Bionic friction pad, preparation method thereof and clamp comprising bionic friction pad

Abstract

The invention discloses a bionic friction pad, a preparation method of the bionic friction pad and a clamp comprising the bionic friction pad, and belongs to the technical field of object clamping, a core component of the clamp is the bionic friction pad, and the bionic friction pad comprises a contact curved surface, a fixing groove and a transverse pin hole; the fixing plate comprises a convex groove, a bearing plate and end face glue, and the contact curved surface comprises a bionic micro-column array and an inter-column micro-channel; according to the bionic friction pad, silica gel consumables are pressed into a metal-based mold through a hot press molding process, and the bionic friction pad is obtained through demolding. Compared with a micro-structure-free clamp, stable contact can be achieved under the condition that the wetness degree is 10 mg / cm < 2 > or above, a liquid film existing between the contact faces is extruded into grooves between the micro columns through pre-pressure, the contact area between the liquid film and the surface of an object is increased, friction force is improved, clamping stability is guaranteed, and the clamping effect is good. The industrial problem that an object of a curved surface structure is unstable in clamping and not easy to carry in a wet environment is solved.

Description

Technical Field

[0001] This invention belongs to the field of object clamping technology, specifically relating to a biomimetic friction pad, its preparation method, and a clamp containing the biomimetic friction pad. Background Technology

[0002] Object clamping technology refers to the techniques and methods of fixing, moving, or manipulating objects using mechanical means. It is involved in various engineering applications. Among them, the clamping technology for curved objects in humid environments has always been a research direction that urgently needs to be solved but has yielded little result. In humid environments, the liquid film on the surface of the object reduces the effective contact area between the end structure and the object surface, causing traditional mechanical grippers to fail. Curved objects, due to their surface curvature, further exacerbate this phenomenon. Examples include the clamping and handling of medicine bottles and reagents in the medical field, and the clamping and fixing of reagent bottles required in chemical production. The main solution to the technical difficulties of clamping curved objects is to ensure the contact area and friction area during the clamping process, and to ensure that the van der Waals force between the clamping structure and the object surface meets the clamping requirements.

[0003] While some mechanical structures exist for clamping and handling curved objects, they generally suffer from significant clamping force deviations and poor stability. This leads to low industrial production efficiency, increased product defect rates, high costs, and limitations on the development of related industries. For example, patent CN218776423U discloses a workpiece gripper that includes a chassis, a fixture, a robotic arm, and anti-slip pads. The anti-slip pads enhance clamping strength and control the robotic arm's opening and closing operations, preventing abnormal detachment and improving workpiece clamping efficiency. However, the gripping part of this workpiece gripper is planar, which cannot guarantee sufficient surface friction area for clamping non-planar objects, resulting in unstable clamping performance. Patent CN219387822U discloses a sleeve clamp, which includes a traction plate, a side plate, and a clamping mechanism. When lowering the sleeve, the main body of the clamp is fitted to the spliced ​​sleeve body to ensure the safety of personnel splicing the sleeve and to meet the clamping and splicing requirements of cylindrical structures such as sleeves. However, this sleeve clamp only meets the clamping effect of cylindrical structures, and the clamping effect of other non-circular curved structures such as elliptical structures cannot meet the expected clamping effect. Summary of the Invention

[0004] This invention provides a biomimetic friction pad, its preparation method, and a clamp containing the biomimetic friction pad. The prepared biomimetic friction pad has curved surface adaptability in a humid environment and has the characteristic of being able to adaptively change the curvature of the contact surface according to the curved object to be clamped and the magnitude of the applied pre-pressure. Since the material used to prepare the biomimetic friction pad has good deformation characteristics, it can ensure the actual contact surface area with the object, improve the friction force, and eliminate the need for manual operation to change the clamping effect.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A biomimetic friction pad is disclosed, wherein the biomimetic friction pad has a curved surface structure, and one side surface is provided with a micropillar array structure. The array distribution requires that the spacing between the centers of the micropillars in each direction be equal. The micropillar array distribution can be a cylindrical array distribution, a prism array distribution, etc., preferably a hexagonal prism array distribution. The size of the micropillars needs to be designed to ensure that the liquid film can be quickly discharged under pre-pressure, while ensuring that the micropillars have sufficient structural strength. Microchannels are provided between the micropillars, and the size of the microchannels is smaller than the length of the inscribed circle of the micropillars to ensure a large contact area.

[0006] The biomimetic friction pad is made of rubber material, which can be different types of rubber such as fluororubber, perfluoroether rubber, silicone rubber, nitrile rubber or hydrogenated nitrile rubber.

[0007] The preparation method of the above-mentioned biomimetic friction pad includes the following steps: Step 1: Use 3D design software to construct a 3D model of the contact surface of the biomimetic friction pad, and set the curvature of the contact surface to 40mm. -1 The micropillars have a height of 15 μm, an inscribed circle radius of 30 μm, and a spacing of 2.5 μm. Step 2: Using photolithography, fabricate a hexagonal array of the same size on a glass substrate based on the micropillar dimensions set in Step 1, and then perform development. After development, use a magnetron sputtering device to perform magnetron sputtering and electroplating to obtain a planar nickel mold. Step 3: Roll the processed planar nickel mold obtained in Step 2 to obtain a metal-based mold with specific curvature characteristics; Step 4: Place the curvature metal-based mold obtained in Step 3 into a vacuum vulcanizing machine, mix the rubber material and vulcanizing agent thoroughly at a weight ratio of 100:1, and use a roller press to mix and roll for 30 minutes. Step 5: Place the mixed material obtained in Step 4 on the curved metal base mold, set the vacuum plate vulcanizing machine imprinting temperature to 200℃, imprinting pressure to 100MPa, and imprinting time to 10 minutes, and perform the imprinting process. Step 6: Take out the imprinted structure obtained in Step 5 and place it at room temperature to cool. After cooling, the biomimetic friction pad is obtained.

[0008] In the steps described above, the photolithography process in step 2 is set to an exposure parameter of 400 mJ / cm during actual exposure. 2 During electroplating, the electroplating time is set to 1 hour, and the electroplating material is set to nickel.

[0009] The curvature of the contact surface in step 3 is determined by the radius of curvature of the roller during rolling, and the curvature can be adjusted according to the actual situation.

[0010] A fixture comprising the aforementioned biomimetic friction pad includes: a biomimetic friction pad, a fixing groove, and a fixing plate; the upper surface of the fixing plate is connected to an external mechanism, and a convex block is provided on the lower surface; the convex block is inserted into the fixing groove and fixed by a locking pin; the bottom end of the fixing groove is fitted with the biomimetic friction pad.

[0011] The clamp requires multiple clamp blocks to work together to complete the clamping and handling process.

[0012] The fixing plate only serves as an auxiliary connection in the overall fixture, and its shape can be square, rectangle, or other standard shapes.

[0013] The external structure can be a movable mechanical structure such as a robotic arm, robotic hand, or lifting rod.

[0014] Beneficial effects: This invention provides a biomimetic friction pad, its preparation method, and a fixture containing the biomimetic friction pad, which has the following advantages compared with the prior art: 1. The biomimetic friction pad structure of this invention has stable and efficient liquid drainage characteristics, strong controllability, and is suitable for mass production; 2. The micro-pillar structure set on the contact surface of the biomimetic friction pad of the present invention, in a humid environment, squeezes the water film originally formed between the contact surfaces into the grooves between the micro-pillar structures through pre-pressure, thereby increasing the contact area and improving the friction between the surfaces. 3. After applying clamping force, the curved surface adaptive fixture can adaptively adjust the curvature of the contact surface according to the magnitude of the clamping force, ensuring the actual contact surface area with the object, improving friction, and eliminating the need for manual operation to change the clamping effect, saving manpower, while ensuring the stability of object clamping. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the preparation process of the metal-based mold in an embodiment of the present invention; Figure 2 This is a flowchart illustrating the biomimetic friction pad structure imprinting process in an embodiment of the present invention. Figure 3 This is a micrograph of the lateral three-dimensional micropillars of the contact surface of the biomimetic friction pad in an embodiment of the present invention; Figure 4 This is a top-view micrograph of the contact surface of the biomimetic friction pad in an embodiment of the present invention. Figure 5 This is a comparison chart of the friction force values ​​of the biomimetic friction pad and other friction pads under different humidity conditions in the embodiments of the present invention; Figure 6 This is a graph showing the friction force values ​​of the biomimetic friction pad under different preload conditions in an embodiment of the present invention. Figure 7 This is a schematic diagram of the biomimetic friction pad in an embodiment of the present invention; Figure 8 for Figure 7 Enlarged view of the biomimetic friction pad; Figure 9 This is a schematic diagram of the curved surface fixture structure and overall assembly in an embodiment of the present invention; Figure 10 This is a diagram illustrating the actual clamping process of the fixture in a wet environment, as described in this embodiment of the invention. Figure 11 This is a schematic diagram of the intercolumn microchannel drainage process during the clamping process in an embodiment of the present invention; In the figure: 1-Contact surface; 2-Fixing groove; 3-Transverse pin hole; 4-Bionic friction pad; 5-Convex groove; 6-End face adhesive; 7-Fixing plate; 8-Bearing plate; 9-Fixing pin; 10-Clamping block; 11-External structure; 12-Clamped object; 13-Micro-column structure; 14-Inter-column groove. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example 1: Preparation of a biomimetic friction pad like Figures 1-2 As shown, the fabrication of the biomimetic friction pad consists of two main processes: the fabrication of the metal-based mold and the biomimetic friction pad imprinting process. The specific operation steps are as follows: S1. Align the glass substrate covered with photoresist with the photomask, wherein the photomask is designed with a closely packed array of hexagonal cells. During ultraviolet light exposure, the exposure energy is set to 400 mJ / cm², so that the hexagonal patterned areas of the photomask can be selectively exposed on the photoresist.

[0017] S2. Subsequently, after development, the photoresist in the unexposed areas is removed, and a hexagonal micropillar structure array is revealed on the substrate.

[0018] S3. A thin film of metallic nickel was uniformly deposited on the surface of the micropillar array using magnetron sputtering for 1 hour to ensure complete coverage of the microstructure surface and good continuity and conductivity. After sputtering, the sample was transferred to an electroplating bath for thickening treatment. By precisely controlling the electroplating parameters, the nickel layer continued to grow on the surface of the micropillar structure and eventually filled the gaps, thus successfully replicating a nickel imprint mold with a flat shape and a hexagonal blind hole array structure on the surface.

[0019] S4. Using high-precision rolling equipment, controllable plastic deformation is applied to the flat blind hole nickel mold, bending it into a curved surface mold with a preset curvature. After this rolling process, the micro-blind hole structure of the mold can still maintain good shape accuracy and integrity. After completion, the prepared curved blind hole nickel embossing mold is securely placed in the corresponding groove of the special embossing mold base plate.

[0020] S5. Thoroughly mix the silicone and vulcanizing agent at a weight ratio of 100:1. After mixing, place the mixture into a roller press for 5 minutes. After rolling, cut the mixture into appropriately sized blocks and fill them into the grooves of the embossing mold, ensuring complete coverage of the blind hole nickel mold. Place the entire mold in a vacuum flat vulcanizing machine, set the hot pressing temperature to 200℃, the extrusion stress to 100MPa, and the hot pressing time to 10 minutes for hot pressing molding.

[0021] S6. After hot pressing, remove the overall mold, separate the upper and lower molds, and then remove the sample structure. The friction pad is now fully prepared. Next, place the friction pad structure on a cooling table for room temperature cooling for 20 minutes.

[0022] S7. After cooling, place the friction pad into a beaker, add an appropriate amount of alcohol to completely submerge all the friction pad structures, place the beaker in the center of the ultrasonic cleaning table, set the oscillation frequency to 50HZ, and the oscillation time to 10min to perform ultrasonic cleaning of the friction pad surface.

[0023] S8. Use tweezers to remove the friction pad and place it in a drying oven for drying. Set the drying temperature to 70℃ and the drying time to 30 minutes. After drying, remove the friction pad structure. The required bionic friction pad is now complete.

[0024] Characterization and performance testing of micropillar arrays for biomimetic friction pad contact surfaces 1. Characterization of the contact surface micropillar array: The dimensions of the contact surface micropillar array of the biomimetic friction pad prepared in Example 1 were examined using a scanning electron microscope. The biomimetic friction pad was placed in the center of the electron microscope stage, and the three-dimensional morphology of the micropillar array was observed using a scanning electron microscope. The three-dimensional morphology of the micropillar array is as follows: Figure 3 , Figure 4 As shown. Figure 3 This is a lateral three-dimensional micrograph of a micropillar. Figure 4The image shows a top-down view of the micropillars. From the electron microscope image, it can be seen that the height of the micropillars prepared in this invention is 15 μm, the radius of the inscribed circle of the micropillar is 30 μm, and the spacing between the micropillars is 2.5 μm.

[0025] 2. Performance testing of biomimetic friction pads: (1) Description of the setting method for a humid environment Distilled water is used as the wetting medium in humid environments. The wetting process involves preparing a spray bottle, filling it with distilled water, and spraying the substrate from a distance of 20 cm, with each spray lasting 1 second. The amount of liquid deposited per unit area is precisely controlled by the number of sprays (T), a value pre-calibrated through weighing analysis (comparing the mass of the substrate before and after spraying). When T = 3 sprays, the humidity reaches 10 mg / cm². By adjusting the T value, surfaces with different levels of wettability can be created.

[0026] (2) Instructions for testing transverse friction force The transverse friction performance of the biomimetic friction pad prepared in Example 1 was tested under different wet conditions and different preload conditions using a mechanical performance testing instrument. To emphasize the friction performance of the biomimetic friction pad, a curved surface-without micro-friction pad and a planar friction pad were introduced for comparative analysis when testing the friction force values ​​under different wet conditions. The curvature of the curved surface-without micro-friction pad was the same as that of the biomimetic friction pad in this example. A sensor with a range of 200N and an accuracy of 0.5N was selected for data recording. The friction pad was fixed to the upper plate of the sensor with colloid, and a 40mm... -1 The curvature substrate was fixed to the lower plate of the stage of the mechanical performance tester using colloid. The sensor moving speed was set to 0.5 mm / s, and the loading preload range was set to 0.5 N-4 N. With 0.5 N increments, the lateral friction force of the bionic friction pad was recorded during the contact and movement of the wet substrate with the bionic friction pad. A curve was plotted with the preload as the abscissa and the lateral friction force value as the ordinate.

[0027] A comparison of the friction force values ​​of the biomimetic friction pad and other friction pads under different humidity conditions is shown in the figure below. Figure 5 As shown, under different humidity conditions, the friction performance of the three friction pads all showed a certain decreasing trend with increasing humidity. However, the decreasing trend of the lateral friction force of the biomimetic friction pad in this embodiment was significantly smaller than that of the other two comparative friction pads. The friction force value could be stabilized at more than 90% of the dry friction force value, and the humidity level was greater than 10 mg / cm². 2 When the friction force is greater than the other two friction force values, it indicates that the biomimetic friction pad of the present invention can achieve stable contact under wet conditions.

[0028] The friction force data of the biomimetic friction pad in this embodiment under different preload conditions are shown in the figure below. Figure 6As shown, the lateral friction of the bionic friction pad increases with the increase of preload and reaches its maximum when the preload is 3N. The ratio of its friction value to the preload is greater than 1, which can achieve stable contact.

[0029] Example 2: Explanation of the clamping function of the bionic gripper like Figure 7-11 As shown, the bionic fixture containing the bionic friction pad prepared in Example 1 includes a bionic friction pad 4, a fixing plate 7, and a fixing pin 9; the bionic friction pad 4 includes a contact curved surface 1, a fixing groove 2, and a transverse pin hole 3; the fixing plate 7 includes a convex groove 5, a load-bearing plate 8, and an end face adhesive 6; the bionic friction pad 4 is made of rubber; the fixing plate 7 is 3D printed using PLA material.

[0030] During the assembly process, the curved self-adaptive fixture first aligns and connects the fixing groove 2 with the convex groove 5, then locks and connects the transverse pin hole 3 with the fixing pin 9, and finally inserts the fixing pin 9 into the concentric position until it is fully inserted, and the fixture block 10 is assembled as a whole.

[0031] When this adaptive curved surface fixture is used under wet conditions, firstly, the end face adhesive 6 of the two fixture blocks 10 is connected to the external structure 11. The contact surface 1 of one fixture block 10 is in contact with the curved surface of the object 12 being held, and the contact surface 1 of the other fixture block 10 is in contact with the other side of the curved surface of the object 12 being held. The included angle formed by the two sides is 180°. The external structure 11 applies opposing clamping forces to the two fixture blocks. The water film formed between the contact surfaces 1 is forced into the intercolumnar groove 14, which increases the contact area between the microcolumnar structure 13 on the contact surface 1 and the curved surface of the object 12 being held, increases the friction between the contact surfaces, and enhances the clamping stability.

[0032] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art, within the technical scope disclosed in the present invention, shall make equivalent substitutions or changes according to the technical solution and inventive concept of the present invention, and such substitutions or changes shall be covered within the scope of protection of the present invention.

Claims

1. A biomimetic friction pad, characterized in that, The biomimetic friction pad has a curved surface structure, with micropillar structures on one side surface. The micropillar structures are distributed in an array, and the spacing between the centers of the micropillars in each orientation is equal. Microchannels are provided between the micropillars, and the size of the microchannels is smaller than the length of the inscribed circle of the micropillar.

2. The biomimetic friction pad according to claim 1, characterized in that, The biomimetic friction pad is made of rubber material.

3. The biomimetic friction pad according to claim 2, characterized in that, The micro-pillar array is distributed as a cylindrical array or a prism array.

4. The method for preparing the biomimetic friction pad according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Use 3D design software to construct a 3D model of the contact surface of the biomimetic friction pad, and set the surface curvature, micropillar height, micropillar inscribed circle radius, and micropillar spacing. Step 2: Using photolithography, fabricate a hexagonal array of the same size on a glass substrate based on the micropillar dimensions set in Step 1, and then perform development processing. After development, a magnetron sputtering and electroplating process is performed using a magnetron sputtering device to obtain a planar metal-based mold. Step 3: Roll the processed planar nickel mold obtained in Step 2 to obtain a metal base mold with specific curvature characteristics. The curvature of the surface is determined by the curvature radius of the rolling roller during rolling. The curvature can be adjusted according to the actual situation. Step 4: Thoroughly mix the rubber material and vulcanizing agent according to the formula, and use a roller press to mix and roll the mixture; Step 5: Place the mixed material obtained in Step 4 onto the metal-based mold with specific curvature characteristics obtained in Step 3, and perform an imprinting process; Step 6: Take out the embossed structure obtained in Step 5 and place it at room temperature to cool. After cooling, the biomimetic friction pad is obtained.

5. The method for preparing the biomimetic friction pad according to claim 4, characterized in that, The curvature of the contact surface is 40mm. -1 The micropillars have a height of 15 μm, an inscribed circle radius of 30 μm, and a spacing of 2.5 μm.

6. The method for preparing the biomimetic friction pad according to claim 4, characterized in that, In step 2, the photolithography process involves setting the exposure parameters to 400 mJ / cm² during actual exposure. 2 During electroplating, the electroplating time is set to 1 hour, and the electroplating material is set to nickel.

7. The method for preparing the biomimetic friction pad according to claim 4, characterized in that, The weight ratio of rubber material to vulcanizing agent is 100:

1.

8. The method for preparing the biomimetic friction pad according to claim 4, characterized in that, In step 5, the imprinting temperature is 200℃, the imprinting pressure is 100MPa, and the imprinting time is 10 minutes.

9. A clamp comprising the biomimetic friction pad according to any one of claims 1-3, characterized in that, It includes a biomimetic friction pad, a fixing groove, and a fixing plate; the upper surface of the fixing plate is connected to an external mechanism, and the lower surface is provided with a convex block. The convex block is inserted into the fixing groove and fixed by a locking pin. The bottom end of the fixing groove is equipped with a biomimetic friction pad.

10. The clamp comprising the biomimetic friction pad according to any one of claims 1-3 according to claim 9, characterized in that, The clamp requires multiple clamp blocks to work together to complete the clamping and handling process.

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