A flexible lactic acid and pH dual-function sensor and its preparation method and application

Abstract

The present invention provides a flexible lactate and pH dual-function sensor and its preparation method and application. The preparation method comprises the following steps: (1) coating a mixed slurry of hydroxyethyl cellulose and sodium lignin sulfonate on a polyethersulfone film, and using a CO2 laser to engrave the polyethersulfone film to obtain an ‑O‑S / PES‑LIG electrode, wherein the ‑O‑S / PES‑LIG electrode comprises 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) arranging a reference electrode in the peripheral area of ​​the first functional region and the second functional region of the ‑O‑S / PES‑LIG electrode, and drop-coating a conductive slurry. The sensor of the present invention has the characteristics of good flexibility and adaptability, controllable enzyme activity, and high structural integration, and can achieve synchronous and accurate detection of key metabolic indicators such as lactate and pH.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical sensors, and in particular to a flexible lactic acid and pH dual-function sensor, a preparation method thereof, and applications thereof. Background Art

[0002] Sweat is a non-invasive, real-time biomarker carrier that reflects the metabolic state of the body. It contains many important indicators such as lactate, glucose, pH, and electrolytes. Its dynamic changes are closely related to a variety of metabolic-related diseases such as diabetic ketoacidosis (DKA) and metabolic syndrome. Therefore, sweat-based multi-parameter wearable sensors have important application prospects in the fields of personalized health management and disease early warning. In recent years, the rapid development of flexible electronic technology has promoted significant progress in the practicality and comfort of wearable sweat sensors. However, the realization of high-precision, spatiotemporal synchronization of multi-parameter detection still faces the following key challenges: (1) Poor mechanical adaptability of materials, resulting in insufficient interface stability: Traditional sensors use glassy carbon electrodes (thickness > 500 μm, bending modulus > 50 GPa) or precious metal electrodes (such as Au / Pt, strain limit < 5%), which have a mismatch in mechanical properties with flexible substrates (PDMS, PET, etc.) (the elastic modulus difference is up to 3 orders of magnitude), resulting in interface delamination and signal drift, which seriously affects the reliability and life of the device under dynamic deformation. (2) There is cross-interference between multiple parameters, which affects the detection accuracy: Lactate, as an important metabolic marker, usually relies on lactate oxidase for electrochemical catalytic detection, but this enzyme is highly sensitive to pH changes. pH fluctuations in sweat (4.5~7.0) may cause a significant decrease in enzyme activity (activity can be reduced by more than 60% when the pH is <5 in an acidic environment), resulting in significant deviations in lactate detection results. Existing single-function sensors lack the ability to monitor and control the enzyme reaction microenvironment in real time, making it difficult to balance detection accuracy and environmental adaptability. (3) Flexible sensors have poor dynamic signal fidelity: In sports scenarios, the skin surface has a large range of deformation (the stretching rate is usually more than 20%), which causes a significant change in the contact impedance between the sensor and the skin, thereby causing signal drift or distortion. Most traditional rigid electrodes or flexible patches cannot achieve conformal adhesion to the skin surface in actual applications and lack the ability to adapt to dynamic stress. (4) The sensor life is short and 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 exposed to sweat for a long time, the biosensor layer is prone to swelling and inactivation, resulting in rapid degradation of sensor performance and insufficient stability. Generally, the working life is difficult to exceed 24 hours. (5) There is a trade-off between integration and spatial resolution: To achieve multi-parameter detection, some existing solutions adopt spatial separation (such as microfluidic shunt) or multi-sensor unit parallel structure, but this design often sacrifices the consistency of response speed and spatial consistency, making it difficult to obtain the high synchronization data required for metabolic association analysis. In addition, the split structure also increases the overall thickness of the device, affecting wearing comfort.

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

[0004] In response to the deficiencies in the prior art, the present invention proposes a flexible dual-function sensor for lactate and pH, and its preparation method and application. The present invention realizes homologous in situ detection of lactate and pH by constructing a -OS / PES-LIG electrode, which significantly improves the spatial synchronization and integration of detection; wherein, the pH response layer is not only used for pH monitoring, but also can provide real-time feedback on the enzyme reaction microenvironment in lactate detection, effectively monitoring the interference of pH fluctuations on enzyme activity; at the same time, the sensor is coated with a flexible substrate structure with a gradient modulus, which can effectively disperse mechanical stress and control the signal fluctuation rate under dynamic deformation within 5%, thereby ensuring stable and reliable sensing performance. The overall solution realizes dual-function, real-time, synchronous monitoring of lactate and pH, providing important technical support for continuous analysis of metabolic status and early warning of diseases.

[0005] The present invention provides a method for preparing a flexible lactic acid and pH dual-function sensor, comprising the following steps:

[0006] (1) A mixed slurry of hydroxyethyl cellulose and sodium lignin sulfonate is coated on a polyethersulfone film, and the polyethersulfone film is engraved using a CO2 laser to obtain an -OS / PES-LIG electrode, wherein the -OS / PES-LIG electrode includes a first functional area and a second functional area.

[0007] (2) modifying the first functional region with polyaniline and modifying the second functional region with an enzyme immobilization layer consisting of Prussian blue and lactate oxidase;

[0008] (3) A reference electrode is set in the peripheral area of ​​the first functional area and the second functional area of ​​the -OS / PES-LIG electrode, and a conductive slurry is drop-coated.

[0009] In some embodiments, in the mixed slurry of step (1), the mass ratio of hydroxyethyl cellulose to sodium lignin sulfonate is 1:(12~36).

[0010] In some embodiments, 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 length of 1-5 mm.

[0011] In some embodiments, the conductive paste in step (3) is a mixed conductive paste containing silver and silver chloride.

[0012] In some embodiments, the drop coating volume of the conductive paste is 5-20 μL.

[0013] In some embodiments, the specific steps of modifying the first functional region include:

[0014] The -OS / PES-LIG electrode was immersed in a mixed solution containing aniline and sulfuric acid, and a polyaniline layer was formed by electrodeposition via cyclic voltammetry.

[0015] 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.

[0016] In some embodiments, the second functional region modification step comprises:

[0017] Prussian blue was electrodeposited by cyclic voltammetry, and then a mixed solution containing chitosan, lactate oxidase and bovine serum albumin was drop-coated to cover the perfluorinated resin membrane.

[0018] 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.

[0019] The present invention also provides a flexible lactic acid and pH dual-function sensor obtained by the preparation method.

[0020] The present invention also provides the use of the flexible lactic acid and pH dual-function sensor in any one of the following:

[0021] (1) Application in the preparation of products for detecting lactic acid concentration;

[0022] (2) Application in the preparation of products for pH detection;

[0023] (3) Application in the preparation of products for simultaneous detection of lactic acid concentration and pH.

[0024] In summary, compared with the prior art, the present invention achieves the following technical effects:

[0025] (1) The present invention constructs a PANI / -OS / PES-LIG composite sensitive layer and utilizes the protonation / deprotonation buffering effect of polyaniline to achieve dynamic detection of the microenvironment pH (stable at 4.0-8.0), thereby monitoring the operation of lactate oxidase in the optimal catalytic range and significantly improving the activity and stability of the enzyme reaction.

[0026] (2) The present invention uses laser-induced porous graphene technology to construct a three-dimensional micro-nanopore structure (pore size 5-20 μm) on the surface of the PES electrode, effectively increasing 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.

[0027] (3) The present invention introduces a gradient modulus interface design, forming a mechanical gradient structure by combining a high modulus PES substrate (2.1 GPa) with a flexible coating (surface modulus 50 kPa) through a sodium lignin sulfonate doping layer. Under the bending strain generated by wearing and movement, the current fluctuation rate can be controlled within 5%, significantly reducing motion artifact interference.

[0028] (4) The present invention constructs a dual-function integrated sensing platform that can simultaneously monitor the lactate concentration and pH changes in sweat in situ. The detection limit of lactate is as low as 0.021 mM. It is particularly suitable for early identification and dynamic tracking of metabolic-related diseases (such as diabetic ketoacidosis), significantly improving the accuracy and response speed of pathological state identification.

[0029] (4) The present invention combines functional diversity with structural simplification, laying the foundation for the development of multi-parameter intelligent diagnostic equipment and has the potential to be expanded to detect more sweat biomarkers. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 SEM image of PES-LIG electrode;

[0032] Figure 2 SEM image of the -OS / PES-LIG electrode prepared in Example 1;

[0033] Figure 3 CV curves of PES-LIG and -OS / PES-LIG electrodes of Test Example 1;

[0034] Figure 4 EIS curves of PES-LIG and -OS / PES-LIG electrodes of Test Example 1;

[0035] Figure 5 This is the current-time (it) curve test graph corresponding to test example 2 at room temperature with a lactic acid concentration of 0 to 12 mM;

[0036] Figure 6 This is a linear fitting curve diagram of the current steady state of test example 2;

[0037] Figure 7 The current response of the lactate sensor of Test Example 2 to the interferent;

[0038] Figure 8 This is a graph showing the effect of bending on the performance of the lactate sensor in test example 2;

[0039] Figure 9 This is the OCP response diagram of the pH sensor in test example 3 when the pH value is between 4 and 8;

[0040] Figure 10 is a linear relationship diagram between the pH sensor and OCP response of Test Example 3;

[0041] Figure 11 The OCP response of the pH sensor of Test Example 3 to the interferent;

[0042] Figure 12 This is a graph showing the effect of bending on pH sensor performance in Test Example 3;

[0043] Figure 13 This is the current response test result of Test Example 4;

[0044] Figure 14 This is the current response test result of Test Example 5;

[0045] Figure 15 This is the current response test result of Test Example 6. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the solutions 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 of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0047] In recent years, laser engraving on various polymer films has become a facile, low-cost, and efficient method for preparing porous graphene. Sulfur-doped graphene, in particular, can enhance interlayer spacing and form thiophene functional groups, which facilitate ion storage and improve electrode electrochemical performance. However, most research has focused on encapsulating heterogeneous precursors onto polyimide (PI) to obtain heteroatom-doped LSG. In this case, the weak surface affinity of PI limits the type of doping precursor. Polyethersulfone (PES) films can be directly converted into sulfur-doped porous graphene. However, few studies have focused on further modifying PES films for high-performance biosensing applications. Here, we report the first preparation of sodium ligninsulfonate (SLS)-doped PES porous films for high-performance electrochemical biosensing. Biomass SLS possesses a rich variety of functional groups (sulfonic acid, carbonyl, and hydroxyl groups), which can serve as a carbon, oxygen, and sulfur source for doping. After laser engraving, the prepared -OS / PES-LIG has a high S doping rate and a large electrochemical surface area, which is beneficial for improving its electrochemical sensing performance. This simple and efficient in situ doping method provides a new path for the large-scale production of biomass-derived graphene.

[0048] Reagents:

[0049] Potassium ferrocyanide (K3[Fe(CN)6]), potassium ferrocyanide (K4[Fe(CN)6]), anhydrous ferric chloride (FeCl3), chitosan (CS), phosphate buffered saline (PBS), bovine serum albumin (BSA), sodium lignin sulfonate (SLS), hydroxyethyl cellulose (HEC), aniline (ANI), glucose (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 silica gel (Ecoflex).

[0050] Phosphate saline solution (PBS, 10 mM) was used as solvent and 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).

[0051] instrument:

[0052] The sensing electrodes were prepared using a CO2 laser cutting system. The laser engraving platform used to prepare the laser-induced graphene electrodes was a QT-3020 model purchased from Qintang Laser Technology Co., Ltd. It is equipped with a carbon dioxide (CO2) laser as a light source. The accompanying software enables the drawing of various shapes, and the CO2 light source can be freely moved within the XY two-dimensional plane according to the set parameters. The parameters for the prepared laser-induced graphene electrodes were set to 11 W power and 80 mm / s speed. -1 , line gap 0.01 mm.

[0053] All electrochemical experiments (cyclic voltammetry, CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (ITEM) were performed at room temperature on a Shanghai Chenhua workstation (CHI 660E). This workstation utilizes a three-electrode system. The pH sensor consists of a PANI / -OS / PES-LIG working electrode (3 mm diameter) and an Ag / AgCl reference electrode. Lactic acid sensors, using LOx / PB / -OS / PES-LIG as the working electrode (WE), and -OS / PES-LIG and Ag / AgCl as the counter electrode (CE) and reference electrode (RE), respectively, were used for all sensor fabrication.

[0054] The flexible electrode was characterized by an environmental scanning electron microscope (SEM, ThermoFisher Quattro). The QuattroS model had a resolution of ≤1.0 nm, an accelerating voltage of 20 kV, and a high-resolution Schottky field emission electron gun as the emission source to characterize the electrode morphology.

[0055] The CV measurement scan rate was set at 50 mV s -1 The potential sweep range was -0.30 V to +0.70 V. The EIS frequency range was 0.1 Hz to 1000 kHz, with an AC amplitude of 5 mV and an open circuit potential. The sensing performance of the lactate sensor was tested by amperometric testing at 0.2 V for 60 s in 0.1 M PBS buffer. The L-OS / PES-LIG counter electrode was electrochemically characterized at room temperature in a 0.1 M KCl + 5.0 mM K3 / K4 redox probe solution using a homemade Ag / AgCl reference electrode. All measurements were performed at room temperature. All solutions were prepared in 10 mM PBS (pH 7.0).

[0056] Example 1 Preparation of a dual-function sensor for lactic acid and pH

[0057] (1) Preparation of PES-LIG and -OS / PES-LIG electrodes

[0058] First, commercial PES film was cut into 2.5 × 6 cm 2 A PES-LIG electrode was obtained by directly engraving the PES film 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. Another piece of PES film was cut into 2.5×6 cm 2 A rectangular-shaped film was prepared. 3.0 g of SLS and 0.125 g of HEC were added to 10 mL of deionized water and magnetically stirred at 55°C for 2 h to obtain a HEC-SLS slurry. Subsequently, 1 g of the HEC-SLS slurry was applied to a PES membrane and dried in a 50°C oven for 30 min. A HEC-SLS-coated PES film was engraved using a CO2 laser with a laser power of 12 W, a scan rate of 80 mm / s, and a step size of 1 mm to obtain the -OS / PES-LIG electrode. The engraved film was then soaked in deionized water to remove excess HEC-SLS slurry. Finally, the prepared -OS / PES-LIG electrode was connected to a copper wire using silver paste to achieve better contact. To passivate the sensor connection, Ecoflex was drop-coated on the non-working area of ​​the electrode and allowed to dry at room temperature for 30 min.

[0059] (2) Preparation of pH sensor

[0060] To assemble the reference electrodes for the lactate and pH sensors, approximately 10 µL of Ag / AgCl ink was dropped onto the corresponding area of ​​the -OS / PES-LIG electrode, which was then heated in a 70°C oven for 30 min. To functionalize the working electrode, the -OS / PES-LIG electrode was immersed in a 1 M H₂SO₄ solution containing 0.1 M aniline and electrodeposited using a constant potential from -0.20 to +1.0 V at a scan rate of 100 mV / s (40 cycles). Next, the polyaniline (PANI)-modified -OS / PES-LIG was carefully rinsed with ultrapure water and dried at room temperature. The pH sensor consists of a PANI / -OS / PES-LIG working electrode (3 mm diameter) and an Ag / AgCl reference electrode.

[0061] (3) Preparation of lactate sensor

[0062] The fabrication process of the lactate biosensor is as follows:

[0063] Prussian blue (PB) was electrodeposited by potentiostatic method at a potential of -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. 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 air-dried at room temperature. Bovine serum albumin (BSA) was used as an enzyme stabilizer to immobilize the enzyme to achieve 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 and dissolved in 0.5 wt% acetic acid. To prepare the lactate biosensor, the chitosan solution was mixed with a BSA solution containing LOx (40 mg / mL) in a 1:1 (v / v) ratio, and 10 µL of the mixture was drop-cast onto the working electrode surface. After the respective 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 / -OS / PES-LIG working electrode, dried at room temperature for 1 h, and then stored in a refrigerator at 4°C until use.

[0064] (4) Electrode morphology and composition characterization

[0065] The surface morphology and porous structure of PES-LIG and -OS / PES-LIG electrodes were characterized by scanning electron microscopy. Figures 1 and 2 The top-view SEM images of PES-LIG and -OS / PES-LIG show that both electrodes exhibit a reticular porous structure. After being engraved with the PES electrode containing lignin, the surface of -OS / PES-LIG is rougher than that of PES-LIG, with significantly enhanced porosity. Its surface is embedded with a large number of interconnected macroporous foam structures, and the graphene skeleton is significantly thickened. This is likely due to the integration of lignin-derived amorphous carbon on the PES matrix. The increase in -OS / PES-LIG membrane thickness facilitates the transport of electrolytes. These results indicate that the addition of lignin has a significant effect on the morphology of PES-LIG, densifying PES and regulating its porous structure.

[0066] Example 2

[0067] The difference between this embodiment and embodiment 1 is that the amount of SLS used is 1.5 g.

[0068] Example 3

[0069] The difference between this embodiment and embodiment 1 is that the amount of SLS used is 4.5 g.

[0070] Comparative Example 1

[0071] The difference between this comparative example and Example 1 is that the PES film is replaced by fiber paper.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 1 is that the PES film is replaced by wood paper.

[0074] Comparative Example 3

[0075] The difference between this comparative example and Example 1 is that SLS is replaced by soy protein isolate.

[0076] Comparative Example 4

[0077] The difference between this comparative example and Example 1 is that SLS is replaced by chitosan.

[0078] Comparative Example 5

[0079] The difference between this comparative example and Example 1 is that SLS is replaced by λ-carrageenan.

[0080] Comparative Example 6

[0081] The difference between this comparative example and Example 1 is that no SLS is added.

[0082] Test Example 1 Electrochemical Performance Characterization

[0083] PES-LIG was not modified with -O / -S and the laser power was 12 W and the scanning rate was 80 mm·s. -1 PES-LIG was obtained by engraving the PES film using a CO2 laser with a step size of 1 mm.

[0084] In order to evaluate the charge transfer behavior of PES-LIG and -OS / PES-LIG electrodes in Example 1, 5 mM Fe(CN)6 3 / 4- The redox probe was tested by cyclic voltammetry. Figure 3 As shown, for the PES-LIG electrode, a weak current is observed. Despite a clear redox peak, the peak potential is low, indicating a low electron transfer rate at the interface. In contrast, for the -O / -S co-doped modified electrode -OS / PES-LIG, the peak current is significantly increased, approximately 2.6 times that of the PES-LIG electrode. This indicates that the -O / -S modification increases the electroactive surface area on the PES-LIG electrode and accelerates electron transfer between the redox probe and the electrode.

[0085] Electrochemical impedance spectroscopy (EIS) further confirmed that the -O / -S modified PES-LIG electrode had a high charge transfer rate.

[0086] like Figure 4 As shown in the figure, 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 They are double layer capacitance, Warburg impedance element, electron transfer resistance and solution resistance. R ct The diameter of the semicircle in the Nyquist plot corresponds to the charge transfer resistance ( R ct ). All modified electrodes show semicircles of different diameters, corresponding to different R ct -OS / PES-LIG modified electrode has the smallest semicircle radius. R ct The value is also the smallest, showing better electron transfer ability compared with the PES-LIG electrode.

[0087] Test Example 2: Study on the Sensing Performance of Lactic Acid Sensor

[0088] Figure 5 The amperometric response of the LOx / PB / -OS / PES-LIG electrode at a test potential of 0.2 V for lactate concentrations ranging from 0 to 12 mM is shown. The linear calibration curve of the current response versus lactate concentration is shown in Figure 1. Figure 6 As shown, the correlation coefficient R 2 The sensitivity is 0.995 and 15.43 μA mM -1 cm -2 The detection limit was 0.021 mM (signal-to-noise ratio S / N = 3), significantly lower than the clinical lactate concentration level, and has significant advantages over previously reported lactate sensors. The fabricated LOx / PB / -OS / PES-LIG lactate sensor exhibits a wide linear range and low detection limit, demonstrating promising clinical application prospects.

[0089] In the complex physiological environment of the human body, the coexistence of multiple substances may affect the accuracy of the lactate sensor. Therefore, selectivity is particularly important for improving sensor performance. Here, this example selects several interfering substances commonly present in sweat to test the anti-interference ability of the lactate sensor. Figure 7 As shown, even in the presence of interfering substances, the change in sensor signal is very small, indicating that the sensor has good selectivity and can accurately identify lactate.

[0090] like Figure 8 As shown in the figure, the sensor was attached to the wall of a tube with a diameter of 2 cm and subjected to multiple bending tests. The results showed that the sensor performance changed very little. Compared with the original current, the maximum loss current did not exceed 5%, indicating that it can well cope with the deformation caused by human movement.

[0091] Test Example 3: Study on the Sensing Performance of pH Sensor

[0092] Figure 9 The OCP-time curves of the pH sensor in commercial standard buffer solutions with different pH values ​​are shown, ranging from 4 to 8. In addition, this experiment shows that the sensor has good reversibility in the pH range of 4 to 8. Figure 10 As shown in Figure 2, the sensor exhibited a good linear response with a sensitivity of -67.8 mV / pH and a high regression coefficient (R 2 =0.995), which is superior to existing pH sensors.

[0093] The prepared pH sensor was sensitive to other ions including glucose and lactate, AA, UA, DA, Mg 2+ , Ca 2+ 、Na + and K + ) in the presence of selectivity such as Figure 11 The pH sensor showed no significant response to other interfering ions and maintained a good response even after the addition of the interfering ions. These experimental results demonstrate that the PANI / -OS / PES-LIG sensor can effectively achieve both electron conduction and pH response.

[0094] like Figure 12 As shown in the figure, the sensor was attached to the wall of a tube with a diameter of 2 cm and subjected to multiple bending tests. The results showed that the sensor performance changed very little. Compared with the original current, the maximum loss current did not exceed 5%, indicating that it can effectively cope with the deformation caused by human movement.

[0095] Test Example 4: Current response test of different substrates

[0096] This test example is a CV test. The electrodes obtained in Example 1 and Comparative Examples 1-2 were placed in a 5 mM [Fe(CN)6]3- / 4- CV measurements of redox probes were performed in 0.1 M KCl.

[0097] The test results are as follows Figure 13 As shown, among the three substrates, the response current of the PES substrate is the largest.

[0098] Test Example 5 Current Response Test of Different Doping Materials

[0099] Then, the electrodes obtained in Example 1 and Comparative Examples 3-5 were subjected to CV tests. 3- / 4- Redox probe in 0.1 M KCl solution.

[0100] The test results are as follows Figure 14 As shown, it is a test comparison chart of different doping materials. The current in the figure shows that compared with SLS, the current response of soy protein isolate, chitosan, and λ-carrageenan does not exceed that of the SLS modified electrode.

[0101] Test Example 6 Optimization of SLS doping amount

[0102] The substrate was determined to be PES-LIG, the doping material was SLS, and three contents were selected for optimization. CV tests were performed on the electrodes of Examples 1 to 3 and Comparative Example 6. In the presence of 5 mM [Fe(CN)6] 3- / 4- Redox probe in 0.1 M KCl solution.

[0103] The results are as follows Figure 15 As shown, the SLS concentrations are 0 g, 1.5 g, 3.0 g, and 4.5 g, respectively. When the SLS doping content is 3.0 g, the current response is the largest.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. 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 method for preparing a flexible lactic acid and pH dual-function sensor, characterized in that: The following steps are involved: (1) coating a mixed slurry of hydroxyethyl cellulose and sodium lignin sulfonate on a polyethersulfone film, and engraving the polyethersulfone film using a CO2 laser to obtain an -OS / PES-LIG electrode, wherein the -OS / PES-LIG electrode comprises a first functional region and a second functional region; (2) modifying the first functional region with polyaniline and modifying the second functional region with an enzyme immobilization layer consisting of Prussian blue and lactate oxidase; (3) setting a reference electrode in the peripheral area of ​​the first functional area and the second functional area of ​​the -OS / PES-LIG electrode, and drop-coating a conductive slurry; In the mixed slurry of step (1), the mass ratio of hydroxyethyl cellulose to sodium lignin sulfonate is 1:(12-36); The second functional region modification step comprises: Cyclic voltammetry was used to electrodeposit Prussian blue, followed by drop coating of a mixed solution containing chitosan, lactate oxidase, and bovine serum albumin to cover the perfluorinated resin membrane. 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.

2. 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 length of 1-5 mm.

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

4. The preparation method according to claim 1, characterized in that The specific steps of modifying the first functional region include: The -OS / PES-LIG electrode was immersed in a mixed solution containing aniline and sulfuric acid, and a polyaniline layer was formed by electrodeposition via cyclic voltammetry.

5. The preparation method according to claim 4, characterized in that In the mixed solution, the concentration of aniline is 0.1-1.5M, and the concentration of sulfuric acid is 1.0-5.0M.

6. A flexible lactic acid and pH dual-function sensor, characterized in that: Obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the flexible lactate and pH dual-function sensor according to claim 6 in any of the following: (1) Application in the preparation of products for detecting lactic acid concentration; (2) Application in the preparation of products for pH detection; (3) Application in the preparation of products for simultaneous detection of lactic acid concentration and pH.

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