Bio-piezoelectric layer, method for manufacturing bio-piezoelectric layer, piezoelectric generator comprising same, and method for manufacturing piezoelectric generator

Abstract

Disclosed in the present invention are a bio-piezoelectric layer, a method for manufacturing the bio-piezoelectric layer, a piezoelectric generator comprising same, and a method for manufacturing the piezoelectric generator. The present invention comprises: a substrate; and a diphenylalanine crystal layer formed on the substrate and containing diphenylalanine crystals, wherein the diphenylalanine crystals comprise at least one of a non-centrosymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

Description

Bio-piezoelectric layer, method for manufacturing a bio-piezoelectric layer, piezoelectric power generation device including the same, and method for manufacturing a piezoelectric power generation device

[0001] The present invention relates to a bio-piezoelectric layer, a method for manufacturing a bio-piezoelectric layer, a piezoelectric power generation device including the same, and a method for manufacturing a piezoelectric power generation device. More specifically, the present invention relates to a bio-piezoelectric layer capable of realizing an MPB structure, which was previously found only in inorganic materials, in a biomaterial through a new crystal structure called a central asymmetric orthorhombic structure, a method for manufacturing a bio-piezoelectric layer, a piezoelectric power generation device including the same, and a method for manufacturing a piezoelectric power generation device.

[0002]

[0003] Recently, the development of telecommunications technology has led to the emergence of various types of electronic devices. For instance, the demand for electronic devices such as portable devices is exploding as they enable user-centric ubiquitous computing. Portable devices may include portable power sources like batteries, but battery technology has limitations as it is disposable or requires periodic charging. Consequently, the need for energy harvesting in electronic devices is emerging.

[0004] Energy harvesting refers to a technology capable of converting wasted mechanical energy—such as vibrations from trains, vacuum pumps, mechanical motors, automobile engines, and human movements—into electrical energy. In piezoelectric energy harvesting devices, displacement is amplified when the frequency of ambient vibrations matches their resonance frequency, generating the greatest electrical energy at the resonance frequency.

[0005] In addition, conventionally, a technology has been studied to self-assemble peptide structures using HFIP solvent to produce structures with various colors through various process conditions, and to fabricate color sensors that respond to organic matter, vacuum, and heat using these peptide structures. However, biocompatible piezoelectric materials based on PLA have a problem in that high voltage and heat are required during the process to enhance the piezoelectric performance of the material itself.

[0006]

[0007] Embodiments of the present invention aim to provide a bio-piezoelectric layer comprising a central asymmetric orthorhombic structure formed by the aggregation of neutral diphenylalanine molecules and a very small amount of water molecules, and a piezoelectric power generation device comprising the same.

[0008] Embodiments of the present invention aim to provide a method for manufacturing a bio-piezoelectric layer and a method for manufacturing a piezoelectric power generation device that can thermodynamically and kinetically control the phase change of the self-assembled crystal structure of a peptide by controlling the ratio of water and ethanol included in a diphenylalanine solution and the pulling speed of the substrate.

[0009]

[0010] A biopiezoelectric layer according to an embodiment of the present invention comprises a substrate; and a diphenylalanine crystal layer formed on the substrate and comprising diphenylalanine crystals, wherein the diphenylalanine crystals comprise at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

[0011] The above-mentioned central asymmetric orthorhombic structure may belong to the C2v point group.

[0012] The above morphotropic phase boundary structure may include a central asymmetric orthorhombic structure and a hexagonal tube structure.

[0013] The above hexagonal tube structure may belong to the C6 point group.

[0014] The above substrate may include at least one of aluminum (Al), gold (Au), chromium (Cr), silicon wafer (Si), silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), and glass.

[0015] A method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention comprises the steps of: preparing a diphenylalanine solution by mixing diphenylalanine and ethanol in water; immersing a substrate in the diphenylalanine solution; and pulling the substrate upward from the diphenylalanine solution to produce a diphenylalanine crystal, wherein the diphenylalanine crystal comprises at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

[0016] The step of preparing the diphenylalanine crystals above can control the crystal structure of the diphenylalanine crystals by adjusting the volume ratio (water:ethanol) of water and ethanol contained in the diphenylalanine solution.

[0017] The volume ratio of water to ethanol (water:ethanol) included in the above diphenylalanine solution may be 5:95 to 25:75.

[0018] The step of manufacturing the diphenylalanine crystals above can control the crystal structure of the diphenylalanine crystals by controlling the pulling speed of the substrate.

[0019] The above pulling speed may be 10㎛ / min to 80㎛ / min.

[0020] A piezoelectric power generation element according to an embodiment of the present invention comprises: a lower electrode formed on a lower substrate; a diphenylalanine crystal layer formed on the lower electrode; a protective layer formed on the diphenylalanine crystal layer; an upper electrode formed on the protective layer; and an upper substrate formed on the upper electrode; wherein the diphenylalanine crystal layer comprises diphenylalanine crystals, and the diphenylalanine crystals comprise at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

[0021] A method for manufacturing a piezoelectric power generation element according to an embodiment of the present invention comprises the steps of: forming a lower electrode on a lower substrate; forming a diphenylalanine crystal layer on the lower electrode; forming a protective layer on the diphenylalanine crystal layer; and forming an upper substrate coated with an upper electrode on the protective layer; wherein the step of forming the diphenylalanine crystal layer comprises the steps of: preparing a diphenylalanine solution by mixing diphenylalanine and ethanol in water; immersing a substrate in the diphenylalanine solution; and pulling the substrate upward from the diphenylalanine solution to produce a diphenylalanine crystal; wherein the diphenylalanine crystal comprises at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

[0022]

[0023] According to an embodiment of the present invention, a bio-piezoelectric layer comprising a central asymmetric orthorhombic structure formed by the aggregation of neutral diphenylalanine molecules and a very small amount of water molecules, and a piezoelectric power generation device comprising the same can be provided.

[0024] According to an embodiment of the present invention, a method for manufacturing a bio-piezoelectric layer and a method for manufacturing a piezoelectric power generation device can be provided, which can thermodynamically and kinetically control the phase change of the self-assembled crystal structure of a peptide by controlling the ratio of water and ethanol included in a diphenylalanine solution and the pulling speed of a substrate.

[0025]

[0026] FIG. 1 is a schematic diagram illustrating a bio-piezoelectric layer according to an embodiment of the present invention and a method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention.

[0027] FIG. 2 is a schematic diagram illustrating a piezoelectric power generation element according to an embodiment of the present invention.

[0028] FIG. 3 is an optical microscope (OM) image showing the shape of diphenylalanine crystals formed on an aluminum substrate or a gold substrate according to the ratio of water, and FIG. 4 is a transmission electron microscope (SEM) image showing the shape of diphenylalanine crystals according to the ratio of water.

[0029] Figure 5 is a graph showing the coverage area and Out-of-Plane (OOP) of diphenylalanine crystals formed on an aluminum substrate or a gold substrate according to the ratio of water.

[0030] Figure 6 is a graph showing the X-ray diffraction (XRD) analysis results of diphenylalanine crystals formed on a gold substrate according to the ratio of water and the crystal structure of diphenylalanine crystals formed on a gold substrate according to the ratio of water and the pulling speed, and Figure 7 is a graph showing the X-ray diffraction (XRD) analysis results of diphenylalanine crystals formed on an aluminum substrate according to the ratio of water and the crystal structure of diphenylalanine crystals formed on an aluminum substrate according to the ratio of water and the pulling speed.

[0031] FIG. 10 is a graph showing the X-ray diffraction (XRD) analysis results of diphenylalanine crystals according to Example 1-1 and diphenylalanine crystals according to Example 1-7, and FIG. 11 is a schematic diagram showing the structure of the identical amorphous compounds of diphenylalanine.

[0032] FIG. 12 is a graph showing the piezoelectric constant values ​​of diphenylalanine crystals formed on a gold substrate according to the ratio of water, FIG. 13 is a graph showing the piezoelectric constant values ​​of diphenylalanine crystals formed on an aluminum substrate according to the ratio of water, and FIG. 14 and FIG. 15 are images showing the piezoelectric response microscope (PFM) measurement results of diphenylalanine crystals formed on a gold substrate or an aluminum substrate according to the ratio of water.

[0033] Figure 16 is a graph showing the simulation results of calculating the molecular state of diphenylalanine in a solvent.

[0034] Figure 17 is a graph showing the molecular state of diphenylalanine in a solvent.

[0035] Figure 18 is a graph showing the results of X-ray diffraction analysis of diphenylalanine crystals according to Example 2-1, and a graph showing the results of X-ray diffraction analysis of diphenylalanine crystals according to Example 2-2.

[0036] FIG. 19 is a schematic diagram illustrating a piezoelectric power generation element according to Example 3-1 and a piezoelectric power generation element according to Example 3-2.

[0037] FIG. 20 is a graph showing the voltage over time of a piezoelectric power generation element according to Example 3-1 manufactured by adjusting the ratio of water, FIG. 21 is a graph showing the current over time, and FIG. 22 is a graph showing the power density over resistance.

[0038] FIG. 23 is a graph showing the voltage over time of a piezoelectric power generation element according to Example 3-2 manufactured by adjusting the ratio of water, FIG. 24 is a graph showing the current over time, and FIG. 25 is a graph showing the power density according to resistance.

[0039] FIG. 26 is a graph showing the voltage and current according to the power of the piezoelectric power generation element according to Example 3-2.

[0040] FIG. 27 is a graph showing the results of a stability test of a piezoelectric power generation element according to Example 3-2.

[0041]

[0042] Embodiments of the present invention will be described in detail below with reference to the attached drawings and the contents described therein, but the present invention is not limited or restricted by the embodiments.

[0043] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components or steps mentioned in the description.

[0044] As used herein, terms such as “examples,” “examples,” “aspects,” “examples,” etc., are not to be interpreted as implying that any described aspect or design is superior or advantageous to other aspects or designs.

[0045] Furthermore, the term 'or' refers to an inclusive or rather an exclusive or. That is, unless otherwise noted or is clear from the context, the expression 'x uses a or b' refers to any one of the natural inclusive permutations.

[0046] Additionally, singular expressions (“a” or “an”) used in this specification and claims should generally be interpreted to mean “one or more” unless otherwise stated or it is clear from the context that they relate to the singular form.

[0047] The terms used in the following description have been selected as common and universal in the relevant technical field, but other terms may exist depending on technological development and / or changes, conventions, preferences of the skilled technician, etc. Therefore, the terms used in the following description should not be understood as limiting the technical concept, but as illustrative terms to explain the embodiments.

[0048] In addition, in specific cases, there are terms arbitrarily selected by the applicant, and in such cases, their detailed meanings will be described in the relevant explanatory section. Therefore, the terms used in the description below must be understood not merely as their names, but based on their meanings and the content throughout the specification.

[0049] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0050] Meanwhile, in describing the present invention, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted. Furthermore, the terminology used in this specification is used to appropriately express embodiments of the present invention, and such terminology may vary depending on the intent of the user or operator, or the conventions of the field to which the invention belongs. Accordingly, the definitions of these terms should be based on the content throughout this specification.

[0051]

[0052] FIG. 1 is a schematic diagram illustrating a bio-piezoelectric layer according to an embodiment of the present invention and a method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention.

[0053] A bio-piezoelectric layer according to an embodiment of the present invention comprises a substrate (120) and a diphenylalanine crystal layer formed on the substrate (120) and comprising diphenylalanine crystals (130).

[0054] First, the bio-piezoelectric layer according to an embodiment of the present invention includes a substrate (120).

[0055] The substrate (120) may include at least one of an organic substrate and an inorganic substrate.

[0056] The inorganic substrate may include at least one of metal, silicon wafer (Si), glass, quartz, Al2O3, Si, and SiO2.

[0057] The metal may include at least one of aluminum (Al), gold (Au), chromium (Cr), silver (Ag), platinum (Pt), palladium (Pd), and copper (Cu).

[0058] The organic substrate may include at least one of Kapton foil, polyimide (PI), polyethersulfone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyarylate, polycarbonate (PC), cellulose triacetate (CTA), and cellulose acetate propionate (CAP).

[0059] Preferably, the substrate (120) may include a metal, and more preferably, the substrate (120) may include aluminum.

[0060] For example, since the phase change of diphenylalanine proceeds more slowly in aluminum than in gold and forms a more stable MPB structure (increasing the degree of peak shift in XRD), using aluminum as the substrate (120) can improve piezoelectric performance.

[0061] In addition, aluminum can be used for both the upper and lower electrodes of the piezoelectric power generation element. Since the piezoelectric constant is much higher on an aluminum substrate than on a gold substrate, the piezoelectric performance can be improved when aluminum is used for both the upper and lower electrodes of the piezoelectric power generation element.

[0062] According to an embodiment, the substrate (120) serves to support diphenylalanine crystals and, when applied to a piezoelectric power generation element, can be used as a lower substrate / lower electrode or lower electrode.

[0063] For example, when the substrate (120) serves as a lower substrate / lower electrode, the substrate (120) may include a stacked structure of an organic substrate / inorganic substrate or an inorganic / substrate / inorganic substrate.

[0064] A bio-piezoelectric layer according to an embodiment of the present invention is formed on a substrate (120) and includes a diphenylalanine crystal layer comprising diphenylalanine crystals (130).

[0065] According to an example, the diphenylalanine crystal layer (230) may include diphenylalanine nanotubes.

[0066] The diphenylalanine crystal (130) includes at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

[0067] The central asymmetric orthorhombic structure can contain diphenylalanine molecules and water molecules.

[0068] The center-asymmetric orthorhombic structure is difficult to express in a chemical formula because it changes depending on how diphenylalanine C15H15NO2 interacts with water molecules, but the structure can be confirmed through the experimental examples described below.

[0069] Specifically, in the conventional orthorhombic structure of diphenylalanine, when the temperature is increased from a hexagonal column to 150°C or higher, water molecules inside the diphenylalanine are completely removed and an orthorhombic P22121 structure is formed; however, in the central asymmetric orthorhombic structure included in the bio-piezoelectric layer according to the embodiment of the present invention, the amount of water is reduced, and neutral diphenylalanine molecules in the diphenylalanine solution and a very small amount of water molecules can clump together to form an orthorhombic structure.

[0070] Therefore, unlike the conventional orthorhombic structure formed when there are no water molecules at all, the central asymmetric orthorhombic structure included in the biopiezoelectric layer according to the embodiment of the present invention is C 2vIt has a space group and can exhibit piezoelectric performance with a central asymmetric structure.

[0071] For example, the amount of water molecules contained in the diphenylalanine crystal (130) of the center-asymmetric orthorhombic structure can form a C2v structure when the volume ratio of water in the mixed solvent (water:ethanol) is 3% to 8% for gold and 3% to 9% for aluminum. If the water ratio is less than 3%, an amorphous structure is formed, and if it exceeds 8% or 9%, the diphenylalanine can form an MPB structure.

[0072] The diphenylalanine crystal (130) having a central asymmetric orthorhombic structure included in the bio-piezoelectric layer according to an embodiment of the present invention has a structure different from the conventional central symmetric orthorhombic structure formed by increasing the temperature to completely remove water molecules, has non-central symmetry and has a piezoelectric effect, and as one of the diphenylalanine allotropes, the thermodynamically unstable central asymmetric orthorhombic structure can appear before the thermodynamically stable hexagonal prism structure by adjusting the ratio of the mixed solvent according to the Ostwald step rule.

[0073] Morphotropic phase boundary structures may include centered asymmetric orthorhombic structures and hexagonal tube structures.

[0074] The morphotropic phase boundary structure is difficult to express in a chemical formula because it changes depending on how diphenylalanine C15H15NO2 interacts with water molecules, but the structure can be confirmed through the experimental examples described below.

[0075] Specifically, in morphotropic phase boundary structures, the piezoelectric effect can be maximized in the region having a lower center of symmetry where two crystal structures coexist or compete.

[0076] For example, the amount of water molecules included in the diphenylalanine crystal (130) of the morphotropic phase boundary structure can form an MPB structure when the volume ratio of water in the mixed solvent (water:ethanol) is 8% to 12.5% ​​for gold and 8% to 15% for aluminum.

[0077] The bio-piezoelectric layer according to an embodiment of the present invention can maximize piezoelectric performance by including diphenylalanine crystals (130) of a morphotropic phase boundary structure. In addition, the bio-piezoelectric layer according to an embodiment of the present invention can obtain the maximum value of the piezoelectric performance of diphenylalanine very simply by adjusting the ratio of mixed solvents without additional processes.

[0078] Therefore, the bio-piezoelectric layer according to the embodiment of the present invention can realize an MPB structure in a biomaterial that was previously found only in inorganic materials.

[0079] In addition, by applying the bio-piezoelectric layer according to an embodiment of the present invention to a bio-piezoelectric element with an enhanced output value, a bio-material-based piezoelectric energy conversion element applicable to actual medical devices can be realized.

[0080]

[0081] Hereinafter, a method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention will be described in detail.

[0082] The method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can selectively realize a polymorphism through a self-assembly process of a peptide structure through thermodynamic and kinetic control, control the crystal structure, and improve piezoelectric properties.

[0083] A method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention comprises the steps of: preparing a diphenylalanine solution (110) by mixing diphenylalanine and ethanol in water (S110); immersing a substrate in the diphenylalanine solution (S120); and pulling the substrate (120) upward from the diphenylalanine solution to produce a diphenylalanine crystal (130) (S130).

[0084] A method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention controls the synthesis conditions of diphenylalanine dimorphic compounds rather than the crystallinity, density, and alignment of diphenylalanine, and can synthesize a diphenylalanine crystal (130) comprising at least one of a morphotropic phase boundary (MPB) structure in which a central asymmetric orthorhombic structure and crystal structures coexist (a structure in which the piezoelectric effect is maximized in the portion having a lower center of symmetry where the two crystal structures coexist or compete).

[0085] Specifically, for the self-assembly process of diphenylalanine, diphenylalanine is dissolved in a mixed solvent containing water and ethanol, and then a substrate (120) is pulled up from the diphenylalanine solution (110) at a constant speed using a syringe pump to synthesize the crystal structure of diphenylalanine (FF).

[0086] At this time, the diphenylalanine isomorphic form can be synthesized by appropriately adjusting the ratio of water to ethanol, and the crystal structure of diphenylalanine can also be controlled through the speed at which the substrate (110) is attracted. The method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can synthesize the diphenylalanine isomorphic form through such phase change control, and can manufacture an MPB structure during the process of changing two different crystal structures (central asymmetric orthorhombic structure and hexagonal tube structure).

[0087] Therefore, unlike conventional technologies, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention enables a phase change of the peptide in a simple manner.

[0088] Hereinafter, each step of the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention will be described in more detail.

[0089] First, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention proceeds with the step (S110) of preparing a diphenylalanine solution (110) by mixing diphenylalanine and ethanol in water.

[0090] Diphenylalanine is a peptide that can be used as a natural piezoelectric biomaterial, and by using diphenylalanine as a piezoelectric material, it can have biocompatible processability, biocompatibility, and biodegradability.

[0091] Specifically, natural piezoelectric biomaterials possess the advantages of biocompatibility, processability, biocompatibility, and biodegradability; among them, diphenylalanine, unlike other materials, exhibits strong piezoelectric performance, excellent mechanical properties, and a low dielectric constant.

[0092] Furthermore, unlike other piezoelectric materials, diphenylalanine is a paraelectric material that has the characteristic of self-assembly with polarization aligned in one direction, and unlike ferroelectric materials, it can align the polarization direction without other processes.

[0093] Water molecules react with the reactive groups (amino group, carboxyl group) at both ends of diphenylalanine to form an amphoteric (NH 3+ , COO -It is made to have a hydrophobic (FFZ) charge, and six FFZ rings form a hexagonal ring through hydrogen bonding. Through pi-pi bonding between the benzene rings in diphenylalanine, the hexagonal rings can be stacked to form a hexagonal prism. At this time, the hydrophobic benzene rings face outward, and the interior of the hexagonal prism becomes hydrophilic, allowing water molecules to form hydrogen bonds with diphenylalanine inside.

[0094] Ethanol is a solvent that dissolves diphenylalanine and is highly volatile; through a meniscus-driven self-assembly mechanism, ethanol evaporates rapidly, causing the diphenylalanine dissolved inside to instantaneously precipitate and form a crystal structure.

[0095] Conventionally, peptide structures were self-assembled using HFIP as a solvent, but HFIP is an organic toxic solvent and is expensive, posing a problem for future application to implantable piezoelectric power generation devices. The method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention includes ethanol as a solvent, thereby utilizing a biocompatible, eco-friendly, and economical synthesis method that can be applied as a piezoelectric power generation device in various medical fields.

[0096] Accordingly, the bio-piezoelectric layer manufactured using the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can be used as a biocompatible piezoelectric material based on PLA.

[0097] According to an example, the method for manufacturing a bio-piezoelectric layer according to an example of the present invention can control the crystal structure by adjusting the ratio of water to ethanol.

[0098] The crystal structure of the diphenylalanine crystal can be controlled by adjusting the ratio of water and ethanol contained in the diphenylalanine solution (110).

[0099] Preferably, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention controls the ratio of water and ethanol included in the diphenylalanine solution (110) so that the diphenylalanine can change from an amorphous structure to an orthorhombic and hexagonal prism structure, and a morphotropic phase boundary (MPB) structure can be synthesized between the orthorhombic structure (preferably, a central asymmetric orthorhombic structure) and the hexagonal prism structure, and precise control of the evaporation rate and the structure of the diphenylalanine are required to synthesize at least one of the orthorhombic structure and the morphotropic phase boundary (MPB) structure.

[0100] Specifically, the structure of the diphenylalanine molecule can be controlled depending on the amount of water; when the amount of water is small, the terminal functional groups of diphenylalanine exist in an unreacted neutral state and can form an orthorhombic structure with a small amount of water molecules. Additionally, in an ethanol solvent completely devoid of water, an amorphous structure lacking crystallinity and piezoelectric properties can be formed.

[0101] However, when the water content is 3% or more, neutral diphenylalanine and a very small amount of water combine to form an orthorhombic system, and as the amount of water increases, the amino and carboxyl groups present at both ends of diphenylalanine react with water molecules to exist as amphoteric ions, forming hydrogen bonds between diphenylalanine molecules and with water molecules, thereby forming a long, unidirectionally aligned hexagonal columnar structure.

[0102] Accordingly, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can control the crystal structure of the diphenylalanine crystals by controlling the degree of reaction of the terminal groups of diphenylalanine according to the ratio of water and ethanol included in the diphenylalanine solution (110).

[0103] Additionally, if there is a large amount of highly volatile ethanol in the diphenylalanine solution (110), the diphenylalanine solution (110) evaporates rapidly at the interface when the substrate (120) is pulled up from the diphenylalanine solution (110), and the rate of precipitation of diphenylalanine within the diphenylalanine solution (110) can be accelerated. On the other hand, as the amount of water included in the diphenylalanine solution (110) increases, the rate of evaporation of the diphenylalanine solution (110) becomes relatively slower, and since sufficient time is given for the diphenylalanine to form a structure within the diphenylalanine solution (110), there is insufficient time for the diphenylalanine to form the most stable hexagonal column when the water is relatively low during self-assembly, thus forming a thermodynamically unstable structure.

[0104] The volume ratio of water and ethanol (water:ethanol) included in the diphenylalanine solution (110) may be 5:95 to 25:75, and if the volume ratio of water included in the diphenylalanine solution (110) is less than 5%, an amorphous structure is formed, and if it is 25% or more, the solubility of diphenylalanine decreases and the crystallinity of the crystal structure decreases.

[0105] Accordingly, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can change the alignment direction of the superelectric diphenylalanine crystals (130) without additional processes by adjusting the ratio of the mixed solvent (including water and ethanol).

[0106] In addition, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention uses ethanol as a solvent, thereby enabling a simple, economical, and environmentally friendly process using water and ethanol.

[0107] The method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can control the self-assembly of diphenylalanine by controlling process humidity.

[0108] For example, when diphenylalanine is precipitated from ethanol and exposed to the external environment, there must be enough water molecules present to not interfere with self-assembly.

[0109] The process humidity can be 33% to 40%, and if the humidity of the diphenylalanine solution is less than 33%, there is a problem that crystal formation is difficult because there are insufficient water molecules necessary for the diphenylalanine to self-assemble, and if it exceeds 40%, the precipitating diphenylalanine is already exposed to water molecules in the air, and there is a problem that the final crystal structure, a hexagonal columnar structure, is synthesized regardless of the ratio of the solvent.

[0110] According to the example, the temperature and process humidity of the diphenylalanine solution (110) can be maintained the same from S110 to S130.

[0111] Afterwards, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention proceeds with the step (S120) of immersing a substrate (120) in a diphenylalanine solution (110).

[0112] The step (S120) of immersing the substrate (120) in the diphenylalanine solution involves immersing the substrate (120) in the diphenylalanine solution (110) and then pulling it at a constant speed, during which the solvent evaporates at the gas-liquid-solid interface, and at that point, the concentration of the solute increases rapidly, and nucleation and growth may occur.

[0113] A method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can control the crystal structure of the diphenylalanine crystal by controlling the concentration of the diphenylalanine solution (110).

[0114] Specifically, when the concentration of the diphenylalanine solution (110) increases, ethanol evaporates at the gas-liquid-solid interface and reaches a supersaturated state of diphenylalanine quickly, allowing the crystal structure to be formed more quickly and, because there is relatively more diphenylalanine dissolved in the solvent, the coverage area, degree of alignment (OOP), and crystallinity may increase, and when the concentration of the diphenylalanine solution (110) decreases, it takes time to reach a supersaturated state at the gas-liquid-solid interface, making it difficult to obtain a thermodynamically unstable crystal structure, and because there is relatively less diphenylalanine dissolved in the solvent, the coverage area, degree of alignment (OOP), and crystallinity may decrease.

[0115] Accordingly, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can produce diphenylalanine crystals having a desired crystal structure by adjusting the concentration of the diphenylalanine solution (110).

[0116] In the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention, the tendency of the crystals can be controlled depending on the material coated on the substrate (120).

[0117] For example, since phase transitions are faster in gold than in aluminum depending on the water volume ratio (the transition from a centered asymmetric orthorhombic structure to a morphotropic phase boundary structure is rapid, and the transition from an MPB structure to a hexagonal columnar structure is also rapid), MPB or hexagonal columnar crystal structures can be obtained depending on the material coated on the substrate at the same solvent volume ratio.

[0118] The material of the substrate itself does not affect the crystal structure, but the same crystal structure can be obtained when using a substrate with gold deposited on an organic substrate and a substrate with gold deposited on an inorganic substrate.

[0119] The substrate (120) may include at least one of an organic substrate and an inorganic substrate.

[0120] The inorganic substrate may include at least one of metal, silicon wafer (Si), glass, quartz, Al2O3, Si, and SiO2.

[0121] The metal may include at least one of aluminum (Al), gold (Au), chromium (Cr), silver (Ag), platinum (Pt), palladium (Pd), and copper (Cu).

[0122] The organic substrate may include at least one of Kapton foil, polyimide (PI), polyethersulfone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyarylate, polycarbonate (PC), cellulose triacetate (CTA), and cellulose acetate propionate (CAP).

[0123] Preferably, the substrate (120) may include a metal, and more preferably, the substrate (120) may include aluminum.

[0124] According to an embodiment, the substrate (120) serves to support diphenylalanine crystals and, when applied to a piezoelectric power generation element, can be used as a lower substrate / lower electrode or lower electrode.

[0125] For example, when the substrate (120) serves as a lower substrate / lower electrode, the substrate (120) may include a stacked structure of an organic substrate / inorganic substrate or an inorganic / substrate / inorganic substrate.

[0126] Finally, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention proceeds to the step (S130) of pulling the substrate (120) upward from the diphenylalanine solution (110) to produce a diphenylalanine crystal (130).

[0127] The step (S130) of manufacturing the diphenylalanine crystal (130) allows the substrate (120) to be pulled up from the diphenylalanine solution (110) while the solvent volatilizes, thereby enabling the growth of a thermodynamic-kinetic control-based self-assembled peptide structure.

[0128] The step (S130) of manufacturing the diphenylalanine crystal (130) can control the crystal structure of the diphenylalanine crystal (130) by controlling the pulling speed of the substrate (120).

[0129] Specifically, if the pulling speed of the substrate (120) increases, sufficient time is not given for diphenylalanine to nucleate and grow during the meniscus-driven self-assembly process, so a thermodynamically more unstable structure can be synthesized, and if the concentration of the diphenylalanine solution (110) decreases, sufficient time is given for the formation of the crystal structure of diphenylalanine, so a thermodynamically more stable structure can be synthesized.

[0130] Accordingly, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can produce diphenylalanine crystals having a desired crystal structure by controlling the pulling speed of the substrate (120).

[0131] The pulling speed of the substrate (120) may be 10 μm / min to 80 μm / min, and if the pulling speed of the substrate (130) is less than 10 μm / min, there is a problem that the pulling speed of the substrate is slower than the rate at which ethanol evaporates at the gas-liquid-solid interface, and if it exceeds 80 μm / min, there is a problem that the substrate is pulled faster than the time at which diphenylalanine precipitates at the gas-liquid-solid interface, so there is not enough time to form a crystal structure of diphenylalanine on the substrate.

[0132] For example, if the pulling speed of the substrate (120) increases, the solution evaporates more quickly at the interface, and the nucleation and growth rate of diphenylalanine increases, so a thermodynamically more unstable structure can be formed.

[0133]

[0134] FIG. 2 is a schematic diagram illustrating a piezoelectric power generation element according to an embodiment of the present invention.

[0135] Since the piezoelectric power generation element according to the embodiment of the present invention includes the same components as the bio-piezoelectric layer according to the embodiment of the present invention, the description of the same components is omitted.

[0136] A piezoelectric power generation element according to an embodiment of the present invention comprises a lower electrode (220) formed on a lower substrate (210), a diphenylalanine crystal layer (230) formed on the lower electrode (220), a protective layer (240) formed on the diphenylalanine crystal layer (230), an upper electrode (250) formed on the protective layer (240), and an upper substrate (260) formed on the upper electrode.

[0137] A piezoelectric power generation element according to an embodiment of the present invention includes a lower electrode (220) formed on a lower substrate (210).

[0138] The lower substrate (210) may include at least one of an organic substrate and an inorganic substrate.

[0139] The inorganic substrate may include at least one of glass, quartz, Al2O3, Si, and SiO2.

[0140] The organic material substrate may include at least one of Kapton foil, polyimide (PI), polyethersulfone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyarylate, polycarbonate (PC), cellulose triacetate (CTA), and cellulose acetate propionate (CAP).

[0141] The lower electrode (210) may include at least one of aluminum (Al), gold (Au), chromium (Cr), silver (Ag), platinum (Pt), palladium (Pd) and copper (Cu).

[0142] A piezoelectric power generation element according to an embodiment of the present invention includes a diphenylalanine crystal layer (230) formed on a lower electrode (220).

[0143] The diphenylalanine crystal layer (230) may include the same components as the bio-piezoelectric layer according to an embodiment of the present invention.

[0144] The diphenylalanine crystal layer (230) may include diphenylalanine crystals, and the diphenylalanine crystals include at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

[0145] A piezoelectric power generation element according to an embodiment of the present invention includes a protective layer (240) formed on a diphenylalanine crystal layer (230).

[0146] The protective layer (240) physically protects the crystal structure of diphenylalanine when measuring the piezoelectric power generation element, and since PMMA itself has no piezoelectric performance, the piezoelectric performance of diphenylalanine itself can be measured.

[0147] The protective layer (240) may include at least one of polymethacrylic acid (PMMA) and polylactic acid (PLA).

[0148] A piezoelectric power generation element according to an embodiment of the present invention includes an upper electrode (250) formed on a protective layer (240) and an upper substrate (260) formed on the upper electrode.

[0149] The upper substrate (260) may include at least one of an organic substrate and an inorganic substrate.

[0150] The inorganic substrate may include at least one of glass, quartz, Al2O3, Si, and SiO2.

[0151] The organic material substrate may include at least one of Kapton foil, polyimide (PI), polyethersulfone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyarylate, polycarbonate (PC), cellulose triacetate (CTA), and cellulose acetate propionate (CAP).

[0152] The upper electrode (250) may include at least one of aluminum (Al), gold (Au), chromium (Cr), silver (Ag), platinum (Pt), palladium (Pd) and copper (Cu).

[0153] The piezoelectric power generation device according to an embodiment of the present invention can verify whether the MPB structure synthesized by using diphenylalanine crystals as a piezoelectric material can be applied to an actual device, and whether the resulting value is higher than the measured value when using a conventional hexagonal prism structure. In addition, different piezoelectric performance can be verified depending on the diphenylalanine polymorph.

[0154] Hereinafter, a method for manufacturing a piezoelectric power generation element according to an embodiment of the present invention will be described.

[0155]

[0156] A method for manufacturing a piezoelectric power generation element according to an embodiment of the present invention comprises the steps of forming a lower electrode (220) on a lower substrate (210) (S210), forming a diphenylalanine crystal layer on the lower electrode (220) (S220), forming a protective layer on the diphenylalanine crystal layer (S230), and forming an upper substrate coated with an upper electrode on the protective layer (S240).

[0157] First, the method for manufacturing a piezoelectric power generation element according to an embodiment of the present invention proceeds with the step (S210) of forming a lower electrode (220) on a lower substrate (210).

[0158] The lower electrode (220) can be formed on the lower substrate (210) by any one of the following methods: thermal evaporation, electron beam evaporation, radio frequency sputtering, magnetron sputtering, vacuum deposition, or chemical vapor deposition.

[0159] Subsequently, the method for manufacturing a piezoelectric power generation element according to an embodiment of the present invention proceeds to the step (S220) of forming a diphenylalanine crystal layer on a lower electrode (220).

[0160] The step of forming a diphenylalanine crystal layer (S220) includes the step of preparing a diphenylalanine solution by mixing diphenylalanine and ethanol in water (S221), the step of immersing a substrate in the diphenylalanine solution (S222), and the step of pulling the substrate upward from the diphenylalanine solution to produce diphenylalanine crystals (S223).

[0161] Diphenylalanine crystals include at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

[0162] Subsequently, the method for manufacturing a piezoelectric power generation element according to an embodiment of the present invention proceeds to the step (S230) of forming a protective layer on a diphenylalanine crystal layer.

[0163] The protective layer (240) can be formed by any one of the following methods: spin coating, spray coating, ultra-spray coating, electrospinning coating, slot die coating, gravure coating, bar coating, roll coating, dip coating, shear coating, screen printing, inkjet printing, or nozzle printing.

[0164] Finally, the method for manufacturing a piezoelectric power generation element according to an embodiment of the present invention proceeds with the step (S240) of forming an upper substrate coated with an upper electrode on a protective layer.

[0165] The upper electrode (250) can be formed on the upper substrate (260) by any one of the following methods: tape adhesion, thermal evaporation, electron beam evaporation, radio frequency sputtering, magnetron sputtering, vacuum deposition, or chemical vapor deposition.

[0166]

[0167] Experimental Example 1: Characteristics of Crystal Structure According to Water Ratio

[0168] Comparative Example 1-1: Au H2O 0%

[0169] 6 mg of diphenylalanine and 10 ml of ethanol were added to a vial and vortexed for at least 30 minutes to completely dissolve the diphenylalanine. 10 nm of chromium and 50 nm of gold were thermally deposited onto a silicon wafer and then cut into pieces measuring 0.5 cm x 2 cm. 10 ml of the diphenylalanine solution was divided into 2 ml microtubes, and the gold substrate was suspended from a syringe pump. The gold substrate was immersed vertically into the solution using the syringe pump and pulled back at a constant speed.

[0170]

[0171] Comparative Example 1-2: Al H2O 0%

[0172] It was manufactured in the same manner as Comparative Example 1-1, except that a substrate with 100 nm of aluminum thermally deposited on a silicon wafer was used as the substrate.

[0173]

[0174] Example 1-1: Au H2O 5%

[0175] 6 mg of diphenylalanine, 9.5 ml of ethanol, and 0.5 ml of water were added to a vial and vortexed for at least 30 minutes to completely dissolve the diphenylalanine. 10 nm of chromium and 50 nm of gold were thermally deposited onto a silicon wafer and then cut into pieces measuring 0.5 cm x 2 cm. 10 ml of the diphenylalanine solution was divided into 2 ml microtubes, and the gold substrate was suspended from a syringe pump. The gold substrate was immersed vertically into the solution using the syringe pump and pulled back at a constant speed.

[0176]

[0177] Examples 1-2: Au H2O 8%

[0178] It was prepared in the same manner as Example 1-1, except that 0.8 ml (8%) of H2O was used.

[0179]

[0180] Examples 1-3: Au H2O 10%

[0181] It was prepared in the same manner as Example 1-1, except that 1 ml (10%) of H2O was used.

[0182]

[0183] Examples 1-4: Au H2O 12.5%

[0184] It was prepared in the same manner as Example 1-1, except that 1.25 ml (15%) of H2O was used.

[0185]

[0186] Examples 1-5: Au H2O 15%

[0187] It was prepared in the same manner as Example 1-1, except that 1.5 ml (12.5%) of H2O was used.

[0188]

[0189] Examples 1-6: Au H2O 16.7%

[0190] It was prepared in the same manner as Example 1-1, except that 1.67 ml (16.7%) of H2O was used.

[0191]

[0192] Examples 1-7: Au H2O 25%

[0193] It was prepared in the same manner as Example 1-1, except that 2.5 ml (25%) of H2O was used.

[0194]

[0195] Examples 1-8: Al H2O 5%

[0196] It was manufactured in the same manner as Example 1-1, except that a substrate with 100 nm of aluminum thermally deposited on a silicon wafer was used as the substrate.

[0197]

[0198] Examples 1-9: Al H2O 8%

[0199] It was manufactured in the same manner as Example 1-2, except that a substrate with 100 nm of aluminum thermally deposited on a silicon wafer was used as the substrate.

[0200]

[0201] Examples 1-10: Al H2O 10%

[0202] It was manufactured in the same manner as Examples 1-3, except that a substrate with 100 nm of aluminum thermally deposited on a silicon wafer was used as the substrate.

[0203]

[0204] Example 1-11: Al H2O 15%

[0205] It was manufactured in the same manner as Examples 1-4, except that a substrate with 100 nm of aluminum thermally deposited on a silicon wafer was used as the substrate.

[0206]

[0207] Examples 1-12: Al H2O 12.5%

[0208] It was manufactured in the same manner as Examples 1-5, except that a substrate with 100 nm of aluminum thermally deposited on a silicon wafer was used as the substrate.

[0209]

[0210] Example 1-13: Al H2O 16%

[0211] It was manufactured in the same manner as Examples 1-6, except that a substrate with 100 nm of aluminum thermally deposited on a silicon wafer was used as the substrate.

[0212]

[0213] Example 1-14: Al H2O 25%

[0214] It was manufactured in the same manner as Examples 1-7, except that a substrate with 100 nm of aluminum thermally deposited on a silicon wafer was used as the substrate.

[0215]

[0216] FIG. 3 is an optical microscope (OM) image showing the shape of diphenylalanine crystals formed on an aluminum substrate or a gold substrate according to the ratio of water, and FIG. 4 is a transmission electron microscope (SEM) image showing the shape of diphenylalanine crystals according to the ratio of water.

[0217] Referring to Figures 3 and 4, it can be seen that at 0% H2O, very thin fibers form a structure aligned in one direction.

[0218] When 5% water is added, 2D structures aligned in random directions are formed, and when 8% or 9% water is added, it can be seen that two structures are visible simultaneously, one side forms the same structure as 5%, and the other side forms a shape in which tubes that are thicker and three-dimensional than H2O 0% are aligned in a single direction.

[0219] It can be seen that in Au with H2O from 10% to 16% and in Al with H2O from 10% to 12.5%, thicker and more three-dimensional tubes are formed in a single direction compared to 0% H2O, and in Au with H2O 25% and in Al with H2O 16.7% and 25%, thick hexagonal prism structures are formed in a single direction.

[0220] In addition, as can be seen in Figure 3, as the volume ratio of water increases, it can be seen that the thickness of the nanotubes is formed unevenly due to the stick-slip phenomenon.

[0221]

[0222] Figure 5 is a graph showing the coverage area and Out-of-Plane (OOP) of diphenylalanine crystals formed on an aluminum substrate or a gold substrate according to the ratio of water.

[0223] Referring to Figure 5, it can be seen that the coverage area is very small because very thin fibers form a structure aligned in one direction at 0% H2O, but the OOP has a very high value.

[0224] In addition, it can be seen that when 5% water is added, the OOP decreases sharply due to the formation of 2D structures aligned in random directions, and the coverage area and OOP increase due to morphotropic phase boundary structures formed from 8% or 9% water.

[0225] In addition, it can be seen that in both substrates, the thickest nanotubes at 25% H2O have a shape aligned in one direction, thus having the highest coverage area and OOP value.

[0226]

[0227] Figure 6 is a graph showing the X-ray diffraction (XRD) analysis results of diphenylalanine crystals formed on a gold substrate according to the ratio of water and the crystal structure of diphenylalanine crystals formed on a gold substrate according to the ratio of water and the pulling speed, and Figure 7 is a graph showing the X-ray diffraction (XRD) analysis results of diphenylalanine crystals formed on an aluminum substrate according to the ratio of water and the crystal structure of diphenylalanine crystals formed on an aluminum substrate according to the ratio of water and the pulling speed.

[0228] Figure 8 is a graph showing the X-ray diffraction (XRD) analysis results of diphenylalanine crystals formed on a gold substrate according to the ratio of water and the pulling speed, and Figure 9 is a diphenylalanine crystal formed on an aluminum substrate according to the ratio of water and the pulling speed.

[0229] In Figures 6 to 9, the pulling speed of the substrate was varied to 10 μm / min, 20 μm / min, 40 μm / min, 60 μm / min, and 80 μm / min.

[0230] Referring to FIGS. 6 to 9, it can be seen that the crystal structure of diphenylalanine varies not only depending on the ratio of the mixed solvent (preferably, the ratio of water to ethanol, more preferably, the ratio of water to ethanol) but also on the pulling speed of the substrate.

[0231] In addition, it can be seen that the crystal structure of diphenylalanine shows different tendencies depending on the type of substrate, and that the tendency is faster in gold than in aluminum.

[0232]

[0233] FIG. 10 is a graph showing the X-ray diffraction (XRD) analysis results of diphenylalanine crystals according to Example 1-1 and diphenylalanine crystals according to Example 1-7, and FIG. 11 is a schematic diagram showing the structure of the identical amorphous compounds of diphenylalanine.

[0234] Referring to Fig. 10, it can be seen that by adjusting the ratio of water, not only the existing hexagonal prism-shaped crystal structure but also the centrosymmetric orthorhombic structure can be formed.

[0235] Figure 11 is an image showing a molecular model in the ab direction of a hexagonal prism-shaped structure and a central asymmetric orthorhombic structure.

[0236] Referring to Fig. 11, in the case of an asymmetric orthorhombic structure, ethanol molecules exist between the diphenylalanine structures and form a 2D structure, after which each layer is stacked by bonding between benzene rings to form the structure. In the hexagonal columnar structure, hydrogen bonds are formed between water and diphenylalanine to form hexagonal rings, and each layer is stacked by bonding between benzene rings to form a hexagonal columnar shape.

[0237]

[0238] FIG. 12 is a graph showing the piezoelectric constant values ​​of diphenylalanine crystals formed on a gold substrate according to the ratio of water, FIG. 13 is a graph showing the piezoelectric constant values ​​of diphenylalanine crystals formed on an aluminum substrate according to the ratio of water, and FIG. 14 and FIG. 15 are images showing the piezoelectric response microscope (PFM) measurement results of diphenylalanine crystals formed on a gold substrate or an aluminum substrate according to the ratio of water.

[0239] Referring to Figures 12 to 15, it can be seen that the piezoelectric performance is lowest at 0%, which is an amorphous structure, and the piezoelectric constant in the MPB structure is much higher than that of the conventional C6 structure.

[0240] In addition, when measuring the piezoelectric constant of each allotrope, it was found that both gold and aluminum exhibited the highest values ​​in the MPB structure, and that the value was higher in aluminum than in gold.

[0241]

[0242] Figure 16 is a graph showing the simulation results of calculating the molecular state of diphenylalanine in a solvent.

[0243] Referring to Figure 16, it can be seen that in areas with a high concentration of ethanol, the functional groups remain in an unreacted FFN state, but as water is added, both functional groups react to form an amphoteric (FFZ) state.

[0244]

[0245] Figure 17 is a graph showing the molecular state of diphenylalanine in a solvent.

[0246] Referring to Figure 17, it can be seen that when water is scarce, both reactive groups of diphenylalanine exist in a neutral state (FFN), but as water is added, the water and both reactive groups of FF (carboxyl group, amine group) react to exist as zwitterions (FFZ).

[0247] Specifically, the reason why the bio-piezoelectric layer according to the embodiment of the present invention forms different structures of diphenylalanine depending on the ratio of the mixed solvent (preferably, the ratio of water) is as follows.

[0248] First, since the structure of the diphenylalanine molecule varies depending on the amount of water, when the amount of water is small, the terminal functional groups of diphenylalanine exist in an unreacted neutral state and can form an orthorhombic structure together with a small amount of water molecules. Therefore, in an ethanol solvent completely devoid of water, an amorphous structure lacking crystallinity and piezoelectric properties can be formed.

[0249] However, when the water content is 3% or more, the neutral diphenylalanine and a very small amount of water can clump together to form an orthorhombic structure, and as the amount of water increases, the amino and carboxyl groups present at both ends of the diphenylalanine react with water molecules to exist in the state of amphoteric ions, forming hydrogen bonds between diphenylalanine molecules and hydrogen bonds with water molecules, and can form a long, unidirectionally aligned hexagonal columnar structure.

[0250] Furthermore, if the mixed solvent (containing water and ethanol, e.g., water and ethanol) contains a high amount of highly volatile ethanol, the diphenylalanine solution evaporates rapidly at the interface when the substrate is pulled up from the diphenylalanine solution, and the precipitation rate of diphenylalanine within the diphenylalanine solution may increase. Conversely, as the amount of water in the mixed solvent (containing water and ethanol, e.g., water and ethanol) increases, the rate of evaporation of the diphenylalanine solution relatively slows down, providing sufficient time for diphenylalanine to form a structure within the diphenylalanine solution.

[0251] Therefore, diphenylalanine can form a thermodynamically unstable structure because there is insufficient time to form the most stable hexagonal prisms when water is relatively scarce during self-assembly.

[0252] Accordingly, when manufacturing a bio-piezoelectric layer according to an embodiment of the present invention, the center-asymmetric orthorhombic and MPB structures of diphenylalanine can be synthesized for the two reasons explained above.

[0253] However, since the center-asymmetric orthorhombic and MPB structures of diphenylalanine require precise control of the evaporation rate and the structure of diphenylalanine, it must be manufactured by precisely adjusting process parameters.

[0254]

[0255] Experimental Example 2: Center-asymmetric orthorhombic structure

[0256] Example 2-1: FF / Au

[0257] 6 mg of diphenylalanine, 9.5 ml of ethanol, and 0.5 ml of water were added to a vial and vortexed for at least 30 minutes to completely dissolve the diphenylalanine. 10 nm of chromium and 50 nm of gold were thermally deposited onto a silicon wafer and then cut into pieces measuring 0.5 cm x 2 cm. 10 ml of the diphenylalanine solution was divided into 2 ml microtubes, and the gold substrate was suspended from a syringe pump. The gold substrate was immersed vertically into the solution using the syringe pump and pulled back at a constant speed.

[0258] Changes in the crystal structure were confirmed by measuring XRD after placing the synthesized substrate with a centered asymmetric orthorhombic structure in a place with high humidity (90–99%) for a certain period of time (0, 6, 9, 12, 15 hours).

[0259]

[0260] Example 2-2: FF / Al

[0261] It was manufactured in the same manner as Example 2-1, except that a substrate with 100 nm of aluminum thermally deposited on a silicon wafer was used as the substrate.

[0262]

[0263] Figure 18 is a graph showing the results of X-ray diffraction analysis of diphenylalanine crystals according to Example 2-1, and a graph showing the results of X-ray diffraction analysis of diphenylalanine crystals according to Example 2-2.

[0264] Referring to Fig. 18, the synthesized center-asymmetric orthorhombic structure is thermodynamically unstable as the substrate is attracted to a state lacking water molecules. However, if the crystal structure is placed in a high-humidity environment for a certain period after it is formed, the crystal may encounter water molecules through external air, causing it to transform into the thermodynamically most stable hexagonal prism structure. During synthesis, not only is the crystal structure of diphenylalanine controlled through the water ratio, but changes in the crystal structure can also be induced by providing water molecules to the synthesized crystal structure.

[0265] Specifically, the existing orthorhombic structure of diphenylalanine is formed by increasing the temperature from a hexagonal column to 150°C or higher, at which point water molecules inside the diphenylalanine are completely removed, forming an orthorhombic P22121 structure.

[0266] However, the orthorhombic structure included in the biopiezoelectric layer according to the embodiment of the present invention is formed as the amount of water decreases, with neutral diphenylalanine molecules in the diphenylalanine solution and a very small amount of water molecules aggregating to form an orthorhombic structure (different from the structure formed when there are no water molecules at all). Unlike P22121, this structure is C 2v It has a spatial group and different XRD measurement results, and can exhibit piezoelectric performance with a central asymmetric structure.

[0267] Specifically, the diphenylalanine crystals included in the biopiezoelectric layer according to an embodiment of the present invention may first form a relatively thermodynamically unstable orthorhombic structure in an amorphous structure according to the ratio of the mixed solvent in accordance with the Ostwald step rule, and finally form the most stable hexagonal prism.

[0268] In fact, it can be confirmed via XRD that the crystal structure of the synthesized orthorhombic crystal changes into a stable hexagonal columnar structure over time when exposed to high humidity.

[0269] Accordingly, the method for manufacturing a bio-piezoelectric layer according to an embodiment of the present invention can control the crystalline phase structure using the Ostwald step rule of diphenylalanine.

[0270] This suggests that, rather than simply synthesizing polymorphs based on solvent ratio control, the phase transition of diphenylalanine polymorphs follows the Ostwald step rule, and an MPB structure in which two crystal structures coexist can be formed during this phase transition.

[0271]

[0272] Experimental Example 3: Performance Analysis of Piezoelectric Elements

[0273] Example 3-1: FF / Au piezoelectric power generation element

[0274] 6 mg of diphenylalanine was added to a vial along with (10 ml of ethanol and 0 ml of water), (9 ml of ethanol and 1 ml of water), and (7.5 ml of ethanol and 2.5 ml of water), and then vortexed for more than 30 minutes to completely dissolve the diphenylalanine. 10 nm of chromium and 50 nm of gold were thermally deposited onto a PEN film and then cut into a 0.5 cm x 3 cm size. 10 ml of the diphenylalanine solution was divided into 2 ml microtubes, and the gold substrate was suspended from a syringe pump.

[0275] The gold substrate was immersed vertically in the solution using a syringe pump and pulled back at a constant speed (20 μ / min). 150 mg of PMMA and 1 ml of acetonitrile (150 mg / ml concentration) were placed in a vial and mixed in a stirrer for about 12 hours. The PMMA solution was spin-coated onto the substrate containing diphenylalanine at a speed of 3000 rpm for about 30 seconds, and then placed in a 60-degree oven for about 30 minutes to evaporate the remaining acetonitrile solvent. A PEN / Au film (a substrate cut to 0.5 cm x 3 cm by thermally depositing 10 nm of chromium and 50 nm of gold onto PEN) was placed on the PMMA-coated substrate and secured with tape. Wires were connected to each electrode.

[0276]

[0277] Example 3-2: FF / Al piezoelectric power generation element

[0278] 6 mg of diphenylalanine was added to a vial along with (10 ml of ethanol and 0 ml of water), (8.75 ml of ethanol and 1.25 ml of water), and (7.5 ml of ethanol and 2.5 ml of water), and then vortexed for more than 30 minutes to completely dissolve the diphenylalanine. 100 nm of aluminum was thermally deposited onto a PEN film and then cut into a 0.5 cm x 3 cm size. 10 ml of the diphenylalanine solution was divided into 2 ml microtubes, and the aluminum substrate was suspended from a syringe pump. The aluminum substrate was immersed vertically into the solution using the syringe pump and pulled back at a constant speed (20 μ / min).

[0279] Add 150 mg of PMMA and 1 ml of acetonitrile (150 mg / ml concentration) to a vial and mix in a stirrer for about 12 hours. Spin-coat the PMMA solution onto a substrate containing diphenylalanine at 3000 rpm for about 30 seconds, then place in a 60-degree oven for about 30 minutes to evaporate the remaining acetonitrile solvent. Place a PEN / Al film (a substrate cut to 0.5 cm x 3 cm by thermally depositing 100 nm of aluminum onto PEN) onto the PMMA-coated substrate and secure it with tape. Connect wires to each electrode.

[0280]

[0281] The piezoelectric power generation element according to Example 3-1 and the piezoelectric power generation element according to Example 3-2 are shown in FIG. 19.

[0282]

[0283] FIG. 20 is a graph showing the voltage over time of a piezoelectric power generation element according to Example 3-1 manufactured by adjusting the ratio of water, FIG. 21 is a graph showing the current over time, and FIG. 22 is a graph showing the power density over resistance.

[0284] FIG. 23 is a graph showing the voltage over time of a piezoelectric power generation element according to Example 3-2 manufactured by adjusting the ratio of water, FIG. 24 is a graph showing the current over time, and FIG. 25 is a graph showing the power density according to resistance.

[0285] FIG. 26 is a graph showing the voltage and current according to the power of the piezoelectric power generation element according to Example 3-2.

[0286] Referring to FIGS. 20 to 26, it can be seen that the voltage, current, and power density values ​​are increased compared to conventional hexagonal columns.

[0287] Specifically, when aluminum is used as a substrate, it can be seen that the amount of water molecules required to form the MPB structure is greater than that of gold, and the piezoelectric constant is also generally much higher than that of gold.

[0288] In the case of MPB, gold is 62.15 pm / V at 10% H2O, while aluminum is 80.8 pm / V at 12.5% ​​H2O, and the output values ​​of the piezoelectric element are also 2.4 V and 8.48 μA / cm² for aluminum. 2 It is the highest value, and this value is the highest value among existing diphenylalanine measurements.

[0289]

[0290] FIG. 27 is a graph showing the results of a stability test of a piezoelectric power generation element according to Example 3-2.

[0291] Referring to FIG. 27, it can be seen that the piezoelectric power generation element (PENG) according to Example 3-2 containing 12.5% ​​H2O operates stably for 10,000 cycles.

[0292]

[0293] As described above, although the present invention has been explained by limited embodiments and drawings, the present invention is not limited to the above embodiments, and various modifications and variations are possible from this description by those skilled in the art to which the present invention belongs. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

1. Substrate; and A diphenylalanine crystal layer formed on the above substrate and comprising diphenylalanine crystals; Includes, A biopiezoelectric layer characterized in that the above-mentioned diphenylalanine crystal comprises at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

2. In Paragraph 1, A bio-piezoelectric layer characterized by the above-mentioned central asymmetric orthorhombic structure belonging to the C2v point group.

3. In Paragraph 1, A biopiezoelectric layer characterized in that the above-mentioned morphotropic phase boundary structure includes a central asymmetric orthorhombic structure and a hexagonal tube structure.

4. In Paragraph 3, A bio-piezoelectric layer characterized by the above-mentioned hexagonal tube structure belonging to the C6 point group.

5. In Paragraph 1, A bio-piezoelectric layer characterized by the substrate comprising at least one of aluminum (Al), gold (Au), chromium (Cr), silicon wafer (Si), silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), and glass.

6. A step of preparing a diphenylalanine solution by mixing diphenylalanine and ethanol in water; A step of immersing a substrate in the above diphenylalanine solution; A step of producing diphenylalanine crystals by pulling the substrate upward from the diphenylalanine solution; Includes, A method for manufacturing a bio-piezoelectric layer, characterized in that the above-mentioned diphenylalanine crystal comprises at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

7. In Paragraph 6, The step of manufacturing the above-mentioned diphenylalanine crystals is, A method for manufacturing a bio-piezoelectric layer characterized by controlling the crystal structure of the diphenylalanine crystal by adjusting the volume ratio (water:ethanol) of water and ethanol contained in the diphenylalanine solution.

8. In Paragraph 7, A method for manufacturing a bio-piezoelectric layer characterized by the volume ratio (water:ethanol) of water and ethanol included in the above diphenylalanine solution being 5:95 to 25:

75.

9. In Paragraph 8, The step of manufacturing the above-mentioned diphenylalanine crystals is, A method for manufacturing a bio-piezoelectric layer characterized by controlling the crystal structure of the diphenylalanine crystal by adjusting the pulling speed of the substrate.

10. In Paragraph 9, A method for manufacturing a bio-piezoelectric layer characterized by the above-mentioned pulling speed being 10 μm / min to 80 μm / min.

11. A lower electrode formed on a lower substrate; A diphenylalanine crystal layer formed on the lower electrode above; A protective layer formed on the above-mentioned diphenylalanine crystal layer; An upper electrode formed on the above protective layer; and An upper substrate formed on the upper electrode; Includes, The above diphenylalanine crystal layer comprises diphenylalanine crystals, and A piezoelectric power generation device characterized in that the above-mentioned diphenylalanine crystal comprises at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

12. A step of forming a lower electrode on a lower substrate; A step of forming a diphenylalanine crystal layer on the lower electrode; A step of forming a protective layer on the diphenylalanine crystal layer; and A step of forming an upper substrate coated with an upper electrode on the above protective layer; Includes, The step of forming the above diphenylalanine crystal layer is, A step of preparing a diphenylalanine solution by mixing diphenylalanine and ethanol in water; A step of immersing a substrate in the above diphenylalanine solution; A step of producing diphenylalanine crystals by pulling the substrate upward from the diphenylalanine solution; Includes, A method for manufacturing a piezoelectric power generation device characterized in that the above-mentioned diphenylalanine crystal comprises at least one of a central asymmetric orthorhombic structure and a morphotropic phase boundary (MPB) structure.

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