Hydrogel-integrated carbon dioxide sensor, preparation method and intelligent mask thereof

Abstract

The invention discloses a hydrogel-integrated carbon dioxide sensor, a preparation method and an intelligent mask thereof, and relates to the field of blood glucose monitoring, the hydrogel-integrated carbon dioxide sensor comprises a substrate, an interdigital electrode and a hydrogel film; the interdigital electrode comprises a first electrode and a second electrode; the first electrode and the second electrode are symmetrically arranged on the substrate, and a set distance is arranged between the first electrode and the second electrode; the hydrogel film is coated on the first electrode, the second electrode and the substrate. The integrated hydrogel carbon dioxide sensor is integrated on the intelligent mask. According to the carbon dioxide sensor integrated with the hydrogel, the principle that reversible adsorption and desorption reaction of CO2 molecules and the hydrogel causes electrical parameter change is utilized, high-sensitivity detection of the CO2 concentration is achieved, and the blood glucose level of a wearer is indirectly monitored through the change of the CO2 concentration.

Description

Technical Field

[0001] This application relates to the field of blood glucose monitoring, and in particular to a carbon dioxide sensor integrated with hydrogel, a preparation method thereof, and a smart mask thereof. Background Technology

[0002] In recent years, with the global emphasis on the coordinated advancement of health management and "dual carbon" goals, the demand for accurate monitoring of human respiratory gases (especially CO2) has become increasingly prominent in areas such as chronic disease prevention and control and personalized health management. Particularly in blood glucose monitoring and respiratory function assessment, traditional testing technologies have significant drawbacks: existing blood glucose monitoring mainly relies on invasive blood sampling or subcutaneous implanted sensors, which are not only cumbersome to operate, increasing patient discomfort and infection risks, but also difficult to achieve continuous, undisturbed monitoring; while traditional respiratory monitoring devices (such as large pulmonary function instruments) are bulky, uncomfortable to wear, and unsuitable for everyday activities. Against this backdrop, developing a non-invasive, real-time, and portable smart breathing mask that indirectly reflects human blood glucose levels and respiratory function by monitoring changes in CO2 concentration in respiratory gases is of great significance for promoting intelligent health management. Summary of the Invention

[0003] The purpose of this application is to provide an integrated hydrogel carbon dioxide sensor, its preparation method, and a smart mask thereof, so as to achieve highly sensitive detection of CO2 concentration and indirectly monitor human blood glucose levels through changes in CO2 concentration.

[0004] To achieve the above objectives, this application provides the following solution:

[0005] In a first aspect, this application provides a carbon dioxide sensor integrated with hydrogel, comprising: a substrate, interdigitated electrodes, and a hydrogel film; the interdigitated electrodes include a first electrode and a second electrode;

[0006] The first electrode and the second electrode are symmetrically disposed on the substrate, and the first electrode and the second electrode are spaced apart by a certain distance; the hydrogel film is coated on the first electrode, the second electrode and the substrate.

[0007] In one embodiment, it further includes two pins; the two pins are respectively connected to the first electrode and the second electrode.

[0008] Secondly, this application provides a method for fabricating an integrated hydrogel carbon dioxide sensor. The method for fabricating the integrated hydrogel carbon dioxide sensor includes:

[0009] Metals Ti and Pt were deposited on the substrate by magnetron sputtering, and interdigitated electrodes with a finger width of 100 μm and a spacing of 50 μm were formed by photolithography.

[0010] 500 μL of 99% pure dimethylaminopropylmethacrylamide and 100 μL of 99% pure dimethylacetamide were mixed as monomers, and then ultrasonically mixed with 200 mg of 99% pure crosslinking agent N,N'-methylenebisacrylamide, 1000 μL of deionized water and 20 μL of 97% pure photoinitiator for 5 minutes to form a precursor solution.

[0011] The precursor solution is drop-coated onto a substrate having the interdigitated electrodes. After uniform spin-coating, it is irradiated for 10 minutes under ultraviolet light with a wavelength of 365 nm and an intensity of 150 mW / cm2 to 200 mW / cm2 to initiate a free radical polymerization reaction and form a hydrogel film, thus obtaining an integrated hydrogel carbon dioxide sensor.

[0012] In one embodiment, the substrate is selected from, but is not limited to, silicon and polyimide.

[0013] In one embodiment, the sputtering target includes, but is not limited to, platinum, gold, and silver.

[0014] In one embodiment, the photoinitiator is 2-hydroxy-2-methylphenylacetone.

[0015] Thirdly, this application provides a smart mask, including: a mask body, a carbon dioxide sensor with integrated hydrogel, a temperature and humidity sensor, a main control module, and a wireless communication module;

[0016] The integrated hydrogel carbon dioxide sensor, the temperature and humidity sensor, the main control module, and the wireless communication module are all mounted on the mask body;

[0017] The integrated hydrogel carbon dioxide sensor and the temperature and humidity sensor are both connected to the main control module;

[0018] The integrated hydrogel carbon dioxide sensor is used to collect the concentration of carbon dioxide exhaled by the wearer;

[0019] The temperature and humidity sensor is used to collect ambient temperature and humidity;

[0020] The main control module is used to process the temperature, humidity, and carbon dioxide concentration;

[0021] The wireless communication module is used to transmit the processed temperature, processed humidity, and processed carbon dioxide concentration to the terminal device.

[0022] In one embodiment, a micro airflow channel is provided on the inner side of the nose bridge of the mask body, and the integrated hydrogel carbon dioxide sensor is embedded in the micro airflow channel and fixed by a detachable sensor compartment.

[0023] In one embodiment, it further includes a power management circuit; the power management circuit is used to select between USB power supply and lithium battery power supply.

[0024] In one embodiment, it further includes a charging circuit; the charging circuit is used to charge the integrated hydrogel carbon dioxide sensor, the temperature and humidity sensor and the main control module when USB power is selected.

[0025] According to the specific embodiments provided in this application, this application has the following technical effects:

[0026] This application provides an integrated hydrogel carbon dioxide sensor, its preparation method, and a smart mask thereof. The integrated hydrogel carbon dioxide sensor includes: a substrate, interdigitated electrodes, and a hydrogel film; the interdigitated electrodes include a first electrode and a second electrode; the first electrode and the second electrode are symmetrically disposed on the substrate, with a predetermined distance between them; the hydrogel film is coated on the first electrode, the second electrode, and the substrate. Furthermore, the smart mask integrating the integrated hydrogel carbon dioxide sensor includes: a mask body, an integrated hydrogel carbon dioxide sensor, a temperature and humidity sensor, a main control module, and a wireless communication module; the integrated hydrogel carbon dioxide sensor, the temperature and humidity sensor, the main control module, and the wireless communication module are all disposed on the mask body; the integrated hydrogel carbon dioxide sensor and the temperature and humidity sensor are both connected to the main control module; the integrated hydrogel carbon dioxide sensor is used to collect the carbon dioxide concentration exhaled by the wearer; the temperature and humidity sensor is used to collect the ambient temperature and humidity; the main control module is used to process the temperature, humidity, and carbon dioxide concentration; the wireless communication module is used to transmit the processed temperature, humidity, and carbon dioxide concentration to a terminal device. The carbon dioxide sensor integrated with hydrogel in this application utilizes the principle that the reversible adsorption-desorption reaction between CO2 molecules and hydrogel causes changes in electrical parameters to achieve highly sensitive detection of CO2 concentration, and indirectly monitors the wearer's blood glucose level through changes in CO2 concentration. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1A schematic diagram of an integrated hydrogel carbon dioxide sensor structure provided in an embodiment of this application;

[0029] Figure 2 A top view of an integrated hydrogel carbon dioxide sensor structure provided in an embodiment of this application;

[0030] Figure 3 A structural block diagram of a smart mask provided in one embodiment of this application;

[0031] Figure 4 This is a schematic diagram of the MCU's peripheral circuitry.

[0032] Figure 5 This is a schematic diagram of the ESP32 automatic download circuit.

[0033] Figure 6 This is a schematic diagram of a power management circuit.

[0034] Figure 7 This is a schematic diagram of the charging circuit;

[0035] Figure 8 This is a schematic diagram of the UI interface;

[0036] Figure 9 This is a flowchart of the data transmission process;

[0037] Figure 10 A flowchart of the smart mask workflow;

[0038] Figure 11 The schematic diagram shows the response-recovery curves of a carbon dioxide sensor prepared at 25°C under CO2 gas at 500ppm, 1000ppm, 2000ppm, 5000ppm and 10000ppm.

[0039] Figure 12 A schematic diagram showing how a smart mask with this sensor integrated into the human body monitors the human body's breathing under different exercise states by detecting changes in the resistance of carbon dioxide.

[0040] Figure 13 A schematic diagram showing the change in carbon dioxide response value before and after a meal when a smart mask with this sensor integrated is worn on the human body.

[0041] Figure 14 A schematic diagram illustrating how a smart mask, integrated with this sensor, monitors changes in blood sugar levels by detecting changes in carbon dioxide response values.

[0042] Reference numerals: 1. Substrate; 2. Interdigitated electrode; 3. Hydrogel film; 4. Lead. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] This application relates to the field of human health monitoring technology, specifically to a carbon dioxide sensor integrated with hydrogel, its preparation method, and a smart mask thereof, for application in respiratory detection and blood glucose monitoring.

[0046] This application proposes a CO2 sensor based on p(DMAPMA-co-DMA) hydrogel and its application in respiratory monitoring and blood glucose assessment. This sensor integrates a DMAPMA-containing hydrogel film into an electrode system, utilizing the principle that the reversible adsorption-desorption reaction between CO2 molecules and the hydrogel causes changes in electrical parameters (such as resistance and capacitance) to achieve highly sensitive CO2 concentration detection. Compared to traditional electrochemical sensors, its innovation lies in three aspects: First, the hydrogel enhances the sensor's gas response performance through deprotonation with carbon dioxide; second, the flexibility and hydrophilic properties of the hydrogel adapt to the integration requirements of wearable devices, allowing it to be combined with masks, patches, and other forms to support non-invasive, continuous monitoring; third, it can complete CO2 response at room temperature, eliminating the need for an additional heating module, significantly reducing power consumption and meeting the design requirements of portable devices. By embedding this sensor into a smart mask, it can not only capture real-time fluctuations in CO2 concentration in breath gas but also indirectly determine the human respiratory and metabolic status through changes in the carbon dioxide response value, providing non-invasive monitoring for human health.

[0047] In one exemplary embodiment, such as Figure 1 and Figure 2 As shown, an integrated hydrogel carbon dioxide sensor is provided, comprising: a substrate 1, interdigitated electrodes 2, and a hydrogel film 3; the interdigitated electrodes 2 include a first electrode and a second electrode.

[0048] The first electrode and the second electrode are symmetrically disposed on the substrate 1, and the first electrode and the second electrode are spaced apart by a certain distance; the hydrogel film 3 is coated on the first electrode, the second electrode and the substrate 1.

[0049] In one embodiment, it further includes two pins; the two pins are respectively connected to the first electrode and the second electrode.

[0050] In one exemplary embodiment, this application provides a method for fabricating an integrated hydrogel carbon dioxide sensor. The method for fabricating the integrated hydrogel carbon dioxide sensor includes:

[0051] S1: Deposit Ti and Pt metals on the substrate by magnetron sputtering, and then form interdigitated electrodes with a finger width of 100 μm and a spacing of 50 μm by photolithography.

[0052] In this embodiment, metal Ti (adhesive layer) and Pt (conductive layer) are deposited on a polyimide (PI) substrate by magnetron sputtering, and then photolithography is used to form interdigitated electrodes (IDEs) with a finger width of 100 μm and a spacing of 50 μm. The substrate can be selected from, but is not limited to, silicon, polyimide (PI), etc., and the sputtering target can be, but is not limited to, platinum, gold, silver, etc.

[0053] S2: Mix 500 μL of 99% pure dimethylaminopropylmethacrylamide and 100 μL of 99% pure dimethylacetamide monomers, then ultrasonically mix with 200 mg of 99% pure crosslinking agent N,N'-methylenebisacrylamide, 1000 μL of deionized water and 20 μL of 97% pure photoinitiator for 5 minutes to form a precursor solution.

[0054] In this embodiment, 500 μl of dimethylaminopropylmethacrylamide (DMAPMA) with a purity of 99% was mixed with 100 μl of dimethylacetamide (DMA) with a purity of 99%, and then mixed with 200 mg of crosslinking agent N,N'-methylenebisacrylamide (MBA) with a purity of 99%, 1000 μl of deionized water, and 20 μl of photoinitiator HMPP. The mixture was ultrasonically mixed for 5 minutes to form a homogeneous and transparent precursor solution. The photoinitiator was 2-hydroxy-2-methylphenylacetone (HMPP) with a purity of 97%.

[0055] S3: The precursor solution is drop-coated onto a substrate having the interdigitated electrodes. After uniform spin coating, it is irradiated under ultraviolet light with a wavelength of 365nm and a light intensity of 150mW / cm2 to 200mW / cm2 for 10 minutes to initiate a free radical polymerization reaction and form a hydrogel film, thereby obtaining an integrated hydrogel carbon dioxide sensor.

[0056] In this embodiment, the precursor solution is drop-coated onto a clean substrate (flexible PI), and after uniform spin-coating, it is placed under light with a wavelength of 365 nm and an intensity of 150 mW / cm². 2 ~200mW / cm 2 Irradiation under ultraviolet light for 10 minutes initiates a free radical polymerization reaction, forming a solid p(DMAPMA-co-DMA) hydrogel film.

[0057] After the hydrogel film and interdigitated electrodes are prepared, the hydrogel solution is spin-coated onto the interdigitated electrodes and polymerized under ultraviolet light to form an integrated hydrogel carbon dioxide sensor.

[0058] This sensor utilizes a polymer network containing a dimethylamine structure to achieve a reversible adsorption-desorption reaction of CO2, enabling a highly sensitive response to changes in environmental CO2 concentration. By controlling the crosslinking agent content and introducing the flexible additive DMA, the prepared hydrogel maintains good CO2 response performance while possessing excellent mechanical flexibility and stability. The sensor is integrated into a flexible printed circuit board and applied to a mask for real-time monitoring of exhaled carbon dioxide. Experiments have demonstrated that this sensor can detect CO2 levels from 500 ppm to 10000 ppm and can operate stably under various physiological states, including exercise and rest. More importantly, this sensor can indirectly reflect respiratory and metabolic states through changes in exhaled CO2 concentration, achieving non-invasive health monitoring and demonstrating broad application prospects in personalized health management, diabetes monitoring, and smart wearable devices.

[0059] In one exemplary embodiment, such as Figure 3 As shown, this application provides a smart mask, including: a mask body, a carbon dioxide sensor with integrated hydrogel, a temperature and humidity sensor, a main control module, and a wireless communication module.

[0060] The integrated hydrogel carbon dioxide sensor, the temperature and humidity sensor, the main control module, and the wireless communication module are all mounted on the mask body.

[0061] As an alternative implementation, a micro airflow channel is provided on the inner side of the nose bridge of the mask body, and the integrated hydrogel carbon dioxide sensor is embedded in the micro airflow channel and fixed by a detachable sensor compartment.

[0062] In this embodiment, the hydrogel film and interdigital electrodes are integrated onto a flexible FPCB (flexible printed circuit board) and encapsulated with medical-grade silicone (thickness < 0.5 mm) to ensure breathability and waterproofness. A micro airflow channel (5 mm × 2 mm) is created inside the nose bridge of the smart mask, and a carbon dioxide sensor with integrated hydrogel is embedded in the channel, allowing exhaled air to directly contact the hydrogel surface.

[0063] The detachable sensor compartment (magnetic / clamp-on) allows for periodic replacement of the hydrogel film (lifespan approximately 7 days).

[0064] The integrated hydrogel carbon dioxide sensor and the temperature and humidity sensor are both connected to the main control module.

[0065] The integrated hydrogel carbon dioxide sensor is used to collect the concentration of carbon dioxide exhaled by the wearer.

[0066] The temperature and humidity sensor is used to collect ambient temperature and humidity.

[0067] In this embodiment, an integrated temperature and humidity sensor (such as AHT20) is used to synchronously collect ambient temperature and humidity data to determine the impact of ambient temperature and humidity on the hydrogel, thereby enabling timely assessment of the product's lifespan.

[0068] At room temperature (25-35℃), when the ambient humidity is high (greater than 70%), the hydration level inside the hydrogel increases, and the structure is in a highly expanded state, increasing in volume by 1.5 to 2 times compared to dry conditions. The internal water content increases significantly, allowing for continued use. However, when the humidity is low (less than 30%), the hydrogel shrinks significantly, the water content decreases, the internal network becomes denser, the water migration ability weakens, and slight dry cracks may even form on the surface, requiring timely replacement. At normal humidity (30%-70%), the need for replacement can be assessed based on sensor performance (normal response value is 30% or higher). Similarly, outside of room temperature conditions, the need for sensor replacement can be determined based on the response value (response value should be 30% or higher).

[0069] The main control module is used to process the temperature, humidity and carbon dioxide concentration.

[0070] A low-power microcontroller (such as ESP32-C3) is selected as the main control module. It has a built-in 12-bit ADC to collect the conditioned voltage signal and transmit the data to a mobile phone or cloud via Wi-Fi or Bluetooth.

[0071] The low-power microcontroller supports rechargeable lithium battery power and implements low-power modes (deep sleep + breathing-triggered wake-up) through a software watchdog.

[0072] In one embodiment, the smart mask further includes a power management circuit; the power management circuit is used to select between USB power supply and lithium battery power supply.

[0073] In one embodiment, the smart mask further includes a charging circuit; the charging circuit is used to charge the integrated hydrogel carbon dioxide sensor, the temperature and humidity sensor, and the main control module when USB power is selected.

[0074] In this embodiment, the smart mask also includes MCU peripheral circuitry, ESP32 automatic download circuitry, power management circuitry, and charging circuitry.

[0075] MCU peripheral circuits such as Figure 4As shown, the MCU peripheral circuit is used to connect all IIC slave devices and provides external pull-up protection. For environmental monitoring, after comparing various options, the AHT20, a small and high-precision temperature and humidity sensor, was ultimately selected, and a serial port pin was brought out for subsequent debugging and programming. To improve the measurement accuracy of the ADC voltage divider circuit, digital-analog isolation was implemented, and digital and analog components were isolated in the subsequent PCB layout to avoid electromagnetic interference.

[0076] ESP32 automatic download circuit, such as Figure 5 As shown, the ESP32 automatic download circuit differs from the classic ESP32 download circuit. It avoids the need for an additional BOOT button for programming and downloading, saving space and reducing costs.

[0077] Power management circuits such as Figure 6 As shown, the first function of the power management circuit is to select between 5V (USB power supply) and lithium battery (3.7V power supply). Otherwise, a short circuit will occur. When USB power is available, USB power is selected as the MCU power source and can be charged through the TP4057 chip. The LDO is responsible for stepping down the power source to 3.3V for the MCU to work normally.

[0078] Charging circuit such as Figure 7 As shown, the TP4057 is used as the charging chip. When the CHEG terminal is powered by USB, it is pulled low and the indicator light is on, indicating that charging is in progress. When the power is fully charged, the STDBY terminal is pulled low and the CHEG terminal is pulled high, stopping charging. The fully charged indicator light is on to protect the battery and prevent overcharging.

[0079] The peripheral circuit is responsible for leading out pins that connect to the ESP32 automatic download circuit, power management circuit, and charging circuit. The power management circuit is responsible for providing power to the MCU peripheral circuit, ESP32 automatic download circuit, and charging circuit. The ESP32 automatic download circuit is responsible for burning the code into the MCU of the MCU peripheral circuit and can print and debug via serial port. The charging circuit works with the power management circuit to provide power and charge the device.

[0080] The wireless communication module is used to transmit the processed temperature, processed humidity, and processed carbon dioxide concentration to the terminal device.

[0081] Terminal equipment development:

[0082] 1) Embedded design:

[0083] By using the Arduino built-in library and third-party libraries, code was written to complete the WiFi protocol and the ternary information related to the MQTT protocol, enabling the hardware circuit to connect to the Alibaba Cloud platform.

[0084] 2) Host computer software design:

[0085] By adding devices and products on the Alibaba Cloud platform, filling in self-written formats in cloud product flow and message parsing, and finally using Android Studio with the help of MPAndroidChart and MQTT JAR packages, the UI design and communication with the lower-level machine were completed. The UI interface is as follows: Figure 8 As shown. Figure 8 In the text, "Intelligent Mask Detection" means "intelligent mask detection"; Res is short for Resistance; Temp is short for Temperature; Humi is short for Humidity; On and Off below the image mean on and off.

[0086] The smart mask based on the above-mentioned integrated hydrogel membrane carbon dioxide sensor can monitor blood glucose. The blood glucose calculation process of this application is as follows:

[0087] 1. Carbon dioxide collection.

[0088] The integrated hydrogel carbon dioxide sensor inside the smart mask collects real-time data on changes in CO2 concentration in the user's exhaled breath, reflecting respiratory metabolic status.

[0089] 2. Signal amplification and processing.

[0090] The carbon dioxide signal obtained in step 1 is input into the ADC voltage divider circuit in the main control module. After filtering, the impedance change of the integrated hydrogel carbon dioxide sensor is low-pass filtered to remove high-frequency noise and effectively convert it into a recognizable voltage signal.

[0091] 3. Signal filtering.

[0092] Based on the voltage signal obtained in step 2, the signal is further input to the subsequent filtering and temperature compensation circuit in the main control module. A designed second-order Butterworth low-pass filter (cutoff frequency 10Hz) filters out high-frequency noise in the breathing signal, improving data stability and accuracy. It should be noted that the hardware design employs large-area copper plating for physical hardware heat dissipation, and this application uses a low-power communication method, resulting in good heat dissipation and eliminating the need for a specially designed temperature compensation circuit.

[0093] 4. Data communication and transmission.

[0094] The effective CO2 response signal after the above signal conditioning is transmitted to the cloud through the wireless communication module to realize remote real-time data upload.

[0095] 5. Smart terminal data processing.

[0096] After receiving the signal from step 4, the cloud platform parses the transmitted data frame by frame according to the user-defined data frame format on the Alibaba Cloud platform, extracting and analyzing the signal characteristics. For example... Figure 9 As shown, the cloud then sends the hardware data to the mobile APP (terminal device) "High-Performance Hydrogel Carbon Dioxide Sensor Monitoring System," which uses the Android Studio development platform and Java technology, is designed based on the Groovy DSL framework, and is used in conjunction with the embedded system designed by the team. It is suitable for real-time monitoring needs in a wide area network environment. The flowchart is as follows. Figure 10 As shown.

[0097] 6. Respiratory and metabolic trend analysis to help identify changes in human physiological state.

[0098] After completing the aforementioned signal amplification and filtering processes, the system can continuously acquire the dynamic response signal of the carbon dioxide sensor and analyze its trend changes over time. By observing the direction of change (increasing, decreasing, or stabilizing), rate of change, and amplitude of fluctuations in the response value, the real-time state of human respiration and metabolic activities can be reflected.

[0099] Example 1: Response performance test of CO2 gas at multiple concentrations.

[0100] like Figure 11 As shown, the gas response performance improves with increasing carbon dioxide concentration. This embodiment tested the response-recovery behavior of a CO2 sensor based on p(DMAPMA-co-DMA) hydrogel at 25°C for different CO2 concentrations (500ppm, 1000ppm, 2000ppm, 5000ppm, and 10000ppm). The sensor's resistance rapidly decreased after each CO2 exposure, exhibiting a significant signal response, and gradually recovered to its initial value under the return of N2 background gas. The sensor's response value increased with increasing CO2 concentration, reaching a maximum of approximately 40%, demonstrating good concentration correlation and repeatability. This proves its advantages of high sensitivity and a wide linear detection range, making it suitable for respiratory gas monitoring needs in various environments.

[0101] Example 2: Respiratory monitoring under different exercise states.

[0102] like Figure 12 As shown, this embodiment uses a smart mask with integrated sensor to monitor the human body's breathing behavior in real time during three states: running, walking, and sleeping. Figure 12The data shows that the amplitude and frequency of resistance changes caused by breathing vary significantly under different exercise states: during running, the resistance fluctuation frequency is high and the amplitude is large, indicating an increase in breathing rate and CO2 production; the resistance fluctuation is weaker during walking; and the fluctuation is minimal during sleep. These differences in electrical signals can directly reflect the intensity of human activity and metabolic level, indicating that this sensor can be used for physiological state recognition and daily behavior tracking.

[0103] Example 3: Correlation analysis of CO2 changes before and after eating and blood glucose levels.

[0104] like Figure 13 and Figure 14 As shown, this embodiment explores the dynamic correlation between CO2 response signals and human blood glucose concentration. Volunteers wore smart masks at six time points: fasting, immediately after eating, and 0.5h, 1h, 2h, and 4h post-eating, and the real-time response values ​​of the CO2 sensor were recorded. The results showed that the ΔR / R0 response value rose rapidly after eating and then gradually decreased, highly consistent with the trend of blood glucose value changes. The response value increased from approximately 76.7% in the fasting state to approximately 83.2% post-meal, consistent with the trend of blood glucose concentration increasing from 6.3mmol / L to 10.1mmol / L.

[0105] Studies have shown a certain coupling relationship between human metabolic activity and blood glucose levels: when blood glucose rises, cellular glucose oxidation increases, producing more CO2, which manifests as a continuous change in sensor response values ​​(such as a decrease in resistance); while when blood glucose falls or stabilizes, CO2 production decreases, and sensor response values ​​tend to stabilize or rise again. This application, through this trend correlation, infers the user's current blood glucose change direction (rising, falling, or stabilizing) based on the shape, amplitude, and rhythm of the response curve, without relying on a specific mathematical model, to assist in judging the dynamic state of blood glucose. This result indicates that changes in CO2 concentration in exhaled breath can serve as a non-invasive proxy indicator of metabolic state (such as blood glucose changes), validating the potential of this sensor in non-invasive metabolic health monitoring.

[0106] This application presents a health monitoring platform based on a wearable smart mask. Its circuit design and IoT implementation both employ advanced technical solutions, achieving miniaturization, low power consumption, and high-precision monitoring.

[0107] First, the entire circuit design is based on a flexible printed circuit board (FPCB) platform, which has excellent flexibility and durability. After 500 bending tests with a radius of 5mm, the deviation of each detection circuit on the FPCB was controlled within 1.2%, fully meeting the requirements for use of masks under prolonged wearing and repeated bending.

[0108] The main control module uses the ESP32-C3 (VFQFN-32-EP package), which measures only 5mm × 5mm × 0.85mm. This chip not only integrates powerful IoT functions but also incorporates a high-precision ADC channel. The ADC has 12-bit resolution, and with the help of hardware filtering algorithms, the hydrogel resistor detection error is controlled within ±1.5%. Notably, in WiFi communication mode, the system's measured peak current is 63mA, meeting the stringent requirements of dynamic power management.

[0109] Temperature and humidity monitoring uses a high-precision AHT20 digital sensor. The AHT20 digital sensor is connected to the main control module through an I2C interface. Its measurement accuracy reaches ±2%RH and ±0.3℃, and the sampling interval is set to 2 seconds to ensure the real-time and reliability of environmental data.

[0110] To ensure the stability of the hydrogel resistor detection signal, this application uses a combination of decoupling capacitors to construct a multi-stage parallel filter structure, which effectively filters out low-frequency ripple on the power line (such as LDO output noise) and high-frequency interference caused by digital circuit switching.

[0111] In terms of power management, this application uses a TP4057 lithium battery management IC in conjunction with a TC1262-3.3V LDO. After multiple rounds of performance comparison and screening, the LDO ultimately selected has a voltage difference of only 60mV between input and output under a typical load current of 60mA (VIN is 3.36V, VOUT is 3.3V), which is far superior to the performance index of conventional LDOs that require a voltage difference of 200mV, thus significantly improving voltage utilization and overall system energy efficiency.

[0112] For IoT communication implementation, a lightweight communication framework is built using the Alibaba Cloud IoT platform, with the cloud platform acting as an intermediary to achieve efficient data transmission. A 16-byte fixed-length data frame is designed, containing a 4-byte timestamp, 8 bytes of sensor data, 2 bytes of CRC16 checksum, and a status bit, ensuring the integrity and real-time performance of data transmission. Furthermore, actual testing shows that the system's data transmission latency remains extremely low, ensuring the accurate presentation of mask monitoring data in real-time applications.

[0113] Overall, this smart mask not only possesses precise data monitoring capabilities but also achieves seamless data integration with the cloud platform through IoT communication. This allows users to view real-time temperature, humidity, and ADC monitoring data via a beautifully designed UI, with monitoring trends presented intuitively as dynamic curves. The interface is simple and aesthetically pleasing, and the data updates rapidly, providing users with an excellent interactive experience and high practical value.

[0114] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A carbon dioxide sensor integrating hydrogel, characterized in that, include: Substrate, interdigitated electrodes, and hydrogel film; the interdigitated electrodes include a first electrode and a second electrode; The first electrode and the second electrode are symmetrically disposed on the substrate, and the first electrode and the second electrode are spaced apart by a certain distance; the hydrogel film is coated on the first electrode, the second electrode and the substrate.

2. The integrated hydrogel carbon dioxide sensor according to claim 1, characterized in that, Also includes: Two pins; the two pins are connected to the first electrode and the second electrode respectively.

3. A method for preparing an integrated hydrogel carbon dioxide sensor, characterized in that, The method for preparing the integrated hydrogel carbon dioxide sensor is used to prepare the integrated hydrogel carbon dioxide sensor according to any one of claims 1-2, wherein the method for preparing the integrated hydrogel carbon dioxide sensor includes: Metals Ti and Pt were deposited on the substrate by magnetron sputtering, and interdigitated electrodes with a finger width of 100 μm and a spacing of 50 μm were formed by photolithography. 500 μL of 99% pure dimethylaminopropylmethacrylamide and 100 μL of 99% pure dimethylacetamide were mixed as monomers, and then ultrasonically mixed with 200 mg of 99% pure crosslinking agent N,N'-methylenebisacrylamide, 1000 μL of deionized water and 20 μL of 97% pure photoinitiator for 5 minutes to form a precursor solution. The precursor solution is drop-coated onto a substrate having the interdigitated electrodes. After uniform spin-coating, it is irradiated for 10 minutes under ultraviolet light with a wavelength of 365 nm and an intensity of 150 mW / cm2 to 200 mW / cm2 to initiate a free radical polymerization reaction and form a hydrogel film, thus obtaining an integrated hydrogel carbon dioxide sensor.

4. The method for preparing the integrated hydrogel carbon dioxide sensor according to claim 3, characterized in that, The substrate may include, but is not limited to, silicon and polyimide.

5. The method for preparing the integrated hydrogel carbon dioxide sensor according to claim 3, characterized in that, Sputtering targets include, but are not limited to, platinum, gold, and silver.

6. The method for preparing the integrated hydrogel carbon dioxide sensor according to claim 3, characterized in that, The photoinitiator is 2-hydroxy-2-methylphenylacetone.

7. A smart mask, characterized in that, include: The mask body, a carbon dioxide sensor with integrated hydrogel, a temperature and humidity sensor, a main control module, and a wireless communication module; The integrated hydrogel carbon dioxide sensor, the temperature and humidity sensor, the main control module, and the wireless communication module are all mounted on the mask body; The integrated hydrogel carbon dioxide sensor and the temperature and humidity sensor are both connected to the main control module; The integrated hydrogel carbon dioxide sensor is used to collect the concentration of carbon dioxide exhaled by the wearer; The temperature and humidity sensor is used to collect ambient temperature and humidity; The main control module is used to process the temperature, humidity, and carbon dioxide concentration; The wireless communication module is used to transmit the processed temperature, processed humidity, and processed carbon dioxide concentration to the terminal device.

8. The smart mask according to claim 7, characterized in that, The mask body has a micro airflow channel on the inner side of the nose bridge, and the integrated hydrogel carbon dioxide sensor is embedded in the micro airflow channel and fixed by a detachable sensor compartment.

9. The smart mask according to claim 7, characterized in that, Also includes: Power management circuitry; The power management circuit described is used to select between USB power supply and lithium battery power supply.

10. The smart mask according to claim 9, characterized in that, Also includes: A charging circuit is used to charge the integrated hydrogel carbon dioxide sensor, the temperature and humidity sensor, and the main control module when USB power is selected.

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