Method for manufacturing biological surface structure replicas using secondary electrohydraulic instability

Abstract

One embodiment of the present invention provides a method for manufacturing a replica of a biological surface structure using secondary electrohydrodynamic instability. The method for manufacturing a replica of a biological surface structure according to one embodiment of the present invention has the effect of being able to use a biological surface exhibiting flexible and non-uniform surface roughness as a master mold because it uses an electric field, which is a remote force rather than mechanical compression force, as the driving force.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a replica of a biological surface structure, and more specifically, to a method for manufacturing a replica of a biological surface structure using secondary electrohydrodynamic instability. Background Technology

[0002] Traditional molding techniques or capillary lithography utilize relatively weak capillary forces, resulting in low aspect ratios of replicated fine patterns and problems such as partial replication.

[0003] At this time, for uniform and large-area patterning, uniform contact between the master mold and the polymer thin film must be ensured, but there is a problem in that it is difficult to achieve this using only simple capillary force.

[0004] Accordingly, techniques were developed to replicate biological surfaces using low surface tension and viscosity, but this limited the range of materials that could be selected.

[0005] Conventional nanoimprinting techniques achieve uniform large-area patterning by utilizing high mechanical compression force; however, for similarly uniform large-area patterning, the master mold and the polymer thin film must be in uniform contact.

[0006] When the master mold and the polymer thin film are in uniform contact, a complex alignment system is generally required to precisely control the distance and contact between the two, which can increase the process cost of the technique.

[0007] In addition, biological surfaces are generally composed of flexible materials, and when replicating such biological surfaces using nanoimprinting techniques, the flexible biological surface structure can be easily deformed due to high mechanical compression.

[0008] At this time, the 'buckling effect' caused by high mechanical compression forces deforms the flexible biological surface structure, posing a problem that makes it difficult to use the biological surface as a master mold.

[0009] In addition, since biological surfaces composed of complex microstructures generally exhibit non-uniform surface roughness, there was a problem in that precise large-area replication was difficult using conventional methods.

[0010] Therefore, there are still many challenges remaining in achieving replicas of biological surface structures in secondary replication methods. Prior art literature

[0011] Republic of Korea Published Patent No. 10-2011-0032381 The problem to be solved

[0012] The technical problem that the present invention aims to solve is to provide a method for manufacturing a replica of a biological surface structure.

[0013] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention belongs from the description below. means of solving the problem

[0014] To achieve the above technical objectives, one embodiment of the present invention provides a method for manufacturing a replica of a biological surface structure.

[0015] A method for manufacturing a replica of the biological surface structure according to one embodiment of the present invention is,

[0016] A step of preparing a capacitor comprising a substrate having a liquid polymer layer formed thereon as a lower electrode and a mask pattern spaced apart from the upper surface of the substrate as an upper electrode;

[0017] A step of manufacturing an engraved replica by applying current to the electrodes of the above capacitor to generate an electric field and inducing secondary electrohydrodynamic instability to form an engraved pattern in a liquid polymer layer;

[0018] A step of manufacturing an intaglio replica having a metal layer formed by applying a metal material to the surface of the above-mentioned intaglio replica; and

[0019] The method may include the step of preparing a capacitor comprising a master mold consisting of a substrate having a liquid polymer layer formed as a lower electrode and a metal layer formed spaced apart from the upper surface of the substrate as an upper electrode, and applying current to the electrodes of the capacitor to generate an electric field to generate secondary electrohydrodynamic instability, thereby forming the liquid polymer layer into an intaglio pattern to manufacture a three-dimensional bio-surface structure replica with a relief shape.

[0020] In addition, according to one embodiment of the present invention, in the step of preparing the capacitor, the mask pattern may be a biological surface structure.

[0021] In addition, according to one embodiment of the present invention, in the step of preparing the capacitor, the mask pattern may be an uneven structure composed of alternating protrusions and non-protrusions.

[0022] In addition, according to one embodiment of the present invention, in the step of preparing the capacitor, the gap between the substrate on which the polymer layer is formed and the mask pattern may be 0 μm to 4 μm.

[0023] In addition, according to one embodiment of the present invention, in the step of preparing the capacitor, the thickness of the liquid polymer layer may be 150 nm to 2000 nm.

[0024] In addition, according to one embodiment of the present invention, the method for manufacturing a replica of the biological surface structure can be performed at a temperature above the glass transition temperature of the liquid polymer material.

[0025] In addition, according to one embodiment of the present invention, in the step of manufacturing the intaglio replica, the voltage applied to the electrode may be 0.5 kV to 1.8 kV.

[0026] In addition, according to one embodiment of the present invention, in the step of manufacturing the intaglio replica, the electric field strength applied to the capacitor is 10 8 It can be greater than V / m.

[0027] In addition, according to one embodiment of the present invention, in the step of manufacturing the intaglio replica, the initial growth rate for forming the intaglio pattern is 10 2 s -1 to 10 7 s -1 It could be.

[0028] In addition, according to one embodiment of the present invention, in the step of manufacturing the intaglio replica,

[0029] The above initial growth rate is given by the following Equation 1 (τ m Method for manufacturing a replica of a biological surface structure characterized by following the reciprocal of ):

[0030] <Equation 1>

[0031]

[0032] In Equation 1 above, η is the viscosity of the fluid thin film, γ is the surface tension of the fluid thin film, and ε r ε₀ is the permittivity of the fluid thin film, ε₀ is the vacuum permittivity, U is the intensity of the applied voltage, h₀ is the thickness of the dielectric (fluid thin film), and d is the distance between the two electrodes.

[0033] In addition, according to one embodiment of the present invention, in the step of manufacturing an intaglio replica having the metal layer formed thereon, the metal layer may be composed of an electrically conductive metal material.

[0034] In addition, according to one embodiment of the present invention, in the step of manufacturing an intaglio replica having the metal layer formed thereon, the thickness of the metal layer may be 10 nm to 20 nm.

[0035] In addition, according to one embodiment of the present invention, in the step of manufacturing the three-dimensional biological surface structure replica,

[0036] The growth rate of the above 3D biological surface structure replica is given by the following Equation 1 (τ m It can follow the reciprocal of ).

[0037] <Equation 1>

[0038]

[0039] In Equation 1 above, η is the viscosity of the fluid thin film, γ is the surface tension of the fluid thin film, and ε r ε₀ is the permittivity of the fluid thin film, ε₀ is the vacuum permittivity, U is the intensity of the applied voltage, h₀ is the thickness of the dielectric (fluid thin film), and d is the distance between the two electrodes. Effects of the invention

[0040] The method for manufacturing a replica of a biological surface structure according to one embodiment of the present invention utilizes an electric field, which is a remote force rather than mechanical compression force, as the driving force, thereby having the effect of utilizing a biological surface that exhibits flexible and non-uniform surface roughness as a master mold.

[0041] In addition, the present invention has the effect of producing a precise intaglio replica by controlling the three-dimensional behavior of a polymer fluid in a secondary replication method after attaching a biological surface as a mask pattern.

[0042] In addition, the above intaglio replica can be reused as a master mold through the deposition of a thin metal material.

[0043] In addition, it is possible to replicate sophisticated biological surface structures through an electrohydrosecondary replication method by reusing a biological surface master mold.

[0044] In this case, the resulting precisely replicated biological surface structures can realize various original surface properties (e.g., superhydrophobicity, antibacterial effects, etc.), making them applicable in various industrial fields. Brief explanation of the drawing

[0045] Figure 1 is a schematic diagram illustrating a method for precisely replicating a given biological surface structure through secondary electrohydrodynamic instability. FIG. 2 is a schematic diagram illustrating a method for replicating a biological surface structure through an intaglio replication process using an electro-hydraulic control technique. Figure 3 is a schematic diagram and graph illustrating the electrohydrodynamic instability induced at the polymer-polymer interface in the electrohydrodynamic secondary replication method and a method to control it through numerical analysis. Figure 4 is a schematic diagram and scanning electron microscope image illustrating the replication method of a biological surface structure due to secondary instability. Figure 5 is a scanning electron microscope image showing the results of controlling electrohydrodynamic instability at the polymer-polymer interface. Figure 6 shows the result of generating the original biological surface structure using an intaglio replica coated with a metal thin film as a master mold. Figure 7 shows the result of controlling the vertical growth of the cicada wing structure as the electric field strength increases. Figure 8 shows the result of an antibacterial effect realized on a surface replicating a cicada wing nanostructure. Figure 9 shows the result of replicating a micro-nano hybrid structure on the surface of a rose petal through an electro-hydrosecondary replication method. Figure 10 is an image illustrating a comparison of replication fidelity in the vertical direction as the applied voltage (electric field) strength increases. Figure 11 shows the results of observing the replication area trend of rose petal hybrid structures according to planar growth. Specific details for implementing the invention

[0046] The present invention will be described below with reference to the attached drawings. However, the present invention may be implemented in various different forms and is therefore not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification have been given similar reference numerals.

[0047] Throughout the specification, when it is stated that a part is "connected (connected, in contact, combined)" with another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" with other members interposed between them. Furthermore, when it is stated that a part "includes" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but rather allows for the inclusion of additional components.

[0048] The terms used herein are merely for describing specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to indicate the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0050] Hereinafter, the present invention will be described with reference to the drawings presented in this specification. For reference, the drawings may be partially exaggerated to illustrate the features of the present invention. In such cases, it is preferable to interpret them in light of the entire intent of this specification.

[0051] Referring to FIGS. 1 to 11, a method for manufacturing a replica of a biological surface structure according to one embodiment of the present invention will be described.

[0052] A method for manufacturing a replica of a biological surface structure according to one embodiment of the present invention is,

[0053] The method may include the steps of: preparing a capacitor comprising a substrate having a liquid polymer layer formed as a lower electrode and a mask pattern spaced apart from the upper surface of the substrate as an upper electrode; applying current to the electrodes of the capacitor to generate an electric field and create secondary electrohydrodynamic instability to form a liquid polymer layer in an intaglio pattern to produce an intaglio replica; applying a metal material to the surface of the intaglio replica to produce an intaglio replica having a metal layer formed thereon; and preparing a capacitor comprising a master mold composed of a substrate having a liquid polymer layer formed as a lower electrode and an intaglio replica having a metal layer spaced apart from the upper surface of the substrate as an upper electrode, and applying current to the electrodes of the capacitor to generate an electric field and create secondary electrohydrodynamic instability to form a liquid polymer layer in an intaglio pattern to produce a three-dimensional biological surface structure replica with a positive shape.

[0054] In the first step, the method may include the step of preparing a capacitor comprising a substrate having a liquid polymer layer formed thereon as a lower electrode and a mask pattern spaced apart from the upper surface of the substrate as an upper electrode. (S100)

[0055] At this time, the above mask pattern is characterized as being a biological surface structure.

[0056] In this case, the above biological surface structure utilizes a cicada wing nanostructure and a rose leaf micro-nano hybrid structure as representative biological surface structures, but the content of the present invention is not limited, and various other biological surface structures are permitted, such as an anisotropic hybrid structure of a rice leaf surface, a porous structure of a black butterfly wing, and a micro-nano hybrid structure of a lotus leaf.

[0057] In addition, the present invention is preferably in the form of a capacitor composed of upper and lower electrodes for applying a uniform electric field across the entire surface of the thin film.

[0058] The lower electrode of the capacitor used in the present invention is a substrate, and the upper electrode is a mask pattern.

[0059] At this time, the mask pattern is characterized by having an uneven structure composed of alternating protrusions and non-protrusions.

[0060] The target subject to which electrohydrodynamic instability is induced according to the present invention is a fluid thin film surface, characterized by having an allowable range in a liquid phase material that generally has a thickness of several micrometers or less and exhibits the properties of an incompressible Newtonian fluid.

[0061] In this case, 'polymer fluid' in the present invention refers to a polymer thin film in which fluidity is secured under heat treatment conditions above the glass transition temperature. The polymer material is not particularly limited in type, but polystyrene, poly(methyl methacrylate), polyvinylidene fluoride, poly(vinylidene fluoride-trifluoroethylene), polyvinyl alcohol, polyvinyl acetate, polydimethylsioxane, polyvinylpyrrolidone, ethyl cellulose or polycaprolactone, poly(chlorotrifluoroethylene), etc. may be used.

[0062] At this time, the present invention includes a step of using a duplicated intaglio replica again as a master mold, and when making the master mold, it is appropriate to use a water-soluble polymer to preserve the structure of the final replica.

[0063] Suitable types of water-soluble polymers include preferably polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, dextran, carboxymethyl cellulose, and salmon deoxyribonucleic acid.

[0064] At this time, the thickness of the liquid polymer layer of the present invention is characterized to be 150 nm to 2000 nm.

[0065] At this time, when the thickness of the liquid polymer layer is 150 nm to 2000 nm, it is suitable for inducing secondary instability and implementing a secondary replication method accordingly.

[0066] In addition, in the present invention, thin film fluidity must be secured for structural deformation due to the application of electrostatic pressure, so a process temperature above the glass transition temperature is required.

[0067] Accordingly, the present invention is characterized by being performed in a temperature range of 100°C to 200°C.

[0068] For example, one embodiment of the present invention uses a polystyrene thin film, and the process can be carried out at a glass transition temperature (about 100 °C) or higher.

[0069] In addition, the present invention is preferably such that the thin film surface is uniform for the application of a uniform electric field. At this time, processes such as spin coating, spray coating, and dip coating may be performed to apply a polymer thin film on the substrate.

[0070] At this time, the gap between the substrate on which the polymer layer of the present invention is formed and the mask pattern is characterized as being 0 to 4 μm.

[0071] If the gap between the substrate on which the polymer layer is formed and the mask pattern exceeds 4 μm, there may be a problem in that the electric field strength is insufficient, making it difficult to form an effective structure.

[0072] In the second step, the method may include the step of applying current to the electrodes of the capacitor to generate an electric field, thereby generating secondary electrohydrodynamic instability to form an intaglio pattern in the liquid polymer layer, and manufacturing an intaglio replica. (S200)

[0073] For an effective secondary replication method, securing an air layer with a thickness of 2 micrometers or less is preferred.

[0074] The present invention is characterized in that the gap between the substrate on which the polymer layer is formed and the mask pattern is 0 to 4 μm.

[0075] In addition, the power supply connected to the upper and lower electrodes generates high-voltage pulses to generate an electric field, and at this time, 0.5 kV or higher is appropriate, and the maximum applied voltage can be controlled through the thickness of the air layer, the insulation characteristics of the substrate and the thin film, and the circuit design of the power supply.

[0076] In addition, preferably, the voltage applied to the electrode may be 0.5 kV to 1.8 kV.

[0077] In addition, for effective induction of second-order instability, the electric field strength on the surface of the fluid thin film is 10 8 It is desirable that it be greater than V / m.

[0078] At this time, a flat rigid substrate (e.g., silicon, silicon oxide, ITO glass, ordinary glass, etc.) is preferred for the uniform application of an electric field in the capacitor structure and for a uniform surface of the polymer thin film applied thereto, but this does not limit the content of the invention, and a flexible substrate (e.g., PET substrate, ordinary polymer sheet, etc.) can also be used due to the characteristics of the invention.

[0079] In addition, a substrate coated with a polymer thin film is suitable for use as a bottom electrode in a capacitor structure.

[0080] At this time, in the case of an insulating substrate, deposition of a conductive material is required or a high applied voltage exceeding the insulating properties is required.

[0081] In addition, a 'high-speed control' method that rapidly increases the growth rate of the electrohydroelectric structure is effective for the effective induction of secondary instability; in this invention, 1 / τ, the reciprocal of the natural time, which refers to the initial growth rate of the structure across the entire thin film surface, is used. m A method is used to increase the relatively slow secondary instability development speed by increasing it.

[0082] Specifically, the above τ m It is as follows.

[0083]

[0084] In Equation 1 above, η is the viscosity of the fluid thin film, γ is the surface tension of the fluid thin film, and ε r ε₀ is the permittivity of the fluid thin film, ε₀ is the vacuum permittivity, U is the intensity of the applied voltage, h₀ is the thickness of the dielectric (fluid thin film), and d is the distance between the two electrodes.

[0085] In the above formula An increase in [the amount] can accelerate the growth of secondary structures, which were relatively slow, thereby helping to reproducibly form structures within a short period of time.

[0086] Through this, high According to this, the structure based on secondary instability formed at a small distance between electrodes is an intaglio replica with a shape opposite to the mask pattern, producing results similar to existing nanoimprinting or molding techniques.

[0087] In this case, the 'secondary replication method' in the present invention refers to the process in which the upper electrode structure is engraved and replicated by 'secondary electro-hydrodynamic instability'.

[0088] The above 'secondary electrohydrodynamic instability' refers to the phenomenon in which, after the polymer fluid that has become primarily unstable forms a structure with the same shape as the protrusion of the upper electrode, the polymer fluid forms a structure due to the applied electric field in the region below the non-protrusion.

[0089] The aforementioned 'electrohydrodynamic instability' refers to the phenomenon in which fine structures are formed on the surface of a polymer thin film to reduce the free energy (electrostatic energy) stored inside the capacitor.

[0090] 'Electro-hydraulic control technique' refers to a technique for fabricating artificial surface structures based on the aforementioned electro-hydraulic instability.

[0091] In order to effectively induce the above secondary replication method, the distance between the electrodes needs to be sufficiently small while implementing the electro-hydraulic control technique.

[0092] 'Distance between electrodes' refers to the distance between the upper electrode and the lower electrode.

[0093] A 'sufficiently small distance between electrodes' is generally suitable when the filling ratio (thickness of the coated polymer film / distance between electrodes) is 0.5 or higher.

[0094] In addition, 'intaglio replication' means that a structure with a shape opposite to that of the structure given on the upper electrode is formed on the surface of the polymer thin film above the lower electrode.

[0095] Therefore, the above-mentioned biological surface structure can form an intaglio replica on the surface of a polymer thin film located at the lower electrode through a secondary replication method of the electrohydrodynamic control technique.

[0096] Referring to Fig. 2(a), the negative replication of a biological surface structure through an electrohydrodynamic secondary replication method is illustrated.

[0098] In the third step, the method may include the step of applying a metallic material to the surface of the engraved replica to produce an engraved replica with a metallic layer formed thereon. (S300)

[0099] The negative replica of the generated biological surface structure, which will be explained later, can again be used as a mask pattern in electrohydrodynamic control techniques.

[0100] Figure 2(b) illustrates the process of forming a replica of a biological surface structure in an electrohydrosecondary replication method through the reuse of an intaglio replica.

[0101] At this time, the above-mentioned replica is formed of a polymer, and in this case, a polymer-polymer interface may be formed due to contact with another polymer thin film located on the lower electrode.

[0102] In this case, if an electro-hydraulic control technique is implemented, instability can be induced even at the polymer-polymer interface, leading to the formation of additional structures.

[0103] Since the above additional structure is an undesirable result in the replication of the original biological surface structure, the electrohydrodynamic instability of the corresponding polymer-polymer interface needs to be suppressed.

[0104] At this time, the present invention may optionally disclose a method for controlling electro-hydroelectric instability.

[0105] Figure 3 is a schematic diagram illustrating the electrohydrodynamic instability induced at the polymer-polymer interface.

[0106] Time constant of electrohydrodynamic instability induced at polymer-polymer interfaces ( The reciprocal of ) is as follows.

[0107]

[0109] In the above formula is the dielectric constant of the polymer thin film (thin film 1) on the lower electrode, is the dielectric constant of the polymer thin film under the upper electrode, Electric field strength applied to thin film 1, is the electric field strength applied to thin film 2, is the interfacial tension between thin film 1 and thin film 2, and is a function composed of the height and viscosity of two polymer thin films.

[0110] At this time, considering that the permittivity, interfacial tension, and electric field strength are maintained constant in the electrohydroelectric control method, the control of instability at the polymer-polymer interface in the above equation is It depends on lowering, and the above It is as follows.

[0111]

[0113] In the above formula is the thickness of thin film 1, Viscosity of silver thin film 1, is the thickness of thin film 2, This is the viscosity of thin film 2.

[0114] Viscosity ratio ( ) and thickness ratio( After introducing ), the above formula can be simplified.

[0115] Considering the experimental conditions used in the embodiment of the present invention, assuming h1=-h2, C is as follows.

[0116]

[0117] In addition, using the thickness ratio S, C can be expressed as follows.

[0118]

[0119] In order to lower C as described above, R or S must be increased. In this case, the present invention can utilize a method of lowering R and S by increasing the viscosity of thin film 2 and reducing its thickness.

[0120] Therefore, by applying a thin layer of a metallic material with a generally very high viscosity—that is, close to infinity—on top of the intaglio replica, the rate of instability development induced at the polymer-polymer interface can be suppressed.

[0121] Therefore, the engraved replica produced by the simultaneous application of a conductive metal material can be used as an upper electrode.

[0122] At this time, the metal layer may be composed of an electrically conductive metal material.

[0124] In the fourth step, the method may include the step of preparing a capacitor comprising a master mold consisting of a substrate having a liquid polymer layer formed as a lower electrode and an intaglio replica having a metal layer formed spaced apart from the upper surface of the substrate as an upper electrode, and applying current to the electrodes of the capacitor to generate an electric field to induce secondary electrohydrodynamic instability, thereby forming the liquid polymer layer into an intaglio pattern to manufacture a three-dimensional bio-surface structure replica with a raised shape. (S300)

[0125] The method for manufacturing a three-dimensional biological surface structure replica of the present invention utilizes the same replication method as the step of manufacturing an intaglio replica of the second step described above, so that a structure identical to the original biological surface structure can be finally formed.

[0126] Specifically, the present invention allows for three-dimensional flow of a polymer fluid that behaves due to secondary instability, which can be classified into planar flow and vertical flow.

[0127] At this time, the area and uniformity of the replica structure can be determined in 'planar flow,' i.e., 'planar growth,' and the height / aspect ratio and the vertical tip of the replica structure can be determined in 'vertical flow,' i.e., 'vertical growth.'

[0128] In addition, the three-dimensional flow of polymer fluids indicates high-size rapid growth of electrohydrodynamic structures It can be controlled in the way it is maintained.

[0129] At this time, the planar growth of the structure is Viscosity of fluid thin films contributing to ( ) has a significant impact, and the lower the viscosity, the better the area and uniformity of the structure formed by the secondary replication method.

[0130] This is because the fluctuating polymer thin film in the electrohydrodynamic phenomenon behaves as Poiseuille flow, and the velocity of this flow is inversely proportional to viscosity.

[0131] In addition, the vertical growth of the structure The applied electric field strength (applied voltage) contributing to this has a significant effect, and the higher the electric field, the greater the aspect ratio / height of the structure formed by the secondary replication method.

[0132] In this invention, a method for controlling an electric field to enhance the vertical growth of a structure may be utilized.

[0133] In addition, in the secondary replication method, the polymer thin film located below the mold structure can grow upward by an applied electric field.

[0134] In this case, the primary driving force is electrostatic pressure, and the force repelling vertical growth is Laplace pressure; the final height and end shape of the structure can be determined from the competitive relationship between the two.

[0135] In addition, the higher the electric field (applied voltage), the more effective vertical growth is ensured, allowing a high aspect ratio to be achieved and enabling the material to fully permeate the mold structure, thereby precisely replicating the shape of the ends.

[0136] In addition, the present invention can appropriately control the three-dimensional flow of a polymer fluid in an electrohydrosecondary replication method through the control of viscosity and electric field strength.

[0137] Therefore, regarding parameter control, the present invention lowers viscosity and increases the electric field (applied voltage) in a manner By increasing it, not only is the process time drastically shortened, but appropriate control of the area, uniformity, and aspect ratio of the replicated biological surface structure is also possible.

[0138] As a result, it is possible to precisely replicate the original three-dimensional biological surface structure while simultaneously performing uniform large-area replication.

[0139] After the electrohydrodynamic control technique is terminated, a replicated biological surface structure can be obtained by separating the master mold or, in the case of a water-soluble master mold, by immersing it in water.

[0140] The above-described sophisticated replicated structure can replicate even the unique characteristics of the original biological surface, and in an embodiment of the present invention, the antibacterial effect on the surface of the replicated structure can be verified through the replication of cicada wings.

[0141] Accordingly, the method for manufacturing a replica of a biological surface structure according to one embodiment of the present invention utilizes an electric field, which is a remote force rather than mechanical compression force, as the driving force, thereby having the effect of using a biological surface exhibiting flexible and non-uniform surface roughness as a master mold.

[0142] In addition, the present invention has the effect of producing a precise intaglio replica by controlling the three-dimensional behavior of a polymer fluid in a secondary replication method after attaching a biological surface as a mask pattern.

[0143] In addition, the above intaglio replica can be reused as a master mold through the deposition of a thin metal material.

[0144] In addition, it is possible to replicate sophisticated biological surface structures through an electrohydrosecondary replication method by reusing a biological surface master mold.

[0145] In this case, the resulting precisely replicated biological surface structures can realize various original surface properties (e.g., superhydrophobicity, antibacterial effects, etc.), making them applicable in various industrial fields.

[0147] Figures 1 to 11 will be described below.

[0148] FIG. 2 relates to a method for replicating biological surface structures using electrohydrodynamic instability, and specifically illustrates a series of processes for obtaining a desired replica after the fabrication of a master mold.

[0149] In the present invention, 'secondary electro-hydrodynamic instability' or 'secondary instability' is distinguished from primary electro-hydrodynamic instability induced earlier in time in the protruding region, and can be defined as electro-hydrodynamic instability induced in the region below the non-protruding region after the occurrence of primary electro-hydrodynamic instability.

[0150] In addition, in the present invention, 'electrohydrodynamic instability' is defined as a competitive relationship between the deformation of the thin film surface structure caused by electrostatic pressure and the Laplace pressure that stabilizes it, and in this case, the process of surface structure deformation over time may necessarily be implied to lower the free energy within the system.

[0151] Generally, primary instability induced below the protrusions of a mask pattern grows a structure with the same shape as the mask pattern, whereas secondary electrohydrodynamic instability additionally occurring below the non-protrusions pulls the polymer fluid upward to fill the non-protrusion regions, resulting in the formation of a secondary replica structure different from the primary structure.

[0152] In the present invention, the ‘secondary replication method’ or ‘electric hydroelectric secondary replication method’ refers to the process of producing an intaglio replication formed through the secondary electric hydroelectric instability described above.

[0153] Unlike conventional patterning methods that utilize capillary force or mechanical compression force, the above secondary replication method is based on the use of an electric field, specifically electrostatic pressure, which enables polymer fluid behavior even at a predetermined separation distance.

[0154] At this time, these process characteristics can allow patterning even with non-uniform contact.

[0155] Furthermore, in the present invention, 'non-uniform contact' refers to the fact that in the electro-hydraulic control technique, the distance between electrodes (i.e., the thickness of the air layer between the upper and lower electrodes) is not uniformly distributed across the entire surface of the thin film on the lower electrode.

[0156] More specifically, (1) the polymer fluid is drawn up and forms a structure even at a predetermined distance due to the rapid growth rate, and (2) at the same time, uniform contact can be achieved without a separate device because the voltage applied between the two electrodes attracts the upper and lower electrodes due to the Coulomb force (electrostatic force).

[0157] In the above secondary replication method, polymer fluid behavior occurs in three dimensions and can be divided into (1) planar growth and (2) vertical growth.

[0158] Regarding (1), the secondary replica formed initially grows outward, and the final replica size (area) can be determined during this process.

[0159] In addition, regarding (2), the vertical growth of the secondary structure toward the non-protrusion can determine the aspect ratio of the structure according to the Laplace pressure that stabilizes the surface.

[0160] Through the above Fig. 2a, the formation of a structure with an intaglio shape through a secondary replication method after positioning the biological surface on the upper electrode can be illustrated.

[0161] In addition, through FIG. 2b, the process of forming the original biological surface structure through a secondary replication method using the intaglio replica produced at this time as a master mold can be illustrated.

[0162] In addition, through FIG. 2c, it can be illustrated that the original biological surface structure is obtained from the above.

[0163] Figure 3 illustrates the electrohydrodynamic instability induced at the polymer-polymer interface in the electrohydrodynamic secondary replication method [Figure 3a] and a method to control it through numerical analysis [Figure 3b].

[0165] Figure 4 can illustrate a biological surface structure that is replicated by secondary instability.

[0166] At this time, Fig. 4a illustrates the process of replicating a given biological surface structure (cicada wing nanostructure) through an electrohydrosecondary replication method, and it can be seen that three-dimensional flow control of the polymer fluid is required.

[0167] Additionally, Fig. 4b is a scanning electron microscope image showing a tendency for the area and uniformity of the planar intaglio structure to improve with increasing growth rate (decreasing viscosity).

[0168] Fig. 4c is a scanning electron microscope image showing that the replica object (cicada wing nanostructure) was precisely replicated in three dimensions as a result of the experiment.

[0169] Figure 4d above illustrates that when the corresponding intaglio replica is fabricated with a water-soluble polymer, it can be easily dissolved in water.

[0171] FIG. 5 illustrates that polymer-polymer interface instability is effectively controlled through the deposition of a thin metal material (see Example 1).

[0172] Referring to Fig. 5a, it can be seen that when a metal thin film is not deposited, the replication fidelity is reduced due to instability at the polymer-polymer interface, but when a metal thin film is deposited, the development of such instability is suppressed and the replication fidelity is improved.

[0174] Figure 6 shows the result of generating the original biological surface structure using an intaglio replica coated with a metal thin film as a master mold.

[0175] In particular, Fig. 6 illustrates the improvement in area and uniformity according to planar growth control in the electric hydroelectric secondary replication method.

[0176] FIG. 6a illustrates that uniform large-area replication of a biological surface structure can be achieved through planar growth control.

[0177] Additionally, Fig. 6b illustrates, through scanning electron microscope observations, the results showing that the area and uniformity of the planar intaglio structure improve with increasing growth rate (decreasing viscosity).

[0178] FIG. 6c illustrates the result in which the replica object (cicada wing nanostructure) and the replicated structure exhibit the same shape.

[0179] Figure 6d illustrates the area (approx. 1 cm²) and uniformity of the replicated cicada wing nanostructure. A platinum thin film (thickness: 10 nm) was applied to effectively visualize the area of ​​the replicated structure, and it can be seen that the replicated area appears black as light is absorbed on the surface.

[0181] Figure 7 illustrates the result of the increase in aspect ratio / height of the replicated structure according to vertical growth control in the electric hydroelectric secondary replication method.

[0182] Figure 7a is a scanning electron microscope image illustrating the trend of the aspect ratio / height of the structure increasing with increasing electric field strength ().

[0183] Figure 7b illustrates the degree of replication fidelity of the structure as the electric field strength increases, based on a combination of experimental and simulation results.

[0184] In addition, Fig. 7c illustrates simulation results showing that the aspect ratio / height of the biological surface structure (cicada wing structure) improves with increasing electric field strength.

[0186] Figure 8 illustrates the results of an antibacterial effect realized on the surface of a replicated cicada wing nanostructure.

[0187] Referring to FIG. 8, the surface of a biological cicada wing exhibits an antibacterial effect in which bacteria cannot proliferate. As a result of precisely replicating the surface through the present invention, it can be confirmed that the antibacterial effect, which is an important feature of the surface, is also replicated.

[0188] Figure 8a illustrates the results of confocal fluorescence microscopy observing the tendency of bacteria (Escherichia coli) on a replication surface to die over time (Green: living Escherichia coli, Red: dead Escherichia coli).

[0189] Figure 8b illustrates the implementation of an antibacterial effect through a comparison between a replica surface and a control (PS thin film), and after 90 minutes, less than 20% of the bacteria on the replica surface were alive.

[0190] Figure 8c shows the results for the comparison group (PS thin film), where it can be seen that most of the bacteria remain alive even after 90 minutes.

[0191] Fig. 8d illustrates the bactericidal effect realized on the replicated surface, and it can be seen that bacteria are penetrated and killed on the surface of the precisely replicated cicada wing nanostructure.

[0193] Figure 9 illustrates the result of intaglio replication of a micro-nano hybrid structure of a rose petal (Rosa hybrid tea petal) as the biological surface to be replicated.

[0194] Figure 9a above shows an optical microscope image and a scanning electron microscope image of a rose petal surface structure.

[0195] The above rose petal has a three-dimensional micro-nano hybrid structure in which wrinkles of several hundred nanometers are mixed with a cone-shaped structure with rounded ends of several tens of micrometers.

[0196] Figure 9b above shows the result of producing an intaglio structure through a secondary replication method using rose petals as the upper electrode. At this time, it can be confirmed that uniform intaglio replication can be achieved over a large area (approx. 5 cm²).

[0198] Figure 10 is the result of producing the original rose petal surface structure using an intaglio replica of a rose petal surface coated with a metal thin film as a master mold.

[0199] Figure 10a illustrates results showing that the replication fidelity of the structure is improved by the increase in electric field strength as the voltage increases.

[0200] Figure 10b shows that a rose petal with hundreds of nanometer wrinkles mixed into a rounded cone structure of tens of micrometers was successfully replicated at 1.3 kV.

[0201] Figure 11 shows the area and uniformity of the micro-nano hybrid structure on the surface of a replicated rose petal.

[0202] Figure 11a illustrates the results showing that the vertical fidelity of the structure is improved by the increase in electric field strength as the voltage increases.

[0203] FIG. 11b shows the result (4 cm²) of a full replication of a micro-nano hybrid structure on the surface of a rose petal.

[0204] Further details regarding the experiment will be explained in detail in the following experimental examples.

[0206] The present invention will be explained in more detail below through manufacturing examples and experimental examples. These manufacturing examples and experimental examples are solely for the purpose of illustrating the present invention, and the scope of the present invention is not limited by these manufacturing examples and experimental examples.

[0208] Preparation Example: Preparation of a replica of a biological surface structure

[0209] First, a capacitor was prepared comprising a substrate having a liquid polymer layer composed of a thermoplastic polymer material formed to a thickness of 100 nm as a lower electrode, and a mask pattern composed of a bio-surface material spaced apart from the upper surface of the substrate as an upper electrode.

[0210] At this time, the above-mentioned distance is at least 1 μm.

[0211] Next, apply a voltage of 0.5 kV to the electrodes of the capacitor to 10 8 An electric field of V / m strength was generated to create secondary electrohydrodynamic instability, and a liquid polymer layer was formed into an intaglio pattern to produce an intaglio replica.

[0212] Next, an intaglio replica with a metal layer formed thereon was manufactured by applying a metal material composed of 10 nm to the surface of the intaglio replica.

[0213] Next, a capacitor is prepared comprising a master mold consisting of a substrate having a liquid polymer layer formed as a lower electrode and an intaglio replica having a metal layer formed spaced apart from the upper surface of the substrate as an upper electrode, and a voltage of 0.5 kV is applied to the electrodes of the capacitor to 10 8 An electric field of V / m strength was generated to create secondary electrohydrodynamic instability, forming a liquid polymer layer in an intaglio pattern to produce a three-dimensional bio-surface structure replica with an embossed shape.

[0215] Experimental Example 1: Experiment of Fig. 4 (confirmation of the replication method of biological surface structures due to secondary instability)

[0216] Figure 4 is a schematic diagram and scanning electron microscope image illustrating the replication method of a biological surface structure due to secondary instability.

[0217] Figure 4 uses a cicada wing (Oncotympana fuscata) as the subject for the biological surface structure.

[0218] In addition, the collected cicada wings were placed in acetone, ethanol, deionized water, etc., and washed for 10 minutes each.

[0219] Afterwards, the cicada wing was carefully cut to obtain a wing membrane with an area of ​​2×12 mm².

[0220] In addition, PMMA (poly(methyl methacrylate)) with a thickness of 100 nm or less was applied to a silicon substrate, and the cicada wing membrane was placed on top and fixed in a heat treatment environment of 120 °C for about 3 minutes.

[0221] At this time, PVA (polyvinyl alcohol) was added to deionized water and heated and stirred at 95 °C to prepare a solution of 2.5 to 7 wt%.

[0222] Subsequently, a PVA solution was applied onto a substrate using a spin coating technique to form a PVA thin film with a thickness of approximately 300 to 800 nm.

[0223] At this time, the upper electrode where the cicada wing is located was placed on the PVA thin film, and then a voltage was applied to perform an electro-hydro control technique.

[0224] At this time, the growth rate of the structure was changed by utilizing the decrease in PVA viscosity with increasing applied voltage and temperature.

[0225] In this embodiment To express the structure growth rate by defining it as 53.71 used .

[0226] When α was 2.44, a nanohole structure, which is an intaglio replica of a cicada wing nanostructure, was observed.

[0227] since Planar growth of the electro-hydro secondary replication method can be promoted as the amount increases.

[0228] especially, At 6.60, an engraved replica of a cicada wing nanostructure can be replicated across the entire surface.

[0230] Experimental Example 2: Experiment of Fig. 6 (using an intaglio replica coated with a metal thin film as a master mold)

[0231] Figure 6 shows the result of generating the original biological surface structure using an intaglio replica coated with a metal thin film as a master mold.

[0232] The intaglio replica obtained in Experimental Example 1 was subjected to an electrohydrosecondary replication method using an upper electrode after applying a 10 nm thick platinum thin film using a sputtering technique.

[0233] At this time, polystyrene (PS) was added to toluene and heated and stirred at 80 °C to prepare a solution of 3 to 8 wt%.

[0234] Subsequently, a PS solution was applied onto a substrate using a spin coating technique to fabricate a thin film with a thickness of approximately 200 to 800 nm.

[0235] At this time, the formed thin film was heat-treated at 150 °C for 30 minutes to evaporate the remaining solvent.

[0236] At this time, the heat treatment temperature was varied from 100 to 220 °C, and other parameters were fixed (applied voltage: 0.6 kV, thin film thickness: 600 nm, process time: 10 min) to vary the process viscosity.

[0237] At this time With fixed at 354813 Pa·s The growth trend of planar structures was observed according to the change (3.44–6.91).

[0238] When the value was 13.22, the area of ​​the replica structure was found to be similar to the original wing membrane area (2×12 mm²).

[0239] At this time, If is 25 or more, the area of ​​the replica structure becomes larger and reaches 1 cm².

[0241] Experimental Example 4: Experiment of Fig. 7 (observation of the vertical growth trend of the replicated structure)

[0242] Figure 7 shows the result of controlling the vertical growth of the cicada wing structure as the electric field strength increases.

[0243] Referring to Fig. 7, the vertical growth trend of the replicated structure with increasing electric field strength was observed under the same experimental conditions as Experimental Examples 1 and 2.

[0244] To represent electric field strength used ( ).

[0245] The above Replication features began to be observed when α was 154.39.

[0246] However, the electric field strength is insufficient, so the aspect ratio may be found to be 0.3 or less.

[0247] In addition, the above When α was 241.23, the aspect ratio was nearly 1, and When it was 347.38, it was 1.67 to 2.33.

[0248] Also, a perfect replica is It can be confirmed when ga is 472.82.

[0250] Experimental Example 3: Experiment of FIGS. 9 and 10 (using rose petals as the biological surface structure object)

[0251] Figure 9 shows the result of replicating a micro-nano hybrid structure on the surface of a rose petal through an electro-hydrosecondary replication method.

[0252] Figure 10 is an image illustrating a comparison of replication fidelity in the vertical direction as the applied voltage (electric field) strength increases.

[0253] Rose petals as a biological surface structure object ( Rosa hybrid tea petal) was used.

[0254] Rose petals were placed in acetone, ethanol, deionized water, etc., and washed for 10 minutes each, after which a tissue with an area of ​​25×25 mm² was obtained.

[0255] In addition, PDMS (polydimethylsiloxane) was mixed with a PDMS base (silicone elastomer base) and a PDMS curing agent (silicone elastomer curing agent) in a ratio of 10:1, and then air bubbles were removed under vacuum.

[0256] PDMS with a thickness of 200 nm or less was applied to a silicon substrate, and the rose petal tissue was placed on top and fixed. Subsequently, PDMS was applied to the substrate to form a thin film with a thickness of approximately 40 μm.

[0257] After placing the upper electrode, where the rose petals are located, on the PDMS thin film, an electro-hydroelectric control technique was performed by applying voltage.

[0258] At this time, in this embodiment according to the applied voltage 47.84 To express the structure growth rate by defining it as used .

[0259] In 7.78, it was confirmed that an intaglio replica of the rose petal micro-nano hybrid structure was replicated across the entire surface.

[0260] The intaglio replica obtained in this way was subjected to an electrohydrosecond replication method using a 10 nm thick platinum thin film applied by sputtering and then used again as the top electrode.

[0261] A solution of 10–15 wt% was prepared by adding PVDF (polyvinylidene fluoride) to the organic solvent DMF (dimethylformamide) and heating and stirring at 100 °C.

[0262] Subsequently, a PVDF solution was applied onto a substrate using a drop casting technique to fabricate a thin film with a thickness of approximately 35–45 μm.

[0263] The thin film formed at this time was heat-treated at 100 °C for 60 minutes to evaporate the remaining solvent.

[0264] In addition, the vertical growth trend of the replicated structure with increasing electric field strength was observed by varying the applied voltage from 0.4 kV to 1.3 kV and fixing other parameters (thin film thickness: 35–45 μm, process time: 10 min).

[0265] In addition, the structure begins to replicate at 0.4 kV, and the replication fidelity in the vertical direction can be improved as the applied voltage increases.

[0266] In addition, according to Fig. 10b, it can be seen that it is replicated identically to the given biological surface structure at 1.3 kV.

[0268] Experimental Example 3: Experiment of Fig. 11 (replication of rose petal surface)

[0269] Figure 11 shows the results of observing the replication area trend of rose petal hybrid structures according to planar growth.

[0270] An attempt was made to replicate the surface of a rose petal under the same conditions as Experimental Example 4 above.

[0271] At this time, the trend of the structure area according to planar growth was observed.

[0272] In addition, it was confirmed that almost no replication occurred when no applied voltage was applied, but as the applied voltage increased, an intact structural area was replicated.

[0273] Figure 11 above illustrates the trend of area increase due to planar growth.

[0275] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0276] The scope of the present invention is defined by the claims set forth below, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention.

Claims

Claim 1 A method for manufacturing a bio-surface structure replica, characterized by comprising: a step of preparing a capacitor including a substrate having a liquid polymer layer formed as a lower electrode and a mask pattern spaced apart from the upper surface of the substrate as an upper electrode; a step of manufacturing an intaglio replica by applying current to the electrodes of the capacitor to generate an electric field and generate secondary electrohydrodynamic instability to form an intaglio pattern of the liquid polymer layer; a step of manufacturing an intaglio replica having a metal layer formed by applying a metal material to the surface of the intaglio replica; and a step of preparing a capacitor including a master mold composed of a substrate having a liquid polymer layer formed as a lower electrode and an intaglio replica having a metal layer formed spaced apart from the upper surface of the substrate as an upper electrode, and a step of manufacturing a three-dimensional bio-surface structure replica having a relief shape by applying current to the electrodes of the capacitor including the master mold to generate an electric field and generate secondary electrohydrodynamic instability to form an intaglio pattern of the liquid polymer layer. Claim 2 A method for manufacturing a replica of a bio-surface structure according to claim 1, wherein, in the step of preparing a capacitor including the mask pattern, the mask pattern is a bio-surface structure. Claim 3 A method for manufacturing a replica of a biological surface structure according to claim 1, wherein, in the step of preparing a capacitor including the mask pattern, the mask pattern is characterized as having an uneven structure composed of alternating protrusions and non-protrusions. Claim 4 A method for manufacturing a replica of a biological surface structure according to claim 1, characterized in that, in the step of preparing a capacitor including the mask pattern, the gap between the substrate on which the polymer layer is formed and the mask pattern is 0 μm to 4 μm. Claim 5 A method for manufacturing a replica of a biological surface structure according to claim 1, characterized in that, in the step of preparing a capacitor including the mask pattern, the thickness of the liquid polymer layer is 150 nm to 2000 nm. Claim 6 A method for manufacturing a bio-surface structure replica according to claim 1, characterized in that the method is performed at a temperature above the glass transition temperature of a liquid polymer material. Claim 7 A method for manufacturing a bio-surface structure replica according to claim 1, characterized in that, in the step of manufacturing the intaglio replica, the voltage applied to the electrode is 0.5 kV to 1.8 kV. Claim 8 delete Claim 9 In claim 1, in the step of manufacturing the intaglio replica, the initial growth rate for forming the intaglio pattern is 10 2 s -1 to 10 7 s -1 A method for manufacturing a replica of a biological surface structure characterized by the following. Claim 10 In claim 9, in the step of manufacturing the above-mentioned intaglio replica, the initial growth rate is given by the following Equation 1 (τ m Method for manufacturing a replica of a biological surface structure characterized by following the reciprocal of ): <Equation 1> In Equation 1 above, η is the viscosity of the fluid thin film, γ is the surface tension of the fluid thin film, and ε r ε₀ is the permittivity of the fluid thin film, ε₀ is the vacuum permittivity, U is the intensity of the applied voltage, h₀ is the thickness of the dielectric (fluid thin film), and d is the distance between the two electrodes. Claim 11 A method for manufacturing a bio-surface structure replica according to claim 1, wherein, in the step of manufacturing an intaglio replica having a metal layer formed thereon, the metal layer is composed of an electrically conductive metal material. Claim 12 A method for manufacturing a bio-surface structure replica according to claim 1, wherein, in the step of manufacturing an intaglio replica having the metal layer formed thereon, the thickness of the metal layer is 10 nm to 20 nm. Claim 13 In claim 1, in the step of manufacturing the replica of the three-dimensional biological surface structure, the growth rate of the replica of the three-dimensional biological surface structure is given by the following Equation 1 (τ m Method for manufacturing a replica of a biological surface structure characterized by following the reciprocal of ): <Equation 1> In Equation 1 above, η is the viscosity of the fluid thin film, γ is the surface tension of the fluid thin film, and ε r ε₀ is the permittivity of the fluid thin film, ε₀ is the vacuum permittivity, U is the intensity of the applied voltage, h₀ is the thickness of the dielectric (fluid thin film), and d is the distance between the two electrodes.

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