A method for producing a mushroom-shaped array via hole mold and application thereof

Abstract

The application discloses a kind of production methods and application of mushroom-shaped array via hole mould which avoid blockage, easy to clean, including steps: round hole array mould processing, hot-press forming, conductive treatment, end insulation, electroforming;The mushroom-shaped array via hole mould obtained by the method is applied in the preparation of mushroom-shaped bionic array by rolling;The metal mould prepared by the method has high mechanical strength, high thermal conductivity and good durability, and converts the processing problem of mushroom-shaped blind hole into mushroom-shaped via hole, forms mushroom-shaped via hole by inducing non-uniform deposition of metal ions in 3D limited space, effectively eliminates the limitation that the morphology of plating layer is completely determined by the morphology of core mould in conventional electrodeposition process, simplifies the geometry of electroforming core mould, reduces the manufacturing difficulty of electroforming core mould, and improves the controllability of plating layer morphology.

Description

Technical Field

[0001] This invention relates to the field of mold manufacturing, specifically to a biomimetic mold, and particularly to a method for producing and applying a mushroom-shaped array of through-hole molds. Background Technology

[0002] Inspired by the remarkable adhesive abilities of insects like beetles, geckos, and flies, biomimetic adhesive arrays with terminal enlargement structures have been developed. These arrays, with their high viscosity-pressure ratio, residue-free operation, and controllable adhesion-detachment, hold great promise in fields such as biomedicine, flexible grasping, climbing robots, and space operations, making them one of the most popular commercial topics in biomimetic science today. Among the various fabrication techniques for terminally enlarged biomimetic adhesive arrays, molding technology is currently the mainstream method due to its ability to efficiently and precisely replicate polymer surface microstructures. Existing molds typically use silicon-based photolithography templates or soft templates. However, these two types of molds are either expensive to manufacture, prone to wear and breakage, and have short lifespans, requiring frequent replacements and resulting in expensive equipment, complex processes, and high manufacturing costs; or they are easily deformed, leading to poor replication accuracy, severely reducing the adhesive performance of the product, and are not heat-resistant, limiting the use of certain thermosetting polymers. Therefore, a controllable manufacturing process for metal molds for biomimetic adhesive arrays remains an important technological requirement.

[0003] However, the mold cavity used to manufacture biomimetic arrays with bulging end structures is complex in shape, featuring a long, narrow inlet and a bulging bottom blind hole structure. Traditional subtractive manufacturing methods (machining, laser processing) make it difficult to directly machine onto metal. Laser processing and anodizing, methods commonly used in metal mold making, are also difficult to implement directly. Due to the high array density, with a hole density greater than 20,000 / cm², this is particularly challenging. 2Such a high-density microporous array is highly susceptible to severe deformation due to processing stress, resulting in low processing efficiency. While 3D printing additive manufacturing is theoretically feasible, its "step effect" significantly impacts the precision and demolding performance of metal molds. The performance of the adhesive material is closely related to the height, diameter, and density of the end-expanded microstructures; that is, the local geometry of the biomimetic array can significantly affect adhesion performance. Conventional micro-electroforming, as a metal additive manufacturing process, is feasible, but requires the fabrication of a matching mushroom-shaped array core mold. The electroformed core mold, as the preform for the electroformed microstructure, plays a decisive role in the deposition morphology and quality. Although existing theoretical research has proposed optimization models for the shape and size of biomimetic adhesive arrays, most of these models are obtained through numerical simulation and computational calculations. The optimized morphology is extremely difficult to process, neglecting the crucial factor that manufacturing constraints must be considered during the design process. Due to the presence of the "expanded ends" in the microstructure of biomimetic adhesive materials, traditional micro-electroforming methods have difficulty in completely filling the metal plating layer in the areas blocked by the "expanded ends". Therefore, even if the filling is completed through process optimization, there is still a manufacturing challenge for the electroforming core mold.

[0004] Meanwhile, due to the blind-hole, mushroom-shaped micro-pits in the metal mold, demolding is difficult during actual use, leading to blockage of the "blind holes." Furthermore, the polymer material used in the mushroom-shaped biomimetic array makes it difficult to clean the polymer material clogging the "blind holes" in the metal mold, resulting in a high scrap rate for the finished products.

[0005] Scanning electron microscopy (SEM) is an observational technique that falls between transmission electron microscopy and optical microscopy. It utilizes a narrow, focused beam of high-energy electrons to scan a sample. Through the interaction between the beam and the material, various physical information is excited, collected, magnified, and re-imaged to characterize the microscopic morphology of the material. Modern scanning electron microscopes can achieve a resolution of 1 nm; magnification can be continuously adjusted to 300,000x or higher; and they offer large depth of field, wide field of view, and excellent three-dimensional imaging. Furthermore, combining scanning electron microscopy with other analytical instruments allows for simultaneous observation of microscopic morphology and analysis of the composition of micro-areas. Scanning electron microscopy has wide applications in the study of rocks, soils, graphite, ceramics, and nanomaterials. Therefore, scanning electron microscopy plays a significant role in scientific research. Summary of the Invention

[0006] The purpose of this invention is to provide a production method and application of a mushroom-shaped array through-hole mold that avoids clogging and is easy to clean.

[0007] This invention achieves its objective by employing the following technical solution: a method for producing a mushroom-shaped array through-hole mold, comprising the following steps:

[0008] (1) Circular hole array mold processing: A circular hole array is processed on the surface of photoresist or silicon wafer using photolithography and / or deep silicon etching. The diameter and density of the cylindrical holes are determined by the mask pattern, while the hole depth can be adjusted by the photolithography and / or deep silicon etching process parameters to obtain the circular hole array mold.

[0009] (2) Hot pressing: Then, using a circular hole array mold, hot melt polymers such as PMMA (polymethyl methacrylate) and PS (polystyrene) are planar imprinted to prepare a cylindrical array with ball heads;

[0010] (3) Conductivity treatment: The pre-prepared cylindrical array with ball heads is subjected to (surface) conductivity treatment so that an electroforming seed layer is formed on all surfaces of the cylindrical array with ball heads;

[0011] (4) End insulation: The spherical ends of the conductive cylindrical array with spherical heads are insulated by the surface dipping (insulating coating) method to obtain a locally conductive 3D confined electroforming core mold.

[0012] (5) Electroforming: Electroforming is performed using a prepared 3D confined electroforming mandrel, which induces the non-uniform deposition of metal ions (of the plating metal) in the 3D local space to form mushroom-shaped through holes;

[0013] During electroforming, the electroforming time should be strictly controlled according to the morphology requirements. Electroforming should be stopped when the plating metal is about to completely cover the spherical insulating end of the 3D confined electroforming core mold. Finally, the mushroom-shaped array through-hole mold can be obtained by removing the 3D confined electroforming core mold.

[0014] In order to ensure the deposition morphology and quality, and to obtain the microstructure of the desired curvature end, this invention achieves the control of parameters such as the microstructure height, diameter, microstructure density, and end morphology of the core mold. The imprinting in step (2) is carried out at a temperature of 110℃~120℃, a pressure of 500KPa~550KPa, and a holding time of 15 minutes~20 minutes.

[0015] As mentioned above, the mushroom-shaped array through-hole mold is used in the roll forming of mushroom-shaped biomimetic arrays. In order to form a crown-shaped cavity with one open end by the through-holes with open ends, the mushroom-shaped array through-hole (nickel) mold is wrapped around the cylindrical surface of the roller of the roll-to-roll nano (roll forming) imprinting device. The circumferential pre-tightening force is used to make the mushroom-shaped array through-hole mold and the substrate fit tightly together. The mushroom-shaped array through-hole mold and the substrate are treated with anti-sticking to ensure that the mushroom-shaped end can be easily demolded. During imprinting, the polymer prepolymer is uniformly coated on the PET film. The curing problem is set according to the polymer type, and the curing time is controlled by the roller speed.

[0016] By adopting the above technical solution, the present invention has achieved its objective well. The metal mold produced has high mechanical strength, high thermal conductivity, and good durability. It transforms the processing problem of mushroom-shaped blind holes into mushroom-shaped through holes. By inducing the non-uniform deposition of metal ions in a 3D confined space to form mushroom-shaped through holes, it effectively removes the limitation that the coating morphology is completely determined by the core mold morphology in conventional electrodeposition processes. It simplifies the geometry of the electroforming core mold, reduces the manufacturing difficulty of the electroforming core mold, and improves the controllability of the coating morphology. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the principle structure of the circular hole array mold obtained by photolithography and deep silicon etching in step (1) of Embodiment 1 of the present invention.

[0018] Figure 2 This is a schematic diagram of the principle structure of step (2) in this invention;

[0019] Figure 3 This is a schematic diagram of the principle structure of steps (3) and (4) in this invention;

[0020] Figure 4 This is a schematic diagram of the principle structure of step (5) in this invention;

[0021] Figure 5 This is a schematic diagram comparing the individual morphological structures of a blind hole A constructed by electroforming in the prior art with that of a through hole B constructed by electroforming in step (5) of this invention.

[0022] Figure 6 This invention is a simulation of the evolution mechanism of individual micropore morphology during the preparation of a crown-shaped microporous metal mold by 3D localized induced electrodeposition.

[0023] Figure 7 This is a schematic diagram illustrating the principle of preparing a mushroom-shaped biomimetic array structure by rolling with a through-hole nickel mold in this invention.

[0024] Figure 8 It is the microstructure morphology index obtained under different imprinting parameters when imprinting polymethyl methacrylate (PMMA) using a mushroom-shaped array through-hole mold;

[0025] Figure 9 These are images of the coating morphology of the microstructure obtained through electrochemical deposition simulation using a mushroom-shaped array through-hole mold;

[0026] Figure 10 It is a microstructure morphology index simulated by electrochemical deposition using a mushroom-shaped array through-hole mold;

[0027] Figure 11 These are photographs and SEM images of the tip-extended microstructure of the adhesive structure of the mushroom-shaped biomimetic array during the fabrication and performance testing of the adhesive structure.

[0028] Figure 12 These are the test results of the adhesion performance of mushroom-shaped biomimetic array structures prepared under different pre-pressure conditions;

[0029] Figure 13 These are the test results of adhesion performance at different desorption rates under a pre-pressure of 0.02 MPa;

[0030] Figure 14 These are the test results of the adhesive strength of the adhesive under different pressures;

[0031] In the diagram: 1. Mask, 2. Photoresist, 3. Silicon wafer, 4. (Deep silicon etching) cylindrical hole, 5. Circular hole array mold, 6. Hot melt polymer, 7. Rigid substrate with planar imprinting, 8. Hot-pressed ball head, 9. Cylindrical array with ball head, 10. Electroforming seed layer, 11. Insulating coating, 12. 3D confined electroforming core mold, 13. Plated metal, 14. Mushroom-shaped array through-hole mold;

[0032] 15. (Roll forming) Roller body, 16. Roll forming pad, 17. Mushroom-shaped biomimetic array, 18. Roll forming heating module, 19. Polyethylene terephthalate (PET) film, 20. (Roll forming) Support roller, 21. Polymer top polymer. Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments. Example

[0034] Depend on Figures 1 to 6 It is known that a method for producing a mushroom-shaped array of through-hole molds includes the following steps:

[0035] (1) Fabrication of circular hole array mold: A circular hole array is fabricated on the surface of photoresist or silicon wafer using photolithography and / or deep silicon etching. The diameter and density of the cylindrical holes are determined by the mask pattern, while the hole depth can be adjusted by the photolithography and / or deep silicon etching process parameters to obtain the circular hole array mold (this embodiment uses photolithography and deep silicon etching).

[0036] (2) Hot pressing: Then, the hot melt polymer is pressed into a planar shape using a circular hole array mold to prepare a cylindrical array with ball heads (the hot melt polymer described in this embodiment is polymethyl methacrylate).

[0037] (3) Conductivity treatment: The pre-prepared cylindrical array with ball heads is subjected to surface conductivity treatment so that an electroforming seed layer is formed on all surfaces of the cylindrical array with ball heads;

[0038] (4) End insulation: The spherical ends of the conductive cylindrical array with spherical heads are insulated by using a surface dipping method to obtain a locally conductive 3D confined electroforming core mold.

[0039] (5) Electroforming: Electroforming is performed using a prepared 3D confined electroforming mandrel, which induces non-uniform deposition of metal ions in the local space to form mushroom-shaped through holes;

[0040] Electroforming is stopped when the plating metal is about to completely cover the spherical insulating end of the 3D confined electroforming core mold; finally, the mushroom-shaped array through-hole mold is obtained by removing the 3D confined electroforming core mold.

[0041] In order to ensure the deposition morphology and quality, and to obtain the microstructure with the required curvature at the end, this invention achieves the control of parameters such as the microstructure height, diameter, microstructure density, and end morphology of the core mold. The imprinting in step (2) is performed at a temperature of 110℃~120℃, a pressure of 500KPa~550KPa, and a holding time of 15 minutes~20 minutes (in this embodiment, the imprinting is performed at a temperature of 110℃, a pressure of 500KPa, and a holding time of 15 minutes).

[0042] Depend on Figure 7 As can be seen, in the application of the mushroom-shaped array through-hole mold in the roll forming of mushroom-shaped biomimetic array, in order to make the through-hole with open ends form a crown-shaped cavity with one end open, the mushroom-shaped array through-hole mold is wrapped around the cylindrical surface of the roller of the (roll forming) device, and the circumferential pre-tightening force is used to make the mushroom-shaped array through-hole mold and the substrate fit tightly together; the mushroom-shaped array through-hole mold and the substrate are subjected to anti-stick treatment to ensure that the mushroom end can be demolded smoothly; during imprinting, the polymer prepolymer is uniformly coated on the polyethylene terephthalate (PET) film, the curing problem is set according to the polymer type, and the curing time is controlled by the roller speed. Example

[0043] The photolithography method used in step (1) of this embodiment; the hot-melt polymer mentioned in step (2) is polystyrene (PS).

[0044] The imprinting described in this embodiment is performed at a temperature of 115°C, a pressure of 520 kPa, and a holding time of 20 minutes.

[0045] Same as Example 1. Example

[0046] The deep silicon etching method used in step (1) of this embodiment; the hot-melt polymer mentioned in step (2) is polystyrene (PS).

[0047] The imprinting described in this embodiment is performed at a temperature of 115°C, a pressure of 520 kPa, and a holding time of 20 minutes.

[0048] Same as Example 1. Example

[0049] The deep silicon etching method used in step (1) of this embodiment; the hot-melt polymer mentioned in step (2) is polymethyl methacrylate (PMMA).

[0050] The imprinting described in this embodiment is performed at a temperature of 120°C, a pressure of 500 kPa, and a holding time of 15 minutes.

[0051] Same as Example 1. Example

[0052] The imprinting described in this embodiment is performed at a temperature of 120°C, a pressure of 550 kPa, and a holding time of 20 minutes.

[0053] Same as Example 1.

[0054] Experimental example:

[0055] 1. Imprinting control of the microstructure of electroformed core mold

[0056] A thorough preliminary study was conducted on the fabrication of 3D polymer core molds using 2D topological structure molds: PMMA was imprinted using a planar hot pressing device and a mushroom-shaped array through-hole mold, and microstructures with different curvature ends were obtained by adjusting different imprinting parameters.

[0057] The curvature at the end is shown in Table 1:

[0058] Table 1: Influence of Imprinting Parameters on End Curvature

[0059] sample temperature pressure Holding time End curvature a 110℃ 500 kPa 15 minutes 0.36 b 115℃ 520 kPa 20 minutes 0.27 c 120℃ 500 kPa 15 minutes 0.14 d 120℃ 550 kPa 20 minutes 0.10

[0060] like Figure 8 As shown, the imprinting parameters corresponding to the end curvature of sample a are temperature 110℃, pressure 500KPa, and holding time 15 minutes. When the pressure and holding time remain constant, and the imprinting temperature is increased to 120℃, the end curvature obtained is shown in sample c. When the imprinting parameters are adjusted to temperature 115℃, pressure 520KPa, and holding time 20 minutes, the end curvature obtained is shown in sample b. When the imprinting parameters are adjusted to temperature 120℃, pressure 550KPa, and holding time 20 minutes, the end curvature obtained is shown in sample c.

[0061] Preliminary experiments on PMMA imprinting using a mushroom-shaped array through-hole mold fully demonstrate that the microstructure height and spherical end curvature of the electroformed core mold can be controlled by adjusting parameters such as imprinting temperature, time, and pressure. Through in-depth analysis of the rheological and interfacial mechanical behavior of the polymer in the microporous cavity during hot pressing, the evolution mechanism of microstructure morphology is further clarified, process parameters are optimized, and the accuracy of morphology control is improved.

[0062] 2. Research on electrochemical deposition process

[0063] The electroforming formula and process specifications are shown in Table 2:

[0064] Table 2

[0065] Mushroom-shaped array through-hole molds with different geometric morphologies were prepared using the above-mentioned formulation and process. Multi-field coupled simulations of electric field, electrochemical reaction, mass transfer, and heat transfer during the electrodeposition process were conducted to clarify the coating morphology (e.g., Figure 9 , Figure 10 The evolution mechanism (as shown in the figure).

[0066] 3. Preparation and performance testing of adhesive structures

[0067] A mushroom-shaped biomimetic array adhesive structure was successfully prepared using a nickel metal mushroom-shaped array through-hole mold by employing a roll-to-roll embossing process (roll pressing preparation), and its adhesive properties were characterized.

[0068] like Figure 11 As shown, the macroscopic effective area of ​​the adhesive material is 3cm×3cm, the height of the micro-adhesive structure is about 100μm, the diameter of the rod is about 50μm, the diameter of the enlarged end is 55-80μm (depending on the pre-pressure), and the center-to-center distance between adjacent microstructures is about 130μm.

[0069] like Figures 12 to 14 The adhesion performance test results shown indicate that the geometry of the mushroom-shaped ends has a significant impact on adhesion performance. The polymer-integrated molding of microstructured metal molds lays a solid theoretical, technical, and application foundation for all process stages, from microcavity filling to curing and demolding.

Claims

1. A method of producing a mushroom array via mold, characterized by It comprises the following steps: (1) Processing of circular hole array mold: using photoetching method to process on the surface of photoresist, or using photoetching method or / and deep silicon etching method to process on the surface of silicon wafer, to obtain circular hole array mold; (2) Hot press forming: then using the circular hole array mold to prepare cylindrical array with ball head by planar imprinting of hot melt polymer; (3) Conductive treatment: conducting conductive treatment on the cylindrical array with ball head prepared in advance, to form electroforming seed layer on all surfaces of the cylindrical array with ball head; (4) Terminal insulation: using surface dipping method to insulate the spherical terminal of the cylindrical array with ball head after conductive treatment, to obtain 3D limited electroforming core mold with local conductivity; (5) Electroforming: using the prepared 3D limited electroforming core mold to conduct electroforming, to form mushroom-shaped through hole by inducing non-uniform deposition of metal ions in local space; Stopping the electroforming when the plated metal is about to cover the spherical insulated terminal of the 3D limited electroforming core mold; finally, removing the 3D limited electroforming core mold to obtain mushroom-shaped array through hole mold; The imprinting in step (2) is at a temperature of 110-120℃, a pressure of 500-550KPa, and a pressure maintaining time of 15-20 minutes.

2. Application of the mushroom-shaped array through hole mold of claim 1 in roller pressing to prepare mushroom-shaped bionic array.

Images