Gradient array micro-nano structure with water collection function, application and preparation method

Abstract

The present invention discloses a gradient array micro-nano structure with a water collection function, its application and preparation method, which relates to the technical field of nano-material preparation. The preparation method includes: preparing a culture dish and dividing the culture dish into at least two regions using spacers; preparing PS microsphere templates in each region, and the diameters of the PS microspheres in each region are different; removing the spacers, preparing liquid silicone and covering the PS microsphere templates with it; performing curing, film taking, and sphere removing operations in sequence to obtain a silicone film with a conical gradient array. Based on the hydrophobicity difference caused by the conical gradient array, the droplets located on the surface of the silicone film are spontaneously driven towards the positive gradient direction, and the positive gradient direction is the direction in which the diameters of the arrays increase from small to large. This structure completely relies on the surface hydrophobicity difference caused by the conical gradient array, thereby causing spontaneous driving of water droplets, and is a water collection surface with durability and safety advantages.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial preparation, and in particular to a gradient array micro-nano structure with a water collection function, its application and preparation method. Background Art

[0002] With the rapid growth of economic activities and poor water resource management, water pollution has led to a severe shortage of clean water. Therefore, obtaining clean water is essential for human society and maintaining the diversity of our living environment. To find a practical and reliable water collection or purification method, researchers need to minimize the use of chemicals and energy to reduce the impact on the environment. Fog is a potential water resource that can be obtained from the surrounding environment using existing technologies. In principle, fog is a cloud that physically touches the ground. One process that generates fog is the formation of low-level clouds over relatively cold water bodies, and another process is the adiabatic cooling of moist air masses during uphill transport.

[0003] Over the past hundreds of millions of years, animals and plants have evolved and survived under extreme conditions. For example, Namib Desert beetles, spiders, cacti, and pitcher plants have all adopted unique water collection functions. Inspired by natural organisms, biomimetic water collection materials have been gradually studied and widely concerned. Generally speaking, fog collection technology has been relatively mature after decades of development, and it is simple, economical, and does not rely on energy consumption. However, many water collection materials use metal coatings on their surfaces to change the wettability of the materials. The long-term exposure of metal materials in water will cause corrosion and aging, seriously affecting the water collection efficiency, and at the same time, it will also bring water quality safety problems. Therefore, it is particularly important to develop a durable and safe water collection material. Summary of the Invention

[0004] In order to overcome the problems of the short lifespan of the water collection materials prepared in the prior art and the threat to water quality, the inventor of the present invention proposed a gradient array micro-nano structure with a water collection function, its application and preparation method. This structure completely relies on the surface hydrophobicity difference caused by the conical gradient array, thereby causing the spontaneous driving of water droplets. It is a water collection surface with the advantages of durability and safety. The technical solution of the present invention is as follows:

[0005] In a first aspect, the present application proposes a gradient array micro-nano structure with a water collection function. This structure is a silicone film, and the surface of the silicone film has at least two conical gradient arrays with different diameters and inward depressions. Based on the hydrophobicity difference caused by the conical gradient array, the droplets located on the surface of the silicone film are spontaneously driven in the positive gradient direction, and the positive gradient direction is the direction in which the diameters of the arrays increase from small to large.

[0006] A further technical solution thereof is that the material of the silicone film is PDMS.

[0007] A further technical solution is that, based on the hydrophobicity difference caused by the conical gradient array, the spontaneous driving of the droplets located on the surface of the silica gel film towards the positive direction of the gradient means that the contact angle of the droplets on the small-diameter array is greater than that of the droplets on the large-diameter array. Based on the surface energy gradient law, it can be inferred that when the contact angle of the droplet is larger, its surface hydrophobicity is stronger and the surface energy is smaller. Therefore, the conclusion is that the droplet spontaneously moves from the low surface energy region to the high surface energy region.

[0008] In a second aspect, the present application also proposes a preparation method of a gradient array micro-nano structure with a water collection function, including the following steps:

[0009] Prepare a petri dish and divide the petri dish into at least two regions using a spacer;

[0010] Prepare PS microsphere templates in each region, and the diameters of the PS microspheres in each region are different;

[0011] Remove the spacer, prepare liquid silica gel and make it cover the PS microsphere templates;

[0012] Perform curing, film taking, and sphere removing operations in sequence to obtain a silica gel film with a conical gradient array.

[0013] A further technical solution is that the method for preparing the PS microsphere templates in each region includes:

[0014] Add the same volume of deionized water to each region;

[0015] Mix the first PS microsphere aqueous solution with the same volume of ethanol evenly, and then drop it on the surface of the deionized water in one region to form a first PS microsphere monolayer film;

[0016] Mix the second PS microsphere aqueous solution with the same volume of ethanol evenly, and then drop it on the surface of the deionized water in another region to form a second PS microsphere monolayer film;

[0017] Among them, the diameter of the first PS microspheres is smaller than that of the second PS microspheres, and the PS microspheres in the first and second PS microsphere monolayer films float on the liquid surface.

[0018] A further technical solution is that the method for preparing liquid silica gel and making it cover the PS microsphere templates includes:

[0019] Mix the PDMS monomer and the curing agent in a certain proportion to obtain a PDMS precursor solution;

[0020] Use a syringe to drop the PDMS precursor solution drop by drop on the PS microsphere templates floating on the liquid surface until the entire liquid surface is covered and the PS microsphere templates and the microsphere gaps are covered, obtaining a PDMS precursor solution film.

[0021] A further technical solution thereof is that the method for performing the curing operation includes:

[0022] The culture dish is placed statically in the water bath container of a magnetic heating stirrer. After the liquid silicone curing and crosslinking process is completed, a silicone film with a PS microsphere template is formed on the liquid surface.

[0023] A further technical solution thereof is that the method for film taking and sphere removing operations includes:

[0024] Use tweezers to lift the silicone film with the PS microsphere template from the water surface and place it in a dimethylformamide solution for a period of time to dissolve the PS microspheres.

[0025] A further technical solution thereof is that the method for preparing the PS microsphere template in each region further includes:

[0026] Add several drops of an aqueous solution of sodium dodecyl sulfate to the edge of the liquid surface to stabilize the first and second PS microsphere monolayer films.

[0027] In a third aspect, the present application also proposes an application of a gradient array micro-nano structure with a water collection function, including: attaching the silicone film as described in the first aspect to a vertically downward sample stage, and making the gradient positive direction of the silicone film consistent with the gravity direction, and placing a water receiving container below the sample stage;

[0028] The conical gradient array on the surface of the silicone film serves as a water collection surface for enabling the liquid droplets to quickly fall into the water receiving container based on the dual actions of the surface energy gradient and gravity, thereby realizing the water collection function.

[0029] The beneficial technical effects of the present invention are:

[0030] 1. The process for preparing the gradient array micro-nano structure by using the method provided in the present application is simple, the raw materials are easily available, the cost is low, and it is non-toxic and harmless;

[0031] 2. The water collection efficiency on the surface of the silicone film based on the conical gradient array is high, persistent, and reusable;

[0032] 3. Using the surface of the silicone film as the water collection surface will not cause pollution to the water quality;

[0033] 4. The surface of the silicone film can achieve spontaneous water drive, improving the water collection efficiency. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the gradient array micro-nano structure provided by the present application; wherein: (a) is a three-dimensional schematic diagram, and (b) is a front view of the surface.

[0035] Figure 2 (a) to (d) are the process flowcharts for preparing the gradient array micro-nano structure provided by the present application.

[0036] Figure 3 This is a schematic diagram of the application scenario where the gradient array micro-nano structure provided by this application is used as a water collection surface. Specific embodiments

[0037] The following further describes the specific embodiments of the present invention with reference to the accompanying drawings.

[0038] Example 1:

[0039] This example proposes a gradient array micro-nano structure with a water collection function. This structure is a silicone film 1. Optionally, the material of the silicone film 1 is PDMS. The surface of the silicone film has at least two kinds of conical gradient arrays with different diameters and inward depressions. In this example, the surface of the silicone film has three conical structures with diameters d1, d2, and d3 and inward depressions, and they are arranged in order of diameter size to form a conical gradient array, as shown in Figure 1 (a) and (b). Among them, d1 > d2 > d3, and the direction of the diameter arranged from small to large is set as the positive gradient direction.

[0040] Due to the hydrophobicity difference caused by the conical gradient array, the droplets on the surface of the silicone film are spontaneously driven in the positive gradient direction. The water driving principle is as follows: Surface wettability is the key factor controlling the contact state between water droplets and solids. The apparent surface energy of the hydrophilic region is always higher than that of the hydrophobic region. Liquids always tend to move from the low surface energy region to the high surface energy region. The surface energy gradient rule is as follows:

[0041]

[0042] Among them, γ is the surface tension of water, cosθ A and cosθ R are the advancing and receding contact angles of water respectively, and dl is the integral variable of the length from the low surface energy region (hydrophobic region L1) to the high surface energy region (hydrophilic region L2). When the contact angles at both ends of the droplet are inconsistent, the difference in contact angles drives the droplet to move from the high contact angle region to the low contact angle region.

[0043] The superhydrophobicity of the PDMS film on the surfaces formed by conical structures with different diameters is different. After many experiments, when d3 is 500 nm, the maximum measured contact angle can reach 143.9°; when d2 is 750 nm, the maximum measured contact angle can reach 137.5°; when d1 is 1000 nm, the maximum measured contact angle can reach 133.2°. Therefore, the larger the contact angle of the droplet, the stronger its surface hydrophobicity and the smaller its surface energy; on the contrary, the smaller the contact angle of the droplet, the worse its surface hydrophobicity and the larger its surface energy. Due to the surface energy gradient law, the droplet will spontaneously move from the 500 nm region to the 1000 nm region, as shown in Figure 1(b) As shown by the arrow direction.

[0044] Using the surface of the silicone film provided in this embodiment as the water collection surface will not cause pollution to the water quality, and this silicone film surface can achieve spontaneous water drive, improving the water collection efficiency.

[0045] Embodiment 2:

[0046] Based on the same inventive concept, this embodiment proposes a preparation method of a gradient array micro-nano structure with a water collection function for preparing the silicone film proposed in Embodiment 1. As Figure 2 shown, it includes the following steps:

[0047] Step 1: Prepare a petri dish and divide the petri dish into at least two regions using spacers.

[0048] As Figure 2 (a) shown, take a square petri dish 2 (12 cm * 12 cm), take two glass sheets 3 of the same size as spacers, and use the glass sheets 3 to divide the petri dish 2 into three equal-sized regions, which are sequentially labeled as petri dish a, petri dish b, and petri dish c.

[0049] Step 2: Prepare PS microsphere templates in each region, and the diameters of the PS microspheres in each region are different. Specifically, it includes:

[0050] Step 2.1: Add the same volume of deionized water to petri dish a, petri dish b, and petri dish c for use.

[0051] Step 2.2: Mix the first PS microsphere aqueous solution (2.5 wt%) with the same volume of ethanol evenly, and then drop it on the surface of the deionized water in petri dish a to form a first PS microsphere monolayer film 4a, as Figure 2 (a) shown. Optionally, drop a few drops of sodium dodecyl sulfate aqueous solution (1 wt%) on the liquid surface edge to stabilize the first PS microsphere monolayer film 4a.

[0052] Step 2.3: Similarly, mix the second PS microsphere aqueous solution (2.5 wt%) with the same volume of ethanol evenly, and then drop it on the surface of the deionized water in petri dish b to form a second PS microsphere monolayer film 4b. Optionally, drop a few drops of sodium dodecyl sulfate aqueous solution (1 wt%) on the liquid surface edge to stabilize the second PS microsphere monolayer film 4b.

[0053] The formation principle of the third PS microsphere monolayer film 4c in petri dish c is the same as the above, and will not be elaborated here.

[0054] Among them, the diameter of the first PS microsphere is less than that of the second PS microsphere, and the diameter of the second PS microsphere is less than that of the third PS microsphere. In this embodiment, the diameter of the first PS microsphere is 500 nm, the diameter of the second PS microsphere is 750 nm, and the diameter of the third PS microsphere is 1000 nm. Although the density of the PS microspheres is 1.05 g / cm 3 , due to the existence of the surface tension of the liquid surface, the PS microspheres can float on the liquid surface.

[0055] Step 3: After the PS microspheres are relatively stable, quickly remove the glass sheet 3 between the culture dishes, so that the single-layer films 4a, 4b, and 4c of the first, second, and third PS microspheres form a continuous but gradient single-layer film template 4 of PS microspheres, as Figure 2 (b) shown.

[0056] Step 4: Prepare liquid silicone and cover the PS microsphere template.

[0057] First, mix the PDMS (polydimethylsiloxane) monomer and the curing agent in a mass ratio of 10:1, and mix them evenly by mechanical stirring to obtain the PDMS precursor solution. Then, use a syringe to drop the PDMS precursor solution onto the single-layer film template 4 of PS microspheres floating on the liquid surface one by one until the entire liquid surface is covered and the single-layer film template 4 of PS microspheres and the gaps between the PS microspheres are covered, obtaining a PDMS precursor solution film 5 with a thickness of about 1 mm, as Figure 2 (b) shown.

[0058] Since the PDMS precursor solution film 5 is an oil phase, it is not miscible with deionized water, and the density of the PDMS precursor solution film 5 is about 0.8 g / cm 3 , which is less than the density of water 1 g / cm 3 , so the PDMS precursor solution film 5 can stably exist on the upper surface of the liquid surface. Because the PS microspheres have been assembled on the liquid surface, the PDMS precursor solution film 5 will wet the surface of the PS microspheres and fill the gaps between adjacent PS microspheres and between the PS microspheres and the liquid surface. Thus, a coexisting three-phase interface is formed among PS, PDMS, and water.

[0059] Step 5: Perform curing, film taking, and microsphere removing operations in sequence to obtain a silicone thin film with a conical gradient array, specifically including:

[0060] Step 5.1: Place the culture dish 2 statically in the water bath container of the magnetic heating stirrer for 5 hours (50 °C). After the curing and cross-linking process of the PDMS precursor solution film 5 is completed, a PDMS film 6 with a single-layer film template 4 of PS microspheres is formed on the liquid surface.

[0061] Step 5.2: As Figure 2As shown in (c), the PDMS film 6 was peeled off from the water surface with tweezers and placed in a dimethylformamide (DMF) solution for 4 hours to dissolve the PS microspheres.

[0062] Step 5.3: After taking out the PDMS film 6, wash it with deionized water and blow it dry with nitrogen to obtain a PDMS film 1 with a tapered gradient array, as shown in FIG. Figure 2 (d) shown.

[0063] The method provided in this embodiment is simple in process for preparing gradient array micro-nanostructures, has readily available raw materials, is low in cost, and is non-toxic and harmless.

[0064] Example 3:

[0065] Based on the same inventive concept, this embodiment provides an application of a gradient array micro-nanostructure with a water collection function, including:

[0066] like Figure 3 As shown, the silica gel (PDMS) film 1 of Example 1, prepared using the preparation method provided in Example 2, is attached to a vertically downward sample stage 7, and a water collection container 8 is placed below the sample stage 7. The positive gradient direction of the silica gel film 1 is aligned with the direction of gravity, i.e., the small-diameter array is on top and the large-diameter array is on the bottom. An ultrasonic humidifier 9 is used to generate a mist stream composed of tiny water droplets. The conical gradient array on the surface of the silica gel film serves as a water collection surface, allowing the droplets to continuously condense and grow under the dual effects of the surface energy gradient and gravity, thereby quickly falling into the water collection container 8, achieving a water collection function.

[0067] The entire process is recorded by camera 10. The water collection process based on the wettability principle generally includes the following three steps: condensation of water vapor, growth of water droplets, and rolling off of water droplets. Gravity is the simplest and most convenient driving force for removing droplets.

[0068] The silica film surface based on the conical gradient array is used as a water collection surface, and its water collection efficiency is high, durable, and reusable.

[0069] The above description is only a preferred embodiment of the present application, and the present invention is not limited to the above embodiment. It is understood that other improvements and variations directly derived or imagined by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the scope of protection of the present invention.

Claims

1. A gradient array micro-nano structure with a water collection function, characterized in that This structure is a silicone film. The surface of the silicone film has at least two kinds of conical gradient arrays with different diameters and inward depressions. Based on the hydrophobicity differences caused by the conical gradient arrays, the droplets located on the surface of the silicone film are spontaneously driven towards the positive gradient direction, and the water collection function is achieved under the dual action of gravity. Among them, the positive gradient direction of the silicone film is consistent with the direction of gravity, and the positive gradient direction is the direction in which the diameters of the arrays increase from small to large. Among them, the hydrophobicity differences caused by the conical gradient arrays make the droplets located on the surface of the silicone film be spontaneously driven towards the positive gradient direction, which means that the contact angle of the droplets on the small-diameter array is larger than that of the droplets on the large-diameter array. Based on the surface energy gradient law, it is deduced that when the contact angle of the droplet is larger, its surface hydrophobicity is stronger and the surface energy is smaller, so the conclusion is that the droplet spontaneously moves from the low surface energy area to the high surface energy area.

2. The gradient array micro-nano structure with a water collection function according to claim 1, wherein The material of the silicone film is PDMS.

3. A preparation method of a gradient array micro-nano structure with a water collection function, characterized in that, It includes: Prepare a culture dish and use a spacer to divide the culture dish into at least two areas. Prepare PS microsphere templates in each area, and the diameters of the PS microspheres in each area are different. Remove the spacer, prepare liquid silicone and make it cover the PS microsphere templates. Perform curing, film taking, and microsphere removing operations in sequence to obtain a silicone film with conical gradient arrays. Among them, the surface of the silicone film has at least two kinds of conical gradient arrays with different diameters and inward depressions. Based on the hydrophobicity differences caused by the conical gradient arrays, the droplets located on the surface of the silicone film are spontaneously driven towards the positive gradient direction, and the water collection function is achieved under the dual action of gravity. Among them, the positive gradient direction of the silicone film is consistent with the direction of gravity, and the positive gradient direction is the direction in which the diameters of the arrays increase from small to large. Among them, the hydrophobicity differences caused by the conical gradient arrays make the droplets located on the surface of the silicone film be spontaneously driven towards the positive gradient direction, which means that the contact angle of the droplets on the small-diameter array is larger than that of the droplets on the large-diameter array. Based on the surface energy gradient law, it is deduced that when the contact angle of the droplet is larger, its surface hydrophobicity is stronger and the surface energy is smaller, so the conclusion is that the droplet spontaneously moves from the low surface energy area to the high surface energy area.

4. The preparation method of the gradient array micro-nano structure with a water collection function according to claim 3, characterized in that, The method for preparing PS microsphere templates in each area includes: Add the same volume of deionized water to each area. Mix the first PS microsphere aqueous solution with the same volume of ethanol evenly, and then drop it on the surface of the deionized water in one area to form a first PS microsphere monolayer film. Mix the second PS microsphere aqueous solution with the same volume of ethanol evenly, and then drop it on the surface of the deionized water in another area to form a second PS microsphere monolayer film. Among them, the diameter of the first PS microsphere is smaller than that of the second PS microsphere, and the PS microspheres in the first and second PS microsphere monolayer films float on the liquid surface.

5. The preparation method of the gradient array micro-nano structure with a water collection function according to claim 3, characterized in that, The method for preparing liquid silicone and making it cover the PS microsphere templates includes: Mix the PDMS monomer and the curing agent in a certain proportion to obtain a PDMS precursor solution. Use a syringe to drop the PDMS precursor solution drop by drop on the PS microsphere templates floating on the liquid surface until the entire liquid surface is covered and the PS microsphere templates and the microsphere gaps are covered, obtaining a PDMS precursor solution film.

6. The preparation method of the gradient array micro-nano structure with a water collection function according to claim 3, characterized in that, The method for performing the curing operation includes: The petri dish is placed statically in the water bath container of a magnetic heating stirrer. After the liquid silicone curing and crosslinking process is completed, a silicone film with a PS microsphere template is formed on the liquid surface.

7. The preparation method of the gradient array micro-nano structure with a water collection function according to claim 3, characterized in that The method for performing the film taking and sphere removing operations includes: Use tweezers to lift the silicone film with the PS microsphere template from the water surface and place it in a dimethylformamide solution for a period of time to dissolve the PS microspheres.

8. The preparation method of the gradient array micro-nano structure with a water collection function according to claim 4, characterized in that, The method for preparing the PS microsphere template in each region further includes: Add a few drops of sodium dodecyl sulfate aqueous solution to the edge of the liquid surface to stabilize the first and second PS microsphere monolayer films.

9. Application of a gradient array micro-nano structure with a water collection function, characterized in that, Includes: Attach the silicone film as described in claim 1 or 2 to the vertically downward sample stage, and make the gradient positive direction of the silicone film consistent with the gravity direction. Place a water receiving container below the sample stage; The conical gradient array on the surface of the silicone film serves as a water collection surface, which is used to enable the liquid droplets to quickly fall into the water receiving container under the dual action of the surface energy gradient and gravity, thereby realizing the water collection function.

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