Preparation method of addressable disc ultramicro electrode array for electrochemical imaging

Abstract

The invention discloses a preparation method of an addressable disc ultramicro electrode array for electrochemical imaging, which comprises the following steps of: 1, preparing a nanowire array by using an ultrathin slicing machine as processing equipment and a silicon wafer with a micron groove array structure as a template; 2, transferring the nanowire array to a silicon wafer, performing three-dimensional alignment on a molybdenum mask plate with a lead pattern and the nanowire array, and realizing lap joint of a lead and the nanowire array and preparation of the lead by combining a physical vapor deposition method; 3, resin is poured on the silicon wafer for normal-temperature curing, and the pattern is transferred to the resin; 4, macroscopic wire lap joint and packaging are carried out, a resin block with an embedded array structure is obtained, the end face is trimmed through an ultra-thin slicing machine, the dot array is exposed, and preparation of the addressable disc ultramicro electrode array is completed. According to the method, the addressable disc ultramicro electrode array which is high in consistency, high in spatial resolution and capable of being expanded at will can be prepared simply and efficiently at low cost.

Description

Technical Field

[0001] This invention relates to a method for fabricating a disk-based ultramicroelectrode array, specifically a method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging. Background Technology

[0002] Disk-based microelectrodes not only possess advantages such as fast response rate, low detection limit, and low background noise, but also, thanks to their extremely small size, enable non-destructive in-situ detection of live cells and individual nanoparticles within a small space. However, their small size also leads to low scanning efficiency during spatial imaging. Addressable disk-based microelectrode arrays can achieve simultaneous independent scanning detection across multiple channels, significantly improving detection efficiency while maintaining highly localized electrochemical detection. Addressable disk-based microelectrode arrays not only possess the advantages of disk-based microelectrodes but also exhibit significant advantages in signal strength, detection throughput, selectivity, anti-interference capability, and multifunctional integration, making them a synchronous multiplexer with broad application prospects.

[0003] In the fabrication of addressing electrodes, the fabrication of the ultramicroelectrode array is crucial to the effective realization of the addressing function. Existing methods for fabricating ultramicroelectrode arrays mainly include electron beam lithography, focused ion beam lithography, electrochemical template methods, self-assembled template methods, nanoimprinting, and nanoslicing. While the first few methods are mature, they often suffer from high costs, stringent equipment requirements, complex processing steps, and poor consistency. Nanoslicing, due to its advantages of controllable size, high efficiency, strong maneuverability, and multi-material compatibility, has been widely used in the fabrication of high-resolution ultramicroelectrode arrays. For ultramicroelectrode arrays with small size and small spacing, precisely positioning individual metal nanowires and aligning the entire array is also a challenging task. Summary of the Invention

[0004] The purpose of this invention is to provide a method for fabricating an addressable disk microelectrode array for electrochemical imaging. This method can simply, efficiently, and at low cost fabricate an addressable disk microelectrode array with high consistency, high spatial resolution, and arbitrary scalability.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging includes the following steps:

[0007] Step 1: Nanowire Array Fabrication: Using an ultrathin slicer as the processing equipment and a silicon wafer with a micron-groove array structure as a template, the nanowire array is fabricated through soft photolithography, magnetron sputtering, and nanoslicing techniques. The specific steps are as follows:

[0008] Step 1-1: Transfer the micro-groove array structure onto the resin to obtain a resin block containing the micro-groove array;

[0009] Steps 1-2: Apply magnetron sputtering technology to deposit a gold film on the surface of the micron trench array. The thickness of the gold film is 300~400nm.

[0010] Steps 1-3: After cutting the resin block coated with gold film, place it in a silicone embedding mold, inject resin, and cure at room temperature to obtain the embedding block sample.

[0011] Steps 1-4: Use a glass cutter to trim and polish the embedding block until the gold film end face is exposed. Trim the gold film portion of the embedding block into a protrusion, controlling the trimming speed to be 30~60mm / s and the trimming thickness to be 200~400nm.

[0012] Steps 1-5: Use a straight-edged diamond blade to slice the protrusions of the gold-containing thin film to obtain a resin sheet containing a nanowire array. Control the slicing speed to be 0.5~1mm / s, the slicing direction to be parallel to the surface of the metal microstructure and at a 90° angle to the nanowire array, and the slicing thickness to be 150~250nm.

[0013] Step 2, Metal Lead Fabrication and Lead-to-Nanowire Array Connection: The nanowire array is transferred onto a silicon wafer. A molybdenum mask with a lead pattern is three-dimensionally aligned with the nanowire array. Physical vapor deposition is then used to connect the leads to the nanowire array and fabricate the leads. The specific steps are as follows:

[0014] Step 2-1: Transfer the nanowire array onto the silicon substrate and use a high-precision micro-transfer stage to perform high-precision three-dimensional alignment between the molybdenum mask with the lead pattern and the nanowire array.

[0015] Step 2-2: A gold layer is deposited on a silicon substrate using a thermal evaporation process. After removing the mask, metal leads are fabricated on the silicon substrate, and high-precision bonding between the leads and the nanowire array is achieved. The thickness of the gold layer is controlled to be 100~200nm.

[0016] Step 3, Structure Transfer: Pour resin onto the silicon wafer and cure it at room temperature to transfer the pattern onto the resin. The specific steps are as follows:

[0017] Step 3-1: After thoroughly mixing the resin and curing agent, place them in a vacuum dryer for degassing treatment;

[0018] Step 3-2: Cast resin onto the surface of a silicon wafer with nanowire array and metal lead structure and cure it at room temperature to transfer the pattern onto the resin.

[0019] Step 4, Encapsulation and Polishing: Macroscopic wire bonding and encapsulation are performed to obtain a resin block with an embedded array structure. The end faces are trimmed and the point array is exposed using an ultrathin slicer to complete the fabrication of the addressable disk-based ultramicroelectrode array. The specific steps are as follows:

[0020] Step 4-1: Connect the copper wire to the center of the metal pad at the end of each metal lead, use conductive silver paste to make the connection, ensure current conduction, and use UV-curing adhesive to locally encapsulate the conductive silver paste.

[0021] Step 4-2: Place the sample prepared in step 4-1 into a silicone embedding mold, pour in the de-bubbled resin to cover the nanowire array, metal leads and some macroscopic wires, and cure at room temperature to obtain a well-encapsulated addressable disk microelectrode array sample.

[0022] Step 4-3: Use an ultrasonic cutter to trim the sample to a shape and size slightly larger than the overall structure, and use an ultrathin slicer to trim and polish the sample to ensure that the end face of the nanowire array is exposed.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] Given the advantages of nano-cutting, the method of this invention can easily, efficiently, and cost-effectively fabricate addressable disk-based microelectrode arrays with high consistency. This method not only achieves high-efficiency, high-spatial-resolution scanning but also allows for arbitrary displacement and rotation, and can even be extended to n channels to enable applications in multiple fields. Attached Figure Description

[0025] Figure 1 Flowchart of gold nanowire array fabrication process;

[0026] Figure 2 Flowchart for the fabrication of addressable disk-based microelectrode arrays;

[0027] Figure 3 This is a schematic diagram of the electrochemical imaging feedback mode. Detailed Implementation

[0028] 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.

[0029] This invention provides a method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging, the method comprising the following steps:

[0030] Step (1) Fabrication of gold nanowire arrays: The fabrication process of gold nanowire arrays is as follows: Figure 1As shown, the process is mainly achieved through soft lithography, magnetron sputtering, and nanoslicing techniques. First, a two-stage transfer process is performed to transfer the microgroove array structure from the silicon mask onto the resin. For the first transfer, Sylgard 184 from DowCorining (USA) was used, with a PDMS to curing agent mass ratio of 10:1. After thorough mixing, the mixture was placed in a vacuum dryer for 30 minutes to remove air bubbles. PDMS was then poured onto the silicon template containing the microgroove array and cured in an 80°C oven for 3 hours to obtain a PDMS mold containing the microgroove array. For the second transfer, Epo-fix from Struers A / S (Denmark) was used, with the resin and curing agent mixed at a mass ratio of 25:3. After thorough mixing, the mixture was placed in a vacuum dryer for 30 minutes to remove air bubbles. Resin was then poured onto the surface of the PDMS mold containing the microgroove array and cured at room temperature for 12 hours to obtain a resin block containing the microgroove array. Finally, a 300nm gold film was deposited on the surface of the microgroove array using magnetron sputtering. After appropriate trimming, the gold-coated resin block was placed in a silicone embedding mold, and more resin was injected. It was then cured at room temperature for 12 hours to obtain a cuboid embedding block sample with dimensions of 14×5×3mm (length×width×height). The nanoslicing process was mainly performed using a commercial ultramicrotome (EMUC7) from Leica, Germany. First, the embedding block was trimmed and polished with a glass cutter until the gold film end face was exposed. The trimming speed was 60mm / s, and the trimming thickness was 200nm. Then, the gold-film-containing portion of the embedding block was trimmed into a 500um×500um square protrusion. A straight-edged diamond cutter was then used to slice the gold-film-containing protrusion at a speed of 1mm / s, with the slicing direction parallel to the metal microstructure surface and at a 90° angle to the gold nanowire array. The slice thickness was 200nm. A resin sheet containing the nanowire array was obtained.

[0031] Step (2) Metal lead fabrication and lead-to-nanowire array bonding: The metal lead fabrication process is as follows Figure 2 As shown in (a)-(d), the process is mainly achieved through a combination of mask technology and thermal evaporation. First, the single-crystal silicon wafer is ultrasonically cleaned for 6 minutes each using anhydrous ethanol-acetone-anhydrous ethanol-ultrapure water, then dried with high-purity air, followed by oxygen plasma treatment to hydrophilize the substrate surface, completing the substrate preparation. The prepared nanowire array is transferred to the single-crystal silicon substrate using a Perfect Loop. A high-precision micro-transfer stage is used to precisely align the molybdenum mask with the nanowire array in three dimensions. High-temperature resistant polyimide tape is used to fix the four sides of the mask to prevent displacement during the evaporation process. A 150nm thick gold layer is deposited on the substrate using thermal evaporation. After removing the mask, metal leads are fabricated on the single-crystal silicon substrate, achieving high-precision bonding between the leads and the nanowire array.

[0032] Step (3) Structural transfer: The structural transfer process is as follows Figure 2 As shown in (e)-(f), successful transfer mainly relies on the greater bonding force between the overall structure and the resin than to the silicon substrate. The transfer material used is the same as the Epo-fix used previously. The resin and curing agent are mixed at a mass ratio of 25:3, thoroughly stirred, and then placed in a vacuum dryer for 30 minutes to remove air bubbles. The resin is poured onto the surface of a silicon wafer with a nanowire array and metal lead structure, cured at room temperature for 12 hours, and the entire structure is completely transferred onto the resin surface after the resin is gently peeled off.

[0033] Step (4) Encapsulation and Polishing: The encapsulation and polishing process is as follows Figure 2 As shown in (g)-(i), firstly, copper wires with a diameter of 0.1 mm were overlapped at the center of the metal pad at the end of each metal lead, and conductive silver paste was used for connection to ensure current conduction. UV-curable adhesive was then used for local encapsulation at the conductive silver paste. Next, the prepared sample was placed in a silicone embedding mold, and de-bubbled resin was poured in to cover the nanowire array, metal leads, and some macroscopic wires. The mold was cured at room temperature for 12 hours to obtain a well-encapsulated addressable disk-based microelectrode array sample. The sample was trimmed to a shape and size slightly larger than the overall structure using an ultrasonic cutter; a smaller volume facilitates subsequent integration. An ultrathin slicer was used to trim and polish the sample, ensuring the nanowire array end faces were exposed and that the end face dimensions were minimized. In summary, the fabrication of the addressable disk-based microelectrode array was completed.

[0034] (5) Electrochemical performance testing: Electrochemical performance testing was conducted using the CHI760E series electrochemical workstation from Shanghai Chenhua Instruments Co., Ltd. The prepared addressable disk-based microelectrode array was subjected to cyclic voltammetry scanning in a 1 mmol / L ferrocene methanol aqueous solution, with a supporting electrolyte of 0.5 mol / L KCl aqueous solution. The potential range was -0.1 V to 0.6 V, and the scan rate was 0.1 V / s. The cyclic voltammetric patterns obtained from each channel were all standard S-shaped. The consistency of the results from multiple repeated detections of a single channel demonstrated the repeatability of the electrode response. The consistency of the results from simultaneous detections across different channels demonstrated the effectiveness of simultaneous multi-channel detection, indicating that the addressable disk-based microelectrode array was successfully prepared.

[0035] (6) Electrochemical Imaging: To achieve rapid scanning imaging of micron-structured array samples, an addressable disk-based ultramicroelectrode array is integrated with a micron-precision scanning and positioning device. The principle of electrochemical imaging is as follows: Figure 3As shown, when the working electrode is close to an inert substrate, the substrate blocks the diffusion of redox substances R, causing the actual current to be lower than the steady-state value, exhibiting "negative feedback." If the substrate is electroactive, it will reduce the product O back to R, enhancing the local supply of R, causing the actual current to be higher than the steady-state value, forming "positive feedback." When the disk-based microelectrode array is scanned at a constant height relative to the sample, the electrochemical activity of multiple regions can be obtained simultaneously and rapidly.

Claims

1. A method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging, characterized in that... The method includes the following steps: Step 1, Nanowire Array Fabrication: Using an ultrathin slicer as the processing equipment and a silicon wafer with a micron-groove array structure as a template, the nanowire array is fabricated through soft photolithography, magnetron sputtering, and nanoslicing techniques. Step 2, Metal lead fabrication and lead-to-nanowire array bonding: The nanowire array is transferred onto a silicon wafer, and a molybdenum mask with lead pattern is three-dimensionally aligned with the nanowire array. The bonding of the lead to the nanowire array and lead fabrication are achieved by physical vapor deposition. Step 3, Structure Transfer: Pour resin onto the silicon wafer and cure it at room temperature to transfer the pattern onto the resin; Step 4, Encapsulation and Polishing: Macroscopic wire bonding and encapsulation are performed to obtain a resin block with an embedded array structure. The end face is trimmed and the point array is exposed using an ultrathin slicer to complete the fabrication of the addressable disk microelectrode array.

2. The method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging according to claim 1, characterized in that... The specific steps of step 1 are as follows: Step 1-1: Transfer the micro-groove array structure onto the resin to obtain a resin block containing the micro-groove array; Steps 1-2: Apply magnetron sputtering technology to deposit a gold film on the surface of the micron trench array; Steps 1-3: After cutting the resin block coated with gold film, place it in a silicone embedding mold, inject resin, and cure at room temperature to obtain the embedding block sample. Steps 1-4: Use a glass cutter to trim and polish the embedding block until the gold film end face is exposed, and trim the gold film portion of the embedding block into a protrusion. Steps 1-5: Use a straight-edged diamond blade to slice the protrusions of the gold-containing thin film to obtain resin sheets containing nanowire arrays.

3. The method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging according to claim 2, characterized in that... In steps 1-2, the thickness of the gold film is 300~400nm.

4. The method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging according to claim 2, characterized in that... In steps 1-4, the trimming speed is 30~60mm / s, and the trimming thickness is 200~400nm.

5. The method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging according to claim 2, characterized in that... In steps 1-5, the slicing speed is 0.5~1mm / s, the slicing direction is parallel to the surface of the metal microstructure and at a 90° angle to the nanowire array, and the slicing thickness is 150~250nm.

6. The method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging according to claim 1, characterized in that... The specific steps of step 2 are as follows: Step 2-1: Transfer the nanowire array onto the silicon substrate and use a high-precision micro-transfer stage to perform high-precision three-dimensional alignment between the molybdenum mask with the lead pattern and the nanowire array. Step 2-2: A gold layer is deposited on the silicon substrate using a thermal evaporation process. After removing the mask, metal leads are fabricated on the silicon substrate, and high-precision bonding between the leads and the nanowire array is achieved.

7. The method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging according to claim 6, characterized in that... In step 2-2, the thickness of the gold layer is 100~200nm.

8. The method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging according to claim 1, characterized in that... The specific steps of step 3 are as follows: Step 3-1: After thoroughly mixing the resin and curing agent, place them in a vacuum dryer for degassing treatment; Step 3-2: Cast resin onto the surface of a silicon wafer with nanowire array and metal lead structure and cure it at room temperature to transfer the pattern onto the resin.

9. The method for fabricating an addressable disk-based ultramicroelectrode array for electrochemical imaging according to claim 1, characterized in that... The specific steps of step 4 are as follows: Step 4-1: Connect the copper wire to the center of the metal pad at the end of each metal lead, use conductive silver paste to make the connection, ensure current conduction, and use UV-curing adhesive to locally encapsulate the conductive silver paste. Step 4-2: Place the sample prepared in step 4-1 into a silicone embedding mold, pour in the de-bubbled resin to cover the nanowire array, metal leads and some macroscopic wires, and cure at room temperature to obtain a well-encapsulated addressable disk microelectrode array sample. Step 4-3: Use an ultrasonic cutter to trim the sample to a shape and size slightly larger than the overall structure, and use an ultrathin slicer to trim and polish the sample to ensure that the end face of the nanowire array is exposed.

Images