Ampere type electrochemical micro-nano sensor capable of resisting water flow interference and preparation method of ampere type electrochemical micro-nano sensor

Abstract

The invention discloses a water flow interference resistant amperometric electrochemical micro-nano sensor and a preparation method thereof, and belongs to the technical field of electrochemical sensors. The sensor comprises a Si / SiO2 substrate, an interdigital structure metal electrode arranged on the substrate and a PDMS mesoporous film covering the surface of the metal electrode, and the three parts form a sandwich structure. The preparation method comprises the following steps: carrying out magnetron sputtering on a metal layer on the surface of a Si / SiO2 substrate, and carrying out photoetching and dry etching to form an interdigital electrode; pMMA particles and liquid PDMS are mixed, PMMA is removed after curing, and a PDMS mesoporous film with a penetrating type mesoporous channel is formed; performing oxygen plasma activation on the interdigital electrode and the PDMS mesoporous film; and covering the surface of the interdigital electrode with the treated PDMS mesoporous film, and forming a sandwich structure through thermocompression bonding. Through a special structural design and a preparation process, the technical problem that a traditional electrochemical sensor is easily interfered by water flow in a flowing environment is solved, and the detection stability and accuracy of the sensor in the flowing environment are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical sensors, and in particular to an amperometric electrochemical micro-nano sensor resistant to water flow interference and a preparation method thereof. Background Art

[0002] Electrochemical sensors are widely used in a variety of technical fields, including environmental monitoring, industrial process control, and life sciences, due to their high sensitivity, fast response, and simple detection process. Based on their detection principles, electrochemical sensors can be divided into three main types: amperometric, potentiometric, and resistive. Amperometric electrochemical sensors, among others, achieve quantitative analysis of the concentration of the analyte by monitoring the current changes generated by the charge transfer reaction occurring on the electrode surface, thus possessing extremely high practical value.

[0003] In practice, amperometric electrochemical sensors typically create a potential difference across the interface between electrodes and an electrolyte solution. During this process, ions with opposite surface charge, known as counterions or balancing ions, are adsorbed on the electrode surface, forming a double layer near the electrode surface. Because the amperometric sensing signal primarily originates from electrochemical reactions within the double layer, the structural stability of the double layer directly determines the accuracy of the detection results.

[0004] However, in dynamic liquid environments, especially when disturbed by water flow, the balance between ion diffusion and drift in the electrolyte is disrupted, causing changes in the distribution of ions in the double layer. Water flow can not only alter the ion concentration distribution but also induce additional electromotive force due to shear forces, which can cause a shift in the sensor's output current. This interference caused by changes in the flow field often results in significant errors in the sensor response, the extent of which is closely related to the speed and direction of the water flow, seriously affecting the repeatability and stability of the detection.

[0005] To reduce this type of interference, existing technologies typically rely on installing auxiliary structures around the sensor, such as flow-stabilizing housings or fluid buffer zones, to artificially create a localized static liquid environment. However, these approaches not only increase the complexity and size of the system structure, affecting sensor integration and deployment, but also hinder their application in environments with limited space or complex field conditions. Furthermore, the manufacturing costs and maintenance requirements associated with these additional structures have hindered the widespread adoption of electrochemical sensors in areas such as online water quality monitoring.

[0006] Therefore, how to reduce or shield the interference of water flow on the electrochemical reaction interface from the sensor body structure and achieve stable and accurate detection in a disturbed water environment is one of the key technical issues in the current research of amperometric electrochemical sensors, and new solutions are urgently needed. Summary of the Invention

[0007] One of the technical problems to be solved by the present invention is to provide a method for preparing an amperometric electrochemical micro-nano sensor that is resistant to water flow interference, so as to solve the problem in the prior art that the sensor is unstable in measurement in a dynamic water environment and is easily affected by water flow disturbances and causes detection deviations.

[0008] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for preparing an amperometric electrochemical micro-nano sensor resistant to water flow interference, comprising the following steps: S1: magnetron sputtering a metal layer on the surface of Si / SiO2 substrate, and forming interdigital electrodes through photolithography and dry etching; S2: Mixing PMMA particles with liquid PDMS, and removing PMMA after curing to form a PDMS mesoporous film with through-type mesoporous channels; S3: performing oxygen plasma activation on the interdigital electrodes obtained in step S1 and the PDMS mesoporous film obtained in step S2; S4: Covering the PDMS mesoporous film treated in step S3 on the surface of the interdigital electrode, forming a sandwich structure of Si / SiO2 substrate-interdigital electrode-PDMS mesoporous film by hot pressing bonding, and completing the preparation.

[0009] Compared with the prior art, the preparation method of an amperometric electrochemical micro-nanosensor resistant to water flow interference disclosed in the present application has the following advantages: unlike traditional amperometric electrochemical sensors that are directly exposed to water and whose double electric layer is susceptible to flow disturbances, the present invention introduces a honeycomb-like mesoporous PDMS film structure on the electrode surface, covering the electrode interface originally exposed to the liquid environment with a flexible film having mesoporous channels running through it, thereby constructing an ion diffusion buffer zone with a buffering effect; the mesoporous channels in the PDMS mesoporous film of the present invention allow the target ions in the electrolyte to slowly diffuse to the electrode surface, which not only ensures the ion transmission required for the detection reaction, but also effectively shields the direct influence of the shear force and flow velocity gradient of the external water flow on the double electric layer near the electrode, thereby suppressing the induced electromotive force and ion distribution reconstruction caused by the disturbance flow. In the preparation method of the present invention, a PDMS+PMMA particle system is used to prepare a mesoporous structure, which has the advantages of strong controllability, good material compatibility, and excellent mechanical flexibility; oxygen plasma surface activation is combined with hot pressing bonding technology to achieve reliable integration of PDMS film and micro-nano electrodes, and construct an overall stable sandwich structure; and the interdigitated electrode pattern is constructed based on the standard MEMS process to ensure the dimensional accuracy and batch consistency of the electrode structure; the above technical features work together to enable the electrochemical micro-nano sensor prepared by the present invention to not only have high sensitivity and low noise response in static water bodies, but also maintain good detection stability and result consistency in dynamic disturbance flow fields. Therefore, the present invention essentially solves the problem of serious interference of environmental water flow disturbance on sensor response output from the two levels of device structure design and material processing method. In summary, the preparation method proposed by the present invention not only improves the anti-interference ability of the sensor to water flow disturbance, but also has the advantages of simple process, batch replication of structure, and high system stability. It is suitable for complex scenarios such as long-term online detection of multiple parameters in actual water environments, and has broad engineering application value and industrial promotion potential.

[0010] In a possible implementation, in step S1, the Si / SiO2 substrate is a double-sided polished substrate, and the oxide layer thickness of the Si / SiO2 substrate is 1±0.1 μm, and the surface flatness is less than 1 μm.

[0011] Compared with the existing technology, the double-sided polishing process using the above-mentioned technical solution can effectively reduce micro-defects and thickness variations on the substrate surface, thereby avoiding graphic distortion or resolution degradation in the subsequent patterning process. At the same time, controlling the thickness of the silicon oxide layer within the range of 1±0.1μm and the flatness less than 1μm helps to ensure the electrode insulation performance and structural stability, and meet the dielectric strength requirements for micro-nano electrode production.

[0012] In a possible implementation, in step S1, the step of magnetron sputtering the metal layer includes: preparing a Cr—Au metal layer with a thickness of 30-220 nm on the surface of the substrate by using a magnetron sputtering process.

[0013] Compared with the existing technology, the above technical solution can improve the adhesion and corrosion resistance of the metal layer while maintaining good conductive properties. The Cr layer as the bottom layer has good adhesion properties and can be firmly bonded to the SiO2 surface, while the Au layer has excellent chemical inertness and electrical conductivity, and is suitable for constructing a stable electrochemical working electrode.

[0014] In one possible embodiment, in step S1, the step of forming interdigitated electrodes by photolithography and dry etching includes: coating the surface of the metal layer with positive photoresist, performing photolithography development to prepare an electrode layer window, and then using plasma etching technology to etch the metal layer in the area without photoresist protection, and using oxidation to remove the remaining photoresist.

[0015] Compared with the existing technology, the above-mentioned technical solution can achieve high-resolution and high-precision electrode pattern transfer. The positive photoresist combined with the high-contrast exposure process can form a clear pattern window on the surface of the metal layer; the dry etching provides anisotropic etching control capability, which can achieve vertical and non-diffusion of the pattern edge; the oxidation treatment can completely remove the residual photoresist, avoiding the impact of organic residue on electrode performance.

[0016] In a possible implementation, in step S2, the mixing mass ratio of the PMMA particles to the liquid PDMS is 1:(7-12).

[0017] Compared with the existing technology, the above technical solution can achieve precise balanced control of the porosity and mechanical strength of the mesoporous film. Controlling the mixing mass ratio of the PMMA particles and the liquid PDMS to 1: (7-12) can form a uniformly distributed microporous structure after curing, while ensuring that the PDMS film still has sufficient structural integrity and flexibility, thereby forming a mesoporous PDMS membrane with penetrating mesoporous channels, stable mechanical properties and good bond compatibility, providing a basic guarantee for achieving stable ion diffusion and sensor structure integration; when the PMMA ratio is small, the pore size and porosity of the obtained PDMS membrane are small, which helps to significantly enhance the membrane's shielding ability against external water flow disturbances, and is suitable for detection tasks in high water flow interference environments, and can be used effectively. Effectively maintain the stability of the sensor response; when the PMMA ratio is large, the pore size formed is larger and the porosity is increased, which can improve the membrane's permeability to target ions and thereby enhance the sensor's current output, but the anti-disturbance ability is relatively weakened, and it is more suitable for sensitive detection scenarios in low flow rates or static water environments. The above-mentioned ratio control can also effectively prevent the film from failing during template removal or long-term immersion, such as brittle cracking and pore collapse, and maintain the film's good flexibility and structural integrity; at the same time, this type of mesoporous PDMS membrane has a stable through-pore structure and good micro-nano interface bonding ability, and can serve as an interface medium for stable ion diffusion, and can be reliably integrated with the electrode sheet structure, significantly improving the overall anti-disturbance ability and response stability of the micro-nano sensor.

[0018] In a possible embodiment, in step S2, the PMMA is removed by immersion in an organic solvent, and the organic solvent includes one or both of acetone and chloroform, and the immersion time is 50±10 min.

[0019] Compared with the existing technology, the above technical solution can efficiently remove the PMMA pore-forming agent and obtain a clean and regular mesoporous channel structure. PMMA has good solubility in organic solvents such as acetone and chloroform. Soaking within the immersion time range of 50±10min can completely release the space occupied by the particle position, thereby forming a penetrating mesoporous structure without damaging the PDMS matrix.

[0020] In a possible implementation, in step S3, the oxygen plasma activation is performed under the condition of: cleaning the sensor electrode layer and PDMS at least once respectively using oxygen plasma technology.

[0021] Compared with the existing technology, the above technical solution can introduce hydrophilic groups on the surfaces of two heterogeneous materials to improve their bonding activity. Oxygen plasma treatment will generate polar groups such as Si-OH and PDMS-OH on the surfaces of Si and PDMS, enabling them to undergo dehydration condensation reactions during the subsequent hot pressing process to form stable Si-O-Si covalent bond connections, thereby achieving a firm bond between the PDMS film and the electrode layer, avoiding peeling and liquid penetration, and improving the overall sealing and long-term stability of the sensor structure.

[0022] In a possible embodiment, in step S4, the conditions for the hot pressing bonding are: hot pressing temperature 70-90°C, hot pressing pressure 50-200g / cm 2 , hot pressing time ≥8 hours.

[0023] Compared with the existing technology, the above technical solution can promote the further cross-linking of PDMS and the surface reactive functional groups of the Si / SiO2 substrate under moderate thermal action. Maintaining a certain temperature and pressure during the hot pressing process can accelerate the dehydration condensation reaction of the surface hydroxyl groups to form stable chemical bonds. At the same time, appropriately extending the bonding time helps to fully contact the interface and eliminate bubbles or unreacted areas, and finally obtains a highly reliable and strongly adhesive PDMS-Si bonding interface, ensuring that the sandwich structure maintains its integrity during long-term use, avoiding stratification or leakage, thereby improving the structural stability and working life of the sensor in actual application environments.

[0024] Another technical problem to be solved by the present invention is to provide an amperometric electrochemical micro-nano sensor that is resistant to water flow interference, so as to solve the problem in the prior art that the sensor electrodes are easily affected by water flow disturbances, resulting in unstable double-layer structure, significant measurement errors, and poor online detection reliability.

[0025] To overcome the above-mentioned defects of the prior art, the present invention provides an amperometric electrochemical micro-nano sensor resistant to water flow interference. The amperometric electrochemical micro-nano sensor resistant to water flow interference is prepared by the above-mentioned preparation method, comprising: Si / SiO2 substrate; An interdigitated metal electrode is provided on the substrate, wherein the interdigitated metal electrode comprises a working electrode and a counter electrode; A PDMS mesoporous film covering the surface of the metal electrode, wherein the PDMS mesoporous film has a through-type mesoporous channel; The PDMS mesoporous film is consolidated with the Si / SiO2 substrate through an oxygen plasma activation bonding process to form a sandwich structure of Si / SiO2 substrate-interdigitated electrode-PDMS mesoporous film.

[0026] Compared with the existing technology (related technology), the present application discloses an amperometric electrochemical micro-nano sensor that is resistant to water flow interference and has the following advantages: the electrochemical micro-nano sensor of the present invention introduces a layer of PDMS mesoporous film with penetrating micropores on the electrode surface to construct a stable "physical barrier + ion buffer zone" combination structure, which effectively weakens the interference of water flow disturbance on the ion migration behavior at the electrode interface. Among them, the honeycomb mesoporous channels formed in the PDMS film allow the target ions in the water to slowly diffuse to the electrode surface, but the convection disturbance is difficult to directly penetrate the film and disturb the electrode interface, thereby achieving the dual protection of "physical isolation and diffusion regulation" of the double electric layer structure. Through this structural setting, the sensor can still maintain a stable diffusion layer morphology in a flowing water environment and achieve a smooth output of the response signal; and the sandwich structure design, through-type mesoporous channel structure and oxygen plasma bonding process characteristics in the structure of the present invention work synergistically, so that the sensor of the present invention not only has excellent resistance to water flow interference, but also maintains the comprehensive advantages of high sensitivity, low power consumption and mass production brought by MEMS micro-nano structure, which substantially solves the technical problem of "large detection deviation and poor stability of sensors in dynamic water environment" in the background technology, and provides an electrochemical micro-nano sensing solution with advanced structure, stable performance and feasible process for application scenarios such as online detection of water environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 An exploded view of an amperometric electrochemical sensor resistant to water flow interference; Figure 2 A cross-sectional view of an amperometric electrochemical sensor resistant to water flow interference; Figure 3 Schematic diagram of the principle of resisting water flow disturbance interference by constructing an internal circulation sensor based on mesoporous channels; Figure 4 Flow chart of the sensor preparation method; Description of reference numerals: Figure 1-2 In the figure, 1. Si / SiO2 substrate, 2. interdigitated electrodes, 3. PDMS mesoporous film, 4. mesoporous channel; Figure 3 In the middle, 22, working electrode, 23, counter electrode; Figure 4 Among them, 11, silicon dioxide; 12, silicon wafer; 21, Au; 5, photoresist; 31, PDMS; 32, PMMA particles; 41, micropores. DETAILED DESCRIPTION

[0028] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of the present application and are not intended to limit the scope of protection of the embodiments of the present application. Those skilled in the art may adjust them as needed to suit specific application scenarios.

[0029] In the description of the embodiments of this application, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on the specific circumstances.

[0030] In the embodiments of the present application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0031] The present invention provides a method for preparing an amperometric electrochemical micro-nano sensor resistant to water flow interference, comprising the following steps: S1: magnetron sputtering a metal layer on the surface of Si / SiO2 substrate 1, and forming interdigital electrodes 2 by photolithography and dry etching; S2: mixing PMMA particles with liquid PDMS, and removing PMMA after curing to form a PDMS mesoporous film 3 with through-type mesoporous channels; S3: performing oxygen plasma activation on the interdigital electrodes obtained in step S1 and the PDMS mesoporous film 3 obtained in step S2; S4: Covering the PDMS mesoporous film 3 treated in step S3 on the surface of the interdigital electrode 2, forming a sandwich structure of Si / SiO2 substrate 1-interdigital electrode 2-PDMS mesoporous film 3 by hot pressing bonding, and completing the preparation.

[0032] As a preferred solution, in step S1, the Si / SiO2 substrate 1 is a substrate that has been double-sided polished, and the oxide layer thickness of the Si / SiO2 substrate 1 is 1±0.1 μm, and the surface flatness is less than 1 μm.

[0033] As a preferred solution, in step S1, the step of magnetron sputtering the metal layer includes: preparing a Cr—Au metal layer with a thickness of 30-220 nm on the surface of the silicon oxide wafer by using a magnetron sputtering process.

[0034] As a preferred solution, in step S1, the step of photolithography and dry etching to form interdigital electrodes includes: spin coating a positive photoresist on the surface of the metal layer, photolithography development, preparing an electrode layer window, then using plasma etching technology to etch the metal layer in the area without photoresist protection, and using oxidation method to remove the remaining photoresist (such as Figure 4 (d)).

[0035] As a preferred solution, in step S2, the mixing mass ratio of the PMMA particles to the liquid PDMS is 1:(7-12).

[0036] As a preferred solution, in step S2, the PMMA is removed by immersion in an organic solvent, and the organic solvent includes one or both of acetone and chloroform, and the immersion time is 50±10 min.

[0037] As a preferred solution, in step S3, the conditions for the oxygen plasma activation are: the sensor electrode layer and the PDMS are cleaned at least once respectively using oxygen plasma technology.

[0038] As a preferred solution, in step S4, the conditions for the hot pressing bonding are: hot pressing temperature 70-90°C, hot pressing pressure 50-200g / cm 2 , hot pressing time ≥8 hours.

[0039] Figure 4 The figure below is a flow chart of the specific preparation process for the water flow-resistant amperometric electrochemical micro-nanosensor described in the present invention, illustrating the key steps from substrate pretreatment, metal electrode pattern formation, PDMS mesoporous membrane preparation, and device assembly. The specific steps include:

[0040] Figure 4 a: A double-sided polished Si / SiO2 substrate is used, and silicon dioxide 12 is formed on the surface of the silicon 11 substrate, providing a uniform foundation for subsequent metal electrode deposition; Figure 4 b: A metal film (Au21) is deposited on the surface of silicon dioxide 12 using magnetron sputtering technology. Au is used as an example to form sensor electrodes. Figure 4 c: Structural definition of the metal layer by photoresist 5 patterning and dry etching technology; Figure 4 d: Transferring the pattern of the photoresist 5 onto the metal film to achieve patterning of the metal film and form the desired interdigital electrodes 2; Figure 4 e. Mixing PMMA particles 32 and PDMS 31 prepolymer in proportion, coating to form a film and thermally curing to form a composite film; Figure 4 f: Soaking the composite film in an organic solvent (such as acetone or chloroform) to dissolve the PMMA particles, thereby obtaining a PDMS mesoporous film 3 having micropores 41 formed therein; Figure 4 g: The interdigital electrode 2 obtained in step c and the porous PDMS mesoporous film 3 obtained in step e are positioned and aligned, and hot-pressed bonded after oxygen plasma activation treatment to complete the integration of the overall sandwich structure of the sensor.

[0041] The present invention also provides an amperometric electrochemical micro-nano sensor that is resistant to water flow interference, such as Figure 1 、 Figure 2 Shown, including: Si / SiO2 substrate; An interdigitated metal electrode is provided on the substrate, wherein the interdigitated metal electrode comprises a working electrode 22 and a counter electrode 23; A PDMS mesoporous film covering the surface of the metal electrode, wherein the PDMS mesoporous film has a through-type mesoporous channel; The PDMS mesoporous film is consolidated with the Si / SiO2 substrate through an oxygen plasma activation bonding process to form a sandwich structure of Si / SiO2 substrate-interdigitated electrode-PDMS mesoporous film.

[0042] The present invention proposes a novel structure that is resistant to water flow interference, an amperometric electrochemical micro-nano sensor. The sensor adopts a sandwich configuration: the top layer is a honeycomb-like mesoporous film structure, and the bottom layer is a micro-nano sensing electrode structure. This structural design allows the double layer formed on the electrode surface to fully exchange ions with the water body through the porous film. When there is external water flow disturbance, the mesoporous structure can significantly weaken the influence of the water flow on the double layer, thereby physically achieving effective isolation between the water flow disturbance and the electrochemical reaction interface. This mechanism effectively avoids the electrochemical response deviation caused by water flow changing the distribution of double layer ions, maintains the stability of the diffusion layer, significantly reduces the fluctuation of the sensor output signal, and improves the accuracy and repeatability of the detection results, thereby solving the technical problem that amperometric electrochemical sensors are susceptible to interference and have large detection errors in dynamic water environments. The anti-water flow interference solution proposed by the present invention effectively promotes the practical application of amperometric micro-nano sensors in complex flow field environments and has broad engineering application prospects and industrial value.

[0043] like Figure 3 As shown, Figure 3This is a schematic diagram of the working principle of the amperometric electrochemical micro-nanosensor with resistance to water flow interference described in the present invention, showing how the sensor relies on the microporous channel structure to form a stable internal circulation of ion diffusion when there is external water flow disturbance, thereby achieving anti-disturbance electrochemical detection; Figure 3 The loop mark in the middle represents the ion diffusion inner circulation region formed within the microporous channels of the mesoporous PDMS film. This structure can establish a relatively closed diffusion environment inside the film, so that the sensing reaction mainly relies on the diffusion process within the pores and is not affected by external flows. The working electrode 22 provided on the surface of the sensor is used to undergo redox reactions with the target species. The counter electrode is used to close the loop and provide a stable reference. Figure 3 The arrow at the top represents external water flow disturbances. Although these disturbances exist within the overall detection environment, their kinetic energy is significantly weakened as they pass through the micropores of the PDMS film, preventing them from directly affecting the electrode surface. Through the above structural design, the present invention creates a physically isolated and diffusion-dominated microenvironment within the sensor. This allows the ion migration path to be dominated by the film pores, making it difficult for water flow disturbances to alter the ion distribution state of the double layer, thereby achieving highly stable and anti-interference capabilities in the current signal response.

[0044] To achieve the above structure and function, the present invention adopts the following key technical routes: First, a method for preparing MEMS micro-nano electrodes based on silicon substrates was proposed. This method uses double-sided polished silicon oxide wafers as the substrate, first deposits a metal film layer by magnetron sputtering, then uses photolithography technology to prepare patterned photoresist, and finally achieves precise transfer of the metal pattern through dry etching to complete the construction of high-precision MEMS electrodes.

[0045] Secondly, a method for preparing mesoporous films that can form porous structures was developed. This method uses PDMS, which is compatible with MEMS technology, as the film matrix and PMMA particles as the pore-forming agent. The two are first mixed in proportion and solidified into a film. Then, the PMMA particles are dissolved and removed using organic solvents such as acetone or chloroform to form a mesoporous film with a through-pore structure that is both flexible and liquid permeable.

[0046] Third, a high-strength bonding process between the porous PDMS membrane and the silicon-based electrode was established. This process uses Si-PDMS bonding technology. The PDMS and Si surfaces are activated separately through oxygen plasma treatment to generate hydrophilic Si-OH and PDMS-OH groups. Subsequently, a counter-position hot pressing treatment is performed to form a stable chemical bond between the two materials at the interface, completing the assembly of the overall structure of the sensor. Finally, the electrode leads are connected and the sensor can be put into electrochemical experiments or practical applications.

[0047] In summary, the present invention provides an amperometric micro-nano sensor structure and a preparation method thereof that can significantly reduce the impact of water flow disturbances and improve the accuracy of electrochemical detection. This method is based on standard MEMS technology, has good repeatability and mass production capabilities, can effectively reduce manufacturing costs, and improve product consistency, providing technical support and solutions for the large-scale application of electrochemical microsensors in fields such as water quality monitoring.

[0048] The following provides specific examples in combination with actual data to further illustrate the above-mentioned technical solutions of the present invention: Example 1 This embodiment provides an amperometric electrochemical micro-nano sensor resistant to water flow interference and a preparation method thereof. The amperometric electrochemical micro-nano sensor resistant to water flow interference is prepared by the preparation method, which includes the following steps: S1: magnetron sputtering a metal layer on the surface of Si / SiO2 substrate, and forming interdigital electrodes through photolithography and dry etching; Specifically, a double-sided polished Si / SiO2 substrate is selected, the oxide layer thickness of the substrate is 1±0.1μm, and the surface flatness is less than 1μm; a Cr-Au metal layer with a thickness of 30-220nm is prepared on the surface of the silicon oxide wafer by a magnetron sputtering process; in this embodiment, a 10nm thick Cr layer is first sputtered on the surface of the silicon oxide wafer as an adhesion layer, and then a 200nm thick Au layer is sputtered as a conductive layer.

[0049] A positive photoresist is spin-coated on the metal layer surface and developed by photolithography to create an electrode layer window. Subsequently, plasma etching is used to etch the metal layer in areas not protected by the photoresist, and oxidation is used to remove the remaining photoresist. In this embodiment, AZ5214 photoresist is used, and the spin-coating speed is 4000 rpm for 30 seconds, resulting in a photoresist layer with a thickness of approximately 1.4 μm. After exposure and development, an interdigitated electrode pattern is formed, wherein the interdigitated electrodes have a width of 20 μm and a spacing of 20 μm. Argon plasma etching is used at a power setting of 100 W for 5 minutes to etch away the metal layer not protected by the photoresist. Finally, an oxidation treatment is performed in an oxygen atmosphere at 120°C for 30 minutes to remove the remaining photoresist.

[0050] S2: PMMA particles are mixed with liquid PDMS, and PMMA is removed after curing to form a PDMS mesoporous film with through-type mesoporous channels.

[0051] Specifically, PMMA particles and liquid PDMS were mixed uniformly in a mass ratio of 1:10. In this example, 10g of liquid PDMS (comprising a base and curing agent in a 10:1 ratio) was mixed with 1g of PMMA particles (50μm in diameter). After thorough stirring, the mixture was poured into a mold and cured at 80°C for 2 hours. The cured PDMS-PMMA composite was then soaked in an organic solvent (a 1:1 volume ratio of acetone and chloroform) for 50 minutes to remove the PMMA particles. After soaking, the PMMA particles were completely dissolved, forming a PDMS mesoporous film with through-hole mesoporous channels. The micropores had a diameter of approximately 50μm and a honeycomb pattern. The resulting PDMS mesoporous film was rinsed three times with deionized water and then dried at 60°C for 1 hour.

[0052] S3: performing oxygen plasma activation on the interdigital electrodes obtained in step S1 and the PDMS mesoporous film obtained in step S2; Specifically, the sensor electrode layer and the PDMS mesoporous film were cleaned separately using oxygen plasma technology. In this example, an oxygen plasma cleaning machine was used with a power setting of 50W, an oxygen flow rate of 20sccm, and a treatment time of 60 seconds to activate the surfaces of the interdigitated electrodes and the PDMS mesoporous film. This treatment significantly increased the surface hydrophilicity, facilitating the subsequent bonding process.

[0053] S4: Covering the PDMS mesoporous film treated in step S3 on the surface of the interdigital electrode, forming a sandwich structure of Si / SiO2 substrate-interdigital electrode-PDMS mesoporous film by hot pressing bonding, and completing the preparation.

[0054] Specifically, the PDMS mesoporous film that had been activated by oxygen plasma was carefully covered on the surface of the interdigitated electrode to ensure that the PDMS mesoporous film completely covered the electrode area; then the entire structure was placed in a hot press for bonding, with the hot pressing temperature set to 80°C and the hot pressing pressure set to 100g / cm 2 During the hot pressing process, the PDMS mesoporous film forms a strong chemical bond with the Si / SiO2 substrate surface, forming a stable sandwich structure.

[0055] The water flow-resistant amperometric electrochemical micro-nanosensor fabricated through the aforementioned steps exhibits excellent structural stability and electrochemical performance. The through-mesoporous channels in the PDMS mesoporous film effectively reduce water flow interference on the sensor surface while ensuring that analyte molecules can reach the electrode surface for electrochemical reactions. The interdigitated electrode design increases the effective electrode area and improves the sensor's sensitivity.

[0056] An amperometric electrochemical micro-nano sensor resistant to water flow interference is prepared by the above preparation method, such as Figure 1 As shown, Figure 1 Its exploded diagram includes: Si / SiO2 substrate; an interdigitated metal electrode arranged on the substrate, the interdigitated metal electrode including a working electrode 22 and a counter electrode 23; a PDMS mesoporous film covering the surface of the metal electrode, the PDMS mesoporous film having a through-type mesoporous channel; the PDMS mesoporous film is consolidated with the Si / SiO2 substrate through an oxygen plasma activation bonding process to form a sandwich structure of Si / SiO2 substrate-interdigitated electrode-PDMS mesoporous film.

[0057] Specifically, the Si / SiO2 substrate is a double-sided polished substrate with an oxide layer thickness of 1 μm and a surface flatness of less than 0.5 μm; the interdigitated metal electrode is composed of a Cr-Au double-layer metal, wherein the Cr layer is 10 nm thick and the Au layer is 200 nm thick; the interdigitated electrode includes a working electrode 22 and a counter electrode 23, and both the working electrode 22 and the counter electrode 23 have a comb-like structure and are arranged in an interlaced manner to form an interdigitated structure; the width of the interdigitated electrode is 20 μm, the spacing is 20 μm, and the effective electrode area is 4 mm × 4 mm.

[0058] The PDMS mesoporous film is 200 μm thick and has evenly distributed through-type mesoporous channels. The micropore diameter is about 50 μm and the porosity is about 30%. After oxygen plasma activation treatment, the PDMS mesoporous film forms a strong chemical bond with the surface of the Si / SiO2 substrate, forming a stable sandwich structure.

[0059] The sensor's operating principle is that when immersed in a solution containing the analyte, the analyte diffuses through the mesoporous channels of the PDMS membrane to the electrode surface, where an electrochemical reaction occurs, generating a current signal. The presence of the PDMS membrane significantly reduces direct impact of water on the electrode surface, thereby minimizing interference with electrochemical measurements. Furthermore, the interdigitated electrode design increases the effective electrode area, enhancing the sensor's sensitivity.

[0060] The sensor can be applied to water quality monitoring, biomedical testing, environmental monitoring and other fields, and is particularly suitable for situations where electrochemical detection is required in a flowing environment.

[0061] Example 2 This embodiment provides an amperometric electrochemical micro-nano sensor resistant to water flow interference and a preparation method thereof. The amperometric electrochemical micro-nano sensor resistant to water flow interference is prepared by the preparation method, which includes the following steps: S1: magnetron sputtering a metal layer on the surface of Si / SiO2 substrate, and forming interdigital electrodes through photolithography and dry etching; Specifically, a double-sided polished Si / SiO2 substrate with an oxide layer thickness of 0.9 μm and a surface flatness of less than 0.8 μm was used. A 30 nm thick Cr-Au metal layer was deposited on the surface of the oxidized silicon wafer using a magnetron sputtering process. In this embodiment, a 5 nm thick Cr layer was first sputtered onto the surface of the oxidized silicon wafer as an adhesion layer, followed by a 25 nm thick Au layer as a conductive layer.

[0062] A positive photoresist is spin-coated on the surface of the metal layer, and photolithographic development is performed to prepare an electrode layer window. Subsequently, a plasma etching technique is used to etch the metal layer in the area not protected by the photoresist, and an oxidation method is used to remove the remaining photoresist. In this embodiment, the photoresist is AZ1350 model, the spin-coating speed is 3500 rpm, and the time is 40 seconds, resulting in a photoresist layer with a thickness of approximately 1.2 μm. After exposure and development, an interdigitated electrode pattern is formed, wherein the interdigitated electrodes have a width of 15 μm and a spacing of 15 μm. Argon plasma etching technology is used with a power setting of 80 W and an etching time of 3 minutes to etch away the metal layer not protected by the photoresist. Finally, the metal layer is oxidized in an oxygen atmosphere at a temperature of 100° C. for 20 minutes to remove the residual photoresist.

[0063] S2: Mixing PMMA particles with liquid PDMS, and removing PMMA after curing to form a PDMS mesoporous film with through-type mesoporous channels; Specifically, PMMA particles and liquid PDMS were mixed uniformly in a mass ratio of 1:7. In this example, 7g of liquid PDMS (comprising a base and curing agent in a 10:1 ratio) was mixed with 1g of PMMA particles (30μm in diameter). After thorough stirring, the mixture was poured into a mold and cured at 70°C for 3 hours. The cured PDMS-PMMA composite was then soaked in an organic solvent (acetone) for 40 minutes to remove the PMMA particles. After soaking, the PMMA particles were completely dissolved, forming a PDMS mesoporous film with through-hole mesoporous channels. The micropores had a diameter of approximately 30μm and a honeycomb pattern. The resulting PDMS mesoporous film was rinsed three times with deionized water and then dried at 50°C for 2 hours.

[0064] S3: performing oxygen plasma activation on the interdigital electrodes obtained in step S1 and the PDMS mesoporous film obtained in step S2; Specifically, the sensor electrode layer and the PDMS mesoporous film were each cleaned twice using oxygen plasma technology. In this example, an oxygen plasma cleaning machine was used with a power setting of 40W, an oxygen flow rate of 15sccm, and a treatment time of 45 seconds to activate the surfaces of the interdigitated electrodes and the PDMS mesoporous film. This treatment significantly increased the surface hydrophilicity, facilitating the subsequent bonding process.

[0065] S4: Covering the PDMS mesoporous film treated in step S3 on the surface of the interdigital electrode, forming a sandwich structure of Si / SiO2 substrate-interdigital electrode-PDMS mesoporous film by hot pressing bonding, and completing the preparation.

[0066] Specifically, the PDMS mesoporous film that has been activated by oxygen plasma is carefully covered on the surface of the interdigitated electrode to ensure that the PDMS mesoporous film completely covers the electrode area. The entire structure is then placed in a hot press for bonding. The hot pressing temperature is set to 70°C, the hot pressing pressure is 50g / cm², and the hot pressing time is 8 hours. During the hot pressing process, the PDMS mesoporous film forms a strong chemical bond with the surface of the Si / SiO2 substrate, forming a stable sandwich structure, such as Figure 1 As shown, Figure 1 The exploded diagram of the amperometric electrochemical micro-nano sensor resistant to water flow interference prepared in Example 1 of the present invention includes: a Si / SiO2 substrate; an interdigitated metal electrode arranged on the substrate, the interdigitated metal electrode including a working electrode 22 and a counter electrode 23; a PDMS mesoporous film covering the surface of the metal electrode, the PDMS mesoporous film having a through-type mesoporous channel; the PDMS mesoporous film is consolidated with the Si / SiO2 substrate through an oxygen plasma activation bonding process to form a sandwich structure of Si / SiO2 substrate-interdigitated electrode-PDMS mesoporous film.

[0067] Example 3 This embodiment provides an amperometric electrochemical micro-nano sensor resistant to water flow interference and a preparation method thereof. The amperometric electrochemical micro-nano sensor resistant to water flow interference is prepared by the preparation method, which includes the following steps: S1: magnetron sputtering a metal layer on the surface of Si / SiO2 substrate, and forming interdigital electrodes through photolithography and dry etching; Specifically, a double-sided polished Si / SiO2 substrate with an oxide layer thickness of 1.1 μm and a surface flatness of less than 0.5 μm was used. A 220 nm thick Cr-Au metal layer was deposited on the surface of the oxidized silicon wafer using a magnetron sputtering process. In this embodiment, a 20 nm thick Cr layer was first sputtered onto the surface of the oxidized silicon wafer as an adhesion layer, followed by a 200 nm thick Au layer as a conductive layer.

[0068] A positive photoresist is spin-coated on the surface of the metal layer, and photolithography development is performed to prepare an electrode layer window; then, plasma etching technology is used to etch the metal layer in the area without photoresist protection, and oxidation is used to remove the remaining photoresist; in this embodiment, the photoresist is AZ6130 model, the spin-coating speed is 4500 rpm, and the time is 35 seconds, resulting in a photoresist layer with a thickness of about 1.6 μm; after exposure and development, an interdigitated electrode pattern is formed, wherein the interdigitated electrode has a width of 25 μm and a spacing of 25 μm; argon plasma etching technology is used, with a power setting of 120 W and an etching time of 7 minutes to etch away the metal layer not protected by the photoresist; finally, oxidation treatment is performed in an oxygen atmosphere at a temperature of 130° C. for 40 minutes to remove the residual photoresist.

[0069] S2: Mixing PMMA particles with liquid PDMS, and removing PMMA after curing to form a PDMS mesoporous film with through-type mesoporous channels; Specifically, PMMA particles and liquid PDMS were mixed uniformly in a mass ratio of 1:12. In this example, 12g of liquid PDMS (including a base and a curing agent in a ratio of 10:1) was mixed with 1g of PMMA particles (70μm in diameter). After thorough stirring, the mixture was poured into a mold and cured at 90°C for 1.5 hours. The cured PDMS-PMMA composite was then soaked in an organic solvent (chloroform) for 60 minutes to remove the PMMA particles. After soaking, the PMMA particles were completely dissolved, forming a PDMS mesoporous film with through-hole mesoporous channels. The micropores had a diameter of approximately 70μm and a honeycomb-like distribution. The resulting PDMS mesoporous film was rinsed three times with deionized water and then dried at 70°C for 1.5 hours.

[0070] S3: performing oxygen plasma activation on the interdigital electrodes obtained in step S1 and the PDMS mesoporous film obtained in step S2; Specifically, the sensor electrode layer and the PDMS mesoporous film were each cleaned three times using oxygen plasma technology. In this example, an oxygen plasma cleaning machine was used with a power setting of 60W, an oxygen flow rate of 25sccm, and a treatment time of 90 seconds to activate the surfaces of the interdigitated electrodes and the PDMS mesoporous film. This treatment significantly increased the surface hydrophilicity, facilitating the subsequent bonding process.

[0071] S4: Covering the PDMS mesoporous film treated in step S3 on the surface of the interdigital electrode, forming a sandwich structure of Si / SiO2 substrate-interdigital electrode-PDMS mesoporous film by hot pressing bonding, and completing the preparation.

[0072] Specifically, the PDMS mesoporous film that has been activated by oxygen plasma is carefully covered on the surface of the interdigitated electrode to ensure that the PDMS mesoporous film completely covers the electrode area; then the entire structure is placed in a hot press for bonding, and the hot pressing temperature is set to 90°C and the hot pressing pressure is 200g / cm 2 During the hot pressing process, the PDMS mesoporous film forms a strong chemical bond with the Si / SiO2 substrate surface, forming a stable sandwich structure.

[0073] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0074] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0075] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing an amperometric electrochemical micro-nano sensor resistant to water flow interference, characterized in that: The following steps are involved: S1: magnetron sputtering a metal layer on the surface of a Si / SiO2 substrate (1), and forming interdigitated electrodes (2) by photolithography and dry etching; S2: Mixing PMMA particles with liquid PDMS, and removing PMMA after curing to form a PDMS mesoporous film (3) with through-type mesoporous channels (4); S3: performing oxygen plasma activation on the interdigital electrode (2) obtained in step S1 and the PDMS mesoporous film (3) obtained in step S2; S4: Covering the PDMS mesoporous film (3) treated in step S3 on the surface of the interdigital electrode (2), and forming a sandwich structure of Si / SiO2 substrate-interdigital electrode-PDMS mesoporous film by hot pressing bonding, thereby completing the preparation.

2. The method for preparing the amperometric electrochemical micro-nano sensor resistant to water flow interference according to claim 1, characterized in that: In the step S1, the Si / SiO2 substrate (1) is a substrate that has been subjected to double-side polishing, and the oxide layer thickness of the Si / SiO2 substrate (1) is 1±0.1 μm, and the surface flatness is less than 1 μm.

3. The method for preparing the amperometric electrochemical micro-nano sensor resistant to water flow interference according to claim 1, characterized in that: In the step S1, the step of magnetron sputtering the metal layer includes: preparing a Cr-Au metal layer with a thickness of 30-220 nm on the surface of the substrate by using a magnetron sputtering process.

4. The method for preparing the amperometric electrochemical micro-nano sensor resistant to water flow interference according to claim 1, characterized in that: In step S1, the steps of photolithography and dry etching to form the interdigitated electrodes (2) include: coating the surface of the metal layer with a positive photoresist, photolithography development, preparing an electrode layer window, then using plasma etching technology to etch the metal layer in the area without photoresist protection, and using oxidation to remove the remaining photoresist.

5. The method for preparing the amperometric electrochemical micro-nano sensor resistant to water flow interference according to claim 1, characterized in that: In the step S2, the mixing mass ratio of the PMMA particles to the liquid PDMS is 1:(7-12).

6. The method for preparing the amperometric electrochemical micro-nano sensor resistant to water flow interference according to claim 1, characterized in that: In the step S2, the PMMA is removed by soaking in an organic solvent, and the organic solvent includes one or both of acetone and chloroform, and the soaking time is 50±10 min.

7. The method for preparing the amperometric electrochemical micro-nano sensor resistant to water flow interference according to claim 1, characterized in that: In step S3, the oxygen plasma activation condition is: the sensor electrode layer and the PDMS are cleaned at least once respectively using oxygen plasma technology.

8. The method for preparing the amperometric electrochemical micro-nano sensor resistant to water flow interference according to claim 1, characterized in that: In step S4, the conditions for the hot pressing bonding are: hot pressing temperature 70-90°C, hot pressing pressure 50-200g / cm 2 , hot pressing time ≥8 hours.

9. An amperometric electrochemical micro-nano sensor resistant to water flow interference, characterized in that: The amperometric electrochemical micro-nano sensor resistant to water flow interference is prepared by the preparation method according to any one of claims 1 to 8, comprising: Si / SiO2 substrate (1); An interdigitated electrode (2) provided on the substrate, the interdigitated metal electrode comprising a working electrode (22) and a counter electrode (23); A PDMS mesoporous film (3) covering the surface of the metal electrode, wherein the PDMS mesoporous film (3) has a through-type mesoporous channel (4); The PDMS mesoporous film (3) is bonded to the Si / SiO2 substrate (1) through an oxygen plasma activation bonding process to form a sandwich structure of Si / SiO2 substrate (1)-interdigitated electrodes (2)-PDMS mesoporous film (3).

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