3-dimensional nanostructure based on metamaterials and fabrication method thereof

Abstract

The present disclosure relates to a 3-dimensional nanostructure based on metamaterials. More specifically, the 3-dimensional nanostructure is a fibrous structure comprising: meta molecules including non-conductive nanoparticles and first conductive nanoparticles that are smaller than the non-conductive nanoparticles and surround the surface of the non-conductive nanoparticles; and second conductive nanoparticles positioned in spaces between the meta molecules, wherein the fibrous structure includes a straight region, a curved region that is bent or folded, a twisted region, a tapering region in which the minor axis diameter decreases or increases, or a combination thereof.

Description

Metamaterial-based 3D nanostructure and its manufacturing method

[0001] The present disclosure relates to a metamaterial-based three-dimensional nanostructure and a method for manufacturing the same, and relates to a three-dimensional nanostructure based on fibers but having no practical restrictions on its shape and controllable properties, and a method for manufacturing the same.

[0002] Metamaterials are materials that can obtain optical properties that were not previously observed by controlling the interaction between the electromagnetic field of light and the material in a region smaller than the wavelength.

[0003] Metamaterials can exhibit negative refractive indices for waves such as electromagnetic waves and acoustic waves, and can exhibit negative magnetic permeability and inverse Doppler effects, and are therefore utilized in various fields such as ultra-high-resolution imaging, quantum photonics, nonlinear optics, biosensing, optical circuit elements, photolithography, plasmonic optical antennas, wireless power transmission, and electromagnetic cloaking (absorbers).

[0004] Most metamaterials are fabricated using top-down methods, such as electron beam lithography and focused ion beam milling. While conventional top-down methods can produce precise, high-resolution, targeted nanostructures within one or two dimensions, they have limitations in fabricating complex, three-dimensional nanostructures.

[0005] Accordingly, bottom-up processes for fabricating metamaterials have been proposed, utilizing chemical linker-based self-assembly of nanostructures, such as DNA origami, and the self-assembly of colloidal nanoparticles. However, these methods are also limited to programmed chemical linkers and, like top-down approaches, rely on self-assembly templates, limiting their ability to fabricate three-dimensional structures.

[0006] One aspect of the present disclosure is to provide a metamaterial-based three-dimensional nanostructure that is substantially free from three-dimensional shape constraints and a method for manufacturing the same.

[0007] Another aspect of the present disclosure is to provide a metamaterial-based three-dimensional nanostructure capable of controlling physical properties and a method for manufacturing the same.

[0008] The objectives of the present invention are not limited to the above-described content. Those skilled in the art will have no difficulty understanding the additional objectives of the present invention from the overall description of the present invention.

[0009] The objectives of the present invention are not limited to the above-described content. Those skilled in the art will have no difficulty understanding the additional objectives of the present invention from the overall description of the present invention.

[0010] A three-dimensional metamaterial-based nanostructure according to the present invention comprises a metamolecule comprising a first conductive nanoparticle having a size smaller than the first non-conductive nanoparticle and surrounding the surface of the first non-conductive nanoparticle; and a fiber comprising a second conductive nanoparticle positioned in a space between the metamolecules, wherein the fiber comprises a straight region, a curved region that is bent or folded, a twisted region, a tapered region in which the minor axis diameter decreases or increases, or a combination thereof.

[0011] In one specific example, the average diameter (D) of the first conductive nanoparticles c1 ) is the average diameter (D) of the non-conductive nanoparticles. i ) divided by the diameter ratio (D c1 / D i ) can be 0.10 to 0.45.

[0012] In one specific embodiment, the meta molecules can be densely packed on the fiber.

[0013] In one specific example, the ratio of the number of particles of the conductive component including the non-conductive nanoparticles: the first conductive nanoparticles and the second conductive nanoparticles on the fiber may be 1:10 to 150.

[0014] In one specific example, the first conductive nanoparticle and the second conductive nanoparticle may each be a plasmonic metal nanoparticle.

[0015] In one specific example, the non-conductive nanoparticles may be transparent nanoparticles.

[0016] In one specific example, the non-conductive nanoparticle may be a dielectric having a dielectric constant of 1.5 to 10.0.

[0017] In one embodiment, the fibers may further contain an organic binder.

[0018] In one specific example, the non-conductive nanoparticle, the first conductive nanoparticle, and the second conductive nanoparticle may independently have one or more shapes selected from a spherical shape, an angular shape, a rod shape, a plate shape, and a flake shape.

[0019] In one specific example, the effective refractive index of the nanostructure can be controlled by the ratio of the number of particles of the conductive component including the first conductive nanoparticle and the second conductive nanoparticle contained in the nanostructure.

[0020] In one specific example, the nanostructure may have a wavelength at which the maximum effective refractive index is present in a range of 550 nm to 700 nm and a value of the maximum effective refractive index in a range of 2.0 to 6.0.

[0021] In one specific example, a fiber phase that does not contain the first conductive particle and the second conductive particle and is filled with the same nanoparticles as the non-conductive nanoparticles contained in the three-dimensional nanostructure is used as a reference fiber phase, and the nanostructure can have a light scattering intensity of 0 to 0.20 times the light scattering intensity of the reference fiber phase at a wavelength of 532 nm.

[0022] A metamaterial-based polarizer according to the present invention is based on a fiber comprising a meta molecule comprising a first conductive nanoparticle having a size smaller than a non-conductive nanoparticle and a first conductive nanoparticle surrounding a surface of the non-conductive nanoparticle; and a second conductive nanoparticle positioned in a space between the meta molecules, and may have a helical structure due to a curved region that is bent or folded.

[0023] A method for manufacturing a three-dimensional nanostructure according to the present invention may include the steps of: injecting a nanoparticle solution containing non-conductive nanoparticles, first conductive nanoparticles and second conductive nanoparticles having a smaller size than the non-conductive nanoparticles and being conductive, and a liquid medium into a micropipette; a step of contacting a tip of the micropipette with a solid substrate; and a step of moving the micropipette in contact with the solid substrate to manufacture a three-dimensional nanostructure having a fiber shape according to a movement trajectory of the micropipette.

[0024] The metamaterial-based 3D nanostructure according to the invention is based on a fiber, but has no practical restrictions on its shape, has optical magnetism, and thus allows for control of optical properties including the effective refractive index, and has the advantage of effectively controlling light scattering characteristics.

[0025] Metamaterial-based 3D nanostructures based on the invention have controlled optical properties and a high degree of morphological freedom, and can be effectively utilized in various fields such as nano-optics, sensors, and electronic devices.

[0026] The various advantageous and beneficial effects of the present invention are not limited to the above-described contents, and will be more easily understood in the course of explaining specific embodiments of the present invention.

[0027] FIG. 1 is a scanning electron microscope photograph of a three-dimensional nanostructure implemented according to one embodiment of the present invention.

[0028] FIG. 2 is a scanning electron microscope photograph of a metamaterial-based spiral-structured polarizing plate implemented according to one embodiment of the present invention.

[0029] FIG. 3 is a process diagram illustrating a step-by-step process for manufacturing a three-dimensional nanostructure according to one embodiment of the present invention.

[0030] FIG. 4 is a drawing illustrating the observation of light scattering characteristics of a three-dimensional nanostructure implemented according to one embodiment of the present invention.

[0031] FIG. 5 is a diagram showing the measurement of light scattering intensity according to wavelength of a nanostructure implemented according to one embodiment of the present invention.

[0032] FIG. 6 is a scanning electron microscope photograph of a short-axis cross-section of a nanostructure implemented according to one embodiment of the present invention.

[0033] FIG. 7 is a drawing illustrating the measurement of the effective refractive index of a nanostructure implemented according to one embodiment of the present invention.

[0034] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. However, the embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0035] In addition, the embodiments of the present invention are provided to more completely explain the present invention to a person having average knowledge in the relevant technical field.

[0036] The shape and size of elements in the drawing may be exaggerated for clearer explanation.

[0037] In describing the embodiments of the present invention, if a detailed description of a known technology related to the present invention is judged to unnecessarily obscure the gist of the present invention, such detailed description will be omitted. In addition, the terms described below are terms defined in consideration of their functions in the present invention, and these may vary depending on the intention or custom of the user or operator. Therefore, the definitions should be made based on the contents throughout this specification. The terminology used in the detailed description is only for the purpose of describing the embodiments of the present invention and should in no way be limiting. Unless clearly defined otherwise, expressions in the singular form include plural meanings.

[0038] In this description, expressions such as “including” or “having” are intended to indicate certain features, numbers, steps, operations, elements, portions or combinations thereof, and should not be construed to exclude the presence or possibility of one or more other features, numbers, steps, operations, elements, portions or combinations thereof other than those described.

[0039] Unless otherwise specified in the specification of the present invention, the % unit means weight %.

[0040] Additionally, throughout the specification, when we say that a part is 'connected' to another part, this includes not only cases where it is 'directly connected', but also cases where it is 'indirectly connected' with other elements in between.

[0041] Below, the present invention will be described in detail through each embodiment or example of the present invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may be combined with other embodiments or examples. Therefore, the citation of a claim in the patent claims is only an example of an embodiment, and the technical concept of the present invention should not be interpreted solely as a combination with the cited claim, and combinations with various claims also fall within the scope of the technical concept of the present invention.

[0042] The terms used herein are for the purpose of describing the invention and are not intended to limit the invention. Furthermore, the singular forms used herein also include the plural forms, unless the relevant definition clearly indicates a contrary meaning.

[0043] The meaning of 'comprising' as used in the specification is to specify a configuration and not to exclude the presence or addition of other configurations.

[0044] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in the dictionary are to be interpreted to have meanings consistent with the relevant technical literature and the present disclosure.

[0045] A metamaterial-based 3D nanostructure (hereinafter, 3D nanostructure) according to one aspect comprises a metamolecule including a non-conductive nanoparticle and a first conductive nanoparticle having a smaller size than the non-conductive nanoparticle and surrounding the surface of the non-conductive nanoparticle; and a fiber including a second conductive nanoparticle positioned in a space between the metamolecules, wherein the fiber includes a straight region, a curved region that is bent or folded, a twisted region, a tapered region in which a minor axis diameter decreases or increases, or a region by a combination thereof.

[0046] A three-dimensional nanostructure according to one aspect has a fibrous shape based on meta molecules, and, by positioning conductive nanoparticles in the space between the meta molecules, can exhibit unique controllable physical properties (effective refractive index, optomagnetism, optical properties, etc.).

[0047] In addition, the 3D nanostructure according to one aspect is based on a fiber, but there are practically no restrictions on the physical shape of the fiber, such as bending, twisting, or bending, and thus can have various desired 3D shapes.

[0048] In one specific example, the meta-molecule may be a composite nanoparticle having a core-shell structure, comprising a non-conductive nanoparticle as a core and a first conductive nanoparticle as a shell that surrounds the surface of the non-conductive nanoparticle. The shell may be a particle layer of the first conductive nanoparticle, and may be a single-layer particle layer or a multi-layer particle layer of two or more layers. In practice, the shell may be a single-layer layer of the first conductive nanoparticle.

[0049] The non-conductive nanoparticles may be oxides, carbides, nitrides, carbonitrides, or composites thereof of one or more elements selected from the group consisting of alkali metals, alkaline earth metals, transition metals, post-transition metals, and metalloids.

[0050] Non-conductive nanoparticles can be optically transparent or opaque, and can be appropriately selected based on the intended use of the 3D nanostructure. However, since metamolecules rely on light interaction, the non-conductive nanoparticles can be optically transparent, non-conductive transparent nanoparticles, ensuring that the 3D nanostructure exhibits uniform and effective light interaction throughout.

[0051] The non-conductive transparent nanoparticles may be nanoparticles of a non-conductive material having a light transmittance of 60% or more, specifically 70% or more, more specifically 80% or more, and even more specifically 85% or more, for light belonging to the visible light wavelength band (380 to 780 nm) based on a plate shape having a thickness corresponding to the diameter of the non-conductive nanoparticles.

[0052] As an advantageous example, the non-conductive nanoparticles may be dielectric. If the non-conductive nanoparticles are dielectric, the 3D nanostructures may exhibit opto-magnetic properties in the presence of second conductive nanoparticles, may have controlled effective permittivity, and may have controlled light scattering properties.

[0053] The dielectric may be a material having a dielectric constant (relative permittivity) of 1.5 to 10.0, specifically 2.0 to 8.0, and more specifically 3.0 to 7.0. In this case, the dielectric constant may be measured according to ASTM D150, but is not limited thereto.

[0054] Practical examples of non-conductive transparent nanoparticles that are dielectrics include, but are not limited to, silica, alumina, hafnium oxide, tantalum oxide, titanium oxide, zirconium oxide, yttrium oxide, lanthanum oxide, mixtures thereof, or composite oxides thereof.

[0055] In one specific example, the average diameter (D) of the first conductive nanoparticles c1 ) is the average diameter (D) of non-conductive nanoparticles i ) divided by the diameter ratio (D) c1 / D i ) may be at the level of 0.10 to 0.45, specifically 0.10 to 0.30. This diameter ratio is advantageous for the first conductive nanoparticle to wrap the particle surface of the non-conductive nanoparticle to form a dense particle layer. The average diameter (D) of the second conductive nanoparticle c2 ) is the average diameter (D) of non-conductive nanoparticles i ) divided by the diameter ratio (D)c2 / D i ) may also be at the level of 0.10 to 0.45, specifically 0.10 to 0.30. Since the second conductive nanoparticle has the diameter ratio described above, the second conductive nanoparticle can fill the void space between meta molecules with a high filling rate.

[0056] The average diameter of the non-conductive nanoparticles may be 10 to 500 nm, specifically 50 to 300 nm, more specifically 50 to 250 nm, and even more specifically 50 to 200 nm. The average diameter of the non-conductive nanoparticles described above is a size that allows the core-shell structured composite nanoparticles to stably exhibit the unique properties of the metamaterial for light above the visible light band, ensures fluidity and processability suitable for the process described below, and also secures mechanical stability in the form of fibers.

[0057] Experimentally, the average diameter of non-conductive nanoparticles and conductive nanoparticles can be measured from microscopic images using observation devices such as a scanning electron microscope or a transmission electron microscope. The average diameter of non-conductive nanoparticles and conductive nanoparticles can be measured by measuring 100 or more, and substantially 100 to 500 particles, calculating the diameter with a circle having the same area as the area of ​​each particle, and averaging the diameters of the circles to obtain the calculated value.

[0058] The first conductive nanoparticle or the second conductive nanoparticle may be a metal nanoparticle, and preferably a plasmonic metal nanoparticle. When the first conductive nanoparticle and the second conductive nanoparticle are plasmonic metal nanoparticles, the three-dimensional nanostructure may have surface plasmon resonance characteristics.

[0059] In detail, the 3D nanostructure can have localized surface plasmon resonance (LSPR) characteristics due to hot spots and propagating plasmon characteristics at the interface of the dielectric core and the plasmonic metal shell. The 3D nanostructure can have a high density of hot spots including hot spots between first conductive nanoparticles surrounding the surface of non-conductive nanoparticles in the metamolecule and hot spots between the first conductive nanoparticles located on the surface of the metamolecule and second conductive nanoparticles located between the metamolecule.

[0060] Examples of plasmonic metals include, but are not limited to, gold, silver, platinum, palladium, nickel, aluminum, copper, mixtures thereof, or alloys thereof.

[0061] The first conductive nanoparticle and the second conductive nanoparticle may be different from each other or may be the same. In one example, the first conductive nanoparticle and the second conductive nanoparticle may be the same. That is, the first conductive nanoparticle and the second conductive nanoparticle may be substantially the same in size, material, and shape. When the first conductive nanoparticle and the second conductive nanoparticle are substantially the same, the three-dimensional nanostructure may also be interpreted as a fiber including a matrix of conductive nanoparticles and non-conductive nanoparticles (dispersed phase) dispersed and incorporated in the matrix of conductive nanoparticles (continuous phase) while being spaced apart from each other. In this case, the matrix of conductive nanoparticles may mean a continuous phase in terms of the conductive nanoparticles continuously contacting each other.

[0062] In one specific example, the non-conductive nanoparticle, the first conductive nanoparticle, and the second conductive nanoparticle may independently have one or more shapes selected from a spherical shape, an angular shape, a rod shape, a plate shape, and a flake shape. In terms of the mechanical stability of the fiber, the regular packing structure of the meta-molecules in the fiber, and the homogeneous space-filling characteristics of the particles, the non-conductive nanoparticle, the first conductive nanoparticle, and the second conductive nanoparticle may each have a spherical shape. In this case, the spherical shape may be interpreted as a spherical shape when the length of the perimeter of the nanoparticle is within 120% of the perimeter of a perfect circle (or sphere) with the same area when the nanoparticle is observed in a planar view.

[0063] In one specific embodiment, the meta-molecules contained in the fiber may have a three-dimensionally regular structure and may be substantially close-packed. The close-packing may be a hexagonal close-packed (HCP) and / or a face-centered cubic (FCC) structure. Specifically, the number of meta-molecules adjacent (nearest neighbors) to one meta-molecule may be 5 to 6 based on a cross-section perpendicular to the elongated direction of the fiber.

[0064] Experimentally, the number of adjacent meta-molecules can be calculated using images taken by a microstructure observation device, such as a scanning electron microscope or transmission electron microscope, of a cross-section perpendicular to the longitudinal direction of the fiber. Specifically, in the image, the number of non-conducting nanoparticles adjacent to any non-conducting nanoparticle can be calculated. More specifically, the number of adjacent non-conducting nanoparticles can be calculated for each of 20 to 50 non-conducting nanoparticles and the average of the numbers can be obtained.

[0065] The close-packed structure of these meta-molecules implies that the meta-molecules (i.e., non-conductive nanoparticles encased in conductive nanoparticles) within the fibers have a regular packing structure. When considering only the conductive components comprising the first conductive nanoparticle and the second conductive nanoparticle, the fibers can also be interpreted as a structure comprising a layer of hollow spherical conductive nanoparticles with a close-packed structure and continuous conductive channels (having a shape corresponding to the empty space) that fill the empty space between the layers of hollow spherical conductive nanoparticles.

[0066] As described above, by forming a conductive channel by positioning a second conductive nanoparticle in the empty space between the metamolecules along with a three-dimensional regular structure of transparent non-conductive nanoparticles and metamolecules, the three-dimensional nanostructure can have controlled light scattering properties.

[0067] Specifically, the three-dimensional nanostructure can have significantly reduced light scattering characteristics for light in the visible light band (400-700 nm). The light scattering characteristics of the three-dimensional nanostructure can be precisely controlled by the content of the conductive component including the first conductive particle and the second conductive particle.

[0068] More specifically, when a fiber that does not contain the first conductive particles and the second conductive particles and is filled with the same nanoparticles as the non-conductive nanoparticles contained in the three-dimensional nanostructure is referred to as a first reference fiber, and the light scattering intensity of the first reference fiber at one wavelength (e.g., 532 nm) in the visible light band is 1, the three-dimensional nanostructure can have a light scattering intensity of 0 to 0.20, specifically 0 to 0.15, and more substantially 0.01 to 0.10 or less. A light scattering intensity of 0 means that substantial light scattering does not occur in the three-dimensional nanostructure.

[0069] Furthermore, the 3D nanostructure may have a light scattering intensity of 0 to 0.90, substantially 0.01 to 0.80, when the light scattering intensity of the second reference fiber phase is 1, and the 3D nanostructure has the same fiber phase as the 3D nanostructure except that it does not contain non-conductive nanoparticles.

[0070] In detail, the first reference fiber may be a fiber having substantially the same diameter and shape as the fiber of the three-dimensional nanostructure, but containing only non-conductive nanoparticles contained in the three-dimensional nanostructure as nanoparticles. In terms of the manufacturing method, the first reference fiber may be manufactured using the same method as the meniscus-guided three-dimensional printing method according to the disclosure described below, but the solid content of the printed nanoparticle solution may be manufactured using a solution composed of non-conductive nanoparticles.

[0071] In detail, the second reference fiber may have substantially the same diameter and shape as the fiber of the three-dimensional nanostructure, but may be a fiber containing only the first conductive nanoparticle and the second conductive nanoparticle contained in the three-dimensional nanostructure as nanoparticles. In terms of the manufacturing method, the second reference fiber may be manufactured using the same method as the meniscus guided three-dimensional printing method according to the disclosure described below, but may be manufactured using a solution in which the solid content of the nanoparticle solution to be printed is composed of the first conductive nanoparticle and the second conductive nanoparticle.

[0072] Additionally, the three-dimensional nanostructure can have a maximum refractive index wavelength and a maximum effective refractive index controlled by the content of the conductive component including the first conductive particle and the second conductive particle.

[0073] Specifically, the three-dimensional nanostructure exhibits magneto-photonic properties by having a three-dimensionally regular structure of dielectric non-conductive nanoparticles and meta-molecules, and second conductive nanoparticles are positioned in the empty spaces between the meta-molecules to form conductive channels, and the wavelength exhibiting the maximum effective refractive index (hereinafter collectively referred to as the maximum refractive index wavelength) can be controlled in the range of 550 nm to 700 nm, and the value of the maximum effective refractive index can also be controlled in the range of 2.0 to 6.0. Specifically, the three-dimensional nanostructure can have a controlled value of the maximum refractive index wavelength in the range of 600 nm to 700 nm and the maximum effective refractive index value in the range of 4.0 to 6.0.

[0074] In the 3D nanostructure, the ratio of the number of particles of non-conductive nanoparticles: conductive components (first conductive nanoparticles + second conductive nanoparticles) may be 1:10 to 150, specifically 1:20 to 150. When this ratio of particle numbers is satisfied, a dense shell surrounding the non-conductive nanoparticles by the conductive component can be created, and the conductive component can be positioned in the empty space between the meta molecules, and a conductive channel can be stably formed.

[0075] Furthermore, as the ratio of non-conductive particles to the number of conductive particles increases, the distance between meta-molecules regularly arranged in a close-packed structure may also increase. At this time, the distance between meta-molecules may correspond to the distance between the centers of non-conductive particles and adjacent non-conductive particles. Depending on the distance between meta-molecules, one or more of the following properties may be controlled: the wavelength of the maximum refractive index of the three-dimensional nanostructure, the value of the maximum effective refractive index, and / or the light scattering intensity of the three-dimensional nanostructure.

[0076] In the three-dimensional nanostructure, when the ratio of the number of non-conductive nanoparticles to the number of particles of the conductive component is satisfied from 1:10 to 150, specifically from 1:20 to 150, the maximum refractive index wavelength can be controlled to a range of 550 nm to 700 nm, and the value of the maximum effective refractive index can be controlled to a range of 2.0 to 6.0. Furthermore, when the ratio of the number of non-conductive nanoparticles to the number of particles of the conductive component is satisfied from 1:50 to 150, the maximum refractive index wavelength can be controlled to a range of 600 nm to 700 nm, and the value of the maximum effective refractive index can be controlled to a range of 4.0 to 6.0. In the range of the ratio of the number of particles of the non-conductive nanoparticles to the number of particles of the conductive component, the wavelength of the maximum refractive index can be shifted toward a long wavelength by increasing the conductive component, and the value of the maximum effective refractive index can be increased. In addition, or independently of this, by satisfying the ratio of the number of particles of non-conductive nanoparticles: conductive components to be 1:10 to 150, specifically 1:10 to 35, the light scattering intensity of the three-dimensional nanostructure at a wavelength of 532 nm can be controlled in the range of 0 to 0.20 compared to the light scattering intensity on the first reference fiber.

[0077] In one specific example, the three-dimensional nanostructure may further contain an organic binder. The organic binder can bind particles together, such as non-conductive nanoparticles and first conductive nanoparticles, first conductive nanoparticles, and metamolecules and second conductive nanoparticles, thereby enhancing the mechanical strength of the three-dimensional nanostructure.

[0078] The binder may be an organic binder, specifically an aqueous organic polymer binder. Examples of aqueous organic polymer binders include, but are not limited to, polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, polyacrylamide, carboxymethylcellulose, polyvinylpyrrolidone, polyvinylpyridine, styrene butadiene rubber, and acrylonitrile-butadiene rubber.

[0079] The three-dimensional nanostructure may contain an organic binder at a level of 0.05 to 15.00 wt% based on the total weight of the three-dimensional nanostructure. This organic binder content is an amount that can improve the mechanical strength of the three-dimensional nanostructure while not interfering with contact between conductive components, including between the first conductive nanoparticles, between the second conductive nanoparticles, and / or between the first conductive nanoparticles and the second conductive nanoparticles.

[0080] In one specific example, the three-dimensional nanostructure is based on a fiber, and the fiber may include a straight region, a curved region that is bent or kinked, a twisted region, a tapering region in which the minor axis diameter decreases or increases, or a combination thereof.

[0081] The short axis diameter of the fiber may be 1 to 20 μm, specifically 1 to 10 μm, and more specifically 1 to 5 μm. In this case, the short axis diameter of the fiber may mean the diameter of a cross-section perpendicular to the longitudinal direction in a fiber region whose size is substantially the same over a length section of at least 2 μm.

[0082] The cross-section perpendicular to the longitudinal direction of the fiber may be circular, elliptical, or square with rounded corners (square or rectangle). If the cross-sectional shape of the fiber is elliptical or square with rounded corners, the minor axis diameter of the fiber may be the diameter converted to a circle having the same cross-sectional area as the cross-sectional area of ​​the fiber cross-section.

[0083] Additionally, when the fiber includes a twisted region or a tapering region in which the short-axis diameter decreases or increases, it may mean a diameter calculated by converting the cross-sectional area of ​​the cross-section having the minimum area in cross-sections perpendicular to the longitudinal direction into a circle of the same area.

[0084] Specifically, the three-dimensional nanostructure may be a simple fiber composed of straight regions, as illustrated in Fig. 1 (a). As illustrated in the example illustrated in Fig. 1 (a), the nanostructure can maintain mechanical stability up to a macroscale size ranging from tens of μm to several millimeters.

[0085] Specifically, the 3D nanostructure may have an array structure in which one or more fibers are arranged spaced apart from each other on the substrate. For example, as shown in (b) of FIG. 1, the substrate may provide a flat surface, and one end of a simple fiber may be bonded to the substrate surface, and may have an array structure in which one or more simple fibers are arranged spaced apart from each other.

[0086] Figure 1 (b) is merely an example of a three-dimensional nanostructure having an array structure, and is an example of a simple fiber in which the fiber, which is a repeating unit constituting the array, is composed of straight regions. However, it is obvious that the fiber, which is a unit, may not be a simple fiber, but may be a fiber including a straight region, a curved region that is bent or folded, a twisted region, a tapering region in which the minor axis diameter decreases or increases, or a region resulting from a combination thereof.

[0087] In addition, (b) of FIG. 1 is an example of a structure in which one end (one end in the longitudinal direction) of a fiber, which is a unit constituting an array, is bonded to a substrate and the fiber stands vertically, but, unlike this, the longitudinal side of the fiber, which is a unit, may be bonded to the substrate, or one end in the longitudinal direction of the fiber may be bonded to the substrate, but the angle between the longitudinal direction of the fiber and the surface of the substrate may not be 90 degrees (vertical), but may form a certain angle (for example, an angle of 10 to 80 degrees).

[0088] In addition, (b) of Fig. 1 is an example in which the fibers, which are units, are uniformly spaced apart and arranged over the entire surface of the substrate using two vectors forming an angle of approximately 120° as separation direction vectors, but the fibers, which are units, may be spaced apart and arranged in a single direction or in the direction of two vectors forming an arbitrary angle, and the arrangement of the fibers, which are units, or the spherical shape of the fibers may vary depending on the surface area of ​​the substrate.

[0089] Fig. 1(c) is an example of a three-dimensional structure having a curved region bent at a 90° angle. However, in the curved region of the bent shape, the angle of bending is not limited to 90°. For example, in the curved region of the bent shape, two straight regions (fiber regions) may meet at an angle exceeding 0° and less than 90°.

[0090] Although not shown in the drawing, a curved region may refer to a region where the longitudinal direction of the fibers changes smoothly, rather than two straight regions meeting at a constant angle. In this case, the smoothly curved part may correspond to an arc of a circle.

[0091] Fig. 1(d) is an example of a three-dimensional structure having a twisted region. The twisted region may refer to a region formed with a surface having a spiral bend in the longitudinal direction of the fiber. Fig. 1(d) is an example having a counterclockwise spiral bend, but it is understood that the twisted region may have a clockwise spiral bend. Furthermore, Fig. 1(d) is an example in which the overall shape of the twisted region in the longitudinal direction of the fiber is a straight line, but it is also understood that the twisted region may be bent or folded simultaneously with the twist.

[0092] Fig. 1(e) is a diagram illustrating an example of a three-dimensional nanostructure having multiple folded regions. As shown in the example in Fig. 1(e), the three-dimensional nanostructure may have a shape in which regions are repeated by a straight region, a curved or bent region, a twisted region, and a tapered region in which the minor axis diameter decreases or increases, or a combination thereof, or a shape in which different types of regions are combined.

[0093] FIG. 1(f) is a diagram illustrating an example of a three-dimensional nanostructure having a tapering region in which the minor axis diameter decreases or increases. As in the example illustrated in FIG. 1(f), the three-dimensional nanostructure may have one or more tapering regions, and the minor axis diameter in the tapering region may continuously increase or decrease.

[0094] Figure 2 is an example of a 3D nanostructure, which is a polarizer designed and implemented using metamaterials. The 3D nanostructure of Figure 2 is a spiral shape composed of 7 folds (curved regions) and 8 nodes (straight regions), depending on the design for the purpose of the broadband polarizer. As shown in the examples in Figures 1 and 2, the 3D nanostructure is based on a fiber shape, but can have virtually unlimited freedom in its shape design.

[0095] As shown in the example of Fig. 2, the present disclosure includes a polarizing plate having a spiral structure by a curved region that is bent or folded based on the fiber phase described above. In this case, if the curved region is a folded shape, the spiral structure may be an angular spiral structure, and if the curved region is a curved shape, the spiral structure may be a circular spiral structure. In addition, although the example of Fig. 2 is an example in which the spiral progresses along the central axis of the spiral and gradually widens, the present invention is not limited thereto. For example, in the spiral structure of the polarizing plate, the width of the spiral, which is the distance from the central axis of the spiral to the spiral, may be constant, or two or more regions having different widths may be continuously connected, or the width may gradually increase or decrease.

[0096] The present disclosure includes a method for manufacturing a three-dimensional nanostructure based on the above-described metamaterial.

[0097] A method for manufacturing a three-dimensional nanostructure according to one aspect includes the steps of: s1) injecting a nanoparticle solution containing non-conductive nanoparticles, first conductive nanoparticles having a smaller size than the non-conductive nanoparticles and being conductive, second conductive nanoparticles, and a liquid medium into a micropipette; s2) contacting a tip of the micropipette with a solid substrate; and s3) moving the micropipette in contact with the solid substrate to manufacture a three-dimensional nanostructure having a fiber shape according to a movement trajectory of the micropipette.

[0098] In step s1), which is a step of injecting a nanoparticle solution into a micropipette, the materials, physical properties, relative content between nanoparticles, size, shape, etc. of the non-conductive nanoparticles, the first conductive nanoparticles, and the second conductive nanoparticles are the same as or similar to those described above in the metamaterial-based three-dimensional nanostructure. Accordingly, the method for manufacturing a three-dimensional nanostructure includes all of the contents described above in the metamaterial-based three-dimensional nanostructure.

[0099] In the nanoparticle solution, the solvent may be an aqueous solvent. The aqueous solvent may be a mixture of water and an organic solvent miscible with water, and may be specifically, but is not limited to, water.

[0100] The nanoparticle solution may contain solid particles comprising non-conductive nanoparticles, first conductive nanoparticles, and second conductive nanoparticles at a concentration of 0.1 to 5 per fL. This ensures fluidity that facilitates easy printing using a micropipette, while stably producing a fibrous material filled with solids by solvent evaporation.

[0101] The micropipette may be a glass capillary puller equipped with a nozzle. By adjusting the nozzle size of the glass capillary puller, the minor axis diameter of the fiber forming the nanostructure can be controlled. The size of the nozzle can correspond to the minor axis diameter of the fiber, and may be, for example, 1 to 20 μm, specifically 1 to 10 μm, and more specifically 1 to 5 μm. Furthermore, by varying the speed or direction of movement of the nozzle at a constant nozzle size, the minor axis diameter of the fiber can be controlled by adjusting the curvature of the meniscus.

[0102] Figure 3 is a process diagram showing a step-by-step process for manufacturing a 3D nanostructure. As in the example shown in Figure 3, a step of forming a meniscus of the nanoparticle solution between the nozzle and the base of the micropipette by bringing a micropipette containing a nanoparticle solution close to a base that provides a contact surface (see Figures 3(a) and (b)), a step of manufacturing a fiber-based 3D nanostructure according to a designed shape by moving the micropipette (V) (see Figure 3(c)), and a step of rapidly moving the micropipette (V) so that the meniscus of the nanoparticle solution is broken. d ) may include a step of stopping the production of the nanostructure (see Fig. 3(d)).

[0103] In detail, when the micropipette comes into contact with the base, a nanoparticle solution can be released at the point of contact, and when the micropipette is moved slightly away from the base, the released nanoparticle solution can form a meniscus due to surface tension and be located between the base and the micropipette.

[0104] Thereafter, as the micropipette moves in a designed random direction at a predetermined speed, a nanoparticle solution of a predetermined flow rate is discharged from the nozzle at the tip of the micropipette, and at the same time, a portion of the nanoparticle solution that has already been discharged can be solidified as the solvent evaporates. At this time, the solidified portion again functions as a base, so that as the micropipette moves, a nanoparticle solution (in a solvent-free state) having a meniscus can be continuously formed and maintained between the solidified portion and the micropipette.

[0105] In detail, in the nanoparticle solution located between the solidified portion and the micropipette, the surface tension due to the meniscus acts in a direction that minimizes the surface area of ​​the nanoparticle solution and generates a pulling force so that the nanoparticle solution within the nozzle of the micropipette is ejected, so that the nanoparticle solution can be ejected out of the nozzle without interruption.

[0106] By this, by moving the direction of the nozzle of the tip of the micropipette as designed, a three-dimensional nanostructure having a shape corresponding to the movement trajectory of the tip of the micropipette can be manufactured.

[0107] At this time, the volume of the nanoparticle solution having a meniscus may be at the level of 10 to 500 fL, but is not limited thereto.

[0108] The movement speed of the micropipette nozzle may be, but is not limited to, 10 nm / sec to 800 nm / sec.

[0109] As described above in the three-dimensional nanostructure, the three-dimensional nanostructure may further contain an organic binder, and thus, the nanoparticle solution may also further contain an organic binder. The nanoparticle solution may contain an organic binder such that the content of the organic binder contained in the three-dimensional nanostructure is 0.05 to 15.00 wt%, but is not necessarily limited thereto.

[0110] The above-described manufacturing method may be collectively referred to as meniscus-guided 3D printing.

[0111] FIGS. 4 (a) and (b) are diagrams illustrating the light scattering characteristics of simple fiber-like three-dimensional nanostructures manufactured by a meniscus-guided three-dimensional printing method. Specifically, the nanostructures of FIGS. 4 (a) and (b) are examples manufactured by a meniscus-guided three-dimensional printing method (nozzle diameter of approximately 5 ㎛, nozzle movement speed of 500 nm / sec) using a nanoparticle solution in which 100 nm silica is used as a non-conductive nanoparticle, 20 nm gold (Au) is used as first and second conductive nanoparticles, polyvinylpyrrolidone (PVP) is used as an organic binder, distilled water is used as a solvent, and the ratio of silica nanoparticles to the particle number of the conductive component is 1:12.5. For comparison, silica fibers were manufactured using the same method except that only silica nanoparticles were used as the solid component without any conductive components, and the light scattering characteristics of these silica fibers are also shown in Figs. 4 (c) and (d). As shown in Fig. 4, it can be seen that the light scattering of the nanostructures is significantly reduced.

[0112] Fig. 5 shows the light scattering intensity according to the wavelength of the manufactured nanostructure (using a usb2000 spectrometer). In Fig. 5, the light scattering intensity spectrum indicated as 'SiO2NP fiber' refers to the light scattering result of the silica fiber described above with respect to Fig. 4. The light scattering spectrum indicated as 'AuNP fiber' in Fig. 5 refers to the light scattering result of the gold fiber manufactured in the same manner as described above in Fig. 4, but using only the conductive component (20 nm Au nanoparticles) as the solid without the silica nanoparticles. The light scattering intensity spectra indicated as 'RMM-0.5 fiber', 'RMM-1.0 fiber', and 'RMM-1.5 fiber' in Fig. 5 refer to the light scattering results of the nanostructure manufactured in the same manner as described above in Fig. 4 using nanoparticle solutions in which the ratios of the number of silica nanoparticles: conductive component particles are 1:12.5, 1:25, and 1:34.5, respectively.

[0113] As can be seen in Fig. 5, the fabricated nanostructure exhibited significantly lower light scattering intensity than the silica fiber in all measured wavelength bands including the visible light wavelength band, and in particular, it can be seen that it had lower light scattering intensity than the gold fiber in the band from 510 nm to 620 nm. In addition, it can be seen that the light scattering intensity of the nanostructure decreased further as the content of the conductive component increased in the near-infrared band, specifically, in the near-infrared band from 750 nm to 800 nm.

[0114] Fig. 6 is a scanning electron microscope photograph of a short-axis cross-section of the 'RMM-1.0 fiber' nanostructure of Fig. 5. As shown in the example in Fig. 6, the nanostructure has a close-packed structure in which the number of (nearest) adjacent meta-molecules is substantially 6 based on one meta-molecule. In addition, it can be seen that the space between meta-molecules is filled with Au nanoparticles, forming a conductive channel.

[0115] Figure 7 is a drawing illustrating the measurement of the effective refractive index of a nanostructure. Specifically, in Figure 7, the solid line represents the real part of the refractive index (n), and the dotted line represents the imaginary part of the extinction coefficient (k, extinction coefficient). In Fig. 7, the solid and dotted lines indicated as 'Au' represent the results of measuring the effective refractive index of gold fibers manufactured in the same manner as described above in Fig. 4, using only the conductive component (20 nm Au nanoparticles) as the solid component without silica nanoparticles, and the results of the solid and dotted lines indicated as 'f=0.35' represent the results of nanostructures manufactured in the same manner as described above in Fig. 4 using a nanoparticle solution in which the ratio of the number of silica nanoparticles to the number of conductive components is 1:83, and the results of the solid and dotted lines indicated as 'f=0.45' represent the results of nanostructures manufactured in the same manner as described above in Fig. 4 using a nanoparticle solution in which the ratio of the number of silica nanoparticles to the number of conductive components is 1:144. As can be seen in Fig. 7, the wavelength indicating the maximum effective refractive index (maximum refractive index wavelength) and the maximum effective refractive index value are controlled by the content of the conductive component contained in the nanostructure, and it can be seen that it has a maximum refractive index wavelength of 600 nm to 700 nm and a maximum effective refractive index value of 4.0 to 6.0. In addition, it can be seen that as the content of the conductive component contained in the nanostructure increases, the maximum refractive index wavelength moves to a longer wavelength, and the maximum effective refractive index value also increases.

[0116] The above embodiments are merely examples and the present invention is not limited thereto. Anything that has substantially the same configuration and achieves the same operational effects as the technical concepts described in the claims of the present invention is included within the technical scope of the present invention.

Claims

1. A meta molecule comprising a first conductive nanoparticle having a size smaller than that of a non-conductive nanoparticle and a single non-conductive nanoparticle and surrounding the surface of the non-conductive nanoparticle; and a fiber comprising a second conductive nanoparticle positioned in the space between the meta molecules. A metamaterial-based three-dimensional nanostructure, wherein the fibers include a straight region, a curved region that is bent or folded, a twisted region, a tapering region with a decreasing or increasing minor diameter, or a region with a combination thereof.

2. In paragraph 1, The average diameter (D) of the first conductive nanoparticles c1 ) is the average diameter (D) of the non-conductive nanoparticles. i ) divided by the diameter ratio (D) c1 / D i ) is a metamaterial-based three-dimensional nanostructure with a thickness of 0.10 to 0.

45.

3. In paragraph 1, In the above fiber, the meta molecule is a close-packed, metamaterial-based three-dimensional nanostructure.

4. In paragraph 1, A metamaterial-based three-dimensional nanostructure, wherein the ratio of the number of particles of the conductive component including the first conductive nanoparticle and the second conductive nanoparticle on the above fiber is 1:10 to 150.

5. In paragraph 1, A metamaterial-based three-dimensional nanostructure, wherein the first conductive nanoparticle and the second conductive nanoparticle are each plasmonic metal nanoparticles.

6. In paragraph 1, The above non-conductive nanoparticles are transparent nanoparticles, and are metamaterial-based three-dimensional nanostructures.

7. In paragraph 6, The above non-conductive nanoparticles are a metamaterial-based three-dimensional nanostructure having a dielectric constant of 1.5 to 10.

0.

8. In paragraph 1, The above-mentioned fibrous structure is a metamaterial-based three-dimensional nanostructure further containing an organic binder.

9. In paragraph 1, A metamaterial-based three-dimensional nanostructure, wherein the non-conductive nanoparticles, the first conductive nanoparticles and the second conductive nanoparticles independently have at least one shape selected from a spherical shape, an angular shape, a rod shape, a plate shape and a flake shape.

10. In paragraph 1, A metamaterial-based three-dimensional nanostructure, wherein the effective refractive index of the nanostructure is controlled by the ratio of the number of particles of the conductive component including the first conductive nanoparticle and the second conductive nanoparticle contained in the above nanostructure.

11. In paragraph 10, The above nanostructure is a metamaterial-based three-dimensional nanostructure having a wavelength showing a maximum effective refractive index of 550 nm to 700 nm and a maximum effective refractive index value of 2.0 to 6.

0.

12. In paragraph 1, A metamaterial-based three-dimensional nanostructure, wherein the nanostructure has a light scattering intensity of 0 to 0.20 times that of the reference fiber, wherein the fiber does not contain first conductive particles and second conductive particles and is filled with nanoparticles identical to the non-conductive nanoparticles contained in the three-dimensional nanostructure.

13. A metamaterial-based polarizer having a fiber-like structure by a curved region that is bent or folded, wherein the metamolecule comprises a first conductive nanoparticle having a size smaller than that of the nonconductive nanoparticle and surrounding the surface of the nonconductive nanoparticle; and a second conductive nanoparticle positioned in the space between the metamolecules.

14. A step of injecting a nanoparticle solution including non-conductive nanoparticles, first conductive nanoparticles and second conductive nanoparticles having a smaller size than the non-conductive nanoparticles and being conductive, and a liquid medium into a micropipette; a step in which the tip of the micropipette comes into contact with the solid substrate; and A step of manufacturing a three-dimensional nanostructure having a fiber shape according to the movement trajectory of the micropipette by moving a micropipette in contact with a solid substrate; A method for manufacturing a three-dimensional nanostructure based on metamaterials including:

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