A method for designing a durable biomimetic concave lubricant wetted surface
By designing concave structural surfaces and biomimetic orange peel surfaces, combined with the Laplace effect and pinning action, the problem of lubricating oil loss under high-temperature environments was solved, achieving stable distribution and improved durability of the lubricating oil.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI UNIVERSITY OF ARCHITECTURE
- Filing Date
- 2026-01-20
- Publication Date
- 2026-06-19
AI Technical Summary
Existing lubricating oils are prone to loss of moisture on surfaces due to factors such as evaporation, shear loss, and miscibility under high-temperature conditions, which affects their long-term stability and durability.
By designing a concave surface structure and incorporating the lubricating oil wetting and loss mechanism, and through a biomimetic orange peel surface design, the closed sidewalls and narrow openings of the concave structure, combined with the Laplace effect and pinning action, enhance the lubricating oil locking ability.
This achieves stable distribution of lubricating oil within the structure, enhances surface durability, reduces loss, and improves the oil-locking ability and wetting effect of the lubricating oil.
Smart Images
Figure CN122241959A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for designing a durable, biomimetic concave lubricating oil wetting surface. Background Technology
[0002] Inspired by the super-slippery surface of pitcher plants, oil-wetted surfaces (LIS) rely on the rough structure of a solid substrate to retain lubricant, forming a composite interface with low contact angle hysteresis and low slip angle. The solid substrate has micron or nanometer-level roughness, and a stable composite solid-lubricant interface is formed by injecting lubricant. This smooth lubricant layer endows the LIS surface with unique lubricating properties, enabling it to effectively repel various liquids. The lubricant layer on the LIS surface not only provides excellent liquid repellency but also exhibits good mechanical load-bearing capacity due to the incompressibility of the lubricant. These unique properties of LIS surfaces have attracted considerable attention in various fields such as corrosion prevention, antifouling, anti-icing, drag reduction, fog collection, and bubble transfer applications.
[0003] In practical applications, lubricating oil is easily lost due to various factors, including evaporation at high temperatures, shear loss under external flow, miscibility between lubricating oil and working fluid, and displacement by working fluid. These factors lead to the loss of surface lubricating oil, which will seriously affect the super-lubricating properties of the LIS surface. Summary of the Invention
[0004] This invention provides a durable biomimetic concave lubricating oil wetting surface design method. The method is rationally designed and adopts a biomimetic orange peel surface design to improve the durability of the lubricating oil wetting surface. The closed sidewalls of the concave re-entrant structure of the biomimetic orange peel prevent lubricating oil loss caused by shear force, and the closed narrow opening structure hinders the loss of lubricating oil. Furthermore, the combination of the Laplace effect and pinning effect of the lubricating oil in the microcavity of the concave base structure makes the overall structure have stronger oil locking ability and wetting effect, thus solving the problems existing in the prior art.
[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: A method for designing a durable biomimetic concave lubricating oil wetting surface, the method comprising the following steps: S1 features a concave surface design that allows lubricating oil to maintain a stable distribution within the structure, reducing loss and improving surface durability. S2, establish a lubricating oil wetting mechanism, decompose and calculate the forces acting on the gas-liquid interface, and make the lubricating oil wet the interior of the structure. S3, establish a lubricating oil loss mechanism, compare the static contact angle and the tilt angle of the top edge of the structure relative to the vertical direction, determine the degree of concavity and oil locking ability of the concave structure surface, determine the shape coefficient of the concave structure surface, and obtain a concave structure surface with excellent performance in both lubricating oil wetting and lubricating oil loss.
[0006] Designing a concave surface structure to ensure stable distribution of lubricating oil within the structure, reducing loss and improving surface durability includes the following steps: S1.1, Define the shape coefficient K, set W as the width of the opening, and L as the vertical distance from the center of the plane at the opening to the bottom of the pit; S1.2, different K values correspond to different concave opening angles β. The larger the K value, the smaller the opening angle β, and the greater the degree of concavity of the concave structure surface, that is: .
[0007] To establish a lubricating oil wetting mechanism, the forces acting on the gas-liquid interface are decomposed and calculated, and the lubricating oil wetting structure includes the following steps: S2.1, The forces acting on the gas-liquid interface include the pressure F caused by the pressure difference between the liquid pressure and the gas near the interface. p Surface tension F on the three-phase contact line v It is the perpendicular component of F, that is:
[0008] Where λ is the contact linear density, γ is the liquid surface tension, θ0 is the actual contact angle, β is the penetration angle, A is the contact area, and f lg The ratio of the projected area of the liquid-gas interface to the apparent contact area of the droplet, where r is the droplet radius; S2.2, If the gas-liquid interface is in equilibrium, then the net force in the vertical direction is 0, i.e., F. v =F p When lubricating oil penetrates the structure, and the penetration angle β is greater than the maximum slope angle φ, we get:
[0009] For wetting, as the shape factor K increases, the maximum slope angle φ increases. In order to achieve wetting, the actual contact angle θ0 needs to be reduced.
[0010] The static contact angle is set as θ, and the inclination angle of the top edge of the structure relative to the vertical direction is α. The larger the value of α, the deeper the concavity of the concave structure surface. When θ > ɑ, we get
[0011] Where R is the radius of the concave structure; Adjust the tilt angles of the top edge of the structure relative to the vertical direction to α1 and α2, and let α1 > α2. Then compare the liquid meniscus pressure ΔP = P1 - P2.
[0012] Since cosɑ2>cosɑ1 and cos(θ-ɑ1)>cos(θ-ɑ2), then P1>P2 and ΔP>0; When θ < α, we get
[0013] Where R is the radius of the concave structure; Adjust the tilt angles of the top edge of the structure relative to the vertical direction to α1 and α2, and let α1 > α2. Then compare the liquid meniscus pressure ΔP = P1 - P2.
[0014] Since cosα2sinα1sinθ>cosα1sinα2sinθ, that is, tanα1>tanα2, Then P1 > P2, ΔP > 0; The above calculations prove that the larger the shape factor K is, the greater the Laplace pressure generated. Therefore, for concave structures, the greater the degree of concavity, the stronger the oil-locking ability.
[0015] For recessed surfaces with sharp edges, the lubricating oil will be fixed by the sharp edges. The movement of the lubricating oil under shear force will be affected by the fixing effect of the structural edges. The maximum pinning angle θ of the edge is defined. pin To achieve stronger oil-locking ability and wetting effect; Specifically,
[0016] Where θ is the contact angle and α is the tilt angle of the top edge of the structure relative to the vertical direction.
[0017] This invention employs the aforementioned structure, designing a concave surface to ensure stable distribution of lubricating oil within the structure, reducing leakage and improving surface durability. By establishing a lubricating oil wetting mechanism, the forces acting on the gas-liquid interface are decomposed and calculated, allowing lubricating oil to permeate the interior of the structure. Furthermore, by establishing a lubricating oil loss mechanism, the static contact angle and the tilt angle of the top edge of the structure relative to the vertical direction are compared to determine the degree of concavity and oil-locking ability of the concave surface, thus determining the shape coefficient of the concave surface and obtaining a concave surface with excellent performance in both lubricating oil wetting and lubricating oil loss. This invention offers the advantages of simplicity, practicality, stability, and reliability. Attached Figure Description
[0018] Figure 1 This is a planar schematic diagram of the shape factor of the present invention.
[0019] Figure 2 This is a schematic diagram illustrating the effect of gas-liquid interfacial forces according to the present invention.
[0020] Figure 3 This is a schematic diagram of the Laplace effect of lubricating oil in the concave structure of the present invention and a schematic diagram of lubricating oil pinning under shear force.
[0021] Figure 4 This diagram illustrates the wetting ratio and remaining ratio of the lubricating oil in this invention. Detailed Implementation
[0022] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific implementation methods and in conjunction with the accompanying drawings.
[0023] like Figure 1-4 As shown, a method for designing a durable biomimetic concave lubricating oil wetting surface includes the following steps: S1 features a concave surface design that allows lubricating oil to maintain a stable distribution within the structure, reducing loss and improving surface durability. S2, establish a lubricating oil wetting mechanism, decompose and calculate the forces acting on the gas-liquid interface, and make the lubricating oil wet the interior of the structure. S3, establish a lubricating oil loss mechanism, compare the static contact angle and the tilt angle of the top edge of the structure relative to the vertical direction, determine the degree of concavity and oil locking ability of the concave structure surface, determine the shape coefficient of the concave structure surface, and obtain a concave structure surface with excellent performance in both lubricating oil wetting and lubricating oil loss.
[0024] Designing a concave surface structure to ensure stable distribution of lubricating oil within the structure, reducing loss and improving surface durability includes the following steps: S1.1, Define the shape coefficient K, set W as the width of the opening, and L as the vertical distance from the center of the plane at the opening to the bottom of the pit; S1.2, different K values correspond to different concave opening angles β. The larger the K value, the smaller the opening angle β, and the greater the degree of concavity of the concave structure surface, that is: .
[0025] To establish a lubricating oil wetting mechanism, the forces acting on the gas-liquid interface are decomposed and calculated, and the lubricating oil wetting structure includes the following steps: S2.1, The forces acting on the gas-liquid interface include the pressure F caused by the pressure difference between the liquid pressure and the gas near the interface.p Surface tension F on the three-phase contact line v It is the perpendicular component of F, that is:
[0026] Where λ is the contact linear density, γ is the liquid surface tension, θ0 is the actual contact angle, β is the penetration angle, A is the contact area, and f lg The ratio of the projected area of the liquid-gas interface to the apparent contact area of the droplet, where r is the droplet radius; S2.2, If the gas-liquid interface is in equilibrium, then the net force in the vertical direction is 0, i.e., F. v =F p When lubricating oil penetrates the structure, and the penetration angle β is greater than the maximum slope angle φ, we get:
[0027] For wetting, as the shape factor K increases, the maximum slope angle φ increases. In order to achieve wetting, the actual contact angle θ0 needs to be reduced.
[0028] The static contact angle is set as θ, and the inclination angle of the top edge of the structure relative to the vertical direction is α. The larger the value of α, the deeper the concavity of the concave structure surface. When θ > ɑ, we get
[0029] Where R is the radius of the concave structure; Adjust the tilt angles of the top edge of the structure relative to the vertical direction to α1 and α2, and let α1 > α2. Then compare the liquid meniscus pressure ΔP = P1 - P2.
[0030] Since cosɑ2>cosɑ1 and cos(θ-ɑ1)>cos(θ-ɑ2), then P1>P2 and ΔP>0; When θ < α, we get
[0031] Where R is the radius of the concave structure; Adjust the tilt angles of the top edge of the structure relative to the vertical direction to α1 and α2, and let α1 > α2. Then compare the liquid meniscus pressure ΔP = P1 - P2.
[0032] Since cosα2sinα1sinθ>cosα1sinα2sinθ, that is, tanα1>tanα2, Then P1 > P2, ΔP > 0; The above calculations prove that the larger the shape factor K is, the greater the Laplace pressure generated. Therefore, for concave structures, the greater the degree of concavity, the stronger the oil-locking ability.
[0033] For recessed surfaces with sharp edges, the lubricating oil will be fixed by the sharp edges. The movement of the lubricating oil under shear force will be affected by the fixing effect of the structural edges. The maximum pinning angle θ of the edge is defined. pin To achieve stronger oil-locking ability and wetting effect; Specifically,
[0034] Where θ is the contact angle and α is the tilt angle of the top edge of the structure relative to the vertical direction.
[0035] The working principle of a durable biomimetic concave lubricating oil wetting surface design method in this embodiment of the invention is as follows: the biomimetic orange peel surface design improves the durability of the lubricating oil wetting surface. The closed sidewalls of the concave re-entrant structure of the biomimetic orange peel prevent lubricating oil loss caused by shear force. The closed narrow opening structure hinders the loss of lubricating oil. Furthermore, the combination of the Laplace effect and pinning effect of the lubricating oil in the microcavity of the concave base structure makes the overall structure have a stronger oil-locking ability and wetting effect.
[0036] In oranges and other citrus fruits, lubricating oil is stored in concave reservoirs in the peel. These concave structures have a unique reentrant structure, which not only efficiently stores oil but also limits oil leakage through the following mechanisms: the sidewalls of the reservoir isolate individual concave structures, preventing oil from flowing between different reservoirs and maintaining stable oil storage; the narrow openings of the concave structures limit oil leakage, ensuring that the stored lubricating oil is not easily lost; the biomimetic concave structure has durability advantages, providing important inspiration for the optimized design of LIS surfaces. Through reasonable concave structure design, the durability of LIS surfaces can be improved.
[0037] In the development of oil-wetted surfaces (LIS), lubricant loss has always been a key challenge affecting their long-term stability and durability. Researchers have proposed various strategies to improve lubricant retention. For example, using anti-volatile lubricants, such as fluorinated fluids and high-viscosity oils, can reduce the evaporation rate and mitigate lubricant loss due to miscibility or liquid displacement. Simultaneously, a shear-resistant biomimetic super-lubricating surface system, its preparation method, and its drag-reduction application are provided. This system includes a super-lubricating surface substrate, a super-oleophilic / super-oleophobic alternating surface, and a lubricating oil film. The super-lubricating surface substrate comprises two types of surface microstructure regions with different heights, each with a roughness in the micrometer range. The height difference is 0.1 mm to 0.3 mm. The super-oleophilic / super-oleophobic alternating surface includes super-oleophilic and super-oleophobic surfaces arranged in a predetermined pattern. The super-oleophilic surface is located on the upper surface of the lower-height surface microstructure region on the substrate, and the super-oleophobic surface is located on the upper surface of the higher-height surface microstructure region. The lubricating oil is injected into the super-oleophilic surface, wetting the entire surface and forming a sub-millimeter-thick lubricating oil film. The invented super-lubricating surface system ensures the stable preservation of the sub-millimeter-thick lubricating oil film, resulting in a stable and efficient drag reduction of the biomimetic super-lubricating surface.
[0038] However, while these methods can reduce the risks of evaporation and miscibility to some extent, they cannot completely prevent the gradual loss of lubricating oil, especially during long-term use or in extreme environments. Ultraviolet curing enhances the stability of the lubricating layer and reduces lubricating oil loss due to shear flow or external flow fields. While this method improves durability, the cured lubricating layer loses its fluidity, reducing its self-healing ability and making it ineffective in dealing with localized lubricating layer damage.
[0039] To further reduce lubricant loss, self-replenishing lubricant surfaces have been developed; while this strategy can maintain the surface lubrication layer to some extent, its manufacturing process is relatively complex. In contrast, optimizing the texture structure design to allow the lubricant to be more stably retained in the surface texture is a simpler and more effective solution.
[0040] The concave structure creates a stable storage area for lubricating oil within the structure. Simultaneously, the Laplace pressure generated within the concave structure provides oil-locking capability. Furthermore, the sharp edges of the concave structure surface further secure the lubricating oil. This invention proposes a durable biomimetic concave lubricating oil wetting surface by optimizing the biomimetic concave lubricating oil wetting surface design, thereby improving the durability of the LIS surface and achieving efficient lubricating oil locking in a simpler manner.
[0041] In this invention, a structural optimization strategy is adopted to improve the locking ability of lubricating oil and enhance the durability of the lubricating oil-wetting surface by optimizing the design of the concave lubricating oil-wetting surface structure. In the overall scheme, the design method includes the following steps: designing a concave structural surface to enable the lubricating oil to maintain a stable distribution within the structure, reduce loss, and improve surface durability; establishing a lubricating oil wetting mechanism by decomposing the forces acting on the gas-liquid interface to allow the lubricating oil to wet the interior of the structure; and establishing a lubricating oil loss mechanism by comparing the static contact angle and the tilt angle of the top edge of the structure relative to the vertical direction, judging the degree of concavity and oil locking ability of the concave structural surface, determining the shape coefficient of the concave structural surface, and obtaining a concave structural surface with excellent performance in both lubricating oil wetting and lubricating oil loss.
[0042] In this invention, theoretical analysis and molecular dynamics simulations can be used to explore the effects of impregnation and depletion processes on different concave structures, based on... Figure 4 The data shows that the pit structures with shape factors K=0.5, 0.866, 1, and 1.866 were completely wetted, while the wettability was only 50.21% when K=3.128. Meanwhile, the remaining lubricating oil percentages for the five structures were 0.91219%, 15.27806%, 24.93574%, 39.89748%, and 49.93576%, respectively. Overall, K=1.866 exhibits relatively strong advantages in both lubricating oil wetting and lubricating oil loss, possessing both good oil-locking performance and easy wetting of the substrate structure, making it an excellent and reliable concave structure.
[0043] Preferably, designing a concave surface structure to ensure stable distribution of lubricating oil within the structure, reducing leakage and improving surface durability includes the following steps: defining a shape factor K, setting W as the width of the opening, and L as the vertical distance from the center of the plane at the opening to the bottom of the recess; different K values correspond to different concave opening angles β, the larger the K value, the smaller the opening angle β, and the greater the degree of concavity of the concave surface structure, that is: .
[0044] Preferably, a lubricating oil wetting mechanism is constructed, and the forces acting on the gas-liquid interface are decomposed and calculated. The lubricating oil wetting structure includes the following steps: the forces acting on the gas-liquid interface include the pressure F caused by the pressure difference between the liquid pressure and the gas near the interface. p Surface tension F on the three-phase contact line v It is the perpendicular component of F, that is:
[0045] Where λ is the contact linear density, γ is the liquid surface tension, θ0 is the actual contact angle, β is the penetration angle, A is the contact area, and f lg The ratio of the projected area of the liquid-gas interface to the apparent contact area of the droplet, where r is the droplet radius; If the gas-liquid interface is in equilibrium, then the net force in the vertical direction is 0, i.e., F. v =F p When lubricating oil penetrates the structure, and the penetration angle β is greater than the maximum slope angle φ, we get:
[0046] For wetting, as the shape factor K increases, the maximum slope angle φ increases. In order to achieve wetting, the actual contact angle θ0 needs to be reduced.
[0047] For the theoretical calculations of this invention, the static contact angle is set as θ, and the inclination angle of the top edge of the structure relative to the vertical direction is α. The larger the value of α, the deeper the concavity of the concave structure surface. When θ > ɑ, we get
[0048] Where R is the radius of the concave structure; Adjust the tilt angles of the top edge of the structure relative to the vertical direction to α1 and α2, and let α1 > α2. Then compare the liquid meniscus pressure ΔP = P1 - P2.
[0049] Since cosɑ2>cosɑ1 and cos(θ-ɑ1)>cos(θ-ɑ2), then P1>P2 and ΔP>0; When θ < α, we get
[0050] Where R is the radius of the concave structure; Adjust the tilt angles of the top edge of the structure relative to the vertical direction to α1 and α2, and let α1 > α2. Then compare the liquid meniscus pressure ΔP = P1 - P2.
[0051] Since cosα2sinα1sinθ>cosα1sinα2sinθ, that is, tanα1>tanα2, Then P1 > P2, ΔP > 0; The above calculations prove that the larger the shape factor K is, the greater the Laplace pressure generated. Therefore, for concave structures, the greater the degree of concavity, the stronger the oil-locking ability.
[0052] Furthermore, for recessed surfaces with sharp edges, the lubricating oil will be fixed by the sharp edges. The movement of the lubricating oil under shear force will be affected by the fixing effect of the structural edges. The maximum pinning angle θ of the edge is defined. pin To achieve stronger oil-locking ability and wetting effect; Specifically,
[0053] Where θ is the contact angle and α is the tilt angle of the top edge of the structure relative to the vertical direction.
[0054] It should be noted that the Laplace effect and pinning effect of the lubricating oil in the concave microcavity structure give the overall structure a stronger oil-locking ability, which is also an innovative technical feature of this invention compared with the prior art.
[0055] In summary, the durable biomimetic concave lubricating oil wetting surface design method in this embodiment of the invention uses a biomimetic orange peel surface design to improve the durability of the lubricating oil wetting surface. The closed sidewalls of the concave re-entrant structure of the biomimetic orange peel prevent lubricating oil loss caused by shear force, the closed narrow opening structure hinders the loss of lubricating oil, and the combination of the Laplace effect and pinning effect of the lubricating oil in the microcavity of the concave base structure makes the overall structure have stronger oil locking ability and wetting effect.
[0056] The above specific embodiments should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, any alternative improvements or modifications made to the embodiments of the present invention shall fall within the scope of protection of the present invention.
[0057] Any aspects of this invention not described in detail are well-known to those skilled in the art.
Claims
1. A method for designing a durable, biomimetic concave lubricating oil wetting surface, characterized in that, The design method includes the following steps: S1 features a concave surface design that allows lubricating oil to maintain a stable distribution within the structure, reducing loss and improving surface durability. S2, establish a lubricating oil wetting mechanism, decompose and calculate the forces acting on the gas-liquid interface, and make the lubricating oil wet the interior of the structure. S3, establish a lubricating oil loss mechanism, compare the static contact angle and the tilt angle of the top edge of the structure relative to the vertical direction, determine the degree of concavity and oil locking ability of the concave structure surface, determine the shape coefficient of the concave structure surface, and obtain a concave structure surface with excellent performance in both lubricating oil wetting and lubricating oil loss.
2. The method for designing a durable biomimetic concave lubricating oil wetting surface according to claim 1, characterized in that, Designing a concave surface structure to ensure stable distribution of lubricating oil within the structure, reducing loss and improving surface durability includes the following steps: S1.1, Define the shape coefficient K, set W as the width of the opening, and L as the vertical distance from the center of the plane at the opening to the bottom of the pit; S1.2, different K values correspond to different concave opening angles β. The larger the K value, the smaller the opening angle β, and the greater the degree of concavity of the concave structure surface, that is: 。 3. The method for designing a durable biomimetic concave lubricating oil wetting surface according to claim 2, characterized in that, To establish a lubricating oil wetting mechanism, the forces acting on the gas-liquid interface are decomposed and calculated, and the lubricating oil wetting structure includes the following steps: S2.1, The forces acting on the gas-liquid interface include the pressure F caused by the pressure difference between the liquid pressure and the gas near the interface. p Surface tension F on the three-phase contact line v It is the perpendicular component of F, that is:
4. Among them, λ is the contact linear density, γ is the liquid surface tension, θ0 is the actual contact angle, β is the penetration angle, A is the contact area, and f lg The ratio of the projected area of the liquid-gas interface to the apparent contact area of the droplet, where r is the droplet radius; S2.2, If the gas-liquid interface is in equilibrium, then the net force in the vertical direction is 0, i.e., F. v =F p When lubricating oil penetrates the structure, and the penetration angle β is greater than the maximum slope angle φ, we get:
5. For wetting, as the shape factor K increases, the maximum slope angle φ increases. In order to achieve wetting, the actual contact angle θ0 needs to be reduced.
6. The method for designing a durable biomimetic concave lubricating oil wetting surface according to claim 3, characterized in that: The static contact angle is set as θ, and the inclination angle of the top edge of the structure relative to the vertical direction is α. The larger the value of α, the deeper the concavity of the concave structure surface. When θ > ɑ, we get 7. Among them, R is the radius of the concave structure; Adjust the tilt angles of the top edge of the structure relative to the vertical direction to α1 and α2, and let α1 > α2. Then compare the liquid meniscus pressure ΔP = P1 - P2.
8. Since cosɑ2>cosɑ1 and cos(θ-ɑ1)>cos(θ-ɑ2), then P1>P2 and ΔP>0; When θ < α, we get 9. Among them, R is the radius of the concave structure; Adjust the tilt angles of the top edge of the structure relative to the vertical direction to α1 and α2, and let α1 > α2. Then compare the liquid meniscus pressure ΔP = P1 - P2.
10. Since cosα2sinα1sinθ>cosα1sinα2sinθ, that is, tanα1>tanα2, Then P1 > P2, ΔP > 0; The above calculations prove that the larger the shape factor K is, the greater the Laplace pressure generated. Therefore, for concave structures, the greater the degree of concavity, the stronger the oil-locking ability.
11. The method for designing a durable biomimetic concave lubricating oil wetting surface according to claim 4, characterized in that: For recessed surfaces with sharp edges, the lubricating oil will be fixed by the sharp edges. The movement of the lubricating oil under shear force will be affected by the fixing effect of the structural edges. The maximum pinning angle θ of the edge is defined. pin To achieve stronger oil-locking ability and wetting effect; Specifically, 12. Where θ is the contact angle and ɑ is the tilt angle of the top edge of the structure relative to the vertical direction.