Super-hydrophobic surface durability testing device and method

Abstract

The invention provides a super-hydrophobic surface durability testing device and method. The device comprises a driving module, a testing module, an optical supporting module and a water changing module. The driving module adopts coaxial arrangement and low-resistance bearing design, so that stable rotation is guaranteed; the test module realizes tight fixation of a test piece through a prismatic table array embedment and an elastic tongue mechanism; the optical support module constructs a constant-temperature low-distortion observation environment; and the water changing module realizes liquid circulation and purification. According to the testing method, stable von K-alpha-rm-alpha-n rotational flow is generated by controlling parameters of the servo motor, multi-working-condition data are obtained through a single experiment by means of the radial shear stress progressive increase characteristic, the wettability attenuation of the super-hydrophobic surface is quantitatively evaluated in combination with optical monitoring and periodic water pumping, and a shear force-service life relation model is established. The device solves the problems of low test efficiency, difficulty in quantification of shear force, unstable flow field and the like in the prior art, has the advantages of high test precision, good repeatability and compact structure, and has wide popularization and application values.

Description

Technical Field

[0001] This invention relates to the field of superhydrophobic material performance testing technology, and in particular to a device and method for testing the durability of superhydrophobic surfaces. Background Technology

[0002] Superhydrophobic surfaces, with their superior properties such as drag reduction, antifouling, and anti-icing, have shown broad application prospects in various fields, including aerospace, marine navigation, energy pipelines, and transportation. However, in actual service, superhydrophobic surfaces are subjected to complex fluid shear forces and various environmental factors over a long period of time, which can easily damage their surface wetting properties, leading to the failure of core functions such as drag reduction and antifouling. Insufficient durability has become a key bottleneck restricting the large-scale practical application of superhydrophobic surfaces.

[0003] Currently, common methods for testing the durability of superhydrophobic surfaces include friction and wear, water flow impact, and gravel abrasion. However, these methods generally have significant drawbacks: the testing cycle is lengthy and the experimental efficiency is low; the shear strength is difficult to control quantitatively, and the test results can only be used as a qualitative reference; the experimental conditions are singular and fixed, and cannot truly simulate the complex working conditions in actual applications; most testing devices can only test a single sample at a time, making it difficult to conduct multi-condition comparative experiments.

[0004] Other studies have attempted to use the von Kármán vortex apparatus for shear force failure testing of superhydrophobic surfaces. While this improved the flow field uniformity to some extent, it still has many shortcomings: the large vibration amplitude of the rotating disk causes flow field disturbance and affects test accuracy; the lack of a unified standard for sample installation makes samples prone to loosening or gaps, leading to test errors; the apparatus has a single function, usually only capable of single-point measurement, resulting in low testing efficiency; and environmental parameters such as liquid temperature and cleanliness are uncontrollable, making it difficult to guarantee the repeatability of experimental results.

[0005] Therefore, there is an urgent need for a device and method that can achieve parallel testing under multiple operating conditions, stable flow field, controllable environmental parameters, and predict the durability and lifespan of superhydrophobic surfaces through quantitative methods in a single experiment, so as to solve many problems existing in the current technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an efficient, quantitative, and parallel superhydrophobic surface durability testing device and method to solve the problems of low testing efficiency, difficulty in quantifying shear force, unstable flow field, and uncontrollable environment in existing testing devices and methods.

[0007] The present invention was made in view of the above-mentioned existing conditions, and its purpose is to provide a device and method for testing the durability of superhydrophobic surfaces, including a driving module, a testing module, an optical support module and a water exchange module;

[0008] The drive module includes a servo controller, a servo motor, a coupling, a drive shaft, a first low-resistance bearing, and a second low-resistance bearing arranged in sequence. The servo motor, coupling, drive shaft, first low-resistance bearing, and second low-resistance bearing are placed coaxially. The coupling connects the servo motor and the drive shaft. The first low-resistance bearing and the second low-resistance bearing are sleeved on the drive shaft.

[0009] The testing module includes a conical fixing component, a rotating disk, a specimen fixing device, and a test specimen. The conical fixing component is coaxial with the transmission shaft, and the rotating disk is coaxial with both the conical fixing component and the transmission shaft. The rotating disk and the specimen fixing device are respectively machined with equally spaced frustum arrays. The rotating disk and the test specimen are fixed together by spatially fitting the frustum arrays. The rotating disk surface has multiple grooves along the radial direction. The upper and lower boundaries of the grooves are arcs concentric with the rotating disk. The upper left and lower right of the grooves are provided with spring-loaded mechanisms. The upper left and lower right of the specimen fixing device are provided with grooves that cooperate with the spring-loaded mechanisms. The specimen fixing device has set screw holes on its upper, lower, left, and right sides. The test specimen is placed in the specimen fixing device, and the upper and lower boundaries of the test specimen are arcs concentric with the rotating disk.

[0010] The optical support module includes a motor support base, a water pressure plate, a VK rotary cylinder, a water bath outer cylinder, and an industrial camera. The inner walls of the motor support base, the water pressure plate, and the VK rotary cylinder are coaxial with the servo motor's rotating shaft, transmission shaft, and rotating disk. The motor support base is fixedly fitted to the servo motor. The upper surface of the water pressure plate has a groove that mates with the cylindrical side wall of the motor support base. The center of the upper surface of the water pressure plate has a groove that mates with the first low-resistance bearing. The water pressure plate is fixedly fitted to the VK rotary cylinder. The lower surface of the water pressure plate has a raised frustum structure. The VK rotary cylinder has a groove that mates with the frustum structure. The VK rotary cylinder has a cylindrical inner wall and a polygonal prism outer wall. The lower surface of the inner wall of the VK rotary cylinder has a groove that mates with the second low-resistance bearing. The water bath outer cylinder is a polygonal prism-shaped cylinder with the same number of sides as the outer wall of the VK rotary cylinder. The water bath outer cylinder contains evenly distributed resistance heaters and temperature sensors. The industrial camera is located at the bottom of the water bath outer cylinder.

[0011] The water exchange module includes a one-way water injection valve, a one-way water extraction valve, a water pump, and a filter unit. The one-way water injection valve and the one-way water extraction valve are both located below the VK rotary cylinder. The water pump is connected to the one-way water injection valve and the one-way water extraction valve. The filter unit works in conjunction with the water pump.

[0012] Therefore, by integrating four major modules—drive, testing, optical support, and water exchange—the core requirements of parallel testing under multiple operating conditions, stable flow field control, and controllable environmental parameters are achieved. The coaxial design of the drive module reduces vibration, the truncated pyramid array and spring mechanism of the testing module ensure stable sample fixation, the optical support module constructs a constant-temperature, low-distortion observation environment, and the water exchange module ensures clean water quality. The collaborative work of these modules significantly improves testing accuracy, efficiency, and repeatability.

[0013] The servo controller is used to control the start and stop time, acceleration and rotation speed of the servo motor. The coupling is a double diaphragm elastic coupling. The first low-resistance bearing and the second low-resistance bearing are both ceramic bearings.

[0014] Therefore, the selection of functions and materials for key components of the drive module, the servo controller to achieve precise control of motor parameters, and the quantitative analysis of shear force provide a foundation for this. The double diaphragm elastic coupling effectively eliminates vibration between the motor and the drive shaft, and the ceramic bearing has low resistance and rust-proof characteristics, further reducing non-coaxial vibration during drive shaft rotation, ensuring uniform and stable flow field, and improving test accuracy.

[0015] The conical fastener is composed of two stacked cylinders, one smaller than the other. The center of the conical fastener has a through hole in the shape of an approximately hexagonal star. The inscribed circles of the six concave endpoints of the through hole are equal to the radius of the drive shaft. The six convex portions form a gap. The conical fastener is fixed to the drive shaft by a set screw.

[0016] Therefore, the structure of the conical fixing part can stabilize the rotating disk, reduce the vibration interference when the rotating disk rotates, and improve the flow field quality. The hexagonal star-shaped through hole not only ensures a stable connection with the drive shaft, but its convex gap can also effectively discharge the air accumulated in the center of the disk when it rotates, avoid the interference of air on the swirling flow field, and ensure the stability of the test environment.

[0017] The rotating disk has a through hole with a radius larger than that of the transmission shaft at its center. The spring mechanism is a rust-proof spring mechanism. The rotating disk and the conical fixing member are fixed by six threaded holes and screws evenly distributed along the center. The motor support base and the servo motor are fixed by threaded holes and screws evenly distributed along the center. The water pressure plate and the VK rotary cylinder are fixed by threaded holes and screws evenly distributed along the center.

[0018] Therefore, the structure of the rotating disk and the fixing method of each component, the central through hole of the rotating disk to help expel the air accumulated in the center, the anti-rust spring mechanism to extend the service life of the device, and the evenly distributed threaded holes and screw fixing method to ensure the coaxiality and stability of the connection of each component, avoid loosening or displacement during high-speed rotation, and further improve the operational stability of the device and the reliability of the test results.

[0019] The motor support base consists of an annular upper surface and a side cylindrical wall. A through hole with a radius larger than that of the coupling is opened at the center of the upper surface of the motor support base. A through hole with a radius slightly larger than that of the transmission shaft is opened at the bottom of the groove of the water pressure plate. The motor support base, water pressure plate, VK rotary cylinder and water bath outer cylinder are all made of polymethyl methacrylate.

[0020] This clarified the structure of the motor support base and the water pressure plate, as well as the materials of related components. The light transmittance and refractive index of polymethyl methacrylate (PMMA) are similar to those of water, effectively reducing optical distortion and ensuring the clarity of industrial camera images. The design of each through hole meets the assembly requirements of the components, while not affecting the sealing and coaxiality of the device, providing good conditions for optical monitoring.

[0021] This invention also provides a method for testing the durability of superhydrophobic surfaces, using the above-mentioned testing apparatus, and comprising the following steps:

[0022] S1. The specimen fixing device is provided with an inner groove. The test specimen is cut into a size that matches the inner groove. The contact angle θ0 is measured and recorded. The test specimen is installed in the inner groove. The specimen fixing device is installed in the corresponding groove of the rotating disk and fixed by the spring mechanism and the frustum array.

[0023] S2. Inject test liquid into the VK rotary cylinder through the water pump, filter unit and one-way water injection valve, fill the space between the VK rotary cylinder and the water bath outer cylinder with water, set the constant temperature and turn on the heating.

[0024] S3. Based on the target shear force range and the shear force calculation formula τ(r)=0.616ρ(νω) 1 / 2 ωr, calculate and set the rotational speed ω and revolutions n of the drive module;

[0025] S4. The servo motor is controlled by the servo controller to rotate at a set speed ω and acceleration a1. The servo motor drives the rotating disk to rotate through the coupling, transmission shaft and conical fixing component to generate von Kármán vortex.

[0026] S5. When the rotating disk rotates to a set number of revolutions n, the servo controller controls the servo motor to stop rotating according to a set acceleration a2, and the water pump draws the test liquid out through the one-way pumping valve until the liquid level is lower than the lower surface of the rotating disk, and the industrial camera takes pictures of the liquid film adhesion on the surface of the test piece.

[0027] S6. Determine whether there is a liquid film adhering to the surface of the test piece. If so, remove the test piece, measure its static water contact angle θ1, and record θ1 and the total number of revolutions n. 总Otherwise, repeat steps S2 to S5 until a liquid film adheres to the test piece and record the relevant data.

[0028] S7. After measuring the contact angle, reassemble the test piece according to steps S1 to S5 and determine whether the liquid film coverage area on the surface of the test piece has increased compared to the previous test. If it has not increased, repeat the measurement according to steps S2 to S5; if it has increased, remove the test piece and measure its static water contact angle θ. n Record θ n and the total number of revolutions n 总 Then reinstall and test the disk following steps S1 to S5;

[0029] S8. Once the total number of rotations of the servo motor reaches the target number of rotations, remove the test piece and integrate the static water contact angle θ recorded each time. i and corresponding test time t i ,in

[0030] S9. Based on the static water contact angle θ i Corresponding test time t i Based on the shear force τ at the location of the test piece, construct the shear force-service life relationship curve and fitting model.

[0031] This provides a complete testing procedure for the durability of superhydrophobic surfaces. By utilizing the radial shear stress increment characteristics of von Kármán vortices, data from multiple operating conditions can be obtained in a single experiment, significantly improving testing efficiency. Shear force is controllable through quantitative control of rotation speed, and quantitative assessment of wettability decay is achieved by combining optical monitoring and contact angle measurement. Finally, the constructed shear force-lifetime model can predict the lifetime under different shear forces, providing data support for the practical application of superhydrophobic materials.

[0032] In step S1, the specimen fixing device fixes the test specimen by the set screws in the set screw holes on the four sides, and the specimen fixing device and the rotating disk are fixed by the spatial interlocking effect of the frustum array.

[0033] Thus, the fixing methods of the test piece and the specimen fixing device, and the specimen fixing device and the rotating disk are clarified. The set screws ensure that the test piece does not loosen in the specimen fixing device, and the spatial interlocking effect of the truncated pyramid array can still keep the test piece and the rotating disk in close contact under the action of fluid shear force and centrifugal force, avoiding the formation of gaps and reducing test errors.

[0034] In step S2, the test liquid injected into the VK rotary cylinder is defoamed ultrapure water.

[0035] Therefore, the type of test liquid is limited. Defoamed ultrapure water can avoid the uncontrollable influence of unstable gas saturation in the test liquid on the surface durability of the superhydrophobic test piece, while ensuring the cleanliness of the test liquid, reducing the interference of impurities on the test results, and improving the repeatability of the experiment.

[0036] In step S3, the shear force calculation formula includes ρ as the density of the test liquid, ν as the kinematic viscosity of the test liquid, and r as the radial radius of the test piece on the rotating disk.

[0037] This clarifies the meaning of each parameter in the shear force calculation formula, provides a clear basis for setting the rotation speed and revolutions, ensures the accuracy of shear force calculation, realizes quantitative control of shear force, and makes the test results under different experimental conditions comparable.

[0038] In step S5, the industrial camera captures images of the liquid film adhesion on the lower surface of the test piece. In step S7, the change in the liquid film coverage area on the lower surface of the test piece is determined.

[0039] Therefore, the specific objects and judgment criteria of optical monitoring are clarified. The lower surface of the test piece directly bears the shearing action of the swirling flow, and its liquid film adhesion can accurately reflect the degree of degradation of superhydrophobic properties. By monitoring the change of liquid film coverage area, the performance degradation process of the test piece can be accurately tracked, ensuring the authenticity and validity of the test data. Attached Figure Description

[0040] Figure 1 A longitudinal sectional view of the superhydrophobic surface durability testing device according to an embodiment of the present invention is shown;

[0041] Figure 2 A schematic diagram of the rotating disk structure of the superhydrophobic surface durability testing device according to an embodiment of the present invention is shown.

[0042] Figure 3 A schematic diagram of the specimen fixing device structure of the superhydrophobic surface durability testing device according to an embodiment of the present invention is shown;

[0043] Figure 4 A schematic diagram of the conical fixing component structure of the superhydrophobic surface durability testing device according to an embodiment of the present invention is shown;

[0044] Figure 5 A schematic diagram of the VK rotary cylinder structure of the superhydrophobic surface durability testing device according to an embodiment of the present invention is shown;

[0045] Figure 6 A flowchart of the superhydrophobic surface durability testing method according to an embodiment of the present invention is shown. Detailed Implementation

[0046] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same reference numerals are used for the same parts, and repeated descriptions are omitted. Furthermore, the drawings are merely schematic diagrams, and the proportions of the parts or the shapes of the parts may differ from the actual figures.

[0047] like Figures 1 to 5 As shown, this invention provides a superhydrophobic surface durability testing device 1, which includes a driving module, a testing module, an optical support module, and a water exchange module. The modules work together to achieve efficient and quantitative testing of the superhydrophobic surface durability.

[0048] In this embodiment, the drive module includes a servo controller 11, a servo motor 12, a coupling 13, a transmission shaft 14, a first low-resistance bearing 15, and a second low-resistance bearing 16 arranged in sequence, which is the core power source to ensure the stable operation of the device.

[0049] The servo controller 11 is used to control the rotation of the servo motor 12, and can precisely regulate the start and stop time, acceleration and speed of the servo motor 12, providing a basis for quantitative control of shear force. The servo motor 12, coupling 13, drive shaft 14, first low-resistance bearing 15 and second low-resistance bearing 16 are placed coaxially, which effectively avoids component wear and additional vibration caused by non-coaxial rotation and ensures the stability of the flow field.

[0050] Coupling 13 is a double-diaphragm elastic coupling, whose core function is to connect the servo motor 12 and the drive shaft 14. It also effectively eliminates vibration transmission between the servo motor 12 and the drive shaft 14, further improving rotational stability. The first low-resistance bearing 15 and the second low-resistance bearing 16 are both low-resistance, rust-resistant ceramic bearings, fitted onto the drive shaft 14. These bearings significantly eliminate non-coaxial vibration of the drive shaft 14 during high-speed rotation, reducing disturbance to the swirling flow field and improving testing accuracy.

[0051] In this embodiment, the test module includes a conical fixing member 21, a rotating disk 22, a specimen fixing device 23, and a test specimen 24, which mainly realizes the stable fixing of the test specimen and multi-condition testing.

[0052] The conical fixing member 21 consists of two stacked cylinders, one smaller at the top and one larger at the bottom, and is coaxially arranged with the drive shaft 14. A through hole in an approximately hexagonal star shape is machined at its center. The inscribed circles of the six concave endpoints are equal in radius to the drive shaft 14. It is fixed to the drive shaft 14 by set screws (in this embodiment, three evenly distributed M4 threaded holes and M4 set screws), ensuring a stable connection and high coaxiality. The core function of the six convex orifices is to expel the air that accumulates at the center of the rotating disk 22 after rotation, preventing air from interfering with the stability of the swirling flow field.

[0053] The rotating disk 22 is coaxial with the conical fixing member 21 and the drive shaft 14, and is securely connected to the conical fixing member 21 by six threaded holes evenly distributed along the center and screws. A through hole with a radius larger than that of the drive shaft 14 is opened at the center of the rotating disk 22 to expel air that accumulates at the center of the drive shaft 14 during rotation, further optimizing the swirling flow environment. Multiple grooves are provided radially on the surface of the rotating disk 22, with the upper and lower boundaries of the grooves being concentric arcs, providing installation space for the specimen fixing device 23.

[0054] Rust-proof spring-loaded mechanisms 221 are provided on the upper left and lower right sides of the groove of the rotating disk 22. Grooves 232 that cooperate with the spring-loaded mechanisms 221 are provided on the upper left and lower right sides of the specimen fixing device 23. The spring-loaded mechanisms 221 can help fix the specimen fixing device 23 and prevent it from falling off due to gravity or pressure difference during rotation. The rotating disk 22 and the specimen fixing device 23 are respectively machined with equally spaced frustum arrays. Through the spatial interlocking effect of the frustums, the two can still maintain the tight fit between the test specimen 24 and the rotating disk 22 under the action of fluid shear force and centrifugal force, avoiding the formation of gaps and loosening of the specimen.

[0055] The specimen fixing device 23 has set screw holes 231 on its top, bottom, left, and right sides. The superhydrophobic test specimen 24 at the center position is fixed by the set screws to ensure that the test specimen 24 does not shift under high-speed rotation and fluid shear. The upper and lower boundaries of the test specimen 24 are circular arcs concentric with the rotating disk 22 and match the groove shape of the rotating disk 22 to ensure that the swirling flow field structure is not affected after installation.

[0056] In this embodiment, the optical support module includes a motor support base 31, a water pressure plate 32, a VK rotary cylinder 33, a water bath outer cylinder 34, and an industrial camera 35. It mainly constructs a constant temperature and low distortion observation environment to ensure the accuracy of optical monitoring.

[0057] The inner walls of the motor support 31, the pressure plate 32, and the VK rotary cylinder 33 are all coaxial with the rotating shaft of the servo motor 12, the transmission shaft 14, and the rotating disk 22, ensuring the coaxiality of each component after assembly and avoiding flow field disturbances and optical distortions caused by eccentricity. The motor support 31 consists of an annular upper surface and a cylindrical side wall. A through hole with a radius larger than that of the coupling 13 is drilled at the center of the upper surface. The upper surface is fixed to the servo motor 12 by threaded holes and screws evenly distributed along the center, ensuring a stable connection.

[0058] The upper surface of the pressure plate 32 has a groove that mates with the cylindrical side wall of the motor support 31, used to fix the motor support 31 and ensure the coaxiality of the connection between the two. A groove at the center of the upper surface of the pressure plate 32 mates with the first low-resistance bearing 15, used to place and fix the first low-resistance bearing 15. A through hole with a radius slightly larger than that of the drive shaft 14 is formed at the bottom of the groove, allowing the drive shaft 14 to pass through without affecting its rotation. The pressure plate 32 and the VK rotary cylinder 33 are fixed together by six M6 threaded holes and M6 screws evenly distributed along the center, ensuring a reliable connection. A raised frustum structure is formed on the lower surface of the pressure plate 32, and a corresponding groove is formed on the VK rotary cylinder 33. This structure is mainly used for positioning and initial sealing to prevent leakage of the test liquid.

[0059] The VK vortex cylinder 33 has a cylindrical inner wall and a polygonal prism outer wall, which ensures that the vortex structure is not affected while effectively suppressing the optical distortion caused by the equipment materials to the optical camera. The VK vortex cylinder 33 includes an inner wall 331. A groove is formed at the bottom of the VK vortex cylinder 33 to mate with the second low-resistance bearing 16, securing the bearing and ensuring stable rotation of the drive shaft 14. The water bath outer cylinder 34 is a polygonal prism-shaped cylinder with the same number of sides as the outer wall of the VK vortex cylinder 33. Placed outside the VK vortex cylinder 33, it creates a constant-temperature water bath environment through evenly distributed resistance heaters and temperature sensors, facilitating precise control of the test liquid temperature. Simultaneously, the polygonal structure facilitates imaging by the industrial camera 35, reducing optical obstruction.

[0060] An industrial camera 35 is located at the bottom of the water bath outer tank 34 and is used to photograph the liquid film coverage state on the surface of the test piece 24, providing a direct basis for judging the degradation of superhydrophobic properties. The motor support 31, the pressure plate 32, the VK rotary cylinder 33, and the water bath outer tank 34 are all made of polymethyl methacrylate (PMMA, acrylic). This material has a light transmittance and refractive index similar to water, which can significantly reduce optical distortion and ensure the clarity and accuracy of the images captured by the industrial camera 35.

[0061] In this embodiment, the water exchange module includes a one-way water injection valve 41, a one-way water extraction valve 42, a water pump 43, and a filter unit 44, which mainly realizes the circulation of test liquid and water purification, and ensures the stability of the test environment.

[0062] Both the one-way injection valve 41 and the one-way extraction valve 42 are located below the VK rotary cylinder 33. The one-way injection valve 41 prevents the test liquid in the VK rotary cylinder 33 from flowing back when not injecting water, while the one-way extraction valve 42 prevents external air or impurities from entering the VK rotary cylinder 33 when not pumping water. Both valves also reduce the influence of the inlet and outlet positions on the rotating flow field, ensuring flow field stability. The water pump 43 is mainly used to control the water injection and extraction process, realizing the injection and discharge of the test liquid. The filter unit 44 is used for water purification before injection, reducing test result errors caused by test liquid contamination and improving experimental repeatability.

[0063] like Figure 6 As shown, this invention also provides a method for testing the durability of superhydrophobic surfaces, using the aforementioned testing apparatus. The specific steps are as follows:

[0064] S1. Test specimen preparation and installation: Cut the superhydrophobic test specimen 24 to be tested into a size that matches the inner groove of the specimen fixing device 23. First, use a contact angle measuring instrument to measure and record its initial static water contact angle θ0. Then, install the test specimen 24 into the inner groove of the specimen fixing device 23 and tighten it with the set screw in the set screw hole 231. Finally, install the specimen fixing device 23 into the corresponding grooves of the rotating disk 22 and fix it with the spring mechanism 221 and the truncated pyramid array to ensure a stable installation.

[0065] S2. Test Environment Preparation: The test liquid is injected into the VK rotary cylinder 33 through the water pump 43, filter unit 44 and one-way water injection valve 41. In this embodiment, defoamed ultrapure water is selected as the test liquid to prevent the unstable gas saturation in the test liquid from having an uncontrollable impact on the surface durability of the superhydrophobic test piece 24. The space between the VK rotary cylinder 33 and the water bath outer cylinder 34 is filled with water. The constant temperature to be maintained is set according to the experimental requirements and the resistance heater is turned on. The temperature is monitored in real time by the temperature sensor to ensure that the temperature is stable during the test.

[0066] S3. Drive parameter setting: Based on the target shear force range and the shear force calculation formula τ(r)=0.616ρ(νω) at the fixed point on the rotating disk 22. 1 / 2 ωr (where ρ is the density of the test liquid, ν is the kinematic viscosity of the test liquid, r is the radial position radius of the test piece 24 on the rotating disk 22, and ω is the angular velocity of the rotating disk 22) is calculated and the rotation speed ω and the number of revolutions n of the drive module are set by the servo controller 11.

[0067] S4. Swirl generation: The servo motor 12 is controlled by the servo controller 11 to start rotating according to the set speed ω and acceleration a1. The servo motor 12 drives the rotating disk 22 to rotate through the coupling 13, the transmission shaft 14 and the conical fixing part 21. The rotation of the rotating disk 22 causes the test liquid in the VK swirling cylinder 33 to generate a stable von Kármán swirling flow.

[0068] S5. Stop observation: When the rotating disk 22 rotates to the set number of revolutions n, the servo controller 11 controls the servo motor 12 to stop rotating according to the set acceleration a2; then the water pump 43 draws the test liquid out through the one-way pumping valve 42 until the liquid level is lower than the lower surface of the rotating disk 22, so as to avoid the test liquid from blocking the shooting field of the industrial camera 35; then the industrial camera 35 at the bottom takes pictures of the liquid film adhesion on the lower surface of the test piece 24.

[0069] S6. First Data Recording: Determine if there is liquid film adhesion on the surface of test piece 24. If liquid film adhesion occurs, remove test piece 24, measure its static water contact angle θ1, and then record the static water contact angle θ1 and the total number of revolutions n. 总 If no liquid film adhesion occurs, repeat steps S2 to S6 until liquid film adhesion occurs on test piece 24 and record the relevant data.

[0070] S7. Repeat Testing and Data Supplementation: After measuring the contact angle, reassemble the test piece 24 according to steps S1 to S5, and then determine whether the liquid film coverage area on the lower surface of the test piece 24 has increased compared to the previous test. If it has not increased, repeat the measurement according to steps S2 to S5. If it has increased, remove the test piece 24 and measure its static water contact angle θ. n Record the static water contact angle θ n and the total number of revolutions n 总 Then reinstall and test the disk following steps S1 to S5.

[0071] S8. Data Integration: Once the total number of rotations of servo motor 12 reaches the target number, the test of test piece 24 ends, and test piece 24 is removed; then, the static water contact angle θ recorded each time is integrated. i and corresponding test time t i ,in i represents the number of tests.

[0072] S9. Model Building and Lifetime Prediction: Based on the experimental data obtained in S8 (static water contact angle θ) i Corresponding test time t i By measuring the shear force τ at position 24 and the shear force τ at position 24, a shear force-lifetime relationship curve and fitting model for the superhydrophobic test piece 24 are constructed. This model can predict the lifetime of the superhydrophobic surface under more rotational speeds (i.e., shear force changes).

[0073] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A device for testing the durability of superhydrophobic surfaces, characterized in that, Includes a drive module, a testing module, an optical support module, and a water exchange module; The drive module includes a servo controller, a servo motor, a coupling, a drive shaft, a first low-resistance bearing, and a second low-resistance bearing arranged in sequence. The servo motor, coupling, drive shaft, first low-resistance bearing, and second low-resistance bearing are placed coaxially. The coupling connects the servo motor and the drive shaft. The first low-resistance bearing and the second low-resistance bearing are sleeved on the drive shaft. The testing module includes a conical fixing component, a rotating disk, a specimen fixing device, and a test specimen. The conical fixing component is coaxial with the transmission shaft, and the rotating disk is coaxial with both the conical fixing component and the transmission shaft. The rotating disk and the specimen fixing device are respectively machined with equally spaced frustum arrays. The rotating disk and the test specimen are fixed together by spatially fitting the frustum arrays. The rotating disk surface has multiple grooves along the radial direction. The upper and lower boundaries of the grooves are arcs concentric with the rotating disk. The upper left and lower right of the grooves are provided with spring-loaded mechanisms. The upper left and lower right of the specimen fixing device are provided with grooves that cooperate with the spring-loaded mechanisms. The specimen fixing device has set screw holes on its upper, lower, left, and right sides. The test specimen is placed in the specimen fixing device, and the upper and lower boundaries of the test specimen are arcs concentric with the rotating disk. The optical support module includes a motor support base, a water pressure plate, a VK rotary cylinder, a water bath outer cylinder, and an industrial camera. The inner walls of the motor support base, the water pressure plate, and the VK rotary cylinder are coaxial with the servo motor's rotating shaft, transmission shaft, and rotating disk. The motor support base is fixedly fitted to the servo motor. The upper surface of the water pressure plate has a groove that mates with the cylindrical side wall of the motor support base. The center of the upper surface of the water pressure plate has a groove that mates with the first low-resistance bearing. The water pressure plate is fixedly fitted to the VK rotary cylinder. The lower surface of the water pressure plate has a raised frustum structure. The VK rotary cylinder has a groove that mates with the frustum structure. The VK rotary cylinder has a cylindrical inner wall and a polygonal prism outer wall. The lower surface of the inner wall of the VK rotary cylinder has a groove that mates with the second low-resistance bearing. The water bath outer cylinder is a polygonal prism-shaped cylinder with the same number of sides as the outer wall of the VK rotary cylinder. The water bath outer cylinder contains evenly distributed resistance heaters and temperature sensors. The industrial camera is located at the bottom of the water bath outer cylinder. The water exchange module includes a one-way water injection valve, a one-way water extraction valve, a water pump, and a filter unit. The one-way water injection valve and the one-way water extraction valve are both located below the VK rotary cylinder. The water pump is connected to the one-way water injection valve and the one-way water extraction valve. The filter unit works in conjunction with the water pump.

2. The superhydrophobic surface durability testing device according to claim 1, characterized in that, The servo controller is used to control the start and stop time, acceleration and rotation speed of the servo motor. The coupling is a double diaphragm elastic coupling. The first low-resistance bearing and the second low-resistance bearing are both ceramic bearings.

3. The superhydrophobic surface durability testing device according to claim 1, characterized in that, The conical fastener is composed of two stacked cylinders, one smaller than the other. The center of the conical fastener has a through hole in the shape of an approximately hexagonal star. The inscribed circles of the six concave endpoints of the through hole are equal to the radius of the drive shaft. The six convex portions form a gap. The conical fastener is fixed to the drive shaft by a set screw.

4. The superhydrophobic surface durability testing device according to claim 1, characterized in that, The rotating disk has a through hole with a radius larger than that of the transmission shaft at its center. The spring mechanism is a rust-proof spring mechanism. The rotating disk and the conical fixing member are fixed by six threaded holes and screws evenly distributed along the center. The motor support base and the servo motor are fixed by threaded holes and screws evenly distributed along the center. The water pressure plate and the VK rotary cylinder are fixed by threaded holes and screws evenly distributed along the center.

5. The superhydrophobic surface durability testing device according to claim 1, characterized in that, The motor support base consists of an annular upper surface and a cylindrical side wall. A through hole with a radius larger than that of the coupling is opened at the center of the upper surface of the motor support base. A through hole with a radius slightly larger than that of the drive shaft is opened at the bottom of the groove of the water pressure plate. The motor support base, water pressure plate, VK rotary cylinder and water bath outer cylinder are all made of polymethyl methacrylate.

6. A method for testing the durability of superhydrophobic surfaces, characterized in that, The testing apparatus according to any one of claims 1-5 includes the following steps: S1. The specimen fixing device is provided with an inner groove. The test specimen is cut into a size that matches the inner groove. The contact angle θ0 is measured and recorded. The test specimen is installed in the inner groove. The specimen fixing device is installed in the corresponding groove of the rotating disk and fixed by the spring mechanism and the frustum array. S2. Inject test liquid into the VK rotary cylinder through the water pump, filter unit and one-way water injection valve, fill the space between the VK rotary cylinder and the water bath outer cylinder with water, set the constant temperature and turn on the heating. S3. Based on the target shear force range and the shear force calculation formula τ(r)=0.616ρ(νω) 1 / 2 ωr, calculate and set the rotational angular velocity ω and the number of revolutions n of the drive module; S4. The servo motor is controlled by the servo controller to rotate according to the set rotational angular velocity ω and acceleration a1. The servo motor drives the rotating disk to rotate through the coupling, transmission shaft and conical fixing component to generate von Kármán vortex. S5. When the rotating disk rotates to a set number of revolutions n, the servo controller controls the servo motor to stop rotating according to a set acceleration a2, and the water pump draws the test liquid out through the one-way pumping valve until the liquid level is lower than the lower surface of the rotating disk, and the industrial camera takes pictures of the liquid film adhesion on the surface of the test piece. S6. Determine whether there is a liquid film adhering to the surface of the test piece. If so, remove the test piece, measure its static water contact angle θ1, and record θ1 and the total number of revolutions n. 总 Otherwise, repeat steps S2 to S5 until a liquid film adheres to the test piece and record the relevant data. S7. After measuring the contact angle, reassemble the test piece according to steps S1 to S5 and determine whether the liquid film coverage area on the surface of the test piece has increased compared to the previous test. If it has not increased, repeat the measurement according to steps S2 to S5; if it has increased, remove the test piece and measure its static water contact angle θ. n Record θ n and the total number of revolutions n 总 Then reinstall and test the disk following steps S1 to S5; S8. Once the total number of rotations of the servo motor reaches the target number of rotations, remove the test piece and integrate the static water contact angle θ recorded each time. i and corresponding test time t i ,in S9. Based on the static water contact angle θ i Corresponding test time t i Based on the shear force τ at the location of the test piece, construct the shear force-service life relationship curve and fitting model.

7. The method for testing the durability of superhydrophobic surfaces according to claim 6, characterized in that, In step S1, the specimen fixing device fixes the test specimen by the set screws in the set screw holes on the four sides, and the specimen fixing device and the rotating disk are fixed by the spatial interlocking effect of the frustum array.

8. The method for testing the durability of superhydrophobic surfaces according to claim 6, characterized in that, In step S2, the test liquid injected into the VK rotary cylinder is defoamed ultrapure water.

9. The method for testing the durability of superhydrophobic surfaces according to claim 6, characterized in that, In step S3, in the shear force calculation formula, ρ is the density of the test liquid, ν is the kinematic viscosity of the test liquid, and r is the radial position radius of the test piece on the rotating disk.

10. The method for testing the durability of superhydrophobic surfaces according to claim 6, characterized in that, In step S5, the industrial camera captures images of the liquid film adhesion on the lower surface of the test piece. In step S7, the change in the liquid film coverage area on the lower surface of the test piece is determined.

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