US20150368824A1

US20150368824A1 - Water and oil ultra-repellent structure and manufacturing method therefor

Info

Publication number: US20150368824A1
Application number: US14/766,649
Authority: US
Inventors: Si Hyung LIM; Sumit BARTHWAL
Original assignee: Industry Academic Cooperation Foundation of Kookmin University
Current assignee: Industry Academic Cooperation Foundation of Kookmin University
Priority date: 2013-02-08
Filing date: 2014-02-06
Publication date: 2015-12-24
Also published as: WO2014123376A1; KR20140101193A; KR101569460B1

Abstract

Provided are a superhydrophobic/superoleophobic structure and a method of manufacturing the superhydrophobic/superoleophobic structure. The superhydrophobic/superoleophobic structure includes: a roughened primary structure formed on a surface of a metal base; nanopores formed in the roughened primary structure; and a hydrophobic/oleophobic layer formed on a surface of the roughened primary structure. The superhydrophobic/superoleophobic structure makes a large contact angle and a small sliding angle with both aqueous solutions and oily solutions, thereby having a high degree of superhydrophobicity/superoleophobicity. In addition, the superhydrophobic/superoleophobic structure may be formed on large or curved structural objects by the manufacturing method without using a special device.

Description

TECHNICAL FIELD

The present invention relates to a superhydrophobic/superoleophobic structure and a method of manufacturing the superhydrophobic/superoleophobic structure, and more particularly, to a superhydrophobic/superoleophobic structure having a very high degree of superhydrophobicity/superoleophobicity and usable for imparting superhydrophobicity/superoleophobicity even to curved or large structural objects without using a special device, and a method of manufacturing the superhydrophobic/superoleophobic structure.

BACKGROUND ART

Generally, hydrophobicity and oleophobicity refer to hardly wettable properties with respect to water and oil. In the related art, when the contact angle between a solid surface and water contacting the solid surface is 150° or greater and the contact angle between the solid surface and oil contacting the solid surface is 150° or greater, the solid surface is considered as having superhydrophobicity/superoleophobicity.
Much attention has been given to superhydrophobic surfaces making a contact angle of 150° or greater with water because such surfaces are important in fundamental research and practical applications. Superhydrophobicity and superoleophobicity refer to hardly wettable properties of a material with respect to water and oil. For example, contaminants are naturally removed from leaves of plants, wings of insets, or wings of birds without any special actions, or contaminants are not attached thereto. This is because leaves of plants, wings of insets, and wings of birds have superhydrophobicity.
Wettability is one of important properties of solid materials and is mainly determined by both the chemical composition and the geographical micro/nano structure of solid. There have been increasing interest in wettable surfaces because of potential applicability in various fields such as oil-water separation, anti-reflection, anti-adhesion between bodily parts, anti-sticking, anti-pollution, self washing, and turbulent flow prevention.
Aluminum has a high degree of thermal and electric conductivity and is relatively light, inexpensive, and easily machinable compared to copper. Therefore, aluminum is widely used in many industrial fields. Recently, several methods of manufacturing superhydrophobic aluminum have been reported. However, much attention has not yet been given to methods of imparting superhydrophobicity/superoleophobicity to aluminum bases.

DETAILED DESCRIPTION OF THE INVENTION

Technical Problem

A first technical object of the present invention is to provide a superhydrophobic/superoleophobic structure having a high degree of superhydrophobicity/superoleophobicity and thus making a large contact angle with aqueous solutions and oily solutions.
A second technical object of the present invention is to provide a method of manufacturing a superhydrophobic/superoleophobic structure for easily imparting superhydrophobicity/superoleophobicity even to large or curved structural objects without using a special device.
A third technical object of the present invention is to provide an electronic device or a mechanical device including a superhydrophobic/superoleophobic structure.
However, aspects of the present disclosure are not limited thereto. Additional aspects will be set forth in part in the description which follows, and will be apparent from the description to those of ordinary skill in the related art.

Technical Solution

According to an inventive concept for realizing the first technical object of the present invention, there is provided a superhydrophobic/superoleophobic structure including: a roughened primary structure formed on a surface of a metal base; nanopores formed in the roughened primary structure; and a hydrophobic/oleophobic layer formed on a surface of the roughened primary structure.
The nanopores may have a diameter of 1 nm to 300 nm. Preferably, the nanopores may have a diameter of 10 nm to 50 nm. Particularly, the metal base may be an aluminum (Al) base.
In addition, the roughened primary structure may include identical or different sidewalls and plateaus that are continuously arranged. In this case, each of the plateaus may have a horizontal length within a range of 500 nm to 5 μm. In addition, the nanopores may be formed in the sidewalls and the plateaus of the roughened primary structure in directions substantially perpendicular to the sidewalls and the plateaus.
In addition, the hydrophobic/oleophobic layer may include fluorine (F). Particularly, the hydrophobic/oleophobic layer may be a fluorine-containing silane compound layer or a fluorine-containing thiol compound layer. In addition, the hydrophobic/oleophobic layer may not be substantially formed in the nanopores.
According to an inventive concept for realizing the second technical object of the present invention, there is provided a method of manufacturing a superhydrophobic/superoleophobic structure, the method including: etching a metal base with an acid so as to form a roughened primary structure on the metal base; anodizing the metal base on which the roughened primary structure is formed, so as to form nanopores in the roughened primary structure; and forming a hydrophobic/oleophobic layer on a surface of the roughened primary structure.
The anodizing of the metal base may be performed for 3 minutes to 25 minutes. In addition, the etching of the metal base may be performed by a wet etching method. Particularly, the etching of the metal base may be performed using a hydrochloric acid solution. In addition, the metal base may be an aluminum (Al) base.
Optionally, the method may further include drying the metal base at a temperature of about 50° C. to about 200° C. between the etching of the metal base and the anodizing of the metal base.
According to an inventive concept for realizing the third technical object of the present invention, there are provided an electronic device or a device for transportation including the superhydrophobic/superoleophobic structure. Non-limiting examples of the electronic device and the device for transportation vehicles may include: automobile/airplane/train/ship interior or exterior devices; automobile/airplane/train/ship or home/office/industrial heating, refrigerating, and air-conditioning systems (air conditioners and heat pumps); televisions; cellular phones; computer systems; portable computers; monitors; phones; printers; keyboards; mouses; pumps; fluid transfer pipes; powder transfer pipes; tanks storing fluids for transportation; illumination devices; and backlight units.

Advantageous Effects of the Invention

The superhydrophobic/superoleophobic structure of the present invention makes a very large contact angle with both aqueous solutions and oily solutions owing to its superior superhydrophobicity/superoleophobicity. In addition, the superhydrophobic/superoleophobic structure may be formed on large or curved structural objects by the manufacturing method of the present invention without using a special device.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a superhydrophobic/superoleophobic structure according to an embodiment of the inventive concept.

FIG. 2 is an enlarged view illustrating a portion II in FIG. 1.

FIG. 3 is a cross-sectional view illustrating one of plateaus and one of sidewalls shown in FIG. 2.

FIG. 4 is a flowchart illustrating a method of manufacturing a superhydrophobic/superoleophobic structure according to an embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view illustrating a superhydrophilic/superoleophilic structure according to an embodiment of the present invention.

FIGS. 6A and 6B are scanning electron microscope (SEM) images of a surface of an aluminum base of Example 1 taken immediately after operation 2 at magnifications of about 10,000 times and about 50,000 times, respectively.

FIGS. 7A and 7B are SEM images showing a surface of an aluminum base at magnifications of about 10,000 times and about 50,000 times, respectively, the aluminum base being prepared by setting the etching time in operation 2 of Example 1 to 6 minutes.

FIGS. 8A to 8D are SEM images of the surface of the aluminum base of Example 1 taken immediately after operation 3 at magnifications of about 10,000 times, about 30,000 times, about 100,000 times, and about 300,000 times, respectively.

FIGS. 9A and 9B are SEM images of a surface of an aluminum base of Comparative Example 1 prepared through an anodizing operation without operation 2 of Example 1, the SEM images being taken immediately after the anodizing process at magnifications of about 10,000 times and about 100,000 times.

FIG. 10 shows plan and side images of water, glycerol, ethylene glycol (EG), olive oil, and hexadecane dripped on a superhydrophobic/superoleophobic structure of Example 1.

FIG. 11 is a graph illustrating average contact angles of water, glycerol, ethylene glycol, olive oil, and hexadecane with each of samples prepared in Examples 2 to 5.

FIGS. 12A to 12F are sequential images taken when water and olive oil were dripped onto a surface of a sample.

BEST MODE

The inventive concept will now be described in detail with reference to the accompanying drawings, in which preferred embodiments are illustrated. The inventive concept may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. The embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art. In the accompanying drawings, like reference numerals refer to like elements throughout. In addition, elements and regions are schematically illustrated in the accompanying drawings. Therefore, the inventive concept is not limited to relative sizes or distances shown in the accompanying drawings.
Although terms such as first and second are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from other elements. For example, a first element may be termed a second element, or a second element may be termed a first element without departing from the teachings of the inventive concept.
In the following description, technical terms are used only for explaining specific embodiments, and are not purposes of limitation. The terms of a singular form may include plural forms unless referred to the contrary. The meaning of ‘include’ or ‘comprise’ specifies a property, a fixed number, a step, a process, an element, a component, and a combination thereof but does not exclude other properties, fixed numbers, steps, processes, elements, components, and combinations thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the inventive concept belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In the present disclosure, the slashes (/) used in “hydrophobic/oleophobic” and “superhydrophobic/superoleophobic” refer to “and.” That is, the expression “hydrophobic/oleophobic” indicates “hydrophobic and oleophobic,” and the expression “superhydrophobic/superoleophobic” indicates “superhydrophobic and superoleophobic.”
The present invention provides a superhydrophobic/superoleophobic structure including: a roughened primary structure formed on a surface of a metal base; nanopores formed in the roughened primary structure; and a hydrophobic/oleophobic layer formed on a surface of the roughened primary structure.
FIG. 1 is a perspective view illustrating a superhydrophobic/superoleophobic structure 100 according to an embodiment of the inventive concept, and FIG. 2 is an enlarged view illustrating a portion II in FIG. 1.
Referring to FIG. 1, the superhydrophobic/superoleophobic structure 100 has a pipe shape. Although the superhydrophobic/superoleophobic structure 100 is illustrated as having a pipe shape in FIG. 1, the superhydrophobic/superoleophobic structure 100 is not limited thereto. For example, the superhydrophobic/superoleophobic structure 100 may have another shape such as a planar shape, a curved shape, a spherical shape, or a combination thereof.
The superhydrophobic/superoleophobic structure 100 may include a metal such as copper (Cu), titanium (Ti), aluminum (Al), tungsten (W), zinc (Zn), or tin (Sn) as a base material. Particularly, the base material may preferably be aluminum (Al). However, the base material is not limited thereto.
Referring to FIG. 2, the superhydrophobic/superoleophobic structure 100 may include: plateaus 104 substantially parallel with the surface of the superhydrophobic/superoleophobic structure 100; and sidewalls 102 substantially perpendicular to the plateaus 104. The expression “the sidewalls 102 are substantially perpendicular to the plateaus 104” indicates that the sidewalls 102 connect the plateaus 104 having various levels and help to distinguish the plateaus 104 rather than the angle between the sidewalls 102 and the plateaus 104 being definitely 90°.
In addition, the sidewalls 102 and the plateaus 104 may be continuously arranged in a regular or irregular pattern along the surface of the superhydrophobic/superoleophobic structure 100. However, the sidewalls 102 and the plateaus 104 may not be entirely formed along the surface of the superhydrophobic/superoleophobic structure 100, but may be formed in a region of the surface of the superhydrophobic/superoleophobic structure 100 which requires superhydrophobicity/superoleophobicity.
In addition, the plateaus 104 may each have a horizontal length W defined between the most distant two edge points and ranging from about 500 μm to about 5 μm.
The sidewalls 102 and the plateaus 104 illustrated in FIG. 2 constitute a roughened primary structure 106. A plurality of nanopores 110 may be formed in the roughened primary structure 106. The nanopores 110 may have a pore diameter within the range of about 1 nm to about 300 nm, more preferably about 10 nm to 50 nm.
If the nanopores 110 have an excessively large or small diameter, the superhydrophobic/superoleophobic structure 100 may not have superhydrophobicity/superoleophobicity. Without being bound to a particular theory, if the diameter of the nanopores 110 is excessively large, the nanopores 110 may coalesce with each other. In this case, a surface on which pillars are formed may appear instead of a surface in which pores are formed, resulting in poor superhydrophobicity/superoleophobicity. On the contrary, if the diameter of the nanopores 110 is excessively small, the nanopores 110 may contribute to superhydrophobicity/superoleophobicity to a very low degree, thereby also resulting in poor superhydrophobicity/superoleophobicity.
The nanopores 110 may be defined as a secondary structure of the superhydrophobic/superoleophobic structure 100. The nanopores 110 may extend in directions substantially perpendicular to the plateaus 104 and the sidewalls 102. The expression “the nanopores 110 extend in directions substantially perpendicular to the plateaus 104 and the sidewalls 102” indicates that the nanopores 110 extend in directions different from the surface directions of the plateaus 104 and the sidewalls 102 rather than the nanopores 110 extending at an angle of 90° to the plateaus 104 and the sidewalls 102.
FIG. 3 is a cross-sectional view illustrating one of the plateaus 104 and one of the sidewalls 102 shown in FIG. 2. Referring to FIG. 3, it could be understood that a hydrophobic/oleophobic layer 120 is formed on the plateaus 104 and the sidewalls 102. The hydrophobic/oleophobic layer 120 may include fluorine (F). In detail, the hydrophobic/oleophobic layer 120 may include a fluorine-containing silane compound or a fluorine-containing thiol compound.
The nanopores 110 are formed in each surface of the base material 101, and entrances of the nanopores 110 are not covered with the hydrophobic/oleophobic layer 120 but are opened. Methods and materials that may be used to form the hydrophobic/oleophobic layer 120 will be described in more detail when a method of manufacturing the superhydrophobic/superoleophobic structure 100 is described later.
Substantially, the hydrophobic/oleophobic layer 120 may not be formed inside the nanopores 110.
FIG. 4 is a flowchart illustrating a method of manufacturing a superhydrophobic/superoleophobic structure 100 according to an embodiment of the present invention. Hereinafter, an explanation will be given of the method of manufacturing a superhydrophobic/superoleophobic structure 100 according to the embodiment of the present invention.
Referring to FIG. 4, a metal base 101 is etched with an acid so as to form a roughened primary structure 106 on the metal base 101 (S1). The metal base 101 may be etched in an acid solution for about 10 seconds to about 10 minutes, preferably, about 1 minute to 5 minutes. In addition, the etching may be performed at room temperature.
If the etching time is excessively short or long, the roughened primary structure 106 including plateaus 104 and sidewalls 102 may not be formed. The etching time is not limited to the above-mentioned ranges. That is, the etching time may be properly adjusted according to factors such as the kind of the metal base 101, the kind of the acid, and the concentration of the acid solution.
The acid may be an inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid; an organic acid such as organic acetic acid, organic sulfonic acid, or perfluorinated carboxylic acid; or a mixture of one or more of the limited acids. The acid may be used directly or after being diluted with a solvent such as water. In the latter case, the acid may be properly diluted according to properties of the acid. For example, if the acid is hydrochloric acid, the acid may be diluted with deionized water at a ratio of about 1:1 to about 1:5, preferably about 1:2.
The metal base 101 may be simply immersed into the acid solution to each the metal base 101 by a wet etching method. In this case, a space such as a chamber may not be necessary, and even if the metal base 101 is large, the metal base 101 may be easily etched by the wet etching method.
Optionally, after the metal base 101 is etched, the metal base 101 may be washed with deionized water (DI water) and may then be dried at an increased temperature. The drying of the metal base 101 may be performed at about 50° C. to about 200° C. for about 5 minutes to about 3 hours. However, the drying condition of the metal base 101 is not limited thereto.
Thereafter, the metal base 101 is anodized (S2). Methods of anodizing a metal material are well-known to those of ordinary skill in the related art. For example, the metal base 101 may be immersed into a sulfuric acid solution, an oxalic acid solution, an citric acid solution, a sodium nitrate solution, a sodium chloride solution, a chromic acid solution, or a phosphoric acid solution, and a voltage may be applied to the metal base 101 serving as an anode. The voltage may range from about 10 V to about 30 V. The anodizing may be performed at room temperature for about 1 minute to about 30 minutes, preferably 3 minutes to 25 minutes.
Like the wet etching method described above, since the anodizing is simply performed by dipping the metal base 101 into a solution, a room such as a chamber may not be necessary, and even if the metal base 101 is large, the anodizing may be easily performed.
Finally, a hydrophobic/oleophobic layer 120 is formed on the metal base 101 (S3). The function of the hydrophobic/oleophobic layer 120 is to modify the surface of the metal base 101. The surface of the metal base 101 may be fluorinated to form the hydrophobic/oleophobic layer 120. The metal base 101 may be dipped into a hydrophobic/oleophobic treatment chemical so as to form the hydrophobic/oleophobic layer 120.
A material such as a fluorine-containing silane compound, a fluorine-containing thiol compound, or a fluorine-containing polymer may be used to form the hydrophobic/oleophobic layer 120. However, the hydrophobic/oleophobic layer 120 is not limited thereto.
The metal base 101 may be coated with one or more of the above-listed material to form the hydrophobic/oleophobic layer 120. In this case, a coating method such as a spin-coating method or a dip-coating method may be used. However, the coating method is not limited thereto.
Non-limiting examples of one or materials that may be used to form the hydrophobic/oleophobic layer 120 include a compound having Formula 1 below:
(R₁)_4-nSiX_n [Formula 1]
In Formula 1, R1 is a fluoroalkyl group “—(CH₂)_p(CF₂)_mCF₃”, X is selected from the group consisting of hydrogen; a halogen selected from the group consisting of F, Cl, Br, and I; a C₁-C₁₀alkoxy group; a C₃-C₈aromatic alkoxy group; and a C₂-C₈heteroaromatic alkoxy group having at least one heteroatom selected from the group consisting of O, N, S, and P, n is an integer from 1 to 3, p is an integer from 0 to 3, and m is an integer from 0 to 17.
In more detail, non-limiting examples of one or materials that may be used to form the hydrophobic/oleophobic layer 120 include: 1H,1H-perfluorooctyltrichlorosilane, 1H,1H-perfluorodecyltrichlorosilane, 1H,1H-perfluorododecyltrichlorosilane, 1H,1H-perfluorooctyltriethoxysilane, 1H,1H-perfluorodecyltriethoxysilane, 1H,1H-perfluorododecyltriethoxysilane, 1H,1H-perfluorooctyltrimethoxysilane, 1H,1H-perfluorodecyltrimethoxysilane, 1H,1H-perfluorododecyltrimethoxysilane, 1H,1H-perfluorooctyltridimethylchlorosilane, 1H,1H-perfluorodecyltridimethylchlorosilane, 1H,1H-perfluorododecyltridimethylchlorosilane, 1H,1H,2H,2H-perfluorooctyltrichlorosilane, 1H,1H,2H,2H-perfluorodecyltrichlorosilane, 1H,1H,2H,2H-perfluorododecyltrichlorosilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorododecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorododecyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltridimethylchlorosilane, 1H,1H,2H,2H-perfluorodecyltridimethylchlorosilane, 1H,1H,2H,2H-perfluorododecyltridimethylchlorosilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilanei, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, heptadecafluorodecyltriethoxysilane, pentafluorophenylpropyltrimethoxysilane, pentafluorophenylpropyltriethoxysilane, tetrakis(trifluoroacetoxy)silane, tris(trifluoroacetoxy)silane, tetrafluorosilane, trifluorosilane, methyltrifluorosilane, (tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane, (tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane, heptadecafluorohexyltrimethoxysilane, 1-pentafluorosulfuranyl-3-triethoxysilylmethane, 1-pentafluorosulfuranyl-3-triethoxysilylethane, 1-pentafluorosulfuranyl-3-triethoxysilylpropane, 1-pentafluorosulfuranyl-4-triethoxysilylbutane, 1-pentafluorosulfuranyl-5-triethoxysilylpentane, 1-pentafluorosulfuranyl-6-triethoxysilylhexane, 1-pentafluorosulfuranyl-3-trimethoxysilyl-1-propene, 1-pentafluorosulfuranyl-4-trimethoxysilyl-1-butene, 1-pentafluorosulfuranyl-5-trimethoxysilyl-1-pentene, 1-pentafluorosulfuranyl-6-trimethoxysilyl-1-hexene, (1,2,3,4,5-pentafluorosulfuranylphenyl)propyl trimethoxysilane, perfluorodecanethiol, and pentafluorobenzenethiol.
In addition, non-limiting examples of one or materials that may be used to form the hydrophobic/oleophobic layer 120 include a polysiloxane-containing material. For example, the polysiloxane-containing material may include one or more of linear, branched, or cyclic polydimethylsiloxanes; polysiloxanes having a hydroxyl group in the molecular chain such as silanol-terminated polydimethylsiloxane, silanol-terminated polydiphenylsiloxane, diphenylsilanol-terminated polydimethylsiloxane, carbinol-terminated polydimethylsiloxane, hydroxypropyl-terminated polydimethylsiloxane, and polydimethylhydroxyalkyleneoxide methylsiloxane; polysiloxanes having an amino group in the molecular chain such as bis(aminopropyldimethyl)siloxane, aminopropyl-terminated polydimethylsiloxane, T-structured polydimethylsiloxane having an aminoalkyl group, dimethylamino-terminated polydimethylsiloxane, and bis(aminopropyldimethyl)siloxane; polysiloxanes having a glycidoxyalkyl group in the molecular chain such as glycidoxypropyl-terminated polydimethylsiloxane, T-structured polydimethylsiloxane having a glycidoxypropyl group, polyglycidoxypropylmethylsiloxane, and a polyglycidoxypropylmethyldimethylsiloxane copolymer; polysiloxanes having a chlorine atom in the molecular chain such as chloromethyl-terminated polydimethylsiloxane, chloropropyl-terminated polydimethylsiloxane, polydimethyl-chloropropylmethylsiloxane, chloro-terminated polydimethylsiloxane, and 1,3-bis(chloromethyl)tetramethyldisiloxane; polysiloxanes having a methacryloxyalkyl group in the molecular chain such as methacryloxypropyl-terminated polydimethylsiloxane, T-structured polydimethylsiloxane having a methacryloxypropyl group, and polydimethyl-methacryloxypropylmethylsiloxane; polysiloxanes having a mercaptoalkyl group in the molecular chain such as mercaptopropyl-terminated polydimethylsiloxane, polymercaptopropylmethylsiloxane, and T-structured polydimethylsiloxane having a mercaptopropyl group; polysiloxanes having an alkoxy group in the molecular chain such as ethoxy-terminated polydimethylsiloxane, polydimethylsiloxane having a trimethoxysilyl group on one terminal and a polydimethyloctyloxymethylsiloxane copolymer; polysiloxanes having a carboxyalkyl group in the molecular chain such as carboxylpropyl-terminated polydimethylsiloxane, T-structured polydimethylsiloxane having a carboxylpropyl group, and carboxylpropyl-terminated T-structured polydimethylsiloxane; polysiloxanes having a vinyl group in the molecular chain such as vinyl-terminated polydimethylsiloxane, tetramethyldivinyldisiloxane, methylphenylvinyl-terminated polydimethylsiloxane, a vinyl-terminated polydimethyl-polyphenylsiloxane copolymer, a vinyl-terminated polydimethyl-polydiphenylsiloxane copolymer, a polydimethyl-polymethylvinylsiloxane copolymer, methyldivinyl-terminated polydimethylsiloxane, a vinyl terminated polydimethylmethylvinylsiloxane copolymer, T-structured polydimethylsiloxane having a vinyl group, vinyl-terminated polymethylphenetylsiloxane, and cyclic vinylmethylsiloxane; polysiloxanes having a phenyl group in the molecular chain such as a polydimethyl-diphenylsiloxane copolymer, a polydimethyl-phenylmethylsiloxane copolymer, polymethylphenylsiloxane, a polymethylphenyl-diphenylsiloxane copolymer, a polydimethylsiloxane-trimethylsiloxane copolymer, a polydimethyl-tetrachlorophenylsiloxane copolymer, and tetraphenyldimethylsiloxane; polysiloxanes having a cyanoalkyl group in the molecular chain such as polybis(cyanopropyl)siloxane, polycyanopropylmethylsiloxane, a polycyanopropyl-dimethylsiloxane copolymer, and a polycyanopropylmethyl-methyphenylsiloxane copolymer; polysiloxanes having a long-chain alkyl group in the molecular chain such as polymethylethylsiloxane, polymethyloctylsiloxane, polymethyloctadecylsiloxane, a polymethyldecyl-diphenylsiloxane copolymer, and a polymethylphenetylsiloxane-methylhexylsiloxane copolymer; polysiloxanes having a fluoroalkyl group in the molecular chain such as polymethyl-3,3,3-trifluoropropylsiloxane and polymethyl-1,1,2,2-tetrahydrofluorooctylsiloxane; polysiloxanes having a hydrogen atom in the molecular chain such as hydrogen-terminated polydimethylsiloxane, polymethylhydrosiloxane, and tetramethyldisiloxane; hexamethyldisiloxane; and a polydimethylsiloxane-alkylene oxide copolymer. However, materials that may be used to form the hydrophobic/oleophobic layer 120 are not limited thereto.
After the hydrophobic/oleophobic layer 120 is formed on the metal base 101 as described above, the metal base 101 may be heated to a high temperature so as to fix the hydrophobic/oleophobic layer 120. For example, the metal base 101 may be heated within the temperature range of about 40° C. to about 150° C. for about 10 minutes to 3 hours. Optionally, the metal base 101 may be washed with an organic solvent or deionized water before the metal base 101 is heated.
If the heating temperature of the metal base 101 is excessively high, the roughened primary structure 106 and the nanopores 110 (secondary structure) may be damaged. On the other hand, if the heating temperature of the metal base 101 is excessively low, it may take a long time to fix the hydrophobic/oleophobic layer 120.
The superhydrophobic/superoleophobic structure 100 described above may be applied to various electronic devices or devices for transportation. Examples of such electronic devices or devices for transportation may include: automobile/airplane/train/ship interior or exterior devices; automobile/airplane/train/ship or home/office/industrial heating, refrigerating, and air-conditioning systems (air conditioners and heat pumps); televisions; cellular phones; computer systems; portable computers; monitors; phones; printers; keyboards; mouses; pumps; fluid transfer pipes; powder transfer pipes; tanks storing fluids for transportation; illumination devices; and backlight units. The application of the superhydrophobic/superoleophobic structure 100 is not limited thereto. For example, components of heating, refrigerating, and air conditioning systems for home/office/industrial applications such as transportation vehicles including automobiles, airplanes, ships, and trains may be treated to have hydrophobicity/oleophobicity for preventing harmful substances or mold from growing on or adhering to the components or removing such harmful substances or mold. In this case, indoor areas may be protected from harmful substances or mold, and thus pleasant environments may be provided. In addition, surfaces on which the formation of ice or frost is retarded at freezing temperatures may be realized using the above-mentioned hydrophobic/oleophobic characteristics, and the surfaces may be applied to components of heating, refrigerating, and air-conditioning systems (air conditioners and heat pumps) for home/office/industrial applications such as automobiles, airplanes, and trains, so as to improve energy efficiency.
In addition, surprisingly it has been found that if the hydrophobic/oleophobic layer 120 is not formed on the superhydrophobic/superoleophobic structure 100, the superhydrophobic/superoleophobic structure 100 has superhydrophilicity/superoleophilicity. FIG. 5 is a schematic cross-sectional view illustrating a superhydrophilic/superoleophilic structure 200 according to an embodiment of the present invention.
Referring to FIG. 5, the superhydrophilic/superoleophilic structure 200 is formed by the same method as that used to form the superhydrophobic/superoleophobic structure 100 except that a hydrophobic/oleophobic layer forming process is not performed. The superhydrophilic/superoleophilic structure 200 includes a roughened primary structure 206 including plateaus 204 and sidewalls 202 and formed on a base material 201. In addition, a plurality of pores 210 are formed in the plateaus 204 and the sidewalls 202. Since the pores 210 are the same as the nanopores 110 of the superhydrophobic/superoleophobic structure 100, a detailed description thereof will not be repeated here.
The plateaus 204 may each have a horizontal length W defined between the most distant two edge points and ranging from about 500 μm to about 5 μm.
In addition, according to an embodiment of the present invention, the superhydrophilic/superoleophilic structure 200 may be manufactured in the same manner as the method of manufacturing the superhydrophobic/superoleophobic structure 100 described with reference to FIG. 4 except that operation S3 for forming the hydrophobic/oleophobic layer 120 is omitted. That is, the metal base 201 may be etched with an acid so as to form the roughened primary structure 206 on the metal base 201, and then the metal base 201 may be anodized. The anodizing may be performed at room temperature for about 1 minute to about 30 minutes, preferably 3 minutes to 25 minutes.
As described above, a hydrophobic/oleophobic layer is not formed on the roughened primary structure 206. That is, a fluorine-containing compound layer is not formed on the roughened primary structure 206.

MODE OF THE INVENTION

Hereinafter, the configuration and effects of the present invention will be described in detail with reference to specific examples and comparative examples. However, the examples are for a clearer understanding of the present invention and are not intended to limit the scope of the present invention.

Example 1

Operation 1: a flat aluminum base (thickness: 0.81 mm, Al: 95.8 wt % to 98.6 wt %, Mg: 0.8 wt % to 1.2 wt %, Si: 0.4 wt % to 0.8 wt %, Cr: 0.04 wt % to 0.35 wt %, Cu: 0.15 wt % to 0.4 wt %, Fe: 0.7 wt % max, Zn: 0.25 wt % max, Mn: 0.15 wt % max, and Ti: 0.15 wt % max) was washed using ultrasonic waves in acetone and ethanol for 3 minutes and in deionized water (DI) for 3 minutes and was then dried under a nitrogen atmosphere.
Operation 2: the washed aluminum base was etched for 3 minutes in a room-temperature acidic solution in which deionized water and HCl are mixed at a volume ratio of 2:1. The etched aluminum base was washed with deionized water and was then dried at 120° C. for 1 hour.
FIGS. 6A and 6B are scanning electron microscope (SEM) images showing a surface of the 3-minute etched aluminum base at magnifications of 10,000 times and 50,000 times, respectively. As shown in FIGS. 6A and 6B, a roughened primary structure having sidewalls and plateaus was formed.
In addition, an aluminum base was etched for 6 minutes independently of Example 1. FIGS. 7A and 7B are SEM images showing a surface of the 6-minute etched aluminum base at magnifications of 10,000 times and 50,000 times, respectively. As shown in FIGS. 7A and 7B, a roughened primary structure having various sidewalls and plateaus was formed.
Operation 3: the dried aluminum base was anodized for 10 minutes in a 10° C. sulfuric acid solution while applying a constant voltage of 25 V. After the anodizing, the aluminum base was rinsed with deionized water and dried in the air.
FIGS. 8A to 8D are SEM images taken from the surface of the aluminum base at magnifications of 10,000 times, 30,000 times, 100,000 times, and 300,000 times immediately after the aluminum base was anodized for 10 minutes. As shown in FIGS. 8A to 8D, many fine pores were formed.
Operation 4: finally, the aluminum base treated as described above was immersed for 8 minutes in a 1H,1H,2H,2H-perfluorooctyltrichlorosilane solution diluted with n-hexane (solvent) to a concentration of 0.5%. Thereafter, the aluminum base was taken away from the solution and was washed with n-hexane. Then, the aluminum base was dried by heating the aluminum base on a 100° C. hot plate for 30 minutes. In this manner, a superhydrophobic/superoleophobic structure (sample) was prepared.

Comparative Example 1

A sample was prepared in the same manner as in Example 1 except that operation 2 was omitted.
FIGS. 9A and 9B are SEM images taken from a surface of an aluminum base at magnifications of 10,000 times and 100,000 times immediately after the aluminum base was anodized for 10 minutes. As shown in FIGS. 9A and 9B, although many fine pores were formed, a roughened primary structure was not formed.

Comparative Example 2

A sample was prepared in the same manner as in Example 1 except that operation 3 was omitted.

Comparative Example 3

A sample was prepared through operations 1 and 4 of Example 1 without performing operations 2 and 3 of Example 1.
The contact angles of water, glycerol, ethylene glycol, olive oil, and hexadecane with each of the samples prepared in Example 1 and Comparative Examples 1 to 3 were measured. Each of the fluids was dripped to at least five points of each of the samples in an amount of 5 μl, and contact angles were measured with SEO Phoenix 300 Touch. The contact angles were measured by a tangent line method, and optical images of droplets were taken with a SONY digital camera.
Averages of the measured contact angles are shown in Table 1.

TABLE 1

Fluid

	Surface
	tension	Exam-	Comparative	Comparative	Comparative
Kinds	(mN/m)	ple 1	Example 1	Example 2	Example 3

Water	72	163	153	157	110
Glycerol	63.6	159	150	152	102
Ethylene	48	158	147	147	86
glycol
Olive Oil	32	153	134	145	74
Hexa-	27.5	150	126	139	54
decane

Unit: degree (°)

As shown in Table 1, although a hydrophobic/oleophobic layer was formed on a smooth surface (Comparative Example 3), a large contact angle could not be obtained. In contrast, when a roughened primary structure and/or a secondary structure were formed (Example 1, and Comparative Examples 1 and 2), a relatively large contact angle could be obtained.
Particularly, the superhydrophobic/superoleophobic structure of Example 1 showed a significantly high degree of hydrophobicity/oleophobicity compared to the other structures. The structure of Example 1 showed a contact angle of 150° or greater with respect to olive oil and hexadecane but the structures of Comparative Examples 1 to 3 did not showed high oleophobicity with respect to olive oil and hexadecane.
FIG. 10 shows plan and side images of water, glycerol, ethylene glycol (EG), olive oil, and hexadecane (in order of left to right) dripped onto the superhydrophobic/superoleophobic structure of Example 1. As shown in FIG. 10, the surface of the superhydrophobic/superoleophobic structure showed a significantly large contact angle, that is, superhydrophobicity/superoleophobicity.
In addition, the sliding angles of water, glycerol, ethylene glycol, olive oil, and hexadecane with respect to each of the samples prepared in Example 1 and Comparative Examples 1 to 3 were measured. Each of the fluids was dripped to at least five points of each of the samples in an amount of 5 μl, and sliding angles were measured with SEO Phoenix 300 Touch. Averages of the measured sliding angles are shown in Table 2.

TABLE 2

Fluid

Water	72	2	6	21	N/A
Glycerol	63.6	3	10	25	N/A
Ethylene	48	4.3	16	N/A	N/A
glycol
Olive Oil	32	5.3	35	N/A	N/A
Hexa-	27.5	20.6	N/A	N/A	N/A
decane

Unit: degree (°)

As shown in Table 2, although a hydrophobic/oleophobic layer was formed on a smooth surface (Comparative Example 3), a sliding angle greater than a measurable angle limit was obtained. However, when a roughened primary structure and/or a secondary structure were formed (Example 1, and Comparative Examples 1 and 2), a relatively small sliding angle was measured.
Particularly, the superhydrophobic/superoleophobic structure of Example 1 showed a significantly high degree of superhydrophobicity/superoleophobicity compared to the other structures. The structure of Example 1 showed very small sliding angles of about 5° and about 20° with respect to olive oil and hexadecane, but the structures of Comparative Examples 1 to 3 did not showed high oleophobicity with respect to olive oil and hexadecane.
Therefore, even at a very small tilt angle, aqueous fluids or oily fluids may easily slide off from the structure of Example 1.
In addition, samples were prepared in the same manner as in Example 1 except that the anodizing time of the samples was varied as described below, so as to evaluate the effect of the anodizing time on hydrophobicity/oleophobicity.

Example 2

A sample was prepared in the same manner as in Example 1 except that anodizing was performed for 25 minutes.

Example 3

A sample was prepared in the same manner as in Example 1 except that anodizing was performed for 30 minutes.

Example 4

A sample was prepared in the same manner as in Example 1 except that anodizing was performed for 3 minutes.

Example 5

A sample was prepared in the same manner as in Example 1 except that anodizing was performed for 1 minute.
The contact angles of water, glycerol, ethylene glycol, olive oil, and hexadecane with each of the samples prepared in Examples 2 to 5 were measured, and averages of the measured contact angles are calculated as shown in FIG. 11. The contact angles were measured in the same manner as described above, and thus a detailed description thereof is not repeated here.
Referring to FIG. 11, the contact angles were maximal when anodizing was performed for 10 minutes and were slightly decreased when anodizing was performed for 3 minutes or 25 minutes. Particularly, when anodizing was performed for 1 minute or 30 minutes, the contact angles of olive oil and hexadecane were significantly decreased.

Example 6

A sample was prepared in the same manner as in Example 1 except that operation 4 was omitted.
Although it was tried to measure the contact angles of water, glycerol, ethylene glycol, olive oil, and hexadecane with a surface of the sample, all of the fluids were absorbed in the surface of the sample, and thus contact angles could not be measured. That is, the contact angles of the fluids were substantially zero.
FIGS. 12A to 12F are sequential images taken when water and olive oil were dripped onto a surface of the sample. The left side of each image shows water dripping from a pipette, and the right side of each image shows olive oil dripping from a pipette.
Referring to FIG. 12A, droplets were suspended on ends of the pipettes and were not yet delivered to the sample.
Referring to FIG. 12B, the droplet of olive oil was brought into contact with the surface of the sample. Those of ordinary skill in the art may understand that the contact angle of the droplet of olive oil could not be yet measured because the droplet of olive oil was not yet separated from the pipette.
Referring to FIG. 12C, the droplet of water was delivered from the end of the left pipette to the sample. An unclear circle on the end of the left pipette was an afterimage of the droplet of water immediately before the droplet of water was delivered to the sample. Actually, the droplet of water was completely delivered to the sample and spread in a slightly convex shape.
Referring to FIG. 12D, the droplet of water considerably spread, and a new droplet began to form on the end of the left pipette. That is, although the droplet of water was delivered to the surface of the sample, the droplet of water did not maintained its shape on the surface of the sample, but the droplet of water spread while being absorbed in the surface of the sample. That is, the surface of the sample was superhydrophilic.
The droplet of olive oil was not yet completely separated from the pipette. This was due to a slight difference between the volumetric flow rates of the fluids and a difference between the surface energy levels of the fluids caused by factors such as different viscosity levels of the fluids. Therefore, it took different times for the droplets of the fluids to leave the pipettes.
Referring to FIG. 12E, the droplet of water spread over a wider area, and the droplet of olive oil was completely separated from the pipette. Although the droplet of olive oil looks having a certain contact angle in the image of FIG. 12E, the droplet of olive oil was actually in the middle of spreading. That is, the contact angle of the olive oil could not be measured from the image of FIG. 12E.
Referring to FIG. 12F, the droplet of olive oil spread over a wider area compared to FIG. 12E, and thus the height of the droplet of olive oil was significantly decreased. In FIG. 12F, the droplet of olive oil did not form a contact angle with the surface of the sample but spread while the edge of the droplet of olive oil was being absorbed in the surface of the sample. That is, the surface of the sample had superoleophilicity.
While preferred embodiments of the present invention have been described in detail, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention defined by the following claims. Therefore, changes or modifications made in the embodiments of the present invention should be construed as being within the scope of the present invention.

REFERENCE NUMERALS


100: Superhydrophobic/superoleophobic structure	101: Metal base

102, 202: Sidewalls

104, 204: Plateaus

106, 206: Roughened primary structure	110, 210: nanopores
120: Hydrophobic/oleophobic layer	200: Superhydrophilic/
	superoleophilic structure

INDUSTRIAL APPLICABILITY

The present invention may be usefully used in the electronic industry and mechanical industry.

Claims

1. A superhydrophobic/superoleophobic structure comprising:

a roughened primary structure formed on a surface of a metal base;

nanopores formed in the roughened primary structure; and

a hydrophobic/oleophobic layer formed on a surface of the roughened primary structure.

2. The superhydrophobic/superoleophobic structure of claim 1, wherein the nanopores have a diameter of 1 nm to 300 nm.

3. The superhydrophobic/superoleophobic structure of claim 1, wherein the nanopores have a diameter of 10 nm to 50 nm.

4. The superhydrophobic/superoleophobic structure of claim 1, wherein the metal base is an aluminum (Al) base.

5. The superhydrophobic/superoleophobic structure of claim 1, wherein the roughened primary structure comprises identical or different sidewalls and plateaus that are continuously arranged.

6. The superhydrophobic/superoleophobic structure of claim 5, wherein each of the plateaus has a horizontal length within a range of 500 μm to 5 μm.

7. The superhydrophobic/superoleophobic structure of claim 5, wherein the nanopores are formed in the sidewalls and the plateaus of the roughened primary structure in directions substantially perpendicular to the sidewalls and the plateaus.

8. The superhydrophobic/superoleophobic structure of claim 1, wherein the hydrophobic/oleophobic layer comprises fluorine (F).

9. The superhydrophobic/superoleophobic structure of claim 8, wherein the hydrophobic/oleophobic layer is a fluorine-containing silane compound layer or a fluorine-containing thiol compound layer.

10. The superhydrophobic/superoleophobic structure of claim 1, wherein the hydrophobic/oleophobic layer is substantially not formed inside the nanopores.

11. A method of manufacturing a superhydrophobic/superoleophobic structure, the method comprising:

etching a metal base with an acid so as to form a roughened primary structure on the metal base;

anodizing the metal base on which the roughened primary structure is formed, so as to form nanopores in the roughened primary structure; and

forming a hydrophobic/oleophobic layer on a surface of the roughened primary structure.

12. The method of claim 11, wherein the anodizing of the metal base is performed for 3 minutes to 25 minutes.

13. The method of claim 11, wherein the etching of the metal base is performed by a wet etching method.

14. The method of claim 13, wherein the etching of the metal base is performed using an acid solution.

15. The method of claim 11, wherein the metal base is an aluminum (Al) base.

16. The method of claim 11, further comprising drying the metal base at a temperature of 50° C. to 200° C. between the etching of the metal base and the anodizing of the metal base.

17. (canceled)

18. (canceled)

19. A superhydrophilic/superoleophilic structure comprising:

a roughened primary structure formed on a surface of a metal base; and

nanopores formed in the roughened primary structure.

20. The superhydrophilic/superoleophilic structure of claim 19, wherein the nanopores have a diameter of 10 nm to 50 nm.

21. The superhydrophilic/superoleophilic structure of claim 19, wherein the roughened primary structure comprises identical or different sidewalls and plateaus that are continuously arranged.

22. The superhydrophilic/superoleophilic structure of claim 21, wherein each of the plateaus has a horizontal length within a range of 500 nm to 5 μm.

23. The superhydrophilic/superoleophilic structure of claim 19, wherein a fluorine-containing compound is not formed on the roughened primary structure.

24. A method of manufacturing a superhydrophilic/superoleophilic structure, the method comprising:

etching a metal base with an acid so as to form a roughened primary structure on the metal base; and

anodizing the metal base on which the roughened primary structure is formed, so as to form nanopores in the roughened primary structure.

25. The method of claim 24, wherein the anodizing of the metal base is performed for 3 minutes to 25 minutes.

26. The method of claim 24, wherein the etching of the metal base is performed by a wet etching method.

27. The method of claim 26, wherein the etching of the metal base is performed using an acid solution.

28. The method of claim 24, wherein the method does not comprise forming a fluorine-containing compound layer on the roughened primary structure.

29. (canceled)