Stress regulation type surface wettability switching thin film as well as preparation method and application thereof

Abstract

The invention belongs to the field of micro-nano processing, and particularly relates to a stress regulation type surface wettability switching thin film and a preparation method and application thereof. The thin film is prepared from an elastic material; the thin film comprises a plurality of micro-column units which are generated after annular cutting from any one side or two sides in the thickness direction and are connected with the root of the main body part of the thin film. Hydrophobic modification layers are arranged on the top and the side surface of the micro-column unit; a hydrophilic modified layer is arranged on the surface of the main body part except the micro-column unit in the film; when the thin film is stretched by external force parallel to the thin film, the thin film is extended, and each micro-column unit protrudes out of the main body; at the moment, the surface of the film is in a super-hydrophobic state. When the thin film recovers to a natural state, each micro-column unit is flush with the main body part or is in a concave state; at the moment, the surface of the film is in a super-hydrophilic state. According to the invention, the problems of complex operation, high energy consumption, insufficient durability, lack of expandability and universality and the like of the existing material with adjustable humidity are solved.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano processing, and specifically relates to a stress-regulated surface wettability switching film and a preparation method and application thereof. Background Art

[0002] Wettability controllable material is a new type of material that can regulate the wettability of the material surface through technical means. The existing surface property switching methods of wettability controllable materials include temperature control method, light control method, and electric field control method. Among them, temperature-controlled wettability switching materials refer to materials that can adjust the surface wettability through temperature changes to achieve switching between superhydrophilic and superhydrophobic. Common materials include thermosensitive polymers, polyurethanes, etc. Light-controlled wettability switching materials refer to materials that can use lasers such as ultraviolet light or visible light to irradiate the surface and activate chemical or physical reactions on the surface to adjust the wettability. For example, some special materials can change the surface structure through photosensitive chemicals, thereby achieving the effect of wettability regulation. Electric field-controlled wettability switching materials refer to materials that can change the surface structure by applying an electric field, thereby adjusting the wettability. For example, some materials can use electrostatic force to displace the surface micro-nano structure and change the wettability of the material surface.

[0003] However, the existing wettability switching materials still have many defects and limited practical value. Among them, temperature-controlled wettability switching materials have the characteristics of slow response speed, high energy consumption and high temperature control precision. For example, it takes a long time for temperature changes to achieve the expected effect, and it is difficult to achieve rapid switching; temperature control usually requires heating or cooling equipment, which consumes a lot of energy and reduces the efficiency of the system; the temperature needs to be precisely controlled during wettability switching, otherwise it may affect the performance of the material or cause material aging. Light-controlled wettability switching materials have the disadvantages of relying on external light sources, being sensitive to ambient light and having fast material loss. For example, when using, they need to be matched with a specific light source, and the light intensity and wavelength need to be precisely controlled; in practical applications, the interference of ambient light may cause unstable wettability switching; long-term illumination may cause material degradation or performance decline, limiting its long-term application. Electric field-controlled wettability switching materials have the disadvantages of high complexity, electric field strength limitation and limited scope of application. For example, an additional electric field control system is required during the application process, which is complicated to operate; an excessively strong electric field may damage the material and affect its sustainability; it can only be applied on the surface of materials with a certain conductivity, limiting its scope of application, etc.

[0004] In summary, existing wettability controllable materials generally have problems such as complex operation, high energy consumption, insufficient durability, lack of scalability and universality, and slow response speed. Summary of the invention

[0005] In order to solve the problem that existing wettability controllable materials have many shortcomings and limited practical value, the present invention provides a stress-controlled surface wettability switching film and a preparation method and application thereof.

[0006] The technical solution provided by the present invention is:

[0007] A stress-regulated surface wettability switching film is made of elastic material. The film contains a plurality of micro-column units connected to the root of the main part of the film after circular cutting from any one or both sides along the thickness direction. The top and side of the micro-column unit are provided with a hydrophobic modification layer; the surface of the main part of the film except the micro-column unit is provided with a hydrophilic modification layer.

[0008] When the film is stretched by an external force parallel to the film, each micro-column unit protrudes from the main body; at this time, the film surface is super hydrophobic. Conversely, when the external force is removed and the film returns to its natural state, each micro-column unit is flush with the main body or is concave; at this time, the film surface is super hydrophilic.

[0009] As a further improvement of the present invention, the maximum cutting depth of the microcolumn unit is equal to 40%-80% of the film thickness.

[0010] As a further improvement of the present invention, a portion of a specified thickness at the top of the cut microcolumn unit is first removed, and then a hydrophobic modification layer is formed, so that the film is flush with the main body or in a concave state when it returns to its natural state.

[0011] As a further improvement of the present invention, the film is made of silicone, rubber, PDMS or other elastic polymers.

[0012] The present invention also includes a method for preparing a stress-regulated surface wettability switching film, which comprises:

[0013] (1) The elastic material film is uniformly stretched to a maximum elastic deformation state, and subsequent processes are performed in the stretched state.

[0014] (2) A femtosecond laser is used to scan a target area on the film surface to form a roughened surface.

[0015] (3) Using any hydrophilic modifier to modify the surface of the film to form a hydrophilic modified layer.

[0016] (4) A mask layer that can be specifically removed is formed on the surface of the hydrophilic modified layer of the film.

[0017] (5) A femtosecond laser is used to perform a circular scan of the target area according to a preset shape, depth, and space, thereby cutting out a plurality of microcolumn units connected to the root of the main part of the film.

[0018] (6) Scanning the top of the formed microcolumn unit by femtosecond laser to remove the mask layer, the hydrophilic modification layer and the thin film material of a specified thickness, and forming a roughened surface.

[0019] (7) using any hydrophobic modifier to perform surface modification on one side of the film containing the microcolumn units to form a hydrophobic modified layer;

[0020] (8) Using a specified means to specifically remove the mask layer and peel off the hydrophobic modified layer thereon; then restoring the film to its natural state, thereby obtaining the desired product.

[0021] As a further improvement of the present invention, in steps (2) and (6), a mesh groove with a depth of 10-20 μm and a spacing of 20-50 μm is processed by femtosecond laser to form the desired roughened surface.

[0022] As a further improvement of the present invention, a PET film is used as a mask layer in step (4), and in step (8), a mechanical stripping or solvent dissolution method is used to specifically remove the mask layer.

[0023] As a further improvement of the present invention, in step (3), the film is immersed in a hydrophilic reagent solution to form a hydrophilic modified layer. In step (7), hydrophobic silica particles are sprayed onto the surface of the film to form a hydrophobic modified layer.

[0024] The present invention also includes an application of the aforementioned stress-regulated surface wettability switching film in liquid phase component separation. After unfolding a plurality of stress-regulated surface wettability switching films, they are immersed in a suspension containing water phase and oil phase components to adsorb the water phase components contained therein; then the stress-regulated surface wettability switching film is taken out and horizontally stretched to a super-hydrophobic state, thereby allowing the adsorbed water phase components to slide off the film; and the above process is repeated to achieve component separation in the suspension.

[0025] The present invention also includes a liquid phase component separator, which is used to separate the aqueous phase material and the oil phase material in the suspension. The liquid phase component separator includes a movable support and a plurality of stress-regulated surface wettability switching films as described above. The movable support has a switchable natural state and an expanded state; the stress-regulated surface wettability switching film is installed on the movable support and satisfies: when the movable support is in the natural state, each stress-regulated surface wettability switching film is unfolded and presents a super-hydrophilic state; when the movable support is in the expanded state, each stress-regulated surface wettability switching film is stretched and presents a super-hydrophobic state.

[0026] The present invention also includes an application of the aforementioned stress-regulated surface wettability switching film in a controllable chemical reaction. The stress-regulated surface wettability switching film is used as a container for the reaction between liquid-phase chemicals, and the chemical reaction between the liquid-phase chemicals is regulated by switching the wettability state of the film.

[0027] The technical solution provided by the present invention has the following beneficial effects:

[0028] The present invention combines the surface microstructure processing of femtosecond laser with the surface modification process of materials, and then uses elastic materials to design a new material that can achieve reversible regulation of the surface wettability of the film under the influence of stress. Through the synergistic effect of the surface microstructure and chemical coating of the material in the stretched state and the relaxed state, the reversible wettability regulation of the material from super-hydrophilic to super-hydrophobic is achieved. This dynamic regulation characteristic has broad application prospects in the fields of flexible sensors, smart surfaces, microfluidic devices, etc. It can also be applied to multiple fields such as intelligent control of liquid flow and distribution, adjustable surface optical properties, dynamic information display, anti-fouling and waterproof surface design, droplet capture and release devices, etc., showing significant cross-domain adaptability.

[0029] The surface wettability regulating material designed by the present invention switches states through stress, thus effectively overcoming many defects of traditional temperature regulation, light regulation, and electric field regulation materials in terms of energy consumption, response characteristics, and anti-interference characteristics. The product provided by the present invention has a simple manufacturing process and low production cost, thus having higher practical value.

[0030] The product provided by the present invention effectively improves the accuracy and uniformity of microstructure preparation through stress-induced microstructure morphology changes. After multiple stretching and relaxation cycles, the silicone surface structure and functional coating of the product can still maintain stable wettability switching performance, reflecting excellent durability and reliability. This performance advantage lays the foundation for the long-term use of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of the stress-regulated surface wettability switching film in a relaxed state provided in Example 1 of the present invention.

[0032] Figure 2 This is a schematic diagram of the structure of the stress-regulated surface wettability switching film under tension provided in Example 1 of the present invention.

[0033] Figure 3 This is a schematic diagram of the cross-sectional structure of a stress-regulated surface wettability switching film in which the micro-column units provided in Example 1 of the present invention can protrude to both sides.

[0034] Figure 4This is a flow chart of the method for preparing a stress-regulated surface wettability switching film provided in Example 2 of the present invention.

[0035] Figure 5 This is a schematic diagram of the structure of the liquid component separator provided in Example 3 of the present invention.

[0036] Figure 6 To verify the micromorphology and line profile analysis of the samples in the tensile state in the experiment.

[0037] Figure 7 To verify the microstructure and line profile analysis of the samples in the relaxed state in the experiment.

[0038] Figure 8 To verify the micromorphology and line profile analysis of the sample in the experiment after 20 stretching cycles and then stretching again.

[0039] Fig. 9 To verify the changing curves of contact angle and rolling angle on the sample surface under different strain conditions in the experiment. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] Example 1

[0042] The present embodiment provides a stress-regulated surface wettability switching film, which is made of elastic material. The film contains a plurality of micro-column units connected to the root of the main part of the film after circular cutting from any one or both sides along the thickness direction. The top and side of the micro-column unit are provided with a hydrophobic modification layer; the surface of the main part of the film other than the micro-column unit is provided with a hydrophilic modification layer. In practical applications, the hydrophobic modification layer and the hydrophilic modification layer can be obtained by surface modification of the original film material by physical or chemical means.

[0043] In the natural state, Figure 1 As shown, each micro-column unit in the film of this embodiment is tightly "embedded" into the main part, and the height of each micro-column unit is flush with the main part or slightly lower than the main part in a concave state. Therefore, when the liquid contacts the surface of the film material, the droplet mainly contacts the main part of the film. Since the surface of the main part contains a hydrophilic modification layer and forms a mesh structure, the film mainly exhibits a super-hydrophilic state under this condition.

[0044] Furthermore, after stress analysis of the thin film material with this specific structure and material surface characteristics, it can be found that: when this type of film is subjected to tensile stress along the water surface, the part other than the micro-column units forms a complete grid-like main body, which will undergo elastic deformation and be gradually stretched under the tensile action of the external force. In this process, the area of ​​the main body gradually expands and the thickness gradually becomes thinner. As for the independent micro-column units "embedded" in the main body, since they are basically not affected by external stress except for the roots, their shapes will remain in their original state. Therefore, if Figure 2 As shown in the figure, the external force stretching causes the main part to become thinner and causes each micro-column unit to protrude upward along the main part. In this state, when the liquid contacts the surface of the film material, the droplet mainly contacts the top of the micro-column unit protruding from the film surface. Since the top of the main unit contains a hydrophobic modification layer, the film mainly exhibits a super-hydrophobic state under this condition.

[0045] In addition, since the film provided in this embodiment is made of elastic material, such as silicone, rubber, PDMS or other elastic polymers, the deformation state of the main part within the elastic limit can be restored. When the tensile stress acting on the film is removed, the main part of the film will shrink and thicken, so that each micro-column unit is re-embedded into the interior of the main part. At this time, the surface of the film is restored to a super-hydrophilic state.

[0046] In summary, the film material provided in this embodiment can undergo elastic deformation under stress, and combined with the surface property differences of different structures after deformation, the wettability of the film surface can be freely switched between hydrophilicity and hydrophobicity. That is, the film material provided in this embodiment is a stress-regulated surface wettability film.

[0047] By analyzing the inherent principle of the stress-regulated surface wettability switching performance generated by the film material provided in this embodiment, it can be found that: after the material is divided, the film material includes two parts, the main body and the microcolumn unit, which are only connected at the root; and the surfaces of these two parts in the film show different wettability. When the film is subjected to tensile stress, the main body parts connected to each other will undergo obvious strain, while the strains of the independent microcolumn units are relatively slight. Based on the characteristic that the elastic film will become thinner under tension, the relative height between the main body part and the microcolumn unit of the film of this embodiment will change with the magnitude of the tensile stress; when the microcolumn unit is higher than the main body, the film surface is hydrophobic corresponding to the top of the microcolumn unit, and when the microcolumn unit is flush with the main body or shorter, the film surface is hydrophilic corresponding to the main body.

[0048] Based on the working principle described above, it can be known that the cutting depth of the microcolumn unit in the stress-regulated surface wettability switching film provided in this embodiment has an impact on the product performance. In practical applications, when the cutting depth of the microcolumn unit part is too shallow, the change in the relative height difference between the microcolumn unit and the main part when the film is stretched is not obvious, and it is difficult to achieve a good wettability switching effect. When the cutting depth of the microcolumn unit part is too deep, the difference in the strain effect between the main part and the microcolumn unit part when the film is stretched may cause the combined part of the roots of the two to tear, thereby causing the wettability regulation characteristics of the film to fail. Therefore, in a more optimized solution, the cutting depth of the microcolumn unit should be equal to 40%-80% of the overall thickness of the film.

[0049] The stress-regulated surface wettability switching film provided in this embodiment is formed by partially cutting a completed elastic film in an annular manner to form two parts, a main body and a micro-column unit, which are adhered at the root. Under such process conditions, it is difficult to achieve the technical effect that the height of the micro-column unit is lower than the main body. In view of this situation, this embodiment first removes a portion of a specified thickness at the top of the cut micro-column unit, and then forms a hydrophobic modification layer, so that the film is concave relative to the main body when it returns to its natural state.

[0050] In addition, it is necessary to further explain that the above mainly introduces the solution of cutting along one side of the film, thereby obtaining a solution in which the microcolumn unit "pops out" from the corresponding side under the stretching state, thereby changing the wettability of the film surface on that side. Figure 3 As shown, in other more optimized solutions, the film can also be cut simultaneously along both sides, leaving the middle part of the micro-column unit connected to the main part of the film, and the micro-column units on both sides and both sides of the main part of the film are surface modified. Under this film structure, when the film is stretched, the embedded micro-column units will pop out from both sides at the same time, thereby changing the wettability of the surfaces on both sides of the film.

[0051] Example 1

[0052] This embodiment provides a method for preparing a stress-regulated surface wettability switching film, which is used to prepare the stress-regulated surface wettability switching film in Example 1. Specifically, the preparation method of this embodiment combines femtosecond laser processing technology and functional surface coating treatment, so that the surface wettability of the elastic film can be reversibly switched between stretched and relaxed states. Figure 4 As shown, the preparation method provided in this embodiment includes:

[0053] (1) The elastic material film is uniformly stretched to a maximum elastic deformation state, and subsequent processes are performed in the stretched state.

[0054] In this embodiment, silicone is selected as the elastic film. Of course, in practical applications, in addition to silicone, other materials that can withstand stretching and show obvious thickness changes during stretching can be used as the required elastic base material. The specific material can be selected according to actual needs. Moreover, the thickness of the silicone film can also be adjusted according to the actual application requirements to meet different functional requirements. During the processing, in this embodiment, the elastic film can be clamped along the edge by a holding device, and then each clamping device can be expanded outward synchronously to stretch the elastic film in the middle. In this embodiment, in order to ensure better processing effects and avoid damage to the material, the film should be stretched to the maximum elastic deformation state.

[0055] (2) A femtosecond laser is used to scan a target area on the film surface to form a roughened surface.

[0056] According to the needs of the application scenario, this embodiment can choose to process the entire area of ​​the surface of the thin film material so that it all has the characteristic of switchable wettability, or it can choose to process a local area of ​​the surface of the thin film material and make the treated local area have the characteristic of switchable wettability.

[0057] Among them, the first femtosecond laser scanning treatment on the surface of the film material is to obtain a roughened interface that allows the hydrophilic modified layer to adhere more stably, which can make the final film have a longer service life in frequent "stretching-recovery" cycles and is not prone to hydrophilic failure. Specifically, this embodiment chooses to form the required roughened surface by processing a regular groove structure. For example, a mesh groove with a depth of 10-20μm and a spacing of 20-50μm is processed by femtosecond laser to form the required roughened surface.

[0058] (3) Using any hydrophilic modifier to modify the surface of the film to form a hydrophilic modified layer.

[0059] Specifically, in this embodiment, the surface roughened silicone film in a stretched state is immersed in a hydrophilic reagent solution for chemical modification, so that the inside of the groove and the surface of the substrate are super-hydrophilic, thereby obtaining the desired hydrophilic modified layer. Of course, in practical applications, the hydrophilic reagent can be selected according to actual needs, and even reagents with high surface energy can be used, or the surface of the silicone can be hydrophilized by surface treatment technology.

[0060] (4) A mask layer that can be specifically removed is formed on the surface of the hydrophilic modified layer of the film.

[0061] In this embodiment, a PET film with a thickness of 10-20 μm is covered on the surface of the super-hydrophilic substrate as a mask layer. The mask layer can be used for the selective "growth" of subsequent micro-column units and for hydrophobic modification of the material surface at specific locations.

[0062] It should be noted that the mask layer in this embodiment should be made of a material that can be specifically removed. For example, when a PET film is selected as the mask layer, the PET film can be directly peeled off to directionally remove the material. In other embodiments, a material that can be specifically removed by chemical solvents or light, such as photoresist, can also be selected to form the mask layer. In practical applications, the mask material can be selected to be no more than 100 microns thick, insoluble in water, and non-reactive with silica gel to ensure accuracy and stability during processing.

[0063] (5) A femtosecond laser is used to perform a circular scan of the target area according to a preset shape, depth, and space, thereby cutting out a plurality of microcolumn units connected to the root of the main part of the film.

[0064] This step is mainly used to perform annular cutting of the film material to form the required micro-column unit. As we all know, before the annular femtosecond laser scans in an annular shape, the film is a whole and is subjected to tensile stress and undergoes overall strain. After the femtosecond laser processes an annular groove with a certain depth on the film, the elastic material in the middle of the annular groove is out of contact with the elastic material on the periphery. At this time, most of the elastic material on the periphery is still deformed by the tensile stress, while the elastic material in the middle is no longer affected by the tensile stress and returns to its natural state (i.e., shrinks and thickens). From a macroscopic point of view, it is equivalent to "growing" an upwardly protruding micro-column unit from the middle of the film.

[0065] Finally, this embodiment cuts annular grooves of corresponding shapes according to the shapes of the required micro-column units. For example, when a circular column is required, a circular groove is cut, but when a square column is required, a square groove is cut. And a micro-column array composed of multiple micro-column units is cut in combination with the spatial distribution of the required micro-column units. Among them, the height (depth of the annular groove) of the processed micro-column unit is mainly regulated by adjusting the laser power and the number of scans during the femtosecond laser processing. In actual application, processing parameters such as laser power, scanning speed, micro-column spacing, number of scans, and micro-column diameter can be adjusted according to actual needs to optimize the surface structure.

[0066] (6) Scanning the top of the formed microcolumn unit by femtosecond laser to remove the mask layer, the hydrophilic modification layer and the thin film material of a specified thickness, and forming a roughened surface.

[0067] In order from bottom to top, each microcolumn unit cut out in the above step includes a matrix composed of the original elastic material, a hydrophilic modification layer generated in step (3), and a mask layer generated in step (4). In this step, the top of each processed microcolumn unit is scanned by a femtosecond laser, and the mask layer and the hydrophilic modification layer can be removed respectively, so as to perform hydrophobic modification on the microcolumn unit in the subsequent step. In addition, it should be emphasized that in order to make the thickness of the area corresponding to the microcolumn unit of the film flush with other parts or present a concave structure when the external force is removed, this step will continue to scan downward after removing the hydrophilic modification layer during scanning to remove the elastic material of the specified thickness. In addition, in order to ensure that a more solid hydrophobic modification layer can be formed on the surface of the microcolumn unit in the subsequent steps, the top of the microcolumn unit of this embodiment also needs to be roughened. The roughening treatment of the top of the microcolumn unit is still achieved by cross-scanning the femtosecond laser to form a gridded microgroove.

[0068] (7) Using any hydrophobic modifier to perform surface modification on one side of the film containing the microcolumn units to form a hydrophobic modified layer.

[0069] In this step, a spraying device is used to evenly spray the hydrophobic silica particles onto the surface of the microcolumn array composed of microcolumn units, especially onto the top structure, thereby achieving super-hydrophobic performance through the self-assembly effect of the particles. It should be noted that in this embodiment, when spraying the hydrophobic modifier onto the microcolumn unit, the hydrophobic modifier will inevitably be sprayed onto the corresponding area of ​​the main body, and this area is currently covered by the mask layer, that is, the hydrophobic modification layer will be formed on the mask layer of the main body, as well as on the surface of the elastic material of the microcolumn unit. Of course, in the scheme of this embodiment, the hydrophobic agent can be reasonably selected according to actual needs, and even low surface energy agents can be used, or the surface of the silica gel can be made hydrophobic by surface treatment technology.

[0070] (8) Using a specified means to specifically remove the mask layer and peel off the hydrophobic modified layer thereon; then restoring the film to its natural state, thereby obtaining the desired product.

[0071] In step (7), the hydrophobic modified material covers the main part of the film. This step removes the mask layer and then simultaneously peels off the hydrophobic modified layer above the mask layer to expose the hydrophilic modified layer below, so that the surface of the micro-column unit of the film material finally obtained is covered with the hydrophobic modified layer, and the main part other than the micro-column unit is covered with the hydrophilic modified layer. Among them, since the mask layer used in this embodiment is a PET film, the mask layer can be removed by mechanical peeling. In other embodiments, when the mask layer is made of other materials, the corresponding mask layer material can be specifically removed by methods such as light, chemical reagents and solvents.

[0072] After completing the structural design and surface modification of the above materials, the stress applied to the film material is removed, and a new material can be obtained whose overall appearance is similar to that of a conventional film, but which can reversibly adjust the wettability of the material surface after being subjected to tensile stress.

[0073] Example 3

[0074] The thin film material with reversible wettability switching performance provided in Examples 1 and 2 has broad application prospects in the fields of flexible sensors, smart surfaces, microfluidic devices, etc. This embodiment develops the functions of the product and provides two typical application scenarios. Specifically including: (1) Application of a stress-regulated surface wettability switching film as described above in liquid phase component separation. (2) Application of a stress-regulated surface wettability switching film as described above in controllable chemical reactions. Among them, the former refers to unfolding multiple stress-regulated surface wettability switching films and immersing them in a suspension containing water phase and oil phase components, and using the hydrophilic properties of the film in its natural state to adsorb the water phase components contained therein. Then take out the stress-regulated surface wettability switching film and stretch it horizontally to a super-hydrophobic state, so that the adsorbed water phase components slide off the film; repeat the above process to achieve component separation in the suspension. In this application, the film is used as a specific extraction material for water phase substances in the suspension, and can replace traditional complex and energy-intensive material purification processes such as chromatography and distillation. The latter refers to using a stress-regulated surface wettability switching film as a container for reactions between liquid-phase chemicals, and regulating the chemical reactions between liquid-phase chemicals by switching the wettability state of the film.

[0075] In combination with the first application mentioned above, this embodiment further provides a liquid phase component separator, which is used to separate the water phase material and the oil phase material in the suspension. Figure 5 As shown, the liquid phase component separator includes a movable support and a plurality of stress-regulated surface wettability switching films as described above. The movable support has a switchable natural state and an expanded state; the stress-regulated surface wettability switching films are installed on the movable support and meet the following conditions: when the movable support is in the natural state, each stress-regulated surface wettability switching film is unfolded and presents a super-hydrophilic state; when the movable support is in the expanded state, each stress-regulated surface wettability switching film is stretched and presents a super-hydrophobic state.

[0076] Verification experiment

[0077] In order to verify the stress-regulated surface wettability switching film provided by the present invention, technicians used silica gel materials and a femtosecond laser processing system to prepare corresponding samples and tested the performance of the film.

[0078] 1. Product Manufacturing

[0079] (1) Four-axis stretching and groove processing

[0080] The silicone substrate is mounted on a four-axis stretching device and uniform tensile stress is applied along four directions to cause uniform deformation on the silicone surface.

[0081] A femtosecond laser is used to process regular groove microstructures on a stretched silicone substrate. The groove depth and spacing can be adjusted according to demand. The generally recommended depth is 10-20μm and the spacing is 20-50μm.

[0082] (2) Preparation of super-hydrophilic substrate

[0083] The silicone substrate processed in a stretched state is immersed in a hydrophilic reagent solution and chemically modified to make the inside of the groove and the surface of the substrate super hydrophilic.

[0084] (3) Mask coverage

[0085] A PET film with a thickness of 10-20 μm is covered on the surface of the super-hydrophilic substrate as a mask layer for the subsequent selective growth of micro-column structures.

[0086] (4) Self-growth and modification of micropillar arrays

[0087] A femtosecond laser is used to scan the stretched silicone surface along a circular path, and the synergistic effect of laser processing and stress is used to form a regular microcolumn array on the silicone surface.

[0088] Continuing to scan out fine groove structures on the top of the micro-pillars can not only accurately remove the mask layer, but also enhance the adhesion effect of the hydrophobic coating.

[0089] (5) Formation of hydrophobic coating

[0090] The hydrophobic silica particles are evenly sprayed onto the surface of the microcolumn array, especially the top structure, using a spraying device to achieve super-hydrophobic properties through the self-assembly effect of the particles.

[0091] (6) Mask removal and wettability switching

[0092] The PET film mask is removed by mechanical stripping or solvent dissolution, leaving the microcolumn structure and the bottom hydrophilic substrate.

[0093] 2. Analysis of performance morphology and circulation effect

[0094] In this experiment, the manufactured film samples were stretched and relaxed multiple times, and the surface morphology of the film in different states was observed through a confocal microscope; the height changes in different areas of the film surface were measured to complete the line profile analysis of the longitudinal section of the film. After the three-dimensional morphology of the silicone material under different strain states was photographed and measured and analyzed, this analysis result provided a detailed structural background for subsequent wettability tests, helping technicians understand how the surface microstructure changes the wettability as the deformation changes.

[0095] Among them, the microscopic morphology and line profile analysis diagram of the film material under tension are as follows: Figure 6 The microstructure and line profile analysis diagrams in the relaxed state are shown in Figure 7 After 20 stretching cycles, the microscopic morphology and line profile analysis of the film material in the stretched state are shown in Figure 8 shown.

[0096] contrast Figure 6 and Figure 7 It can be found that: in the stretched state, the height of the micropillars increases significantly, showing a clear periodic arrangement, which helps to form the surface superhydrophobic properties. In the relaxed state, the micropillars are partially embedded in the substrate, and the surface tends to be flat, resulting in superhydrophilic properties. Further comparison Figure 6 and Figure 8 It can be found that even after 20 stretching cycles, the microcolumn morphology and profile height in the film material prepared in this experiment did not show obvious changes, which shows that the microstructure has excellent stability and durability under multiple mechanical loadings.

[0097] 3. Wettability Control Effect

[0098] During the stretching cycle, this experiment further measured the contact angle and rolling angle of the sample surface under different strains, and then explored the specific effect of stress on the wettability of the film material surface. The change curves of the contact angle and rolling angle of the sample surface under different strain conditions drawn according to the experimental results are shown in the figure below: Fig. 9 shown.

[0099] analyze Fig. 9 From the experimental data, it can be found that when the film is stretched less than 20 mm, the silicone surface is in a superhydrophilic state, and a droplet added to the surface will spread rapidly, showing a contact angle close to 0°; this is because when the stretch is small, the microcolumns have not yet appeared, and the surface properties are dominated by the superhydrophilicity of the substrate.

[0100] When stretched over 20 mm, the micro-column structure is high enough and the silicone surface changes to a super-hydrophobic state, with a contact angle of more than 150° and a rolling angle of less than 10°, showing a typical "Cassie-Baxter" state. This super-hydrophobicity comes from the appearance of the micro-column structure, which significantly reduces the contact area between the droplet and the surface, forming an air bag effect and reducing the adhesion of the droplet.

[0101] Therefore, the above results show that the film material provided by the present invention can achieve dynamic switching from superhydrophilicity to superhydrophobicity through microstructural changes under stretching. This new material property can provide a new research direction for smart surface design.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A stress-regulated surface wettability switching film, characterized in that: It is made of elastic material; the film contains a plurality of micro-column units connected to the root of the main part of the film after circular cutting from any one side or both sides along the thickness direction; the top and side of the micro-column unit are provided with a hydrophobic modification layer; the surface of the main part of the film except the micro-column unit is provided with a hydrophilic modification layer; When the film is stretched by an external force parallel to the film, each microcolumn unit protrudes from the main body; at this time, the surface of the film is in a superhydrophobic state; when the film returns to its natural state, each microcolumn unit is flush with the main body or is concave; at this time, the surface of the film is in a superhydrophilic state.

2. The stress-regulated surface wettability switching film according to claim 1, characterized in that: The maximum cutting depth of the microcolumn unit is equal to 40-80% of the thickness of the film.

3. The stress-regulated surface wettability switching film according to claim 2, characterized in that: First, a portion of a specified thickness at the top of the cut microcolumn unit is removed, and then a hydrophobic modification layer is formed, so that the film is flush with the main part or in a concave state when it returns to its natural state.

4. The stress-regulated surface wettability switching film according to claim 2, characterized in that: The film is made of silicone, rubber, PDMS or other elastic polymers.

5. A method for preparing a stress-regulated surface wettability switching film, characterized in that: The film used for stress-regulated surface wettability switching according to any one of claims 1 to 4 comprises: (1) uniformly stretching the elastic material film to a maximum elastic deformation state, and performing subsequent processes in the stretched state; (2) scanning a target area on the film surface by a femtosecond laser to form a roughened surface; (3) using any hydrophilic modifier to modify the surface of the film to form a hydrophilic modified layer; (4) forming a mask layer that can be specifically removed on the surface of the hydrophilic modified layer of the film; (5) scanning the target area in a circular manner according to a preset shape, depth and space by using a femtosecond laser, thereby cutting out a plurality of micro-column units connected to the root of the main part of the film; (6) scanning the top of the formed microcolumn unit by a femtosecond laser to remove the mask layer, the hydrophilic modification layer, and the thin film material of a specified thickness, and form a roughened surface; (7) using any hydrophobic modifier to perform surface modification on one side of the film containing the microcolumn units to form a hydrophobic modified layer; (8) Using a specified means to specifically remove the mask layer and peel off the hydrophobic modified layer thereon; then restoring the film to its natural state, thereby obtaining the desired product.

6. The method for preparing a stress-regulated surface wettability switching film according to claim 5, characterized in that: In steps (2) and (6), a mesh groove with a depth of 10-20 μm and a spacing of 20-50 μm is processed by femtosecond laser to form the desired roughened surface.

7. The method for preparing a stress-regulated surface wettability switching film according to claim 5, characterized in that: In step (4), a PET film is used as a mask layer, and in step (8), the mask layer is specifically removed by mechanical stripping or solvent dissolution; In step (3), the film is immersed in a hydrophilic reagent solution to form the hydrophilic modified layer; in step (7), hydrophobic silica particles are sprayed onto the surface of the film to form the hydrophobic modified layer.

8. Use of a stress-regulated surface wettability switching film according to any one of claims 1 to 4 in liquid phase component separation, characterized in that: After unfolding a plurality of stress-regulated surface wettability switching films, they are immersed in a suspension containing water and oil phase components to adsorb the water phase components contained therein; then, the stress-regulated surface wettability switching films are taken out and horizontally stretched to a superhydrophobic state, thereby allowing the adsorbed water phase components to slide off the films; and the above process is repeated to achieve the separation of components in the suspension.

9. A liquid phase component separator, which is used to separate water phase substances and oil phase substances in a suspension, characterized in that: It comprises a movable support and a plurality of stress-regulated surface wettability switching films as described in any one of claims 1 to 4; the movable support has a switchable natural state and an expanded state; The stress-regulated surface wettability switching film is installed on a movable bracket and satisfies the following conditions: when the movable bracket is in a natural state, each stress-regulated surface wettability switching film is unfolded and presents a superhydrophilic state; when the movable bracket is in an expanded state, each stress-regulated surface wettability switching film is stretched and presents a superhydrophobic state.

10. An application of a stress-regulated surface wettability switching film according to any one of claims 1 to 4 in a controllable chemical reaction, characterized in that: The stress-regulated surface wettability switching film is used as a container for reactions between liquid-phase chemicals, and the chemical reactions between liquid-phase chemicals are regulated by switching the wettability state of the film.

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