Directional frosting and self-falling anti-frosting surface based on super-hydrophilic-super-hydrophobic patterning as well as preparation method and application of directional frosting and self-falling anti-frosting surface

Abstract

The invention discloses a directional frosting and self-falling anti-frosting surface based on super-hydrophilic-super-hydrophobic patterning as well as a preparation method and application of the directional frosting and self-falling anti-frosting surface. According to the directional frosting and self-falling anti-frosting surface based on the super-hydrophilic-super-hydrophobic patterning, the morphology, the size and the distance of the super-hydrophilic dot matrix area and the super-hydrophobic background area can be optimally designed according to specific environmental conditions, so that the optimal anti-frosting effect is achieved. The surface does not pursue complete frosting prevention, a random and harmful frosting process is converted into a controllable and harmless frosting process through an elaborate surface energy design, and self-falling is realized by utilizing the physical characteristics of a frost layer, so that the efficient anti-icing performance of the surface is maintained for a long time.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering and anti-frost technology, specifically relating to a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning, its preparation method and application. Background Technology

[0002] When critical equipment such as air source heat pumps, refrigeration equipment, aerospace equipment, and power transmission facilities operate in low-temperature and high-humidity environments, their heat exchangers, wings, or insulator surfaces are highly susceptible to frost and ice formation. The formation of frost and ice layers severely hinders airflow, increases additional load, reduces heat transfer efficiency, and can potentially lead to equipment failure, safety hazards, and significant energy waste. Therefore, developing efficient, energy-saving, and reliable anti-frost technologies has always been a focus of attention for relevant industrial sectors and the scientific research community.

[0003] Existing defrosting solutions are divided into active and passive defrosting technologies. Active defrosting includes electrothermal defrosting, photothermal defrosting, and chemical antifreeze doping. However, electrothermal defrosting is energy-intensive, photothermal defrosting is subject to environmental constraints, and adding chemical antifreeze may pose long-term stability and environmental problems. Passive defrosting technology mainly utilizes the anti-frost properties of superhydrophobic coatings. However, superhydrophobic coatings lose their effectiveness in high-humidity environments due to capillary condensation. Therefore, there is an urgent need for an active anti-frost technology that does not rely on external energy, does not consume chemical substances, and can operate stably for a long period of time. Summary of the Invention

[0004] To overcome the shortcomings and drawbacks of existing technologies, the primary objective of this invention is to provide a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning. This surface does not aim to completely prevent frost formation, but rather, through careful surface energy design, transforms the random and harmful frosting process into a controllable and harmless one, and utilizes the physical properties of the frost layer itself to achieve self-removal, thereby maintaining the surface's highly efficient anti-icing performance over a long period.

[0005] The second objective of this invention is to provide a method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning.

[0006] The third objective of this invention is to provide an application of a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning.

[0007] The primary objective of this invention can be achieved through the following technical solution: A directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning includes a substrate, on which superhydrophilic lattice regions and superhydrophobic background regions are disposed; the wetting properties of the superhydrophilic lattice regions and the superhydrophobic background regions are opposite; the superhydrophilic lattice regions are discretely distributed on the surface of the substrate; the shape of the superhydrophilic lattice regions is a regular geometric shape or a convex polygon structure derived from a regular geometric shape.

[0008] Preferably, the shape of the superhydrophilic lattice region is one of the following: circular, elliptical, square, rectangular, triangular, star-shaped, or cross-shaped.

[0009] Preferably, the surface of the superhydrophilic lattice region has photocatalytic activity, which originates from photocatalytic nanomaterials doped or composited therein, wherein the photocatalytic nanomaterials are at least one of titanium dioxide, zinc oxide, graphitic carbon nitride, or bismuth tungstate.

[0010] Preferably, the size of the superhydrophilic lattice region is from 1 micrometer to 1000 micrometers.

[0011] Preferably, the spacing between adjacent superhydrophilic lattice regions is 10 micrometers to 5000 micrometers.

[0012] Preferably, the substrate may also have an intermediate region, which is a wettability gradient transition region between the superhydrophilic lattice region and the superhydrophobic background region.

[0013] Preferably, the width of the intermediate region is 1 micrometer to 5 micrometers.

[0014] Preferably, the substrate is at least one of aluminum and its alloys, copper and its alloys, titanium and its alloys, magnesium and its alloys, stainless steel, carbon steel, ceramics, glass, and plastics.

[0015] The second objective of this invention can be achieved through the following technical solution: A method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning includes the following steps: (A1) A micro-nano hierarchical rough structure is constructed on the substrate surface, and the surface energy of the micro-nano hierarchical rough structure is modified to form an initial superhydrophobic surface. (A2) The initial superhydrophobic surface is selectively patterned using patterning technology to remove or degrade the surface energy modification layer within the preset pattern area, thereby exposing the unmodified micro-nano hierarchical rough structure in the preset pattern area, forming a region with the opposite wettability to the initial superhydrophobic surface, namely the superhydrophilic lattice region, while the remaining background region is the superhydrophobic background region. The superhydrophilic lattice region and the superhydrophobic background region are spatially complementary, together forming a complete directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning.

[0016] Preferably, the patterning process described in step (A2) is a mask-assisted plasma etching, laser direct writing etching, or photocatalytic degradation.

[0017] The second objective of this invention can also be achieved through the following technical solutions: A method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning includes the following steps: (B1) On the substrate surface, a first functional material with hydrophilicity and micro-nano rough structure is selectively deposited or grown in a first preset area by means of a first mask-assisted or direct-write coating technology to form a superhydrophilic lattice region. (B2) Using a second mask-assisted or direct-write coating technique, a second functional material with hydrophobicity and micro-nano rough structure is selectively deposited or grown in a second preset region to form a superhydrophobic background region. The micro-nano rough structure of at least one of the first and second functional materials is formed by the stacking or in-situ growth of nanoparticles of the material itself; The superhydrophilic lattice region and the superhydrophobic background region are spatially complementary, together forming a complete directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning.

[0018] The reason for limiting the micro / nano rough structure of at least one of the first and second functional materials to be formed by the stacking or in-situ growth of nanoparticles of the material itself is to emphasize that the material itself possesses a micro / nano structure, or that a functional coating is directly constructed on a smooth substrate, and the core function of the functional coating is entirely derived from the material itself, eliminating the need for substrate pretreatment. Preferably, the first mask-assisted or direct-write coating technology and the second mask-assisted or direct-write coating technology are independently selected from mask-assisted spraying, inkjet printing, or aerosol jet direct-write technology.

[0019] The second objective of this invention can also be achieved through the following technical solutions: A method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning includes the following steps: (C1) Pre-treat the substrate to construct micro / nano rough structures; (C2) The first preset area of ​​the substrate is subjected to surface modification technology to make it hydrophilic and form a superhydrophilic lattice region; (C3) The second preset area of ​​the substrate is subjected to surface modification technology to make it hydrophobic and form a superhydrophobic background area; The processing order of steps (C2) and (C3) can be interchanged, and the superhydrophilic lattice region and the superhydrophobic background region together constitute the required directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning.

[0020] Preferably, the surface modification technology treatment of the first preset area and the surface modification technology treatment of the second preset area are independently selected from micro-contact printing, local electrochemical deposition or scanning probe-induced chemical reaction.

[0021] The third objective of this invention can also be achieved through the following technical solutions: Applications of a superhydrophilic-superhydrophobic patterned directional frosting and self-removing anti-frost surface in refrigeration system evaporators, aircraft wings, wind turbine blades, solar photovoltaic panels, outdoor sensor equipment, power transmission equipment, and other fields.

[0022] like Figure 1 This is a schematic diagram illustrating the frosting and self-removal process of the superhydrophilic-superhydrophobic patterned directional frosting and self-removing anti-frost surface of the present invention; the process includes the following three stages. In the early stage of condensation: water vapor will bypass the superhydrophobic background region and preferentially condense into nuclei on the superhydrophilic lattice region; Freezing and growth: Water droplets freeze into ice nuclei and continue to capture water vapor to grow into isolated needle-like ice; Self-detachment: Needle-shaped ice breaks off from its root and detaches from the surface under weak external force; Surface recovery: The surface is cleaned and ready to enter the next cycle.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) Controllable frosting mechanism: The superhydrophilic lattice region of the superhydrophilic anti-frosting surface based on the superhydrophilic-superhydrophobic patterned directional frosting and self-detaching anti-frosting surface described in this invention serves as the nucleation center. Under high temperature conditions, it will preferentially capture and condense water vapor, transforming the random and overall frosting process into a local frosting process that occurs at a predetermined location. Frost crystals are restricted to grow on discrete hydrophilic points, thus having a controllable frosting mechanism.

[0024] (2) Self-detached frost layer morphology: Since the frost crystals are confined to tiny hydrophilic points, the frost crystals tend to grow upwards, forming tall, isolated "needle-shaped ice" or "ice pillar" with a small contact area with the substrate. This type of ice has extremely weak adhesion and is very easy to detach.

[0025] (3) Continuous and efficient anti-icing capability: The isolated needle-shaped ice generated by the super-hydrophilic-super-hydrophobic patterned directional frost and self-detaching anti-frost surface described in this invention is very easy to automatically detach under gravity, natural wind or slight vibration of equipment, so that the surface is restored to its initial clean state, thereby realizing a virtuous cycle of "frost-detachment-re-frost-re-detachment", making the anti-icing performance of the surface long-lasting.

[0026] (4) Low energy consumption and high reliability: The directional frosting and self-detaching anti-frost surface based on superhydrophilic-superhydrophobic patterning described in this invention does not require external energy input or consume chemical substances during the entire anti-icing process. It achieves its function solely through surface design, resulting in high system reliability and low maintenance costs.

[0027] (5) Customizable design: The morphology, size and spacing of the superhydrophilic dot matrix area and superhydrophobic background area of ​​the superhydrophilic-superhydrophobic patterned directional frosting and self-removing anti-frost surface described in this invention can be optimized according to specific environmental conditions to achieve the best anti-frost effect. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the frosting and self-removal process of the directional frosting and self-removing anti-frost surface based on the superhydrophilic-superhydrophobic patterned surface of the present invention. Figure 2 The image shows the effect of the patterned surface frosting and self-removing anti-frost surface prepared in Example 1 under frosting conditions captured by a high-definition camera. Figure 3 Several optional pattern designs (circular array, square array, cross array) for the superhydrophilic dot matrix region described in this invention. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. All materials used in the examples of the present invention are commercially available.

[0030] Example 1 The method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning described in this embodiment includes the following steps: (1) The cleaned aluminum substrate is anodized to form a porous alumina nanostructure; (2) Immerse it in a fluorosilane solution for full surface modification to obtain a superhydrophobic aluminum sheet with a contact angle >150°; (3) Using an ultraviolet femtosecond laser, the surface of the superhydrophobic aluminum sheet is scanned according to a circular dot pattern; after processing, the surface energy at the laser scanning points increases, becoming hydrophilic, forming the desired superhydrophilic dot pattern region, and the remaining background region becomes a superhydrophobic background region. Finally, a directional frosting and self-detaching anti-frost surface based on superhydrophilic-superhydrophobic patterning is prepared, such as... Figure 2 The image shown is a photograph of the dotted icicles formed when the ice was frosted.

[0031] Example 2 The method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning described in this embodiment includes the following steps: (1) Cover the substrate with a metal mask plate with a square array of through holes on a cleaned aluminum substrate. (2) A hydrophilic titanium dioxide nanoparticle sol is sprayed onto the square array through-hole area (the hollow area of ​​the mask) through a mask plate and solidified to form a superhydrophilic lattice area; (3) Using another set of opposite masks, a fluorosilane-modified silica nanoparticle ethanol dispersion was sprayed on the entire area except for the square array through holes, and solidified to form a superhydrophobic area (contact angle > 150°), i.e., the superhydrophobic background area.

[0032] Among them, under sunlight, the hydrophilic titanium dioxide coating can continuously decompose organic pollutants attached to its surface, keeping the coating surface chemically clean and thus maintaining its superhydrophilicity for a long time.

[0033] Example 3 The method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning described in this embodiment includes the following steps: (1) Chemical etching is performed on the cleaned copper mesh substrate to form a micro-nano rough surface; (2) Cover the copper mesh with a mask plate with circular through-hole area, spray a layer of fluorosilane onto the circular through-hole area through the mask plate, and cure to form a superhydrophobic area (contact angle > 150°), i.e. superhydrophobic background area; (3) Replace the mask with the opposite pattern, spray 3-aminopropyltriethoxysilane, and cure to form a superhydrophilic region, i.e., a superhydrophilic lattice region.

[0034] Comparative Example 1 The aluminum fins are left untreated.

[0035] Comparative Example 2 3-aminopropyltriethoxysilane-modified silica nanoparticles are sprayed onto the surface of aluminum fins and then cured to form a superhydrophilic surface.

[0036] Comparative Example 3 Fluorosilane-modified silica nanoparticles are sprayed onto the surface of aluminum fins and then cured to form a superhydrophobic surface.

[0037] The performance test comparison is shown in Table 1 below.

[0038] Table 1

[0039] Analysis of the data in Table 1 shows that the contact angle between the superhydrophobic and superhydrophilic patterned directional frosting surface and the superhydrophobic background area of ​​the self-detaching anti-frost surface prepared in Examples 1 to 3 is ≥150°, and the superhydrophilic lattice area is ≤10°, indicating that it has good superhydrophobicity and superhydrophilicity. At -10°C, the frosting delay time (50% of the surface is covered by frost) is ≥270 minutes, and the ice adhesion strength is ≤30kPa, which also shows good anti-frost performance. It is expected to be widely used in refrigeration system evaporators, aircraft wings, wind turbine blades, solar photovoltaic panels, outdoor sensor equipment, power transmission equipment and other fields.

[0040] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning, characterized in that, The device includes a substrate on which a superhydrophilic lattice region and a superhydrophobic background region are disposed; the superhydrophilic lattice region and the superhydrophobic background region have opposite wetting properties; the superhydrophilic lattice region is discretely distributed on the surface of the substrate; the shape of the superhydrophilic lattice region is a regular geometric shape or a convex polygon structure derived from a regular geometric shape.

2. The directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning as described in claim 1, characterized in that, The shape of the superhydrophilic lattice region is one of the following: circular, elliptical, square, rectangular, triangular, star-shaped, or cross-shaped.

3. The directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning as described in claim 1, characterized in that, The surface of the superhydrophilic lattice region has photocatalytic activity, which originates from photocatalytic nanomaterials doped or composited therein. The photocatalytic nanomaterials are at least one of titanium dioxide, zinc oxide, graphitic carbon nitride, or bismuth tungstate.

4. A method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning according to any one of claims 1 to 3, characterized in that, Includes the following steps: (A1) A micro-nano hierarchical rough structure is constructed on the substrate surface, and the surface energy of the micro-nano hierarchical rough structure is modified to form an initial superhydrophobic surface. (A2) The initial superhydrophobic surface is selectively patterned using patterning technology to remove or degrade the surface energy modification layer within the preset pattern area, thereby exposing the unmodified micro-nano hierarchical rough structure in the preset pattern area, forming a region with the opposite wettability to the initial superhydrophobic surface, namely the superhydrophilic lattice region, while the remaining background region is the superhydrophobic background region. The superhydrophilic lattice region and the superhydrophobic background region are spatially complementary, together forming a complete directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning.

5. The method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning according to claim 4, characterized in that, The patterning process described in step (A2) is a mask-assisted plasma etching, laser direct writing etching, or photocatalytic degradation.

6. A method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning according to any one of claims 1 to 3, characterized in that, Includes the following steps: (B1) On the substrate surface, a first functional material with hydrophilicity and micro-nano rough structure is selectively deposited or grown in a first preset area by means of a first mask-assisted or direct-write coating technology to form a superhydrophilic lattice region. (B2) Using a second mask-assisted or direct-write coating technique, a second functional material with hydrophobicity and micro-nano rough structure is selectively deposited or grown in a second preset region to form a superhydrophobic background region. The micro-nano rough structure of at least one of the first and second functional materials is formed by the stacking or in-situ growth of nanoparticles of the material itself; The superhydrophilic lattice region and the superhydrophobic background region are spatially complementary, together forming a complete directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning.

7. The method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning according to claim 6, characterized in that, The first mask-assisted or direct-write coating technology and the second mask-assisted or direct-write coating technology are independently selected from mask-assisted spraying, inkjet printing or aerosol jet direct-write technology.

8. A method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning according to any one of claims 1 to 3, characterized in that, Includes the following steps: (C1) Pre-treat the substrate to construct micro / nano rough structures; (C2) The first preset area of ​​the substrate is subjected to surface modification technology to make it hydrophilic and form a superhydrophilic lattice region; (C3) The second preset area of ​​the substrate is subjected to surface modification technology to make it hydrophobic and form a superhydrophobic background area; The processing order of steps (C2) and (C3) can be interchanged, and the superhydrophilic lattice region and the superhydrophobic background region together constitute the required directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning.

9. The method for preparing a directional frosting and self-removing anti-frost surface based on superhydrophilic-superhydrophobic patterning according to claim 8, characterized in that, The surface modification technology treatment of the first preset area and the surface modification technology treatment of the second preset area are independently selected from micro-contact printing, local electrochemical deposition or scanning probe-induced chemical reaction.

10. The application of a superhydrophilic-superhydrophobic patterned directional frosting and self-removing anti-frost surface according to any one of claims 1 to 3 in the fields of evaporators of refrigeration systems, aircraft wings, wind turbine blades, solar photovoltaic panels, outdoor sensor equipment, and power transmission equipment.

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