Electrically conductive polyether ester fiber foot pressure sensor, foot pressure insole and preparation method thereof

Abstract

The application provides a kind of electrically conductive polyether ester fiber foot pressure sensor, foot pressure insole and preparation method thereof, comprising the following steps: S1, polyether ester fiber membrane is prepared by electrospinning method;S2, polyether ester fiber membrane is soaked in alcohol solution containing pyrrole and tannic acid for a period of time;S3, polyether ester fiber membrane is soaked in ferric chloride solution for a period of time, and a kind of electrically conductive polyether ester fiber foot pressure sensor is obtained.The preparation process of the electrically conductive polyether ester fiber foot pressure sensor is simple, the cost is low, the superior stretchability, the excellent conductivity, the relatively superior sensing.

Description

Technical Field

[0001] This invention relates to a foot pressure sensor made of conductive polyether ester fiber, a foot pressure insole, and a method for preparing the same, belonging to the technical field of footwear components. Background Technology

[0002] The feet are the only part of the human body that comes into contact with the ground during normal activities, and they have a significant impact on an individual's health, especially for the elderly, athletes, and individuals with certain medical conditions. Abnormal changes in foot pressure can lead to a range of health problems, such as lower limb deformities, sports injuries, and plantar fasciitis. Currently, existing foot pressure measurement methods mainly consist of traditional foot pressure plates combined with thin-film pressure sensors. These methods suffer from low accuracy, poor repeatability, poor comfort, and high cost. Furthermore, calibration is required before each use, which significantly limits their long-term usability in daily life.

[0003] Polyether esters possess numerous advantages, including excellent heat resistance, flexural fatigue resistance, abrasion resistance, high strength and toughness, and ease of processing and molding. These properties make them an ideal carrier material for foot pressure insole sensors. Firstly, polyether ester fibers exhibit excellent elasticity, allowing sensors made from them to maintain good shape while maintaining high sensitivity. Secondly, polyether ester fibers possess high durability and breathability, resulting in good comfort and stability for wearable devices. However, since polyether esters, as traditional polymers, are non-conductive, modification of polyether ester fibers is necessary. Achieving low-cost, mass-producible, and highly stable modification of polyether ester fibers and the fabrication of foot pressure monitoring sensors presents significant challenges. Summary of the Invention

[0004] This invention provides a foot pressure sensor made of conductive polyether ester fiber, a foot pressure insole, and a method for preparing the same, which can effectively solve the above-mentioned problems.

[0005] This invention is implemented as follows:

[0006] A method for preparing a foot pressure sensor made of conductive polyether ester fiber includes the following steps:

[0007] S1, polyether ester fiber membrane is prepared by electrospinning;

[0008] S2, the polyether ester fiber membrane is immersed in an alcohol solution containing pyrrole and tannic acid for a period of time; the alcohol solution containing pyrrole and tannic acid has an alcohol content of 40-60%, wherein the concentration of pyrrole is 10-15 v / v and the concentration of tannic acid is 2-12 wt%.

[0009] S3. Then, immerse the polyether ester fiber membrane in ferric chloride solution for a period of time to obtain a foot pressure sensor made of conductive polyether ester fiber.

[0010] In some embodiments, the solvent of the electrospinning solution is hexafluoroisopropanol; the concentration of the electrospinning solution is 4-6 wt%.

[0011] In some embodiments, the electrospinning parameters are: voltage 25-30kV, flow rate 15-25μL / min, roller speed 280-320rpm, humidity 40-50%, and spinning time 3.5-4.5h.

[0012] In some embodiments, the concentration of the ferric chloride solution is 5-10 wt%.

[0013] In some embodiments, the soaking time in step S2 is 50-70 minutes and the temperature is 3.5-4.5°C.

[0014] In some embodiments, the soaking time in step S3 is 22-26 hours, and the temperature is 3.5-4.5°C.

[0015] A foot pressure sensor made of conductive polyether ester fiber prepared by the method described above.

[0016] A foot pressure insole comprising a foot pressure sensor made of the aforementioned conductive polyether ester fiber.

[0017] A method for preparing a foot pressure insole includes the following steps:

[0018] (1) First, a patterned electrode is deposited on the polyimide substrate by dispensing and spraying. Then, the polyimide with the electrode deposited is placed in a constant temperature drying oven for curing.

[0019] (2) The foot pressure sensor of the conductive polyether ester fiber is fixed to the patterned electrode with glue;

[0020] (3) Finally, place the polyimide encapsulation layer on top and encapsulate it.

[0021] In some embodiments, the electrode is made of conductive silver paste material.

[0022] The beneficial effects of this invention are:

[0023] This invention obtains a conductive polyether ester fiber sensor by modifying polyether ester. The foot pressure monitoring insole assembled from the sensor has many advantages such as high sensitivity, good stability, good biocompatibility, portability and ease of use. It can maintain stable detection performance even after long-term use and is suitable for different environments such as daily walking, sports rehabilitation and medical monitoring. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a flowchart of the preparation process for polyether ester fibers.

[0026] Figure 2 This is a flowchart illustrating the preparation process of conductive polyether ester fibers.

[0027] Figure 3 This is a schematic diagram of a foot pressure monitoring insole assembled based on a conductive polyether ester fiber sensor. The components are: 1-polyimide substrate, 2-conductive silver electrode, 3-conductive polyether ester fiber sensor, and 4-polyimide encapsulation layer.

[0028] Figure 4 The breaking elongation and electrical conductivity of polyether ester fibers with different pyrrole contents are shown.

[0029] Figure 5 The images are scanning electron microscope images of polyether ester fibers, in which (a) polyether ester, (b) polypyrrole / polyether ester, (c) tannic acid 0.25 / polypyrrole / polyether ester, (d) tannic acid 0.5 / polypyrrole / polyether ester, and (e) tannic acid 1 / polypyrrole / polyether ester.

[0030] Figure 6 The mechanical properties of polyether ester-based fibers are shown. Among them, (a) is the stress-strain curve of polyether ester-based fibers, and (b) is the stress-strain curve of polyether ester fibers with different tannic acid contents.

[0031] Figure 7 The conductivity of polyether ester fibers with different tannic acid contents.

[0032] Figure 8 Sensing properties of tannic acid / polypyrrole / polyether ester fibers. (a) finger flexion, (b) wrist flexion, (c) elbow flexion. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] This invention provides a method for preparing a foot pressure sensor made of conductive polyether ester fiber, comprising the following steps:

[0035] S1, polyether ester fiber membrane is prepared by electrospinning;

[0036] S2, the polyether ester fiber membrane is immersed in an alcohol solution containing pyrrole and tannic acid for a period of time; the alcohol solution containing pyrrole and tannic acid has an alcohol content of 40-60%, wherein the concentration of pyrrole is 10-15 v / v and the concentration of tannic acid is 2-12 wt%.

[0037] S3. Then, immerse the polyether ester fiber membrane in ferric chloride solution for a period of time to obtain a foot pressure sensor made of conductive polyether ester fiber.

[0038] This invention discloses a method for preparing polyether ester fibers via electrospinning. The polyether ester fibers are first immersed in a 50% alcohol solution, and then immersed in a ferric chloride solution. Pyrrole monomers and ferric chloride can undergo in-situ polymerization to generate conductive black polypyrrole. Polypyrrole is a rigid material and would compromise the flexibility of the polyether ester fibers. However, due to the large number of active groups on the surface of tannic acid, it can form a cross-linked network structure with the polyether ester molecular chains, thus maintaining the flexibility of the polyether ester fibers to a certain extent. The conductive polyether ester fibers successfully prepared by this method possess both good mechanical properties and excellent conductivity.

[0039] Adding tannic acid resulted in a more uniform deposition of spore-like polypyrrole on the fiber surface. Since tannic acid is an active substance, it can improve the interfacial bonding between the polyether ester fiber membrane and polypyrrole, facilitating the formation of a more uniform polypyrrole coating. While the increase in fiber elongation at break was not significant with increasing tannic acid content, the fiber conductivity decreased substantially. This is because tannic acid molecules contain numerous polar groups, which can interact with the polypyrrole molecular chains, resulting in a toughening effect. Furthermore, the phenolic hydroxyl groups in tannic acid molecules can form a cross-linked network structure with the polypyrrole molecular chains. When the material is subjected to external force, this cross-linked network can absorb more energy, thereby increasing the material's elongation at break. In addition, tannic acid can react with ferric chloride. When the tannic acid content is excessive, it will consume some ferric chloride, affecting the degree of polymerization of polypyrrole. On the other hand, tannic acid carries a negative charge, which will neutralize the positive charge on the polypyrrole chains, leading to a decrease in charge carrier concentration and thus reducing conductivity. Preferably, when the tannic acid content is 2.75%, the conductivity and elongation at break of the tannic acid / polypyrrole / polyether ester fiber membrane can be balanced, which is beneficial for subsequent sensing performance testing.

[0040] In some embodiments, the solvent of the electrospinning solution is hexafluoroisopropanol, and the concentration of the spinning solution is 4-6 wt%, which can ensure the stability of the spinning process and the quality of the final fiber product.

[0041] In some specific implementation cases, the parameters used in electrospinning are set as follows: the applied voltage is controlled between 25 and 30 kV to ensure suitable electric field strength; the solution flow rate is precisely adjusted between 15 and 25 μL per minute to ensure the continuity and stability of fiber formation; the roller speed is set between 280 and 320 rpm to maintain uniform fiber deposition; the ambient humidity is strictly controlled between 40% and 50% to reduce electrostatic interference and optimize fiber quality; the entire spinning process lasts for 3.5 to 4.5 hours to ensure sufficient fiber deposition and solidification. Under these optimized parameter conditions, it is evident that no beading occurs during the spinning process, the fiber morphology is uniform, and it exhibits excellent spinnability, thus providing a reliable guarantee for the preparation of high-quality fiber materials.

[0042] In some specific embodiments, the concentration range of the ferric chloride solution is set to 5% to 10% by weight (wt%) to ensure that the solution can achieve the best chemical reaction effect during the treatment process. This concentration is selected based on multiple experimental verifications to achieve the desired treatment effect and reaction efficiency.

[0043] In some specific embodiments, the soaking time in step S2 is precisely controlled between 50 and 70 minutes, while the soaking temperature is strictly maintained within the range of 3.5 to 4.5 degrees Celsius. This combination of time and temperature is to ensure that the material can fully react with the solution during the soaking process, thereby achieving the desired treatment effect and avoiding incomplete reaction due to insufficient time or improper temperature.

[0044] In some detailed embodiments, the soaking time in step S3 is set to 22 to 26 hours, and the soaking temperature is also controlled within the range of 3.5 to 4.5 degrees Celsius. This long soaking period and precise temperature control are to ensure that the material undergoes sufficient chemical changes in this step to achieve the final treatment goal, and to ensure the stability and reliability of the entire process.

[0045] This invention provides a foot pressure sensor made of conductive polyether ester fibers prepared by a specific method. This sensor utilizes the unique properties of conductive polyether ester fibers to accurately sense and transmit foot pressure information. Furthermore, this invention also provides a novel foot pressure insole, the core component of which is the aforementioned conductive polyether ester fiber foot pressure sensor. By assembling multiple conductive polyether ester fiber sensors in a specific layout, a foot pressure insole that fully covers the sole of the foot is formed. Further, advanced deep learning technology is used to intelligently analyze the collected foot pressure data, thereby achieving accurate detection of lower limb deformities.

[0046] In the field of lower limb deformity detection, existing technologies often rely on traditional imaging methods such as X-rays and CT scans, or on manual analysis by specialists. These traditional methods not only depend on the experience and judgment of specialists, but also involve cumbersome and time-consuming diagnostic processes, making it difficult to meet the needs of real-time monitoring and automated diagnosis. Furthermore, the high cost of these methods limits their widespread application in daily health management. Therefore, developing a highly efficient, low-cost, and automated foot pressure sensor for early detection and timely intervention of lower limb deformities has become a crucial technical challenge that urgently needs to be addressed. This invention aims to fill this technological gap and provide a novel solution.

[0047] This invention provides a method for preparing a foot pressure insole, which specifically includes the following steps: First, an electrode layer with a specific pattern is uniformly deposited on a polyimide substrate material using a dispensing and spraying technique. After the electrode layer is deposited, the polyimide substrate with the electrode deposited is placed in a constant temperature drying oven for a certain period of time for curing to ensure a tight bond between the electrode layer and the substrate material, enhancing its stability and durability. Next, a pre-prepared foot pressure sensor made of conductive polyether ester fiber is firmly fixed onto the cured patterned electrode by applying an appropriate amount of adhesive, ensuring good conductivity between the sensor and the electrode and stable signal transmission. Finally, a layer of polyimide encapsulation material is placed on top for overall encapsulation to protect the internal electrodes and sensor from interference from external environmental factors.

[0048] In some specific embodiments, the electrode material is selected from silver paste material with excellent conductivity, so as to further improve the conductivity of the electrode and the overall sensing accuracy of the insole.

[0049] Example 1: Preparation of polyether ester fibers by electrospinning:

[0050] like Figure 1 As shown, 0.798 g of polyether ester particles were added to 10 mL of hexafluoroisopropanol (HFIP), and the mixture was stirred continuously at room temperature until the polyether ester particles were completely dissolved, thus preparing a polyether ester spinning solution with a concentration of 5 wt%. This spinning solution was subjected to electrospinning for 4 hours at a voltage of 25 kV, a flow rate of 20 µL / min, and a roller speed of 300 rpm, and polyether ester fibers were successfully collected on the roller.

[0051] Example 2: Preparation of conductive polyether ester fibers:

[0052] As shown in Example 1, polyether ester fibers were prepared by electrospinning.

[0053] The preparation process of conductive polyether ester fibers is as follows: First, 0.3 mL and 1.2 mL of pyrrole monomer were added to a 50% ethanol solution to prepare a 10 mL pyrrole / 50% ethanol solution, which was then stored at 4°C. Next, an 8% ferric chloride solution was prepared and stored at 4°C. Subsequently, the polyether ester fiber membranes were immersed in pyrrole / 50% ethanol solutions with different pyrrole contents at 4°C for 1 hour, and then immersed in an 8% ferric chloride solution for another 24 hours at 4°C. The fiber samples were named polypyrrole X / polyether ester (where x represents the volume of added pyrrole monomer).

[0054] Mechanical properties were determined at room temperature using a miniature tensile tester (TST 250V, Linkam, UK). The test sample was cut into a dumbbell shape, and the elongation at break was measured using a 20N sensor at a tensile rate of 50 μm / min. The electrical conductivity of the TPEE-PPY-TAX fiber was measured using a four-probe tester (RTS-9, Guangzhou Four-Probe Technology Co., Ltd.). The sample fiber membrane was placed directly below the four probes, the knob was adjusted to bring the probes into contact with the sample surface, and the test button was pressed to perform the test.

[0055] After comparative analysis, the optimal pyrrole content was selected. The experimental results are as follows: Figure 4 As shown.

[0056] Example 3: Preparation of conductive polyether ester fibers:

[0057] As shown in Example 1, electrospun polyether ester fibers were prepared.

[0058] The preparation process of conductive polyether ester fiber is as follows: First, a tannic acid / polypyrrole / 50% ethanol solution is prepared. 1.2 mL of pyrrole monomer is dissolved in 8.8 mL of 50% ethanol solution, and then 0 g, 0.25 g, 0.5 g, and 1 g of tannic acid are added respectively. After complete dissolution, the solution is stored at 4 °C in a refrigerator. At this point, the concentrations of tannic acid are 0%, 2.75%, 5.51%, and 11.01%, respectively. Next, an 8% ferric chloride solution is prepared and similarly stored at 4 °C in a refrigerator.

[0059] Polyether ester fiber membranes were immersed in tannic acid / polypyrrole / 50% alcohol solutions with varying tannic acid contents for 1 hour at 4 °C. Subsequently, the polyether ester fiber membranes were immersed in an 8% ferric chloride solution for 24 hours at 4 °C. Excess polypyrrole was rinsed off with deionized water, and the membranes were dried at 60 °C for 1 hour to obtain tannic acid / polypyrrole / polyether ester fibers. The fiber samples were named tannic acid X / polypyrrole / polyether ester (where X represents the mass of added tannic acid).

[0060] The optimal amount of tannic acid added was determined through experiments, and the tannic acid / polypyrrole / polyether ester fiber was selected as the sample for subsequent experiments.

[0061] Example 4: Assembly of foot pressure monitoring insoles:

[0062] First, a patterned electrode layer is deposited on a polyimide substrate using a dispensing and spraying process. The electrode material is conductive silver paste. Then, the polyimide with the deposited electrode is placed in a constant-temperature drying oven for curing at 120°C for 10 minutes. Next, the aforementioned conductive polyether ester fiber sensor is fixed to the patterned electrode with adhesive. Finally, a polyimide encapsulation layer is placed on top and sealed with adhesive to prevent the sensor from being exposed to air and causing performance changes. See the detailed structural diagram for further details. Figure 3 .

[0063] Figure 4 This study compares the elongation at break and electrical conductivity of two conductive fibers with different pyrrole contents. Figure 1 Data analysis showed that when the pyrrole content increased from 0.3 mL to 1.2 mL, the change in elongation at break was relatively small, while the electrical conductivity significantly increased from 1.0417 S / cm to 2.7924 S / cm. This indicates that polypyrrole 1.2 / polyether ester fiber has superior electrical conductivity. Therefore, 1.2 mL was determined to be the optimal addition amount of pyrrole monomer for subsequent experiments. To further improve the flexibility of the conductive polyether ester fiber, different proportions of tannic acid were added to the pyrrole / 50% ethanol solution to explore the optimal addition amount of tannic acid.

[0064] Figure 5 Scanning electron microscope images of polyether ester fibers are shown, revealing the absence of beading during spinning, indicating the excellent spinnability of polyether ester fibers. The addition of tannic acid resulted in a more uniform deposition of spore-like polypyrrole on the fiber surface. Since tannic acid is an active substance, it enhances the interfacial bonding between the polyether ester fiber membrane and polypyrrole, contributing to the formation of a more uniform polypyrrole coating.

[0065] Figure 6 The tensile stress-strain curves of polyether ester fibers are presented. From... Figure 6 As shown in part (a), the elongation at break of polyether ester fibers is as high as 450%. However, when conductive polypyrrole is deposited on its surface, the elongation at break of the fibers decreases significantly to only 40%. Tannic acid is rich in phenolic hydroxyl groups and can form a cross-linked network structure with polypyrrole molecular chains. Adding tannic acid to a pyrrole / 50% alcohol solution resulted in tannic acid / polypyrrole / polyether ester fibers with an elongation at break of up to 380%. To determine the optimal amount of tannic acid added, 0 g, 0.25 g, 0.5 g, and 1 g of tannic acid were added to a pyrrole / 50% alcohol solution, respectively, resulting in conductive fibers with tannic acid contents of 0%, 2.75%, 5.51%, and 11.01%, respectively. Their tensile properties are as follows: Figure 6As shown in (b), as the tannic acid content increases from 0.25 g to 1 g, the elongation at break of the fiber does not increase significantly, remaining at approximately 380%. However, the electrical conductivity decreases sharply with increasing tannic acid content, dropping from 2.99 S / cm to 0.1 S / cm. Figure 7 This is because tannic acid molecules contain a large number of polar groups, which interact with polypyrrole molecular chains to produce a toughening effect. Furthermore, the cross-linked network structure formed by the phenolic hydroxyl groups and polypyrrole molecular chains can absorb more energy when the material is subjected to external force, increasing the elongation at break. In addition, tannic acid can react with ferric chloride. When the tannic acid content is too high, it will consume some ferric chloride, affecting the degree of polymerization of polypyrrole. On the other hand, the negative charge of tannic acid will neutralize the positive charge on the polypyrrole chains, reducing the carrier concentration and decreasing the conductivity. When the tannic acid content is 2.75%, the conductivity of the tannic acid / polypyrrole / polyether ester fiber membrane is 2.99 S / cm, and the elongation at break can reach 380%. Therefore, this sample was selected for subsequent sensing performance testing.

[0066] Figure 8 The response curves were plotted by recording the resistance change (R-R0) / R0 using a source meter, where R and R0 represent the resistance of the coated sensor before and after the applied motion, respectively. Because the composite fiber surface is covered with a polypyrrole conductive coating, the curling and releasing of the fingers, wrists, and elbows drives the stretching and recovery of the tannic acid / polypyrrole / polyether ester fibers, causing multi-scale deformation of the conductive pathways formed by the polypyrrole coating. Therefore, when the tannic acid / polypyrrole / polyether ester fibers undergo repetitive stretching and bending movements, their (R-R0) / R0 ratio exhibits regular fluctuations. Figure 8 As shown in (a), the rate of change in resistivity generated by tannic acid / polypyrrole / polyether ester fibers increases with the increase of the finger flexion angle. Corresponding resistivity changes also occur when the wrist and elbow are flexed. Figure 8 (b) and (c)).

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a foot pressure sensor made of conductive polyether ester fiber, characterized in that, Includes the following steps: S1, polyether ester fiber membrane is prepared by electrospinning; S2, the polyether ester fiber membrane is immersed in an alcohol solution containing pyrrole and tannic acid for a period of time; the alcohol solution containing pyrrole and tannic acid is 50% alcohol, wherein the concentration of pyrrole is 12v / v and the concentration of tannic acid is 2.75wt%; S3, the polyether ester fiber membrane is then immersed in a ferric chloride solution for a period of time to obtain a foot pressure sensor made of conductive polyether ester fiber; the concentration of the ferric chloride solution is 8 wt%. The soaking time in step S2 is 50-70 minutes, and the temperature is 3.5-4.5℃; The soaking time in step S3 is 22-26 hours, and the temperature is 3.5-4.5℃. The resulting conductive polyether ester fiber foot pressure sensor has a conductivity of 2.99 S / cm and an elongation at break of 380%. The solvent in the electrospinning solution is hexafluoroisopropanol; the concentration of the spinning solution is 4-6 wt%. The electrospinning parameters are: voltage 25-30kV, flow rate 15-25μL / min, roller speed 280-320rpm, humidity 40-50%, and spinning time 3.5-4.5h.

2. A foot pressure sensor made of conductive polyether ester fiber prepared by the method of preparing a foot pressure sensor of conductive polyether ester fiber as described in claim 1.

3. A foot pressure insole, characterized in that, The foot pressure sensor includes the conductive polyether ester fiber as described in claim 2.

4. A method for preparing a foot pressure insole, characterized in that, Includes the following steps: (1) First, a patterned electrode is deposited on the polyimide substrate by dispensing and spraying. Then, the polyimide with the electrode deposited is placed in a constant temperature drying oven for curing. (2) The foot pressure sensor of the conductive polyether ester fiber as described in claim 2 is fixed to the patterned electrode with glue; (3) Finally, place the polyimide encapsulation layer on top and encapsulate it.

5. The method for preparing the foot pressure insole according to claim 4, characterized in that, The electrodes are made of conductive silver paste.

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