A cortisol and sodium ion bifunctional detection sensor and a preparation method thereof

Abstract

The application discloses a cortisol and sodium ion bifunctional detection sensor and a preparation method thereof, and belongs to the technical field of sensing and detection, and comprises a substrate layer, a sodium ion detection module and a cortisol detection module arranged on the substrate layer, a bionic microfluidic unit, the bionic microfluidic unit is provided with a plurality of flow channel holes, and an embedded capillary pump structure is arranged in each flow channel hole to guide a to-be-detected liquid to the sodium ion detection module and the cortisol detection module, and a shielding layer covering the surface of the bionic microfluidic unit. The sodium ion detection module and the cortisol detection module are specifically designed, wide-range detection of a sodium ion concentration and low-concentration detection of cortisol are realized, the high-altitude low-pressure environment of a pilot can be matched, the sodium ion concentration and the cortisol concentration of the pilot can be accurately detected, and accurate detection of physical signs of the pilot in a high-altitude flight process is realized.

Description

Technical Field

[0001] This invention belongs to the field of sensing and detection technology, specifically relating to a dual-function sensor for detecting cortisol and sodium ions and its preparation method. Background Technology

[0002] Cortisol is a corticosteroid hormone that the body produces naturally. When a person is under physiological or psychological stress, cortisol levels rise, leading to increased blood pressure, decreased bone density, and reduced immune response, significantly impacting health. Meanwhile, the concentration of sodium ions in sweat has a significant influence on the body's fluid osmotic pressure balance, neuromuscular excitability regulation, cardiovascular function, and body temperature regulation.

[0003] Conventional cortisol and sodium ion concentration measurements in sweat primarily rely on laboratory-grade instruments, requiring sample pretreatment before measurement, which lacks convenience and real-time testing capabilities. While instruments can detect cortisol and sodium ion concentrations in sweat under normal conditions to assess bodily vital signs, existing laboratory-grade instruments are not portable and wearable for use in special environments, such as monitoring pilots' vital signs at high altitudes. Furthermore, pilots are affected by altitude and flight environment, resulting in a high-altitude, low-pressure environment. These changes significantly alter sweat secretion rates, electrolyte composition, and hormone levels, necessitating detectors capable of detecting concentrations within a high threshold range, which current equipment cannot meet. Summary of the Invention

[0004] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a dual-function sensor for detecting cortisol and sodium ions, which solves the problem that existing sensors cannot effectively detect sodium ion concentration and cortisol concentration in pilots under high-altitude and low-pressure environments.

[0005] To achieve the above objectives, the present invention provides a dual-function sensor for detecting cortisol and sodium ions, comprising:

[0006] basal layer;

[0007] A sodium ion detection module, which is disposed above the substrate layer, is used to detect the sodium ion concentration in the liquid to be tested;

[0008] A cortisol detection module is provided, which is arranged in parallel with the sodium ion detection module on the substrate layer. The cortisol detection module is used to detect the concentration of cortisol in the liquid to be tested.

[0009] A biomimetic microfluidic unit is provided, which covers the surfaces of the sodium ion detection module and the cortisol detection module. The biomimetic microfluidic unit has multiple flow channels and each flow channel is provided with an embedded capillary pump structure to guide the liquid to be tested to the sodium ion detection module and the cortisol detection module.

[0010] A shielding layer covers the surface of the biomimetic microfluidic unit.

[0011] As a further improvement of the present invention, the sodium ion detection module includes:

[0012] A carbon nanotube / silver wire composite electrode, wherein a gradient PEDOT:PSS interface layer is formed on the surface of the carbon nanotube / silver wire composite electrode by pulse electrodeposition, and the impedance of the PEDOT:PSS interface layer is 8~15Ω·cm. 2 ;

[0013] or

[0014] A boron-doped diamond electrode, wherein the surface of the boron-doped diamond electrode is modified with an ionic liquid-plasticized PVC film, wherein the PVC film contains: 1.2~1.8wt% sodium ion carrier X, 0.5~1.0wt% Na-TFPB, 62~68wt% DOS and 0.3~2.0wt% MXene nanosheets.

[0015] As a further improvement of the present invention, the PEDOT:PSS interface layer is prepared by a multi-pulse electrochemical deposition process, and the PEDOT:PSS interface layer forms a three-dimensional conductive network with nanopores along the vertical direction.

[0016] As a further improvement of the present invention, the cortisol detection module includes:

[0017] A gold nanopillar array electrode, wherein a cysteine-modified layer is formed on the surface of the gold nanopillar array electrode through molecular self-assembly;

[0018] or

[0019] A gold nanoparticle electrode was fabricated using electrohydrodynamic printing. Following in-situ photocuring, a PPy-PB-MIP composite film was electropolymerized on the surface of the gold nanoparticle electrode. The MIP film, after electrochemical-solvent synergistic elution, exhibited a bimodal pore size distribution and a binding site density ≥1.2 × 10⁻⁶. 4 sites / cm 2 .

[0020] As a further improvement of the present invention, the sodium ion detection module and the cortisol detection module further include a counter electrode and a common reference electrode, wherein the sodium ion detection module and the cortisol detection module share the counter electrode and the common reference electrode;

[0021] The common reference electrode comprises a multilayer structure consisting of an inkjet-printed silver nanowire layer, an AgCl porous layer generated by electrochemical chlorination, and a Nafion selectively permeable membrane.

[0022] As a further improvement of the present invention, the diameter of the inkjet-printed silver nanowire layer is 50 nm, the porosity of the AgCl porous layer generated by electrochemical chlorination is 40-60%, and the thickness of the Nafion selective permeation membrane is 2-5 μm.

[0023] As a further improvement of the present invention, the biomimetic microfluidic unit has a spiral flow channel structure formed by 3D printing PDMS, and the spiral flow channel structure is modified with a silica nanopillar array.

[0024] The spiral flow channel has an embedded capillary pump structure, which includes a hydrophilic cellulose filter membrane and a hydrophobic fluorocarbon valve. The embedded capillary pump structure enables the test liquid to be transported in the spiral flow channel at a flow rate of 0.2~0.5μL / min without external force.

[0025] As a further improvement of the present invention, the shielding layer is a layer-by-layer self-assembly structure, the shielding layer is a multi-layer structure, and the shielding layer includes at least a graphene oxide layer treated by plasma and an ethylene oxide-caprolactone block copolymer layer.

[0026] The ethylene oxide-caprolactone block copolymer is cross-linked under ultraviolet light to form a nano-network structure. The pore size of the ethylene oxide-caprolactone block copolymer is ≤5 nm, the surface contact angle is 112±3°, and the protein adsorption capacity is ≤5 ng / cm³. 2 .

[0027] This application also includes a method for preparing a dual-function sensor for detecting cortisol and sodium ions, comprising the following steps:

[0028] S1. Cut and clean the substrate material to obtain the substrate layer;

[0029] S2. The working electrode of the sodium ion detection module, the working electrode of the cortisol detection module, the counter electrode, and the common reference electrode are respectively set on the substrate layer;

[0030] S3. Modify the working electrode of the sodium ion detection module;

[0031] S4. Modify the working electrode of the cortisol detection module;

[0032] S5. A biomimetic microfluidic unit is formed above the sodium ion detection module and the cortisol detection module, and a shielding layer is formed on the surface of the biomimetic microfluidic unit.

[0033] As a further improvement of the present invention, the modification of the working electrode of the sodium ion detection module in step S3 specifically includes:

[0034] S301, Preparation of sodium ion selective membrane: Prepare membrane mixtures according to the mass percentage, weigh the set amount of membrane mixture, dissolve it in tetrahydrofuran, sonicate until completely dissolved, and then store it in the dark for later use.

[0035] S302, Ion conversion layer deposition: Electrochemical deposition of a PEDOT:PSS interface layer on the working electrode surface formed by carbon paste;

[0036] S303, Selective membrane coating: Sodium ion selective membrane solution is drop-coated onto the working electrode surface modified with PEDOT:PSS interface layer and cured at room temperature to finally obtain a sensitive membrane with a thickness of 50±5μm.

[0037] The aforementioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0038] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include:

[0039] (1) The cortisol and sodium ion dual-function detection sensor of the present invention realizes dual detection of cortisol and sodium ion concentration through sodium ion detection module and cortisol detection module above the base layer, and by cooperating with the biomimetic microfluidic unit, the embedded capillary structure of the biomimetic microfluidic unit enables sweat to self-drive into the sodium ion detection module and cortisol detection module area, thereby realizing efficient detection of human stress hormones and electrolyte concentration.

[0040] (2) The cortisol and sodium ion dual-function detection sensor of the present invention employs a carbon-based / nanocomposite electrode in its sodium ion detection module, and uses a surface-modified PEDOT:PSS interface layer and an ion-selective membrane enhanced with MXene, enabling the sodium ion detection module to achieve a wide linear detection range of 0.1~100mM; meanwhile, the cortisol detection module employs a gold electrode and a polypyrrole-Prussian blue molecularly imprinted membrane with a cavity density ≥10 4 / cm 2 It can specifically identify low concentrations of cortisol from 1 to 50 nM. This application achieves wide-range detection of sodium ion concentration and low concentration detection of cortisol by specifically designing sodium ion detection module and cortisol detection module. It can match the high-altitude low-pressure environment of pilots and accurately detect the sodium ion concentration and cortisol concentration of pilots, so as to realize accurate detection of pilots' vital signs during high-altitude flight. Attached Figure Description

[0041] Figure 1This is a schematic diagram of the preparation method of the dual-function detection sensor for cortisol and sodium ions in this embodiment of the invention;

[0042] Figure 2 This is a graph showing the open-circuit potential test results of the sodium ion detection module for different concentrations of test liquids in this embodiment of the invention.

[0043] Figure 3 This is a graph showing the fitting relationship between the current response of the sodium ion detection module and the change in sodium ion concentration in an embodiment of the present invention.

[0044] Figure 4 This is a current response diagram of the cortisol detection module in this embodiment of the invention, which uses the chronoamperometry method to test the current response of liquids of different concentrations. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0046] In the description of this invention, it should be understood that, unless otherwise stated, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0047] Furthermore, unless otherwise stated, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0048] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0050] Example:

[0051] Please see Figures 1-4 The preferred embodiment of the present invention includes a dual-function detection sensor for cortisol and sodium ions, comprising a substrate layer; a sodium ion detection module and a cortisol detection module on the substrate layer, wherein the sodium ion detection module is used to detect the concentration of sodium ions in the liquid to be tested, and the cortisol detection module is used to detect the concentration of cortisol in the liquid to be tested, and the sodium ion detection module and the cortisol detection module are arranged in parallel on the substrate layer; and a biomimetic microfluidic unit covering the sodium ion detection module and the cortisol detection module, the biomimetic microfluidic unit having multiple flow channels, and each flow channel having an embedded capillary pump structure to guide the liquid to be tested to the sodium ion detection module and the cortisol detection module; the detection sensor also includes a shielding layer covering the surface of the biomimetic microfluidic unit, the shielding layer generating a flexible sensor structure through the spatial steric hindrance effect, which facilitates the sensor to be attached to the surface of human skin, thereby achieving effective monitoring of cortisol and sodium ion concentrations.

[0052] The dual-function detection sensor for cortisol and sodium ions in this application achieves dual detection of cortisol and sodium ion concentrations through sodium ion detection modules and cortisol detection modules above the substrate layer. By cooperating with a biomimetic microfluidic unit and utilizing the embedded capillary pump structure of the biomimetic microfluidic unit, sweat is self-driven into the sodium ion detection module and cortisol detection module area, thereby achieving efficient detection of human stress hormone (cortisol) and electrolyte (sodium ion) concentrations.

[0053] Furthermore, as an optional embodiment of the present invention, the sodium ion detection module in this application includes: a carbon nanotube / silver wire composite electrode, and a gradient PEDOT:PSS interface layer is formed on the surface of the carbon nanotube / silver wire composite electrode by pulse electrodeposition, and the impedance of the PEDOT:PSS interface layer is 8~15 Ω·cm. 2 PEDOT: PSS stands for poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate).

[0054] Furthermore, the PEDOT:PSS interface layer in this application is prepared using a multi-pulse electrochemical deposition process, and the resulting PEDOT:PSS interface layer forms a three-dimensional conductive network with nanopores along the vertical direction. Specifically, by depositing a PEDOT:PSS interface layer with a three-dimensional conductive network on the surface of the working electrode, this application can significantly enhance the specific surface area and active site density of the working electrode, increase the adsorption capacity of sodium ions on the working electrode surface, enhance the sensitivity and signal-to-noise ratio of the detection signal, and the pore structure on the three-dimensional conductive network can serve as a rapid diffusion channel for sodium ions to achieve rapid detection of sodium ion concentration. Moreover, the electron-ion mixed conductivity of PEDOT:PSS can synergistically improve the transmission efficiency of electrons and ions and reduce the interface impedance to further accelerate the response rate of the sensor. At the same time, the three-dimensional continuous conductive network can reduce the breakpoints in the electron transport path, make the charge uniformly distributed, significantly reduce the internal resistance of the working electrode, and improve the output signal strength of the sensor. In addition, the selective permeation characteristics of the nanopores help improve the specificity of detection to reduce interference from other ions and active molecules in the sodium ion concentration test.

[0055] As another optional embodiment of the present invention, the working electrode in this application can also be a boron-doped diamond electrode, and the surface of the boron-doped diamond electrode is modified with an ionic liquid-plasticized PVC film, wherein the ionic liquid-plasticized PVC film contains 1.2~1.8wt% sodium ion carrier X, 0.5~1.0wt% Na-TFPB, 62~68wt% DOS, and 0.3~2.0wt% MXene nanosheets. Boron-doped diamond has a wide electrochemical window, allowing the sensor to operate under high pressure, avoiding water decomposition interference, and its low current density significantly improves the signal-to-noise ratio of the sensor. Simultaneously, the working electrode prepared with boron-doped diamond has a hydrophobic surface, reducing the adsorption of organic matter, and combined with the anti-swelling properties of the PVC film, it can prevent phase separation of the first working electrode during long-term use, improving the overall service life of the sensor. Among them, sodium ion carrier X is 4-tert-butylcalix (4) aryl-tetraacetic acid tetraethyl ester, Na-TFPB is sodium tetra(4-chlorophenyl)borate, DOS is dioctyl sebacate, and MXene nanosheets are inorganic non-metallic materials with a two-dimensional layered structure, belonging to transition metal carbides, nitrides or carbonitrides.

[0056] Furthermore, as an optional embodiment of the present invention, the cortisol detection module in this application includes a gold nanopillar array electrode, the surface of which is formed with a cysteine-modified layer through molecular self-assembly. Cysteine ​​molecules form stable Au-S covalent bonds with the gold nanopillar surface through thiol groups (-SH), constituting an ordered self-assembled monolayer, which can effectively regulate the electron transport path, thereby reducing electrode impedance and improving the kinetic efficiency of the electrochemical reaction. This application utilizes the high specific surface area of ​​the gold nanopillar array combined with the conductivity of cysteine ​​to further increase the active site density and increase the detection signal intensity for cortisol.

[0057] As another optional embodiment of the present invention, the cortisol detection module can also be a gold nanoparticle electrode printed by electrohydrodynamics, and the gold nanoparticle electrode is electropolymerized on its surface after in-situ photocuring to form a PPy-PB-MIP (polypyrrole-Prussian blue-molecularly imprinted polymer) composite film; wherein, after electrochemical-solvent synergistic elution, the MIP film exhibits a bimodal pore size distribution and a binding site density ≥1.2×10 4 sites / cm 2 .

[0058] As an optional embodiment of the present invention, the sodium ion detection module and the cortisol detection module in this application further include a counter electrode and a common reference electrode; the common reference electrode includes a multilayer structure composed of an inkjet-printed silver nanowire layer, an AgCl porous layer generated by electrochemical chlorination, and a Nafion selectively permeable membrane.

[0059] Furthermore, the inkjet-printed silver nanowire layer has a diameter of 50 nm, the AgCl porous layer generated by electrochemical chlorination has a porosity of 40-60%, and the Nafion selective permeation membrane has a thickness of 2-5 μm.

[0060] Furthermore, as an optional embodiment of the present invention, the biomimetic microfluidic unit in this application has a spiral flow channel structure formed by 3D printing PDMS, and the spiral flow channel structure is internally modified with a silica nanopillar array; the spiral flow channel has an embedded capillary pump structure, which includes a hydrophilic cellulose filter membrane and a hydrophobic fluorocarbon valve. Through the above-mentioned spiral flow channel structure, the liquid to be tested can be transported within the biomimetic microfluidic unit at a flow rate of 0.2~0.5μL / min without external force. The biomimetic microfluidic unit structure allows human sweat secreted quickly to enter the sodium ion detection module area, achieving a rapid response for sodium ion concentration detection.

[0061] Furthermore, as an optional embodiment of the present invention, the shielding layer in this application is a multilayer structure that is self-assembled layer by layer. This shielding layer includes at least a graphene oxide layer treated with plasma and an ethylene oxide-caprolactone block copolymer layer. The ethylene oxide-caprolactone block copolymer is cross-linked under ultraviolet light to form a nano-network structure. The resulting ethylene oxide-caprolactone block copolymer has a pore size ≤5nm, a surface contact angle of 112±3°, and a protein adsorption capacity ≤5ng / cm³. 2 The shielding layer in this application adopts a combination structure of graphene oxide layer and ethylene oxide-caprolactone block copolymer layer, which makes the shielding layer have good flexibility and suitable for adhesion to the skin surface of pilots in motion; the hydrophobic structure of ethylene oxide-caprolactone block copolymer can allow sweat secreted by the human body to detach from the sensor surface, and by controlling the contact angle of the shielding layer surface, the sensor has good anti-sweat interference capability, which facilitates real-time and accurate monitoring of pilot vital signs.

[0062] Furthermore, regarding the cortisol and sodium ion dual-function detection sensor in this application, this application also includes a method for preparing the cortisol and sodium ion dual-function detection sensor, which includes the following steps:

[0063] S1. Cut and clean the substrate material to obtain the substrate layer;

[0064] S2. The working electrode of the sodium ion detection module, the working electrode of the cortisol detection module, the counter electrode, and the common reference electrode are respectively set on the substrate layer;

[0065] S3. Modify the working electrode of the sodium ion detection module;

[0066] S4. Modify the working electrode of the cortisol detection module;

[0067] S5. A biomimetic microfluidic unit is formed above the sodium ion detection module and the cortisol detection module, and a shielding layer is formed on the surface of the biomimetic microfluidic unit.

[0068] Specifically, step S1, which involves cutting and cleaning the substrate material, includes: cutting a PET film to a predetermined size, sequentially cleaning it with acetone, ethanol, and deionized water using ultrasonic cleaning, and then drying it with nitrogen. The PET film, as a substrate layer, possesses excellent flexibility and chemical stability, making it suitable for wearable application to the skin. The gradient cleaning with acetone, ethanol, and deionized water removes grease, polar contaminants, and other pollutants from the PET film surface, while the final nitrogen purging prevents fiber residue from remaining on the PET film surface. Optionally, the acetone is used to clean the PET film at 40°C, the ethanol at 30°C, the deionized water at room temperature, and the nitrogen purging pressure is 0.3 MPa.

[0069] Furthermore, as an optional embodiment of the present invention, the preparation of the working electrode of the sodium ion detection module in step S2 of this application specifically includes: using a microelectronic printer to dispense carbon paste onto the substrate layer to form a circular working electrode with a diameter of 1.8~2.0mm, wherein the thickness of the working electrode formed by the carbon paste is between 20±2μm. The dispensing printing method can achieve a positioning accuracy of 5μm to form the working electrode on the substrate layer; secondly, the working electrode adopts a stepped curing method to avoid thermal stress concentration during the curing process, which could cause deformation of the flexible substrate layer.

[0070] As another optional embodiment of the present invention, the preparation of the working electrode of the sodium ion detection module in step S2 of this application also includes another optional method: printing with a high-precision microelectronic printer, using nano-carbon / silver composite conductive ink (15% solid content), directly writing a circular electrode with a diameter of 2.2 mm through a 200 nm diameter nozzle, and performing step-curing to control the thickness of the circular electrode to 25 ± 3 μm. The step-curing temperature here is: first, the circular electrode is cured at 80°C for 10 min, and then cured at 120°C for 20 min. The resistivity of the nano-carbon / silver composite conductive ink is typically less than 5 Ω·cm, lower than that of traditional carbon paste, which can improve the sensitivity of the prepared working electrode.

[0071] Furthermore, as an optional embodiment of the present invention, the preparation of the working electrode of the cortisol detection module in step S2 of this application specifically includes: preparing a circular working electrode with a linewidth of 0.5 μm, a thickness of 100 nm, and a diameter of 3 mm on the substrate layer using photolithography.

[0072] As another optional embodiment of the present invention, the preparation of the working electrode of the cortisol detection module in step S2 of this application can also be carried out in another way: using inkjet printing of gold nanoparticle ink, and forming a gold electrode with a diameter of 3.5 mm by laser sintering. Here, the particle size of the gold nanoparticle ink is 20±2 nm, the laser sintering wavelength is 532 nm, the power is 0.5 W, and the surface roughness of the prepared gold electrode is <50 nm.

[0073] Furthermore, as an optional embodiment of the present invention, the preparation of the counter electrode in step S2 of this application specifically includes: using a microelectronic printer to spray platinum paste onto the substrate layer to form a circular counter electrode with a diameter of 3 mm and a thickness of 20 ± 2 μm.

[0074] As another optional embodiment of the present invention, the preparation of the counter electrode in step S2 of this application specifically includes: spraying platinum / graphene composite ink and curing it by infrared radiation to form a porous structure. The platinum / graphene composite ink has a platinum loading of 30%, an infrared radiation curing temperature of 150°C, a curing time of 15 min, and a porous structure porosity of 40%, resulting in a counter electrode with good catalytic activity.

[0075] Further, as an optional embodiment of the present invention, the preparation of the common reference electrode in step S2 specifically includes: printing Ag / AgCl slurry on the substrate layer, and forming a stable reference electrode by a constant potential oxidation method. Here, the potential difference between the reference electrode and the Ag / AgCl electrode in the constant potential oxidation method is 0.5V.

[0076] As another optional embodiment of the present invention, the preparation of the common reference electrode in step S2 of this application specifically includes: printing Ag / AgCl composite ink, the composite ink containing 10% polydopamine modified nanoparticles, forming a stable chlorination layer through in-situ electrochemical chlorination, and the thickness of the common reference electrode being 15±2μm.

[0077] Furthermore, as an optional embodiment of the present invention, the modification of the working electrode of the sodium ion detection module in step S3 of this application specifically includes:

[0078] S301, Preparation of sodium ion selective membrane: Prepare membrane mixtures according to the mass percentage, weigh the set amount of membrane mixture, dissolve it in tetrahydrofuran, sonicate until completely dissolved, and then store it in the dark for later use; The membrane mixture specifically includes: sodium ion carrier X (1%), sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate (Na-TFPB, 0.55%), polyvinyl chloride (PVC, 33%), and diisooctyl sebacate (DOS, 65%). Among them, sodium ion carrier X represents tetraethyl 4-tert-butylcalix (4)arene-tetraacetate. The membrane mixture is composed of sodium ion carrier X, Na-TFPB, PVC and DOS, with the overall composition close to 100%, and the remaining part is polyvinyl chloride and DOS with a small amount of component fluctuation.

[0079] S302, Ion Conversion Layer Deposition: Electrochemical deposition of a PEDOT:PSS interface layer on the working electrode surface formed by carbon paste. Specifically: a phosphate buffer (PBS, pH 6.8) of 0.01 mol / L 3,4-ethylenedioxythiophene (EDOT) and 0.1 mol / L sodium polystyrene sulfonate (NaPSS) was prepared; then a galvanostatic method (2 mA / cm²) was used. 2 The electrolyte is polymerized to accumulate a charge of 10 mC / electrode to form a uniform conductive polymer layer (PEDOT:PSS interface layer) to suppress potential drift.

[0080] S303, Selective membrane coating: Sodium ion selective membrane solution is drop-coated onto the working electrode surface modified with PEDOT:PSS interface layer and cured at room temperature to finally obtain a sensitive membrane with a thickness of 50±5μm.

[0081] Furthermore, as another optional embodiment of the present invention, the modification of the working electrode of the sodium ion detection module in step S3 of this application specifically includes:

[0082] A PBS electrolyte of 0.02 M EDOT and 0.15 M PSS was prepared, and a graded conductive PEDOT:PSS layer was formed using pulse electrodeposition, thereby reducing the impedance to 8 Ω·cm. 2 ;

[0083] Sodium ion carrier X (1.5%), Na-TFBP (0.8%), polyurethane (30%), DOS (67.7%), and 0.5% MXene nanosheets (Ti3C2T) were added. x The process employs micro-droplet jetting technology to print layer by layer, with each layer cured and then laser annealed to obtain a total thickness of 55±5μm.

[0084] Furthermore, as an optional embodiment of the present invention, the modification of the working electrode of the cortisol detection module in step S4 of this application specifically includes:

[0085] S401. Pretreatment of the working electrode: Immerse the gold electrode in HCl solution, clean the gold electrode using cyclic voltammetry, rinse with deionized water, and then dry with nitrogen gas. Specifically, the potential range of the cyclic voltammetry is -0.2 to +0.9 V relative to the Ag / AgCl reference electrode, the scan rate is 50 mV / s, and 10 cycles are performed.

[0086] S402, Preparation of molecularly imprinted polymer films:

[0087] To obtain the electropolymerization solution: Prepare a PBS solution containing 0.02 mol / L pyrrole, 5 mmol / L FeCl3, 5 mmol / L K3[Fe(CN)6], and 6 mmol / L cortisol (template molecule). The pH of the PBS solution is 7.4.

[0088] Electropolymerization process: A polypyrrole-Prussian blue composite film is generated on the surface of the gold electrode using cyclic voltammetry, and cortisol molecules are embedded therein; the potential range of the cyclic voltammetry is -0.2 to +0.9 V between the working electrode and the Ag / AgCl reference electrode, the scan rate is 50 mV / s, and 10 cycles are performed.

[0089] Template molecule elution: The modified gold electrode was placed in blank PBS and cyclic voltammetry was performed to remove cortisol template molecules, forming a specific recognition cavity. The cyclic voltammetry potential range was -0.2 to +0.8 V between the working electrode and the Ag / AgCl reference electrode, with a scan rate of 50 mV / s, for 20 cycles.

[0090] As another optional embodiment of the present invention, the modification of the working electrode of the cortisol detection module in step S4 of this application can also be carried out in the following ways:

[0091] Preparation of electropolymerizable ink: Prepare a PBS solution containing 0.03 M pyrrole, 8 mM FeCl3, 8 mM K3[Fe(CN)6], and 10 mM cortisol template, and add 0.1% graphene quantum dots to improve conductivity;

[0092] A PPy-PB-MIP composite film with a thickness of 200 nm was generated by constant voltage electropolymerization, and the cavity density of the composite film reached 10. 4 / cm 2 In the constant voltage electropolymerization method, the potential difference between the working electrode and the Ag / AgCl reference electrode is +0.8 V, and the number of cycles is 5.

[0093] Combined electrochemical-solvent elution: Desorption is performed by applying a potential of -0.8V in 0.1M MaOH, followed by immersion in a methanol / acetic acid solution for ultrasonic treatment. The methanol and acetic acid are mixed at a ratio of 8:2 to obtain a mixed solution, which can remove cortisol template molecules with a removal rate of over 95%. The resulting working electrode has a cavity diameter of 80~120nm.

[0094] Furthermore, as an optional embodiment of the present invention, step S5 of this application specifically includes: spin-coating polyethylene glycol on the surface of the substrate layer to avoid non-specific adsorption of sweat proteins;

[0095] A Y-shaped flow channel made of PDMS material is used to cover the working electrode areas of the sodium ion detection module and the cortisol detection module to achieve directional introduction of the liquid to be tested.

[0096] Furthermore, as an optional embodiment of the present invention, this application also includes morphological recognition of the dual-function detection sensor for cortisol and sodium ions:

[0097] Scanning electron microscopy (SEM) was used to ensure the porous structure of the molecularly imprinted polymer (MIP) membrane and the uniformity of the PEDOT:PSS layer. The uniformity of pore distribution on the MIP membrane surface was determined, as well as the presence of cracks or delamination in the PEDOT:PSS layer.

[0098] The surface roughness and three-dimensional morphology of the sensitive membrane in the sodium ion detection module were measured using atomic force microscopy (AFM).

[0099] The crystallization state of the PVC-based selective membrane was verified by X-ray diffraction to determine whether the PVC selective membrane suffered lattice distortion due to solvent evaporation.

[0100] Furthermore, as an optional embodiment of the present invention, this application also includes performance testing of the sodium ion detection module: verifying the linearity of the electrical signal for 0.1~100mM NaCl by detecting the selectivity of the open-circuit voltage sensor for sodium ions. Specifically, the open-circuit potential test results of the sodium ion detection module for different concentrations of test liquids are as follows: Figure 2 As shown in the figure, open-circuit testing based on sodium ion solutions with multiple concentration gradients (0.1~100mM) demonstrates that the dual-function cortisol and sodium ion detection sensor in this application exhibits significant differences in potential response to four orders of magnitude concentration gradients (100mM, 10mM, 1mM, and 0.1mM), indicating that the surface sensor possesses reliable wide-range concentration detection. Furthermore, the linear fitting relationship between the current response of the sodium ion detection module and the change in sodium ion concentration is shown in the figure. Figure 3 As shown, the linear fitting results between the open-circuit potential signal and the sodium ion concentration indicate that the sensor exhibits significant differences in electrochemical response under multiple concentration gradients, and the surface sensor can effectively distinguish sodium ions of different concentrations.

[0101] Furthermore, as an optional embodiment of the present invention, this application also includes performance testing of the cortisol detection module: verifying the linearity of the 1-50 nM cortisol current signal by detecting the selectivity of the sensor to cortisol using chronoamperometry (IT). Specifically, the cortisol detection module uses chronoamperometry to test the current response of the test liquid at different concentrations, as shown in the figure. Figure 4 As shown, the sensor has a high degree of differentiation for the current difference corresponding to the 0nM, 5nM, 10nM, and 20nM gradients, indicating that it has high differentiation sensitivity in the low concentration range.

[0102] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual-function sensor for detecting cortisol and sodium ions, characterized in that, include: basal layer; A sodium ion detection module, which is disposed above the substrate layer, is used to detect the sodium ion concentration in the liquid to be tested; The sodium ion detection module includes a carbon nanotube / silver wire composite electrode. A gradient PEDOT:PSS interface layer is formed on the surface of the carbon nanotube / silver wire composite electrode by pulse electrodeposition. The impedance of the PEDOT:PSS interface layer is 8~15 Ω·cm. 2 ; A cortisol detection module is provided, which is arranged in parallel with the sodium ion detection module on the substrate layer. The cortisol detection module is used to detect the concentration of cortisol in the test liquid. The cortisol detection module includes a gold nanopillar array electrode, on the surface of which a cysteine-modified layer is formed by molecular self-assembly. A biomimetic microfluidic unit is provided, covering the surfaces of the sodium ion detection module and the cortisol detection module. The biomimetic microfluidic unit has multiple flow channels, and each flow channel has an embedded capillary pump structure to guide the liquid to be tested to the sodium ion detection module and the cortisol detection module. The biomimetic microfluidic unit has a spiral flow channel structure formed by 3D printing PDMS, and the spiral flow channel structure is internally modified with a silica nanopillar array. The spiral flow channel has an embedded capillary pump structure, which includes a hydrophilic cellulose filter membrane and a hydrophobic fluorocarbon valve. The embedded capillary pump structure can realize the transmission of the test liquid in the spiral flow channel at a flow rate of 0.2~0.5μL / min without external force. A shielding layer covering the surface of the biomimetic microfluidic unit; The shielding layer is a layer-by-layer self-assembly structure, and the shielding layer is a multi-layer structure. The shielding layer includes at least a graphene oxide layer treated by plasma and an ethylene oxide-caprolactone block copolymer layer. The ethylene oxide-caprolactone block copolymer is cross-linked under ultraviolet light to form a nano-network structure. The pore size of the ethylene oxide-caprolactone block copolymer is ≤5 nm, the surface contact angle is 112±3°, and the protein adsorption capacity is ≤5 ng / cm³. 2 .

2. The dual-function detection sensor for cortisol and sodium ions according to claim 1, characterized in that, The PEDOT:PSS interface layer is prepared using a multi-pulse electrochemical deposition process, and the PEDOT:PSS interface layer forms a three-dimensional conductive network with nanopores along the vertical direction.

3. The dual-function detection sensor for cortisol and sodium ions according to claim 1, characterized in that, The sodium ion detection module and the cortisol detection module also include a counter electrode and a common reference electrode, and the sodium ion detection module and the cortisol detection module share the counter electrode and the common reference electrode; The common reference electrode comprises a multilayer structure consisting of an inkjet-printed silver nanowire layer, an AgCl porous layer generated by electrochemical chlorination, and a Nafion selectively permeable membrane.

4. The dual-function detection sensor for cortisol and sodium ions according to claim 3, characterized in that, The inkjet-printed silver nanowire layer has a wire diameter of 50 nm, the AgCl porous layer generated by electrochemical chlorination has a porosity of 40-60%, and the Nafion selective permeation membrane has a thickness of 2-5 μm.

5. A method for preparing a dual-function detection sensor for cortisol and sodium ions, used to prepare the dual-function detection sensor for cortisol and sodium ions as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Cut and clean the substrate material to obtain the substrate layer; S2. The working electrode of the sodium ion detection module, the working electrode of the cortisol detection module, the counter electrode, and the common reference electrode are respectively set on the substrate layer; S3. Modify the working electrode of the sodium ion detection module; S4. Modify the working electrode of the cortisol detection module; S5. A biomimetic microfluidic unit is formed above the sodium ion detection module and the cortisol detection module, and a shielding layer is formed on the surface of the biomimetic microfluidic unit.

6. The method for preparing the dual-function detection sensor for cortisol and sodium ions according to claim 5, characterized in that, The modification of the working electrode of the sodium ion detection module in step S3 specifically includes: S301, Preparation of sodium ion selective membrane: Prepare membrane mixtures according to the mass percentage, weigh the set amount of membrane mixture, dissolve it in tetrahydrofuran, sonicate until completely dissolved, and then store it in the dark for later use. S302, Ion conversion layer deposition: Electrochemical deposition of a PEDOT:PSS interface layer on the working electrode surface formed by carbon paste; S303, Selective membrane coating: Sodium ion selective membrane solution is drop-coated onto the working electrode surface modified with PEDOT:PSS interface layer and cured at room temperature to finally obtain a sensitive membrane with a thickness of 50±5μm.

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