1.

3. The display changes color tone according to the concentration of the fuel. A self-driving biosensor according to claim 1 or claim 2.

4. The aforementioned display includes an electrochromic material, A self-driving biosensor according to claim 1 or claim 2.

5. The aforementioned display includes PEDOT:PSS, A self-driving biosensor according to claim 1 or claim 2.

6. A self-driving biosensor according to claim 1 or claim 2, It comprises an adhesive member for attaching to the wearer's skin, Wearable devices.

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