Preparation method of multifunctional sensing hollow gel fiber based on aqueous two-phase system

Abstract

This invention discloses a method for preparing multifunctional sensing hollow gel fibers based on an aqueous two-phase system. The technical solution is based on an aqueous two-phase system formed by polyvinyl alcohol (PVA) and dextran in water. Using a coaxial spinning process, a PVA solution is injected into the shell channel of a coaxial spinning device, and a dextran solution is injected into the core channel. Relying on the ultra-low tension between the two aqueous phase interfaces, the PVA solution and dextran solution after extrusion are kept in a parallel laminar flow state. After coagulation treatment, a core-shell structure gel fiber is obtained. Subsequently, it undergoes solvent evaporation treatment, water washing treatment, and eutectic solvent replacement to finally prepare the hollow gel fiber. The gel fiber of this invention possesses stretchability, compression resilience, high conductivity, and a wide operating temperature range. It can be made into multidimensional sensors and humidity sensors to monitor strain, direction, pressure, and humidity, exhibiting considerable sensitivity and stability.

Description

Technical Field

[0001] This invention relates to a method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system, belonging to the fields of hydrogel fiber materials and flexible sensing. Background Technology

[0002] As intelligent sensing technology upgrades towards human adaptability, the demand for flexible wearable devices in scenarios such as human health monitoring and electronic skin is becoming increasingly urgent. The performance of these devices hinges on their ability to simultaneously achieve good tensile properties, environmental tolerance, and conductivity. Traditional electronic devices are mostly rigid structures, with significantly different mechanical properties from human soft tissue, making them difficult to adapt to dynamic human activities and prone to problems such as detachment and functional degradation. Among various flexible materials, hydrogels have become one of the core candidate materials for constructing wearable flexible electronic devices due to their adjustable electrical properties, mechanical strength, and biocompatibility. By rationally designing the composition and microstructure, hydrogels can acquire customized functions such as super-stretchability, environmental tolerance, and adhesion. At the same time, their conductivity can be flexibly controlled by introducing ionic components to adapt to the needs of different sensing scenarios. Compared with traditional bulk hydrogels, hydrogel fibers, with their unique fibrous morphology, provide a new structural option for flexible sensing applications. Its larger specific surface area can effectively improve the tightness of the fit with human tissue and avoid the problem of falling off; the fibrous structure significantly optimizes the material's ductility and tensile recovery performance, which can better adapt to various dynamic movements of the human body.

[0003] In 2023, *Advanced Functional Materials* reported a self-lubricating spinning strategy that continuously prepared covalent network hydrogel fibers by polymerizing and crosslinking acrylamide and acrylic acid in a UV-induced hydrophobic mold. After ionic crosslinking, these hydrogel fibers exhibited good ionic conductivity and low swelling behavior, making them suitable for integration into other fabrics for applications such as motion monitoring, pressure detection, and underwater communication. However, the mechanical properties of this hydrogel fiber were weak (tensile strength <7 MPa), and its performance at low temperatures was not reported (Continuous spinning of high-toughhydrogel fibers for flexible electronics by using regional heterogeneous polymerization, 2023, 10, 2305226). In 2024, *International Journal of Biological Macromolecules* reported the preparation of hydrogel fibers with an interlocking dual-network structure by combining sodium alginate with a borax crosslinked network and a polyvinyl alcohol crystalline network. The negatively charged sodium alginate promoted ion transport within the hydrogel fiber, resulting in high ionic conductivity. A strain sensor based on this hydrogel fiber is designed for wearable human-computer interaction applications. However, the mechanical properties of this hydrogel fiber are weak (tensile strength 4.31 MPa), and its performance at low temperatures has not been reported (Continuous dual-network alginate hydrogel fibers with superior mechanical and electrical performance for flexible multi-functional sensors, 2024, 273, 133151).

[0004] To date, most hydrogel fibers and their flexible sensors have faced problems such as poor mechanical properties, easy freezing at low temperatures, and easy water loss at high temperatures, which inhibit mechanical properties and other functions. Hollow hydrogel fibers not only solve the above problems of existing hydrogel fibers, but also exhibit significant performance advantages over traditional solid hydrogel fibers due to their unique axially through-cavity structure: higher specific surface area and shorter ion transport paths can significantly improve sensing response speed and sensitivity; the cavity structure provides ample space for functional component loading, making it easy to integrate multiple sensing functions; at the same time, the through-cavity provides an efficient mass transfer channel for subsequent solvent replacement, which can solve the pain points of low functionalization modification efficiency and poor uniformity of solid fibers.

[0005] However, the performance advantages of hollow gel fibers are highly dependent on the controllable fabrication of their structure. Existing coaxial spinning technology faces core bottlenecks: traditional spinning systems suffer from poor spinning stability, significant pollution during core removal, and a high risk of structural collapse; furthermore, the core and shell are prone to mutual dissolution, making it impossible to form a stable hollow structure and severely impacting the performance of hollow gel fibers. Therefore, developing hollow gel fiber materials that can maintain mechanical flexibility, conductivity, high sensitivity, temperature resistance, and multiple sensing functions is of great significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-strength, wide-temperature-range hollow gel fiber material for wearable multifunctional integration, prepared by coaxial spinning through spontaneous phase separation in a two-aqueous-phase system. This material can be used to construct flexible wearable multifunctional sensors for various complex environments (such as high and low temperatures), enabling sensitive and stable monitoring of strain, direction, pressure, and humidity over a wide monitoring range.

[0007] To achieve the above objectives, the technical solution of this invention provides a method for preparing multifunctional sensing hollow gel fibers based on an aqueous two-phase system. Based on an aqueous two-phase system formed by polyvinyl alcohol (PVA) and dextran in water, a coaxial spinning process is employed. The PVA solution is injected into the shell channel of the coaxial spinning device, and the dextran solution is injected into the core channel. Relying on the ultra-low tension between the aqueous two-phase interfaces, the PVA solution and the dextran solution after extrusion are kept in a parallel laminar flow state. After coagulation treatment, a core-shell structured gel fiber is obtained. Subsequently, the fiber undergoes solvent evaporation treatment, water washing treatment, and eutectic solvent (DES) replacement to finally prepare the hollow gel fiber. The specific steps are as follows: (1) Add polyvinyl alcohol to deionized water, heat and stir to obtain a uniformly mixed polyvinyl alcohol solution, and transfer it into a syringe after degassing treatment; add dextran to deionized water, stir to obtain a uniformly mixed dextran solution, and transfer it into a syringe after degassing treatment; (2) The coaxial wet spinning process is adopted, and two spinning methods are set up: horizontal and vertical. Polyvinyl alcohol solution is used as the shell channel liquid. The syringe containing polyvinyl alcohol solution is horizontally installed on the injection pump, and the front end of the syringe is connected to the side port of the coaxial spinning needle. Dextran solution is used as the core channel liquid. The syringe containing dextran solution is vertically installed on the injection pump, and the front end of the syringe is connected to the top port of the coaxial spinning needle. The two injection pumps are pushed simultaneously to inject the two solutions into the cold anhydrous methanol coagulation bath for coagulation and molding to obtain the nascent gel fiber. (3) The collected nascent gel fibers were soaked in cold anhydrous methanol to prepare gel fibers with a continuous core-sheath structure. (4) The gel fiber with a core-sheath structure is washed with water after the solvent evaporates to obtain a gel fiber with a hollow structure; it is then soaked in a eutectic solvent for a certain period of time to form a microphase separation structure, and then sealed and placed to obtain a high-strength, high-toughness, wide-temperature-range hollow gel fiber.

[0008] Furthermore, the heating temperature in step (1) is 60-95℃; the mass fraction of the polyvinyl alcohol solution is 12.5-17.5%, and the mass fraction of the dextran solution is 12.5-25%.

[0009] Preferably, the mass fraction of the polyvinyl alcohol solution in step (1) is 15%.

[0010] Furthermore, in step (2), the outer diameter of the coaxial spinning needle is 13-17G and the inner diameter is 18-22G; the injection pump with a syringe containing polyvinyl alcohol solution has a propulsion speed of 0.6-0.8 mL / min, and the injection pump with a syringe containing dextran solution has a propulsion speed of 0.2-0.4 mL / min.

[0011] Furthermore, the soaking time in step (3) is 6 hours.

[0012] Furthermore, the temperature of cold anhydrous methanol is -5 to -15°C.

[0013] Furthermore, in step (4), the molar ratio of zinc chloride (ZnCl2), ethylene glycol (EG), and glycerol (Gly) in the eutectic solvent is 1:2-4:1-3; the immersion time in the eutectic solvent is 0.5-6 h, and the sealing time is 5-360 h.

[0014] Preferably, in step (4), the immersion time in the eutectic solvent is 6 h, and the sealing time is 12 h.

[0015] Furthermore, the degree of polymerization of polyvinyl alcohol is 2000, and the degree of alcoholysis is 99%.

[0016] The beneficial effects of this invention are as follows: (1) This invention constructs polyvinyl alcohol hollow hydrogel fibers through a two-phase aqueous system, and then replaces the solvent with a eutectic solvent to promote the interaction of hydrogen bonds between polyvinyl alcohol polymers, thus forming a strong polyvinyl alcohol physical network and obtaining high-strength, high-toughness, wide-temperature-range hollow gel fibers. The high density of hydrogen bonds endows the hollow gel fibers with high tensile strength, high tensile strain and high toughness.

[0017] (2) The aqueous two-phase system used in this invention has spontaneous phase separation characteristics. Polyvinyl alcohol is rich in side hydroxyl groups, which easily form intermolecular / internal hydrogen bonds. It is highly hydrophilic but relatively "compact". The dextran backbone is rich in glycosidic bonds and hydroxyl groups, which are even more hydrophilic but the molecular chains are more extended and the volume is larger. Due to the mismatch between the molecular chain conformation and size, the two produce strong steric hindrance and mutual repulsion. At a certain concentration, the thermodynamic conditions for the formation of aqueous two-phase are met, and they will spontaneously separate into two aqueous layers, that is, spontaneously separate into two phases. The interphase interface has ultra-low tension. The spontaneous liquid-liquid phase separation can make the core-sheath interface achieve a natural and stable structure without relying on complex viscosity matching. It significantly reduces defects such as "core layer fracture" and "sheath layer rupture", and significantly improves the molding stability and continuity of hollow fibers. Meanwhile, this invention selects polyvinyl alcohol and dextran as aqueous two-phase. The polyvinyl alcohol solution is injected into cold methanol, and the prepared polyvinyl alcohol gel fiber has good mechanical properties. However, the dextran does not gel but precipitates after contact with methanol. Therefore, the dextran can be easily removed after rehydration, thereby realizing the preparation of hollow gel fiber.

[0018] (3) The method of the present invention can stably prepare hollow gel fibers of various sizes, regular and continuous. Capillary phenomenon and cavity liquid carrying experiments confirm that the prepared hollow gel fibers have good mass transfer and permeation performance, and can realize the exchange of substances inside and outside the cavity.

[0019] (4) The present invention introduces a eutectic solvent into the gel fiber system. The design of glycerol and ethylene glycol in the eutectic solvent enables the hollow gel fiber to maintain excellent temperature resistance performance in a wide temperature range (-75~60℃). At the same time, the introduction of the eutectic solvent can greatly enhance the intermolecular forces of polyvinyl alcohol, giving the hollow gel fiber excellent mechanical properties.

[0020] (5) The solid content and crosslinking density of the hollow gel fiber can be adjusted by changing the concentration of the polyvinyl alcohol solution. The solvent replacement time affects the degree of phase separation, polymer interactions, and crosslinking density. Changing the ethylene glycol / glycerol ratio in the eutectic solvent can regulate the strength of hydrogen bonding in the gel network and the slippage between molecular chains. This invention obtains high-strength, high-toughness, wide-temperature-range hollow gel fibers by optimizing the polyvinyl alcohol solution concentration, the eutectic solvent replacement time, and the ethylene glycol / glycerol ratio in the eutectic solvent.

[0021] (6) The hollow gel fiber of this invention has stretchability, compression resilience, high conductivity, and a wide temperature range, and can be made into multidimensional sensors and humidity sensors to monitor strain, direction, pressure, and humidity, with considerable sensitivity and stability. This hollow gel fiber can be integrated with other fabrics, amplify the differences in electrical signals caused by strain in different directions, and self-weave into complex multidimensional structures. Attached Figure Description

[0022] Figure 1 The preparation process of polyvinyl alcohol hollow gel fiber in Example 1 is as follows.

[0023] Figure 2 (A) is the phase separation interface generated during coaxial spinning of the polyvinyl alcohol / dextran aqueous two-phase system in Example 1. (B) is an image of the prepared uniform and continuous hollow hydrogel fiber (i is before dextran removal with deionized water, and ii is after dextran removal with deionized water).

[0024] Figure 3 The load-time curve is shown in Example 1 during 50 stretching cycles of the hollow gel fiber.

[0025] Figure 4 Images showing the flexible deformation of hollow gel fibers in Example 1. (A) is an image of the twisting deformation of hollow gel fibers at -20°C; (B) is an image of hollow gel fibers at room temperature; (C) is an image of the bending deformation of hollow gel fibers at 60°C.

[0026] Figure 5 The image shows the DSC curve of the hollow gel fiber in Example 1.

[0027] Figure 6 The curve shows the mass change of the hollow gel fiber in Example 1 at 60°C.

[0028] Figure 7 The swelling curves of the hollow gel fiber in Example 1 in various water environments are shown.

[0029] Figure 8 The figure shows the response behavior of the hollow gel fiber material in Example 1. In the figure, (A) is the tensile strain response behavior of the hollow gel fiber, (B) is the directional response behavior of the hollow gel fiber, and (C) is the pressure response behavior of the hollow gel fiber.

[0030] Figure 9 The humidity response and respiration detection of the hollow gel fiber material in Example 1 are shown. (A) shows the humidity response behavior of the hollow gel fiber, (B) shows the cyclic humidity response behavior of the hollow gel fiber, and (C) shows the application of the hollow gel fiber sensor to nasal respiration detection.

[0031] Figure 10 The diagrams show the flexible deformation, weaving, and stretching experiments of the hollow gel fiber material in Example 1. (A) shows the knotting and twisting shape of the hollow gel fiber, (B) shows the fabric woven from the hollow gel fiber, (C) shows the stretching deformation of the hollow gel fiber, and (D) shows the hollow gel fiber bearing a heavy load.

[0032] Figure 11The wearable flexible sensor constructed from hollow gel fiber material in Example 1 is used to monitor various human activities. The activities shown in the figure are: (A) bending fingers, (B) bending elbows, and (C) sitting and standing.

[0033] Figure 12 This is a radar chart comparing the five key properties of the hollow gel fiber in Example 1.

[0034] Figure 13 Tensile curves of hollow gel fibers of different diameters prepared by different models of coaxial spinning needles in Examples 1, 2 and 3.

[0035] Figure 14 The tensile curves are for hollow gel fibers with different polyvinyl alcohol contents in Examples 1, 4 and 5.

[0036] Figure 15 The tensile curves are for hollow gel fibers soaked in different eutectic solvents for Examples 1, 6 and 7.

[0037] Figure 16 The conductivity of hollow gel fibers soaked in different eutectic solvents in Examples 1, 6 and 7 is shown.

[0038] Figure 17 The tensile curves are for hollow gel fibers with different dextran contents in Examples 1, 8, and 9.

[0039] Figure 18 Tensile curves of hollow gel fibers soaked in eutectic solvents with different ratios of ethylene glycol and glycerol in Examples 1, 10, and 11.

[0040] Figure 19 The gel fibers were prepared for Comparative Examples 1 and 2.

[0041] Figure 20 (A) is a cross-sectional image of the hollow gel fiber prepared in Example 1; (B) and (C) are cross-sections and partial collapse images of the hollow gel fiber prepared in Comparative Example 1.

[0042] Figure 21 The results are from the capillary phenomenon experiments of gel fibers in Example 1 and Comparative Example 3.

[0043] Figure 22 The results of the hollow gel fiber cavity liquid loading experiment in Example 1 are shown. Detailed Implementation

[0044] The specific embodiments of the present invention will be further described in detail below with reference to the examples. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available; unless otherwise specified, the methods used in the embodiments of the present invention are all methods mastered by those skilled in the art.

[0045] The degree of polymerization of polyvinyl alcohol is 2000, and the degree of alcoholysis is 99%.

[0046] Preparation method of eutectic solvent (ZnCl2 / EG / Gly): Zinc chloride (ZnCl2), ethylene glycol (EG) and glycerol (Gly) are mixed in proportion, heated and stirred at 90°C until a transparent solution is formed, and then cooled to room temperature. The test methods for the properties of hollow gel fibers are as follows: (1) Mechanical property testing: The tensile properties of the hollow gel fiber were tested using an electronic universal testing machine (UTM6104 type). The sensor used was 500N. The uniaxial tensile speed was 50 mm·min. -1 Tensile fracture stress ( σ b ) and tensile fracture strain ( ε t These are defined as the stress and strain of a hollow gel fiber specimen at fracture, respectively. Young's modulus ( E The stress-strain ratio (TSR) is calculated from the initial linear portion (10-30%) of the stress-strain curve. Toughness is simply calculated as the integral area of ​​the stress-strain curve. In the mechanical stability test, the tensile strain is set to 100%, and the tensile speed is set to 50 mm / min. -1 The hollow gel fiber was subjected to 50 consecutive loading and unloading experiments.

[0047] (2) Conductivity test: The conductivity of the hollow gel fibers was measured using a CHI-760E electrochemical workstation. Conductivity ( σ The calculation formula is: σ =Δ L / ( R × S (1) Note: Δ L , R and S These represent the length, resistance, and cross-sectional area of ​​the hollow gel fiber, respectively.

[0048] (3) Sensing performance testing: The real-time resistance of the hollow gel fiber under various humidity, deformation, and pressure conditions was measured using a combination of an electronic universal testing machine (UTM6104 type) and an electrochemical workstation (CHI-760E). The sensor used was 500N. The uniaxial tensile speed was 50 mm·min. -1 The uniaxial compression rate is 5 mm·min -1The hollow gel fiber sensor consists of hollow gel fibers and two copper wires. The hollow gel fiber sample acts as a conductor, and the copper wires serve as electrodes. The sensor is connected to an electrochemical workstation via the copper wires to record the changes in resistance and current of the hollow gel fiber in real time during operation. The relative resistance change (ΔR / R0) and relative current change (ΔI / I0) of the hollow gel fiber are defined as follows: ΔR / R0(%)=(R-R0) / R0×100 (2) ΔI / I0(%)=(I-I0) / I0×100 (3) Note: R0 is the initial resistance of the hollow gel fiber, R is the real-time resistance of the hollow gel fiber during the stretching process, and ΔR is the change in resistance of the hollow gel fiber during the stretching process. I0 is the initial current of the hollow gel fiber, I is the real-time current of the hollow gel fiber during the compression process, and ΔI is the change in current of the hollow gel fiber during the compression process.

[0049] The slope of the relative resistance change-strain curve is defined as the strain sensitivity coefficient (GF); the slope of the relative current change-pressure curve is defined as the pressure sensitivity. Hollow gel fiber sensors are integrated into gloves and elbow / wrist braces, connected to an electrochemical workstation via copper wires. The sensors record real-time resistance changes in the hollow gel fibers during movement after the volunteers wear them, and the real-time monitoring curves of the hollow gel fiber sensors on the human movement process are obtained based on the relative resistance changes.

[0050] (4) Freeze-thaw resistance test: Differential scanning calorimetry (DSC) was used to determine the freeze-thaw resistance of the hollow gel fibers under N2 atmosphere. The test temperature range was -75~25℃, and the cooling rate was 3℃·min. -1 .

[0051] (5) High-temperature resistance test: After being placed at 60℃ for a period of time, the weight change of the hollow gel fibers was recorded. The weight retention rate W (weight ratio) of the gel fibers can be defined as: W (%)= m d / m 0×100 (4) Note: m 0 represents the initial weight of the hollow gel fiber. m d It is the weight of the hollow gel fiber after it loses water.

[0052] (6) Humidity Sensing Test: A self-made humidity sensing characterization system (using a bubbling humidification method, where dry nitrogen gas is passed through a bottle containing deionized water to generate humid nitrogen gas; then, the dry nitrogen gas and the balanced humid nitrogen gas are injected into the buffer bottle chamber, and the gas flow ratio between dry and humid nitrogen gas is adjusted by a mass flow controller to provide an environment of 25~95% RH) was used in conjunction with an electrochemical workstation (CHI-760E) to test the humidity sensing performance of hollow gel fiber at room temperature. The hollow gel fiber sensor consists of hollow gel fiber and two copper wires. The hollow gel fiber sample serves as the conductor, and the copper wires serve as the electrodes, connected to the electrochemical workstation via the copper wires. Under different relative humidity conditions, a fixed voltage was applied to the hollow gel fiber sensor, and its humidity sensing characteristics were tested by monitoring the current change when alternately exposed to 10% RH (relative humidity) and specific different RH environments (the sensor was exposed to a specific RH environment for 300 s, and then purged with dry air for 300 s in each cycle).

[0053] (7) Respiratory monitoring test: The hollow gel fiber sensor is integrated into the N95 mask (the hollow gel fiber has good flexibility and weavability, the hollow gel fiber is directly woven into the mask and connected to copper wires), and kept at a certain distance from the mouth and nose to detect human breathing.

[0054] (8) Capillary effect experiment: Insert hollow hydrogel fibers into an aqueous solution containing red dye, then mark and measure the position of the red dye in the hollow hydrogel fibers after equilibrium.

[0055] (9) Hollow cavity liquid loading experiment: After injecting an aqueous solution containing red dye into the cavity of the hollow gel fiber, observe the condition of the outside of the hollow gel fiber at different time periods (0 h, 0.5 h, 2.5 h and 4 h).

[0056] Example 1 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: 1.5 g of polyvinyl alcohol (PVA) was added to 8.5 mL of deionized water and stirred at 95°C until dissolved. After standing to remove air bubbles, the solution was transferred to a syringe. 1.5 g of dextran powder was added to 8.5 mL of deionized water and stirred until dissolved. After standing to remove air bubbles, the solution was transferred to a syringe. Both horizontal and vertical spinning devices were set up for coaxial wet spinning. The coaxial spinning needle used had an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution was horizontally mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump's advance rate was set to 0.6 mL / min. Using Dextran solution as the core channel fluid, the syringe containing Dextran solution was vertically mounted on the syringe pump, with the syringe tip connected to the needle head. The syringe pump's advance rate was set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers with a continuous core-sheath structure (intermediate 1). After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers with a hollow structure (intermediate 2). The hollow gel fibers (intermediate 2) were completely immersed in a zinc chloride / ethylene glycol / glycerol (ZnCl2 / EG / Gly) eutectic solvent (DES) with a molar ratio of 1:3:2 for 6 hours. After being removed and sealed for 12 hours, high-strength, high-toughness, wide-temperature-range hollow gel fibers were obtained.

[0057] Example 1 illustrates the preparation process of hollow gel fibers ( Figure 1 PVA and Dextran form an aqueous two-phase (ATPS) system. Through coaxial spinning, the shell layer is injected with PVA solution, and the core layer with Dextran solution, relying solely on interfacial tension. Figure 2 A) After extrusion through the needle, the PVA solution and Dextran solution flow in parallel laminar flow to obtain gel fibers with a core-sheath structure. The gel fibers, after solvent evaporation, are washed with water to remove dextran. Figure 2 B), and then DES replacement to obtain hollow gel fibers.

[0058] The tensile strength of the hollow gel fiber obtained in Example 1 ( σ b The tensile stress (abbreviated as tensile stress in the attached figure) is 28.8 MPa, and the fracture strain ( ε tThe tensile strain (abbreviated as tensile strain in the attached figure) is 1427.1%, the elastic modulus is 7.4 MPa, and the toughness is 236.4 MJ / m. 3 This indicates that it possesses excellent toughness and ductility, and superior mechanical properties. Meanwhile... Figure 3 The results show that under 50 loading and unloading cycles, the load borne by the hollow gel fiber gradually stabilizes, indicating that it has good fatigue resistance.

[0059] The glycerol and ethylene glycol components in the DES system allow hollow gel fibers to maintain excellent flexibility at both low and high ambient temperatures. Figure 4 The DSC test results show that ( Figure 5 Under a nitrogen atmosphere, hollow gel fibers did not exhibit any crystallization peaks within a test temperature range of -75 to 25°C. This indicates that after DES solvent replacement, the water content inside the gel fibers was significantly reduced, and ice crystal formation was effectively suppressed, thus confirming the low-temperature tolerance of hollow gel fibers. Figure 6 As shown, the hollow gel fiber retained approximately 93.3% of its mass after being placed at 60℃ for 5 h, with only a slight decrease in mass, indicating that the hollow gel fiber after DES solvent replacement exhibited good high-temperature resistance.

[0060] The hollow gel fiber obtained in Example 1 has an electrical conductivity of 7.0 × 10⁻⁶. -2 S / m has the potential to be used as a flexible conductor, which can meet the basic requirements of flexible sensors, wearable electronic devices and other conductive materials.

[0061] The strong inter-chain interactions formed by dense hydrogen bonds in hollow gel fibers effectively resist water intrusion, thus maintaining a stable volume under different aqueous environments. For example... Figure 7 As shown, after swelling equilibrium, the hollow gel fiber has a relatively low overall swelling ratio, exhibiting good anti-swelling properties.

[0062] The relative resistance change of the hollow gel fiber sensor obtained in Example 1 increases with increasing tensile strain. Figure 8 A). The strain sensitivity coefficient (GF) represents the sensitivity of a strain sensor, increasing monotonically with increasing strain, reaching 2.82 at strains of 300-400%. For example... Figure 8 As shown in Figure B, the relative resistance changes of two hollow gel fibers were collected by stretching them at different angles. The results show a clear direction-dependent change in relative resistance. This model can be used to determine the stretching angle for a given relative resistance change. Figure 8During the dynamic pressurization process shown in Figure C, the current of the hollow gel fiber sensor increases rapidly, exhibiting a sensitive response to the applied pressure. Similar to most pressure sensors, the curve of relative current change versus pressure can be divided into several regions, with corresponding sensitivities of 0.22 N. -1 and 0.043 N -1 .

[0063] In such Figure 9 During the dynamic humidification process shown in Figure A, the current of the hollow gel fiber sensor increases rapidly, demonstrating a sensitive response to humidity. The curve of current change versus humidity can be divided into several regions, with corresponding sensitivities of 14.4, 71.8, and 326.4 % / % RH, respectively. Figure 9 As shown in Figure B, the hollow gel fiber sensor exhibits regular electrical signal changes during repeated humidification / dehumidification, demonstrating its outstanding cyclic stability during long-term operation. Simultaneously, the hollow gel fiber demonstrates excellent detection sensitivity during respiration detection, accurately capturing and identifying subtle respiratory movement characteristics. Figure 9 C).

[0064] The method in Example 1 can stably prepare regular and continuous hollow gel fibers. The hollow gel fibers can be used to form flexible sensors with considerable sensitivity and stability to monitor strain, direction, pressure and humidity: tensile strain detection window (0~400%), strain direction detection window (0~90°), pressure detection window (0.05~5 N), and humidity detection window (25~95%RH).

[0065] The hollow gel fiber obtained in Example 1 exhibits excellent flexibility, weavability, extensibility, and load-bearing capacity, such as... Figure 10 As shown, hollow gel fibers can withstand various deformations, such as knotting, twisting and plying, and weaving into fabrics; at the same time, they can withstand large deformations without breaking, and can also bear loads of 30,000 times their own weight while maintaining structural integrity.

[0066] The hollow gel fiber wearable sensor obtained in Example 1 can be fixed to various parts of the body for monitoring and identifying various movements. For example... Figure 11 As shown in AC, the deformation of the hollow gel fiber sensor caused by fingers, elbows, sitting and standing generates regular and repeatable electrical signals through relative resistance or relative current changes, enabling comprehensive human motion monitoring in daily life.

[0067] The hollow gel fiber obtained in Example 1 exhibits outstanding performance in five key dimensions: mechanics, temperature resistance, hollow structure, multidimensional sensing, and humidity sensing. Figure 12 This achieves multi-performance synergy and multi-functional integration, with overall performance significantly superior to existing solutions.

[0068] Example 2 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: Add 1.5 g of PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Add 1.5 g of Dextran powder to 8.5 mL of deionized water, stir until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 17 G and an inner diameter of 22 G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump advance rate is set to 0.6 mL / min. Using Dextran solution as the core channel fluid, the syringe containing Dextran solution is vertically mounted on the syringe pump, with the syringe tip connected to the needle head. The syringe pump advance rate is set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers (intermediate 1) with a continuous core-sheath structure. After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers (intermediate 2) with a hollow structure. The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:3:2) for 6 hours, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range hollow gel fibers.

[0069] The hollow gel fibers prepared by this invention have very similar high and low temperature resistance, swelling resistance and sensing performance, and their conductivity after being soaked in DES for the same amount of time is very close. Therefore, Examples 2-11 mainly focus on testing the mechanical properties of the hollow gel fibers.

[0070] The hollow gel fiber obtained in Example 2 has a tensile strength of 17.1 MPa, a fracture strain of 1543.2%, an elastic modulus of 5.2 MPa, and a toughness of 190.4 MJ / m. 3 ( Figure 13 ).

[0071] Example 3 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: Add 1.5 g of PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Add 1.5 g of Dextran powder to 8.5 mL of deionized water, stir until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 15 G and an inner diameter of 20 G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump advance rate is set to 0.6 mL / min. Using Dextran solution as the core channel fluid, the syringe containing Dextran solution is vertically mounted on the syringe pump, with the syringe tip connected to the needle head. The syringe pump advance rate is set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers (intermediate 1) with a continuous core-sheath structure. After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers (intermediate 2) with a hollow structure. The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:3:2) for 6 hours, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range hollow gel fibers.

[0072] The hollow gel fiber obtained in Example 3 has a tensile strength of 24.7 MPa, a fracture strain of 1514.6%, an elastic modulus of 6.0 MPa, and a toughness of 227.5 MJ / m. 3 ( Figure 13 ).

[0073] Example 4 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: 1.25 g of PVA was added to 8.75 mL of deionized water and stirred at 95°C until dissolved. After standing to remove air bubbles, the solution was transferred to a syringe. 1.5 g of Dextran powder was added to 8.5 mL of deionized water and stirred until dissolved. After standing to remove air bubbles, the solution was transferred to a syringe. Both horizontal and vertical spinning devices were set up for coaxial wet spinning. The coaxial spinning needle used had an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, a syringe containing PVA solution was horizontally mounted on a syringe pump, with the syringe tip connected to the needle side port. The syringe pump's advance rate was set to 0.6 mL / min. Using Dextran solution as the core channel fluid, a syringe containing Dextran solution was vertically mounted on a syringe pump, with the syringe tip connected to the needle side port. The syringe pump's advance rate was set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers with a continuous core-sheath structure (intermediate 1). After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers with a hollow structure (intermediate 2). The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:3:2) for 6 hours, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range hollow gel fibers.

[0074] The hollow gel fiber material obtained in Example 4 has a tensile strength of 11.2 MPa, a fracture strain of 1121.1%, an elastic modulus of 2.0 MPa, and a toughness of 64.6 MJ / m. 3 ( Figure 14 ).

[0075] Example 5 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: 1.75 g of PVA was added to 8.25 mL of deionized water and stirred at 95°C until dissolved. After standing to remove air bubbles, the solution was transferred to a syringe. 1.5 g of Dextran powder was added to 8.5 mL of deionized water and stirred until dissolved. After standing to remove air bubbles, the solution was transferred to a syringe. Both horizontal and vertical spinning devices were set up for coaxial wet spinning. The coaxial spinning needle used had an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, a syringe containing PVA solution was horizontally mounted on a syringe pump, with the syringe tip connected to the needle side port. The syringe pump's advance rate was set to 0.6 mL / min. Using Dextran solution as the core channel fluid, a syringe containing Dextran solution was vertically mounted on a syringe pump, with the syringe tip connected to the needle side port. The syringe pump's advance rate was set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers with a continuous core-sheath structure (intermediate 1). After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers with a hollow structure (intermediate 2). The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:3:2) for 6 hours, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range, low-hollow gel fibers.

[0076] The hollow gel fiber material obtained in Example 5 has a tensile strength of 36.4 MPa, a fracture strain of 1929.2%, an elastic modulus of 10.6 MPa, and a toughness of 383.3 MJ / m. 3 ( Figure 14 In this embodiment, the PVA concentration is increased to 17.5%, which significantly enhances the mechanical properties, but also increases the solution viscosity and makes operation more difficult, although it is within the acceptable operating range in the art.

[0077] Example 6 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: Add 1.5 g of PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Add 1.5 g of Dextran powder to 8.5 mL of deionized water, stir until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump advance rate is set to 0.6 mL / min. Using Dextran solution as the core channel fluid, the syringe containing Dextran solution is vertically mounted on the syringe pump, with the syringe tip connected to the needle head. The syringe pump advance rate is set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers with a continuous core-sheath structure (intermediate 1). After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers with a hollow structure (intermediate 2). The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:3:2) for 0.5 hours, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range hollow gel fibers.

[0078] The hollow gel fiber obtained in Example 6 has a tensile strength of 18.0 MPa, a fracture strain of 1105.7%, an elastic modulus of 6.1 MPa, and a toughness of 105.5 MJ / m. 3 ( Figure 15 The conductivity is 5.2 × 10⁻⁶. -2 S / m ( Figure 16 ).

[0079] Example 7 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: Add 1.5 g of PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Add 1.5 g of Dextran powder to 8.5 mL of deionized water, stir until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump advance rate is set to 0.6 mL / min. Using Dextran solution as the core channel fluid, the syringe containing Dextran solution is vertically mounted on the syringe pump, with the syringe tip connected to the needle head. The syringe pump advance rate is set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers with a continuous core-sheath structure (intermediate 1). After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers with a hollow structure (intermediate 2). The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:3:2) for 1 hour, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range hollow gel fibers.

[0080] The hollow gel fiber obtained in Example 7 has a tensile strength of 23.5 MPa, a fracture strain of 1216.5%, an elastic modulus of 6.9 MPa, and a toughness of 152.8 MJ / m. 3 ( Figure 15 The conductivity is 6.5 × 10⁻⁶. -2 S / m ( Figure 16 ).

[0081] Example 8 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: Add 1.5 g PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Add 1.25 g Dextran powder to 8.75 mL of deionized water, stir until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump advance rate is set to 0.6 mL / min. Using Dextran solution as the core channel fluid, the syringe containing Dextran solution is vertically mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump advance rate is set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers with a continuous core-sheath structure (intermediate 1). After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers with a hollow structure (intermediate 2). The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:3:2) for 6 hours, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range hollow gel fibers.

[0082] The hollow gel fiber obtained in Example 8 has a tensile strength of 27.5 MPa, a fracture strain of 1337.5%, an elastic modulus of 7.1 MPa, and a toughness of 234.1 MJ / m. 3 ( Figure 17 ).

[0083] Example 9 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: Add 1.5 g of PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Add 2.5 g of Dextran powder to 7.5 mL of deionized water, stir until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump advance rate is set to 0.6 mL / min. Using Dextran solution as the core channel fluid, the syringe containing Dextran solution is vertically mounted on the syringe pump, with the syringe tip connected to the needle head. The syringe pump advance rate is set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers (intermediate 1) with a continuous core-sheath structure. After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers (intermediate 2) with a hollow structure. The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:3:2) for 6 hours, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range hollow gel fibers.

[0084] The hollow gel fiber obtained in Example 9 had a tensile strength of 28.8 MPa, a fracture strain of 1461.2%, an elastic modulus of 6.9 MPa, and a toughness of 251.1 MJ / m. 3 ( Figure 17 ).

[0085] Example 10 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: Add 1.5 g of PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Add 1.5 g of Dextran powder to 8.5 mL of deionized water, stir until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump advance rate is set to 0.6 mL / min. Using Dextran solution as the core channel fluid, the syringe containing Dextran solution is vertically mounted on the syringe pump, with the syringe tip connected to the needle head. The syringe pump advance rate is set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers with a continuous core-sheath structure (intermediate 1). After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers with a hollow structure (intermediate 2). The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:2:3) for 6 hours, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range hollow gel fibers.

[0086] The hollow gel fiber obtained in Example 10 had a tensile strength of 31.4 MPa, a fracture strain of 1167.8%, an elastic modulus of 10.1 MPa, and a toughness of 209.4 MJ / m. 3 ( Figure 18 ).

[0087] Example 11 A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system includes the following steps: Add 1.5 g of PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Add 1.5 g of Dextran powder to 8.5 mL of deionized water, stir until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the syringe pump, with the syringe tip connected to the needle side port. The syringe pump advance rate is set to 0.6 mL / min. Using Dextran solution as the core channel fluid, the syringe containing Dextran solution is vertically mounted on the syringe pump, with the syringe tip connected to the needle head. The syringe pump advance rate is set to 0.2 mL / min. Two syringe pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers with a continuous core-sheath structure (intermediate 1). After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers with a hollow structure (intermediate 2). The hollow gel fibers (intermediate 2) were completely immersed in DES (ZnCl2 / EG / Gly molar ratio 1:4:1) for 6 hours, then removed and sealed for 12 hours to obtain high-strength, high-toughness, wide-temperature-range hollow gel fibers.

[0088] The hollow gel fiber obtained in Example 11 has a tensile strength of 24.0 MPa, a fracture strain of 1452.7%, an elastic modulus of 4.7 MPa, and a toughness of 197.0 MJ / m. 3 ( Figure 18 ).

[0089] Comparative Example 1 A conventional method for preparing hollow gel fibers (non-aqueous two-phase) includes the following steps: Add 1.5 g PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Transfer 10 mL of anhydrous methanol to the syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 13 G and an inner diameter of 18 G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the injection pump, with the syringe tip connected to the needle side port. The injection pump's advance rate is set to 0.6 mL / min. Using anhydrous methanol as the core channel fluid, the syringe containing anhydrous methanol is vertically mounted on the injection pump, with the syringe tip connected to the needle side port. The injection pump's advance rate is set to 0.2 mL / min. Two injection pumps were simultaneously used to inject two liquids through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound up by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers (intermediate 1) with a continuous core-sheath structure. After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours and then rinsed with deionized water to obtain gel fibers with a hollow structure.

[0090] Comparative Example 2 A conventional method for preparing hollow gel fibers (non-aqueous two-phase) includes the following steps: Add 1.5 g PVA to 8.5 mL of deionized water, stir at 95°C until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Add 0.3 g sodium alginate to 9.7 mL of deionized water, stir until dissolved, allow to stand to remove air bubbles, and then transfer to a syringe. Set up both horizontal and vertical spinning devices for coaxial wet spinning. The coaxial spinning needle used has an outer diameter of 13G and an inner diameter of 18G. Using PVA solution as the shell channel fluid, the syringe containing PVA solution is horizontally mounted on the injection pump, with the syringe tip connected to the needle side port. The injection pump advance rate is set to 0.6 mL / min. Using sodium alginate solution as the core channel fluid, the syringe containing sodium alginate solution is vertically mounted on the injection pump, with the syringe tip connected to the needle head. The injection pump advance rate is set to 0.2 mL / min. Two injection pumps were used simultaneously to inject two solutions through needles into a cold anhydrous methanol (-10℃) coagulation bath for coagulation and molding, resulting in nascent gel fibers. After being wound up by a servo motor, the fibers were immersed in cold anhydrous methanol (-10℃) for 6 hours to obtain gel fibers (intermediate 1) with a continuous core-sheath structure. After the core-sheath gel fibers (intermediate 1) were allowed to evaporate the solvent (methanol) (by leaving them at room temperature for more than 6 hours or at a temperature not exceeding 40℃ to allow the solvent to evaporate completely), they were immersed in deionized water for 6 hours. The core component gelled after reacting with methanol, so it could not be completely removed by washing. A section of the gel fiber was taken and a slight external force was applied to slowly extrude the core, ultimately producing hollow gel fibers.

[0091] Since the purpose of DES replacement is to give hollow hydrogel fibers with good morphology and complete structure better performance (such as high and low temperature resistance, swelling resistance, sensing, etc.), when the nascent gel fibers obtained by coaxial spinning in Comparative Examples 1 and 2 were in poor condition (uneven, defective, etc.), DES replacement was not used and relevant performance tests were not conducted.

[0092] Comparative Example 3 A conventional method for preparing solid gel fibers includes the following steps: Add 1.5 g PVA to 8.5 mL of deionized water and stir at 95°C until dissolved. After standing to remove air bubbles, transfer the solution to a syringe. Horizontally mount the syringe containing the PVA solution onto a syringe pump, setting the pump's injection rate to 0.2 mL / min. Using a standard needle, inject the solution into a cold anhydrous methanol (-10°C) coagulation bath for coagulation and shaping, obtaining nascent gel fibers. After being wound up by a servo motor, immerse the fibers in cold anhydrous methanol (-10°C) for 6 hours. Then, allow the solvent (methanol) to evaporate (by standing at room temperature for at least 6 hours or at a temperature not exceeding 40°C until the solvent has fully evaporated), and finally immerse the fibers in deionized water for 6 hours to obtain solid gel fibers.

[0093] Comparison of the morphology of gel fibers obtained in Example 1 with those in Comparative Examples 1 and 2: Figure 19 and 20 As shown. Comparative Example 1 uses coaxial spinning with anhydrous methanol flowing through the core layer of ordinary PVA solution. Although hollow gel fibers can be obtained, the phase separation is severe (the core layer of the coaxial spinning is spun with methanol, and the external bath is also methanol. Although a stable hollow structure can be formed, both the core and the outer layer are methanol, and the PVA chains will undergo synchronous and strong desolvation at the interface, so that the phase separation is completed in a very short time). This results in an eccentric hollow cross-section and an irregular shape. It can be seen that white flocculent matter appears in the methanol in the core (the interface is unstable during spinning, and some solidified PVA fragments are carried away by the methanol in the core layer, thus producing white flocculent matter). This indicates that the inner surface of the gel fiber is relatively rough and is prone to uneven wall thickness and local collapse. Figure 19 A and Figure 20 B, C). Comparative Example 2, however, is a non-aqueous two-phase system of coaxial spinning (sodium alginate is an anionic polyelectrolyte with a large negative charge. PVA is a neutral nonionic polymer. There is no strong repulsion between them; instead, they have some hydrogen bond compatibility. Their charge interactions are weak, and they do not spontaneously separate. After mixing, it is a homogeneous single-phase solution, meaning PVA and sodium alginate are well-compatible, and there is no strong intermolecular repulsion, making it impossible to form an aqueous two-phase system). The overall appearance of the fibers is uneven in thickness, with inconsistent thickness, poor cavity continuity, and a tendency to necking and bulging, resulting in numerous defects. Figure 19 B); The present invention's aqueous two-phase system-assisted coaxial spinning can rely on a stable core-shell phase interface to prepare hollow, well-structured, uniformly thick, and integrally continuous gel fibers. Figure 20 A), which shows a significant difference from the gel fibers of Comparative Example 1 and Comparative Example 2.

[0094] The capillary effect experimental results of the gel fibers obtained in Example 1 and Comparative Example 3 are as follows: Figure 21 As shown, compared to gel fibers prepared by ordinary wet spinning, gel fibers prepared by coaxial spinning combined with a two-phase aqueous system have more diverse structures, exhibiting a hollow morphology and capillary action. The red liquid column inside the hollow gel fiber cavity shows a slow upward trend, indicating that it can act as a capillary to achieve mass transfer, and the mass transfer capacity can be controlled by adjusting the inner diameter of the gel fiber. In contrast, the gel fiber in Comparative Example 3 has a solid structure and does not possess this function.

[0095] The experimental results of the cavity liquid-carrying structure of the gel fiber obtained in Example 1 are as follows: Figure 22 As shown, after injecting an aqueous solution containing red dye into the cavity of the hollow gel fiber obtained in Example 1, the dye began to diffuse from the cavity to the outside within 30 minutes and completely diffused out of the cavity after 4 hours. This phenomenon confirms that the hollow gel fiber has good permeability and can realize the exchange of substances between the inside and outside of the gel fiber cavity.

Claims

1. A method for preparing multifunctional sensing hollow gel fibers based on a two-phase aqueous system, characterized in that, Based on the aqueous two-phase system formed by polyvinyl alcohol and dextran in water, a coaxial spinning process is adopted. The polyvinyl alcohol solution is injected into the shell channel of the coaxial spinning device, and the dextran solution is injected into the core channel. Relying on the ultra-low tension between the aqueous two-phase interface, the polyvinyl alcohol solution and the dextran solution after extrusion needle are kept in a parallel laminar flow state. After coagulation treatment, a core-shell structured gel fiber is obtained. Subsequently, the fiber is subjected to solvent evaporation treatment, water washing treatment, and eutectic solvent replacement to finally prepare hollow gel fiber.

2. The method for preparing hollow gel fibers according to claim 1, characterized in that, The specific steps are as follows: (1) Add polyvinyl alcohol to deionized water, heat and stir to obtain a uniformly mixed polyvinyl alcohol solution, and transfer it into a syringe after degassing treatment; add dextran to deionized water, stir to obtain a uniformly mixed dextran solution, and transfer it into a syringe after degassing treatment; (2) The coaxial wet spinning process is adopted, and two spinning methods, horizontal and vertical, are set up: polyvinyl alcohol solution is used as the shell channel liquid, and the syringe containing polyvinyl alcohol solution is horizontally installed on the injection pump, and the front end of the syringe is connected to the side port of the coaxial spinning needle. Using a dextran solution as the core layer channel fluid, a syringe containing the dextran solution is vertically mounted on an injection pump, with the front end of the syringe connected to the inlet of a coaxial spinning needle. Two injection pumps are simultaneously pushed forward to inject the two solutions into a cold anhydrous methanol coagulation bath for coagulation and molding, thus obtaining nascent gel fibers. (3) The collected nascent gel fibers were soaked in cold anhydrous methanol to prepare gel fibers with a continuous core-sheath structure. (4) The gel fibers with a core-sheath structure are washed with water after solvent evaporation to obtain gel fibers with a hollow structure. The fiber was immersed in a eutectic solvent for a certain period of time to form a microphase separation structure. After being removed and sealed, a high-strength, high-toughness, wide-temperature-range hollow gel fiber was obtained.

3. The method for preparing hollow gel fibers according to claim 2, characterized in that, The heating temperature in step (1) is 60-95℃; the mass fraction of the polyvinyl alcohol solution is 12.5-17.5%, and the mass fraction of the dextran solution is 12.5-25%.

4. The method for preparing hollow gel fiber material according to claim 3, characterized in that, The mass fraction of the polyvinyl alcohol solution in step (1) is 15%.

5. The method for preparing hollow gel fibers according to claim 2, characterized in that, In step (2), the outer diameter of the coaxial spinning needle is 13-17G and the inner diameter is 18-22G; the injection pump with a syringe containing polyvinyl alcohol solution has a propulsion speed of 0.6-0.8 mL / min, and the injection pump with a syringe containing dextran solution has a propulsion speed of 0.2-0.4 mL / min.

6. The method for preparing hollow gel fibers according to claim 2, characterized in that, The soaking time in step (3) is 6 hours.

7. The method for preparing hollow gel fibers according to claim 2, characterized in that, The temperature range for cold anhydrous methanol is -5 to -15℃.

8. The method for preparing hollow gel fibers according to claim 2, characterized in that, In step (4), the molar ratio of zinc chloride, ethylene glycol, and glycerol in the eutectic solvent is 1:2-4:1-3; the immersion time in the eutectic solvent is 0.5-6 h, and the sealing time is 5-360 h.

9. The method for preparing hollow gel fibers according to claim 8, characterized in that, Step (4) involves immersing the sample in a eutectic solvent for 6 hours and then sealing it for 12 hours.

10. The method for preparing hollow gel fibers according to any one of claims 1-9, characterized in that, The degree of polymerization of polyvinyl alcohol is 2000, and the degree of alcoholysis is 99%.

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