A method and application of underwater perfusion of lubricating oil to construct a stable Nepenthes-like super-slip surface

Abstract

The present invention belongs to the technical field of preparation of environmental functional materials, and discloses a method and application for underwater perfusion of lubricating oil to construct a stable Nepenthes-like super-slip surface. After cleaning a copper sheet, it is immersed in a strong alkaline solution containing a strong oxidant, and then immersed in an ethanol solution containing perfluorosilane. After being taken out and dried, lubricating oil is perfused in an aqueous medium to obtain a stable Nepenthes-like super-slip surface. The prepared Nepenthes-like super-slip surface has good stability. After spin coating experiments and fog water collection tests, it has low oil loss and good stability in fog water collection applications. The preparation method is simple and the process is short. It can be prepared on a large scale and is suitable for industrial production and use.

Description

Technical Field

[0001] The invention relates to a new method for constructing a stable Nepenthes-like super-slip surface by underwater perfusion of lubricating oil and application thereof, belonging to the technical field of preparation of environmental functional materials. Background Art

[0002] The Earth's surface is rich in water resources, but freshwater accounts for only 3% of the world's total water supply, with the majority stored in glaciers and snow, making it difficult to access. Surface water, the primary source of water for daily production and domestic use, accounts for only 0.3% of total freshwater, creating an increasingly severe global freshwater shortage. Harvesting freshwater from nature is an effective way to alleviate this problem. Fog, a widespread atmospheric vapor with a water content equivalent to 10% of surface water reserves, holds the potential to serve as a valuable new freshwater reservoir in arid and water-scarce regions. Therefore, developing new, energy-saving technologies to efficiently capture airborne fog is crucial to alleviating the global freshwater crisis.

[0003] The collection of fog droplets on a material surface often requires three steps: droplet capture, droplet aggregation, and droplet shedding. Studies have shown that compared to the droplet capture and aggregation process, the timely shedding of water droplets is an important step in achieving efficient fog water collection. Therefore, seeking to construct a new surface on which water droplets can be quickly transferred and shed is of great significance for the preparation of fog water collection materials. Inspired by the insect-capturing behavior of pitcher plants in nature, domestic and foreign scholars injected lubricating oil with low surface energy into a rough porous structure to obtain a lubricating oil-infused super-slip surface. The super-slip surface can significantly increase the transmission speed of water droplets on the material surface, causing the water droplets to slide off the surface quickly, exposing the droplet capture site in time, accelerating the fog water collection cycle, and helping to improve the overall fog water collection rate. Currently, the research focus of the lubricating oil-infused super-slip surfaces reported at home and abroad is mostly on the design of the physical and chemical properties of the substrate surface and the multifunctional application of the super-slip surface, while the research on the lubricating oil infusion method is often overlooked. Currently, most of the reported lubricant infusion processes are carried out in air. In order to improve the stability of the super-slip surface from the perspective of the infusion process, this work proposes to carry out the lubricant infusion process in a water medium. Compared with the conventional lubricant infusion in air, the oil droplets in the water will be subjected to additional downward pressure from the water, so that the lubricant can not only spread better on the multi-level substrate, but also achieve dense filling in the longitudinal depth of the substrate structure. Summary of the Invention

[0004] The present invention selects the widely used perfluoropolyether as the lubricant, uses a copper-based nano-scale rough structure modified with fluorinated silane as the substrate, and perfuses the lubricant in an aqueous medium. From the perspective of the lubricant perfusion process, the problem of poor perfusion effect in the longitudinal depth direction in the traditional lubricant perfusion process is improved, and the stability and durability of the super-slip surface are enhanced.

[0005] A method for constructing a stable Nepenthes-like super-slip surface by underwater injection of lubricating oil, comprising the following steps:

[0006] Step 1: Cleaning the copper sheet: First, ultrasonically treat the copper sheet, then clean it with acetone, ethanol, and deionized water, and then vacuum dry it.

[0007] Step 2: Preparation of a nano-scale rough substrate: Immerse the cleaned copper sheet in a strong alkaline solution containing a strong oxidant, chemically etch and clean it, and then dry it at room temperature to obtain a Cu / Cu(OH)2 substrate with a nano-scale rough structure;

[0008] Step 3, super-hydrophobic treatment of the nano-scale rough structure substrate: immersing the Cu / Cu(OH)2 substrate with the nano-scale rough structure in an ethanol solution containing perfluorosilane, taking it out and drying it to obtain a super-hydrophobic Cu / Cu(OH)2-F substrate with the nano-scale rough structure;

[0009] Step 4, underwater perfusion of lubricating oil: Place the superhydrophobic Cu / Cu(OH)2-F substrate with a nanoscale rough structure prepared in step 3 in a culture dish filled with water. Use a pipette to draw a certain amount of perfluoropolyether lubricating oil and perfuse it on the surface of the substrate underwater. After standing for a while, place it vertically to obtain a stable super-slip surface.

[0010] In step 1, the washing is performed with deionized water or distilled water, and the temperature is controlled below 30° C. during ultrasonic cleaning.

[0011] In step 1, vacuum drying refers to drying in a vacuum drying oven at 50 to 60° C. for 2 to 3 hours.

[0012] In step 2, the strong oxidant used is ammonium persulfate, the strong base is sodium hydroxide, and the molar concentration of ammonium persulfate is 0.13-0.15 mol L -1 The molar concentration of sodium hydroxide is 2.5-3.0 mol L -1 .

[0013] In step 2, the cleaning is performed by rinsing with deionized water and anhydrous ethanol several times in sequence.

[0014] In step 3, the full name of the perfluorosilane used is 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

[0015] In step 3, the mass concentration of perfluorosilane in the ethanol solution containing perfluorosilane is 0.1 to 0.5 g / L -1 .

[0016] In step 3, the soaking time is 15 to 20 minutes, and the drying refers to drying in an air atmosphere at 25 to 50° C. for 1 to 2 hours.

[0017] In step 4, the aqueous medium used is deionized water or distilled water.

[0018] In step 4, the full name of the perfluoropolyether lubricant used is polymerized oxidized 1,1,2,3,3,3,-hexafluoro-1-propylene.

[0019] In step 4, the amount of perfluoropolyether used is 100-200 μL per square centimeter of the superhydrophobic metal sheet.

[0020] In step 4, the standing is to stand in the water medium horizontally for 5 to 10 minutes, and to stand vertically for more than 12 hours.

[0021] The prepared stable Nepenthes-like super-slip surface has good water transmission ability and can be used for stable fog water collection under high humidity.

[0022] Beneficial effects of the present invention:

[0023] (1) The super-hydrophobic substrate used in the present invention is modified with fluorinated silane, and the lubricant used is perfluoropolyether. The two have similar chemical groups and chemical properties, so that the lubricant has good intermolecular interaction at the molecular level when in contact with the substrate.

[0024] (2) The super-hydrophobic nano-scale rough structure substrate used in the present invention has a strong capillary effect on the lubricating oil, which enhances the longitudinal diffusion ability of the oil droplets between the nano-scale structure arrays and increases the amount of lubricating oil poured on the rough substrate.

[0025] (3) Thanks to the unique new underwater lubricating oil infusion process, the obtained pitcher plant-like super-slip surface has good stability. After spin coating experiments and mist water collection tests, it has low oil loss and good stability in mist water collection applications.

[0026] (4) The present invention proposes a new process for perfusing a porous substrate with lubricating oil, which obtains a stable pitcher plant-like super-slip surface. The preparation method is simple and the process is short, and large-scale stable super-slip surfaces can be prepared, which is suitable for industrial production and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The cross-section (a) and planar scanning electron micrograph (b) of the stable Nepenthes-like super-slip surface prepared in Example 1;

[0028] Figure 2 The water contact angle (a) and sliding angle (b) of the stable Nepenthes-like super-slip surface prepared in Example 1, and the state after sliding (c);

[0029] Figure 3 Comparison of the oil filling rates of Example 1 when filling lubricating oil underwater and in the air;

[0030] Figure 4 Comparison of the lubricant loss rate after spin coating on the super-slip surface obtained by perfusing lubricant underwater and in air in Example 1;

[0031] Figure 5 This is a comparison of the changes in the mist water collection rate of the super-slip surface obtained by injecting lubricating oil underwater and in the air in Example 1;

[0032] Figure 6 The figure shows a comparison of the lubricating oil loss rate of the super-slip surface obtained by injecting lubricating oil underwater and in the air in Example 1 after multiple mist water collections. DETAILED DESCRIPTION

[0033] 1. The present invention will be further described below with reference to the accompanying drawings:

[0034] Example 1:

[0035] First, the copper sheet was cleaned by ultrasonic cleaning with ethanol, acetone, and deionized water for 30 minutes each, and then vacuum dried.

[0036] The cleaned copper sheet was then immersed in a solution with a molar concentration of 0.13 mol L -1 Chemical etching was performed in a strong alkaline solution of ammonium persulfate to obtain a Cu / Cu(OH)2 substrate with a nanoscale rough structure on the surface;

[0037] Then the mass concentration was 0.1 g L -1 The substrate was immersed in an ethanol solution of 1H,1H,2H,2H-perfluorooctyltriethoxysilane for 15 min and then dried in air at 50 °C for 1 h to obtain a superhydrophobic Cu / Cu(OH)2-F substrate with a nanoscale rough structure.

[0038] Finally, the super-hydrophobic substrate prepared above was cut into 2*2cm 2A square of size was prepared, and 400 μL of perfluoropolyether (i.e., polymerized oxidized 1,1,2,3,3,3,-hexafluoro-1-propylene) was measured with a pipette. The superhydrophobic Cu / Cu(OH)2-F substrate prepared above was fully perfused underwater to allow the perfluoropolyether lubricant to fully spread on the superhydrophobic surface. After standing underwater for 5 minutes, it was taken out and placed vertically overnight to allow the excess perfluoropolyether lubricant to fall off under gravity, thereby obtaining a stable superslip surface. The scanning electron microscope images of its cross section and plane are shown in Figure 2. Figure 1 , its surface water contact angle and sliding angle are as follows Figure 2 .

[0039] Figure 1 The cross-section (a) and plane scanning electron microscope image (b) of the stable Nepenthes-like super-slip surface prepared in Example 1 show that the perfluoropolyether lubricant is tightly filled between the nano-scale needle arrays.

[0040] Figure 2 These are the water contact angle (a) and sliding angle (b, c) of the stable pitcher plant-like super-slip surface prepared in Example 1. It can be seen that the prepared super-slip surface is hydrophobic, and water droplets can slide down a slope with an inclination of about 5°, realizing water transmission.

[0041] 2. The present invention will be further described below with reference to specific implementation examples:

[0042] For comparison, using the same superhydrophobic Cu / Cu(OH)2-F substrate, 400 μL of perfluoropolyether lubricant was perfused in air. After standing in air for 5 minutes, the surface was placed vertically overnight to obtain a superslip surface perfused in air. The oil perfusion rate (R1%) obtained in the present invention was calculated as follows:

[0043]

[0044] Where M0(g) and M1(g) are the masses of the metal sheet before and after lubricating oil injection, respectively.

[0045] Figure 3 The oil filling rate of the super-slip surface obtained by the two methods of filling lubricating oil underwater and in the air in Example 1 is compared. It can be seen that compared with the air, filling lubricating oil in water can achieve a higher lubricating oil load.

[0046] The stability of the super-slip surface prepared in the present invention was characterized by spin coating method, which was carried out as follows: two metal sheets with super-slip surfaces prepared in air and underwater were taken and subjected to 1000 r min -1 The stability of the super-slip surface was tested by spin coating for 30 seconds. The results are as follows Figure 3 As shown, the lubricating oil loss rate (R2%) can be calculated as follows:

[0047]

[0048] Where M0(g) and M2(g) are the masses of the metal sheet before and after spin coating on the super-slip surface, respectively.

[0049] Figure 4 The super-slip surface obtained by perfusing lubricating oil underwater and in air in Example 1 is compared with the loss rate of lubricating oil after spin coating. It can be seen that the lubricating oil loss rate of the super-slip surface obtained by perfusing lubricating oil in water is significantly reduced, indicating that the lubricating oil perfused underwater can better fill the nanoscale arrays and has better stability.

[0050] The mist collection capacity under high humidity in the specific embodiment of the present invention is measured as follows: an ultrasonic humidifier is used as the mist source, a metal sheet with a super-slip surface prepared in water and air is fixed with a clip 5 cm from the humidifier outlet, and the angle is adjusted so that the mist flow direction is perpendicular to the metal sheet surface. The fixed water mist flow rate is about 300 g L -1 The ambient temperature and humidity were 20℃ and 80%RH respectively. The captured water was collected under the metal sheet, and every 10 minutes was considered as a cycle. The collected water was weighed. The multiple fog water collection cycles of the two super-slip surfaces are shown in Figure 2. Figure 5 As shown, its fog water collection rate WCR (mg cm - 2 h -1 ) is calculated by the following method:

[0051]

[0052] Where m (mg) is the mass of water collected in each cycle, A (cm -2 ) is the effective area of ​​fog water collection, and t(h) is the time of fog water collection.

[0053] By weighing the mass change of the metal sheet before and after the fog water collection, the loss rate of lubricating oil (R3%) during the fog water collection process is characterized. Figure 6 As shown, the calculation method is:

[0054]

[0055] Where M0(g) and M3(g) are the masses of the metal sheet before and after multiple fog water collection cycle experiments on the super-slip surface.

[0056] Figure 5 This is a comparison of the changes in the mist water collection rate of the super-slip surface obtained by injecting lubricating oil underwater and in air in Example 1;

[0057] Figure 6The figure shows a comparison of the lubricating oil loss rate of the super-slip surface obtained by perfusing lubricating oil underwater and in the air after multiple mist water collection in Example 1. It can be seen that the super-slip surface obtained by perfusing lubricating oil underwater has stable performance and low oil loss during the long-term mist water collection process, indicating that compared with the super-slip surface obtained by perfusing lubricating oil in the air, the super-slip surface prepared by the new process of underwater perfusion lubricating oil has better stability and durability.

Claims

1. A method for constructing a stable Nepenthes-like super-slip surface by underwater perfusion of lubricating oil, characterized in that: Here are the steps: Step 1: Cleaning the copper sheet: First, ultrasonically treat the copper sheet, then clean it with acetone, ethanol, and deionized water, and then vacuum dry it. Step 2: Preparation of a nano-scale rough substrate: Immerse the cleaned copper sheet in a strong alkaline solution containing a strong oxidant, chemically etch and clean it, and then dry it at room temperature to obtain a Cu / Cu(OH)2 substrate with a nano-scale rough structure; Step 3, super-hydrophobic treatment of the nano-scale rough structure substrate: immersing the Cu / Cu(OH)2 substrate with the nano-scale rough structure in an ethanol solution containing perfluorosilane, taking it out and drying it to obtain a super-hydrophobic Cu / Cu(OH)2-F substrate with the nano-scale rough structure; Step 4, underwater perfusion of lubricating oil: Place the superhydrophobic Cu / Cu(OH)2-F substrate with a nanoscale rough structure prepared in step 3 in a culture dish filled with water. Use a pipette to draw a certain amount of perfluoropolyether lubricating oil and perfuse it on the surface of the substrate underwater. After standing for a while, place it vertically to obtain a stable super-slip surface.

2. The method for constructing a stable Nepenthes-like super-slip surface by underwater injection of lubricating oil according to claim 1, characterized in that: In step 1, during ultrasonic cleaning, the temperature is controlled below 30° C.; vacuum drying refers to drying in a vacuum drying oven at 50 to 60° C. for 2 to 3 hours.

3. The method for constructing a stable Nepenthes-like super-slip surface by underwater injection of lubricating oil as claimed in claim 1, characterized in that: In step 2, the strong oxidant used is ammonium persulfate, the strong base is sodium hydroxide, and the molar concentration of ammonium persulfate is 0.13-0.15 mol·L -1 The molar concentration of sodium hydroxide is 2.5-3.0 mol·L -1 .

4. The method for constructing a stable Nepenthes-like super-slip surface by underwater injection of lubricating oil as claimed in claim 1, characterized in that: In step 2, the cleaning is performed by rinsing with deionized water and anhydrous ethanol several times in sequence.

5. The method for constructing a stable Nepenthes-like super-slip surface by underwater injection of lubricating oil as claimed in claim 1, characterized in that: In step 3, the mass concentration of perfluorosilane in the ethanol solution containing perfluorosilane is 0.1 to 0.5 g·L -1 The full name of the perfluorosilane used is 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

6. The method for constructing a stable Nepenthes-like super-slip surface by underwater injection of lubricating oil as claimed in claim 1, characterized in that: In step 3, the soaking time is 15 to 20 minutes, and the drying refers to drying in an air atmosphere at 25 to 50° C. for 1 to 2 hours.

7. The method for constructing a stable Nepenthes-like super-slip surface by underwater injection of lubricating oil as claimed in claim 1, characterized in that: In step 4, the water used is deionized water or distilled water; the full name of the perfluoropolyether lubricant used is polymerized oxidized 1,1,2,3,3,3,-hexafluoro-1-propylene.

8. The method for constructing a stable Nepenthes-like super-slip surface by underwater injection of lubricating oil as claimed in claim 1, characterized in that: In step 4, the amount of perfluoropolyether lubricating oil used per square centimeter of the superhydrophobic metal sheet is 100 to 200 μL.

9. The method for constructing a stable Nepenthes-like super-slip surface by underwater injection of lubricating oil as claimed in claim 1, characterized in that: In step 4, the standing is to stand in the water medium horizontally for 5 to 10 minutes, and to stand vertically for more than 12 hours.

10. Use of the stable Nepenthes-like super-slip surface prepared by the method according to any one of claims 1 to 9 for collecting fog water under high humidity.

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