CN114397344A

CN114397344A - Single-wall carbon nanotube-based flexible electrode array, wearable sensor and sweat in-situ monitoring method thereof

Info

Publication number: CN114397344A
Application number: CN202210014662.9A
Authority: CN
Inventors: 刘志洪; 郝俊兴; 朱泽强
Original assignee: Hubei University
Current assignee: Hubei University
Priority date: 2022-01-07
Filing date: 2022-01-07
Publication date: 2022-04-26

Abstract

The invention discloses a single-walled carbon nanotube-based flexible electrode array, an intelligent wearable sensor and application of the intelligent wearable sensor in-situ sweat analysis. The SWCNTs conductive layer is selectively deposited in an electrode array area of a template filter membrane by using a high-dispersity SWCNTs solution as a raw material in a vacuum filtration mode, and a high-precision SWCNTs-based flexible electrode array can be rapidly prepared in batches by PDMS transfer printing; the flexible electrode array is further integrated with a signal acquisition and processing circuit system after being functionalized, the processed sensing signals are transmitted to a display module (such as a mobile phone APP), so that the acquisition amount is intelligently read, the real-time presentation of the concentrations of various target objects is realized, and the flexible electrode array has wide application prospects in the field of intelligent electrochemical in-situ monitoring.

Description

Single-wall carbon nanotube-based flexible electrode array, wearable sensor and sweat in-situ monitoring method thereof

Technical Field

The invention belongs to the technical field of intelligent wearable equipment, and particularly relates to a single-wall carbon nanotube-based flexible electrode array, an intelligent wearable sensor and application of the intelligent wearable sensor in-situ sweat analysis.

Background

To date, advanced wearable sensors that can be worn on human skin to continuously and sensitively monitor human physiological signals without interfering with or limiting the wearer's daily activities have received much attention in the field of smart medical monitoring. With the rapid development of wearable physical sensors for tracking human body vital signs (temperature, blood pressure, pulse, heart rate, etc.) in real time in the commercial field, wearable chemical sensors providing personal health information based on molecular level are also developing. Among them, wearable electrochemical sensors have made a major breakthrough in sweat sensing, and realize non-invasive in-situ analysis of various health-related target analytes (metabolites, electrolytes, heavy metal ions, etc.) in human sweat. From the practical applicability of medical health management or motion monitoring, the flexible electrode array in the sensor should have excellent characteristics of high sensitivity, high selectivity, high uniformity, low cost and the like. At present, the reported methods for preparing flexible electrode arrays mainly include photolithography (Nature 2016,529, 509-. Therefore, the development of simple, efficient, and economical methods for the fabrication of flexible electrode arrays remains an urgent need for commercial applications of wearable sweat sensors.

Disclosure of Invention

The invention aims to solve the technical problem of providing a simple, efficient and low-cost batch preparation method of a single-walled carbon nanotube-based flexible electrode array aiming at the defects in the prior art, and further integrating with a signal acquisition and processing system and the like to construct an intelligent wearable sensor so as to realize multi-path, continuous and in-situ sweat analysis.

The technical scheme adopted by the invention for solving the problems is as follows:

the single-walled carbon nanotube (SWCNTs) based flexible electrode array comprises an upper layer and a lower layer which are respectively a conductive layer and a flexible substrate layer; the flexible substrate layer is Polydimethylsiloxane (PDMS); the conductive layer is SWCNTs uniformly modified by Pt nano particles. Further, the conductive layer is a patterned electrode array conductive layer.

The preparation method of the single-wall carbon nanotube-based flexible electrode array mainly comprises the following steps:

(1) constructing a hollowed-out electrode array pattern on a polyvinylidene fluoride (PVDF) filter membrane by utilizing the strong hydrophobicity of PDMS according to the required electrode array pattern, and taking the hollowed-out electrode array pattern as a PVDF/PDMS hollowed-out filter template; the surface of the hollow template consists of two parts, namely a hydrophilic PVDF body in an electrode array pattern area and a hydrophobic PDMS in a non-electrode array pattern area;

(2) depositing SWCNTs in an electrode array pattern area of the PVDF/PDMS hollow filtering template by adopting vacuum filtration, then uniformly spreading a flexible substrate PDMS on the surface of the SWCNTs, heating and curing, and based on an interface adhesion modulation principle, easily peeling the PVDF/PDMS hollow filtering template to obtain a SWCNTs/PDMS flexible electrode array;

(3) and uniformly depositing Pt nano particles on the SWCNTs/PDMS electrode array by adopting a constant potential deposition method to obtain the SWCNTs-Pt flexible electrode array, namely the SWCNTs-based flexible electrode array.

According to the scheme, the step (1) is specifically as follows: uniformly mixing a PDMS monomer and a polymerization agent (the mass ratio is 10:1) to obtain a hydrophobic PDMS inkpad; designing an electrode array pattern through drawing software such as Potoshop and the like, and printing the electrode array pattern on parchment paper to prepare an electrode array mask; thirdly, the photosensitive stamp pad, the PET transparent film and the electrode array mask are sequentially placed on a glass panel of the exposure box (the electrode array mask is printed face down), then the photosensitive stamp pad is placed in a photosensitive stamp machine for exposure, and the PET transparent film and the electrode array mask are removed, so that an electrode array pattern can be constructed on the photosensitive stamp pad, and the electrode array patterned photosensitive stamp is manufactured; and fourthly, placing the patterned photosensitive stamp in the inkpad in the step I to be absorbed to a saturated state, then placing the stamp on the PVDF filter membrane for pressing, transferring the electrode array pattern (namely the hydrophobic hollow pattern of the PDMS) to the surface of the PVDF filter membrane, and further heating and curing to obtain the PVDF/PDMS hollow filtering template with the hydrophilic/hydrophobic interface.

According to the scheme, the step (2) is specifically as follows: preparing a mixture dispersion liquid of Sodium Dodecyl Sulfate (SDS) -SWCNTs, and preparing the SDS-SWCNTs mixture dispersion liquid by using ultrapure water as a solvent; secondly, placing the PVDF/PDMS hollow filtering template in a stainless steel vacuum filtering device, then pouring a certain volume of SDS-SWCNTs mixture dispersion liquid, realizing selective deposition of SWCNTs in the hydrophilic electrode array pattern area on the surface of the template through vacuum filtration, and finally washing off the SWCNTs by using ultrapure waterDrying redundant SDS to obtain a patterned SWCNTs electrode array; uniformly spreading flexible substrate PDMS on the pattern part of the SWCNTs electrode array, heating and curing, and finally stripping the template to obtain the SWCNTs/PDMS electrode array with flexibility and tensile property. Wherein the spreading dosage of the flexible substrate PDMS is 0.2-0.5g/cm²。

According to the scheme, the step (3) is specifically as follows: placing the SWCNTs/PDMS electrode array in H₂PtCl₆In the HCl solution, Pt nano particles are uniformly modified on the surfaces of the SWCNTs by a constant potential deposition method, and the SWCNTs-based flexible electrode array is prepared after the SWCNTs are washed by ultrapure water and dried. Wherein H₂PtCl₆The pH of the HCl solution of (1-4), H₂PtCl₆The concentration is 2-8mM, the applied potential of electrodeposition is-0.4-0V (vs Ag/AgCl), and the electrodeposition time is 2-8 min.

On the basis of the SWCNTs-based flexible electrode array, by selecting different areas for functional modification, a multifunctional electrochemical sensor can be prepared to serve as a sensing array of a wearable sensor; electrochemical sensors include sweat metabolite sensors (e.g., glucose, lactate sensors) and electrolyte sensors (e.g., Na)⁺，K⁺A sensor). The preparation method of each electrochemical sensor is as follows:

(1) the preparation method of the glucose sensor comprises the following steps: a first working electrode area is selected on the surface of the SWCNTs-based flexible electrode array, the first working electrode area is placed in a Prussian Blue (PB) precursor solution for constant potential deposition of a PB layer, after drying, a mixture of glucose oxidase/chitosan/multi-walled carbon nanotubes (GOx/Chi/SWCNTs) is further dripped on the PB layer for modification, and a glucose sensor is obtained after drying. Further, the specific preparation steps of the glucose sensor are as follows: firstly, selecting a first working electrode area on the surface of the SWCNTs-based flexible electrode array, placing the first working electrode area in a prepared PB precursor solution, uniformly modifying the surface of SWCNTs-Pt with a thin PB layer by adopting a constant potential deposition method, washing with ultra-pure water and drying to obtain a SWCNTs-Pt-PB working electrode; wherein the prepared PB precursor solution is 1-5mM FeCl₃、1-5mM K₃[Fe(CN)₆]0.05-0.25M KCl and 0.05-0.25M HCl, wherein the applied potential of the electrodeposition is 0-0.6V (vs Ag/AgCl), and the electrodeposition time is 50-200 s; ② dissolving chitosan (Chi) by 2 percent acetic acid to prepare Chi solution with the mass fraction of 0.1-0.5 percent, and then adding SWCNTs (0.5-5mg mL)^-1) Performing ultrasonic treatment, and preparing a Chi/SWCNTs mixture; ③ mixing the Chi/SWCNTs mixture in the step (II) with 2-8mg mL^-1The GOx solution is fully and uniformly mixed according to the volume ratio of 1:1 to prepare a GOx/Chi/SWCNTs mixture; dripping and coating the modified GOx/Chi/SWCNTs mixture (0.8-0.9 mu L mm) on the surface of the SWCNTs-Pt-PB working electrode^-2) And drying to obtain the glucose sensor, and storing at 2-8 ℃ for later use.

(2) The preparation method of the lactic acid sensor comprises the following steps: selecting a second working electrode area on the surface of the SWCNTs-based flexible electrode array, placing the second working electrode area in Prussian Blue (PB) precursor solution for constant potential deposition of a PB layer, drying, sequentially dripping a Chi/SWCNTs mixture (the same as the Chi/SWCNTs mixture in the glucose sensor preparation method), a lactate oxidase (LOx) solution and the Chi/SWCNTs mixture on the surface of the PB layer, and drying to obtain the lactic acid sensor. Further, the specific preparation steps of the lactate sensor are as follows: selecting a second working electrode area on the surface of the SWCNTs-based flexible electrode array, placing the second working electrode area in a prepared PB precursor solution, uniformly modifying the surface of SWCNTs-Pt with a thick PB layer by adopting a constant potential deposition method, washing with ultrapure water and drying to obtain a SWCNTs-Pt-PB working electrode; wherein the applied potential of the electrodeposition is 0-0.6V (vs Ag/AgCl), and the electrodeposition time is 300-600 s; secondly, sequentially dripping and coating a Chi/SWCNTs mixture (0.3-0.5 mu L mm) on the surface of the SWCNTs-Pt-PB working electrode^-2)、2mg mL^-1LOx solution (0.8-0.9. mu.L mm) of (C)^-2) Chi/SWCNTs mixture (0.3-0.5. mu.L mm)^-2) And drying to obtain the lactic acid sensor, and storing at 2-8 ℃ for later use.

(3)Na⁺The preparation method of the sensor comprises the following steps: selecting a third working electrode area on the surface of the SWCNTs-based flexible electrode array, and modifying a layer of poly (3, 4-ethylenedioxythiophene) (PEDOT) film by a constant current polymerization method to obtain a SWCNTs-Pt-PEDOT-based working electrode;further dropping and coating modified Na on the surface⁺After selective membrane, Na is obtained⁺A sensor. Further, the Na⁺The specific preparation steps of the sensor are as follows: firstly, selecting a third working electrode area on the surface of the SWCNTs-based flexible electrode array, placing the third working electrode area in a prepared PEDOT precursor solution, uniformly modifying a PEDOT film on the surface of SWCNTs-Pt by adopting a constant current polymerization method, washing with ultrapure water and drying to obtain the SWCNTs-Pt-PEDOT working electrode; wherein the prepared PEDOT precursor solution is a mixed solution of 0.01-0.05M of 3, 4-Ethylenedioxythiophene (EDOT) and 0.1-0.5M of sodium polystyrene sulfonate (NaPSS), and the current density is 0.1-0.5mA cm^-2；②Na⁺The selective membrane mixture is composed of Na⁺Ion carrier X, ion exchanger Na-TFPB, polymer matrix PVC and plasticizer DOS, the mass percentages are 1%, 0.55%, 33% and 65.45%, then 50-300mg Na⁺The selective membrane mixture is completely dissolved in 1-4mL tetrahydrofuran, and sealed for storage, i.e. Na⁺A selective membrane mixture; thirdly, dropping and coating modified Na on the surface of the SWCNTs-Pt-PEDOT working electrode⁺Selective Membrane mixture solution (0.8-0.9. mu.L mm^-2) Drying to obtain Na⁺And the sensor is stored for later use under the conditions of constant temperature and constant humidity.

(4)K⁺The preparation method of the sensor comprises the following steps: selecting a fourth working electrode area on the surface of the SWCNTs-based flexible electrode array, and modifying a PEDOT film, namely a SWCNTs-Pt-PEDOT-based working electrode, by a constant current polymerization method; further dropping and coating a decoration K on the surface⁺After selective membrane, K is obtained⁺A sensor. Further, K is⁺The specific preparation steps of the sensor are as follows: firstly, preparing a SWCNTs-Pt-PEDOT working electrode; ② K⁺The selective membrane mixture is composed of K⁺Ion carrier (valinomycin), ion exchanger Na-TPB, polymer matrix PVC and plasticizer DOS, the mass ratio is 2%, 0.5%, 32.8% and 64.7%, K is 50-300mg⁺The selective membrane mixture is completely dissolved in 0.5-2mL of cyclohexanone and then is sealed and stored for standby, namely K⁺A selective membrane mixture; thirdly, dropping and coating the modified K on the surface of the SWCNTs-Pt-PEDOT working electrode⁺Selective Membrane mixture solution (0.5-0.65. mu.L mm^-2) And drying to obtain K⁺And the sensor is stored for later use under the conditions of constant temperature and constant humidity.

It is further noted that the two-electrode system is a general strategy for high-sensitivity electrochemical sensors. Therefore, when amperometric glucose sensors and lactate sensors are used as working electrodes, a reference electrode (defined as: first reference electrode) is also required; when the glucose sensor and the lactic acid sensor are used independently, reference electrodes are respectively adopted; when both are used together, one reference electrode may be used in common or two reference electrodes may be used separately. Likewise, potential form K⁺Sensor and Na⁺When the sensor is used as a working electrode, a reference electrode (defined as: a second reference electrode) is also required; k⁺Sensor and Na⁺When the sensor is used independently, reference electrodes are adopted respectively; when both are used together, one reference electrode may be used in common or two reference electrodes may be used separately.

The preparation method of the first reference electrode comprises the following steps: a first reference electrode area is selected on the surface of the SWCNTs-based flexible electrode array, and modified Ag/AgCl slurry (0.6-0.8 mu L mm) is dripped^-2) And drying to obtain the first reference electrode.

The preparation method of the second reference electrode comprises the following steps: selecting a second reference electrode area on the surface of the SWCNTs-based flexible electrode array, and dripping modified Ag/AgCl slurry (1.2-1.6 mu L mm)^-2) Drying, and then dripping and coating a modified PVB-based stabilizer (0.6-0.8 mu L mm)^-2) Preparing a second reference electrode; the PVB-based stabilizing solution is prepared by dissolving 79.1mg of PVB, 50mg of NaCl, 2mg of F127 and 0.2mg of MWCNTs in 0.5-4mL of methanol and is used for reducing potential drift.

On the basis of the SWCNTs-based flexible electrode array and the functionalized electrochemical sensor, the invention also provides an intelligent wearable sensor which comprises an electrode sensing array, a signal acquisition and processing circuit module, a power supply module and a display module; the electrode sensing array is contacted with an absorption layer (water-absorbing sponge or sweat-absorbing paste, microfluidic chip, etc.) for collecting sweat in real time, and the electrode sensing array is connected with the absorption layerThe sensing array, the signal acquisition and processing circuit module and the display module are electrically connected with the power supply module; the sensing array includes a first working electrode (i.e., glucose sensor), a second working electrode (i.e., lactate sensor), and a third working electrode (i.e., Na)⁺Sensor) and a fourth working electrode (K)⁺Sensor) including one or both of a first reference electrode and a second reference electrode; each electrode is electrically connected with the signal acquisition and processing circuit module in a parallel connection mode, and can monitor glucose, lactic acid and Na in sweat⁺Or K⁺One or more of these targets, producing an electrical signal; the signal acquisition and processing circuit module amplifies and filters the electric signals (current or voltage) of the electrode sensing array and outputs the electric signals as voltage signals; finally, the output voltage is mixed with glucose, lactic acid and Na in sweat⁺Or K⁺The linear relation of the concentration is used for subsequent data processing, and finally the glucose, the lactic acid and the Na in the sweat are obtained⁺Or K⁺And outputting the concentration to a display module.

According to the scheme, the detection sample of the intelligent wearable sensor is not limited to sweat, and is also suitable for biological samples such as urine, saliva, tears and the like.

Compared with the prior art, the invention has the beneficial effects that:

(1) the SWCNTs conductive layer is selectively deposited in an electrode array area of a template filter membrane by using a high-dispersity SWCNTs solution as a raw material in a vacuum filtration mode, and a high-precision SWCNTs-based flexible electrode array can be economically, rapidly and in batches prepared by PDMS transfer printing; the hollow template filtering and transfer printing strategy is novel in concept, an external fixed geometric template (such as a reported viscous PVC template or a reported rigid plastic template) is not needed, the preparation device and the preparation process are simple, the utilization rate of materials is up to 100%, the preparation cost is low, and the patterns of the flexible electrode array can be designed in a personalized and independent mode.

(2) The flexible electrode array prepared by the invention has the characteristics of easy modification or functionalization, controllable thickness, high uniformity and flexibility, excellent conductivity and mechanical stretchability and the like, and has wide application prospects in the fields of electrochemical sensors, flexible electronic devices and the like;

(3) the functional flexible electrode array prepared by the invention can be further integrated with a signal acquisition and processing circuit system, can realize intelligent reading of acquisition quantity of sensing signals through a conversion algorithm, wirelessly transmits the sensing signals to a user side (such as a mobile phone APP) through a Bluetooth module, and displays the concentration of various target objects in real time in the form of the mobile phone APP, so that in-situ, real-time and continuous monitoring of various target analytes in sweat in the process of human motion is realized, the sensitivity is high, the accuracy is good, and the invention has wide application prospect in the field of intelligent electrochemical in-situ monitoring.

Drawings

Fig. 1 is a preparation process (a) of SWCNTs-based flexible electrode array, a physical diagram (B) of a smart wearable sweat sensor, and a schematic diagram (C) of a sensing array for multi-channel sweat in-situ analysis.

Fig. 2 is a patterned ps (a) imbibed with PDMS; a PDMS/PVDF hollow filtering template (B); SWCNTs/PVDF-based electrode array (C); a SWCNTs-based flexible electrode array (D); (E, F) SWCNTs based school logos and butterfly patterns (E, F); resolution (G) of different line widths; SWCNTs-based electronic circuit (H).

FIG. 3 is SEM (A, B) and TEM (C, D) characterization of patterned SWCNTs electrode arrays (A, C) and SWCNTs-Pt flexible electrode arrays (B, D) in the examples.

FIG. 4 is SEM (A, B), TEM (C, D), EDX (E, F) characterization of SWCNTs-Pt-PB (A, C, E) and SWCNTs-Pt-PEDOT (B, D, F) in the examples; raman (G), XPS (H) and XRD (I) characterization of SWCNTs electrode arrays, SWCNTs-Pt flexible electrode arrays, SWCNTs-Pt-PB working electrodes and SWCNTs-Pt-PEDOT working electrodes.

FIG. 5 shows the cyclic voltammetry (A), AC impedance (B), electrochemical surface area (C) and comparison of the results for SWCNTs electrode array (I), SWCNTs-Pt flexible electrode array (II), SWCNTs-Pt-PEDOT working electrode (III) and SWCNTs-Pt-PB working electrode (IV) in the examples.

FIG. 6 shows four sensors (glucose, lactate, Na) at different analyte concentrations in the example⁺And K⁺) The sensing performance of (1).

FIG. 7 shows four sensors (glucose, lactate, Na) in the example⁺And K⁺) Selective testing of (2).

FIG. 8 shows four sensors (glucose, lactate, Na) in the example⁺And K⁺) The repeatability of (2).

FIG. 9 shows four sensors (glucose, lactate, Na) in the example⁺And K⁺) Storage life test of (2).

FIG. 10 shows four sensors (glucose, lactate, Na) in the example⁺And K⁺) Mechanical stability test of (2).

Fig. 11 is a workflow diagram of a smart wearable sensor for sweat detection in situ.

Fig. 12 is a customized handset APP for data display and analysis.

Fig. 13 is a smart wearable sensor for multiplexed in situ sweat analysis.

Detailed Description

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

In the following examples, the enzyme-based sensor and various stock solutions were stored in a refrigerator at 4 ℃ before and after use.

In the following examples, PDMS monomers and polymerizers are used, commercially available from Dow Corning Inc. (Sylgard 184).

Examples

(1) Preparation of PVDF/PDMS hollow filtering template

(a) Weighing 4g (mass ratio of 10:1) of commercially available PDMS monomer and polymerization agent, placing in a plastic culture dish, stirring with a glass rod to disperse uniformly (a large amount of bubbles are released during the polymerization process), removing bubbles with a vacuum pump to obtain PDMS inkpad, and storing in a refrigerator (4 deg.C).

(b) First, an electrode array pattern (in which the diameter of the working electrode is 3mm) was drawn by software such as Potoshop, and the electrode array pattern was printed on a parchment paper by a Hewlett packard laser printer (M1005,1200X 600dpi) to obtain an electrode array mask. Subsequently, the photosensitive stamp pad, the PET transparent film, and the electrode array mask were sequentially placed on the glass panel of the exposure cassette (electrode array mask printing side down), and then the exposure cassette was tightly pressed and closed with a handle. And finally, placing the exposure box in a photosensitive seal machine, and once exposing by strong light emitted by a built-in xenon lamp, so that an electrode array or a patterned Photosensitive Seal (PS) can be constructed on the photosensitive seal pad, wherein the bright black area of the PS is closed, and the gray unsealed area can store PDMS (polydimethylsiloxane) "inkpad", so that the electrode array or the pattern can be transferred to a target substrate during imprinting.

(c) The patterned PS was placed in a hydrophobic PDMS "stamp" for 15min of absorption (with the PS patterned side facing the PDMS, the PS could spontaneously absorb the PDMS to saturation due to capillary action). Then, a press is used to apply a certain pressure to the patterned Ps (PDMS) to transfer the hollow pattern of the PDMS onto the surface of the PVDF filter membrane. And finally, curing the PDMS patterned PVDF filter membrane at 80 ℃ for 2h to obtain the PVDF/PDMS hollow filtering template.

(2) Preparation of SWCNTs-based flexible electrode array

Preparation of SWCNTs dispersion: under the condition of room temperature, 60mg of SWCNTs are placed in 5mM 500mL of Sodium Dodecyl Sulfate (SDS) surfactant aqueous solution, and ultrasonic dispersion is carried out for 2h (regular uniform stirring is required); after the ultrasonic dispersion was allowed to stand for 2 days, the upper layer of stably dispersed SWCNTs solution was collected for further use (about 0.06mg mL)^-1)。

Preparing the SWCNTs/PDMS-based electrode array by vacuum filtration and transfer printing of the SWCNTs electrode array: firstly, placing a patterned PVDF/PDMS hollow filtering template in an ethanol solution for soaking for 5min, then washing and replacing ethanol with a large amount of secondary water, and soaking the template in the secondary water for 20min to maintain the hydrophilic capacity of the filter membrane in the area not sealed by PDMS. Subsequently, 5mL of the SWCNTs dispersion solution was diluted to 50mL of the twoAnd (2) after the treatment of the secondary water for 10min by ultrasonic treatment, pouring the diluted SWCNTs dispersion liquid into a stainless steel vacuum filter device assembled with a patterned PVDF/PDMS hollow filter template at a constant speed, so that a patterned SWCNTs electrode array can be selectively deposited in a specific area on the surface of a template filter membrane, washing off redundant surfactant SDS by using a large amount of secondary water, and drying at 60 ℃ for 30min for later use. Next, a flexible substrate PDMS (0.33g cm) was spread evenly over the surface of the patterned SWCNTs electrode array^-2) And then curing the PVDF/PDMS hollow filtering template for 2 hours at 80 ℃ to completely strip the PVDF/PDMS hollow filtering template, so as to obtain the SWCNTs/PDMS-based electrode array with flexibility and tensile properties.

Preparation of SWCNTs-Pt flexible electrode array (i.e., SWCNTs-based flexible electrode array): placing the SWCNTs/PDMS-based electrode array in a medium containing 5mM H₂PtCl₆Uniformly modifying Pt nanoparticles on the surface of SWCNTs (SWCNTs-Pt) by a constant potential deposition method through-0.1V potential deposition for 5min in 0.1M HCl solution, washing with secondary water, and drying at 60 ℃ for 30min for later use.

FIG. 1A shows that a hydrophobic PDMS electrode array pattern is constructed on the surface of a PVDF filter membrane, and the SWCNTs are arrayed and deposited by vacuum filtration, and then a customized SWCNTs-based flexible electrode array can be prepared by a PDMS transfer strategy based on an interface adhesion modulation principle; fig. 1B and C show that the intelligent wearable sensor is constructed by integrating the functionalized SWCNTs-based flexible electrode array and the signal acquisition and processing circuit system, so as to realize sweat glucose, lactic acid and Na in the process of human body movement⁺And K⁺In-situ, real-time, continuous monitoring.

FIGS. 2A, B show that the patterned PS can sufficiently absorb the hydrophobic PDMS "inkpad" and accurately imprint the electrode array pattern onto the PVDF filter membrane by pressing; FIG. 2C and D show that the diluted SWCNTs dispersion can be selectively deposited on the hydrophilic region of PDMS/PVDF to form a patterned SWCNTs electrode array, and then the SWCNTs/PDMS flexible electrode array is obtained by a transfer printing strategy; fig. 2E, F show that the preparation strategy of the SWCNTs/PDMS flexible electrode array can also be used to prepare more fine and complex patterns (school badge and butterfly); fig. 2G and H show that the method for preparing the SWCNTs/PDMS flexible electrode array can control the line width resolution of the deposited SWCNTs conductive layer to be as low as 50 μm, and in addition, the electronic circuit deposited by the method is connected to a green LED bulb, and can emit light after being electrified, which indicates that the deposited SWCNTs conductive layer has good conductivity.

FIGS. 3A and C show that SWCNTs in the SWCNTs electrode array have a diameter of 50nm, and exhibit a 3D wound nanofiber network structure; fig. 3B, D shows that a large number of quasi-spherical nano Pt particles of size-200 nm are tightly anchored to the surface of SWCNTs after electrodeposition of Pt.

FIGS. 4A, C show a large number of PB cubic nanostructures (Fe) with size 50nm₄[Fe(CN)₆)₃]) Completely filling gaps of the SWCNTs nanofiber network structure, and in addition, tightly fixing the gaps on the surface of Pt nanoparticles to form a 3D interwoven SWCNTs-Pt-PB composite material; FIG. 4B and D show that a layer of PEDOT dense film with a thickness of 15nm completely covers the gaps of SWCNTs and the surface of nano Pt to form a SWCNTs-Pt-PEDOT composite material with a 3D heterostructure; FIG. 4E, F shows that the elements C, Pt, Fe and S in the characterization of energy dispersive X-ray (EDX) are uniformly distributed, corresponding to SWCNTs, Pt, PB and PEDOT, respectively, and the successful preparation of SWCNTs-Pt-PB and SWCNTs-Pt-PEDOT composite materials on the working electrode is proved; FIGS. 4G-I show that Raman, photoelectron spectroscopy and physical characterization results of X-ray diffraction further confirm that Pt, PB and PEDOT successfully modify the surface of SWCNTs.

FIG. 5A shows the anode-to-cathode peak potential difference (Δ E) for the working electrodes SWCNTs-Pt-PEDOT and SWCNTs-Pt-PB in Cyclic Voltammetry (CV) testing_p) Smaller and oxidation peak current (I)_pa) Larger, demonstrating their greater electron transfer capability; FIG. 5B shows the charge transfer resistance (R) of the working electrodes SWCNTs-Pt-PEDOT and SWCNTs-Pt-PB in an alternating current impedance (EIS) test_ct) Smaller, demonstrating their greater charge transfer capability; FIG. 5C shows the double layer capacitance (C) of the working electrodes SWCNTs-Pt-PEDOT and SWCNTs-Pt-PB in the electrochemical surface area (ECSA) test_dl) Smaller, demonstrating that they have more active sitesPoint and higher electrochemical activity; FIG. 5D shows that the above CV, EIS and ECSA results are consistent.

As shown in fig. 1C, on the prepared SWCNTs-Pt flexible electrode array, areas of the first to fourth working electrodes and the first and second reference electrodes were respectively selected, and the working electrodes and the reference electrodes were both circular with a diameter of 3 mm; subsequently, a glucose sensor is prepared in the first working electrode area and used as a first working electrode of a multi-path wearable sensor for in-situ sweat detection; respectively preparing a lactic acid sensor and Na in a second working electrode area, a third working electrode area and a fourth working electrode area⁺Sensor and K⁺The sensor is used as a second working electrode, a third working electrode and a fourth working electrode; first and second reference electrodes are prepared in the first and second reference electrode areas. Subsequently, the first and second working electrodes share the first reference electrode, and the third and fourth working electrodes share the second reference electrode.

(3) Preparation of glucose and lactate sensors

Firstly, Chi is dissolved in 2% acetic acid solution and magnetically stirred for 1h to prepare 0.5% Chi solution, and then SWCNTs is added for ultrasonic treatment for 30min to prepare the solution containing 2mg mL^-1Chi solution of SWCNTs (i.e., Chi/SWCNTs solution). Furthermore, Chi/SWCNTs solution was mixed with 5mg mL^-1The GOx solution is fully and uniformly mixed according to the volume ratio of 1:1 to prepare an enzyme-based stock solution (GOx/Chi/SWCNTs mixed solution) of the glucose sensor.

The glucose sensor was prepared as follows: place the first working electrode area of the SWCNTs-Pt flexible electrode array in a freshly prepared solution containing 2.5mM FeCl₃、2.5mM K₃[Fe(CN)₆]Applying 0.4V (vs. Ag/AgCl) in a solution of 0.1M KCl and 0.1M HCl for electrodeposition for 100s to modify a thin PB layer on the surface of the SWCNTs-Pt flexible electrode array to prepare the SWCNTs-Pt-PB working electrode (the thin PB layer has more excellent sensitivity to the detection of low-content glucose in sweat); and then, dripping and modifying the 6 mu L GOx/Chi/SWCNTs mixed liquid to the surface of the SWCNTs-Pt-PB working electrode, and airing to obtain the glucose sensor, namely the first working electrode.

The preparation process of the lactic acid sensor is as follows: SWCNTs-Pt softThe second working electrode area of the sex electrode array was placed in a freshly prepared solution containing 2.5mM FeCl₃、2.5mM K₃[Fe(CN)₆]Applying 0.4V (vs. Ag/AgCl) in a solution of 0.1M KCl and 0.1M HCl for electrodeposition for 480s to modify a thick PB layer on the surface of the SWCNTs-Pt flexible electrode array to prepare the SWCNTs-Pt-PB working electrode (the thick PB layer has a wider linear range for detecting lactic acid in sweat); then, the 3 mu L Chi/SWCNTs solution is dripped and modified to the surface of the SWCNTs-Pt-PB working electrode to be dried under the condition of room temperature, and then 6 mu L2 mg mL of solution is dripped and modified successively^-1And drying the LOx solution and 3 mu L of Chi/SWCNTs solution to obtain the lactic acid sensor, namely a second working electrode.

For amperometric glucose and lactate sensors, the Ag/AgCl electrode serves as both a reference electrode and a counter electrode, i.e., the first reference electrode. The preparation process comprises the following steps: and (3) dripping and coating a modified commercial Ag/AgCl slurry on the first reference electrode area of the SWCNTs-Pt flexible electrode array, and drying to obtain the first reference electrode.

(4)Na⁺Sensor and K⁺Preparation of the sensor

The third working electrode region of the SWCNTs-Pt flexible electrode array was placed in a mixed solution containing 0.01M EDOT and 0.1M NaPSS by constant current polymerization (current density 0.2mA cm)^-2With a polymer charge of 10mC and a reference electrode of Ag/AgCl) to produce a SWCNTs-Pt-PEDOT working electrode.

Na⁺The selective membrane mixture is composed of Na⁺Ion carrier X, ion exchanger Na-TFPB, polymer matrix PVC and plasticizer DOS, the mass ratio is 1%, 0.55%, 33% and 65.45%, 200mg Na⁺After the selective membrane mixture was completely dissolved in 1.32mL of tetrahydrofuran, it was stored in a sealed state for further use, i.e., Na⁺Selective membrane mixture solution.

Furthermore, K⁺The selective membrane mixture is composed of K⁺Ion carrier (valinomycin), ion exchanger Na-TPB, polymer matrix PVC and plasticizer DOS, wherein the mass ratio is 2%, 0.5%, 32.8% and 64.7%, respectively, and K is 200mg⁺After the selective membrane mixture is completely dissolved in 0.7mL of cyclohexanone, the mixture is sealed and protectedFor storage, i.e. K⁺Selective membrane mixture solution.

Subsequently, 6. mu.L of Na was dropped on each of the SWCNTs-Pt-PEDOT working electrodes⁺Selective Membrane mixture solution and 4. mu.L of K⁺Selective membrane mixture solution, dried and prepared Na respectively⁺Sensor and K⁺The sensors, i.e. the third and fourth working electrodes.

For potential form Na⁺And K⁺The sensor, the common second reference electrode, was prepared as follows: and (3) dripping and modifying commercial Ag/AgCl slurry on a second reference electrode area of the SWCNTs-Pt flexible electrode array, drying, further dripping and modifying 10 mu L of PVB-based reference electrode stabilizer on the surface of the Ag/AgCl reference electrode, and drying to obtain the second reference electrode. The PVB-based reference electrode stabilizer can further reduce potential drift, and the specific preparation method comprises the following steps: 79.1mg PVB, 50mg NaCl, 2mg F127 and 0.2mg SMWCNTs were dissolved in 1mL methanol.

And (4) placing the third working electrode and the fourth working electrode under the conditions of constant temperature and constant humidity, and airing for later use. To further reduce the potential drift of the third and fourth working electrodes, incubation treatments were performed for 1h with 0.1M NaCl (third working electrode) and 0.01M KCl (fourth working electrode) solutions, respectively, prior to detection.

Through the process, the first working electrode, the fourth working electrode, the first reference electrode and the second reference electrode are successfully prepared on the SWCNTs-Pt flexible electrode array. As shown in fig. 1C.

FIGS. 6A, B and tables 1 and 2 show that the glucose and lactate sensors exhibit steady-state current responses in phosphate buffered saline, measured by chronoamperometry in 0-200. mu.M glucose and 5-25mM lactate solutions, respectively, wherein the glucose sensor has a sensitivity of 345.5nA mM^-1cm^-2(R²0.9978), the sensitivity of the lactate sensor was 3169nA mM^-1cm^-2(R²＝0.9985)。

FIGS. 6C, D and tables 3 and 4 show that Na is present at physiologically relevant concentrations⁺Sensor and K⁺The sensors measure open circuit potentials of 10-160mM NaCl and 1-32mM NaCl, respectively. Theoretically, ion selectivityThe electrode should follow the Nernst equation (sensitivity should be 59mV dec)^-1) In the present invention, Na⁺Sensor and K⁺The sensitivity of the sensor is very close to Nernst behavior, respectively 60mV dec^-1And 58.1mV dec^-1。

TABLE 1 correspondence of glucose concentration and response current

C_Glu(μM)	0	50	100	150	200
						I(μA)	-20.48	-21.65	-22.88	-23.97	-25.43

TABLE 2 correlation between lactate concentration and response current

C_Lac(mM)	5	10	15	20	25
						I(μA)	-18.95	-20.13	-21.09	-22.32	-23.45

TABLE 3Na⁺Correspondence between concentration and response potential

C_Na ⁺(mM)	10	20	40	80	160
						E(V)	0.2370	0.2557	0.2741	0.2922	0.3102

TABLE 4K⁺Correspondence between concentration and response potential

C_K ⁺(mM)	1	2	4	8	16	32
							E(V)	0.1875	0.2074	0.2287	0.2420	0.2618	0.2746

FIG. 7 shows that there are a large number of interferents in human sweat(UA、AA、NH₄Cl、MgCl₂And CaCl₂Etc.), even in the presence of relatively high concentrations of interferents, the individual sensors (i.e., glucose, lactate, Na)⁺And K⁺Sensor) is not substantially affected, demonstrating the glucose, lactate, Na, of the invention⁺And K⁺The sensor has good selectivity.

FIG. 8 shows glucose, lactic acid, Na⁺And K⁺Selecting 8 sensors respectively, and adding glucose, lactic acid and Na⁺And K⁺The RSD of the measurement results are 2%, 1.93%, 0.37% and 0.57% respectively by parallel measurement in the solution, and the glucose, the lactic acid and the Na of the invention are proved⁺And K⁺The sensors all have excellent reproducibility.

FIG. 9 shows that when each sensor is tested again after 1 to 2 months of standing, the current or potential response signal of each sensor is reduced by not more than 2.4% compared with the initial state, and the glucose, the lactic acid and the Na of the invention are proved⁺And K⁺The sensor has long-term stability.

FIGS. 10A-C show that, due to the inherent properties of SWCNTs and PDMS, the SWCNT-based electrode array has excellent flexibility and conformal properties in the stretched, bent, and twisted states; FIGS. 10D-G show that the current or potential response signals of the individual sensors remained essentially unchanged after different bending test cycles (radius of curvature of 2cm, 0, 20, 40 and 60 bending cycles, respectively), demonstrating that glucose, lactate, Na, according to the invention⁺And K⁺The sensor has excellent flexibility and mechanical stability.

(5) Intelligent wearable sensor

Through the above process, the first to fourth working electrodes and the first and second reference electrodes have been successfully prepared on the SWCNTs-Pt flexible electrode array, as shown in fig. 1C, and are used as a sensing array of the intelligent wearable sensor, and the four working electrodes and the two reference electrodes are all electrically connected with the signal acquisition and processing circuit system in a parallel connection manner. The intelligent wearable sensor also comprises a signal acquisition and processing circuit system, a power supply module and a display module; the electrode sensing array, the signal acquisition and processing circuit system and the display module are all electrically connected with the power module (as shown in fig. 11). The external connection wires that make the electrical connection need to be insulated to avoid electrical contact of their circuitry with the skin or perspiration that may be present.

Wherein, the electrode sensing array is contacted with a water-absorbing sponge or a sweat-absorbing patch for collecting sweat in real time, and the sensing interface is efficiently collected to the sweat through capillary action along with glucose, lactic acid and Na in the sweat⁺Or K⁺The concentration of the targets changes to generate four paths of corresponding electrochemical response signals, wherein the first working electrode and the second working electrode generate current signals, and the third working electrode and the fourth working electrode generate voltage signals; in the signal acquisition and processing circuit system, an electrochemical response signal is converted into a singlechip-readable electrochemical response signal after being processed by a voltage buffer, a differential amplifier and a fourth-order low-pass filter, then the electrochemical response signal is intelligently read by a powerful ADC (analog-to-digital converter) function of the singlechip, a read target concentration signal is wirelessly transmitted to a customized mobile phone APP through a Bluetooth module, and four targets (glucose, lactic acid and Na) are transmitted in the form of the mobile phone APP⁺Or K⁺) The concentration of (c) is presented in real time.

In the embodiment, an STM32F103C8T6 model 32-bit singlechip manufactured by Italian semiconductor corporation is selected as a control center of a processor, mainly used as an ADC functional module of STM32, and four external channels of two ADCs are used for alternately measuring 4 target analytes (glucose, lactic acid, Na⁺Or K⁺) The concentration of (c). Wherein, the Bluetooth module adopts a CC2541 chip of American Ti company; the power supply block adopts a commercial rechargeable lithium battery with the rated voltage of 5.0V, and the battery and circuit board interface adopts a common USB power supply port on the market. According to the power supply characteristic of the differential amplifier, a-5V voltage conversion module is arranged, and 5V voltage can be converted into-5V; in addition, the supply voltage of STM32 singlechip and bluetooth module is 3.3V, consequently still need be furnished with 3.3V voltage conversion module.

For the acquisition circuit, the glucose and lactate concentrations are measured based on current signals, the current response signal ratio of which is dependent on the characteristics of the respective sensorThe signal is weak, so the signal needs to be amplified and filtered. Firstly, current signals obtained by a glucose sensor and a lactic acid sensor are converted into voltage signals by using a transimpedance amplifier, the voltage signals are amplified by 50 ten thousand times, the voltage input to a Microcontroller (MCU) can reach a readable range after the signals are processed, the voltage is a negative value due to the use of the transimpedance amplifier, the negative value needs to be converted into a positive value by using the transimpedance amplifier again, finally, clutter is filtered by using a fourth-order low-pass filter circuit, and the voltage signals are led into an ADC (analog to digital converter) module of the MCU. For Na⁺Sensor and K⁺The potential range of direct output between the sensors and the reference electrode is between 0 and 3.3V, so that extra signal amplification is not needed, but signals at two input ends are converted into a signal by a differential subtraction operation circuit, then clutter is filtered by a fourth-order low-pass filter circuit, and finally the clutter is led into an ADC module to read a voltage signal value. The four signal conditioning channels described above (corresponding to the four working electrodes, respectively) exhibit good linear response with each target in sweat, as demonstrated by FIG. 6; in addition, in order to eliminate voltage offset and other non-ideal effects and obtain accurate signal readings, the original input signals are mapped to analog circuit readings by means of accurate digital linear relation between output and input, so that subsequent signal calibration and processing are allowed to be carried out at a software level, after data are processed and averaged, the data are relayed to a Bluetooth module through an MCU (microprogrammed control unit) for wireless transmission and are output to a display module such as a mobile phone APP. In addition, APP is completed on the basis of Bluetooth LeGatt (android) and LightBlue (IOS), and glucose, lactic acid and Na can be continuously read in real time⁺And K⁺The concentration value of (c).

The in-situ sweat analysis data of the smart wearable sensor is verified by ex-situ sweat analysis. The ex situ sweat analysis is realized by detecting sweat samples of arms or forehead of a volunteer, wiping and cleaning the arms or forehead of the volunteer by gauze before and after each sweat collection, and scraping the arm or forehead sweat samples by a microtube every 5min (about 0.3mL each time, 5 times in total). At the same time, adoptDetermining the concentration of glucose and lactic acid in the sweat of the volunteer by using a high performance liquid chromatography-mass spectrometer (HPLC-MS); detection of Na in sweat of volunteers by inductively coupled plasma emission spectrometer (ICP-OES)⁺And K⁺The specific experimental process refers to the national standards GB/T30986-.

Fig. 13A, B show that a volunteer wears the smart wearable sensor of the present embodiment on her wrist, then performs a continuous, real-time, in-situ sweat analysis on her during a fitness exercise, and presents the sweat analysis results in the form of a cell phone APP; FIG. 13C shows that during exercise in volunteers, the glucose content in sweat decreased gradually from 52. mu.M to 36. mu.M, while the lactate content fluctuated less, remaining essentially at around 9 mM. In addition, continuous exercise allows for Na in her sweat⁺The content was significantly increased from 40mM to 80mM, while K⁺The content was significantly reduced from 9mM to 4.5 mM.

Further, comparing the in-situ monitoring result with the non-in-situ sweat analysis test result (as shown in tables 5 to 8), it is shown that the in-situ sweat analysis result and the non-in-situ sweat analysis result of the smart wearable sensor of the present embodiment are substantially consistent, and it is proved that the smart wearable sensor of the present invention is accurate and reliable in-situ, real-time, and continuous sweat monitoring.

TABLE 5 comparison of ex situ and in situ test results for glucose in sweat

TABLE 6 comparison of ex situ and in situ test results for lactic acid in sweat

TABLE 7 Na in sweat⁺Comparison of ex situ and in situ test results

TABLE 8 sweat K⁺Comparison of ex situ and in situ test results

In addition, all consumables of the intelligent wearable sweat sensor are low in price and easy to purchase and obtain from the online or the offline. The cost price of one SWCNTs-based flexible electrode array is about 2.14 yuan, and the cost of the intelligent wearable sensor prepared on the basis can be controlled within 200 yuan (comprising four parts of the SWCNTs-based flexible electrode array, a signal acquisition and processing circuit system, a Bluetooth module and a power supply module); moreover, the SWCNTs-based flexible electrode array is convenient to replace after testing is completed, and other parts can be used for a long time.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The single-wall carbon nanotube-based flexible electrode array is characterized by comprising an upper layer and a lower layer which are respectively a conductive layer and a flexible substrate layer; the flexible substrate layer is polydimethylsiloxane; the conducting layer is a single-walled carbon nanotube uniformly modified by Pt nanoparticles, and the conducting layer is a patterned electrode array conducting layer.

2. A preparation method of a single-wall carbon nanotube-based flexible electrode array is characterized by mainly comprising the following steps:

(1) constructing an electrode array pattern on the PVDF by utilizing the hydrophobicity of PDMS (polydimethylsiloxane) on the PVDF according to the required electrode array pattern, and taking the electrode array pattern as a PVDF/PDMS hollow filtering template; the surface of the hollow template consists of two parts, namely a hydrophilic PVDF body in an electrode array pattern area and a hydrophobic PDMS in a non-electrode array pattern area;

(2) depositing single-walled carbon nanotube SWCNTs in an electrode array pattern area of the PVDF/PDMS hollow filtering template by adopting a vacuum filtering method, then uniformly spreading a flexible substrate PDMS on the surface of the SWCNTs, heating and curing, and then stripping the PVDF/PDMS hollow filtering template to obtain a SWCNTs/PDMS flexible electrode array;

3. The preparation method of the single-walled carbon nanotube-based flexible electrode array according to claim 2, wherein the step (1) is specifically divided into the following four steps: uniformly mixing a PDMS monomer and a polymerization agent to obtain a hydrophobic PDMS inkpad; secondly, printing the needed electrode array pattern on parchment paper to prepare an electrode array mask; thirdly, the photosensitive stamp pad, the PET transparent film and the electrode array mask are sequentially placed on a glass panel of the exposure box, then the photosensitive stamp pad, the PET transparent film and the electrode array mask are exposed in a photosensitive stamp machine, and then the PET transparent film and the electrode array mask are uncovered, so that an electrode array pattern can be constructed on the photosensitive stamp pad, and the electrode array patterned photosensitive stamp is manufactured; and fourthly, placing the patterned photosensitive seal in the inkpad in the step I to be absorbed to a saturated state, then placing the photosensitive seal on the PVDF filter membrane for imprinting, transferring the electrode array pattern to the surface of the PVDF filter membrane, and heating and curing to obtain the PVDF/PDMS hollow filtering template with the hydrophilic/hydrophobic interface.

4. The preparation method of the single-walled carbon nanotube-based flexible electrode array according to claim 2, wherein the step (2) is specifically divided into the following three steps: preparing a mixture dispersion liquid of Sodium Dodecyl Sulfate (SDS) and SWCNTs, and taking ultrapure water as a solvent to obtain a SDS-SWCNTs mixed dispersion liquid; placing the PVDF/PDMS hollow filtering template in a vacuum filtering device, then pouring the mixture dispersion liquid of SDS-SWCNTs, depositing SWCNTs in an electrode array pattern area on the surface of the template through vacuum filtration, washing and drying to obtain a patterned SWCNTs electrode array; and thirdly, uniformly spreading the flexible substrate PDMS in the pattern area of the SWCNTs electrode array, heating and curing, and stripping the template to obtain the SWCNTs/PDMS flexible electrode array.

5. The method for preparing the single-walled carbon nanotube-based flexible electrode array according to claim 4, wherein the spreading amount of PDMS (polydimethylsiloxane) on the flexible substrate is 0.2-0.5g/cm²。

6. The method for preparing the single-walled carbon nanotube-based flexible electrode array according to claim 2, wherein the step (3) is specifically as follows: placing the SWCNTs/PDMS flexible electrode array in H₂PtCl₆In the HCl solution, Pt nano particles are uniformly modified on the surfaces of the SWCNTs by a constant potential deposition method, and the SWCNTs-based flexible electrode array is prepared after washing and drying.

7. The method for preparing the single-walled carbon nanotube-based flexible electrode array according to claim 6, wherein H is₂PtCl₆The pH of the HCl solution of (1-4), H₂PtCl₆The concentration is 2-8mM, the applied potential of constant potential deposition is-0.4-0V, and the deposition time is 2-8 min.

8. An electrode sensing array for a wearable sensor, which is characterized in that on the basis of the single-walled carbon nanotube-based flexible electrode array of claim 1, one or more electrochemical sensors are prepared by selecting different areas for functional modification so as to identify different targets, namely, the electrode sensing array can be used as the electrode sensing array of the wearable sensor.

9. The electrode sensing array for a wearable sensor of claim 8, wherein the wearable sensor is a wearable sensor that monitors sweat; the electrochemical sensor comprises a metabolite sensor and an electrolyte sensor of sweat; the sweat metabolite sensor is a glucose sensor and a lactic acid sensor, and the sweat electrolyte sensor is a potassium ion sensor and a sodium ion sensor.

10. The electrode sensing array for the wearable sensor according to claim 9, wherein the glucose sensor is prepared by: selecting a first working electrode area on the surface of the SWCNTs-based flexible electrode array, placing the first working electrode area in a Prussian blue precursor solution for constant potential deposition of a Prussian blue layer, drying, further dropwise coating a mixture of glucose oxidase/chitosan/multi-walled carbon nanotubes on the surface of the Prussian blue layer for modification, and drying to obtain a glucose sensor;

the preparation method of the lactic acid sensor comprises the following steps: selecting a second working electrode area on the surface of the SWCNTs-based flexible electrode array, placing the second working electrode area in a Prussian blue precursor solution for constant potential deposition of a Prussian blue layer, drying, sequentially dripping a chitosan/multi-walled carbon nanotube mixture, a lactate oxidase solution and a chitosan/multi-walled carbon nanotube mixture on the surface of the Prussian blue layer, and drying to obtain the lactic acid sensor;

Na⁺the preparation method of the sensor comprises the following steps: selecting a third working electrode area on the surface of the SWCNTs-based flexible electrode array, and modifying a layer of poly (3, 4-ethylenedioxythiophene) PEDOT film by a constant current polymerization method to prepare a SWCNTs-Pt-PEDOT-based working electrode; further dropping and coating Na on the surface⁺After selective membrane, Na is obtained⁺A sensor;

K⁺the preparation method of the sensor comprises the following steps: selecting a fourth working electrode area on the surface of the SWCNTs-based flexible electrode array, and modifying a PEDOT film, namely the SWCNTs-Pt-PEDOT-based working electrode, by a constant current polymerization method; further dropping and coating a decoration K on the surface⁺After selective membrane, K is obtained⁺A sensor.

11. A wearable sweat sensor comprising the electrode sensing array of claim 8, a signal acquisition and processing circuitry module, a power module, and a display module; the electrode sensing array is contacted with the absorption layer for collecting sweat in real time, and the electrode sensing array, the signal acquisition and processing circuit module and the display module are all electrically connected with the power supply module;

the electrode sensing array comprises a first working electrode (glucose sensor), a second working electrode (lactic acid sensor) and a third working electrode (Na)⁺One or more of a sensor and a fourth working electrode, i.e., a K + sensor, including one or both of a first reference electrode and a second reference electrode;

each electrode in the electrode sensing array is electrically connected with the signal acquisition and processing circuit module in a parallel connection mode and is used for monitoring glucose, lactic acid and Na in sweat⁺Or K⁺One or more of these targets, producing an electrical signal; the signal acquisition and processing circuit module is used for amplifying and filtering the electric signal, outputting the electric signal as a voltage signal, and converting the electric signal into glucose, lactic acid and Na in sweat⁺Or K⁺The concentration of (c); the display module is used for displaying glucose, lactic acid and Na in sweat⁺Or K⁺Of the composition of (a).

12. A method of wearable sensor for in situ monitoring of sweat as claimed in claim 11 comprising the steps of:

s1, attaching the wearable sensor to the human epidermis through an absorption layer for collecting sweat in real time, wherein the electrode sensing array is in contact with the absorption layer for collecting sweat in real time along with glucose, lactic acid and Na in the sweat⁺Or K⁺The concentration of the target substances changes, and corresponding real-time electrochemical response signals are generated;

s2, the signal acquisition and processing circuit module amplifies and filters the real-time electrochemical signal obtained in S1, outputs the signal as a voltage signal, and converts the signal into glucose, lactic acid and Na in sweat⁺Or K⁺The real-time concentration of one or more targets in (a);

s3, glucose, lactic acid and Na in sweat obtained from S2⁺Or K⁺The real-time concentration of the one or more targets is presented in real time by the display module.