Self-assembling membrane structure, method for manufacturing self-assembling membrane structure, method for manufacturing injection body, method for controlling injection body, self-migrating body, self-migrating metal catalyst, and method for manufacturing self-migrating metal catalyst

Abstract

The present invention comprises a semipermeable membrane and a basic solution 10 and a membrane-forming solution 11 separated by the semipermeable membrane. The semipermeable membrane is provided with, in a continuous manner, at least two kinds of inorganic membranes 21, 22 having different formation rates, the inorganic members being formed by self-assembly through contact between the basic solution and the membrane-forming solution. With the osmotic pressure difference across the semipermeable membrane as the driving force, the membrane-forming solution 11 is injected into the basic solution 10, accompanied by localized damage to the semipermeable membrane, and the semipermeable membrane is reformed at the damaged location.

Description

Self-assembled film structure, method for manufacturing self-assembled film structure, method for manufacturing projected body, method for controlling projected body, self-migrating body, self-migrating metal catalyst, and method for manufacturing self-migrating metal catalyst

[0001] The present invention relates to a self-assembled film structure, a method for manufacturing a self-assembled film structure, a method for manufacturing an ejected body, a method for controlling an ejected body, a self-migrating body, a self-migrating metal catalyst, and a method for manufacturing a self-migrating metal catalyst.

[0002] Conventionally, the minute amounts of liquid required for the manufacture of microstructures have been delivered or injected by combining a pump, such as a syringe pump using the rotation of a motor, a peristaltic pump, or a micropump using a piezoelectric element, with a microfluidic device, and the recurrent injection of a solution has been achieved by generating shear stress in the fluid. For example, Patent Documents 1 and 2 disclose examples of micro diaphragm pumps that use the vibration of a piezoelectric element.

[0003] Japanese Patent No. 5982117 Japanese Patent Application Laid-Open No. 2023-183637

[0004] However, conventional micro-injection requires a built-in pump to deliver the liquid and a microfluidic device fabricated using microfabrication technology to induce shear stress, which results in problems such as high costs, inefficiency, and the need for sophisticated and complex setup techniques.

[0005] The present disclosure has been made in consideration of such problems, and its purpose is to provide a self-assembled film structure, a method for manufacturing a self-assembled film structure, a method for manufacturing an ejected body, a method for controlling an ejected body, a self-mover, a self-migrating metal catalyst, and a method for manufacturing a self-migrating metal catalyst, which are capable of realizing material saving, cost reduction, and simplification of setup technology.

[0006] In order to solve the above problems, one aspect of the self-assembled membrane structure disclosed herein includes a semipermeable membrane, and a first solution and a second solution separated by the semipermeable membrane, wherein the semipermeable membrane has at least two types of inorganic membranes in series that are formed through self-assembly upon contact of the first solution and the second solution and have different formation rates, and is characterized in that the osmotic pressure inside and outside the semipermeable membrane is used as a driving force to perform injection of the second solution into the first solution, accompanied by localized damage to the semipermeable membrane, and reformation of the semipermeable membrane at the damaged site.

[0007] According to the above configuration, a membrane structure is spontaneously formed on-site through self-assembly, enabling the injection of minute amounts of solution. This reduces the use of materials and costs for the micropump, simplifies the setup process, and enables labor savings, improved mass production efficiency, and reduced environmental impact. Furthermore, according to the present invention, the energy required for injection is the osmotic pressure inside and outside the membrane structure, eliminating the need for an external energy supply, as required by conventional micropumps, thereby achieving energy and space savings. Furthermore, according to the present invention, the injection cycle, liquid delivery volume, and the like can be controlled depending on the concentration of the solution and the type, combination, or concentration of metals forming the inorganic membrane. This allows operators to efficiently and suitably deliver liquid by injection of minute volumes, regardless of their level of skill or technique.

[0008] One aspect of the method for producing a self-assembled membrane structure disclosed herein is characterized by comprising: an adding step of adding a membrane-forming solution containing water-soluble salts of at least two types of metals to a basic solution containing hydroxide ions; and a semipermeable membrane-forming step of forming a semipermeable membrane by contacting the basic solution with the membrane-forming solution to form, through self-assembly, a soluble membrane formed by a hydroxide of an amphoteric metal and a stable membrane formed by a metal hydroxide that is less soluble and forms at a slower rate than the soluble membrane.

[0009] One aspect of the method for producing a self-assembled membrane structure disclosed herein is characterized in that, in the above-mentioned method for producing a self-assembled membrane structure, it further comprises an injection step in which the membrane-forming solution is injected from within the semipermeable membrane into the basic solution using osmotic pressure inside and outside the semipermeable membrane as a driving force, resulting in localized damage to the semipermeable membrane.

[0010] One aspect of the method for producing an ejected body disclosed herein is characterized by comprising: an adding step of adding a membrane-forming solution containing water-soluble salts of at least two types of metals to a basic solution containing hydroxide ions; a semipermeable membrane-forming step of forming a semipermeable membrane by contacting the basic solution with the membrane-forming solution, whereby a soluble membrane formed from an amphoteric metal hydroxide and a stable membrane formed from a metal hydroxide that is less likely to dissolve and forms at a slower rate than the soluble membrane through self-assembly; an ejection step of ejecting the membrane-forming solution from within the semipermeable membrane into the basic solution using osmotic pressure inside and outside the semipermeable membrane as a driving force, accompanied by localized damage to the semipermeable membrane; and an ejected body-forming step of forming an ejected body from the basic solution, which is made of the same metal hydroxide as the stable membrane.

[0011] One aspect of the method for controlling an ejection body disclosed herein is characterized in that, in the above-mentioned method for manufacturing an ejection body, the shape of the ejection body to be manufactured is changed based on the amount of the film-forming solution added or the concentration of the basic solution in the adding step.

[0012] One aspect of the self-electrophoresis element disclosed herein is based on a self-electrophoresis element that migrates in a reaction solution, and is characterized in that the self-electrophoresis element contains a hydroxide of a metal other than an amphoteric metal that is less soluble in a basic solution than the hydroxide of the amphoteric metal, catalyzes a reaction in the reaction solution, is capable of stirring the reaction solution by migration, has a head and a tail extending from the head, and the tail has a smaller radial cross-sectional area than the head.

[0013] One aspect of the self-migrating metal catalyst disclosed herein is based on a metal catalyst that migrates in a reaction solution, and contains a hydroxide of a metal other than an amphoteric metal that is less soluble in a basic solution than the hydroxide of the amphoteric metal, and is characterized in that it catalyzes a reaction in the reaction solution, is capable of stirring the reaction solution by migration, has a head and a tail extending from the head, and the tail has a smaller radial cross-sectional area than the head.

[0014] One aspect of the method for producing a self-migrating metal catalyst disclosed herein is based on the premise of a method for producing a self-migrating metal catalyst that migrates in a reaction solution, and includes: an adding step of adding a membrane-forming solution containing water-soluble salts of at least two types of metals to a basic solution containing hydroxide ions; and a semipermeable membrane-forming step of forming a semipermeable membrane by contacting the basic solution with the membrane-forming solution to form a soluble membrane formed by hydroxide of an amphoteric metal and a stable membrane formed by hydroxide of a metal that is less soluble and forms at a slower rate than the soluble membrane through self-assembly. The method includes an injection step in which the membrane-forming solution is injected from inside the semipermeable membrane into the basic solution using the osmotic pressure inside and outside the semipermeable membrane as a driving force, accompanied by localized damage to the semipermeable membrane, and an injection body formation step in which the injected membrane-forming solution becomes an injection body made of the same metal hydroxide as the stable membrane in the basic solution, wherein the injection body is a self-migrating metal catalyst that catalyzes a reaction in the reaction solution, is capable of stirring the reaction solution by migration, has a head and a tail extending from the head, and the tail has a smaller cross-sectional area than the head.

[0015] According to the above configuration, the self-migrating metal catalyst can be used as a heterogeneous catalyst in the injection body obtained by injection of a self-assembled monolayer structure. Conventional heterogeneous catalysts require stirring of the reaction solution during the catalytic reaction. However, the self-migrating metal catalyst of the present disclosure catalyzes the reaction in the reaction solution and can self-migrate due to the gas generated by the catalytic reaction, thereby reducing the energy required for stirring in the catalytic reaction solution. For example, the self-migrating metal catalyst can decompose hydrogen peroxide into water and oxygen in a reaction solution containing hydrogen peroxide, enabling self-migration due to the generation of oxygen. Furthermore, the shape of the injection body can be controlled by the amount of film-forming solution added or the concentration of the basic solution. By changing the shape of the injection body, the migration trajectory can be changed when used as an electrophoretic body.

[0016] According to the present invention, a membrane structure is spontaneously formed on-site through self-assembly, and the membrane structure can be used to eject a small amount of solution. Furthermore, a self-migrating ejected object can be obtained from the ejected solution. This allows for material saving, cost reduction, and a reduction in the environmental burden.

[0017] FIG. 1 is a schematic diagram of an ejection body. FIG. 2 is a diagram explaining the trajectory of a self-mover and the circle of curvature formed by the shape of the self-mover. FIG. 3 is a heat map of frequencies for k1', k2', and k3' obtained by simulation. FIG. 4 is a heat map of frequencies for k1', k2', and k3' obtained by simulation. FIG. 5 is a heat map of frequencies for k1', k2', and k3' obtained by simulation. FIG. 6 is a heat map of frequencies for k1', k2', and k3' obtained by simulation. FIG. 7 is a flow diagram showing a method for manufacturing a self-assembled film structure and an ejection body. FIG. 8 is a schematic diagram showing the operating principle of a self-assembled film structure according to an embodiment. FIG. 9 is a schematic diagram showing the operating principle of a self-assembled film structure according to an embodiment. FIG. 10 is a schematic diagram showing the operating principle of a self-assembled film structure according to an embodiment. 1-1 is a snapshot showing the time series change of the self-assembled actuator according to Example 1-1. FIG. 1-2 is a graph showing the relationship between the concentration of a basic solution and the injection volume of the self-assembled actuator according to Example 1-1. FIG. 1-3 is a graph showing the relationship between the volume of a film-forming solution and the injection volume of the self-assembled actuator according to Example 1-1. FIG. 1-4 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of aluminum and copper. FIG. 1-5 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of aluminum and nickel. FIG. 1-6 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of aluminum and manganese. FIG. 1-7 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of aluminum and magnesium. FIG. 1-8 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of aluminum and iron (III). FIG. 1-9 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of aluminum and cobalt. FIG. 1-10 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of aluminum and lanthanum. FIG. 1-11 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of aluminum and calcium. FIG. 1-12 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of aluminum and terbium. FIG. 1-13 is a diagram showing the dynamics of the self-assembled monolayer structure and the concentrations of gallium and copper. 1 is a diagram showing the dynamics of the self-assembled monolayer structure in relation to the concentrations of zinc and copper, and cadmium and copper, respectively.1 is a diagram showing the dynamics of a self-assembled monolayer structure in relation to the concentrations of indium and copper; 2 is a diagram showing the dynamics of a self-assembled monolayer structure in relation to the concentrations of tin and copper; 3 is a diagram showing the change in the morphology of an ejected body depending on the amount of film-forming solution added; 4 is a diagram showing the change in the morphology of an ejected body depending on the concentration of a basic solution; 5 is a diagram showing the change in the concentration of rhodamine B, a model substance for water stains, over time in Examples 3-1 to 3-3; 6 is an image showing the change in color of a reaction solution over time in Examples 3-1 to 3-3; 7 is a diagram showing various forms of an autophoretic body and the change in its position over time; 8 is a diagram showing the relationship between the radius of curvature r of an autophoretic body and the radius of curvature R of the orbit; 9 is a diagram showing the relationship between the radius of curvature r of an autophoretic body and the orbital period T; 10 is a diagram showing the relationship between the angle θ of an autophoretic body and the ratio L of the length of the autophoretic body to the circumference of radius r.

[0018] Hereinafter, the embodiments will be described in detail. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0019] [Self-assembled membrane structure] The self-assembled membrane structure according to this embodiment includes a semipermeable membrane and a first solution and a second solution separated by the semipermeable membrane. The semipermeable self-assembled membrane structure uses the osmotic pressure inside and outside the semipermeable membrane as a driving force to inject the second solution into the first solution, causing localized damage to the semipermeable membrane, and then reforming the semipermeable membrane at the damaged site. The first solution is a basic solution, and the second solution is a membrane-forming solution.

[0020] The self-assembled monolayer structure can perform recursive motion by repeatedly ejecting a solution and reforming a semipermeable membrane through the self-assembled monolayer structure, depending on the combination of metals contained in the membrane-forming solution and the composition ratio of the soluble and stable membranes in the self-assembled monolayer structure. The recursive motion of the self-assembled monolayer structure is performed as self-excited vibration. When the self-assembled monolayer structure undergoes self-excited vibration, it can also be used as an actuator. The period, liquid delivery rate, etc. of such a self-assembled actuator can be controlled by changing the combination of metals contained in the membrane-forming solution and the composition ratio of the soluble and stable membranes in the self-assembled monolayer structure.

[0021] (Semipermeable Membrane) A semipermeable membrane is formed by self-assembly upon contact between a first solution, a basic solution, and a second solution, a membrane-forming solution. The semipermeable membrane comprises at least two types of inorganic membranes, each of which has a different formation rate in the basic solution. The semipermeable membrane is a metal hydroxide formed from the membrane-forming solution. Specifically, the semipermeable membrane is a metal hydroxide containing a metal contained in the membrane-forming solution. The inorganic membrane includes a soluble membrane formed from an amphoteric metal hydroxide and a stable membrane formed from a metal hydroxide that forms slower in the solution than the soluble membrane and is less likely to dissolve. The semipermeable membrane is formed between the membrane-forming solution and the basic solution. Because the semipermeable membrane is a mixture of a soluble membrane and a stable membrane, osmotic pressure locally damages the soluble membrane, allowing the membrane-forming solution to be injected into the basic solution from the damaged area. The semipermeable membrane preferably has a total length of approximately 1 mm to 10 mm, more preferably 1 mm to 5 mm.

[0022] (Basic Solution) The first solution that constitutes the self-assembled film structure is a basic solution containing hydroxide ions. Examples of basic solutions containing hydroxide ions include an aqueous solution of a normal salt of a weak acid and a strong base, and an aqueous solution of a basic salt of a strong acid and a strong base. More specific examples include an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium bicarbonate solution, an aqueous sodium carbonate solution, and aqueous ammonia. One or more basic solutions may be used in combination. The basic solution is preferably an aqueous sodium hydroxide solution. Depending on the type and concentration of the basic solution, the self-assembled film structure can become a self-assembled actuator capable of self-excited vibration, and it is also possible to control the injection period and amount of solution.

[0023] (Film-forming solution) The second solution constituting the self-assembled monolayer structure is a film-forming solution containing water-soluble salts of at least two types of metals. The film-forming solution is an aqueous solution containing a water-soluble salt of an amphoteric metal capable of forming a soluble film and a water-soluble salt of a metal other than the amphoteric metal capable of forming a stable film. Examples of amphoteric metals include aluminum, zinc, tin, lead, gallium, etc., with aluminum or gallium being preferred, and aluminum being more preferred. Examples of metals other than the amphoteric metal include manganese, magnesium, iron (III), cobalt, copper, nickel, etc. When aluminum is included as the amphoteric metal, the metal other than the amphoteric metal is preferably one or more selected from manganese, magnesium, iron (III), cobalt, copper, and nickel. When gallium is included as the amphoteric metal, the metal other than the amphoteric metal is preferably copper. Any type of water-soluble salt of these metals may be used, but examples include chlorides, bromides, iodides, sulfates, nitrates, acetates, ammonium salts, etc., with chlorides being preferred. When the membrane-forming solution comes into contact with a basic solution, at least two types of metal hydroxides are formed from the metals in the membrane-forming solution. The two types of metal hydroxides form a soluble film and a stable film, respectively. The self-assembled film structure can become a self-assembled actuator capable of self-excited vibration, depending on the concentration of the basic solution containing hydroxide ions, the concentrations of the metals capable of forming a soluble film and the metals capable of forming a stable film in the membrane-forming solution, the amount of membrane-forming solution added to the basic solution, etc., and it is also possible to control the solution injection period, liquid delivery amount, etc.

[0024] In order to form a self-assembled film structure that enables recurrent ejection of a solution by self-excited vibration, the film-forming solution, when containing aluminum and copper, preferably has an aluminum molar concentration of 0.8 to 2.5 M and a copper molar concentration of 0.2 to 0.8 M, more preferably an aluminum molar concentration of 1.0 to 2.2 M and a copper molar concentration of 0.4 to 0.6 M; when containing aluminum and nickel, preferably has an aluminum molar concentration of 1.3 to 2.5 M and a nickel molar concentration of 0.05 to 0.3 M, more preferably an aluminum molar concentration of 1.6 to 2.2 M and a nickel molar concentration of 0.05 to 0.2 M; When aluminum and manganese are contained, preferably, the molar concentration of aluminum is 1.8 to 2.5M and the molar concentration of manganese is 0.2 to 0.8M, more preferably, the molar concentration of aluminum is 2.0 to 2.2M and the molar concentration of manganese is 0.4 to 0.6M; when aluminum and magnesium are contained, preferably, the molar concentration of aluminum is 1.3 to 2.5M and the molar concentration of magnesium is 0.05 to 0.4M, more preferably, the molar concentration of aluminum is 1.6 to 2.2M and the molar concentration of magnesium is 0.05 to 0.3M; when aluminum and iron(III) are contained, preferably, the molar concentration of aluminum is 0.3 to 2.5M and the molar concentration of iron(III) is 0.3 to 1.8M, more preferably, the molar concentration of aluminum is 0.5 to 2.2M and the molar concentration of iron(III) is 0.5 to 1.7M; When aluminum and cobalt are contained, the molar concentration of aluminum is preferably 1.8 to 2.5 M and the molar concentration of cobalt is preferably 0.2 to 0.8 M, more preferably 2.0 to 2.2 M and 0.4 to 0.6 M; or when gallium and copper are contained, the molar concentration of gallium is preferably 9 to 12 M and 0.05 to 0.3 M, more preferably 10 to 11 M and 0.1 to 0.2 M.

[0025] (Soluble membrane) One of the inorganic membranes constituting the semipermeable membrane is a soluble membrane that is easily formed and easily dissolved. The soluble membrane is an inorganic metal membrane formed from a metal hydroxide. The soluble membrane is more preferably an inorganic membrane formed from a hydroxide of an amphoteric metal. Examples of amphoteric metals include aluminum, zinc, tin, lead, and gallium. From the viewpoint of the membrane formation rate, aluminum or gallium is preferred, and aluminum is more preferred because many metals can be used in combination as a stable membrane. The soluble membrane may be composed of hydroxides of one or more amphoteric metals.

[0026] A soluble membrane is formed at the contact interface between the aqueous solutions when an aqueous solution of a metal salt such as aluminum or gallium comes into contact with a basic solution such as sodium hydroxide. After the soluble membrane is formed, it can form a complex ion with hydroxide ions. Once the soluble membrane forms a complex ion with hydroxide ions, it redissolves in the basic solution. The soluble membrane is a semipermeable membrane containing a precipitate of metal hydroxide.

[0027] (Stable membrane) One of the inorganic membranes constituting the semipermeable membrane is a stable membrane, which has a slower formation rate in a solution and is less likely to dissolve than a soluble membrane. The stable membrane is formed at the contact interface between an aqueous solution of a metal salt and a basic solution when they come into contact. The stable membrane is an inorganic metal membrane containing a non-redissolved precipitate of a metal hydroxide. Examples of metals that can form a stable membrane include manganese, magnesium, iron (III), cobalt, copper, and nickel. The soluble membrane may be composed of hydroxides of one or more of the above metals.

[0028] The combination of metals that form a soluble film and a stable film can be determined, for example, by the following simple method. When an aqueous solution containing a water-soluble salt of the raw metal is added to a basic solution, it diffuses and then solidifies. Since the wider the diffusion range, the slower the film formation rate is thought to be. Therefore, the combination can be determined by comparing the diffusion ranges, with the wider being the soluble film and the narrower being the stable film. It is also thought that the combination of a soluble film and a stable film can be determined, for example, using the solubility product of the metal hydroxide or the HSAB (Hard and Soft Acids and Bases) law.

[0029] As a specific example of a combination of a soluble film and a stable film, for example, when the metal forming the soluble film is aluminum, the metal forming the stable film is preferably one or more selected from manganese, magnesium, iron (III), cobalt, copper, and nickel, and when the metal forming the soluble film is gallium, the metal forming the stable film is preferably copper.

[0030] [Projectile] In a self-assembled monolayer structure, when the dissolvable membrane is damaged by osmotic pressure and the membrane-forming solution is injected into a basic solution through the damaged area, water penetrates into the basic solution, leaving behind a metal hydroxide, forming a solid projectile. As shown in FIG. 1 , the projectile 100 has a head 101 and a tail 102 extending from the head 101. The tail 102 has a smaller radial cross-sectional area than the head 101. The head 101 is not limited to a sphere as shown in FIG. 1 , but may also be ellipsoidal or cylindrical. The projectile may be linear, curved, wavy, or the like, and may have an unclear boundary between the head and tail. The projectile is a metal hydroxide contained in the membrane-forming solution added to the basic solution. The projectile contains a hydroxide of a metal other than an amphoteric metal that is less soluble in a basic solution than an amphoteric metal hydroxide. The projectile is composed of the same components as the stable membrane. The shape of the projectile changes depending on the amount of membrane-forming solution added to the basic solution or the concentration of the basic solution. The shape refers to, for example, the cross-sectional area when the projectile is cut along the longitudinal direction or the length ratio of the head and tail. When the amount of membrane-forming solution added to the basic solution increases, the cross-sectional area of ​​the projectile when cut along the longitudinal direction increases. When the concentration of the basic solution increases, the length ratio of the head to the tail of the projectile decreases.

[0031] [Self-mover] In a self-assembled monolayer structure, the ejected body formed from the ejected film-forming solution is capable of migrating in a reaction solution. The self-mover is an ejected body capable of migrating in a reaction solution. The self-mover can, for example, decompose hydrogen peroxide into water and oxygen. In this case, the self-mover can self-migrate in a solution containing hydrogen peroxide using oxygen generated when hydrogen peroxide is decomposed as a propulsion force. 2 , the self-electrophoresis body 200 has a radius of curvature R of the orbit O along which the self-electrophoresis body 200 swims, a radius of curvature r of the circle C when the curved shape of the self-electrophoresis body 200 is considered as a part of the circle C, an orbit period T of the self-electrophoresis body 200 orbiting the orbit O, and an overall length Q measured in a straight line from the tip of the head to the end of the tail of the self-electrophoresis body 200, and an angle θ formed between the overall length Q and a line extending from the center of the overall length Q to the center of the orbit O. The larger the radius of curvature r of the circle C, the larger the radius of the orbit O and the orbit period T. Furthermore, the larger the ratio L of the length of the self-electrophoresis body to the circumference of radius r, the smaller the angle θ. The length of the self-electrophoresis body mentioned above is not the overall length Q but the length of the arc-shaped self-electrophoresis body along the circumference of radius r.

[0032] [Self-migrating metal catalyst] In a self-assembled monolayer structure, the ejected body formed from the ejected film-forming solution can be used as a self-migrating metal catalyst that migrates in a reaction solution. A self-migrating metal catalyst is a self-migrating body that can be used as a metal catalyst in a catalytic reaction. The self-migrating metal catalyst can, for example, decompose hydrogen peroxide into water and oxygen. The self-migrating metal catalyst is, for example, a hydroxide of magnesium, manganese, iron (II), iron (III), cobalt, nickel, palladium, silver, cerium, platinum, or gold.

[0033] The self-migrating metal catalyst is, for example, a projectile that is projected when a membrane-forming solution containing a metal salt of aluminum and iron (III) comes into contact with a basic solution containing sodium hydroxide, and contains iron (II) hydroxide, and can be used as a Fenton reaction catalyst. In the Fenton reaction, the reaction solution is stirred by the migration of the self-migrating metal catalyst, so stirring using a stirrer or the like is not required.

[0034] [Mathematical Model of Self-Assembled Actuator] Next, the requirements for the self-assembled film structure of the present disclosure to self-oscillate as a self-assembled actuator will be described using a mathematical model. ｍ＋ and Y ｎ＋ X is Cu that forms a stable film. ２＋ and Fe ３＋ Y is a soluble film-forming metal ion such as Al ３＋ These ions mimic amphoteric metal ions, and the film-forming reactions shown in the following formulas (1) and (2) occur.

[0035]

[0036] Also, Y(OH) ｎ In the case of the above, a complex formation reaction (membrane dissolution) occurs as shown in the following formula (3).

[0037]

[0038] X(OH) ｍ and Y(OH) ｎ is a semipermeable membrane. In addition, since the outflow of metal ions to the outside of the self-assembled monolayer is suppressed by the formation of the membrane, the formation of each membrane is subjected to negative feedback by the formation of both membranes. Therefore, X(OH) ｍ and Y(OH) ｎ Based on the law of mass action, the reaction rate follows the ordinary differential equations (4) and (5).

[0039]

[0040] Here, φ(ρ-θ) represents a step function, which takes the value of 1 when the sum ρ of the hydrostatic pressure and osmotic pressure inside the semipermeable membrane is equal to or less than the membrane's yield stress θ, and takes the value of 0 when it is greater than θ. That is, the following equation (6) is obtained.

[0041]

[0042] The sum of the hydrostatic pressure and osmotic pressure inside the semipermeable membrane, ρ, is the sum of the metal ions [X ｍ＋ ] + [Y ｎ＋ ], so it follows the following equation (7).

[0043]

[0044] In formula (7), 1-exp(-γ(α[X(OH) ｍ ] + β [Y(OH) ｎ The part marked with an asterisk ( ) indicates that the osmotic pressure increases due to the formation of an inorganic membrane. The yield stress θ of the membrane is expressed as a linear sum of the thicknesses of the respective membranes.

[0045]

[0046] θ ０ can be considered as the upper limit of the internal pressure difference (strength of the water flow) at which membrane formation can begin. When the sum of the hydrostatic pressure and osmotic pressure ρ inside the self-assembled membrane exceeds the membrane's yield stress θ, the semipermeable membrane is destroyed, i.e., the semipermeable membrane is partially lost, and [X ｍ＋ ] = [Y ｎ＋ ]=0.

[0047] The above equations (4) to (8) are made dimensionless by performing a variable transformation as shown in Table 1. This non-dimensionalization allows redundant parameters to be consolidated.

[0048]

[0049] Also, we focused on the dynamics of the initial molecular concentration, which indicates whether oscillation occurs or not, and ｍ＋ Ya Y ｎ＋ YaOH － Assuming that there is almost no change over time in the equations (4) to (8), the equations (4) to (8) are transformed into the following equations (9) to (13):

[0050]

[0051] Simulations were performed using equations (9) to (13) with the parameters and initial values ​​shown in Table 2. As before non-dimensionalization, when ρ'>θ', u=ν=0. In the simulation, specifically, CuCl ２ and AlCl ３ In this case, m = 2 and n = 3. ２ and AlCl ３ From the experimental results of each element, CuCl ２ Vibration does not occur by itself, but AlCl ３ Since vibration occurs when it is a single unit, θ ν <θ ｕThe simulation was performed using the fourth-order Runge-Kutta method and written in C. The compiler used was Apple clang version 15.0.0 (clang-1500.3.9.4).

[0052]

[0053] By simulation, the parameter k １ ', k ２ ', k ３ 3A-3F show heat maps of the number of oscillations per unit time in the steady state for different k ３ Create a heat map for each ' and sort by k in the order of A-F. ３ '=0, 10 －３ , 10 －２ , 10 －１ , 10 ０ , 10 １ The horizontal axis of Figures 3A-3F represents the parameter k １ ' on the logarithmic axis, and the vertical axis is the parameter ratio k ２ ' logarithmic axis, the colored areas represent self-oscillating conditions, and the white areas represent non-oscillating conditions.

[0054] Simulations have revealed that the region in which self-excited vibration occurs is the region in which all of the following conditions are satisfied: １ '<k ２ ': The formation of a soluble film is faster than the formation of a stable film. １ '<1: Slower than the time constant of the internal pressure ρ (= 1). ２ '≧k ３ ': The rate of hydroxide formation is at most the same as the rate of complex formation.

[0055] [Method for Manufacturing Self-Assembled Film Structure and Injected Body] As shown in Figure 4, the method for manufacturing a self-assembled film structure includes an adding step S1 in which a membrane-forming solution containing water-soluble salts of at least two types of metals is added to a basic solution containing hydroxide ions, and a semipermeable membrane forming step S2 in which a soluble film formed by amphoteric metal hydroxide and a stable film formed by metal hydroxide, which form in the solution at a slower rate and are less likely to dissolve than the soluble film, are successively formed by self-assembly to form a semipermeable membrane, as shown in Figure 4. The method for manufacturing a self-assembled film structure may further include an ejection step S3 in which the osmotic pressure inside and outside the semipermeable membrane is used as a driving force to eject the membrane-forming solution from within the semipermeable membrane into the basic solution, accompanied by localized damage to the semipermeable membrane. The self-assembled film structure can be used as an actuator by ejecting the solution from the damaged portion of the semipermeable membrane. The ejected film-forming solution is exposed to a basic solution for a predetermined time, whereby the same components as those in the soluble film dissolve in the basic solution, leaving behind the same metal hydroxide as those in the stable film, thereby forming an ejected body (ejected body formation step S4).

[0056] In the addition step S1, the self-assembled film structure can change the shape of the ejected body formed from the ejected film-forming solution based on the amount of film-forming solution added or the concentration of the basic solution.

[0057] The self-migrating metal catalyst can be produced by the same production method as the injection body. Among the injection bodies, the self-migrating metal catalyst is one that can self-migrate in the reaction solution and can be used as a metal catalyst in a catalytic reaction.

[0058] [Mechanism of Self-Assembled Actuator] The mechanism by which the self-assembled membrane structure of the present disclosure functions as an actuator is shown with reference to FIGS. 5 to 8 . Soluble membranes are easier to form and more easily dissolved than stable membranes. Stable membranes are harder to form and less easily dissolved than soluble membranes. In a self-assembled actuator, a soluble membrane and a stable membrane, which have different properties, are successively formed in a basic solution to form a semipermeable membrane, enabling the recurrent ejection of the solution as self-excited vibration. Specifically, as shown in FIG. 5 , the self-assembled membrane structure 1 of this embodiment formed by the addition step S1 and the semipermeable membrane formation step S2 includes a semipermeable membrane 2, a basic solution 10, and a membrane-forming solution 11 separated by the semipermeable membrane 2. When water moves into the semipermeable membrane 2 due to osmotic pressure and the pressure inside the semipermeable membrane increases, only the soluble membrane 21 portion of the semipermeable membrane 2 is locally damaged, melted, and disappears, as shown in FIGS. 6 and 7 , and the membrane-forming solution 11 is ejected from the inside to the outside of the membrane. At this time, the form of the self-assembled film structure is maintained by the stabilizing film 22. Furthermore, when the ejected film-forming solution 11 is exposed to the basic solution 10 for a predetermined time, for example, several tens of minutes, the components that make up the soluble film 21 dissolve in the basic solution 10, and the same metal hydroxide as the stabilizing film 22 remains, which solidifies into the ejected body 100 as shown in FIG.

[0059] When the pressure inside the membrane decreases due to the breakage of the soluble membrane 21 and the ejection of the membrane-forming solution 11, the ejection flow rate decreases and the semipermeable membrane 2 is reformed. When the semipermeable membrane 2 is reformed, the soluble membrane 21, which has a faster membrane-forming rate, is reformed preferentially over the stable membrane 22. After the semipermeable membrane 2 is reformed, water moves into the semipermeable membrane 2 due to osmotic pressure, and the pressure inside the semipermeable membrane 2 increases. Once again, only a portion of the soluble membrane 21 is locally broken, melted, and disappears, and the membrane-forming solution 11 is ejected from the inside to the outside of the membrane. When the pressure inside the semipermeable membrane 2 decreases, the soluble membrane 21 is reformed. In this way, the self-assembled membrane structure 1 undergoes self-excited vibration due to the ejection of the solution caused by the breakage of the soluble membrane 21 and the reformation of the soluble membrane 21. Because the self-assembled membrane structure of the present invention has such functions as a self-assembled actuator, it can autonomously form a microfluidic device, and the device can also function as an autonomous pump.

[0060] [Example 1: Formation of a self-assembled film structure] Example 1-1: Aluminum and copper The results of an experiment using a combination of aluminum as the metal that forms a soluble film and copper as the metal that forms a stable film are shown below as Example 1. In Example 1-1, a self-assembled film structure was formed in the following manner.

[0061] 2 mL of 5 M sodium hydroxide solution was prepared as the basic solution, and a 35 mm diameter polystyrene petri dish that had been hydrophilically treated was prepared. Additionally, 10 μL of an aqueous solution containing 0.54 M copper chloride and 1.08 M aluminum chloride was prepared as the membrane-forming solution. The membrane-forming solution was added to the wall of the petri dish, and a semipermeable membrane consisting of a stable membrane and a soluble membrane autonomously formed near the contact interface between the aqueous solutions, resulting in a self-assembled membrane structure. The semipermeable membrane of this self-assembled membrane structure had long sides of 3 mm, short sides of 2 mm, and a height of 3 mm, and was capable of operating as a self-assembled actuator.

[0062] When the internal pressure of the resulting self-assembling actuator increased due to the movement of water into the interior due to osmotic pressure, the semipermeable membrane locally broke, melted, and disappeared, and the membrane-forming solution was ejected from the lost area. As the membrane broke and the solution was ejected, the membrane pressure decreased, the ejection flow rate decreased, and the membrane reformed. The autonomous operation of this self-assembling actuator due to self-excited vibration was observed with a video camera. Figure 9 shows snapshots of the time series changes in the self-assembling actuator formed in Example 1-1. The captured images were analyzed using the image analysis software ImageJ. Specifically, a video camera was placed above the Petri dish to capture images of the spherical membrane-forming solution ejected from the self-assembling actuator. The spherical portion was approximated as a circle using ImageJ to determine its diameter. From this diameter, the volume of the membrane-forming solution was calculated as the ejection amount.

[0063] The amount of solution ejected per vibration during self-excited vibration (ejection amount) of the self-assembling actuator according to Example 1-1, which was formed using a film-forming solution containing 0.54 M copper chloride and 1.08 M aluminum chloride, was approximately 15 μL per vibration. The amount of solution ejected by the self-assembling actuator increases, for example, in proportion to the initial substrate concentration of the basic solution and the amount of film-forming solution added, and can be controlled, for example, within a range of 25 nL to 20 μL per vibration. Figure 10 shows the relationship between the concentration of the basic solution and the ejection volume for the self-assembling actuator according to Example 1, and Figure 11 shows the relationship between the volume of the film-forming solution and the ejection volume for the self-assembling actuator according to Example 1-1.

[0064] Next, the aluminum (Al ３＋ ) and copper (Cu ２＋ The dynamics of the formed self-assembled film structures were observed by combining aluminum with molar concentrations of 0.54M, 1.08M, 1.62M, and 2.16M and copper with molar concentrations of 0.54M, 1.08M, 1.62M, and 2.16M. Self-assembled film structures were formed by combining aluminum with molar concentrations of 1.08-2.16M and copper with molar concentrations of 0.54M. Self-assembled film structures formed with 1.08-2.16M aluminum and 0.54M copper demonstrated autonomous and continuous solution pumping due to self-excited vibration. Hemispherical films exhibiting repeated recurrent partial protrusions (blebbing) were observed to form in self-assembled film structures formed with 1.08-1.62M copper and 0.54-1.62M aluminum, as well as with 0.54M copper and 0.54M aluminum. At 2.16 M copper and 2.16 M aluminum, a stabilizing, non-dissolving film was formed without significant film movement. When a self-assembled monolayer structure is formed using a combination of aluminum and copper, the molar concentration of aluminum is preferably 0.8 to 2.5 M, more preferably 1.0 to 2.2 M, and the molar concentration of copper is preferably 0.2 to 0.8 M, more preferably 0.4 to 0.6 M.

[0065] In Example 1-1, the speed of formation of a soluble film and the speed of formation of a stable film were compared by observing how the film spread when copper chloride aqueous solution and aluminum chloride aqueous solution were dropped into sodium hydroxide aqueous solution. As a result, in the region where pumping was confirmed in Figure 12, the formation of a soluble film was faster than the formation of a stable film. This result is consistent with the simulation results of the mathematical model of the self-organizing actuator described above. １ '<k ２ ' was in line with this.

[0066] <Example 1-2: Aluminum and Nickel> Aluminum (Al ３＋ ), nickel (Ni) as a metal that forms a stable film ２＋ ) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure was the same as in Example 1-1. The molar concentrations of aluminum and nickel in the film-forming solution were varied and combined, and the dynamics of the formed self-assembled film structure was observed. The results are shown in Figure 13. Specifically, self-assembled film structures were formed by combining aluminum with molar concentrations of 0.54M, 1.08M, 1.62M, and 2.16M and nickel with molar concentrations of 0.054M, 0.108M, 0.162M, 0.216M, 0.54M, 1.08M, 1.62M, and 2.16M. In the self-assembled film structures formed with aluminum of 1.62 to 2.16M and nickel of 0.054 to 0.162M, autonomous and continuous solution ejection (pumping) due to self-excited vibration was confirmed. When a self-assembled monolayer structure is formed using a combination of aluminum and nickel, the molar concentration of aluminum is preferably 1.3 to 2.5 M, more preferably 1.6 to 2.2 M, and the molar concentration of nickel is preferably 0.05 to 0.3 M, more preferably 0.05 to 0.2 M.

[0067] In Example 1-2, the speed of the formation of a soluble film and the formation of a stable film were compared by observing how the film spread when a nickel chloride aqueous solution and an aluminum chloride aqueous solution were dropped into a sodium hydroxide aqueous solution. As a result, in the region where pumping was confirmed in Figure 13, the formation of a soluble film was faster than the formation of a stable film. This result is consistent with the simulation results of the mathematical model of the self-organizing actuator described above. １ '<k ２ ' was in line with this.

[0068] <Example 1-3: Aluminum and Manganese> Aluminum (Al ３＋ ), manganese (Mn ２＋ ) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure is the same as in Example 1-1. FIG. 14 shows the results of observing the dynamics of the self-assembled film structure formed by combining aluminum and manganese in a film-forming solution with different molar concentrations. Specifically, self-assembled film structures were formed by combining aluminum with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M and manganese with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M. In a self-assembled film structure formed with 2.16 M aluminum and 0.054 M manganese, autonomous and continuous solution ejection (pumping) due to self-excited vibration was confirmed. In the case of a combination of aluminum and manganese, the molar concentration of aluminum is preferably 1.8 to 2.5M, more preferably 2.0 to 2.2M, and the molar concentration of manganese is preferably 0.2 to 0.8M, more preferably 0.4 to 0.6M.

[0069] In Example 1-3, the speed of formation of a soluble film and the speed of formation of a stable film were compared by observing how the film spread when a manganese chloride aqueous solution and an aluminum chloride aqueous solution were dropped into a sodium hydroxide aqueous solution. As a result, in the region where pumping was confirmed in Figure 14, the formation of a soluble film was faster than the formation of a stable film. This result is consistent with the simulation results of the mathematical model of the self-organizing actuator described above. １ '<k２ ' was in line with this.

[0070] <Example 1-4: Aluminum and magnesium> Aluminum (Al ３＋ ), magnesium (Mg ２＋ ) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure was the same as in Example 1-1. FIG. 15 shows the results of observing the dynamics of the self-assembled film structure formed by combining aluminum and magnesium in a film-forming solution with different molar concentrations. Specifically, self-assembled film structures were formed by combining aluminum with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M and magnesium with molar concentrations of 0.054 M, 0.10 M, 0.108 M, 0.20 M, 0.25 M, 0.54 M, 1.08 M, 1.62 M, and 2.16 M. In the self-assembled film structures formed with aluminum at 1.62 to 2.16 M and magnesium at 0.054 to 0.25 M, autonomous and continuous solution pumping due to self-excited vibration was observed. In the case of a combination of aluminum and magnesium, the molar concentration of aluminum is preferably 1.3 to 2.5M, more preferably 1.6 to 2.2M, and the molar concentration of magnesium is preferably 0.05 to 0.4M, more preferably 0.05 to 0.3M.

[0071] In Example 1-4, the speed of formation of a soluble film and a stable film was compared by observing how the film spread when magnesium chloride aqueous solution and aluminum chloride aqueous solution were dropped into a sodium hydroxide aqueous solution. As a result, in the region where pumping was confirmed in Figure 15, the formation of a soluble film was faster than the formation of a stable film. This result is consistent with the simulation results of the mathematical model of the self-organizing actuator described above. １ '<k ２ ' was in line with this.

[0072] <Example 1-5: Aluminum and iron (III)> Aluminum (Al) is used as a metal that forms a soluble film. ３＋ ), iron (III) (Fe) as a metal that forms a stable film ３＋) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure was the same as in Example 1-1. Figure 16 shows the results of observing the dynamics of the self-assembled film structure formed by combining aluminum and iron(III) in a film-forming solution with different molar concentrations. Specifically, self-assembled film structures were formed by combining aluminum with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M and iron(III) with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M. In the self-assembled film structures formed with aluminum from 0.54 to 2.16 M and iron(III) from 0.54 to 1.62 M, autonomous and continuous solution pumping due to self-excited vibration was observed. In the case of a combination of aluminum and iron(III), the molar concentration of aluminum is preferably 0.3 to 2.5M, more preferably 0.5 to 2.2M, and the molar concentration of iron(III) is preferably 0.3 to 1.8M, more preferably 0.5 to 1.7M.

[0073] In Example 1-5, the speed of the formation of a soluble film and the formation of a stable film were compared by observing how the film spread when an iron (III) chloride aqueous solution and an aluminum chloride aqueous solution were dropped into an aqueous sodium hydroxide solution. As a result, in the region where pumping was confirmed in Figure 16, the formation of a soluble film was faster than the formation of a stable film. This result is consistent with the simulation results of the mathematical model of the self-organizing actuator described above. １ '<k ２ ' was in line with this.

[0074] <Example 1-6: Aluminum and Cobalt> Aluminum (Al) is used as a metal for forming a soluble film. ３＋ ), and cobalt (Co) as a metal that forms a stable film. ２＋) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure is the same as in Example 1-1. FIG. 17 shows the results of observing the dynamics of the self-assembled film structure formed by combining aluminum and cobalt in a film-forming solution with different molar concentrations. Specifically, self-assembled film structures were formed by combining aluminum with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M and cobalt with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M. In the self-assembled film structure formed with 2.16 M aluminum and 0.54 M cobalt, autonomous and continuous solution ejection (pumping) due to self-excited vibration was confirmed. In the case of a combination of aluminum and cobalt, the molar concentration of aluminum is preferably 1.8 to 2.5M, more preferably 2.0 to 2.2M, and the molar concentration of cobalt is preferably 0.2 to 0.8M, more preferably 0.4 to 0.6M.

[0075] In Example 1-6, the speed of the formation of a soluble film and the formation of a stable film were compared by observing how the film spread when a cobalt chloride aqueous solution and an aluminum chloride aqueous solution were dropped into a sodium hydroxide aqueous solution. As a result, in the region where pumping was confirmed in Figure 17, the formation of a soluble film was faster than the formation of a stable film. This result is consistent with the simulation results of the mathematical model of the self-organizing actuator described above. １ '<k ２ ' was in line with this.

[0076] <Example 1-7: Aluminum and Lanthanum> Aluminum (Al ３＋ ), lanthanum (La) as a metal that forms a stable film ３＋) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure is the same as in Example 1-1. FIG. 18 shows the results of observing the dynamics of the self-assembled film structure formed by combining aluminum and cobalt at different molar concentrations in the film-forming solution. Specifically, self-assembled film structures were formed by combining aluminum with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M and lanthanum with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M. In the self-assembled film structure formed by aluminum and cobalt, autonomous and continuous solution ejection (pumping) due to self-excited vibration was not observed.

[0077] <Example 1-8: Aluminum and calcium> Aluminum (Al ３＋ ), calcium (Ca) as a metal that forms a stable film ２＋ ) to form a self-assembled film structure. The method for manufacturing the self-assembled film structure is the same as in Example 1-1. FIG. 19 shows the results of observing the dynamics of the self-assembled film structure formed by combining aluminum and calcium in a film-forming solution with different molar concentrations. Specifically, self-assembled film structures were formed by combining aluminum with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M and calcium with molar concentrations of 0.98 M, 1.96 M, 2.94 M, and 3.92 M. In the self-assembled film structure formed by aluminum and calcium, autonomous and continuous solution pumping due to self-excited vibration was not observed.

[0078] <Example 1-9: Aluminum and terbium> Aluminum (Al ３＋ ), terbium (Tb ３＋) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure is the same as in Example 1-1. FIG. 20 shows the results of observing the dynamics of the self-assembled film structure formed by combining aluminum and terbium at different molar concentrations in the film-forming solution. Specifically, self-assembled film structures were formed by combining aluminum with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M and terbium with molar concentrations of 0.108 M, 0.216 M, 0.324 M, 0.432 M, 0.54 M, 1.08 M, 1.62 M, and 2.16 M. In the self-assembled film structure formed by aluminum and terbium, autonomous and continuous solution ejection (pumping) due to self-excited vibration was not observed.

[0079] <Example 1-10: Gallium and copper> Gallium (Ga) is used as a metal for forming a soluble film. ３＋ ), copper (Cu) as a metal for forming a stable film ２＋ ) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure is the same as in Example 1-1. FIG. 21 shows the results of observing the dynamics of the self-assembled film structure formed by changing the molar concentration of gallium and the molar concentration of copper in the film-forming solution and combining them. Specifically, self-assembled film structures were formed by combining gallium with molar concentrations of 0.52M, 1.04M, 1.56M, 2.08M, 2.6M, 5.2M, 7.8M, and 10.4M and copper with molar concentrations of 0.14M, 0.27M, 0.41M, 0.54M, 1.08M, 1.62M, and 2.16M. In the self-assembled film structure formed with 10.4M gallium and 0.14M copper, autonomous and continuous solution ejection (pumping) due to self-excited vibration was confirmed. In the case of a combination of gallium and copper, the molar concentration of gallium is preferably 9 to 12M, more preferably 10 to 11M, and the molar concentration of copper is preferably 0.05 to 0.3M, more preferably 0.1 to 0.2M.

[0080] <Example 1-11: Zinc and Copper> Zinc (Zn) is used as a metal that forms a soluble film. ２＋ ), copper (Cu) as a metal for forming a stable film ２＋) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure is the same as in Example 1-1. FIG. 22 shows the results of observing the dynamics of the self-assembled film structure formed by combining zinc and copper in a film-forming solution with different molar concentrations. Specifically, self-assembled film structures were formed by combining zinc with molar concentrations of 0.54 M, 1.08 M, 1.62 M, 2.00 M, 2.16 M, 3.00 M, and 4.00 M and copper with molar concentrations of 0.54 M, 1.08 M, 1.62 M, 2.00 M, 2.16 M, 3.00 M, and 4.00 M. In the self-assembled film structure formed by zinc and copper, autonomous and continuous solution ejection (pumping) due to self-excited vibration was not observed.

[0081] <Example 1-12: Cadmium and copper> Cadmium (Cd ２＋ ), copper (Cu) as a metal for forming a stable film ２＋ ) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure is the same as in Example 1-1. FIG. 23 shows the results of observing the dynamics of the self-assembled film structure formed by combining cadmium and copper in a film-forming solution with different molar concentrations. Specifically, self-assembled film structures were formed by combining cadmium with molar concentrations of 1.54 M, 3.08 M, 4.62 M, and 6.16 M and copper with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M. In the self-assembled film structure formed by cadmium and copper, autonomous and continuous solution ejection (pumping) due to self-excited vibration was not observed.

[0082] <Example 1-13: Indium and Copper> Indium (In ３＋ ), copper (Cu) as a metal for forming a stable film ２＋) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure is the same as in Example 1-1. FIG. 24 shows the results of observing the dynamics of the self-assembled film structure formed by combining different molar concentrations of indium and copper in the film-forming solution. Specifically, self-assembled film structures were formed by combining indium with molar concentrations of 1.24 M, 2.48 M, 3.72 M, and 4.96 M and copper with molar concentrations of 0.011 M, 0.02 M, 0.032 M, 0.054 M, 0.108 M, 0.162 M, 0.216 M, 0.54 M, 1.08 M, 1.62 M, and 2.16 M. In the self-assembled film structure formed by indium and copper, autonomous and continuous solution ejection (pumping) due to self-excited vibration was not observed.

[0083] <Example 1-14: Tin and Copper> Tin (Sn ２＋ ), copper (Cu) as a metal for forming a stable film ２＋ ) to form a self-assembled film structure. The manufacturing method of the self-assembled film structure is the same as in Example 1-1. FIG. 25 shows the results of observing the dynamics of the self-assembled film structure formed by combining different molar concentrations of tin and copper in the film-forming solution. Specifically, self-assembled film structures were formed by combining tin with molar concentrations of 0.82 M, 1.64 M, 2.46 M, and 3.28 M and copper with molar concentrations of 0.54 M, 1.08 M, 1.62 M, and 2.16 M. In the self-assembled film structure formed by tin and copper, autonomous and continuous solution ejection (pumping) due to self-excited vibration was not observed.

[0084] [Example 2: Control of the morphology of projectiles] In a self-assembled monolayer structure, an experiment was carried out to change the morphology of projectiles projected from a semipermeable membrane based on a basic solution or a membrane-forming solution.

[0085] (Study on the Amount of Membrane-Forming Solution Added) 2 mL of 5.0 M aqueous sodium hydroxide solution was prepared as a basic solution in a hydrophilic dish (35 mm diameter, Violamo cell culture dish VTC-D35N, water depth 2.1 mm), and a mixed aqueous solution containing 0.84 M aqueous copper chloride and 1.7 M aqueous aluminum chloride was prepared as a membrane-forming solution. Varying amounts of the membrane-forming solution were added dropwise to the sodium hydroxide solution in the dish along the wall of the dish, and the morphology of the projectile formed at each volume of the membrane-forming solution added (hereinafter referred to as "addition amount") was observed. Specifically, the addition amounts were 10 μL, 20 μL, 40 μL, 60 μL, 80 μL, and 100 μL. Images of the projectile formed in the dish were obtained by capturing images from above using a video camera. The obtained images were then analyzed using image analysis software (ImageJ) to calculate the cross-sectional area of ​​the projectile. As a result, as shown in Figure 26, the cross-sectional area of ​​the ejected body when cut along the longitudinal direction increased as the amount of membrane-forming solution added increased. This result indicates that the volume of the ejected body can be controlled by the amount of membrane-forming solution added.

[0086] (Study on the Concentration of Basic Solution) As basic solutions, 2 mL of six different concentrations of aqueous sodium hydroxide solutions were prepared in hydrophilic Petri dishes (35 mm diameter, Violamo cell culture dish VTC-D35N, water depth 2.1 mm). Additionally, an aqueous solution containing a 0.84 M copper chloride solution and a 1.7 M aluminum chloride solution was prepared as a membrane-forming solution. Varying amounts of the membrane-forming solution were added dropwise to the sodium hydroxide solution in the Petri dish along the wall of the dish, and the morphology of the projectile formed at each added amount was observed. Specifically, 2 mL of 3 M, 3.5 M, 4 M, 4.5 M, 5 M, and 5.5 M aqueous sodium hydroxide solutions were prepared in each Petri dish, and 10 μL of the membrane-forming solution was added dropwise to each sodium hydroxide solution. Images of the projectiles formed in the Petri dishes were obtained by filming the Petri dishes from above with a video camera. The obtained images were then analyzed using image analysis software (ImageJ). Specifically, the projectile was measured as a straight line from the tip of the head to the end of the tail, and the ratio of the length of the head 101 to the length of the tail 102 on that line was calculated, as shown in Figure 27. As a result, as shown in Figure 27, when the concentration of the basic solution was increased, the ratio of the length of the head to the tail, that is, the ratio of the head when the tail is set to 1, became smaller.

[0087] Example 3: Production of self-migrating metal catalyst and investigation of its catalytic activity The catalytic activity of the ejected material ejected from the semipermeable membrane in the self-assembled membrane structure as a self-migrating metal catalyst was confirmed.

[0088] As a basic solution, 2 mL of 5.0 M aqueous sodium hydroxide solution was prepared in a hydrophilic dish (diameter 35 mm, Violamo cell culture dish VTC-D35N, water depth 2.1 mm), and as a membrane-forming solution, a mixed aqueous solution of 0.5 M aqueous iron (III) chloride solution and 1.0 M aqueous aluminum chloride solution was prepared. 10 μL of the membrane-forming solution was dropped onto the sodium hydroxide solution in the dish along the wall of the dish. After a semipermeable membrane was formed and the membrane-forming solution was ejected from the semipermeable membrane, Al(OH) ３After the addition, the solution was left to stand for 20 minutes to dissolve the cations, and the solution was allowed to stand for 20 minutes until the cations were formed into an ejected body. The ejected body was removed from the basic solution using a cell strainer (mesh 40 μm, Falcon (registered trademark) Cell Strainer 352340) and washed three times each with pure water, ethanol, and acetone. The ejected body was then dried in a desiccator for at least one hour.

[0089] The Fenton reaction was carried out using the injection body produced as described above as a self-migrating metal catalyst. In this Fenton reaction, the reaction solution was stirred by the self-migration of the metal catalyst, so stirring with a stirrer or the like was not carried out. Specifically, in Example 3-1, H ２ O ２ A 50 μL well plate was filled with 50 μL of an aqueous solution consisting of rhodamine B (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., model number: 183-00122) and HCl as a reaction solution, and one tube of self-migrating metal catalyst was added thereto. Photographs were taken from above with a video camera, and the resulting images were subjected to color analysis using image analysis software (ImageJ), and the changes in RGB G values ​​over time were recorded. In this case, as comparative examples, a reaction solution (Example 3-2) in which the self-migrating metal catalyst was removed from the combination of Example 3-1, and a reaction solution in which the H ２ O ２ The same data was recorded for the reaction solution (Example 3-3) excluding the rhodamine B. The results are shown in Figures 28 and 29. Figure 28 shows the change over time in the concentration of rhodamine B, a model substance of soiling in Examples 3-1 to 3-3. In Figure 28, rhodamine B is referred to as "RhB." Figure 29 shows images of the solutions of Examples 3-1 to 3-3, recorded every 10 minutes, showing the change in color over time. As shown in Figure 28, a significant decrease in the G value was observed in Example 3-1, but almost no change was observed in Figures 3-2 and 3-3. In Example 3-1, migration of the self-migrating metal catalyst was observed in the solution, and as shown in Figure 29, the gradual disappearance of the rhodamine dye was visually confirmed. In Example 3-2, no color change occurred. In Example 3-3, the self-migrating metal catalyst did not migrate, and no color change was observed. This experiment confirmed that the self-migrating metal catalyst of this embodiment has catalytic ability for the Fenton reaction.

[0090] Next, the reaction rate of the Fenton reaction was evaluated under different conditions. The Fenton reaction was carried out under the conditions of Examples 3-4 to 3-8 shown in Table 3, and the reaction rate constant was determined. In Table 3, the standard conditions for the Fenton reaction, Example 3-4, were set to 1, and the relative values ​​of the reaction rate constants under each condition were determined and evaluated. In this Fenton reaction, the reaction solution was stirred by the self-migration of the metal catalyst, so stirring with a stirrer or the like was not performed.

[0091]

[0092] Specifically, in Example 3-4 under standard conditions, H ２ O ２ A 50 μL aqueous solution consisting of rhodamine B (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., model number: 183-00122, designated "RhB" in Table 3), and HCl was prepared as a reaction solution. One tube of a self-migrating metal catalyst (designated "catalyst" in Table 3) prepared in the same manner as above was added to this reaction solution, and the Fenton reaction was carried out to determine the reaction rate constant. The reaction rate constant was determined using a pseudo-first-order method. Specifically, since [A] = [A]0 * exp(-kt), kt = -ln([A] / [A]0). This was plotted, and a linear equation passing through the origin was determined using the least squares method, and the slope was taken as the reaction rate constant k. In Example 3-5, sodium chloride was added to the reaction solution under standard conditions, and the Fenton reaction was carried out at a sodium chloride concentration of 0.83 M. In Example 3-6, H ２ O ２ In Example 3-7, the Fenton reaction was carried out in a reaction solution from which the self-migrating metal catalyst was removed. In Example 3-8, the self-migrating metal catalyst was fixed using a neodymium magnet, and the Fenton reaction was carried out in a state in which the self-migrating metal catalyst did not migrate. As a result, in Example 3-5, the self-migrating metal catalyst was H ２ O ２ The reaction solution was stirred by electrophoresis in the presence of the metal catalyst, and a higher reaction rate constant was observed compared to the standard conditions (Example 3-4) even without the use of a stirrer. Furthermore, as shown in Example 3-8, it was found that the movement of the self-migrating metal catalyst can be stopped using a magnet, and that the migration and stopping can be controlled.

[0093] [Example 4: Morphology of Self-Migrating Objects and Their Migration Tracks] In the same manner as in Example 3, a 5.0 M aqueous solution of sodium hydroxide was prepared as the basic solution, and a mixed aqueous solution of 0.5 M aqueous iron (III) chloride and 1.0 M aqueous aluminum chloride was prepared as the membrane-forming solution. Various shapes of projectiles were produced by varying the amount of the membrane-forming solution and the concentration of the basic solution. The projectiles were then subjected to electrophoresis in a 0.33 M H ２ O ２ The sample was added to 19 mL of an aqueous solution of 4.8 M NaCl (diameter 86 mm, Azunol Petri dish 1-8549-04, water depth 3.3 mm) and allowed to autophorese. The migration of the autophorese was filmed from above with a video camera. The migration trajectories of the autophoreses varied depending on their shape. Figure 30 shows various shapes of autophoreses and the changes in their positions over time.

[0094] The autophoretic body shown on the left side of Figure 30 is a superimposed image of images taken every 30 seconds from 0 seconds. This autophoretic body migrated in a manner that drew the periphery of a large circle, completing one revolution in approximately 210 seconds. The autophoretic body shown in the center of Figure 30 is a superimposed image of images taken every 10 seconds from 0 seconds. This autophoretic body migrated in a manner that drew a smaller circle than the one shown on the left, completing one revolution in approximately 60 seconds. The autophoretic body shown on the right side of Figure 30 is a superimposed image of images taken every 5 seconds from 0 seconds. This autophoretic body migrated in a manner that drew a smaller circle with its head as the center of rotation, completing one revolution in approximately 40 seconds.

[0095] The self-migration of projectiles of various shapes was observed using the same method as described above, and the correlation between their shapes and movements was clarified. As shown in Figure 2, the radius of curvature R of the orbit O along which the self-migrating body 200 migrates, the radius of curvature r of the circle C when the curved shape of the self-migrating body 200 is considered as part of the circle C, the orbit period T of the self-migrating body 200 orbiting the orbit O, the total length L measured in a straight line from the tip of the head to the end of the tail of the self-migrating body 200, the angle θ formed between the line extending from the center of the total length Q to the center of the orbit O and the total length Q, and the ratio L of the length of the self-migrating body to the circumference of the radius r were calculated using image analysis software (ImageJ). Note that the length of the self-migrating body refers to the arc length of the self-migrating body, not Q in Figure 2. The results are shown in Figures 31 to 33. 31 and 32, the more gently the self-moving body 200 curves, that is, the larger the radius of curvature r, the larger the radius of curvature of the orbit O and the orbit period T. Furthermore, as shown in Fig. 33, the larger the ratio L of the length of the self-moving body to the circumference of radius r, the smaller the angle θ.

[0096] Example 5: Evaluation of self-assembled film structure as an actuator The ability of the self-assembled film structure of the present disclosure as an actuator was evaluated. A 5.0 M aqueous solution of sodium hydroxide was prepared as the basic solution, and a mixed solution of a 0.84 M aqueous solution of copper chloride and a 1.7 M aqueous solution of aluminum chloride was prepared as the membrane-forming solution. 10 μL of the membrane-forming solution was dropped into the aqueous solution of sodium hydroxide in a petri dish to form a semipermeable membrane. The energy density was calculated from the amount added, the volume of absorbed water, and the height of the center of gravity of the absorbed water, assuming that the water that had permeated from the water surface was being lifted. The energy density was 4×10 －５ J / cm ３ It was.

[0097] The present invention is particularly useful in the technical fields of microfluidic devices and catalytic reactions using metal catalysts.

[0098] REFERENCE SIGNS LIST 1 Self-assembled membrane structure (self-assembled actuator) 2 Semipermeable membrane 10 Basic solution 11 Membrane-forming solution 21 Soluble membrane 22 Stable membrane 100 Projectile 101 Head 102 Tail 200 Self-mover

Claims

1. A self-assembling membrane structure comprising a semipermeable membrane and a first solution and a second solution separated by the semipermeable membrane, wherein the semipermeable membrane has at least two types of inorganic membranes in series that are formed through self-assembly upon contact between the first solution and the second solution and have different formation rates, and wherein the driving force is the osmotic pressure inside and outside the semipermeable membrane, and the injection of the second solution into the first solution, accompanied by localized damage to the semipermeable membrane, and the reformation of the semipermeable membrane at the damaged site is carried out.

2. A self-assembled film structure according to claim 1, wherein the first solution is a basic solution containing hydroxide ions, the second solution is a film-forming solution containing water-soluble salts of at least two types of metals, and the inorganic film comprises a soluble film formed from an amphoteric metal hydroxide and a stable film formed from a metal hydroxide that is less likely to dissolve and forms at a slower rate than the soluble film.

3. In the self-assembled film structure described in claim 2, the metal that forms the stable film is designated as X, and the metal that forms the soluble film is designated as Y, and film-forming reactions occur according to the following formulas (1) and (2), and in formula (2), Y(OH) ｎ The complex formation reaction of the following formula (3) occurs, and X(OH) ｍ and Y(OH) ｎ Assuming that is a semipermeable membrane, the differential equation of the reaction rate gives the following equations (9) to (13) for membrane formation. In equations (9) and (10), the parameter k １ ', k ２ ', k ３ ' is under the following conditions. １ '<k ２ ': The formation of the soluble film is faster than the formation of the stable film. １ '<1: Slower than the time constant of the internal pressure ρ (= 1) k ２ '≧k ３ ': A self-assembled membrane structure that satisfies all of the following conditions: the hydroxide formation rate is slow but the same as the complex formation rate. (X(OH) ｍ and Y(OH) ｎ is a semipermeable membrane. When ρ>θ, u=ν=0, and θ ν <θ ｕ It is assumed that φ(ρ-θ) represents a step function, which takes the value of 1 when the sum ρ of the hydrostatic pressure and osmotic pressure inside the semipermeable membrane is equal to or less than the membrane's yield stress θ, and takes the value of 0 when ρ is greater than θ.

4. A self-assembled film structure according to claim 3, wherein the metal forming the soluble film is aluminum or gallium, and the metal forming the stable film is one or more selected from manganese, magnesium, iron (III), cobalt, copper, and nickel.

5. The self-assembled film structure according to claim 4, wherein the metal forming the soluble film is aluminum, and the metal forming the stable film is one or more selected from manganese, magnesium, iron (III), cobalt, copper, and nickel.

6. A self-assembled film structure according to claim 4, wherein the metal forming the dissolvable film is gallium, and the metal forming the stable film is copper.

7. A method for producing a self-assembled membrane structure, comprising: an adding step of adding a membrane-forming solution containing water-soluble salts of at least two types of metals to a basic solution containing hydroxide ions; and a semipermeable membrane-forming step of forming a semipermeable membrane by contacting the basic solution with the membrane-forming solution to successively form, by self-assembly, a soluble membrane formed by a hydroxide of an amphoteric metal and a stable membrane formed by a metal hydroxide that is less likely to dissolve and forms at a slower rate than the soluble membrane.

8. A method for producing a self-assembled membrane structure according to claim 7, comprising: an injection step in which the membrane-forming solution is injected from within the semipermeable membrane into the basic solution using the osmotic pressure inside and outside the semipermeable membrane as a driving force, accompanied by localized damage to the semipermeable membrane.

9. A method for producing an ejected body, comprising: an adding step of adding a membrane-forming solution containing at least two types of water-soluble salts of metals to a basic solution containing hydroxide ions; a semipermeable membrane forming step of forming a semipermeable membrane by contacting the basic solution with the membrane-forming solution to form a soluble membrane formed by a hydroxide of an amphoteric metal and a stable membrane formed by a metal hydroxide that is less likely to dissolve and forms at a slower rate than the soluble membrane through self-assembly; an ejection step of ejecting the membrane-forming solution from within the semipermeable membrane into the basic solution using osmotic pressure inside and outside the semipermeable membrane as a driving force, accompanied by localized damage to the semipermeable membrane; and an ejected body forming step of forming the ejected membrane-forming solution into the basic solution to form an ejected body made of the same metal hydroxide as the stable membrane.

10. A method for controlling an ejection body, in the method for manufacturing an ejection body described in claim 9, wherein the shape of the ejection body to be manufactured is changed based on the amount of the film-forming solution added or the concentration of the basic solution in the adding step.

11. An autophoretic body that migrates in a reaction solution, comprising a hydroxide of a metal other than an amphoteric metal that is less soluble in a basic solution than the hydroxide of the amphoteric metal, catalyzing a reaction in the reaction solution and capable of stirring the reaction solution by migration, having a head and a tail extending from the head, the tail having a smaller radial cross-sectional area than the head.

12. The autophoretic element according to claim 11, which is capable of decomposing hydrogen peroxide into water and oxygen in the reaction solution containing hydrogen peroxide, and which migrates in the reaction solution containing hydrogen peroxide.

13. A self-migrating metal catalyst that migrates in a reaction solution, comprising a hydroxide of a metal other than an amphoteric metal that is less soluble in a basic solution than the hydroxide of the amphoteric metal, catalyzing a reaction in the reaction solution, being capable of stirring the reaction solution by migration, having a head and a tail extending from the head, and the tail having a smaller radial cross-sectional area than the head.

14. The self-migrating metal catalyst according to claim 13, which is capable of decomposing hydrogen peroxide into water and oxygen in the reaction solution containing hydrogen peroxide, and migrates in the reaction solution containing hydrogen peroxide.

15. A method for producing a self-migrating metal catalyst that migrates in a reaction solution, comprising: an adding step of adding a membrane-forming solution containing water-soluble salts of at least two types of metals to a basic solution containing hydroxide ions; a semipermeable membrane-forming step of forming a semipermeable membrane by contacting the basic solution with the membrane-forming solution, whereby a soluble membrane formed from an amphoteric metal hydroxide and a stable membrane formed from a metal hydroxide that is less likely to dissolve and forms at a slower rate than the soluble membrane through self-assembly; an ejection step of ejecting the membrane-forming solution from within the semipermeable membrane into the basic solution using the osmotic pressure inside and outside the semipermeable membrane as a driving force, accompanied by localized damage to the semipermeable membrane; and an ejection body-forming step of forming an ejection body in the basic solution from the ejected membrane-forming solution, the ejected membrane-forming solution being made of the same metal hydroxide as the stable membrane. A method for producing a self-migrating metal catalyst, wherein the projectile is a self-migrating metal catalyst that catalyzes a reaction in a reaction solution, is capable of stirring the reaction solution by migration, has a head and a tail extending from the head, and the tail has a smaller radial cross-sectional area than the head.

16. A method for producing a self-migrating metal catalyst according to claim 15, wherein the projectile is capable of decomposing hydrogen peroxide into water and oxygen in the reaction solution containing hydrogen peroxide, and migrates in the reaction solution containing hydrogen peroxide.

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