Hydrophobic surface with multi-level micro-nano structure

Abstract

The invention discloses a hydrophobic surface with a multi-level micro-nano structure. A multi-level micro-nano geometric structure which firstly decreases step by step and then increases step by step is formed on a solid surface through one-step forming technologies such as photoetching, laser and imprinting. The multi-level micro-nano structure is based on a plurality of designed micro-nano levels with different heights or scales, and a plurality of energy barriers are arranged for the process of wetting the wall surface by liquid. Liquid must break through all the energy barriers layer by layer and can be completely immersed into the surface of the substrate. Due to the existence of multi-scale and multi-energy-level barriers, the liquid is difficult to break through each energy barrier finally, so that the multi-level micro-nano structure wall surface can effectively keep a hydrophobic state. The multi-level hydrophobic surface has the good non-infiltration characteristic, has the functions of self-cleaning, water prevention, pollution prevention and the like, and is suitable for multiple fields of self-cleaning, resistance reduction, ice prevention, microfluidics, military affairs, biomedical engineering and the like. In addition, the invention also has the advantages of one-step molding, simple processing, convenient process, good economical efficiency and the like.

Description

Technical Field

[0001] The present invention relates to the field of surface technology, and in particular to a hydrophobic surface with a multi-level micro-nano structure. Background Art

[0002] Hydrophobic surfaces have the functions of self-cleaning, waterproofing, anti-fogging, anti-adhesion and anti-pollution, and are widely used in microfluidics, military, biomedical engineering and daily life. When the static contact angle of the surface is between 90° and 150°, the surface can be defined as a hydrophobic surface. In order to achieve this hydrophobic property, researchers have developed a variety of artificial micro-nano structures, among which common single-scale structures include columns of different shapes, cones, trapezoidal monomer structures, or periodically arranged hole structures. These micro-nano structures can affect the wetting behavior of water droplets on the surface, making the water droplets present Wenzel state or Cassie state. However, when the external pressure or energy is high enough, the droplets can easily break through the energy barrier, resulting in unstable surface hydrophobic properties, which is very unfavorable for engineering applications such as anti-corrosion, self-cleaning, and drag reduction.

[0003] In the prior art, although a single-scale micro-nano structure can effectively construct a hydrophobic surface, its hydrophobic stability is poor and it is easily penetrated by liquid, resulting in failure of the rough structure. In addition, although the existing multi-level micro-nano composite structure can enhance the hydrophobic stability of the surface, its processing steps are complicated and difficult to achieve large-scale production. Therefore, how to improve the mechanical stability while maintaining the hydrophobic properties of the surface has become an urgent problem to be solved. Summary of the invention

[0004] In view of the above-mentioned problems existing in the prior art, the present invention provides a multi-level micro-nano structure. By changing the depth of laser ablation or photolithography, a multi-level micro-nano structure is constructed, which effectively enhances the hydrophobic stability between the droplets and the rough surface. These multi-level structures are equivalent to setting up multiple different energy barriers for the water droplets. The liquid needs to gradually break through these barriers to completely wet the surface. Therefore, this multi-level structural design makes it extremely difficult for the water droplets to transform from the Cassie state to the Wenzel state, thereby maintaining the non-wetting characteristics and stable hydrophobic properties of the surface. The structure has the characteristics of simple implementation process, convenient process, good economy, and strong hydrophobic stability.

[0005] The technical solution of the present invention is as follows:

[0006] A hydrophobic surface with a multi-level micro-nano structure, comprising a base material and a multi-level micro-nano structure located on the surface of the base material;

[0007] The multi-level micro-nano structure is composed of no less than one structural unit; the structural unit is a columnar structure or a conical structure, and the heights are not completely the same;

[0008] The structural units are arranged as follows:

[0009] (1-1) A direction is selected on the surface of the substrate material as the X-axis direction; a group of structural units with the same height are arranged in a straight line along the X-axis direction;

[0010] (1-2) Along the Y-axis direction perpendicular to the X-axis direction, another group of structural units with the same height and also arranged in a straight line are copied, but the height of this group of structural units is slightly smaller than that of the previous group;

[0011] (1-3) A new set of structural units is repeatedly arranged along the Y-axis direction, and the height continues to decrease; when the height decreases to a certain extent, it increases instead;

[0012] Observing along the X-axis direction, the structural units are arranged into multiple straight lines, and the height of the structural units on each straight line is the same; observing along the Y-axis direction, the structural units are also arranged into multiple straight lines, but the height of the structural units on each straight line changes in a wave-like manner, first decreasing and then increasing, and repeating continuously;

[0013] When described in plane geometry, the structural units are arranged as follows:

[0014] (2-1) A plane perpendicular to the surface of the base material that passes through a series of structural units is called a section plane. The projection outline of the structural unit on the section plane is called a cross-sectional view. The shapes of the cross-sectional view of the structural unit include: rectangle, trapezoid, triangle;

[0015] (2-2) Along the direction of the section plane, a number of structural units of not less than one are grouped into a group, which is called a one-dimensional primitive group; the structural units within the one-dimensional primitive group are arranged according to different heights, for example: the height increases first and then decreases, or the height decreases first and then increases;

[0016] (2-3) On the surface of the substrate material, one-dimensional primitives are continuously replicated along two mutually perpendicular directions, namely, the direction parallel to the cross-sectional view and the direction perpendicular to the cross-sectional view, to form a rough structure composed of structural units of different heights, namely, a multi-level micro-nanostructure.

[0017] Furthermore, the hydrophobic static contact angle of the base material is greater than 90°.

[0018] Furthermore, the structural units are arranged as follows:

[0019] (3-1) A region is selected on the surface of the substrate material, and a number of structural units of not less than one are arranged in the region, which is called a two-dimensional primitive group; the structural unit located at the center of the region has the smallest height; the structural unit farther from the center of the region has a larger height;

[0020] (3-2) A direction is selected on the surface of the substrate material as the X-axis direction; the two-dimensional primitive group is continuously replicated along the X-axis direction to obtain a straight line with the two-dimensional primitive group as a point; the straight line is continuously replicated along the Y-axis direction perpendicular to the X-axis direction to obtain a multi-level micro-nano structure.

[0021] Furthermore, the shapes of the structural units include: cuboid, cube, prism, sphere, cylinder, cone, and prism.

[0022] The beneficial technical effects of the present invention are:

[0023] (1) The constructed multi-level micro-nano structure greatly increases the resistance of the liquid in the process of wetting the wall surface, thereby reducing the possibility of the liquid completely wetting the wall surface. Compared with the existing single-layer structure, the multi-level structure design proposed in the present invention creates multiple hydrophobic energy barriers for the wall surface. The liquid can only contact the substrate surface after breaking through the multiple layers of obstacles. Therefore, the wall surface is extremely difficult to infiltrate, which significantly improves the hydrophobic stability of the wall surface. Especially in high collision speed or high kinetic energy environment, the proposed multi-level structure surface can still maintain long-term superhydrophobic properties;

[0024] (2) The multi-level structure is directly constructed on the substrate through lithography, laser, imprinting and other technologies, avoiding the disadvantages of the cumbersome processing steps of micro-nano composite structures in the existing technology. This method does not require additional templates or complex etching processes, and can achieve efficient, precise and controllable structure manufacturing, which is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the surface processing process of multi-level micro-nano structures;

[0026] Figure 2 It is a three-dimensional diagram and a cross-sectional diagram of a multi-level micro-nano structure with a rectangular cross section;

[0027] Figure 3 It is a three-dimensional diagram and cross-sectional diagram of a multi-level micro-nano structure with a trapezoidal cross section;

[0028] Figure 4 It is a three-dimensional image and cross-sectional image of a multi-level micro-nano structure with a triangular cross section;

[0029] Figure 5 It is a three-dimensional image of a multi-level micro-nano structure that decreases from the periphery to the center. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] Example 1: A multi-level micro-nano structure is constructed on a substrate by laser ablation technology. The specific implementation process is as follows: Figure 1 As shown, first, a material that can be processed by laser for microstructure is selected as a substrate, such as metal, ceramic, polymer and glass, and then the surface of the substrate is processed by an orthogonal cross linear laser ablation process to construct a multi-level micro-nano structure.

[0033] like Figure 2 As shown in the figure, the multi-level micro-nano structure is composed of a large number of structural units. The structural units are columnar in shape and are repeatedly arranged according to a certain pattern on the surface of the base material to form a rough structure that can improve the hydrophobic performance. The arrangement of the structural units is as follows:

[0034] (1-1) Along one direction, such as the X-axis, a group of structural units with the same height are arranged in a straight line;

[0035] (1-2) Along the Y-axis direction perpendicular to the X-axis direction, another group of structural units with the same height and also arranged in a straight line are copied, but the height of this group of structural units is slightly smaller than that of the previous group;

[0036] (1-3) A new set of structural units continues to be repeatedly arranged along the Y-axis direction, and the height continues to decrease; when the height decreases to a certain extent, it increases instead.

[0037] Figure 2 The three-dimensional stereogram and two-dimensional cross-sectional diagram show the specific structure of the multi-level micro-nano structure. Figure 2 As shown in the left figure, the structural units are arranged into multiple straight lines, and the height of the structural units on each straight line is the same; observing along the Y-axis direction, the structural units are also arranged into multiple straight lines, but the height of the structural units on each straight line changes in a wave-like manner, first decreasing and then increasing, repeating continuously.

[0038] When described in plane geometry, the structural units are arranged as follows: Figure 2 As shown in the right figure:

[0039] (2-1) A plane perpendicular to the surface of the base material that passes through a series of structural units is called a section plane. The projection outline of the structural unit on the section plane is called a cross-sectional view. The shapes of the cross-sectional view of the structural unit include: rectangle, trapezoid, triangle;

[0040] (2-2) The number of structural units that are not less than one is grouped into a group, which is called a one-dimensional primitive group; the structural units within the one-dimensional primitive group are arranged according to different heights, for example: the height increases first and then decreases, or the height decreases first and then increases;

[0041] (2-3) On the surface of the substrate material, one-dimensional primitives are continuously replicated along two mutually perpendicular directions, namely, the direction parallel to the cross-sectional view and the direction perpendicular to the cross-sectional view, to form a rough structure composed of structural units of different heights, namely, a multi-level micro-nanostructure.

[0042] This multi-level design of decreasing first and increasing later provides multiple energy barriers for the wall to resist wetting by droplets. When the droplets move on the surface, they must gradually overcome the energy barriers of each layer, which greatly reduces the possibility of contact and wetting with the substrate surface, and effectively improves the hydrophobicity and hydrophobic stability of the substrate wall.

[0043] The hydrophobic static contact angle of the base material in Example 1 needs to be greater than 90°. According to the Cassie wetting theory, by constructing a multi-level micro-nano structure, the contact angle of the droplet on the modified surface can be increased to more than 160°, and the sliding angle is less than 5°.

[0044] Example 2

[0045] The difference from Example 1 is that the structural unit of Example 2 is a step platform ( Figure 3 ) and cone ( Figure 4 ), and the cross-section is trapezoidal and triangular.

[0046] in conclusion: Figure 3 and Figure 4 The multi-level structural wall is constructed by terraces and cones respectively, which also provides multiple energy barriers for the wall to resist the wetting of droplets. When the droplets move on the surface, they must overcome the energy barrier of each layer step by step, which greatly reduces the possibility of contact and ease of wetting with the substrate surface, and effectively improves the hydrophobic performance and hydrophobic stability of the substrate wall. The structural units include but are not limited to cuboids, cubes, pyramids, spheres, cylinders, cones, prisms, etc., which are arranged repeatedly in a gradient on the surface of the substrate material to form a multi-level micro-nano structure surface. The above two embodiments can both have a good hydrophobic effect on the surface when actually used. Compared with the coarse-bottom and fine-top structural units in Example 2, the hydrophobic stability of the multi-level prismatic structure wall in Example 1 is more significant.

[0047] Example 3

[0048] The difference from Example 1 is that the structural units are distributed in descending order from the periphery to the center, rather than being arranged in sequence as in Example 1. The specific arrangement of the structural units is as follows Figure 5 As shown:

[0049] (3-1) A region is selected on the surface of the substrate material, and a number of at least one structural unit is arranged inside the region, which is called a two-dimensional primitive group; the height of the structural unit located at the center of the region is the smallest; the farther the structural unit is from the center of the region, the greater its height;

[0050] (3-2) A direction is selected on the surface of the substrate material as the X-axis direction; the two-dimensional primitive group is continuously replicated along the X-axis direction to obtain a straight line with the two-dimensional primitive group as a point; the straight line is continuously replicated along the Y-axis direction perpendicular to the X-axis direction to obtain a multi-level micro-nano structure.

[0051] in conclusion: Figure 5 The structure shows a shape that gradually decreases from the periphery to the center, forming a clearly layered surface. Such a design not only increases the roughness of the surface, but also effectively ensures the force symmetry of the liquid in the process of breaking through the multi-level structure. In Example 1, due to the sequential arrangement of the multi-level structure, the force distribution of the liquid along the ridge direction and the vertical direction along the ridge is uneven, which may cause the multi-level energy barrier to fail. Figure 5 The central gradient distribution structure ensures the symmetry of the force on the liquid, reduces the possibility of asymmetric contact between the droplet and the substrate, and thus maintains the good super-hydrophobic performance of the multi-level surface. Compared with the sequential arrangement structure in Example 1, the central gradient distribution structure wall in Example 3 has better hydrophobic stability.

[0052] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes, and can be fully applicable to various fields suitable for the present invention. For those familiar with the art, for those of ordinary skill in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A hydrophobic surface with a multi-level micro-nano structure, characterized in that: It includes a base material and a multi-level micro-nano structure located on the surface of the base material; The multi-level micro-nano structure is composed of no less than one structural unit; the structural unit is a columnar structure or a conical structure, and the heights are not completely the same; The structural units are arranged as follows: (1-1) A direction is selected on the surface of the substrate material as the X-axis direction; a group of structural units with the same height are arranged in a straight line along the X-axis direction; (1-2) Along the Y-axis direction perpendicular to the X-axis direction, another group of structural units with the same height and also arranged in a straight line are copied, but the height of this group of structural units is slightly smaller than that of the previous group; (1-3) A new set of structural units is repeatedly arranged along the Y-axis direction, and the height continues to decrease; when the height decreases to a certain extent, it increases instead; Observing along the X-axis direction, the structural units are arranged into multiple straight lines, and the height of the structural units on each straight line is the same; observing along the Y-axis direction, the structural units are also arranged into multiple straight lines, but the height of the structural units on each straight line changes in a wave-like manner, first decreasing and then increasing, and repeating continuously; When described in plane geometry, the structural units are arranged as follows: (2-1) A plane perpendicular to the surface of the base material passing through a series of structural units is made, which is called the section plane; The projected outline of the structural unit on the section plane is called the profile; The cross-sectional shapes of the structural units include: rectangle, trapezoid, triangle; (2-2) Along the direction of the section plane, a number of structural units of not less than one are grouped into a group, which is called a one-dimensional primitive group; the structural units within the one-dimensional primitive group are arranged according to different heights, for example: the height increases first and then decreases, or the height decreases first and then increases; (2-3) On the surface of the substrate material, one-dimensional primitives are continuously replicated along two mutually perpendicular directions, namely, the direction parallel to the cross-sectional view and the direction perpendicular to the cross-sectional view, to form a rough structure composed of structural units of different heights, namely, a multi-level micro-nanostructure.

2. The hydrophobic surface with a multi-level micro-nano structure according to claim 1, characterized in that: The hydrophobic static contact angle of the base material is greater than 90°.

3. The hydrophobic surface with a multi-level micro-nano structure according to claim 1, characterized in that: The structural units are arranged as follows: (3-1) A region is selected on the surface of the substrate material, and a number of structural units of not less than one are arranged in the region, which is called a two-dimensional primitive group; the structural unit located at the center of the region has the smallest height; the structural unit farther from the center of the region has a larger height; (3-2) Select a direction on the surface of the substrate material as the X-axis direction; The two-dimensional primitive group is continuously replicated along the X-axis direction to obtain a straight line with the two-dimensional primitive group as a point; the straight line is continuously replicated along the Y-axis direction perpendicular to the X-axis direction to obtain a multi-level micro-nano structure.

4. The hydrophobic surface with a multi-level micro-nano structure according to claim 1, characterized in that: The shapes of the structural units include: cuboid, cube, prism, sphere, cylinder, cone and prism.

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