A method for preparing nano-pores and arrays thereof based on ultra-thin sectioning technology combined with wet etching

Abstract

The application discloses a method for preparing nano-pores and arrays thereof based on an ultrathin slicing technology combined with a wet etching method, and the method comprises the following steps: step 1, preparation of a silver-containing resin block; step 2, primary slicing and secondary embedding; step 3, secondary slicing to obtain a resin flake containing nano-silver points; step 4, alkaline etching to form a nano-pore array; and step 5, cleaning and drying. The method can realize the preparation of nano-pores with accurate pore positions, controllable pore diameters and stable morphologies in a polymer matrix, and has the advantages of a mild process, strong device versatility, suitability for the preparation of high-performance nano-pore devices of an epoxy resin substrate, and wide application in industrial scenes such as nano-fluidic control, single-molecule detection, precise screening and flexible electronic devices, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing nanopores, specifically a method for preparing nanopores and their arrays based on ultrathin slicing technology combined with wet etching. Background Technology

[0002] Nanopore structures, as important functional units for micro / nanofluidics, biomolecule detection, and single-molecule analysis, offer advantages such as small size, high sensitivity, and wide applicability. The core requirement for their fabrication methods is to achieve precise control of pore size and stable morphology, while maintaining the structural integrity and chemical stability of the substrate material.

[0003] Currently, commonly used methods for preparing nanopores mainly include the following categories:

[0004] (1) High-energy beam direct writing method

[0005] For example, focused ion beam (FIB) and electron beam lithography (EBL) technologies can directly fabricate single pores with diameters as small as tens of nanometers on inorganic films such as silicon nitride (SiN) and silicon dioxide (SiO2), with high precision in pore size and position. However, these methods suffer from problems such as expensive equipment, low processing efficiency, and limited pore throughput. Furthermore, high-energy beams can cause thermal damage and stress defects to flexible or polymeric substrates (such as epoxy resin), making them unsuitable for polymeric material applications.

[0006] (2) Template-assisted etching method

[0007] Self-assembly using templates such as polystyrene (PS) nanospheres and anodic aluminum oxide (AAO) is performed, followed by the fabrication of pores through chemical etching or physical dissolution of the template. This method is suitable for batch processing of large-area, arrayed pores, but the pore size distribution is not uniform, the pore positions are highly random, and the template removal process can easily cause chemical damage to the substrate or lead to residual blockage around the pores.

[0008] (3) Chemical etching and electrochemical dissolution method

[0009] Researchers have developed pores by depositing thin metal layers or introducing metal nanoparticles onto a substrate surface, followed by chemical or electrochemical dissolution using strong oxidants such as nitric acid or hydrogen peroxide. While this method demonstrates good metal dissolution efficiency, the strong acid or oxidizing conditions have poor compatibility with the polymer matrix, easily causing matrix degradation, shrinkage, or even microcracks, thus affecting the pore morphology and function.

[0010] (4) Dispersion-corrosion strategy

[0011] One approach involves dispersing metal nanoparticles into the polymer through physical mixing or solution impregnation, followed by chemical etching to dissolve the metal particles and form channels. While this strategy is relatively simple, the metal particles are unevenly distributed within the polymer, their position and size are difficult to control, and residues from the etching process can easily clog the channels, resulting in poor repeatability and reliability.

[0012] In summary, existing nanopore preparation methods still face significant challenges in achieving precise pore size control, mild processing, and matrix integrity in polymer matrices (especially epoxy resins). How to efficiently remove metals from polymers under mild conditions while simultaneously achieving nanopores with controllable size, precise location, and stable morphology is a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0013] To address the problems of precise pore size control, random pore distribution, and easy damage to the matrix during the preparation of nanopores in polymer materials, this invention provides a method for preparing nanopores and their arrays based on ultrathin slicing technology combined with wet etching, which features precise structure, controllable size, and mild process.

[0014] The objective of this invention is achieved through the following technical solution:

[0015] A method for preparing nanopores and their arrays based on ultrathin slicing technology combined with wet etching includes the following steps:

[0016] Step 1: Preparation of silver-containing resin blocks:

[0017] A regularly arranged array of silver wires is constructed in a resin matrix to obtain a resin-silver composite block;

[0018] Step 2, First sectioning and second embedding:

[0019] Step 2-1: Perform an ultrathin section on the resin-silver composite block to obtain a resin section with a silver wire array;

[0020] Step 2-2: Transfer the resin slice with silver wire array to an epoxy resin substrate for secondary embedding and curing to form a resin block with silver wire array embedded inside.

[0021] Step 3: Obtain resin thin films containing silver nanoparticles through secondary slicing.

[0022] The resin block with an internal silver wire array is sliced ​​a second time in a direction perpendicular to the silver wire axis. By adjusting the thickness of the second slice, the original continuous silver wire is divided into regularly arranged nano silver dots, thereby obtaining a resin sheet with an internal nano silver dot array.

[0023] Step 4: Alkaline etching to form a nanopore array:

[0024] Step 4-1: Immerse the resin sheet containing nano-silver dots in an alkaline solution containing ammonia and triiodine anions to etch the silver dots. The concentration of triiodine anions in the alkaline solution is 30-60 mM, the concentration of ammonia is 0.5-1.5 M, and the pH is 8-9.

[0025] Step 4-2: After the silver dots are almost completely dissolved, a nanopore array is formed in their original locations;

[0026] Step 5: Cleaning and drying:

[0027] The etched resin sheets were cleaned and dried to remove residual metal ions and reaction byproducts, resulting in structurally stable nanoporous array resin sheets.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] The method of this invention can achieve precise pore location, controllable pore size and stable morphology preparation of nanopores inside polymer matrices. The process is mild and the equipment is highly versatile. It is suitable for the preparation of high-performance nanoporous devices on epoxy resin substrates and can be widely used in industrial scenarios such as nanofluidics, single-molecule detection, precision sieving and flexible electronic devices, and has good application prospects. Attached Figure Description

[0030] Figure 1 Flowchart of nanopore fabrication;

[0031] Figure 2 Image of a silver nanowire array optical microscope;

[0032] Figure 3 AFM scan image of silver nanowires;

[0033] Figure 4 This is an optical microscope image of a nano-silver dot array;

[0034] Figure 5 AFM scan image of silver nanoparticles;

[0035] Figure 6 SEM scan image of silver nanoparticles;

[0036] Figure 7 AFM scan image of nanopores;

[0037] Figure 8 AFM scan image of resin height;

[0038] Figure 9 This is a SEM scan image of a nanopore. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0040] This invention provides a method for preparing nanopores and their arrays based on ultrathin slicing technology combined with wet etching, such as... Figure 1 As shown, the method includes the following steps:

[0041] Step 1: Preparation of silver-containing resin blocks:

[0042] A regularly arranged array of silver wires can be constructed in an EpoFix resin matrix. This can be achieved through processes such as microstructure silicon template replication, elastic mold transfer, resin casting and curing, and silver film deposition. Silver is deposited on the sidewalls of the grooves on the resin surface, forming a silver wire structure that is continuously distributed along a predetermined direction, thus obtaining a resin-silver composite block. The thickness of the silver layer is determined based on the required size of the nanopores. The silver dots are considered as cuboids, and the thickness of the coating is directly related to the length of the silver dots. The thickness of the first slice is directly related to the width of the silver dots, and the thickness of the second slice is directly related to the height of the silver dots.

[0043] Step 2, First sectioning and second embedding:

[0044] Step 2-1: Perform an ultrathin section on the resin-silver composite block to obtain a resin section with a silver wire array;

[0045] Step 2-2: Transfer the resin slice with silver wire array to an epoxy resin substrate for secondary embedding and curing to form a resin block with silver wire array embedded inside, which provides mechanical support and structural stability for subsequent secondary slicing.

[0046] Step 3: Obtain resin thin films containing silver nanoparticles through secondary slicing.

[0047] A resin block embedded with an array of silver wires is subjected to a second ultrathin slice along a direction perpendicular to the axis of the silver wires. By adjusting the thickness of the second slice, the original continuous silver wires are divided into regularly arranged silver nanoparticles, thus obtaining a resin sheet embedded with an array of silver nanoparticles. The thickness of the silver film coating determines the basic thickness and width of the silver wires along the trench sidewall direction, the thickness of the first slice determines the normal dimension of the silver wire cross-section, and the thickness of the second slice determines the thickness of the silver nanoparticles. By combining and adjusting the silver film thickness, the first slice thickness, and the second slice thickness, precise control over the three-dimensional dimensions and aspect ratio of the silver nanoparticles can be achieved within a predetermined range. This provides geometric constraints for the pore size, depth, and shape of subsequent nanopores while maintaining the array period consistent with the initial microstructure.

[0048] Step 4: Alkaline etching to form a nanopore array:

[0049] Step 4-1: Immerse the resin sheet containing nano-silver dots in an alkaline solution containing ammonia and triiodine anions. Under preset concentration and pH conditions, the silver dots are etched to gradually dissolve and remove them from the resin, while the resin matrix remains basically intact.

[0050] Step 4-2: After the silver dots are basically completely dissolved, a nanopore array is formed at their original locations. The pore size and depth of the resulting nanopores correspond to the size of the silver dots.

[0051] Step 5: Cleaning, drying, and structural characterization:

[0052] Step 5-1: Clean and dry the etched resin sheet to remove residual metal ions and reaction byproducts, and obtain a structurally stable nanoporous array resin sheet.

[0053] Step 5-2: The pore size, pore shape and array order were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and combined with the sheet thickness measurement results, it was confirmed that the nanopores penetrated through the resin sheet and were a through-pore structure.

[0054] This invention has the following innovative features and advantages:

[0055] 1. Constructing a nano-silver dot array by secondary slicing of silver wires:

[0056] First, a regularly arranged array of silver wires is formed inside the resin. After one slicing and two embeddings, a second ultrathin slicing is performed in a direction perpendicular to the axis of the silver wires. This divides the continuous silver wires into an array of silver nanoparticles, so that the metal template is geometrically constrained in terms of position, orientation and array period, resulting in a silver nanoparticle array with controllable spatial arrangement.

[0057] 2. The three-dimensional size of nanopores can be designed through three process parameters:

[0058] The thickness of the silver film coating, the thickness of the first slice, and the thickness of the second slice are used to define the geometric dimensions of the silver lines and silver dots in three spatial directions. By adjusting the combination of the three, the planar size, thickness, and aspect ratio of the nano-silver dots can be preset and controlled. After the silver dots are etched and removed, the pore size and depth of the nanopores can be designed and predicted and controlled.

[0059] 3. Obtaining a regular through-pore nanopore array in ultrathin resin sheets:

[0060] Through the above structural design and selective etching, a nanopore array corresponding to the silver nanoparticles is formed in a resin sheet with a thickness of tens of nanometers. The pore positions are defined by the initial array structure, and the pore diameter matches the size of the silver nanoparticles. The resulting nanopores are through-hole structures that penetrate the resin sheet, while maintaining the basic integrity of the resin matrix, thus obtaining a polymer nanopore array with stable structure and high dimensional consistency.

[0061] Example:

[0062] This embodiment provides a etching method based on an ammonia-triiodine anion system for removing silver nanoparticles from epoxy resin to prepare nanopores and their arrays. The specific steps are as follows:

[0063] Step 1: A silicon wafer with a 15 μm groove array on its surface was selected as a template. The groove array structure was copied onto the surface of uncured epoxy resin using a PDMS replication transfer process. The resin was then cured at room temperature to obtain a cured epoxy resin block with an ordered array microstructure on its surface. This cured block was then loaded into a vacuum magnetron sputtering system, and silver was deposited by magnetron sputtering under set process parameters to form a silver film with a nominal thickness of approximately 400 nm. The target silver structure was located on the sidewall of the groove, and the actual effective thickness of the silver layer at the sidewall was approximately 1 / 5 of the nominal coating thickness, or approximately 80 nm. This result was verified by AFM scanning of the nano-silver wire array sample obtained from the first slice. Subsequently, uncured epoxy resin was poured onto the silver film surface to complete the embedding. After curing, sample 1 was obtained for the first ultrathin slice.

[0064] Step 2: Sample 1 was ultrathinly sectioned with a section thickness of 130 nm to obtain an epoxy resin section containing an internal silver wire array structure. Under the sectioning parameters used in this embodiment, considering the cutting tool's squeezing effect during sectioning and the difference in strain constants between silver and epoxy resin, the actual thickness of the epoxy resin layer was expected to increase by approximately 10 nm relative to the set section thickness, and the silver wire height by approximately 20 nm relative to the set section thickness. AFM measurement results showed that the resin layer thickness after sectioning was approximately "section thickness + 10 nm", and the silver wire height was approximately "section thickness + 20 nm", consistent with the above strain analysis. The epoxy resin section was transferred and placed onto a pre-cured and smooth epoxy resin substrate for secondary epoxy embedding and fixation. After complete curing at room temperature, Sample 2 was obtained for the second ultrathin sectioning.

[0065] Step 3: Sample 2 was subjected to a second ultrathin section along a direction perpendicular to the silver wire array, with a section thickness of 30 nm, resulting in an epoxy resin sheet with a thickness of 40 nm and embedded silver nanoparticles in the cross-section. Morphological characterization results showed that the obtained silver nanoparticles had a planar size of approximately 80 nm × 150 nm and a thickness of approximately 40 nm, which were used as metal templates for subsequent etching to create pores.

[0066] Step 4: Take 10 mL of 60 mM triiodine anion (I3) - The aqueous solution was placed in a beaker equipped with a magnetic stirrer. The stirring speed was adjusted to approximately 100 rpm. Under stirring conditions, 5 mL of 1 M ammonia solution was added in four portions, mixing thoroughly after each addition to prepare the ammonia-triiodine anion etching working solution. The epoxy resin sheet containing the silver nanoparticles was immersed in this etching working solution for etching treatment. The total etching time was 15 min, during which time a new etching working solution was needed. After 6 mins 30 s, the sample was transferred to another freshly prepared etching working solution with the same proportions to continue etching until the end, in order to achieve complete dissolution and removal of the silver nanoparticles.

[0067] Step 5: After etching, the sample is immersed in a 0.5 M sodium thiosulfate (Na2S2O3) aqueous solution for 15 min, and then in a 0.1 M sodium thiosulfate aqueous solution for 5 min to complex and remove residual silver and related intermediates. Subsequently, the sample is placed sequentially in a 30% (v / v) ethanol aqueous solution and anhydrous ethanol, each for 90 s, to complete the dehydration treatment. The sample is then removed, and residual liquid on the surface is dried using compressed air. It is then dried at 60°C for 5 min to obtain an epoxy resin sample with an internal nanoporous structure.

[0068] Step 6: Perform AFM and SEM characterization on the obtained nanopore sample to obtain the surface morphology, pore size and array order of the nanopores. Further, perform AFM measurement on the thickness of the resin layer after etching and compare the thickness data with the aforementioned silver spot size and slice parameters to verify that the prepared nanopores penetrate the resin layer and are through-hole structures.

Claims

1. A method for preparing nanopores and arrays thereof based on ultrathin sectioning technique combined with wet etching, characterized in that The method includes the following steps: Step 1: Preparation of silver-containing resin blocks: A regularly arranged array of silver wires is constructed in a resin matrix to obtain a resin-silver composite block: through microstructure silicon template replication, elastic mold transfer, resin casting and curing, or silver film deposition process, silver is deposited on the sidewalls of the grooves on the resin surface to form a silver wire structure continuously distributed along a predetermined direction, thereby obtaining a resin-silver composite block. Step 2, First sectioning and second embedding: Step 2-1: Perform an ultrathin section on the resin-silver composite block to obtain a resin section with a silver wire array; Step 2-2: Transfer the resin slice with silver wire array to an epoxy resin substrate for secondary embedding and curing to form a resin block with silver wire array embedded inside. Step 3: Obtain resin thin films containing silver nanoparticles through secondary slicing. The resin block with an internal silver wire array is sliced ​​a second time in a direction perpendicular to the silver wire axis. By adjusting the thickness of the second slice, the original continuous silver wire is divided into regularly arranged nano silver dots, thereby obtaining a resin sheet with an internal nano silver dot array. Step 4: Alkaline etching to form a nanopore array: Step 4-1: Immerse the resin sheet containing nano-silver dots in an alkaline solution containing 0.5~1.5 M ammonia and 30~60 mM triiodide anions to etch the silver dots. Step 4-2: After the silver dots are almost completely dissolved, a nanopore array is formed in their original locations; Step 5: Cleaning and drying: The etched resin sheets were cleaned and dried to remove residual metal ions and reaction byproducts, resulting in structurally stable nanoporous array resin sheets.

2. The method for fabricating nanopores and arrays thereof based on the ultrathin sectioning technique combined with wet etching according to claim 1, characterized in that The pH of the alkaline solution is 8-9.

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