JP2016175173A - Composite fine structure, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new technology for producing a composite fine structure formed of a metal portion having a micrometer size and a metal oxide portion containing an oxide of the metal by utilizing a direct drawing technology.SOLUTION: A method for producing a composite fine structure containing a metal portion and an oxide portion of the metal includes: preparing metal oxide nanoparticles and a metal oxide nanoparticle-containing liquid containing a laser curable resin cured by irradiation with a laser beam; irradiating the metal oxide nanoparticles with an ultrashort pulse laser; and forming a composite fine structure which contains a metal oxide portion containing a resin portion obtained by curing the thermosetting resin and the metal oxide nanoparticles, and a metal portion obtained by reducing the metal oxide nanoparticles and bonding the reduced nanoparticles together, by irradiation with the ultrashort pulse laser, and has at least one dimension of 100 micrometer or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite microstructure comprising a micrometer-sized metal portion and a metal oxide portion, and a method for producing the same.

  As electronic devices and semiconductor devices become more sophisticated, faster, and more integrated, attention has been focused on the formation technology of micro structures such as micro mechanical parts and micro electro mechanical systems (MEMS). . In particular, direct lithography technology such as laser additive manufacturing, hot melt deposition, and ink jet method can simplify the process, unlike lithography technology using a mask. Development of the manufacturing technology of the fine structure using is being advanced. However, most of these direct drawing techniques are directed to drawing on a photosensitive resin material, and the manufacturing technology of a fine structure made of a metal material is still in the research stage.

JP2013-247181A

J. Phys. Chem. C 2011, 115, 23664-23670 ACS Nano, 2014, 8 (10), pp 9807-9814

For example, Patent Document 1 discloses a sintered body made of a metal nanoparticle sintered body by applying a paste containing metal nanoparticles to a substrate to form a coating film and then irradiating the coating film with laser light. A method of manufacturing is disclosed. However, this method has a drawback that overheating of the base material by a laser is unavoidable in an air atmosphere and, for example, processing in an inert atmosphere is necessary.
In Non-Patent Documents 1 and 2, after a paste containing metal oxide nanoparticles is applied to a substrate to form a coating film, the coating film is irradiated with laser light to reduce the metal oxide. A method of manufacturing a fine metal electrode by sintering together is disclosed. However, these methods cannot control the reoxidation phenomenon that occurs simultaneously with the reduction and sintering of the metal oxide nanoparticles. Therefore, for example, it has been difficult to accurately manufacture a metal microstructure having a low resistance at a micrometer size level.

  As described above, the manufacturing technology of the fine structure made of the metal material using the direct drawing technology is not yet put into practical use, and further improvement is demanded. In view of such circumstances, the present invention provides a micrometer-sized composite microstructure comprising a metal oxide portion and a metal portion obtained by reducing the metal oxide using direct drawing technology. It is aimed. Another object of the present invention is to provide a new technique for manufacturing a micrometer-sized composite microstructure.

  The technique disclosed herein provides a method for manufacturing a composite microstructure including a metal portion and an oxide portion. Such a manufacturing method includes preparing a nanoparticle-containing liquid containing a metal oxide nanoparticle and a laser curable resin that is cured by irradiation with laser light, and supplying the metal oxide nanoparticle-containing liquid to the surface of a substrate. Irradiating the metal oxide nanoparticle-containing liquid supplied to the surface of the substrate with an ultrashort pulse laser. Then, by irradiation with the ultrashort pulse laser, the metal oxide portion including the resin portion where the laser curable resin is cured and the metal oxide nanoparticles are reduced and the metal oxide nanoparticles are bonded to each other. And forming a composite microstructure on the order of micrometers having at least one dimension of 100 micrometers or less.

  In the technology disclosed herein, by using an ultrashort pulse laser, the thermal effect in the reduction of the metal oxide nanoparticles is controlled, and the metal oxide portion containing the metal oxide nanoparticles, This makes it different from the reduced metal part. Thus, for example, a composite microstructure comprising a combination of a metal portion and a metal oxide portion that can be easily provided with various compositions, structures, and physical properties from one material and one ultrashort pulse laser oscillation device. Can be manufactured.

As used herein, “ultrashort pulse laser” means a pulse laser having a pulse width smaller than nano (10 ⁻⁹ ) seconds, and typically has a pulse width of several hundred picoseconds (10 ⁻¹⁰ seconds). It can be a pulse laser of about 10 to ¹² seconds or less, typically about 10 to ¹⁴ seconds or less. Such an ultrashort pulse laser can include what is called a picosecond laser, a femtosecond laser, an attosecond laser, or the like.

  This ultrashort pulse laser generally has a shorter pulse width than heat transfer. That is, the pulse width of the ultrashort pulse laser is smaller than the time required for heat to travel through the crystal lattice and diffuse to adjacent atoms. Therefore, it was expected that most of the energy provided by the laser was absorbed by the atoms without diffusing and contributed to the reaction. The technique disclosed here enables precise modeling of a composite microstructure using such a pulsed laser.

  In addition, the “laser curable resin” widely includes a high molecular organic compound that is cured by irradiation with laser light. Here, the curing of the polymer organic compound may be a polymer (photosensitive polymer) in which a curing reaction (typically crosslinking or polymerization) proceeds rapidly upon irradiation with laser light, or the energy of laser light. It may be a polymer that cures by heat generation based on thermal energy converted from.

  In a preferred embodiment of the method for producing a composite microstructure disclosed herein, the metal oxide nanoparticles include gold (Au), silver (Ag), copper (Cu), nickel (Ni), iron (Fe). And at least one selected from the group consisting of titanium (Ti) oxides. Thereby, a composite microstructure having various chemical, physical, mechanical, electrical, and magnetic characteristics can be easily produced.

  In a preferred embodiment of the method for producing a composite microstructure disclosed herein, the laser curable resin contains polyvinyl pyrrolidone. Thereby, a metal oxide part can be made into the arbitrary shapes which hardened the metal oxide nanoparticle with these laser curable resins.

  In a preferred embodiment of the method for producing a composite microstructure disclosed herein, the nanoparticle-containing liquid further includes a reducing agent. Here, the reducing agent preferably includes at least one selected from the group consisting of ethylene glycol, polyethylene glycol, formic acid, hydrogen peroxide solution, and toluene. Thereby, said composite microstructure can be manufactured efficiently.

  In a preferred embodiment of the method for producing a composite microstructure disclosed herein, the nanoparticle-containing liquid further includes a dispersant. Here, the dispersant preferably contains at least one of polyvinyl pyrrolidone and silicone resin. As a result, it is possible to manufacture a fine composite microstructure with less texture unevenness.

  In a preferred embodiment of the method for producing a composite microstructure disclosed herein, at least a part of the metal oxide nanoparticles contained in the metal oxide portion has a core-shell structure in which the surface of the metal nanoparticles is oxidized. It is characterized by having. Thereby, for example, composite microstructures having various configurations, such as suppressing physical properties based on the metal oxide portion, can be manufactured.

  In another aspect, the technology disclosed herein provides a composite microstructure. The composite microstructure includes a metal oxide portion including metal oxide nanoparticles and a metal portion formed by reducing and bonding the metal oxide nanoparticles to each other. It is characterized in that at least one dimension of the metal portion is 100 micrometers or less. Thus, a composite microstructure including a metal portion and a metal oxide portion having different characteristics from each other on a micrometer order scale is provided.

In the composite microstructure disclosed herein, the metal portion is preferably configured by reducing at least a part of the metal oxide nanoparticles and directly bonding to each other. The metal oxide portion and the metal portion are integrated.
The metal oxide nanoparticles are at least one selected from the group consisting of gold (Au), silver (Ag), copper (Cu), nickel (Ni), iron (Fe), and titanium (Ti). An oxide of a metal element can be preferably contained.

  In a preferred embodiment of the composite microstructure disclosed herein, the metal oxide portion further includes a laser curable resin, and at least some of the metal oxide nanoparticles are bonded to each other by the laser curable resin. It is characterized by being. Thereby, more various characteristics can be imparted to the metal oxide portion. Such a metal oxide portion is referred to as a first metal oxide portion.

  In a preferred embodiment of the composite microstructure disclosed herein, at least a part of the metal oxide nanoparticles are directly bonded to each other in the metal oxide portion. Thereby, the mechanical strength of the metal portion can be increased. Such a metal oxide portion is formed by re-oxidation of the metal portion, and the laser curable resin is lost. This metal oxide portion is referred to as a second metal oxide portion.

In a preferred aspect of the composite microstructure disclosed herein, the ratio of the first metal oxide portion to the total of the first metal oxide portion and the second metal oxide portion is 50% by volume or less. Above. Thereby, re-oxidation of the metal part is suppressed, and a composite microstructure can be realized in which the metal part and the metal oxide part can be more clearly distinguished.

  In a preferred embodiment of the composite microstructure disclosed herein, at least a part of the metal oxide nanoparticles contained in the metal oxide portion is a surface of the metal nanoparticles on which the metal oxide nanoparticles are reduced. It is characterized by having a core-shell structure formed by oxidation. Thereby, a metal oxide part can be made into various structures.

  In the above composite microstructure, various elements can be considered as metal elements constituting the metal portion and the metal oxide portion. Therefore, composite microstructures having various physical properties can be realized. As an article including such a composite microstructure, for example, a micro turbine component, a micro wiring, a temperature sensor, and the like are preferable examples.

It is a flowchart of the manufacturing method of the composite microstructure which concerns on one Embodiment. It is a figure explaining formation of the (A) metal part and the (B) metal oxide part in the manufacturing method of the composite microstructure concerning one embodiment. It is an example of an Ellingham diagram of a metal oxide. (A) is a CAD drawing of the microturbine body according to the embodiment, and (b) is an optical microscope image of the microturbine body according to the embodiment. It is the (a) perspective view and (b) lamination | stacking sectional drawing of the microwire which concern on one Embodiment. It is an optical microscope image of the microwire which concerns on one Embodiment. It is an optical microscope image of the microwire which concerns on other embodiment. It is (a) drawing pattern and (b) optical microscope image of the composite microstructure according to one embodiment. It is a figure which shows the relationship between the pulse energy of the ultrashort pulse laser in the manufacture of the composite microstructure which concerns on one Embodiment, and the line | wire width of a composite microstructure. It is a figure which shows the relationship between the pulse energy of the ultrashort pulse laser in the manufacture of the composite microstructure which concerns on other embodiment, and the line | wire width of a composite microstructure. (A) and (b) are optical microscope images of composite microstructures produced under different laser conditions. It is a figure which shows the relationship between the line | wire width and electrical resistance in the composite microstructure which concerns on one Embodiment. It is a figure which shows the relationship between the scanning speed of an ultrashort pulse laser, and Ni / NiO ratio in manufacture of the composite microstructure which concerns on one Embodiment. It is a figure which shows the relationship between the scanning speed of the ultrashort pulse laser in the manufacture of the composite microstructure which concerns on one Embodiment, and the line | wire width of a composite microstructure. FIGS. 13A and 13B are diagrams illustrating the formation of a drawing pattern of a composite microstructure according to an embodiment. FIG. 14A is a diagram for explaining the configuration of a microelement according to an embodiment, and FIG. 14B is an SEM image of a composite microstructure. FIG. 15 is a diagram showing resistance temperature characteristics of a composite microstructure _having (a) Cu- _rich composition and (b) Cu ₂ O- _rich composition according to an embodiment.

  Hereinafter, the composite microstructure provided by the present invention will also be described while mainly explaining the method for producing the composite microstructure of the present invention. In addition, matters other than matters specifically mentioned in the present specification and matters necessary for the implementation of the present invention (general technical matters such as raw materials and apparatuses used in the production of composite microstructures) It can be grasped as a design matter of those skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed in this specification and the drawings and common general technical knowledge in the field. Moreover, in this specification, the numerical range represented by "A-B" shows A or more and B or less.

FIG. 1 is a flow diagram of a method for manufacturing a composite microstructure disclosed herein. As will be described in detail later, the composite microstructure is a structure including (A) a metal portion and (B) a metal oxide portion. This manufacturing method essentially includes the following steps (S1) to (S3). Hereinafter, each step will be described.
(S1) Preparation of a metal oxide nanoparticle-containing liquid.
(S2) Supply of the liquid containing metal oxide nanoparticles.
(S3) Ultra short pulse laser irradiation.

[S1. Preparation of liquid containing metal oxide nanoparticles]
First, in process S1, the metal oxide nanoparticle containing liquid used for manufacture of a composite microstructure is prepared. This metal oxide nanoparticle-containing liquid contains metal oxide nanoparticles that are part of the constituent material of the composite microstructure and an uncured laser curable resin. When the laser curable resin is in a liquid state, the laser curable resin may be used as a dispersion medium for the metal oxide nanoparticles. If the laser curable resin is not in an appropriate liquid state or is not suitable for the next supply step, in addition to the metal oxide nanoparticles and the laser curable resin, these are appropriately dispersed. The resulting dispersion medium can be included.

  Metal oxide nanoparticles are included in the metal oxide portion in the composite microstructure. Along with this, a metal element constituting the metal oxide constitutes a metal portion. The metal oxide nanoparticles may be nanoparticles that include the metal oxide at least in part. Further, the metal portion of the composite microstructure is a metal made of a metal element constituting the metal oxide nanoparticles, and typically contains a metal formed by reducing the metal oxide nanoparticles. Therefore, the metal oxide portion and the metal portion have a common metal element mainly constituting them. In this respect, the composition of the metal oxide nanoparticles is important for obtaining a composite microstructure with desired properties. The metal element constituting the metal oxide nanoparticles is not particularly limited, and various metal elements can be considered. Specifically, for example, metalloid elements such as beryllium (B), silicon (Si), germanium (Ge), antimony (Sb), bismuth (Bi), manganese (Mg), calcium (Ca), strontium (Sr ), Barium (Ba), zinc (Zn), aluminum (Al), gadolinium (Ga), indium (In), tin (Sn), typical elements such as lead (Pb), scandium (Sc), yttrium (Y) , Titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn) , Transition metal elements such as iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), and gold (Au).

For example, in the Ellingham diagram shown in FIG. 3, the metal oxide shown above (with a higher standard free energy of formation) is a suitable material in that it can be reduced relatively easily. In addition, the metal oxide shown below the Ellingham diagram (which has a smaller standard free energy of formation) is a suitable material in that it is stable as an oxide and can stabilize the shape accuracy of the composite microstructure. possible. Here, for example, the present inventors have confirmed that the composite microstructure disclosed herein can be manufactured using metal oxide nanoparticles ranging from AgO to TiO ₂ in the Ellingham diagram. ing. Moreover, in this invention, reduction | restoration and reoxidation of a metal oxide nanoparticle can be controlled highly. Therefore, a desired metal element can be selected as the metal element constituting the metal oxide nanoparticles based on the inherent properties of the metal element.

For example, as the metal element, among these, Au, Ag, Cu, Ni, Fe, titanium Ti, and the like that are required to be used in MEMS and the like are preferable. For example, in an application for forming a microwire used as a conductive wire, Au, Ag, Cu or the like having good electrical conductivity is selected as a metal element, and an oxide of the metal element (that is, Au ₂ O ₃ , Ag). ₂ O ₃ , AgO, Ag ₂ O, CuO, Cu ₂ O, etc.) may be prepared. Alternatively, metal oxide nanoparticles containing at least part of these metal element oxides (ie, Au ₂ O ₃ , Ag ₂ O ₃ , AgO, Ag ₂ O, CuO, and Cu ₂ O) may be prepared. . Any one of these metal elements may constitute a metal oxide alone, or two or more thereof may be combined to constitute a metal element oxide.

  Moreover, the whole metal oxide nanoparticle may be comprised with the metal oxide, and one part may be comprised with the metal oxide. For example, the metal oxide nanoparticles can be nanoparticles that include at least some or all of the metal oxide. For example, the metal oxide nanoparticles can be nanoparticles comprising a metal oxide on at least some or all of the surface. In this case, the metal oxide nanoparticles may be core-shell particles having a core-shell structure. The metal oxide nanoparticles having a core-shell structure may preferably include a metal oxide as a shell portion. The material constituting the core portion of the core-shell particle is not particularly limited. For example, the above metal oxides, metal oxides other than the above, various metals, ceramics, glass, organic polymer materials, and the like may be used. The shape of the metal oxide nanoparticles is not particularly limited, and may be various shapes such as a spherical shape, a rod shape, a plate shape, and an indefinite shape.

The average particle diameter of the metal oxide nanoparticles is not particularly limited, and for example, those having a size of about 100 nm or less can be used. However, in order to make the composite microstructure more dense and high in dimensional accuracy, it is preferable that the average particle diameter of the metal oxide nanoparticles is smaller. For example, the average particle size is preferably 50 nm or less, more preferably 20 nm or less, and particularly preferably 10 nm or less (for example, about 2 to 5 nm).
In addition, the value measured based on a dynamic light scattering method (DLS) can be employ | adopted for the average particle diameter of a metal oxide nanoparticle. For example, in the particle size distribution based on the frequency analysis of scattered light, it can be represented by a particle size (median diameter D ₅₀ ) equivalent to 50% cumulative.

  Further, the metal oxide nanoparticles may be prepared from raw materials and used, for example, commercially available metal oxide nanoparticles in the state of a dispersion or the like may be obtained and used. Also in this respect, the metal oxide nanoparticle-containing liquid can contain a dispersion medium capable of suitably dispersing the metal oxide nanoparticles. The dispersion medium is not particularly limited, and typically includes various hydrocarbons; halogenated hydrocarbons; alcohols such as methanol, ethanol, isopropyl alcohol, butanol, isobutanol, and isopropanol; glycols such as polyethylene glycol; Phenols; ethers; ketones such as acetone and methyl ethyl ketone; acetals such as polyacetal; esters; amines such as n-butylamine; unsaturated fatty acids; water such as ion-exchanged water, distilled water and pure water; Can be mentioned.

  As the laser curable resin, as described above, various resins that can be cured by irradiation with laser light can be used. For example, it may be a photosensitive resin that can be cured by starting a polymerization reaction by irradiation with a laser beam of a predetermined wavelength, or a thermosetting property that can be cured by starting a polymerization reaction by heat generated by irradiation with a laser beam. It may be a resin or the like. These laser curable resins may contain an appropriate polymerization initiator as required.

  The photosensitive resin can broadly include a resin material that initiates crosslinking or polymerization and cures based on light absorption by laser light irradiation. Such a photosensitive resin may be a polymerizable monomer that directly absorbs light and initiates polymerization, or is a polymerizable monomer containing a sensitizer and has an absorption wavelength. It may be a sensitized photopolymerization resin that starts polymerization by absorbing light outside the region. It is a fact known to those skilled in the art that a myriad of such photosensitive resins are known. For example, direct photopolymerization systems represented by vinyl chloride, styrene, methyl methacrylate, and derivatives thereof are given as examples. Resin; sensitized photopolymerization resin represented by ethylene, vinyl chloride, acetone, butadiene, styrene, triphenylphosphine, methyl methacrylate, and derivatives thereof; and the like.

  As the thermosetting resin, resin materials that can be polymerized and cured by heating based on heat energy converted from light energy by laser light irradiation can be widely included. Specifically, for example, phenol resin (PF), epoxy resin (EP), melamine resin (MF), urea resin (urea resin, UF), unsaturated polyester resin (UP), alkyd resin, polyurethane (PUR), Examples thereof include thermosetting polyimide (PI).

  The above laser-curable resin can be contained in the metal oxide portion as a cured product after curing in the composite microstructure. Therefore, an appropriate thermosetting resin can be selected and used in accordance with desired characteristics to be imparted to the metal oxide portion. For example, when high insulation is required for the metal oxide portion of the composite microstructure, it is preferable to use a phenol resin such as polyvinyl phenol, a thermosetting polyimide, or the like as the laser curable resin. This laser curable resin may be in the state of being added to the metal oxide nanoparticle-containing liquid, for example, in the form of a mixture of low molecular monomers, or a polymer that has been polymerized to a certain extent. Also good. Any one kind of resin (which may be a monomer) may be used alone, or two or more kinds may be used in combination (including a blend).

  Further, the laser curable resin can play a role of bonding metal oxide nanoparticles or bonding to a base material in a metal oxide portion after irradiation with an ultrashort pulse laser. Although the ratio of the laser curable resin in the metal oxide nanoparticle-containing liquid is not particularly limited, for example, it can be an amount necessary to bind the metal oxide nanoparticles. The ratio of such a laser curable resin can be 5-30 mass parts with respect to 100 mass parts of metal oxide nanoparticles, for example, It is preferable to set it as 5-25 mass parts, 10-20 masses More preferably, it is a part.

In addition, the metal oxide nanoparticle-containing liquid is not necessarily limited thereto, but may contain an additive typified by a reducing agent and / or a dispersant.
As the reducing agent, various compounds capable of promoting the reduction reaction of the metal oxide nanoparticles in the ultra-short pulse laser irradiation step (S3), which will be described later, can be used. Specific examples include glycols such as ethylene glycol and polyethylene glycol, compounds having an aldehyde group such as aldehyde, formic acid and formate, hydrogen peroxide, sulfur dioxide, toluene, polyvinylpyrrolidone and the like. Any of these may be used alone or in combination of two or more.
The amount of the reducing agent added is not particularly limited. For example, specifically, it may be 1 to 250 parts by mass, preferably 5 to 100 parts by mass, and more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the metal oxide nanoparticles. preferable.

  As the dispersant, various compounds having an action of preventing aggregation of metal oxide nanoparticles can be used without particular limitation. For example, an anionic, cationic or nonionic dispersant can be used. Specifically, examples of the anionic dispersant include polycarboxylic acid-based dispersants such as polycarboxylic acid sodium salt and polycarboxylic acid ammonium salt, naphthalenesulfonic acid sodium salt such as naphthalenesulfonic acid sodium salt and naphthalenesulfonic acid ammonium salt. Examples thereof include a system dispersant, an alkyl sulfonic acid type dispersant, and a polyphosphoric acid type dispersant. Examples of the cationic dispersant include a polyalkylene polyamine dispersant, a quaternary ammonium dispersant, an alkyl polyamine dispersant, and the like. Nonionic dispersants include, for example, alkylene oxide dispersants, polyhydric alcohol ester dispersants, N-vinyl lactam dispersants such as polyvinylpyrodon, and silicone resin dispersions such as cyclopentasiloxane and dimethylpolysiloxane. Agents and the like. Any of these may be used alone or in combination of two or more.

  The amount of the dispersant added is not particularly limited, and can be determined according to, for example, the average particle diameter or surface properties of the metal oxide nanoparticles used. For example, specifically, it can be 1 to 30 parts by mass, preferably 1 to 25 parts by mass, and preferably 1 to 20 parts by mass with respect to 100 parts by mass of the metal oxide nanoparticles. More preferred.

The metal oxide nanoparticle-containing liquid may contain additives other than the above reducing agent and dispersant as long as the object of the present invention is not impaired. As such an additive, a viscosity modifier is mentioned as an example, for example. By appropriately adjusting the viscosity of the metal oxide nanoparticle-containing liquid, the dispersibility of the metal oxide nanoparticles can be improved, and the supply of the metal oxide nanoparticle-containing liquid onto the substrate in the next step is suitably performed It can be carried out. Although it does not restrict | limit especially as a viscosity modifier, Nonionic polymers, for example, polyethers, such as polyethyleneglycol, are mentioned.
About the above reducing agent, a dispersing agent, and another additive, the same compound may function as two or more types of additives.

  By uniformly mixing the above materials, a metal oxide nanoparticle-containing liquid can be prepared. The ratio (concentration) of the metal oxide nanoparticles in the entire metal oxide nanoparticle-containing liquid is not particularly limited, and is, for example, 5 to 80% by mass, preferably 10 to 80% by mass, and particularly preferably 30 to 60% by mass. It can be prepared with reference to the degree. For mixing each material, various known stirring, mixing, and emulsifying devices such as a mixer, an ultrasonic stirring device, a shearing stirrer, and a homogenizer can be used. The order of stirring the materials is not particularly limited. For example, all the materials may be mixed at once, or may be mixed in a plurality of times. For example, in a system using a dispersion medium, metal oxide nanoparticles and a dispersant may be added to the dispersion medium and stirred, and then additives such as a laser curable resin and a reducing agent may be added later.

[S2. Supply of liquid containing metal oxide nanoparticles]
In step S2, the metal oxide nanoparticle-containing liquid prepared above is supplied to the surface of the substrate.
The material and shape of the substrate are not limited. For example, it may be a substrate made of a semiconductor material, an inorganic material such as ceramic, an amorphous material such as glass, a metal material, or a resin material. Further, the surface of the substrate may be a smooth surface, a curved surface, a surface provided with irregularities, or the like. Furthermore, the base material may be configured to be deformable (flexible) such as a curve, or the shape may be fixed. Moreover, the material which can be separated from the composite microstructure after manufacture may be sufficient, and the material which can be removed from the composite microstructure after manufacture may be sufficient. For example, a treatment (easy peeling treatment) may be performed so that the composite microstructure after manufacture can be easily separated.

The method for supplying the metal oxide nanoparticle-containing liquid to the substrate is not particularly limited. For example, it can be supplied using various methods such as a coating method, a screen printing method, a casting method, a dip coating method, a spin coating method, an electrophoresis method, a spray method, and an ink jet method. Thereby, the layered product which consists of a metal oxide nanoparticle containing liquid can be formed on a base material.
Note that the supply of the metal oxide nanoparticle-containing liquid is not limited to be performed at a time, and can be performed a plurality of times. That is, for example, in order to supply (apply) the metal oxide nanoparticle-containing liquid to a desired thickness, the number of times of supplying the metal oxide nanoparticle-containing liquid can be adjusted once or a plurality of times. Moreover, the irradiation process (S3) of the next ultrashort pulse laser and the supply process (S2) of the metal oxide nanoparticle-containing liquid can be alternately repeated a plurality of times. For example, a composite fine structure having a three-dimensionally complicated structure can be formed by repeatedly supplying the metal oxide nanoparticle-containing liquid and irradiating with an ultrashort pulse laser.

[S3. Ultrashort pulse laser irradiation]
In step S3, the metal oxide nanoparticle-containing liquid supplied to the surface of the base material as described above is irradiated with an ultrashort pulse laser. The ultrashort pulse laser can be irradiated using various laser oscillation devices that can oscillate a pulse laser having a pulse width smaller than nanoseconds (10 ⁻⁹ seconds). For example, laser irradiation can be easily performed by using a commercially available ultrashort pulse laser drawing apparatus.
In the technique disclosed herein, as shown in FIG. 2, by adjusting the irradiation conditions of the ultrashort pulse laser to the metal oxide nanoparticle-containing liquid supplied to the substrate, (A) the metal portion And (B) the metal oxide portion are formed with different structures. In the metal oxide nanoparticle-containing liquid after irradiation with the ultrashort pulse laser, in addition to (A) the metal part and (B) the metal oxide part, (C) the metal oxide nanoparticle-containing liquid There are unreacted parts. Here, (C) the unreacted portion is a supply portion of the metal oxide nanoparticle-containing liquid in which the laser curable resin has not been cured. By removing this (C) unreacted part by washing away with an appropriate solvent, a composite microstructure comprising (A) a metal part and (B) a metal oxide part can be obtained. As the solvent used for the washing, for example, a dispersion medium that can be used for the metal oxide nanoparticle-containing liquid can be suitably used. Alternatively, (C) even if an ultra-short pulse laser is irradiated on the entire metal oxide nanoparticle-containing liquid so that the laser curable resin is cured at least so that an unreacted portion is not formed, a composite microstructure can be manufactured. Good. The composite microstructure obtained in this manner can be one in which (A) a metal portion and (B) a metal oxide portion are formed with extremely high dimensions in the order of micrometers.

  Here, (B) a metal oxide part is a part containing a metal oxide nanoparticle. More typically, the (B) metal oxide portion includes a resin portion obtained by curing the laser curable resin contained in the metal oxide nanoparticle-containing liquid, and metal oxide nanoparticles. Specifically, the laser curable resin is cured by irradiation with an ultrashort pulse laser to become a resin portion, and bonds adjacent metal oxide nanoparticles to each other or bonds metal oxide nanoparticles to a substrate. To do. Therefore, for example, by irradiating a desired region with an ultrashort pulse laser under a condition capable of curing the laser curable resin, a metal oxide portion having a shape corresponding to the irradiation region can be formed. Such (B) metal oxide portion may have physical properties mainly based on the metal oxide, though depending on the ratio.

  The (A) metal portion is a portion formed by reducing metal oxide nanoparticles into metal nanoparticles and bonding the metal nanoparticles to each other. The reduction and bonding of the metal oxide nanoparticles may proceed simultaneously, or one of them may proceed first. Note that, under the laser irradiation conditions in which reduction of the metal oxide nanoparticles occurs, the resin portion found in the (B) metal oxide portion can be decomposed and disappear. Therefore, it can be considered that the (A) metal portion essentially does not contain an organic compound such as a laser curable resin and other additives. Such (A) metal portion can essentially have physical properties based on the metal.

  In addition, (A) A metal part is typically formed when metallized nanoparticles couple | bond together after the reduction | restoration of a metal oxide nanoparticle begins. The reduction of the metal oxide nanoparticles may be realized by reducing all of the metal oxides contained in the metal oxide nanoparticles, or may be realized by reducing a part of the metal oxide nanoparticles. In other words, the metal oxide contained in the metal oxide nanoparticles may be entirely metallized into a single metal element constituting the metal oxide, or may be partially metallized. The metal part (A) is formed by directly bonding at least a part of the metal oxide nanoparticles made of metallized metal (hereinafter simply referred to as “metallized part”). ing. Accordingly, (A) the metal portion may be composed of only the metal that has been included in the metal oxide, or may include an unreduced metal oxide or a modified product of the metal oxide. For example, when the entire metal oxide nanoparticle is made of a metal oxide, and the entire metal oxide is reduced, (A) the metal portion is the metal constituting the metal oxide. It is formed as a combined product of metal nanoparticles.

  (A) Since the metal portion is formed by reducing metal oxide nanoparticles by laser irradiation, the metal portion has at least a metallized portion on the laser scanning surface. The laser scanning surface may typically be an exposed surface, but when the composite microstructure has a three-dimensionally shaped shape, the laser scanning surface may be included inside the structure. Further, (A) the metallized portion is at least partially metallized, so that a so-called metallic luster is recognized. Metallic luster can also be observed when (A) the metallization site contains an unreduced metal oxide. Therefore, when the entire composite microstructure is observed, (B) metal oxidation is observed in that (A) the metallization site has a metallic luster compared to the (B) metal oxide portion in the unreduced state. Can be distinguished from physical parts. For example, (A) the metallized part can be grasped as a part having a higher light reflectance than the (B) metal oxide part.

  Although it cannot be said unequivocally because it depends on the metal species constituting the metal oxide and the form of the metal oxide nanoparticles, (A) the metal part is composed of a part made of the metal oxide and the metal constituting the oxide. It is preferable that the metallized site occupies 10% by mass or more of the total with the metallized site. (A) The ratio of the metallization site in the metal part is preferably 30% by mass or more, more preferably 40% by mass or more, for example, more preferably 50% by mass or more.

  (A) In the metal portion, the reduced metal oxide nanoparticles may be solidified after at least a part of the particle surface is melted, and adjacent metal nanoparticles may be bonded to each other. Part of the reduced metal oxide nanoparticles may be melted, or all may be melted. Alternatively, the reduced adjacent metal oxide nanoparticles may be bonded to each other by sintering without melting. When the surface of the metal oxide nanoparticles is melted, (A) the metal portion can be firmly bonded to the substrate.

  Note that the composite microstructure disclosed herein is not necessarily limited to this, but (B) in the metal oxide portion, (B ′) a portion containing essentially no resin portion and containing a metal oxide. (For convenience, referred to as a second metal oxide portion) may be present. That is, in this (B ′) second metal oxide portion, it can be considered that the resin portion seen in the above (B) metal oxide portion has disappeared by the irradiation with the ultrashort pulse laser. At this time, the (B ′) second metal oxide portion is not present as it is (unreacted) of the metal oxide nanoparticles used as a raw material, but typically (A) above. The metal portion may be formed by being oxidized again. That is, although (B) the metal oxide portion, the metal oxide nanoparticles are directly bonded to each other in the (B ′) second metal oxide portion. Or while the metal oxide nanoparticles are melted and integrated, at least the laser scanning surface (which may be an exposed portion or the like) is made of a metal oxide. Such (B ′) second metal oxide portion may be in a form in which (A) the entire metal portion is reoxidized. This is because (A) a form in which only a part of the metal portion is reoxidized can still be regarded as (A) the metal portion.

  As will be described later, according to the technology disclosed herein, (A) the re-oxidation of the metal portion can be suitably suppressed to produce a composite microstructure. Therefore, in the composite microstructure, the proportion of the first metal oxide portion in the total of the first metal oxide portion and the second metal oxide portion can be 50% by volume or more, and 60% by volume or more. Is more preferable, and 70% by volume or more is particularly preferable. As the re-oxidation proceeds, the metal part is completely melted and foamed, and it is difficult to obtain the effect of fine processing by the ultrashort pulse laser. From this viewpoint, it is preferable that the ratio of the first metal oxide portion is large. In other words, the proportion of the second metal oxide portion is preferably small.

  In addition, when the metal element of the prepared metal oxide nanoparticles constitutes an oxide having a valence of 2 or more, an oxide having a different valence between the metal oxide and the metal (zero valence) A low-order metal oxide). That is, the original metal oxide may be reduced to form a new lower-order metal oxide. This low-order metal oxide may be contained in (A) the metal part or (B) in the metal oxide part. Therefore, the composite microstructure disclosed herein is not necessarily limited to this, but (B) a metal composed of a lower-order metal oxide different from the original metal oxide in the (B) metal oxide portion. An oxide portion (for convenience, referred to as a third metal oxide portion) may be included. This (B ″) third metal oxide portion has physical properties that are essentially based on the lower-order metal oxide. be able to.

In the above composite microstructure, (A) the metal portion and (B) to (B ″) metal oxide portions may be arbitrarily arranged in the composite microstructure, respectively, in one composite microstructure. May include one or more (A) metal moieties and (B) to (B ″) metal oxide moieties.
Also, according to the technique disclosed herein, the degree of reduction of the metal oxide nanoparticles can be controlled in detail, so that (B) the metal oxide portion, (B ′) the second metal oxide portion, and (B ″) ) The third metal oxide portion has been described separately, however, (B) the metal oxide portion and (B ′) the second metal oxide portion can both have physical properties based on the same metal oxide. It is not always necessary to distinguish clearly, for example, it may be distinguished when necessary depending on the use of the composite microstructure, etc. Also, (B ″) the third metal oxide portion is also, for example, composite fine Depending on the use of the structure, etc., it may be distinguished from the (B) metal oxide portion or not. Hereinafter, the description will be made without distinguishing the metal oxide portions (B) to (B ″) unless necessary.

  The above (A) metal part and (B) metal oxide part can be made separately, for example, by partially changing the ultrashort pulse laser irradiation conditions. In other words, by using the same material and the same ultrashort pulse laser drawing apparatus and adjusting the irradiation conditions of the ultrashort pulse laser oscillated from the apparatus, (A) the metal portion and (B) the metal It can be made separately from the oxide part.

  The ultrashort pulse laser is a laser having a pulse width smaller than 1 nanosecond. In metals, metal oxides, and the like, it is said that it takes about 1 picosecond for heat to travel through a lattice (crystal lattice) constituting a solid and diffuse to adjacent atoms. More specifically, such heat transfer is caused by an average free time (also referred to as relaxation time, collision relaxation time, etc.) that is the average time required for the next collision after a conduction electron collides with another atom. It can be estimated and depends on the target substance and the heating temperature. And it is known that it is about several picoseconds about a general metal. The mean free time can be calculated from, for example, an electron-phonon coupling parameter. Thus, when the laser pulse width is shorter than the heat transfer, most of the energy provided by the laser can be absorbed by the atoms without diffusing. After the laser irradiation is completed and before the next laser irradiation, the lattice is heated and cooled based on the energy absorbed by the atoms. Alternatively, if there is a lot of absorbed energy, the grid can heat up or conduct heat.

  In the technique disclosed herein, pulse energy is supplied to the metal oxide nanoparticles by a period shorter than heat transfer (mean free time) by using an ultrashort pulse laser. Further, the pulse energy supplied by one pulse laser can be controlled in detail. Therefore, for example, the metal oxide nanoparticles can be heated while suppressing thermal diffusion. Accordingly, by supplying an appropriate amount of pulse energy by an ultrashort pulse laser according to the composition of the metal oxide constituting the nanoparticle, (A) the reaction for forming the metal portion, B) The reaction for forming the metal oxide portion can occur locally and selectively. Then, a part other than (A) the metal part and (B) the metal oxide part can remain as (C) an unreacted part.

  (B) In order to form the metal oxide portion, an ultrashort pulse laser is irradiated on the condition where the laser curable resin is cured at a position where the (B) metal oxide portion is to be formed. For example, when the laser curable resin is a photocurable resin, a laser beam having a wavelength that can start polymerization of the resin may be irradiated. Further, for example, when the laser curable resin is a thermosetting resin, pulse energy is supplied to the metal oxide nanoparticles so that the thermosetting resin is heated to a temperature at which the resin can start polymerization. That's fine. Alternatively, another metal oxide such that the heat transferred from another metal oxide nanoparticle that generates heat by being supplied with pulse energy to the thermosetting resin is higher than the temperature at which the resin can start polymerization. What is necessary is just to supply pulse energy to a nanoparticle. As described above, the amount of pulse energy can be calculated based on the composition and volume of the metal oxide nanoparticles, the environmental temperature, the physical properties of the thermosetting resin, and the like.

  (A) In order to form a metal part, (A) If a metal oxide nanoparticle contained in a location where a metal part is to be formed is irradiated with an ultrashort pulse laser under conditions that allow the metal oxide to be reduced, Good. The reduction mechanism of the metal oxide is not particularly limited. For example, specifically, the metal oxide nanoparticles may be irradiated with an ultrashort pulse laser under conditions where the metal oxide can be heated to a temperature at which the metal oxide can be thermally reduced. The thermal reduction of the metal oxide can be represented by, for example, the following general formulas (1) and (2). The amount of energy required for the thermal reduction can be calculated based on the composition and volume of the metal oxide nanoparticles, the standard free energy of formation, the environmental temperature, and the like. The metal oxide nanoparticles thus thermally reduced can be sintered by the temperature increase of the metal oxide nanoparticles themselves. Further, at a temperature at which thermal reduction can occur, the laser curable resin can be generally burned off by heating. Thereby, (A) metal part formed by sintering the reduced metal nanoparticles is formed.

(When the metal oxide is CuO and EG is used as the reducing agent)
2HO (CH ₂ ) ₂ OH → 2C ₂ H ₄ O + H ₂ O ↑ (1)
2C ₂ H ₄ O + CuO
→ C ₄ H ₆ O ₂ + 2H ⁺ + 2e ⁻ + CuO
→ Cu + H ₂ O (2)

Note that when the metal oxide nanoparticles are supplied with more energy than required for reduction, the metal oxide nanoparticles may be reduced to metal nanoparticles and then, for example, part or all of the surface may be melted. In such a case, (A) a metal portion formed by solidifying the reduced metal nanoparticles after melting is formed.
When such melting of the metal nanoparticles occurs, heat conduction can occur from the heated and melted metal nanoparticles to the surroundings. By such heat conduction, a region where the thermosetting resin is cured can be formed around the metal portion (A) although the metal oxide nanoparticles are not thermally reduced. Thereby, (B) a metal oxide part can be formed.

On the other hand, (B) the metal oxide part can be obtained by heating the metal oxide nanoparticles to a temperature at which the thermosetting resin is cured, although the metal oxide nanoparticles are not reduced (for example, thermal reduction). Can be formed. The amount of energy required for this reaction can be calculated based on the physical properties (curing temperature) of the thermosetting resin used, the composition and volume of the metal oxide nanoparticles, and the like.
And when the metal oxide nanoparticles can form a lower order oxide, the metal oxide nanoparticles are not reduced to metal (zero valence) (for example, thermal reduction), but the lower order metal oxide The metal oxide nanoparticles can be heated so as to be thermally reduced. Thus, (B ″) the third metal oxide portion can be formed. The amount of pulse energy necessary for forming the (B ″) third metal oxide portion is less than that of the original metal oxide and lower order. It can be calculated based on the composition of metal oxide, standard free energy of formation, volume, ambient temperature, and the like.

On the other hand, the (B ′) second metal oxide portion can be formed when the metal oxide nanoparticles are supplied with sufficiently more energy than required for reduction. That is, once reduced metal nanoparticles are easily oxidized by excessive energy and can be oxidized again to metal oxides. As a result, (A) the metal portion is re-oxidized, and (B ′) the second metal oxide portion is formed.
Even when an ultrashort pulse laser is used, if excessive energy is supplied, the metal oxide nanoparticles can be rapidly heated and melted to be in a bumping state. Such a bumped portion can be regarded as a second metal oxide portion when cooled, but the dimensional accuracy can be greatly disturbed by bumping. Such a state may be an undesirable form in the composite microstructure disclosed herein. Therefore, it can be said that it is not preferable to supply an excessive pulse energy such that the metal oxide nanoparticles are rapidly heated and melted.

  Even if the ultrashort pulse laser is irradiated to the metal oxide nanoparticle-containing liquid, as long as the curing reaction of the laser curable resin and the reduction reaction of the metal oxide nanoparticles are not caused, the irradiation region is (C) Unreacted. That is, since the pulse width of the ultrashort pulse laser is extremely short, energy that cannot cause a curing reaction or a reduction reaction is absorbed by the lattice and then cooled, so that it does not contribute to the reaction. Therefore, the irradiation condition of the ultrashort pulse laser can be adjusted in consideration of the intensity distribution of the laser oscillated from the ultrashort pulse laser oscillation apparatus to be used. As a result, a composite microstructure in which (A) a metal portion and (B) to (B ″) metal oxide portions are arbitrarily combined is realized.

By controlling the irradiation conditions of the ultrashort pulse laser, various adjustments can be made based on the amount of pulse energy to be supplied to the metal oxide nanoparticles as described above. Although it is difficult to unconditionally define the irradiation conditions of an ultrashort pulse laser that enables suitable production of a composite microstructure, as an approximate guideline, for example, the laser oscillation conditions are a wavelength of 350 to 1560 nm, a pulse width As a suitable example, adjustment is performed in the range of 10 fs to 300 ps, repetition frequency 10 kHz to 100 MHz, maximum pulse energy 0.2 to 1.2 nJ, fluence 1.5 to 15000 J / m ² , and scanning speed 30 to 1500 μm / s. Indicated.
In the following embodiment, for each target metal oxide nanoparticle, (A) a metal portion, (B) to (B ″) a metal oxide portion, and (C) an unreacted portion can be formed. The person skilled in the art, on the basis of such disclosure, will produce (A) a metal portion, (B) to (B ″) a metal oxide portion, and (C) an ultrashort pulse that forms an unreacted portion. Laser irradiation conditions can be appropriately determined.

The conditions under which (A) the metal part, (B) to (B ″) metal oxide part, and (C) the unreacted part are not necessarily calculated based on the calculation. A condition for obtaining a desired structure can be grasped by producing a composite microstructure by changing the laser irradiation conditions and observing the structure of the formed structure. It is also possible to easily confirm the ratio of the metal part and the metal oxide part contained in the sample by observing with an electron microscope, for example, by combining a plurality of composite fine particles produced by changing the irradiation conditions of an ultrashort pulse laser. For the structure, the ratio of the metal portion to the metal oxide portion may be examined by using an X-ray diffraction analysis method, etc. In this case, for example, the diffraction peak intensity I _M attributed to the metal oxide The ratio of the diffraction peak intensity I _M attributed to metal to _{O (I MO /} I _M) by mapping can be efficiently formed metal parts or ultrashort pulse laser irradiation conditions, it can form a metal oxide portions Ultrashort pulse laser irradiation conditions can be confirmed.

  Further, according to detailed examinations by the inventors, when the ultrashort pulse laser is scanned linearly (for example, in one direction) on the metal oxide nanoparticle-containing solution supplied in a film shape under a predetermined preferable condition, FIG. A linear composite microstructure as shown in (a) is formed. This scanning direction is referred to as “main scanning direction”. This composite microstructure has a solidified portion x with a metallic luster (hereinafter referred to as a glossy portion x) in the unreacted portion z of the metal oxide nanoparticle-containing liquid, and a solidified but not glossy 2 Two portions y (hereinafter referred to as “joined portions y”) are formed in a linear shape along the main scanning direction. In FIG. 13, the scanning lines are indicated by two-dot chain lines. The glossy portion x and the coupling portion y are typically formed symmetrically on both sides with the scanning line as the center. When the laser irradiation conditions are the same, the width of the glossy part x and the line width of the joint part y are substantially constant.

  Here, the unreacted portion z coincides with the (C) unreacted portion. The glossy portion x is formed as a straight line centered on the scanning line, and is considered to be a portion that is reduced, melted and solidified or sintered by direct irradiation of the ultrashort pulse laser and the heat generated therewith. The glossy portion x is considered to coincide with the (A) metal portion. In general, the sintering temperature of metal is lower than that of metal oxide. Therefore, the reduced (A) metal portion is likely to be sintered. The coupling portion y is formed adjacent to both ends of the metallic gloss portion x so as to sandwich the linear metallic gloss portion x in a direction perpendicular to the scanning direction. The joint portion y is considered to be a portion formed by being joined by a resin portion that has been cured by heat transfer (thermal influence) due to heat generated by the ultrashort pulse laser. Therefore, this bonding portion y is considered to coincide with the above (B) metal oxide portion. Further, the two joint portions y formed at both ends of the metallic gloss portion x are basically the same width.

  Here, as shown in FIG. 13B, the scanning line is shifted by a predetermined width in the sub-scanning direction orthogonal to the main scanning direction, and the ultrashort pulse laser is scanned in the main scanning direction. At this time, the laser irradiation conditions are the same as before, and (1) the ultrashort pulse laser is scanned so that the glossy portions x overlap in the first and second times. Then, the portion where the glossy portion x is doubled can be configured as a metal oxide portion that has been substantially re-oxidized. That is, formation of a metal part is suppressed. Further, (2) when the ultrashort pulse laser is scanned so that the glossy part x and the coupling part y overlap, the part where the glossy part x and the coupling part y overlap is generally composed of a reoxidized metal oxide part. Tend to be. That is, also in this case, the formation of the metal portion is suppressed. Then, in the first time and the second time, (3) when the ultrashort pulse laser is scanned so that only the coupling portion y overlaps, the portion formed by overlapping the coupling portion y is generally composed of a reduced metal portion. Tend. In other words, in this case, the metal portion can be suitably formed. On the other hand, (4) when the ultra-short pulse laser is scanned so that the coupling portions y are arranged in parallel closely without overlapping, the composite microstructure shown in FIG. 13A is arranged. From the above, by setting the pitch in the sub-scanning line direction of the ultrashort pulse laser as (the width of the glossy portion x + 1 the width of one coupled portion y), the ultrashort pulse laser is applied twice only to the coupled portion y. The ultrashort pulse laser can be scanned so that it is irradiated one by one. And thereby, a metal part can be formed in the continuous planar shape. Because of these features, it is possible to efficiently obtain a composite microstructure of a desired form by investigating the dimensions of the glossy portion x and the joint portion y that are formed (solidified) under a predetermined ultrashort pulse laser irradiation condition in advance. Can be formed.

  As described above, since the ultrashort pulse laser suppresses the thermal diffusion in the irradiated object, the influence of the thermal diffusion is minimized and the (A) metal part and the (B) metal oxide part are formed. can do. Such dimensional accuracy can be controlled on the order of micrometers although it depends on the physical properties (composition, particle size, etc.) of the metal oxide nanoparticles. For example, it is usually possible to easily form a model while controlling the dimension of at least one of the metal oxide portion and the metal portion in the composite microstructure at 100 micrometers or less. Therefore, the composite microstructure disclosed herein can be realized as a case where the dimension of at least one of the metal oxide portion and the metal portion is controlled to be 100 micrometers or less. More suitably, for example, at least one dimension (for example, line width) of the composite microstructure can be formed to 50 μm or less, preferably 20 μm or less, particularly preferably 10 μm or less, for example, about 1 to 8 μm. For example, even if the planar shape is 100 μm × 100 μm or more, it can be formed into a sheet having a thickness of about 1 to 8 μm. Such a micrometer-order sheet-like material can be provided with a hollow portion having an arbitrary shape in the plane, for example. For example, by using a precision laser drawing apparatus (laser processing apparatus, three-dimensional laser additive manufacturing apparatus, etc.) capable of oscillating a femtosecond laser intended for processing of a known photosensitive resin, the composite fine structure disclosed herein is used. A structure can be suitably manufactured.

  As shown in the embodiments described later, when the metal oxide portion and the metal portion in the composite microstructure are continuously formed, the dimensions of the metal oxide portion and the metal portion are 100 micrometers. It can be exceeded. The “continuous” is not limited to an aspect in which, for example, a metal oxide portion having a width of 100 micrometers or less and / or a metal portion is formed to be long along the laser scanning direction (that is, one-dimensionally). . For example, it includes an embodiment in which a metal oxide portion and / or a metal portion having a width of 100 micrometers or less are formed by being laminated and bonded two-dimensionally or three-dimensionally. However, the composite microstructure disclosed herein can be useful in that its dimensional accuracy can be achieved at a level of 100 micrometers or less as described above.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to such examples.
(Embodiment 1)
In this embodiment, a microturbine that can be used for a microfluidic device was produced. FIG. 4A is a perspective view illustrating the configuration of the micro turbine main body. The drawing of the micro turbine main body (helical coil) can be created as 3D data indicating a three-dimensional shape by, for example, CAD. For example, the 3D data can be converted into slice data sliced in a predetermined cross-sectional direction by CAD or the like. This slice data is, for example, in the STL format. By scanning a precision laser drawing apparatus based on the slice data, laser drawing corresponding to the cross-sectional shape of the microturbine body can be performed. In FIG. 4A, in order to show the shape of the turbine body in an easy-to-understand manner, the shaft portion that serves as the axis of rotation of the turbine is omitted. Actually, a cylindrical shaft portion having a diameter that fits into the central through hole is combined with the main body of the microturbine. Here, for example, the illustrated micro turbine main body is made of a magnetic material, and the shaft portion is made of a non-magnetic material, whereby a micro turbine for electromagnetic induction power generation can be constructed.

  Therefore, NiO nanoparticles (average particle diameter of 50 nm), which is a nonmagnetic material, are used as metal oxide nanoparticles, and the gear-shaped microturbine body shown in FIG. 4A and a shaft portion (not shown) are included. An attempt was made to fabricate a composite microstructure. Ethylene glycol (EG) was used as the dispersion medium and reducing agent, and thermosetting polyvinyl pyrrolidone (PVP) was used as the laser curable resin. And these were mix | blended so that the ratio of NiO nanoparticle: EG: PVP might be 46.9: 42.9: 10.2 by mass ratio, and the base solution was prepared by mixing with an ultrasonic stirrer. . This base solution was uniformly applied to a glass substrate with a film thickness of about 9 μm by spin coating, and an ultrashort pulse laser was irradiated on the base solution coating film in a pattern so as to correspond to a desired microturbine structure. . A femtosecond laser drawing system (manufactured by Nanoscribe Co., Ltd., Photonic Professional GT) was used for irradiation with an ultrashort pulse laser.

In this embodiment, (A) the microturbine body reduces NiO nanoparticles to Ni by irradiating a paste-like base solution of NiO nanoparticles and a thermosetting resin with an ultrashort pulse laser. It is produced by bonding (including sintering and welding). In addition, (B) the shaft portion of the micro turbine is irradiated with an ultrashort pulse laser on the paste-like (uncured) base solution of the NiO nanoparticles and the thermosetting resin, so that the NiO nanoparticles remain as they are. It is produced by curing a thermosetting resin.
(A) The irradiation condition of the ultrashort pulse laser for forming the micro turbine main body is an objective lens having a numerical aperture of 0.75, which is a laser oscillated in the atmosphere under the conditions of a wavelength of 780 nm, a pulse width of 120 fs, and a repetition frequency of 80 MHz. , The spot diameter was 1 μm, the scanning speed was 1300 μm / s, and the pulse energy was 0.24 nJ.
(B) The irradiation condition of the ultrashort pulse laser for forming the shaft portion of the micro turbine is that a laser oscillated in the atmosphere under the conditions of a wavelength of 780 nm, a pulse width of 120 fs, and a repetition frequency of 80 MHz has a numerical aperture of 0.75. While condensing to a spot diameter of 1 μm using an objective lens, the scanning speed was 1300 μm / s and the pulse energy was 0.06 nJ.

  The irradiation with the ultrashort pulse laser was directly drawn using the femtosecond laser drawing system based on the CAD data as shown in FIG. That is, first, the laser was scanned under the condition (A) so as to fill the shape of the microturbine body, and a microturbine body made of a sintered body of Cu nanoparticles was constructed as shown in FIG. It was confirmed that the microturbine body was composed of a phase containing metallic Ni, and a phase mainly containing NiO particles and a thermosetting resin was present at the periphery. Subsequently, the laser was scanned in the hole at the center of the microturbine body under the above condition (B) to form a shaft portion. It was confirmed that the shaft portion was constituted by a phase mainly containing NiO particles and a thermosetting resin. The micro turbine main body and the shaft were integrated. Thereby, it was confirmed that the composite fine structure which consists of a micro turbine main body and a shaft part can be manufactured suitably. The micro turbine main body (helical coil) has a diameter of 300 μm and a thickness of about 8 μm. The diameter of the cross section of the shaft portion is about 80 μm, and the length in the axial direction is about 40 μm.

(Embodiment 2)
In this embodiment, a three-dimensional microwire is produced. FIG. 5A is a (a) perspective view for explaining the structure of the three-dimensional microwire, and (b) a schematic cross-sectional view for explaining a laminated pattern when the three-dimensional microwire is manufactured by using a layered manufacturing method. is there. As shown in FIG. 5A, in this embodiment, a three-dimensional microwire is manufactured by coating a metal microwire with a mixed cured product of the metal oxide nanoparticles and a laser curable resin.
First, CuO nanoparticles having an average particle diameter of 50 μm were used as metal oxide nanoparticles, ethylene glycol (EG) as a dispersion medium and reducing agent, and polyvinylpyrrolidone (PVP) as a laser curable resin. And these were mix | blended so that the ratio of CuO nanoparticle: EG: PVP might be set to 60:27:13 by mass ratio, and the base solution was prepared by mixing with an ultrasonic stirrer. This base solution is uniformly applied to a glass substrate with a film thickness of about 8 μm by spin coating, and an ultrashort pulse laser is applied on the base solution coating so as to form a laminated pattern corresponding to a desired 3D wire structure. Irradiated with a pattern.

  In the present embodiment, (A) the microwire portion irradiates the metal oxide nanoparticles by irradiating a paste-like (uncured) mixture of the metal oxide nanoparticles and the laser curable resin with an ultrashort pulse laser. It is produced by reduction and bonding (including sintering and welding). In addition, (B) the coating portion is formed by irradiating a paste-like mixture of metal oxide nanoparticles and a laser curable resin with an ultrashort pulse laser so that the metal oxide nanoparticles remain as they are and the laser curable resin is applied. It is made by curing.

(A) The irradiation condition of the ultrashort pulse laser for forming the microwire portion is an objective lens having a numerical aperture of 0.75, which is a laser oscillated in the atmosphere under the conditions of a wavelength of 780 nm, a pulse width of 120 fs, and a repetition frequency of 80 MHz. , The spot diameter was 1 μm, the scanning speed was 1000 μm / s, and the pulse energy was 1.2 nJ.
(B) The irradiation condition of the ultrashort pulse laser for forming the coating portion is that the laser oscillated in the atmosphere under the conditions of a wavelength of 780 nm, a pulse width of 120 fs, and a repetition frequency of 80 MHz, and an objective lens having a numerical aperture of 0.75. The light was condensed to a spot diameter of 1 μm, the scanning speed was 50 μm / s, and the pulse energy was 0.1 nJ.

  In addition, irradiation of such an ultrashort pulse laser was performed using a layered manufacturing method. That is, as shown in FIG. 5A (b), the three-dimensional shape of the microwire is cut into a cross section, and in order from the bottom layer, (A) a metal portion (microwire portion) and (B) a metal oxide portion. Corresponding to (coating part), each of the parts was irradiated with an ultrashort pulse laser under conditions suitable for forming both parts. In addition, each time one layer is formed, the application of the base solution and the irradiation with the ultrashort pulse laser are repeated. In this way, after sequentially forming the (A) metal portion and the (B) metal oxide portion in the thickness direction from the bottom layer to the top layer, by removing the paste-like mixture of the laser non-irradiated portion, A three-dimensional microwire was obtained. 5B and 5C show scanning electron microscope images of the 3D microwires produced in this embodiment. Thus, it was confirmed that the composite microstructure comprising the microwire portion and the coating portion can be suitably manufactured by the manufacturing method disclosed herein.

(Embodiment 3)
Hereinafter, in each example, the formation method of (A) metal part and (B) metal oxide part is examined in detail, and the method of making (A) metal part and (B) metal oxide part is explained. To do.
(Example 1)
As metal oxide nanoparticles, copper oxide (CuO) nanoparticles having an average particle diameter of 50 nm or less were prepared. Ethylene glycol (EG) was used as a dispersion medium and a reducing agent, and thermosetting polyvinyl pyrrolidone (PVP) was used as a laser curable resin. And these were mix | blended so that the ratio of CuO nanoparticle: EG: PVP might be set to 60:27:13 by mass ratio, and the base solution was prepared by mixing with an ultrasonic stirrer.

  This base solution was uniformly supplied on a glass substrate with a film thickness of about 8 μm by spin coating. Next, using a femtosecond laser drawing system (manufactured by Nanoscribe Co., Ltd., Photonic Professional GT), the base solution was irradiated with an ultrashort pulse laser in a fine pattern. The ultrashort pulse laser condenses a laser oscillated in the atmosphere under the conditions of a wavelength of 780 nm, a pulse width of 120 fs, and a repetition frequency of 80 MHz to a spot diameter of 1 μm using an objective lens having a numerical aperture of 0.75 and The pulse energy was changed at a scanning speed of 1000 μm / s, and the base solution was irradiated with a predetermined drawing pattern. The glass substrate after irradiation with the ultrashort pulse laser was washed away with EG to remove the unreacted base solution.

The glass substrate after laser irradiation was observed with an optical microscope. FIG. 6 shows (a) a laser drawing pattern and (b) an SEM image of the glass substrate after laser irradiation. Note that the interval between the scanning lines in the horizontal direction in the laser drawing pattern in FIG. 6A is 100 μm. As shown in FIG. 6B, it was confirmed that the fine line pattern corresponding to the laser drawing pattern was directly drawn in the base solution after the laser irradiation. Therefore, the composition of the fine line pattern portion was confirmed by X-ray diffraction (XRD) analysis. As a result, diffraction peaks attributed to Cu, Cu ₂ O (copper oxide (I)) and CuO (copper oxide (II)) were confirmed. From this, it was found that CuO nanoparticles were reduced to Cu ₂ O or Cu by irradiation with an ultrashort pulse laser to construct a fine line pattern. In addition, this reduction involves fixing the CuO nanoparticles to each other and the CuO nanoparticles to the glass substrate, and the CuO nanoparticles are reduced by thermal reduction and simultaneously sintered or melted (including partial melting). It was thought that a fine line pattern was formed on the top. Although specific data is not shown, when this fine line pattern is observed in more detail, a glossy part x with metallic luster is observed at the center in the width direction of the fine line, and a joined part having no metallic luster on both sides thereof. y was observed. Therefore, it was confirmed that this thin line is the composite microstructure disclosed herein.

The line width of the formed thin line pattern was measured, and the relationship between the pulse energy and the line width is shown in FIG. This pulse energy means output energy per pulse. As shown in FIG. 7, the line width tends to increase as the pulse energy increases and the scanning speed decreases. It was confirmed that the minimum line width in this example was 10 μm and the maximum line width was 28 μm. That is, it was expected that CuO nanoparticles were directly heated by the irradiation energy of the ultrashort pulse laser, and CuO nanoparticles in a wider area than the laser direct irradiation area were also heated by thermal diffusion or the like.
From the above, it has been found that by irradiating the CuO nanoparticles with an ultrashort pulse laser, a fine line-like microstructure can be formed by a thermal process.

(Example 2)
Next, the spot diameter of the ultrashort pulse laser in Example 1 is increased from 1 μm to 23 μm, the scanning speed is slowed down to 20 to 100 μm / s, and other conditions are the same as in Example 1 except that CuO nanoparticles A thin line pattern was directly drawn using a base solution. Then, the line width of the formed thin line pattern was measured, and the relationship between the pulse energy and the line width is shown in FIG. FIG. 9 shows (a) a fine structure formed when the pulse energy is 0.36 nJ and the scanning speed is 100 μm / s, and (b) the pulse energy is 1.2 nJ and the scanning speed is 20 μm / s. The observation image about the microstructure formed in the case is shown.

As shown in FIG. 8, as in the case of Example 1, the line width tended to be thicker as the pulse energy was larger and the scanning speed was slower as a whole. However, the minimum line width in this example was 5 μm, and the maximum line width was 45 μm.
That is, in this example, although the scanning speed is slower than that in Example 1, the pulse energy is as low as 0.36 nJ, and the line width is about 5 μm when the scanning speed is 50 and 100 μm / s. It was confirmed that it was thinner than any of the samples. As can be seen from FIG. 9A, the value of 5 to 10 μm, which is the line width when the pulse energy is 0.36 nJ, is smaller than the spot diameter of the irradiated ultrashort pulse laser, A fine structure is formed approximately near the center (on the scanning line). Even in the region irradiated with the ultrashort pulse laser a plurality of times, no fine structure is formed in the peripheral portion of the laser spot. That is, under the laser irradiation conditions of this example, the threshold value (whether the pattern formation is possible or not is the energy input to the CuO nanoparticles adjusted by the intensity distribution of the laser beam in the laser irradiation spot and the laser scanning speed). It shows that it includes a boundary.

  From this, the following was found. That is, when a femtosecond laser is used, if the scanning speed is too slow, CuO nanoparticles absorb excessive laser energy, generate heat and diffuse, as in the case of using a conventional nanosecond laser. A phenomenon of reduction or melting can occur. However, for example, a femtosecond laser is used to increase the scanning speed, and the irradiation region is irradiated with a sufficiently strong laser for an extremely short time (that is, the minimum necessary amount) shorter than the mean free time, thereby eliminating the heat effect as much as possible. Thus, it is considered that only the irradiation region of a predetermined laser intensity and energy can be heated. This is achieved by controlling the laser intensity, laser irradiation time (which may include the scanning speed), and the like, with the minimum amount required for thermal reduction as a threshold value, thereby suppressing the thermal effect on the surroundings to obtain a desired CuO. It can be said that this means that only nanoparticles can be heated and thermally reduced.

It was found that when the pulse energy was increased to 0.96 nJ and 1.2 nJ, the line width was increased, and when the scanning speed was as low as 20 μm / s, the line width was thicker than any of the samples in Example 1. At this time, for example, as shown in FIG. 9B, the CuO nanoparticles were seen as if they were melted, resulting in large variations in line width.
From the above, it was found that in the reduction of metal oxide (here, CuO) nanoparticles in the atmosphere by an ultrashort pulse laser, a fine structure having a size of about 5 μm can be formed. Further, this dimension can be adjusted by adjusting the laser input energy by, for example, the drawing speed and the laser output, and it has been confirmed that reduction and drawing of the metal oxide can be performed with high efficiency.

(Example 3)
Therefore, the scanning speed and pulse energy were changed variously, and other conditions were the same as in Example 1 above (spot diameter was 1 μm), and an attempt was made to form a fine structure consisting of a fine line pattern by reduction of CuO nanoparticles. It was. When a fine structure could be formed, the composition of the fine structure was examined by XRD. The results are shown in Table 1 below.
In addition, the notation in Table 1 means the following.
“X” indicates that the fine structure of CuO nanoparticles was not formed and was washed away by EG.

“CuO” indicates that the XRD diffraction peak was almost attributed to CuO. That is, it shows that (B) a metal oxide portion is mainly formed under these conditions.
“CuO 2 _-rich ” indicates that although the XRD diffraction peak was almost attributed to CuO, a peak attributed to Cu ₂ O was also detected. That is, this condition indicates that (B) the third metal oxide portion is mainly formed in the (B) metal oxide portion.
“Cu ₂ O _-rich ” indicates that although the XRD diffraction peak was almost attributed to Cu ₂ O, a peak attributed to Cu was also detected. That is, (A) a metal portion is mainly formed under these conditions, but this metal portion is a phase mainly composed of Cu ₂ O.
“Cu 2 _-rich ” indicates that although the XRD diffraction peak was almost attributed to Cu, a peak attributed to Cu ₂ O was also detected. That is, this condition mainly indicates that (A) the metal portion was formed and metallization was performed more appropriately.
“Cu ₂ O + Cu” indicates that the peak attributed to Cu ₂ O and Cu in the XRD diffraction peak was approximately the same ratio. That is, it shows that (A) a metal part is mainly formed under these conditions.
“CuO 2 _-rich (melted)” indicates that the XRD diffraction peak is the same as the above “CuO 2 _-rich ”, but it was difficult to control the line width because the nanoparticles were melted. That is, this condition indicates that (B) the second metal oxide portion is formed mainly in the (B) metal oxide portion.

  As shown in Table 1, when the pulse energy was 0.01 nJ, fine structures could not be formed at all scanning speeds, and CuO nanoparticles were washed away by EG cleaning. On the other hand, in the range where the pulse energy exceeds 0.01 nJ, it was confirmed that a fine structure can be formed at almost all scanning speeds. It was also confirmed that even when a fine structure is formed, the composition of the fine structure and its ratio can be controlled by adjusting the scanning speed and pulse energy. That is, it was found that the microstructure can be formed by controlling the ratio of the metal oxide (here CuO) and the reduced product thereof. At this time, it was found that, as a whole, the pulse energy was increased relatively and the scanning speed was increased, whereby the reduction of the metal oxide can be promoted and a fine structure having a high reduction rate can be easily obtained.

Here, in the sample having a pulse energy of 0.05 nJ, the reduction of the metal oxide nanoparticles tends to progress as the scanning speed becomes slower, whereas in the sample having a pulse energy of 0.1 to 1.2 nJ, the scanning speed is increased. As the speed increased, the metal oxide was reduced. Further, when the pulse energy is 1.2 nJ and the scanning speed is 20 μm / s, the CuO nanoparticles are completely melted, and it is difficult to form a fine structure with a desired line width (for example, FIG. 9 ( b)). From these facts, in the sample having a pulse energy of 0.1 to 1.2 nJ, the pulse energy input to the metal oxide nanoparticles is high intensity, and therefore, when the scanning speed is slow, the metal oxidation that is non-metallic is performed. It can be expected that the metal nanoparticles once reduced from the product (CuO) to the semiconductor or metal (Cu ₂ O, Cu) are re-oxidized to the metal oxide or semiconductor (CuO, Cu ₂ O) again. It was. Therefore, the reduction of the metal oxide is not simply dependent on the total amount of input energy, and the ratio of the metal oxide and the reduced product can be further increased by selecting the pulse energy and the scanning speed in consideration of such reoxidation. It was confirmed that it can be reliably controlled. Further, for example, by controlling the pulse energy and the scanning speed as described above, in the microstructure, a metal part (in this case, a part mainly composed of Cu) and a metal oxide part (in this case, mainly CuO and And / or a portion made of Cu ₂ O).

Incidentally, _"Cu 2 O _-rich" in Table 1, "Cu _-Rich", conditions represented by _"Cu 2 O + Cu" is in the art referred to here is (A) a metal part is formed. However, for example, under the condition indicated by “Cu ₂ O _{2 -rich} ”, even if (A) the metal portion, a phase mainly composed of Cu ₂ O as a semiconductor is formed. In this respect, the (A) metal portion disclosed herein can be grasped as, for example, a second metal portion (for example, a semiconductor main portion) or the like (A ′) which is also understood as a metal reoxidation portion.

  Further, in the above-described laser irradiation conditions, (B) a metal oxide portion is incidentally formed on the periphery of the microstructure formed mainly under the conditions that (A) the metal portion is formed. Therefore, the composite irradiation structure disclosed here can be manufactured only under such laser irradiation conditions. On the other hand, in the microstructure formed mainly under the condition that the (B) metal oxide portion is formed, for example, the (A) metal portion can be formed in the portion irradiated with the laser twice at the same location. Therefore, (B) laser irradiation conditions for forming a metal oxide portion are mainly (1) repeated laser irradiation, or (2) combined with modeling under laser irradiation conditions for mainly forming a metal portion. Thus, the composite microstructure disclosed herein can be manufactured.

The combinations of scanning speed and pulse energy shown in Table 1 above are an example of setting conditions for an ultrashort pulse laser. A person skilled in the art will be able to manufacture a composite microstructure under the laser irradiation conditions including the conditions, with the combination of scanning speed and pulse energy indicating that the composite microstructure has been manufactured in the table as a critical value. Can understand that is possible. Similarly, one skilled in the art, in the table, "CuO", "CuO _{-Rich", "Cu} 2 O _-rich", "Cu _{-Rich", "Cu} 2 O + Cu", "CuO _-Rich (melt) Each of the structures (composite composites) under the laser irradiation conditions including the conditions, with a combination of the scanning speed and the pulse energy indicating that the structure (composite microstructure) including the phase represented by It can be understood that a fine structure) can be produced. It is understood that the same applies to Tables 2 and 3 described later.

(Example 4-1)
In Example 1 above, the pulse energy is 1.2 nJ, the spot diameter is 1 μm, the scanning speed is 500 μm / s and 1000 μm / s, and the other conditions are the same as in Example 1 and are composed of a combination of thin line patterns. A microstructure was prepared. According to such conditions, it is possible to manufacture a microstructure having a composition mainly composed of Cu ₂ O- _rich or Cu- _rich , respectively. At this time, by drawing thin lines without gaps for each composition, strip-like microstructures having three dimensions of length 100 μm × width 160 to 600 μm were formed. This composite microstructure is mainly composed of (A) phases classified as metal parts, and has (B) metal oxide parts at both ends in the width direction.
Electrodes for resistance measurement were installed at both ends in the length direction of the microstructure thus formed, and the electrical resistance was measured by a two-point method. The results are shown in FIG.

As shown in FIG. 10, the electrical resistance of the fine structure was lower as the width was increased. The resistance value is 11 to _54Ω for the Cu- _rich structure and 0.22 to 8.9 MΩ for the Cu ₂ O- _rich structure, and the electrical resistance of the microstructure can be controlled by the composition. Was confirmed. Assuming that the thickness of the fine structure is equal to the film thickness of 8 μm, the resistivity of the structure was a minimum value of 528 _μΩm for Cu- _rich . This resistivity is considered to show a higher value because the formed microstructure is relatively porous, and the resistivity can also be reduced by improving the concentration and supply method of CuO nanoparticles, etc. Conceivable.

(Example 4-2)
Next, 150 μm × 150 μm square composite microstructures were formed under two conditions, and the resistance temperature characteristics of these composite microstructures were evaluated. Specifically, as shown in FIG. 14A, a Cu thin film was formed on a glass substrate by a lithography method to produce two Cu electrodes having an interelectrode distance of 100 μm. Then, a drawing pattern of 150 μm × 150 μm is drawn under the laser irradiation conditions shown in the following conditions (1) and (2) so as to cover the two Cu electrodes, respectively, and the composite microstructures (1) and (2) Formed. Note that the condition (1) is a condition for forming a composite microstructure mainly composed of a Cu- _rich composition that is a metal part. In this Cu- _rich composition, a phase containing 50% or more of Cu is mainly used. The condition (2) is a condition for forming a composite microstructure mainly composed of a Cu ₂ O- _rich composition which is a metal part (for example, grasped as a semiconductor main part or the like). The Cu ₂ O- _rich composition is mainly composed of a phase containing 50% or more of Cu ₂ O. In any composite microstructure, the (B) metal oxide portion was incidentally formed on the periphery of the square (A) metal portion. For reference, an SEM observation image of the composite microstructure formed under the condition (2) is shown in FIG. Then, Pt lead wires were connected to the Cu electrodes of the composite microstructures (1) and (2) to produce evaluation microelements (1) and (2).

Condition (1); pulse energy: 1.2 nJ,
Spot diameter: 1 μm
Scanning speed: 500 μm / s
Condition (2); pulse energy: 1.2 nJ,
Spot diameter: 1 μm
Scanning speed: 1000 μm / s

The microelement was placed on a hot plate, and the resistance temperature characteristics of the composite microstructure were examined by passing an electric current while changing the temperature of the composite microstructure in the range of 30 ° C to 70 ° C. The results are shown in FIGS. 15 (a) and 15 (b).
As shown in FIG. _{15A, the} temperature coefficient of resistance of the composite microstructure (1) having the Cu- _rich composition obtained in this example was about 1.0 × 10 ⁻³ / ° C. Although this value does not coincide with the resistance temperature coefficient (theoretical value) of Cu, it was confirmed that it shows a positive resistance temperature coefficient found in metal materials. From this, it was found that the composite microstructure (2) can be used as, for example, conductive members such as wirings and electrodes. On the other hand, as shown in FIG. 15B, the temperature coefficient of resistance of the composite microstructure (2) having a Cu ₂ O- _rich composition is about −15 × 10 ⁻³ / ° C. Is classified as a “metal part”, but was confirmed to exhibit a large negative temperature coefficient of resistance found in semiconductor materials. From this, it was found that this composite microstructure (2) can be used as a highly sensitive temperature sensor in a low temperature range of about 30 ° C. to 70 ° C., for example. It is understood by those skilled in the art that in the microelement (2) shown in FIGS. 14 (a) and 14 (b), the Cu electrode portion produced by the lithography technique in this example can be formed by laser irradiation under the condition (1). obtain. From this, it was found that the greater part of the temperature sensor can be easily manufactured by the composite microstructure disclosed herein. Those skilled in the art can understand that such a composite microstructure can also be used as an acceleration sensor, a flow sensor, a stress sensor, or the like.

From the above, according to the art disclosed herein, (A) it is a composite microstructure consisting mainly of metal parts, its composition, different _{Cu -Rich} composition as _Cu 2 _{O -rich} composition physical properties In addition, we were able to confirm that it can be made more reliably with dimensions of nanometer order. It was also found that composite microstructures having various functions can be produced by utilizing the physical properties of each composition.

(Example 5)
Next, instead of CuO nanoparticles, NiO nanoparticles having an average particle diameter of 50 nm were used to try to form a fine structure. EG was used as a dispersion medium and a reducing agent, and PVP was used as a laser curable resin. And these were mix | blended so that the ratio of NiO nanoparticle: EG: PVP might be 46.9: 42.9: 10.2 by mass ratio, and the base solution was prepared by mixing with an ultrasonic stirrer. . This base solution was uniformly applied to a glass substrate with a film thickness of about 9 μm by spin coating, and an ultrashort pulse laser was irradiated onto the base solution coating film in a fine pattern. The ultrashort pulse laser condenses a laser oscillated in the atmosphere under conditions of a wavelength of 780 nm, a pulse width of 120 fs, and a repetition frequency of 80 MHz to a spot diameter of 1 μm using an objective lens having a numerical aperture of 0.75, The pulse energy was changed in six ways shown in Table 2 below at a scanning speed of 1500 μm / s, and irradiation was performed in a predetermined drawing pattern. The glass substrate after irradiation with the ultrashort pulse laser was washed away with EG to remove the unreacted base solution.

Thereby, formation of the fine structure which consists of a fine line pattern by the reduction | restoration of NiO nanoparticle was tried. When a fine structure could be formed, the composition of the fine structure was examined by XRD. The results are shown in Table 2.
In addition, the notation in Table 2 means the following.
“X” indicates that the fine structure of NiO nanoparticles was not formed and was washed away by EG.
“NiO” indicates that the XRD diffraction peak was almost attributed to NiO. That is, it shows that (B) a metal oxide portion is mainly formed under these conditions.
“NiO + Ni” indicates that the peak attributed to NiO and Ni in the XRD diffraction peak was in approximately the same proportion. That is, it shows that (A) a metal part is mainly formed under these conditions.
“NiO- _rich (melting)” means that although the XRD diffraction peak was almost attributed to NiO, the peak attributed to Ni was also detected, and the nanoparticles melted, making it difficult to manage the line width. Show. That is, under this condition, (A) a metal portion including a reoxidized portion is formed although it is a metal portion.

As shown in Table 2, when the pulse energy was 0.01 nJ, fine structures could not be formed at all scanning speeds, and NiO nanoparticles were washed away by EG cleaning. When the pulse energy was 1.2 nJ, the NiO nanoparticles were completely melted, and it was difficult to form a fine structure with a desired line width. It was confirmed that a fine structure can be formed at almost all scanning speeds in a range where the pulse energy exceeds 0.01 nJ and is lower than 1.2 nJ.
In addition, when a fine structure is formed, it was confirmed that the composition of the fine structure and the ratio thereof can be controlled by adjusting the scanning speed and the pulse energy. That is, it was found that the microstructure can be formed by controlling the ratio of the metal oxide (here, NiO) and its reduced product (Ni).

Therefore, the scanning speed when the pulse energy was 0.24 nJ was changed more finely, and the relationship between the scanning speed and the composition of the fine structure was examined. The scanning speed was changed at 200 μm / S or more at which the “NiO + Ni” composition, which is mainly the metal part (A), was obtained with certainty. The results are shown in FIG. The vertical axis in FIG. 11 represents the diffraction intensity ratio of the diffraction peak from the Ni (111) plane to the diffraction peak from the NiO (200) plane in the XRD pattern of the formed microstructure I _{Ni (111)} / I _{NiO ( 200)} , and the higher this value is, the more NiO is reduced to Ni.

  As is apparent from FIG. 11, in this example, the ratio of Ni in the fine structure is the highest when the scanning speed is near 1300 μm / s, and the scanning speed is 1300 μm / s, whether it is faster or slower than 1300 μm / s. It was found that the proportion of Ni decreases with distance from s. Based on the results in Examples 1 to 4 so far, in this example, when the scanning speed is faster than 1300 μm / s, the pulse energy supplied from the ultrashort pulse laser to the NiO nanoparticles is not sufficient, and Ni It was considered that unreduced NiO that was not reduced was left in the microstructure. In addition, when the scanning speed is slower than 1300 μm / s, the pulse energy supplied from the ultrashort pulse laser to the NiO nanoparticles is larger than the amount necessary for thermal reduction of NiO, and Ni reduced by excess energy. Was again oxidized to NiO.

Therefore, in Table 2, NiO when the pulse energy is 0.06 nJ is expected to be in an unoxidized state, and NiO when the pulse energy is 0.48 nJ or more is re-applied when the scanning speed is slow. There is a possibility that it is oxidized NiO and is unoxidized NiO when the scanning speed is high.
Moreover, even if it is identified as the same NiO as a result of XRD analysis, NiO in an unreduced state is not sufficiently heated. Therefore, it is considered that PVP exists around the NiO and contributes to the construction of a fine structure. It is done. On the other hand, since the reoxidized NiO is in a sufficiently heated state, the NiO nanoparticles of the starting material are welded or sintered together, and the PVP contained in the base solution is considered to have disappeared. It is done.

  Further, it was confirmed that the composition of the metal part (A) can be controlled in detail by controlling the laser irradiation conditions even in the case of a fine structure mainly composed of the metal part (A). Note that, in the above-described laser irradiation conditions, (B) metal oxide portions are incidentally formed on the periphery of the microstructure formed mainly under the conditions that (A) metal portions are formed. Therefore, the composite irradiation structure disclosed here can be manufactured only under such laser irradiation conditions. On the other hand, in the microstructure formed mainly under the condition that the (B) metal oxide portion is formed, for example, the (A) metal portion can be formed in the portion irradiated with the laser twice at the same location. Therefore, (B) laser irradiation conditions for forming a metal oxide portion are mainly (1) repeated laser irradiation, or (2) combined with modeling under laser irradiation conditions for mainly forming a metal portion. Thus, the composite microstructure disclosed herein can be manufactured. From the above, it can be seen that a structural member made of Ni (magnetic material) and NiO (nonmagnetic material) can be precisely modeled on the order of micrometers. Such a shaped article is preferably realized as, for example, a non-magnetic actuator on the order of micrometers.

(Example 6)
In addition to the case where the pulse energy in Example 5 is 0.24 nJ, the scanning speed is changed more finely in the case where the pulse energy is 0.48 nJ, and the other conditions are the same as in Example 5 above. Attempts were made to form fine structures consisting of fine line patterns by reduction. Then, the line width of the formed fine structure was measured, and the result is shown in FIG.
As shown in FIG. 12, upon reduction of NiO nanoparticles, it was found that when the pulse energy was 0.24 nJ and 0.48 nJ, the line width was stabilized and narrowed without greatly depending on the scanning speed. For example, while the scanning speed is 100 μm / s and 500 μm / s, the amount of ultrashort pulse laser irradiated to the NiO nanoparticles is completely different, while the line width is maintained at about 15 μm or less, and the thin line width It was found that a fine structure can be obtained stably. This is because the amount of heating of the NiO nanoparticles is suppressed because the energy supplied by one pulse laser is small, and when the next pulse laser is irradiated, the heated NiO nanoparticles are cooled, It is assumed that temperature accumulation and avalanche heat storage do not occur.
In this example, in particular, when the pulse energy is 0.24 nJ, it has been found that even if the scanning speed is 1500 μm / s, there is no significant difference in line width from that of 100 μm / s. On the other hand, at 0.48 nJ, when the scanning speed is about 300 μm / s or less, excessive energy is supplied and the line width tends to widen. However, at 400 μm / s or more, the line width is stable regardless of the scanning speed. I understood that it was kept. Further, when the line width is stable in this way, the line width is considered to be thicker when the pulse energy is larger.

(Example 7)
Furthermore, as the metal oxide nanoparticles, TiO ₂ nanoparticles having an average particle diameter of 20 nm were used to try to form a fine structure. EG was used as a dispersion medium and a reducing agent, and PVP was used as a laser curable resin. Then these, TiO ₂ nanoparticles: EG: at a ratio of PVP mass ratio 30: 63.5: 6.5 to become so blended, the base solution was prepared by mixing with an ultrasonic stirrer. This base solution was uniformly applied to a glass substrate with a film thickness of about 7 μm by spin coating, and an ultrashort pulse laser was irradiated onto the base solution coating film in a fine pattern. In the ultrashort pulse laser, a laser oscillated in the atmosphere under the conditions of a wavelength of 780 nm, a pulse width of 120 fs, and a repetition frequency of 80 MHz was condensed to a spot diameter of 1 μm using an objective lens having a numerical aperture of 0.75. The ultrashort pulse laser was irradiated with a predetermined drawing pattern with a pulse energy of 1.0 nJ, 1.1 nJ or 1.2 nJ and a scanning speed of 30 μm / s. Further, when the pulse energy was 1.1 nJ, the fine structure was formed even under the conditions where the scanning speed was changed to 20 and 40 μm / s. The glass substrate after irradiation with the ultrashort pulse laser was washed away with EG to remove the unreacted base solution.

As a result, it was confirmed that the structures were formed on the substrate in all cases where the pulse energy was 1.0 nJ, 1.1 nJ and 1.2 nJ. At this time, the minimum line width was 20 μm, and the maximum line width was 40 μm.
Incidentally, when the composition of the formed fine structure was confirmed by XRD analysis, pulse energy 1.0NJ, the composition of the resulting structure as the scanning speed of 30 [mu] m / s from TiO ₂ single-phase, TiO ₂ nano It was found that the particles were not reduced and that the laser curable resin PVP was cured to form a structure. That is, the fine structure including the metal portion and the metal oxide portion disclosed herein has not been formed. On the other hand, the composition of the structure obtained with pulse energies of 1.1 nJ and 1.2 nJ contains TiO and TiO _2, and at least some of the TiO ₂ nanoparticles are reduced to TiO and bonded to each other to form a fine structure. It was found that a structure was formed. That is, it can be said that a fine composite structure composed of a reducing portion and a non-reducing portion was produced. TiO ₂ has a property that the standard free energy of formation is small among metal oxides and is difficult to be reduced. Therefore, it was confirmed that reduction can be stably generated at a relatively slow scanning speed, and a fine structure having a narrow line width can be stably formed.

(Example 8)
Furthermore, as metal oxide nanoparticles, Cu / CuO core-shell nanoparticles (made by Ionic Liquids Technologies Gmbh, particle size <50 nm) with Cu as the core and CuO as the shell were used to try to form a fine structure. EG was used as a dispersion medium and a reducing agent, and PVP was used as a laser curable resin. And these were mix | blended so that the ratio of core-shell nanoparticle: EG: PVP might be set to 60:27:13 by mass ratio, and the base solution was prepared by mixing with an ultrasonic stirrer. This base solution was uniformly applied to a glass substrate with a film thickness of about 7 μm by spin coating, and an ultrashort pulse laser was irradiated onto the base solution coating film in a fine pattern. In the ultrashort pulse laser, a laser oscillated in the atmosphere under the conditions of a wavelength of 780 nm, a pulse width of 120 fs, and a repetition frequency of 80 MHz was condensed to a spot diameter of 1 μm using an objective lens having a numerical aperture of 0.75. Note that the ultrashort pulse laser has four pulse energies of 0.01 nJ, 0.05 nJ, 0.6 nJ, or 1.2 nJ, and six scan speeds of 50 to 2000 μm / s in a predetermined drawing pattern. By irradiation, a fine structure was formed. The glass substrate after irradiation with the ultrashort pulse laser was washed away with EG to remove the unreacted base solution.

As a result, it was confirmed that a fine structure was formed on the substrate for all pulse energy conditions and scanning speed conditions. At this time, the minimum line width was 10 μm, and the maximum line width was 60 μm. The composition of the formed microstructure was confirmed by XRD analysis, and the results are shown in Table 3. In addition, the notation in Table 3 means the following.
“Present” indicates that the XRD diffraction peak is a condition in which a peak attributed to CuO is detected. In addition, although not specifically shown, the conditions indicated as “present” include those in which a peak attributed to Cu is detected and those in which no peak is detected. The peak attributed to Cu was not detected under the conditions where the scanning speed was 50 μm / s and the pulse energy was 1.2 nJ.
“None” indicates that no peak attributed to CuO was detected in the XRD diffraction peak.

  From comparison between Table 3 and Table 1 in Example 3, it was found that the core-shell nanoparticles were used in this example, so that the metal oxide portion can be formed with smaller pulse energy. Further, when the pulse energy is 0.6 nJ or more and the scanning speed is 1000 μm / s or more, the reduction of CuO in the shell portion is almost completely performed, and almost all is composed of Cu particles (that is, almost no CuO is contained). It was found that a microstructure can be obtained. However, it was confirmed that when the pulse energy was 1.2 nJ or more and the scanning speed was 2000 μm / s or more, the energy supplied to the core-shell nanoparticles decreased, so that the CuO shell portion could remain. Note that the microstructure formed by irradiating the ultrashort pulse laser under the irradiation condition of the region indicated as “None” in Table 1 has a core shell in which the CuO shell portion remains in the peripheral portion of the heat-affected portion by the laser irradiation. It was confirmed that there were very few particles. That is, it was confirmed to be a composite microstructure.

In this composite microstructure, in addition to the core portion of the core-shell structure being Cu, most of the shell portion is reduced to Cu. In other words, CuO is not detected in most parts of the composite microstructure, and is composed only of Cu. Therefore, it was confirmed that by using the technique disclosed herein, a composite microstructure having extremely excellent electrical conductivity can be obtained. It was also confirmed that a composite microstructure can be formed even when core-shell nanoparticles are used.
As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

Claims (18)

A metal oxide portion comprising metal oxide nanoparticles;
A metal portion in which at least a part of the metal oxide nanoparticles are reduced and directly bonded to each other;
Including
A composite microstructure in which the metal oxide portion and the metal portion are integrated and at least one dimension thereof is 100 micrometers or less.   The metal oxide nanoparticles are at least one metal element selected from the group consisting of gold (Au), silver (Ag), copper (Cu), nickel (Ni), iron (Fe), and titanium (Ti). The composite microstructure according to claim 1, comprising: The metal oxide portion further includes a laser curable resin,
3. The composite microstructure according to claim 1, wherein at least a part of the metal oxide nanoparticles includes a first metal oxide portion bonded to each other by the laser curable resin. The metal oxide portion is
The composite microstructure according to claim 1, wherein at least some of the metal oxide nanoparticles include second metal oxide portions that are directly bonded to each other.   The ratio of the said 1st metal oxide part which occupies for the sum total of the said 1st metal oxide part and the said 2nd metal oxide part is 50 volume% or more, Any one of Claims 1-4. Composite microstructure.   The composite microstructure according to claim 1, wherein the metal oxide nanoparticles are nanoparticles containing a metal oxide at least in part.   The composite microstructure according to claim 6, wherein the metal oxide nanoparticle is a core-shell nanoparticle including a shell made of a metal oxide on at least a part of the surface of the core particle. A micro turbine component comprising the composite microstructure according to any one of claims 1 to 7,
A gear-shaped micro-turbine body, and a shaft portion serving as a rotation shaft of the micro-turbine body,
The microturbine body is constituted by the metal part including nickel,
The said shaft part is a micro turbine component comprised by the said metal oxide part containing a nickel oxide. A microwiring including the composite microstructure according to any one of claims 1 to 7,
A linear microwire portion having a cross-sectional diameter of 100 micrometers or less, and a coating portion covering the surface of the microwire portion,
The microwire portion is constituted by the metal portion containing copper,
The said coating part is the micro wiring comprised by the said metal oxide part containing a copper oxide. A temperature sensor comprising the composite microstructure according to any one of claims 1 to 7,
A sensor portion; and an edge formed on the periphery of the sensor portion;
The sensor portion is constituted by the metal portion including copper and copper (I) oxide,
The said edge part is a temperature sensor comprised by the said metal oxide part containing copper oxide (II).   An article comprising the composite microstructure according to any one of claims 1 to 7. Preparing a metal oxide nanoparticle-containing liquid containing a metal oxide nanoparticle and a laser curable resin that is cured by irradiation with laser light;
Supplying the metal oxide nanoparticle-containing liquid to the surface of the substrate;
Irradiating the metal oxide nanoparticle-containing liquid supplied to the surface of the substrate with an ultrashort pulse laser,
By irradiation with the ultrashort pulse laser,
A metal oxide portion including a resin portion obtained by curing the laser curable resin and the metal oxide nanoparticles;
A metal portion formed by reducing the metal oxide nanoparticles and bonding to each other;
Including
Forming a composite microstructure having at least one dimension of 100 micrometers or less;
A method for producing a composite microstructure.   The metal oxide nanoparticles are at least one selected from the group consisting of gold (Au), silver (Ag), copper (Cu), nickel (Ni), iron (Fe) and titanium (Ti) oxides. The manufacturing method of Claim 12 containing these.   The manufacturing method according to claim 12 or 13, wherein the laser curable resin contains polyvinylpyrrolidone.   The metal oxide nanoparticle-containing liquid further includes at least one reducing agent selected from the group consisting of ethylene glycol, polyethylene glycol, formic acid, hydrogen peroxide solution, and toluene. 2. The production method according to item 1.   The said metal oxide nanoparticle containing liquid is a manufacturing method of any one of Claims 12-15 containing the dispersing agent of at least one of polyvinylpyrrolidone and silicone resin further.   The said metal oxide nanoparticle is a manufacturing method of any one of Claims 12-16 which is a nanoparticle which contains a metal oxide in at least one part.   The said metal oxide nanoparticle is a manufacturing method of Claim 17 which is a core-shell nanoparticle containing the shell which consists of a metal oxide in at least one part of the surface of a core particle.