Flexible sweat sensor based on surface enhanced Raman technology

Abstract

The invention discloses a flexible sweat sensor based on a surface enhanced Raman technology. The flexible sweat sensor comprises a flexible substrate, and an SERS substrate is mounted on the flexible substrate; the flexible substrate comprises an adhesion layer, a gel layer, a flexible electrode and a microfluid channel layer which are sequentially connected from bottom to top in the vertical direction; the microfluid channel layer comprises a microfluid substrate and a covering layer connected above the microfluid substrate; detection ports for mounting the SERS substrate are formed in the microfluid substrate, fluid channels communicated with the detection ports in sequence are formed in the microfluid substrate, and a sweat inlet connected with the fluid channels is formed in the center of the microfluid substrate; sweat channels corresponding to the sweat inlets are reserved in the adhesion layer, the gel layer and the flexible electrode. According to the invention, high sensitivity, high stability, low detection lower limit and real-time monitoring of multiple components in sweat can be realized, the environmental adaptability is excellent, and stable operation in a complex physiological environment can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of flexible sensors, and in particular relates to a flexible sweat sensor based on surface enhanced Raman technology. Background Art

[0002] In recent years, with the development of personalized medicine, flexible sensors have shown great potential in vital sign monitoring and other aspects, and have received more and more attention. Flexible sensors are devices that can be worn on the human body or closely integrated with the skin. They can continuously monitor personal activities and provide sufficient information for health monitoring and preliminary medical diagnosis. They have become the key to improving the efficiency and effectiveness of medical care.

[0003] At present, the flexible sensors on the market mainly focus on monitoring physical signals such as heart rate, body temperature and humidity, and cannot provide deeper molecular level detection information. At present, most of the biochemical substances (such as glucose, urea, etc.) in body fluids are analyzed through blood and interstitial fluid, and invasive equipment is required. On the one hand, invasive equipment is expensive, which increases the economic burden on patients; on the other hand, invasive equipment will cause physiological trauma and psychological pressure to patients, and even cause secondary infection. Compared with blood, sweat is a biological fluid that has not received enough attention and has great potential in monitoring human health status. Sweat glands are widely distributed in the human body, especially the biochemical substances related to the physiological state of the human body (such as potassium, calcium, sodium, chloride, glucose, amino acids, urea, etc.) in sweat make sweat a feasible and ideal non-invasive biosensing medium.

[0004] However, the current research on flexible sweat sensors suitable for human wear still faces many problems, mainly focusing on the following aspects:

[0005] First, the concentration of some biological molecules in human sweat is extremely low, such as glucose concentration, which may be as low as micromolar level, and the detection limit of existing sensors is difficult to accurately measure these biochemical substances, which limits their effective detection of trace biomarkers and affects the accuracy of health monitoring and disease early warning. Therefore, improving the sensitivity of sensors and reducing their detection limits are the key to improving their practical application value.

[0006] Secondly, current flexible sweat sensors can usually only detect a single biochemical substance, while sweat contains multiple biochemical substances. In order to fully monitor these biochemical substances, the monitor needs to wear multiple sensors, which not only increases the burden, but also significantly reduces the efficiency and convenience of detection, making it complicated and cumbersome to fully understand the physiological state. Therefore, the development of sensors that can detect multiple biochemical substances at the same time will greatly improve the comprehensive monitoring capabilities and the comfort of the monitor.

[0007] In addition, when analyzing physiological samples in situ, sensors are affected by a variety of environmental factors, which have a negative impact on the stability, reproducibility and sensitivity of the test results. In particular, the concentration of biomolecules in sweat fluctuates with changes in the environment, such as temperature, humidity and sweat secretion rate, and sensors need to maintain stable performance in these complex dynamic microenvironments. Therefore, developing sensor materials with high environmental adaptability and anti-pollution ability, improving the stability and reliability of sensors in complex environments, and extending their service life are the keys to solving these challenges. Summary of the invention

[0008] The purpose of the present invention is to provide a flexible sweat sensor based on surface enhanced Raman technology, which can achieve high sensitivity, high stability, low detection limit and real-time monitoring of multiple components in sweat, has excellent environmental adaptability, and can operate stably in complex physiological environments.

[0009] To achieve the above object, the present invention provides a flexible sweat sensor based on surface enhanced Raman (SERS) technology, comprising a flexible substrate, on which a SERS substrate is mounted;

[0010] The flexible substrate comprises an adhesion layer, a gel layer, a flexible electrode, and a microfluidic channel layer which are sequentially connected from bottom to top along a vertical direction;

[0011] The SERS substrate includes a pH detection substrate, a glucose detection substrate, a creatinine detection substrate, and a urea detection substrate;

[0012] The microfluidic channel layer includes a microfluidic substrate and a cover layer connected to the microfluidic substrate;

[0013] The microfluidic substrate is provided with detection ports for installing the SERS substrate, including a pH detection port, a glucose detection port, a creatinine detection port, and a urea detection port;

[0014] The pH detection port, the glucose detection port, the creatinine detection port, and the urea detection port are distributed in a ring shape. The microfluidic substrate is provided with a fluid channel that sequentially connects the pH detection port, the glucose detection port, the creatinine detection port, and the urea detection port. The center of the microfluidic substrate is provided with a sweat inlet that connects the fluid channel.

[0015] Sweat channels are reserved on the adhesion layer, the gel layer, and the flexible electrode corresponding to the sweat inlets.

[0016] As a further solution of the present invention: the adhesive layer is provided with a notch corresponding to the gel layer.

[0017] As a further solution of the present invention: the flexible electrode is prepared by cutting a copper film.

[0018] As a further solution of the present invention: the preparation of the SERS substrate comprises the following steps:

[0019] Step 1: Prepare a gold seed dispersion with a particle size of 45 nm by sodium citrate reduction method;

[0020] Step 2: taking a gold seed dispersion, and preparing a gold nanoparticle dispersion with a particle size of 120 nm according to a seed growth method;

[0021] Step 3: Add cyclohexane to the gold nanoparticle dispersion to form a water / cyclohexane immiscible interface, and then add ethanol until a golden mirror reflection appears; then, immerse the silicon wafer in the nanoparticle monolayer film and slowly withdraw it, and a gold nanofilm is formed after the cyclohexane evaporates;

[0022] Step 4: immerse the gold nanofilm in an aqueous solution of p-mercaptobenzoic acid for 2 to 4 hours, wash it with anhydrous ethanol and deionized water, and then dry it to obtain a pH detection substrate; immerse the gold nanofilm in an aqueous solution of p-mercaptophenylboric acid for 2 to 4 hours, wash it with anhydrous ethanol and deionized water, and then dry it, add glucose oxidase solution on the surface, and obtain a glucose detection substrate after drying; wash the gold nanofilm with anhydrous ethanol and deionized water, and then dry it to obtain a urea detection substrate and a creatinine detection substrate.

[0023] As a further embodiment of the present invention, the preparation of the gel layer comprises the following steps:

[0024] Step ①: Mix a phosphate buffer solution with a concentration of 1 to 3 mol / L with agarose and heat for 1 to 3 minutes to form a solution precursor;

[0025] Step ②: after the solution precursor is cooled to 45-55° C., acetylcholine chloride is dissolved in the solution precursor to form a composite gel solution;

[0026] Step ③: curing the composite gel solution at 4°C for 1 to 3 hours to obtain a composite gel;

[0027] Step ④: Cut the composite gel into desired shapes to form a gel layer.

[0028] As a further solution of the present invention: the preparation of the microfluidic channel layer comprises the following steps:

[0029] Step 1: pouring polydimethylsiloxane on the mold and vacuum degassing for 1 to 2 hours, removing bubbles and curing at 80 to 120° C. for 2 to 6 hours to obtain a microfluidic substrate;

[0030] Step 2: pouring polydimethylsiloxane on a culture dish and vacuum degassing for 1 to 2 hours, removing bubbles and curing at 80 to 120° C. for 2 to 6 hours to obtain a covering layer;

[0031] Step 3: oxygen plasma treatment of the cover layer and the microfluidic substrate, and bonding the cover layer to the microfluidic substrate.

[0032] As a further solution of the present invention: in step 1 and step 2, the volume ratio of the polydimethylsiloxane matrix to the curing agent is 10:1 to 20:1, in step 3, the oxygen plasma power is 50 to 100 watts, and the treatment time is 10 seconds to 1 minute.

[0033] As a further solution of the present invention: the mold preparation in step 1 includes the following steps:

[0034] Step 1): Import the 2D plane figure into Sketch up 3D modeling software, convert the 2D lines into a 2D plane, stretch the plane to different degrees according to the design height, and obtain a 3D model;

[0035] Step 2): Export the 3D model to STL format, import it into Photon Workshop slicing software, slice the model and obtain the slice file;

[0036] Step 3): Import the slice file into the mono x-ray curing 3D printer, import the resin into the sample slot, clean the residual resin after printing, and obtain the mold after secondary curing.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] By enhancing the Raman signal with gold nanoparticles, the sensor can achieve high-sensitivity detection of trace biochemical substances in sweat; in addition, a SERS substrate capable of detecting multiple sweat components such as pH, glucose, urea and creatinine is designed and integrated into a microfluidic substrate, so that the flexible sweat sensor can simultaneously detect multiple markers in sweat, avoiding the limitation of existing sensors that detect a single component and improving detection efficiency; moreover, the design of the sensor ensures its stable operation in a complex physiological environment, and ensures the reliability and accuracy of the detection results. As a non-invasive detection device, it does not require invasive sampling, provides a convenient and non-invasive health monitoring method, can achieve real-time and continuous monitoring of biochemical substances, and provide timely and accurate health information for the monitor. The gel layer in the sensor can fit the skin surface, release drugs to the human skin, stimulate the local sweat glands of the human body to produce sweat, is suitable for long-term wear and avoids the limitations of the sensor in daily monitoring. At the same time, the sensor has good tissue conformality, can adapt to the shape changes of the skin surface, ensure stable signal transmission, improve the signal-to-noise ratio, and make the detection data more accurate and reliable. The present invention can achieve high sensitivity, high stability, low detection limit and real-time monitoring of multiple components in sweat, has excellent environmental adaptability, and can operate stably in complex physiological environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1This is a schematic diagram of the structure of the flexible sweat sensor based on surface enhanced Raman technology of the present invention.

[0040] Figure 2 for Figure 1 Plan view of the microfluidic substrate.

[0041] Figure 3 This is the detection performance of the SERS substrate of the present invention for pH value.

[0042] Figure 4 The figure shows the detection performance of the SERS substrate of the present invention for glucose.

[0043] Figure 5 The figure shows the detection performance of the SERS substrate of the present invention for urea.

[0044] Figure 6 The figure shows the detection performance of the SERS substrate of the present invention for creatinine.

[0045] Figure 7 The figure shows the detection result of human sweat by the flexible sweat sensor of the present invention.

[0046] In the figure: 1. Adhesion layer, 2. Gel layer, 3. Flexible electrode, 4. Microfluidic substrate, 5. SERS substrate, 6. Covering layer, 7. Notch, 8. Sweat channel, 9. Sweat inlet, 10. Detection port, 11. Fluid channel. DETAILED DESCRIPTION

[0047] The present invention will be further described below by way of examples.

[0048] like Figure 1 and Figure 2 As shown, a flexible sweat sensor based on surface enhanced Raman technology includes a flexible substrate, on which a SERS substrate 5 is mounted;

[0049] The flexible substrate includes an adhesion layer 1, a gel layer 2, a flexible electrode 3, and a microfluidic channel layer which are sequentially connected from bottom to top along a vertical direction;

[0050] The SERS substrate 5 includes a pH detection substrate, a glucose detection substrate, a creatinine detection substrate, and a urea detection substrate;

[0051] The microfluidic channel layer includes a microfluidic substrate 4 and a cover layer 6 connected to the microfluidic substrate 4;

[0052] The microfluidic substrate 4 is provided with detection ports 10 for mounting the SERS substrate 5, including a pH detection port, a glucose detection port, a creatinine detection port, and a urea detection port;

[0053] The pH detection port, the glucose detection port, the creatinine detection port, and the urea detection port are arranged in a ring shape. The microfluidic substrate 4 is provided with a fluid channel 11 which sequentially connects the pH detection port, the glucose detection port, the creatinine detection port, and the urea detection port. The center of the microfluidic substrate 4 is provided with a sweat inlet 9 connected to the fluid channel 11.

[0054] A sweat channel 8 is reserved on the adhesive layer 1 , the gel layer 2 , and the flexible electrode 3 corresponding to the sweat inlet 9 .

[0055] The flexible electrode 3 and the gel layer 2 both adopt a symmetrical distribution structure, and the sweat channel 8 formed by the intermediate interval is not smaller than the sweat inlet 9; the adhesive layer 1 adopts a double-sided tape to adhere the flexible sweat sensor to the skin surface.

[0056] Furthermore, the adhesive layer 1 is provided with a notch 7 corresponding to the gel layer 2 .

[0057] Furthermore, the flexible electrode 3 is prepared by cutting a copper film.

[0058] The flexible sweat sensor is adhered to the skin surface. By applying a voltage of 5 to 10 volts to the flexible electrode 3, acetylcholine chloride in the gel layer 2 is released under the skin to stimulate the surrounding sweat glands to secrete sweat; the sweat enters the fluid channel 11 from the sweat channel 8 and the sweat inlet 9, and then enters the four detection ports 10 of the microfluidic substrate 4 in turn for Raman detection.

[0059] Furthermore, the preparation of the SERS substrate includes the following steps:

[0060] Step 1: Prepare a gold seed dispersion with a particle size of 45 nm by sodium citrate reduction method;

[0061] Step 2: taking a gold seed dispersion, and preparing a gold nanoparticle dispersion with a particle size of 120 nm according to a seed growth method;

[0062] Step 3: Add cyclohexane to the gold nanoparticle dispersion to form a water / cyclohexane immiscible interface, and then add ethanol until a golden mirror reflection appears; then, immerse the silicon wafer in the nanoparticle monolayer film and slowly withdraw it, and a gold nanofilm is formed after the cyclohexane evaporates;

[0063] Step 4: immerse the gold nanofilm in an aqueous solution of p-mercaptobenzoic acid for 2 to 4 hours, wash it with anhydrous ethanol and deionized water, and then dry it to obtain a pH detection substrate; immerse the gold nanofilm in an aqueous solution of p-mercaptophenylboric acid for 2 to 4 hours, wash it with anhydrous ethanol and deionized water, and then dry it, add glucose oxidase solution on the surface, and obtain a glucose detection substrate after drying; wash the gold nanofilm with anhydrous ethanol and deionized water, and then dry it to obtain a urea detection substrate and a creatinine detection substrate.

[0064] Further, the preparation of the gel layer comprises the following steps:

[0065] Step ①: Mix a phosphate buffer solution with a concentration of 1 to 3 mol / L with agarose and heat for 1 to 3 minutes to form a solution precursor;

[0066] Step ②: after the solution precursor is cooled to 45-55° C., acetylcholine chloride is dissolved in the solution precursor to form a composite gel solution;

[0067] Step ③: curing the composite gel solution at 4°C for 1 to 3 hours to obtain a composite gel;

[0068] Step ④: Cut the composite gel into a desired shape to form a gel layer 2.

[0069] Further, the preparation of the microfluidic channel layer includes the following steps:

[0070] Step 1: pouring polydimethylsiloxane on the mold and vacuum degassing for 1 to 2 hours, removing bubbles and curing at 80 to 120° C. for 2 to 6 hours to obtain a microfluidic substrate 4;

[0071] Step 2: pouring polydimethylsiloxane on a culture dish and vacuum degassing for 1 to 2 hours, removing bubbles and curing at 80 to 120° C. for 2 to 6 hours to obtain a covering layer 6;

[0072] Step three: treating the cover layer 6 and the microfluidic substrate 4 with oxygen plasma, and bonding the cover layer 6 to the microfluidic substrate 4 .

[0073] Furthermore, in step 1 and step 2, the volume ratio of the polydimethylsiloxane matrix to the curing agent is 10:1 to 20:1, in step 3, the oxygen plasma power is 50 to 100 watts, and the treatment time is 10 seconds to 1 minute.

[0074] Furthermore, the mold preparation in step 1 includes the following steps:

[0075] Step 1): Import the 2D plane figure into Sketch up 3D modeling software, convert the 2D lines into a 2D plane, stretch the plane to different degrees according to the design height, and obtain a 3D model;

[0076] Step 2): Export the 3D model to STL format, import it into Photon Workshop slicing software, slice the model and obtain the slice file;

[0077] Step 3): Import the slice file into the mono x-ray curing 3D printer, import the resin into the sample slot, clean the residual resin after printing, and obtain the mold after secondary curing.

[0078] When the present invention is specifically implemented:

[0079] Preparation of flexible sweat sensor based on surface enhanced Raman technology:

[0080] S1: Import the two-dimensional plane figure into Sketch Up three-dimensional modeling software, stretch the plane to different degrees according to the design height to obtain an ideal three-dimensional model; import the three-dimensional model into Photon Workshop slicing software for slicing; import the slice file into a mono X-ray curing 3D printer for printing, clean the residual resin after printing, and obtain a mold through secondary curing; pour polydimethylsiloxane (the volume ratio of matrix to curing agent is 10:1) on the mold, degas under vacuum for 1 hour to remove bubbles, and then cure at 80°C for 4 hours to obtain an 800μm thick microfluidic substrate 4; in addition, pour polydimethylsiloxane on a culture dish, degas under vacuum for 1 hour to remove bubbles, and then cure at 80°C for 4 hours to obtain a 200μm thick covering layer 6.

[0081] S2: Synthesis of 120 nm gold nanoparticle dispersion: 100 mL of chloroauric acid solution (the volume ratio of chloroauric acid to deionized water is 1:100) was stirred and heated to boiling, and then 1 mL of sodium citrate solution (the mass ratio of sodium citrate to deionized water is 1:100) was added and kept boiling for 20 min. After the solution was cooled to room temperature, a gold seed dispersion with a particle size of about 45 nm was obtained; 3 mL of the gold seed dispersion and 20 mL of ultrapure water were mixed and stirred, and placed in an ice water bath and stirred for 10 min. in, followed by adding 100 μL of sodium citrate solution (the mass ratio of sodium citrate to deionized water is 1:100) and 400 μL of ascorbic acid solution (the mass ratio of ascorbic acid to deionized water is 1:100) in sequence, stirring for 20 min, then adding 654 μL of chloroauric acid solution (the volume ratio of chloroauric acid to deionized water is 1:100) dropwise, stirring for 25 min, heating to 70 ° C, and continuing stirring for 30 min to obtain a gold nanoparticle dispersion with an average particle size of 120 nm.

[0082] S3: Add 6 mL of gold nanoparticle dispersion into a glass beaker, add 1.5 mL of cyclohexane to form a water / cyclohexane immiscible interface; then add ethanol until a golden mirror reflection appears; then, immerse the silicon wafer in the nanoparticle monolayer film and slowly withdraw it; after the cyclohexane evaporates naturally, a gold nanofilm composed of gold nanoparticles is formed.

[0083] S4: Immerse the gold nanofilm in a 0.1mM p-mercaptobenzoic acid aqueous solution for 2 hours, wash it with anhydrous ethanol and deionized water, and dry it to obtain a pH detection substrate; immerse the gold nanofilm in a 0.1mM p-mercaptophenylboric acid aqueous solution for 2 hours, wash it with anhydrous ethanol and deionized water, and dry it, then add 10μL of glucose oxidase solution (1mg / mL) on the surface, and dry it to obtain a glucose detection substrate; wash the gold nanofilm with anhydrous ethanol and deionized water, and dry it to obtain a urea detection substrate and a nuclear creatinine detection substrate.

[0084] S5: transferring the pH detection substrate, the glucose detection substrate, the urea detection substrate, and the creatinine detection substrate to the four detection ports 10 of the microfluidic substrate 4 respectively.

[0085] S6: The cover layer 6 and the microfluidic substrate 4 are treated with oxygen plasma (power of 100 watts, time of 1 minute), and the cover layer 6 is bonded to the microfluidic substrate 4 to obtain a microfluidic channel layer.

[0086] S7: Cut the copper film into a desired shape and load it on the bottom of the microfluidic channel layer as the flexible electrode 3.

[0087] S8: Preparation of gel layer 2: add 10 mL of phosphate buffer solution (concentration of 1 moL / L) and 0.4 g of agarose into a beaker, heat to dissolve and form a solution precursor; cool the solution to 50°C while stirring, and then dissolve 1 g of acetylcholine chloride in the solution precursor to form a composite gel solution; transfer the composite gel solution to a culture dish and solidify it at 4°C for 1 hour to obtain a composite gel with a thickness of 600 μm; cut the composite gel into a desired shape to obtain gel layer 2.

[0088] S9: Place gel layer 2 on the bottom of the copper film.

[0089] S10: Use medical double-sided tape to stick to the bottom of gel layer 2.

[0090] Verify the detection performance of the flexible sweat sensor prepared above for various biomarkers.

[0091] PBS solutions of different pH values ​​were dripped onto the surface of the pH detection substrate; standard solutions of glucose, urea and creatinine of different concentrations were dripped onto the corresponding SERS detection substrates for detection.

[0092] Figure 3 The detection range of pH value of SERS substrate 5 is 3.7 to 8.2.

[0093] Figure 4 The detection range of glucose by SERS substrate 5 is 0.05 to 1000 micromolar.

[0094] Figure 5 The detection of urea by SERS substrate 5 has a detection range of 1 to 100 micromoles.

[0095] Figure 6 The detection of creatinine by SERS substrate 5 has a detection range of 1 to 500 micromoles.

[0096] Verify that the flexible sweat sensor prepared above can detect real human sweat.

[0097] The flexible sweat sensor is attached and worn on the surface of human arm skin to collect sweat produced during human exercise, and the collected sweat is detected using portable Raman.

[0098] Figure 7 The sweat test results collected by the flexible sweat sensor show that the sweat pH value is 7.3, the glucose content is 17μm, and the urea and creatinine contents are 30μm and 12μm, respectively.

Claims

1. A flexible sweat sensor based on surface enhanced Raman technology, comprising a flexible substrate, characterized in that: A SERS substrate (5) is mounted on the flexible substrate; The flexible substrate comprises an adhesive layer (1), a gel layer (2), a flexible electrode (3), and a microfluidic channel layer which are sequentially connected from bottom to top along a vertical direction; The SERS substrate (5) includes a pH detection substrate, a glucose detection substrate, a creatinine detection substrate, and a urea detection substrate; The microfluidic channel layer comprises a microfluidic substrate (4) and a covering layer (6) connected to the microfluidic substrate (4); The microfluidic substrate (4) is provided with detection ports (10) for mounting the SERS substrate (5), including a pH detection port, a glucose detection port, a creatinine detection port, and a urea detection port; The pH detection port, the glucose detection port, the creatinine detection port, and the urea detection port are distributed in an annular manner; a fluid channel (11) is provided on the microfluidic substrate (4) and is connected to the pH detection port, the glucose detection port, the creatinine detection port, and the urea detection port in sequence; and a sweat inlet (9) connected to the fluid channel (11) is provided at the center of the microfluidic substrate (4); A sweat channel (8) is reserved on the adhesive layer (1), the gel layer (2), and the flexible electrode (3) corresponding to the sweat inlet (9).

2. A flexible sweat sensor based on surface enhanced Raman technology according to claim 1, characterized in that: The adhesive layer (1) is provided with a notch (7) corresponding to the gel layer (2).

3. The flexible sweat sensor based on surface enhanced Raman technology according to claim 1, characterized in that: The flexible electrode (3) is prepared by cutting a copper film.

4. The flexible sweat sensor based on surface enhanced Raman technology according to claim 1, characterized in that: The preparation of SERS substrate includes the following steps: Step 1: Prepare a gold seed dispersion with a particle size of 45 nm by sodium citrate reduction method; Step 2: taking a gold seed dispersion, and preparing a gold nanoparticle dispersion with a particle size of 120 nm according to a seed growth method; Step 3: Add cyclohexane to the gold nanoparticle dispersion to form a water / cyclohexane immiscible interface, and then add ethanol until a golden mirror reflection appears; then, immerse the silicon wafer in the nanoparticle monolayer film and slowly withdraw it, and a gold nanofilm is formed after the cyclohexane evaporates; Step 4: immerse the gold nanofilm in an aqueous solution of p-mercaptobenzoic acid for 2 to 4 hours, wash it with anhydrous ethanol and deionized water, and then dry it to obtain a pH detection substrate; immerse the gold nanofilm in an aqueous solution of p-mercaptophenylboric acid for 2 to 4 hours, wash it with anhydrous ethanol and deionized water, and then dry it, add glucose oxidase solution on the surface, and obtain a glucose detection substrate after drying; wash the gold nanofilm with anhydrous ethanol and deionized water, and then dry it to obtain a urea detection substrate and a creatinine detection substrate.

5. The flexible sweat sensor based on surface enhanced Raman technology according to claim 1, characterized in that: The preparation of the gel layer includes the following steps: Step ①: Mix a phosphate buffer solution with a concentration of 1 to 3 mol / L with agarose and heat for 1 to 3 minutes to form a solution precursor; Step ②: after the solution precursor is cooled to 45-55° C., acetylcholine chloride is dissolved in the solution precursor to form a composite gel solution; Step ③: curing the composite gel solution at 4°C for 1 to 3 hours to obtain a composite gel; Step ④: Cut the composite gel into a desired shape to form a gel layer (2).

6. The flexible sweat sensor based on surface enhanced Raman technology according to claim 1, characterized in that: The preparation of the microfluidic channel layer includes the following steps: Step 1: pouring polydimethylsiloxane on the mold and vacuum degassing for 1 to 2 hours, removing bubbles and curing at 80 to 120° C. for 2 to 6 hours to obtain a microfluidic substrate (4); Step 2: pouring polydimethylsiloxane on a culture dish and vacuum degassing for 1 to 2 hours, removing bubbles and curing at 80 to 120° C. for 2 to 6 hours to obtain a covering layer (6); Step 3: Treat the cover layer (6) and the microfluidic substrate (4) with oxygen plasma, and bond the cover layer (6) to the microfluidic substrate (4).

7. The flexible sweat sensor based on surface enhanced Raman technology according to claim 6, characterized in that: In step 1 and step 2, the volume ratio of the polydimethylsiloxane matrix to the curing agent is 10:1 to 20:1, in step 3, the oxygen plasma power is 50 to 100 watts, and the treatment time is 10 seconds to 1 minute.

8. The flexible sweat sensor based on surface enhanced Raman technology according to claim 6, characterized in that: The mold preparation in step 1 includes the following steps: Step 1): Import the 2D plane figure into Sketch up 3D modeling software, convert the 2D lines into a 2D plane, stretch the plane to different degrees according to the design height, and obtain a 3D model; Step 2): Export the 3D model to STL format, import it into Photon Workshop slicing software, slice the model and obtain the slice file; Step 3): Import the slice file into the mono x-ray curing 3D printer, import the resin into the sample slot, clean the residual resin after printing, and obtain the mold after secondary curing.

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