Method for preparing stable super-hydrophobic surface capable of preventing liquid drop impact

Abstract

The invention relates to the technical field of super-hydrophobic surface preparation, in particular to a method for preparing a stable super-hydrophobic surface capable of preventing liquid drop impact. Comprising the following steps: performing lineation scanning on the surface of a metal sample by using a delayed femtosecond laser pulse string to form a periodic micro-nano structure on the surface of the metal sample; the periodic micro-nano structure is formed by alternately arranging ablation grooves and ridge-shaped bulge structures at the edges of the ablation grooves; performing secondary lineation scanning on the surface of the metal sample by adopting a delay femtosecond laser pulse string which is orthogonal to the scanning direction in the previous step, so that the ridge-shaped bulge structure is bent and extended from the bulge center area to the two sides to form a bulge stoop-shaped microstructure; and carrying out ultrasonic cleaning on the surface of the treated metal sample, and then carrying out annealing treatment for 3-10 hours. The method has the advantages that the continuously twisted wavy topological contour is constructed, collaborative optimization of multiple elements in breakthrough pressure of the air bag in the micro-nano structure is achieved, and the stability of liquid drop impact prevention of the super-hydrophobic surface in the Cassie state is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of super-hydrophobic surface preparation, and particularly relates to a method for preparing a stable super-hydrophobic surface capable of preventing liquid drop impact. BACKGROUND

[0002] Super-hydrophobic surfaces have attracted much attention due to their potential applications in the fields of ice and stain repellency, and corrosion resistance. The core idea of super-hydrophobic surfaces is to realize the de-wetting phenomenon of water droplets based on the low surface energy of the material and the air pocket layer formed by the micro-nano structure. However, due to the metastable nature of the solid-gas interface, the air pocket in the micro-nano structure has a significant defect in maintaining ability: especially in the case of external liquid droplets impacting the surface at a certain speed, the air pocket is easily pierced by the liquid and collapses, leading to the irreversible transition of the super-hydrophobic surface from the Cassie state to the Wenzel state, which greatly restricts the actual application. Therefore, it is urgent to optimize the micro-nano structure morphology design to inhibit the escape of air in the structure, so as to improve the thermodynamic stability of the Cassie state of the super-hydrophobic surface.

[0003] Previous studies have shown that the actual ability of the super-hydrophobic surface to transition from the Cassie state to the Wenzel state can be quantitatively characterized by the breakthrough pressure (P break ) value of the air pocket in the micro-nano structure, i.e. P break =Lγ|sin(Ψ)| / A, where A is the projected area of the liquid-gas interface, L is the contact line length of the solid-liquid-gas three-phase, γ represents the surface tension of the liquid, and Ψ is the angle between the tangent direction of the solid-liquid-gas three-phase contact line and the liquid droplet impact force. Based on the above theory, researchers have successively proposed and developed various structure design methods, aiming to further improve P break by increasing γ|sin(Ψ)| and L, or reducing A. For example: (1) it has been reported that a re-entrant multi-layer structure was constructed on the surface of a rigid material using photolithography technology, which maximized the support of the upward component of the liquid surface tension to the liquid droplet impact, successfully increasing P break from 876 Pa to 2262 Pa. (2) it has been reported that a mixed hollow structure of fused and connected air pockets and non-connected air pockets was constructed on a rigid substrate using ion etching technology, which increased the solid-liquid-gas three-phase length and increased P break to 2.94 kPa. (3) it has been reported that a vertical column array structure was prepared on a silicon material using laser processing technology, and the thermodynamic stability of the super-hydrophobic state was effectively improved by reducing the liquid-gas interface projected area A by changing the micro-structure spacing. However, the existing methods have limitations in that they mainly use one or two of the above factors to enhance P break , thus resulting in limited improvement and complex process, which seriously restricts the development of the practical application of super-hydrophobic surfaces. SUMMARY

[0004] The application provides a method for preparing a stable super-hydrophobic surface resistant to liquid drop impact.

[0005] The application aims to provide a method for preparing a stable super-hydrophobic surface resistant to liquid drop impact, and specifically comprises the following steps. S1. performing line scanning on the surface of a metal sample by using a delayed femtosecond laser pulse train to form a periodic micro-nano structure on the surface of the metal sample; the periodic micro-nano structure is composed of ablation grooves and ridge-shaped protruding structures on the edges of the ablation grooves and is alternately arranged; S2. performing secondary line scanning on the surface of the metal sample by using a delayed femtosecond laser pulse train orthogonal to the scanning direction in step S1 to make the ridge-shaped protruding structures bend and extend from the center of the protruding structures to both sides to form protruding bent microstructures; S3. performing ultrasonic cleaning on the surface of the metal sample after step S2, and then performing annealing treatment at 100-200 DEG C for 3-10 hours to obtain a stable super-hydrophobic surface resistant to liquid drop impact.

[0006] Preferably, the longitudinal depth of the ablation grooves is 10-100 μm, and the center distance between adjacent ablation grooves is 40-150 μm; the longitudinal height of the ridge-shaped protruding structure is 10-60 μm.

[0007] Preferably, the bending and extending direction of the protruding bent microstructure is consistent with the scanning forward direction of the delayed femtosecond laser pulse train; The end of the protruding bent microstructure is hook-shaped; The protruding bent microstructure forms an arched overhanging structure above the ablation groove area.

[0008] Preferably, the arched overhanging structure and the sidewall surface of the ablation groove are covered with a multi-scale nano structure.

[0009] Preferably, the inclination angle between the protruding bent microstructure and the surface of the metal sample is 20-60 DEG; and the horizontal span of the top end of the protruding bent microstructure is 20-40 μm.

[0010] Preferably, the scanning direction of the delayed femtosecond laser pulse train is Z-shaped; and with the scanning direction of the delayed femtosecond laser pulse train, the plurality of protruding bent microstructures are continuously distributed in space and have a wave-shaped topological morphology.

[0011] Preferably, the total energy of the delayed femtosecond laser pulse train is 200-800 μJ, the laser pulse width is 20 fs-5 ps, the repetition frequency is 1-30 kHz, and the time delay between adjacent pulses is 5-100 ps.

[0012] Preferably, the scribing speed is 0.1-3 mm / s, and the interval between the scribing lines is 40-100 μm.

[0013] Preferably, the time-delayed femtosecond laser pulse train is generated by a laser light splitting time-delay assembly, which comprises a beam splitter and a mirror arranged coaxially; the reflectance / transmittance ratio of the beam splitter is 3:7, 2:8, 4:6 or 5:5.

[0014] Preferably, the ultrasonic cleaning time in step S3 is 10-30 minutes; and the metal sample material is an aluminum alloy, a copper alloy or a titanium alloy.

[0015] Compared with the prior art, the present application can achieve the following beneficial effects: The present application provides a method for preparing a stable super-hydrophobic surface resistant to liquid drop impact, which adopts a femtosecond laser pulse train processing mode to regulate the ablation removal behavior of a metal surface material, and then constructs a wave-shaped topological profile with a groove and a convex bent shape combined and continuously twisted, which has a significant advantage in improving the breakthrough pressure of the air bag in the micro-nano structure: (1) the mutual connection of the convex bent shape microstructure prolongs the solid-liquid-gas three-phase contact line length L; (2) the convex bent shape microstructure is curved on the top of both sides of the groove, forming an arch structure, which narrows the groove opening and reduces the liquid-gas projection area A; (3) the end of the curved convex ridge-shaped structure is in the form of a hook structure, which can significantly enhance the component of the liquid surface tension in the opposite impact direction γ|sin(Ψ)|.

[0016] In summary, the stable super-hydrophobic surface prepared by the preparation method of the present application can realize the synergistic optimization of multiple factors break , and significantly improve the stability of the super-hydrophobic surface in the Cassie state resistant to liquid drop impact. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a flow chart of the method for preparing a stable super-hydrophobic surface resistant to liquid drop impact according to an embodiment of the present application.

[0018] Figure 2 is a topographic map of the stable super-hydrophobic surface resistant to liquid drop impact processed by the time-delayed femtosecond laser pulse train according to an embodiment of the present application.

[0019] Figure 3 is a 3D microscopic profile map of the stable super-hydrophobic surface resistant to liquid drop impact processed by the time-delayed femtosecond laser pulse train according to an embodiment of the present application.

[0020] Figure 4 is an experimental diagram of the contact angle and the rolling angle of the stable super-hydrophobic surface resistant to liquid drop impact according to an embodiment of the present application.

[0021] Figure 5 This is a dynamic frame diagram of a droplet impacting a super-hydrophobic surface provided by an embodiment of the present invention.

[0022] Figure 6 3 is a comparison diagram of the super-hydrophobic surface provided by an embodiment of the present invention in a high-speed water jet experiment. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, identical modules are denoted by identical reference numerals. In the case of identical reference numerals, their names and functions are also identical. Therefore, their detailed description will not be repeated.

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0025] In order to construct a groove-convex bent waist topological profile structure, the present invention provides a method for preparing a stable super-hydrophobic surface that is resistant to droplet impact. By using a femtosecond laser pulse train processing method to control the ablation removal behavior of the metal surface material, a topological profile with a combination of grooves and convex bent waist shapes is constructed to achieve an airbag breakthrough pressure P break The multi-factor synergistic optimization of the super-hydrophobic surface significantly improves the stability of the Cassie state against droplet impact. The specific steps include: S1. Scanning the surface of a metal sample using a delayed femtosecond laser pulse train to form periodic micro-nanostructures on the surface of the metal sample. The periodic micro-nanostructure is composed of alternating ablation grooves and ridge-like protrusions at the edges of the ablation grooves. Specifically, the metal sample materials are aluminum alloy, copper alloy and titanium alloy; Specifically, the longitudinal depth of the ablation groove is 10-100 μm, the center distance between adjacent ablation grooves is 40-150 μm; the longitudinal height of the ridge-like protrusion structure is 10-60 μm; S2. Using a delayed femtosecond laser pulse train orthogonal to the scanning direction in step S1, the metal sample surface is scanned a second time, so that the ridge-like protrusion structure bends and extends from the center area of ​​the protrusion to both sides, forming a protruding waist-shaped microstructure; The bending and extension direction of the raised, waist-shaped microstructure is consistent with the scanning direction of the delayed femtosecond laser pulse train; the end of the raised, waist-shaped microstructure is hook-shaped; the raised, waist-shaped microstructure covers the ablation groove area to form an arched overhanging structure, thereby reducing the opening size of the ablation groove; The tilt angle of the convex hump-shaped microstructure with the surface of the metal sample is 20-60°; and the transverse span of the top of the convex hump-shaped microstructure is 20-40 μm. The arch-shaped overhanging structure (the top and sidewall region of the convex hump-shaped microstructure) and the ablation groove sidewall surface are covered with multi-scale nanostructures (nano-scale textures such as micro-protrusions, particles or corrugations), further enhancing the super-hydrophobic performance. The scanning direction of the time-delayed femtosecond laser pulse train is a zigzag shape; and the plurality of convex hump-shaped microstructures are continuously distributed in space along the scanning direction of the time-delayed femtosecond laser pulse train, and a wave-shaped topography is constructed as a whole. S3. The metal sample surface treated in step S2 is ultrasonically cleaned, and then annealed at 100-200 °C for 3-10 hours, to finally obtain a stable super-hydrophobic surface resistant to liquid drop impact. Specifically, the ultrasonic cleaning time is 10-30 minutes.

[0026] Preferably, the total energy of the time-delayed femtosecond laser pulse train is 200-800 μJ, the laser pulse width is 20 fs-5 ps, and the repetition frequency is 1-30 kHz; and the time delay between adjacent pulses in the time-delayed femtosecond laser pulse train is 5-100 ps. The speed of the scribe scanning is 0.1-3 mm / s, and the interval between the scanning lines is 40-100 μm. The time-delayed femtosecond laser pulse train is generated by a laser light splitting and time-delaying assembly, which comprises a beam splitter and a mirror arranged coaxially; the incident laser light generates a first sub-pulse and a plurality of subsequent sub-pulses after passing through the light splitting and time-delaying assembly; the subsequent sub-pulses are sequentially formed by the round-trip light path between the mirror and the beam splitter, and the time-delayed femtosecond laser pulse train is finally output. Specifically, the reflectance / transmittance ratio of the beam splitter is selected from any one of 3:7, 2:8, 4:6 and 5:5; when the reflectance / transmittance ratio of the beam splitter is 3:7, the sub-pulse energy ratio of the time-delayed femtosecond laser pulse train is 0.3, 0.49, 0.147, 0.044, etc. in turn. In specific embodiments, the time-delayed femtosecond laser pulse train can also be generated by a 4f pulse shaping system or a multi-pulse experimental device.

[0027] Embodiment 1 The embodiment provides a method for preparing a stable super-hydrophobic surface resistant to liquid drop impact, which specifically comprises the following steps: S1. A convex-plate lens with a focal length of 200 mm is used to focus and irradiate a time-delayed femtosecond laser pulse train to an aluminum alloy surface; under the condition that the aluminum alloy sample position is fixed, the sample surface is scanned and irradiated by a computer-controlled three-dimensional moving platform, to form a periodic micro-nano structure on the aluminum alloy surface; the periodic micro-nano structure is composed of alternating ridge-shaped protruding structures on the edges of ablation grooves and the ablation grooves. The time-delayed femtosecond laser pulse train is generated by a laser light splitting and time-delaying assembly, which comprises a beam splitter and a mirror arranged coaxially; the reflectance / transmittance ratio of the beam splitter is 3:7; The total laser energy of the time-delayed femtosecond laser pulse train is 600 μJ, the pulse width is 40 fs, and the time delay between adjacent pulses is 20 ps; the sub-pulse energies in the generated pulse train are set as E1=180 μJ, E2=294 μJ, E3=88.2 μJ, E4=26.5 μJ, and so on. The scanning speed is 1 mm / s, and the interval between scanning lines is 50 μm.

[0028] S2. A time-delayed femtosecond laser pulse train orthogonal to the scanning direction in step S1 is used to perform secondary line scanning on the surface of the aluminum alloy sample, so that the ridge-shaped protrusion structure is curved and extended from the protrusion center region to both sides, and finally a protrusion bent-topology structure is formed on the surface of the sample, and the macroscopic morphology presents a continuous twisted wave-shaped profile. Figure 2 The protruding curved ridge-shaped top end presents a negative curvature hook-shaped morphology. Figure 2 The oblique ridge curved angle is 30°. Figure 3 In addition, the microstructure top end and the ablation groove sidewall surface are both covered with multi-scale nanostructures. Figure 2 The parameters in Pbreak are quantified by 3D confocal microscopy, and the theoretical value is Pbreak≈6.1×10 4 Pa, and the results are shown in Figure 3 .

[0029] S3. Then, the surface of the sample is ultrasonically cleaned with deionized water for 20 min, and then placed in a vacuum drying oven at a temperature of 200℃ for annealing for 3 h, to obtain a stable superhydrophobic surface resistant to liquid drop impact.

[0030] After the annealing treatment is completed, the water droplet contact angle of the surface of the sample is measured to be 162°, and the rolling angle is 0.5°, as shown in Figure 4 a. In a single liquid droplet bouncing experiment, the surface appears to be liquid droplet fragmentation at a liquid droplet impact speed V=6 m / s, but no residual liquid droplet pinning phenomenon occurs, and the superhydrophobic surface remains in the Cassie state, as shown in Figure 5 a. In addition, in a water flow impact experiment at a speed of V=10.6 m / s, it is observed that the surface liquid droplets can bounce back, and no liquid droplet pinning phenomenon occurs, and at this time the superhydrophobic surface still maintains a good Cassie state, as shown in Figure 6 .

[0031] Embodiment 2 The embodiment provides a method for preparing a stable superhydrophobic surface resistant to liquid drop impact, specifically comprising the following steps: S1. A plano-convex lens with a focal length of 200 mm is used to focus a delayed femtosecond laser pulse train onto the surface of an aluminum alloy. The sample position is fixed, and the sample surface is scanned by a computer-controlled three-dimensional moving platform. Periodic micro-nano structures are formed on the surface of the aluminum alloy. The periodic micro-nano structures are composed of alternating ablation grooves and ridge-like protrusions at the edges of the ablation grooves. The total laser energy of the delayed femtosecond laser pulse train is 600 μJ, the pulse width is 40 fs, and the time delay between adjacent pulses is 60 ps. The sub-pulse energies in the generated pulse train are set as E1 = 180 μJ, E2 = 294 μJ, E3 = 88.2 μJ, E4 = 26.5 μJ, and so on. The scanning speed is 1 mm / s, and the interval between scanning lines is 40 μm.

[0032] Steps S2-S3 are the same as in Example 1.

[0033] After the annealing treatment is completed, the water droplet contact angle on the surface of the sample is measured to be 160°, and the rolling angle is 1°, as shown in FIG. b. In a single droplet bouncing experiment, droplet fragmentation occurs at a droplet impact speed V = 6 m / s, but no residual droplet pinning phenomenon occurs, and the superhydrophobic surface remains in the Cassie state, as shown in FIG. b. Figure 4 Figure 5

[0034] Example 3 The present embodiment provides a method for preparing a stable superhydrophobic surface resistant to droplet impact, which specifically comprises the following steps: S1. A plano-convex lens with a focal length of 200 mm is used to focus a delayed femtosecond laser pulse train onto the surface of an aluminum alloy. The sample position is fixed, and the sample surface is scanned by a computer-controlled three-dimensional moving platform. Periodic micro-nano structures are formed on the surface of the aluminum alloy. The periodic micro-nano structures are composed of alternating ablation grooves and ridge-like protrusions at the edges of the ablation grooves. The total laser energy of the delayed femtosecond laser pulse train is 400 μJ, the pulse width is 40 fs, and the time delay between adjacent pulses is 20 ps. The sub-pulse energies in the generated pulse train are set as E1 = 120 μJ, E2 = 196 μJ, E3 = 58.8 μJ, E4 = 17.7 μJ, and so on. The scanning speed is 1 mm / s, and the interval between scanning lines is 40 μm.

[0035] Steps S2-S3 are the same as in Example 1.

[0036] After the annealing treatment is completed, the water droplet contact angle on the surface of the sample is measured to be 158°, and the rolling angle is 1.5°, as shown in FIG. b. In a single droplet bouncing experiment, droplet fragmentation occurs at a droplet impact speed V = 6 m / s, but no residual droplet pinning phenomenon occurs, and the superhydrophobic surface remains in the Cassie state, as shown in FIG. b. Figure 4 ​​As shown in Figure c. In the single droplet bouncing experiment, the surface showed droplet fragmentation when the droplet impact velocity V = 6m / s, but no residual droplet pinning occurred. The water on the superhydrophobic surface maintained the Cassie state, as shown in Figure 4. Figure 5 As shown in c.

[0037] Example 4 This embodiment provides a method for preparing a stable super-hydrophobic surface that is resistant to droplet impact, which specifically includes the following steps: S1. Using a plano-convex lens with a focal length of 200 mm, a delayed femtosecond laser pulse train was focused and irradiated onto the aluminum alloy surface. With the aluminum alloy sample fixed in position, a computer-controlled three-dimensional mobile platform was used to scan and irradiate the sample surface, forming a periodic micro-nanostructure on the aluminum alloy surface. The periodic micro-nanostructure consisted of alternating ablation grooves and ridge-like protrusions at the edges of the ablation grooves. The delayed femtosecond laser pulse train is generated by a laser beam splitter delay assembly, which includes a coaxially arranged beam splitter and a reflector. The reflection / transmission ratio of the beam splitter is 5:5. The total laser energy of the delayed femtosecond laser pulse train is 600 μJ, the pulse width is 40 fs, the time delay between adjacent pulses is 20 ps, ​​and the neutron pulse energies of the generated pulse train are set to E1=300 μJ, E2=150 μJ, E3=75 μJ, E4=37.5 μJ, etc.; The scanning speed was 1 mm / s and the interval between scanning lines was 50 μm.

[0038] Steps S2-S3 are the same as in Example 1.

[0039] After the annealing treatment, the water droplet contact angle on the sample surface was measured to be 158° and the rolling angle was 3°. Figure 4 As shown in Figure d. In the single droplet bouncing experiment, the surface showed droplet fragmentation when the droplet impact velocity V = 6m / s, but no residual droplet pinning occurred, and the superhydrophobic surface maintained the Cassie state, as shown in Figure d. Figure 5 As shown in d.

[0040] The key technical point and advantage of the present application is that: by using the strong thermodynamic coupling characteristics in the process of the delay femtosecond laser pulse train interacting with the material, the high-temperature evaporation and plasma sputtering phenomena in the ablation process are suppressed, so that the material at the groove position is not removed in the form of evaporation or plasma, but is directionally extruded and migrated to the two side edges through local thermal expansion, and finally a ridge-shaped protruding structure is formed above the material plane; then the laser shock wave effect in the orthogonal scanning process is used to bend and deform the ridge-shaped structure. Among them, since the ridge structure bends over the groove, the liquid cannot form an impact effect in the vertical direction on the air bag, and the impact force of the high-speed liquid is mainly borne by the solid top end of the bent ridge-shaped structure. On the other hand, due to the vertical downward of the tip of the air bag's inner wall side bending structure, it is similar to a reentrant structure, so that the liquid surface tension is maximized in the direction resisting the impact of the liquid drop. In addition, the continuous expansion and distortion of the wave-shaped protruding structure profile in space along the groove direction further prolongs the contact length of the solid-liquid-gas three-phase line. The above structure helps to slow down the impact and penetration of high-speed liquid drops and water flow on the surface air bag, thereby significantly improving the thermodynamic stability of the super-hydrophobic surface. At the same time, the multi-level nanostructure constructed synchronously on the microstructure surface can further reduce the adhesion of the solid-liquid interface. The experimental measurement shows that the rolling angle of the laser-processed aluminum alloy surface is as low as 0.5°, and under the impact of liquid drops at V=6m / s, it shows complete rebound characteristics, and can withstand water jet impact at a speed of up to V=10.6m / s. Experiments prove that this surface has excellent Cassie state anti-liquid drop impact stability and at the same time has ultra-low solid-liquid interface adhesion characteristics.

[0041] It should be understood that the various forms of flow shown above can be reordered, added to, or deleted from without departing from the scope of the present application. For example, the steps described in the present disclosure can be performed in parallel, in series, or in a different order, as long as the desired results of the technical solutions of the present disclosure can be achieved, and the present disclosure is not limited herein.

[0042] The above detailed description does not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing a stable super-hydrophobic surface that is resistant to droplet impact, characterized in that: The specific steps include: S1. Scanning the surface of a metal sample using a delayed femtosecond laser pulse train creates a periodic micro-nanostructure on the surface. The periodic micro-nanostructure consists of alternating ablation grooves and ridge-like protrusions at the edges of the grooves. S2. Using a delayed femtosecond laser pulse train orthogonal to the scanning direction in step S1, the metal sample surface is scanned a second time, so that the ridge-like protrusion structure bends and extends from the center area of ​​the protrusion to both sides, forming a protruding waist-shaped microstructure; S3. Ultrasonic cleaning is performed on the surface of the metal sample treated in step S2, and then annealing is performed at 100-200° C. for 3-10 hours to obtain a stable superhydrophobic surface that is resistant to droplet impact.

2. The method for preparing a stable super-hydrophobic surface resistant to droplet impact according to claim 1, wherein: The longitudinal depth of the ablation groove is 10-100 μm, and the center distance between adjacent ablation grooves is 40-150 μm; the longitudinal height of the ridge-shaped protrusion structure is 10-60 μm.

3. The method for preparing a stable super-hydrophobic surface resistant to droplet impact according to claim 1, wherein: The bending and extending direction of the convex bent-waist microstructure is consistent with the scanning and advancing direction of the delayed femtosecond laser pulse train; The end of the raised bent microstructure is hook-shaped; The raised bent-waist microstructure covers the ablation groove area to form an arched suspended structure.

4. The method for preparing a stable super-hydrophobic surface resistant to droplet impact according to claim 3, wherein: The arched suspended structure and the sidewall surface of the ablation groove are covered with multi-scale nanostructures.

5. The method for preparing a stable super-hydrophobic surface resistant to droplet impact according to claim 1, wherein: The inclination angle between the raised bent-waist microstructure and the surface of the metal sample is 20-60°; the lateral span of the top of the raised bent-waist microstructure is 20-40 μm.

6. The method for preparing a stable super-hydrophobic surface resistant to droplet impact according to claim 3, wherein: The scanning direction of the delayed femtosecond laser pulse train is Z-shaped; along the scanning direction of the delayed femtosecond laser pulse train, a plurality of raised bent-waist microstructures are continuously distributed in space and present a wavy topological morphology.

7. The method for preparing a stable super-hydrophobic surface resistant to droplet impact according to claim 1, wherein: The total energy of the delayed femtosecond laser pulse train is 200-800 μJ, the laser pulse width is 20 fs-5 ps, the repetition frequency is 1-30 kHz, and the time delay between adjacent pulses is 5-100 ps.

8. The method for preparing a stable super-hydrophobic surface resistant to droplet impact according to claim 1, wherein: The speed of the line scanning is 0.1-3 mm / s, and the interval between the scanning lines is 40-100 μm.

9. The method for preparing a stable super-hydrophobic surface resistant to droplet impact according to claim 1, wherein: The delayed femtosecond laser pulse train is generated by a laser splitter delay component, which includes a coaxially arranged beam splitter and a reflector; the reflection / transmission ratio of the beam splitter is 3:7, 2:8, 4:6 or 5:

5.

10. The method for preparing a stable super-hydrophobic surface resistant to droplet impact according to claim 1, wherein: The ultrasonic cleaning time in step S3 is 10 to 30 minutes; the metal sample material is aluminum alloy, copper alloy or titanium alloy.

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