A multi-layer microstructure biomimetic dry adhesion structure, a mold and a preparation method thereof

Abstract

A multilayer microstructure biomimetic dry adhesion structure, mold, and its fabrication method are disclosed. The multilayer microstructure biomimetic dry adhesion structure comprises multiple multilayer microstructure units. Each multilayer microstructure unit includes a bottom layer of micron-scale columnar structures, a middle layer of micron-scale mushroom-shaped structures, and a top layer of nanoarray structures, wherein the nanoarray structures are either nanopillar array structures or nanopore array structures. The multilayer microstructure biomimetic dry adhesion structure, mold, and its fabrication method provided by this invention, by setting the top layer of nanoarray structures, transforms the contact end between the microstructure and the object surface from a micron-scale mushroom-shaped "surface structure" into a nanoscale nanobead array or nanopore array "point structure," increasing the contact area, further improving the adhesion performance of the product, and enhancing structural stability.

Description

Technical Field

[0001] This invention relates to the fields of biomimetic dry adhesion and micro / nano manufacturing technology, and in particular to a multilayer microstructure biomimetic dry adhesion structure, mold, and preparation method thereof. Background Technology

[0002] Nature abounds with creatures possessing extraordinary adhesive abilities, such as geckos, flies, spiders, ants, beetles, and other animals and insects. They can freely crawl and stay on vertical objects and various rough surfaces, even hanging upside down from ceilings with ease. Geckos, being the largest creatures in nature with exceptional adhesive abilities, hold greater research value, which is why they are often used as a design template for biomimetic adhesive structures. Research has found that the gecko's extraordinary adhesive ability stems from a unique and complex surface superstructure system on the soles of its toes. This complex system consists of millions of layered, fibrous setae ranging in size from millimeters to nanometers. When a gecko's toes come into contact with a surface, an intermolecular force, van der Waals force, forms between the setae and the surface. Van der Waals forces are weak electromagnetic attraction generated when neutral molecules are very close to each other; the accumulation of a large number of van der Waals forces is sufficient to support the entire weight of a gecko's body. The gecko's hierarchical, multi-level system structure has its smallest units at the nanometer scale. No matter how rough the surface, these nanostructures can achieve near-zero-distance "perfect contact," thereby accumulating a large amount of van der Waals forces and forming super-strong adhesion. This ability to adhere to the surface of an object by relying on the van der Waals forces between molecules is called "dry adhesion."

[0003] Inspired by the fibrous setae-like adhesion structures of organisms such as geckos, research teams both domestically and internationally have conducted extensive research on the biomimetic dry adhesion and fabrication processes of micro- and nanostructures of various shapes. Biomimetic dry adhesion is gradually becoming an important research area that is receiving increasing attention, showing broad application prospects in aerospace, biomedicine, microelectronic devices, biomimetic robots, and other fields.

[0004] Among them, the cylindrical array microstructure with a mushroom-shaped tip is a more effective biomimetic dry adhesion structure. The reason for this is that, compared with other pointed shapes, the mushroom-shaped tip micropillar structure can effectively increase the contact area per unit region while reducing the cylinder diameter, and has the function of significantly enhancing the van der Waals forces at the contact surface, thereby generating greater adhesive force.

[0005] However, existing biomimetic dry adhesion microstructures are prone to failure, have low stability, and are difficult to process on a large scale, which is not conducive to large-scale production. Therefore, they have not yet been widely used.

[0006] The preceding description is intended to provide general background information and does not necessarily constitute prior art. Summary of the Invention

[0007] The purpose of this invention is to provide a multilayer microstructure biomimetic dry adhesion structure, mold, and preparation method thereof with excellent adhesion performance and structural stability.

[0008] This invention provides a multilayer microstructure biomimetic dry adhesion structure, comprising multiple multilayer microstructure units, each of which includes a bottom layer of micron-scale columnar structure, a middle layer of micron-scale mushroom-shaped structure, and a top layer of nanoarray structure.

[0009] Furthermore, the nanoarray structure is a nanopillar array structure or a nanopore array structure.

[0010] Furthermore, the top surface of the mushroom-shaped structure is hexagonal, and the multi-layered microstructure units are arranged in a honeycomb pattern.

[0011] Furthermore, the mushroom-shaped structure has an aperture size ranging from 10µm to 250µm and a thickness ranging from 2µm to 20µm; the columnar structure has a period size ranging from 20µm to 500µm, a diameter size ranging from 5µm to 150µm, and a height size ranging from 10µm to 250µm; the nanopillar array structure has a period size ranging from 100nm to 1000nm, a diameter size ranging from 10nm to 500nm, and a height size ranging from 50nm to 2.5µm; and the nanopore array structure has a period size ranging from 100nm to 1000nm, a diameter size ranging from 10nm to 500nm, and a depth size ranging from 50nm to 2.5µm.

[0012] The present invention also provides a method for preparing the multilayer microstructure biomimetic dry adhesion structure as described above, comprising: forming a photoresist structure of a mushroom-shaped column array microstructure on a substrate; performing nanoscale laser interference lithography on the surface of the photoresist structure to process a nanopillar array structure or a nanopore array structure on the surface of the mushroom-shaped column array microstructure.

[0013] Further, the photoresist structure for forming a mushroom-shaped columnar array microstructure on the substrate includes: providing a substrate; coating the substrate surface with photoresist; soft-baking the photoresist, and after coating, quickly placing the substrate with the photoresist on it inside an oven at a predetermined temperature for rapid baking, forming an exposure passivation layer on the photoresist surface, while the intermediate and bottom layers of the photoresist are in a semi-solid state required for normal exposure, thereby reducing the solvent content and hardness of the photoresist layer by layer from top to bottom and from the surface to the inside; patterning exposure and development, utilizing the fact that the photochemical reaction degree of the exposure passivation layer is lower than that of the intermediate and bottom layers of photoresist, removing part of the photoresist, and retaining the photoresist to form the mushroom-shaped columnar array microstructure.

[0014] Further, a substrate is provided; photoresist is coated on the surface of the substrate; the photoresist is soft-baked; the photoresist is patterned and exposed, including: adsorbing a certain amount of alkaline molecules on the surface of the photoresist to form a development passivation layer, wherein the alkaline molecules can neutralize the acidic molecules generated by the exposure and consume a portion of the acidic molecules; and patterning and exposing the photoresist that has formed the development passivation layer; developing and exposing the patterned and exposed photoresist, taking advantage of the fact that the development passivation layer has a lower development rate than the intermediate and bottom photoresist layers, removing a portion of the photoresist, and retaining the photoresist to form the mushroom-shaped columnar array microstructure.

[0015] Furthermore, the step of adsorbing a certain amount of alkaline molecules on the surface of the photoresist to form a development and passivation layer includes coating the surface of the photoresist with a weak alkaline solution.

[0016] Furthermore, in the step of performing nanoscale laser interference lithography on the surface of the photoresist structure to fabricate a nanopillar array structure or a nanopore array structure on the surface of the mushroom-shaped column array microstructure, the laser interference lithography includes using at least two laser beams to irradiate the surface of the photoresist structure for interference exposure and developing the exposed photoresist structure. During the lithography process, by precisely controlling the laser power, interference exposure time, and development process parameters, a nanopillar array structure or a nanopore array structure of the required structural size is prepared.

[0017] The present invention also provides a mold having a groove structure that is complementary to the multilayer microstructure unit described above.

[0018] The present invention also provides a method for preparing the mold as described above, characterized in that it includes: surface metallizing the structural surface of the multilayer microstructure biomimetic dry adhesion structure as described above; forming a metal mold structure complementary to the multilayer microstructure unit using a micro-electroforming process; and demolding to form a metal mold having the groove structure.

[0019] The multilayer microstructure biomimetic dry adhesion structure, mold and preparation method provided by the present invention, by setting the top layer nanoarray structure, changes the contact end between the microstructure and the object surface from the micrometer-scale mushroom head "surface structure" to the nanometer-scale nanobead array or nanopore array "point structure", which increases the contact area, further improves the adhesion performance of the product and makes the structure more stable. Attached Figure Description

[0020] Figure 1 This is a top view of the multilayer microstructure biomimetic dry adhesion structure according to an embodiment of the present invention.

[0021] Figure 2 for Figure 1 A partial cross-sectional view of the multilayer microstructure biomimetic dry adhesion structure shown.

[0022] Figure 3 for Figure 1 A partial cross-sectional view of another embodiment of the multilayer microstructure biomimetic dry adhesion structure shown.

[0023] Figure 4 for Figure 1 This diagram illustrates the front-end steps in the fabrication method of the multilayer microstructure biomimetic dry adhesion structure.

[0024] Figure 5 for Figure 1 This diagram illustrates the back-end steps in the fabrication method of the multilayer microstructure biomimetic dry adhesion structure.

[0025] Figure 6 for Figure 1 This diagram illustrates another method for preparing the front-end step in the multilayer microstructure biomimetic dry adhesion structure shown.

[0026] Figure 7 This is a schematic diagram of the mold preparation method according to an embodiment of the present invention. Detailed Implementation

[0027] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0028] like Figure 1 , Figure 2 As shown, this embodiment provides a multilayer microstructure biomimetic dry adhesion structure, including a substrate 2 and multiple multilayer microstructure units 1 located on the surface of the substrate 2. Each multilayer microstructure unit 1 includes a bottom layer of micron-scale pillar structures 10, a middle layer of micron-scale mushroom-shaped structures 11, and a top layer of nanoarray structures 12. In this embodiment, the nanoarray structure 12 is a nanopillar array structure (e.g., ...). Figure 2 In other embodiments, a nanopore array structure (such as...) can also be used. Figure 3 (or other types of array structures.)

[0029] In this embodiment, the top surface of the mushroom head structure 11 is hexagonal, and the multilayer microstructure units 1 are arranged in a honeycomb pattern (from a top view, such as...). Figure 1 The top surface of the mushroom-shaped structure 11 can also be circular or other shapes, but the effective contact area of ​​the hexagon per unit area can be larger than that of a circle. This is because, when comparing the areas of a hexagon and a circle with the same diameter, assuming the diameter is r, the area of ​​a single hexagon is... The area of ​​a single circle is S² = πr 2Calculations show that the area ratio of a hexagon to a circle of the same diameter, S1 / S2, is 1.103. Therefore, the area of ​​a hexagon per unit area can be larger than that of a circle, allowing for the creation of more nanoarray structures 12. Consequently, this multilayer microstructure biomimetic dry adhesion structure can achieve better adhesion properties.

[0030] In this embodiment, the mushroom-shaped structure has an aperture size ranging from 10µm to 250µm (µm being a micrometer) and a thickness ranging from 2µm to 20µm; the columnar structure has a period size ranging from 20µm to 500µm, a diameter size ranging from 5µm to 150µm, and a height size ranging from 10µm to 250µm; the nanopillar array structure has a period size ranging from 100nm to 1000nm (nm being a nanometer), a diameter size ranging from 10nm to 500nm, and a height size ranging from 50nm to 2.5µm. In other embodiments, if the nanoarray structure is a nanopore array structure, then the period size of the nanopore array structure ranges from 100nm to 1000nm, the diameter size ranges from 10nm to 500nm, and the depth size ranges from 50nm to 2.5µm.

[0031] like Figure 4 , Figure 5 As shown, the fabrication method of the above-mentioned multilayer microstructure biomimetic dry adhesion structure includes two main steps: a front-end step and a back-end step. The front-end step involves forming a photoresist structure of a mushroom-shaped columnar array microstructure on a substrate. The back-end step involves performing nanoscale laser interference lithography on the surface of the photoresist structure to fabricate a nanopillar array structure or a nanopore array structure on the surface of the mushroom-shaped columnar array microstructure.

[0032] like Figure 4 As shown, the photoresist structure for forming a mushroom-shaped columnar array microstructure on the substrate in the front-end steps includes the following steps S11-S14.

[0033] Step S11, provide substrate 2. The provided substrate can be pre-cleaned and surface-treated. Select a substrate of appropriate size according to the processing area requirements, and clean the substrate according to the process of degreasing, decontamination, and removal of particles / debris 21. The cleaning steps include acid washing, alkaline washing, high-pressure deionization rinsing, and spin drying. Multiple rounds of cleaning can be performed until the substrate surface meets the photolithography cleanliness requirements, such as... Figure 3 Step S111. The cleaned substrate can then undergo surface treatment to increase the adhesion between the photoresist and the substrate surface, such as... Figure 3Step S112. Specifically, the cleaned and dried substrate is first placed in a convection oven for high-temperature baking at 120°C for 30-60 minutes until the substrate surface is fully dried. Then, it is placed in a sealed vacuum chamber 3 and a layer of adhesion promoter 31, such as HMDS (hexamethyldisilazane), is deposited on the substrate surface using a vapor phase coating method to achieve surface modification.

[0034] Step S12: Coat the surface of substrate 2 with photoresist 4. Select a photoresist of appropriate viscosity based on the structural height requirements and coat it onto the substrate surface after adhesion enhancement. Spin coating, slot coating, or spray coating can all be used; the goal is simply to achieve the desired thickness after optimizing the coating parameters.

[0035] Step S13, softening the photoresist 4. After coating, the substrate with photoresist is quickly placed inside an oven 5 at a predetermined temperature for rapid baking. This forms an exposure passivation layer 41 on the surface of the photoresist 4. Simultaneously, the intermediate and bottom layers of the photoresist are in a semi-solid state required for normal exposure. This results in a gradual decrease in solvent content and hardness of the photoresist 4 from top to bottom and from the surface to the interior. This method can be understood as a baking method from the outside in. When the coated photoresist substrate is placed in the high-temperature oven, the solvent in the surface photoresist evaporates first. As baking continues, the solvent in the intermediate and bottom layers of the photoresist evaporates sequentially and gradually. At the same time, the solvent in the surface photoresist continues to evaporate and gradually changes from liquid to solid, while the intermediate and bottom layers of the photoresist remain in a semi-liquid or liquid state. In other words, the photoresist at this time exhibits a state of decreasing solvent content from top to bottom and from the surface to the interior, which can also be described as a state of decreasing photoresist hardness layer by layer. In this embodiment, the photoresist thickness is 10um-80um, the oven temperature for soft baking is 90℃-120℃, and the baking time is 1min-30min.

[0036] Step S14, patterned exposure and development. Taking advantage of the lower photochemical reaction rate of the passivation layer compared to the intermediate and bottom photoresist layers, part of the photoresist is removed, leaving a mushroom-shaped microstructure 1. In this embodiment, maskless laser direct writing technology is used for exposure. Based on digital light processing (DLP), a computer control system uploads and displays the micro / nano structure design layout to a digital micro-reflective element (DMD). Under ultraviolet light source 6, the microstructure pattern data is refreshed and displayed in real-time at high speed on the pixel display element of the DMD. Synchronous scanning with a high-precision motion platform completes the patterned exposure of the micro / nano structure. Maskless laser direct writing lithography technology has advantages such as high resolution, high precision, and flexible design, effectively reducing processing costs and facilitating large-scale industrial processing. After exposure, the photoresist substrate is developed using a developer of appropriate type. A commonly used developer is 2.38% TMAH (tetramethylammonium hydroxide), and the development time is adjusted according to the exposure dose (1 min-10 min). As mentioned earlier, after the photoresist is coated and baked in an oven, an "exposure passivation layer" of a certain thickness is formed on its surface. The photochemical reaction degree of this "exposure passivation layer" is lower than that of the intermediate and bottom photoresist layers. Therefore, by controlling the baking parameters, the thickness of the "exposure passivation layer" can be effectively controlled. Combined with development control, key dry adhesion factors such as the mushroom head aperture, thickness, and cylinder diameter can be precisely controlled, resulting in the desired mushroom-shaped microstructure after development. In other embodiments, mask exposure and other methods can also be used, and it is not limited to maskless laser direct writing technology.

[0037] The above steps cleverly employ a simple and effective method to form an "exposure passivation layer" on the photoresist surface, and based on micro-lithography technology, a mushroom-shaped microstructure is obtained through a single exposure.

[0038] like Figure 5 As shown, the back-end laser interference lithography step includes the following steps S21 and S22. Step S21 involves using at least two laser beams to irradiate the surface of the photoresist structure for interference exposure, and step S22 involves developing the exposed photoresist structure.

[0039] According to the laser interference lithography period formula

[0040]

[0041] The period P of the nanostructure formed by interference lithography is related to the laser wavelength λ and the angle θ between the two laser beams. The structural period P is directly proportional to the laser wavelength λ and inversely proportional to the angle θ. By selecting different laser light sources of different wavelengths or adjusting the angle between the two laser beams, nanostructures with different periods can be obtained. For example, when selecting a 157nm wavelength laser with a laser beam angle of 51.72°, an interference light field with a structural period of 100nm can be obtained. With a duty cycle of 0.5, the pattern linewidth is 50nm. In actual interference lithography processes, the duty cycle of the nanostructure pattern on the photoresist can be precisely controlled by adjusting the exposure dose and development process parameters. Theoretically, the pattern linewidth can reach 10nm or even smaller. Furthermore, the depth of focus in interference lithography is related to the laser coherence length, which can reach the meter level. This makes the depth of focus of interference lithography greater than that of conventional mask lithography or laser direct writing lithography, easily obtaining nanostructures with large aspect ratios. Therefore, by precisely controlling the laser power, interference exposure time, and development process parameters, nanopore array structures of different structural sizes can be fabricated. Figure 5 (as shown in the lower left) or nanopillar array structure ( Figure 5 (As shown in the lower right).

[0042] like Figure 6 As shown, the photoresist structure that forms the mushroom-shaped columnar array microstructure on the substrate in the front-end step can also adopt another approach, which includes the following steps S31-S34.

[0043] Step S31: Provide substrate 2. The provided substrate can be pre-cleaned and surface-treated. Select a substrate of appropriate size according to the processing area requirements, and clean the substrate according to the process of degreasing, decontamination, and removal of particles / debris 21. The cleaning steps include acid washing, alkaline washing, high-pressure deionization rinsing, and spin drying. Multiple rounds of cleaning can be performed until the substrate surface meets the photolithography cleanliness requirements, such as... Figure 3 Step S311. The cleaned substrate can then undergo surface treatment to increase the adhesion between the photoresist and the substrate surface, such as... Figure 3 Step S312. Specifically, the cleaned and dried substrate is first placed in a convection oven for high-temperature baking at 120°C for 30-60 minutes until the substrate surface is fully dried. Then, it is placed in a sealed vacuum chamber 3 and a layer of adhesion promoter 31, such as HMDS (hexamethyldisilazane), is deposited on the substrate surface using a vapor phase coating method to achieve surface modification.

[0044] Step S32: Coat the surface of substrate 2 with photoresist 4. Select a photoresist of appropriate viscosity based on the structural height requirements and apply it to the adhesive-enhanced substrate surface. Spin coating, slot coating, or spray coating can be used; the goal is simply to achieve the desired thickness after optimizing the coating parameters.

[0045] Step S33, Soft Baking of Photoresist 4. Place the photoresist substrate on a hot plate / heating stage for contact or proximity baking. Depending on the photoresist type and thickness, the baking temperature is set between 90℃ and 110℃, and the baking time varies from 1 minute to 60 minutes. For thicker photoresist films, a stepped heating method is required, with the hot plate temperature gradually increasing to allow the solvent to evaporate slowly and evenly, avoiding defects such as bubbles and cracks on the surface of the photoresist film.

[0046] Steps S341 and S342 involve patterning the photoresist 4 using ultraviolet light. This includes step S341: adsorbing a certain amount of alkaline molecules onto the photoresist surface to form a development and passivation layer 42, where the alkaline molecules can neutralize the acidic molecules generated by ultraviolet exposure, thus consuming some of the acidic molecules; and step S342: patterning the photoresist with the developed and passivation layer using ultraviolet light.

[0047] According to the exposure and development mechanism of positive photoresist, the photosensitive compounds in the photoresist components generate a certain amount of acidic molecules during ultraviolet exposure. Some of these acidic molecules can neutralize the alkaline molecules in the developer and be dissolved by the developer, while others can promote the decomposition of the photoresist resin and be dissolved by the developer. Furthermore, the dissolution rate is positively correlated with the exposure dose. Therefore, in step S341, the alkaline molecules adsorbed on the photoresist surface will neutralize the acidic molecules generated by ultraviolet exposure, thereby consuming some acidic molecules. This reduces the concentration of acidic molecules in the photoresist, thus lowering the dissolution rate. Additionally, the reduction in acidic molecules also decreases the decomposition ability of the surface photoresist resin, resulting in a significantly lower dissolution rate for the surface photoresist compared to the intermediate and bottom layers. In this way, a "development passivation layer" can be formed on the photoresist surface, meaning the development rate of the surface photoresist is significantly lower than that of the intermediate and bottom layers.

[0048] In this embodiment, forming a development and passivation layer by adsorbing a certain amount of alkaline molecules onto the photoresist surface includes coating the photoresist surface with a weak alkaline solution 41, such as a sodium-based or potassium-based developer. The coating can be done by spin coating or spray coating. Of course, in other embodiments, methods other than coating can also be used to adsorb a certain amount of alkaline molecules onto the photoresist surface.

[0049] The photochemical reaction of the passivation layer is lower than that of the intermediate and bottom photoresist layers. Part of the photoresist is removed, leaving a mushroom-shaped microstructure 1. In this embodiment, the ultraviolet exposure in step S342 employs maskless laser direct writing technology, based on digital light processing (DLP). A computer control system uploads and displays the micro / nano structure design layout to a digital micro-reflective element (DMD). Under ultraviolet light source 6 irradiation, the microstructure graphic data is refreshed and displayed in real-time at high speed on the pixel display element of the DMD. Synchronous scanning by a high-precision motion platform completes the final exposure of the micro / nano structure pattern. Maskless laser direct writing lithography technology has advantages such as high resolution, high precision, and flexible design, effectively reducing processing costs and facilitating large-scale industrial processing. Other embodiments may also use mask exposure methods, and are not limited to maskless laser direct writing technology.

[0050] Step S35: Develop the patterned UV-exposed photoresist. The exposed photoresist substrate is developed using a developer of appropriate type, commonly 2.38% TMAH (tetramethylammonium hydroxide). The development time is adjusted according to the exposure dose (1-10 min). As mentioned earlier, a "development passivation layer" of a certain thickness is formed on the surface of the patterned UV-exposed photoresist. The development rate of this "development passivation layer" is significantly lower than that of the intermediate and bottom layers of photoresist. Therefore, by precisely controlling the concentration of the alkaline solution and the residence time, the thickness of the "development passivation layer" can be effectively controlled. Combined with development control, key dry adhesion factors such as the mushroom head diameter, thickness, and cylinder diameter can be precisely controlled, resulting in the desired mushroom-shaped microstructure after development.

[0051] The above steps cleverly employ a simple and effective method to form a "development and passivation layer" on the photoresist surface, and based on microlithography, a mushroom-shaped microstructure is obtained through a single exposure.

[0052] like Figure 7 As shown, this embodiment also provides a mold 8 having a groove structure 81 complementary to the above-described multilayer microstructure unit 1. The preparation method of the mold 8 includes the following steps S41-S43.

[0053] Step S41 involves surface metallization of the multilayer microstructure biomimetic dry-adhesion structure surface for use as a cathode model in the micro-electroforming process. This can be achieved by depositing a conductive metal layer 71, such as uniformly covering the photoresist surface with a layer of metallic silver using silver mirror chemical reaction technology, or by depositing a uniform conductive metal layer using methods such as electron beam evaporation or magnetron sputtering.

[0054] Step S42 involves using a micro-electroforming process to form a metal mold structure complementary to the multi-layered microstructure units. Specifically, the surface-metallized structure is placed on the cathode device of the micro-electroforming equipment and fixed with conductive adhesive. Anode metal raw material 72 is added to the electroforming bath and thoroughly mixed; the anode metal raw material 72 can be metallic nickel or other alloy metals. After the cathode device is placed in the electroforming bath, a suitable current density is set according to process requirements. After a period of electroforming, a metal mold structure complementary to the multi-layered microstructure units is formed.

[0055] Step S43: Demolding to form a metal mold 8 with a groove structure 81. Specifically, after electroforming, the electroformed sample is removed and rinsed. A certain force is applied to separate the metal plate structure and the photoresist structure to form a metal mold 8 with a groove structure 81.

[0056] This embodiment uses a multi-layered microstructure biomimetic dry-adhesion structure as a mold. Micro-electroforming technology is employed to replicate and transfer the multi-layered microstructure units onto a metal substrate, forming a metal mold with a groove structure complementary to the multi-layered microstructure units. This mold offers advantages such as high precision and long lifespan, and can be mass-produced.

[0057] In this embodiment, a multi-layered microstructure biomimetic dry adhesion structure is added to the top layer of the mushroom-shaped columnar microstructure, creating a nano-array structure. This transforms the contact point between the microstructure and the object surface from a micrometer-scale mushroom head "surface structure" to a nanometer-scale nano-array "point structure." This significantly reduces the contact size between the microstructure and the object surface while ensuring the effectiveness and stability of the dry adhesion microstructure. Consequently, the microstructure adheres more tightly to the complex object surface, accumulating more van der Waals forces. Therefore, the adhesion effectiveness and stability to complex object surfaces can be further improved.

[0058] Furthermore, this embodiment employs a clever and efficient process to prepare a high-performance multilayer microstructured biomimetic dry adhesive structure. By optimizing process parameters to reduce the diameter of the columnar structure, and simultaneously adjusting the geometric dimensions of the mushroom-shaped structure and nanostructures, optimal biomimetic adhesive properties are obtained. The biomimetic dry adhesive microstructure preparation method of this embodiment is not only simple and reproducible, but also offers controllable precision, high stability, and the ability to perform large-area uniform processing. Further, the biomimetic microstructure prepared by this method can be processed into a metal mold, and the microstructure on the surface of the metal mold can be replicated and transferred into the adhesive material, ultimately forming a biomimetic dry adhesive material with a multilayered mushroom-shaped columnar array microstructure. Utilizing the advantages of the metal mold, such as high structural fidelity, durability, and long service life, mass production is possible, thereby improving production efficiency and reducing costs.

[0059] In the accompanying drawings, the dimensions and relative dimensions of layers and regions are exaggerated for clarity. It should be understood that when an element, such as a layer, region, or substrate, is referred to as "formed on," "disposed on," or "located on" another element, the element may be directly disposed on said other element, or there may be intermediate elements present. Conversely, when an element is referred to as "directly formed on" or "directly disposed on" another element, there are no intermediate elements.

[0060] In this article, the sequential adjectives "first," "second," etc., used to describe elements are merely to distinguish elements with similar attributes and do not imply that the elements described in this way must follow a given order, or be subject to time, space, hierarchy, or other restrictions.

[0061] In this document, unless otherwise stated, "multiple" or "several" means two or more.

[0062] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium, and when executed, the program performs the steps of the above method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0063] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] In this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0065] 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 variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a multilayer microstructured biomimetic dry adhesive structure, characterized in that, include: A photoresist structure is formed on a substrate to form a mushroom-shaped columnar array microstructure; nanoscale laser interference lithography is performed on the surface of the photoresist structure to fabricate a nanopillar array structure or a nanopore array structure on the surface of the mushroom-shaped columnar array microstructure. The photoresist structure for forming a mushroom-shaped columnar array microstructure on a substrate includes: providing a substrate; coating the substrate surface with photoresist; soft baking the photoresist; and patterning the photoresist, including: adsorbing a certain amount of alkaline molecules on the surface of the photoresist to form a development passivation layer, wherein the alkaline molecules can neutralize the acidic molecules generated by the exposure and consume a portion of the acidic molecules; and patterning the photoresist that has formed the development passivation layer; developing the patterned photoresist, and removing a portion of the photoresist by utilizing the fact that the development passivation layer has a lower development rate than the intermediate and bottom photoresist layers, leaving the remaining photoresist to form the mushroom-shaped columnar array microstructure; The laser interference lithography includes using at least two laser beams to irradiate the surface of the photoresist structure for interference exposure and developing the exposed photoresist structure. During the lithography process, by precisely controlling the laser power, interference exposure time, and development process parameters, a nanopillar array structure or a nanopore array structure of the required structural size is prepared.

2. A multilayer microstructure biomimetic dry adhesion structure, characterized in that, Made by the preparation method of claim 1, the multilayer microstructure biomimetic dry adhesion structure includes multiple multilayer microstructure units, each of which includes a bottom layer of micron-scale columnar structure, a middle layer of micron-scale mushroom head structure, and a top layer of nanoarray structure.

3. The multilayer microstructured, bioinspired dry adhesive structure of claim 2, wherein, The nanoarray structure is either a nanopillar array structure or a nanopore array structure.

4. The multilayer microstructured, bioinspired dry adhesive structure of claim 2, wherein, The top surface of the mushroom-shaped structure is hexagonal, and the multi-layered microstructure units are arranged in a honeycomb pattern.

5. The multilayer microstructured, bioinspired dry adhesive structure of claim 3, wherein, The mushroom-shaped structure has an aperture size ranging from 10µm to 250µm and a thickness ranging from 2µm to 20µm; the columnar structure has a period size ranging from 20µm to 500µm, a diameter size ranging from 5µm to 150µm, and a height size ranging from 10µm to 250µm; the nanopillar array structure has a period size ranging from 100nm to 1000nm, a diameter size ranging from 10nm to 500nm, and a height size ranging from 50nm to 2.5µm; the nanopore array structure has a period size ranging from 100nm to 1000nm, a diameter size ranging from 10nm to 500nm, and a height size ranging from 50nm to 2.5µm.

6. A mold characterized by, It has a groove structure that is complementary to the multilayer microstructure unit as described in any one of claims 2 to 5.

7. A method of producing a mould as claimed in claim 6, characterised in that, include: Surface metallization is performed on the structural surface of the multilayer microstructure biomimetic dry adhesion structure as described in any one of claims 2 to 5; A micro-electroforming process is used to form a metal mold structure that complements the multi-layered microstructure unit; demolding is then performed to form a metal mold with the groove structure.

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