A microstructure with a superhydrophobic surface and a preparation method thereof

Abstract

The present application relates to a microstructure with a superhydrophobic surface and a preparation method thereof. The preparation method includes: pretreating and drying the surface of a substrate, coating a fluoropolymer on the surface of the substrate and performing a heat treatment to obtain a substrate (upper plate) with a fluoropolymer hydrophobic coating, irradiating the substrate with the polymer hydrophobic coating through a mask plate with an array pattern to obtain a substrate with staggered hydrophilic and hydrophobic arrays, then coating a UV glue polymer to obtain a convex array on the surface of the substrate (lower plate), bringing the upper plate into contact with the lower plate, applying a DC voltage between the upper plate and the lower plate, subjecting the obtained lower plate to UV curing and demolding treatments to obtain a microstructure with a fixed morphology, and vapor-depositing a hydrophobic fluoropolymer on the surface of the microstructure, thereby obtaining a microstructure with a superhydrophobic surface. This preparation method does not require expensive equipment, the process is simple, the formed structure morphology is controllable, the structure has high fidelity and the process flow is stable.

Description

Technical Field

[0001] This application belongs to the field of micro-nano structures, and particularly relates to a micro-structure with a superhydrophobic surface and a preparation method thereof. Background Art

[0002] Superhydrophobic surfaces are a class of extremely hydrophobic surfaces with a contact angle with water greater than 180° and a contact angle hysteresis less than 10°. With the rapid development of science and technology in recent years and their unique wetting properties, superhydrophobic surfaces have shown great commercial value in the fields of self-cleaning, anti-corrosion, anti-icing, oil-water separation, microfluidics, etc., and have broad application prospects.

[0003] Micro-nano structures are one of the ways to achieve superhydrophobic surfaces. For example, in the case of lotus leaves, the superhydrophobic phenomenon on their surfaces is due to the combined action of micro-nano hierarchical papilla structures and waxy hydrophobic substances on the surface. The research on achieving superhydrophobic surfaces mainly focuses on structures at the micro and nano scales, which have the following excellent characteristics: there are voids between the microstructures, which can store a certain volume of air, thus forming a stable gas-liquid contact area; due to the designability of the micro-nano structures themselves, the appearance geometry and the spacing design between the structures will change the surface hydrophobicity, and extremely difficult oil repellency can also be achieved. Therefore, achieving superhydrophobic surfaces through the design of the morphology, spacing, and height of micro-nano structures has become a hot topic in this field, and finding a preparation method with simple process, large-scale production, and low cost is an urgent need at present.

[0004] The above content described in this background art is only used for the understanding of related technologies and is not considered to be the prior art known to those skilled in the art. Summary of the Invention

[0005] This application aims to solve at least one of the technical problems existing in the prior art. For this purpose, this application provides a micro-structure with a superhydrophobic surface and a preparation method thereof. This preparation method does not require expensive equipment, has a simple process, has almost no requirements for polymer materials, the formed structure morphology is controllable, the structure has high fidelity, and the process flow is stable. It is a large-scale and high-precision micro-nano processing method, providing a new idea for the realization of superhydrophobic surfaces.

[0006] According to the first aspect of this application, a preparation method of a micro-structure with a superhydrophobic surface is provided, including the following steps:

[0007] Step (1): Pretreat the surface of the substrate and dry it for standby;

[0008] Step (2): Coat the surface of the substrate obtained in step (1) with a fluoropolymer, and then perform a heat treatment to obtain a substrate with a fluoropolymer hydrophobic coating;

[0009] Step (3): Irradiate the substrate with a polymer hydrophobic coating obtained in step (2) in ultraviolet light through a mask plate with an array pattern to obtain a substrate with staggered hydrophilic and hydrophobic arrays;

[0010] Step (4): Wet the substrate obtained in step (3), and then coat a layer of ultraviolet glue polymer on the surface of the staggered hydrophilic and hydrophobic arrays, so as to obtain a convex array on the substrate surface;

[0011] Step (5): Take the substrate in step (2) as the upper plate and the substrate in step (4) as the lower plate, bring the upper plate into contact with the lower plate, and apply a DC voltage of 200V - 800V between the upper plate and the lower plate. The convex array in the lower plate is formed by upward flow under the action of an electric field and traction force;

[0012] Step (6): Cure the lower plate obtained in step (5) with ultraviolet light and perform demolding treatment to obtain a microstructure with a fixed morphology;

[0013] Step (7): Evaporate a layer of hydrophobic fluoropolymer on the surface of the microstructure in step (6) to obtain a microstructure with a superhydrophobic surface.

[0014] The preparation method of the microstructure with a superhydrophobic surface according to the embodiment of the present application has at least the following beneficial effects: This preparation method proposes to use ultraviolet light for local modification and photoetching of a low-energy hydrophobic polymer thin film coating. Among them, the ultraviolet light source is an incoherent light source with high energy. After irradiation, the fluorocarbon bonds in the surface (hydrophobic layer) of the fluoropolymer are broken (mainly playing a hydrophobic role), and the exposed carbon after bond breaking combines with oxygen root ions to form active groups, thereby increasing the polarity of the hydrophobic surface. In addition, ultraviolet light irradiation will produce an etching effect on the surface of the fluoropolymer. This process combines chemical and physical perspectives to achieve the confinement effect of light processing on the polymer in a micro-region. In the subsequent process of adding a spatial electric field to traction the polymer, the requirements for the polymer material properties are not high.

[0015] It should be noted that in the preparation method of the present application, the combination of electro-traction and a new confinement process realizes complex, precise and controllable pre-structured patterns on a low-energy surface. The joint participation of the electric field and the traction force, compared with the traditional spatially modulated electric field, greatly improves the upper limit of the polymer's upward growth, increases the variable range, greatly improves the aspect ratio of the structure, and realizes pre-structured patterns on the hydrophobic layer surface. Compared with the method of preparing pre-structured patterns by imprinting, the new confinement process for realizing pre-structured patterns is convenient to operate, has a simple process flow, low equipment cost, can be manufactured in large areas and with high efficiency, has a high replication rate, and hardly introduces pollution to the hydrophobic layer. This method does not require expensive equipment, has a simple process, has almost no requirements for the polymer material, the formed structure morphology is controllable, the structure has high fidelity and the process flow is stable. It is a large-scale and high-precision micro-nano processing method, providing a new idea for the realization of superhydrophobic surfaces.

[0016] According to some embodiments of the present application, the irradiation treatment conditions in step (3) are: in the ultraviolet light range of 100 nm - 200 nm, the light intensity is greater than 10 mW / cm 2 , and the irradiation time is 10 min to 15 min.

[0017] According to some embodiments of the present application, in step (4), the ultraviolet glue polymer includes at least one of ultraviolet curable hybrid polymers and polyurethane resin ultraviolet glue.

[0018] It can be understood that the ultraviolet curable hybrid polymer may include OrmoStamp. Among them, OrmoStamp has hydrophilicity, its dielectric constant is 13, the dynamic viscosity coefficient is 0.3 pa·s, and the surface tension coefficient is 0.032 N·m -1 , and the boundary slip length is 100 nm. The polyurethane resin ultraviolet glue may include NOA75, and NOA75 may be prepared by doping 1-ethyl-3-methyl-1H-imidazolium salt with a mass ratio of 0.01% into NOA75.

[0019] According to some embodiments of the present application, in step (2), the fluoropolymer includes at least one of Hyflon and AF.

[0020] According to some embodiments of the present application, in step (2), the heat treatment includes pre-curing by heating on a hot plate at 82°C - 88°C for 0.5 min - 2 min, and then heating in a dust-free oven at 180°C - 185°C for 30 - 90 min.

[0021] According to some embodiments of the present application, the substrate in step (1) includes at least one of ITO transparent glass and a conductive rigid substrate.

[0022] According to some embodiments of the present application, in step (3), the shape of the array includes at least one of a circle, a square, a triangle, and a hexagon.

[0023] According to some embodiments of the present application, in step (4), the coating method is the doctor blade coating method. Further, the doctor blade coating method includes using a flat film doctor to scrape from one end to the other end at a speed of 0.1 mm / s to 1 mm / s.

[0024] According to some embodiments of the present application, in step (6), the time for ultraviolet curing is 30 s - 40 s, and the demolding treatment is carried out by using the Coulomb repulsion between the interfacial frozen charges and the trapped charges.

[0025] According to the second aspect of the present application, there is provided a microstructure having a superhydrophobic surface, which is prepared by using the preparation method described in any one of the above. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following further describes the present application with reference to the drawings and embodiments, where:

[0027] Figure 1 is a schematic diagram of the reaction process of steps (1) - (3) in an embodiment of the present application;

[0028] Figure 2 is a schematic diagram of the reaction process of steps (4) - (5) in an embodiment of the present application;

[0029] Figure 3 is a schematic diagram of the reaction process of step (6) in an embodiment of the present application;

[0030] Figure 4 is a schematic diagram of the reaction process of step (7) in an embodiment of the present application;

[0031] Figure 5 is a schematic diagram of the structure for realizing the superhydrophobic surface in an embodiment of the present application;

[0032] Among them, the reference numerals are respectively:

[0033] 1 - substrate, 2 - fluoropolymer hydrophobic layer, 3 - ultraviolet light, 4 - photolithography mask plate, 5 - modified fluoropolymer surface, 6 - ultraviolet glue, 7 - wire bar, 8 - Coulomb repulsion, 9 - power supply, 10 - ultraviolet light, 11 - vapor-deposited fluoropolymer, 12 - ultrapure water, 13 - fluoropolymer coating DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In the following, the concept of the present application and the technical effects generated will be clearly and completely described in combination with embodiments to fully understand the purpose, features, and effects of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of the present application.

[0035] In the description of the present application, the description referring to terms such as "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0036] The specific embodiments of the present application will be described in detail below.

[0037] According to an embodiment of the present application, a preparation method for a microstructure with a superhydrophobic surface is provided, including the following steps:

[0038] Step (1): Pretreat the surface of the substrate and dry it for later use;

[0039] Step (2): Coat the surface of the substrate obtained in step (1) with a fluoropolymer, and then perform a heat treatment to obtain a substrate with a fluoropolymer hydrophobic coating;

[0040] Step (3): Irradiate the substrate with a polymer hydrophobic coating obtained in step (2) through a mask plate with an array pattern in ultraviolet light to obtain a substrate with an interlaced hydrophilic-hydrophobic array;

[0041] Step (4): Wet the substrate obtained in step (3), and then coat a layer of ultraviolet glue polymer on the surface of the interlaced hydrophilic-hydrophobic array, so as to obtain a convex array on the surface of the substrate;

[0042] Step (5): Take the substrate in step (2) as the upper plate and the substrate in step (4) as the lower plate, bring the upper plate into contact with the lower plate, and apply a DC voltage of 200V - 800V between the upper plate and the lower plate. The convex array in the lower plate is upwardly deformed by the action of an electric field and traction force;

[0043] Step (6): Perform ultraviolet curing and demolding treatment on the lower plate obtained in step (5) to obtain a microstructure with a fixed morphology;

[0044] Step (7): Evaporate a layer of hydrophobic fluoropolymer on the microstructure surface in step (6) to obtain a microstructure with a superhydrophobic surface.

[0045] It can be understood that in the imprinting technology based on the physical forming method, a template with micro-nano patterns is tightly pressed on a polymer-coated substrate in the form of mechanical force to replicate the patterns proportionally. However, problems such as uneven structure filling and missing formed structures after demolding are likely to occur during the imprinting process. In addition, for the formation of microstructures induced by a spatially uniform electric field, the electric field is used to strengthen a specific capillary perturbation to grow and form a column array. However, it is difficult to control the column spacing and the column sizes are inconsistent, so a stable superhydrophobic surface cannot be achieved.

[0046] Generally speaking, for the mainstream micro-nano manufacturing technologies to achieve superhydrophobic surfaces, such as lithography technology, it has high requirements and great limitations on the types of forming materials, such as positive and negative photoresists. Chemical effects will inevitably be introduced during the structure forming process, which will have a certain impact on the properties of the polymer. In view of the above dilemmas, the embodiments of this application propose to locally modify the low-energy hydrophobic polymer thin film coating and perform photoetching using ultraviolet light. Among them, the ultraviolet light source is an incoherent light source with high energy. The fluorocarbon bonds in the fluoropolymer surface (hydrophobic layer) after irradiation are broken (which mainly plays a hydrophobic role), and the exposed carbon after the bond breaking combines with oxygen root ions to form active groups, thereby increasing the polarity of the hydrophobic surface. In addition, ultraviolet light irradiation will etch the fluoropolymer surface. This process combines chemical and physical perspectives to achieve the confinement effect of the polymer in the photo-processed micro-region. In the subsequent process of adding a spatial electric field to traction the polymer, the requirements for the properties of the polymer material are not high.

[0047] In addition, processing methods such as lasers and focused ion beams have complex process flows and high equipment costs. In the imprinting process of the imprinting technology, the filling and demolding of the polymer in the template cavity will cause defects in the formed structure, thus affecting the fidelity and integrity of the replicated structure and being unfavorable for the formation of a superhydrophobic surface. To solve the above problems, the ultraviolet light processing of the low-energy surface for precise patterning and confined wetting in the embodiments of this application is combined with a simple coating process (such as wire bar coating) to achieve large-scale polymer confinement and restraint. Control the pre-structured arrays of the upper plate and the lower plate to make contact, add a spatial electric field between the upper and lower plates, and complete the micro-nano structure forming through the traction force of the upper plate itself and the spatial electric field force. Under the action of the electric traction force, the polymer grows upward.

[0048] Att Figures 1-4 Figure 1 shows a schematic diagram of the reaction process of steps (1) - (7) in the embodiments of this application. The following will further explain the related embodiments of this application with reference to the accompanying drawings.

[0049] According to some embodiments of the present application, the substrate in step (1) includes at least one of ITO transparent glass and a conductive rigid substrate. For example, the substrate in Figure 1 is an ITO transparent glass substrate.

[0050] It should be noted that the surface of substrate 1 can be pretreated. The surface of the substrate can be cleaned with an ultrasonic cleaner for 15 minutes to remove surface impurities. During the drying process, nitrogen can be used for air drying.

[0051] According to some embodiments of the present application, the shape of the array in step (3) includes at least one of a circle, a square, a triangle, and a hexagon.

[0052] According to some embodiments of the present application, in step (2), the fluoropolymer 2 includes at least one of Hyflon and AF. Among them, Hyflon is a perfluoroalkoxide, and AF is the fluoropolymer Teflon AF1600.

[0053] It can be understood that in step (2), the coating process can be carried out by spin coating with the help of a spin coater. The spin coating method is relatively simple, low-cost, and belongs to the coating method with the highest flatness.

[0054] According to some embodiments of the present application, in step (2), the heat treatment includes pre-curing by heating on a hot plate at 82°C - 88°C for 0.5 min - 10 min, and then heating in a dust-free oven at 180°C - 185°C for 30 - 90 min.

[0055] It can be understood that after the heat treatment, the solvent in the coating can be evaporated to obtain a smooth fluoropolymer hydrophobic coating with a thickness of 780 nm - 820 nm.

[0056] According to some embodiments of the present application, the irradiation treatment conditions in step (3) are: the wavelength range of ultraviolet light 3 is 100 nm - 200 nm, the light intensity is greater than 10 mW / cm 2 , and the irradiation time is 10 min - 15 min.

[0057] In some preferred embodiments, the substrate coated with the polymer hydrophobic coating can be exposed through a mask plate 4 with an array (such as a circle, a triangle, a square, a hexagon) pattern, and then irradiated with ultraviolet light of 172 nm at a light intensity of 10 mW / cm 2 for 600 s to achieve the effect of alternating hydrophilic and hydrophobic arrays. The modified fluoropolymer surface 5 is shown in Figure 1 .

[0058] According to some embodiments of the present application, in step (4), the ultraviolet glue 6 polymer includes at least one of an ultraviolet curable hybrid polymer and a polyurethane resin ultraviolet glue.

[0059] It can be understood that the ultraviolet curable hybrid polymer may include OrmoStamp. Among them, OrmoStamp has hydrophilicity, its dielectric constant is 13, the dynamic viscosity coefficient is 0.3 pa·s, and the surface tension coefficient is 0.032 N·m -1 , and the boundary slip length is 100 nm. The polyurethane resin ultraviolet glue may include NOA75, where NOA75 may be prepared by doping 1-ethyl-3-methyl-1H-imidazolium salt with a mass ratio of 0.01% into NOA75.

[0060] According to some embodiments of the present application, in step (4), the coating method is the doctor blade method. Further, the doctor blade method includes using a flat film applicator to scrape from one end to the other end at a speed of 0.1 mm / s to 1 mm / s.

[0061] In some preferred embodiments, on the basis of selectively wetting the substrate, with the help of a flat film applicator, the polymer is scraped from one end to the other end at a speed of 0.5 mm / s (attached Figure 2 The wire bar 7 used in the doctor blade process is shown), so as to obtain a raised array with uniform size and no obvious polymer residue in the hydrophobic region, such as a circular raised array, with a diameter of 200 um. After scraping different patterned substrates, it is found that the height of the droplets confined in the circular modified area is the highest, followed by the hexagonal shape, then the square shape, and the triangular shape is lower. As the bottom area increases, the complexing rate shows an increasing trend. When the distance between the doctor blade and the sample is kept constant, the scraping speed does not have a great impact on the confinement of the polymer. On the contrary, if the distance is too large, it is difficult to achieve the confinement of the polymer. If the distance is too small, the confined polymer volume is small, which has an adverse effect on the subsequent point traction stretching. As the viscosity of the polymer increases, the pollution residue in the unmodified area increases.

[0062] In some embodiments, in step (5), a piezoelectric ceramic moving control platform is used to make the upper plate coated with a fluoropolymer contact the pre-structured polymer, and then an external DC voltage of 200 v - 800 v is applied between the pre-structured lower plate and the upper plate by using a signal generator and an amplifier controller (that is, the power supply 9 is turned on in the attached Figure 2 ), and this voltage variable can control the stretching height. A space electric field is formed between the upper and lower plates, and the pre-structured polymer flows and deforms upward under the action of the electric field and traction force until the target preset height is reached.

[0063] According to some embodiments of the present application, in step (6), the curing time of the ultraviolet light 10 is 30 s - 40 s, and the demolding process utilizes the Coulomb repulsion between the interfacial frozen charges and the trapped charges (such as the Coulomb repulsion 8 shown in the appendix). Figure 2 is carried out as shown in

[0064] It can be understood that under the action of the electric field force, the mobile charges in the ultraviolet glue gather on the upper surface of the polymer. Keeping the voltage constant or continuing to increase the voltage, some of the mobile charges at the solid-liquid interface will enter the dielectric layer under the action of the electric field, forming trapped charges. The ultraviolet light cures the charges gathered on the polymer surface to freeze the charges. After ultraviolet light curing, the Coulomb repulsion between the interfacial frozen charges and the trapped charges is used to assist demolding, realizing a precise and non-destructive micro-nano structure.

[0065] According to some embodiments of the present application, in step (7), a hydrophobic fluoropolymer 11 is evaporated on the surface of the microstructure. The main reason is that the micro-nano structure formed by the ultraviolet glue is hydrophilic. If the fluoropolymer is not evaporated on the surface of the microstructure, the super pure water dropped will present a Wenzel state. The fluoropolymer evaporated on the surface of the microstructure will make the dropped liquid droplets present a Cassie state, presenting the superhydrophobic state desired in the present application. It can be understood that after evaporating the fluoropolymer 13, a pipette is used to drop 5 μl of super pure water 12 on the surface of the structure, and a contact angle measuring instrument is used to measure that its contact angle is greater than 150°, thereby realizing a superhydrophobic surface.

[0066] It should be noted that the evaporated hydrophobic fluoropolymer may include at least one of Hyflon and AF.

[0067] It is understandable that in this application, different-shaped confinement is achieved through the photolithography etching effect of ultraviolet light on the surface modifier of the hydrophobic film. By using a simple doctor blade coating process, the confinement of large-scale polymers is realized, revealing the confinement mechanism of light processing as an energy barrier for fluids, that is, through the light shielding of the mask plate, light irradiation of the specified area is achieved on the surface of the fluoropolymer. The specified area is at least 500 nm. The irradiated area causes some fluorine groups on the surface to defluorinate, and the molecular chains after bond breaking are oxidized into hydroxyl groups, carbonyl groups, and carboxyl groups, increasing the surface energy of the hydrophobic layer and changing it from hydrophobic to hydrophilic. When the photoresist is coated or dropped on the irradiated area, the chemical bond binding force at this time is greater than the line tension, achieving the confinement effect on the polymer. The etching effect at the physical level is strengthened by geometric pinning. After the doctor blade coating process, the pre-structured polymer formed on the surface of the hydrophobic film serves as the substrate. A fluoropolymer is spin-coated on the surface of the substrate as the upper plate. Through the piezoelectric ceramic moving control platform, the upper plate is moved until it touches the surface of the polymer. At this time, a spatial electric field is applied. Under the action of the electric field and traction force, the pre-structured polymer grows upward. After reaching the expected target height, ultraviolet curing and demolding are carried out, and the micro-nano structure can be obtained. A fluoropolymer is evaporated on the surface of the micro-nano structure to achieve a superhydrophobic surface.

[0068] It should be noted that whether it is optical lithography, which is the mainstream micro-nano manufacturing technology, or electron beam lithography technology and ion beam processing technology, there are certain requirements for the properties of the processed polymer materials, or they have a certain impact on the material characteristics of the polymer. Moreover, the process flow is complex, the efficiency is low, and the equipment cost is expensive. Although the imprinting technology has a simple process and can be mass-produced, it is difficult to control the high fidelity and process stability.

[0069] This application combines electric traction with a new confinement process. Among them, the new confinement process is low-energy surface microfluidic confinement additive manufacturing based on external light processing. This combination realizes complex, precise, and controllable pre-structured patterns on the low-energy surface. It realizes the selective wetting of liquids by means of the doctor blade coating technology, thereby forming a micro-droplet array with a hemispherical morphology. Among them, the liquid forms a liquid film under the action of a wire bar or a doctor blade. Due to the difference in wettability, the liquid film finally thins and breaks under the action of surface tension, and finally independent droplets are formed in the hydrophilic area. The joint participation of the electric field and the traction force, compared with the traditional spatial modulation electric field, greatly improves the upper limit of the upward growth of the polymer, increases the variable range, and greatly improves the aspect ratio of the structure. Pre-structured patterns are realized on the surface of the hydrophobic layer. Compared with the method of preparing pre-structured patterns by imprinting (imprinting requires the preparation of an imprinting template, the process flow is complex, and secondly, the fidelity of imprinting is insufficient, and the morphology is easily lost during the demolding process), the new confinement process is convenient for realizing pre-structured patterns, has a simple process flow, low equipment cost, can be manufactured in large areas and with high efficiency, has a high replication rate, and hardly introduces pollution to the hydrophobic layer.

[0070] Due to the excessive solid-liquid contact area in the demolding of imprinting technology, it has always been unable to maintain stable, long-term, and damage-free structure manufacturing. Especially for structures with a large aspect ratio, the structure is more likely to be missing after demolding. The solution proposed in the embodiments of this application reduces the solid-liquid contact area. Only the upper surface contacts the hydrophobic dielectric layer. In addition, the spin-coated hydrophobic layer has a relatively large thickness, generally reaching 800 nm, which reduces the force during demolding, greatly improving the long-term performance and stability. It can induce the formation of precise and damage-free micro-nano structures. A fluoropolymer is evaporated on its surface to achieve a superhydrophobic surface. This method does not require expensive equipment, the process is simple, and there are almost no requirements for the polymer material. The morphology of the formed structure is controllable, the structure has high fidelity, and the process flow is stable. It is a large-scale and high-precision micro-nano processing method, providing a new idea for the realization of superhydrophobic surfaces. The structure morphology is similar to the combination of two frustums of a cone. The upper and lower morphologies are circular, and the middle shrinkage area decreases. The advantage of this structure is that the key parameter affecting the structure is the angle formed between the side wall of the indentation and the horizontal line, which is called θ overhang , when θ overhang >θ flat , from the water side, the water-air interface (meniscus force) is concave. The force generated by the meniscus at the water-air interface is directed towards the inside of the groove, increasing the difficulty of achieving a superhydrophobic surface. The angle formed by this structure is θ overhang <θ flat . At this time, the meniscus is convex, and the net force generated by the meniscus is directed towards the outside of the notch, preventing water from entering the notch. Moreover, the arc-shaped structure not only increases its roughness but also reduces the contact area between the liquid and the side of the substrate, making it easier to achieve a superhydrophobic surface compared to traditional micro-nano structures.

[0071] According to the second aspect of this application, a micro-structure with a superhydrophobic surface is provided. This micro-structure is prepared by using the preparation method described in any one of the above. This micro-structure can be applied to fields such as self-cleaning, oil-water separation, and drag reduction.

[0072] The above has described the embodiments of this application in detail in combination with specific implementation manners. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the purpose of this application. In addition, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other.

Claims

1. A preparation method of a microstructure with a superhydrophobic surface, characterized in that, the preparation method includes: Step (1): Pretreat the surface of the substrate and dry it for later use; Step (2): Coat the surface of the substrate obtained in step (1) with a fluoropolymer, and then perform a heat treatment to obtain a substrate with a fluoropolymer hydrophobic coating; Step (3): Irradiate the substrate with a polymer hydrophobic coating obtained in step (2) through a mask plate with an array pattern in ultraviolet light to obtain a substrate with an interlaced hydrophilic and hydrophobic array; Step (4): Wet the substrate obtained in step (3), and then coat a layer of ultraviolet glue polymer on the interlaced hydrophilic and hydrophobic array surface, so as to obtain a convex array on the substrate surface; Step (5): Use the substrate in step (2) as the upper plate and the substrate in step (4) as the lower plate, contact the upper plate with the lower plate, and apply a DC voltage of 200V - 800V between the upper plate and the lower plate. The convex array in the lower plate undergoes upward flow forming under the action of an electric field and traction force; Step (6): Perform ultraviolet curing and demolding treatment on the lower plate obtained in step (5) to obtain a microstructure with a fixed morphology; Step (7): Evaporate a layer of hydrophobic fluoropolymer on the surface of the microstructure in step (6) to obtain a microstructure with a superhydrophobic surface.

2. The preparation method according to claim 1, characterized in that, The irradiation treatment conditions described in step (3) are as follows: the ultraviolet light range is 100 nm - 200 nm, the light intensity is greater than 10 mW / cm 2 , and the irradiation time is 10 min to 15 min.

3. The preparation method according to claim 1, characterized in that, In step (4), the ultraviolet glue polymer includes at least one of an ultraviolet curable hybrid polymer and a polyurethane resin ultraviolet glue.

4. The preparation method according to claim 1, characterized in that, In step (2), the fluoropolymer includes at least one of Hyflon and AF.

5. The preparation method according to any one of claims 1 to 4, characterized in that, In step (2), the even heating treatment includes pre-curing by heating on a hot plate at 82°C - 88°C for 0.5 min - 2 min, and then heating in a dust-free oven at 180°C - 185°C for 30 - 90 min.

6. The preparation method according to any one of claims 1 to 4, characterized in that, The substrate in step (1) includes at least one of ITO transparent glass and a conductive rigid substrate.

7. The preparation method according to claim 1, characterized in that, The shape of the array in step (3) includes at least one of a circle, a square, a triangle, and a hexagon.

8. The preparation method according to any one of claims 1 to 4, characterized in that, In step (4), the coating method is a doctor blade coating method. Further, the doctor blade coating method includes using a flat film doctor to scrape from one end to the other end at a speed of 0.1 mm / s - 1 mm / s.

9. The preparation method according to any one of claims 1 to 4, characterized in that, In step (6), the time for ultraviolet curing is 30 s - 40 s, and the demolding treatment is carried out by using the Coulomb repulsion of like charges between the interfacial frozen charges and the trapped charges.

10. A micro-structure with a superhydrophobic surface, characterized in that, the micro-structure is prepared by the preparation method described in any one of claims 1-9.

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