Design and preparation method of mimic common nepenthes slippage area super-hydrophobic microstructure

Abstract

The invention discloses a common nepenthes slippage area imitating super-hydrophobic microstructure design and a preparation method. According to the design of the super-hydrophobic microstructure, a unique moon bone body and a wax crystal structure of a common nepenthes slippage area are used for reference, the moon bone body is approximate to a concave cylinder, the wax crystal is approximate to an irregular blind hole structure, and the super-hydrophobic surface is prepared by utilizing the femtosecond laser ablation characteristic. The method comprises the following steps: establishing a three-dimensional model based on a theoretical model of a composite microstructure of a lunar bone body and a waxy crystal in a common nepenthes slippage area and a droplet infiltration super-hydrophobic microstructure, obtaining an original numerical equation between the composite microstructure and a super-hydrophobic function, namely wettability, and determining characteristic parameters of the corresponding composite microstructure when a contact angle is greater than 150 degrees; and finishing the design of the super-hydrophobic microstructure. A titanium alloy material is selected and polished to 0.8 mu m, the composite microstructure composed of concave cylinders and irregular blind holes is etched in the polished titanium alloy surface by means of the characteristics of femtosecond laser, and chemical fluorination treatment is carried out to prepare the super-hydrophobic surface with the common nepenthes slip area imitating composite microstructure. A new thought is provided for design and preparation of the bionic functional super-hydrophobic surface microstructure, and the method has important scientific significance and application value.

Description

Technical Field

[0001] The present invention belongs to the field of bionic design and preparation of super-hydrophobic microstructures on titanium alloy surfaces, and in particular relates to a design of a composite microstructure of a lunate body and wax crystals imitating the slip zone of a pitcher plant and a preparation method based on femtosecond laser and chemical fluorination. Background Art

[0002] Titanium alloy Ti6Al4V is widely used in aerospace, marine engineering, medical equipment and other fields due to its high strength, corrosion resistance, low density and biocompatibility. However, titanium alloys are prone to corrosion, surface biological attachment pollution, icing and other adverse phenomena in harsh environments (such as seawater, blood, and high altitude), which affect the service life and efficiency of the equipment. Therefore, giving titanium alloy surfaces superhydrophobic properties has attracted widespread attention from researchers. With the continuous deepening of research, the preparation of superhydrophobic surfaces of titanium alloys mainly focuses on constructing micro-nano composite structures on the surface of titanium alloys and combining chemical treatment to reduce surface energy. The design of micro-nano composite structures is the key to achieving superhydrophobicity of titanium alloys. Their scale, morphology and distribution have an important influence on the morphology and wettability of droplets on the surface, thereby affecting their superhydrophobic properties. Therefore, the design and preparation of superhydrophobic micro-nano composite structures of titanium alloys are particularly important.

[0003] A super-hydrophobic surface refers to a material surface with a water droplet contact angle greater than 150° and a rolling angle less than 10°. It has important application value in the fields of self-cleaning, corrosion protection, and frost suppression. The contact angle of a droplet on a solid surface is an important indicator for measuring wetting properties. The contact angle is the result of the surface tension balance between the three interfaces of solid, liquid, and gas. When the tension is balanced, the total energy of the system tends to the lowest, and the droplet on the solid surface is in a stable state. Micro-topography is a key factor affecting the high contact angle of water droplets on the surface of a material. Therefore, the preparation of super-hydrophobic surfaces mainly involves modifying low-surface-energy substances on rough surfaces with micro-topography, or constructing micro-topography on the surface of low-surface-energy materials. With the continuous exploration of surface modification technology, femtosecond laser processing technology has been widely used in the processing of surface micro-topography due to its high precision, contact-free, and controllable features.

[0004] Based on the principle of super-hydrophobic surface design and preparation, the inventor of this patent application has conducted research on super-hydrophobic surface design. Taking the micro-morphological structure of the pitcher plant slip zone that can exhibit super-hydrophobic properties as a bionic prototype, a super-hydrophobic surface was designed and prepared using 3D printing technology and high-voltage electrostatic adsorption technology. The test results show that the water droplet contact angle of the prepared super-hydrophobic surface is 152.6°, indicating that it has good super-hydrophobic function (authorized invention patent, patent number ZL 202010458218.7; academic paper, Bioinspired, Biomimetic and Nanobiomaterials, 2022, 11(1): 1-7). Therefore, the patent applicant has the basic conditions for the design and preparation of bionic super-hydrophobic surfaces.

[0005] Invention patent 202211565535.4 discloses a method for improving the superhydrophobicity of nickel-titanium alloy by laser composite processing. The surface of the nickel-titanium alloy sample is textured in sequence by femtosecond laser and nanosecond laser to form a multi-level nested mesh micro-nano composite structure, thereby effectively increasing the surface roughness of the nickel-titanium alloy sample. Through further chemical modification, a nickel-titanium alloy superhydrophobic surface with excellent superhydrophobic properties and corrosion resistance is obtained. However, this patent does not involve the biomimetic structural design and the preparation process is relatively complicated. Invention patent 202111480397.5 discloses a method for preparing a green bionic superhydrophobic bio-based multifunctional textile. The surface adopts environmentally friendly bio-based flame retardants and low surface energy modifiers. Through layer-by-layer self-assembly technology, a superhydrophobic multifunctional textile material with the characteristics of simple operation, non-toxicity, harmlessness, cheapness and easy availability is prepared. Although this patent also provides a bionic superhydrophobic microstructure, the preparation process is relatively complicated and not suitable for large-area applications.

[0006] In summary, in the field of design and preparation of super-hydrophobic bionic microstructures of titanium alloys, there are few studies on the existing design of super-hydrophobic bionic microstructures of titanium alloys, and the current designs are deficient in terms of retaining air and reducing contact area. Therefore, the present invention provides a design and preparation method for a super-hydrophobic microstructure imitating the slip zone of a pitcher plant, which uses the micro-nano composite structure of waxy crystals and lunate bodies in the slip zone of the pitcher plant as a bionic prototype to design a micro-nano composite structure, derives a numerical equation, realizes the controllable design of the theoretical value of the contact angle, and completes the processing of the microstructure by etching the titanium alloy surface through femtosecond laser, and reduces the surface energy through chemical fluorination, thereby realizing the preparation of a micro-nano composite structure of lunate bodies and waxy crystals in the slip zone of the pitcher plant. The present invention provides a design and preparation method for a super-hydrophobic microstructure imitating the slip zone of a pitcher plant, which provides a new method and a low-cost preparation approach for the design and preparation of super-hydrophobic bionic microstructures of titanium alloys, and has important application value and practical significance. Summary of the Invention

[0007] The present invention discloses a design and preparation method for a super-hydrophobic microstructure simulating the slip zone of a pitcher plant. The method uses a micro-nano composite structure of wax crystals and lunates in the slip zone of the pitcher plant as a biomimetic prototype, designs a composite microstructure consisting of periodic arrangements of concave cylinders and blind holes, derives and establishes a numerical equation based on an infiltration model in which a droplet is in a relatively low-energy, more stable state on a super-hydrophobic surface, clarifies microstructural characteristic parameters corresponding to a contact angle greater than 150°, and completes the design of the super-hydrophobic microstructure. A titanium alloy Ti6Al4V material is selected and polished to 0.8 μm. The polished surface is subjected to femtosecond laser etching to prepare a composite microstructure of periodic arrangements of concave cylinders and blind holes simulating the lunates and wax crystals in the slip zone of the pitcher plant. To eliminate the high adhesion characteristics of the Ti6Al4V super-hydrophobic microstructure, the material is chemically fluorinated and dried at a constant temperature to obtain a super-hydrophobic surface having the composite microstructure simulating the slip zone of the pitcher plant. The technical solution adopted by the present invention is as follows: A method for designing and preparing a super-hydrophobic microstructure imitating the slip zone of a pitcher plant, characterized by comprising the following steps: Step 1, designing a super-hydrophobic surface microstructure by imitating the composite microstructure of the lunate and wax crystals in the slip zone of Nepenthes, that is, the lunate is a concave cylinder and the wax crystals are blind holes; Step 2: Based on the theoretical model of droplet wetting superhydrophobic microstructures, an original numerical equation is obtained between the microstructure of periodic arrangement of concave cylinders and blind holes and the superhydrophobic function, i.e., wettability. The numerical equation is:

[0008] Where: θ T and θ c Represent the theoretical contact angle and the intrinsic contact angle, respectively. The intrinsic contact angle of water droplets on the titanium alloy surface θ c is 101°; R cp 、 R bh 、 R c are the radius of the pit circle, the radius of the blind hole, and the radius of the cylinder respectively; H c 、 H cp 、 H bh They are the cylinder height, pit depth, and blind hole depth respectively; n is the number of blind holes in the array, D c and D bh are the spacing of concave cylinders and blind holes respectively; λ is the wetting coefficient, that is, the degree of wetting of the concave cylinder by the water droplet. When the water droplet floats on the top of the concave cylinder, λ =0, when the water droplet completely soaks the concave cylinder λ =1; The original numerical equation is used to determine the microstructure characteristic parameters corresponding to a water droplet contact angle greater than 150°, completing the design of the superhydrophobic microstructure. Step 3: Select titanium alloy Ti6Al4V and perform surface polishing to achieve a surface roughness of 0.8 μm. Then, clean the surface and place it in a constant temperature box at 30-40°C for 50 minutes to dry the polished Ti6Al4V surface. Step 4, femtosecond laser etching is performed on the polished and dried Ti6Al4V surface to prepare a composite microstructure of periodic arrangement of concave cylinders and blind holes that simulates the lunate body and wax crystals in the slip zone of Nepenthes; Step 5: After femtosecond laser etching, the Ti6Al4V surface exhibits high adhesion properties, so a fluorination treatment is performed to reduce the surface energy. The specific steps include placing the superhydrophobic microstructure in a 1% to 3% by mass solution of heptafluorosilane in anhydrous ethanol for 2.5 to 3.5 hours, and drying it at a constant temperature of 80 to 90°C for 35 to 45 minutes to obtain a Ti6Al4V superhydrophobic surface.

[0009] Step 1 specifically includes: (1) A super-hydrophobic surface microstructure was designed by imitating the composite microstructure of the lunate and wax crystals in the slip zone of Nepenthes, where the lunate is a concave cylinder and the wax crystals are blind holes; (2) When water droplets infiltrate the bionic superhydrophobic microstructure, the microstructure with periodic arrangement of concave cylinders and blind holes can effectively retain air, forming an air film layer, reducing the contact area and achieving superhydrophobic function.

[0010] Step 2 specifically includes: (1) The designed concave cylinder and blind hole have micron-scale structural characteristic parameters, among which the radius of the concave circle is R cp Designed for 5.5 - 10.5 μm depth H cp Designed for 1.5 - 2.5 μm; cylinder radius R c Designed to be 8 - 12 μm, column height H c 48 - 52 μm; blind hole radius R bh Designed to be 1.5 - 2.5 μm deep H bh Designed to 1 - 2 μm, concave cylinder spacing D c Designed to be 140~- 180 μm, blind hole spacingD bh Designed to be 20 μm; (2) The characteristic parameters of the microstructure of the periodic arrangement of concave cylinders and blind holes are substituted into the numerical equation to calculate the theoretical value of the water droplet contact angle. The super-hydrophobic function is determined based on whether the contact angle is greater than 150°. This enables the controllable design of the super-hydrophobic surface and clarifies the characteristic parameters of the super-hydrophobic microstructure.

[0011] Step 3 specifically includes: (1) Titanium alloy Ti6Al4V was selected as the matrix material of the superhydrophobic microstructure and cut into Ti6Al4V samples with a length × width of 2 cm × 2 cm; (2) The surface of the Ti6Al4V sample was polished to a surface roughness of 0.8 μm; (3) The polished Ti6Al4V sample was placed in anhydrous ethanol and ultrasonically cleaned for 3 min. After cleaning, it was placed in a constant temperature box at 30-40 °C for 50 min to dry the polished Ti6Al4V surface.

[0012] Step 4 specifically includes: (1) Place the polished and dried Ti6Al4V sample on the femtosecond laser system platform, adjust the laser focus to the sample surface, and determine the laser scanning path based on the characteristic parameters of the bionic superhydrophobic microstructure determined in step 2; (2) Set the femtosecond laser processing parameters: average power 15 W, beam radius 5 μm, pulse width 1000 fs, and laser frequency 350 kHz; (3) Through multiple femtosecond laser etching on the sample surface, the processing of the lunate body and wax crystal micro-nano composite structure in the slip zone of Nepenthes was completed.

[0013] Step 5 specifically includes: (1) After femtosecond laser etching, the Ti6Al4V surface has high adhesion properties, so fluorination treatment is performed to reduce the surface energy. The etched sample is placed in a beaker, and a 1% to 3% by mass solution of heptafluorosilane in anhydrous ethanol is added. The sample is sealed and placed in a cool environment for 2.5 to 3.5 hours. (2) The sample after chemical fluorination treatment was placed in a constant temperature box at 80-90℃ and kept warm for 35-45 minutes to prepare a superhydrophobic surface with a composite microstructure that simulates the slip zone of pitcher plants.

[0014] The present invention discloses a design and preparation method for a super-hydrophobic microstructure simulating the slip zone of a pitcher plant. The method uses a micro-nano composite structure of wax crystals and lunate bodies in the slip zone of the pitcher plant as a biomimetic prototype, designs a microstructure consisting of a periodic arrangement of concave cylinders and blind holes, obtains an original numerical equation based on a theoretical model of a droplet infiltrating a super-hydrophobic microstructure, and determines the relationship between the microstructure with the periodic arrangement of concave cylinders and blind holes and the super-hydrophobic function, i.e., wettability. The method specifies characteristic parameters of the microstructure corresponding to a contact angle greater than 150°, thereby completing the design of the super-hydrophobic microstructure. The method also utilizes the advantages of a femtosecond laser, such as high precision, controllability, flexibility, and efficiency, to complete the processing of the microstructure with the periodic arrangement of concave cylinders and blind holes on a titanium alloy surface. A 1% to 3% by mass heptafluorosilane anhydrous ethanol solution is used to reduce the surface energy of the sample, thereby achieving the preparation of a super-hydrophobic surface simulating the slip zone of the pitcher plant. The method has important application value in the fields of medical devices, aerospace, and ice suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The bionic microstructure design diagram of the present invention; Figure 2 Schematic diagram of the concave cylinder and blind hole of the present invention; Figure 3 Schematic diagram of femtosecond laser processing and fluorination treatment of the present invention; Figure 4 Scanning electron microscope image of the femtosecond laser etching sample of the present invention; Figure 5 Three-dimensional white light scanning image of the femtosecond laser etched sample of the present invention; Figure 6 Contact angle and rolling angle test diagram of the Ti6Al4V sample of the present invention; Figure 7 Diagram of the droplet bouncing process on the Ti6Al4V superhydrophobic surface characterized by the present invention; Figure 8 The present invention shows the freezing of droplets on the Ti6Al4V super-hydrophobic surface; Figure 9 Design and preparation flow chart of the present invention.

[0016] In the figure: 1, concave cylinder; 1-1, pit; 1-2, cylinder; 2, blind hole; 3, Ti6Al4V substrate. DETAILED DESCRIPTION

[0017] The following describes in detail the design and preparation method of a Nepenthes-like slip zone super-hydrophobic microstructure of the present invention in conjunction with the embodiments and drawings.

[0018] The present invention discloses a design and preparation method for a super-hydrophobic microstructure that simulates the slip zone of a pitcher plant. Taking the micro-nano composite structure of wax crystals and lunate bodies in the slip zone of a pitcher plant as a bionic prototype, a microstructure consisting of a periodic arrangement of concave cylinders and blind holes is designed. Based on the theoretical model of a droplet infiltrating a super-hydrophobic microstructure, an original numerical equation is obtained between the microstructure of the periodic arrangement of concave cylinders and blind holes and the super-hydrophobic function, i.e., wettability. The characteristic parameters of the microstructure of the periodic arrangement of concave cylinders and blind holes corresponding to a water droplet contact angle greater than 150° are clearly calculated. A titanium alloy Ti6Al4V material is selected for polishing, and the super-hydrophobic biomimetic microstructure designed by femtosecond laser etching is then chemically fluorinated and dried at a constant temperature to eliminate the high adhesion characteristics of the super-hydrophobic microstructure, thereby obtaining a super-hydrophobic surface having a composite microstructure that simulates the slip zone of a pitcher plant.

[0019] The design and preparation method of a Nepenthes-like slip zone super-hydrophobic microstructure of the present invention specifically comprises the following steps: 1. The super-hydrophobic surface microstructure is designed by imitating the micro-composite structure of the lunate body and wax crystals in the slip zone of the pitcher plant, that is, the lunate body is a concave cylinder and the wax crystals are blind holes, specifically including: (1) The super-hydrophobic surface microstructure is designed by imitating the micro-composite structure of the lunate body and wax crystals in the slip zone of Nepenthes, that is, the lunate body is a concave cylinder and the wax crystals are blind holes, such as Figure 1 As shown; (2) When water droplets infiltrate the bionic superhydrophobic microstructure, the microstructure with periodic arrangement of concave cylinders and blind holes can effectively retain air, forming an air film layer, reducing the contact area and achieving superhydrophobic function.

[0020] 2. Based on the theoretical model of droplet wetting in super-hydrophobic microstructures, we obtained an original numerical equation for the relationship between the microstructure of periodic arrangement of concave cylinders and blind holes and the super-hydrophobic function, i.e., wettability. We also determined the microstructure characteristic parameters corresponding to a water droplet contact angle greater than 150°, and completed the design of the super-hydrophobic microstructure. Specifically, we included: (1) The designed concave cylinder and blind hole have micron-scale structural characteristic parameters, among which the radius of the concave circle is R cp Designed for 5.5 - 10.5 μm depth H cp Designed for 1.5 - 2.5 μm; cylinder radius R c Designed to be 8 - 12 μm, column height H c 48 - 52 μm; blind hole radius R bh Designed to be 1.5 - 2.5 μm deep H bh Designed to 1 - 2 μm, concave cylinder spacing Dc Designed for 140-180 μm blind hole spacing D bh Designed to be 20 μm; (2) Based on the wetting model in which the droplet is in a relatively low energy and more stable state on the super-hydrophobic surface, a numerical equation is derived to establish the relationship between the microstructural characteristics of the periodic arrangement of concave cylinders and blind holes and the super-hydrophobic function, i.e., wettability. The Cassie-Baxter wetting model assumes that when a droplet infiltrates a solid surface, air can be retained in the microstructure of the solid surface. Therefore, the contact surface consists of three parts: the droplet, air, and the solid surface microstructure. Based on this, the Cassie-Baxter equation is proposed:

[0021] Where, θ T is the contact angle, θ C is the intrinsic contact angle, f s1 is the ratio of the actual wetted solid area of ​​the droplet to the apparent geometric contact area. f r Indicates the roughness coefficient, that is, the non-smoothness of the surface. Figure 1 、 Figure 2 As shown in the figure, the designed super-hydrophobic microstructure is composed of periodically arranged concave cylinders and blind holes, and the projected area of ​​the unit microstructure is S P It can be calculated by formula (2)

[0022] The actual surface area S generated by the unit microstructure S It consists of a concave cylindrical pit 1-1, a cylinder 1-2, a blind hole 2, and a base 3, and is calculated using the following formula:

[0023] Where, R cp 、 R bh 、 R c are the radius of the pit circle, the radius of the blind hole, and the radius of the cylinder respectively; H c 、 H cp 、 H bh They are the cylinder height, pit depth, and blind hole depth respectively; n is the number of blind holes in the array.

[0024] According to this roughness coefficient f rIt can be expressed as:

[0025]

[0026] When water droplets infiltrate the composite microstructure of the periodic arrangement of concave cylinders and blind holes in the lunate body and wax crystals in the slip zone of Nepenthes, different degrees of infiltration are produced on the concave cylinder 1, so the infiltration coefficient is introduced. λ .

[0027] At this time, the water droplet infiltrates the concave cylinder, so the ratio of the area of ​​the concave cylinder 1 actually infiltrated by the water droplet to the apparent geometric contact area is f s1 It can be obtained by formula (5):

[0028]

[0029] Where: f s1 It represents the ratio of the actual solid area wetted by the droplet to the apparent geometric contact area; λ Represents the wetting coefficient.

[0030] Substituting formula (4) and formula (5) into formula (1), we can obtain the numerical relationship between the composite microstructure characteristics of the periodic arrangement of concave cylinders and blind holes of the lunate body and wax crystals in the slip zone of the pitcher plant and the superhydrophobic function, i.e., wettability, as shown below:

[0031] Where: θ T and θ c Represent the theoretical contact angle and the intrinsic contact angle, respectively. The intrinsic contact angle of water droplets on the titanium alloy surface θ c It is 101°.

[0032] (3) Substitute the characteristic parameters of the composite microstructure into the numerical equation, calculate the theoretical value of the contact angle, and clarify the characteristic parameters of the superhydrophobic microstructure corresponding to the contact angle greater than 150°. In the embodiment, the characteristic parameters of the composite microstructure are: the radius of the pit circle R cp Designed to be 7.5 μm deep H cp Designed to be 2.5 μm; cylindrical radius R c Designed to be 10 μm, the column height H c 50 μm; blind hole radius R bh Designed to be 2.5 μm deep H bh Designed to be 1 μm, the concave cylinder spacingD c Designed for 160 μm blind hole pitch D bh 20 μm; 3. Select titanium alloy material for polishing to make the surface roughness reach 0.8 μm, then clean and place it in a constant temperature box at 30-40℃ for 50 minutes to dry the polished Ti6Al4V surface. Specifically include: (1) Ti6Al4V was selected from titanium alloy materials as the superhydrophobic microstructure matrix material and cut into Ti6Al4V samples with a length × width of 2 cm × 2 cm; (2) The surface of the Ti6Al4V sample was polished to a surface roughness of 0.8 μm; (3) The polished Ti6Al4V sample was placed in anhydrous ethanol and ultrasonically cleaned for 3 min. After cleaning, it was placed in a constant temperature box at 30-40 °C for 50 min to dry the polished Ti6Al4V surface.

[0033] 4. Femtosecond laser etching is performed on the polished and dried Ti6Al4V surface to produce a microstructure with periodic arrangement of concave cylinders and blind holes, specifically including: (1) The polished and dried sample was placed on the three-dimensional motion platform of a femtosecond laser (YLC-03, Changzhou Company, China) system. The laser focus was adjusted to the sample surface, and the laser scanning path was determined by the characteristic parameters of the superhydrophobic microstructure determined in step 2. (2) Set the femtosecond laser processing parameters: average power 15 W, beam radius 5 μm, pulse width 1000 fs, and laser frequency 350 kHz; (3) Through multiple etchings on the sample surface by femtosecond laser, the processing of the micro-nano composite structure of the lunate body and wax crystal structure in the slip zone of the pitcher plant is completed.

[0034] 5. After femtosecond laser etching, the Ti6Al4V surface exhibits high adhesion properties, so fluorination treatment is performed to reduce the surface energy of the Ti6Al4V surface. The specific steps include: (1) The Ti6Al4V surface has high adhesion properties after femtosecond laser etching, so fluorination treatment is performed to reduce the surface energy of the Ti6Al4V surface. The etched sample is placed in a beaker, and a 1% by mass solution of heptafluorosilane in anhydrous ethanol is added. The beaker is sealed to prevent the solution from volatilizing and placed in a cool environment for 3 hours. (2) The sample after chemical fluorination treatment was placed in a constant temperature box at 80℃ for 40 min to prepare a super hydrophobic surface with a composite microstructure imitating the slip zone of Nepenthes. The process is as follows: Figure 3 shown.

[0035] To verify the superiority and feasibility of the design and preparation method of the pitcher plant-mimicking superhydrophobic microstructure, the wettability of the superhydrophobic surface was characterized by multiple measurements of the contact angle and rolling angle of a water droplet on the superhydrophobic surface; the morphology and three-dimensional structure of the superhydrophobic surface were obtained; and the bouncing and ice suppression properties of the superhydrophobic surface were characterized by the following tests: (1) The super-hydrophobic surface morphology of the titanium alloy was characterized by scanning electron microscopy (SEM, SU 8600, Carl Zeiss AG, Germany). Figure 4 shown.

[0036] Depend on Figure 4 It can be seen that under the scanning electron microscope images of different magnifications, the composite microstructure of concave cylinders and blind holes periodically arranged in the lunate body and wax crystals of the slip zone of the pitcher plant obtained by femtosecond laser etching and chemical fluorination treatment can be clearly seen.

[0037] (2) The three-dimensional morphology of the super-hydrophobic surface of the titanium alloy was characterized by scanning white light interferometry (SWLI, SuperViewW3, Chotest Corp, China). Figure 5 shown.

[0038] Depend on Figure 5 It can be seen that under the three-dimensional white light interference pattern, the three-dimensional structural dimensions of the composite microstructure of concave cylinders and blind holes periodically arranged in the lunate body and wax crystals of the pitcher plant slip zone obtained by multiple femtosecond laser etching and chemical fluorination treatment can be clearly seen. The microstructure obtained by femtosecond laser etching meets the design expectations within the error and accuracy range.

[0039] (3) The contact angle and rolling angle of the droplet on the Ti6Al4V superhydrophobic surface were measured using a contact angle meter (SL-200KS, Solon, USA). Figure 6 shown.

[0040] The specific detection method is to use a contact angle meter to measure the contact angle of a water droplet on a super-hydrophobic surface. The super-hydrophobic sample is placed on the measuring platform, and a 5 μL water droplet is dropped on the super-hydrophobic surface. The test results show that its contact angle is 150.51°, which is the same as the contact angle calculated by the numerical equation. The tilt angle of the platform is controlled by a motor to record the angle of the water droplet rolling on the super-hydrophobic surface. α It is 9.85°.

[0041] (4) Drop a water droplet from a height of 1 cm onto the prepared Ti6Al4V superhydrophobic surface, observe its dynamic behavior with a high-speed camera, and calculate the rebound coefficient, as follows: Figure 7 shown.

[0042] The specific experimental method is: a 5 μL water droplet is dropped from a height of 1 cm onto the prepared Ti6Al4V superhydrophobic surface, its dynamic behavior is observed by a high-speed camera, the state of the water droplet when it rebounds is analyzed, and the highest height of the water droplet rebound is recorded as 3.41 mm. The rebound coefficient is calculated to be 0.34 based on the water drop height.

[0043] (5) Place the prepared Ti6Al4V superhydrophobic sample on a -10℃ refrigerator, pre-cool for 30s, drop water on the surface, and record the freezing time of the water droplets with a camera. Figure 8 shown.

[0044] The specific experimental method is: place the prepared Ti6Al4V super-hydrophobic sample on a -10°C refrigerator, pre-cool for 30 seconds, drop 5 μL of water on the super-hydrophobic surface, and record the time it takes for the droplet to completely freeze on the super-hydrophobic surface using a camera, which is 624 seconds.

Claims

1. A design and preparation method of a super-hydrophobic microstructure imitating the slip zone of a pitcher plant, characterized in that The design steps include: Step 1, designing a super-hydrophobic surface microstructure by imitating the composite microstructure of the lunate and wax crystals in the slip zone of Nepenthes, that is, the lunate is a concave cylinder and the wax crystals are blind holes; Step 2: Based on the theoretical model of droplet wetting super-hydrophobic microstructures, an original numerical equation is obtained between the microstructure of periodic arrangement of concave cylinders and blind holes and the super-hydrophobic function, i.e., wettability. The numerical equation is: ， Where: θ T and θ c Represent the theoretical contact angle and the intrinsic contact angle, respectively. The intrinsic contact angle of water droplets on the titanium alloy surface θ c is 101°; R cp 、 R bh 、 R c are the radius of the pit circle, the radius of the blind hole, and the radius of the cylinder respectively; H c 、 H cp 、 H bh They are cylinder height, pit depth, and blind hole depth respectively; n is the number of blind holes in the array, D c and D bh are the spacing of concave cylinders and blind holes respectively; λ is the wetting coefficient, that is, the degree of wetting of the concave cylinder by the water droplet. When the water droplet floats on the top of the concave cylinder, λ =0, when the water droplet completely soaks the concave cylinder λ =1; The original numerical equation is used to determine the microstructure characteristic parameters corresponding to a water droplet contact angle greater than 150°, completing the design of the superhydrophobic microstructure. Step 3: Select titanium alloy Ti6Al4V and perform surface polishing to achieve a surface roughness of 0.8 μm. Then, clean the surface and place it in a constant temperature oven at 30-40°C for 50 minutes to dry the polished Ti6Al4V surface. Step 4, femtosecond laser etching is performed on the polished and dried Ti6Al4V surface to prepare a composite microstructure with periodic arrangement of concave cylinders and blind holes, imitating the lunate body and wax crystals in the slip zone of Nepenthes; Step 5: After femtosecond laser etching, the Ti6Al4V surface exhibits high adhesion properties, so a fluorination treatment is performed to reduce the surface energy. The specific steps include placing the superhydrophobic microstructure in a 1% to 3% by mass solution of heptafluorosilane in anhydrous ethanol for 2.5 to 3.5 hours, and drying it at a constant temperature of 80 to 90°C for 35 to 45 minutes to obtain a Ti6Al4V superhydrophobic surface.

2. The design and preparation method of a Nepenthes-like slip zone super-hydrophobic microstructure according to claim 1, characterized in that: Step 1 specifically includes: (1) A superhydrophobic surface microstructure was designed by imitating the composite microstructure of the lunate and wax crystals in the slip zone of Nepenthes, where the lunate is a concave cylinder and the wax crystals are blind holes; (2) When water droplets infiltrate the bionic superhydrophobic microstructure, the superhydrophobic microstructure with periodic arrangement of concave cylinders and blind holes can effectively retain air, form an air film layer, reduce the contact area, and achieve superhydrophobic function.

3. The design and preparation method of a Nepenthes-like slip zone super-hydrophobic microstructure according to claim 1, characterized in that: Step 2 specifically includes: (1) The designed concave cylinder and blind hole have micron-scale structural characteristic parameters, among which the radius of the concave circle is R cp Designed to be 5.5-10.5 μm deep H cp Designed for 1.5 - 2.5 μm; cylinder radius R c Designed to be 8 - 12 μm, column height H c 48-52 μm; blind hole radius R bh Designed to be 1.5 - 2.5 μm deep H bh Designed to 1 - 2 μm, concave cylinder spacing D c Designed to be 140~180 μm, blind hole spacing D bh Designed to be 20 μm; (2) The characteristic parameters of the microstructure of the periodic arrangement of concave cylinders and blind holes are substituted into the numerical equation to calculate the theoretical value of the water droplet contact angle. The super-hydrophobic function is determined based on whether the contact angle is greater than 150°. This enables the controllable design of the super-hydrophobic surface and clarifies the characteristic parameters of the super-hydrophobic microstructure.

4. The design and preparation method of a Nepenthes-like slip zone super-hydrophobic microstructure according to claim 1, characterized in that: Step 3 specifically includes: (1) Titanium alloy Ti6Al4V was selected as the matrix material of the superhydrophobic microstructure and cut into Ti6Al4V samples with a length × width of 2 cm × 2 cm; (2) The surface of the Ti6Al4V sample was polished to a surface roughness of 0.8 μm; (3) The polished Ti6Al4V sample was placed in anhydrous ethanol and ultrasonically cleaned for 3 min. After cleaning, it was placed in a constant temperature box at 30-40 °C for 50 min to dry the polished Ti6Al4V surface.

5. The design and preparation method of a Nepenthes-like slip zone super-hydrophobic microstructure according to claim 1, characterized in that: Step 4 specifically includes: (1) Place the polished and dried Ti6Al4V sample on the femtosecond laser system platform, adjust the laser focus to the sample surface, and determine the laser scanning path based on the characteristic parameters of the bionic superhydrophobic microstructure determined in step 2; (2) Set the femtosecond laser processing parameters: average power 15 W, beam radius 5 μm, pulse width 1000 fs, and laser frequency 350 kHz; (3) Through multiple etchings on the sample surface by femtosecond laser, the processing of the lunate body and wax crystal micro-nano composite structure in the slip zone of Nepenthes was completed.

6. The design and preparation method of a Nepenthes-like slip zone super-hydrophobic microstructure according to claim 1, characterized in that: Step 5 specifically includes: (1) The Ti6Al4V surface has high adhesion properties after femtosecond laser etching, so fluorination treatment is performed to reduce the surface energy of the Ti6Al4V surface. The etched sample is placed in a beaker, and a 1% to 3% by mass solution of heptafluorosilane in anhydrous ethanol is added. The sample is sealed and placed in a cool environment for 2.5 to 3.5 hours. (2) The sample after chemical fluorination treatment was placed in a constant temperature box at 80-90℃ and kept warm for 35-45 minutes to prepare a superhydrophobic surface with a composite microstructure that simulates the slip zone of pitcher plants.

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