Solution-interface measurement device based on nano slit confinement effect, preparation method and measurement method

Abstract

The invention discloses a solution-interface measuring device based on a nano-slit confinement effect, a preparation method and a measuring method, the measuring device comprises a sample preparation layer, the sample preparation layer comprises a silicon substrate, the silicon substrate is provided with two electrodes which are arranged in parallel at an interval based on an MEMS technology, and the upper surfaces of the electrodes are provided with mercaptan self-assembly modification layers; a nano groove is formed between the two electrodes, an inlet of the nano groove is provided with an inclined lead-in surface, and a hydrophilic layer is formed on the surface of the inclined lead-in surface; the online monitoring layer comprises a temperature control module, and thermistor dot matrixes of the temperature control module are arranged at the bottom of the silicon substrate; the optical fiber surface plasma resonance sensor is arranged on the upper surface of the electrode; the pH optical fiber probe is arranged on the side wall of the nano groove; and the signal processing layer comprises an electrochemical impedance spectroscopy circuit board arranged at the bottom of the online monitoring layer. The measuring device can solve the problems that a traditional measuring device is complex in structure, prone to blockage, weak in interface signal and uneven in solution introduction.

Description

Technical Field

[0001] The present invention relates to the technical field of nanofluid measurement, and more particularly to a solution-interface measurement device based on the nano-slit confinement effect, a preparation method thereof, and a measurement method thereof. Background Art

[0002] In the study of the nano-slit confinement effect, it is crucial to accurately measure the characteristics of the electric double layer (EDL) at the electrode-solution interface. Currently, there are many problems with the measurement devices for the characteristics of the electric double layer (EDL) at the electrode-solution interface. For example, the complex structure of the measurement device makes it difficult to prepare and costly; the nano-scale slits are easily blocked, and the uneven introduction of the solution affects the measurement repeatability; there is a lack of precise control over environmental parameters such as temperature and pressure; the interface signal is weak and it is impossible to simulate real application scenarios.

[0003] The present invention aims to provide a solution-interface measurement device based on the nano-slit confinement effect, a preparation method thereof, and a measurement method thereof, so as to solve the problems of the existing measurement devices such as complex structure, easy blockage of nano-slits, and uneven introduction of the solution. Summary of the Invention

[0004] The object of the present invention is to provide a solution-interface measurement device based on the nano-slit confinement effect, a preparation method thereof, and a measurement method thereof. The measurement device of the present invention has an overall flattened layered structure, which is more convenient to operate and can be easily held by hand or integrated into a measurement platform. The measurement device of the present invention can solve the problems of the traditional measurement devices such as complex structure, easy blockage of nano-slits, weak interface signal, and uneven introduction of the solution.

[0005] To this end, the present invention provides a solution-interface measurement device based on the nano-slit confinement effect, comprising: a sample preparation layer, which includes a silicon substrate, on which two parallel and spaced electrodes are formed, and a thiol self-assembled modification layer is formed on the upper surface of the electrodes; a nano-groove is formed between the two electrodes, and an inclined inlet surface is provided at the entrance of the nano-groove, and a hydrophilic layer is formed on the surface of the inclined inlet surface; an on-line monitoring layer, which includes a temperature control module, and the thermistor array of the temperature control module is arranged at the bottom of the silicon substrate; it further includes an optical fiber surface plasmon resonance sensor arranged on the upper surface of the electrodes, and a pH optical fiber probe arranged on the side wall of the nano-groove; a signal processing layer, which includes an electrochemical impedance spectroscopy circuit board arranged at the bottom of the on-line monitoring layer.

[0006] Preferably, the electrodes are aluminum electrodes, and a gold layer is coated on the surface of the aluminum electrodes, and the thickness of the gold layer is 2 nm; the distance between the two electrodes is 40-60 nm, and the thickness of the electrodes is 100-200 nm.

[0007] Preferably, the thickness of the thiol self-assembled modification layer is 1-2 nm.

[0008] Preferably, the depth of the nano-grooves is 100 - 200 nm, and the length is 10 - 100 μm.

[0009] Preferably, the thickness of the hydrophilic layer is 5 - 10 nm, and the contact angle ≤ 15°.

[0010] The present invention also provides a method for preparing the solution-interface measurement device based on the nano-slit confinement effect, and the method includes: S1: Fabricate a metal electrode pattern with a pitch of 50 nm on a silicon substrate using a mask lithography technique; uniformly coat a photoresist on the silicon substrate, transfer the mask pattern to the photoresist by lithography, and develop to form an aluminum mask electrode with a gap of 50 nm; deposit a gold layer on the surface of the exposed aluminum mask electrode to form two parallel electrodes; S2: Immerse the electrodes in a mixed solution of 11-mercaptoundecanoic acid and ethanol to form a thiol self-assembled monolayer on the electrode surface; S3: Use a spin-coating method to coat a polyethylene glycol solution on the surface of the inclined introduction layer in the nano-groove entrance region to form a hydrophilic layer; S4: Parallelly attach an optical fiber surface plasmon resonance sensor to the electrode surface, and the optical path direction of the optical fiber surface plasmon resonance sensor is perpendicular to the length direction of the nano-grooves to form a "cross" layout; Embed multiple pH optical fiber probes into the side walls of the nano-grooves at an interval of 15 μm, and the ends of the pH optical fiber probes are flush with the electrode surface; Install a temperature control module at the bottom of the silicon substrate, and the thermistor of the temperature control module is arranged in a dot matrix; S5: Install a signal processing layer at the bottom of the on-line monitoring layer.

[0011] Preferably, use a magnetron sputtering method to deposit a gold layer on the surface of the exposed aluminum mask electrode, control the deposition power at 150 - 251 W, and the gas pressure at 1 - 5 mTorr.

[0012] Preferably, immerse the electrodes in a mixed solution of 11-mercaptoundecanoic acid and ethanol, and the molar concentration of 11-mercaptoundecanoic acid in the mixed solution is 0.8 mmol / L - 1.2 mmol / L; react at room temperature for 15 - 20 hours to form a dense thiol self-assembled monolayer on the electrode surface.

[0013] Preferably, the thickness of the hydrophilic layer is 5 - 10 nm, and the contact angle ≤ 15°.

[0014] The present invention also provides a measurement method for the solution-interface measurement device based on the nano-slit confinement effect, and the method includes: S1: Select a target electrolyte solution, KCl solution, and ensure that the solution is free of bubbles and impurities; Adjust the temperature of the measuring device to 32°C ± 0.5°C, and adjust the external air pressure of the nano-slit to 105 kPa ± 30 Pa; Utilize capillary action to fill the nano-groove with KCl solution from bottom to top within 15 s with a uniformity deviation < 5%, wait for 1 - 2 minutes to allow the solution-electrode interface to reach equilibrium; measure the local pH value at the solution-electrode interface through a pH optical fiber probe; S2: Apply a sinusoidal alternating excitation signal with a frequency range of 10 3 -10 6 Hz and an amplitude of 5 - 10 mV; Use an EIS circuit to record the impedance spectrum, and collect 30 - 50 data points per decade; Start the fiber optic surface plasmon resonance sensor, and monitor the surface plasmon resonance signal of the electrode at a sampling rate of 8 Hz; calculate the real-time charge density through the change in reflected light intensity with an accuracy of 0.2 - 0.3 mC / m²; Synchronously apply a ±0.8 V linear sweep voltage at a rate of 15 mV / s and record the current response curve; S3: Input the EIS impedance spectrum, SPR charge density sequence, and I-V curve into a simplified neural network algorithm; algorithm structure: 5 - 7 convolutional layers and 3 - 4 fully connected layers, and train with a synthetic data training set with an input noise < 8%; Output the electrode polarization resistance Rp, solution resistance Rs, and double-layer impedance ZEDL; use SPR data to correct the polarization effect; Inverse model calculation: Debye length, Zeta potential, ion mobility; S4: Drain the solution, rinse the nano-groove with deionized water, and dry it with nitrogen; check the integrity of the electrode and the thiol self-assembled monolayer, and re-modify if necessary.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are: The measuring device of the present invention has an overall flattened layered structure, which is more convenient to operate and can be easily held by hand or integrated into a measurement platform. The measuring device of the present invention can solve the problems of complex structure, easy blockage, weak interface signal, and uneven solution introduction of traditional measuring devices. Specifically: First, the present invention forms an embedded trench electrode on the silicon substrate 11 to form a three-dimensional structure, that is, the aluminum electrode is embedded in parallel trenches etched on the silicon substrate. The depth of the parallel trenches is 100 - 200 nm, and the top surface of the electrode is flush with the top surface of the silicon substrate, forming a "groove-type slit". Cross-sectional shape: similar to the shape of "[", the side walls of the electrode are perpendicular, and the bottom is the silicon substrate. The electrode of the present invention is embedded and formed in the trenches of the silicon substrate, with a stable and reliable structure, which can avoid the mechanical instability of traditional suspended electrodes, and at the same time can form nano-grooves with precise dimensions (accuracy ±8 nm).

[0016] Second, two parallel electrodes of the present invention (spacing ≤ 50 nm) are spaced apart to form a long and narrow open channel (length 10–100 μm), which resembles an "ultra-narrow slit formed by two parallel metal sheets", forming an open nano-groove. The nano-groove of the present invention is open, which can avoid the dead corners and easy blockage problems of traditional closed nano-grooves. The nano-groove of the present invention is easy to clean and maintain and can be reused. Most traditional measuring devices use closed pipes (such as PDMS microfluidic channels) and require an external pump to drive the introduction of the solution, while the nano-groove of the present invention can achieve self-filling of the solution through an open structure.

[0017] An inclined inlet surface is formed at the opening of the nano-groove of the present invention, and a hydrophilic layer is coated on the inclined inlet surface, which can reduce the flow resistance of the solution, thereby making it more convenient to achieve the introduction and filling of the solution.

[0018] Third, the optical path direction of the fiber optic surface plasmon resonance sensor is perpendicular to the length direction of the nano-groove, forming a "cross" layout, which can improve the sensitivity and intensity of the interface signal. Multiple pH fiber optic probes are embedded in the side wall of the nano-groove at intervals of 15 μm, and the ends of the pH fiber optic probes are flush with the surface of the parallel aluminum electrodes, which can avoid protrusions interfering with the flow field and improve the measurement accuracy and sensitivity. The thermistors of the temperature control module are distributed in a dot matrix form and do not occupy the space of the nano-groove.

[0019] After reading the specific embodiments of the present invention in conjunction with the accompanying drawings, other features and advantages of the present invention will become clearer. Description of the Drawings

[0020] Figure 1 is one of the schematic structural diagrams of an embodiment of the sample preparation layer of the present invention; Figure 2 is the second of the schematic structural diagrams of an embodiment of the sample preparation layer of the present invention; Figure 3 is Figure 2 the enlarged view of part A in Figure 4 is the schematic structural diagram of an embodiment of the on-line monitoring layer of the present invention; Figure 5 is the schematic structural diagram of an embodiment of the signal processing layer of the present invention; Figure 6 is the schematic structural diagram of an embodiment of the solution-interface measuring device based on the nano-slit confinement effect of the present invention. Detailed Description of the Invention

[0021] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0022] As Figures 1-6 shown, the present invention provides a solution-interface measurement device based on the nano-slit confinement effect. The measurement device includes a sample preparation layer, an on-line monitoring layer, and a signal processing layer arranged in sequence from top to bottom.

[0023] The sample preparation layer includes a silicon substrate 11, on which two parallel and spaced electrodes 12 are formed. The upper surface of the silicon substrate 11 is flush with the upper surface of the electrodes 12, and a thiol self-assembled modification layer 13 is formed on the upper surface of the electrodes 12. A nano-groove 13 is formed between the two electrodes 12, and an inclined introduction surface 14 is provided at the entrance of the nano-groove 13, and a hydrophilic layer is formed on the surface of the inclined introduction surface 14.

[0024] The electrode 12 is an aluminum electrode, and a gold layer is coated on the surface of the aluminum electrode, and the thickness of the gold layer is 2 nm.

[0025] In the present invention, gold is plated on the surface of the aluminum electrode, which has the advantages of enhancing electrode performance, adapting to surface functionalization modification, reducing material costs and preparation difficulties, etc., as follows: Enhancing electrode performance: The gold layer can improve the performance of the electrode, making the electrode perform better during measurement. When performing measurement operations such as electrochemical impedance spectroscopy (EIS) scanning, surface charge density monitoring (SPR), and volt-ampere characteristics (I-V) detection, the gold-plated electrode can work more stably, ensuring the accuracy of measurement.

[0026] Adapting to surface functionalization modification: The gold-plated layer is beneficial to subsequent surface functionalization modification. The thiol self-assembled modification layer is anchored on the gold-plated electrode surface through Au-S bonds, and then provides carboxyl (-COOH) functional groups to achieve the purpose of regulating the surface charge density by adjusting the solution pH value, enabling the electrode to play a better role under different experimental conditions.

[0027] Reducing costs and difficulties: Compared with other solutions, the method of fabricating an aluminum electrode on a silicon substrate and plating it with gold has the advantages that the silicon substrate is widely available and low-cost, and the preparation process of the aluminum electrode is relatively simple. While ensuring the measurement accuracy, it greatly reduces the material costs and preparation difficulties, and improves the overall cost performance of the device.

[0028] The distance between the two electrodes 12 is 40 - 60 nm, which has the advantages of precisely controlling the electric field and adapting to nano-scale applications. Specifically: Precisely controlling the electric field: The electrode distance of 40 - 60 nm can generate a relatively uniform and appropriately intense electric field between the electrodes. This is beneficial for precisely controlling the electric field of substances or particles between the electrodes. For example, in nanoelectronic devices, the movement trajectory and behavior of electrons can be precisely controlled, improving the performance and stability of the device.

[0029] Adaptation to nanoscale applications: The 40-60nm electrode spacing matches the scale of many nanomaterials and nanostructures. For example, in nanosensors, nanoscale analytes react or interact between electrodes, which helps to improve the sensitivity and resolution of the sensor and can detect extremely small amounts of substances or weak signal changes.

[0030] The thickness of the electrode 12 is 100-200 nm, which has the advantages of ensuring structural stability, optimizing electrical performance, and facilitating integration. Specifically: Ensure structural stability: The electrode thickness of 100-200nm can provide sufficient mechanical strength and stability for the electrode, making it not easy to deform or damage in various environments and working conditions. In some miniaturized electronic devices or nano devices, it can withstand the process stress during the manufacturing process and the external force during use.

[0031] Optimize electrical performance: The electrode thickness of 100-200nm can ensure that the electrode has good conductivity and charge transfer ability. Sufficient thickness can reduce the resistance of the electrode, reduce the energy loss during charge transfer, and improve the conductivity of the electrode, thereby improving the electrical performance and working efficiency of the entire device.

[0032] Facilitates integration: The electrode thickness of 100-200nm is in line with the integration trend of nanodevices, and is convenient for integration with other nanoscale components or structures to form complex nanosystems or circuits, which helps to achieve miniaturization and high performance of the equipment.

[0033] The thickness of the thiol self-assembly modification layer 13 is 1-2 nm, and it has the advantages of precise control of molecular scale, good electron transfer performance, effective blocking and protection, and adaptation to nanostructures. Specifically: Precisely control the molecular scale: This thickness is within the molecular scale range, which can accurately control the interaction between the modified layer and the electrode surface and external substances. The thiol molecules in the modified layer can be adsorbed on the electrode surface in a specific orientation and arrangement to form a compact and orderly monolayer, thereby achieving precise control of the electrode surface properties.

[0034] Good electron transfer performance: This thickness can ensure effective electron coupling between the thiol molecules and the electrode, which is conducive to the transfer of electrons between the electrode and the modified layer, but will not increase the resistance of electron transfer due to being too thick. For example, in electrochemical sensors, it helps to improve the sensor's response speed and sensitivity to target substance detection.

[0035] Effective Barrier and Protection: The thiol self-assembled monolayer 13 with a thickness of 1-2 nm can serve as an effective barrier layer to prevent the electrode surface from being eroded by impurities, oxygen, moisture, etc. in the external environment, playing a role in protecting the electrode. At the same time, it can selectively allow certain molecules of specific sizes and properties to pass through, functionalize the electrode surface, and improve the selectivity and anti-interference ability of the electrode.

[0036] Adaptation to Nanostructures: The thickness of 1-2 nm matches the sizes of nanoscale electrodes and other nanomaterials. In the construction of nanodevices, it is conducive to achieving good interfacial bonding and collaborative work among the components, helping to improve the performance and stability of the entire nanosystem.

[0037] The depth of the nano-groove 13 is 100-200 nm, including the following advantages: Accommodation and Positioning: This depth can provide a suitable accommodation space for some nanoscale substances or structures. For example, it can accurately position and fix nanoparticles, biomolecules, etc., which is conducive to achieving specific functions. For instance, in a nanosensor, the target analyte can be restricted to a specific area, improving the detection accuracy.

[0038] Enhanced Interaction: This depth can increase the interaction area between the nano-groove 13 and the internal substances. For example, in applications such as surface-enhanced Raman scattering, it can enhance the interaction between light and matter, increase the signal intensity, and thus improve the detection sensitivity.

[0039] The length of the nano-groove 13 is 10–100 μm, including the following advantages: Mass Transfer and Distribution: This length range is conducive to the mass transfer and distribution of substances within the nano-groove 13. For example, in microfluidics-related applications, sufficient length allows the analytes in the fluid to have enough time to diffuse, react, etc. within the groove, facilitating their manipulation and analysis.

[0040] Integration and Compatibility: This length is compatible with the sizes of many micro-nano devices, facilitating integration with other micro-nano structures on the same chip or device, realizing the integration of multiple functions, and being conducive to constructing complex micro-nano systems.

[0041] The width of the nano-groove 13 is the spacing between the two electrodes 12, including the following advantages: Electric Field Uniformity: The width being the same as the electrode spacing helps generate a uniform electric field between the electrodes, making the electric field distribution within the nano-groove 13 relatively stable and uniform. This is very important for manipulating charged particles within the nano-groove 13 or influencing chemical reactions therein, etc., and can improve the consistency and repeatability of related processes.

[0042] Precise regulation: The width matching the electrode spacing enables precise regulation of the environment within the nano-groove 13. For example, in an electrically driven nano-device, the movement of ions or electrons within the nano-groove 13 can be precisely controlled to achieve precise control of specific processes, which is beneficial to improving the performance and reliability of the device.

[0043] The included angle between the inclined inlet surface 14 and the bottom surface of the nano-groove 13 is an acute angle, which can reduce the solution flow resistance, thus making it more convenient to achieve the introduction and filling of the solution.

[0044] The thickness of the hydrophilic layer is 5 - 10 nm, and the contact angle ≤ 15°. It has the following advantages: Good hydrophilicity and wettability: A smaller contact angle means that the liquid can spread rapidly on the surface of the hydrophilic layer, enabling the surface energy of the material to be quickly wetted by the liquid, which is beneficial to improving the interaction efficiency between the material and the liquid. The thickness of the hydrophilic layer of 5 - 10 nm can ensure that the hydrophilic layer has sufficient functional groups to interact with water molecules, and at the same time, it will not affect other properties of the material, such as mechanical properties and light transmittance, due to being too thick.

[0045] Improve anti-fouling performance: Since the hydrophilic layer can form a continuous water film on its surface, this can prevent substances such as dirt and bacteria from directly contacting the material surface, thereby reducing the attachment of dirt and the adhesion of bacteria, making the material have good self-cleaning and anti-fouling properties.

[0046] Improve surface stability: The presence of the hydrophilic layer can reduce the free energy of the material surface, making the surface more stable. This helps to resist the influence of external environmental factors (such as temperature, humidity, chemical substances, etc.) on the material surface, reduce the occurrence of surface aging, corrosion and other phenomena, and extend the service life of the material.

[0047] The on-line monitoring layer includes a monitoring bottom plate 21, which is installed at the bottom of the silicon substrate 11. A temperature control module 22, a pressure sensor 23 and an air pump 24 are provided on the monitoring bottom plate 21, and the thermistor array of the temperature control module 22 is arranged on the monitoring bottom plate 21.

[0048] The on-line monitoring layer further includes an optical fiber surface plasmon resonance sensor 25, which is arranged on the upper surface of one of the electrodes 12. The optical path direction of the optical fiber surface plasmon resonance sensor 25 is perpendicular to the length direction of the nano-groove 13, forming a "cross" layout, and has the following advantages:

[0049] Improving detection sensitivity: The optical path direction of the fiber optic surface plasmon resonance sensor 25 is perpendicular to the length direction of the nano-groove 13 to form a "cross" layout, which can make the interaction path between light and the substances in the nano-groove 13 longer during the propagation process. If there are substances to be detected in the nano-groove 13, the chance of light interacting with them increases, and it can more sensitively detect the changes in the substances, thereby improving the detection sensitivity of the fiber optic surface plasmon resonance sensor.

[0050] Facilitating signal acquisition and analysis: This layout enables the fiber optic surface plasmon resonance sensor 25 to more conveniently acquire the optical signal changes caused by the substance changes in the nano-groove 13. The perpendicular optical path setting allows light to irradiate the surface of the nano-groove 13 and the electrode 12 at a specific angle, and the signals of the reflected or transmitted light are more easily collected and transmitted by the optical fiber, facilitating subsequent analysis and processing, and is conducive to obtaining stable and accurate detection signals.

[0051] Achieving efficient utilization of space: The "cross" layout can effectively combine the fiber optic surface plasmon resonance sensor 25 and the nano-groove 13 structure within a limited space. The sensor is set on the upper surface of the electrode 12 without occupying too much extra space. At the same time, the perpendicular layout method can make full use of the planar space, which is conducive to the miniaturization and integration of the entire device, making the device more compact and facilitating installation and operation in practical applications.

[0052] Avoiding mutual interference: The perpendicular layout helps to reduce the mutual interference between the optical path system of the fiber optic surface plasmon resonance sensor 25 and other physical processes (such as electric field action, mass transfer, etc.) in the nano-groove 13. The optical path is independent of the length direction of the nano-groove 13, which can avoid the influence of factors such as the mass flow or electric field distribution in the nano-groove 13 on the optical path, ensuring the accuracy and stability of optical detection, and enabling the sensor to more purely detect the changes related to optical properties without being interfered by other irrelevant factors.

[0053] The on-line monitoring layer also includes a plurality of pH fiber optic probes 26. The plurality of pH fiber optic probes 26 are symmetrically arranged on the side walls of the two nano-grooves 13. The distance between adjacent two pH fiber optic probes 26 is 15 μm. The ends of the pH fiber optic probes 26 are flush with the surface of the parallel aluminum electrode to avoid protrusions interfering with the flow field.

[0054] This application uses the fiber optic surface plasmon resonance sensor 25 for charge monitoring. The electrode 12 is connected to the sensing area of the fiber optic surface plasmon resonance sensor 25. When the incident light propagates in the optical fiber and irradiates the surface of the electrode 12, it triggers surface plasmon resonance, resulting in a change in the intensity of the reflected light. By monitoring the change in the intensity of the reflected light and using the calibration curve to calculate the surface charge density. Through optimizing the fiber surface modification and signal processing algorithm, the charge density resolution can reach 0.2 - 0.3 mC / m².

[0055] The temperature control of this application uses a thermistor heating element, in conjunction with a temperature control module 22, to maintain the temperature control accuracy within ±0.5°C. The pressure control uses a pressure sensor 23 and an air pump 24. Through a feedback control algorithm, the regulation accuracy of the external air pressure of the nano-groove 13 is controlled within ±20 - ±30 Pa. The micro-region pH sensing uses a fluorescence ratio method optical fiber sensor. A plurality of pH optical fiber probes 26 are embedded at intervals of 15 μm on both sides of the nano-groove 13. The surface of the sensor is modified with a pH-sensitive fluorescent dye (such as BCECF). The local pH value is inverted through the dual-channel fluorescence intensity ratio (490 nm / 535 nm), and the spatial resolution is 15 μm.

[0056] The signal processing layer includes a processing base plate 31. The processing base plate 31 is installed at the bottom of the monitoring base plate 21, and an electrochemical impedance spectroscopy circuit board 32 is provided on the processing base plate 31.

[0057] The electrochemical impedance spectroscopy circuit board 32 uses a potentiostat and a lock-in amplifier to construct a measurement circuit. The frequency range is set to 10 3 -10 6 Hz. A filter circuit is introduced to suppress high-frequency noise and reduce the electrode polarization effect. During EIS measurement, a ±0.8 V linear sweep voltage is applied, the sweep rate is 15 mV / s, and the current response is synchronously recorded to obtain the volt-ampere characteristic curve.

[0058] Optimized impedance decomposition algorithm: Adopt a neural network structure, including 5 - 7 convolutional layers and 3 - 4 fully connected layers. The input is the EIS impedance spectrum (real part / imaginary part varying with frequency), the SPR charge density sequence, and the I-V curve, and the output is the electrode polarization impedance (Rp), the solution resistance (Rs), and the double-layer impedance (ZEDL). Use COMSOL Multiphysics simulation to generate a synthetic data set with ion concentrations in the range of 10 -5 -10 -3 M and temperatures in the range of 28 - 35°C, and add a certain amount of noise for training. Optimize the network parameters through the backpropagation algorithm to make the impedance component separation error <8% - 10%.

[0059] The measurement device of the present invention as a whole presents a flattened layered structure, which is more convenient to operate and can be easily held by hand or integrated into a measurement platform. The measurement device of the present invention can solve the problems of complex structure, easy blockage, weak interface signal, and uneven solution introduction of traditional measurement devices. Specifically: First, the present invention forms an embedded trench electrode 12 on a silicon substrate 11 to form a three-dimensional structure, that is, an aluminum electrode is embedded in parallel trenches etched in the silicon substrate 11. The depth of the parallel trenches is 100 - 200 nm. The top surface of the electrode 12 is flush with the top surface of the silicon substrate 11, forming a "groove-type slit". Cross-sectional shape: similar to a "[" shape, the side wall of the electrode 12 is vertical, and the bottom is the silicon substrate 11. The electrode 12 of the present invention is embedded and formed in the trenches of the silicon substrate 11, with a stable and reliable structure, which can avoid the mechanical instability of traditional suspended electrodes. At the same time, a nano-groove 13 with precise dimensions (accuracy ±8 nm) can be formed.

[0060] Second, two parallel electrodes 12 (spacing ≤ 50 nm) of the present invention are spaced apart to form a long and narrow open channel (length 10 - 100 μm), similar to an "ultra-narrow slit formed by two parallel metal sheets", forming an open nano-groove 13. The nano-groove 13 of the present invention is open, which can avoid the dead corners and easy blockage problems of traditional closed nano-grooves. The nano-groove 13 of the present invention is easy to clean and maintain and can be reused. Most traditional measuring devices use closed pipes (such as PDMS microfluidic channels), which require an external pump to drive for solution introduction, while the nano-groove 13 of the present invention can achieve self-filling of the solution through an open structure.

[0061] An inclined inlet surface 14 is formed at the opening of the nano-groove 13 of the present invention, and a hydrophilic layer is coated on the inclined inlet surface 14, which can reduce the solution flow resistance, thereby making it more convenient to achieve the introduction and filling of the solution.

[0062] Third, the optical path direction of the fiber optic surface plasmon resonance sensor 25 is perpendicular to the length direction of the nano-groove 13, forming a "cross" layout, which can improve the sensitivity and intensity of the interface signal. Multiple pH fiber optic probes 26 are embedded in the side wall of the nano-groove 13 at intervals of 15 μm, and the ends of the pH fiber optic probes 26 are flush with the surface of the parallel aluminum electrode, which can avoid protrusions interfering with the flow field and improve the measurement accuracy and sensitivity. The thermistors of the temperature control module 22 are distributed in a dot matrix form, without occupying the space of the nano-groove 13.

[0063] The on-line monitoring layer and the electrochemical impedance spectroscopy circuit board of the signal processing layer cooperate with each other. The on-line monitoring layer is responsible for real-time acquisition of various key data in the measuring device, such as temperature, pressure, solution pH value, and electrode surface plasmon resonance signal and other information. These data are crucial for accurately analyzing the solution-interface characteristics. The electrochemical impedance spectroscopy circuit board of the signal processing layer is mainly used for performing electrochemical impedance spectroscopy (EIS) scans, recording impedance spectrum data, and comprehensively processing and analyzing the collected various data.

[0064] During the actual measurement process, the data collected by the on-line monitoring layer is transmitted to the signal processing layer and processed subsequently together with the impedance spectrum data obtained from the electrochemical impedance spectroscopy circuit board. For example, the charge density data monitored by the fiber optic surface plasmon resonance sensor, the pH value data measured by the pH fiber optic probe, and the impedance spectrum data obtained from the EIS scan are jointly input into the simplified neural network algorithm for data fusion and parameter inversion, so as to obtain key parameters such as electrode polarization impedance, solution resistance, and double layer impedance, as well as important indicators reflecting the solution-interface characteristics such as Debye length, Zeta potential, and ion mobility.

[0065] In the measuring device of the present invention, the optical fiber mainly plays a role through the fiber optic surface plasmon resonance sensor and the pH fiber optic probe to realize the monitoring of multiple key parameters.

[0066] Surface charge density monitoring: The optical path direction of the fiber optic surface plasmon resonance sensor is perpendicular to the length direction of the nano-groove, forming a "cross" layout. When the incident light propagates in the optical fiber and irradiates the electrode surface connected to the optical fiber, it will trigger the surface plasmon resonance phenomenon, resulting in a change in the intensity of the reflected light. By monitoring this change in the reflected light intensity and using the calibration curve, the surface charge density can be calculated, and its resolution can reach 0.2-0.3 mC / m², thereby realizing the real-time monitoring of the surface charge density of the electrode surface.

[0067] Micro-region pH value measurement: Multiple pH fiber optic probes are embedded in the side wall of the nano-groove at intervals of 15 μm, and their ends are flush with the surface of the parallel aluminum electrode. The surfaces of these pH fiber optic probes are modified with pH-sensitive fluorescent dyes such as BCECF. By detecting the fluorescence intensity ratio of the 490 nm / 535 nm double channel and using the fluorescence ratio method to invert the local pH value, the spatial resolution is 15 μm, thereby realizing the accurate measurement of the local pH value at the solution-electrode interface.

[0068] The present invention also provides a preparation method for a solution-interface measuring device based on the nano-slit confinement effect, including S1: Use the mask lithography technology to fabricate a metal electrode pattern with a pitch of 50 nm on the silicon substrate 11. The photoresist is evenly coated on the silicon substrate 11, and the mask pattern is transferred to the photoresist by the lithography method, and an aluminum metal mask with a gap of 50 nm is formed after development. Then, use the magnetron sputtering method to deposit a gold layer on the exposed electrode area, the thickness of the gold layer is 2 nm, the deposition power is controlled at 150-251 W, and the air pressure is 1-5 mTorr to form parallel electrodes 12 with a pitch of 50 nm and a thickness of 100-200 nm.

[0069] S2: Immerse the electrode in a mixed solution of 11-mercaptoundecanoic acid and ethanol. The molar concentration of 11-mercaptoundecanoic acid in the mixed solution is 0.8 mmol / L - 1.2 mmol / L. React at room temperature for 15 - 20 hours to form a dense thiol self-assembled monolayer 13 on the surface of electrode 12. The thickness of the thiol self-assembled monolayer 13 is 1 - 2 nm. The thiol self-assembled monolayer 13 is anchored on the surface of electrode 12 through Au-S bonds, providing carboxyl (-COOH) functional groups, and the surface charge density can be regulated by adjusting the solution pH value.

[0070] S3: On the inclined inlet surface 14 of the nano-groove 13, spin-coat a polyethylene glycol solution to form a hydrophilic layer with a thickness of 5 - 10 nm and a contact angle ≤ 15°. Using the capillary effect, the solution can fill the inlet nano-groove 13 within 15 s with a uniformity deviation < 5%.

[0071] S4: Install the monitoring bottom plate 21 at the bottom of the silicon substrate 11. Attach the fiber optic surface plasmon resonance sensor 25 parallel to the surface of electrode 12. The optical path direction of the fiber optic surface plasmon resonance sensor 25 is perpendicular to the length direction of the nano-groove 13, forming a "cross" layout.

[0072] Embed multiple pH fiber optic probes 26 into the sidewall of the nano-groove 13 at an interval of 15 μm. The end of the pH fiber optic probe 26 is flush with the surface of the parallel electrode 12 to avoid protrusions interfering with the flow field.

[0073] S5: Install the signal processing layer at the bottom of the online monitoring layer.

[0074] The preparation method of the solution-interface measurement device based on the nano-slit confinement effect of the present invention has the following advantages: First, optimize electrode preparation and material selection: Fabricate an aluminum electrode on a silicon substrate and then deposit gold, replacing the traditional process. Compared with other solutions, the silicon substrate is widely available and low-cost, and the preparation process of the aluminum electrode is relatively simple. Subsequent gold deposition not only enhances the electrode performance but also better adapts to surface functionalization modification. While ensuring the measurement accuracy, it significantly reduces the material cost and preparation difficulty, and improves the overall cost performance of the device.

[0075] Second, optimize the monitoring scheme and improve practicality: The fiber optic surface plasmon resonance sensor has low cost, small size, and convenient installation. The equipment such as thermistors and ordinary pressure sensors used for micro-region environment regulation has low cost, and the temperature and pressure control accuracy can meet the requirements of some experiments.

[0076] Third, efficient algorithm, reducing resource requirements: The simplified neural network structure reduces the demand for computing resources, shortens the training time, and can still effectively separate impedance components and achieve multi-parameter measurement under specific experimental conditions.

[0077] The present invention also provides a measurement method for a solution-interface measurement device based on the nano-slit confinement effect, including: S1: Sample and device preparation, specifically including the following steps: S1.1: Select the target electrolyte solution, KCl solution, with a concentration of 10 -4 M, ensuring no bubbles and impurities.

[0078] Adjust the pH value of the solution (by acid-base titration) according to experimental requirements to match the charge characteristics of the thiol self-assembled monolayer. The adjustment of the solution pH value needs to match the charge characteristics of the thiol self-assembled monolayer. For example, if the thiol self-assembled monolayer is negatively charged (such as a carboxylic acid terminus), the solution pH should be higher than its pKa (such as pH > 5) to ensure the ionization of the thiol self-assembled monolayer (-COO - ); if the thiol self-assembled monolayer is positively charged (such as an amino terminus), the pH should be lower than its pKa (such as pH < 9).

[0079] S1.2: Temperature / pressure setting, set the target temperature through a thermistor heating element, such as 32 °C ± 0.5 °C; use a small air pump to adjust the air pressure outside the slit, such as 105 kPa ± 30 Pa. The temperature fluctuation needs to be < ±0.5 °C, and the air pressure fluctuation < ±30 Pa, so as to avoid affecting capillary filling and measurement repeatability.

[0080] S1.3: Hydrophilic layer activation, confirm that the PEG hydrophilic coating at the slit entrance is intact, and the contact angle ≤ 15°.

[0081] Utilize the capillary effect to fill the nano-groove with the KCl solution from bottom to top within 15 s with a uniformity deviation of < 5%, and wait for 1 - 2 minutes to make the solution-electrode interface reach equilibrium and the double layer form stably; the solution-electrode interface reaching equilibrium means that in an electrochemical system, the mass exchange and charge transfer between the solution and the electrode reach a dynamic equilibrium state. Waiting for 1 - 2 minutes to make the solution-electrode interface reach equilibrium is to ensure the accuracy and reliability of the local pH value at the solution-electrode interface measured by the pH optical fiber probe, because only in the equilibrium state can the measured value truly reflect the properties of the system.

[0082] The local pH value at the solution-electrode interface (such as near the double layer) is measured by a micro-region pH optical fiber sensor, such as detecting the 490 nm / 535 nm ratio by BCECF fluorescent dye.

[0083] S2: Multi-parameter synchronous measurement, signal synchronization: The EIS, SPR, and I-V data need to be strictly time-aligned, using a unified trigger signal; specifically including the following steps: S2.1: Electrochemical impedance spectroscopy (EIS) scan; Apply a sinusoidal AC excitation signal (frequency range 10 3 –10 6 Hz, amplitude 5 - 10 mV).

[0084] Use an EIS circuit to record the impedance spectrum (real part / imaginary part), and collect 30 - 50 data points per decade.

[0085] For the electrochemical impedance spectroscopy (EIS) scan, the frequency range is relatively narrow, and 30 - 50 data points are collected per decade. This can not only ensure the acquisition of key data to reflect the changing trend of the impedance spectrum, but also effectively shorten the measurement time, improve the experimental efficiency, and at the same time will not overly lose the measurement accuracy; it is also possible to further improve the data accuracy and reduce the error influence that may be brought about by the reduction of data points by taking the average value of multiple measurements.

[0086] S2.2: Surface charge density monitoring (SPR); Start the fiber optic surface plasmon resonance sensor and monitor the surface plasmon resonance signal of the gold electrode at a sampling rate of 8 Hz.

[0087] Calculate the real-time charge density (accuracy 0.2 - 0.3 mC / m²) through the change in the intensity of the reflected light.

[0088] S2.3: Volt - ampere characteristic (I - V) detection; Synchronously apply a ±0.8 V linear sweep voltage (rate 15 mV / s) and record the current response curve.

[0089] S3: Data processing and parameter inversion, which specifically includes the following steps: S3.1: Data fusion; Input the EIS impedance spectrum, SPR charge density sequence, and I - V curve into the simplified neural network algorithm.

[0090] Algorithm structure: 5 - 7 layer convolutional network and 3 - 4 layer fully connected, trained with a synthetic data training set with input noise < 8%.

[0091] S3.2: Impedance component separation; Output the electrode polarization impedance (Rp), solution resistance (Rs), and double - layer impedance (ZEDL).

[0092] Use SPR data to correct the polarization effect (formula: , α fitting coefficient), which can make the impedance - related data obtained by measurement more accurate and reduce the interference of the polarization effect on the measurement result.

[0093] S3.3: Multi - parameter output; Inversion model calculation: Debye length (λD, reflecting the double - layer thickness).

[0094] Zeta potential (characterizing the interfacial electric potential).

[0095] Ion mobility (reflecting the electrical conductivity characteristics of the solution).

[0096] S4: Drain the solution, rinse the nano-groove 3 times with deionized water, and dry it with nitrogen. Check the integrity of the electrode and the SAM modification layer, re-modify if necessary, and immerse it in a 11-mercaptoundecanoic acid (MUA) ethanol solution for 15 - 20 hours.

[0097] The present invention realizes the efficient collaborative measurement of nano-confined interfacial parameters through "capillary filling of solution → multi-sensor synchronous measurement → intelligent algorithm analysis", significantly improving the measurement simplicity and the reliability of measurement data. Specifically: First, the solution introduction method: In this application, a hydrophilic layer is formed by coating polyethylene glycol (PEG) on the inclined introduction surface 14 in the inlet area of the nano-groove 13, and the solution is introduced by capillary action, enabling the solution to fill and enter the nano-groove 13 from bottom to top along the inclined introduction surface 14 with a uniformity deviation < 5% within 15 s. Without complex external equipment, the operation process is simplified, and the uniformity of solution distribution is improved. While traditional measurement devices mostly use an external pump to drive the solution flow, which is likely to cause uneven solution introduction, affecting the measurement repeatability and accuracy.

[0098] Second, multi-parameter synchronous measurement: This application uses an optical fiber surface plasmon resonance sensor 25 to monitor the charge density in real time, synchronously perform electrochemical impedance spectroscopy (EIS) scanning and volt-ampere characteristics (I-V) measurement, and obtain multiple key parameters within the same time period, ensuring the synchronism and relevance of the data, and more comprehensively and accurately reflecting the solution-interface characteristics. While traditional methods usually have difficulty in achieving multi-parameter synchronous and accurate measurement, or require multiple independent devices to measure different parameters respectively, with cumbersome operation and easy introduction of errors.

[0099] Third, data processing and analysis: This application uses an impedance decomposition algorithm with a simplified neural network structure to process data. Input the EIS impedance spectrum, SPR charge density sequence, and I-V curve into the algorithm, and output parameters such as electrode polarization impedance, solution resistance, and double-layer impedance. It also uses SPR data to correct the influence of electrode polarization, and obtains parameters such as Debye length, Zeta potential, and ion mobility through a multi-parameter inversion model, improving the data processing efficiency and accuracy, and exploring the potential value of the data. While the data processing method of traditional measurement devices is relatively simple, and it is difficult to accurately extract key information from complex data.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, for those of ordinary skill in the art, it is still possible to modify the technical solutions recorded in the foregoing embodiments, or to equivalently replace some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions required to be protected by the present invention.

Claims

1. A solution-interface measurement device based on the nano-slit confinement effect, characterized in that Comprising: A sample preparation layer, which includes a silicon substrate, on which two parallel and spaced electrodes are formed, and a thiol self-assembled monolayer is formed on the upper surface of the electrodes; A nano-groove is formed between the two electrodes, an inclined inlet surface is provided at the inlet of the nano-groove, and a hydrophilic layer is formed on the surface of the inclined inlet surface; An on-line monitoring layer, which includes a temperature control module, and a thermistor matrix of the temperature control module is arranged at the bottom of the silicon substrate; it also includes an optical fiber surface plasmon resonance sensor arranged on the upper surface of the electrodes, and a pH optical fiber probe arranged on the side wall of the nano-groove; A signal processing layer, which includes an electrochemical impedance spectroscopy circuit board arranged at the bottom of the on-line monitoring layer.

2. The solution-interface measurement device based on the nano-slit confinement effect according to claim 1, wherein The electrodes are aluminum electrodes, and a gold layer is coated on the surface of the aluminum electrodes, and the thickness of the gold layer is 2 nm; The distance between the two electrodes is 40 - 60 nm, and the thickness of the electrodes is 100 - 200 nm.

3. The solution-interface measurement device based on the nano-slit confinement effect according to claim 1, wherein The thickness of the thiol self-assembled monolayer is 1 - 2 nm.

4. The solution-interface measurement device based on the nano-slit confinement effect according to claim 1, wherein The depth of the nano-groove is 100 - 200 nm, and the length is 10 - 100 μm.

5. The solution-interface measurement device based on the nano-slit confinement effect according to claim 1, wherein The thickness of the hydrophilic layer is 5 - 10 nm, and the contact angle ≤ 15°.

6. A preparation method of a solution-interface measurement device based on the nano-slit confinement effect as described in any one of claims 1-5, characterized in that, The method includes: S1: Using a mask lithography technique to fabricate a metal electrode pattern with a 50 nm spacing on a silicon substrate; uniformly coating a photoresist on the silicon substrate, transferring the mask pattern to the photoresist by a lithography method, and forming an aluminum mask electrode with a 50 nm gap after development; depositing a gold layer on the surface of the exposed aluminum mask electrode to form two parallel electrodes; S2: Immersing the electrodes in a mixed solution of 11-mercaptoundecanoic acid and ethanol to form a thiol self-assembled monolayer on the surface of the electrodes; S3: Using a spin coating method to coat a polyethylene glycol solution on the surface of the inclined inlet layer in the nano-groove inlet area to form a hydrophilic layer; S4: Parallelly attaching the optical fiber surface plasmon resonance sensor to the surface of the electrodes, and the optical path direction of the optical fiber surface plasmon resonance sensor is perpendicular to the length direction of the nano-groove to form a "cross" layout; Embedding multiple pH optical fiber probes into the side wall of the nano-groove at an interval of 15 μm, and the end of the pH optical fiber probe is flush with the surface of the electrodes; Installing the temperature control module at the bottom of the silicon substrate, and arranging the thermistor matrix of the temperature control module; S5: Installing the signal processing layer at the bottom of the on-line monitoring layer.

7. The preparation method of the solution-interface measurement device based on the nano-slit confinement effect according to claim 6, wherein, Using a magnetron sputtering method to deposit a gold layer on the surface of the exposed aluminum mask electrode, with a deposition power of 150 - 251 W and a gas pressure of 1 - 5 mTorr.

8. The preparation method of the solution-interface measurement device based on the nano-slit confinement effect according to claim 6, characterized in that, Immerse the electrode in a mixed solution of 11-mercaptoundecanoic acid and ethanol, where the molar concentration of 11-mercaptoundecanoic acid in the mixed solution is 0.8 mmol / L - 1.2 mmol / L; react at room temperature for 15 - 20 hours to form a dense thiol self-assembled monolayer on the electrode surface.

9. The preparation method of the solution-interface measurement device based on the nano-slit confinement effect according to claim 6, wherein, The thickness of the hydrophilic layer is 5 - 10 nm, and the contact angle ≤ 15°.

10. A measuring method for a solution-interface measuring device based on the nano-slit confinement effect according to any one of claims 1-5, characterized in that, The method includes: S1: Select the target electrolyte solution, KCl solution, and ensure that the solution is free of bubbles and impurities; Adjust the temperature of the measuring device to 32 °C ± 0.5 °C, and adjust the external air pressure of the nano-slit to 105 kPa ± 30 Pa; Utilize the capillary effect to fill the nano-groove with the KCl solution from bottom to top within 15 s with a uniformity deviation < 5%; wait for 1 - 2 minutes to allow the solution-electrode interface to reach equilibrium; measure the local pH value at the solution-electrode interface using a pH optical fiber probe; S2: Apply a sinusoidal AC excitation signal with a frequency range of 10 3 - 10 6 Hz and an amplitude of 5 - 10 mV; Use an EIS circuit to record the impedance spectrum, and collect 30 - 50 data points per decade; Activate the fiber optic surface plasmon resonance sensor to monitor the surface plasmon resonance signal of the electrode at a sampling rate of 8 Hz; calculate the real-time charge density through the change in reflected light intensity, with an accuracy of 0.2 - 0.3 mC / m²; Synchronously apply a ±0.8 V linear sweep voltage at a rate of 15 mV / s and record the current response curve; S3: Input the EIS impedance spectrum, SPR charge density sequence, and I-V curve into a simplified neural network algorithm; algorithm structure: 5 - 7 convolutional layers and 3 - 4 fully connected layers, and train with a synthetic data training set with an input noise < 8%; Output the electrode polarization impedance Rp, solution resistance Rs, and double-layer impedance ZEDL; use SPR data to correct the polarization effect; Inverse model calculation: Debye length, Zeta potential, ion mobility; S4: Drain the solution, rinse the nano-groove with deionized water, and dry it with nitrogen; check the integrity of the electrode and the thiol self-assembled monolayer, and re-modify if necessary.

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