A super-hydrophobic coating, its preparation method and use

Abstract

The application discloses a super-hydrophobic coating and a preparation method and application thereof, wherein PDMS is mixed with a curing agent to configure a PDMS solution; then PTFE microparticles are mixed with the PDMS solution, ultrasonic dispersion is carried out, and spin coating is carried out on a substrate surface; vacuumizing, drying and solidifying are carried out to form, and then nanosecond laser processing is carried out to obtain the super-hydrophobic coating. The application adds the PTFE microparticles in the PDMS solution, improves the power generation effect, reduces the light transmittance of the friction layer, makes nanosecond laser processing on the coating surface feasible, and ensures that the super-hydrophobic friction layer prepared by laser processing can keep excellent power generation effect of the friction nanogenerator in a high-humidity environment.

Description

TECHNICAL FIELD

[0001] The application relates to an ultrahydrophobic friction nanogenerator friction layer working in a high-humidity environment and a preparation method and application thereof, and belongs to the technical field of friction nanogenerators BACKGROUND

[0002] With the growth of global energy demand and the improvement of environmental protection awareness, seeking clean, renewable and environmentally friendly new energy technologies has become the focus of the scientific research field. Rainwater, as a widely distributed and energy potential natural resource, has attracted widespread attention in its development and utilization. As a new energy collection technology, the friction nanogenerator can convert mechanical energy into electrical energy based on the contact separation electrification and electrostatic induction effect. It has great application potential in collecting low-frequency mechanical energy in nature and can be well used to collect the energy of raindrops.

[0003] In rainy weather, the air humidity is high. When facing high-humidity conditions, the water film formed on the friction layer of the friction nanogenerator will deteriorate the charge transfer and induce charge dissipation, thereby reducing the output effect of the friction nanogenerator. Therefore, it is urgent to solve the problem of low power generation efficiency of the friction nanogenerator in a high-humidity environment. The ultrahydrophobic surface can well inhibit the formation of the water film on the friction layer due to its good water repellency, thereby ensuring the good power generation effect of the friction nanogenerator in a high-humidity environment. Domestic and foreign researchers have constructed ultrahydrophobic friction layers through etching, photolithography and reverse molding processes. For example, scholars such as Chang Jingjing of Xi'an University of Electronic Science and Technology prepared an ultrahydrophobic surface through a reverse film method (patent publication number CN116915084A). However, this method for preparing the ultrahydrophobic surface has the shortcomings of high processing precision requirement, expensive mold, easy mold contamination and inability to customize the processed ultrahydrophobic surface according to requirements.

[0004] Nanosecond laser processing is a technology that uses a laser with a pulse width of nanoseconds to ablate materials, and has the advantages of high precision, wide applicability, strong controllability and low cost. It can effectively construct an ultrahydrophobic surface. However, since the material of the friction layer of the friction nanogenerator is usually a transparent film, it is difficult to prepare an ultrahydrophobic structure on the surface thereof by using nanosecond laser processing, and the surface of the film is easily damaged. Therefore, how to reduce the light transmittance of the friction layer without reducing the power generation effect of the friction nanogenerator in a high-humidity environment to realize nanosecond laser processing is a problem to be solved. SUMMARY

[0005] Invention purposes: In order to overcome the deficiencies existing in the prior art, the first purpose of the present application is to provide a super-hydrophobic friction nanogenerator friction layer suitable for working in a high-humidity environment, the second purpose of the present application is to provide a preparation method of the super-hydrophobic friction nanogenerator friction layer, by adding PTFE microparticles, not only the power generation effect of the friction nanogenerator is improved, but also the nanosecond laser processing of the surface of the friction layer is realized, the super-hydrophobic structure of the friction layer ensures that the friction nanogenerator works in a high-humidity environment, and the third purpose of the present application is to provide the application of the super-hydrophobic friction nanogenerator friction layer in collecting raindrop energy of the friction nanogenerator in a high-humidity environment.

[0006] Technical scheme: The super-hydrophobic coating comprises PDMS and PTFE microparticles as raw materials, and is obtained by nanosecond laser processing on the surface of a substrate.

[0007] The substrate can be one of copper, aluminum or conductive glass.

[0008] The preparation method of the super-hydrophobic coating comprises the following steps:

[0009] (1) mixing PDMS and a curing agent to configure a PDMS solution;

[0010] (2) mixing PTFE microparticles and the PDMS solution, ultrasonic dispersion, to obtain a mixture;

[0011] (3) spin coating the mixture obtained in step (2) on the surface of the substrate, vacuumizing, drying and curing to form a coating on the surface of the substrate;

[0012] (4) nanosecond laser processing the coating obtained in step (3) to obtain a super-hydrophobic coating.

[0013] In step (1), the curing agent is one of dibutyl phthalate and dibutyltin dilaurate.

[0014] In step (1), the mass ratio of the PDMS to the curing agent is 9-12:1.

[0015] In step (2), the diameter of the PTFE microparticles is 3-10 um.

[0016] In step (2), the mass ratio of the PDMS solution to the PTFE microparticles is 1:8 or more, preferably 1:8.

[0017] In step (2), the ultrasonic dispersion temperature is 15-30 DEG C, the ultrasonic dispersion time is 10-20 min, the ultrasonic frequency is 20-60 KHz, and the ultrasonic power is 60-120 W.

[0018] In step (3), the mixture is spin-coated on the surface of the substrate, the first stage spin-coating time is 30-50s, the rotation speed is 400-600r / min, the second stage spin-coating time is 50-60s, and the rotation speed is 600-1200r / min, preferably 800r / min.

[0019] In step (3), the pressure during vacuum extraction is 0.04-0.08MPa, and the vacuum extraction time is 15-30min.

[0020] In step (3), the drying and curing temperature is 60-120℃, and the drying and curing time is 2-4h.

[0021] In step (3), the thickness of the coating is 50-150um.

[0022] In step (4), the nanosecond laser processing surface pattern is one of triangle, rectangle, and rhombus.

[0023] In step (4), during nanosecond laser processing, the scanning speed is 400-600mm / s, the laser frequency is 20-50kHz, the pulse width is 2-5 microseconds, the current is 0.3-3A, and the scanning layer number is 15-20.

[0024] When the processing is rhombic, the long diagonal is 100-600um, preferably 200um.

[0025] The application also includes the application of the super-hydrophobic coating in collecting raindrop energy for a friction nanogenerator in a high-humidity environment.

[0026] Preparation principle: After adding PTFE microparticles to the PDMS solution, the prepared friction layer surface will be embedded with PTFE microparticles. Since the side chain functional groups of PTFE contain F, which has a stronger electronegativity than CH3 in the side chain functional groups of PDMS, the electron-accepting ability is stronger. Therefore, during the power generation process, when the raindrops rub against the surface of the friction layer, the friction layer doped with PTFE can increase the number of charge transfer in the triboelectric process, and then more charges flow through the external circuit from the raindrops, thereby improving the power generation effect of the friction nanogenerator. The friction layer prepared from PDMS is colorless and transparent, and the laser will directly penetrate the surface during laser processing, and the microstructure cannot be processed on the surface. After doping with PTFE microparticles, the prepared film is milky white, and after controlling the PTFE content, a rough structure can be constructed on the surface by nanosecond laser to obtain a super-hydrophobic surface. In high-humidity weather, the super-hydrophobic friction layer can prevent the formation of a water film, and the rough structure on the surface can expand the solid-liquid contact area and improve the transferred charge density, i.e., improve the power generation effect.

[0027] Beneficial effects: Compared with the prior art, the present application has the following remarkable advantages:

[0028] (1) The super-hydrophobic friction layer prepared by nanosecond laser processing of the present application is simple to operate and low in cost. Different sizes of surface patterns can be obtained by nanosecond laser processing according to different actual needs, so as to realize different hydrophobicity of the friction layer.

[0029] (2) The super-hydrophobic friction layer prepared by the present application has excellent power generation effect through the addition of PTFE microparticles and the increase of solid-liquid contact area by super-hydrophobic surface, and the power generation voltage of one drop of water can reach 220V, which can be well used to collect energy in raindrops.

[0030] (3) The super-hydrophobic friction layer prepared by the present application can work normally in a high humidity environment, and the power generation voltage remains basically unchanged under the conditions of 30%, 60% and 90% environmental humidity, still having excellent power generation effect.

[0031] (4) Compared with short pulse femtosecond laser processing, the present application has faster processing speed when reaching the same hydrophobicity of the friction layer surface, significantly reducing the preparation cost and efficiency of the friction layer. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the power generation voltage diagram of the friction nanogenerator when the mass ratio of PTFE microparticles and PDMS solution is different in Example 1;

[0033] Figure 2 is the surface structure diagram of the super-hydrophobic friction layer obtained after nanosecond laser processing in Example 2;

[0034] Figure 3 is the surface contact angle diagram of the super-hydrophobic friction layer obtained after nanosecond laser processing in Example 2;

[0035] Figure 4 is the schematic diagram of the friction nanogenerator used for testing the present application;

[0036] Figure 5 is the power generation voltage diagram of the friction nanogenerator using the super-hydrophobic friction layer obtained after nanosecond laser processing in Example 2;

[0037] Figure 6 is the surface contact angle of the friction layer without laser processing in Comparative Example 1;

[0038] Figure 7 is the surface contact angle of the friction layer with different size patterns after nanosecond laser processing in Example 3;

[0039] Figure 8is the effect picture of nanosecond laser processing when the mass ratio of PTFE microparticles and PDMS solution is 1:9 and 1:7 in Example 4;

[0040] Figure 9 is the power generation voltage of the friction nanogenerator with different rotation speeds in the second stage of spin coating in Example 6;

[0041] Figure 10 is the power generation voltage of the friction nanogenerator under different humidity conditions in Example 7. DETAILED DESCRIPTION

[0042] The preparation process of the friction nanogenerator used in the following examples is as follows:

[0043] Example 1

[0044] The ITO conductive glass with a size of 30mmx30mmx1.1mm was used as the substrate, and a friction layer was prepared on the surface of the ITO conductive glass:

[0045] (1) The PDMS basic component was mixed with dibutyl phthalate according to a mass ratio of 10:1 to prepare a PDMS solution;

[0046] (2) 3um diameter PTFE microparticles and PDMS solution were mixed according to a mass ratio of 1:7, 1:8, 1:9 and 1:10 respectively, and stirred to obtain four groups of PTFE microparticle and PDMS solution mixtures, followed by ultrasonic dispersion, ultrasonic temperature was 20℃, ultrasonic time was 10min, ultrasonic frequency was 40KHz, output power was 100W, to obtain four groups of mixtures;

[0047] (3) 3mL of the four groups of mixtures obtained in step (2) were spin coated on the surfaces of four ITO conductive glass substrates, the first stage of spin coating time was 40s, the rotation speed was 600r / min, the second stage of spin coating time was 60s, the rotation speed was 800r / min. Then vacuumize at 0.08MPa pressure for 10min, dry at 80℃ for 2h to solidify and form, and form four groups of coatings on the surface of the ITO conductive glass substrate, the thickness of the coating was about 90um;

[0048] The ITO conductive glass with a size of 30mmx30mmx1.1mm was used as the substrate, and a friction layer was prepared on the surface of the ITO conductive glass: Figure 1 Figure 1 ​It can be seen that the addition of PTFE microparticles has a significant effect on the power generation effect of the triboelectric nanogenerator. When the mass ratio of PTFE microparticles to PDMS solution reaches 1:8, the average power generation voltage is 150V, and the power generation effect is the best. When the content of PTFE microparticles is too low, the triboelectric charge accumulation is less; when the content of PTFE microparticles is too high, the microparticles on the surface of the prepared triboelectric layer are distributed more densely, resulting in a smaller contact angle of the triboelectric layer, and liquid droplets adhere during power generation, reducing the power generation effect.

[0049] Example 2

[0050] An ITO conductive glass with a size of 30mmx30mmx1.1mm was used as a substrate, and the optimal mass ratio of PTFE microparticles to PDMS solution in Example 1 was 1:8 to prepare the triboelectric layer:

[0051] Steps (1)-(3) are the same as in Example 1.

[0052] (4) The coating obtained in step (3) was subjected to nanosecond laser processing, and the surface pattern was a rhombus with rhombus angles of 30° and 120°, a long diagonal of 200um, a scanning speed of 400mm / s, a laser frequency of 50kHz, a pulse width of 5 microseconds, a current of 1A, and 15 layers of scanning, to obtain a superhydrophobic triboelectric layer.

[0053] In order to verify the hydrophobicity and power generation effect of the triboelectric layer, the surface structure and contact angle of the triboelectric layer prepared in this example were measured, and the results are shown in Figures 2-3 . Figure 2 is a surface structure diagram of the superhydrophobic triboelectric layer after nanosecond laser processing in Example 2, and Figure 2 it can be seen that after adding PTFE microparticles, the transparency of the PDMS triboelectric layer is reduced, and a rhombic micro-nano structure is successfully obtained on the surface of the triboelectric layer by laser processing. The contact angle is measured as Figure 3 . Figure 3 is a surface contact angle diagram of the superhydrophobic triboelectric layer after nanosecond laser processing in Example 2, and Figure 3 it can be seen that the contact angle reaches 159°, realizing the superhydrophobicity of the surface of the triboelectric layer, which can prevent the formation of liquid film on the surface in a high humidity environment and ensure the power generation effect in a high humidity environment.

[0054] The ITO conductive glass with a superhydrophobic triboelectric layer prepared in this example was used as a lower electrode, and a conductive Ag wire was placed horizontally on the surface of the triboelectric layer as an upper electrode, which was used as a triboelectric nanogenerator for power generation. The schematic diagram is shown in Figure 4 , and the results are shown in Figure 5 . Figure 5 is a power generation voltage diagram of the superhydrophobic triboelectric layer obtained after nanosecond laser processing in Example 2 for use in a triboelectric nanogenerator, and Figure 5It can be seen that the super-hydrophobic friction layer prepared in the embodiment is used for power generation of the friction nanogenerator, and the voltage reaches 220V, which can well collect raindrop energy

[0055] Comparative Example 1

[0056] The coating prepared by mixing the 3um diameter PTFE microparticles and the PDMS solution in a mass ratio of 1:8 in Example 1 was measured for the contact angle, and the result is shown in Figure 6 The contact angle of the friction layer without nanosecond laser processing is 117°, and the surface is a hydrophobic structure. Compared with the super-hydrophobic surface prepared after nanosecond laser processing in the present embodiment 2, the adhesion to water is stronger, and in a high humidity environment, water in the air is easily adsorbed to form a liquid film on the surface, which reduces the power generation effect of the friction nanogenerator and is not conducive to the operation of the friction nanogenerator in a high humidity environment.

[0057] Example 3

[0058] The super-hydrophobic friction layer was prepared in the same manner as in Example 2, except that the length of the long diagonal of the laser-processed rhombic pattern was different, specifically 100um, 400um and 600um. The contact angles of the prepared super-hydrophobic friction layers were measured and compared with those in Example 2, and the results are shown in Figure 7 It can be seen from Figure 7 that as the processing size increases, the air layer between the friction layer and the liquid droplet decreases and the solid-liquid contact area increases when the liquid droplet stays on the surface, resulting in a decrease in the contact angle of the surface of the friction layer and a decrease in the hydrophobicity. When the processing size is 100um, the surface microstructure size is too small, and when the liquid droplet stays on the surface, pinning phenomenon occurs, the liquid droplet wets the solid surface, and the contact angle decreases. By controlling the pattern size, the hydrophobicity of the surface can be controlled. When the length of the long diagonal of the processed rhombic pattern is 200um, the friction layer can achieve the best hydrophobicity, and the contact angle reaches 159°.

[0059] Example 4

[0060] (1) The super-hydrophobic friction layer was prepared in the same manner as in Example 2, except that the mass ratio of PTFE microparticles to PDMS solution was changed to 1:7 and 1:9. The PDMS base component was mixed with dibutyl phthalate in a mass ratio of 10:1 to prepare the PDMS solution.

[0061] (2) The 3um diameter PTFE microparticles and the PDMS solution were mixed in a mass ratio of 1:9, and the mixture was obtained by stirring. Then, the mixture was ultrasonically dispersed at a temperature of 20℃ for 10min, an ultrasonic frequency of 40KHz and an output power of 100W to obtain the mixture.

[0062] (3) Take 3 mL of the mixture obtained in step (2) and spin-coat on the surface of the ITO conductive glass substrate, the first stage of spin-coating time is 40 s, the rotation speed is 600 r / min, the second stage of spin-coating time of the coating is 60 s, and the rotation speed is 800 r / min. Then vacuumize at a pressure of 0.08 MPa for 10 min, dry at 80°C for 2 h to solidify and form a coating on the surface of the ITO conductive glass substrate, and the thickness of the coating is about 90 um.

[0063] (4) Perform nanosecond laser processing on the coating obtained in step (3), the surface pattern is rhombus with opposite angles of 30° and 120°, the long diagonal is 200 um, the scanning speed is 400 mm / s, the laser frequency is 50 kHz, the pulse width is 5 microseconds, the current is 1A, and the scanning layer number is 15. The surface structure of the prepared friction layer is observed, and the results are shown in Figure 8 .

[0064] As can be seen from Figure 8 , through the nanosecond laser processing experiment, it is found that when the mass ratio of PTFE microparticles to PDMS solution is less than 1:8, the light transmittance of the prepared friction layer is limited, and the nanosecond laser is easy to melt the friction layer during processing, which is specifically manifested as that the friction layer is locally foamed due to the influence of high temperature. When the mass ratio of PTFE microparticles to PDMS solution is 1:8 or 1:7, the nanosecond laser can be used to construct patterns on the surface of the friction layer to achieve super-hydrophobicity.

[0065] Example 5

[0066] The preparation process of the super-hydrophobic friction layer is the same as that of Example 1, except that the second stage rotation speed of the friction layer spin-coating is different, specifically 600 r / min, 1000 r / min, 1200 r / min, and 800 r / min of Example 1. Four different friction layers are prepared, and the power generation effect of the friction nanogenerator is measured, and the results are shown in Figure 9 .

[0067] During the preparation of the friction layer by spin-coating, the thickness of the prepared sample is related to the second stage rotation speed of spin-coating. As can be seen from the experimental results, when the spin-coating rotation speed reaches 800 r / min, the friction nanogenerator has the best power generation effect, because the higher rotation speed makes the prepared friction layer thinner, which reduces the PTFE contained in the friction layer and reduces the accumulation of triboelectric charges; lower rotation speed leads to thicker friction layer, which hinders the electrostatic induction, both of which reduce the triboelectric charge transfer and reduce the power generation effect of the friction nanogenerator. When the rotation speed is 800 r / min, the prepared friction layer has the best power generation effect.

[0068] Example 6

[0069] To verify that the superhydrophobic triboelectric layer prepared in this invention can maintain good power generation performance in high humidity environments, the triboelectric nanogenerator sample prepared in Example 2 was used to observe the power generation performance of the triboelectric nanogenerator under different environmental humidity levels: 30%, 60%, and 90%. The results are as follows: Figure 10 As shown.

[0070] Depend on Figure 10 As can be seen, with the increase of ambient humidity, the power generation voltage of the triboelectric nanogenerator drops from the original 220V to 200V, but still maintains a high output. This is due to the excellent superhydrophobic properties of the triboelectric layer surface. In high-humidity environments, the superhydrophobic structure of the triboelectric layer surface inhibits the adhesion of moisture in the air, preventing the formation of a liquid film. This, in turn, avoids the formation of the electric double layer and the dissipation of charge by the liquid film, ensuring the excellent power generation effect of the triboelectric nanogenerator in high-humidity environments.

[0071] Comparative Example 2

[0072] Compared with Example 1 in patent publication number CN113054865A, the present invention, by adding PTFE micron particles, not only improves the power generation effect of the triboelectric nanogenerator, but also realizes nanosecond laser processing on the surface of the triboelectric layer. Compared with plasma etching, it has the advantages of simple process, no environmental pollution, and low cost.

[0073] Compared with the maximum power generation voltage of 110V in Embodiment 1 of Patent Publication No. CN113054865A, the power generation voltage in Embodiment 2 of the present invention reaches 220V, and the effect of collecting raindrop energy is significantly improved.

[0074] Comparative Example 3

[0075] In the comparative document "Zhang H, Yin K, Wang L, et al. A Robust Droplet Triboelectric Nanogenerator with Self-Cleaning Ability Achieved by Femtosecond Laser [J]. ACS Applied Materials & Interfaces, 2023, 15(25): 30902-30912.", Zhang et al. use femtosecond laser to linearly scan on PTFE film to obtain super-hydrophobic structure, and the contact angle with water reaches 160°, which is basically the same as the effect achieved in Example 2 of the present application by nanosecond laser. However, the cost of purchasing, using and maintaining femtosecond laser is much higher than that of nanosecond laser, and the operation is complex. Compared with long-pulse nanosecond laser, short-pulse femtosecond laser has a slower processing speed. The present application achieves the same hydrophobic effect of the friction layer as femtosecond laser processing through material design and nanosecond laser processing, significantly reducing the preparation cost and efficiency of the friction layer.

Claims

1. A superhydrophobic coating, characterized in that, The super-hydrophobic coating comprises PDMS and PTFE microparticles as raw materials, and is obtained by nanosecond laser processing on the surface of a substrate, wherein the substrate is one of copper, aluminum or conductive glass, and the preparation method of the super-hydrophobic coating comprises the following steps: (1) mixing PDMS and a curing agent to configure a PDMS solution, wherein the curing agent is one of dibutyl phthalate and dibutyl tin dilaurate; (2) mixing PTFE microparticles and the PDMS solution, and ultrasonic dispersion to obtain a mixture, wherein the mass ratio of the PDMS solution to the PTFE microparticles is 1:8 or more; (3) spin coating the mixture obtained in step (2) on the surface of the substrate, vacuumizing, drying and curing to form a coating on the surface of the substrate, wherein the second-stage spin coating time is 50-60s, and the rotation speed is 600-1200r / min; (4) nanosecond laser processing the coating obtained in step (3) to obtain a super-hydrophobic coating, wherein the surface pattern of the nanosecond laser processing is a rhombus, the length of the long diagonal of the rhombus is 200μm, the scanning speed of the nanosecond laser processing is 400-600mm / s, the laser frequency is 20-50kHz, the pulse width is 2-5μs, the current is 0.3-3A, and the scanning layer number is 15-20.

2. The method of claim 1, wherein the superhydrophobic coating is prepared by, comprises the following steps: (1) mixing PDMS and a curing agent to configure a PDMS solution, wherein the curing agent is one of dibutyl phthalate and dibutyl tin dilaurate; (2) mixing PTFE microparticles and the PDMS solution, and ultrasonic dispersion to obtain a mixture, wherein the mass ratio of the PDMS solution to the PTFE microparticles is 1:8 or more; (3) spin coating the mixture obtained in step (2) on the surface of the substrate, vacuumizing, drying and curing to form a coating on the surface of the substrate, wherein the second-stage spin coating time is 50-60s, and the rotation speed is 600-1200r / min; (4) nanosecond laser processing the coating obtained in step (3) to obtain a super-hydrophobic coating, wherein the surface pattern of the nanosecond laser processing is a rhombus, the length of the long diagonal of the rhombus is 200μm, the scanning speed of the nanosecond laser processing is 400-600mm / s, the laser frequency is 20-50kHz, the pulse width is 2-5μs, the current is 0.3-3A, and the scanning layer number is 15-20.

3. The method of claim 2, wherein, In step (1), the mass ratio of the PDMS to the curing agent is 9-12:

1.

4. The preparation method according to claim 2, characterized in that, In step (2), the diameter of the PTFE microparticles is 3-10μm.

5. The preparation method according to claim 2, characterized in that, In step (2), the ultrasonic dispersion temperature is 15-30℃, the ultrasonic dispersion time is 10-20min, the ultrasonic frequency is 20-60KHz, and the ultrasonic power is 60-120W.

6. The preparation method according to claim 2, characterized in that, In step (3), when the mixture is spin coated on the surface of the substrate, the first-stage spin coating time is 30-50s, and the rotation speed is 400-600r / min.

7. The preparation method according to claim 2, characterized in that, In step (3), the pressure during vacuumizing is 0.04-0.08MPa, the vacuumizing time is 15-30min, the drying and curing temperature is 60-120℃, the drying and curing time is 2-4h, and the thickness of the coating is 50-150μm.

8. Use of the superhydrophobic coating of claim 1 in harvesting raindrop energy for a triboelectric nanogenerator in high humidity environment.

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