A flexible sweat sensor based on surface-enhanced Raman technology

Abstract

The present invention discloses a flexible sweat sensor based on surface-enhanced Raman technology, comprising a flexible substrate with a SERS substrate mounted thereon; the flexible substrate comprising an adhesive layer, a gel layer, a flexible electrode, and a microfluidic channel layer connected vertically from bottom to top; the microfluidic channel layer comprising a microfluidic substrate and a cover layer connected above the microfluidic substrate; the microfluidic substrate being provided with detection ports for mounting the SERS substrate, fluid channels sequentially connecting the detection ports, and a sweat inlet at the center of the microfluidic substrate connected to the fluid channels; sweat channels corresponding to the sweat inlets are reserved on the adhesive layer, gel layer, and flexible electrode. The present invention can achieve high sensitivity, high stability, low detection limits, and real-time monitoring of multiple components in sweat, has excellent environmental adaptability, and can operate stably in complex physiological environments.

Description

Technical Field

[0001] The present 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 are gaining increasing attention. Flexible sensors are wearable devices or devices that are tightly integrated with the skin. They can continuously monitor personal activities and provide sufficient information for health monitoring and preliminary medical diagnosis. They have become key to improving the efficiency and effectiveness of healthcare.

[0003] Currently, commercially available flexible sensors primarily focus on monitoring physical signals such as heart rate, body temperature, and humidity, failing to provide deeper, molecular-level information. Currently, the detection of biochemical substances in body fluids (such as glucose and urea) is mostly performed through analysis of blood and interstitial fluid, requiring invasive equipment. On the one hand, invasive equipment is costly, increasing the financial burden on patients; on the other hand, invasive equipment can cause physical trauma and psychological stress to patients, and even lead to secondary infections. Compared to blood, sweat is an underappreciated biofluid with enormous potential for monitoring human health. Sweat glands are widely distributed throughout the human body, and the presence of biochemical substances in sweat that are relevant to human physiological status (such as potassium, calcium, sodium, chloride, glucose, amino acids, and urea) makes sweat a viable 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 concentrations of some biomolecules in human sweat are extremely low. For example, glucose concentrations can be as low as micromolar levels. However, the detection limits of existing sensors make it difficult to accurately measure these biochemical substances, limiting their ability to effectively detect trace biomarkers and affecting the accuracy of health monitoring and disease early warning. Therefore, improving the sensitivity of sensors and lowering their detection limits are key to enhancing their practical application value.

[0006] Secondly, current flexible sweat sensors can usually only detect a single biochemical substance, while sweat contains multiple biochemical substances. To comprehensively 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 a comprehensive understanding of physiological status complicated and cumbersome. Therefore, the development of sensors that can simultaneously detect multiple biochemical substances will greatly improve the comprehensive monitoring capabilities and the comfort of the monitor.

[0007] Furthermore, during in situ analysis of physiological samples, sensors are subject to a variety of environmental factors, negatively impacting the stability, reproducibility, and sensitivity of the test results. In particular, the concentration of biomolecules in sweat fluctuates with environmental changes, such as temperature, humidity, and sweat secretion rate. Sensors must maintain stable performance in these complex, dynamic microenvironments. Therefore, developing sensor materials with high environmental adaptability and anti-fouling capabilities, improving the stability and reliability of sensors in complex environments, and extending their service life are key to addressing 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 adhesive layer, a gel layer, a flexible electrode, and a microfluidic channel layer connected in sequence 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 mounting 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, glucose detection port, creatinine detection port, and urea detection port are distributed in a ring. The microfluidic substrate is provided with a fluid channel that connects the pH detection port, glucose detection port, creatinine detection port, and urea detection port in sequence. The center of the microfluidic substrate is provided with a sweat inlet connected to the fluid channel.

[0015] Sweat channels are reserved on the adhesive 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: Take the gold seed dispersion and prepare a gold nanoparticle dispersion with a particle size of 120 nm according to the seed growth method;

[0021] Step 3: Cyclohexane is added dropwise to the gold nanoparticle dispersion to form a water / cyclohexane immiscible interface, and ethanol is then added until a golden specular reflection appears. Next, a silicon wafer is immersed in the nanoparticle monolayer and slowly withdrawn, allowing the cyclohexane to evaporate to form a gold nanofilm.

[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 embodiment of the present invention, the preparation of the microfluidic channel layer comprises the following steps:

[0029] Step 1: pour polydimethylsiloxane onto the mold and vacuum degas for 1-2 hours. After removing bubbles, cure at 80-120°C for 2-6 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 then curing at 80 to 120° C. for 2 to 6 hours to obtain a covering layer;

[0031] Step 3: treating the cover layer and the microfluidic substrate with oxygen plasma and bonding the cover layer to the microfluidic substrate.

[0032] As a further solution of the present invention: in steps 1 and 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 Sketchup 3D modeling software, convert the 2D lines into a 2D plane, and stretch the plane to different degrees according to the design height to 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, introduce the resin into the sample tank, 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 achieves highly sensitive detection of trace biochemical substances in sweat. Furthermore, a SERS substrate capable of detecting multiple sweat components, including pH, glucose, urea, and creatinine, was designed and integrated into a microfluidic substrate. This enables the flexible sweat sensor to simultaneously detect multiple biomarkers in sweat, avoiding the limitations of existing sensors that typically detect a single component and improving detection efficiency. Furthermore, the sensor's design ensures stable operation in complex physiological environments, guaranteeing the reliability and accuracy of detection results. As a non-invasive detection device, without the need for invasive sampling, it provides a convenient and noninvasive health monitoring method, enabling real-time, continuous monitoring of biochemical substances and providing timely and accurate health information. The gel layer in the sensor conforms to the skin surface and releases drugs into the skin, stimulating local sweat glands to produce sweat, making it suitable for long-term wear and avoiding the limitations of the sensor for daily monitoring. Furthermore, the sensor exhibits excellent tissue conformality, adapting to the changing shape of the skin surface, ensuring stable signal transmission, improving the signal-to-noise ratio, and making 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 structural diagram 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 pH value detection performance of the SERS substrate of the present invention.

[0042] Figure 4 This is the detection performance of the SERS substrate of the present invention for glucose.

[0043] Figure 5 This is the detection performance of the SERS substrate of the present invention for urea.

[0044] Figure 6 This is the detection performance of the SERS substrate of the present invention for creatinine.

[0045] Figure 7 This is 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 adhesive layer 1, a gel layer 2, a flexible electrode 3, and a microfluidic channel layer connected in sequence 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, glucose detection port, creatinine detection port, and urea detection port are distributed in a ring. The microfluidic substrate 4 is provided with a fluid channel 11 that connects the pH detection port, glucose detection port, creatinine detection port, and urea detection port in sequence. The center of the microfluidic substrate 4 is provided with a sweat inlet 9 connected to the fluid channel 11.

[0054] Sweat channels 8 are reserved on the adhesive layer 1 , the gel layer 2 , and the flexible electrode 3 corresponding to the sweat inlet 9 .

[0055] The flexible electrodes 3 and the gel layer 2 both adopt a symmetrical distribution structure, and the sweat channel 8 formed by the middle interval is not smaller than the sweat inlet 9; the adhesion layer 1 adopts 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, stimulating 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: Take the gold seed dispersion and prepare a gold nanoparticle dispersion with a particle size of 120 nm according to the seed growth method;

[0062] Step 3: Cyclohexane is added dropwise to the gold nanoparticle dispersion to form a water / cyclohexane immiscible interface, and ethanol is then added until a golden specular reflection appears. Next, a silicon wafer is immersed in the nanoparticle monolayer and slowly withdrawn, allowing the cyclohexane to evaporate to form a gold nanofilm.

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

[0070] Step 1: pouring polydimethylsiloxane onto a mold and vacuum degassing for 1 to 2 hours, removing bubbles, and then 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 then curing at 80 to 120° C. for 2 to 6 hours to obtain a covering layer 6;

[0072] Step 3: 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 steps 1 and 2, the volume ratio of the polydimethylsiloxane matrix to the curing agent is 10:1 to 20:1, and 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 Sketchup 3D modeling software, convert the 2D lines into a 2D plane, and stretch the plane to different degrees according to the design height to 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, introduce the resin into the sample tank, 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 a two-dimensional plane figure into Sketch Up 3D 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 sliced ​​file into a Mono X-ray curing 3D printer for printing, clean off the residual resin after printing, and perform secondary curing to obtain a mold; 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 (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 (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 approximately 45 nm was obtained; 3 mL of the gold seed dispersion was mixed with 20 mL of ultrapure water, and the mixture was placed in an ice-water bath and stirred for 10 min. in, followed by the addition of 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), stirring for 20 min, and then adding 654 μL of chloroauric acid solution (the volume ratio of chloroauric acid to deionized water is 1:100) dropwise. After stirring for 25 min, the temperature was raised to 70 ° C and stirring was continued 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 to a glass beaker, add 1.5 mL of cyclohexane dropwise 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: The pH detection substrate, the glucose detection substrate, the urea detection substrate, and the creatinine detection substrate are transferred 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 to a beaker, heat and dissolve to 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 at 4°C for 1 hour to obtain a composite gel with a thickness of 600 μm; cut the composite gel into the 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 pH value is detected by SERS substrate 5, and the detection range 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 range of urea by SERS substrate 5 is 1 to 100 micromoles.

[0095] Figure 6 The detection range of creatinine by SERS substrate 5 is 1 to 500 μM.

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

[0097] The flexible sweat sensor is attached to the surface of the 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 spectroscopy, 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 connected in sequence 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 includes 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. A sweat inlet (9) connected to the fluid channel (11) is provided in the center of the microfluidic substrate (4). Sweat channels (8) are reserved on the adhesive layer (1), the gel layer (2), and the flexible electrode (3) corresponding to the sweat inlet (9); The preparation of the 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: Take the gold seed dispersion and prepare a gold nanoparticle dispersion with a particle size of 120 nm according to the seed growth method; Step 3: Cyclohexane is added dropwise to the gold nanoparticle dispersion to form a water / cyclohexane immiscible interface, and ethanol is then added until a golden specular reflection appears. Next, a silicon wafer is immersed in the nanoparticle monolayer and slowly withdrawn, allowing the cyclohexane to evaporate to form a gold nanofilm. 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.

2. The flexible sweat sensor based on surface-enhanced Raman spectroscopy 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 spectroscopy 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 spectroscopy 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 1-3 mol / L with agarose and heat for 1-3 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 1-3 hours to obtain a composite gel; Step ④: Cut the composite gel into desired shapes to form a gel layer (2).

5. The flexible sweat sensor based on surface-enhanced Raman spectroscopy according to claim 1, characterized in that: The preparation of the microfluidic channel layer includes the following steps: Step 1: Pour polydimethylsiloxane onto the mold and vacuum degas for 1-2 hours. After removing bubbles, cure at 80-120°C for 2-6 hours to obtain a microfluidic substrate (4). Step 2: Pour polydimethylsiloxane onto a culture dish and vacuum degas for 1-2 hours, remove bubbles, and then cure at 80-120°C for 2-6 hours to obtain a covering layer (6); Step 3: treating the covering layer (6) and the microfluidic substrate (4) with oxygen plasma, and bonding the covering layer (6) to the microfluidic substrate (4).

6. The flexible sweat sensor based on surface-enhanced Raman spectroscopy according to claim 5, characterized in that: In steps 1 and 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.

7. The flexible sweat sensor based on surface-enhanced Raman spectroscopy according to claim 5, characterized in that: The mold preparation in step 1 includes the following steps: Step 1): Import the 2D plane figure into Sketchup 3D modeling software, convert the 2D lines into a 2D plane, stretch the plane to different degrees according to the design height to 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 tank, clean the residual resin after printing, and obtain the mold after secondary curing.

Images