Preparation method of intelligent super-hydrophobic fog water collection surface imitating beetle sheath wing structure

Abstract

The application discloses a preparation method of an intelligent super-hydrophobic fog water collecting surface simulating a beetle sheath wing structure, which comprises the following steps: firstly, performing experimental pretreatment; secondly, preparing a re-entrant corner hole array micro-nano structure in a tessellation arrangement; and finally, constructing a fog water collecting structure surface, wherein the re-entrant corner hole array micro-nano structure in the tessellation arrangement prepared by laser is soaked in a silane solution, so that a fluorine-containing low surface energy functional group is bonded to the micro-nano structure surface; in order to obtain a more firm bonding force, the fluorinated sample needs to be placed in a constant temperature drying box for a period of time, so that the structure surface reaches hydrophobicity; the structure obtained by the application has the advantages of a hydrophilic, hydrophobic and hydrophilic-hydrophobic alternating three typical fog water collecting surfaces, and has a significant advantage for expanding the preparation method and application field of the fog water wetting surface.

Description

Technical Field

[0001] This invention relates to the field of functional micro / nano structure manufacturing, specifically to a method for preparing an intelligent superhydrophobic mist collection surface that mimics the elytra structure of a desert beetle. Background Technology

[0002] Benefiting from the unique wettability of natural plant and animal surfaces, researchers have developed a variety of functional wettable surfaces based on biomimetic principles. Examples include lotus leaf surfaces with self-cleaning properties due to low adhesion, rose petal surfaces with droplet transport properties due to high adhesion, and spider silk, cactus spines, and nanofiber desert beetle surfaces with mist collection capabilities. Research on mist collection using wettable surfaces remains a hot topic. The main reasons for this are as follows: First, severe global environmental pollution and a sharp decline in freshwater resources have led to a continuous increase in water demand for both drinking water and agricultural irrigation, requiring substantial financial resources to address. Second, with the development of the "chip" era, research on heat pipe cooling, a key approach to solving the heat dissipation problem of electronic components, has become crucial. Heat pipe cooling works by condensing heated vapor at the condenser end, which needs high liquid condensation collection efficiency and drainage rate. In conclusion, developing high-performance mist (liquid condensation) collection surfaces would be of great significance in alleviating the water crisis and addressing the overheating issues of electronic devices.

[0003] In recent years, femtosecond laser processing has emerged as a promising technology. Due to its maskless operation, environmental friendliness, extremely small heat-affected zone, and high processing precision, it has been widely applied to the fabrication of micro / nanostructures on non-metallic and metallic surfaces. It exhibits strong versatility and has been extensively used in the fabrication of micro / nanostructures with extreme wettability, including water mist collection surfaces. The wettability of the fabricated water mist surfaces mainly includes superhydrophilic, superhydrophobic, and alternating hydrophilic and hydrophobic properties. Although these surfaces have achieved significant breakthroughs in water mist collection, they still possess unavoidable drawbacks. For example, superhydrophilic surfaces possess both high mist collection rates and high adhesion, resulting in water collection via film condensation. However, this leads to poor heat transfer and extremely low drainage rates, failing to meet practical needs for clean water collection. Superhydrophobic surfaces, while exhibiting high drainage rates due to merging and jumping phenomena and ultra-low adhesion, suffer from low droplet nucleation rates. They typically form easily evaporating, small-surface-area droplets (the surface area of ​​the droplets often allows for contact with water vapor, increasing nucleation and growth rates), often resulting in insufficient mist collection rates and clean water collection volumes. Hydrophilic-hydrophobic surfaces combine the advantages of both, but the presence of hydrophilic regions often results in weak wetting stability (the ability to maintain Cassie wetting stability with low adhesion) and self-cleaning effects. Based on the above analysis, fabricating a structure that combines the advantages of hydrophilic, hydrophobic, and hydrophilic-hydrophobic hybrid surfaces would provide a new direction for future mist collection research. Summary of the Invention

[0004] To overcome the aforementioned shortcomings, the present invention aims to provide a method for preparing a smart superhydrophobic mist collection surface with a structure mimicking the elytra of a desert beetle. The resulting structure combines the advantages of three typical mist collection surfaces: hydrophilic, hydrophobic, and a combination of both. This method offers significant advantages for expanding the preparation methods and application areas of mist wettable surfaces.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a smart superhydrophobic mist collection surface with a structure mimicking the elytra of a desert beetle includes the following steps:

[0007] 1) Experimental pretreatment:

[0008] 1.1) Select the required substrate material based on the actual functional application and technical operating conditions;

[0009] 1.2) Polishing the substrate material to create a smooth surface texture facilitates the programmable design and manufacturing of functional structures;

[0010] 1.3) The mixture was subjected to an ultrasonic bath for 15 minutes in sequence with acetone, anhydrous ethanol and deionized water, while being dried with nitrogen.

[0011] 2) Fabrication of topologically aligned reentry concave-angle aperture array micro / nano structures:

[0012] 2.1) Based on the processing and manufacturing requirements, make preliminary adjustments to the femtosecond laser micro-nano processing and manufacturing system, including collimation and correction of the optical path transmission system, adjustment and design of relevant processing and manufacturing laser parameters (repetition frequency and single pulse energy, etc.);

[0013] 2.2) Set the pulse width of the femtosecond laser to the picosecond range via the femtosecond laser parameter control panel on the computer;

[0014] 2.3) Functional structure processing path trajectory design and planning are performed through the integrated control interface of the femtosecond laser micro / nano fabrication system;

[0015] 2.4) Place the surface of the substrate material at the processing rear end and on the focal plane of the laser beam emitted from the field lens, and perform programmed texturing according to the pre-designed laser parameters and processing planning path;

[0016] 2.5) After processing is completed, use a cleaning air blower to clean the residual ablation residue on the fabric surface to facilitate further cleaning work.

[0017] 2.6) The processed concave micro-nano structure was cleaned sequentially with acetone, anhydrous ethanol and deionized water in an ultrasonic bath for 15 minutes, and then dried with nitrogen to lay the foundation for subsequent processes.

[0018] 3) Construction of the mist collection structure surface: The laser-prepared topologically arranged reentry concave-angle hole array micro / nano structure was immersed in a silane solution, allowing the fluorinated low surface energy functional groups to bond with the micro / nano structure surface. To obtain a stronger bonding force, the fluorinated sample was placed in a constant temperature drying oven and heated for a period of time to make the structure surface hydrophobic. Finally, the wettability of the surface was tested using the seat drop method. After characterization, the static contact angle of water was greater than 150°, indicating good superhydrophobicity.

[0019] The substrate material is aluminum and its alloys, titanium and its alloys, and other metals and their alloys.

[0020] The overall characteristics of the concave corner structure are different from those of structures prepared by other methods such as photolithography and chemical oxidation. It has typical concave corner features. Specifically, the prepared concave corner structure monomer exists in the form of a micron-sized hole. Unlike a typical micron-sized hole, due to the impact strengthening effect between the high-energy laser and the material, a spiral groove structure is generated from top to bottom on the inner wall of the hole. The groove structure has a certain depth, thus indirectly forming the concave corner feature structure on the inner wall of the hole.

[0021] The aforementioned intelligent superhydrophobic mist collection surface refers to a repeatable periodic change in surface wettability before, during, and after mist collection. This change occurs due to the special interaction between the concave pore array structure and the surface condensate.

[0022] The aforementioned topological arrangement refers to the coordinated distribution of hydrophilic and hydrophobic regions during the mist collection process. On the one hand, when hydrophilic protrusions detach, they facilitate the removal of small droplets from the hydrophobic regions. On the other hand, it increases the rolling path of the detached droplets on the surface of the hydrophobic regions, thereby increasing the inertial impact force.

[0023] Compared with existing technologies, the present invention has the following advantages and beneficial effects:

[0024] Firstly, this invention uses femtosecond lasers to prepare micro-nano textured surfaces for mist collection. Femtosecond laser processing has a series of advantages such as high processing precision, no mask required, environmental friendliness, and flexible and controllable structural morphology.

[0025] Secondly, the mist collection surface prepared by this invention combines the advantages of three typical mist collection surfaces: hydrophilic, hydrophobic, and hydrophilic / hydrophobic combination. At the same time, it overcomes their corresponding disadvantages to a certain extent. For example, although the hydrophilic / hydrophobic combination mist collection surface combines the advantages of hydrophilic and hydrophobic mist collection surfaces, the high adhesion of the hydrophilic protrusions often results in the droplets on the hydrophilic protrusions not combining with the easily evaporating small droplets collected in the hydrophobic area in time, which greatly reduces the mist collection efficiency. At the same time, the presence of the hydrophilic area makes the self-cleaning effect poor. In addition, the structure is usually characterized by a conical structure, and the wetting stability does not meet the requirements. The functional surface prepared by this invention can fully utilize the capillary accumulation effect between the micron-sized pores and the condensed water during mist collection to form a superhydrophobic region with micron-sized hydrophilic droplet protrusions and nano-roughness between the porous structure monomers. The hydrophilic droplet protrusions correspond to the solid hydrophilic protrusions of the elytra structure. Not only can the surface area of ​​the protruding droplets be increased to increase the water vapor condensation area, but the low surface energy chemical components inside the porous structure can also make the weight of a droplet of a certain size easily overcome the capillary force and roll off without residue. The nano-sized superhydrophobic region easily collects smaller droplets and triggers the droplet merging and jumping phenomenon. The detached hydrophilic protrusion droplets roll off along the superhydrophobic region and collect smaller droplets along the way in a timely manner.

[0026] In addition to possessing the advantages of three typical mist collection surfaces, the wettability of the mist collection surface proposed in this invention can intelligently and periodically switch. When the humidity in the air is high, the surface wettability alternates between hydrophilic and hydrophobic, enabling efficient mist collection. When the humidity in the air is low, the surface wettability becomes hydrophobic. Due to the presence of re-entry concave pores, the Cassie's wettability is greatly enhanced, and it also exhibits good self-cleaning properties. The method for preparing the mist collection surface proposed in this invention is of great significance for addressing and alleviating the water resource crisis and promoting the use of functional surfaces. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of femtosecond laser processing in Embodiment 1 of the present invention.

[0028] Figure 2 This is a cross-sectional view of the wettability distribution on the surface of the elytra structure of the desert beetle according to the present invention.

[0029] Figure 3 This is a process flow diagram of the preparation method of a smart superhydrophobic mist collection surface with a structure mimicking the elytra of a desert beetle, according to the present invention.

[0030] Figure 4 This is a side view of the wettability distribution of the intelligent superhydrophobic mist collection surface of the present invention.

[0031] Figure 5 This is a partially enlarged side view of the wettability distribution of the intelligent superhydrophobic mist collection surface of the present invention.

[0032] Figure 6 (a) shows the vertically placed intelligent superhydrophobic mist collection surface of the present invention, and (b) shows the dynamic process of mist collection on the superhydrophobic surface prepared by the present invention. Detailed Implementation

[0033] The present invention will now be described in detail with reference to embodiments and accompanying drawings.

[0034] Examples, such as Figure 3 As shown, a method for preparing a smart superhydrophobic mist collection surface with a structure mimicking the elytra of a desert beetle includes the following steps:

[0035] 1) Experimental pretreatment:

[0036] 1.1) Select the required substrate material based on the actual functional application and technical operating conditions;

[0037] 1.2) Polishing the substrate material to create a smooth surface texture facilitates the programmable design and manufacturing of functional structures;

[0038] 1.3) The mixture was subjected to an ultrasonic bath for 15 minutes in sequence with acetone, anhydrous ethanol and deionized water, while being dried with nitrogen.

[0039] In this embodiment, a metal substrate (such as 6061 aluminum alloy) with suitable area and thickness is selected as the substrate material.

[0040] 2) Fabrication of topologically aligned reentry concave-angle aperture array micro / nano structures:

[0041] 2.1) Based on the processing and manufacturing requirements, make preliminary adjustments to the femtosecond laser micro-nano processing and manufacturing system, including collimation and correction of the optical path transmission system, adjustment and design of relevant processing and manufacturing laser parameters (repetition frequency and single pulse energy, etc.);

[0042] like Figure 1 As shown, the femtosecond laser micro / nano fabrication system in this embodiment includes a femtosecond laser 1, a reflector 2, a beam expander 3, a biaxial scanning galvanometer 4, a platform 5 for placing the substrate material, and a computer control system 6. The Gaussian beam with a wavelength of 1030 nm and an adjustable pulse width (default 240 fs) output by the femtosecond laser 1 is sequentially focused onto the surface of the substrate material on the platform 5 by the reflector 2, the beam expander 3, and the biaxial scanning galvanometer 4. The optical path components are adjusted to obtain a suitable beam quality for processing, and the plane where the laser beam focus is located is found using a step-by-step scribing method. The diameter of the focus of the laser beam on the surface of the substrate material to be processed on the platform 5 is approximately 30 micrometers.

[0043] 2.2) Set the pulse width of the femtosecond laser to the picosecond range via the femtosecond laser parameter control panel on the computer;

[0044] In this embodiment, the computer control system 6 is first set to output Gaussian light with a wavelength of 1030nm from the femtosecond laser, and the pulse width is tuned from 240fs to 6ps.

[0045] 2.3) Functional structure processing path trajectory design and planning are performed through the integrated control interface of the femtosecond laser micro / nano fabrication system;

[0046] This embodiment is based on Figure 2 Preparation of wetting properties such as Figure 4 and Figure 5 The structure shown, Figure 5 The process involves a structured substrate material surface where hydrophilic droplets protrude due to capillary accumulation, and small droplets condense and grow in superhydrophobic regions. This requires two processing steps with a femtosecond laser. First, the laser scanning path is planned as a vertically intersecting array with a spacing smaller than the diameter of the focused spot (typically 15 micrometers). Then, the second laser processing path is a topologically arranged lattice.

[0047] 2.4) Place the surface of the substrate material at the processing rear end and on the focal plane of the laser beam emitted from the field lens, and perform programmed texturing according to the pre-designed laser parameters and processing planning path;

[0048] 2.5) After processing is completed, use a cleaning air blower to clean the residual ablation residue on the fabric surface to facilitate further cleaning work.

[0049] 2.6) The processed concave micro-nano structure was cleaned sequentially with acetone, anhydrous ethanol and deionized water in an ultrasonic bath for 15 minutes, and then dried with nitrogen to lay the foundation for subsequent processes.

[0050] 3) Construction of the mist collection structure surface: The laser-prepared topologically arranged reentry concave-angle hole array micro / nano structure was immersed in a silane solution, allowing the fluorinated low surface energy functional groups to bond with the micro / nano structure surface. To obtain a stronger bonding force, the fluorinated sample was placed in a constant temperature drying oven and heated for a period of time to make the structure surface hydrophobic. Finally, the wettability of the surface was tested using the seat drop method. After characterization, the static contact angle of water was greater than 150°, indicating good superhydrophobicity.

[0051] In this embodiment, the laser-prepared topologically arranged reentry concave-angle hole array micro / nano structure was immersed in a 1% 1H,1H,2H,2H-perfluorodecyltrimethoxysilane methanol solution for 2 hours, and finally heated in a constant temperature drying oven at 90°C for 30 minutes to achieve superhydrophobicity.

[0052] The beneficial effects of this embodiment are: it can not only achieve... Figure 6 The described dynamic mist collection effect allows for intelligent, periodic changes in the wettability of the mist collection surface. When not collecting mist, the surface is superhydrophobic, meeting the requirements for wettability stability and self-cleaning. During mist collection, the capillary action of the micropores on the water droplets creates hydrophilic droplet protrusions, which, combined with the superhydrophobic regions, create a mist collection effect similar to the elytra structure of a desert beetle. However, unlike the beetle, the protruding droplets, due to the presence of superhydrophobic, low-surface-energy material within the pores, are more easily overcome by gravity and detach completely from the capillary force. When mist collection ends, the surface wettability returns to superhydrophobicity. The mist collection surface prepared in this invention exhibits corresponding changes in wettability under different operating conditions to meet practical needs and overcome the shortcomings of traditional mist collection surfaces. Furthermore, relevant literature indicates that fluorosilane-modified metal superhydrophobic surfaces have strong durability; therefore, the mist collection surface proposed in this invention possesses excellent cycle performance. In summary, this invention has profound significance for solving the problem of mist collection and expanding the engineering applications of wettable surfaces.

Claims

1. A method for preparing an intelligent super-hydrophobic fog-collecting surface imitating the structure of the beetle's sheath, comprising the following steps: 1) Experimental pretreatment: 1.1) Select the required substrate material according to the actual functional application and technical working condition requirements; 1.2) Polishing treatment is performed on the substrate material to make the surface smooth and textured to facilitate the programmable design and manufacture of functional structures; 1.3) Sequentially use acetone, anhydrous ethanol, and deionized water for ultrasonic bath for 15 min, and dry treatment with nitrogen gas; 2) Preparation of re-entrant corner hole array micro-nano structure in a staggered arrangement: 2.1) Preliminary adjustment of the femtosecond laser micro-nano machining system according to the working condition machining and manufacturing requirements, including collimation and correction of the optical transmission system, adjustment and design of related machining laser parameters; 2.2) Set the pulse width of the femtosecond laser to picosecond level through the femtosecond laser parameter control panel on the computer; 2.3) Design and plan the functional structure machining path trajectory through the integrated control interactive interface of the femtosecond laser micro-nano machining system; 2.4) Place the substrate material surface on the machining backend and at the focal plane of the outgoing laser beam from the field lens, and perform programmable texturing according to the pre-designed laser parameters and machining planning path; 2.5) After machining is completed, clean the textured surface residual ablation residue with clean gas; 2.6) After machining, the re-entrant corner hole array micro-nano structure is sequentially cleaned with acetone, anhydrous ethanol, and deionized water ultrasonic bath for 15 minutes, and then dried with nitrogen gas; 3) Construction of fog water collection structure surface: immerse the above laser prepared re-entrant corner hole array micro-nano structure in a staggered arrangement in a silane solution, so that the fluorine-containing low surface energy functional group is bonded to the micro-nano structure surface; in order to obtain a more firm bonding force, the fluorinated sample needs to be placed in a constant temperature drying oven for heating, so that the structure surface reaches hydrophobicity; finally, the surface wettability is tested by the sessile drop method, and after characterization, the static contact angle of water is greater than 150°, showing good superhydrophobicity.

2. The method of claim 1, wherein: The substrate material is aluminum and its alloys or titanium and its alloys.

3. The method of claim 1, wherein: The overall features of the re-entrant corner hole array micro-nano structure have typical re-entrant corner features, and the prepared re-entrant corner hole array micro-nano structure monomer exists in the form of micropores. Due to the impact strengthening effect between high-energy laser and material, a "spiral" groove structure is generated on the inner wall of the hole from top to bottom, and the groove structure has a certain depth, indirectly forming the re-entrant corner feature structure on the inner wall of the hole.

4. The method of claim 1, wherein: The intelligent superhydrophobic fog water collection surface refers to the repeatable periodic change of surface wettability before, during, and after fog water collection, which is due to the special interaction between the re-entrant corner hole array micro-nano structure and the surface condensed water.

5. The method of claim 1, wherein: The staggered arrangement refers to the coordinated distribution of hydrophilic and hydrophobic regions during fog water collection, which facilitates the removal of small droplets on the hydrophobic region when the hydrophilic protruding droplet falls off, and increases the rolling path of the falling droplet on the hydrophobic region surface, thereby increasing the inertial impact force.

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