Temperature and pressure dual-function sensor, preparation method and application

Abstract

This invention relates to the field of smart wearable technology, and discloses a dual-function temperature and pressure sensor, its preparation method, and its application. The sensor comprises an upper carbon cloth electrode, a dual-network hydrogel, a polypropylene tape, and a lower carbon cloth electrode arranged sequentially. The polypropylene tape is placed between the dual-network hydrogel and the lower carbon cloth electrode to reduce the initial capacitance and improve pressure sensing sensitivity. The dual-network hydrogel is synthesized using a one-pot chemical crosslinking method. The dual-network hydrogel includes: acrylamide and chitosan as polymerizable monomers, with acrylamide and chitosan forming a dual-network crosslinking system; glycerol for moisturizing and lubrication, enhancing stretchability, enhancing freeze resistance, and enhancing biocompatibility; zinc sulfate heptahydrate for ion transport and charge transfer, and improving electrochemical performance; acetic acid to provide slightly acidic conditions, thereby promoting chitosan dissolution; ammonium persulfate as an initiator; and N,N'-methylenebisacrylamide as a crosslinking agent.

Description

Technical Field

[0001] This invention relates to the field of smart wearable technology, and in particular to a dual-function temperature and pressure sensor, its fabrication method, and its application. Background Technology

[0002] With the rapid development of wearable electronic devices and human-computer interaction technologies, flexible sensors, due to their excellent flexibility and adaptability to complex curved surfaces, have shown broad application prospects in fields such as health monitoring and intelligent robotics. Among various flexible sensing materials, hydrogel-based sensors, by mimicking the softness and wettability of biological tissues, exhibit excellent biocompatibility and are particularly suitable for long-term monitoring scenarios involving direct contact with human skin. Among these, bifunctional hydrogel sensors capable of simultaneously sensing temperature and pressure signals can provide richer environmental perception information and have become one of the current research hotspots.

[0003] Currently, most flexible sensors are fabricated using elastomer materials such as polydimethylsiloxane (PDMS) and polyurethane (PU). Although these materials possess a certain degree of flexibility, their tensile and deformation capabilities remain limited, resulting in insufficient fit and stability of the constructed sensors when adapting to large deformation surfaces such as human joints. Furthermore, sensors based on these traditional elastomers are easily constrained by the physicochemical properties of the materials themselves in terms of pressure sensitivity and temperature response range, exhibiting limited sensitivity adjustability and a relatively narrow response range. This, to some extent, limits their further application in scenarios requiring high precision and multi-parameter sensing. Summary of the Invention

[0004] This invention provides a dual-function temperature and pressure sensor, its fabrication method, and its application. It features ultra-high flexibility, a wide temperature response range, and high pressure sensitivity, enabling synchronous and stable detection of temperature and pressure signals. This addresses the technical problems of existing flexible sensors made of elastomers, which suffer from insufficient fit and stability, limited sensitivity adjustability, and a relatively narrow response range due to the limited flexibility of the material itself.

[0005] According to one aspect of the present invention, a dual-function temperature and pressure sensor is provided, comprising, from top to bottom, an upper carbon cloth electrode, a dual-network hydrogel, a polypropylene tape, and a lower carbon cloth electrode. The polypropylene tape is disposed between the dual-network hydrogel and the lower carbon cloth electrode to reduce the initial capacitance and improve the pressure sensing sensitivity. The dual-network hydrogel is synthesized by one-pot chemical crosslinking and includes acrylamide, glycerol, chitosan, acetic acid, zinc sulfate heptahydrate, ammonium persulfate, and N,N'-methylenebisacrylamide. Acrylamide and chitosan are polymerizable monomers, and a dual-network crosslinking system is constructed by acrylamide and chitosan. Glycerol is used for moisturizing and lubrication, enhancing stretchability, enhancing antifreeze properties, and enhancing biocompatibility. Zinc sulfate heptahydrate is used for ion transport and charge transfer and to improve electrochemical performance. Acetic acid is used to provide slightly acidic conditions, thereby promoting the dissolution of chitosan. Ammonium persulfate is used as an initiator. N,N'-methylenebisacrylamide is used as a crosslinking agent.

[0006] Furthermore, the dual-network hydrogel comprises 2g-10g of acrylamide, 3g-8g of glycerol, 6g-30g of deionized water, 0.05g-0.5g of chitosan, acetic acid with pH adjusted to 4-6, 0.2g-0.6g of zinc sulfate heptahydrate, 4mg-8mg of ammonium persulfate, and 4mg-8mg of N,N'-methylenebisacrylamide.

[0007] Furthermore, in the same container, acrylamide, glycerol, deionized water, chitosan, acetic acid, zinc sulfate heptahydrate, ammonium persulfate, and N,N'-methylenebisacrylamide were added sequentially, and the mixture was stirred for 1-3 hours to crosslink and prepare a prepolymer solution. Then, TEMED coagulant was added, and the solution was thermosetting at 50-80°C for 25-40 minutes to obtain a double-network hydrogel.

[0008] Furthermore, the upper carbon cloth electrode, the dual-network hydrogel, the polypropylene tape, and the lower carbon cloth electrode constitute a hydrogel sensing unit, which is integrated with the wires; the dual-network hydrogel also serves as a sensitive medium for sensing temperature and pressure.

[0009] Furthermore, a 3×3 array composed of hydrogel sensing units arranged in a spatial array is used. Through the inherent flexibility and extensibility of the dual-network hydrogel, stable and conformal contact between the hydrogel sensing units and the irregular curved surface to be measured is achieved. By the spatial arrangement of the array of hydrogel sensing units and the independent addressing of unit signals, the capacitance changes of each hydrogel sensing unit caused by external pressure are detected and distinguished, thereby expanding the limited sensing area of ​​a single hydrogel sensing unit to the function of spatial positioning and identification of a large-area pressure field.

[0010] According to another aspect of the present invention, a method for fabricating a dual-function temperature and pressure sensor is also provided, comprising the following steps: S100, preparing a dual-network hydrogel; S200, preparing a lower carbon cloth electrode and laying polypropylene tape on the lower carbon cloth electrode, exposing a portion of the surface of the lower carbon cloth electrode; S300, placing the dual-network hydrogel on the polypropylene tape and contacting it with the exposed portion of the lower carbon cloth electrode; S400, covering and attaching an upper carbon cloth electrode to the dual-network hydrogel to form a hydrogel sensing unit; S500, arranging the hydrogel sensing units in a spatial array.

[0011] Further, step S100 specifically involves: adding acrylamide, glycerol, deionized water, chitosan, acetic acid, zinc sulfate heptahydrate, ammonium persulfate, and N,N'-methylenebisacrylamide sequentially to the same container, stirring for 1-3 hours to crosslink and prepare a prepolymer solution, then adding TEMED accelerator, and thermally curing at 50-80°C for 25-40 minutes to obtain a double-network hydrogel.

[0012] Furthermore, the acrylamide is 2g-10g, the glycerol is 3g-8g, the deionized water is 6g-30g, the chitosan is 0.05g-0.5g, the pH is adjusted to 4-6 by acetic acid, the zinc sulfate heptahydrate is 0.2g-0.6g, the ammonium persulfate is 4mg-8mg, and the N,N'-methylenebisacrylamide is 4mg-8mg.

[0013] Further, 6g acrylamide, 5.5g glycerol, 18g deionized water, 0.1g chitosan, acetic acid adjusted to pH 5, 0.4g zinc sulfate heptahydrate, 6mg ammonium persulfate, and 6mg N,N'-methylenebisacrylamide were added sequentially; then the mixture was stirred for 1.5h to crosslink and prepare a prepolymer solution; then 60uL of TEMED coagulant was added, and the mixture was thermosetting at 60℃ for 30min to obtain a double-network hydrogel.

[0014] According to another aspect of the present invention, an application of a dual-function temperature and pressure sensor is also provided, which is used in health monitoring, smart healthcare, human-computer interaction, or electronic skin.

[0015] The present invention has the following beneficial effects:

[0016] 1. Achieving a stable "sandwich" configuration and signal acquisition: By stacking "upper carbon cloth electrode - dual-network hydrogel - polypropylene tape - lower carbon cloth electrode", a well-defined sensing unit is formed. The insulating effect of the polypropylene tape can reduce the initial capacitance value and improve the pressure sensing sensitivity, providing a basis for reliable and repeatable electrical signal detection. For pressure sensing, the dual-network hydrogel undergoes elastic deformation under pressure, changing its contact area and spacing with the upper and lower carbon cloth electrodes, thereby causing a significant change in capacitance. This contact area and spacing change mechanism endows the sensor with high pressure sensitivity.

[0017] 2. Imparting overall flexibility to the sensor: The upper and lower carbon cloth electrodes themselves have good bendability, the dual-network hydrogel has super flexibility, and the polypropylene tape also has a certain degree of flexibility. The combination of the three enables the entire sensor device to adapt to bending, twisting and other deformations, thus having the ability to conform to irregular surfaces (such as human skin) and meet the basic requirements of wearable devices.

[0018] 3. Achieving dual-function sensing of temperature and pressure: As the core sensing material, the dual-network hydrogel has an ionic conductivity that changes with temperature and a physical deformation (thickness, contact area) that changes with pressure. This inherent temperature resistance and pressure-capacitance characteristics enable a single sensing unit to respond to both temperature and pressure stimuli simultaneously without a complex structure, thus realizing the dual-function and miniaturization of the device.

[0019] 4. Obtaining a sensitive material with excellent and stable mechanical properties: A one-pot synthesis method is used to synthesize a dual-network hydrogel constructed from acrylamide (forming a covalently bonded chemical cross-linked network) and chitosan (forming a physical network through ionic or hydrogen bonds). The method is simple and efficient. It is expected that the resulting dual-network structure can combine the high strength of the chemical cross-linked network and the energy dissipation mechanism of the physical cross-linked network, giving the hydrogel excellent toughness, stretchability, and fatigue resistance, thereby improving the durability of the sensor under repeated mechanical stress. The dual-network structure forms a stable and elastic three-dimensional network through chemical cross-linking, giving the hydrogel extremely high flexibility and excellent resilience, allowing it to closely conform to large deformation surfaces such as human skin or joints, thereby improving the fit and signal acquisition stability.

[0020] 5. Significantly Optimized Practical Performance of Hydrogels: The synergistic effect of the components in the formulation brings about an overall performance improvement; the addition of glycerol can effectively lower the freezing point of water, enhance antifreeze properties, prevent freezing failure in low-temperature environments, and at the same time act as a moisturizer and lubricant, slowing down water evaporation and extending the lifespan of the device. Its biocompatibility is also enhanced, and through hydrogen bonding with the hydrogel network, it further enhances the stretchability and antifreeze ability of the material, ensuring the stable operation of the sensor in a wide temperature range; the introduction of zinc sulfate heptahydrate not only provides zinc ions as physical cross-linking points to enhance mechanical properties, but its ionized ions are also responsible for ion transport and charge transfer, which is beneficial for realizing resistive or capacitive sensing. At the same time, zinc ions may also improve electrochemical performance (such as stability). In terms of sensing mechanism, zinc ions (Zn) in the hydrogel 2+ The migration rate of chitosan changes significantly with temperature, thus achieving high sensitivity and wide-range response to temperature; the acidic environment provided by acetic acid effectively promotes the dissolution of chitosan, ensuring the uniform formation of the dual network structure.

[0021] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 This is a schematic diagram of the structure of a temperature and pressure dual-function sensor according to a preferred embodiment of the present invention;

[0024] Figure 2 This is a mechanical tensile property diagram of a preferred embodiment of the dual-network hydrogel of the present invention, wherein... Figure 2 (a) is a graph showing the effect of different acrylamide contents on the mechanical properties of the hydrogel. Figure 2 (b) is a graph showing the effect of different chitosan contents on the mechanical properties of the hydrogel. Figure 2 (c) is a graph showing the dynamic response performance of the sensor;

[0025] Figure 3 This is a pressure sensing performance diagram of a preferred embodiment of the present invention, wherein... Figure 3 (a) is a sensitivity performance graph. Figure 3 (b) is the capacitance-pressure stability diagram. Figure 3 (c) is a pressure detection limit chart. Figure 3 (d) is the response / recovery time graph. Figure 3 (e) is a graph showing long-term stability and cycle durability;

[0026] Figure 4 This is a temperature sensing performance and signal decoupling diagram of a preferred embodiment of the present invention, wherein... Figure 4 (a) shows the pressure sensing performance at different temperatures. Figure 4 (b) is a graph showing the relationship between relative capacitance change and pressure. Figure 4 (c) is a graph showing the relationship between resistance change and pressure. Figure 4 (d) is a graph showing the relationship between resistance change and temperature. Figure 4 (e) shows the repeated response at different temperatures. Figure 4 (f) is the performance radar chart;

[0027] Figure 5 This is a 3×3 pressure sensor array diagram of a preferred embodiment of the present invention, wherein... Figure 5 (a) is a diagram of a single-point pressure test. Figure 5 (b) is a linear multi-point pressure test chart. Figure 5 (c) is a test diagram of simultaneous pressure at multiple points in the area;

[0028] Figure 6 This is a schematic diagram illustrating the application of pressure sensing in limb motion capture according to a preferred embodiment of the present invention, wherein... Figure 6 (a) is a real-time monitoring chart of finger bending degree. Figure 6 (b) is a graph showing the cyclic stability test of repeated finger bending. Figure 6 (c) is a graph showing the cyclic stability test of wrist flexion. Figure 6 (d) is a graph of cyclic stability test of knee flexion;

[0029] Figure 7 This is a schematic diagram illustrating the application of a preferred embodiment of the present invention in Morse code recognition and translation, wherein... Figure 7 (a) is a table of international Morse code characters. Figure 7 (b) is a diagram showing the recognition waveform and decoding process of the word "YES". Figure 7 (c) is a diagram showing the recognition waveform and decoding process of the word "NO". Figure 7 (d) is a diagram showing the recognition waveform and decoding process of the phrase "THANK YOU". Figure 7 (e) is a diagram showing the recognition waveform and decoding process of the phrase "I NEED HELP". Figure 7 (f) is a diagram showing the recognition waveform and decoding process of the word "HELLO". Detailed Implementation

[0030] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available or can be prepared by known methods.

[0031] This embodiment of a temperature and pressure dual-function sensor includes, from top to bottom, an upper carbon cloth electrode, a dual-network hydrogel, a polypropylene tape, and a lower carbon cloth electrode. The polypropylene tape is placed between the dual-network hydrogel and the lower carbon cloth electrode to reduce the initial capacitance and improve the pressure sensing sensitivity. The dual-network hydrogel is synthesized using a one-pot chemical crosslinking method. The dual-network hydrogel includes acrylamide, glycerol, chitosan, acetic acid, zinc sulfate heptahydrate, ammonium persulfate, and N,N'-methylenebisacrylamide. Acrylamide and chitosan are polymerizable monomers, and a dual-network crosslinking system is constructed through acrylamide and chitosan. Glycerol is used for moisturizing and lubrication, enhancing stretchability, enhancing antifreeze properties, and enhancing biocompatibility. Zinc sulfate heptahydrate is used for ion transport and charge transfer and to improve electrochemical performance. Acetic acid is used to provide slightly acidic conditions, thereby promoting the dissolution of chitosan. Ammonium persulfate is used as an initiator. N,N'-methylenebisacrylamide is used as a crosslinking agent. This invention relates to a dual-function temperature and pressure sensor. Through a layered arrangement of "upper carbon cloth electrode - dual-network hydrogel - polypropylene tape - lower carbon cloth electrode," a well-defined sensing unit is formed. The insulating effect of the tape reduces the initial capacitance, improving pressure sensing sensitivity and providing a foundation for reliable and repeatable electrical signal detection. For pressure sensing, the dual-network hydrogel undergoes elastic deformation under pressure, altering its contact area and spacing with the upper and lower carbon cloth electrodes, thus causing a significant change in capacitance. This mechanism of contact area and spacing change endows the sensor with high pressure sensitivity. The upper and lower carbon cloth electrodes themselves possess good flexibility, the dual-network hydrogel exhibits superior flexibility, and the polypropylene tape also possesses a certain degree of flexibility. The combination of these three elements allows the entire sensor device to adapt to bending, twisting, and other deformations, thereby enabling it to conform to irregular surfaces (such as human skin), meeting the basic requirements of wearable devices. Dual-network hydrogels, as the core sensing material, exhibit varying ionic conductivity with temperature and physical deformation (thickness, contact area) with pressure. These inherent thermoresistivity and pressure-capacitance characteristics allow a single sensing unit to simultaneously respond to both temperature and pressure stimuli without complex structures, achieving dual functionality and miniaturization of the device. A one-pot synthesis method was employed to create dual-network hydrogels constructed from acrylamide (forming a covalently cross-linked chemical network) and chitosan (forming a physical network through ionic or hydrogen bonds). This method is simple and efficient. The resulting dual-network structure is expected to combine the high strength of the chemically cross-linked network with the energy dissipation mechanism of the physically cross-linked network, giving the hydrogel excellent toughness, stretchability, and fatigue resistance, thereby improving the sensor's durability under repeated mechanical stress. The dual-network structure, through chemical cross-linking, forms a stable and elastic three-dimensional network, endowing the hydrogel with extremely high flexibility and excellent resilience, enabling it to closely conform to large-deformation surfaces such as human skin or joints, thus improving fit and signal acquisition stability.The synergistic effect of the components in the formula brings about an overall performance improvement; the addition of glycerol can effectively lower the freezing point of water, enhance antifreeze properties, prevent freezing failure in low-temperature environments, and at the same time play a moisturizing and lubricating role, slow down water evaporation, extend the service life of the device, and its biocompatibility also enhances the biocompatibility of the device. Through hydrogen bonding with the hydrogel network, it further enhances the stretchability and antifreeze ability of the material, ensuring the stable operation of the sensor in a wide temperature range; the introduction of zinc sulfate heptahydrate not only provides zinc ions as physical cross-linking points to enhance mechanical properties, but its ionized ions are also responsible for ion transport and charge transfer, which is conducive to realizing resistive or capacitive sensing. At the same time, zinc ions may also improve electrochemical performance (such as stability). In terms of sensing mechanism, zinc ions (Zn) in the hydrogel 2+ The migration rate of chitosan changes significantly with temperature, thus achieving high sensitivity and wide-range response to temperature. The acidic environment provided by acetic acid effectively promotes the dissolution of chitosan, ensuring the uniform formation of the dual-network structure. This invention's temperature and pressure dual-function sensor, through the synergistic effect of a "sandwich" structure design and a dual-network hydrogel material formulation, obtains a sensor with stable structure, good overall flexibility, and dual-mode response to temperature and pressure stimuli. A one-pot method is used to easily and efficiently synthesize a dual-network hydrogel with excellent mechanical properties, freeze resistance, moisture retention, and high biocompatibility. This hydrogel is integrated with a flexible electrode as a sensitive medium, ensuring the consistency and repeatability of sensor performance and overcoming the limitations of traditional elastomer sensors in terms of flexibility, sensitivity, and response range.

[0032] In this embodiment, the dual-network hydrogel comprises 2g-10g of acrylamide, 3g-8g of glycerol, 6g-30g of deionized water, 0.05g-0.5g of chitosan, acetic acid with pH adjusted to 4-6, 0.2g-0.6g of zinc sulfate heptahydrate, 4mg-8mg of ammonium persulfate, and 4mg-8mg of N,N'-methylenebisacrylamide. The 2g-10g of acrylamide serves as the main network monomer, with a significantly higher dosage than the 0.05g-0.5g of chitosan, indicating that the hydrogel uses a covalently cross-linked network of polyacrylamide as its framework, providing structural strength. Chitosan, as the second network component, is used in relatively small amounts to introduce physical cross-linking points (such as with Zn). 2+ The chitosan is used to enhance toughness and functional properties, rather than as the primary structural carrier, by combining coordination groups and functional groups. This ratio range ensures that the two networks exist in a synergistic manner with clear primary and secondary components, avoiding network failure or mutual interference due to imbalance. Limiting the pH of acetic acid to a weakly acidic range of 4-6 provides the necessary environment for the dissolution and stable existence of chitosan, thus ensuring its effective participation in network construction and facilitating the addition of Zn in 0.2g-0.6g of zinc sulfate heptahydrate. 2+The stable presence of the initiator and crosslinking agent allows it to play a role in ionic crosslinking. The amounts of 4 mg-8 mg ammonium persulfate and 4 mg-8 mg N,N'-methylenebisacrylamide are on the same order of magnitude and close in value, indicating that the ratio of initiator to crosslinking agent has been optimized to ensure that the polymerization reaction proceeds at a moderate rate and forms a complete and moderately crosslinked polyacrylamide network. This avoids runaway reaction, network defects, or embrittlement due to excessive or insufficient initiator or crosslinking agent. The amount of 3 g-8 g glycerol is on the same order of magnitude as acrylamide, indicating that as an important component, it can significantly play a role in moisturizing and plasticizing, thus effectively achieving antifreeze and enhanced stretchability in the final product; the amount of 0.2 g-0.6 g zinc sulfate heptahydrate provides sufficient Zn to the system. 2+ Effective ion transport and cross-linking are fundamental to realizing electrochemical sensing functions.

[0033] In this embodiment, acrylamide, glycerol, deionized water, chitosan, acetic acid, zinc sulfate heptahydrate, ammonium persulfate, and N,N'-methylenebisacrylamide were added sequentially to the same container. The mixture was stirred for 1-3 hours to prepare a prepolymer solution for crosslinking. Then, TEMED coagulant was added, and the mixture was thermosetting at 50℃-80℃ for 25-40 minutes to obtain a double-network hydrogel. This one-pot process, where all raw materials are added and stirred sequentially in the same container, simplifies the operation, avoids the transfer, separation, and purification of intermediate products, thereby reducing preparation steps and time, improving synthesis efficiency, and reducing the risk of contamination or material loss due to multiple steps. The stirring process, lasting 1-3 hours, ensures that all components, especially solid chitosan and acrylamide, are fully dissolved, dispersed, and mixed, providing the necessary conditions for forming a uniform and stable prepolymer solution, which is the foundation for obtaining a hydrogel product with consistent structure and properties.

[0034] Acrylamide (AM), glycerol (Gly), deionized water, chitosan (CS), acetic acid (HAc), zinc sulfate heptahydrate (ZnSO4·7H2O), ammonium persulfate (APS), and N,N'-methylenebisacrylamide (MBA) were added sequentially with stirring. This sequential addition and stirring method created the necessary physical and chemical environment for the successful synthesis of the dual-network hydrogel, ensuring the controllability of the reaction and the uniformity of the network. First, acrylamide (AM), glycerol (Gly), deionized water (H2O), chitosan (CS), and acetic acid (HAc) were added and stirred. This first dissolved the chitosan and formed a homogeneous solution system. Chitosan is insoluble in water but soluble in dilute acid. Acetic acid initially provides an acidic environment, promoting the protonation of the amino groups on the chitosan molecular chains, thus dissolving it. This ensures that chitosan, one of the two major monomers, is uniformly dispersed in the system in the form of molecular chains, a prerequisite for constructing a uniform dual-network structure. After the chitosan was completely dissolved in the acidic environment, zinc sulfate heptahydrate (ZnSO4·7H2O) was added to prevent Zn... 2+ To prevent premature redox reaction and consumption of the subsequently added initiator APS, and to avoid the formation of hydroxide precipitates under strongly alkaline conditions; if Zn is added first... 2+ It may react prematurely with APS to generate free radicals, leading to runaway polymerization; under alkaline conditions, Zn 2+ A precipitate will form; this order ensures that Zn... 2+ It can remain intact in the system for subsequent ionic crosslinking with chitosan chains. Finally, ammonium persulfate (APS) and the crosslinking agent N,N'-methylenebisacrylamide (MBA) are added. The introduction of the initiator and crosslinking agent is delayed until all reactants are uniformly dispersed, avoiding localized rapid polymerization of acrylamide in the early stages of mixing, thus preventing the formation of uneven gel blocks or network structure defects. This sequence aims to ensure that the polymerization reaction is initiated only after the entire system has achieved molecular-level homogeneity, resulting in a hydrogel product with a regular structure and consistent properties. AM, Gly, H2O, CS, HAc → Zn 2+ →By adding APS and MBA in a specific order, combined with stirring, and by constructing the reaction environment step by step and controlling the triggering timing of key chemical reactions, the complete dissolution of chitosan, the establishment of a homogeneous system, and the addition of Zn were achieved sequentially. 2+The stable existence of the polymer and the orderly initiation of the final polymerization reaction provide key process guarantees for the successful preparation of a dual-network hydrogel with uniform structure, controllable component ratio, and stable performance. This is the core link in the success of the entire one-pot synthesis. Acrylamide (AM), glycerol (Gly), deionized water (H2O), chitosan (CS), acetic acid (HAc), zinc sulfate heptahydrate (ZnSO4·7H2O), ammonium persulfate (APS), and N,N'-methylenebisacrylamide (MBA) were added sequentially and stirred. Then, tetramethylethylenediamine (TEMED) was added and heated. This stepwise operation had a clear chemical purpose. Before the addition of TEMED and heating, the decomposition and polymerization rate of APS was slow; this stage mainly involved physical mixing, avoiding premature or excessively rapid polymerization and preventing uneven network formation or gel formation due to localized violent reactions. After the addition of TEMED, under heating conditions of 50℃-80℃, it formed a redox initiation system with APS, which significantly accelerated the free radical polymerization reaction. The 25-40 minute thermosetting time, matched with the reaction temperature range, ensured that the acrylamide monomer could fully and rapidly polymerize and crosslink, forming a complete and stable first-level covalent crosslinked network. During this process, the chitosan chains also expanded through ZnSO4·7H2O. 2+ The interactions are initially fixed, thus constructing a dual-network structure. By using a "one-pot" mixing method and a step-by-step reaction control of "mixing first, then initiating," the complex dual-network hydrogel synthesis process is integrated into a simple, mild, and easily controllable process. By controlling the stirring time, the uniformity of the precursor is ensured, and by controlling the initiation timing and curing temperature / time, the orderly and complete polymerization reaction is ensured. In principle, this provides a reliable and efficient process guarantee for the reproducible preparation of dual-network hydrogels with uniform structure and complete network, which is key to achieving the expected performance of hydrogel materials and ultimately meeting the requirements of sensor applications.

[0035] In this embodiment, the upper carbon cloth electrode, the dual-network hydrogel, the polypropylene tape, and the lower carbon cloth electrode constitute the hydrogel sensing unit, which is integrated with the wires. The dual-network hydrogel also serves as the sensitive medium for sensing both temperature and pressure. The sandwich structure consisting of the upper carbon cloth electrode, the dual-network hydrogel, and the lower carbon cloth electrode forms a capacitive sensing unit with a clearly defined structure and stable interface. The upper and lower carbon cloth electrodes, as flexible conductors, reliably achieve electrical connection with external circuits and provide mechanical support and protection for the hydrogel medium. Using the dual-network hydrogel as the sensitive medium for sensing both temperature and pressure achieves the ability to respond to two different physical signals in a single material and structure, avoiding the complex structure of separately integrating temperature and pressure sensors. This significantly simplifies sensor design and facilitates miniaturization and high spatial density integration of the sensing unit. Temperature sensing mechanism: The ionic conductivity or dielectric constant of the hydrogel is sensitive to temperature changes. When the temperature changes, it causes a change in the bulk resistance of the hydrogel. This structure provides a direct pathway for detecting this change in electrical parameters. Pressure sensing mechanism: When pressure is applied, the hydrogel deforms, causing changes in its thickness and contact area with the electrodes. This directly alters its capacitance. This sandwich structure efficiently converts pressure into hydrogel deformation, which in turn converts into a detectable electrical signal. This provides the physical basis for decoupling and synchronously monitoring temperature and pressure signals by detecting changes in resistance and capacitance through different electrical interfaces. Integrating the dual-network hydrogel with wires effectively extracts the electrical signals generated by the flexible sensing unit. In particular, integration with the upper and lower carbon cloth electrodes achieves a smooth transition from flexible functional materials to traditional wires, solving common technical challenges in flexible electronic devices such as unreliable interface connections and high signal loss, thus ensuring the stability of signal transmission.

[0036] In this embodiment, a 3×3 array of hydrogel sensing units is spatially arranged. The inherent flexibility and extensibility of the dual-network hydrogel enable stable and conformal contact between the hydrogel sensing units and the irregular curved surface being measured. Through the spatial arrangement of the hydrogel sensing units and independent addressing of unit signals, the capacitance changes of each hydrogel sensing unit caused by external pressure are detected and distinguished. This expands the limited sensing area of ​​a single hydrogel sensing unit to enable spatial localization and identification of a large-area pressure field. Arranging multiple hydrogel sensing units in a 3×3 array expands the ability of a single unit to sense the average pressure at a specific point to cover a continuous area, solving the problem of limited sensing area for a single sensor and providing a physical basis for acquiring spatial distribution information. Leveraging the inherent flexibility and extensibility of the dual-network hydrogel, the entire array can passively adapt to and conform to various irregular curved surfaces (such as human joints and robot fingertips). This conformal contact minimizes the air gap between the sensor and the surface being measured, ensuring that mechanical pressure is efficiently and losslessly transmitted to each sensing unit, thereby significantly improving the accuracy and reliability of the measurement. By independently addressing and detecting the signal of each hydrogel sensing unit in the array, the capacitance change caused by local pressure variations at each unit location can be read separately. By comparing the signal differences between different units, the system can accurately determine the location, distribution range, relative magnitude, and even dynamic changes of the pressure applied. This represents a functional upgrade from simply measuring the presence or absence of pressure or the magnitude of pressure to spatially locating and identifying the pressure field. By expanding the sensing area through spatial arrangement, achieving conformal contact with irregular curved surfaces through material flexibility, and ultimately realizing spatial resolution of pressure distribution information through independent addressing, these three elements work together to qualitatively enhance the simple point-based pressure detection capability of a single unit into an advanced function of accurate spatial perception and identification of pressure fields over a large area. This solves the key technical problem of how to achieve large-area, high-fidelity tactile perception in the field of flexible sensing, and provides a feasible technical path for applications such as electronic skin and intelligent robots.

[0037] The method for fabricating a dual-function temperature and pressure sensor in this embodiment includes the following steps: S100, preparing a dual-network hydrogel; S200, preparing a lower carbon cloth electrode and laying polypropylene tape on the lower carbon cloth electrode, exposing a portion of the surface of the lower carbon cloth electrode; S300, placing the dual-network hydrogel on the polypropylene tape and contacting it with the exposed portion of the lower carbon cloth electrode; S400, covering and attaching the upper carbon cloth electrode to the dual-network hydrogel to form a hydrogel sensing unit; S500, arranging the hydrogel sensing units in a spatial array. Step S100, preparing the dual-network hydrogel, allows the synthesis of the hydrogel to be optimized as an independent and controllable process step. This ensures that the hydrogel, as the core sensitive medium of the sensor, first reaches its optimal state in terms of chemical composition, crosslinking degree, mechanical properties, and electrical properties, avoiding complex processing during subsequent assembly. This ensures the consistency and reliability of the final sensor performance from the source. In step S200, polypropylene tape is laid on the lower carbon cloth electrode, exposing part of the electrode's surface. This precisely defines the placement of the hydrogel and its contact area with the lower electrode. The polypropylene tape acts as a pre-set mold or support layer, providing a positioning reference for subsequent assembly and preventing excessive lateral creep of the hydrogel under pressure. It primarily constrains deformation in the vertical direction, improving the sensitivity and linearity of pressure sensing. By preparing the substrate with the mold or support layer in step S200, placing the hydrogel in step S300, and covering the upper electrode in step S400, a bottom-up sequential lamination process is formed. This sequential operation ensures precise alignment and tight contact between the functional layers (lower electrode - hydrogel - upper electrode), particularly ensuring a stable and complete interface between the hydrogel and the upper and lower electrodes. This is crucial for obtaining reliable and repeatable electrical signals (capacitance / resistance). Step S500 involves arranging the hydrogel sensing units in a spatial array, using individual high-performance sensing units as basic modules for large-scale integration. This strategy of "completing unit fabrication first, then array arrangement" simplifies the manufacturing complexity of large-scale flexible sensing arrays, allowing for flexible design of the array's size and shape according to actual application needs. This provides a practical process route for fabricating large-area electronic skin or tactile sensing systems. Through a process flow of "independently optimizing core materials first, then sequentially and precisely assembling, and finally array integration," multiple functional materials are integrated into a structurally robust and interface-reliable sensing unit. Step S200 utilizes polypropylene tape to pre-define the structure, effectively improving the performance of the sensing unit. Furthermore, the clear division of steps ensures the controllability and reproducibility of the fabrication process, ultimately providing a clear and feasible technical path for the efficient and reliable fabrication of flexible temperature / pressure dual-function sensor arrays suitable for large-area detection.

[0038] In this embodiment, step S100 specifically involves: adding acrylamide, glycerol, deionized water, chitosan, acetic acid, zinc sulfate heptahydrate, ammonium persulfate, and N,N'-methylenebisacrylamide sequentially to the same container, stirring for 1-3 hours to prepare a prepolymer solution for crosslinking, then adding TEMED accelerator, and thermally curing at 50-80°C for 25-40 minutes to obtain a double-network hydrogel. First, acrylamide (AM), glycerol (Gly), deionized water (H2O), chitosan (CS), and acetic acid (HAc) are added and stirred. This first dissolves the chitosan and forms a homogeneous solution system. Chitosan is insoluble in water but soluble in dilute acid. Acetic acid primarily provides an acidic environment, promoting the protonation of the amino groups on the chitosan molecular chains, thus dissolving it. This ensures that chitosan, one of the two major monomers, can be uniformly dispersed in the system in the form of molecular chains, which is a prerequisite for constructing a uniform double-network structure. After the chitosan is completely dissolved in an acidic environment, zinc sulfate heptahydrate (ZnSO4·7H2O) is added to avoid Zn 2+ To prevent premature redox reaction and consumption of the subsequently added initiator APS, and to avoid the formation of hydroxide precipitates under strongly alkaline conditions; if Zn is added first... 2+ It may react prematurely with APS to generate free radicals, leading to runaway polymerization; under alkaline conditions, Zn 2+ A precipitate will form; this order ensures that Zn... 2+ It can remain intact in the system for subsequent ionic crosslinking with chitosan chains. Finally, ammonium persulfate (APS) and the crosslinking agent N,N'-methylenebisacrylamide (MBA) are added. The introduction of the initiator and crosslinking agent is delayed until all reactants are uniformly dispersed, avoiding localized rapid polymerization of acrylamide in the early stages of mixing, thus preventing the formation of uneven gel blocks or network structure defects. This sequence aims to ensure that the polymerization reaction is initiated only after the entire system has achieved molecular-level homogeneity, resulting in a hydrogel product with a regular structure and consistent properties. AM, Gly, H2O, CS, HAc, Zn 2+ By adding specific raw materials such as APS and MBA in a specific order, combined with stirring, and by constructing the reaction environment step by step and controlling the triggering timing of key chemical reactions, the complete dissolution of chitosan, the establishment of a homogeneous system, and the addition of Zn were achieved sequentially. 2+The stable presence of the precursor and the orderly initiation of the final polymerization reaction provide crucial process assurance for the successful preparation of a dual-network hydrogel with uniform structure, controllable component ratio, and stable performance. This is the core step in the success of the entire one-pot synthesis. All raw materials are added and mixed sequentially in the same container, forming a one-pot synthesis process that eliminates the need for intermediate separation steps. This simplifies the operation, reduces losses and potential contamination caused by material transfer, and improves preparation efficiency. The stirring time of 1 to 3 hours provides the necessary time for the complete dissolution of solid components (such as chitosan) and the uniform dispersion of each molecular-level component. This is a prerequisite for forming a homogeneous prepolymer and obtaining a hydrogel product with consistent structure and properties. By employing a step-by-step approach of "mixing all components first, then adding TEMED and heating," the initiation timing of the polymerization reaction was precisely controlled. Before adding TEMED, the system was in a mixing phase rather than a rapid polymerization phase, preventing problems such as excessively rapid local reactions, gel blocks, or uneven networks caused by premature polymerization. After adding TEMED, a highly efficient redox initiation system was formed with ammonium persulfate at 50℃-80℃, accelerating the free radical polymerization of acrylamide. The 25-40 minute thermosetting time matched this temperature range, ensuring that the polymerization and crosslinking reaction could proceed fully and rapidly, thus forming a complete and stable first-layer network dominated by covalent bonds. Simultaneously with the formation of the covalent network through acrylamide polymerization, chitosan chains, in an acidic environment, undergo polymerization via zinc ions (Zn). 2+ Through the coordination of the two networks and the physical entanglement and hydrogen bonds between the chains, a second physical network is initially formed. This allows the formation process of the two networks to be highly coordinated and interconnected in time and space, ultimately successfully constructing a double-network cross-linked structure with both high strength and excellent toughness. This structure is the basis for the hydrogel to obtain excellent mechanical properties such as super flexibility and stretchability, thereby realizing its function as a sensitive medium for flexible sensors.

[0039] In this embodiment, acrylamide is 2g-10g, glycerol is 3g-8g, deionized water is 6g-30g, chitosan is 0.05g-0.5g, acetic acid is used to adjust the pH to 4-6, zinc sulfate heptahydrate is 0.2g-0.6g, ammonium persulfate is 4mg-8mg, and N,N'-methylenebisacrylamide is 4mg-8mg. The 2g-10g acrylamide serves as the main network monomer, with a significantly higher dosage than the 0.05g-0.5g chitosan. Establishing this quantitative relationship ensures the formation of a distinct and synergistic dual-network structure, with the strong covalent cross-linked network of polyacrylamide as the main supporting framework and the weak physical cross-linked network of chitosan as the energy dissipation mechanism. This ratio range is fundamental to obtaining the excellent toughness, stretchability, and fatigue resistance of the hydrogel. An imbalance in the ratio will lead to the failure of one network or a decrease in mechanical properties. The amount of acetic acid used was precisely controlled to adjust the pH to 4-6, providing the necessary and optimal weakly acidic environment for the full dissolution and stable existence of chitosan. This ensured the protonation and dissolution of the amino groups on the chitosan molecular chains while avoiding the potential adverse effects of an overly acidic environment on other components (such as the initiator), thus ensuring that chitosan could effectively participate in the construction of the second network. The amounts of 4-8 mg of ammonium persulfate and 4-8 mg of N,N'-methylenebisacrylamide were in the same trace order and close in value. The direct effect of this ratio was to balance the concentrations of the initiator and crosslinking agent, thereby controlling the polymerization reaction to proceed at a moderate rate and forming a uniform network with a moderate degree of crosslinking. This avoided network embrittlement due to excessive crosslinking agent or insufficient network strength due to insufficient crosslinking agent, thus facilitating the acquisition of a well-structured and stable hydrogel. The dosage of 3-8g glycerol is on the same order of magnitude as the main monomer acrylamide, indicating that it, as an important functional component rather than a trace additive, can reach a sufficiently high concentration in the hydrogel, thus significantly exerting its plasticizing and moisturizing effects, providing compositional assurance for excellent antifreeze properties and long-term stability. The dosage of 0.2g-0.6g zinc sulfate heptahydrate provides the system with sufficient Zn. 2+ This is to ensure that it can be effectively used for ion crosslinking and achieve high-efficiency ion conductivity, which is the cornerstone of sensing function.

[0040] In this embodiment, 6g acrylamide, 5.5g glycerol, 18g deionized water, 0.1g chitosan, acetic acid adjusted to pH 5, 0.4g zinc sulfate heptahydrate, 6mg ammonium persulfate, and 6mg N,N'-methylenebisacrylamide were added sequentially. The mixture was then stirred for 1.5h to crosslink and prepare a prepolymer solution. Next, 60µL of TEMED accelerator was added, and the mixture was thermosetting at 60°C for 30min to obtain a dual-network hydrogel. The specific ratio of 6g acrylamide to 0.1g chitosan provides an optimized and feasible example of a dual-network structure with a strongly covalently crosslinked polyacrylamide network as the main component and a weakly physically crosslinked chitosan network as a secondary component, ensuring a good balance between mechanical strength and energy dissipation capacity. The 5.5g glycerol provides significant plasticizing and moisturizing effects, while the 0.4g zinc sulfate heptahydrate provides sufficient Zn. 2+ To effectively facilitate ion crosslinking and ion transport, the pH was precisely adjusted to 5, providing an optimal acidic environment for chitosan dissolution, enabling uniform dispersion at the molecular level. A 1.5-hour stirring time ensured sufficient time for the complete dissolution, diffusion, and mixing of all components, especially solid chitosan, guaranteeing the high homogeneity of the prepolymer solution—a prerequisite for obtaining a uniformly structured hydrogel. The use of 6 mg ammonium persulfate (APS) and 6 mg N,N'-methylenebisacrylamide (MBA) balanced the initiator and crosslinking agent concentrations, providing a quantitative basis for forming a well-ordered network with moderate crosslinking. Subsequently, 60 μL of TEMED accelerator was added, and the reaction was carried out at 60°C for 30 minutes. These specific conditions constituted a highly efficient redox initiation system, capable of initiating acrylamide monomers at a moderate rate and with sufficient reaction time for polymerization and crosslinking, ensuring the formation of a complete and stable double-network hydrogel structure in a short period. By providing a defined and optimized set of process parameters (including component dosage, pH value, stirring time, temperature, and time), the synthesis method of dual-network hydrogels is concretized into a clear, operable, and highly reproducible best practice. This not only demonstrates the feasibility of the aforementioned generalized method, but also, through parameter optimization, enables the efficient and reliable preparation of dual-network hydrogels with the expected uniform structure and comprehensive properties (mechanical properties, ionic conductivity, and antifreeze properties).

[0041] The application of the temperature and pressure dual-function sensor in this embodiment is to use the aforementioned temperature and pressure dual-function sensor in health monitoring, smart healthcare, human-computer interaction, or electronic skin.

[0042] In health monitoring, the sensor's pressure sensing function is mainly used to detect physiological pressure signals such as pulse waves and muscle contractions, and its temperature sensing function is used to monitor body surface temperature simultaneously. The sensor's superior flexibility and biocompatibility enable it to adhere to human skin in a long-term, comfortable, and shape-preserving manner, achieving non-invasive and continuous acquisition of vital signs signals without interfering with the user's normal activities.

[0043] In smart healthcare, in addition to basic vital sign monitoring, its pressure distribution sensing capabilities can be expanded to include monitoring the body pressure distribution of bedridden patients to prevent bedsores, or assessing the biomechanical distribution of movements during rehabilitation training. Besides its flexible fit, its dual-function integration allows it to simultaneously sense changes in local skin temperature while monitoring pressure distribution, providing a more comprehensive information dimension for clinical diagnosis (such as increased skin temperature associated with inflammatory responses).

[0044] In human-computer interaction, its high-sensitivity pressure sensing and spatial positioning capabilities are mainly utilized. For example, it can give robots dexterous hands precise tactile senses, enabling them to perceive the magnitude, distribution, and sliding of gripping force. The sensor's pressure spatial resolution (array function) and rapid response characteristics allow the machine to perceive the shape, hardness, and interaction force of the object it is in contact with, just like human skin, thus achieving more refined and safer anthropomorphic operations.

[0045] In the application of electronic skin, its dual-mode sensing of temperature and pressure, as well as its large-area and array-based capabilities, are fully utilized to simulate the multifunctional sensors of human skin. Through the dual-function, highly flexible, and array-based spatial sensing characteristics, an electronic system that can cover the surface of a robot or prosthesis and sense environmental temperature and tactile information in all directions, just like real skin, can be fabricated.

[0046] The specific applications of the temperature and pressure dual-function sensor of this invention in fields such as health monitoring, smart healthcare, human-computer interaction, and electronic skin demonstrate its broad social applicability and technological advancement due to its inherent dual-function integration, superior flexibility, and arrayability. This proves that the temperature and pressure dual-function sensor has a clear and significant market application prospect.

[0047] In practice, this invention provides a temperature / pressure dual-function sensor based on a highly flexible hydrogel and its applications. To overcome the limitations of flexible sensors, such as limited sensitivity adjustability and narrow response range, this invention proposes a highly flexible hydrogel with dual temperature / pressure sensing capabilities, suitable for flexible wearable sensors in various applications. The highly flexible hydrogel with dual temperature / pressure sensing capabilities is synthesized using a one-pot chemical crosslinking method to synthesize PAAM / CS / GL / Zn. 2+A dual-network hydrogel was prepared by sequentially adding acrylamide AM (6g), glycerol Gly (5.5g), deionized water (18g), chitosan CS (0.1g), acetic acid HAc (adjusted to pH approximately 5), zinc sulfate heptahydrate ZnSO4·7H2O (0.4g), ammonium persulfate APS (6mg), and N,N'-methylenebisacrylamide MBA (6mg) to a beaker and stirring for 1.5h to crosslink and prepare a prepolymer solution. Then, TEMED (60µL) was added as a coagulant, and the hydrogel was thermosetting at 60℃ for 30min. The roles of each substance are as follows:

[0048] Acrylamide / chitosan: polymerized monomers to construct a dual-network crosslinking system;

[0049] Glycerin: moisturizing and lubricating, enhances stretchability, provides antifreeze properties, and is biocompatible;

[0050] Zinc sulfate heptahydrate: Ion transport and charge transfer enhance electrochemical performance;

[0051] Acetic acid: Slightly acidic conditions promote the dissolution of chitosan;

[0052] Ammonium persulfate (APS): Initiator;

[0053] N,N'-Methylenebisacrylamide (MBA): Crosslinking agent.

[0054] Avoiding crosstalk between temperature and pressure sensing signals is crucial for dual-function sensors, and achieving high sensitivity while maintaining signal decoupling is a significant challenge. This can be achieved through methods such as... Figure 1 The temperature / pressure dual-function sensor structure shown can greatly improve the sensitivity of pressure response and simultaneously measure capacitance and resistance signals, facilitating subsequent signal decoupling. The device structure of the temperature / pressure dual-function sensor is as follows: Figure 1 As shown, from top to bottom, the structure consists of an upper carbon cloth electrode, hydrogel, polypropylene tape, and a lower carbon cloth electrode. Resistance and capacitance signals are output from different circuits, which not only reduces interference but also allows for the simultaneous detection of temperature and pressure signals. This dual-function temperature / pressure sensor can monitor various physiological activities such as joint flexion in real time and non-invasively, and possesses multi-channel signal recognition capabilities for pressure sensor arrays.

[0055] like Figure 2As shown, the monomer mass fraction with optimal tensile properties is illustrated. While keeping other variables constant, the amount of acrylamide (AM) was adjusted to measure tensile strain properties, thus obtaining the optimal acrylamide dosage. Similarly, the amount of chitosan (CS) was adjusted to explore the optimal CS dosage for tensile properties. Based on this, it was found that 0.5 wt% chitosan and 20 wt% acrylamide resulted in the best flexibility, with an ultimate tensile strength of 2620%. Furthermore, the mechanical stability after 1000 cycles at 20% strain rate was excellent, with no significant deformation, indicating good reusability.

[0056] like Figure 3 As shown, under an applied pressure of 0-20 kPa, the maximum sensing sensitivity can reach 155.91 kPa. -1 The sensitivity is significantly higher than that of pressure sensors in the same field, and the signal response remains stable across a range of pressures with no noticeable deviation. The pressure detection limit is 12 Pa, demonstrating its immediate response to minute pressures, while at 1 kPa it exhibits rapid response and recovery times of 205 ms and 163 ms, respectively. Furthermore, after 1500 cycles of applying 1 kPa pressure, the temperature / pressure dual-function sensor demonstrates excellent capacitive response stability.

[0057] The temperature / pressure dual-function sensor of this invention solves the signal crosstalk problem of dual-function sensors through a simple structural design. Its core value lies in the real-time measurement of resistance and capacitance signals without the need for complex algorithms for decoupling. Figure 4 As can be seen from (ab), the interference of temperature on the capacitance signal is relatively regular, which can be addressed by normalizing C / C. 20kPa Make corrections based on the C / C ratio at the same pressure at various temperatures. 20kPa The values ​​are basically the same, thus effectively avoiding the interference of temperature. Furthermore, at room temperature, the effect of pressure on the resistance signal is linear and relatively small; therefore, the actual measured resistance change rate is subtracted... Figure 4 (c) The theoretical disturbance of the rate of change of resistance due to pressure, and then from... Figure 4 (d) The corresponding theoretical measured temperature value is obtained from the linear law. The temperature detection range of the temperature / pressure dual-function sensor of this invention is as follows: Figure 4 (d) shows a range of 30℃-120℃, with its upper limit far exceeding the detection range of temperature sensors in the same field. Therefore, it is suitable for most practical temperature detection scenarios, has a good temperature response speed, and its sensitivity is -0.38℃. -1 And can Figure 4 The resistance response shown in (e) is stable under alternating temperatures of 50°C and room temperature (24°C) from the heat source. Figure 4 (f) compares the present invention with 11 documents in the field, and the figure illustrates that the sensor of the present invention is superior to most flexible sensors in terms of pressure sensitivity, temperature detection range and tensile strength.

[0058] Choosing a suitable flexible material for the sensor array helps achieve better performance. Since the array needs to be in direct contact with irregular planes, it must possess excellent flexibility for a perfect fit. Hydrogels, with their superior flexibility and stability, are used to fabricate highly sensitive flexible pressure sensor arrays. Due to their good flexibility, low cost, and biocompatibility, hydrogels offer potential advantages in sensing. By combining hydrogels with wires, high-performance flexible pressure sensor arrays can be created. In practical applications, the limited sensing area of ​​a single sensor unit is insufficient for large-area pressure and tactile signal acquisition. To overcome this limitation, this invention designs a 3×3 sensor array to expand its application range. Figure 5 As shown, the sensors marked 1 to 9 in the array effectively capture spatial information. When the corresponding positions on the array are pressed sequentially, the system accurately distinguishes the pressure zone based on the corresponding capacitance changes.

[0059] like Figure 6 As shown, the sensor of this invention is attached to the index finger to detect various bending movements at different angles (0°, 30°, 60°, and 90°), obtaining stable capacitance signals. This demonstrates the ability to accurately distinguish the direction of finger force. In a continuous cycle of finger bending / releasing at a 90° angle, no significant change or hysteresis in the ΔC / C0 signal was observed. Test experiments were conducted on the wrist and knee joints of humans, and the test results still clearly show the corresponding changes of the joints at different degrees of bending, thus achieving real-time monitoring of human limb movements. Furthermore, as... Figure 7 The pressure sensor shown can recognize and translate Morse code. Based on the fast response characteristics of pressure sensing, it can distinguish between dots and dashes in Morse code by long and short presses of the finger, thus achieving effective information transmission.

[0060] In summary, this invention develops a dual-function temperature / pressure sensor based on a highly flexible hydrogel. The hydrogel possesses excellent mechanical properties, with an ultimate tensile strength of up to 2620%, and can withstand 1000 cycles at a 20% strain rate. As a capacitive pressure sensor, it achieves a maximum sensitivity of 155.91 kPa. -1The sensor exhibits a detection limit of 12 Pa under minimal pressure, with response and recovery times of 205 ms and 163 ms, respectively. The capacitance signal can stably cycle 1500 times under 1 kPa pressure. By designing a structure that measures resistance and capacitance signals in real time, the signal crosstalk problem of the dual-function sensor is solved. Furthermore, a 3×3 sensor array is designed to expand its application range, enabling real-time monitoring of human limb movements and information transmission by distinguishing between dots and dashes in Morse code. This demonstrates the significant application potential of the sensor in wearable devices, healthcare, human-computer interaction, and sensor recognition. It provides a scalable strategy for constructing multifunctional sensor devices, driving the development of next-generation wearable and intelligent sensing devices.

[0061] Matters not covered in this invention are common knowledge.

[0062] 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.

[0063] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual-function temperature and pressure sensor, characterized in that, It includes an upper carbon cloth electrode, a double network hydrogel, a polypropylene tape and a lower carbon cloth electrode arranged from top to bottom. The polypropylene tape is arranged between the double network hydrogel and the lower carbon cloth electrode to reduce the initial capacitance value and improve the pressure sensing sensitivity. The dual-network hydrogel was synthesized by one-pot chemical crosslinking. The dual-network hydrogel includes acrylamide, glycerol, chitosan, acetic acid, zinc sulfate heptahydrate, ammonium persulfate, and N,N'-methylenebisacrylamide. Acrylamide and chitosan are polymerizable monomers. A covalent chemical crosslinking network is formed through acrylamide, and a physical network is formed through the ionic or hydrogen bonds of chitosan to construct the dual-network hydrogel. Glycerin is used for moisturizing and lubrication, enhancing stretchability, enhancing antifreeze properties, and enhancing biocompatibility. Zinc sulfate heptahydrate is used for ion transport and charge transfer and to enhance electrochemical performance; Acetic acid is used to provide slightly acidic conditions, thereby promoting the dissolution of chitosan; Ammonium persulfate was used as an initiator; N,N'-methylenebisacrylamide was used as a crosslinking agent; The synergistic effect of the components in the formulation leads to an overall performance improvement. The addition of glycerol effectively lowers the freezing point of water, enhances antifreeze properties, prevents freezing failure at low temperatures, and also acts as a moisturizer and lubricant, slowing down water evaporation and extending the device's lifespan. Its biocompatibility is also enhanced, and through hydrogen bonding with the hydrogel network, it further enhances the material's stretchability and antifreeze ability, ensuring stable operation of the sensor over a wide temperature range. The introduction of zinc sulfate heptahydrate not only provides zinc ions as physical cross-linking points to enhance mechanical properties, but its ionized ions are also responsible for ion transport and charge transfer, facilitating resistive or capacitive sensing. Zinc ions may also improve electrochemical performance. In terms of sensing mechanism, zinc ions (Zn) in the hydrogel... 2+ The migration rate changes significantly with temperature, thus achieving high sensitivity and wide-range response to temperature; the acidic environment provided by acetic acid effectively promotes the dissolution of chitosan, ensuring the uniform formation of the dual network structure; A 3×3 array composed of hydrogel sensing units arranged in a spatial array; through the inherent flexibility and extensibility of the dual-network hydrogel, stable and conformal contact between the hydrogel sensing units and the irregular curved surface to be measured is achieved; through the spatial arrangement of the array of hydrogel sensing units and the independent addressing of unit signals, the capacitance changes of each hydrogel sensing unit caused by external pressure are detected and distinguished, thereby expanding the limited sensing area of ​​a single hydrogel sensing unit to the function of spatial positioning and identification of a large-area pressure field.

2. The temperature and pressure dual-function sensor according to claim 1, characterized in that, The dual-network hydrogel comprises 2g-10g of acrylamide, 3g-8g of glycerol, 6g-30g of deionized water, 0.05g-0.5g of chitosan, acetic acid with pH adjusted to 4-6, 0.2g-0.6g of zinc sulfate heptahydrate, 4mg-8mg of ammonium persulfate, and 4mg-8mg of N,N'-methylenebisacrylamide.

3. The temperature and pressure dual-function sensor according to claim 2, characterized in that, Acrylamide, glycerol, deionized water, chitosan, acetic acid, zinc sulfate heptahydrate, ammonium persulfate, and N,N'-methylenebisacrylamide were added sequentially to the same container. The mixture was stirred for 1-3 hours to crosslink and prepare a prepolymer solution. Then, TEMED coagulant was added, and the mixture was thermo-cured at 50-80℃ for 25-40 minutes to obtain a double-network hydrogel.

4. The temperature and pressure dual-function sensor according to any one of claims 1 to 3, characterized in that, The upper carbon cloth electrode, the dual-network hydrogel, the polypropylene tape and the lower carbon cloth electrode constitute the hydrogel sensing unit, which is integrated with the wire. The dual-network hydrogel serves as a sensitive medium for sensing both temperature and pressure.

5. A method for fabricating a dual-function temperature and pressure sensor, characterized in that, The method for preparing a temperature and pressure dual-function sensor according to any one of claims 1 to 4 includes the following steps: S100, Preparation of a dual-network hydrogel; S200. Prepare the lower carbon cloth electrode and lay polypropylene tape on the lower carbon cloth electrode, exposing part of the surface of the lower carbon cloth electrode. S300. Place the dual-network hydrogel on the polypropylene tape and make it contact the exposed part of the lower carbon cloth electrode. S400: Cover and attach the upper carbon cloth electrode to the dual-network hydrogel to form a hydrogel sensing unit. S500: Arrange the hydrogel sensing units in a spatial array.

6. The method for fabricating a dual-function temperature and pressure sensor according to claim 5, characterized in that, Step S100 is as follows: Acrylamide, glycerol, deionized water, chitosan, acetic acid, zinc sulfate heptahydrate, ammonium persulfate, and N,N'-methylenebisacrylamide were added sequentially to the same container. The mixture was stirred for 1-3 hours to crosslink and prepare a prepolymer solution. Then, TEMED coagulant was added, and the mixture was thermo-cured at 50-80℃ for 25-40 minutes to obtain a double-network hydrogel.

7. The method for fabricating a dual-function temperature and pressure sensor according to claim 6, characterized in that, Acrylamide 2g-10g, glycerol 3g-8g, deionized water 6g-30g, chitosan 0.05g-0.5g, acetic acid to adjust pH to 4-6, zinc sulfate heptahydrate 0.2g-0.6g, ammonium persulfate 4mg-8mg, N,N'-methylenebisacrylamide 4mg-8mg.

8. The method for fabricating a dual-function temperature and pressure sensor according to claim 7, characterized in that, 6g acrylamide, 5.5g glycerol, 18g deionized water, 0.1g chitosan, acetic acid adjusted to pH 5, 0.4g zinc sulfate heptahydrate, 6mg ammonium persulfate, and 6mg N,N'-methylenebisacrylamide were added successively. Then stir for 1.5 h to crosslink and prepare a prepolymer solution; Add 60 μL of TEMED accelerator and heat-cur at 60 °C for 30 min to obtain a double-network hydrogel.

9. An application of a dual-function temperature and pressure sensor, characterized in that, The temperature and pressure dual-function sensor according to any one of claims 1 to 4 is used in health monitoring, smart medical care, human-computer interaction or electronic skin.

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