KR100987987B1 - Stamp for manufacturing superhydrophobic micro / nano composite structure surface using anodized aluminum, method for manufacturing the same, and structure manufactured therefrom - Google Patents

Abstract

The present invention relates to a stamp capable of producing a superhydrophobic micro / nano composite structure surface in a simple process, and a manufacturing method thereof, and further to a composite structure produced using the stamp.

According to an aspect of the present invention, the present invention provides a method for producing a superhydrophobic micro / nano composite surface stamp, comprising the steps of: forming an anodized aluminum oxide template having a plurality of nano holes; Applying a photoresist on the anodized aluminum template; And removing the photoresist to form a plurality of photoresist holes such that the top surface of the anodized aluminum template is exposed, wherein the photoresist holes are micro-sized in at least one of the spacing and diameter of neighboring holes. Characterized in that formed to be.

Since the stamp of the present invention can be used by solidifying a photoresist, it can be produced at low cost depending on the application.

From the viewpoint of the process, since a separate alignment process is not necessary, the process is not only easy at the time of mass replication, but also has a structural advantage that can be easily separated from the molded article. In addition, since the microstructure of the stamp is designed using a photoresist, there is an advantage in that it is possible to form a variety of patterns while maintaining the micro / nano composite structure. In addition, the stamp of the present invention can be manufactured from metal, thereby providing durability. It is excellent and can be used for a long time.

Superhydrophobic, Hybrid, Stamped, Mold

Description

Stamp for superhydrophobic micro / nano hybrid surface based on anodic aluminum oxide, method of manufacturing the same, and product manufactured with the same}

The present invention relates to a stamp for producing a superhydrophobic surface and a method for manufacturing the same, and more particularly, to a stamp capable of producing a superhydrophobic surface in which nano and micro scales are mixed based on anodized aluminum. It is about.

The invention also relates to a composite structure produced by a stamp.

As a representative method for producing superhydrophobic surfaces, a method of coating an object surface with a chemical having a low surface energy such as Teflon is known. However, this method has also been found to be limited in obtaining water contact angles of more than 150 °, so that the formation of physical structures is inevitable in obtaining superhydrophobic functional surfaces.

Some degree of superhydrophobic properties can be obtained from surfaces containing simple microstructures or nanostructures, and geometrical designs can be made using the Cassie-Baxter equation. For example, vertical growth of carbon nanotubes, molding using an alumina template, manufacturing a microstructure through a MEMS process, an exposure process and a microstructure or nanostructure manufacturing method through an electron beam, and the like.

Recently, it has been found that in order to manufacture a superhydrophobic surface with self-cleaning capability, it is necessary to simultaneously have a sliding angle characteristic of 5 ° or less in addition to a contact angle of more than 150 °. A complex structure with a structure is essential.

As a result, recent research on the manufacture of superhydrophobic surfaces has progressed in the direction of simulating or modeling micro / nano composite structures existing in nature such as lotus leaves and gecko feet.

The fabrication of the micro / nano composites modeled on the lotus leaves has been mainly done in a chemical manner, and the superhydrophobic surface fabrication technique has been very active worldwide for many years. Representatively, for example, a phase separation method in which a very simple polymer such as isotactic polypropylene is conditioned in a suitable solvent, a method of realizing a superhydrophobic surface through micelle aggregation, silica nanoparticles There is a method using a self assembly phenomenon, a method of coating the surface of the carbon nanotubes grown on a micro-scale with PTFE.

This chemical method has the advantage of being easy to process, but it is difficult to control a certain shape to the intended size because the micro / nano structure is difficult to predict by chemical reaction. In addition, it is also impossible to selectively form such a shape at a desired position, control the degree of surface wetting, and not mass replication easily.

Recently, according to these disadvantages, a technique for forming a micro / nano composite structure by a mechanical molding method has been proposed beyond the chemical method. Representative two-stage thermoforming capillary lithography method, with reference to Figure 1 will be briefly described the specific process.

As shown in FIG. 1, first, spin coating is performed on a substrate to form a uniform polymer thin film. A polydimethylsiloxane (PDMS) mold having a negative pattern is contacted on the formed polymer thin film. The temperature is then applied above the glass transition temperature of the polymer to induce capillary action to form microstructures. Subsequently, a polyurethane acrylate (polyurethaneacrylate, PUA) mold having a nano-sized intaglio pattern is contacted on the formed microstructure, and the nanostructure is formed on the preformed microstructure through secondary heating.

Compared to the above-described chemical method, this method has the advantage of enabling precise processing and controlling the degree of surface wetting. However, there is a disadvantage in that the pre-formed microstructure collapses when the thermoforming process conditions are not secured. In order to compensate for these drawbacks, a two-step UV molding capillary molding process has been developed instead of thermoforming.

However, these two-stage thermoforming or UV forming capillary molding processes are commonly required for precise alignment (alignment) when contacting a PUA mold with a second nanoscale engraved pattern, thus making the process difficult and not easy to bulk replicate. Not suitable for In addition, these methods apply a pattern to the thin film after coating the polymer thin film on the substrate, there is a disadvantage that can not be used directly when manufacturing a single material in a bulk form.

It is therefore an object of the present invention to provide a stamp or a mold comprising the same which allows for mass replication of a superhydrophobic surface in a simple process.

In addition, the present invention provides a method of manufacturing a stamp or a mold to facilitate the implementation of various, precise patterns in the stamp.

The above object is a method of manufacturing a stamp for producing a super hydrophobic micro / nano composite structure according to an aspect of the present invention, comprising: forming an anodized aluminum template having a plurality of nanopores; Applying a photoresist on the anodized aluminum template; And removing the photoresist to form a plurality of photoresist holes such that the top surface of the anodized aluminum template is exposed, wherein the photoresist holes are micro-sized in at least one of the spacing and diameter of neighboring holes. It can be achieved by the manufacturing method of the stamp for producing a super hydrophobic micro / nano composite structure, characterized in that formed to be.

In addition, the above object is a method of manufacturing a stamp for producing a super hydrophobic micro / nano-composite surface according to another aspect of the present invention, comprising the steps of: forming an anodized aluminum template having a plurality of nano holes; Applying a photoresist on the anodized aluminum template; Removing the photoresist to form a plurality of photoresist holes to expose the top surface of the anodized aluminum template; Depositing a metal on the exposed anodized aluminum template by removing the photoresist; And removing the remaining photoresist, wherein the diameter of the photoresist hole is formed to be micro sized, and may also be achieved by a method of manufacturing a super hydrophobic micro / nano composite structure surface stamp. have.

Here, the step of depositing a metal on the anodized aluminum template may be formed by one of sputtering, ion beam deposition, laser induced reflow, CVD, electroplating and electroless plating. In addition, the photoresist holes may be configured as micro-sized sidewalls.

In addition, the above object is, according to an aspect of the present invention, a method for manufacturing a superhydrophobic micro / nano composite surface manufacturing stamp, polishing the surface of the bulk aluminum to uniform the surface; Oxidizing the aluminum surface to form a nano dimple structure on the aluminum surface; Applying a photoresist on the aluminum surface; And removing the photoresist to form a plurality of photoresist holes to expose the aluminum surface, wherein the photoresist holes are formed such that at least one of the spacing and diameter of neighboring holes is micro sized. It can be achieved by a method for producing a stamp for producing a super hydrophobic micro / nano composite surface characterized in.

In the above manufacturing methods, the photoresist holes may be made of micro-sized sidewalls.

In addition, it is possible to further include the step of producing an intaglio circle by performing electroplating in a state where the photoresist is patterned and solidified.

In addition, the object is a stamp for producing a super hydrophobic micro / nano composite surface according to another aspect of the present invention, a nano structure layer consisting of anodized aluminum oxide (AAO) having a plurality of nano holes; And a microstructure layer disposed on the nanostructure layer, wherein a plurality of holes are formed with a micro-spacing distance from a neighboring hole, and the upper surface of the nanostructure layer is exposed from the plurality of holes. It can also be achieved by a stamp for producing a superhydrophobic micro / nano composite structure, characterized in that it comprises.

Here, at least one of the diameter and height of the hole formed in the microstructure layer is preferably formed in a micro size. Meanwhile, the microstructure layer may be formed of solidified photoresist or metal.

The present invention also features composite structures having a superhydrophobic micro / nano composite surface that can be fabricated using the stamp.

Since the stamp of the present invention can be used by solidifying a photoresist, it can be produced at low cost depending on the application.

From the viewpoint of the process, since a separate alignment process is not necessary, the process is not only easy at the time of mass replication, but also has a structural advantage that can be easily separated from the molded article. In addition, since the microstructure of the stamp is designed using a photoresist, there is an advantage in that the pattern can be variously formed while maintaining the micro / nano composite structure.

In addition, the stamp of the present invention can be made of a metal is excellent in durability, there is an advantage that can be used for a long time.

Hereinafter, with reference to the accompanying drawings will be described a specific embodiment of the present invention.

2 is a flowchart illustrating a method of manufacturing a stamp according to a first embodiment of the present invention.

Referring to FIG. 2, the manufacturing process of the stamp according to the first embodiment of the present invention starts with forming an anodized aluminum oxide (AOA) template having a plurality of nano holes (S1).

The manufacturing process of the AAO template will be described in more detail with reference to FIGS. 3A to 3D. 3A through 3D are cross-sectional views schematically illustrating a two-step oxidation process for fabricating an anodized aluminum template constituting a part of a stamp according to an embodiment of the present invention. Referring to FIGS. same:

First, prior to the oxidation process, as shown in FIG. 3a, a 99.999% aluminum substrate having a size of 10 mm x 24 mm having a thickness of 1 mm is electropolished to evenly surface the substrate. Electrolytic polishing of aluminum substrate is applied in a solution of 1: 4 volume ratio of perchloric acid (HClO ₄ ) and ethanol (C ₂ H ₅ OH) with the substrate as the anode and platinum as the cathode. Run for about 3 minutes in one condition. At this time, the temperature of the solution is maintained at 7 ℃, the solution is stirred at a constant rate.

Next, a primary oxidation process is performed for about 12 hours by applying a voltage of 195 V at a constant temperature of 0 ° C. in a 0.1 M phosphoric acid (H ₃ PO ₄ ) solution using a polished aluminum substrate as an anode and platinum as a cathode. . The aluminum oxide layer formed in the primary oxidation process has nano holes irregularly arranged as shown in FIG. 3B.

Next, the aluminum substrate on which the aluminum oxide layer was formed was immersed in a mixed solution of 1.8 wt.% Chromic acid (H ₂ CrO ₄ ) and 6 wt. The aluminum oxide layer is etched. When all of the aluminum oxide layer formed through the primary oxidation process is etched, as shown in FIG. 3C, nano-dimple structures regularly arranged on the aluminum substrate are formed. By performing a secondary oxidation process based on this regular nano dimple structure, a denser and ordered nano hole structure can be obtained.

Thus, an oxidation process is performed on the aluminum substrate of FIG. 3C by the same method as the above-described first oxidation process for about 20 minutes to form an aluminum oxide layer having a thickness of about 2 μm. Thereafter, chemical treatment of 5 wt.% Phosphoric acid at a constant temperature of 30 ° C. changes the diameter of the nanopores to obtain the desired nanopores structure. In addition, if desired, the diameter and depth of the nanopores may be selectively changed by changing the magnitude of the applied voltage, the voltage application time, the solution temperature, the kind of the solution, and the like during the secondary oxidation process.

Scanning electron microscope (SEM) photographs of AAO templates formed through the process up to now are shown in FIGS. 4A and 4B.

Referring to FIG. 4A, which is a plan view of an AAO template taken at a higher magnification than FIG. 4B, it can be seen that the nano holes are regularly densely aligned at positions corresponding to the vertices of the hexagon. More specifically, the diameter and depth of the AAO nano holes fabricated on an aluminum substrate of 10 mm × 24 mm were about 200 nm and 1 μm, respectively, and the distance between the nano holes was 450 nm.

Referring now to FIG. 2 again, the process after formation of the AAO template (S1) in the method for manufacturing a stamp according to the first embodiment of the present invention will be described in sequence.

First, a photoresist is applied onto an AAO template formed through two oxidation processes (S2).

Next, the photoresist applied by a photolithography process is etched in a desired pattern (S3).

Although it is possible to etch in various patterns as desired, in the first embodiment of the present invention, at least one of the gap between the holes and the diameter of the photoresist holes is formed while forming a plurality of holes having a micro size diameter in the photoresist. The etching is performed so that one is micro sized.

As a result, a schematic cross-sectional view of the structure in which the photoresist 3 is patterned on top of the AAO template is shown in FIG.

Referring to FIG. 5, it can be seen that the photoresist 3 is solidified on the upper portion of the photoresist 3 without penetrating into the nano-holes of the lower template 1. This is due to the viscosity of the photoresist 3, and in some cases penetrates the nanopores, but most of them are solidified in such a way that they do not penetrate the nanopores and block the upper portion of the pores.

The structure shown in Figure 5 can also be used as a micro hydrophobic superhydrophobic stamp, which will be discussed in more detail below.

Next, the metal is laminated on the surface of the AAO template exposed through the hole of the photoresist (S4). At this time, a variety of methods can be selectively used for laminating metals. For example, any of sputtering, ion beam deposition, laser induced reflow, CVD, electroplating, and electroless plating can be used.

In particular, in the case of laminating the metal by electroplating, the electroplating may be performed until the hole of the photoresist is filled after the seed metal is laminated by the sputtering method. Platinum or carbon may be used as a counter electrode, and the seed electrode may be dipped in an electrolytic solution such as sulfuric acid or phosphoric acid, and then voltage may be applied to both electrodes. The amount of metal to be laminated is adjusted according to the concentration of the electrolyte, the strength of the applied voltage, and the like. Since the general method of performing such electroplating has been described above and is well known, more detailed description thereof will be omitted.

Finally, the stamp 10 composed of the metals 1 and 5 containing aluminum oxide can be completed by removing the remaining photoresist 3 (S5).

A cross section of the completed stamp 10 is shown in FIG. The stamp shown in FIG. 6 can be seen that the surface pattern is similar to that of the stamp shown in FIG. 5, that is, compared to the stamp completed after the etching process of step S3, but with a difference in material.

Therefore, according to the first embodiment of the present invention, it is possible to use the structures shown in FIGS. 5 and 6 as stamps, respectively. However, in terms of materials, the stamp shown in FIG. 5 is difficult to use for a long time or an excessive number of times, and has a disadvantage in that the polymer used for casting is limited.

One skilled in the art will be able to select one of several methods for a method of mass duplication using stamps manufactured according to the first embodiment of the present invention.

For example, it is possible to make a large number of copies by directly stamping stamps according to an embodiment of the present invention, or to use it as a prototype to make a new PDMS mold or the like. In addition, it may be used in fields in which injection molding, hot embossing technology, and nano imprint technology are used.

FIG. 7 shows a cross section of a polymer that is duplicated by casting the polymer onto the stamp of FIG.

Referring to FIG. 7, it can be seen that each of the protrusions is divided into two parts, the upper and lower layers. That is, the upper layer is a nanostructure layer composed of nano-sized holes and pillars, and the lower layer is a microstructure layer supporting the nanostructure layer and having a micro-sized separation distance from neighboring protrusions.

As shown in Fig. 8, this structure 10 exhibits superhydrophobic properties as a micro / nano composite structure. Although the surface structure shown in Fig. 8 is configured so that the protruding portions are spaced at regular intervals, it is possible to design an arbitrary pattern during the etching process of the photoresist.

It will be appreciated by those skilled in the art that, in contrast to the first embodiment, as a method for producing a stamp made of metal, electroplating can be used. For example, in the stamp shown in Fig. 5, nickel electroplating can make an intaglio circle having the same shape, thereby replacing a process such as deposition of metal and removal of photoresist. It should be noted that the first embodiment of the present invention is to form a microstructured layer of photoresist or metal based on AAO, which includes fabricating a metal stamp by nickel electroplating.

The first embodiment of the present invention described so far has been based on AAO based on which a second oxidation process is performed.

Hereinafter, a method of manufacturing a stamp having a different composite structure surface according to the second embodiment of the present invention, and a stamp and the composite structure thereby will be described.

9A to 9E are cross-sectional views schematically illustrating a manufacturing process of a stamp according to a second exemplary embodiment of the present invention. Referring to FIGS. 9A to 9E, the manufacturing process is as follows.

First, the bulk aluminum shown in FIG. 9A is planarized as shown in FIG. 9B prior to the oxidation process. That is, a 99.999% aluminum substrate having a size of 10 mm by 24 mm and having a thickness of 1 mm is electropolished to even the surface of the substrate as shown in FIG. 9B. Electrolytic polishing of aluminum substrates was carried out in a solution of 1: 4 volume ratio of perchlorate (HClO ₄ ) and ethanol (C ₂ H ₅ OH) in which the substrate was used as the anode and platinum as the cathode. It is performed for about 3 minutes in an applied state. At this time, the temperature of the solution is maintained at 7 ℃, the solution is stirred at a constant rate.

Next, an oxidation process is performed for about 12 hours by applying a voltage of 195 V at a constant temperature of 0 ° C. in a 0.1 M phosphoric acid (H ₃ PO ₄ ) solution using a polished aluminum substrate as an anode and platinum as a cathode. The aluminum oxide layer formed in the oxidation process forms rough nano holes as shown in FIG. 9C.

Next, the aluminum substrate was immersed in a mixed solution of 1.8 wt.% Chromic acid (H ₂ CrO ₄ ) and 6 wt.% Phosphoric acid at a constant temperature of 65 ° C. for about 5 hours to etch an irregular layer of aluminum oxide formed during the first oxidation process. do. As a result, as shown in FIG. 9D, a regular nano-dimple structure is formed on the aluminum upper surface.

Next, after the photoresist is applied to the upper surface on which the nano dimple structure is formed, the photoresist applied by a photolithography process is etched in a desired pattern. Fig. 9E shows a cross section after the photoresist is patterned to have circular holes as in the first embodiment.

Looking at the stamp of Fig. 9E in more detail, the left and right widths of the photoresist are formed in a micro size, and the aluminum exposed through the photoresist holes has a surface of a nano size dimple structure.

A schematic cross section of a structure produced, for example, by injection molding using such a stamp is schematically illustrated in FIG. 10 as an example. Compared with the structure of FIG. 7 fabricated in accordance with the first embodiment, the structure shown in FIG. 10 has a disadvantage that there is less space in the nanostructure layer, but it has an advantage of reducing the oxidation process once, so that the manufacturing process is relatively It has the advantage of being simpler.

FIG. 11A is a SEM photograph of a microfabricated structure produced by injection molding using a stamp as shown in FIG. 9E, and FIG. 11B is an enlarged SEM photograph of a surface of a nano dimple structure formed on each microstructure.

Referring to FIG. 11A, it can be seen that the protruding circular island-shaped portions are spaced in units of micro size. In addition, in Fig. 11B, it can be seen that dense nanoscale dimples are formed on the upper surface of each of the protruding portions.

A cross section of a stamp according to a second embodiment of the invention is shown in Fig. 9E. As with the first embodiment, it will be appreciated that a stamp consisting of the metal can be produced by removing the photoresist after applying the metal. Of course, in this case, as described above, it is preferable to form the gaps between the photoresists to have a micro size.

Although only some embodiments of the present invention have been described so far, those skilled in the art will understand that various modifications, substitutions, and the like can be made without departing from the spirit and scope of the present invention.

For example, the photolithography process discussed in the embodiments of the present invention may be replaced with another electron beam etching process or the like. In addition, the photoresist hole formed in the photoresist according to the pattern of the photoresist is not limited to a circle, and may be formed in various shapes. For example, the photoresist apertures can form a line pattern that is open toward a certain direction.

Note that the micro size referred to in the embodiment of the present invention is generally used in the art to refer to a size in the range of 1 to 1000 micrometers, and the nano size is used to encompass the size in the range of 1 to 1000 nanometers. It is a term used to refer to, so that such phrases are not misleading to those skilled in the art to clearly understand the invention.

Accordingly, the examples of the present invention should not be construed as limiting the present invention, but are to be understood as exemplary embodiments of the present invention. The spirit and scope of the present invention are defined by the following claims, and the scope should be construed to include the equivalent range.

1 schematically illustrates a two-step thermoforming capillary lithography process.

2 is a flowchart illustrating a method of manufacturing a stamp according to a first embodiment of the present invention.

3A to 3D schematically illustrate the manufacturing process of the AAO template.

4A and 4B are scanning electron microscope (SEM) images of an AAO template.

5 is a schematic cross-sectional view of a structure in which a photoresist is patterned on an AAO template.

6 is a cross-sectional view of the completed stamp after all the processes according to the flow chart of FIG.

FIG. 7 shows a cross section of a polymer that is duplicated by casting the polymer onto the stamp of FIG.

FIG. 8 is a view showing superhydrophobic properties as a micro / nano composite structure of a polymer cast according to an embodiment of the present invention.

9A to 9E schematically illustrate a manufacturing process of a stamp according to a second embodiment of the present invention.

10 is a schematic diagram of a structure manufactured according to the second embodiment of the present invention.

11A and 11B are SEM photographs of structures fabricated in accordance with a second embodiment of the present invention.

Claims (12)

In the manufacturing method of the stamp for producing a superhydrophobic micro / nano-composite structure, Forming an anodized aluminum template having a plurality of nanopores; Applying a photoresist on the anodized aluminum template; And Removing the photoresist to form a plurality of photoresist holes to expose the top surface of the anodized aluminum template; And the photoresist holes are formed such that at least one of the spacing and the diameter of neighboring holes becomes micro size. In the manufacturing method of the stamp for producing a superhydrophobic micro / nano-composite structure, Forming an anodized aluminum template having a plurality of nanopores; Applying a photoresist on the anodized aluminum template; Removing the photoresist to form a plurality of photoresist holes to expose the top surface of the anodized aluminum template; Depositing a metal on the exposed anodized aluminum template by removing the photoresist; And Removing the remaining photoresist, And a diameter of the photoresist hole is formed to be a micro size. The method of claim 2, The step of depositing a metal on the anodized aluminum template for superhydrophobic micro / nano composite structure surface is formed by one of sputtering, ion beam deposition, laser induced reflow, CVD, electroplating and electroless plating method. Method of making a stamp. In the manufacturing method of the stamp for producing a superhydrophobic micro / nano-composite structure, Polishing the surface of the bulk aluminum to even the surface; Oxidizing the aluminum surface to form a nano dimple structure on the aluminum surface; Applying a photoresist on the aluminum surface; And Removing the photoresist to form a plurality of photoresist holes to expose the aluminum surface; And the photoresist holes are formed such that at least one of the spacing and the diameter of neighboring holes becomes micro size. The method according to any one of claims 1 to 4, And the photoresist hole is formed of micro-sized sidewalls. The method according to claim 1 or 4, The method of manufacturing a stamp for producing a surface of a super hydrophobic micro / nano composite structure further comprising the step of producing an intaglio circle by performing electroplating in a state where the photoresist is patterned and solidified. In the stamp for producing a superhydrophobic micro / nano composite structure, A nanostructure layer composed of anodized aluminum oxide (AAO) having a plurality of nanopores; And A microstructure layer disposed on the nanostructure layer, wherein a plurality of holes are formed in a micro-sized gap with a neighboring hole, and the upper surface of the nanostructure layer is exposed in the plurality of holes. Stamp for producing a super hydrophobic micro / nano composite structure, characterized in that. The method of claim 7, wherein At least one of the diameter and height of the hole formed in the microstructure layer is formed for the micro hydrophobic micro / nano composite structure surface stamp. The method of claim 7, wherein The microstructure layer is a stamp for producing a super hydrophobic micro / nano composite structure, characterized in that formed by a solidified photoresist. The method of claim 7, wherein The microstructure layer is stamped for producing a super hydrophobic micro / nano composite structure, characterized in that the metal is formed. In the stamp for producing a superhydrophobic micro / nano composite structure, A nanostructure layer having a plurality of nano dimples; And A microstructure layer disposed on the nanostructure layer, wherein a plurality of holes are formed in a micro-sized gap with a neighboring hole, and the upper surface of the nanostructure layer is exposed in the plurality of holes. Stamp for producing a super hydrophobic micro / nano composite structure, characterized in that. A composite structure having a superhydrophobic micro / nano composite surface, 12. A composite structure having a superhydrophobic micro / nano composite surface formed by the stamp of any one of claims 7 to 11, wherein the micro and nano-sized structure layer has a mixed surface.

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