A method for preparing a stable superhydrophobic surface resistant to liquid droplet impact

Abstract

The application 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. The method comprises the following steps: performing line scanning on the surface of a metal sample by using a delayed femtosecond laser pulse train, and forming 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; performing secondary line scanning on the surface of the metal sample by using a delayed femtosecond laser pulse train which is orthogonal to the scanning direction in the previous step, so that the ridge-shaped protruding structures are curved and extended from the protruding center area to both sides to form protruding bent microstructures; and performing ultrasonic cleaning on the surface of the processed metal sample and then performing annealing treatment for 3-10 hours. The method has the advantages that a continuous twisted wave-shaped topological profile is constructed and formed, the breakthrough pressure of the air bag in the micro-nano structure is optimized in multiple factors, and the stability of the super-hydrophobic surface in the Cassie state for preventing liquid drop impact is significantly 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.

[0006] S1. A periodic micro-nano structure is formed on the surface of a metal sample by performing line scanning on the surface of the metal sample by using a delayed femtosecond laser pulse train; the periodic micro-nano structure is composed of ablation grooves and ridge-shaped protruding structures at the edges of the ablation grooves, which are arranged alternately.

[0007] S2. The ridge-shaped protruding structures are bent and extended from the center of the protrusions to both sides by performing secondary line scanning on the surface of the metal sample by using a delayed femtosecond laser pulse train which is perpendicular to the scanning direction in step S1, so that a protruding bent microstructure is formed.

[0008] S3. The surface of the metal sample after the treatment in step S2 is ultrasonically cleaned, and then is annealed at 100-200 DEG C for 3-10 hours, so that a stable super-hydrophobic surface resistant to liquid drop impact is obtained.

[0009] 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.

[0010] 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.

[0011] The end of the protruding bent microstructure is hook-shaped.

[0012] The protruding bent microstructure forms an arched overhanging structure above the ablation groove area.

[0013] Preferably, the arched overhanging structure and the sidewall surface of the ablation groove are covered with a multi-scale nanostructure.

[0014] 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.

[0015] 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, a plurality of protruding bent microstructures are continuously distributed in space and present a wave-shaped topological morphology.

[0016] Preferably, the total energy of the delayed femtosecond laser pulse train is 200-800 muJ, 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.

[0017] Preferably, the speed of the scribing scanning is 0.1-3 mm / s, and the interval between scanning lines is 40-100 mu m.

[0018] Preferably, the delayed femtosecond laser pulse train is generated by a laser light splitting delay component, and the laser light splitting delay component 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.

[0019] 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.

[0020] Compared with the prior art, the present application can achieve the following beneficial effects:

[0021] 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 method 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. The morphology 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 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 gamma|sin(Ψ)|.

[0022] In summary, the stable super-hydrophobic surface processed by the preparation method of the present application can realize the synergistic optimization of multiple elements break , and significantly improve the stability of the super-hydrophobic surface in the Cassie state resistant to liquid drop impact. BRIEF DESCRIPTION OF DRAWINGS

[0023] 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.

[0024] Figure 2 is a topographic map of the stable super-hydrophobic surface resistant to liquid drop impact processed by the delayed femtosecond laser pulse train according to an embodiment of the present application.

[0025] Figure 3A 3D micro-profile diagram of a stable super-hydrophobic surface against liquid droplet impact after processing by a delayed femtosecond laser pulse train is provided according to an embodiment of the present application.

[0026] Figure 4 A contact angle and a rolling angle experiment diagram of the stable super-hydrophobic surface against liquid droplet impact is provided according to an embodiment of the present application.

[0027] Figure 5 A dynamic frame diagram of a liquid droplet impacting a super-hydrophobic surface is provided according to an embodiment of the present application.

[0028] Figure 6 A comparison diagram of a super-hydrophobic surface in a high-speed water jet experiment is provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0030] In order to make the objectives, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not constitute a limitation on the present application.

[0031] In order to construct a groove-protrusion bent shape topological profile structure, the present application provides a method for preparing a stable super-hydrophobic surface against liquid droplet impact, which regulates the ablation removal behavior of a metal surface material by using a femtosecond laser pulse train processing method, and then constructs a topological profile with a groove and a protrusion bent shape combined with each other, realizes multi-element synergistic optimization of the airbag breakthrough pressure P break , and further significantly improves the stability of the super-hydrophobic surface in the Cassie state against liquid droplet impact. Specifically, the method comprises the following steps:

[0032] S1. A periodic micro-nano structure is formed on the surface of a metal sample by using a delayed femtosecond laser pulse train to perform line scanning on the surface of the metal sample;

[0033] The periodic micro-nano structure is composed of ablation grooves and ridge-shaped protrusion structures on the edges of the ablation grooves, which are arranged alternately;

[0034] Specifically, the metal sample material is aluminum alloy, copper alloy, titanium alloy, etc.

[0035] Specifically, 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.

[0036] S2. Adopting the time-delayed femtosecond laser pulse train which is orthogonal to the scanning direction in step S1, performing secondary line scanning on the metal sample surface, making the ridge-shaped protrusion structure bend and extend from the protrusion center area to both sides, forming a protrusion crouching-shaped microstructure;

[0037] The bending and extending direction of the protrusion crouching-shaped microstructure is consistent with the scanning forward direction of the time-delayed femtosecond laser pulse train; the end of the protrusion crouching-shaped microstructure is hook-shaped; the protrusion crouching-shaped microstructure covers the ablation groove area to form an arched overhanging structure, thereby reducing the opening size of the ablation groove;

[0038] The inclination angle between the protrusion crouching-shaped microstructure and the metal sample surface is 20-60°; the horizontal span of the top end of the protrusion crouching-shaped microstructure is 20-40 μm;

[0039] The arched overhanging structure (top and sidewall area of the protrusion crouching-shaped microstructure) and the ablation groove sidewall surface are covered with multi-scale nanostructures (nano-level textures such as small protrusions, particles or corrugations), which further enhance the super-hydrophobic performance;

[0040] The scanning direction of the time-delayed femtosecond laser pulse train is Z-shaped; with the scanning direction of the time-delayed femtosecond laser pulse train, multiple protrusion crouching-shaped microstructures are continuously distributed in space, and a wave-shaped topography is constructed as a whole;

[0041] S3. Ultrasonic cleaning is performed on the metal sample surface after step S2, and then annealing treatment is performed at 100-200℃ for 3-10 hours, and finally a stable super-hydrophobic surface resistant to liquid drop impact is obtained;

[0042] Specifically, the ultrasonic cleaning time is 10-30 minutes.

[0043] 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; the time delay between adjacent pulses in the time-delayed femtosecond laser pulse train is 5-100 ps;

[0044] The line scanning speed is 0.1-3 mm / s, and the interval between scanning lines is 40-100 μm;

[0045] The time-delayed femtosecond laser pulse train is generated by a laser light splitting and time-delaying assembly, which includes a beam splitting piece and a mirror arranged coaxially; the incident laser 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 formed in turn by the round-trip optical path between the mirror and the beam splitting piece, and finally the time-delayed femtosecond laser pulse train is output;

[0046] 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 ratios of the delayed femtosecond laser pulse train are 0.3, 0.49, 0.147, and 0.044, respectively.

[0047] In a specific embodiment, the delayed femtosecond laser pulse train can also be generated by a 4f pulse shaping system or a multi-pulse experimental device.

[0048] Example 1

[0049] This embodiment provides a method for preparing a stable superhydrophobic surface resistant to droplet impact, specifically including the following steps:

[0050] S1. A plano-convex lens with a focal length of 200mm is used to focus and irradiate the aluminum alloy surface using a delayed femtosecond laser pulse train. With the aluminum alloy sample position fixed, a computer-controlled three-dimensional moving platform scans and irradiates the sample surface to form a periodic micro-nano structure on the aluminum alloy surface. The periodic micro-nano structure is composed of alternating ablation grooves and ridge-like protrusions on the edges of the ablation grooves.

[0051] The delayed femtosecond laser pulse train is generated by a laser beam splitting delay component, which includes a beam splitter and a mirror arranged coaxially; the reflectivity / transmittance ratio of the beam splitter is 3:7.

[0052] 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 energies of the generated neutron pulses are set to E1=180 μJ, E2=294 μJ, E3=88.2 μJ, E4=26.5 μJ...;

[0053] The scanning speed is 1 mm / s, and the spacing between scan lines is 50 μm.

[0054] S2. Using a delayed femtosecond laser pulse train orthogonal to the scanning direction in step S1, a secondary scribing scan is performed on the surface of the aluminum alloy product, causing the ridge-like protrusion structure to bend and extend from the central region of the protrusion to both sides, ultimately forming a protruding, bent-waist-shaped topological structure on the sample surface, with a macroscopic morphology exhibiting a continuously twisted, wavy contour. Figure 2 (a), its prominent curved ridge-like apex has a negative curvature hook shape ( Figure 2 (b)), and the angle of curvature of the ridge is 30° ( Figure 3 Furthermore, the top of the microstructure and the sidewalls of the ablation groove are both covered with multi-scale nanostructures. Figure 2 (middle cd). For this structure, the parameters in Pbreak were quantified using 3D confocal microscopy, and the theoretical value is Pbreak≈6.1×10. 4Pa, the results are shown in Figure 3

[0055] S3. Then the sample surface was ultrasonically cleaned with deionized water for 20 min, and then placed in a vacuum drying oven at a temperature of 200℃ for annealing for 3h, to obtain a stable superhydrophobic surface resistant to liquid drop impact.

[0056] After the annealing treatment, the water droplet contact angle of the sample surface was measured to be 162°, and the rolling angle was 0.5°, as shown in Figure 4 Fig. 2a. In a single droplet bouncing experiment, the surface appeared to be droplet fragmentation at a droplet impact speed V = 6m / s, but no residual droplet pinning phenomenon occurred, and the superhydrophobic surface remained in the Cassie state, as shown in Figure 5 Fig. 2a. In addition, in the water flow impact experiment at a speed of V = 10.6m / s, it was observed that the surface droplets bounced back and no droplet pinning phenomenon occurred, and the superhydrophobic surface remained in a good Cassie state, as shown in Figure 6 Fig. 2b.

[0057] Example 2

[0058] The present embodiment provides a method for preparing a stable superhydrophobic surface resistant to liquid drop impact, specifically comprising the following steps:

[0059] S1. A plano-convex lens with a focal length of 200mm was used to irradiate the surface of an aluminum alloy with a delayed femtosecond laser pulse train. The sample was fixed, and a computer-controlled three-dimensional moving platform was used to scan and irradiate the sample surface, forming a periodic micro-nano structure on the aluminum alloy surface. The periodic micro-nano structure was composed of alternatingly arranged ablation grooves and ridge-shaped protrusions on the edges of the ablation grooves.

[0060] The total laser energy of the delayed femtosecond laser pulse train was 600μJ, the pulse width was 40fs, the time delay between adjacent pulses was 60ps, and the sub-pulse energies in the generated pulse train were set to E1 = 180μJ, E2 = 294μJ, E3 = 88.2μJ, E4 = 26.5μJ, etc.

[0061] The scanning speed was 1mm / s, and the interval between the scanning lines was 40μm.

[0062] Steps S2-S3 are the same as in Example 1.

[0063] After the annealing treatment, the water droplet contact angle of the sample surface was measured to be 160°, and the rolling angle was 1°, as shown in Figure 4 Fig. 2b. In a single droplet bouncing experiment, the surface appeared to be droplet fragmentation at a droplet impact speed V = 6m / s, but no residual droplet pinning phenomenon occurred, and the superhydrophobic surface remained in the Cassie state, as shown in Figure 5 Fig. 2b.​

[0064] Example 3

[0065] The embodiment provides a method for preparing a stable super-hydrophobic surface against liquid drop impact, and specifically comprises the following steps:

[0066] S1. A plano-convex lens with a focal length of 200 mm is used to irradiate an aluminum alloy surface by focusing a delayed femtosecond laser pulse train. In the case of fixing the position of the aluminum alloy sample, 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 ablation grooves and ridge-shaped protruding structures on the edges of the ablation grooves.

[0067] The total laser energy of the delayed femtosecond laser pulse train is 400 μJ, the pulse width is 40 fs, the time delay between adjacent pulses is 20 ps, and 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.

[0068] The scanning speed is 1 mm / s, and the interval between scanning lines is 40 μm.

[0069] Steps S2-S3 are the same as in Example 1.

[0070] After the annealing treatment is completed, the water drop contact angle of the sample surface is measured to be 158°, and the rolling angle is 1.5°, as shown in FIG. c. In a single liquid drop bouncing experiment, the surface appears to be liquid drop fragmentation at a liquid drop impact speed V=6 m / s, but no residual liquid drop pinning phenomenon occurs, and the super-hydrophobic surface water remains in a Cassie state, as shown in FIG. c. Figure 4 Figure 5

[0071] Example 4

[0072] The embodiment provides a method for preparing a stable super-hydrophobic surface against liquid drop impact, and specifically comprises the following steps:

[0073] S1. A plano-convex lens with a focal length of 200 mm is used to irradiate an aluminum alloy surface by focusing a delayed femtosecond laser pulse train. In the case of fixing the position of the aluminum alloy sample, 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 ablation grooves and ridge-shaped protruding structures on the edges of the ablation grooves.

[0074] The delayed femtosecond laser pulse train is generated by a laser light splitting and delaying assembly, and the laser light splitting and delaying assembly comprises a beam splitting piece and a mirror arranged coaxially, and the reflectance / transmittance ratio of the beam splitting piece is 5:5.

[0075] ​​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 energy of the generated sub-pulse is set as E1=300 μJ, E2=150 μJ, E3=75 μJ, E4=37.5 μJ, and so on.

[0076] The scanning speed is 1 mm / s, and the interval between scanning lines is 50 μm.

[0077] Steps S2-S3 are the same as in Example 1.

[0078] After the annealing treatment, the water droplet contact angle on the surface of the sample is measured to be 158°, and the rolling angle is 3°, as shown in FIG. 2d. Figure 4 In a single droplet bouncing experiment, the surface exhibits droplet fragmentation at a droplet impact speed V=6 m / s, but no residual droplet pinning phenomenon occurs, and the superhydrophobic surface remains in a Cassie state, as shown in FIG. 2d. Figure 5

[0079] The key technical point and advantage of the present application is that: by utilizing the strong thermodynamic coupling characteristics in the process of delayed femtosecond laser pulse train and material interaction, the high-temperature evaporation and plasma sputtering phenomena in the ablation process are suppressed, so that the material in the groove part 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, the bending of the ridge structure suspends and bends above the groove, so that 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, the tip of the air bag's inner wall side bending structure is perpendicular downward, similar to a reentrant structure, so that the liquid surface tension maximizes the component resisting the droplet impact direction. 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 droplets and water flow on the surface air bag, thereby significantly improving the thermodynamic stability of the superhydrophobic surface. At the same time, the multi-level nanostructure constructed 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 it exhibits complete rebounding characteristics under the impact of a liquid droplet at V=6 m / s, and can withstand the impact of a water jet at a speed of up to V=10.6 m / s, which proves that this surface has excellent Cassie state anti-droplet impact stability and at the same time has ultra-low solid-liquid interface adhesion characteristics.

[0080] ​It should be understood that the various forms of flow shown above can be used to reorder, add, or remove steps. For example, the steps recited in the present disclosure can be performed in parallel, in series, or in a different order, as long as the desired results of the present disclosure are achieved, which is not limited herein.

[0081] The specific embodiments described above are not to be taken as limiting the scope of the application. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives of the specific embodiments described above can be made without departing from the spirit and scope of the application. Any such modifications, equivalents, alternatives and combinations, therefore, are expressly included within the scope of the application.

Claims

1. A method of making a stable superhydrophobic surface resistant to liquid droplet impact, characterized by: Specifically comprising 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 at the edges of the ablation grooves arranged alternately; 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 protrusions to both sides to form protruding bent microstructures; the bending and extending direction of the protruding bent microstructures 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; the inclination angle of the protruding bent microstructure with the surface of the metal sample is 20-60°; S3. performing ultrasonic cleaning on the surface of the metal sample processed in step S2 for 10-30 minutes, and then performing annealing treatment at 100-200°C for 3-10 hours to obtain a stable super-hydrophobic surface resistant to liquid drop impact.

2. The method of claim 1, wherein the method comprises: The longitudinal depth of the ablation groove is 10-100μm, and the center distance between adjacent ablation grooves is 40-150μm; the longitudinal height of the ridge-shaped protruding structure is 10-60μm.

3. The method of claim 1, wherein the method further comprises: The arched overhanging structure and the sidewall surface of the ablation groove are covered with multi-scale nano structures.

4. The method of claim 1, wherein the method further comprises: The transverse span of the top end of the protruding bent microstructure is 20-40μm.

5. The method of claim 1, wherein: The scanning direction of the delayed femtosecond laser pulse train is Z-shaped; with the scanning direction of the delayed femtosecond laser pulse train, a plurality of protruding bent microstructures are continuously distributed in space and present a wavy topological morphology.

6. The method of claim 1, wherein: The total energy of the delayed femtosecond laser pulse train is 200-800μJ, the laser pulse width is 20fs-5ps, the repetition frequency is 1-30kHz, and the time delay between adjacent pulses is 5-100ps.

7. The method of claim 1, wherein the method further comprises: The speed of the line scanning is 0.1-3mm / s, and the interval between scanning lines is 40-100μm.

8. The method of claim 1, wherein the method further comprises: The delayed femtosecond laser pulse train is generated by a laser light splitting and delaying assembly, and the laser light splitting and delaying assembly 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.

9. The method of claim 1, wherein: The metal sample material is an aluminum alloy, a copper alloy or a titanium alloy.

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