Integrated stretchable flexible wearable biosensor and method of making the same

Abstract

The application discloses an integrated stretchable flexible wearable biosensor and a preparation method thereof, and belongs to the technical field of electrochemical sensing.The integrated stretchable flexible wearable biosensor is wrapped by a PAN / SiO2 sweat absorption layer.The method comprises the following steps: preparing a stretchable conductive composite fiber; preparing an integrated stretchable flexible sensing fiber; preparing a PAN / SiO2 sweat absorption layer; and preparing a sensor.The conductive composite fiber in the application can maintain stable performance under multiple bending and twisting, the sensor is integrated with a flexible integrated circuit chip and a flexible power supply device to obtain a fabric sensing system, the fabric sensing system can process acquired sensor data, and the detection data can be uploaded to a mobile terminal and a cloud end in real time through Bluetooth technology, real-time monitoring and management of a health condition of the biosensor are realized, six specific biomarkers can be efficiently detected by using only 1 muL of sweat, the amount of sweat required for activating the biosensor is 1 / 3 of that of the prior art, and the fabric sensing system can easily adapt to a tensile strain caused by exercise.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical sensing technology; specifically, it relates to an integrated, stretchable, flexible wearable biosensor and its preparation method. Background Technology

[0002] With increasing public awareness of health, wearable technology is being increasingly applied in the healthcare field. As a crucial component of smart healthcare, wearable medical devices have broken the limitations of traditional medical equipment, rapidly capturing the market with their advanced data collection and analysis capabilities, portability, ease of use, and other advantages. With rapid economic development, the rapid advancement of internet and IoT technologies, the accelerating aging population, and changing lifestyles, wearable biosensors are entering a golden age of development under the strategic backdrop of personalized healthcare, smart healthcare, telemedicine, and mobile healthcare. Currently, many commercially available wearable biosensors have emerged, but most focus on monitoring physical characteristic signals of the human body, such as measuring parameters like heart rate and blood pressure using photoplethysmography. In addition, some biomarkers in human body fluids (including tissue fluid, blood, sweat, and saliva) are closely related to the body's physiological health. Measuring and monitoring the content of biomarkers in body fluids can provide significant value for disease screening, diagnosis, and prognosis. Among various body fluid testing methods, sweat testing offers advantages such as being non-invasive, convenient, readily available, and unaffected by dietary factors. Furthermore, sweat contains a wealth of physiological information: for example, chloride ions in sweat are a recognized biomarker for cystic fibrosis, a hereditary disease that primarily affects newborns and currently has no cure. The best treatment approach involves closely monitoring affected infants and providing early intervention by analyzing chloride ion levels in sweat to slow the progression of cystic fibrosis. Elevated lactic acid levels in sweat are associated with sweat gland fatigue. Studies have shown that during training, athletes experience increased pressure on the skin and soft tissues due to sweat gland fatigue, and these levels return to normal after the inducing factors are removed. Therefore, real-time monitoring of lactic acid levels in sweat can be used to assess athletes' physical condition and athletic performance during physical fitness tests. Finally, dehydration affects skin heat dissipation. As body temperature gradually rises, it can cause functional disorders. Severe dehydration can lead to heatstroke and even threaten life. Sweat pH can effectively reflect the body's water content, thus monitoring dehydration. Potassium and sodium ions in sweat can regulate the balance of osmotic pressure and acid-base levels inside and outside cells. Significant loss of potassium and sodium ions can cause decreased bodily function and metabolic disorders. Uric acid levels in sweat can effectively reflect the state of hyperuricemia and gout. Statistics show that in 2020, the number of people with hyperuricemia and gout worldwide reached 930 million, an increase of 5.86% year-on-year, and is expected to exceed 1 billion by 2022. Therefore, real-time monitoring of uric acid levels in sweat is crucial for the health management of people with hyperuricemia and gout. Trace amounts of glucose in sweat are closely related to blood glucose levels; detecting glucose levels in sweat can help monitor and manage blood sugar. Therefore, biomarkers in sweat play an important indicative role in bodily status and disease development.Therefore, developing wearable biosensors for sweat detection and analysis is an effective way to monitor human health.

[0003] Despite numerous research reports on flexible wearable sensors, most currently exist with several challenges in practical applications: 1) Poor stretchability. While many sensors utilize flexible materials to achieve overall flexibility and withstand bending and torsion, their tensile strength remains poor. Stress generated during movement can strain the device, leading to signal instability or even damage. 2) Low integration, often focusing on single-detection. Cost and crosstalk are critical considerations, resulting in most sensors being single-channel designed for specific analytes. However, disease assessment often requires analyzing multiple indicators, making comprehensive health monitoring difficult with single-channel sensors. 3) Low sweat collection efficiency. Stable sensor operation requires sufficient sweat to penetrate the sensing area for stable circuit connection and activation of electrochemical sensing reactions. However, due to a lack of directional sweat transport, only a small portion of absorbed sweat reaches the sensing area, resulting in low collection efficiency and hindering effective sensor operation and stability. Therefore, it is necessary to optimize and modify the substrate material and internal structure of the sensor to prepare an integrated, stretchable wearable biosensor with high sweat absorption efficiency.

[0004] Patent application No. 202110702379.0, entitled "Flexible Wearable Electrochemical Biosensor," discloses a method for fabricating an integrated flexible wearable electrochemical biosensor by combining a core-shell structured working electrode, reference electrode, and auxiliary electrode. This biosensor can quickly, sensitively, and accurately detect the composition of sweat. However, the biosensor in this application cannot be stretched, is easily damaged, and requires a large amount of sweat to activate the sensor during detection, making it difficult to achieve convenient and efficient detection. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned technical problems by providing an integrated, stretchable, flexible wearable biosensor and its preparation method.

[0006] An integrated, stretchable, flexible wearable biosensor is made of an integrated, stretchable, flexible sensing fiber wrapped in a PAN / SiO2 sweat-absorbing layer.

[0007] The thickness of the PAN / SiO2 sweat-absorbing layer is 100–300 μm;

[0008] The integrated stretchable flexible sensing fiber consists of seven carbon nanotube strips and one silicone elastic fiber substrate fiber; wherein the diameter of the carbon nanotube strips is 500–700 μm; the diameter of the silicone elastic fiber substrate fiber is 1.5–2 mm; one of the seven carbon nanotube strips serves as a reference electrode, and the other six serve as working electrodes, respectively modified with pH sensing electrodes, K... + Sensing electrode, Na + Sensing electrodes, glucose sensing electrodes, lactic acid sensing electrodes, and uric acid sensing electrodes.

[0009] The above-mentioned integrated stretchable flexible wearable biosensor is fabricated according to the following steps:

[0010] I. Preparation of stretchable conductive composite fibers:

[0011] a. The carbon nanotube strips were subjected to oxygen plasma treatment for 3-5 minutes to obtain the treated carbon nanotube strips.

[0012] b. Take out the two components of the two-component Ecoflex00-10 platinum catalytic silica gel in equal mass ratio and mix them. After homogenization and degassing, a polymer mixture is obtained. Then, inject it into a polyethylene terephthalate tube with an inner diameter of 1.5-2 mm and let it stand at room temperature until it is completely cured. After peeling, the silica elastic fiber base fiber is obtained.

[0013] c. Take one of the above-mentioned silicone elastic fiber base fibers, fix it on the stepper motor and pre-stretch it to a deformation of 300%. Then, place the guide rail perpendicular to the stepper motor. Take seven processed carbon nanotube strips, fix one end of each strip to one side of the silicone elastic fiber base fiber and the other end to the guide rail, and perform three-dimensional spiral winding at equal intervals to obtain stretchable conductive composite fiber.

[0014] II. Fabrication of integrated, stretchable, flexible sensing fibers:

[0015] Using existing methods, one reference electrode and six working electrodes are modified onto the above-mentioned stretchable conductive composite fiber to obtain an integrated stretchable flexible sensing fiber.

[0016] The six working electrodes are, in order, a pH sensing electrode, a K... + Sensing electrode, Na + Sensing electrodes, glucose sensing electrodes, lactic acid sensing electrodes, and uric acid sensing electrodes;

[0017] III. Preparation of PAN / SiO2 sweat-absorbing layer:

[0018] PAN (polyacrylonitrile) and SiO2 are mixed in N,N-dimethylformamide at a volume ratio of 10:1 to prepare a PAN / SiO2 spinning solution with a mass fraction of 9% to 11%. Then, the solution is prepared by electrospinning to obtain a PAN / SiO2 sweat-absorbing layer with a thickness of 100 to 300 μm.

[0019] IV. Sensor fabrication:

[0020] The PAN / SiO2 sweat-absorbing layer obtained in step three is wrapped around the outer layer of the integrated stretchable flexible sensing fiber obtained in step two to obtain a composite sensing fiber. Then, the composite sensing fiber is assembled with ordinary commercial elastic fiber material by direct weaving to prepare an electrochemical fabric, thereby obtaining an integrated stretchable flexible wearable biosensor, thus completing the preparation method.

[0021] Furthermore, the carbon nanotube strips mentioned in step one a are continuous carbon nanotube strips with a diameter of 500–700 μm.

[0022] Furthermore, in step one b, the homogenization and degassing process involves using a homogenizer and degassing device for 3-5 minutes.

[0023] Furthermore, in step one c, the equidistant three-dimensional spiral winding is described as follows: simultaneously, the rotary stepper motor and the guide rail are started, so that the seven processed carbon nanotube strips are spirally wound on the surface of the deformed silicone elastic fiber substrate, with equal spacing and parallel to each other.

[0024] Furthermore, the molecular weight of PAN mentioned in step three is 60,000 to 90,000.

[0025] Furthermore, the SiO2 particle size mentioned in step three is 20–50 nm.

[0026] Furthermore, in step three, the specific preparation involves stirring at 50°C for 4–6 hours.

[0027] Furthermore, in step three, electrospinning technology is used for preparation: the receiving distance is 15cm, the liquid supply rate is 0.5mL / h, the roller speed is 500r / min, the spinning voltage is positive 20kV, and the spinning time is 4-6h.

[0028] Furthermore, in step four, electrochemical fabrics are assembled and prepared: based on the wearable application requirements of different application scenarios, the design of electrochemical fabrics includes headbands, neckbands, wristbands, and clothing.

[0029] The principles and advantages of this invention:

[0030] The stretchable conductive composite fiber of this invention is prepared by pre-stretching a silicone elastic substrate fiber and helically winding it with carbon nanotube strips. The synergistic effect of a rotary stepper motor and a guide rail ensures that the carbon nanotube strips are neatly wound onto the silicone elastic substrate fiber, parallel to each other and without cross-linking. Considering the weak interfacial bonding between the carbon nanotube strips and the silicone elastic substrate fiber, this invention proposes a strategy to construct hydrogen bonds to enhance their bonding effect. Specifically, the carbon nanotube strips are treated with oxygen plasma. High-energy oxygen ions collide with the surface of the carbon nanotube strips, transferring a certain amount of energy to the surface molecules of the carbon nanotube strips, thereby generating highly reactive carbon oxide groups. Subsequently, the carbon oxide groups interact with water molecules in the surrounding environment, undergoing a hydrolysis reaction, ultimately leading to the formation and grafting of hydroxyl groups onto the surface of the carbon nanotube strips. The hydroxyl groups on the surface of the carbon nanotube strips can generate hydrogen bond interactions with the hydroxyl groups on the surface of the silicone elastic fiber, further enhancing their adhesion and reducing signal instability caused by electrode slippage.

[0031] To achieve the stretchability of the conductive composite fiber, the pre-stretching operation of the silicone elastic substrate fiber is crucial in the preparation process. The elastic substrate fiber, while recovering from pre-stretch deformation, induces micro-wrinkles on the surface of the carbon nanotube strips, thus imparting stretchability. To verify the stretchability of the conductive composite fiber, carbon nanotube strips were composited with the elastic fiber substrate under 300% deformation conditions, both with and without pre-stretching. Experiments showed that, compared to the unstretched conductive composite fiber, the pre-stretched conductive composite fiber maintained good stability under 300% tensile deformation, and the micro-wrinkles formed under the pre-stretch-recovery effect were clearly visible in the scanning electron microscope images of the carbon nanotube strips. To verify the tensile stability of the conductive composite fiber, it was repeatedly stretched 10,000 times at 300% deformation using a tensile testing machine, and the change in resistance was less than 10%. This demonstrates that the conductive composite fiber prepared by this invention has excellent tensile stability. This invention also bent and twisted the conductive composite fiber 10,000 times, recording the change in resistance during the process. The resistance of the electrode changed by only 4% and 1.5% after multiple bending and torsion, which proves that the prepared conductive composite fiber can maintain stable performance under multiple bending and torsion.

[0032] This invention utilizes electrospinning technology to prepare a PAN / SiO2 sweat-absorbing layer. The SiO2-doped PAN electrospun membrane possesses a highly porous structure. These tiny pores provide a large surface area, allowing water molecules to distribute uniformly and permeate rapidly on the membrane surface. This porous structure also generates a capillary effect. When water molecules enter the pores within the membrane, the interaction forces between the pore size and the water molecules constrain and attract them, promoting diffusion and enhancing the membrane's water absorption and diffusion capacity. Furthermore, doping with SiO2 particles improves the hydrophilicity of the electrospun film, further promoting the adsorption and diffusion of water molecules on the membrane surface and accelerating the absorption and diffusion of moisture.

[0033] In this invention, to quantitatively analyze the performance of the PAN / SiO2 sweat-absorbing layer, the excellent liquid absorption and diffusion capabilities of the sweat-absorbing layer were further verified. Due to the efficient absorption and diffusion capabilities of the sweat-absorbing layer, the amount of sweat required to activate the sensor is significantly reduced. The minimum detection volume of the composite sweat-absorbing layer sensor was then tested. It can be seen that the composite sweat-absorbing layer sensor only requires 1 μL of sweat to achieve circuit connection, while the sensor without the composite sweat-absorbing layer requires nearly 400 μL, further demonstrating the capability of the sweat-absorbing layer. Due to its unique high integration and the excellent water absorption performance of the sweat-absorbing layer, the composite sensing fiber can efficiently detect six specific biomarkers using only 1 μL of sweat, which is only one-third of the amount of sweat required to activate the sensor as currently reported. Therefore, designing an integrated fiber structure and combining it with the sweat-absorbing layer is of significant research importance for improving the sweat absorption efficiency of the sensor.

[0034] This invention discloses the changes in the electrochemical properties of composite sensing fibers encased in a sweat-wicking layer during stretching. Experiments revealed that the detection signal of the composite sensing fiber remained almost unchanged under 300% tensile strain, maintaining stable response characteristics. This indicates that even under large deformation conditions, the sensor can still maintain highly reliable electrochemical performance. Furthermore, after 1000 cycles of 300% deformation stretching, the sensor still exhibits excellent stability and reliable detection performance. This demonstrates that the composite sensing fiber prepared based on the pre-stretch-recovery strategy not only possesses good tensile properties but also maintains stable electrochemical properties, providing more reliable and durable performance for practical applications. Considering that the strain occurring during human movement ranges from 20% to 75%, the tensile properties of the composite sensing fiber are suitable for various wearable applications.

[0035] This invention presents an integrated, stretchable, flexible wearable biosensor, further integrated with a flexible integrated circuit chip and a flexible power supply device to obtain a fabric sensing system. Due to the loose, porous structure of the fabric, compared to polyimide and polydimethylsiloxane, the most commonly used materials for planar biosensors, the fabric structure has excellent breathability and moisture permeability. Therefore, the fabric sensing system can significantly improve the wearer's comfort. The fabric sensing system can process the acquired sensor data and upload the detection data to a mobile device and the cloud in real time via Bluetooth technology, realizing wireless data transmission and remote monitoring. A corresponding mobile application (designed using Biofluids software developed by Beijing Huyi Technology Co., Ltd.) was designed and developed using Java, allowing users to view sweat pH, K+, and other parameters via their mobile phones. + Na + The system monitors the changing trends of physiological indicators such as glucose, lactic acid, and uric acid, and allows for the setting of warning values. When the detected values ​​exceed the preset range, the mobile application promptly sends an alert message to help users take timely measures. Therefore, it enables real-time monitoring and management of one's health status and achieves real-time in-situ monitoring of biomarkers in human sweat. This fabric sensing system is portable, comfortable, and allows for wireless transmission, showing broad application prospects in health management and medical monitoring.

[0036] This invention is applicable to the fabrication of integrated, stretchable, flexible wearable biosensors. Attached Figure Description

[0037] Figure 1 This is a schematic diagram illustrating the preparation of the stretchable conductive composite fiber in the embodiment;

[0038] Figure 2 This is a physical image of the stretchable conductive composite fiber in the embodiment;

[0039] Figure 3 This is a schematic diagram of the interface bonding of the conductive composite fibers in the embodiment;

[0040] Figure 4 The diagram shows the effect of pre-stretching-recovery on the tensile properties of the stretchable conductive composite fiber and the SEM image of the micro-wrinkles formed on the surface in the embodiment.

[0041] Figure 5 This is a graph showing the change in resistance of the stretchable conductive composite fiber under 10,000 stretching cycles with a deformation of 300%.

[0042] Figure 6 This is a graph showing the change in resistance of the stretchable conductive composite fiber after 10,000 bending and torsion cycles in the embodiment.

[0043] Figure 7This is an electrochemical characteristic diagram of the integrated stretchable flexible sensing fiber in the embodiment, where the ac part represents pH, K, etc. in sequence. + and Na + The open-circuit potential response of the sensing electrodes to their respective analytical solutions; the df section represents the current response of the glucose, lactic acid, and uric acid sensing electrodes to their corresponding analytical solutions, in order.

[0044] Figure 8 This is a performance diagram of the amount of sweat required for the composite sensing fiber to activate the sensor in the embodiment;

[0045] Figure 9 This is a graph showing the electrochemical sensing performance of the composite sensing fiber under tension in the embodiment, where part a represents pH and K. + and Na + Part a shows the voltage signal detected by the sensing electrode during 300% tensile deformation; part b shows the current signal detected by the glucose, lactic acid, and uric acid sensing electrodes during 300% tensile deformation; part c shows the current signal detected at pH, K... + and Na + The voltage signal detected by the sensing electrode in 1000 stretching cycles; part d is the current signal detected by the glucose, lactic acid and uric acid sensing electrodes in 1000 stretching cycles.

[0046] Figure 10 This is a schematic diagram illustrating the assembly of composite sensing fibers with ordinary commercial elastic fiber materials through direct weaving to prepare electrochemical fabrics for the analysis of various biomarkers. Part a is a schematic diagram of the assembly of composite sensing fibers with ordinary commercial elastic fiber materials through direct weaving, and part b is a schematic diagram of the assembly of electrochemical fabrics to achieve wireless data transmission and remote monitoring.

[0047] Figure 11 The images shown are of a subject running while wearing the fabric sensing system, bending their elbow, and receiving data wirelessly via a custom-developed app. Part a shows the actual situation of the subject running while wearing the fabric sensing system, and part b shows the state of the electrochemical fabric with the elbow straightened and bent. Parts c and d show the actual situation of the wireless data reception of the custom-developed mobile application and the actual situation of the smartphone's function interface, respectively. Detailed Implementation

[0048] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0049] Specific implementation method one: This implementation method is an integrated stretchable flexible wearable biosensor, which is made of an integrated stretchable flexible sensing fiber wrapped in a PAN / SiO2 sweat-absorbing layer.

[0050] The thickness of the PAN / SiO2 sweat-absorbing layer is 100–300 μm;

[0051] The integrated stretchable flexible sensing fiber consists of seven carbon nanotube strips and one silicone elastic fiber substrate fiber; wherein the diameter of the carbon nanotube strips is 500–700 μm; the diameter of the silicone elastic fiber substrate fiber is 1.5–2 mm; one of the seven carbon nanotube strips serves as a reference electrode, and the other six serve as working electrodes, respectively modified with pH sensing electrodes, K... + Sensing electrode, Na + Sensing electrodes, glucose sensing electrodes, lactic acid sensing electrodes, and uric acid sensing electrodes.

[0052] Specific Implementation Method Two: The preparation method of the integrated stretchable flexible wearable biosensor in this embodiment is implemented according to the following steps:

[0053] I. Preparation of stretchable conductive composite fibers:

[0054] a. The carbon nanotube strips were subjected to oxygen plasma treatment for 3-5 minutes to obtain the treated carbon nanotube strips.

[0055] b. Take out the two components of the two-component Ecoflex00-10 platinum catalytic silica gel in equal mass ratio and mix them. After homogenization and degassing, a polymer mixture is obtained. Then, inject it into a polyethylene terephthalate tube with an inner diameter of 1.5-2 mm and let it stand at room temperature until it is completely cured. After peeling, the silica elastic fiber base fiber is obtained.

[0056] c. Take one of the above-mentioned silicone elastic fiber base fibers, fix it on the stepper motor and pre-stretch it to a deformation of 300%. Then, place the guide rail perpendicular to the stepper motor. Take seven processed carbon nanotube strips, fix one end of each strip to one side of the silicone elastic fiber base fiber and the other end to the guide rail, and perform three-dimensional spiral winding at equal intervals to obtain stretchable conductive composite fiber.

[0057] II. Fabrication of integrated, stretchable, flexible sensing fibers:

[0058] Using existing methods, one reference electrode and six working electrodes are modified onto the above-mentioned stretchable conductive composite fiber to obtain an integrated stretchable flexible sensing fiber.

[0059] The six working electrodes are, in order, a pH sensing electrode, a K... + Sensing electrode, Na + Sensing electrodes, glucose sensing electrodes, lactic acid sensing electrodes, and uric acid sensing electrodes;

[0060] III. Preparation of PAN / SiO2 sweat-absorbing layer:

[0061] PAN (polyacrylonitrile) and SiO2 are mixed in N,N-dimethylformamide at a volume ratio of 10:1 to prepare a PAN / SiO2 spinning solution with a mass fraction of 9% to 11%. Then, the solution is prepared by electrospinning to obtain a PAN / SiO2 sweat-absorbing layer with a thickness of 100 to 300 μm.

[0062] IV. Sensor fabrication:

[0063] The PAN / SiO2 sweat-absorbing layer obtained in step three is wrapped around the outer layer of the integrated stretchable flexible sensing fiber obtained in step two to obtain a composite sensing fiber. Then, the composite sensing fiber is assembled with ordinary commercial elastic fiber material by direct weaving to prepare an electrochemical fabric, thereby obtaining an integrated stretchable flexible wearable biosensor, thus completing the preparation method.

[0064] In step one of this embodiment, the carbon nanotube strips are treated with oxygen plasma to graft hydroxyl groups onto their surface.

[0065] In this embodiment, an integrated, stretchable, flexible wearable biosensor is prepared. This is then integrated with a flexible integrated circuit chip and a flexible power supply device to obtain a fabric sensing system. This system can upload detection data to a mobile device and the cloud in real time via Bluetooth technology, achieving wireless data transmission and remote monitoring. A corresponding mobile application (designed using Biofluids software developed by Beijing Huyi Technology Co., Ltd.) is designed and developed using Java. Users can view sweat pH, K... + Na + The app tracks the changing trends of physiological indicators such as glucose, lactic acid, and uric acid, and allows users to set warning thresholds. When detected values ​​exceed preset ranges, the app promptly sends alerts to help users take timely action, thus enabling real-time monitoring and management of their health.

[0066] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the carbon nanotube strips mentioned in step 1a are continuous carbon nanotube strips with a diameter of 500–700 μm. Other steps and parameters are the same as in Specific Implementation Method 2.

[0067] The continuous carbon nanotube strips described in this embodiment are prepared using a floating catalyst chemical vapor deposition method.

[0068] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two in that the homogenization and degassing described in step one (b) is performed using a homogenizer and the degassing time is 3-5 minutes. Other steps and parameters are the same as in Specific Implementation Method Two.

[0069] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Two in that step three involves stirring at 50°C for 4–6 hours. All other steps and parameters are the same as in Specific Implementation Method Two.

[0070] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Two in that the equidistant three-dimensional spiral winding described in step one (c) involves simultaneously activating a rotary stepper motor and a guide rail, causing seven processed carbon nanotube strips to spirally wind around the deformed silicone elastic fiber substrate surface, with equal spacing and parallel alignment. Other steps and parameters are the same as in Specific Implementation Method Two.

[0071] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Two in that the molecular weight of PAN mentioned in step three is 60,000 to 90,000. Other steps and parameters are the same as in Specific Implementation Method Two.

[0072] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Two in that the SiO2 particle size in step three is 20–50 nm. Other steps and parameters are the same as in Specific Implementation Method Two.

[0073] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Two in that the preparation is carried out using electrospinning technology in step three: the receiving distance is 15cm, the liquid supply rate is 0.5mL / h, the roller speed is 500r / min, the spinning voltage is +20kV, and the spinning time is 4-6h. Other steps and parameters are the same as in Specific Implementation Method Two.

[0074] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Two in that, in step four, the electrochemical fabric is assembled and prepared. Based on the wearable application requirements of different application scenarios, the design of the electrochemical fabric includes headband, neckband, wristband, and apparel types. Other steps and parameters are the same as in Specific Implementation Method Two.

[0075] The beneficial effects of the present invention are verified through the following embodiments:

[0076] Example:

[0077] The fabrication method of an integrated, stretchable, flexible wearable biosensor is specifically implemented according to the following steps:

[0078] I. Preparation of stretchable conductive composite fibers:

[0079] a. Continuous carbon nanotube strips with a diameter of 700 μm were prepared by floating catalyst chemical vapor deposition, and then the carbon nanotube strips were subjected to oxygen plasma treatment for 3 min to obtain the treated carbon nanotube strips.

[0080] b. Take the two components of the two-component Ecoflex00-10 platinum catalytic silica gel in equal mass ratio and mix them. Use a homogenizer to remove bubbles and homogenize for 3 minutes to obtain a polymer mixture. Use a pipette with a volume of 1 mL to draw up the polymer mixture and slowly inject it into a polyethylene terephthalate tube with an inner diameter of 1.5 mm. Let it stand at room temperature for 4 hours to completely cure. After peeling, the silica elastic fiber base fiber is obtained.

[0081] c. Take one of the above-mentioned silicone elastic fiber base fibers, fix it on the stepper motor and pre-stretch it to a deformation of 300%. Then, place the guide rail perpendicular to the stepper motor. Take seven processed carbon nanotube strips, fix one end of each strip to one side of the silicone elastic fiber base fiber and the other end to the guide rail, and perform three-dimensional spiral winding at equal intervals to obtain stretchable conductive composite fiber.

[0082] The equidistant three-dimensional spiral winding: Simultaneously start the rotary stepper motor and guide rail, so that 7 processed carbon nanotube strips are spirally wound on the surface of the deformed silicone elastic fiber substrate, with equal spacing and parallel to each other;

[0083] II. Fabrication of integrated, stretchable, flexible sensing fibers:

[0084] Using existing methods, one reference electrode and six working electrodes are modified onto the above-mentioned stretchable conductive composite fiber to obtain an integrated stretchable flexible sensing fiber.

[0085] The six working electrodes are, in order, a pH sensing electrode, a K... + Sensing electrode, Na + Sensing electrodes, glucose sensing electrodes, lactic acid sensing electrodes, and uric acid sensing electrodes;

[0086] A reference electrode was modified onto a stretchable conductive composite fiber: Using a two-electrode system, a carbon nanotube strip from the stretchable conductive composite fiber was first used as the working electrode, with a silver electrode as the reference electrode. Cyclic voltammetry was performed in a mixed solution of 10 mM AgNO3 and 1 M KNO3, scanning from -0.9 V to 0.9 V for 5 cycles at a scan rate of 100 mV / s to electrodeposit silver metal. Then, the silver-deposited carbon nanotube strip was used as the working electrode, with a commercial silver / silver chloride electrode as the reference electrode. Cyclic voltammetry was performed in a mixed solution of 0.01 M HCl and 0.1 M KCl, scanning from -0.15 V to 0.15 V for 2 cycles at a scan rate of 500 mV / s to chlorinate some of the silver on the surface of the carbon nanotube strip. Finally, 79.1 mg of polyvinyl butyral (PVB), 50.0 mg of NaCl, and 2.0 mg of... F127 and 0.2 mg of multi-walled carbon nanotube powder were dissolved in 1 mL of methanol to prepare a PVB mixed solution, which was then drop-coated onto the carbon nanotube strips to prepare a reference electrode.

[0087] Six working electrodes modified on a stretchable conductive composite fiber, including a pH sensing electrode: polyaniline is electrodeposited on the surface of a carbon nanotube strip in the stretchable conductive composite fiber; specifically, a three-electrode system is used, with a carbon nanotube strip in the stretchable conductive composite fiber as the working electrode, commercial silver / silver chloride as the reference electrode, and commercial platinum wire as the counter electrode. Electrodeposition is performed in a mixed solution of 0.1M aniline and 0.1M H2SO4 by cyclic voltammetry at -0.2 to 1V for 25 cycles, with a scan rate parameter set to 100mV / s. Based on the above operation, the pH sensing electrode was obtained.

[0088] K + Sensing electrode: First, 2 μL of commercial polystyrene sulfonate (PEDOT:PSS) solution was uniformly drop-coated onto the surface of a carbon nanotube strip in a stretchable conductive composite fiber. After drying, the coating was repeated twice. Second, 2 mg of valine, 0.5 mg of sodium tetraphenylborate, 32.7 mg of polyvinyl chloride, and 64.7 mg of di(2-ethylhexyl) sebacate were mixed and dissolved in 350 μL of cyclohexanone to prepare K. + By selecting a mixed solution for the layer, PEDOT:PSS / carbon nanotube strips were immersed in the solution to obtain a uniform coating. After drying overnight, K was obtained. + Sensing electrodes;

[0089] Na +Sensing electrode: First, 2 μL of commercial PEDOT:PSS solution was uniformly drop-coated onto the surface of a carbon nanotube strip in a stretchable conductive composite fiber. After drying, the coating was repeated twice. Second, 1 mg of sodium ion carrier X, 0.55 mg of sodium tetraphenylborate, 33 mg of polyvinyl chloride, and 65.45 mg of di(2-ethylhexyl) sebacate were mixed and dissolved in 660 μL of tetrahydrofuran to prepare Na... + By selecting a mixed solution for the layer, PEDOT:PSS / carbon nanotube strips were immersed in the above solution to obtain a uniform coating. After drying overnight, Na was obtained. + Sensing electrodes;

[0090] Glucose sensing electrode: This is a small molecule selective electrode. First, chitosan is dissolved in 2% acetic acid and magnetically stirred for 1–1.5 h to prepare a 1% chitosan solution. Then, the obtained chitosan solution is mixed with 2 mg / mL single-walled carbon nanotubes, ultrasonically dispersed for 30 min, and then mixed with glucose oxidase to prepare a mixed solution with a concentration of 40 mg / mL. To improve the sensitivity of the glucose sensing electrode, a layer of Prussian blue (PB) is electrodeposited on the surface of a carbon nanotube strip in a stretchable conductive composite fiber using cyclic voltammetry to obtain a PB-coated carbon nanotube strip. A three-electrode system is used, with one carbon nanotube in the stretchable conductive composite fiber as the electrodepositer. The strip was used as the working electrode, commercial silver / silver chloride as the reference electrode, and commercial platinum wire as the counter electrode. The electrodeposition solution consisted of 2.5 mM ferric chloride, 2.5 mM potassium ferricyanide, 100 mM potassium chloride, and 100 mM hydrochloric acid. The deposition voltage ranged from -0.2 V to 1.0 V, the scan rate was 100 mV / s, and the cycle was 10 times. Finally, 10 μL of the above-prepared mixed solution was uniformly drop-coated onto the surface of the carbon nanotube strip coated with PB, and 6 μL of a 0.5% perfluorosulfonic acid polymer (Nafion) solution was drop-coated onto the surface of the working electrode to protect the enzyme layer and prevent it from falling off. After drying, the glucose sensing electrode was obtained.

[0091] Lactic acid sensing electrode: This is a small molecule selective electrode. A 2% chitosan solution is prepared by dissolving chitosan in 2% acetic acid and stirring magnetically for 1–1.5 h. The resulting chitosan solution is then mixed with 2 mg / mL single-walled carbon nanotubes, ultrasonically dispersed for 30 min, and then mixed with lactate oxidase to prepare a 40 mg / mL mixed solution. To improve the sensitivity of the lactic acid sensing electrode, a layer of PB is electrodeposited on the surface of a carbon nanotube strip in a stretchable conductive composite fiber using cyclic voltammetry to obtain a PB-coated carbon nanotube strip. A three-electrode system is used, with a carbon nanotube strip in the stretchable conductive composite fiber as the working electrode, commercial silver / silver chloride as the reference electrode, and commercial platinum wire as the reference electrode. Electrode; the electrodeposition solution consists of 2.5 mM ferric chloride, 2.5 mM potassium ferricyanide, 100 mM potassium chloride and 100 mM hydrochloric acid solution; the deposition voltage range is -0.2 V to 1.0 V, the scan rate is 100 mV / s, and the cycle is 50 times; considering that the concentration of lactic acid in sweat is much higher than that of glucose, a thicker PB layer is chosen to broaden the linear range of the electrode and thus achieve efficient detection of lactic acid concentration; finally, 10 μL of the above-prepared mixed solution is uniformly drop-coated onto the surface of the carbon nanotube strip coated with the PB layer, and 6 μL of 0.5% Nafion solution is drop-coated onto the surface of the working electrode to protect the enzyme layer and prevent it from falling off. After drying, the lactic acid sensing electrode is obtained.

[0092] Uric acid sensing electrode: This is a small molecule selective electrode. It is prepared by electrodeposition, and the deposition process mainly adopts a three-electrode system. A carbon nanotube strip in a stretchable conductive composite fiber is used as the working electrode, a commercial silver / silver chloride electrode is used as the reference electrode, and a platinum wire electrode is used as the counter electrode. The deposition solution is an aqueous solution of 1 mM potassium chloroplatinate and 0.1 M potassium chloride. The deposition program is as follows: using a multi-point step method, deposition is carried out at 0.5 V for 10 s, followed by deposition at -0.7 V for 10 s. This constitutes one cycle. After 25 cycles, the uric acid sensing electrode is obtained.

[0093] III. Preparation of PAN / SiO2 sweat-absorbing layer:

[0094] PAN and SiO2 were mixed in N,N-dimethylformamide at a volume ratio of 10:1 and stirred at 50°C for 5 hours. After the solution became clear and transparent, a PAN / SiO2 spinning solution with a mass fraction of 9% was obtained. Then, an PAN / SiO2 sweat-absorbing layer with a thickness of 200 μm was prepared by electrospinning.

[0095] The electrospinning process is as follows: the PAN / SiO2 spinning solution is drawn into a 20mL syringe, which is then fixed to the injection pump of the spinning machine. A stainless steel needle is attached to the syringe, and the needle is connected to the positive terminal of a high-voltage power supply. The receiving roller is connected to the negative terminal of a high-voltage power supply, and a receiving substrate is attached to the roller. The receiving distance is 15cm, the liquid supply rate is 0.5mL / h, the roller speed is 500r / min, the spinning voltage is positive 20kV, and the spinning time is 5h.

[0096] The particle size of the SiO2 is 20–50 nm;

[0097] The molecular weight of the PAN is 60,000 to 90,000;

[0098] IV. Sensor fabrication:

[0099] The PAN / SiO2 sweat-absorbing layer obtained in step three is wrapped around the outer layer of the integrated stretchable flexible sensing fiber obtained in step two to obtain a composite sensing fiber. Then, the composite sensing fiber is assembled with ordinary commercial elastic fiber material by direct weaving to prepare an electrochemical fabric, thereby obtaining an integrated stretchable flexible wearable biosensor, thus completing the preparation method.

[0100] The assembly and preparation of electrochemical fabrics: Based on the wearable application requirements of different application scenarios, the design of electrochemical fabrics includes headbands, neckbands, wristbands, and clothing.

[0101] The fabrication schematic diagram of the stretchable conductive composite fiber prepared in this embodiment is shown below. Figure 1 As shown, the stretchable conductive composite fiber is prepared by pre-stretching a silicone elastic fiber substrate and then spirally winding it with carbon nanotube strips at equal intervals. A physical image of the stretchable conductive composite fiber can be found below. Figure 2 The synergistic effect of a rotary stepper motor and a guide rail allows carbon nanotube strips to be neatly wound onto a silicone elastic fiber substrate, remaining parallel to each other and without cross-linking. A schematic diagram of the conductive composite fiber interface is shown below. Figure 3 As shown, the hydroxyl groups on the surface of carbon nanotube strips can form hydrogen bond interactions with the hydroxyl groups on the surface of silicone elastic fibers, further enhancing their adhesion and thus reducing signal instability caused by electrode slippage.

[0102] The mechanical property test results of the stretchable conductive composite fiber prepared in this embodiment are as follows: Figure 4 , 5 As shown in Figure 6, Figure 4The image shows the effect of pre-stretching-recovery on the tensile properties of stretchable conductive composite fibers and the SEM image of the micro-wrinkles formed on the surface. It can be seen that compared with the conductive composite fibers without pre-stretching, the pre-stretched conductive composite fibers can maintain good stability under 300% tensile deformation. Furthermore, the SEM image of the carbon nanotube strips can be used to visually observe the micro-wrinkle structure formed under the effect of pre-stretching-recovery.

[0103] Figure 5 The graph shows the change in resistance of the stretchable conductive composite fiber under 10,000 tensile cycles with a deformation of 300%. As can be seen, to verify the tensile stability of the conductive composite fiber, it was repeatedly stretched 10,000 times with a deformation of 300% using a tensile testing machine, and the change in resistance was less than 10%. This demonstrates that the prepared conductive composite fiber has excellent tensile stability. Finally, the conductive composite fiber was bent and twisted 10,000 times respectively, and the change in resistance was recorded during the process.

[0104] Figure 6 The graph shows the resistance change of the stretchable conductive composite fiber after 10,000 bending and torsion cycles. It can be seen that the resistance of the electrode only changed by 4% and 1.5% after multiple bending and torsion cycles, respectively. This proves that the prepared stretchable conductive composite fiber can maintain stable performance under multiple bending and torsion cycles.

[0105] The integrated stretchable flexible sensing fiber prepared in this embodiment has electrochemical properties, such as... Figure 7 As shown, the ac part represents pH and K in sequence. + and Na + The open-circuit potential response of the sensing electrodes to their respective analytical solutions; the df section shows the current response of the sensing electrodes for glucose, lactic acid, and uric acid to their corresponding analytical solutions; it can be seen that pH, K + Na + The sensing electrodes for glucose, lactic acid, and uric acid exhibit excellent detection performance.

[0106] In this embodiment, the pH sensing electrode can perform linear detection within a solution pH range of 4-7 and exhibits a sensitivity of 56.8 mV / pH. + The sensing electrode exhibits linear detection within a potassium ion concentration range of 2-32 mM in the solution, demonstrating a sensitivity of 62.3 mV / dec and a detection limit of 20.4 μM. Na +The sensing electrodes exhibit linear detection within a sodium ion concentration range of 10-160 mM, demonstrating a sensitivity of 49.1 mV / dec and a detection limit of 79 μM. The glucose sensing electrode demonstrates linear detection within a glucose concentration range of 0-200 μM, exhibiting a sensitivity of 0.79 nA / μM and a detection limit of 4 μM. The lactic acid sensing electrode demonstrates linear detection within a lactic acid concentration range of 5-25 mM, exhibiting a sensitivity of 86 nA / μM and a detection limit of 0.4 mM. The uric acid sensing electrode demonstrates linear detection within a uric acid concentration range of 0-160 μM, exhibiting a sensitivity of 3.4 nA / μM and a detection limit of 3.1 μM. These sensing electrodes also demonstrate good repeatability, interference resistance, continuous detection stability, and long-term stability. This demonstrates the excellent detection performance of the integrated, stretchable, flexible sensing fiber.

[0107] In this embodiment, composite sensing fibers were prepared, and their sweat-absorbing properties were analyzed. The results are as follows: Figure 8 As shown, the minimum detection volume of the composite sweat-wicking layer sensor was tested. It can be seen that the composite sweat-wicking layer sensor only requires 1 μL of sweat to achieve circuit connection, while the sensor without a composite sweat-wicking layer requires nearly 400 μL. This is one-third of the amount of sweat required to activate the sensor reported so far, further illustrating the capability of the sweat-wicking layer.

[0108] The composite sensing fiber prepared in this embodiment exhibits electrochemical sensing properties under tension, such as... Figure 9 As shown, part a represents pH and K. + and Na + Part a shows the voltage signal detected by the sensing electrode during 300% tensile deformation; part b shows the current signal detected by the glucose, lactic acid, and uric acid sensing electrodes during 300% tensile deformation; part c shows the current signal detected at pH, K... + and Na + The voltage signal detected by the sensing electrode in 1000 stretching cycles; part d is the current signal detected by the glucose, lactic acid and uric acid sensing electrodes in 1000 stretching cycles.

[0109] from Figure 9 As shown in sections a and b, the detection signal of the composite sensing fiber remains almost unchanged under a tensile strain of 300%, maintaining stable response characteristics. This indicates that the sensor can maintain highly reliable electrochemical performance even under large deformation conditions.

[0110] from Figure 9As shown in sections c and d, the sensor maintains excellent stability and reliable detection performance even after 1000 cycles of 300% deformation stretching. This demonstrates that the composite sensing fiber prepared based on the pre-stretch-recovery strategy not only possesses good tensile properties but also maintains stable electrochemical properties, providing more reliable and durable performance in practical applications. Considering that the strain occurring during human movement ranges from 20% to 75%, the tensile properties of the composite sensing fiber are suitable for various wearable applications.

[0111] In this embodiment, the composite sensing fiber was assembled with ordinary commercial elastic fiber material through direct weaving to prepare an electrochemical fabric. A schematic diagram illustrating its use in the analysis of various biomarkers is shown below. Figure 10 Part a of the figure illustrates the assembly of composite sensing fibers with ordinary commercial elastic fiber materials through direct weaving, while part b illustrates the assembly and preparation of electrochemical fabrics to achieve wireless data transmission and remote monitoring. In this embodiment, an integrated, stretchable, flexible wearable biosensor is obtained, which is then integrated with a flexible integrated circuit chip and a flexible power supply device to form a fabric sensing system. This system can upload detection data to mobile devices and the cloud in real time via Bluetooth technology, achieving wireless data transmission and remote monitoring. A corresponding mobile application (designed using Biofluids software developed by Beijing Huyi Technology Co., Ltd.) is designed and developed using Java, allowing users to view sweat pH, K... + Na + The system monitors the changing trends of physiological indicators such as glucose, lactic acid, and uric acid, and allows users to set warning thresholds. When detected values ​​exceed preset ranges, the mobile application promptly sends alerts to help users take timely action, thus enabling real-time monitoring and management of their health. This fabric-based sensing system is portable, comfortable, and allows for wireless transmission, showing broad application prospects in health management and medical monitoring.

[0112] In this embodiment, the composite sensing fiber is assembled with ordinary commercial elastic fiber material through direct weaving to prepare an electrochemical fabric, i.e., a fabric sensing system; the actual situation of the subject wearing the fabric sensing system during running exercise is as follows: Figure 11 Part a shows the electrochemical fabric in straight and bent elbow positions; Part b shows the actual wireless data reception of the custom-developed mobile application and the actual smartphone interface, respectively; through Figure 11 The image shows a subject wearing a fabric sensor while running, bending their elbows, and using a smartphone to wirelessly receive data via a custom-developed mobile application.

[0113] The fabric sensing system can process acquired sensor data and transmit it to a Bluetooth-enabled smartphone. A corresponding application with a user-friendly interface is used to display, store, and export data. Furthermore, user comfort and freedom of movement are considered. The fabric sensing system can easily accommodate the 20% tensile strain caused by elbow flexion. Through this woven integration method, this embodiment demonstrates the practical application potential of an integrated, stretchable, flexible wearable biosensor in wearable health monitoring, providing users with a convenient and comfortable monitoring experience.

Claims

1. A method for fabricating an integrated, stretchable, flexible wearable biosensor, characterized in that, An integrated, stretchable, flexible wearable biosensor is made by wrapping an integrated, stretchable, flexible sensing fiber with a PAN / SiO2 sweat-absorbing layer. Its fabrication method is achieved through the following steps: I. Preparation of stretchable conductive composite fibers: a. The carbon nanotube strips are subjected to oxygen plasma treatment for 3-5 minutes to obtain the treated carbon nanotube strips. b. Take out the two components of the two-component Ecoflex00-10 platinum catalytic silica gel in equal mass ratio and mix them. After homogenization and degassing, a polymer mixture is obtained. Then, inject it into a polyethylene terephthalate tube with an inner diameter of 1.5~2mm and let it stand at room temperature until it is completely cured. After peeling, the silicone elastic fiber base fiber is obtained. c. Take one of the above-mentioned silicone elastic fiber base fibers, fix it on the rotary stepper motor and pre-stretch it to a deformation of 300%. Then, place the guide rail perpendicular to the rotary stepper motor. Take seven processed carbon nanotube strips, fix one end of each strip to one side of the silicone elastic fiber base fiber and the other end to the guide rail, and perform three-dimensional spiral winding at equal intervals to obtain stretchable conductive composite fiber. II. Fabrication of integrated, stretchable, flexible sensing fibers: Using existing methods, one reference electrode and six working electrodes are modified onto the above-mentioned stretchable conductive composite fiber to obtain an integrated stretchable flexible sensing fiber. The six working electrodes are, in order, a pH sensing electrode, a K... + Sensing electrode, Na + Sensing electrodes, glucose sensing electrodes, lactic acid sensing electrodes, and uric acid sensing electrodes; III. Preparation of PAN / SiO2 sweat-absorbing layer: PAN and SiO2 were mixed in N,N-dimethylformamide at a volume ratio of 10:1 to prepare a PAN / SiO2 spinning solution with a mass fraction of 9%~11%. Then, the solution was prepared by electrospinning to obtain a PAN / SiO2 sweat-absorbing layer with a thickness of 100~300μm. IV. Sensor fabrication: The PAN / SiO2 sweat-absorbing layer obtained in step three is wrapped around the outer layer of the integrated stretchable flexible sensing fiber obtained in step two to obtain a composite sensing fiber. Then, the composite sensing fiber is assembled with ordinary commercial elastic fiber material by direct weaving to prepare an electrochemical fabric, thereby obtaining a flexible wearable electrochemical biosensor, thus completing the preparation method. In step one c, the equidistant three-dimensional spiral winding involves simultaneously activating a rotary stepper motor and a guide rail, causing seven processed carbon nanotube strips to spirally wind around the deformed silicone elastic fiber substrate surface, with equal spacing and parallel to each other.

2. The method for fabricating the integrated stretchable flexible wearable biosensor according to claim 1, characterized in that, The carbon nanotube strips mentioned in step one a: continuous carbon nanotube strips with a diameter of 500~700μm.

3. The method for fabricating the integrated stretchable flexible wearable biosensor according to claim 1, characterized in that, The homogenization and degassing described in step 1b: a homogenizer and degassing device is used, and the degassing time is 3-5 minutes.

4. The method for fabricating the integrated stretchable flexible wearable biosensor according to claim 1, characterized in that, The molecular weight of PAN mentioned in step three is 60,000 to 90,000.

5. The method for fabricating the integrated stretchable flexible wearable biosensor according to claim 1, characterized in that... The SiO2 particles mentioned in step three have a particle size of 20~50nm.

6. The method for fabricating the integrated stretchable flexible wearable biosensor according to claim 1, characterized in that, The preparation in step three involves stirring at 50°C for 4-6 hours.

7. The method for fabricating the integrated stretchable flexible wearable biosensor according to claim 1, characterized in that, In step three, electrospinning technology is used for preparation: the receiving distance is 15cm, the liquid supply rate is 0.5mL / h, the roller speed is 500r / min, the spinning voltage is positive 20kV, and the spinning time is 4~6h.

8. The method for fabricating the integrated stretchable flexible wearable biosensor according to claim 1, characterized in that, In step four, electrochemical fabrics are assembled and prepared: based on the wearable application requirements of different application scenarios, the design of electrochemical fabrics includes clothing.

Images