Bio-transistor

Abstract

[Problem] To provide a bio-transistor that uses a bio-material made of a natural material that is friendly to the global environment and less harmful to living organisms. [Solution] A bio-transistor comprising a bio-material 11 formed from a cellulose composed mainly of wood or plant fibers (pulp). The bio-material 11 is preferably a semiconductor. Moreover, the bio-transistor is preferably a field-effect transistor (FET), and in that case, is preferably a metal-semiconductor field-effect transistor (MESFET), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a junction field-effect transistor (JFET).

Description

Biotransistor

[0001] This invention relates to a biotransistor.

[0002] Semiconductors are electronic components used in low-voltage elements such as transistors, taking advantage of their property that their conductivity changes significantly due to the introduction of impurities and the effects of heat, light, magnetic fields, voltage, current, and radiation. They are indispensable components for electronic devices (see, for example, Non-Patent Documents 1 to 3). Semiconductors are widely applied in various diodes, transistors, FETs, SITs, RAMs, ROMs, CCDs, etc. In recent years, high-performance IT products such as mobile phones and ultra-small memory devices, as well as batteries for electric vehicles, have evolved rapidly, increasing the demand for semiconductors that are even smaller, have higher capacity, and possess high functionality such as memory. In particular, there is a demand for products that are compatible with smart grids (next-generation power transmission networks) that align with green innovation (low-carbonization) to prevent global warming. For example, the market for capacitors, used in automobiles, IT equipment, and energy-saving inverters, is expanding steadily at an average annual rate of approximately 3.7%, and the market has reached 1 trillion yen.

[0003] Conventionally, inorganic and organic materials have been used as semiconductor materials (see, for example, Patent Document 1). These are all artificial, and many of these materials are harmful to the preservation of the global environment and the survival of living organisms, including humans. For this reason, future semiconductor materials should not use toxic elements such as arsenic, lead, cadmium, beryllium, and mercury, or environmental pollutants such as lithium, chromium, and sulfur. In other words, even for semiconductors, there is a demand for materials that are harmless to health and inexpensive.

[0004] Semiconductors are broadly classified into two categories based on their application: those for high-voltage power circuits (heavy electrical equipment) and those for electronic and electrical equipment circuits (low-voltage equipment). Of these, silicon (Si) and compound semiconductors are mainly used as semiconductor materials for electronic and electrical equipment circuits in the major low-voltage sector, while organic semiconductors are also widely used, particularly in organic LEDs and organic solar cells, which have become key components in televisions and smartphones.

[0005] Among organic semiconductor components, those that cause an increase in carbon dioxide or contain microplastics, which contribute to marine pollution, are being increasingly shunned worldwide from the perspective of protecting plants and animals and preserving the global environment. From this standpoint, developing biomass semiconductors using wood or cellulose from plant fibers, which have a low environmental impact in terms of production and disposal, are lightweight, and possess high elasticity, is a timely direction for global environmental conservation.

[0006] However, semiconductors made from carbon-neutral biomaterials are not yet in use. This is because biomaterials are thought to be insulating materials that conduct electricity very little, and no one believes that biomaterials can be used in semiconductors.

[0007] Furthermore, the present inventors have been the first in the world to discover the semiconductor properties of plant-derived cellulose and animal-derived chitosan (see, for example, Non-Patent Documents 4 and 5 or Patent Document 2).

[0008] M. Fukuhara, R. Sato, T. Suzuki, and A. Inoue, “Room-temperature coulomb oscillation of Ni-Nb-Zr-H glassy alloy”, Mod. Phys. Lett. B, 2010, 22, p.2280-2293M. Fukuhara and H. Yoshida, “Room-temperature nonlinear transport phenomena in lowdimensional Ni-Nb-Zr-H glassy alloys and its device”, AIP Conf. Proc., 2014, 1598, p.205M. Fukuhara and H. Kawarada, “Room-temperature amorphous alloy field-effect transistor exhibiting particle and wave electronic transport”, J. Appl. Phys., 2015, 117, 084302M. Fukuhara, T. Yokotsuka, T. Hashida, F. Ogawa, T. Sakamoto, M. Takeda, and S. Arai, “A novel n-type semiconducting biomaterial”, Sci. Rep., 2022, 12, 21899M. Fukuhara, T. Yokotsuka, S. Kayamori, A. Isogai, and T. Hashida, “n-type semiconductor with energy storage made from chitosan”, AIP Adv., 2024, 14, 035103

[0009] International Publication WO2011 / 037003International Publication WO2023 / 203846

[0010] The Coulomb oscillations and transistors described in Non-Patent Documents 1-3 and Patent Document 1 are characterized by being made of amorphous Ni-Nb-Zr-H alloy and being metal / semiconductor type transistors. However, all of these are artificial materials, which poses a problem as they are harmful to the preservation of the global environment and the survival of living organisms, including humans. Therefore, the use of natural materials is highly anticipated.

[0011] This invention addresses these challenges and aims to provide a biotransistor made from natural materials that is environmentally friendly and harmless to living organisms.

[0012] The inventors focused on crystalline amorphous fibers mainly composed of wood or plant fibers (pulp) and discovered that by using semiconductor conductive materials such as cellulose fibers or pulp (an aggregate thereof) as solid semiconductor materials, diode and transistor functions can be achieved, leading to the present invention. For example, the inventors discovered that by using crystalline amorphous fibers with cellulose nanofiber (CNF) bundles of 1 to 30 nm in diameter, produced by mechanical defibration, acidic solution dissolution viscose method, or phosphate esterification method, and cellulose nanoparticles (CNP) with a particle size of 15 nm or less, semiconductor properties are achieved through quantum effects driven by electrons and protons in a thin film, and that transistor phenomena appear when these are formed into a three-electrode device. In other words, similar to the previous amorphous Ni-Nb-Zr-H alloy, the inventors discovered that a phenomenon occurs when proton tunneling (solitonized protons) is formed in crystalline amorphous fibers and aggregates composed thereof.

[0013] Furthermore, the present inventors have found that the molecular formula (C ６ H １０ O ５ ) ｎIn cellulose, a polysaccharide represented by , we focused on the fact that the dipoles formed by hydroxyl groups (OH groups) and carbonyl groups (C-O groups) are ordered in the same direction. Structurally, this behaves similarly to the primary hydrogen bond chains of water. That is, we found that it behaves like a chain of protonic solitons, greatly contributing to electron conduction and the formation of the electrical bilayer.

[0014] The biotransistor according to the present invention is characterized by having a biomaterial consisting of wood or cellulose mainly composed of plant fibers (pulp).

[0015] The biotransistor according to the present invention preferably uses cellulose fibers or particles as the biomaterial, and more preferably CNF or CNP produced by further defibration, pulverization, and classification of these. Furthermore, the biomaterial preferably contains less than 20 wt% water. This water is preferably bound to the cellulose carbon groups of the CNF or CNP as bound water. This bound water, for example, penetrates between the nanofibrils constituting the CNF as a single water molecule, physically behaves as a pseudo-solid, and binds the nanofibrils together.

[0016] The biotransistor according to the present invention preferably has a biomaterial that is a crystalline amorphous fiber or crystalline amorphous particle, but nanocrystals may also be present. Alternatively, the biomaterial may be an amorphous fiber or amorphous particle having atomic vacancies. Furthermore, the diameter of the fiber or particle is preferably 1 nm to 20 nm. Here, the main component refers to a component that is present at a content of 50 wt% or more.

[0017] The biotransistor according to the present invention has a biomaterial made of cellulose, which is a type of natural polymer compound in which numerous β-glucose molecules are polymerized in a linear chain by glycosidic bonds. The biotransistor according to the present invention can exhibit transistor amplification by utilizing the quantum phenomenon of radical electrons induced at the glycoside bond oxygen of the cellulose. Furthermore, because the biomaterial is made of the polysaccharide cellulose, it becomes a semiconductor due to a high dielectric domain structure formed by capacitors created by the bonding of countless hydroxyl groups and carbonyl groups, and can constitute a room-temperature transistor.

[0018] Thus, the biotransistor according to the present invention can exhibit various transistor functions, such as DC / AC elements, insulator / metal conduction switching elements, and rectification. Furthermore, the biotransistor according to the present invention uses a biomaterial consisting mainly of wood or cellulose derived from plant fibers (pulp), making it environmentally friendly, recyclable, and less harmful to living organisms.

[0019] [Cellulose] In the biotransistor according to the present invention, the type of cellulose is not particularly limited, and for example, cellulose originating from plants (e.g., wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), unbleached softwood sulfite pulp (NUSP), bleached softwood sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (e.g., sea squirts), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)), microbial products, etc. can be used. Preferably, the cellulose is cellulose fiber derived from plants or microorganisms, and more preferably, cellulose fiber derived from plants.

[0020] The number-average fiber diameter of cellulose is not particularly limited. For common pulps such as softwood kraft pulp, it is about 30-60 μm, and for hardwood kraft pulp, it is about 10-30 μm. For pulps such as kenaf, after general purification, it is about 50 μm. For example, if the material is a few centimeters in size, such as wood chips, it is preferable to mechanically process it with a disintegrator such as a refiner or beater to adjust it to about 50 μm.

[0021] [Cellulose Nanofibers (CNF)] In the biotransistor according to the present invention, the cellulose nanofibers may be unmodified or chemically modified. Examples of chemically modified cellulose nanofibers (chemically modified CNF) include anionic modified CNF and cation modified CNF, but anionic modified CNF is preferred. Anionic modified CNF is a fine fiber obtained by defibrating anionic modified cellulose fibers, in which anionic groups have been introduced into the cellulose molecular chain, until the fiber diameter reaches the nanoscale.

[0022] Examples of anionically modified cellulose fibers include carboxylated (oxidized) cellulose fibers, carboxymethylated cellulose fibers, phosphate-esterified cellulose fibers, and phosphite-esterified cellulose fibers. By defibrillating these, oxidized cellulose nanofibers, carboxymethylated cellulose nanofibers, phosphate-esterified cellulose nanofibers, and phosphite-esterified cellulose nanofibers can be obtained, respectively.

[0023] Here, cellulose nanofibers (CNF) are obtained by micronizing pulp, the raw material for cellulose, to the nanometer level, and refer to fine fibers with a fiber diameter of approximately 1 nm to 500 nm. Cellulose nanofibers preferably have an aspect ratio of 1000 or less, more preferably 100 or less, and most preferably 10 or less. The average fiber diameter and average fiber length of cellulose nanofibers can be obtained by averaging the fiber diameter and fiber length obtained from observing each fiber using an atomic force microscope (AFM) or a transmission electron microscope (TEM). Cellulose nanofibers can be obtained by micronizing pulp by applying mechanical force, or by defibrating anionic modified cellulose fibers such as carboxylated cellulose fibers (hereinafter also called "oxidized cellulose fibers"), carboxymethylated cellulose fibers, phosphate esterified cellulose fibers, and phosphite esterified cellulose fibers. The average fiber length and average fiber diameter of the fine fibers can be adjusted by oxidation treatment and defibration treatment.

[0024] Cellulose nanoparticles (CNPs) obtained by defibrating and pulverizing cellulose fibers using mechanical shearing, scraping, or chemical shearing methods such as enzymes preferably have an average particle size of 5 nm or more and 20 nm or less. Because particle size determination is difficult due to aggregation caused by the thixotropy inherent in cellulose, the particles are either completely dispersed using t-butyl alcohol and observed with a scanning electron microscope (SEM), or the aggregates are measured using an atomic force microscope (AFM).

[0025] The type of cellulose used as a raw material for anion-modified CNF (hereinafter also referred to as "cellulose raw material") is not particularly limited and may be cellulose originating from plants (e.g., wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (unbleached coniferous kraft pulp (NUKP), bleached coniferous kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), unbleached coniferous sulfite pulp (NUSP), bleached coniferous sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (e.g., sea squirts), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)), microbial products, etc.). The cellulose raw material is preferably cellulose fiber derived from plants or microorganisms, and more preferably cellulose fiber derived from plants.

[0026] [Chemical Modification] Anionic modified cellulose fibers can be obtained by introducing anionic groups into the cellulose raw material described above. The method of introducing anionic groups is not particularly limited, but examples include introducing anionic groups into the pyranose ring of cellulose by oxidation or substitution reactions. Specifically, examples include a reaction in which the hydroxyl group of the pyranose ring is oxidized and converted to a carboxyl group, or a reaction in which a carboxymethyl group, a phosphate ester group, or an ester group of phosphorous acid is introduced into the pyranose ring by substitution reactions.

[0027] [Carboxylation (Oxidation)] As an example of anionic modification, carboxylation (also called "oxidation") can be cited. Carboxylation is a reaction in which the hydroxyl group of the pyranose ring of cellulose is oxidized to a carboxyl group (-COOH (acid form) or -COOM (metal salt form); M is a metal ion). Hereinafter, anionic modified cellulose fibers obtained by carboxylation will also be called "carboxylated cellulose fibers" or "oxidized cellulose fibers". Carboxylated cellulose fibers can be obtained by carboxylating (oxidizing) the above cellulose raw material by known methods.

[0028] One example of a carboxylation (oxidation) method involves oxidizing a cellulose raw material in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromide, iodide, and mixtures thereof. This oxidation reaction selectively oxidizes the primary hydroxyl group at the C6 position of the glucopyranose ring on the surface of the cellulose, yielding cellulose fibers having an aldehyde group and a carboxyl group (-COOH) or carboxylate group (-COO-) on the surface. The concentration of the cellulose raw material in water during the reaction is not particularly limited, but is preferably 5% by mass or less.

[0029] An N-oxyl compound is a compound capable of generating a nitroxyl radical. Any compound that promotes the desired oxidation reaction can be used as the N-oxyl compound. Examples include 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and its derivatives (e.g., 4-hydroxyTEMPO). The amount of N-oxyl compound used is not particularly limited, as long as it is a catalytic amount that can oxidize the cellulose raw material. For example, 0.01 to 10 mmol is preferred, more preferably 0.01 to 1 mmol, and even more preferably 0.05 to 0.5 mmol per 1 g of oven-dried cellulose raw material. Also, about 0.1 to 4 mmol / L of the total reaction solution is preferable.

[0030] As an oxidizing agent, known substances can be used, such as halogens, hypohalous acids, halogenous acids, perhalous acids or their salts, halogen oxides, and peroxides. Among these, sodium hypochlorite is preferred because it is inexpensive and has a low environmental impact. The appropriate amount of oxidizing agent to use is, for example, 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, even more preferably 1 to 25 mmol, and even more preferably 3 to 10 mmol per 1 g of oven-dried cellulose raw material. Also, for example, 1 to 40 mol per 1 mol of N-oxyl compound is preferred.

[0031] The oxidation of cellulose raw materials can proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature may be 4 to 40 °C, or may be room temperature of about 15 to 30 °C. As carboxyl groups are generated in the cellulose chain as the reaction proceeds, a decrease in the pH of the reaction solution is observed. In order to efficiently proceed the oxidation reaction, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution at 8 to 12, preferably about 10 to 11. The medium in the reaction solution is preferably water in view of ease of handling and difficulty in causing side reactions. The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 to 6 hours, preferably about 0.5 to 4 hours.

[0032] As another example of the method of carboxylation (oxidation), there is a method of oxidizing by bringing a gas containing ozone into contact with a cellulose raw material. By this oxidation reaction, at least the hydroxyl groups at the 2-position and 6-position of the glucopyranose ring are oxidized to carboxyl groups, and decomposition of the cellulose chain occurs. The ozone concentration in the gas containing ozone is preferably 50 to 250 g / m ３ and more preferably 50 to 220 g / m ３ The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by mass, more preferably 5 to 30 parts by mass, when the solid content of the cellulose raw material is 100 parts by mass. The ozone treatment temperature is preferably 0 to 50 °C, more preferably 20 to 50 °C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, preferably about 30 to 360 minutes.

[0033] In the molecular structure of carboxylated (oxidized) CNF and CNP, Na in R (R = C １１ H １７ O ９ )COONa may be replaced with RCOOX (X = Li, Mg, K, Ca, Al, Fe, etc.) with hydroxides such as Li, Mg, K, Ca, Al, Fe, etc. in a hydrochloric acid solution.

[0034] [Esterification] Esterification can be cited as an example of anionic modification. Another example of esterification is the introduction of phosphate groups or phosphite groups into cellulose raw materials. Hereinafter, anionic modified cellulose fibers obtained by the introduction of phosphate groups will be called "phosphate-esterified cellulose fibers," anionic modified cellulose fibers obtained by the introduction of phosphite groups will be called "phosphite-esterified cellulose fibers," and both will be collectively referred to as "esterified cellulose fibers."

[0035] One method for producing phosphate-esterified cellulose fibers involves mixing a cellulose raw material or slurry thereof with a powder or aqueous solution of a compound having a phosphate group. Examples of compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium metaphosphate. These may be used individually or in combination of two or more.

[0036] The amount of the phosphate group-containing compound added to the cellulose raw material is preferably 0.1 to 500 parts by mass, more preferably 1 to 400 parts by mass, and even more preferably 2 to 200 parts by mass, per 100 parts by mass of solid content of the cellulose raw material, when converted to the amount of phosphorus element. The reaction temperature is preferably 0 to 95°C, and more preferably 30 to 90°C. The reaction time is not particularly limited, but is about 1 to 600 minutes, and more preferably 30 to 480 minutes. From the viewpoint of suppressing hydrolysis of cellulose, the suspension of phosphate-esterified cellulose fibers obtained is preferably dehydrated and then heat-treated at 100 to 170°C. The degree of phosphate group substitution per glucose unit of the phosphate-esterified cellulose fibers is preferably 0.001 or more and less than 0.40.

[0037] As a method for producing a phosphite esterified cellulose fiber, an alkali metal ion-containing substance and an additive (A) composed of at least one of phosphorous acids and metal phosphites are added to a cellulose raw material or its slurry, and heated to introduce an ester group of phosphorous acid containing a cation composed of an inorganic substance into the cellulose fiber. It is more preferable to add an additive (B) composed of at least one of urea and urea derivatives and heat it to introduce an ester group of phosphorous acid containing a cation composed of an inorganic substance and a carbamate group into the cellulose fiber. As the alkali metal ion-containing substance, for example, hydroxides, metal sulfates, metal nitrates, metal chlorides, metal phosphates, metal phosphites, and metal carbonates can be used. Particularly, metal phosphites that also serve as the additive (A) are preferable, and sodium hydrogen phosphite is more preferable.

[0038] The additive (A) is preferably composed of at least one of phosphorous acids and metal phosphites. As the additive (A), for example, phosphorous acid compounds such as phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, and pyrophosphorous acid can be used. These phosphorous acids or metal phosphites may be used alone or in combination of a plurality thereof. Particularly, it is preferable to use sodium hydrogen phosphite that also serves as an alkali metal ion-containing substance. The addition amount of the additive (A) is preferably 1 to 10,000 g, more preferably 100 to 5,000 g, and further preferably 300 to 1,500 g with respect to 1 kg of the cellulose raw material.

[0039] Additive (B) preferably consists of at least one of urea and a urea derivative. Examples of additive (B) include urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, and tetramethylurea. These ureas or urea derivatives may be used individually or in combination, and urea is particularly preferred. The amount of additive (B) added is preferably 0.01 to 100 mol, more preferably 0.2 to 20 mol, and even more preferably 0.5 to 10 mol, per 1 mol of additive (A).

[0040] The heating temperature is preferably 100 to 200°C, and more preferably 100 to 180°C. The reaction time is not particularly limited, but is about 10 to 180 minutes, and more preferably 30 to 120 minutes. The cellulose fibers into which phosphate ester groups have been introduced are preferably washed before defibration. The degree of substitution of phosphate groups per glucose unit in the phosphate-esterified cellulose fibers is preferably 0.01 or more and less than 0.23.

[0041] [Fibrillation] The method for fibrillating cellulose fibers is not particularly limited, but it is preferable to apply a strong shear force to the cellulose fiber dispersion using a device such as a high-speed rotary type, colloid mill type, high-pressure type, roll mill type, bead mill type, or ultrasonic type. To efficiently fibrillate, it is preferable to use a wet high-pressure or ultra-high-pressure homogenizer that can apply a pressure of 50 MPa or more and a strong shear force to the cellulose fiber dispersion. The pressure is more preferably 100 MPa or more, and even more preferably 140 MPa or more. The number of processing (passes) in the fibrillation device may be one, but two or more is preferable.

[0042] Dispersion is typically carried out by dispersing cellulose fibers in a solvent. The solvent is not particularly limited as long as it can disperse the cellulose fibers, but examples include water, organic solvents (e.g., hydrophilic organic solvents such as methanol), and mixed solvents thereof. Since cellulose fibers are hydrophilic, the solvent is preferably water.

[0043] Furthermore, prior to defibration and dispersion in a high-pressure homogenizer, the cellulose fibers may be pre-treated as needed. Pre-treatment can be carried out using a mixing, stirring, emulsifying, and dispersion device such as a high-speed shear mixer.

[0044] Cellulose fibers may be in the form of an aqueous dispersion obtained after manufacturing, and may undergo post-treatment as necessary. Post-treatments include, but are not limited to, drying (e.g., freeze-drying, spray drying, shelf drying, drum drying, belt drying, drying by spreading thinly on a glass plate, fluidized bed drying, microwave drying, and vacuum drying with a heated fan), redispersion in water (dispersion equipment is not limited), and grinding (e.g., grinding using equipment such as a cutter mill, hammer mill, pin mill, jet mill, or bead mill). For example, it is preferable to perform microfibrillation with a wet centrifuge, recover the suspended layer with a water classifier, and then repeat static classification to collect nanoparticles of 20 nm or less.

[0045] The biotransistor according to the present invention is preferably a thin film with a thickness of 10 μm or less, more preferably 0.2 μm or less, in order to achieve a weight reduction effect.

[0046] The biotransistor according to the present invention has an electrical resistivity of 10 in the biomaterial. －６ Ωm or more 10 ８ Ωm or less, preferably 10 １ Ωm or more 10 ６ Preferably, the capacitance is 100 μF or less and the capacitance is 100 μF or less.

[0047] The biotransistor according to the present invention has a specific surface area of ​​800 m². ２ It is preferable that the amount is 800 to 900 m / g or more. ２ It may also be / g. Furthermore, the biotransistor according to the present invention is preferably an n-type bulk semiconductor. In this case, since it exhibits an N-type negative resistance under a high voltage load of 1 kV / cm or more, it can be used as a DC / AC conversion element or 10 ４ It can be used as a multi-digit semiconductor / metal conduction switching element and also provides rectification.

[0048] The biotransistor according to the present invention is preferably in the form of a thin film sheet, dots, or a comb-shaped sheet. The biotransistor according to the present invention may have a pair of source and drain metal electrodes provided on both sides of the biomaterial so as to sandwich the sheet-like biomaterial, and a metal gate electrode provided perpendicular to the biomaterial. The metal gate electrode may be bonded to the biomaterial directly or via a silicon oxide insulating layer. The biomaterial preferably has a cellulose content of 95 to 100%, and more preferably 100%.

[0049] Furthermore, in the biotransistor according to the present invention, a pair of conductive electrodes made of Al, Cu, gold, polythiophene, etc., may be formed above and below the biomaterial using a micro-electromechanical system (M(N)EMS) with sputtering, casting, or ink printing methods, so as to sandwich the biomaterial. This allows multiple units to be stacked or integrated, with one biomaterial and the pair of conductive electrodes sandwiching it forming a single unit. In addition, it is preferable that the biotransistor according to the present invention is operable in the range of -170°C to 200°C.

[0050] The biotransistor according to the present invention, when composed of a laminate formed by stacking multiple units, can be parallel-stacked, for example, by various M(N)EMS methods, and each parallel equivalent circuit can be a solid quantum semiconductor with electrically lumped-parameter coupling. Furthermore, the biotransistor according to the present invention may consist of a parallel integrator in which multiple biomaterials are arranged along the inner surface of each metal electrode between each metal electrode. In this case, a dielectric strength of 1 MV / m or more can be obtained.

[0051] The biotransistor according to the present invention can be used, for example, as a control device for microelectronic circuits, an overcurrent protection switch, etc. It can also be used in various amplifiers, microwave oscillators, pump sources for parametric amplifiers, police radar, door opening / closing systems, intrusion detection systems, shunt regulators, protection circuits, and other electronic and electrical circuit boards.

[0052] The biotransistor according to the present invention may also be a field-effect transistor (FET). In this case, the field-effect transistor may be a MESFET (metal-semiconductor field-effect transistor), a MOSFET (metal oxide semiconductor field-effect transistor), or a JFET (junction field-effect transistor).

[0053] According to the present invention, it is possible to provide a biotransistor made from natural materials that is environmentally friendly and harmless to living organisms.

[0054] Figure 1(a) shows a front view of a biotransistor according to an embodiment of the present invention, specifically (a) a MESFET (metal-semiconductor field-effect transistor), (b) a MOSFET (metal-oxide-semiconductor field-effect transistor), and (c) a JFET (junction field-effect transistor). Figure 1(a) shows the drain current Id-drain voltage Vd curve when the gate bias Vg is changed, and (b) the Id-Vg curve when Vd is changed, for the MESFET shown in Figure 1(a). Figure 1(b) shows the Id-Vd curve when Vg is changed, and (b) the Id-Vg curve when Vd is changed, for the MOSFET shown in Figure 1(b). Figure 1(a) shows a graph of the On / Off ratio when the gate bias Vg is changed, for the MESFET shown in Figure 1(a). Figures 1(a) show a plan view of a parallel transistor and a comb transistor fabricated using a biotransistor according to an embodiment of the present invention.

[0055] The biotransistor according to an embodiment of the present invention will be described below based on the drawings and examples. The biotransistor according to an embodiment of the present invention has a biomaterial consisting of wood or cellulose mainly composed of plant fibers (pulp), and consists of a field-effect transistor (FET).

[0056] The biotransistor may consist of a MESFET (metal-semiconductor field-effect transistor) as shown in Figure 1(a), a MOSFET (metal oxide semiconductor field-effect transistor) as shown in Figure 1(b), or a JFET (junction field-effect transistor) as shown in Figure 1(c).

[0057] In the case of a MESFET as shown in Figure 1(a), the biotransistor 10 includes, for example, a thin biomaterial 11, a first electrode 12a provided on one surface of the biomaterial 11, a second electrode 12b and a third electrode 12c provided on both sides of the biomaterial 11 so as to sandwich the biomaterial 11, a gate electrode g connected to the first electrode 12a, a source electrode s connected to the second electrode 12b, and a drain electrode d connected to the third electrode 12c. In the example shown in Figure 1(a), the biomaterial 11 is made of CNP, the first electrode 12a is made of gold which has a large work function, and the second electrode 12b and the third electrode 12c are made of aluminum which has a small work function.

[0058] In the case of a MOSFET as shown in Figure 1(b), the biotransistor 10 includes, for example, a P-type silicon substrate (P-Si) 13, an oxide insulating layer 14 formed on the surface of the P-type silicon substrate 13, a thin biomaterial 11 provided on the surface of the oxide insulating layer 14, a pair of electrodes 15a and 15b provided on the surface of the oxide insulating layer 14 so as to sandwich the biomaterial 11, a gate electrode g provided on the surface of the P-type silicon substrate 13 opposite to the oxide insulating layer 14, a source electrode s connected to one electrode 15a, and a drain electrode d connected to the other electrode 15b. In the example shown in Figure 1(b), the biomaterial 11 is made of CNP, the P-type silicon substrate 13 has a thickness of 50 μm, and the oxide insulating layer 14 is made of SiO ２ It consists of a pair of electrodes 15a and 15b, each made of gold.

[0059] In the case of a JFET as shown in Figure 1(c), the biotransistor 10 includes, for example, a p-type silicon substrate (p-Si) 13, a thin biomaterial 11 embedded on the surface of the p-type silicon substrate 13, a p-type channel layer (p-layer) 16 embedded in the center of the surface of the biomaterial 11, a gate electrode g provided on the surface of the p-type channel layer 16, a source electrode s and a drain electrode d provided on the surface of the biomaterial 11 on both sides of the p-type channel layer 16, and an electrode 17 provided on the surface of the p-type silicon substrate 13 and electrically connected to the gate electrode g. In the example shown in Figure 1(c), the biomaterial 11 is an n-type semiconductor and is made of CNP.

[0060] Figures 2 and 3 show the amplification characteristics when the biotransistor 10 consists of a MESFET as shown in Figure 1(a) and when it consists of a MOSFET as shown in Figure 1(b), respectively.

[0061] As shown in Figure 2, in the case of the MESFET shown in Figure 1(a), when a negative voltage is applied as the gate voltage, a depletion layer is formed at the gate junction CNP interface between the gate and source by Schottky coupling. This depletion layer further expands into the CNP, allowing control of the current between the source and drain. The MESFET type shown in Figure 1(a) has a smaller capacitance and is suitable for high-speed operation compared to those in Figures 1(b) and (c) because it lacks a gate insulating film.

[0062] As shown in Figure 3, in the MOSFET shown in Figure 1(b), when a charge is applied from the gate electrode g perpendicular to the CNP sandwiched between the source electrode s and the drain electrode d, via the SiO2 of the oxide insulating layer 14, a depletion layer is formed in the CNP by electrostatic induction, and the current between the source and drain changes depending on the size of this depletion layer. The MOSFET method shown in Figure 1(b) is currently the most widely used FET device, but since it is not possible to create a good gate insulating layer (oxide insulating layer 14) other than Si, its applications are limited when Si is not used.

[0063] Thus, the biotransistor 10 has a biomaterial 11 made of cellulose, and by utilizing the quantum phenomenon of radical electrons induced at the glycoxide bond oxygen of the cellulose, the transistor's amplification effect can be achieved. Furthermore, because the biomaterial 11 is made of the polysaccharide cellulose, it becomes a semiconductor due to the high dielectric domain structure created by capacitors formed by the bonding of countless hydroxyl groups and carbonyl groups, and can be constructed as a room-temperature transistor.

[0064] As a result, the biotransistor 10 can exhibit various transistor functions, such as DC / AC elements, insulator / metal conduction switching elements, and rectification. Therefore, it can be used, for example, as a control device for microelectronic circuits, an overcurrent protection switch, etc. It can also be used in electronic and electrical substrates such as various amplifiers, microwave oscillators, pump sources for parametric amplifiers, police radar, door opening / closing systems, intrusion detection systems, shunt regulators, and protection circuits. The biotransistor 10 uses a biomaterial 11 made of cellulose mainly composed of wood or plant fibers (pulp), making it environmentally friendly, recyclable, and harmless to living organisms.

[0065] In the biotransistor 10, the biomaterial 11 is not limited to CNP, but may also be CNF, or it may be cellulose fibers or particles before defibrillation or other processes. Furthermore, in the biotransistor 10, a trace amount of bound water (less than 20 wt%) is bound to the cellulose carbon groups of the CNF or CNP, which are the biomaterial 11. This bound water penetrates between the nanofibrils constituting the CNF or CNP as a single water molecule, physically behaves as a pseudo-solid, and binds the nanofibrils together. This bound water is not present in conventional artificial semiconductors made of Si, etc., and the presence of bound water in the biomaterial 11 is a crucial difference from conventional artificial semiconductors. Note that if the amount of bound water exceeds 20 wt%, it will not wet the CNF due to the passivation effect of the OH groups.

[0066] Furthermore, in the biotransistor 10, the biomaterial 11 may be crystalline amorphous fibers or crystalline amorphous particles, and nanocrystals may be present. Also, the biomaterial 11 may be amorphous fibers or amorphous particles having atomic vacancies. Furthermore, it is preferable that the diameter of the fibers or particles is 1 nm to 20 nm.

[0067] The biotransistor 10 can be formed using a micro-electromechanical system (M(N)EMS) with sputtering, casting, or ink printing methods when forming the gate electrode g, source electrode s, and drain electrode d. The conductive electrodes g, S, d, 12a, 12b, 12c, 15a, 15b, and 17 may be made of materials other than gold or aluminum, such as Cu or polythiophene.

[0068] Furthermore, the biotransistor 10 may be constructed by stacking or integrating multiple units, with each unit consisting of one biomaterial 11 and conductive electrodes 12b, 12c, 15a, and 15b. In this case, for example, parallel stacking can be performed using various M(N)EMS methods, and each parallel equivalent circuit can be a solid quantum semiconductor with electrically lumped-parameter coupling. Alternatively, the biotransistor 10 may consist of a parallel integrator in which multiple biomaterials 11 are arranged along the inner surfaces of each electrode 12b, 12c, 15a, and 15b. In this case, the withstand voltage can be increased to 1 MV / m or more.

[0069] The following are examples of biotransistors according to embodiments of the present invention. These examples are provided solely for the purpose of explaining the present invention and as reference for specific embodiments, and are not intended to limit or restrict the scope of the invention disclosed herein.

[0070] Using the defibration treatment method shown in Table 1, biomaterials consisting of sample types 1 to 3 were produced. The distinction between crystalline and amorphous forms, density, and electrical resistivity (kΩm) of the produced biomaterials 1 to 3 are also shown in Table 1.

[0071]

[0072] Each of the samples 1 to 3 was prepared as follows: <Sample 1> Kenaf stalks from Bangladesh were dried and stored, then immersed in water at 20°C. After two weeks, the outer layer was removed, the white bark was dried and defibrated to obtain sheet-like pulped fibers (bast fibers). These pulped fibers were immersed in distilled water (3% concentration) for 5 hours and disintegrated in a pulper for 30 minutes. The disintegrated pulp was made into a 2% aqueous solution and ground in a planetary ball mill using zirconia balls at a rotation speed of 100 rpm for 10 hours. Furthermore, the filtrate was centrifuged at 10,000 rpm to recover the particles. The recovered particles were maintained in a constant temperature and humidity chamber at 25°C and 95% relative humidity for 10 hours to obtain a water content of 10.8 wt%. This was immediately used to fabricate a transistor sample device.

[0073] <Sample 2> Cellulose derived from coniferous trees was heat-treated with sodium hydroxide, and carbon disulfide was added to obtain sodium cellulose xanthogenic acid (viscose). This was sprayed into a hydrochloric acid solution to create particles. The resulting aqueous solution was filtered and centrifuged at 15,000 rpm to recover the particles. The recovered particles were maintained in a constant temperature and humidity chamber at 25°C and 95% relative humidity for 7.2 hours to achieve a water content of 13.7 wt%. These particles were immediately used to create a transistor sample device.

[0074] <Sample 3> 10g of bleached, unbeaten kraft pulp derived from coniferous trees (whiteness 85%), mixed with distilled water (15g), urea (12g), and NH ４ H ２ PO ４ The material was immersed in a mixture of (4.5 g) and, after drying, solidified at 165°C for 10 minutes. After solidification, a 2% aqueous solution was prepared, and caustic soda was added to neutralize it while maintaining the pH at 12. This aqueous solution was defibrated using a high-pressure homogenizer to prepare a dispersion of cellulose fibers with a diameter of 30-10 nm. The filtered aqueous solution was centrifuged at 20,000 rpm to recover the sheet. The recovered sheet was maintained in a constant temperature and humidity chamber at 25°C and 95% relative humidity for 30 minutes to achieve a water content of 19.2 wt%. This was immediately used to fabricate a device as a transistor sample.

[0075] Each of the samples 1 to 3 exhibited semiconductor properties and was confirmed to be operable from -269°C to 200°C and up to 200V. Furthermore, measurements using the BET adsorption method revealed that the specific surface area of ​​each of the samples 1 to 3 was 800 m². ２ The result was / g. Furthermore, all three samples (1-3) were carbon neutral and are considered to be ideal materials for both low-voltage and high-voltage applications.

[0076] Using sample 1, the field-effect transistor (FET) sample shown in Figure 1(a) was fabricated; using sample 2, the field-effect transistor (FET) sample shown in Figure 1(b) was fabricated; and using sample 3, the field-effect transistor (FET) sample shown in Figure 1(c) was fabricated. First, in order to produce the CNPs in Figures 1(a) to (c), slurry solutions containing 1 to 2 wt% of the biomaterial obtained during the fabrication process of each of the samples 1 to 3 were added dropwise, and the water was evaporated by natural drying. This process was repeated several times to produce the CNPs in Figures 1(a) to (c), thereby fabricating the three types of field-effect transistor (FET) samples shown in Figures 1(a) to (c).

[0077] Contacts were connected to the source, drain, and gate of each transistor sample using a prober. The I-V characteristics of each transistor sample were measured at room temperature using semiconductor parameters, yielding Figures 2 and 3.

[0078] The On / Off ratio with respect to Vg was measured for the fabricated MESFET shown in Figure 1(a), and is shown in Figure 4. As shown in Figure 4, it was confirmed that the MESFET shown in Figure 1(a) is capable of high-speed switching with an On / Off ratio of up to 4.5 orders of magnitude.

[0079] Using the biomaterial from sample 1, parallel transistors and comb transistors were fabricated by the MEMS method. The fabrication method involved first depositing a 260 nm thick layer of Au onto an oxide-coated Si-wafer. To improve adhesion, a 20 nm thick layer of Cr was sputtered as a base coat immediately beforehand. This was then spin-coated with photoresist (OFPR 800LB 34cP, manufactured by Tokyo Ohka Kogyo Co., Ltd.) at 3000 rpm, and then aligned using a maskless aligner at 405 nm and 85 mJ / cm². ２The pattern was exposed using laser light. After development, it was subjected to oxygen ashing, and the Au was etched with an etching solution ("AURUM-302" manufactured by Kanto Chemical Co., Ltd.). After etching, it was protected with resist and cut into 2 cm squares with a dicer. The parallel transistor and comb transistor samples after acetone washing are shown in Figures 4(a) and (b), respectively.

[0080] The biotransistors of the embodiments of the present invention can be used in a wide range of applications, from low-voltage applications such as mobile phones, drones, and wall-mounted televisions, to heavy-voltage applications such as automobiles, ships, and airplanes. They can also be used in power modules for surge arresters, welding, and over-discharge prevention, as well as in sensors such as noise filters, door opening / closing systems, intrusion detection systems, and pedestrian safety systems, microelectronic control devices, remote vibration detectors, transmitters, and other electronic and electrical circuit boards.

[0081] 10 Biotransistor 11 Biomaterial 12a First electrode 12b Second electrode 12c Third electrode 13 P-type silicon substrate 14 Oxide insulating layer 15a, 15b Electrodes 16 P-type channel layer 17 Electrode

Claims

1. A biotransistor characterized by having a biomaterial consisting mainly of wood or cellulose derived from plant fibers (pulp).

2. The biotransistor according to claim 1, characterized in that the biomaterial is a semiconductor.

3. The biotransistor according to claim 1, characterized in that it is a field-effect transistor (FET).

4. The biotransistor according to claim 3, characterized in that the field-effect transistor is a MESFET (metal-semiconductor field-effect transistor).

5. The biotransistor according to claim 3, characterized in that the field-effect transistor is a MOSFET (metal oxide semiconductor field-effect transistor).

6. The biotransistor according to claim 3, characterized in that the field-effect transistor is a JFET (junction field-effect transistor).

7. The biotransistor according to claim 1, characterized in that it is an n-type semiconductor.

8. The biotransistor according to claim 1, characterized in that the biomaterial is cellulose fibers or particles.

9. The biotransistor according to claim 1, characterized in that the biomaterial is a crystalline amorphous fiber or a crystalline amorphous particle.

10. The biotransistor according to claim 1, characterized in that the biomaterial contains less than 20 wt% water.

11. The electrical resistivity of the biomaterial is 10 －６ ~10 ８ The biotransistor according to claim 1, characterized in that it is Ωm.

12. The biotransistor according to claim 1, characterized in that it is in the shape of a comb-shaped sheet.

Images