Cortisol and sodium ion difunctional detection sensor and preparation method thereof

Abstract

The invention discloses a cortisol and sodium ion difunctional detection sensor and a preparation method thereof, and belongs to the technical field of sensing detection, the cortisol and sodium ion difunctional detection sensor comprises a substrate layer, a sodium ion detection module and a cortisol detection module, the bionic micro-fluidic unit is provided with a plurality of runner holes, and an embedded capillary pump structure is arranged in each runner hole so as to guide liquid to be detected to the sodium ion detection module and the cortisol detection module; and the shielding layer covers the surface of the bionic micro-fluidic unit. The sodium ion detection module and the cortisol detection module are specifically designed, so that wide-range detection of sodium ion concentration and low-concentration detection of cortisol are realized, a 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 the detection accuracy is improved. Accurate detection of the signs of the pilot in the high-altitude flight process is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of sensing detection technology, and specifically relates to a dual-function sensor for detecting cortisol and sodium ions and a preparation method thereof. Background Art

[0002] Cortisol is a naturally occurring corticosteroid hormone produced by the human body. When a person is under physical or psychological stress, cortisol levels rise accordingly, leading to increased blood pressure, decreased bone density, and a reduced immune response, significantly impacting human health. Furthermore, the sodium ion concentration in sweat significantly influences the body's osmotic balance, neuromuscular excitability, cardiovascular function, and temperature regulation.

[0003] Conventional cortisol testing and sodium ion concentration testing in sweat are mainly carried out using laboratory-grade instruments. At the same time, the samples need to be pre-treated before measurement, which is not convenient and does not provide real-time testing. Although under normal circumstances, the human body's cortisol and sodium ion concentration in sweat can be tested by instruments to determine human vital signs. However, in special environments, such as monitoring the vital signs of pilots in high-altitude environments, existing laboratory-grade instruments cannot be portable and wearable, and are not suitable for use in flight cabins. In addition, pilots are affected by the external altitude and flight environment during flight, which puts them in a high-altitude, low-pressure environment. As the flight conditions change, the pilot's sweat secretion rate, electrolyte composition, and hormone levels change significantly. Therefore, a detector is required to complete concentration detection within a high-threshold range, and existing detection equipment cannot meet the above requirements. Summary of the Invention

[0004] In response to one or more of the above-mentioned defects or improvement needs in the prior art, the present invention provides a dual-function sensor for detecting cortisol and sodium ions, which is used to solve the problem that existing sensors are unable to effectively detect the sodium ion concentration and cortisol concentration of pilots in a high-altitude, low-pressure environment.

[0005] To achieve the above objectives, the present invention provides a dual-function sensor for detecting cortisol and sodium ions, comprising: basal layer; A sodium ion detection module is provided above the base layer and is used to detect the sodium ion concentration in the liquid to be tested; a cortisol detection module, the cortisol detection module and the sodium ion detection module being arranged in parallel on the basal layer, the cortisol detection module being used to detect the cortisol concentration in the liquid to be tested; A bionic microfluidic unit, the bionic microfluidic unit covering the surface of the sodium ion detection module and the cortisol detection module, the bionic microfluidic unit having a plurality of flow channel holes, and each of the flow channel holes 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; A shielding layer is covered on the surface of the bionic microfluidic unit.

[0006] As a further improvement of the present invention, the sodium ion detection module includes: A carbon nanotube / silver wire composite electrode having a gradient PEDOT:PSS interface layer formed on the surface of the carbon nanotube / silver wire composite electrode by pulse electrodeposition, wherein the impedance of the PEDOT:PSS interface layer is 8-15Ω·cm 2 ; Or a boron-doped diamond electrode, the surface of the boron-doped diamond electrode is modified with an ionic liquid-plasticized PVC film, wherein the PVC film contains: 1.2-1.8 wt% of sodium ion carrier X, 0.5-1.0 wt% of Na-TFPB, 62-68 wt% of DOS and 0.3-2.0 wt% of MXene nanosheets.

[0007] 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.

[0008] As a further improvement of the present invention, the cortisol detection module includes: A gold nanopillar array electrode, wherein a cysteine ​​modification layer is formed on the surface of the gold nanopillar array electrode through molecular self-assembly; Alternatively, an electrohydrodynamically printed gold nanoparticle electrode is used, wherein the surface of the gold nanoparticle electrode is electropolymerized with a PPy-PB-MIP composite film after in-situ photocuring; wherein the MIP film exhibits a bimodal pore size distribution after electrochemical-solvent co-elution, and the binding site density is ≥1.2×10 4 sites / cm 2 .

[0009] 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, 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 selective permeation membrane.

[0010] 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 permeable membrane is 2-5 μm.

[0011] As a further improvement of the present invention, the bionic microfluidic unit has a spiral flow channel structure formed by 3D printing PDMS, and the interior of the spiral flow channel structure is decorated with a silicon dioxide nanocolumn 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 liquid to be tested in the spiral flow channel at a flow rate of 0.2~0.5μL / min without external force.

[0012] As a further improvement of the present invention, the shielding layer is a layer-by-layer self-assembled structure, the shielding layer is a multi-layer structure, and the shielding layer at least includes a plasma-treated graphene oxide layer and an ethylene oxide-caprolactone block copolymer layer; The ethylene oxide-caprolactone block copolymer is cross-linked by ultraviolet light to form a nano-network structure. The ethylene oxide-caprolactone block copolymer has a mesh size of ≤5nm, a surface contact angle of 112±3°, and a protein adsorption capacity of ≤5 ng / cm 2 .

[0013] The present application also includes a method for preparing a dual-function sensor for detecting cortisol and sodium ions, which comprises the following steps: S1, cutting and cleaning the base material to obtain a base layer; S2. Disposing a working electrode of a sodium ion detection module, a working electrode of a cortisol detection module, a counter electrode, and a common reference electrode on the substrate; S3, modifying the working electrode of the sodium ion detection module; S4, modifying the working electrode of the cortisol detection module; S5. Form a bionic microfluidic unit above the sodium ion detection module and the cortisol detection module, and form a shielding layer on the surface of the bionic microfluidic unit.

[0014] 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: S301, preparation of sodium ion selective membrane: prepare membrane mixtures according to mass percentage, weigh a predetermined amount of the membrane mixture, dissolve it in tetrahydrofuran, ultrasonically vibrate until completely dissolved, and then store in the dark for future use; S302, ion conversion layer deposition: electrochemically depositing a PEDOT:PSS interface layer on the surface of the working electrode formed by the carbon slurry; S303, selective membrane coating: drop-coat the sodium ion selective membrane solution onto the surface of the working electrode modified with the PEDOT:PSS interface layer, and solidify it statically at room temperature to finally obtain a sensitive membrane with a thickness of 50±5 μm.

[0015] The above-mentioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0016] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art: (1) The dual-function cortisol and sodium ion detection sensor of the present invention realizes dual detection of cortisol and sodium ion concentrations through the sodium ion detection module and the cortisol detection module above the basal layer, and by cooperating with the bionic microfluidic unit and utilizing the embedded capillary structure of the bionic microfluidic unit, sweat is self-driven into the sodium ion detection module and the cortisol detection module area, thereby realizing efficient detection of human stress hormones and electrolyte concentrations.

[0017] (2) The dual-function sensor for detecting cortisol and sodium ions of the present invention adopts a carbon-based / nanocomposite electrode, a surface-modified PEDOT:PSS interface layer and an ion-selective membrane enhanced with MXene, so that the sodium ion detection module can achieve a wide linear detection range of 0.1~100nM; at the same time, the cortisol detection module adopts a gold electrode and a polypyrrole-Prussian blue molecular imprinted membrane, and its cavity density is ≥10 4 / cm 2 , which can specifically identify low-concentration cortisol of 1~50nM; this application realizes the wide-range detection of sodium ion concentration and low-concentration detection of cortisol through the specific design of sodium ion detection module and cortisol detection module, which can match the high-altitude and low-pressure environment of pilots, and accurately detect the sodium ion concentration and cortisol concentration of pilots, thereby realizing accurate detection of the pilot's physical signs during high-altitude flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is a flow chart of a method for preparing a dual-function sensor for detecting cortisol and sodium ions according to an embodiment of the present invention; Figure 2 1. This is a graph showing the open circuit potential test results of the sodium ion detection module for liquids with different concentrations according to an embodiment of the present invention; Figure 3 is a fitted relationship diagram of the current response of the sodium ion detection module and the change in sodium ion concentration in an embodiment of the present invention; Figure 4 This is a current response diagram of the cortisol detection module in an embodiment of the present invention using the chronoamperometry method to test liquids with different concentrations. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0020] In the description of the present invention, it should be understood that, unless otherwise specified, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0021] Furthermore, unless otherwise specified, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specified.

[0022] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0023] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0024] Example: See also Figures 1 to 4 The cortisol and sodium ion dual-function detection sensor in a preferred embodiment of the present invention includes a base layer; and a sodium ion detection module and a cortisol detection module above the base layer, wherein the sodium ion detection module is used to detect the sodium ion concentration in the liquid to be tested, and the cortisol detection module is used to detect the cortisol concentration in the liquid to be tested, and the sodium ion detection module and the cortisol detection module are arranged in parallel on the base layer; and a bionic microfluidic unit covering the sodium ion detection module and the cortisol detection module, the bionic microfluidic unit having multiple flow channel holes, and each flow channel hole 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 detection sensor also includes a shielding layer, which covers the surface of the bionic microfluidic unit. The shielding layer generates a sensor structure with good flexibility through a steric effect, which facilitates the sensor to be attached to the surface of human skin and realizes effective monitoring of cortisol and sodium ion concentrations.

[0025] The dual-function cortisol and sodium ion detection sensor in this application realizes dual detection of cortisol and sodium ion concentrations through the sodium ion detection module and the cortisol detection module above the basal layer, and by cooperating with the bionic microfluidic unit and utilizing the embedded capillary pump structure of the bionic microfluidic unit, sweat is self-driven into the sodium ion detection module and the cortisol detection module area, thereby realizing efficient detection of the concentrations of human stress hormones (cortisol) and electrolytes (sodium ions).

[0026] Furthermore, as an optional embodiment of the present invention, the sodium ion detection module in the present 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 8~15Ω·cm 2 PEDOT:PSS stands for poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate).

[0027] 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, and enhance the sensitivity and signal-to-noise ratio of the detection signal. The pore structure on the three-dimensional conductive network serves as a rapid diffusion channel for sodium ions, enabling rapid detection of sodium ion concentration. The electron-ion mixed conductivity of PEDOT:PSS synergistically improves the transmission efficiency of electrons and ions, reduces interfacial impedance, and further accelerates the response rate of the sensor. At the same time, the three-dimensional continuous conductive network reduces breakpoints in the electron transmission path, uniformly distributes charge, significantly reduces the internal resistance of the working electrode, and improves the output signal strength of the sensor. In addition, the selective permeability of the nanopores helps improve the specificity of the detection, reducing the interference of other ionic active molecules in the sodium ion concentration test.

[0028] 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, and the ionic liquid plasticized PVC film contains 1.2~1.8wt% of sodium ion carrier X, 0.5~1.0wt% of Na-TFPB, 62~68wt% of DOS and 0.3~2.0wt% of MXene nanosheets. Boron-doped diamond has a wide electrochemical window, which allows the sensor to work in a high-voltage environment, avoiding the problem of water decomposition interference, and the current density is low, which can significantly improve the signal-to-noise ratio of the sensor; at the same time, the working electrode surface prepared by boron-doped diamond is hydrophobic, which can reduce the adsorption of organic matter, and combined with the anti-swelling properties of the PVC film, it can avoid phase separation of the first working electrode during long-term use, thereby improving the overall service life of the sensor. Among them, the sodium ion carrier X is 4-tert-butylcalix(4)arene-tetraethyl tetraacetate, Na-TFPB is sodium tetrakis(4-chlorophenyl)borate, DOS is dioctyl sebacate, and MXene nanosheets are inorganic non-metallic materials with two-dimensional layered structures, which are transition metal carbides, nitrides or carbonitrides.

[0029] 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 modified with cysteine ​​through molecular self-assembly. Cysteine ​​molecules form stable Au-S covalent bonds with the gold nanopillar surface via thiol (-SH) groups, forming an ordered self-assembled monolayer. This effectively regulates 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 conductive properties of cysteine ​​to further increase the density of active sites and enhance the strength of the cortisol detection signal.

[0030] 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 in situ photocured and then electropolymerized on the surface to form a PPy-PB-MIP (polypyrrole-Prussian blue-molecularly imprinted polymer) composite membrane; wherein the MIP membrane exhibits a bimodal pore size distribution after electrochemical-solvent co-elution, and the binding site density is ≥1.2×10 4 sites / cm 2 .

[0031] As an optional embodiment of the present invention, the sodium ion detection module and the cortisol detection module in the present application further include a counter electrode and a common reference electrode; the common reference electrode includes a multilayer structure consisting of an inkjet-printed silver nanowire layer, an AgCl porous layer generated by electrochemical chlorination, and a Nafion selective permeability membrane.

[0032] Furthermore, 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 permeable membrane is 2-5 μm.

[0033] Furthermore, as an optional embodiment of the present invention, the biomimetic microfluidic unit in this application has a spiral flow channel structure formed using 3D-printed 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 this spiral flow channel structure, the liquid to be tested can be transported within the biomimetic microfluidic unit at a flow rate of 0.2-0.5 μL / min without external force. The biomimetic microfluidic unit structure allows human sweat secretion to quickly enter the sodium ion detection module area, achieving a rapid response in sodium ion concentration detection.

[0034] Furthermore, as an optional embodiment of the present invention, the shielding layer in the present application is a multilayer structure that is self-assembled layer by layer, and the shielding layer comprises at least a plasma-treated graphene oxide layer and an ethylene oxide-caprolactone block copolymer layer. The ethylene oxide-caprolactone block copolymer is cross-linked by ultraviolet light to form a nano-network structure, and the mesh size of the ethylene oxide-caprolactone block copolymer formed thereby is ≤5nm, the surface contact angle is 112±3°, and the protein adsorption capacity is ≤5ng / cm 2 The shielding layer in this application adopts a composite structure of a graphene oxide layer and an ethylene oxide-caprolactone block copolymer layer, which makes the shielding layer have good flexibility and is suitable for attachment to the skin surface of flight personnel in motion; the hydrophobic structure of the ethylene oxide-caprolactone block copolymer can make sweat secreted by the human body detach from the sensor surface, and by controlling the surface contact angle of the shielding layer, the sensor has good resistance to sweat interference, which facilitates real-time and accurate monitoring of the pilot's vital signs. Furthermore, with respect to the dual-function cortisol and sodium ion detection sensor in the present application, the present application also includes a method for preparing the dual-function cortisol and sodium ion detection sensor, which comprises the following steps: S1, cutting and cleaning the base material to obtain a base layer; S2. Disposing a working electrode of a sodium ion detection module, a working electrode of a cortisol detection module, a counter electrode, and a common reference electrode on the substrate; S3, modifying the working electrode of the sodium ion detection module; S4, modifying the working electrode of the cortisol detection module; S5. Form a bionic microfluidic unit above the sodium ion detection module and the cortisol detection module, and form a shielding layer on the surface of the bionic microfluidic unit.

[0035] Specifically, the cutting and cleaning of the substrate material in step S1 includes: cutting the PET film to a predetermined size, ultrasonically cleaning it with acetone, ethanol, and deionized water, followed by drying with nitrogen. The PET film, as the substrate layer, exhibits excellent flexibility and chemical stability, making it suitable for wearable applications. A gradient cleaning process using acetone, ethanol, and deionized water removes grease, polar contaminants, and other surface contaminants from the PET film, while a final nitrogen purge prevents residual fiber residue on the PET film. Optionally, the acetone cleaning temperature for the PET film is 40°C, the ethanol temperature is 30°C, the deionized water temperature is room temperature, and the nitrogen purge pressure is 0.3 MPa.

[0036] 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 the present application specifically includes: using a microelectronic printer to print carbon paste on the substrate layer to form a circular working electrode with a diameter of 1.8-2.0 mm, where the thickness of the working electrode formed by the carbon paste is between 20±2 μm. The dispensing printing method can achieve a positioning accuracy of 5 μm to form the working electrode on the substrate layer; secondly, the working electrode adopts a step-by-step curing method to avoid deformation of the flexible substrate layer caused by concentrated thermal stress during the curing process.

[0037] As another optional embodiment of the present invention, the preparation of the working electrode of the sodium ion detection module in step S2 of the present application also includes another optional method: using a high-precision microelectronic printer for printing, using nanocarbon / silver composite conductive ink (solid content 15%), directly writing a circular electrode with a diameter of 2.2 mm through a 200 nm diameter nozzle, and performing step-by-step curing to control the thickness of the circular electrode to 25±3 μm. The step-by-step curing temperature here is: first, the circular electrode is placed at 80°C for curing for 10 minutes, and then placed at 120°C for curing for 20 minutes. The resistivity of the nanocarbon / silver composite conductive ink is generally less than 5Ω·cm, which is lower than that of traditional carbon paste, and can improve the sensitivity of the prepared working electrode.

[0038] Furthermore, as an optional embodiment of the present invention, the preparation of the working electrode of the cortisol detection module in step S2 of the present application specifically includes: using a photolithography process to prepare a circular working electrode with a line width of 0.5 μm, a thickness of 100 nm, and a diameter of 3 mm on the base layer.

[0039] As another optional embodiment of the present invention, the working electrode of the cortisol detection module in step S2 of the present application can also be prepared by inkjet printing gold nanoparticle ink and then laser sintering to form a gold electrode with a diameter of 3.5 mm. Here, the gold nanoparticle ink has a particle size of 20 ± 2 nm, and the laser sintering is performed at a wavelength of 532 nm and a power of 0.5 W. The surface roughness of the prepared gold electrode is less than 50 nm.

[0040] Furthermore, as an optional embodiment of the present invention, the preparation of the counter electrode in step S2 of the present application specifically includes: using a microelectronic printer to spray-print platinum slurry on the base layer to form a circular counter electrode with a diameter of 3 mm and a thickness of 20±2 μm.

[0041] As another optional embodiment of the present invention, the preparation of the counter electrode in step S2 of the present application specifically includes: spraying a platinum / graphene composite ink, and curing it by infrared radiation to form a porous structure. The platinum loading of the platinum / graphene composite ink is 30%, the infrared radiation curing temperature is 150°C, the curing time is 15 minutes, and the porosity of the porous structure is 40%. The resulting counter electrode has good catalytic activity.

[0042] Furthermore, as an optional embodiment of the present invention, the preparation of the common reference electrode in step S2 of the present application specifically includes: printing an Ag / AgCl slurry on the base 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.

[0043] As another optional embodiment of the present invention, the preparation of the common reference electrode in step S2 of the present application specifically includes: printing Ag / AgCl composite ink, the composite ink contains 10% polydopamine-modified nanoparticles, forming a stable chlorination layer by in situ electrochemical chlorination, and the thickness of the common reference electrode is 15±2 μm.

[0044] 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 the present application specifically includes: S301. Preparation of sodium ion selective membrane: Prepare the membrane mixture according to the mass percentage, weigh the set amount of membrane mixture, dissolve it in tetrahydrofuran, ultrasonically shake until it is completely dissolved, and then store it in the dark for future use; the membrane mixture specifically includes: sodium ion carrier X (1%), sodium tetrakis(3,5-di(trifluoromethyl)phenyl)borate (Na-TFPB, 0.55%), polyvinyl chloride (PVC, 33%), diisooctyl sebacate (DOS, 65%). Among them, sodium ion carrier X represents 4-tert-butylcalix (4)arene-tetraethyltetraacetate, and the membrane mixture as a whole 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 a small amount of DOS components.

[0045] S302, ion conversion layer deposition: electrochemically deposit a PEDOT:PSS interface layer on the working electrode surface formed by carbon slurry. Specifically, phosphate buffer solution (PBS, pH 6.8) containing 0.01 mol / L 3,4-ethylenedioxythiophene (EDOT) and 0.1 mol / L sodium polystyrene sulfonate (NaPSS) was prepared. Then, a constant current method (2 mA / cm 2 ) polymerizes the electrolyte to a cumulative charge of 10 mC / electrode to form a uniform conductive polymer layer (PEDOT:PSS interface layer) to suppress potential drift; S303, selective membrane coating: drop-coat the sodium ion selective membrane solution onto the surface of the working electrode modified with the PEDOT:PSS interface layer, and solidify it statically at room temperature to finally obtain a sensitive membrane with a thickness of 50±5 μm.

[0046] 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 the present application specifically includes: A PBS electrolyte solution containing 0.02M EDOT and 0.15M PSS was used to form a gradient conductive PEDOT:PSS layer using pulse electrodeposition, thereby reducing the impedance to 8Ω·cm. 2 ; Sodium ion carrier X (1.5%), Na-TFBP (0.8%), polyurethane (30%), DOS (67.7%), and 0.5% MXene nanosheets (Ti3C2T x ), using droplet jetting technology to print layer by layer, and laser annealing after each layer is cured to obtain a total thickness of 55±5μm.

[0047] Furthermore, as an optional embodiment of the present invention, the modification of the working electrode of the cortisol detection module in step S4 of the present application specifically includes: S401. Pretreatment of the working electrode: Immerse the gold electrode in an HCl solution, clean it using cyclic voltammetry, rinse it with deionized water, and then blow dry it with nitrogen. Specifically, the cyclic voltammetry range is -0.2 to +0.9 V with respect to the Ag / AgCl reference electrode, and the scan rate is 50 mV / s, with 10 cycles performed.

[0048] S402, molecularly imprinted polymer film preparation: Prepare 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.

[0049] Electropolymerization process: Cyclic voltammetry was used to generate a polypyrrole-Prussian blue composite film on the surface of a gold electrode and embed cortisol molecules. The cyclic voltammetry potential range here was -0.2 to +0.9 V relative to the Ag / AgCl reference electrode, with a scan rate of 50 mV / s and 10 cycles.

[0050] Template molecule elution: The modified gold electrode was placed in blank PBS and cyclic voltammetry was performed to remove the cortisol template molecule and form a specific recognition cavity. The cyclic voltammetry potential range was -0.2 to +0.8 V relative to the Ag / AgCl reference electrode, with a scan rate of 50 mV / s for 20 cycles.

[0051] As another optional embodiment of the present invention, the modification of the working electrode of the cortisol detection module in step S4 of the present application can also be carried out in the following manner: Preparation of electropolymerized 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; The PPy-PB-MIP composite membrane with a thickness of 200 nm was generated by constant voltage electropolymerization, and the cavity density of the composite membrane reached 10 4 / cm 2 In the constant voltage electropolymerization method, the potential difference between the working electrode and the Ag / AgCl reference electrode was +0.8 V, and the number of cycles was 5.

[0052] Combined electrochemical-solvent desorption: Desorption was performed by applying a -0.8V potential in 0.1M MaOH, and then immersing in a methanol / acetic acid solution for ultrasonic treatment. The methanol / acetic acid solution was mixed in an 8:2 ratio to obtain a mixed solution. This can remove the cortisol template molecules with a removal rate of more than 95%. The cavity pore size of the obtained working electrode is between 80 and 120 nm.

[0053] Further, as an optional embodiment of the present invention, step S5 of the present application specifically includes: spin coating polyethylene glycol on the surface of the base layer to avoid nonspecific adsorption of sweat protein; A Y-shaped flow channel made of PDMS material is used to cover the area where the working electrodes of the sodium ion detection module and the cortisol detection module are located, thereby realizing the directional introduction of the liquid to be tested.

[0054] Furthermore, as an optional embodiment of the present invention, the present application also includes morphological recognition of a dual-function sensor for detecting cortisol and sodium ions: Scanning electron microscopy (SEM) was used to confirm the porous structure of the molecularly imprinted polymer (MIP) membrane and the uniformity of the PEDOT:PSS layer. The uniformity of the pore distribution on the MIP membrane surface and the presence of cracks or delamination in the PEDOT:PSS layer were determined.

[0055] Atomic force microscopy (AFM) was used to measure the surface roughness and three-dimensional morphology of the sensitive membrane in the sodium ion detection module. The crystalline state of the PVC-based selective membrane was verified by X-ray diffraction to determine whether the PVC selective membrane had lattice distortion due to solvent evaporation.

[0056] Furthermore, as an optional embodiment of the present invention, the present application also includes a performance test of the sodium ion detection module: the selectivity of the sensor to sodium ions is detected by open circuit voltage, and the linearity of the electrical signal of 0.1~100mM NaCl is verified. Specifically, the open circuit potential test results of the sodium ion detection module for different concentrations of the test liquid are as follows: Figure 2As shown, it can be seen that based on the open circuit test of sodium ion solution with multiple concentration gradients (0.1~100mM), the cortisol and sodium ion dual-function detection sensor in this application can show significant potential response differences for four orders of magnitude concentration gradients (100mM, 10mM, 1mM and 0.1mM), and the surface sensor has the reliability of wide-range concentration detection. At the same time, the linear fitting relationship between the current response of the sodium ion detection module and the change of sodium ion concentration is shown in the figure below. Figure 3 As shown in the figure, the linear fitting results of the open circuit potential signal and the sodium ion concentration indicate that the sensor exhibits significant electrochemical response differences under multiple concentration gradients, and the surface sensor can effectively distinguish sodium ions of different concentrations.

[0057] Furthermore, as an optional embodiment of the present invention, the present application also includes a performance test of the cortisol detection module: the selectivity of the sensor to cortisol is tested by chronoamperometry (IT), and the linearity of the current signal of 1-50nM cortisol is verified. Specifically, the cortisol detection module uses chronoamperometry to test the current response of different concentrations of the test liquid as shown in the figure below. Figure 4 As shown, it can be seen that the sensor has a high degree of discrimination for the current difference corresponding to the gradients of 0nM, 5nM, 10nM, and 20nM, indicating that it has a high discrimination sensitivity in the low concentration range.

[0058] It will be easily understood by those skilled in the art 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 in 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 is provided above the base layer and 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, the surface of which is formed with a gradient PEDOT:PSS interface layer by pulse electrodeposition, and the impedance of the PEDOT:PSS interface layer is 8-15Ω·cm 2 ; A cortisol detection module, which is arranged in parallel with the sodium ion detection module on the base layer, and is used to detect the cortisol concentration in the liquid to be tested; the cortisol detection module includes: a gold nanopillar array electrode, and a cysteine ​​modification layer is formed on the surface of the gold nanopillar array electrode through molecular self-assembly; A bionic microfluidic unit, the bionic microfluidic unit covering the surface of the sodium ion detection module and the cortisol detection module, the bionic microfluidic unit having a plurality of flow channel holes, and each of the flow channel holes 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; A shielding layer is covered on the surface of the bionic microfluidic unit.

2. The dual-function sensor for detecting cortisol and sodium ions according to claim 1, characterized in that: 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 in the vertical direction.

3. The dual-function sensor for detecting cortisol and sodium ions according to claim 1, characterized in that: The sodium ion detection module and the cortisol detection module further 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 selective permeation membrane.

4. The dual-function sensor for detecting cortisol and sodium ions according to claim 3, characterized in that: 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 permeable membrane is 2-5 μm.

5. The dual-function sensor for detecting cortisol and sodium ions according to claim 1, characterized in that: The bionic microfluidic unit has a spiral flow channel structure formed by 3D printing PDMS, and the spiral flow channel structure is decorated with a silicon dioxide nanocolumn 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 liquid to be tested in the spiral flow channel at a flow rate of 0.2~0.5μL / min without external force.

6. The dual-function sensor for detecting cortisol and sodium ions according to claim 1, characterized in that: The shielding layer is a layer-by-layer self-assembled structure, the shielding layer is a multi-layer structure, and the shielding layer at least includes a plasma-treated graphene oxide layer and an ethylene oxide-caprolactone block copolymer layer; The ethylene oxide-caprolactone block copolymer is cross-linked by ultraviolet light to form a nano-network structure. The ethylene oxide-caprolactone block copolymer has a mesh size of ≤5nm, a surface contact angle of 112±3°, and a protein adsorption capacity of ≤5 ng / cm 2 .

7. A method for preparing a dual-function sensor for detecting cortisol and sodium ions, for preparing the dual-function sensor for detecting cortisol and sodium ions as claimed in any one of claims 1 to 6, characterized in that: The steps include: S1, cutting and cleaning the base material to obtain a base layer; S2. Disposing a working electrode of a sodium ion detection module, a working electrode of a cortisol detection module, a counter electrode, and a common reference electrode on the substrate; S3, modifying the working electrode of the sodium ion detection module; S4, modifying the working electrode of the cortisol detection module; S5. Form a bionic microfluidic unit above the sodium ion detection module and the cortisol detection module, and form a shielding layer on the surface of the bionic microfluidic unit.

8. The method for preparing the dual-function sensor for detecting cortisol and sodium ions according to claim 7, wherein: 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 mass percentage, weigh a predetermined amount of the membrane mixture, dissolve it in tetrahydrofuran, ultrasonically vibrate until completely dissolved, and then store in the dark for future use; S302, ion conversion layer deposition: electrochemically depositing a PEDOT:PSS interface layer on the surface of the working electrode formed by the carbon slurry; S303, selective membrane coating: drop-coat the sodium ion selective membrane solution onto the surface of the working electrode modified with the PEDOT:PSS interface layer, and solidify it statically at room temperature to finally obtain a sensitive membrane with a thickness of 50±5 μm.

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