A bidirectional self-excited lubricating wedge texture and its preparation method

Abstract

This invention discloses a bidirectional self-excited lubricating wedge-shaped texture and its preparation method, belonging to the field of biotribology. The wedge-shaped texture is a bidirectional convergent structure, with the depth of each texture unit monotonically varying along its length, and adjacent texture units exhibiting opposite depth variation trends, forming an alternating, jagged topological distribution. The cross-section of the texture unit is a centrally symmetrical semi-circular shape. The wedge-shaped texture achieves integrated molding of the texture geometry and the matrix material through selective laser sintering, eliminating the need for subsequent secondary processing. The bidirectional self-excited lubricating ultra-high molecular weight polyethylene wedge-shaped texture prepared by this invention can form reciprocating hydrodynamic lubrication during movement, achieving bidirectional transport and active lubrication of the lubricating medium. This results in a more uniform oil film distribution and stronger adaptability to lubrication conditions, thereby significantly improving the friction coefficient, wear rate, and lubrication film stability. It has great application potential in the field of biomedical engineering, especially in artificial joints and orthopedic implants.

Description

Technical Field

[0001] This invention belongs to the field of biotribology, specifically relating to a bidirectional self-excited lubricating wedge texture and its preparation method. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE), with its excellent biocompatibility, stable corrosion resistance, and good impact toughness, has become the preferred material for tribological components of artificial joints such as acetabular liners and tibial pads. Crucially, its unique ultra-long molecular chains and highly entangled aggregated structure give the material surface a natural self-lubricating effect, effectively reducing the coefficient of friction and wear between the material and its mating surfaces, providing a reliable material guarantee for long-term clinical implantation applications.

[0003] However, artificial joints often undergo reciprocating motion in the body's physiological environment. This type of directional movement can lead to a sharp increase in UHMWPE wear debris, which can induce long-term complications such as periarticular osteolysis and aseptic loosening, resulting in artificial joint failure.

[0004] To improve the biotribological properties of UHMWPE, existing technologies mainly focus on material modification methods such as radiation crosslinking, or traditional texturing treatments such as introducing micro-dimples on the surface. However, these methods all have significant limitations: material modification is prone to the introduction of residual free radicals, posing potential biosafety risks; and traditional surface texturing designs are mostly based on unidirectional sliding conditions, which limit the friction reduction effect in reciprocating motion. Moreover, the texturing is mostly formed by secondary processing methods such as etching, which not only has a lengthy process and high manufacturing cost, but also easily damages the inherent wear resistance and mechanical properties of the matrix material.

[0005] Therefore, there is an urgent need to develop a bidirectional self-excited lubricating wedge texture that can adapt to the reciprocating motion of artificial joints in physiological environments, so as to significantly improve the biotribological properties of UHMWPE; at the same time, the intrinsic properties of the matrix material are not damaged during the preparation process, and the texture geometry can be integrally formed with the matrix material without the need for subsequent secondary processing. Summary of the Invention

[0006] In view of this, the present invention provides a bidirectional self-excited lubricating wedge texture and its preparation method. The bidirectional wedge texture can generate a hydrodynamic pressure effect in reciprocating motion and can actively release the internally stored lubricant during elastic deformation to lubricate the friction interface in advance.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A bidirectional self-excited lubricating wedge texture and its preparation method are disclosed. The wedge texture is a bidirectional convergent structure. The depth of each texture unit varies monotonically along its length direction, and the depth variation trends of adjacent texture units are opposite, forming an alternating deep and shallow dog-tooth topological distribution. The cross-section of the texture unit is a centrally symmetrical semi-arc. The wedge texture achieves integrated molding of texture geometry and matrix material through selective laser sintering, without the need for subsequent secondary processing.

[0009] Preferably, the depth of the wedge texture exhibits a monotonically changing linear or nonlinear variation, with the nonlinear variation including exponential, logarithmic, or power-law variations.

[0010] Preferably, the symmetrical semi-arc is a circular arc, an elliptical arc, or a parabolic arc, and a straight transition area is provided between adjacent wedge-shaped texture units, the width of which is 1.5 to 3 times the width of the texture.

[0011] Preferably, the wedge-shaped texture has a texture depth of 150~250 μm, a texture inclination angle of 2°~4°, and a texture width of 200~300 μm.

[0012] Preferably, the material of the wedge-shaped texture is ultra-high molecular weight polyethylene, with an average powder particle size of 20~100 µm and a weight-average molecular weight of 3×10⁻⁶. 6 ~6×10 6 .

[0013] The preparation method of the bidirectional self-excited lubrication wedge texture includes the following steps: spreading ultra-high molecular weight polyethylene powder on a molding platform, scanning and sintering layer by layer according to the preset wedge texture model using selective laser sintering process, and then removing powder under high pressure, ultrasonic cleaning and vacuum drying to prepare an integrated ultra-high molecular weight polyethylene wedge texture with bidirectional self-excited lubrication.

[0014] Preferably, the laser spot diameter is 0.1~0.4 mm, the single-layer powder thickness is 0.05~0.15 mm, the laser power is 2~5 W, and the scanning speed is 80~120 mm / s.

[0015] Preferably, the powder removal process employs a high-pressure airflow purging method with a purging pressure of 0.3~0.5 MPa and a purging time of 5~10 min; ultrasonic cleaning with a power of 50~80 W and a cleaning time of 7~10 min; and drying in a vacuum drying oven at 60~80℃ for 9~12 h.

[0016] Preferably, the inner wall surface roughness Ra of the wedge-shaped texture is ≤0.4 μm, and there is no sintering slag or powder residue at the edge of the texture.

[0017] The present invention also provides a sample of a bidirectional self-excited lubricating UHMWPE wedge texture prepared by the method.

[0018] The innovative idea of ​​this invention is to design a bidirectional convergent wedge texture and make the depth change trends of adjacent texture units opposite, forming a hydrodynamic pressure effect of the wedge gap, thereby realizing bidirectional transport and active lubrication of the lubricating medium; at the same time, selective laser sintering process is used to integrate the texture geometry with the matrix material, avoiding the secondary processing required by traditional forming methods, simplifying the texture preparation process and ensuring processing accuracy.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The bidirectional convergent wedge texture designed in this invention, combined with an alternating light and dark dog-tooth topological distribution, enables bidirectional hydrodynamic lubrication. Compared to traditional unidirectional convergent textures, this invention does not rely on a specific direction of motion; the friction pair can form a convergent wedge space within the texture unit during reciprocating motion, resulting in stronger lubrication adaptability.

[0021] 2. The present invention employs selective laser sintering, which can simultaneously form the geometric features of the texture with the substrate material. Compared with traditional secondary processing methods such as photolithography and etching, the present invention has a shorter process flow, higher dimensional accuracy, and avoids morphological damage that may be caused by subsequent secondary processing.

[0022] 3. This invention only needs to utilize the micro-pump effect of alternating depths of adjacent textures to achieve active transport and uniform spreading of the lubricating medium. Compared with traditional uniform depth textures, the wedge-shaped texture of this invention has stronger spontaneous active lubrication, more uniform distribution of the lubricating oil film, and is less prone to local oil film rupture.

[0023] 4. The bidirectional self-excited lubricating wedge texture prepared by the SLS process in this invention has better friction reduction and lubrication effects, and significantly improves the friction coefficient, wear rate and lubrication film stability. It has great application potential in the field of medical devices such as artificial joints. Attached Figure Description

[0024] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0025] Figure 1 This is a three-dimensional structural schematic diagram of the bidirectional self-excited lubrication wedge texture of the present invention.

[0026] Figure 2 This is a schematic diagram of the two-dimensional surface distribution of the bidirectional self-excited lubricating wedge texture of the present invention.

[0027] Figure 3This is a laser confocal microscope image of the bidirectional self-excited lubricating UHMWPE wedge texture of the present invention.

[0028] Figure 4 The average friction coefficient of the bidirectional self-excited lubricating UHMWPE wedge texture obtained in Examples 1-3 and Comparative Examples 1 and 3 of the present invention.

[0029] Figure 5 The wear rate is the bidirectional self-excited lubricating UHMWPE wedge texture obtained in Examples 1-3 and Comparative Examples 1 and 3 of the present invention.

[0030] Figure 6 The hydrophilicity of the bidirectional self-excited lubricating UHMWPE wedge texture obtained in Examples 1-3 and Comparative Examples 1 and 3 of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] Two-way wedge texture design: A two-way convergent wedge texture is constructed in 3D design software. The depth of each texture unit changes linearly along its length direction, and the depth changes of adjacent texture units have opposite trends, forming an alternating deep and shallow ivy topological distribution. The cross-section of the texture unit is a centrally symmetrical semi-ellipse. The maximum depth of the texture unit is 150 μm, the maximum width is 200 μm, and the inclination angle is 3.5°. There is a 300 μm wide straight transition region between adjacent texture units.

[0034] Preparation of bidirectional wedge texture: Particles with an average size of 80 µm and a weight-average molecular weight of 4.5 × 10⁻⁶ were used. 6 UHMWPE powder was spread on a molding platform and sintered layer by layer using selective laser sintering (SLS) according to a pre-designed wedge-shaped texture model. The laser spot diameter was 0.15 mm, the thickness of a single powder layer was 0.10 mm, the laser power was 2.6 W, and the scanning speed was 90 mm / s. After preparation, excess powder was removed by high-pressure airflow purging at a pressure of 0.45 MPa for 6 min. The powder was then ultrasonically cleaned in deionized water at 50 W for 8 min, and finally dried in a vacuum oven at 65℃ for 12 h to obtain a UHMWPE wedge-shaped texture with bidirectional self-excited lubrication.

[0035] Example 2

[0036] Two-way wedge texture design: A two-way convergent wedge texture is constructed in 3D design software. The depth of each texture unit varies logarithmically along its length, and the depth variation trends of adjacent texture units are opposite, forming an alternating deep and shallow ivy topological distribution. The cross-section of the texture unit is a centrally symmetrical semi-circular arc. The maximum depth of the texture unit is 210 μm, the maximum width is 300 μm, and the inclination angle is 2.2°. There is a 750 μm wide straight transition region between adjacent texture units.

[0037] Preparation of bidirectional wedge texture: Particles with an average size of 55 µm and a weight-average molecular weight of 5 × 10⁻⁶ were used. 6 UHMWPE powder was spread on a molding platform and sintered layer by layer using selective laser sintering (SLS) according to a pre-defined wedge-shaped texture model. The laser spot diameter was 0.1 mm, the thickness of a single powder layer was 0.05 mm, the laser power was 3.8 W, and the scanning speed was 100 mm / s. After preparation, excess powder was removed by high-pressure airflow purging at a pressure of 0.5 MPa for 10 min. The powder was then ultrasonically cleaned in deionized water at 75 W for 7 min, and finally dried in a vacuum oven at 80℃ for 9 h to obtain a UHMWPE wedge-shaped texture with bidirectional self-excited lubrication.

[0038] Example 3

[0039] Two-way wedge texture design: A two-way convergent wedge texture is constructed in 3D design software. The depth of each texture unit varies exponentially along its length direction, and the depth variation trends of adjacent texture units are opposite, forming an alternating deep and shallow ivy topological distribution. The cross section of the texture unit is a centrally symmetric parabolic arc. The maximum depth of the texture unit is 240 μm, the maximum width is 250 μm, and the inclination angle is 2.9°. There is a 500 μm wide straight transition region between adjacent texture units.

[0040] Preparation of bidirectional wedge texture: Particles with an average size of 30 µm and a weight-average molecular weight of 6 × 10⁻⁶ were used. 6 UHMWPE powder was spread on a molding platform and sintered layer by layer using selective laser sintering (SLS) according to a pre-designed wedge-shaped texture model. The laser spot diameter was 0.3 mm, the thickness of a single powder layer was 0.15 mm, the laser power was 5 W, and the scanning speed was 115 mm / s. After preparation, excess powder was removed by high-pressure airflow purging at a pressure of 0.32 MPa for 8 min. The powder was then ultrasonically cleaned in deionized water at 60 W for 10 min, and finally dried in a vacuum oven at 70℃ for 10.5 h to obtain a UHMWPE wedge-shaped texture with bidirectional self-excited lubrication.

[0041] Comparative Example 1

[0042] It is basically the same as Example 1, except that the designed wedge texture is not bidirectional convergent, but unidirectional convergent, and the depth change trend of adjacent texture units is the same.

[0043] Comparative Example 2

[0044] It is basically the same as Example 2, except that each texture unit is directly adjacent to the other, rather than having a straight transition area with a certain distance.

[0045] Comparative Example 3

[0046] Similar to Example 3, except that after preparation, the UHMWPE wedge texture was not subjected to a series of treatments including high-pressure powder removal, ultrasonic cleaning, and vacuum drying.

[0047] The following are the performance tests conducted on the samples obtained from the embodiments and comparative examples of the present invention.

[0048] Figure 1 This is a three-dimensional structural diagram of a bidirectional self-excited lubrication wedge texture. The depth of each texture unit varies monotonically along its length, while the depth variation trends of adjacent texture units are opposite. This can effectively eliminate the side leakage offset and hydrodynamic pressure asymmetry caused by unidirectional texture, forming a uniform and stable hydrodynamic pressure lubrication, significantly reducing the friction coefficient and wear rate, and achieving excellent adaptive lubrication and long service life.

[0049] Figure 2 This is a schematic diagram of the two-dimensional surface distribution of the bidirectional self-excited lubricating wedge texture. The texture units form an interlocking topological distribution, which enables continuous entrainment and automatic pumping of lubricant through the alternating squeezing and convergence effect of the wedge units when the friction pair moves in both directions. This forms a continuous hydrodynamic lubrication film at the friction interface, providing reliable lubrication and friction reduction for medical device components with directional movement.

[0050] Figure 3 The image shown is a laser confocal microscope image of the bidirectional self-excited lubricated UHMWPE wedge texture prepared in this invention. The texture has a distinct bidirectional convergent structure, indicating that selective laser sintering can achieve integrated molding of the texture geometry and the matrix material.

[0051] Figure 4The average friction coefficients of the bidirectional self-excited lubricating UHMWPE wedge textures obtained in Examples 1-3 and Comparative Examples 1 and 3 of this invention are shown. The average friction coefficients of the samples in Examples 1, 2, and 3 are 0.12, 0.09, and 0.13, respectively. The friction coefficients of the samples are closely related to the geometric parameters of the wedge texture, and the two show a nonlinear trend. As the texture depth initially increases, the friction coefficient decreases sharply. When the texture depth further increases to a certain range, the friction coefficient increases instead. The average friction coefficients of the samples in Comparative Examples 1 and 3 are 0.18 and 0.17, respectively, indicating that both the unidirectional convergent wedge texture and the bidirectional wedge texture without high-pressure powder removal, ultrasonic cleaning, and vacuum drying will increase the friction coefficient of the samples.

[0052] Figure 5 The wear rates of the bidirectional self-excited lubricating UHMWPE wedge textures obtained in Examples 1-3 and Comparative Examples 1 and 3 of this invention are shown in the figure. The wear rates of the samples in Examples 1, 2, and 3 are 0.74 × 10⁻⁶. -6 mm 3 / N·m, 0.62×10 -6 mm 3 / N·m、0.79×10 -6 mm 3 The wear rate of the sample was closely related to the geometric parameters of the wedge texture, exhibiting a non-linear trend. With the initial increase in texture depth, the wear rate decreased sharply, but when the texture depth further increased to a certain range, the wear rate increased instead. The wear rates of Comparative Example 1 and Comparative Example 3 samples were 1.16 × 10⁻⁶ N·m. -6 mm 3 / N·m、1.08×10 -6 mm 3 / N·m indicates that both unidirectional convergent wedge texture and bidirectional wedge texture without a series of treatments including high-pressure powder removal, ultrasonic cleaning, and vacuum drying will increase the wear rate of the sample.

[0053] Figure 6 To assess the hydrophilicity of the bidirectional self-excited lubricating UHMWPE wedge textures obtained in Examples 1-3 and Comparative Examples 1 and 3 of this invention, the water contact angles of the samples in Examples 1, 2, and 3 were 63.1°, 58.4°, and 54.6°, respectively. The water contact angle of the samples showed a close negative correlation with the geometric parameters of the wedge texture. As the texture depth increased, the water contact angle gradually decreased, indicating that the hydrophilicity was improved. The water contact angles of the samples in Comparative Examples 1 and 3 were 73.7° and 75.0°, respectively, indicating that both the unidirectional convergent wedge texture and the bidirectional wedge texture without high-pressure powder removal, ultrasonic cleaning, and vacuum drying would increase the water contact angle of the samples and reduce the hydrophilicity.

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent modifications or substitutions easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A bidirectional self-excited lubricating wedge texture and its preparation method, characterized in that, The wedge texture is a bidirectional convergent structure. The depth of each texture unit varies monotonically along its length, and the depth variation trends of adjacent texture units are opposite, forming an alternating deep and shallow dog-tooth topological distribution. The cross-section of the texture unit is a centrally symmetrical semi-arc. The wedge texture achieves integrated molding of texture geometry and matrix material through selective laser sintering, without the need for subsequent secondary processing.

2. The bidirectional self-excited lubricating wedge texture according to claim 1, characterized in that, The depth of the wedge texture varies monotonically, either linearly or nonlinearly. The nonlinear variation includes exponential, logarithmic, or power-law variations.

3. The bidirectional self-excited lubricating wedge texture according to claim 1, characterized in that, The symmetrical semi-arc is a circular arc, an elliptical arc, or a parabolic arc. A straight transition area is set between adjacent wedge-shaped texture units, and the width of this area is 1.5 to 3 times the width of the texture.

4. The bidirectional self-excited lubricating wedge texture according to claim 1, characterized in that, The wedge texture has a texture depth of 150~250 μm, a texture inclination angle of 2°~4°, and a texture width of 200~300 μm.

5. The bidirectional self-excited lubricating wedge texture according to claim 1, characterized in that, The wedge-shaped texture is made of ultra-high molecular weight polyethylene, with an average powder particle size of 20-100 µm and a weight-average molecular weight of 3 × 10⁻⁶. 6 ~6×10 6 .

6. The method for preparing the bidirectional self-excited lubricating wedge texture according to any one of claims 1-5, characterized in that, The process includes the following steps: spreading ultra-high molecular weight polyethylene powder on a molding platform, scanning and sintering layer by layer using a selective laser sintering process according to a preset wedge texture model, and then removing powder under high pressure, ultrasonic cleaning and vacuum drying to prepare an integrated ultra-high molecular weight polyethylene wedge texture with bidirectional self-excited lubrication.

7. The preparation method according to claim 6, characterized in that, The laser spot diameter is 0.1~0.4 mm, the single-layer powder thickness is 0.05~0.15 mm, the laser power is 2~5 W, and the scanning speed is 80~120 mm / s.

8. The preparation method according to claim 6, characterized in that, The powder removal process uses a high-pressure airflow purging method with a purging pressure of 0.3~0.5 MPa and a purging time of 5~10 min; the ultrasonic cleaning power is 50~80 W and the cleaning time is 7~10 min; and the powder is dried in a vacuum drying oven at 60~80℃ for 9~12 h.

9. The preparation method according to claim 6, characterized in that, The inner wall surface roughness Ra of the wedge texture is ≤0.4μm, and there is no sintering slag or powder residue at the edge of the texture.

10. The method according to claim 1, characterized in that, The bidirectional self-excited lubricating wedge-shaped texture prepared by the method of any one of claims 1 to 9 is used for friction pair components of medical devices, including acetabular liners, tibial pads, and femoral head prostheses.

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