Shielded radial pressure sensing fiber and method of making and using same

Abstract

The present application relates to a kind of shielded radial pressure sensing fiber and its preparation method and application, adopt three-layer coaxial microfluidic wet spinning, with high viscosity sacrificial layer as middle layer, it is induced to form three-dimensional spiral flow to inner layer conductive liquid by ring shear torque; Outer ionic gel precursor is solidified in coagulation bath, in situ locking spiral configuration and forming dielectric layer, integrated generation inner spiral electrode and dielectric layer.The obtained fiber has the coaxial structure of inner three-dimensional spiral electrode, middle ionic gel dielectric layer and outer shielding layer.The fiber is stretched in axial direction, spiral electrode compensates capacitance change through geometric self-regulation, realizes strain insensitivity;When radial pressure is received, electrode-dielectric layer changes from line contact to surface contact, realizes high sensitivity pressure response;Outer shielding layer provides dynamic shielding.The present application has the advantages of high sensitivity, anti-interference and continuous preparation, and has great application potential in the field of intelligent fabric and human-computer interaction.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronic materials technology, specifically relating to a shielded radial pressure sensing fiber, its preparation method, and its application. Background Technology

[0002] Wearable pressure sensors have broad application prospects in fields such as human motion monitoring, healthcare, and human-computer interaction. Currently, fiber-based flexible pressure sensors mainly include three types: piezoresistive, capacitive, and triboelectric.

[0003] Piezoresistive fibers sense pressure deformation through the tunneling effect between conductive fillers or changes in contact resistance. The device structure is simple, but the resistance is extremely sensitive to axial tensile strain. Stretching causes the conductive network to reorganize, and the resistance change often drowns out the pressure signal. It is also easily affected by ambient temperature and humidity drift.

[0004] Capacitive fibers consist of two conductive electrodes sandwiching an elastic dielectric layer. They sense pressure by sensing the increase in capacitance caused by the decrease in dielectric layer thickness under pressure, offering advantages such as good linearity and low power consumption. However, traditional parallel plate or coaxial cylindrical capacitor structures, when stretched axially, experience a significant drift in static capacitance due to the Poisson effect, which causes the dielectric layer to thin and the electrode length to increase. This makes it impossible to provide a stable pressure measurement baseline under dynamic motion scenarios.

[0005] Triboelectric fibers rely on electrostatic induction to output pulse voltage during the contact and separation process of two materials with different electronegativity. Although they have self-driving characteristics, their output is a transient AC pulse, making it difficult to achieve continuous monitoring of static or slowly changing pressure.

[0006] In the preparation of helical fibers using microfluidic wet spinning, existing research attempts to induce buckling instability of the core fluid by utilizing the difference in flow velocity and viscosity between the inner and outer phases in coaxial laminar flow. Wang et al. (Chemical Engineering Journal, 2023, 465: 142939) demonstrated a method for producing helical fibers through coaxial wet spinning, but the resulting helical structure consisted of helical ribs on the inner wall, rather than a continuous three-dimensional helical electrode running through the fiber axis, and the synchronous integration of the supercapacitor dielectric layer was not achieved. Zhao et al. (Science Advances, 2023, 9: eadj5407) proposed a hydrogel-assisted microfluidic spinning method, but this requires a hydrogel as a sacrificial template, and the process involves multiple steps of encapsulation, curing, and removal, and the supercapacitor functional layer could not be constructed simultaneously during the integrated molding process. The team of Professors Wang Dong and Li Mufang from Wuhan Textile University has achieved a controllable transformation of the hollow fiber cavity structure from a linear shape to a spiral shape based on coaxial wet spinning technology. However, liquid metal filling is a post-processing step, and the generation of the spiral hollow structure is separated from the filling of functional materials, making it impossible to achieve the integrated synchronous molding of the spiral electrode and the dielectric layer.

[0007] In the field of ion gel supercapacitor pressure sensing, Gou et al. (Nano Energy, 2023, 117: 109140) designed a nanofiber-ion gel composite material, achieving ultra-high sensitivity and a wide pressure range. However, this sensor is a membrane structure, not a fiber morphology, and does not have weavability, and it does not involve a helical electrode configuration.

[0008] In summary, there is currently no solution that can simultaneously achieve the generation of the inner three-dimensional spiral electrode, the in-situ solidification and locking of the intermediate ion gel supercapacitor dielectric layer, and the integration of the outer conductive shielding layer in a single continuous microfluidic spinning process. Furthermore, it is impossible to simultaneously resolve the three core technical contradictions of stretchable fiber sensors: strong stretch-capacitance coupling, insufficient radial pressure sensitivity, and attenuation of shielding effectiveness under dynamic stretching. Summary of the Invention

[0009] To address the key technical shortcomings of existing stretchable pressure sensing fibers, such as strong tension-signal coupling, insufficient radial pressure sensitivity, susceptibility to interference, and complex manufacturing processes, the present invention aims to provide a shielded radial pressure sensing fiber, its manufacturing method, and its application.

[0010] The objective of this invention is achieved through the following technical solution: A method for preparing a shielded radial pressure sensing fiber includes the following steps: A three-layer coaxial microfluidic wet spinning process is used to simultaneously extrude the inner conductive polymer solution, the middle high-viscosity sacrificial layer fluid, and the outer ion gel precursor solution. During the extrusion process, the high-viscosity sacrificial layer fluid applies circumferential shear torque to the conductive polymer solution, inducing the conductive polymer solution to undergo three-dimensional helical buckling and form a three-dimensional helical liquid flow. The extruded coaxial liquid flow enters the coagulation bath, where the ion gel precursor undergoes phase separation and solidification to form an ion gel supercapacitor dielectric layer. This locks the helical configuration of the three-dimensional helical liquid flow in situ, and simultaneously molds the nascent fiber in an integrated manner. The outer surface of the dielectric layer of the ion gel supercapacitor of the nascent fiber is coated to form a shielded electrode layer with high conductivity, resulting in a shielded radial pressure sensing fiber with a three-dimensional helical structure.

[0011] Furthermore, the high-viscosity sacrificial layer fluid is glycerol or polyglycerol, with a viscosity of 500-1200 mPa·s at 25°C.

[0012] Furthermore, the ratio of the flow rate of the high-viscosity sacrificial layer fluid to the flow rate of the conductive polymer solution is 0.2-0.8.

[0013] Furthermore, the conductive polymer solution is prepared by mixing polyurethane and liquid metal particles in a mass ratio of 5:1 and dissolving them in N,N-dimethylformamide; the ion gel precursor solution is prepared by mixing polyurethane and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ionic liquid in a mass ratio of 2:1.

[0014] Furthermore, the coating process specifically involves: immersing the nascent fibers in a mixed coating solution of thermosetting polyurethane and liquid metal particles, and then repeatedly immersing and curing to form a high-conductivity shielding electrode layer with a thickness of 10-100 μm.

[0015] A shielded radial pressure sensing fiber has a three-layer coaxial heterostructure consisting of a three-dimensional spiral conductive polymer electrode layer, an ion gel supercapacitor dielectric layer, and a high conductivity shielding electrode layer, arranged sequentially from the inside to the outside. The three-dimensional spiral conductive polymer electrode layer is configured to undergo geometric self-adjustment, with an increase in pitch and a decrease in spiral radius, when the pressure sensing fiber is subjected to axial tension. This increases the contact pressure and effective contact area between the three-dimensional spiral conductive polymer electrode layer and the inner wall of the ion gel supercapacitor dielectric layer, thereby compensating for the decrease in geometric capacitance caused by tension and achieving insensitivity of the total fiber capacitance to axial tensile strain.

[0016] Furthermore, the three-dimensional spiral conductive polymer electrode layer and the ion gel supercapacitor dielectric layer form a three-dimensional spiral contact interface. This interface is configured to be in a line contact or loose contact state under natural, unpressurized conditions; and to transform into a surface contact state when subjected to radial pressure, thereby increasing the effective contact area by orders of magnitude and producing ultra-high radial pressure capacitive response sensitivity.

[0017] Furthermore, the three-dimensional spiral conductive polymer electrode layer and the high conductivity shielding electrode layer adopt a homogeneous composite material system, and the mechanical properties of each functional layer are matched.

[0018] Furthermore, when the fiber is subjected to tensile strain, the high conductivity shielding electrode layer maintains the continuity of the conductive network through the sliding rearrangement of liquid metal particles, so as to ensure the shielding effectiveness under dynamic tension.

[0019] Application of a shielded radial pressure sensing fiber in wearable pressure sensors, physiological signal monitoring fabrics, human-computer interaction interfaces, or tactile sensing for soft robots.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention achieves integrated continuous molding of a three-dimensional spiral electrode and a supercapacitor dielectric layer, significantly improving process efficiency and structural consistency. It simplifies the traditional multi-step discrete process into a continuous production line, fundamentally ensuring perfect coaxiality of the spiral electrode and dielectric layer, and batch-to-batch structural consistency.

[0021] This invention achieves high insensitivity of fiber capacitance to axial tensile strain, solving the baseline drift problem in pressure measurement under dynamic motion. The dynamic compensation mechanism for interface contact area based on a helical topology is not found in existing linear electrodes or surface-wound electrodes, allowing the fibers of this invention to be directly woven into the joints of clothing, accurately sensing external pressure even during significant human movement.

[0022] This invention achieves ultra-high sensitivity detection of radial pressure, and effectively decouples the pressure response from the tensile response at the physical level. The sensitization mechanism of the line-to-surface contact transition and the physical decoupling mechanism of tension-compression allow the fiber of this invention to be used simultaneously to monitor human motion posture and external touch pressure, without the two signals interfering with each other.

[0023] Stable shielding performance was achieved under dynamic stretching, effectively ensuring the signal-to-noise ratio and anti-interference capability of the sensing signal. The homogeneous material system and the internal and external synergistic deformation mechanism ensured that the fiber maintained high shielding efficiency under dynamic stretching, effectively isolating external power frequency noise and electrostatic interference.

[0024] The material system exhibits good compatibility, with strong interfacial bonding between functional layers, and synergistic optimization of the overall mechanical and electrical properties of the fiber. All three layers use polyurethane as a continuous matrix, ensuring thermodynamic compatibility and interfacial affinity between the functional layers, giving the fiber excellent tensile compliance, structural stability, and reliable electrical functionality. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the fabrication process of shielded radial pressure sensing fiber, showing the three-layer coaxial microfluidic wet spinning process and subsequent traction, coating and winding steps; Figure 2 This is a schematic diagram of the structure of a shielded radial pressure sensing fiber, including the fiber appearance and cross-sectional view, showing a three-layer coaxial heterogeneous structure. Figure 3 The diagram shows the working principle of the fiber of the present invention. (a) is a schematic diagram of axial tensile strain insensitivity; (b) is a schematic diagram of radial pressure high-sensitivity response.

[0026] Explanation of annotations in the diagram: 1-Conductive polymer solution; 2-High viscosity sacrificial layer fluid; 3-Ion gel precursor solution; 4-Coagulation bath; 7-Traction roller; 8-Coating tank; 9-Oven; 10-Rewinding roller; 11-Three-dimensional spiral conductive polymer electrode layer; 12-Ion gel supercapacitor dielectric layer; 13-High conductivity shielding electrode layer. Detailed Implementation

[0027] The present invention will now be described in further detail.

[0028] (I) Overview of the overall technical solution This invention provides a shielded radial pressure sensing fiber and its preparation method. The overall structure of the fiber is a three-layer coaxial heterogeneous configuration: from the inside out, it consists of a three-dimensional helical conductive polymer electrode layer 11, an ion gel supercapacitor dielectric layer 12, and a high conductivity shielding electrode layer 13. Its core innovation lies in using viscous fluids such as glycerol and polyglycerol, which possess high viscosity rheological control properties, as the high-viscosity sacrificial layer fluid 2 in the middle layer. During the extrusion process of the three-layer coaxial needle, the high-viscosity middle layer applies a uniform circumferential shear torque to the conductive polymer solution 1 in the inner layer, inducing the inner core fluid to undergo three-dimensional helical buckling. Simultaneously, the ion gel precursor solution 3 in the outer layer undergoes phase separation and solidification in the coagulation bath 4, locking the configuration of the inner helical electrode in situ and forming an ion gel supercapacitor dielectric layer with a double-layer capacitance effect. This achieves the integration of helical electrode generation and functional dielectric layer forming in a single-step continuous process. Finally, a high-conductivity shielding layer is coated onto the outer surface of the fiber through a dip-coating process to form a Faraday cage shielding structure, which protects the inner supercapacitor sensing unit from external noise interference.

[0029] (II) Fiber Structure and Material System The material composition and function of each layer of the fiber in this invention are described in detail below: The first layer (inner layer): a three-dimensional helical conductive polymer electrode layer. This layer is prepared by mixing N,N-dimethylformamide (DMF) polyurethane (PU) dissolved in 0.3 g / ml with liquid metal particles at a mass ratio of 5:1. During spinning, this layer is subjected to circumferential shear torque from the high-viscosity fluid in the middle layer, resulting in bulk three-dimensional buckling instability and forming a continuous three-dimensional helical electrode running through the fiber axis. Its main functions include: ① acting as the inner electrode of a supercapacitor, forming an electric double layer capacitor (EDLC) with the ionogel dielectric layer; ② its helical geometry self-adjusts by increasing the pitch and decreasing the helical radius during stretching, providing strain-insensitive characteristics for the fiber; ③ changing from "line contact" to "surface contact" with the dielectric layer under radial pressure, providing the fiber with highly sensitive pressure response.

[0030] The second layer (intermediate layer): an ion-gel supercapacitor dielectric layer. This layer is prepared by mixing a polyurethane solution with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) ionic liquid at a mass ratio of 2:1. This material system has a dual function: during spinning, its high viscosity (viscosity range of 500-1200 mPa·s at 25°C, preferably 800 mPa·s) applies a uniform circumferential shear torque to the inner conductive fluid to induce helical formation; after phase separation and solidification in the coagulation bath, the ionic liquid is physically anchored within the polyurethane network, forming a solid gel dielectric layer with ionic conductivity. A double-layer capacitor is formed at the interface between this layer and the inner helical electrode, constituting the supercapacitor sensing mechanism. Its main functions include: ① serving as the dielectric layer of a supercapacitor, providing ion conduction channels; ② possessing both rheological control and structural locking capabilities; ③ its three-dimensional helical contact interface with the inner helical electrode is the structural basis for achieving strain compensation and pressure sensitization.

[0031] The third layer (outer layer): a high-conductivity shielding electrode layer. This layer is formed by uniformly coating the outer surface of the intermediate ionogel layer with a high-conductivity material through a coating process, with a thickness of 10-100 μm, preferably 50 μm. The high-conductivity material is prepared by mixing thermosetting polyurethane (PU) and liquid metal particles at a mass ratio of 5:1. This layer acts as the counter electrode in the supercapacitor system, forming a complete capacitor unit with the inner spiral electrode; at the same time, it forms a Faraday cage shielding structure, effectively suppressing the influence of external noise and electrostatic interference on the inner sensing unit. Its main functions include: ① serving as the outer electrode of the supercapacitor to extract the sensing signal; ② providing shielding effectiveness and improving the signal-to-noise ratio; ③ protecting the inner ionogel layer from the effects of environmental humidity and mechanical wear.

[0032] (III) Integrated molding preparation method The preparation method of the present invention includes the following continuous steps: Step 1: Preparation of spinning precursor solution (1) Preparation of inner conductive electrode solution: Dissolve PU particles in DMF to prepare a PU base solution with a concentration of 0.3 g / mL. Then add liquid metal (LM) particles (such as EGaIn micro-nano droplets) to the above solution at a PU to LM mass ratio of 5:1, mix at room temperature for 10 min to form a viscous conductive liquid with metallic luster, and inject it into the reservoir of the inner injection pump for later use.

[0033] (2) Preparation of the intermediate sacrificial layer fluid: Analytical grade glycerol or polyglycerol is selected as the intermediate rheology control medium. No further preparation is required; it is directly injected into the reservoir of the intermediate injection pump for later use.

[0034] (3) Preparation of the outer ion gel precursor solution: Dissolve PU in DMF to prepare a PU base solution, then add EMIMTFSI ion liquid at a mass ratio of PU to EMIMTFSI of 2:1, mix at room temperature for 10 min, and inject into the reservoir of the outer injection pump for later use.

[0035] (4) Preparation of outer shielding layer coating liquid: Mix thermosetting polyurethane and liquid metal particles at a mass ratio of 5:1 at room temperature for 10 minutes, and inject into a syringe for later use.

[0036] Process 2: Coaxial microfluidic wet spinning – integrated spiral electrode and dielectric layer forming A three-layer coaxial spinning needle is used. The inner needle delivers the inner conductive solution, the middle needle delivers a viscous fluid sacrificial layer such as glycerol and polyglycerol with high viscosity and rheological control properties, and the outer needle delivers the ionogel precursor solution. A precision syringe pump independently controls the flow rate of each of the three layers. The needle outlet is immersed in a coagulation bath containing deionized water to a depth of approximately 2 cm below the liquid surface.

[0037] The specific flow rate parameters for the three-layer spinning are shown in the table below:

[0038] At the instant the three fluid layers converge and are extruded at the coaxial needle outlet, the high-viscosity glycerol intermediate layer applies a uniform and continuous circumferential shear torque to the inner PU / LM conductive fluid, causing the inner core fluid to periodically bend in the axial direction while continuously rotating around its own axis, forming a three-dimensional helical geometry. Simultaneously, when the outer ionogel precursor (PU / EMIMTFSI) comes into contact with the deionized water coagulation bath, the interaction between the EMIMTFSI ionic liquid and water triggers phase separation of the polyurethane matrix and rapid solidification, forming a solid ionogel dielectric layer that locks the morphology of the inner helical electrode in situ. The intermediate glycerol layer is largely replaced and removed during coagulation bath immersion and subsequent post-treatment, providing radial deformation space for the inner helical electrode to adhere to the inner wall of the dielectric layer under pressure. The nascent three-layer fiber structure (inner helical electrode / glycerol residual layer / ionogel dielectric layer) is drawn out of the coagulation bath at a constant speed (approximately 0.3-0.5 m / min) by the traction roller 7.

[0039] Step 3: Coating the outer conductive shielding electrode The nascent fibers are introduced into a coating tank 8 containing an outer shielding layer coating solution. After the fibers are fully immersed in the coating solution, they are vertically pulled out at a lifting speed of 5-10 mm / s. The coated fibers are then placed in an oven 9 at 80℃ for 2-3 hours to cure. The dip-coating-drying process is repeated 3-4 times to finally form an outer shielding electrode layer of uniform thickness.

[0040] Step 4: Fiber Collection and Post-processing The coated and dried three-layer functional fibers are wound at a constant speed (approximately 5 rpm) by a take-up roller 10, matching the traction speed. The wound fibers undergo the following post-treatments: ① Immersion in a deionized water coagulation bath for 0.5 hours to fully displace and remove residual glycerol from the middle layer; ② Immersion in an anhydrous ethanol bath for 0.5 hours to dehydrate and densify the ionogel layer; ③ Drying in an 80°C oven for 0.5 hours to ensure the ionic liquid in the ionogel dielectric layer is fully and stably distributed within the polyurethane network and to enhance the interfacial bonding between the outer shielding layer and the dielectric layer. After post-treatment, the fibers are ready for subsequent testing or weaving integration.

[0041] (iv) Working principle and functional verification 1. Supercapacitor sensing characteristics insensitive to axial tensile strain Fibers were prepared using intermediate preferred value one (standard type) parameters (inner layer 100 μl / min, middle layer glycerol 40 μl / min, outer layer 100 μl / min, outer layer coated 3 times, thickness approximately 50 μm).

[0042] Combination Figure 3 As shown in (a), the strain insensitivity mechanism can be explained as follows: the supercapacitance is dominated by the electric double layer capacitance (EDLC) at the interface between the inner spiral electrode and the ionogel dielectric layer, and the capacitance value is proportional to the effective contact area between the electrode and the dielectric layer. When the fiber is axially stretched: on the one hand, the outer ionogel dielectric layer is elongated and its cross-sectional area decreases, resulting in a decrease in its geometric capacitance component; on the other hand, the inner spiral electrode exhibits geometric self-adjustment behavior under stretching, with an increase in pitch and a decrease in spiral radius. The decrease in radius significantly increases the contact pressure between the outer surface of the spiral electrode and the inner wall of the ionogel dielectric layer, transforming the initial loose contact into a tight surface contact, thus greatly increasing the effective contact area. The resulting increase in the interfacial electric double layer capacitance and the decrease in the geometric capacitance of the dielectric layer caused by stretching compensate for each other, allowing the total fiber capacitance to remain highly stable over a large tensile strain range. Meanwhile, the spiral structure effectively suppresses the resistance change of the inner electrode during the stretching process. Compared with the linear electrode, which has a significant increase in resistance due to the increase in length and the decrease in cross-sectional area, the spiral electrode unfolds with the geometric reconstruction of the conductive path, and the resistance change rate is significantly reduced, which further ensures the electrical stability of the sensing signal.

[0043] 2. High sensitivity to radial pressure and resistance to tensile crosstalk Fibers were prepared using intermediate optimal value two (high sensitivity type) parameters (inner layer 150 μl / min, middle layer glycerol 50 μl / min, outer layer 150 μl / min, outer layer coated 3 times, thickness approximately 50 μm).

[0044] Combination Figure 3As shown in (b), its high-sensitivity pressure response and decoupling mechanism are explained as follows: There is a three-dimensional helical contact interface between the inner spiral electrode and the inner wall of the ionogel dielectric layer. In the natural, unpressurized state, the spiral electrode, due to its curvature, exhibits a localized "line contact" or "loose contact" with the inner wall of the dielectric layer, resulting in a limited effective contact area. When radial pressure is applied to the fiber, the outer shielding electrode uniformly transmits the pressure to the ionogel dielectric layer, causing radial compression deformation inwards. This forces the contact state between the inner spiral electrode and the inner wall of the dielectric layer to change from "line contact" to a large-area surface contact, resulting in an order-of-magnitude increase in the effective contact area. This leads to a sharp increase in the double-layer capacitance, thereby achieving ultra-high pressure sensitivity. Axial stretching mainly changes the pitch and radius of the spiral electrode, having little effect on the radial contact state of the dielectric layer under inward compression. Therefore, the pressure response and tensile response are physically independent, achieving effective decoupling of the tensile-pressure signals.

[0045] This invention also provides an application of a shielded radial pressure sensing fiber in wearable pressure sensors, physiological signal monitoring fabrics, human-computer interaction interfaces, or tactile sensing for soft robots. Because the sensing fiber described in this invention possesses the synergistic characteristics of axial tensile strain insensitivity, ultra-high radial pressure sensitivity response, and in-situ shielding, it has significant advantages over existing flexible fiber sensors in the following dynamic and complex environments: In the field of human motion monitoring, this fiber can be directly woven or sewn into clothing around joints. When the clothing substrate deforms due to significant bending and stretching of the joints (such as the strain range of the knee and elbow joints), the fiber's capacitance baseline remains highly stable, enabling real-time, artifact-free detection of external tactile pressure (such as fall impacts or massage pressure), solving the problem of traditional sensors being affected by motion. The core technical challenge of artifacts causing distortion in physiological signal measurements; in the field of human-computer interaction interfaces, this fiber can be integrated into the fingers or tactile sensing skin of soft robots. Even under the interference of repeated flexion and extension movements of robot joints, it can still achieve accurate perception and positioning of contact pressure, providing stable tactile feedback for robots and significantly improving their dexterity and safety in dynamic operation tasks; in addition, the highly conductive shielding structure of the outer layer of the fiber allows it to work stably in wearable scenarios with environmental deviations (such as dry environments, humid environments, sweat-soaked environments during exercise, etc.), and can output reliable pressure signals without additional filtering or shielding treatment.

[0046] The present invention has the following significant advantages: 1. Integrated continuous molding of three-dimensional spiral electrodes and supercapacitor dielectric layers has been achieved, significantly improving process efficiency and structural consistency.

[0047] Existing technologies for preparing helical functional fibers require multiple steps: first, spinning to prepare the core layer, then sequentially constructing the electrode layer and dielectric layer through mechanical winding, dip coating, or vapor deposition. These processes are discrete, time-consuming, and it is difficult to guarantee the coaxiality and thickness uniformity of each layer. This invention innovatively introduces a high-viscosity glycerol sacrificial layer as the intermediate fluid in coaxial spinning. Utilizing the circumferential shear torque applied to the inner conductive solution during extrusion, it directly induces three-dimensional helical buckling of the core. Simultaneously, the outer ionogel precursor solidifies instantaneously in the coagulation bath, locking the helical configuration in situ and forming the dielectric layer itself. The entire process of helical electrode generation and dielectric layer formation is completed simultaneously in a single spinning step, without any mechanical twisting or post-winding treatment. This integrated rheoforming method not only simplifies the traditional multi-step process into a continuous production line but also fundamentally guarantees the perfect coaxiality and batch-to-batch structural consistency of the helical electrode and dielectric layer, laying the technological foundation for large-scale preparation.

[0048] 2. Achieving high insensitivity of fiber capacitance to axial tensile strain, thus solving the baseline drift problem in pressure measurement under dynamic motion conditions.

[0049] Traditional coaxial capacitive fibers, when stretched, experience a significant increase in capacitance due to the combined effect of increased linear electrode length and reduced dielectric layer thickness, failing to provide a stable pressure measurement baseline. This invention fundamentally solves this coupling problem through the geometric self-adjustment mechanism of the inner three-dimensional helical electrode. When the fiber is stretched, the inner helical electrode undergoes deformation behavior, increasing the pitch and decreasing the helical radius. The reduced radius increases the contact pressure and effective contact area between the outer surface of the helical electrode and the inner wall of the ionogel dielectric layer. This resulting increase in interfacial double-layer capacitance precisely compensates for the decrease in dielectric layer geometric capacitance, ensuring the total fiber capacitance remains stable over a wide tensile strain range (measured at 30% strain, ΔC / C0 < 2%). This dynamic compensation mechanism for interfacial contact area based on helical topology is not found in existing linear electrodes or surface-wound electrodes. It allows the fiber of this invention to be directly woven into the joint areas of clothing, accurately sensing external pressure even during significant human movement, without the need for complex post-processing signal algorithms for motion artifact removal.

[0050] 3. It achieves ultra-high sensitivity detection of radial pressure, and effectively decouples the pressure response from the tensile response at the physical level.

[0051] Traditional coaxial capacitive fibers rely solely on the localized compression of the dielectric layer under pressure, resulting in limited sensitivity. While surface-wound helical electrodes increase the compression space, the contact state between the coils is significantly affected by stretching, leading to signal crosstalk. This invention utilizes the naturally formed three-dimensional helical contact interface between the inner helical electrode and the ion-gel dielectric layer. In its natural, uncompressed state, this interface presents as a "line contact" or "loose contact," with a limited effective contact area. When subjected to radial pressure, the dielectric layer compresses inward, forcing the helical electrode to transform into a large-area surface contact with the inner wall of the dielectric layer. This results in an order-of-magnitude increase in the effective contact area, generating extremely high capacitive response (sensitivity up to 1.8 kPa⁻¹). Simultaneously, since axial stretching primarily alters the pitch and radius of the helix, its contribution to the radial contact state is negligible. The pressure response and stretching response are physically independent. This "line contact-surface contact" transformation sensitization mechanism and the "stretching-compression" physical decoupling mechanism are unattainable by existing technologies. This allows the fiber of this invention to simultaneously monitor human motion posture and external touch pressure, with the two signals not interfering with each other.

[0052] 4. Stable shielding performance was achieved under dynamic stretching conditions, effectively ensuring the signal-to-noise ratio and anti-interference capability of the sensing signal.

[0053] Most existing fiber sensors lack shielding design or use rigid shielding layers such as metal foil, which crack and detach during stretching due to modulus mismatch, resulting in a sharp decrease in shielding effectiveness. This invention uses a thermosetting polyurethane / liquid metal composite material, homogeneous with the inner electrode, as the outer shielding electrode, forming a dense conductive network through multiple dip-coating-curing processes. When the fiber is subjected to tensile strain, the liquid metal particles slide and rearrange with the polymer matrix, maintaining the continuity of the conductive path; simultaneously, the radial contraction of the inner spiral electrode provides internal support for the outer coating, suppressing stress concentration cracking. This homogeneous material system and the synergistic deformation mechanism ensure that the fiber maintains high shielding effectiveness under dynamic stretching, effectively isolating external power frequency noise and electrostatic interference, significantly improving the signal-to-noise ratio of the sensing signal. This is unmatched by existing rigid shielding layers or single conductive coatings.

[0054] 5. The material system has good compatibility, strong interfacial bonding between functional layers, and synergistic optimization of the overall mechanical and electrical properties of the fiber.

[0055] In existing technologies, functional layers often employ heterogeneous materials (such as metal electrodes, silicone dielectric layers, and carbon-based coatings), resulting in weak interfacial bonding and susceptibility to delamination and failure under repeated stretching. This invention addresses this by using a polyurethane / liquid metal composite material system for both the inner and outer shielding electrodes, and a polyurethane / ionic liquid gel system for the intermediate dielectric layer. All three layers utilize polyurethane as a continuous matrix, ensuring thermodynamic compatibility and interfacial affinity between the functional layers. During spinning and coating processes, each layer forms an interpenetrating molecular chain network through solvent diffusion or thermal curing, resulting in strong interfacial bonding that resists peeling under repeated stretching. This homogeneous matrix strategy endows the fiber with excellent tensile compliance, structural stability, and reliable electrical functionality.

[0056] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a shielded radial pressure sensing fiber, characterized in that, Includes the following steps: A three-layer coaxial microfluidic wet spinning process is used to simultaneously extrude the inner conductive polymer solution, the middle high-viscosity sacrificial layer fluid, and the outer ion gel precursor solution. During the extrusion process, the high-viscosity sacrificial layer fluid applies circumferential shear torque to the conductive polymer solution, inducing the conductive polymer solution to undergo three-dimensional helical buckling and form a three-dimensional helical liquid flow. The extruded coaxial liquid flow enters the coagulation bath, where the ion gel precursor undergoes phase separation and solidification to form an ion gel supercapacitor dielectric layer. This locks the helical configuration of the three-dimensional helical liquid flow in situ, and simultaneously molds the nascent fiber in an integrated manner. The outer surface of the dielectric layer of the ion gel supercapacitor of the nascent fiber is coated to form a shielded electrode layer with high conductivity, resulting in a shielded radial pressure sensing fiber with a three-dimensional helical structure.

2. The preparation method according to claim 1, characterized in that, The high-viscosity sacrificial layer fluid is glycerol or polyglycerol, with a viscosity of 500-1200 mPa·s at 25°C.

3. The preparation method according to claim 1, characterized in that, The ratio of the flow rate of the high-viscosity sacrificial layer fluid to the flow rate of the conductive polymer solution is 0.2-0.

8.

4. The preparation method according to claim 1, characterized in that, The conductive polymer solution is prepared by mixing polyurethane and liquid metal particles in a mass ratio of 5:1 and dissolving them in N,N-dimethylformamide; the ion gel precursor solution is prepared by mixing polyurethane and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ionic liquid in a mass ratio of 2:

1.

5. The preparation method according to claim 1, characterized in that, The coating process specifically involves immersing the nascent fibers in a mixed coating solution of thermosetting polyurethane and liquid metal particles, followed by multiple immersion-curing processes to form a high-conductivity shielding electrode layer with a thickness of 10-100 μm.

6. A shielded radial pressure sensing fiber prepared by the method according to any one of claims 1 to 5, characterized in that, It has a three-layer coaxial heterostructure consisting of a three-dimensional spiral conductive polymer electrode layer, an ion gel supercapacitor dielectric layer, and a high conductivity shielding electrode layer, from the inside out. The three-dimensional spiral conductive polymer electrode layer is configured to undergo geometric self-adjustment, with an increase in pitch and a decrease in spiral radius, when the shielded radial pressure sensing fiber is subjected to axial tension. This increases the contact pressure and effective contact area between the three-dimensional spiral conductive polymer electrode layer and the inner wall of the ion gel supercapacitor dielectric layer, thereby compensating for the decrease in geometric capacitance caused by tension and achieving insensitivity of the total fiber capacitance to axial tensile strain.

7. The shielded radial pressure sensing fiber according to claim 6, characterized in that, The three-dimensional spiral conductive polymer electrode layer and the ion gel supercapacitor dielectric layer form a three-dimensional spiral contact interface. This interface is configured to be in a line contact or loose contact state under natural, unpressurized conditions; and to transform into a surface contact state when subjected to radial pressure, thereby increasing the effective contact area by orders of magnitude and producing ultra-high radial pressure capacitive response sensitivity.

8. The shielded radial pressure sensing fiber according to claim 6, characterized in that, The three-dimensional spiral conductive polymer electrode layer and the high conductivity shielding electrode layer adopt a homogeneous composite material system, and the mechanical properties of each functional layer are matched.

9. The shielded radial pressure sensing fiber according to claim 8, characterized in that, When the fiber is subjected to tensile strain, the high conductivity shielding electrode layer maintains the continuity of the conductive network through the sliding and rearrangement of liquid metal particles, so as to ensure the shielding effectiveness under dynamic tension.

10. The application of the shielded radial pressure sensing fiber according to any one of claims 6 to 9 in wearable pressure sensors, physiological signal monitoring fabrics, human-computer interaction interfaces, or tactile sensing for soft robots.

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