Flexible lactic acid and pH bifunctional sensor as well as preparation method and application thereof

Abstract

The invention provides a flexible lactic acid and pH bifunctional sensor as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) coating a polyethersulfone film with mixed slurry of hydroxyethyl cellulose and sodium lignin sulfonate, and engraving the polyethersulfone film by using CO2 laser to obtain the-O-S / PES-LIG electrode, the-O-S / PES-LIG electrode comprising a first functional area and a second functional area. (2) modifying polyaniline in the first functional area, and modifying an enzyme immobilization layer composed of Prussian blue and lactate oxidase in the second functional area; and (3) arranging reference electrodes in peripheral areas of the first functional area and the second functional area of the-O-S / PES-LIG electrode, and dispensing conductive slurry. The sensor provided by the invention has the characteristics of good flexible adaptability, controllable enzyme activity and high structural integration, and can realize synchronous and accurate detection of key metabolic indexes such as lactic acid and pH.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical sensors, and particularly relates to a flexible lactate and pH dual-functional sensor, a preparation method thereof, and an application thereof. Background Art

[0002] Sweat, as a non-invasive biomarker carrier that can reflect the in-vivo metabolic state in real time, contains various important indicators such as lactic acid, glucose, pH, electrolytes, etc. Its dynamic changes are closely related to various metabolic-related diseases such as diabetic ketoacidosis (DKA), metabolic syndrome, etc. Therefore, multi-parameter wearable sensors based on sweat have important application prospects in the fields of personalized health management, disease early warning, etc. In recent years, the rapid development of flexible electronic technology has promoted remarkable progress in the practicality and comfort of wearable sweat sensors. However, achieving high-precision, spatio-temporally synchronous multi-parameter detection still faces the following key challenges: (1) Poor mechanical compatibility of materials, resulting in insufficient interface stability: Traditional sensors use glassy carbon electrodes (thickness > 500 μm, bending modulus > 50 GPa) or noble metal electrodes (such as Au / Pt, strain limit < 5%), which are mechanically mismatched with flexible substrates (such as PDMS, PET, etc.) (the difference in elastic modulus reaches 3 orders of magnitude), leading to interface delamination and signal drift, seriously affecting the reliability and lifespan of the device under dynamic deformation. (2) There is cross-interference between multi-parameters, affecting the detection accuracy: As an important metabolic biomarker, lactic acid usually relies on lactate oxidase for electrochemical catalytic detection, but this enzyme is highly sensitive to pH changes. The pH fluctuations in sweat (4.5 - 7.0) may cause a significant decrease in enzyme activity (the activity can be reduced by more than 60% when < 5 in an acidic environment), resulting in obvious deviations in lactic acid detection results. Existing single-functional sensors lack the ability to monitor and regulate the microenvironment of enzyme reactions in real time, and it is difficult to balance detection accuracy and environmental adaptability. (3) Poor dynamic signal fidelity of flexible sensors: In a sports scenario, there is a large range of deformation on the skin surface (the stretching rate usually exceeds 20%), which causes a significant change in the contact impedance between the sensor and the skin, thereby triggering signal drift or distortion. Most traditional rigid electrodes or flexible patches cannot achieve conformal fitting with the skin surface in practical applications and lack the ability to adapt to dynamic stress. (4) Short lifespan of the sensor, making it difficult to adapt to the real sweat environment: Although some sensors can achieve sensitive responses to lactic acid or pH, they do not effectively regulate the microenvironment of the biorecognition unit (such as enzyme molecules). When in the sweat environment for a long time, the biosensing layer is prone to phenomena such as swelling and inactivation, resulting in rapid decline in sensor performance and insufficient stability, and the general working lifespan is difficult to exceed 24 hours. (5) There is a trade-off contradiction between integration and spatial resolution: To achieve multi-parameter detection, some existing solutions adopt a structure of spatial separation (such as microfluidic shunting) or parallel connection of multiple sensing units, but this design often sacrifices the response speed consistency and spatial consistency, and it is difficult to obtain highly synchronous data required for metabolic correlation analysis. In addition, the split structure also increases the overall thickness of the device, affecting the wearing comfort.

[0003] It can be seen that the current wearable sweat sensors still have problems such as low integration, unstable biometric capabilities, and insufficient interface adaptation capabilities. There is an urgent need for a multifunctional sweat sensor solution with good flexible adaptability, adjustable enzyme activity, and high structural integration to achieve synchronous and accurate detection of lactic acid and pH. Summary of the Invention

[0004] In view of the defects in the prior art, the present invention proposes a flexible dual-functional sensor for lactic acid and pH, its preparation method, and application. By constructing an -O-S / PES-LIG electrode, the present invention realizes the homologous in-situ detection of lactic acid and pH, significantly improving the spatial synchronism and integration of detection. Among them, the pH response layer is not only used for pH monitoring but can also feedback the enzyme reaction microenvironment in lactic acid detection in real time, effectively monitoring the interference problem of pH fluctuations on enzyme activity. At the same time, the sensor is coated with a flexible substrate structure with gradient modulus, which can effectively disperse mechanical stress, controlling the signal volatility under dynamic deformation within 5%, thus ensuring stable and reliable sensing performance. The overall solution realizes the dual-functional, real-time, and synchronous monitoring of lactic acid and pH, providing important technical support for the continuous analysis of metabolic status and early warning of diseases.

[0005] The present invention provides a preparation method for a flexible dual-functional sensor for lactic acid and pH, comprising the following steps: (1) Coating a mixed slurry of hydroxyethyl cellulose and sodium lignosulfonate on a polyethersulfone film, and using a CO2 laser to engrave the polyethersulfone film to obtain an -O-S / PES-LIG electrode, the -O-S / PES-LIG electrode comprising a first functional region and a second functional region.

[0006] (2) Modifying polyaniline in the first functional region and modifying an enzyme immobilization layer composed of Prussian blue and lactate oxidase in the second functional region; (3) Setting a reference electrode in the peripheral regions of the first functional region and the second functional region of the -O-S / PES-LIG electrode, and drop-coating a conductive paste.

[0007] In some embodiments, in the mixed slurry of step (1), the mass ratio of hydroxyethyl cellulose to sodium lignosulfonate is 1:(12 - 36).

[0008] In some embodiments, the parameters of the CO2 laser engraving in step (1) include: power of 10 - 12W, scanning rate of 80 - 100mm / s, and step size of 1 - 5mm.

[0009] In some embodiments, the conductive paste in step (3) is a mixed conductive paste containing silver and silver chloride.

[0010] In some embodiments, the drop-coating volume of the conductive paste is 5 - 20μL.

[0011] In some embodiments, the specific steps for modifying the first functional region include: Immerse the -O-S / PES-LIG electrode in a mixed solution containing aniline and sulfuric acid, and electro-deposit a polyaniline layer by cyclic voltammetry.

[0012] In some embodiments, in the mixed solution, the concentration of aniline is 0.1 - 0.5 M, and the concentration of sulfuric acid is 1.0 - 5.0 M.

[0013] In some embodiments, the steps for modifying the second functional region include: Electro-deposit Prussian blue by cyclic voltammetry, and then drop-coat a mixed solution containing chitosan, lactate oxidase, and bovine serum albumin to cover the perfluorinated resin film.

[0014] In some embodiments, in the mixed solution, the mass percentage of chitosan is 0.5 - 1.5 wt%, the concentration of lactate oxidase is 20 - 40 mg / mL, and the concentration of bovine serum albumin is 5 - 15 mg / mL.

[0015] The present invention also provides a flexible lactate and pH dual-functional sensor obtained by the preparation method described above.

[0016] The present invention also provides the application of the flexible lactate and pH dual-functional sensor in any one of the following: (1) Application in the preparation of products for detecting lactate concentration; (2) Application in the preparation of products for detecting pH; (3) Application in the preparation of products for synchronously detecting lactate concentration and pH.

[0017] In summary, compared with the prior art, the present invention achieves the following technical effects: (1) By constructing a PANI / -O-S / PES-LIG composite sensitive layer, the present invention utilizes the protonation / deprotonation buffering effect of polyaniline to achieve dynamic detection of the microenvironment pH (stabilized at 4.0 - 8.0), thereby monitoring the operation of lactate oxidase within the optimal catalytic range, and significantly improving the activity and stability of the enzyme reaction.

[0018] (2) The present invention uses laser-induced porous graphene technology to construct a three-dimensional micro-nano pore structure (pore diameter 5 - 20 μm) on the surface of the PES electrode, effectively improving the specific surface area and enzyme immobilization amount, enhancing the interaction between the electrode and the target molecule, and improving the signal response intensity and reproducibility.

[0019] (3) The present invention introduces a gradient modulus interface design, forming a mechanical gradient structure by doping layers of sodium lignosulfonate between a high modulus PES substrate (2.1 GPa) and a flexible coating (surface modulus 50 kPa). Under the bending strain generated during wearing and exercise, the current volatility can be controlled within 5%, significantly reducing the interference of motion artifacts.

[0020] (4) The present invention constructs a dual-functional integrated sensing platform, which can synchronously and in-situ monitor the changes in lactic acid concentration and pH in sweat. The detection limit of lactic acid is as low as 0.021 mM, which is particularly suitable for the early identification and dynamic tracking of metabolism-related diseases (such as diabetic ketoacidosis), significantly improving the accuracy and response speed of pathological state identification.

[0021] (4) The present invention takes into account both functional diversity and structural simplification, laying a foundation for the development of multi-parameter intelligent diagnostic devices and having the potential to be extended to the detection of more sweat biomarkers. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0023] Figure 1 is the SEM image of the PES-LIG electrode; Figure 2 is the SEM image of the -O-S / PES-LIG electrode prepared in Example 1; Figure 3 is the CV curve graph of the PES-LIG and -O-S / PES-LIG electrodes in Test Example 1; Figure 4 is the EIS curve graph of the PES-LIG and -O-S / PES-LIG electrodes in Test Example 1; Figure 5 is the current-time (i-t) curve test graph corresponding to 0 - 12 mM lactic acid concentration at room temperature in Test Example 2; Figure 6 is the linear fitting curve graph in the current stable state in Test Example 2; Figure 7 is the current response of the lactic acid sensor to interferents in Test Example 2; Figure 8 is the graph of the influence of bending on the performance of the lactic acid sensor in Test Example 2; Figure 9 is the OCP response graph of the pH sensor with a pH value between 4 and 8 in Test Example 3; Figure 10 It is a graph showing the linear relationship between the pH sensor and the OCP response in Test Example 3; Figure 11 It is the OCP response of the pH sensor to interferents in Test Example 3; Figure 12 It is a graph showing the effect of bending on the performance of the pH sensor in Test Example 3; Figure 13 It is the test result of the current response in Test Example 4; Figure 14 It is the test result of the current response in Test Example 5; Figure 15 It is the test result of the current response in Test Example 6. Detailed implementation manners

[0024] In order to enable those skilled in the art of the present technology to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] In recent years, laser engraving on various polymer films is a simple, low-cost and efficient method for preparing porous graphene. Especially sulfur-doped graphene can enhance the interlayer space, form thiophene functional groups, be beneficial to ion storage, and improve the electrochemical performance of the electrode. However, most studies have focused on wrapping heterogeneous precursors on polyimide (PI) to obtain heteroatom-doped LSG. In this case, due to the weak surface affinity of PI, it is easy to limit the types of doping precursors. Polyethersulfone (PES) films can be directly converted into S-doped porous graphene. However, few studies have been devoted to further modifying PES films for their application in high-performance biosensing. The present invention for the first time prepares a sodium ligninsulfonate (SLS)-doped PES porous membrane for high-performance electrochemical biosensing. The biomass SLS has abundant functional groups (sulfonic acid groups, carbonyl groups, hydroxyl groups, etc.) and can be used as a carbon source, an oxygen source and a sulfur source for doping at the same time. After laser engraving, the prepared -O-S / PES-LIG has a high S doping rate and a large electrochemical surface area, which is beneficial to improving its electrochemical sensing performance. This simple and efficient in-situ doping method provides a new way for the large-scale production of biomass-derived graphene.

[0026] Reagents: Potassium ferricyanide (K3[Fe(CN)6]), potassium ferrocyanide (K4[Fe(CN)6]), anhydrous ferric chloride (FeCl3), chitosan (CS), phosphate buffer solution (PBS), bovine serum albumin (BSA), sodium lignosulfonate (SLS), hydroxyethyl cellulose (HEC), aniline (ANI), glucose, L-lactate dehydrogenase (LDH), lactate oxidase (LOx), ascorbic acid (AA), perfluorinated resin (Nafion), sulfuric acid (H2SO4), L-lactic acid (Lactate), polyethersulfone membrane (PES), silver-silver chloride paste (Ag / AgCl), and platinum silicone (Ecoflex).

[0027] Using a phosphated salt solution (PBS, 10 mM) as the solvent, it was prepared by dissolving sodium chloride (NaCl), potassium chloride (KCl), disodium hydrogen phosphate (Na2HPO4), and potassium dihydrogen phosphate (KH2PO4) in deionized water (DI) (18.2 MΩ·cm).

[0028] Instrument: A CO2 laser cutting system was used to prepare the sensing electrode. The laser engraving platform for preparing the laser-induced graphene electrode was a QT-3020 device purchased from Qintang Laser Technology Co., Ltd., equipped with a carbon dioxide (CO2) laser as the light source. The supporting software can realize the drawing of various shapes, and the CO2 light source can move freely in the X-Y two-dimensional plane according to the set parameters. The parameters of the prepared laser-induced graphene electrode were set as follows: power 11 W, speed 80 mm·s -1 , and the line gap was 0.01 mm.

[0029] All electrochemical experiments (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (i-t)) were carried out at room temperature on a Shanghai Chenhua workstation (CHI 660E). This workstation adopted a three-electrode system. The pH sensor consisted of PANI / -O-S / PES-LIG as the working electrode (diameter 3 mm) and an Ag / AgCl reference electrode. The lactate sensor consisted of LOx / PB / -O-S / PES-LIG as the working electrode (WE), -O-S / PES-LIG and Ag / AgCl as the counter electrode (CE) and reference electrode (RE) respectively, and was used for the fabrication of all sensors.

[0030] The flexible electrodes were characterized using an environmental scanning electron microscope (SEM, ThermoFisher Quattro), model QuattroS, with a resolution of ≤1.0 nm, an acceleration voltage of 20 kV, and a high-resolution Schottky field emission electron gun as the electron source for electrode morphology characterization.

[0031] The scanning rate for CV measurement was set at 50 mV s -1 , and the potential scanning range was from -0.30 V to +0.70 V. The EIS frequency range was 0.1 Hz to 1000 kHz, the AC amplitude was 5 mV, and the open-circuit potential. The sensing performance of the lactate sensor was tested by i-t current measurement at 0.2 V for 60 s in 0.1 M PBS buffer solution. At room temperature, in a 0.1 M KCl + 5.0 mM K3 / K4 redox probe solution, a self-made Ag / AgCl reference electrode was used for electrochemical characterization of the -O-S / PES-LIG counter electrode. All measurements were carried out at room temperature. All required solutions were prepared using 10 mM PBS (pH = 7.0).

[0032] Example 1 Preparation of a lactate and pH dual-functional sensor (1) Preparation of PES-LIG electrodes and -O-S / PES-LIG electrodes First, a commercial PES film was cut into a rectangle of 2.5×6 cm 2 . The PES film was directly engraved using a CO2 laser with a laser power of 12 W, a scanning rate of 80 mm / s, and a step size of 1 mm to obtain PES-LIG electrodes. Another PES film was cut into a rectangle of 2.5×6 cm 2 . Then, 3.0 g of SLS and 0.125 g of HEC were added to 10 mL of deionized water, and then magnetically stirred at 55°C for 2 h to obtain HEC-SLS slurry. Then, 1 g of HEC-SLS slurry was spin-coated onto the PES membrane and dried in an oven at 50°C for 30 min. The PES film coated with HEC-SLS was engraved using a CO2 laser with a laser power of 12 W, a scanning rate of 80 mm / s, and a step size of 1 mm to obtain -O-S / PES-LIG electrodes. Subsequently, the engraved film was immersed in deionized water to wash away the excess HEC-SLS slurry. Finally, the prepared -O-S / PES-LIG electrodes were connected to copper wires using silver paste to obtain better contact. To passivate the sensor connection, Ecoflex was drop-coated on the non-working area of the electrode and dried at room temperature for 30 min.

[0033] (2) Preparation of pH sensors To assemble the reference electrode of the lactate and pH sensors, approximately 10 μL of Ag / AgCl ink was dropped onto the corresponding area of the -O-S / PES-LIG electrode, and then it was heated in an oven at 70 °C for 30 min. To functionalize the working electrode, the -O-S / PES-LIG electrode was immersed in a 1 M H2SO4 solution containing 0.1 M aniline, and a constant potential from -0.20 to +1.0 V was applied at a scan rate of 100 mV / s for electrodeposition (40 cycles). Next, the polyaniline (PANI)-modified -O-S / PES-LIG was carefully rinsed with ultrapure water and dried at room temperature. The pH sensor consists of a PANI / -O-S / PES-LIG working electrode (with a diameter of 3 mm) and an Ag / AgCl reference electrode.

[0034] (3) Preparation of the lactate sensor The fabrication process of the lactate biosensor is as follows: Prussian Blue (PB) electrodeposition was carried out by potentiostatic method from -0.30 V to +0.60 V in a solution containing 5×10 -3 M K3[Fe(CN)6] and 5×10 -3 M FeCl3 in 0.1 M HCl + 0.1 M KCl solution. Cyclic voltammetry (CV) was performed for 20 cycles at a scan rate of 50 mV / s. After PB deposition, the electrode was rinsed with distilled water and dried naturally at room temperature. Bovine serum albumin (BSA) was used as an enzyme stabilizer to immobilize the enzyme to achieve a high enzyme loading. A BSA solution was prepared at a concentration of 10 mg / mL in 0.1 M PBS. A chitosan solution was prepared by dissolving it in 0.5 wt% acetic acid. When preparing the lactate biosensor, the chitosan solution was mixed with the BSA solution of LOx (40 mg / mL) in a ratio of 1:1 (v / v), and then 10 μL of the mixture was drop-cast onto the surface of the working electrode. After completing the corresponding immobilization steps, the sensor was stored at 4 °C overnight. Finally, 5 μL of Nafion (0.05% v / v ethanol) was cast onto the LOx / -O-S / PES-LIG working electrode, dried at room temperature for 1 h, and then stored in a 4 °C refrigerator for later use.

[0035] (4) Characterization of the electrode morphology and composition The surface morphology and porous structure of the PES-LIG and -O-S / PES-LIG electrodes were characterized by scanning electron microscopy. From Figures 1 - 2From the top-view SEM images of PES-LIG and -O-S / PES-LIG, it can be seen that both electrodes exhibit a reticulated porous structure. After engraving the PES electrode containing lignin, the surface of -O-S / PES-LIG is rougher than that of PES-LIG, with significantly enhanced porosity. Moreover, a large number of interconnected macroporous foam-like structures are embedded on its surface, and the graphene framework is significantly thickened. This may be due to the integration of lignin-derived amorphous carbon on the PES matrix. The increase in the thickness of the -O-S / PES-LIG film is beneficial to promoting the transport of electrolytes. These results indicate that the addition of lignin has a significant impact on the morphology of PES-LIG, enabling the densification of PES and regulating its porous structure.

[0036] Example 2 The difference between this example and Example 1 is that the dosage of SLS is 1.5 g.

[0037] Example 3 The difference between this example and Example 1 is that the dosage of SLS is 4.5 g.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that the PES film is replaced with fiber paper.

[0039] Comparative Example 2 The difference between this comparative example and Example 1 is that the PES film is replaced with wood paper.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that SLS is replaced with soy protein isolate.

[0041] Comparative Example 4 The difference between this comparative example and Example 1 is that SLS is replaced with chitosan.

[0042] Comparative Example 5 The difference between this comparative example and Example 1 is that SLS is replaced with λ-carrageenan.

[0043] Comparative Example 6 The difference between this comparative example and Example 1 is that no SLS is added.

[0044] Test Example 1 Electrochemical Performance Characterization PES-LIG was not modified with -O / -S. The PES film was engraved with a CO2 laser at a laser power of 12 w, a scanning rate of 80 mm·s -1 and a step size of 1 mm to obtain PES-LIG.

[0045] To evaluate the charge transfer behavior of the PES-LIG and -O-S / PES-LIG electrodes in Example 1, cyclic voltammetry tests were performed using a 5 mM Fe(CN)6 3 / 4- redox probe. As Figure 3 shown, for the PES-LIG electrode, a weak current was observed. Although there were obvious redox peaks, the peak potential was low, indicating a low electron transfer rate at the interface. In contrast, for the -O / -S co-doped modified electrode -O-S / PES-LIG, the peak potential current increased significantly, about 2.6 times that of the PES-LIG electrode peak potential. This indicates that the -O / -S modification increased the electroactive surface area on the surface of the PES-LIG electrode and accelerated the electron transfer between the redox probe and the electrode.

[0046] The higher charge transfer rate of the -O / -S modified PES-LIG electrode was further confirmed by Electrochemical Impedance Spectroscopy (EIS).

[0047] As Figure 4 shown, the inset is the Randles equivalent circuit model used to fit the experimental results. In this circuit, C dl , Z w , R ct and R s are the double-layer capacitance, Warburg impedance element, electron transfer resistance, and solution resistance, respectively. With -O / -S co-doping, R ct significantly decreased. The diameter of the semicircle in the Nyquist plot corresponds to the charge transfer resistance ( R ct ). All modified electrodes showed semicircles with different diameters, corresponding to different R ct . The -O-S / PES-LIG modified electrode had the smallest semicircle radius, and its R ct value was also the smallest, showing better electron transfer ability compared to the PES-LIG electrode.

[0048] Test Example 2 Study on the Sensing Performance of Lactate Sensors Figure 5 Shows the amperometric response corresponding to the lactate concentration in the range of 0 - 12 mM when the test potential is 0.2 V on the LOx / PB / -O-S / PES-LIG electrode. The linear calibration curve of the current response versus lactate concentration is as Figure 6 shown, and the correlation coefficient R2 is 0.995, and the sensitivity is 15.43 μA mM -1 cm -2 , the detection limit is 0.021 mM (signal-to-noise ratio S / N = 3), which is significantly lower than the clinical monitoring lactic acid concentration level, and has obvious advantages compared with the reported lactic acid sensors. The prepared LOx / PB / -O-S / PES-LIG lactic acid sensor has a wide linear range and a low detection limit, showing good clinical application prospects.

[0049] In a complex human physiological environment, the coexistence of multiple substances may affect the accuracy of the lactic acid sensor. Therefore, selectivity is particularly important for improving the performance of the sensor. Here, several interfering substances commonly present in sweat were selected in this example to test the anti-interference ability of the lactic acid sensor. Such as Figure 7 shown, even in the presence of interfering substances, the change in the sensor signal is very small, indicating that the sensor has good selectivity and can accurately identify lactic acid.

[0050] Such as Figure 8 shown, the sensor was attached to the tube wall with a diameter of 2 cm and bent multiple times for testing. The results showed that the change in sensor performance was very small. Compared with the original current, the maximum loss current did not exceed 5%, indicating that it can well cope with the deformation generated during human movement.

[0051] Test Example 3 Study on the Sensing Performance of pH Sensor Figure 9 Shows the OCP-time (time) curves of the pH sensor in commercial standard buffer solutions with different pH values, ranging from 4 to 8. In addition, this experiment shows that the sensor has good reversibility in the range of pH values from 4 to 8. Such as Figure 10 shown, the sensor shows good linear response, with a sensitivity of -67.8 mV / pH and a relatively high regression coefficient value (R 2 = 0.995), which is better than existing pH sensors.

[0052] The selectivity of the prepared pH sensor in the presence of other ions (including glucose and lactic acid, AA, UA, DA, Mg 2+ , Ca 2+ , Na + and K + ) is shown as Figure 11 shown. The pH sensor has no obvious response to other interfering ions and still has a good response after adding the interfering ions. The above experimental results show that the PANI / -O-S / PES-LIG sensor can effectively realize the functions of electron conduction and pH response.

[0053] Such as Figure 12As shown, the sensor was attached to the tube wall with a diameter of 2 cm for multiple bending tests. The results showed that the performance change of the sensor was very small. Compared with the original current, the maximum loss current did not exceed 5%, indicating that it could effectively cope with the deformation generated during human movement.

[0054] Test Example 4 Current Response Test of Different Substrates This test example was a CV test. The electrodes obtained in Example 1 and Comparative Examples 1-2 were subjected to CV tests in 0.1 M KCl containing 5 mM [Fe(CN)6] 3- / 4- redox probe.

[0055] The test results are as Figure 13 shown. Among the three substrates, the PES substrate had the largest response current.

[0056] Test Example 5 Current Response Test of Different Doping Materials Subsequently, the electrodes obtained in Example 1 and Comparative Examples 3-5 were subjected to CV tests in 0.1 M KCl solution containing 5 mM [Fe(CN)6] 3- / 4- redox probe.

[0057] The test results are as Figure 14 shown, which is a test comparison chart of different doping materials. The current in the figure shows that compared with SLS, the current responses of soy protein isolate, chitosan, and λ-carrageenan did not exceed that of the SLS-modified electrode.

[0058] Test Example 6 Optimization of SLS Doping Amount With the substrate determined as PES-LIG and the doping material as SLS, 3 contents were selected for optimization. The electrodes of Examples 1-3 and Comparative Example 6 were subjected to CV tests in 0.1 M KCl solution containing 5 mM [Fe(CN)6] 3- / 4- redox probe.

[0059] The results are as Figure 15 shown. When the SLS was 0 g, 1.5 g, 3.0 g, and 4.5 g respectively, the current response was the largest when the SLS doping content was 3.0 g.

[0060] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a flexible lactic acid and pH dual-functional sensor, characterized in that, It includes the following steps: (1) Coating a mixed slurry of hydroxyethyl cellulose and sodium lignosulfonate on a polyethersulfone film, and using a CO2 laser to engrave the polyethersulfone film to obtain an -O-S / PES-LIG electrode, where the -O-S / PES-LIG electrode includes a first functional region and a second functional region; (2) Modifying polyaniline in the first functional region and modifying an enzyme immobilization layer composed of Prussian blue and lactate oxidase in the second functional region; (3) Setting a reference electrode in the peripheral regions of the first functional region and the second functional region of the -O-S / PES-LIG electrode and drop-coating a conductive paste.

2. The preparation method according to claim 1, wherein In the mixed slurry in step (1), the mass ratio of hydroxyethyl cellulose to sodium lignosulfonate is 1:(12 - 36).

3. The preparation method according to claim 1, characterized in that, The parameters of the CO2 laser engraving in step (1) include: power of 10 - 12 W, scanning rate of 80 - 100 mm / s, and step size of 1 - 5 mm.

4. The preparation method according to claim 1, wherein The conductive paste in step (3) is a mixed conductive paste containing silver and silver chloride.

5. The preparation method according to claim 1, wherein The specific steps for modifying the first functional region include: Immersing the -O-S / PES-LIG electrode in a mixed solution containing aniline and sulfuric acid, and electro-depositing a polyaniline layer by cyclic voltammetry.

6. The preparation method according to claim 5, characterized in that, In the mixed solution, the concentration of aniline is 0.1 - 1.5 M, and the concentration of sulfuric acid is 1.0 - 5.0 M.

7. The preparation method according to claim 1, characterized in that, The steps for modifying the second functional region include: Electro-depositing Prussian blue by cyclic voltammetry, and then drop-coating a mixed solution containing chitosan, lactate oxidase, and bovine serum albumin, and covering it with a perfluorinated resin film.

8. The preparation method according to claim 7, wherein In the mixed solution, the mass percentage of chitosan is 0.5 - 1.5 wt%, the concentration of lactate oxidase is 20 - 40 mg / mL, and the concentration of bovine serum albumin is 5 - 15 mg / mL.

9. A flexible dual-functional sensor for lactic acid and pH, characterized in that, Obtained by the preparation method according to any one of claims 1 - 8.

10. Application of the flexible lactate and pH dual-functional sensor according to claim 9 in any one of the following: (1) Application in the preparation of products for detecting lactate concentration; (2) Application in the preparation of products for detecting pH; (3) Application in the preparation of products for synchronously detecting lactate concentration and pH.

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