Method for controllably generating underwater air bubbles based on surface hydrophilic-hydrophobic wetting step effect

Abstract

The present invention discloses a method for controllably generating underwater large bubbles based on the surface hydrophilic-hydrophobic wetting step effect. The specific steps are as follows: drill a 1-mm through-hole on a hydrophilic surface → prepare superhydrophobic circular surfaces with different diameters centered on the hole center → inject air onto the superhydrophobic circular surfaces through a needle → the air film on the superhydrophobic circular surfaces thickens and desorbs to form bubbles. The method of the present invention can control the area that the air film can cover by adjusting the area size of the superhydrophobic region, and further control the volume or diameter of the bubbles formed after desorption.

Description

Technical Field

[0001] The present invention relates to a method for controllably generating underwater large air bubbles based on the surface hydrophilic-hydrophobic wetting step effect. More particularly, it refers to a method for controlling the size of air bubbles generated underwater by adjusting the area of a superhydrophobic circular region on an underwater hydrophilic surface. Background Art

[0002] The gas-liquid two-phase flow is a very typical flow phenomenon, and the air bubbles in water are gases dispersed in water. In nature and daily life, the air bubbles in water play very important roles and exhibit many novel characteristics, and have wide applications in many fields, such as sewage treatment, mineral flotation, aquaculture, industrial cleaning, and healthcare. At present, there are various ways to generate nanoscale (tens of nanometers) air bubbles and microscale (a few micrometers to hundreds of micrometers) air bubbles in water. When studying the movement law of air bubbles in water, in order to facilitate observation and identification, millimeter-scale air bubbles are often selected. However, the existing methods can stably generate air bubbles with a diameter of less than 3 mm in water, and it is still difficult to stably generate air bubbles with a diameter greater than 3 mm in water.

[0003] The superhydrophobic surface has a strong repulsive effect on water and has a strong adsorption effect on gas underwater. Therefore, a gas film will be adsorbed on the superhydrophobic surface underwater, while the hydrophilic surface cannot adsorb a gas film underwater. By preparing a superhydrophobic surface on a partial region of the hydrophilic surface, due to the difference in the gas film adsorption properties between the hydrophilic surface and the superhydrophobic surface, a wetting step effect will be generated at the junction of the two, so that the gas film is confined in the superhydrophobic surface region and cannot spread to the hydrophilic surface region. Summary of the Invention

[0004] In order to solve the problem that it is currently difficult to generate stable air bubbles with a size greater than 3 mm in water, the present invention proposes a method for controllably generating underwater large air bubbles based on the surface hydrophilic-hydrophobic wetting step effect. The specific steps of the method of the present invention are: making a 1 mm through hole on the hydrophilic surface → preparing superhydrophobic circular surfaces with different diameters with the hole center as the center of the circle → injecting air into the superhydrophobic circular surface through the 1 mm through hole → the gas film on the superhydrophobic circular surface thickens and desorbs to form air bubbles. The method of the present invention can control the area that the gas film can cover by adjusting the area of the superhydrophobic region, and further control the volume or diameter of the air bubbles formed after desorption.

[0005] A method for controllably generating underwater large air bubbles based on the surface hydrophilic-hydrophobic wetting step effect of the present invention includes the following steps:

[0006] Step 1, making a through hole on the substrate;

[0007] Using a mechanical drilling process to drill a through hole (2) on the substrate (1);

[0008] The diameter of the through hole (2) is 1 mm; the distance between through holes is denoted as b, and b = 8 mm to 24 mm;

[0009] Step two, prepare a superhydrophobic circular surface with the hole center as the center of the circle;

[0010] Step 21, roughening treatment of the upper panel;

[0011] Adopt the laser marking method to carry out roughening treatment on the upper panel (3) of the substrate with holes, and obtain the first preform (10) of the rough upper surface (5);

[0012] Laser marking roughening process parameters: the laser power is 10 W to 18 W, and the laser marking speed is 500 mm / s to 2000 mm / s;

[0013] Step 22, low surface energy treatment of the rough upper surface;

[0014] Adopt the atomization spraying process to spray 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10 - heptadecafluorodecyltrimethoxysilane on the rough upper surface (5) of the first preform (10) to form a superhydrophobic layer (6), and obtain the second preform (20);

[0015] Atomization spraying process: atomize the 1% concentration of 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10 - heptadecafluorodecyltrimethoxysilane absolute ethanol solution, and spray it on the rough upper surface (5) under the condition of a flow rate of 1 ml / min;

[0016] Step 23, superhydrophobic circular surfaces with different diameters;

[0017] Adopt the laser marking method to remove part of the superhydrophobic layer (6), leaving superhydrophobic circular surfaces (30A) with different diameters centered on the through hole (2) to obtain the third preform (30); the diameter of the superhydrophobic circular surface (30A) is 4 mm to 20 mm;

[0018] Laser marking process parameters for preparing superhydrophobic circular surfaces: the laser power is 6 W to 12 W, and the laser marking speed is 1000 mm / s to 2000 mm / s;

[0019] Step three, generate bubbles;

[0020] Step 31, place the third preform (30) in the water tank (40) with the superhydrophobic circular surface (30A) facing up;

[0021] Step 32, place a needle in the 1 - mm through hole (2), connect the needle to a syringe through a silicone tube, and control the air flow rate injected by the syringe through an injection pump to deliver gas to the superhydrophobic circular surface (30A) and form an air film, and the air film detaches under the input air pressure to generate single bubbles; the diameter of the obtained single bubbles is 3 mm to 9 mm;

[0022] Bubble-making gas transportation process: The syringe is 10 ml to 100 ml, and the injection pump controls the air flow rate at 1 ml / min to 20 ml / min.

[0023] Compared with the existing underwater bubble generation methods, the method for preparing bubbles with a diameter greater than 3 mm in the water environment of the present invention has the following advantages:

[0024] ① The equipment used is convenient, and a simple injection pump can be used to generate millimeter-sized large bubbles underwater.

[0025] ② The bubble size can be adjusted. By adjusting the diameter of the superhydrophobic circular surface, the diameter of the underwater bubbles can be adjusted, and continuous adjustment of the millimeter-sized bubble size can be achieved.

[0026] ③ The generated bubble size is stable. When the diameter of the superhydrophobic circular surface is determined, the flow rate of the injected air flow varies within a certain range, and the change in the generated bubble size is very small.

[0027] ④ Since the air film on the superhydrophobic circular surface desorbs to form bubbles, the air flow injection speed is slow, and the speed during bubble desorption is low, which has little impact on the water flow field speed. Description of the Drawings

[0028] Figure 1 It is a schematic diagram of the underwater large bubble generation device based on the surface hydrophilic-hydrophobic wetting step effect of the present invention.

[0029] Figure 1A It is a structural diagram of the perforated substrate of the present invention.

[0030] Figure 1B It is a structural diagram of the perforated substrate from another perspective of the present invention.

[0031] Figure 1C It is a structural diagram of the first prefabricated part of the present invention.

[0032] Figure 1D It is a structural diagram of the second prefabricated part of the present invention.

[0033] Figure 2 It is an optical 3D photo of the roughening treatment of the upper panel with an array of strip-shaped micro-rough structures in Example 1.

[0034] Figure 2A It is an optical 2D photo of the roughening treatment of the upper panel with an array of strip-shaped micro-rough structures in Example 1.

[0035] Figure 2B It is a process diagram of the input gas bubbles detaching at different times in Example 1.

[0036] Figure 2C It is a side view of the bubble structure prepared in Example 1.

[0037] Figure 3 It is an optical 3D photograph of the roughening treatment of the upper panel with an array of square columns as the micro-rough structure in Example 2.

[0038] Figure 3A It is an optical 2D photograph of the roughening treatment of the upper panel with an array of square columns as the micro-rough structure in Example 2.

[0039] Figure 3B It is a process diagram of the detachment of input gas bubbles at different times in Example 2.

[0040] Figure 4 It is an optical 3D photograph of the roughening treatment of the upper panel with an array of strips as the micro-rough structure in Example 3.

[0041] Figure 4A It is an optical 2D photograph of the roughening treatment of the upper panel with an array of strips as the micro-rough structure in Example 3.

[0042] Figure 4B It is a process diagram of the detachment of input gas bubbles at different times in Example 3.

[0043] Figure 5 It is a corresponding diagram of the diameter of bubbles and the superhydrophobic circular surface prepared by the method of the present invention.

[0044] 1. Thin substrate 2. Through hole 3. Upper panel 4. Lower panel 5. Rough upper surface 6. Superhydrophobic layer 10. First preform 20. Second preform 30. Third preform 30A. Superhydrophobic circular surface 40. Water tank 40A. Inlet conduit 40B. Outlet conduit Detailed implementation manners

[0045] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0046] In the present invention, in the device for producing millimeter-sized large bubbles as shown in Figure 1 , the third preform 30 is hoisted in the water tank 40, and there is pure water in the water tank 40. The distance that the pure water submerges the upper surface of the third preform 30 is 5 cm to 50 cm.

[0047] A method for controllably generating underwater large bubbles based on the surface hydrophilic-hydrophobic wetting step effect of the present invention includes the following steps:

[0048] Step 1, making through holes on a substrate;

[0049] Referring to Figure 1A 、 Figure 1B shown, a through hole 2 is formed by drilling a hole on the substrate 1 using a mechanical drilling method.

[0050] The diameter of the through hole 2 is 1 mm. The through hole pitch is denoted as b, and b = 8 mm to 24 mm.

[0051] The arrangement of the through holes 2 on the substrate 1 can be an array arrangement, a plum blossom arrangement, or a triangular arrangement.

[0052] In the present invention, the through holes 2 on the substrate 1 enable air to smoothly enter the upper panel 3 of the substrate from the lower panel 4 of the substrate. Specifically, the holes are drilled from the lower panel 4 of the substrate to the upper panel 3 of the substrate.

[0053] In the present invention, the material of the substrate 1 is metal. Specifically, it can be an aluminum sheet or stainless steel. Preferably, 2-series and 7-series alloy aluminum sheets are selected.

[0054] Step 2: Prepare a superhydrophobic circular surface with the hole center as the center of the circle;

[0055] Step 21: Roughening treatment of the upper panel;

[0056] The upper panel 3 of the perforated substrate is roughened by laser marking to obtain a first preform 10 of the rough upper surface 5;

[0057] Laser marking roughening process parameters: laser power is 10W - 18W, and laser marking speed is 500mm / s - 2000mm / s.

[0058] In the present invention, the rough structure of the rough upper surface 5 is an array strip structure or an array square column structure, as shown in Figure 1C shown.

[0059] Step 22: Low surface energy treatment of the rough upper surface;

[0060] As shown in Figure 1D shown, the superhydrophobic layer 6 is formed by spraying 1H,1H,2H,2H-perfluorodecyltrimethoxysilane on the rough upper surface 5 of the first preform 10 by atomization spraying method to obtain a second preform 20.

[0061] In the present invention, the molecular formula of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is C 13 H 13 F 17 O 3 Si, CAS number 83048 - 65 - 1, molecular weight 568.3. C 13 H 13 F 17 O 3 Si is a low surface energy substance that can reduce the surface energy of the rough upper surface 5.

[0062] Atomization spraying process: Atomize the 1% concentration of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane anhydrous ethanol solution, spray it back and forth 4 times on the rough upper surface 5 under the condition of a flow rate of 1ml / min, and the temperature of the entire spraying environment is 25°C. Perform low surface treatment on the rough upper surface 5 to obtain the superhydrophobic layer 6. That is, there is a low surface energy superhydrophobic surface on the upper panel 3 of the substrate 1.

[0063] In the present invention, the upper part of the through hole 2 is also covered with a superhydrophobic layer 6.

[0064] Step 23, superhydrophobic circular surfaces with different diameters;

[0065] See Figure 1 As shown, by using a laser marking method to remove part of the superhydrophobic layer 6, superhydrophobic circular surfaces 30A with different diameters centered on the through hole 2 are left, obtaining a third preform 30. The diameter of the superhydrophobic circular surface 30A is 4 mm to 20 mm.

[0066] Process parameters for preparing superhydrophobic circular surfaces by laser marking: the laser power is 6 W to 12 W, and the laser marking speed is 1000 mm / s to 2000 mm / s.

[0067] Perform laser marking treatment to remove the low surface energy heptadecafluorodecyltrimethoxysilane on the surface part, leaving circular superhydrophobic surfaces with different diameters.

[0068] Step three, bubble generation;

[0069] See Figure 1 As shown, in step 31, place the third preform 30 in the water tank 40 with the superhydrophobic circular surface 30A facing upward;

[0070] In step 32, place a needle in the 1 - mm through hole 2. The needle is connected to a syringe through a silicone tube. Control the air flow rate injected by the syringe through an injection pump to deliver gas to the superhydrophobic circular surface 30A and form an air film, and the air film detaches under the input air pressure to generate single bubbles. The diameter of the obtained single bubbles is 3 mm to 9 mm.

[0071] Bubble - making gas - delivery process: the syringe is 10 ml to 100 ml, and the injection pump controls the air flow rate at 1 ml / min to 20 ml / min.

[0072] Example 1: Prepare bubbles with a diameter of 6.5 mm

[0073] Step one, fabricate through holes on the substrate;

[0074] Use a mechanical drilling method to drill through holes with a diameter of 1 mm on a 2 - mm - thick aluminum plate. The spacing between the through holes is 16 mm, and the through holes are arranged in an array.

[0075] Step two, prepare a superhydrophobic circular surface with a diameter of 8 mm centered on the hole center;

[0076] Step 21, roughen the upper panel with a rough structure of array strips;

[0077] The upper panel 3 of the perforated substrate is roughened by a laser marking method. The laser power is 12 W, the laser marking speed is 600 mm, and the rough structure is an array strip structure.

[0078] Step 22, low surface energy treatment of the rough upper surface;

[0079] Atomize the 1% concentration solution of heptadecafluorodecyltrimethoxysilane in absolute ethanol and spray it back and forth 4 times on the rough upper surface 5 under the condition of a flow rate of 1 ml / min. The temperature of the entire spraying environment is 25 °C to obtain a superhydrophobic surface.

[0080] Step 23, a superhydrophobic circular surface with a diameter of 8 mm;

[0081] Use the laser marking method to remove part of the superhydrophobic layer 6, leaving a superhydrophobic circular surface 30A with a diameter of 8 mm centered on the through hole 2. The microscopic rough structure is as Figure 2 、 Figure 2A shown. Laser marking process parameters: laser power is 8 W, laser marking speed is 1500 mm / s.

[0082] Step three, bubble generation;

[0083] Place the third preform 30 in the water tank 40 with the superhydrophobic circular surface 30A facing up, 20 cm away from the water surface;

[0084] In step 32, place a needle in the 1-mm through hole 2. The needle is connected to a syringe through a silicone tube. Control the air flow rate injected by the syringe through an injection pump to deliver gas to the 8-mm diameter superhydrophobic circular surface 30A and form an air film. The air film detaches under the input air pressure to generate a single bubble with a diameter of 6.5 mm, as Figure 2B shown.

[0085] Bubble generation and gas delivery process: The syringe is 50 ml, and the injection pump controls the air flow rate at 5 ml / min.

[0086] See Figure 2C The side view of the bubble structure prepared in Example 1 shown in the figure. In the figure, the middle part is the detached bubble, there is some residual air at the center of the bottom surface which is the superhydrophobic surface, and the two sides of the bottom surface superhydrophobic surface are hydrophilic surfaces.

[0087] Example 2 Preparation of bubbles with a diameter of 5 mm

[0088] Step one, fabricate through holes on the substrate;

[0089] Use a mechanical drilling method to drill through holes with a diameter of 1 mm on a 2-mm thick aluminum plate. The spacing between the through holes is 10 mm, and the through holes are arranged in an array.

[0090] Step 2: Prepare a superhydrophobic circular surface with a diameter of 4 mm centered on the hole center;

[0091] Step 21: Roughen the upper panel with the rough structure of arrayed square columns;

[0092] Use the laser marking method to roughen the upper panel 3 of the substrate with holes. The laser power is 12 W, the laser marking speed is 1500 mm, and the rough structure is an arrayed square column structure.

[0093] Step 22: Perform low surface energy treatment on the rough upper surface;

[0094] Atomize the anhydrous ethanol solution of 1% concentration of heptadecafluorodecyltrimethoxysilane and spray it back and forth 4 times on the rough upper surface 5 under the condition of a flow rate of 1 ml / min. The temperature of the entire spraying environment is 25 °C to obtain a superhydrophobic surface.

[0095] Step 23: Superhydrophobic circular surface with a diameter of 4 mm;

[0096] Use the laser marking method to remove part of the superhydrophobic layer 6, leaving a superhydrophobic circular surface 30A with a diameter of 4 mm centered on the through hole 2. The microscopic rough structure is as Figure 3 、 Figure 3A shown. Laser marking process parameters: laser power is 8 W, laser marking speed is 1000 mm / s.

[0097] Step 3: Generate bubbles;

[0098] Step 31: Place the third prefabricated part 30 in the water tank 40 with the superhydrophobic circular surface 30A facing up, 20 cm away from the water surface;

[0099] Step 32: Insert a needle into the 1-mm through hole 2. The needle is connected to a syringe through a silicone tube. Control the air flow rate injected by the syringe through an injection pump to deliver gas to the superhydrophobic circular surface 30A with a diameter of 8 mm and form an air film. The air film detaches under the input air pressure to generate a single bubble with a diameter of 5 mm, as Figure 3B shown.

[0100] Bubble generation and gas delivery process: The syringe is 50 ml, and the injection pump controls the air flow rate at 5 ml / min. Example 3 prepares bubbles with a diameter of 8.9 mm

[0101] Step 1: Make through holes on the substrate;

[0102] Use the mechanical drilling method to drill through holes with a diameter of 1 mm on a 2-mm thick aluminum plate. The through hole spacing is 24 mm, and the through holes are arranged in an array.

[0103] Step 2: Prepare a superhydrophobic circular surface with a diameter of 20 mm centered on the hole center;

[0104] Step 21, roughening the upper panel where the rough structure is an array of stripes;

[0105] The upper panel 3 of the perforated substrate is roughened by using a laser marking method. The laser power is 12 W, the laser marking speed is 800 mm, and the rough structure is an array of stripe structures.

[0106] Step 22, low surface energy treatment of the rough upper surface;

[0107] The anhydrous ethanol solution of 1% concentration of heptadecafluorodecyltrimethoxysilane is atomized and sprayed back and forth 4 times on the rough upper surface 5 under the condition of a flow rate of 1 ml / min. The temperature of the entire spraying environment is 25 °C to obtain a superhydrophobic surface.

[0108] Step 23, a 20-mm-diameter superhydrophobic circular surface;

[0109] Part of the superhydrophobic layer 6 is removed by using a laser marking method, leaving a 20-mm-diameter superhydrophobic circular surface 30A centered on the through hole 2. The microscopic rough structure is as Figure 4 、 Figure 4A shown. Laser marking process parameters: the laser power is 8 W, and the laser marking speed is 1800 mm / s.

[0110] Step three, bubble generation;

[0111] Step 31, place the third prefabricated part 30 in the water tank 40 with the superhydrophobic circular surface 30A facing upward, 10 cm away from the water surface;

[0112] Step 32, place a needle in the 1-mm through hole 2. The needle is connected to a syringe through a silicone tube. The flow rate of the air injected by the syringe is controlled by an injection pump to realize the delivery of gas to the 20-mm-diameter superhydrophobic circular surface 30A and form an air film. The air film detaches under the input air pressure to generate a single bubble with a diameter of 8.9 mm, as Figure 4B shown.

[0113] Bubble generation and gas delivery process: The syringe is 100 ml, and the injection pump controls the air flow rate at 12 ml / min.

[0114] Performance analysis of bubble generation

[0115] See Figure 5 shown. The single bubble prepared by the method of the present invention can realize the regulation of the bubble size (diameter from 3 mm to 9 mm) by adjusting the area of the superhydrophobic circular surface 30A. The bubble size can continuously vary in the range of 3 mm to 9 mm, and the size is stable and uniform.

[0116] The method of the present invention can control the number of bubbles by adjusting the number of through-holes, so as to realize the simultaneous preparation of single or multiple bubbles. It can also realize the simultaneous preparation of a series of bubbles of different sizes by adjusting the diameter of the superhydrophobic circle corresponding to each hole.

[0117] The present invention is a method for controllably generating large underwater bubbles based on the surface hydrophilic-hydrophobic wetting step effect. The technical problem to be solved is how to produce bubbles with a diameter greater than 3 mm in a water environment. By adjusting the size of the superhydrophobic circular surface, the method can prepare bubbles with continuously adjustable sizes, thereby realizing the generation of large-sized bubbles and achieving the technical effect of stable bubble sizes.

Claims

1. A method for controllably generating underwater large bubbles based on the surface hydrophilic-hydrophobic wetting step effect, characterized in that it includes the following steps: Step 1, fabricate through holes on the substrate; Use a mechanical drilling process to drill holes on the substrate (1) to form through holes (2); The diameter of the through hole (2) is 1 mm; the through hole pitch is denoted as b, and b = 8 mm to 24 mm; Step 2, prepare a superhydrophobic circular surface with the hole center as the center of the circle; Step 21, roughening treatment of the upper panel; Use a laser marking method to roughen the upper panel (3) of the perforated substrate to obtain a first preform (10) with a rough upper surface (5); Laser marking roughening process parameters: laser power is 10 W to 18 W, and laser marking speed is 500 mm / s to 2000 mm / s; Step 22, low surface energy treatment of the rough upper surface; Use an atomization spraying process to spray 1H,1H,2H,2H-perfluorodecyltrimethoxysilane on the rough upper surface (5) of the first preform (10) to form a superhydrophobic layer (6) and obtain a second preform (20); Atomization spraying process: atomize a 1% concentration of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane anhydrous ethanol solution and spray it on the rough upper surface (5) under the condition of a flow rate of 1 ml / min; Step 23, superhydrophobic circular surfaces with different diameters; Use a laser marking method to remove part of the superhydrophobic layer (6) and leave superhydrophobic circular surfaces (30A) with different diameters centered on the through hole (2) to obtain a third preform (30); the diameter of the superhydrophobic circular surface (30A) is 4 mm to 20 mm; Laser marking process parameters for preparing superhydrophobic circular surfaces: laser power is 6 W to 12 W, and laser marking speed is 1000 mm / s to 2000 mm / s; Step 3, bubble generation; Step 31, place the third preform (30) in the water tank (40) with the superhydrophobic circular surface (30A) facing upward; Step 32, place a needle in the 1-mm through hole (2), connect the needle to a syringe through a silicone tube, and control the air flow rate injected by the syringe through an injection pump to deliver gas to the superhydrophobic circular surface (30A) and form an air film, and the air film detaches under the input air pressure to generate single bubbles; the diameter of the prepared single bubbles is 3 mm to 9 mm; Bubble generation and gas delivery process: the syringe is 10 ml to 100 ml, and the injection pump controls the air flow rate at 1 ml / min to 20 ml / min.

2. The method for controllably generating underwater large bubbles based on the surface hydrophilic-hydrophobic wetting step effect according to claim 1, characterized in that: The through holes arranged on the substrate (1) are arranged in an array.

3. The method for controllably generating underwater large bubbles based on the surface hydrophilic-hydrophobic wetting step effect according to claim 1, characterized in that: The substrate (1) is made of metal.

4. The method for controllably generating underwater large bubbles based on the surface hydrophilic-hydrophobic wetting step effect according to claim 1, characterized in that: The rough structure of the rough upper surface (5) is an array strip structure or an array square column structure.

5. The method for controllably generating underwater large bubbles based on the surface hydrophilic-hydrophobic wetting step effect according to claim 1, characterized in that: The spraying environment temperature for atomized spraying is 20°C to 35°C.

6. The method for controllably generating underwater large bubbles based on the surface hydrophilic-hydrophobic wetting step effect according to claim 1, characterized in that: On the surface of the third prefabricated part (30), superhydrophobic circular surfaces (30A) with different diameters centered on the through hole (2) are arranged in an array, and bubbles with different diameters are generated simultaneously.

7. The method for controllably generating underwater large bubbles based on the surface hydrophilic-hydrophobic wetting step effect according to claim 1, characterized in that: On the surface of the third prefabricated part (30), superhydrophobic circular surfaces (30A) with the same diameter centered on the through hole (2) are arranged in an array, and bubbles with the same diameter are generated simultaneously.

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