A flexible photoelectrochemical sensor for instant detection of uric acid content in sweat and its preparation method

Abstract

The present invention discloses a flexible photoelectrochemical sensor for instant detection of uric acid content in sweat and its preparation method. The sensor comprises a medical double-sided adhesive layer, a sweat extraction electroosmotic electrode pair, a photoelectrochemical sensing trielectrode, a polyimide (PI) substrate, a photoelectrochemical sensitive material, a sweat collection microchannel, and a flexible packaging layer. The sweat extraction electroosmotic electrode pair comprises a pair of electroosmotic anodes and cathodes, and the photoelectrochemical sensing trielectrode comprises a counter electrode, a working electrode, and a reference electrode. The polyimide (PI) substrate is provided with a sweat collection through-hole array, and the sweat collection microchannel is provided with a flow channel inlet and outlet, each connected to each through-hole in the sweat collection through-hole array. The sensor can noninvasively extract and autonomously collect sweat from sweat glands in human skin. The working electrode material of the photoelectrochemical sensing trielectrode undergoes a photoelectrochemical reaction with uric acid in sweat, converting low uric acid concentrations into a strong photoelectrochemical signal, enabling highly sensitive, on-site, instant detection of uric acid content in sweat.

Description

Technical Field

[0001] The present invention relates to a flexible photoelectric chemical sensor for real-time detection of uric acid content in sweat and a preparation method thereof, belonging to the frontier cross-manufacturing technology field of flexible electronics and medical devices. Background Art

[0002] Uric acid, as the final product of purine metabolism in the human body, is of great significance for the clinical diagnosis and treatment of various diseases. When the human body's uric acid metabolism is abnormal, sodium urate and uric acid crystals are easily formed in the synovial membrane of the joints or the kidneys, causing gout or urinary stones. Excessive uric acid levels in the blood can also have an adverse effect on kidney function, thereby inducing serious diseases such as myocardial infarction, hyperuricemia and type 2 diabetes. When the uric acid level in the blood is too low, the risk of the human body suffering from diseases such as liver necrosis and hepatolenticular degeneration will be greatly increased. Therefore, rapid and accurate uric acid content determination is crucial for the precise diagnosis and treatment of various diseases and public health inspections.

[0003] The gold standard for uric acid testing is the blood uric acid concentration. The blood uric acid concentration in adult males should be between 150 and 420 μmol / L; in adult females, it should be between 89 and 360 μmol / L. The uricase-peroxidase coupled method is commonly used in clinical practice to determine blood uric acid levels. This method first requires drawing a sufficient blood sample from the patient. Uricase oxidase then decomposes uric acid into allantoin and hydrogen peroxide. The resulting hydrogen peroxide, catalyzed by catalase, condenses 3,5-dichlorodihydroxybenzenesulfonic acid and 4-aminoantipyrine to form a red quinone compound. This red compound exhibits a distinct absorption characteristic at 520 nm. Therefore, by measuring the absorbance of this compound, the uric acid concentration in the blood can be calculated. This method is suitable for both manual and automated biochemical analysis and meets routine clinical needs. However, this method still has shortcomings such as poor peroxidase specificity, susceptibility to interference from reducing substances, invasive blood sampling process, need for additional optical equipment assistance, and long waiting time for testing, which limits its application in human uric acid instant detection (POCT). In addition, drawing on portable blood glucose meters, domestic and foreign medical POCT equipment research and development companies represented by Sinocare Biotechnology have developed a variety of home-use blood uric acid testers, which to a certain extent meet the POCT needs of patients' uric acid levels. However, these uric acid testing devices still require a needle to pierce the fingertip skin to take blood samples, and long-term use can easily cause infection in patients (especially those with diabetes and liver and kidney dysfunction). In addition, the results of a single test are easily affected by the sampling method, resulting in large reading deviations and low test reliability.

[0004] Therefore, there is an urgent need for a non-invasive, highly sensitive, and easy-to-operate POCT method for uric acid content to help patients with various diseases such as gout, cardiovascular disease, hyperuricemia, type 2 diabetes, and liver and kidney dysfunction to conduct real-time, accurate, and rapid self-testing of their own uric acid levels.

[0005] The sweat secreted by human skin contains a variety of biomolecules such as glucose, lactic acid, uric acid, ions and amino acids, which can reflect the health status of the human body. Compared with other body fluids such as blood, interstitial fluid, and tears, sweat sampling is simpler, the sampling process is non-invasive, and the discomfort caused is low. Therefore, flexible microfluidic sensors for sweat detection have received widespread attention. However, the low concentration of uric acid in sweat (no more than 35.7μmol / L) puts higher requirements on the uric acid sensing ability of the sensitive unit in the flexible microfluidic sensor. Therefore, it is urgent to develop a highly sensitive and low detection limit POCT flexible microfluidic sensor for sweat uric acid content, so as to comprehensively promote the practical application of sweat uric acid content in clinical diagnosis and treatment, related patient health monitoring, etc. Summary of the Invention

[0006] To address the challenge of highly sensitive, on-site, point-of-care (POCT) detection of uric acid in patient sweat, this paper combines microfluidics, photoelectrochemical sensing, and flexible electronics technologies to develop a flexible photoelectrochemical sensor for POCT detection of uric acid in sweat and its preparation method. This sensor enables electroosmotic extraction of sweat from glands in the human skin, efficient collection of exuded sweat, and photoelectrochemical detection of uric acid concentration, thus meeting the requirements for highly sensitive, low-detection-limit, on-site POCT detection of uric acid in patient sweat.

[0007] The present invention is achieved through the following technical solutions.

[0008] In one aspect, the present invention provides a flexible photoelectrochemical sensor for instant detection of uric acid content in sweat, comprising a medical double-sided adhesive layer, a sweat-extracting electroosmotic electrode pair, a photoelectrochemical sensing trielectrode, a polyimide (PI) substrate, a photoelectrochemical sensitive material, a sweat collection microchannel, and a flexible packaging layer, arranged in order from bottom to top.

[0009] The medical double-sided adhesive layer is provided with a sweat collection through-hole array and two upper and lower electroosmotic electrode through-grooves;

[0010] The sweat extraction electroosmotic electrode pair includes a pair of electroosmotic anodes and electroosmotic cathodes, and the electroosmotic anodes and electroosmotic cathodes are respectively overlapped with the upper and lower electroosmotic electrode slots;

[0011] The three electrodes of photoelectrochemical sensing include counter electrode, working electrode and reference electrode;

[0012] A sweat collecting through-hole array is provided on the polyimide PI substrate, and the sweat collecting through-hole array corresponds to the sweat collecting through-hole array on the medical double-sided adhesive layer;

[0013] The sweat collection microchannel is provided with a plurality of channel inlets and a channel outlet respectively connected with the through holes of the sweat collection through hole array;

[0014] The flexible packaging layer is provided with a sweat discharge hole corresponding to the flow channel outlet;

[0015] The sweat is extracted from the sweat glands of the skin non-invasively through the sweat extraction electroosmotic electrode, and the sweat is transported to the photoelectrochemical sensing three electrodes using the sweat collection microchannel. The sweat contacts the photoelectrochemical sensitive material to carry out the photoelectrochemical reaction, thereby realizing the detection of uric acid content in sweat.

[0016] Preferably, the upper and lower electroosmosis electrode slots are arranged from bottom to top, and the sweat collection hole array is located below the lower electroosmosis electrode slot.

[0017] Preferably, the electroosmosis anode and the electroosmosis cathode of the sweat-delivering electroosmosis electrode pair are arranged in a sickle shape facing each other, and the length of the electroosmosis anode sickle hook arc section is shorter than the electroosmosis cathode arc section.

[0018] Preferably, the working electrode is located in the middle of the three photoelectrochemical sensing electrodes and is a straight line segment; the counter electrode and the reference electrode are located on both sides of the three photoelectrochemical sensing electrodes and are symmetrically arched; after superposition, the periphery of the three photoelectrochemical sensing electrodes is located within the sickle-shaped electrode frame of the sweat extraction electroosmotic electrode pair.

[0019] Preferably, the sweat collection microchannel includes a circular flow channel, which is connected to multiple flow channel inlets, each inlet of the multiple flow channels is respectively connected to each through hole of the sweat collection through hole array, and is connected to a flow channel outlet on the circular flow channel; the counter electrode, working electrode and reference electrode of the photoelectrochemical sensor three electrodes are located within the circular flow channel frame.

[0020] Another aspect of the present invention provides a method for preparing the flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat, comprising the following steps:

[0021] Step 1: Polyimide PI substrate sweat extraction electroosmosis electrode to substrate electrode and lead:

[0022] Print sweat-extracting electroosmotic electrodes, substrate electrodes, and lead patterns on one side of the polyimide (PI) film;

[0023] Step 2: Polyimide PI substrate photoelectrochemical sensing three-electrode base electrode and lead:

[0024] Print the base electrode and lead pattern of the photoelectrochemical sensing three electrodes on the other side of the polyimide PI substrate;

[0025] Step 3, modification of the carbon layer on the counter electrode and working electrode in the photoelectrochemical sensing three-electrode:

[0026] Positioning and printing the counter electrode and the working electrode on the polyimide PI substrate surface printed with the base electrode and lead pattern of the photoelectrochemical sensing three electrodes, heating and curing, to obtain the carbon layer-modified counter electrode and working electrode in the photoelectrochemical sensing three electrodes;

[0027] Step 4: modification of the gold nanofilm on the working electrode and chlorination of the reference electrode in the photoelectrochemical sensing three-electrode system:

[0028] Gold nanoparticles are deposited on the surface of the working electrode of the photoelectrochemical sensing three-electrode by electrodeposition in a mixed electrolyte of chloroauric acid / sulfuric acid, and then rinsed and dried to obtain a working electrode with a surface modified with a gold nanofilm;

[0029] The reference electrode was modified by chlorination in a potassium chloride / hydrochloric acid mixed electrolyte by cyclic voltammetry, and then rinsed and dried to obtain a silver / silver chloride reference electrode;

[0030] Step 5: Synthesis of photoelectrochemical sensitive materials and functional modification of the working electrode surface:

[0031] Zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorods were synthesized using hydrothermal and sol-gel methods and dispersed in a solvent.

[0032] Add zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorod dispersions to the surface of the working electrode modified with the gold nanofilm obtained in step 4, respectively, and add urate oxidase solution thereon after natural drying. After drying again, apply Nafion dropwise, and solidify to obtain a working electrode modified with a photoelectrochemical sensitive material.

[0033] Step 6: Forming the sweat collection through-hole array on the polyimide PI substrate:

[0034] The polyimide PI substrate where the photoelectrochemical sensing three electrodes modified with the photoelectrochemical sensitive material obtained in step 5 are located is subjected to laser cyclic cutting and laser etching to obtain a sweat collection through-hole array structure on the polyimide PI substrate;

[0035] Step 7: Forming the sweat collection through-hole array and electroosmotic electrode through-grooves on the medical double-sided adhesive layer:

[0036] The medical double-sided adhesive layer is sandwiched between two pieces of oily paper, and the medical double-sided adhesive layer with the oily paper is subjected to laser circular cutting and laser etching to obtain a sweat collection through-hole array and an electroosmotic electrode through-groove structure on the medical double-sided adhesive layer;

[0037] Step 8: Bonding of the polyimide PI substrate and the medical double-sided adhesive layer:

[0038] Tear off the oily paper attached to one side of the medical double-sided adhesive layer obtained in step 7, and stick it on the sweat extraction electroosmosis electrode pair base electrode and lead covering surface of the structure prepared in step 6, aligning it with the sweat collection through-hole array, the sweat extraction electroosmosis electrode pair base electrode and the electroosmosis electrode through-groove on the double-sided adhesive to obtain a bonded polyimide PI substrate and medical double-sided adhesive layer;

[0039] Step 9: Glue-coating the electroosmotic anode and cathode of the sweat-extracting electroosmotic electrode pair:

[0040] An agarose aqueous solution is prepared, and carbachol and sodium chloride are added to two agarose aqueous solutions respectively and stirred evenly to form anode and cathode colloidal solutions. After the solutions are cooled, they are added to the electroosmotic electrode channels to obtain the electroosmotic anode and cathode of the sweat extraction electroosmotic electrode pair.

[0041] Step 10: Processing and molding of sweat collection microchannels:

[0042] A glass plate covered with waterproof double-sided tape was laser cut and etched to obtain sweat collection microchannels.

[0043] Step 11: Lamination between the sweat collection microchannel and the polyimide PI substrate:

[0044] Tear off the oily paper on one side of the sweat collection microfluidic channel and attach it to the back side of the structure obtained in step 9. Align the inlet of the sweat collection microfluidic channel on the double-sided adhesive layer with the sweat collection through-hole array of the structure obtained in step 6 to obtain a bonded sweat collection microfluidic channel and polyimide PI substrate;

[0045] Step 12: Forming the sweat discharge holes on the flexible packaging layer:

[0046] Prepare a PDMS mixed solution and spin-coat the PDMS mixed solution on a clean glass slide;

[0047] The air bubbles were removed by vacuum filtration, and the PDMS film was cured by constant temperature heating to obtain a glass sheet covered with a flexible encapsulation layer;

[0048] The glass sheet covered with the PDMS film was subjected to laser cyclic cutting and laser etching to obtain the sweat discharge pore structure on the flexible encapsulation layer;

[0049] Step 13: Top packaging of the flexible photoelectrochemical sensor for POCT of sweat uric acid content:

[0050] Tear off the oily paper on the other side of the sweat collection microchannel structure obtained in step 11, and stick it firmly to the flexible packaging layer. Align the sweat discharge holes on the flexible packaging layer with the outlet of the sweat collection microchannel to obtain a top-encapsulated flexible photoelectrochemical sensor for POCT of sweat uric acid content.

[0051] Preferably, in steps 1 and 2, the printing process is set to have a pass spacing of 0.1-0.3 mm, a feed rate of 70-200 mm / min, and a fluidity of 0.5-1.5 mm; the polyimide PI substrate after the dispensing printing is placed on a hot plate at 50-80°C, heated and cured, and then cooled to room temperature.

[0052] Preferably, in step 3, the dispensing machine feed rate is set to 100-300 mm / min and the fluidity is set to 0.3-0.8 mm; the polyimide PI substrate after positioning printing is placed on a hot plate at 80-100°C, heated and cured, and then cooled to room temperature.

[0053] Preferably, in step 4, sulfuric acid, chloroauric acid, and water are uniformly mixed in a mass ratio of (98–295): (0.17–1.36): 1000 to obtain an electrolyte, and gold nanoparticles are deposited on the surface of the working electrode at a constant current of 0.2-0.6 A in the chloroauric acid / sulfuric acid mixed electrolyte for 400-800 s;

[0054] Potassium chloride, hydrochloric acid and water were evenly mixed in a mass ratio of (3.7–15):(0.70–2.8):1000 to obtain an electrolyte. The reference electrode was chlorinated by cyclic voltammetry with a scan range of -0.15–1.05 V, a scan rate of 25–100 mV / s, and 5–10 scans. The electrode was rinsed and dried to obtain a silver / silver chloride reference electrode.

[0055] Preferably, in step 5, the preparation of the working electrode modified with the photoelectrochemical sensitive material comprises:

[0056] a. Prepare precursor solution:

[0057] Zinc acetate, thiourea, water, and ethylenediamine were mixed uniformly in a mass ratio of (9.–37):(8–30):(200–250):(0.67–0.72) to obtain a precursor solution;

[0058] b. Preparation of zinc sulfide nanosheets / redox graphene composite powder:

[0059] Add redox graphene to the precursor solution in a mass ratio of (30–50):(3–10) and heat at 120–150°C for 10–16 hours;

[0060] c. Preparation of bismuth vanadate nanorod powder:

[0061] Bismuth nitrate pentahydrate, polyvinyl pyrrolidone, water, and nitric acid were mixed uniformly in a mass ratio of (3–6):(0.5–3.0):20:(2.5–7.5) to obtain solution A; ammonium vanadate, water, and sodium hydroxide were mixed and dissolved uniformly in a mass ratio of (1–2):(10–30):(1.6–4.8) to obtain solution B; solution B was added dropwise to solution A under stirring conditions, and the pH was adjusted to 7.0; the mixed solution was heated at 160–200°C for 18–24 hours; the reaction product was centrifuged, washed, and dried to obtain bismuth vanadate nanorod powder;

[0062] d. ZnS nanosheet / redox graphene composites and bismuth vanadate nanorod powders were mixed with terpineol at a mass ratio of (0.03–0.10):(0.09–0.36) to form two suspensions.

[0063] A zinc sulfide nanosheet / redox graphene suspension was dropped onto the surface of the working electrode, and the suspension was naturally dried. Then, a bismuth vanadate nanorod powder suspension was added dropwise, and the suspension was dried again to obtain a working electrode surface modified with zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorods.

[0064] The urate oxidase solution was dropped onto the surface of the working electrode, allowed to stand at 4°C to dry, and then Nafion was drop-coated. After solidification, a working electrode modified with a photoelectrochemical sensitive material was obtained.

[0065] Preferably, in steps 7, 10, and 12, laser cutting cycles are performed 5-20 times according to the designed structural contour at a power of 5-10 W and a cutting speed of 1000-2000 mm / min.

[0066] Preferably, in step 9, the electroosmotic anode and cathode of the sweat-extracting electroosmotic electrode pair are formed by coating with glue:

[0067] 2–5% w / w agarose was mixed in deionized water, heated at 200–250°C to prepare a gel solution, cooled to 150–170°C, and 0.8–1.2% w / w carbachol and 0.8–1.2% w / w sodium chloride were added to two portions of the gel solution, respectively, to form anode and cathode colloidal solutions.

[0068] The present invention adopts the above technical solution, which has the following beneficial effects:

[0069] 1. The sensor of the present invention is equipped with a pair of sweat extraction electroosmotic electrodes, which can realize the non-invasive extraction of sweat from the sweat glands of human skin, and is helpful for the real-time detection of uric acid content in patients using this sensor.

[0070] 2. The sensor is equipped with a sweat collection microchannel, which can realize the efficient and automatic collection of sweat to be tested by electroosmosis, avoiding the infection risk brought by the fingertip blood sample used by conventional home uric acid testers and the inaccurate test results caused by irregular sampling.

[0071] 3. The working electrodes in the sensitive unit area of ​​the sensor are modified with a carbon layer, Au nanoparticles, zinc sulfide nanosheets, redox graphene, bismuth vanadate nanorods, and urate oxidase, respectively. The sensor can utilize the specific photoelectrochemical reaction between urate oxidase, zinc sulfide nanosheets, redox graphene, bismuth vanadate nanorods, and uric acid molecules in sweat to convert lower uric acid concentrations into stronger photoelectrochemical signals, thereby achieving highly sensitive, on-site POCT detection of uric acid content in sweat. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute an improper limitation of the present invention. In the drawings:

[0073] Figure 1 This is a schematic diagram of the structure of a flexible photoelectrochemical sensor for POCT of human uric acid content;

[0074] Figure 2 This is a working principle diagram of the flexible photoelectrochemical sensor;

[0075] Figure 3 This is a process flow chart for the preparation of flexible photoelectrochemical sensors. DETAILED DESCRIPTION

[0076] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0077] like Figure 1 and 2 As shown, an embodiment of the present invention provides a flexible photoelectrochemical sensor 1 for POCT of uric acid content in sweat. The sensor comprises, from bottom to top, a medical double-sided adhesive layer 2, a sweat-deriving electroosmotic electrode pair 3, a photoelectrochemical sensing three-electrode 4, a polyimide PI substrate 5, a photoelectrochemical sensitive material 6, a sweat collection microchannel 7 and a flexible packaging layer 8.

[0078] The medical double-sided adhesive layer 2 is provided with a sweat collection hole array a and first and second electroosmotic electrode slots b and c. The first and second electroosmotic electrode slots b and c are arranged from bottom to top, with the sweat collection hole array a located below the first electroosmotic electrode slot b.

[0079] The sweat-extracting electroosmosis electrode pair 3 is a pair of electrodes arranged in a sickle shape facing each other, wherein the tops of the sickle hooks are the electroosmosis anode e and the electroosmosis cathode d, respectively. The electroosmosis anode e overlaps with the first electroosmosis electrode slot b, and the electroosmosis cathode d overlaps with the second electroosmosis electrode slot c, and the length of the sickle hook arc segment of the electroosmosis anode e is smaller than the arc segment of the electroosmosis cathode d.

[0080] The photoelectrochemical sensing triad 4 comprises a counter electrode g, a working electrode i, and a reference electrode h. The working electrode i is located in the center of the triad, forming a straight line. The counter electrode g and reference electrode h are located on either side of the triad, forming a symmetrical arched shape. After stacking, the periphery of the triad 4 lies within the sickle-shaped electrode frame of the sweat-extracting electroosmotic electrode pair 3.

[0081] A sweat collecting through hole array f is provided on the polyimide PI substrate 5 , and the sweat collecting through hole array f corresponds to the sweat collecting through hole array a provided on the medical double-sided adhesive layer 2 .

[0082] The sweat collection microchannel 7 comprises a circular channel connected to multiple channel inlets j, each of which communicates with a through-hole in the sweat collection through-hole array f. The circular channel also connects to a single channel outlet k. The counter, working, and reference electrodes of the photoelectrochemical sensor are located within the circular channel frame.

[0083] The flexible packaging layer 8 is provided with a sweat discharge hole 1, which corresponds to the flow channel outlet k.

[0084] In this embodiment, the medical double-sided adhesive layer 2 is made of 3M 9917, which has the characteristics of breathability, anti-allergy, waterproof and sweat-proof, and long-lasting adhesion, and can ensure that the sensor is permanently attached to the skin.

[0085] The polyimide PI substrate 5 uses a high-temperature resistant insulating PI film with a thickness of 12.5 μm produced by Kapton, which can meet the flexibility requirements of the sensor.

[0086] The sweat collection microchannel 7 uses 3M9448A double-sided tape from 3M Company. This tape has the characteristics of being waterproof and having strong adhesion, and can meet the requirements of sealing the microchannel and preventing leakage during the sweat collection process.

[0087] The flexible encapsulation layer 8 uses Dow Corning's DC184 PDMS high-transparency elastomer to ensure that visible light can effectively illuminate the photoelectrochemical functional material and realize the photoelectrochemical reaction of uric acid on the working electrode.

[0088] The working principle of this sensor is shown in Figure 2The sensor 1 is attached to human skin n. A positive charge is applied to the electroosmotic anode e, and a negative charge is applied to the electroosmotic cathode d. Using the principle of electroosmosis, sweat is extracted from the sweat glands m on the skin n. The extracted sweat enters the sweat collection microchannel inlet j through the sweat collection through-hole arrays a and f. Capillary forces then flow to the photoelectrochemical sensing trielectrode 4, where the counter electrode g, working electrode i, and reference electrode h are located. As sweat accumulates within the collection microchannel 7, it eventually reaches the channel outlet k and exits the device through the sweat discharge holes l in the flexible encapsulation layer 8. As sweat flows through the counter electrode g, working electrode i, and reference electrode h, it comes into contact with the photoelectrochemical sensitive material 6. At this point, light is applied to the photoelectrochemical sensitive material 6, promoting the photoelectrochemical reaction between uric acid in the sweat and the photoelectrochemical sensitive material 6. This successfully converts the uric acid concentration in the sweat into a photoelectrochemical current signal within the photoelectrochemical sensitive material 6, thereby enabling highly sensitive, on-site, point-of-care (POCT) detection of uric acid in sweat.

[0089] like Figure 3 As shown, the present invention further provides a method for preparing a flexible photoelectrochemical sensor for POCT of sweat uric acid content, comprising the following steps:

[0090] Step 1: Polyimide PI substrate (one side) sweat extraction electroosmosis electrode to substrate electrode and lead forming

[0091] Lay the polyimide PI film flat on the clean dispensing printer workbench ( Figure 3 a) and fix the four corners of the film;

[0092] Based on the conductive silver paste, the base electrode and lead pattern of the sweat-derived electroosmotic electrode were printed using a dispensing machine according to the designed sweat-derived electroosmotic electrode. The printing process was set to pass the spacing of 0.1-0.3mm, the feed rate of 70-200mm / min, and the fluidity of 0.5-1.5mm to achieve the patterning of the sweat-derived electroosmotic electrode on one side of the polyimide PI substrate. Figure 3 b);

[0093] The polyimide PI substrate after dispensing printing is placed on a hot plate at 50-80°C, heated and cured, and then cooled to room temperature to obtain a sweat-extracting electroosmosis electrode on one side of the polyimide PI substrate, a substrate electrode, and a lead structure.

[0094] Step 2: Forming the base electrode and lead wires of the polyimide PI substrate (the other side) for the photoelectrochemical sensing three electrodes

[0095] Turn the structure obtained in step 1 over, lay it flat on a clean dispensing printer workbench, and fix the four corners. Be careful not to damage the sweat-extracting electroosmotic electrode to the base electrode and lead structure on the back during the process;

[0096] Based on the conductive silver paste, the dispensing machine is used to print the base electrode and lead pattern of the designed photoelectrochemical sensing three electrodes. The printing process is set to pass the spacing of 0.1-0.3mm, the feed rate of 70-200mm / min, and the fluidity of 0.5-1.5mm to achieve the patterning of the base electrode and lead of the photoelectrochemical sensing three electrodes ( Figure 3 c);

[0097] The polyimide PI substrate after dispensing printing is placed on a hot plate at 50-80°C, heated and cured, and then cooled to room temperature to obtain the base electrode and lead structure of the photoelectrochemical sensing three-electrode on the other side of the polyimide PI substrate.

[0098] Step 3: Carbon layer modification on the counter electrode and working electrode in the photoelectrochemical sensing three-electrode

[0099] Use the positioning printing function of the dispensing machine to select and position the counter electrode and working electrode areas in the photoelectrochemical sensing three electrodes obtained in step 2;

[0100] Based on the conductive carbon paste, a dispensing machine is used to print according to the designed counter electrode and working electrode structure patterns. The dispensing machine feed rate is set to 100-300mm / min and the fluidity is set to 0.3-0.8mm to achieve selective modification of the conductive carbon paste on the counter electrode and working electrode;

[0101] The polyimide PI substrate after positioning printing was placed on a hot plate at 80-100 ° C, heated and cured, and then cooled to room temperature to obtain the carbon layer modified counter electrode and working electrode ( Figure 3 d).

[0102] Step 4: modification of the gold nanofilm on the working electrode and chlorination of the reference electrode in the photoelectrochemical sensing three-electrode

[0103] Using an electrochemical workstation, a commercial counter electrode and a reference electrode, sulfuric acid, chloroauric acid and water were evenly mixed in a mass ratio of (98–295):(0.17–1.36):1000 to obtain an electrolyte. Gold nanoparticles were deposited on the surface of the working electrode by constant current electrodeposition in the chloroauric acid / sulfuric acid mixed electrolyte. The deposition current was 0.2-0.6 A and the deposition time was 400-800 s to achieve the deposition of gold nanoparticles on the surface of the working electrode in the photoelectrochemical sensing three-electrode. The electrode was then rinsed with deionized water and blown dry to obtain a working electrode with a surface modified with a gold nanofilm.

[0104] Using an electrochemical workstation, a commercial counter electrode and a reference electrode, the reference electrode was chlorinated by cyclic voltammetry in a potassium chloride / hydrochloric acid mixed electrolyte. Potassium chloride, hydrochloric acid and water were mixed evenly in a mass ratio of (3.7–15): (0.70–2.8): 1000 to obtain an electrolyte. The reference electrode was chlorinated by cyclic voltammetry with a scan range of -0.15–1.05 V, a scan rate of 25–100 mV / s, and a scan number of 5–10 times. The electrode was then rinsed with deionized water and dried to obtain a silver / silver chloride reference electrode ( Figure 3 e).

[0105] Step 5: Synthesis of photoelectrochemical sensitive materials and functional modification of working electrode surface

[0106] Zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorods are synthesized using hydrothermal and sol-gel methods, and then dispersed in a specific solvent for use.

[0107] Preparation of ZnS nanosheets, redox graphene and bismuth vanadate nanorod dispersions:

[0108] 51) Prepare precursor solution:

[0109] Zinc acetate, thiourea, water and ethylenediamine were mixed uniformly in a mass ratio of (9–367):(8–30):(200–250):(0.67–0.72) to obtain a precursor solution.

[0110] 52) Preparation of zinc sulfide nanosheets / redox graphene composite powder

[0111] 3–10 mg of redox graphene was added to 30–50 mL of the precursor solution. The mixture was then heated to 120–150°C in a Teflon autoclave for 10–16 hours. After heating, the product was cleaned and dried in a vacuum oven. This yielded a zinc sulfide nanosheet / redox graphene composite powder.

[0112] 53) Preparation of bismuth vanadate nanorod powder

[0113] Bismuth nitrate pentahydrate, polyvinyl pyrrolidone, water and nitric acid were mixed uniformly in a mass ratio of (3–6): (0.5–3.0): 20: (2.5–7.5) to obtain solution A. Ammonium vanadate, water and sodium hydroxide were mixed and dissolved uniformly in a mass ratio of (1–2): (10–30): (1.6–4.8) to obtain solution B. Solution B was added dropwise to solution A under stirring conditions, and the pH was adjusted to 7.0 with nitric acid solution or ammonia water. The prepared mixed solution was transferred to a high-temperature reactor, heated to 160–200°C and reacted for 18–24 hours. The reaction product was then centrifuged, washed, and dried to obtain bismuth vanadate nanorod powder;

[0114] 54) Modification of functional materials on the working electrode surface

[0115] Zinc sulfide nanosheets / redox graphene composites and bismuth vanadate nanorod powders were mixed with pineneol in a mass ratio of (0.03–0.10):(0.09–0.36) to form two suspensions.

[0116] Adding zinc sulfide nanosheets, redox graphene and bismuth vanadate nanorod dispersions dropwise onto the surface of the working electrode of the photoelectrochemical sensing three-electrode obtained in step 4;

[0117] A zinc sulfide nanosheet / redox graphene suspension is dropped onto the surface of the working electrode, and after natural drying, a bismuth vanadate nanorod powder suspension is added, and after drying again, a working electrode surface modified with zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorods is obtained.

[0118] Prepare 0.5–2 mg / mL urate oxidase solution, take 5–10 μL and drop it on the working electrode surface, then place it in a 4°C refrigerator to dry, then drop 5–15 μL Nafion and solidify to obtain a working electrode modified with photoelectrochemical sensitive material ( Figure 3 f).

[0119] Step 6: Formation of sweat collection through-hole array on polyimide PI substrate

[0120] The structure obtained in step 5 was placed under a UV femtosecond laser and cut 5–20 times according to the designed structure contour at a power of 5–10 W and a cutting speed of 1000–2000 mm / min. Laser etching was performed to obtain a sweat collection through-hole array structure on a polyimide PI substrate ( Figure 3 g);

[0121] Step 7: Forming the sweat collection through hole array and electroosmotic electrode through slot on the medical double-sided adhesive layer. Figure 3 h) Sandwiched between two sheets of oily paper to protect its adhesiveness;

[0122] The medical double-sided adhesive layer with oily paper was placed under a femtosecond laser and cut 5–20 times according to the designed structure contour at a power of 5–10 W and a cutting speed of 1000–2000 mm / min. The sweat collection through-hole array and the electroosmotic electrode through-groove structure on the medical double-sided adhesive layer were obtained ( Figure 3 i).

[0123] Step 8: Bonding of polyimide PI substrate and medical double-sided adhesive layer

[0124] Tear off the oily paper on one side of the medical double-sided adhesive layer obtained in step 7 and paste it on the surface of the sweat extraction electroosmosis electrode pair substrate and lead covering of the structure prepared in step 6. During the pasting process, attention should be paid to the alignment between the substrate and the sweat collection through-hole array on the double-sided adhesive, and between the sweat extraction electroosmosis electrode pair substrate electrode and the electroosmosis electrode through-groove ( Figure 3 j), to obtain the bonded polyimide PI substrate and the medical double-sided adhesive layer ( Figure 3 k).

[0125] Step 9: Electroosmotic anode and cathode of sweat-extracting electroosmotic electrode pair are coated with glue to form

[0126] The agarose aqueous solution was prepared by heating and stirring, and 2-5% w / w agarose was mixed into deionized water, and the mixture was heated to 200-250°C with continuous stirring until the gel solvent was evenly mixed. The gel solvent was cooled to 150-170°C, and 0.8-1.2% w / w carbachol and 0.8-1.2% w / w sodium chloride were added to the two solvents to form anode and cathode colloidal solutions. Carbachol and sodium chloride were then added to the two agarose aqueous solutions and stirred evenly. After the solutions were cooled, they were poured into the electroosmosis electrode channels, and finally the electroosmosis anode and cathode of the sweat extraction electroosmosis electrode pair ( Figure 3 l).

[0127] Step 10: Processing and molding of sweat collection microchannels

[0128] Put the waterproof double-sided tape with oily paper on both sides ( Figure 3 m) Fix it flatly on a clean glass plate;

[0129] The glass plate covered with waterproof double-sided tape was placed under a femtosecond laser and cut 5–20 times according to the designed structure contour at a power of 5–10 W and a cutting speed of 1000–2000 mm / min. The sweat collection microchannel was obtained by laser etching. Figure 3 n).

[0130] Step 11: Lamination between the sweat collection microchannel and the polyimide PI substrate

[0131] Tear off the oily paper on one side of the sweat collection microfluidic channel and attach it to the back of the structure obtained in step 9. During the attachment process, attention should be paid to the alignment between the flow channel inlet of the double-sided adhesive layer and the sweat collection through-hole array of the structure obtained in step 6. The attached sweat collection microfluidic channel and the polyimide PI substrate ( Figure 3 o).

[0132] Step 12: Forming the sweat discharge holes on the flexible packaging layer

[0133] Prepare a mixed solution of PDMS glue A and B in a mass ratio of 10:1, and spin-coat the PDMS mixed solution on a clean glass slide; then place the PDMS-coated glass slide on a spin coater and spin at a low speed of 200-600 r / min and a high speed of 800-1500 r / min for 10-15 and 20-40 seconds, respectively.

[0134] Vacuum filtration was used to remove air bubbles, and the PDMS film was cured by constant temperature heating at 90–120°C for 1–1.5 h to obtain a film covered with a flexible encapsulation layer ( Figure 3 p) glass;

[0135] The glass sheet covered with the PDMS film encapsulation layer was placed under a femtosecond laser and cut 5–20 times according to the designed structure contour at a power of 5–10 W and a cutting speed of 1000–2000 mm / min. The sweat discharge pore structure on the flexible encapsulation layer was obtained by laser etching ( Figure 3 q).

[0136] Step 13: Top packaging of flexible photoelectrochemical sensor for POCT of sweat uric acid content

[0137] The oily paper on the other side of the sweat collection microchannel structure obtained in S11 was torn off and firmly adhered to the flexible packaging layer. During the pasting process, care should be taken to ensure that there are no bubbles on the bonding surface to prevent leakage during the use of the device. In addition, attention should be paid to the alignment between the sweat discharge hole on the flexible packaging layer and the outlet of the sweat collection microchannel. Finally, a flexible photoelectrochemical sensor for POCT of sweat uric acid content using top packaging was obtained ( Figure 3 r).

[0138] The following is a detailed description of the method for preparing the flexible photoelectrochemical sensor for POCT of sweat uric acid content according to the present invention through specific examples.

[0139] Example 1

[0140] S1, polyimide PI substrate (one side) sweat extraction electroosmosis electrode to substrate electrode and lead forming

[0141] 11) Cut a 8cm x 6cm piece of polyimide PI film, lay it flat on a clean dispensing printer workbench and secure the four corners;

[0142] 12) Using a VOLTERA V-One dispenser and its dedicated conductive silver paste, select the simple printing mode and set the printing process to a pass spacing of 0.1 mm, a feed rate of 100 mm / min, and a flowability of 1.0 mm to achieve patterned printing of the sweat-extracting electroosmotic electrode to the base electrode and leads;

[0143] 13) The polyimide PI substrate with the sweat extraction electroosmosis electrode pair base electrode and lead pattern was placed on a 60°C hot plate and heated until the conductive silver paste solidified and cooled to room temperature to obtain the sweat extraction electroosmosis electrode pair base electrode and lead structure.

[0144] S2, polyimide substrate (the other side) photoelectrochemical sensing three-electrode substrate electrode and lead forming

[0145] 21) Turn the polyimide PI substrate over and lay it flat on a clean dispensing printer workbench. Fix the four corners of the film, taking care not to damage the sweat-extracting electroosmotic electrode on the back, the substrate electrode, and the lead structure.

[0146] 22) Using a VOLTERA V-One dispenser and its dedicated conductive silver paste, select the simple printing mode and set the printing process to a pass spacing of 0.1 mm, a feed rate of 100 mm / min, and a flowability of 1.0 mm to achieve patterned printing of the base electrode and leads of the three-electrode photoelectrochemical sensor;

[0147] 23) The polyimide PI substrate was placed on a hot plate at 60° C. and heated until the conductive silver paste was completely solidified, thereby obtaining the base electrode and lead structure of the photoelectrochemical sensing three electrodes on the other side of the polyimide PI substrate.

[0148] S3, carbon layer modification on the counter electrode and working electrode in the photoelectrochemical sensing three-electrode

[0149] 31) Using the VOLTERA V-One dispensing machine, select the printing mode as positioning printing to achieve the selection and positioning of the counter electrode and working electrode areas;

[0150] 32) Based on Shijo Company's CH-8 carbon paste, the dispensing machine feed rate was set to 200 mm / min and the fluidity to 0.6 mm to achieve selective modification of the conductive carbon paste on the counter electrode and working electrode;

[0151] 33) The polyimide PI substrate was placed on a hot plate at 90°C and heated until the carbon paste solidified, and then cooled to room temperature to obtain the carbon layer-modified counter electrode and working electrode in the photoelectrochemical sensing three-electrode.

[0152] S4, Gold nanofilm modification on the working electrode and chlorination of the reference electrode in the photoelectrochemical sensing three-electrode

[0153] 41) Using a Shanghai Chenhua CHI-660E electrochemical workstation, a commercial platinum wire counter electrode, and a silver / silver chloride reference electrode, sulfuric acid, chloroauric acid, and water were uniformly mixed in a mass ratio of 195:1.36:1000 to obtain an electrolyte, in which gold nanoparticles were deposited on the surface of the working electrode by constant current method with a deposition current of 0.5 A and a deposition time of 600 s. The electrolyte was then rinsed with deionized water and blown dry to obtain a working electrode with a surface modified with a gold nanofilm.

[0154] 42) Using a Shanghai Chenhua CHI-660E electrochemical workstation, a commercial platinum wire counter electrode, and a silver / silver chloride reference electrode, potassium chloride, hydrochloric acid, and water were uniformly mixed in a mass ratio of 10.6:0.70:1000 to obtain an electrolyte, in which the reference electrode was chlorinated by cyclic voltammetry with a scan range of -0.15-1.05 V, a scan rate of 50 mV / s, and 5 scans. The electrolyte was then rinsed with deionized water and blown dry to obtain a silver / silver chloride reference electrode.

[0155] S5. Synthesis of photoelectrochemical sensitive materials and functional modification of working electrode surface

[0156] 51) Prepare precursor solution:

[0157] Zinc acetate, thiourea, water and ethylenediamine were uniformly mixed in a mass ratio of 27:8:220:0.68 to obtain a precursor solution.

[0158] 52) Preparation of zinc sulfide nanosheets / redox graphene composite powder

[0159] 10 mg of redox graphene was added to 40 mL of the precursor solution, which was then heated to 120°C in a Teflon autoclave for 12 hours. After heating, the product was cleaned and dried in a vacuum, resulting in a zinc sulfide nanosheet / redox graphene composite powder.

[0160] 53) Preparation of bismuth vanadate nanorod powder

[0161] Bismuth nitrate pentahydrate, polyvinyl pyrrolidone, water and nitric acid were mixed evenly in a mass ratio of 5:3.0:20:4.5 to obtain solution A. Ammonium vanadate, water and sodium hydroxide were mixed and dissolved evenly in a mass ratio of 1:20:3.2 to obtain solution B. Solution B was added dropwise to solution A under stirring conditions, and the pH was adjusted to 7.0 with nitric acid solution or ammonia water. The prepared mixed solution was transferred to a high-temperature reactor, heated to 200°C and reacted for 18 hours. The reaction product was then centrifuged, washed, and dried to obtain bismuth vanadate nanorod powder;

[0162] 54) Modification of functional materials on the working electrode surface

[0163] A zinc sulfide nanosheet / redox graphene composite and bismuth vanadate nanorod powder were mixed with terpineol at a mass ratio of 0.06:0.26, respectively, to form two suspensions. Seven microliters of the zinc sulfide nanosheet / redox graphene suspension was dropped onto the working electrode surface and allowed to dry naturally. Then, another 7 microliters of the bismuth vanadate nanorod suspension was added. After further drying, the working electrode surface was modified with zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorods.

[0164] Prepare a 1 mg / mL urate oxidase solution, take 5 μL and drop it on the surface of the working electrode, then place it in a 4°C refrigerator to dry, then drop-coat 10 μL of Nafion, and after solidification, obtain a working electrode modified with a photoelectrochemical sensitive material.

[0165] S6, Formation of sweat collection through-hole arrays on polyimide (PI) substrate

[0166] The structure obtained in step S5 was placed under an ultraviolet femtosecond laser and cut 20 times according to the designed structure contour at a power of 10 W and a cutting speed of 1000 mm / min to obtain a sweat collection through-hole array structure on a polyimide PI substrate.

[0167] S7, Formation of sweat collection through-hole array and electroosmotic electrode through-grooves on the medical double-sided adhesive layer

[0168] 71) Sandwich the medical double-sided adhesive layer between two pieces of oily paper to protect its adhesiveness, and fix it flatly on a clean glass plate;

[0169] 72) Place the glass plate with the medical double-sided adhesive layer under a femtosecond laser, perform 10 cycles of cutting according to the designed structure contour at 8W power and a cutting speed of 1500mm / min, and laser etch to obtain the sweat collection through-hole array and electroosmosis electrode through-groove structure on the medical double-sided adhesive layer.

[0170] S8, bonding between polyimide PI substrate and medical double-sided adhesive layer

[0171] Tear off the oily paper on one side of the medical double-sided adhesive layer, and stick it to the sweat-extracting electroosmosis electrode pair on the polyimide PI substrate and the lead-covering surface. During the pasting process, attention should be paid to the alignment between the substrate and the sweat collection through-hole array on the double-sided adhesive, and between the sweat-extracting electroosmosis electrode pair and the electroosmosis electrode through-groove, to obtain a bonded polyimide PI substrate and medical double-sided adhesive layer.

[0172] S9, electroosmotic anode and cathode coating and forming of sweat-extracting electroosmotic electrode pair

[0173] Mix 3% w / w agarose in deionized water and heat to 200°C with constant stirring until the gel solution is uniformly mixed. Cool the gel solution to 170°C. Add 1.0% w / w carbachol and 1.0% w / w sodium chloride to each solution to form the anode and cathode colloidal solutions. These solutions are then added to the electroosmotic electrode channel and cooled to form the electroosmotic anode and cathode of the sweat extraction electroosmotic electrode pair.

[0174] S10, Processing and molding of sweat collection microchannels

[0175] 101) Fix the waterproof double-sided tape with oily paper on both sides flatly on the clean glass plate;

[0176] 102) Place a glass plate covered with waterproof double-sided tape under a femtosecond laser, perform 10 cycles of cutting and laser etching according to the designed structural contour at a power of 8 W and a cutting speed of 1500 mm / min to obtain a sweat collection microchannel.

[0177] S11, bonding between the sweat collection microchannel and the polyimide PI substrate

[0178] Tear off the oily paper on one side of the waterproof double-sided adhesive channel wall and stick it to the back side of the polyimide PI substrate. During the sticking process, attention should be paid to the alignment between the channel inlet of the double-sided adhesive layer and the sweat collection through-hole array of the structure obtained in step 6 to obtain a stuck sweat collection microchannel and polyimide PI substrate.

[0179] S12, forming of sweat discharge holes on the flexible packaging layer

[0180] 121) Prepare a mixed solution of PDMS glue A and B in a mass ratio of 10:1, stir thoroughly with a glass rod for 3–8 min, take a glass slide of size 8 cm × 6 cm, clean and blow dry, evenly apply an appropriate amount of PDMS mixed material on the glass slide, and then place the PDMS-coated glass slide on a glue spreader and rotate at a low speed of 400 rpm and a high speed of 1000 rpm for 12 s and 30 s, respectively.

[0181] 122) Remove the PDMS-coated glass slide from the spin coater and place it in a vacuum filter to remove bubbles from the PDMS film. After extraction, place it on a constant temperature heating table and heat it at 100°C for 1 hour to solidify the PDMS film, thereby obtaining a glass slide covered with a flexible encapsulation layer.

[0182] 123) A glass sheet covered with a PDMS encapsulation layer was placed under a femtosecond laser, and 10 cycles of cutting and laser etching were performed according to the designed structural contour at a power of 8 W and a cutting speed of 1500 mm / min to obtain a sweat discharge pore structure on the flexible encapsulation layer.

[0183] S13, Top-encapsulation of a flexible photoelectrochemical sensor for POCT of sweat uric acid content

[0184] Tear off the oily paper on the other side of the sweat collection microchannel and stick it firmly to the flexible packaging layer. During the pasting process, care should be taken to ensure that there are no bubbles on the bonding surface to prevent leakage during the use of the device. In addition, attention should also be paid to the alignment between the sweat discharge holes on the PDMS packaging layer and the double-sided tape channel outlet, and finally a top-encapsulated flexible photoelectrochemical sensor for POCT of sweat uric acid content was obtained.

[0185] Example 2

[0186] S1, polyimide PI substrate (one side) sweat extraction electroosmosis electrode to substrate electrode and lead forming

[0187] 11) Cut a 8cm x 6cm piece of polyimide PI film, lay it flat on a clean dispensing printer workbench and secure the four corners;

[0188] 12) Using a VOLTERA V-One dispenser and its dedicated conductive silver paste, select the simple printing mode and set the printing process to a pass spacing of 0.3 mm, a feed rate of 70 mm / min, and a flowability of 1.5 mm to achieve patterned printing of the sweat-extracting electroosmotic electrode to the base electrode and leads;

[0189] 13) The polyimide PI substrate with the sweat extraction electroosmosis electrode pair base electrode and lead pattern was placed on a 50°C hot plate and heated until the conductive silver paste solidified and cooled to room temperature to obtain the sweat extraction electroosmosis electrode pair base electrode and lead structure.

[0190] S2, polyimide substrate (the other side) photoelectrochemical sensing three-electrode substrate electrode and lead forming

[0191] 21) Turn the polyimide PI substrate over and lay it flat on a clean dispensing printer workbench. Fix the four corners of the film, taking care not to damage the sweat-extracting electroosmotic electrode on the back, the substrate electrode, and the lead structure.

[0192] 22) Using a VOLTERA V-One dispenser and its dedicated conductive silver paste, select the simple printing mode and set the printing process to a pass spacing of 0.3 mm, a feed rate of 70 mm / min, and a flowability of 1.5 mm to achieve patterned printing of the base electrode and leads of the three-electrode photoelectrochemical sensor;

[0193] 23) The polyimide PI substrate was placed on a hot plate at 50° C. and heated until the conductive silver paste was completely solidified, thereby obtaining the base electrode and lead structure of the photoelectrochemical sensing three electrodes on the other side of the polyimide PI substrate.

[0194] S3, carbon layer modification on the counter electrode and working electrode in the photoelectrochemical sensing three-electrode

[0195] 31) Using the VOLTERA V-One dispensing machine, select the printing mode as positioning printing to achieve the selection and positioning of the counter electrode and working electrode areas;

[0196] 32) Based on Shijo Company's CH-8 carbon paste, the dispensing machine feed rate was set to 100 mm / min and the fluidity to 0.8 mm to achieve selective modification of the conductive carbon paste on the counter electrode and working electrode;

[0197] 33) The polyimide PI substrate was placed on a hot plate at 100°C and heated until the carbon paste solidified, and then cooled to room temperature to obtain the carbon layer-modified counter electrode and working electrode in the photoelectrochemical sensing three-electrode.

[0198] S4, Gold nanofilm modification on the working electrode and chlorination of the reference electrode in the photoelectrochemical sensing three-electrode

[0199] 41) Using a Shanghai Chenhua CHI-660E electrochemical workstation, a commercial platinum wire counter electrode, and a silver / silver chloride reference electrode, sulfuric acid, chloroauric acid, and water were uniformly mixed in a mass ratio of 98:0.86:1000 to obtain an electrolyte, in which gold nanoparticles were deposited on the surface of the working electrode by constant current method with a deposition current of 0.2 A and a deposition time of 800 s. The electrolyte was then rinsed with deionized water and blown dry to obtain a working electrode with a surface modified with a gold nanofilm.

[0200] 42) Using a Shanghai Chenhua CHI-660E electrochemical workstation, a commercial platinum wire counter electrode, and a silver / silver chloride reference electrode, potassium chloride, hydrochloric acid, and water were uniformly mixed in a mass ratio of 3.73:1.75:1000 to obtain an electrolyte, in which the reference electrode was chlorinated by cyclic voltammetry with a scan range of -0.15-1.05 V, a scan rate of 100 mV / s, and 8 scans. The electrolyte was then rinsed with deionized water and blown dry to obtain a silver / silver chloride reference electrode.

[0201] S5. Synthesis of photoelectrochemical sensitive materials and functional modification of working electrode surface

[0202] 51) Prepare precursor solution:

[0203] Zinc acetate, thiourea, water and ethylenediamine were uniformly mixed in a mass ratio of 37:30:250:0.67 to obtain a precursor solution.

[0204] 52) Preparation of zinc sulfide nanosheets / redox graphene composite powder

[0205] 3 mg of redox graphene was added to 30 mL of the precursor solution, which was then heated to 150°C in a Teflon autoclave for 10 hours. After heating, the product was cleaned and dried in a vacuum, resulting in a zinc sulfide nanosheet / redox graphene composite powder.

[0206] 53) Preparation of bismuth vanadate nanorod powder

[0207] Bismuth nitrate pentahydrate, polyvinyl pyrrolidone, water and nitric acid were mixed uniformly in a mass ratio of 6:2.2:20:7.5 to obtain solution A. Ammonium vanadate, water and sodium hydroxide were mixed and dissolved uniformly in a mass ratio of 1.5:10:4.8 to obtain solution B. Solution B was added dropwise to solution A under stirring conditions, and the pH was adjusted to 7.0 with nitric acid solution or ammonia water. The prepared mixed solution was transferred to a high-temperature reactor, heated to 180°C and reacted for 20 hours. The reaction product was then centrifuged, washed, and dried to obtain bismuth vanadate nanorod powder;

[0208] 54) Modification of functional materials on the working electrode surface

[0209] A zinc sulfide nanosheet / redox graphene composite and bismuth vanadate nanorod powder were mixed with terpineol at a mass ratio of 0.03:0.09, respectively, to form two suspensions. 10 μL of the zinc sulfide nanosheet / redox graphene suspension was dropped onto the working electrode surface and allowed to dry naturally. Then, 10 μL of the bismuth vanadate nanorod suspension was added. After further drying, the working electrode surface was modified with zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorods.

[0210] Prepare a 2 mg / mL urate oxidase solution, take 10 μL and drop it on the surface of the working electrode, then place it in a 4°C refrigerator to dry, then drop-coat 5 μL of Nafion, and after solidification, obtain a working electrode modified with a photoelectrochemical sensitive material.

[0211] S6, Formation of sweat collection through-hole arrays on polyimide (PI) substrate

[0212] The structure obtained in step S5 was placed under an ultraviolet femtosecond laser and cut 10 times according to the designed structure contour at a power of 8 W and a cutting speed of 1500 mm / min to obtain a sweat collection through-hole array structure on a polyimide PI substrate.

[0213] S7, Formation of sweat collection through-hole array and electroosmotic electrode through-grooves on the medical double-sided adhesive layer

[0214] 71) Sandwich the medical double-sided adhesive layer between two pieces of oily paper to protect its adhesiveness, and fix it flatly on a clean glass plate;

[0215] 72) Place the glass plate with the medical double-sided adhesive layer under a femtosecond laser, perform 5 cycles of cutting according to the designed structure contour at a power of 10 W and a cutting speed of 1000 mm / min, and laser etch to obtain the sweat collection through-hole array and electroosmosis electrode through-groove structure on the medical double-sided adhesive layer.

[0216] S8, bonding between polyimide PI substrate and medical double-sided adhesive layer

[0217] Tear off the oily paper on one side of the medical double-sided adhesive layer, and stick it to the sweat-extracting electroosmosis electrode pair on the polyimide PI substrate and the lead-covering surface. During the pasting process, attention should be paid to the alignment between the substrate and the sweat collection through-hole array on the double-sided adhesive, and between the sweat-extracting electroosmosis electrode pair and the electroosmosis electrode through-groove, to obtain a bonded polyimide PI substrate and medical double-sided adhesive layer.

[0218] S9, electroosmotic anode and cathode coating and forming of sweat-extracting electroosmotic electrode pair

[0219] Mix 2% w / w agarose in deionized water and heat to 220°C with constant stirring until the gel solution is uniformly mixed. Cool the gel solution to 160°C. Add 0.8% w / w carbachol and 0.8% w / w sodium chloride to each solution to form the anode and cathode colloidal solutions. These solutions are then added to the electroosmotic electrode channel and cooled to form the electroosmotic anode and cathode of the sweat extraction electroosmotic electrode pair.

[0220] S10, Processing and molding of sweat collection microchannels

[0221] 102) Fix the waterproof double-sided tape with oily paper on both sides flatly on the clean glass plate;

[0222] 102) Place a glass plate covered with waterproof double-sided tape under a femtosecond laser, perform five cycles of cutting and laser etching according to the designed structural contour at a power of 10 W and a cutting speed of 1000 mm / min, and obtain a sweat collection microchannel.

[0223] S11, bonding between the sweat collection microchannel and the polyimide PI substrate

[0224] Tear off the oily paper on one side of the waterproof double-sided adhesive channel wall and stick it to the back side of the polyimide PI substrate. During the sticking process, attention should be paid to the alignment between the channel inlet of the double-sided adhesive layer and the sweat collection through-hole array of the structure obtained in step 6 to obtain a stuck sweat collection microchannel and polyimide PI substrate.

[0225] S12, forming of sweat discharge holes on the flexible packaging layer

[0226] 121) Prepare a mixed solution of PDMS glue A and B at a mass ratio of 10:1. Stir thoroughly with a glass rod for 3–8 min. Take a glass slide of size 8 cm × 6 cm, clean it and blow it dry. Apply an appropriate amount of PDMS mixed material evenly on the glass slide. Place the PDMS-coated glass slide on a glue spreader and rotate it at a low speed of 600 rpm and a high speed of 1500 rpm for 10 and 20 s, respectively.

[0227] 122) Remove the PDMS-coated glass slide from the spin coater and place it in a vacuum filter to remove bubbles from the PDMS film. After extraction, place it on a constant temperature heating table and heat at 90°C for 1.5 hours to solidify the PDMS film, obtaining a glass slide covered with a flexible encapsulation layer.

[0228] 123) A glass sheet covered with a PDMS encapsulation layer was placed under a femtosecond laser, and 5 cycles of cutting and laser etching were performed according to the designed structural contour at a power of 10 W and a cutting speed of 1000 mm / min to obtain the sweat discharge pore structure on the flexible encapsulation layer.

[0229] S13, Top-encapsulation of a flexible photoelectrochemical sensor for POCT of sweat uric acid content

[0230] Tear off the oily paper on the other side of the sweat collection microchannel and stick it firmly to the flexible packaging layer. During the pasting process, care should be taken to ensure that there are no bubbles on the bonding surface to prevent leakage during the use of the device. In addition, attention should also be paid to the alignment between the sweat discharge holes on the PDMS packaging layer and the double-sided tape channel outlet, and finally a top-encapsulated flexible photoelectrochemical sensor for POCT of sweat uric acid content was obtained.

[0231] Example 3

[0232] S1, polyimide PI substrate (one side) sweat extraction electroosmosis electrode to substrate electrode and lead forming

[0233] 11) Cut a 8cm x 6cm piece of polyimide PI film, lay it flat on a clean dispensing printer workbench and secure the four corners;

[0234] 12) Using a VOLTERA V-One dispenser and its dedicated conductive silver paste, select the simple printing mode and set the printing process to a pass spacing of 0.2 mm, a feed rate of 200 mm / min, and a flowability of 0.5 mm to achieve patterned printing of the sweat-extracting electroosmotic electrode to the base electrode and leads;

[0235] 13) The polyimide PI substrate with the sweat extraction electroosmosis electrode pair base electrode and lead pattern was placed on an 80°C hot plate and heated until the conductive silver paste solidified and cooled to room temperature to obtain the sweat extraction electroosmosis electrode pair base electrode and lead structure.

[0236] S2, polyimide substrate (the other side) photoelectrochemical sensing three-electrode substrate electrode and lead forming

[0237] 21) Turn the polyimide PI substrate over and lay it flat on a clean dispensing printer workbench. Fix the four corners of the film, taking care not to damage the sweat-extracting electroosmotic electrode on the back, the substrate electrode, and the lead structure.

[0238] 22) Using a VOLTERA V-One dispenser and its dedicated conductive silver paste, select the simple printing mode and set the printing process to a pass spacing of 0.2 mm, a feed rate of 200 mm / min, and a flowability of 0.5 mm to achieve patterned printing of the base electrode and leads of the three-electrode photoelectrochemical sensor;

[0239] 23) The polyimide PI substrate is placed on a hot plate at 80° C. and heated until the conductive silver paste is completely solidified, thereby obtaining the base electrode and lead structure of the photoelectrochemical sensing three electrodes on the other side of the polyimide PI substrate.

[0240] S3, carbon layer modification on the counter electrode and working electrode in the photoelectrochemical sensing three-electrode

[0241] 31) Using the VOLTERA V-One dispensing machine, select the printing mode as positioning printing to achieve the selection and positioning of the counter electrode and working electrode areas;

[0242] 32) Based on Shijo Company's CH-8 carbon paste, the dispensing machine feed rate was set to 300 mm / min and the fluidity to 0.3 mm to achieve selective modification of the conductive carbon paste on the counter electrode and working electrode;

[0243] 33) The polyimide PI substrate was placed on an 80°C hot plate and heated until the carbon paste solidified, and then cooled to room temperature to obtain the carbon layer-modified counter electrode and working electrode in the photoelectrochemical sensing three-electrode.

[0244] S4, Gold nanofilm modification on the working electrode and chlorination of the reference electrode in the photoelectrochemical sensing three-electrode

[0245] 41) Using a Shanghai Chenhua CHI-660E electrochemical workstation, a commercial platinum wire counter electrode, and a silver / silver chloride reference electrode, sulfuric acid, chloroauric acid, and water were uniformly mixed in a mass ratio of 294:0.17:1000 to obtain an electrolyte, in which gold nanoparticles were deposited on the surface of the working electrode by constant current method with a deposition current of 0.6 A and a deposition time of 400 s. The electrolyte was then rinsed with deionized water and blown dry to obtain a working electrode with a surface modified with a gold nanofilm.

[0246] 42) Using a Shanghai Chenhua CHI-660E electrochemical workstation, a commercial platinum wire counter electrode, and a silver / silver chloride reference electrode, potassium chloride, hydrochloric acid, and water were uniformly mixed in a mass ratio of 15:28:1000 to obtain an electrolyte, in which the reference electrode was chlorinated by cyclic voltammetry with a scan range of -0.15-1.05 V, a scan rate of 25 mV / s, and 5 scans. The electrolyte was then rinsed with deionized water and blown dry to obtain a silver / silver chloride reference electrode.

[0247] S5. Synthesis of photoelectrochemical sensitive materials and functional modification of working electrode surface

[0248] 51) Prepare precursor solution:

[0249] Zinc acetate, thiourea, water and ethylenediamine were uniformly mixed in a mass ratio of 9:18:200:0.72 to obtain a precursor solution.

[0250] 52) Preparation of zinc sulfide nanosheets / redox graphene composite powder

[0251] 8 mg of redox graphene was added to 50 mL of the precursor solution, which was then heated to 140°C in a Teflon autoclave for 16 hours. After heating, the product was cleaned and dried in a vacuum, resulting in a zinc sulfide nanosheet / redox graphene composite powder.

[0252] 53) Preparation of bismuth vanadate nanorod powder

[0253] Bismuth nitrate pentahydrate, polyvinyl pyrrolidone, water and nitric acid are mixed evenly in a mass ratio of 3:0.5:20:2.5 to obtain solution A. Ammonium vanadate, water and sodium hydroxide are mixed and dissolved evenly in a mass ratio of 2:30:1.6 to obtain solution B. Solution B is added dropwise to solution A under stirring conditions, and the pH is adjusted to 7.0 with nitric acid solution or ammonia water. The prepared mixed solution is transferred to a high-temperature reactor, heated to 160°C and reacted for 24 hours. The reaction product is then centrifuged, washed, and dried to obtain bismuth vanadate nanorod powder;

[0254] 54) Modification of functional materials on the working electrode surface

[0255] A zinc sulfide nanosheet / redox graphene composite and bismuth vanadate nanorod powder were mixed with terpineol at a mass ratio of 0.10:0.36, respectively, to form two suspensions. Five microliters of the zinc sulfide nanosheet / redox graphene suspension was dropped onto the working electrode surface and allowed to dry naturally. Then, another 5 microliters of the bismuth vanadate nanorod suspension was added. After further drying, the working electrode surface was modified with zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorods.

[0256] Prepare a 0.5 mg / mL urate oxidase solution, take 8 μL and drop it on the surface of the working electrode, then place it in a 4°C refrigerator to dry, then drop-coat 15 μL of Nafion, and after solidification, obtain a working electrode modified with a photoelectrochemical sensitive material.

[0257] S6, Formation of sweat collection through-hole arrays on polyimide (PI) substrate

[0258] The structure obtained in step S5 was placed under an ultraviolet femtosecond laser and cut five times according to the designed structure contour at a power of 5 W and a cutting speed of 2000 mm / min to obtain a sweat collection through-hole array structure on a polyimide PI substrate.

[0259] S7, Formation of sweat collection through-hole array and electroosmotic electrode through-grooves on the medical double-sided adhesive layer

[0260] 71) Sandwich the medical double-sided adhesive layer between two pieces of oily paper to protect its adhesiveness, and fix it flatly on a clean glass plate;

[0261] 72) Place the glass plate with the medical double-sided adhesive layer under a femtosecond laser, perform 20 cycles of cutting according to the designed structural contour at a power of 5W and a cutting speed of 2000mm / min, and laser etch to obtain the sweat collection through-hole array and electroosmotic electrode through-groove structure on the medical double-sided adhesive layer.

[0262] S8, bonding between polyimide PI substrate and medical double-sided adhesive layer

[0263] Tear off the oily paper on one side of the medical double-sided adhesive layer, and stick it to the sweat-extracting electroosmosis electrode pair on the polyimide PI substrate and the lead-covering surface. During the pasting process, attention should be paid to the alignment between the substrate and the sweat collection through-hole array on the double-sided adhesive, and between the sweat-extracting electroosmosis electrode pair and the electroosmosis electrode through-groove, to obtain a bonded polyimide PI substrate and medical double-sided adhesive layer.

[0264] S9, electroosmotic anode and cathode coating and forming of sweat-extracting electroosmotic electrode pair

[0265] Mix 5% w / w agarose in deionized water and heat to 250°C with constant stirring until the gel solution is uniformly mixed. Cool the gel solution to 150°C. Add 1.2% w / w carbachol and 1.2% w / w sodium chloride to each of the two gel solutions to form the anode and cathode colloidal solutions. These colloidal solutions are then added to the electroosmotic electrode channel and cooled to form the electroosmotic anode and cathode of the sweat-extracting electroosmotic electrode pair.

[0266] S10, Processing and molding of sweat collection microchannels

[0267] 103) Fix the waterproof double-sided tape with oily paper on both sides flatly on the clean glass plate;

[0268] 102) Place a glass plate covered with waterproof double-sided tape under a femtosecond laser, perform 20 cycles of cutting and laser etching according to the designed structural contour at a power of 5 W and a cutting speed of 2000 mm / min to obtain a sweat collection microchannel.

[0269] S11, bonding between the sweat collection microchannel and the polyimide PI substrate

[0270] Tear off the oily paper on one side of the waterproof double-sided adhesive channel wall and stick it to the back side of the polyimide PI substrate. During the sticking process, attention should be paid to the alignment between the channel inlet of the double-sided adhesive layer and the sweat collection through-hole array of the structure obtained in step 6 to obtain a stuck sweat collection microchannel and polyimide PI substrate.

[0271] S12, forming of sweat discharge holes on the flexible packaging layer

[0272] 121) Prepare a mixed solution of PDMS glue A and B in a mass ratio of 10:1. Stir thoroughly with a glass rod for 3–8 min. Take a glass slide of size 8 cm × 6 cm, clean it and blow it dry. Apply an appropriate amount of PDMS mixed material evenly on the glass slide. Place the PDMS-coated glass slide on a glue spreader and rotate it at a low speed of 200 r / min and a high speed of 800 r / min for 15 s and 40 s, respectively.

[0273] 122) Remove the PDMS-coated glass slide from the spin coater and place it in a vacuum filter to remove bubbles from the PDMS film. After extraction, place it on a constant temperature heating table and heat at 120°C for 1 hour to solidify the PDMS film, thereby obtaining a glass slide covered with a flexible encapsulation layer.

[0274] 123) A glass sheet covered with a PDMS encapsulation layer was placed under a femtosecond laser, and 20 cycles of cutting and laser etching were performed according to the designed structural contour at a power of 5 W and a cutting speed of 2000 mm / min to obtain a sweat discharge pore structure on the flexible encapsulation layer.

[0275] S13, Top-encapsulation of a flexible photoelectrochemical sensor for POCT of sweat uric acid content

[0276] Tear off the oily paper on the other side of the sweat collection microchannel and stick it firmly to the flexible packaging layer. During the pasting process, care should be taken to ensure that there are no bubbles on the bonding surface to prevent leakage during the use of the device. In addition, attention should also be paid to the alignment between the sweat discharge holes on the PDMS packaging layer and the double-sided tape channel outlet, and finally a top-encapsulated flexible photoelectrochemical sensor for POCT of sweat uric acid content was obtained.

[0277] From the above examples, it can be seen that the flexible photoelectric chemical sensor of the present invention detects the uric acid content in sweat (no more than 35.7 μmol / L) with a high detection sensitivity of 200 μA·mM -1 cm -2 above.

[0278] In addition, compared with conventional clinical blood uricase detection methods, the present invention does not require high-end detection equipment, is not restricted by time and location, and does not require professional technicians to operate. It can better detect changes in uric acid content in patients' sweat in real time online, and provides new strategies and technical guarantees for continuous monitoring of uric acid-related diseases, customization of personalized diagnosis and treatment plans for patients, remote early warning of critically ill patients, home treatment of chronic diseases, research on the pathogenesis of various diseases, analysis of the action mechanism of special drugs, and new drug development.

[0279] The present invention also provides a method for preparing a flexible photoelectrochemical sensor for POCT of sweat uric acid content. This method involves multiple core manufacturing technologies, including multi-scale laser precision machining, microfluidic design and fabrication, gel electrode preparation, 3D dispensing printing, electrochemical modification, hydrothermal synthesis, and electrochemical deposition. This provides a technical solution for the construction and optimization of similar flexible microfluidic sensors for biochemical markers.

[0280] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features therein according to the disclosed technical content without creative labor, and these substitutions and modifications are all within the protection scope of the present invention.

Claims

1. A method for preparing a flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat, characterized in that: The steps include: Step 1: Polyimide PI substrate sweat extraction electroosmosis electrode to substrate electrode and lead: Print sweat-extracting electroosmotic electrodes, substrate electrodes, and lead patterns on one side of the polyimide (PI) film; Step 2: Polyimide PI substrate photoelectrochemical sensing three-electrode base electrode and lead: Print the base electrode and lead pattern of the photoelectrochemical sensing three electrodes on the other side of the polyimide PI substrate; Step 3, modification of the carbon layer on the counter electrode and working electrode in the photoelectrochemical sensing three-electrode: Positioning and printing the counter electrode and the working electrode on the polyimide PI substrate surface printed with the base electrode and lead pattern of the photoelectrochemical sensing three electrodes, heating and curing, to obtain the carbon layer-modified counter electrode and working electrode in the photoelectrochemical sensing three electrodes; Step 4: modification of the gold nanofilm on the working electrode and chlorination of the reference electrode in the photoelectrochemical sensing three-electrode system: Gold nanoparticles are deposited on the surface of the working electrode of the photoelectrochemical sensing three-electrode by electrodeposition in a mixed electrolyte of chloroauric acid / sulfuric acid, and then rinsed and dried to obtain a working electrode with a surface modified with a gold nanofilm; The reference electrode was modified by chlorination in a potassium chloride / hydrochloric acid mixed electrolyte by cyclic voltammetry, and then rinsed and dried to obtain a silver / silver chloride reference electrode; Step 5: Synthesis of photoelectrochemical sensitive materials and functional modification of the working electrode surface: Zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorods were synthesized using hydrothermal and sol-gel methods and dispersed in a solvent. Add zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorod dispersions to the surface of the working electrode modified with the gold nanofilm obtained in step 4, respectively, and add urate oxidase solution thereon after natural drying. After drying again, apply Nafion dropwise, and solidify to obtain a working electrode modified with a photoelectrochemical sensitive material. Step 6: Forming the sweat collection through-hole array on the polyimide PI substrate: The polyimide PI substrate where the photoelectrochemical sensing three electrodes modified with the photoelectrochemical sensitive material obtained in step 5 are located is subjected to laser cyclic cutting and laser etching to obtain a sweat collection through-hole array structure on the polyimide PI substrate; Step 7: Forming the sweat collection through-hole array and electroosmotic electrode through-grooves on the medical double-sided adhesive layer: The medical double-sided adhesive layer is sandwiched between two pieces of oily paper, and the medical double-sided adhesive layer with the oily paper is subjected to laser circular cutting and laser etching to obtain a sweat collection through-hole array and an electroosmotic electrode through-groove structure on the medical double-sided adhesive layer; Step 8: Bonding of the polyimide PI substrate and the medical double-sided adhesive layer: Tear off the oily paper attached to one side of the medical double-sided adhesive layer obtained in step 7, and stick it on the sweat extraction electroosmosis electrode pair base electrode and lead covering surface of the structure prepared in step 6, aligning it with the sweat collection through-hole array, the sweat extraction electroosmosis electrode pair base electrode and the electroosmosis electrode through-groove on the double-sided adhesive to obtain a bonded polyimide PI substrate and medical double-sided adhesive layer; Step 9: Glue-coating the electroosmotic anode and cathode of the sweat-extracting electroosmotic electrode pair: An agarose aqueous solution is prepared, and carbachol and sodium chloride are added to two agarose aqueous solutions respectively and stirred evenly to form anode and cathode colloidal solutions. After the solutions are cooled, they are added to the electroosmotic electrode channels to obtain the electroosmotic anode and cathode of the sweat extraction electroosmotic electrode pair. Step 10: Processing and molding of sweat collection microchannels: A glass plate covered with waterproof double-sided tape was laser cut and etched to obtain sweat collection microchannels. Step 11: Lamination of the sweat collection microchannel with the polyimide PI substrate: Tear off the oily paper on one side of the sweat collection microfluidic channel and attach it to the back side of the structure obtained in step 9. Align the inlet of the sweat collection microfluidic channel on the double-sided adhesive layer with the sweat collection through-hole array of the structure obtained in step 6 to obtain a bonded sweat collection microfluidic channel and polyimide PI substrate; Step 12: Forming the sweat discharge holes on the flexible packaging layer: Prepare a PDMS mixed solution and spin-coat the PDMS mixed solution on a clean glass slide; The air bubbles were removed by vacuum filtration, and the PDMS film was cured by constant temperature heating to obtain a glass sheet covered with a flexible encapsulation layer; The glass sheet covered with the PDMS film was subjected to laser cyclic cutting and laser etching to obtain the sweat discharge pore structure on the flexible encapsulation layer; Step 13: Top packaging of the flexible photoelectrochemical sensor for POCT of sweat uric acid content: Tear off the oily paper on the other side of the sweat collection microchannel structure obtained in step 11, and stick it firmly to the flexible packaging layer. Align the sweat discharge holes on the flexible packaging layer with the outlet of the sweat collection microchannel to obtain a top-encapsulated flexible photoelectrochemical sensor for POCT of sweat uric acid content.

2. The method for preparing a flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat according to claim 1, characterized in that: In steps 1 and 2, set the printing process to a pass spacing of 0.1-0.3 mm, a feed rate of 70-200 mm / min, and a fluidity of 0.5-1.5 mm. Place the polyimide PI substrate after dispensing printing on a 50-80°C hot plate, heat and cure, and then cool to room temperature. In step 3, set the dispensing machine feed rate to 100-300 mm / min and the fluidity to 0.3-0.8 mm; place the polyimide PI substrate that has completed positioning printing on an 80-100°C hot plate, heat and cure, and then cool to room temperature.

3. The method for preparing a flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat according to claim 1, characterized in that: In step 4, sulfuric acid, chloroauric acid, and water are mixed in a mass ratio of (98-295):(0.17-1.36):1000 to prepare an electrolyte. Gold nanoparticles are deposited on the working electrode surface at a constant current of 0.2-0.6 A for 400-800 s in the chloroauric acid / sulfuric acid mixed electrolyte. Potassium chloride, hydrochloric acid, and water were mixed uniformly in a mass ratio of (3.7-15):(0.70-2.8):1000 to obtain an electrolyte. The reference electrode was chlorinated by cyclic voltammetry with a scan range of -0.15-1.05 V, a scan rate of 25-100 mV / s, and 5-10 scans. The electrode was rinsed and dried to obtain a silver / silver chloride reference electrode.

4. The method for preparing a flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat according to claim 1, characterized in that: In step 5, the preparation of the working electrode modified with the photoelectrochemical sensitive material includes: a. Prepare precursor solution: Zinc acetate, thiourea, water and ethylenediamine were uniformly mixed in a mass ratio of (9. – 37): (8 – 30): (200 – 250): (0.67 – 0.72) to obtain a precursor solution; b. Preparation of ZnS nanosheets / redox graphene composite powder: Add redox graphene to the precursor solution in a mass ratio of (30-50):(3-10) and heat at 120-150 °C for 10-16 hours; c. Preparation of bismuth vanadate nanorod powder: Bismuth nitrate pentahydrate, polyvinyl pyrrolidone, water, and nitric acid are mixed uniformly in a mass ratio of (3-6): (0.5-3.0): 20: (2.5-7.5) to obtain solution A; ammonium vanadate, water, and sodium hydroxide are mixed and dissolved uniformly in a mass ratio of (1-2): (10-30): (1.6-4.8) to obtain solution B; solution B is added dropwise to solution A under stirring, and the pH is adjusted to 7.0; the mixed solution is heated at 160-200°C for 18-24 hours; the reaction product is centrifuged, washed, and dried to obtain bismuth vanadate nanorod powder; d. Mix the zinc sulfide nanosheet / redox graphene composite and bismuth vanadate nanorod powder with terpineol at a mass ratio of (0.03-0.10):(0.09-0.36) to form two suspensions; A zinc sulfide nanosheet / redox graphene suspension was dropped onto the surface of the working electrode, and the suspension was naturally dried. Then, a bismuth vanadate nanorod powder suspension was added dropwise, and the suspension was dried again to obtain a working electrode surface modified with zinc sulfide nanosheets, redox graphene, and bismuth vanadate nanorods. The urate oxidase solution was dropped onto the surface of the working electrode, allowed to stand at 4°C to dry, and then Nafion was drop-coated. After solidification, a working electrode modified with a photoelectrochemical sensitive material was obtained.

5. The method for preparing a flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat according to claim 1, characterized in that: In steps 7, 10, and 12, perform 5 to 20 laser cycle cuttings according to the designed structural contour at a power of 5 to 10 W and a cutting speed of 1000 to 2000 mm / min. In step 9, the electroosmotic anode and cathode of the sweat-extracting electroosmotic electrode pair are formed by coating with glue: 2-5% w / w agarose was mixed in deionized water and heated at 200-250°C to prepare a gelling solvent. The mixture was cooled to 150-170°C. 0.8-1.2% w / w carbachol and 0.8-1.2% w / w sodium chloride were added to the two gelling solvents to form the anode and cathode colloidal solutions, respectively.

6. A flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat prepared by the method according to any one of claims 1 to 5, characterized in that: It includes a medical double-sided adhesive layer, a sweat-extracting electroosmotic electrode pair, a photoelectrochemical sensing three-electrode, a polyimide PI substrate, a photoelectrochemical sensitive material, a sweat collection microchannel and a flexible packaging layer, which are distributed in sequence from bottom to top. The medical double-sided adhesive layer is provided with a sweat collection through-hole array and two upper and lower electroosmotic electrode through-grooves; The sweat extraction electroosmotic electrode pair includes a pair of electroosmotic anodes and electroosmotic cathodes, and the electroosmotic anodes and electroosmotic cathodes are respectively overlapped with the upper and lower electroosmotic electrode slots; The three electrodes of photoelectrochemical sensing include counter electrode, working electrode and reference electrode; A sweat collecting through-hole array is provided on the polyimide PI substrate, and the sweat collecting through-hole array corresponds to the sweat collecting through-hole array on the medical double-sided adhesive layer; The sweat collection microchannel is provided with a plurality of channel inlets and a channel outlet respectively connected with the through holes of the sweat collection through hole array; The flexible packaging layer is provided with a sweat discharge hole corresponding to the flow channel outlet; The sweat is extracted from the sweat glands of the skin non-invasively through the sweat extraction electroosmotic electrode, and the sweat is transported to the photoelectrochemical sensing three electrodes using the sweat collection microchannel. The sweat contacts the photoelectrochemical sensitive material to carry out the photoelectrochemical reaction, thereby realizing the detection of uric acid content in sweat.

7. The flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat according to claim 6, characterized in that: The upper and lower electroosmotic electrode slots are arranged from bottom to top, and the sweat collection through-hole array is located below the lower electroosmotic electrode slot.

8. The flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat according to claim 6, characterized in that: The electroosmotic anode and the electroosmotic cathode of the sweat extraction electroosmotic electrode pair are arranged in a pair of sickle shapes facing each other, and the length of the electroosmotic anode sickle hook arc section is smaller than the electroosmotic cathode arc section.

9. The flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat according to claim 6, characterized in that: The working electrode is located in the middle of the three photoelectrochemical sensing electrodes and is a straight line segment; the counter electrode and the reference electrode are located on both sides of the three photoelectrochemical sensing electrodes and are symmetrical bow-shaped; after superposition, the periphery of the three photoelectrochemical sensing electrodes is located within the sickle-shaped electrode frame of the sweat extraction electroosmotic electrode pair.

10. The flexible photoelectrochemical sensor for real-time detection of uric acid content in sweat according to claim 6, characterized in that: The sweat collection microchannel includes a circular flow channel, which is connected to multiple flow channel inlets. Each inlet of the multiple flow channels is respectively connected to a through hole of the sweat collection through hole array, and is connected to a flow channel outlet on the circular flow channel; the counter electrode, working electrode and reference electrode of the photoelectrochemical sensor three electrodes are located within the circular flow channel frame.

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