A fog water collecting structure imitating the back structure of a desert beetle and a method for manufacturing the same

Abstract

The application discloses a fog water collecting structure imitating the back structure of a desert beetle and a preparation method thereof. The structure takes a copper pipe as a carrier, and a hemispherical protrusion array arranged in a regular triangle lattice is constructed on the outer surface of the copper pipe. Each hemispherical protrusion is exposed to an underlying super-hydrophilic region by selective laser ablation; and the copper pipe substrate is covered with a self-assembled hydrophobic molecular layer of mercaptan, so as to form a wetting gradient of "hydrophilic protrusion-hydrophobic substrate" on the outer wall of the copper pipe. A plurality of protrusion units and the hydrophobic substrate therebetween form an anisotropic hydrophilic-hydrophobic alternating pattern imitating the back of the desert beetle, and can realize rapid capture, directional convergence and efficient collection of fog droplets. The application realizes structure forming by using a mature constrained hydraulic bulging process, realizes surface functionalization by combining chemical etching treatment and laser patterning technology, has good structure stability and surface durability, and can be prepared on a large scale for use in the fields of atmospheric water collection and condensation strengthening.

Description

Technical Field

[0001] This invention relates to a mist collection structure that mimics the back structure of a desert beetle and its preparation method, which belongs to the field of mist collection technology. Background Technology

[0002] Freshwater scarcity remains a persistent global problem. While traditional methods such as seawater desalination and wastewater recycling can produce freshwater, they generally suffer from drawbacks such as high energy consumption, low efficiency, and complex processes, making them particularly difficult to apply widely in underdeveloped inland regions. Therefore, a passive water collection method that directly utilizes natural phenomena—fog collection—which converts environmental fog vapor into usable freshwater resources, has recently re-emerged as a research focus.

[0003] With the gradual development of biomimetic technology, organisms in nature capable of efficiently collecting water have provided important guidance for scientists' research. The Namib desert beetle is a prime example; its back contains alternating hydrophobic and hydrophilic regions, and its complex dorsal protrusions allow it to quickly capture moisture from morning fog, achieving condensation, collection, and storage of water droplets. This mechanism has inspired numerous studies on biomimetic water-collecting surfaces.

[0004] However, existing biomimetic water collection technologies have the following shortcomings: First, they mostly use flexible polymer materials (such as PDMS) as substrates, which have poor thermal conductivity and cannot achieve active cooling, thus limiting condensation efficiency; second, polymer materials are prone to aging in outdoor environments, resulting in insufficient long-term durability; third, existing structures are mostly limited to planar substrates, and droplet movement depends on surface energy gradients and tilted flow, which reduces the efficiency of droplet condensation and nucleation; fourth, the preparation process is complex and relies heavily on precision microfabrication technologies such as femtosecond lasers, resulting in high manufacturing costs and making it difficult to scale up applications.

[0005] Therefore, it is indeed necessary to improve existing technologies to address their shortcomings. Summary of the Invention

[0006] This invention addresses the problems of existing technologies by providing a mist collection structure and its preparation method that mimics the back of a desert beetle, offering advantages such as convenient installation, affordability, and minimal space occupation. Using a thermally conductive copper tube as a carrier, a regular array of hemispherical protrusions is constructed on the outer surface through a constrained hydraulic bulging process. Combined with chemical oxidation and selective laser treatment, this achieves a desert beetle-like wettability pattern characterized by "superhydrophilic tops and hydrophobic surrounding areas." This structure combines a highly efficient condensation surface, a directional flow path, and internal cooling channels, employing mature industrial hydraulic forming and laser processing technologies, demonstrating promising prospects for large-scale application.

[0007] The present invention adopts the following technical solution: a mist collection structure that mimics the back structure of a desert beetle, comprising a copper tube substrate, wherein the outer surface of the copper tube substrate is distributed with a plurality of mist collection units arranged periodically in an equilateral triangular lattice, the mist collection unit being a hemispherical protrusion structure, the hemispherical protrusion area being a superhydrophilic surface, and the outer surface of the copper tube substrate between adjacent hemispherical protrusion structures being a hydrophobic surface, wherein the superhydrophilic surface and the hydrophobic surface of the outer surface of the copper tube substrate together constitute a biomimetic wettability pattern in which the hydrophilic protrusions and the hydrophobic substrate are alternately spaced.

[0008] Furthermore, the superhydrophilic surface is a copper oxide layer with a micro-nano hierarchical rough structure.

[0009] Furthermore, the hydrophobic surface is an octadecyl mercaptan self-assembled monolayer.

[0010] Furthermore, the height of the hemispherical protrusion is 0.4 to 0.8 times the wall thickness of the copper tube substrate, the diameter is 1.5 mm to 2.5 mm, and the center distance between adjacent hemispherical protrusions is 5 mm to 9 mm.

[0011] The present invention also adopts the following technical solution: a method for preparing a mist collection structure that mimics the back structure of a desert beetle, comprising the following steps:

[0012] Step 1: Preparation of the regular hemispherical protrusion array: The hemispherical protrusion array is formed on the outer surface of the copper tube using a constrained hydraulic bulging process.

[0013] Step 2, Surface pretreatment: Polish and clean the copper tube with the hemispherical protrusion array to obtain a clean surface;

[0014] Step 3: Construction and preparation of hydrophilic substrate: The pretreated copper tube is placed in an alkaline persulfate solution for chemical oxidation treatment to form a superhydrophilic copper oxide layer with a micro-nano rough structure on its entire surface;

[0015] Step 4: Preparation of hydrophobic coating: The copper tube with hydrophilic substrate is immersed in an alcohol solution of long-chain thiols for soaking reaction, and a self-assembled monomolecular hydrophobic layer is formed on the surface through chemical adsorption.

[0016] Step 5, selective laser ablation: Selective laser ablation is used to ablate the hydrophobic coating on the top of the hemispherical protrusion structure, exposing the superhydrophilic copper oxide layer formed in step 3, thereby obtaining a biomimetic wettability pattern in which the hydrophilic protrusion and the hydrophobic substrate are alternately spaced.

[0017] Furthermore, the specific steps of step one are as follows:

[0018] Soft oxygen-free copper tubes are selected and ultrasonically cleaned in sequence with alkaline cleaning agent, acetone and ethanol to remove oil stains. Then they are dried in an 80℃ oven.

[0019] The process employs a constrained hydraulic bulging technique, in which a copper tube is placed in a lower mold cavity with a hemispherical array of recesses. A polyurethane elastic mandrel is inserted into the copper tube. After the upper mold is closed and evenly locked, the end punch is driven by a hydraulic press to apply axial pressure to the elastic mandrel. The pressure is controlled to rise evenly to 28 MPa within 30 seconds and held for 12 seconds, so that the copper tube wall material completely fills the recesses, thereby forming a corresponding hemispherical array of protrusions on the copper tube wall.

[0020] Finally, the pressure is released, the mold is opened, the workpiece is removed, and the mandrel is extracted.

[0021] Further, the specific steps of step two are as follows: The copper tube with the raised array is polished axially with 600 grit, 1200 grit, 2000 grit and 2500 grit sandpaper until the surface is smooth. Then, the copper tube with the raised array is ultrasonically cleaned in anhydrous ethanol and deionized water for 10 minutes to thoroughly remove oil and copper shavings.

[0022] Further, in step three, the alkaline persulfate solution is a mixed aqueous solution of K2S2O8 and KOH, wherein the concentration of K2S2O8 is 0.004 to 0.01 mol / L and the concentration of KOH is 2.0 to 3.0 mol / L; the chemical oxidation treatment specifically involves placing the container containing the alkaline persulfate solution and the copper tube placed in the alkaline persulfate solution in a constant temperature water bath at 50 to 70°C, continuously immersing and reacting for 0.5 to 2 hours, and then drying and curing at 180 to 200°C after treatment.

[0023] Further, in step four, the alcohol solution of the long-chain thiol is an anhydrous ethanol solution of n-octadecyl thiol with a concentration of 0.001 to 0.005 mol / L; the soaking reaction is specifically carried out by placing the container containing the alcohol solution of the long-chain thiol and the copper tube placed in the alcohol solution of the long-chain thiol in a constant temperature water bath at 60 to 80°C and continuously soaking for 0.5 to 2 hours.

[0024] Furthermore, in step five, a fiber laser marking system is used to focus the laser on each hemispherical protrusion for scanning and ablation according to the distribution coordinates of the hemispherical protrusion array. The laser power is 5 to 15W and the scanning speed is 300 to 800mm / s.

[0025] The present invention has the following beneficial effects:

[0026] (1) The copper tube substrate has strong thermal conductivity, high mechanical strength, and is not easy to age and deform. Moreover, the cooling medium can be introduced into the tube, which greatly improves the condensation efficiency.

[0027] (2) Both constrained hydraulic bulging and fiber laser marking technologies are mature processing techniques that can be put into large-scale production with high yield rates.

[0028] (3) In addition to serving as a condensation component, copper tubes can also be used for flow guidance and heat exchange. A single component can perform multiple functions, which greatly simplifies system design.

[0029] (4) The inherent structure of metal tubing (copper tubing) allows condensate droplets to leave the condensation surface solely through surface wetting gradient and gravity, without consuming additional energy. The surface area of ​​the column is much larger per unit area than that of the substrate, providing more nucleation sites for condensation. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a nanofiber desert beetle that mimics the mist collection structure of this invention.

[0031] Figure 2 This is a schematic diagram of the mist collection structure of the present invention.

[0032] Figure 3 This is a schematic diagram of the preparation method of the mist collection structure of the present invention.

[0033] Figure 4 This is a schematic diagram of a water mist collection device.

[0034] Figure 5 This is a schematic diagram of the condensation and water collection process. Detailed Implementation

[0035] The present invention will now be described in detail with reference to specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0036] like Figure 1 As shown, Figure 1 This is a schematic diagram of a nanofiber desert beetle, inspired by the mist collection structure of this invention. Figure 2 As shown, this invention provides a mist collection structure mimicking the back structure of a desert beetle. Based on the surface of a copper tube, it evolves from the alternating hydrophilic and hydrophobic wetting pattern on the back of a desert beetle. The specific structure is as follows: it includes a copper tube substrate 2, the outer surface of which is distributed with several mist collection units 1 arranged periodically in an equilateral triangular lattice. Each mist collection unit 1 is a hemispherical protrusion structure. The hemispherical protrusion area is a superhydrophilic surface, while the outer surface of the copper tube substrate 2 between adjacent hemispherical protrusion structures is a hydrophobic surface, thus forming a biomimetic wetting pattern of alternating hydrophilic protrusions and hydrophobic substrates on the entire outer surface of the copper tube.

[0037] In this invention, a mist collection structure mimicking the back structure of a desert beetle is used. Each hemispherical protrusion is selectively ablated by laser to expose an underlying copper oxide layer with a micro-nano hierarchical rough structure, forming a superhydrophilic surface that mimics the hydrophilic region of a beetle's back. The surface of the copper tube substrate 2 between adjacent hemispherical protrusions is covered with an octadecyl mercaptan self-assembled monolayer, exhibiting hydrophobicity and mimicking the hydrophobic region of a beetle's back. Thus, each mist collection unit and the surrounding copper tube substrate form a wettability gradient structure of "superhydrophilic center - surrounding hydrophobic region." This invention, through the regular geometric arrangement of the hemispherical protrusions, mimics the collision-capture enhancement effect of the beetle's back protrusions on mist droplets in the airflow. When a droplet contacts the surface, the hydrophobic region causes the droplet to rapidly shrink and slide to the adjacent hydrophilic protrusion, where it is pinned and coalesces. Finally, the water droplets coalescing at the protrusions, under the combined action of gravity and surface tension, leave the copper tube and converge towards the bottom, achieving continuous and efficient collection of atmospheric moisture.

[0038] In the mist collection structure of the present invention, which mimics the back structure of a desert beetle, the height of the hemispherical protrusion is 0.4 to 0.8 times the wall thickness of the copper tube base 2, the diameter is 1.5 mm to 2.5 mm, and the center distance between adjacent hemispherical protrusions is 5 mm to 9 mm.

[0039] The method for preparing the mist collection structure mimicking the back structure of a desert beetle according to the present invention includes the following steps:

[0040] Step 1: Preparation of the Regular Hemispherical Protrusion Array: A soft, oxygen-free copper tube (TU1) with an outer diameter of 20mm and a wall thickness of 1.0mm is selected, cut to the required length, and machined flat at the end. It is then ultrasonically cleaned sequentially with alkaline cleaning agent, acetone, and ethanol to remove oil stains, and dried in an 80℃ oven. A constrained hydraulic bulging process is used, placing the copper tube in a lower mold cavity with a hemispherical pit array (pit diameter 2.0mm, depth 0.6mm, equilateral triangular distribution, center distance 7.0mm). A polyurethane elastic mandrel with a Shore hardness of A92 is inserted into the copper tube. After the upper mold is closed and evenly locked, an axial pressure is applied to the elastic mandrel by a hydraulic press-driven end punch. The pressure is controlled to rise evenly to 28MPa within 30 seconds and held for 12 seconds, allowing the copper tube wall material to completely fill the pits, thus forming a corresponding hemispherical protrusion array on the copper tube wall. The protrusion height is 0.6mm and the protrusion diameter is 2.0mm. The pressure is released, the mold is opened, the workpiece is removed, and the mandrel is extracted.

[0041] Step 2, Surface Pretreatment: The copper tube with the raised array is sequentially sanded axially with 600-grit, 1200-grit, 2000-grit, and 2500-grit sandpaper until the surface is smooth. Then, the copper tube with the raised array is sequentially ultrasonically cleaned in anhydrous ethanol and deionized water for 10 minutes to thoroughly remove oil and copper shavings. After cleaning, the entire surface is purged with dry, high-purity nitrogen gas to obtain a clean copper tube substrate.

[0042] Step 3: Construction and Preparation of the Hydrophilic Substrate: The pretreated copper tube was completely immersed in a mixed solution of 0.0065 mol / L K₂S₂O₈ and 2.5 mol / L KOH. The container containing the mixed solution and the copper tube were then placed in a 60°C constant temperature water bath for 60 minutes. After the reaction, the copper tube was removed and thoroughly rinsed with plenty of deionized water. It was then heat-treated in a 180°C oven for 30 minutes to form a superhydrophilic copper oxide layer with a micro-nano rough structure on the entire surface of the copper tube (including all protrusions). The mixed solution used in Step 3 must be freshly prepared and used immediately; the drying temperature must not be lower than 180°C.

[0043] Step 4: Preparation of the hydrophobic coating: Immerse a copper tube with a hydrophilic substrate in an anhydrous ethanol solution of 0.0025 mol / L n-octadecyl mercaptan. Then, place the container containing the anhydrous ethanol solution of n-octadecyl mercaptan and the copper tube in the anhydrous ethanol solution of n-octadecyl mercaptan in a 70°C constant temperature water bath and continue the immersion reaction for 60 min. This allows the mercaptan molecules to form a self-assembled monomolecular hydrophobic layer on the surface of the copper tube through chemical adsorption. After the constant temperature water bath, rinse the copper tube thoroughly with fresh anhydrous ethanol and deionized water in sequence to remove residual reagents. Finally, dry the copper tube in a 60°C oven for 30 min. At this time, the overall surface of the copper tube changes from superhydrophilic to hydrophobic. Anhydrous ethanol should be used in step (4). An ethanol with a water content greater than 2% will cause uneven thickness of the hydrophobic coating.

[0044] Step 5, Selective Laser Ablation: The copper tube is fixed on a three-dimensional precision moving platform. Using a fiber laser marking system (wavelength 1064nm), the laser focused spot (diameter Φ50μm) is precisely located in the center region of each hemispherical protrusion based on the three-dimensional coordinate data of the protrusion array. The laser power is set to 8W, the frequency to 20 kHz, and the scanning speed to 500 mm / s. Scanning is performed within a circular area with a diameter of 2.0mm at the top of each hemispherical protrusion. The laser energy selectively ablates the hydrophobic molecular layer in this region, completely exposing the superhydrophilic copper oxide layer constructed in step (3), while the hydrophobic coating in the remaining unscanned areas remains intact. After processing, the surface of the copper tube is gently rinsed with anhydrous ethanol to remove etching residues and then dried with nitrogen.

[0045] The mist collection device constructed using the mist collection structure of this invention is as follows: Figure 4 As shown, the prepared biomimetic high-efficiency mist collection structure is placed in a condensation chamber filled with dry steam and maintained under saturated steady-state conditions. During the condensation process, cooling water is continuously introduced into the copper tube from the condensate tank to reduce the surface temperature of the tube wall and improve the condensation efficiency. After use, the cooling water is circulated back to the condensate tank, realizing the recycling of resources.

[0046] The formation and rolling behavior of droplets, such as Figure 5 As shown, droplets preferentially condense and grow in the superhydrophilic region at the top of the hemispherical protrusion on the outer wall of the copper tube, exhibiting a cascading effect. Once the droplets reach a critical size, they rapidly move towards the bottom of the copper tube under gravity along the anisotropic flow-guiding network formed by the hydrophobic matrix on the outer wall. A slope at the bottom of the condensation chamber ensures that the condensate flowing down can effectively collect in the central water storage tank, thus achieving efficient and continuous mist collection.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A mist collection structure mimicking the back structure of a desert beetle, characterized in that: The system includes a copper tube substrate (2), on the outer surface of which are distributed several mist collection units (1) arranged in a periodic lattice of equilateral triangles. Each mist collection unit (1) is a hemispherical protrusion structure. The hemispherical protrusion area is a superhydrophilic surface, and the outer surface of the copper tube substrate (2) between adjacent hemispherical protrusion structures is a hydrophobic surface. The superhydrophilic surface and the hydrophobic surface of the outer surface of the copper tube substrate (2) together form a biomimetic wettability pattern in which the hydrophilic protrusions and the hydrophobic substrate are alternately spaced.

2. The mist collection structure mimicking the back structure of a desert beetle as described in claim 1, characterized in that: The superhydrophilic surface is a copper oxide layer with a micro-nano hierarchical rough structure.

3. The mist collection structure mimicking the back structure of a desert beetle as described in claim 1, characterized in that: The hydrophobic surface is an octadecyl mercaptan self-assembled monolayer.

4. The mist collection structure mimicking the back structure of a desert beetle as described in claim 1, characterized in that: The height of the hemispherical protrusion is 0.4 to 0.8 times the wall thickness of the copper tube substrate (2), the diameter is 1.5 mm to 2.5 mm, and the center distance between adjacent hemispherical protrusions is 5 mm to 9 mm.

5. A method for preparing a mist collection structure mimicking the back structure of a desert beetle as described in claim 1, characterized in that: Includes the following steps: Step 1: Preparation of the regular hemispherical protrusion array: The hemispherical protrusion array is formed on the outer surface of the copper tube using a constrained hydraulic bulging process. Step 2, Surface pretreatment: Polish and clean the copper tube with the hemispherical protrusion array to obtain a clean surface; Step 3: Construction and preparation of hydrophilic substrate: The pretreated copper tube is placed in an alkaline persulfate solution for chemical oxidation treatment to form a superhydrophilic copper oxide layer with a micro-nano rough structure on its entire surface; Step 4: Preparation of hydrophobic coating: The copper tube with hydrophilic substrate is immersed in an alcohol solution of long-chain thiols for soaking reaction, and a self-assembled monomolecular hydrophobic layer is formed on the surface through chemical adsorption. Step 5, selective laser ablation: Selective laser ablation is used to ablate the hydrophobic coating on the top of the hemispherical protrusion structure, exposing the superhydrophilic copper oxide layer formed in step 3, thereby obtaining a biomimetic wettability pattern in which the hydrophilic protrusion and the hydrophobic substrate are alternately spaced.

6. The method for preparing the mist collection structure mimicking the back structure of a desert beetle as described in claim 5, characterized in that: The specific steps for Step One are as follows: Soft oxygen-free copper tubes are selected and ultrasonically cleaned in sequence with alkaline cleaning agent, acetone and ethanol to remove oil stains. Then they are dried in an 80℃ oven. The process employs a constrained hydraulic bulging technique, in which a copper tube is placed in a lower mold cavity with a hemispherical array of recesses. A polyurethane elastic mandrel is inserted into the copper tube. After the upper mold is closed and evenly locked, the end punch is driven by a hydraulic press to apply axial pressure to the elastic mandrel. The pressure is controlled to rise evenly to 28 MPa within 30 seconds and held for 12 seconds, so that the copper tube wall material completely fills the recesses, thereby forming a corresponding hemispherical array of protrusions on the copper tube wall. Finally, the pressure is released, the mold is opened, the workpiece is removed, and the mandrel is extracted.

7. The method for preparing the mist collection structure mimicking the back structure of a desert beetle as described in claim 6, characterized in that: Step two is as follows: Grind the copper tube with the raised array along the axial direction with 600 grit, 1200 grit, 2000 grit and 2500 grit sandpaper until the surface is smooth. Then, place the copper tube with the raised array in anhydrous ethanol and deionized water for ultrasonic cleaning for 10 minutes to thoroughly remove oil and copper shavings.

8. The method for preparing the mist collection structure mimicking the back structure of a desert beetle as described in claim 7, characterized in that: In step three, the alkaline persulfate solution is a mixed aqueous solution of K2S2O8 and KOH, wherein the concentration of K2S2O8 is 0.004 to 0.01 mol / L and the concentration of KOH is 2.0 to 3.0 mol / L. The chemical oxidation treatment specifically involves placing the container containing the alkaline persulfate solution and the copper tube placed in the alkaline persulfate solution in a constant temperature water bath at 50 to 70°C, continuously immersing and reacting for 0.5 to 2 hours, and then drying and curing at 180 to 200°C.

9. The method for preparing the mist collection structure mimicking the back structure of a desert beetle as described in claim 8, characterized in that: In step four, the alcohol solution of the long-chain thiol is an anhydrous ethanol solution of n-octadecyl thiol with a concentration of 0.001 to 0.005 mol / L; the soaking reaction is specifically as follows: the container containing the alcohol solution of the long-chain thiol and the copper tube placed in the alcohol solution of the long-chain thiol are placed in a constant temperature water bath at 60 to 80°C and the soaking reaction is continued for 0.5 to 2 hours.

10. The method for preparing the mist collection structure mimicking the back structure of a desert beetle as described in claim 9, characterized in that: In step five, a fiber laser marking system is used. Based on the distribution coordinates of the hemispherical protrusion array, the laser is focused on each hemispherical protrusion for scanning and ablation. The laser power is 5 to 15W and the scanning speed is 300 to 800mm / s.

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