A super-hydrophobic surface based on stiffness regulation to realize droplet impact behavior manipulation and a preparation method thereof

Abstract

The application provides a kind of super-hydrophobic surface based on stiffness regulation to realize droplet impact behavior manipulation and preparation method;The super-hydrophobic surface is composed of polymer matrix, stiffness regulation filler and hydrophobic functional filler.By accurately adjusting the mass fraction of functional filler in the range of 10% to 30%, the equivalent stiffness of the surface can be continuously and controllably changed, thereby realizing the regulation of the maximum spreading diameter, retraction time and bounce height and other dynamic behaviors of the droplet after impact.During preparation, the stiffness regulation filler is dispersed in the solvent, the soluble resin is added to prepare the composite casting solution, the polymer composite film is formed by coating, drying and curing, and then the spraying liquid containing the hydrophobic functional filler is sprayed on the surface of the film and solidified to obtain the super-hydrophobic surface.The application uses material stiffness regulation as the means of droplet impact behavior manipulation, which is not limited to a single material system or a specific surface structure, and has the advantages of simple preparation process, flexible material selection, wide application range and easy extension.

Description

Technical Field

[0001] This invention relates to the field of superhydrophobic functional materials; and more particularly to a superhydrophobic surface and its preparation method based on stiffness control to manipulate droplet impact behavior. Background Technology

[0002] Superhydrophobic surfaces, due to their self-cleaning, anti-fouling, rapid droplet detachment, and anti-icing properties, have broad application prospects in transportation, energy equipment, aerospace, and cryogenic protection. Existing technologies typically achieve low adhesion and rapid roll-off by constructing micro / nano rough structures, designing special surface textures, or introducing low surface energy materials to induce large contact angles and small roll-off angles in droplets. However, these methods still primarily rely on specific surface structures or chemical modifications to control the dynamic behavior of droplets after impact, including spreading, retraction, contact time, and bounce height.

[0003] In practical applications, the interaction between droplets and functional surfaces is more often manifested as dynamic processes such as impact, spreading, retraction, bouncing, and detachment. Existing droplet dynamics control methods typically require complex micro / nano fabrication, fine template replication, etching, or multi-step surface modification, which presents problems such as complex processes, high equipment requirements, high costs, and difficulties in scale-up. Furthermore, the control effect is easily limited by specific material systems and structural parameters, resulting in insufficient transferability between different materials or structures.

[0004] Material stiffness affects energy transfer, interfacial response, and rebound behavior during droplet impact, thereby altering key parameters such as maximum spreading diameter, retraction time, and bounce height. Compared to relying solely on micro / nano structures or chemical modifications, methods that manipulate droplet impact behavior by controlling material stiffness offer advantages such as simple processing, flexible material selection, wide applicability, and ease of expansion.

[0005] Therefore, the present invention develops a superhydrophobic surface that manipulates droplet impact behavior through material stiffness control and its preparation method, which has important practical application value. Summary of the Invention

[0006] The purpose of this invention is to provide a superhydrophobic surface and its preparation method that enables the manipulation of droplet impact behavior based on stiffness control.

[0007] This invention is achieved through the following technical solution:

[0008] This invention relates to a superhydrophobic surface for manipulating droplet impact behavior based on stiffness control, comprising a polymer matrix, a stiffness-controlled filler, and a hydrophobic functional filler; the stiffness-controlled filler has a mass fraction of 10% to 30% in the solid component, and by adjusting the mass fraction of this component, the surface equivalent stiffness can be continuously and controllably changed, thereby controlling the dynamic behavior of the maximum spreading diameter, retraction time, and bounce height of the droplet after impact.

[0009] Preferably, the stiffness regulating filler and the hydrophobic functional filler are selected from at least one of fluorinated carbon nanotubes, tetrafluoroethylene micro powder, and fluorinated boron nitride nanosheets.

[0010] Preferably, the polymer matrix is ​​formed of a soluble resin; the soluble resin is selected from at least one of polyvinylidene fluoride, polymethyl methacrylate, and polyacrylonitrile.

[0011] This invention also relates to a method for preparing the aforementioned superhydrophobic surface based on stiffness modulation to manipulate droplet impact behavior, comprising the following steps:

[0012] Step 1: Mix the stiffness regulating filler with the dispersion solvent and then disperse it by ultrasonication to obtain a stiffness regulating filler dispersion.

[0013] Step 2: Add soluble resin to the dispersion to make the stiffness regulating filler have a mass fraction of 10% to 30% in the solid component, heat and stir to dissolve and disperse, and obtain polymer composite casting solution;

[0014] Step 3: Apply the casting liquid to the template surface to form a composite wet film, and dry and cure to obtain a polymer composite film;

[0015] Step 4: Spray a coating liquid containing hydrophobic filler onto the surface of the composite membrane and cure it to obtain the superhydrophobic surface.

[0016] Preferably, in step 1, the dispersing solvent is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, and N,N-dimethylacetamide; the frequency of the ultrasonic dispersion is 20–40 kHz, and the ultrasonic time is 10–15 min.

[0017] Preferably, in step 2, the heating and stirring temperature is 60–80°C, and the stirring time is 2–6 h.

[0018] Preferably, in step 3, the template is an unstructured template, a symmetrical microstructure template, or an asymmetrical microstructure template; the drying temperature is 80–100℃, and the drying time is 1–2 h.

[0019] Preferably, in step 4, the concentration of hydrophobic functional filler in the spraying liquid is 0.5–1.0 g / mL, the spraying amount is 0.5–2.5 mL, the curing temperature is 160–180℃, and the curing time is 10–30 min.

[0020] Preferably, in step 4, the static water contact angle of the superhydrophobic surface is greater than 150° and the roll-off angle is less than 10°.

[0021] Preferably, in step 4, the superhydrophobic surface, without changing its surface chemical composition and microstructure, achieves controllable manipulation of the spreading, retraction, bouncing, and directional bouncing behavior of droplets after impact through stiffness adjustment.

[0022] The present invention has the following advantages:

[0023] (1) This invention does not rely on complex micro / nano structure processing or multi-step chemical modification. It can change the energy transfer and rebound behavior during droplet impact by simply adjusting the material stiffness of the superhydrophobic surface, thereby achieving the control of droplet spreading, retraction and bouncing processes. Compared with existing methods such as photolithography, etching, template replication or repeated coating of low surface energy materials, the preparation process of this invention is simple, the equipment requirements are low, the manufacturing cost is low, and it is easy to carry out large-scale production.

[0024] (2) This invention has strong adaptability to substrate materials and good transferability. Compared with existing methods, which usually rely on specific microstructures or low surface energy modification layers, the control effect is easily reduced after changing the substrate material. This invention mainly achieves droplet dynamics control by adjusting the softness and hardness of the material, without relying on specific micro / nano structures or special chemical modifiers, and can be applied to a variety of substrates.

[0025] (3) This invention can effectively control the key dynamic parameters after droplet impact. By setting different material stiffness, parameters such as the maximum spread diameter, retraction speed, contact time, and bounce height of the droplet can be adjusted without changing the surface chemical composition and microstructure. Compared with the method of repeatedly optimizing the surface structure or chemical formula, the control method of this invention is simpler and more intuitive, and it is convenient to obtain the required droplet impact behavior according to the application requirements such as self-cleaning, anti-icing, and anti-fouling. Attached Figure Description

[0026] Figure 1 This is a technical roadmap of the preparation method of the present invention;

[0027] Figure 2 This is a flowchart illustrating the preparation process of the polyvinylidene fluoride / fluorinated carbon nanotube composite film in Example 1 of the present invention.

[0028] Figure 3 This is a graph showing the relationship between filler content, composite material stiffness, and droplet bouncing behavior on a flat plate in Embodiment 1 of the present invention.

[0029] Figure 4 This is a timing diagram of droplet impact behavior on a flat plate under different fluorination treatments and carbon nanotube contents in Example 1 of the present invention. Detailed Implementation

[0030] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are merely further illustrations of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0031] Examples 1-3 below describe in detail the use of fluorinated carbon nanotubes, tetrafluoroethylene micro powder, fluorinated boron nitride nanosheets, N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, polyvinylidene fluoride, polymethyl methacrylate, and polyacrylonitrile, all of which are commercially available.

[0032] Example 1

[0033] This embodiment relates to a method for preparing a structureless superhydrophobic surface based on stiffness modulation to manipulate droplet impact behavior, see [link to documentation]. Figure 1 As shown, the specific steps are as follows:

[0034] Step 1: Select fluorinated carbon nanotubes and mix them with N,N-dimethylformamide. Then, use an ultrasonic cleaner to disperse and homogenize the mixture. The ultrasonic frequency of the ultrasonic cleaner is 20 kHz and the ultrasonic time is 10 min. This will allow the fluorinated carbon nanotubes to be uniformly dispersed in the N,N-dimethylformamide to obtain a fluorinated carbon nanotube dispersion.

[0035] Step two: Polyvinylidene fluoride (PVDF) is added to the fluorinated carbon nanotube dispersion. By adjusting the ratio of fluorinated carbon nanotubes to PVDF, the mass fraction of fluorinated carbon nanotubes in the solid component is made to be 10%, 20%, and 30%, respectively, where the solid component is the sum of fluorinated carbon nanotubes and PVDF. Subsequently, the mixture is heated and stirred at 60°C for 2 hours to fully dissolve the PVDF and uniformly disperse the fluorinated carbon nanotubes in the resin system, thereby obtaining polymer composite casting solutions with different stiffness-controlled filler mass fractions.

[0036] Step 3: Select an unstructured template and clean its surface. Apply the polymer composite casting solution with different mass fractions of fluorinated carbon nanotubes to the template surface using a casting machine to form a composite wet film. Then, dry the composite wet film at 80°C for 1 hour to solidify it, obtaining the polymer composite film. (See attached image) Figure 2 As shown;

[0037] Step 4: Spray the fluorinated carbon nanotube coating solution onto the surface of polymer composite films with different mass fractions of fluorinated carbon nanotubes. The concentration of hydrophobic functional filler in the coating solution is 0.5 g / mL, and the coating amount is 0.5 mL.

[0038] After the spraying is completed, the polymer composite film is cured at a temperature of 160°C for 10 minutes to ensure that the hydrophobic filler is stably attached to the surface of the polymer composite film, thereby obtaining superhydrophobic surfaces with different fluorination treatments and carbon nanotube mass fractions.

[0039] The three unstructured superhydrophobic surfaces prepared in Example 1, with mass fractions of 10%, 20%, and 30%, respectively, exhibit superhydrophobic properties, with static water contact angles greater than 150° and roll-off angles less than 10°.

[0040] The three unstructured superhydrophobic surfaces prepared in Example 1, with mass fractions of 10%, 20%, and 30%, exhibit stable droplet bouncing behavior, all capable of spreading, retracting, and detaching after droplet impact. See Figure 3 and 4 As shown, when the content of fluorinated carbon nanotubes increased from 10 wt.% to 20 wt.%, the stiffness decreased, the droplet spreading diameter increased, and the bounce height decreased. When the content was further increased to 30 wt.%, the stiffness increased, the droplet retraction time shortened, and the bounce height increased. The results indicate that, under the same unstructured surface conditions, the equivalent surface stiffness can be altered by adjusting the content of fluorinated carbon nanotubes, thereby achieving effective control over droplet impact behavior.

[0041] Example 2

[0042] This embodiment relates to a method for preparing a symmetric microstructure superhydrophobic surface based on stiffness control to manipulate droplet impact behavior. The specific steps are as follows:

[0043] Step 1: Select tetrafluoroethylene micro powder and N-methylpyrrolidone for mixing: Dispersion and homogenization treatment is carried out by ultrasonic cleaning instrument with an ultrasonic frequency of 30 kHz and an ultrasonic time of 13 min, so that the tetrafluoroethylene micro powder is uniformly dispersed in N-methylpyrrolidone to obtain a tetrafluoroethylene micro powder dispersion.

[0044] Step two: Polymethyl methacrylate (PMMA) is added to the tetrafluoroethylene (TEF) micro powder dispersion. By adjusting the ratio of TEF micro powder to PMMA, the mass fraction of TEF micro powder in the solid component is made to be 10%, 20%, and 30%, respectively, where the solid component is the sum of TEF micro powder and PMMA. Subsequently, the mixture is heated and stirred at 70°C for 4 hours to fully dissolve the PMMA and uniformly disperse the TEF micro powder in the resin system, thereby obtaining polymer composite casting solutions with different mass fractions of TEF micro powder.

[0045] Step 3: Select a symmetrical microstructure template and clean its surface. Apply the polymer composite casting solution with different mass fractions of tetrafluoroethylene micropowder to the template surface using a casting machine to form a composite wet film. Then, dry the composite wet film at 90°C for 1.5 h to cure it, thus obtaining the polymer composite film.

[0046] Step four: Spray the coating solution of tetrafluoroethylene micro powder onto the surface of polymer composite films with different mass fractions of tetrafluoroethylene micro powder. The concentration of hydrophobic functional filler in the coating solution is 0.7 g / mL, and the spraying amount is 2 mL.

[0047] After the spraying is completed, the polymer composite film is cured at a temperature of 170°C for 20 minutes to ensure that the hydrophobic filler is stably attached to the surface of the polymer composite film, thereby obtaining superhydrophobic surfaces with different mass fractions of tetrafluoroethylene micro powder.

[0048] The three symmetrical microstructured superhydrophobic surfaces prepared in Example 2 with mass fractions of 10%, 20%, and 30% have the same superhydrophobic properties as those in Example 1, with static water contact angles greater than 150° and roll-off angles less than 10°.

[0049] The three symmetrical microstructured superhydrophobic surfaces prepared in Example 2, with mass fractions of 10%, 20%, and 30%, exhibited stable droplet bouncing behavior, all capable of spreading, retracting, and detaching after droplet impact. When the tetrafluoroethylene (TEF) powder content increased from 10 wt.% to 20 wt.%, the stiffness decreased, the droplet spreading diameter increased, and the bouncing height decreased; when the content was further increased to 30 wt.%, the stiffness increased, the droplet retraction time shortened, and the bouncing height increased. The results show that, under the same symmetrical microstructured surface conditions, the equivalent stiffness of the polymethyl methacrylate / TEF composite film surface can be changed by adjusting the TEF powder content, thereby achieving effective control over droplet impact behavior. This further illustrates that the stiffness control method of the present invention is not only applicable to unstructured surfaces but can also be extended to symmetrical microstructured surfaces, demonstrating good universality.

[0050] Example 3

[0051] This embodiment relates to a method for preparing an asymmetric microstructured superhydrophobic surface based on stiffness control to manipulate droplet impact behavior. The specific steps are as follows:

[0052] Step 1: Fluorinated boron nitride nanosheets are mixed with N,N-dimethylacetamide. The mixture is then dispersed and homogenized using an ultrasonic cleaner with an ultrasonic frequency of 40 kHz and an ultrasonic time of 15 min. This process ensures that the fluorinated boron nitride nanosheets are uniformly dispersed in N,N-dimethylacetamide, resulting in a fluorinated boron nitride nanosheet dispersion.

[0053] Step two: Polyacrylonitrile is added to the fluorinated boron nitride nanosheet dispersion. By adjusting the ratio of fluorinated boron nitride nanosheets to polyacrylonitrile, the mass fraction of fluorinated boron nitride nanosheets in the solid component is made up to be 10%, 20%, and 30%, respectively, wherein the solid component is the sum of fluorinated boron nitride nanosheets and polyacrylonitrile. Subsequently, the mixture is heated and stirred at 80°C for 6 hours to fully dissolve the polyacrylonitrile and uniformly disperse the fluorinated boron nitride nanosheets in the resin system, thereby obtaining polymer composite casting solutions with different mass fractions of fluorinated boron nitride nanosheets.

[0054] Step 3: Select an asymmetric microstructure template and clean the surface: Apply polymer composite casting liquid with different mass fractions of boron nitride nanosheets with different fluorination treatments to the template surface using a doctor blade to form a composite wet film, and dry the composite wet film at 100°C for 2 hours to solidify it, thereby obtaining a polymer composite film.

[0055] Step four: The spraying solution of fluorinated boron nitride nanosheets is sprayed onto the surface of polymer composite films with different mass fractions of fluorinated boron nitride nanosheets. The concentration of hydrophobic functional filler in the spraying solution is 1.0 g / mL, and the spraying amount is 2.5 mL.

[0056] After the spraying is completed, the polymer composite film is cured at a temperature of 180°C for 20 minutes to ensure that the hydrophobic filler is stably attached to the surface of the polymer composite film, thereby obtaining superhydrophobic surfaces with different mass fractions of boron nitride nanosheets with different fluorination treatments.

[0057] The three asymmetric microstructure superhydrophobic surfaces prepared in Example 3, with mass fractions of 10%, 20%, and 30%, respectively, have the same superhydrophobic properties as those in Examples 1 and 2, with static water contact angles greater than 150° and roll-off angles less than 10°.

[0058] The three asymmetric microstructure superhydrophobic surfaces prepared in Example 3, with mass fractions of 10%, 20%, and 30%, exhibit stable droplet bouncing behavior, all capable of spreading, retracting, detaching, and directional bouncing after droplet impact. When the content of fluorinated boron nitride nanosheets increased from 10 wt.% to 20 wt.%, the stiffness decreased, and the droplet directionally bounced along the tilt direction of the asymmetric microstructure after impact, with the angle between the bouncing direction and the surface normal changing from 19.18° to 23.14°. When the content was further increased to 30 wt.%, the stiffness increased, and the droplet directionally bounced along the tilt direction of the asymmetric microstructure after impact, with the angle between the bouncing direction and the surface normal changing from 23.14° to 17.25°.

[0059] The results show that, under the same asymmetric microstructure surface conditions, the equivalent stiffness of the polyacrylonitrile / fluorinated boron nitride nanosheet composite film surface can be altered by adjusting the content of fluorinated boron nitride nanosheets, thereby controlling the directional bouncing behavior of droplets after impact. Furthermore, the stiffness control method of this invention is applicable not only to unstructured surfaces and symmetric microstructure surfaces, but also to asymmetric microstructure surfaces, achieving effective control over the droplet bouncing direction, demonstrating good universality and scalability.

[0060] This invention achieves continuous and controllable modification of the equivalent stiffness of a surface by precisely adjusting the mass fraction of functional filler within the range of 10% to 30%, thereby regulating the dynamic behavior of droplets after impact, such as maximum spreading diameter, retraction time, and bounce height. In preparation, stiffness-regulating fillers are dispersed in a solvent, and a soluble resin is added to prepare a composite casting solution. This solution is then coated, dried, and cured to form a polymer composite film. Finally, a spray solution containing hydrophobic functional fillers is sprayed onto the surface of this film and cured to obtain the superhydrophobic surface. This invention uses material stiffness regulation as a means of manipulating droplet impact behavior, and is not limited to a single material system or specific surface structure. It has the advantages of simple preparation process, flexible material selection, wide applicability, and easy expansion.

[0061] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A superhydrophobic surface for manipulating droplet impact behavior based on stiffness control, characterized in that, It is composed of a polymer matrix, stiffness-regulating filler and hydrophobic functional filler; the mass fraction of the stiffness-regulating filler in the solid component is 10% to 30%, and by adjusting the mass fraction of this component, the surface equivalent stiffness can be continuously and controllably changed, thereby realizing the control of the dynamic behavior of the maximum spreading diameter, retraction time and bounce height of the droplet after impact.

2. The superhydrophobic surface for manipulating droplet impact behavior based on stiffness control as described in claim 1, characterized in that, The stiffness-regulating filler and the hydrophobic functional filler are selected from at least one of fluorinated carbon nanotubes, tetrafluoroethylene micro powder, and fluorinated boron nitride nanosheets.

3. The superhydrophobic surface for manipulating droplet impact behavior based on stiffness control as described in claim 1, characterized in that, The polymer matrix is ​​formed from a soluble resin; the soluble resin is selected from at least one of polyvinylidene fluoride, polymethyl methacrylate, and polyacrylonitrile.

4. A method for preparing a superhydrophobic surface based on stiffness control to manipulate droplet impact behavior as described in claim 1, characterized in that, Includes the following steps: Step 1: Mix the stiffness regulating filler with the dispersion solvent and then disperse it by ultrasonication to obtain a stiffness regulating filler dispersion. Step 2: Add soluble resin to the dispersion to make the stiffness regulating filler have a mass fraction of 10% to 30% in the solid component, heat and stir to dissolve and disperse, and obtain polymer composite casting solution; Step 3: Apply the casting liquid to the template surface to form a composite wet film, and dry and cure to obtain a polymer composite film; Step 4: Spray a coating liquid containing hydrophobic filler onto the surface of the composite membrane and cure it to obtain the superhydrophobic surface.

5. The method for preparing a superhydrophobic surface based on stiffness control to manipulate droplet impact behavior as described in claim 4, characterized in that, In step 1, the dispersing solvent is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, and N,N-dimethylacetamide; the frequency of the ultrasonic dispersion is 20-40 kHz, and the ultrasonic time is 10-15 min.

6. The method for preparing a superhydrophobic surface based on stiffness control to manipulate droplet impact behavior as described in claim 4, characterized in that, In step 2, the heating and stirring temperature is 60-80℃, and the stirring time is 2-6 hours.

7. The method for preparing a superhydrophobic surface based on stiffness control to manipulate droplet impact behavior as described in claim 4, characterized in that, In step 3, the template is an unstructured template, a symmetrical microstructure template, or an asymmetrical microstructure template; the drying temperature is 80–100℃, and the drying time is 1–2 h.

8. The method for preparing a superhydrophobic surface based on stiffness control to manipulate droplet impact behavior as described in claim 4, characterized in that, In step 4, the concentration of hydrophobic functional filler in the spraying liquid is 0.5–1.0 g / mL, the spraying amount is 0.5–2.5 mL, the curing temperature is 160–180℃, and the curing time is 10–30 min.

9. The superhydrophobic surface for manipulating droplet impact behavior based on stiffness control as described in claim 1, characterized in that, In step 4, the static water contact angle of the superhydrophobic surface is greater than 150° and the roll-off angle is less than 10°.

10. The superhydrophobic surface for manipulating droplet impact behavior based on stiffness control as described in claim 1, characterized in that, In step 4, the superhydrophobic surface, without changing its surface chemical composition and microstructure, achieves controllable manipulation of the spreading, retraction, bouncing, and directional bouncing behavior of droplets after impact through stiffness control.

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