阅读说明：本技术 一种仿猪笼草滑移区的各向同性超疏水表面设计方法 (Method for designing isotropic super-hydrophobic surface simulating nepenthes sliding region ) 是由 王立新 闫征 于 2020-05-27 设计创作，主要内容包括：本发明公开了一种仿猪笼草滑移区的各向同性超疏水表面设计方法,首先利用扫描电子显微镜与三维白光形貌干涉仪对猪笼草滑移区进行微形貌观测并获取微形貌结构特征参数；根据所提取的微形貌结构特征参数建立一种仿猪笼草滑移区的各向同性超疏水表面仿生模型,基于Cassie--Baxter模型计算出一种仿猪笼草滑移区的各向同性超疏水表面的微形貌结构特征参数与超疏水功能之间的数值关系；根据推导出的数值关系,通过调节微形貌结构特征参数,来调控仿猪笼草滑移区的各向同性超疏水表面的超疏水功效。本设计方法能够实现各向同性超疏水表面的可控设计,设计的超疏水表面具有超疏水功效可调控、超疏水功效各向同性等特点。(The invention discloses a method for designing an isotropic super-hydrophobic surface simulating a nepenthes sliding area, which comprises the steps of firstly, carrying out micro-topography observation on the nepenthes sliding area by utilizing a scanning electron microscope and a three-dimensional white light topography interferometer and obtaining micro-topography structural characteristic parameters; establishing an isotropic super-hydrophobic surface bionic model of the imitation nepenthes sliding region according to the extracted micro-morphological structure characteristic parameters, and calculating a numerical relation between the micro-morphological structure characteristic parameters and the super-hydrophobic function of the isotropic super-hydrophobic surface of the imitation nepenthes sliding region based on a Cassie-Baxter model; according to the deduced numerical relation, the super-hydrophobic efficacy of the isotropic super-hydrophobic surface of the nepenthes-imitating sliding region is regulated and controlled by adjusting the characteristic parameters of the micro-morphology structure. The design method can realize the controllable design of the isotropic superhydrophobic surface, and the designed superhydrophobic surface has the characteristics of controllable superhydrophobic effect, isotropic superhydrophobic effect and the like.)

1. A method for designing an isotropic superhydrophobic surface simulating a nepenthes slipping area is characterized by comprising the following steps:

step 1, firstly, carrying out micro-topography observation on a nepenthes sliding area by using a scanning electron microscope and a three-dimensional white light topography interferometer and obtaining micro-topography structural feature parameters;

step 2, establishing an isotropic super-hydrophobic surface bionic model of the nepenthes-imitating sliding region according to the extracted micro-morphological structure characteristic parameters, and calculating a numerical relation between the micro-morphological structure characteristic parameters and the super-hydrophobic function of the isotropic super-hydrophobic surface of the nepenthes-imitating sliding region based on a Cassie-Baxter model;

and 3, regulating and controlling the superhydrophobic efficacy of the isotropic superhydrophobic surface of the nepenthes-simulated sliding region by regulating the characteristic parameters of the micro-morphology structure according to the deduced numerical relationship.

2. The design method of the isotropic superhydrophobic surface of the imitation nepenthes sliding region according to claim 1, characterized in that the isotropic superhydrophobic surface biomimetic model is a spherical crown structure formed by a lunar skeleton configuration, cylinder arrays are vertically distributed on the surface of the spherical crown structure, and the cylinder arrays are formed by waxy crystal configurations.

3. The method for designing the isotropic superhydrophobic surface of the imitation nepenthes sliding region according to claim 2, wherein the numerical relationship is

In the formula: and respectively representing a theoretical value of a contact angle and an intrinsic contact angle, wherein the intrinsic contact angle of a water drop on the surface of the smooth waxy crystal is generally 100-110 degrees; representing the ratio of the actual wetted solid area of the droplet to the apparent geometric contact area;Ris the radius of the projection circle of the spherical crown,Hheight from the top of the spherical cap to the base, and the radius and height of the single cylinder are respectively represented; representing the ratio of the projected area of the cylinder array to the area of the base.

4. The method for designing the isotropic superhydrophobic surface of the nepenthes-simulated sliding region according to claim 3, wherein characteristic parameters of the micro-morphology structure are taken as preset values and are substituted into the formula in claim 3, the contact angle of liquid drops on the isotropic superhydrophobic surface of the nepenthes-simulated sliding region is calculated, and whether the isotropic superhydrophobic surface has a good superhydrophobic function or not can be judged according to the size of the contact angle.

5. The design method of the isotropic superhydrophobic surface of the nepenthes-simulated sliding region according to claim 4, wherein the superhydrophobic efficacy of the isotropic superhydrophobic surface of the nepenthes-simulated sliding region can be improved by adjusting the ratio of the height to the radius of the cylinders in the characteristic parameters.

6. The method for designing the isotropic superhydrophobic surface of the nepenthes-simulated sliding region according to claim 2, wherein waxy crystal layers of the cylinder array are staggered to form a net structure and have micro-nano-scale structural characteristic parameters, and the generated holes can store air to form a liquid-gas-solid contact interface.

Technical Field

The invention belongs to the field of super-hydrophobic surface design, and particularly relates to a super-hydrophobic surface design method for observing and extracting a micro-topography structure of a nepenthes sliding region with super-hydrophobic characteristics according to a scanning electron microscope and a three-dimensional topography interferometer to obtain characteristic parameters, so that the super-hydrophobic surface with isotropic super-hydrophobic effect and adjustable super-hydrophobic effect is formed.

Background

The super-hydrophobic surface refers to a micro-nano structure surface with a static contact angle larger than 150 degrees and a rolling angle smaller than 10 degrees. In the long-term natural evolution process of organisms, material surfaces with unique configuration and excellent super-hydrophobic performance are formed, such as the surfaces of a pitcher grass slippage area, a water strider palm, a lotus leaf and the like. The micro-topography structural features of the animal and plant body surfaces can intercept an air layer, so that the special infiltration characteristic generated by the contact area of liquid drops and the material surface is effectively reduced, and with the inspiration, researchers successively develop researches and bionically develop super-hydrophobic materials with excellent functions. The super-hydrophobic materials play an extremely important role in the daily life field and the engineering field, such as self-cleaning coatings, antifogging glass, metal corrosion prevention, ship resistance reduction and the like.

The contact angle of the liquid on the solid surface is an important standard for measuring the wetting characteristic, the contact angle is the result of surface tension balance among solid, liquid and gas 3 interfaces, the total energy of the system tends to be minimum when the tension is balanced, and the liquid drop on the solid surface is in a stable state. The Wenzel model considers that when liquid drops contact with the solid surface, the micro-morphological structure of the rough surface can be completely immersed, and a complete wetting state is presented; and a Wenzel equation is proposed, wherein the contact angle of the liquid drop is the roughness factor, and the intrinsic contact angle of the liquid drop on the smooth surface is provided. Subsequently, a Cassie-Baxter model was proposed, which suggests that the contact surface is composed of 3 parts of liquid droplets, solid surface micro-topography, air trapped inside the micro-topography, etc., from which it follows that the contact angle is an intrinsic contact angle, which is a roughness coefficient. The surface of the material has super-hydrophobic property, mainly because the surface micro-morphological structure forms a large proportion of gas-liquid interface to maintain Cassie-Baxter state, so that the surface of the material presents a larger contact angle. The key to designing a superhydrophobic surface is how to design the material surface micro-topography to ensure that the liquid droplets can exist in the Cassie-Baxter state stably. The nepenthes sliding area is covered with a composite micro-morphology structure consisting of a micron-sized corpus lunate and a nano-sized waxy crystal, can present low-adhesion super-hydrophobic wetting characteristic, and provides a bionic prototype for the research of a super-hydrophobic surface.

The Chinese invention patent CN105550476A discloses a controllable design method of a micro-column structure stable super-hydrophobic surface, which provides a critical height criterion for forming a stable Cassie-Baxter state by liquid drops from the perspective of the minimum energy principle and can be used as a theoretical criterion for designing a stable super-hydrophobic micro-morphology structure; theoretical prediction is carried out on whether a stable Cassie-Baxter state can be formed or not by calculating the critical height, so that the controllable design of the super-hydrophobic surface is realized; the method for designing the superhydrophobic surface of the periodically arranged micro-column structure only explains the influence mechanism of the height of the micro-column, the distance between the micro-columns and the side length of the bottom surface of the micro-column, but is limited to a traditional columnar convex structure model, the configuration is relatively complex, and the superhydrophobic performance is not isotropic. The Chinese invention patent CN101819125A discloses a method for designing a stable superhydrophobic surface of a grating structure, which deduces the numerical relationship between the characteristic parameters of the grating structure and the superhydrophobic performance; the super-hydrophobic performance can be improved by regulating and controlling the structural characteristic parameters; however, the super-hydrophobic surface design method still has the problems that the super-hydrophobic efficacy is not isotropic and the like.

In summary, although the existing superhydrophobic surface design method can realize the regulation and control of the efficacy of the designed superhydrophobic surface by adjusting the structural characteristic parameters, the superhydrophobic efficacy is not isotropic. Therefore, the design method of the isotropic superhydrophobic surface simulating the nepenthes sliding region is provided, a designed superhydrophobic surface function representation mechanism is given based on a Cassie-Baxter model, and the design method has the characteristics of controllable superhydrophobic effect, isotropic superhydrophobic effect and the like.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for designing an isotropic superhydrophobic surface simulating nepenthes sliding region, a superhydrophobic function representation mechanism of the designed superhydrophobic surface is given based on a Cassie-Baxter model, and the controllable design of the isotropic superhydrophobic surface can be realized, so that the superhydrophobic surface designed by the method has the characteristics of controllable superhydrophobic effect, isotropic superhydrophobic effect and the like.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a method for designing an isotropic superhydrophobic surface simulating a nepenthes slipping area is characterized by comprising the following steps:

step 1, firstly, carrying out micro-topography observation on a nepenthes sliding area by using a scanning electron microscope and a three-dimensional white light topography interferometer and obtaining micro-topography structural feature parameters;

step 2, establishing an isotropic super-hydrophobic surface bionic model of the nepenthes-imitating sliding region according to the extracted micro-morphological structure characteristic parameters, and calculating a numerical relation between the micro-morphological structure characteristic parameters and the super-hydrophobic function of the isotropic super-hydrophobic surface of the nepenthes-imitating sliding region based on a Cassie-Baxter model;

and 3, regulating and controlling the superhydrophobic efficacy of the isotropic superhydrophobic surface of the nepenthes-simulated sliding region by regulating the characteristic parameters of the micro-morphology structure according to the deduced numerical relationship.

On the basis of the scheme, the isotropic superhydrophobic surface bionic model is a spherical crown structure formed by a lunar structure, a cylinder array is vertically distributed on the surface of the spherical crown structure, and the cylinder array is formed by a waxy crystal configuration. The purpose is to make the designed superhydrophobic surface show isotropy in terms of morphological structure, so that the rolling angles of the liquid drops in any direction are all the same, and finally the isotropy of the superhydrophobic effect is caused.

On the basis of the scheme, the numerical relation is

In the formula: and respectively representing a theoretical value of a contact angle and an intrinsic contact angle, wherein the intrinsic contact angle of a water drop on the surface of the smooth waxy crystal is generally 100-110 degrees; representing the ratio of the actual wetted solid area of the droplet to the apparent geometric contact area;Ris the radius of the projection circle of the spherical crown,Hheight from the top of the spherical cap to the base, and the radius and height of the single cylinder are respectively represented; representing the ratio of the projected area of the cylinder array to the area of the base.

On the basis of the scheme, the characteristic parameters of the micro-morphology structure are taken as preset values and are substituted into the formula in claim 3, the contact angle of the liquid drop on the isotropic super-hydrophobic surface in the nepenthes-imitating sliding area is calculated, and whether the isotropic super-hydrophobic surface has a good super-hydrophobic function or not can be judged according to the size of the contact angle.

On the basis of the scheme, the super-hydrophobic effect of the isotropic super-hydrophobic surface of the nepenthes-imitating sliding region can be improved by regulating and controlling the ratio of the height to the radius of the cylinder in the characteristic parameters.

On the basis of the scheme, the wax crystal layers of the cylinder array are arranged in a staggered mode to form a net shape and have structural characteristic parameters of micro-nano scale, and the generated holes can store air to form a liquid-gas-solid contact interface.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: according to the method, the structural characteristics and the superhydrophobic effect are given out based on a Cassie-Baxter model through the representation of the micro-morphology structural parameters of the nepenthes sliding area, so that the isotropic superhydrophobic surface design method of the nepenthes sliding area can be obtained, and the controllability of the superhydrophobic effect and the isotropy of the superhydrophobic effect can be realized. In the method, the superhydrophobic efficacy of the designed superhydrophobic surface, namely the size of a liquid drop contact angle, can be regulated and controlled by changing the structural parameters of the spherical crown and the cylinder array in the bionic model, namely improving the ratio of the height to the radius of the cylinder array, so that the controllable design of the isotropic superhydrophobic surface is realized.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

FIG. 2 is a schematic view of the spherical cap structure of the present invention;

FIG. 3 is a schematic diagram of a cylinder array structure according to the present invention;

FIG. 4 is a design flow diagram of the present invention.

Detailed Description

The following examples are given to illustrate the present invention, but are not intended to limit the scope of the present invention in any way, and the working process of the present invention will be described in detail below with reference to the accompanying drawings.

The invention relates to a method for designing an isotropic superhydrophobic surface of an imitation nepenthes sliding region, a superhydrophobic function regulation and control mechanism of a designed superhydrophobic surface is given based on a Cassie-Baxter model, controllable design of the isotropic superhydrophobic surface can be realized, and particularly, the isotropy refers to the fact that when liquid drops roll on the superhydrophobic surface along any direction, the rolling angles are the same.

In order to achieve the purpose of the invention, firstly, a scanning electron microscope and a three-dimensional white light morphology interferometer are utilized to carry out micro-morphology observation on the nepenthes sliding area and obtain micro-morphology structure characteristic parameters; establishing an isotropic superhydrophobic surface bionic model simulating a nepenthes sliding area according to the extracted micro-morphological structure characteristic parameters, configuring a lunar structure into a spherical crown structure, and configuring waxy crystals into a cylinder array vertically distributed on the spherical crown surface, wherein the aim is to enable the designed superhydrophobic surface to present isotropy in the aspect of morphological structure, so that the rolling angles of liquid drops in any direction are all the same, and finally leading to isotropy of the superhydrophobic effect. Calculating a numerical relation between the micro-morphological structure characteristic parameters and the super-hydrophobic function (contact angle) of the isotropic super-hydrophobic surface of the imitation nepenthes sliding region based on a Cassie-Baxter model; according to the deduced numerical relation, the super-hydrophobic efficacy of the isotropic super-hydrophobic surface of the imitation nepenthes sliding region, namely the size of the liquid drop contact angle, is regulated and controlled by regulating the characteristic parameters of the micro-morphology structure.

Step 1, characterizing the micro-morphology structure parameters of the nepenthes slippage area. And observing the micro-morphology structure on the surface of the nepenthes sliding area by using a scanning electron microscope and a three-dimensional white light morphology interferometer, and analyzing and extracting the characteristic parameters of the micro-morphology structure. The method specifically comprises the following steps: the height, length, width, spacing and density of the corpus lunatus in the nepenthes slippage area, the height and area ratio of the waxy crystal layer and the like.

Bionic prototype selected from red pitcher plant (Chinese lobelia herb)Nepenthes alata) The testing and characterizing instrument adopts a scanning electron microscope and a three-dimensional white light appearance interferometer. For a red pitcher nepenthes leaf cage, a sample with the length and the width of 10 mm is cut at the position of a slippage area, dried by adopting a critical point drying method, and then adhered to an experiment table by using double-sided adhesive; and observing the micro-topography structure of the sliding area by adopting a scanning electron microscope and a three-dimensional white light topography interferometer. And extracting micro-topography structural feature information of the sliding area micro-topography structural image stored by the scanning electron microscope and the three-dimensional white light topography interferometer, and determining three-dimensional structural feature parameters of the micro-topography structural feature information. Nepenthes slipping areaThe surface of the shell is covered with a corpus lunata with two downward bent ends and a wax crystal layer which is densely arranged, wherein the wax crystal layer consists of flaky wax crystals with irregular shapes and distinguishable outlines, and the flaky wax crystals are approximately vertically arranged and are closely interacted to form a net structure; the height of the outer side of the lunate body changes slowly to form a slope structure, and the inner side changes approximately vertically to form a cliff structure. The characteristic parameters of the micro-morphology structure of the nepenthes slippage area are as follows: the height of the corpus lunata was 20.41 microns, the length was 44.38 microns, the width was 11.55 microns, the spacing was 69.16 microns, and the density was 176 per square millimeter; the wax crystal layer had a height of 0.24 μm and an area ratio (wax crystal layer consisting of wax crystals and pores, area ratio being the ratio of wax crystal area to wax crystal layer total area) of 55.89%.

And 2, establishing a continuous stable Cassie-Baxter theoretical criterion. And establishing a model of the isotropic superhydrophobic surface simulating the nepenthes slipping area according to the extracted micro-morphology structure characteristic parameters. As shown in fig. 1, fig. 2 and fig. 3, in order to enable the constructed isotropic superhydrophobic surface of the imitation nepenthes sliding region to present various significant isotropic superhydrophobic characteristics, the arc-shaped lunar bodies are configured into a spherical crown shape, the waxy crystals are configured into a cylinder array, and the cylinder array is vertically distributed on the arc-shaped surface of the spherical crown, so that the cylinder array presents isotropy in the aspect of micro-morphology structure. On the basis, a numerical relation between the micro-morphological structure characteristic parameters and the super-hydrophobic characteristics (contact angles) of the isotropic super-hydrophobic surface of the imitation nepenthes sliding region is deduced. Waxy crystal layers in nepenthes sliding areas are arranged in a staggered mode to form a net shape and have the structural characteristics of micro-nano scale, air can be stored in generated holes, a liquid-gas-solid contact interface can be formed, therefore, derivation is carried out based on a Cassie-Baxter model, and the obtained equation is as follows:

（1）

in the formula: and respectively representing a theoretical value of a contact angle and an intrinsic contact angle; representing the ratio of the actual wetted solid area of the droplet to the apparent geometric contact area; the roughness factor, i.e. the degree of non-smoothness of the surface, is indicated. In the designed superhydrophobic model, the non-smoothness degree of the surface is influenced by spherical crown and cylinder, the generated surface area can be calculated by formula (2),

（2）

in the formula: the actual surface area is expressed as,Ris a spherical crown (formed by a lunar body configuration) projection circle radius,Hheight from the top of the spherical cap to the base (glide zone matrix), and the radius and height of a single cylinder (constructed from waxy crystals), respectively; representing the ratio of the projected area of the cylinder array to the area of the base; from this, the roughness coefficient can be obtained, which is expressed as follows:

（3）

therefore, the contact angle equation describing the generation of a spherical cap and a cylinder on an isotropic superhydrophobic surface of a simulated nepenthes sliding region by water drops is obtained as follows:

（4）

in the formula: and respectively representing a theoretical value of a contact angle and an intrinsic contact angle, wherein the intrinsic contact angle of a water drop on the surface of the smooth waxy crystal is generally 100-110 degrees, the larger the intrinsic contact angle is, the larger the theoretical contact angle is obtained through calculation, and the intrinsic contact angle is 104 degrees; the liquid drop of the super-hydrophobic wetting characteristic on the surface of the test material is generally 2-4 microliter, wherein 3 microliter is taken, and the radius of the liquid drop is 0.89 millimeter; the ratio of the actual wetted solid area of the droplet to the apparent geometric contact area is expressed, and the calculation is carried out according to complete wetting, namely the droplet is filled with a cylinder array formed by waxy crystal configuration; represents the roughness coefficient, i.e. the degree of non-smoothness of the surface; in the isotropic superhydrophobic surface simulating the nepenthes slippage area, which influences the unsmooth degree of the surface, spherical crown and circleAn array of pillars.RThe radius of the projected circle for the spherical cap (lunar configuration), 22.19 microns;Hthe height from the top of the spherical cap to the base (basal body of the sliding zone) is 9.03 microns; represents the radius of the cylinder (of waxy crystal configuration) and is 0.10 microns; representing the height of the cylinder (due to waxy crystal formation) at 0.24 microns; representing the ratio of the projected area of the cylinder array to the area of the base, was 55.89%.

And 3, regulating and controlling the superhydrophobic efficacy (contact angle) by changing the structural parameters of the cylinder array. And calculating and obtaining the contact angle of the liquid drop on the isotropic super-hydrophobic surface of the imitation nepenthes slipping area. According to the derived formula, the variation range of the contact angle can be calculated; when the contact angle of the super-hydrophobic surface of the nepenthes-imitating sliding region is less than 150 degrees, the contact angle can be increased to 150 degrees by regulating and controlling characteristic parameters, so that the isotropic super-hydrophobic surface of the nepenthes-imitating sliding region has a better super-hydrophobic function. As can be calculated, the contact angle increases with the increase of the ratio () of the height to the radius of the cylinder, the contact angle is 132.7 °; the contact angle was 141.3 °; the contact angle was 150.8 °. Therefore, the ratio of the height to the radius of the cylinder array is improved as much as possible, so that the super-hydrophobic effect of the isotropic super-hydrophobic surface of the nepenthes-imitating sliding region is improved.

As shown in figure 4, the structural characteristics and the superhydrophobic effect are given out based on a Cassie-Baxter model through the representation of micro-morphology structural parameters of the nepenthes sliding region in the isotropic superhydrophobic surface design process of the nepenthes sliding region, so that the isotropic superhydrophobic surface design method of the nepenthes sliding region is obtained, and the controllability of the superhydrophobic effect and the isotropy of the superhydrophobic effect can be realized.

The invention provides a design method of an isotropic superhydrophobic surface of a nepenthes-imitating sliding region, which realizes the controllable design of a superhydrophobic effect, namely the superhydrophobic effect of the designed superhydrophobic surface, namely the size of a liquid drop contact angle, can be regulated and controlled by changing the ratio of the height to the radius of a cylinder formed by waxy crystal configuration; in addition, the super-hydrophobic membrane has the advantages of isotropic super-hydrophobic effect and the like.

Finally, the above examples are only used to illustrate the technical solutions of the present invention, but are not used to limit the scope of the present invention in any way. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that various modifications and equivalent arrangements can be made without departing from the spirit and scope of the present invention, which should be construed as being included in the following claims.