A method for preparing fibers with hybrid conductive networks and its application

Abstract

This invention discloses a method for preparing a hybrid conductive network fiber and its application, comprising the following steps: (1) Adding AgNO3 to a PVA solution dissolved in EG and deionized water and stirring to obtain an AgNO3 / PVA / EG core spinning solution. (2) Adding TPU to DMF and stirring to obtain a TPU / DMF skin spinning solution. (3) Spinning the TPU / DMF skin solution and the AgNPs / PVA core spinning solution through a coaxial needle at a rate of 400 μL·min. ‑1 and 200 μL·min ‑1 The initial fiber is obtained by pressing the fiber into a deionized water coagulation bath at a high speed. (4) The initial fiber is heated and then subjected to freeze-thaw treatment to obtain HCNF. Compared with the prior art, the HCNF prepared by the preparation method of the present invention using mixed conductive network fiber has high safety, excellent low temperature resistance and excellent strain sensing performance. It can be used as a flexible wearable strain sensing material to make strain sensors to monitor human movement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of stretchable conductive fibers, in particular to a preparation method of a fiber with a mixed conductive network and application thereof. BACKGROUND

[0002] With the rapid development of material science and electronic manufacturing, flexible wearable strain sensing materials have shown broad application prospects in human motion monitoring, health monitoring and human-computer interaction due to their ability to respond to external stimuli. However, traditional strain sensing materials are based on metals or semiconductors, which can usually only sense small deformations of small strains, and the rigidity of the materials themselves often affects the comfort of wearing. In addition, in practical applications, the stretchability, cycle stability and biocompatibility of wearable strain sensing materials are also increasing. Therefore, it is urgent to design effective strategies to prepare wearable strain sensing materials with high sensitivity and high stretchability.

[0003] The incorporation of conductive materials into organic gel matrices enables them to have excellent electrical properties, and organic gel-based conductive materials can be manufactured and used as wearable strain sensing materials. However, traditional organic gel-based conductive materials inevitably freeze and lose their good performance in low-temperature environments, thereby limiting their practical applications. In addition, organic gel-based conductive materials also have the risk of electric leakage when in contact with human skin.

[0004] Therefore, how to prepare a flexible wearable strain sensing material with high safety, low-temperature resistance, high sensitivity and linearity is a problem to be solved by the present application. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a fiber with a mixed conductive network and application thereof to solve the problems in the prior art.

[0006] In a first aspect, the present application provides a preparation method of a fiber with a mixed conductive network, comprising the following steps:

[0007] (1) AgNO3 is added to a PVA solution dissolved in EG and deionized water, and then stirred and mixed to prepare an AgNO3 / PVA / EG core layer spinning solution;

[0008] (2) TPU is added to DMF, and then stirred and mixed to obtain a TPU / DMF skin layer spinning solution;

[0009] (3) The TPU / DMF skin layer spinning solution and the AgNPs / PVA core layer spinning solution are respectively extruded into a deionized water coagulation bath through coaxial needles at speeds of 400 μL·min -1 and 200 μL·min -1 to obtain an initial filament;

[0010] (4) heating treatment of the primary filaments, followed by freeze-thaw treatment to obtain the HCNF.

[0011] The preparation method of the mixed conductive network fiber as described above, wherein preferably, the mass of the AgNO3 in step (1) is 0.1699 g.

[0012] The preparation method of the mixed conductive network fiber as described above, wherein preferably, the mass fraction of the PVA solution in step (1) is 5 wt%.

[0013] The preparation method of the mixed conductive network fiber as described above, wherein preferably, the stirring mixing in step (1) is stirring by a magnetic stirrer, and the stirring time is 30 min.

[0014] The preparation method of the mixed conductive network fiber as described above, wherein preferably, the mass fraction of the TPU / DMF skin layer spinning solution in step (2) is 15 wt%.

[0015] The preparation method of the mixed conductive network fiber as described above, wherein preferably, the stirring time in step (2) is 12 h.

[0016] The preparation method of the mixed conductive network fiber as described above, wherein preferably, the specification of the coaxial needle in step (3) is 17G / 21G.

[0017] The preparation method of the mixed conductive network fiber as described above, wherein preferably, the heating treatment time in step (4) is 10 min, and the temperature is 40℃.

[0018] The preparation method of the mixed conductive network fiber as described above, wherein preferably, the freezing time of the freeze-thaw treatment in step (4) is 8 h, the temperature is -24℃, the thawing time is 2 h, the temperature is room temperature, and the freeze-thaw frequency of the freeze-thaw treatment is 3 times.

[0019] In the second aspect, the application provides an application of the mixed conductive network fiber, including the application of the HCNF prepared by the preparation method of the mixed conductive network fiber in human motion monitoring.

[0020] Compared with the prior art, the HCNF prepared by the preparation method of the mixed conductive network fiber has high safety, excellent low-temperature resistance and excellent strain sensing performance, and can be used as a flexible wearable strain sensing material to make a strain sensor to monitor human motion. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1is a picture showing the appearance of HCNF prepared in Example 1;

[0022] Figure 2 is a characterization of the ion / electron mixed conductive network of HCNF prepared in Example 1;

[0023] Figure 3 is the electrical conductivity of HCNF prepared in Example 1 at different temperatures;

[0024] Figure 4 is the tensile cycle curve of HCNF prepared in Example 1 at different strains and frequencies;

[0025] Figure 5 is the tensile cycle curve of HCNF prepared in Example 1 at different temperatures;

[0026] Figure 6 is the GF value comparison curve of HCNF strain sensor prepared in Example 2;

[0027] Figure 7 is the corresponding relative resistance change curve of HCNF strain sensor prepared in Example 2 at different strains;

[0028] Figure 8 is the relative resistance change curve of HCNF strain sensor prepared in Example 2 at different temperatures;

[0029] Figure 9 is the working curve of HCNF strain sensor monitoring finger bending motion in Example 3;

[0030] Figure 10 is the working curve of HCNF strain sensor monitoring arm bending motion in Example 3;

[0031] Figure 11 is the working curve of HCNF strain sensor monitoring knee bending motion in Example 3. DETAILED DESCRIPTION

[0032] The examples described below by reference to the accompanying drawings are exemplary only and are intended to explain the present application, but cannot be interpreted as a limitation of the present application.

[0033] In a first aspect, the present application provides a preparation method of a fiber with a mixed conductive network, comprising the following steps:

[0034] (1) AgNO3 is added to a polyethylene glycol (PVA) solution dissolved in ethylene glycol (EG) and deionized water, and stirred and mixed to prepare an AgNO3 / PVA / EG core layer spinning solution.

[0035] (2) Thermoplastic polyurethane (TPU) fiber was added into N,N-dimethylformamide (DMF) and stirred to obtain a TPU / DMF sheath spinning solution.

[0036] (3) The TPU / DMF sheath spinning solution and the AgNPs / PVA core spinning solution were extruded into a deionized water coagulation bath through coaxial needles at a speed of 400 μL·min -1 and 200 μL·min -1 , respectively, to obtain a primary fiber.

[0037] (4) The primary fiber was heated and then subjected to freeze-thaw treatment to obtain the HCNF.

[0038] After AgNO3 was added to a PVA solution dissolved in EG and H2O and stirred, an AgNO3 / PVA / EG core spinning solution was prepared. TPU was dissolved in N,N-dimethylformamide (DMF) to prepare a TPU / DMF sheath spinning solution. The AgNO3 / PVA / EG solution and the TPU / DMF solution were respectively introduced into a deionized water coagulation bath through the inner and outer channels of coaxial needles to obtain a primary fiber. After the use of a thermal reduction / cold crosslinking strategy, a fiber with a mixed conductive network was prepared. In the thermal reduction process, Ag + in the HCNF core layer solution was partially reduced to AgNPs to form an ion / electron mixed conductive network due to the presence of polyhydroxy alcohol. In the cold crosslinking process, H2O was frozen into ice, and the PVA chains dissolved in H2O were arranged in an orderly and compact manner. Subsequently, the ice melted into H2O, but the PVA chains were still arranged in a compact manner to form a physical crosslinking network. The ion / electron mixed conductive network was constructed in the physical crosslinking network, which endowed the HCNF with excellent strain sensing potential. The TPU sheath encapsulated the core layer gel inside by intermolecular hydrogen bonds, effectively avoiding leakage of the core layer and direct contact with the human body. In addition, the interface between the sheath and the core enabled the HCNF to have good mechanical properties. Benefiting from the addition of EG, the HCNF sensor can also work stably at low temperatures.

[0039] In the embodiments provided in the present application, the mass of AgNO3 in step (1) is 0.1699 g; the mass fraction of the PVA solution in step (1) is 5 wt%; the stirring in step (1) is stirring by a magnetic stirrer, and the stirring time is 30 min; the mass fraction of the TPU / DMF sheath spinning solution in step (2) is 15 wt%; the stirring time in step (2) is 12 h; the specification of the coaxial needle in step (3) is 17G / 21G; the heating time in step (4) is 10 min, and the temperature is 40℃; the freezing time of the freeze-thaw treatment in step (4) is 8 h, the temperature is -24℃, the thawing time is 2 h, the temperature is room temperature, and the freeze-thaw frequency of the freeze-thaw treatment is 3 times.

[0040] Secondly, the present invention provides an application of hybrid conductive network fibers, including the application of HCNF prepared by the aforementioned method for preparing hybrid conductive network fibers in human motion monitoring.

[0041] In the HCNF prepared by the above method, there is a good interfacial interaction between the skin layer and the core layer, resulting in excellent mechanical properties. The HCNF can be tested for sensitivity (GF) within 100% strain range, with a measured value of 2.26, a linearity of 0.998, and a conductivity of 1.812 S / m. -1 This is attributed to the construction of an ion / electron hybrid conductive network. Thanks to the addition of EG, the HCNF sensor can operate stably at -20°C. Its excellent electromechanical properties make the HCNF sensor suitable for monitoring human motion. Therefore, this invention can serve as a flexible wearable strain sensing material, possessing high safety, excellent low-temperature resistance, and superior sensing performance, and can be applied to strain sensors for monitoring changes in human motion.

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1

[0044] This embodiment discloses a method for preparing a hybrid conductive network fiber (HCNF), comprising the following steps:

[0045] 1) Add AgNO3 to a PVA solution dissolved in EG and deionized water and stir to prepare AgNO3 / PVA / EG core spinning solution.

[0046] 2) Add TPU to DMF and mix by stirring to obtain TPU / DMF skin spinning solution.

[0047] 3) Spinning the TPU / DMF skin layer solution and the AgNPs / PVA core layer solution through a coaxial needle at a rate of 400 μL·min. -1 and 200 μL·min -1 The initial fiber is obtained by pressing it into a deionized water coagulation bath at a high speed.

[0048] 4) Heat the raw fiber and then freeze-thaw it to obtain HCNF.

[0049] The HCNF prepared in Example 1 above was then visualized, and the results are as follows: Figure 1As shown; where Figure 1 A is an optical photograph of the obtained HCNF; Figure 1 B is an optical photograph of a fabric woven from HCNF. From Figure 1 As can be seen from A, the core gel is encapsulated within the TPU skin layer, and the core and skin layers of HCNF are tightly adhered together. Figure 1 B indicates that HCNF has good flexibility, weavability, and scalability. Figure 2 Characterization of the HCNF core layer gel. Figure 2 A-2C represent the UV spectrum, Ag fine spectrum, and TEM image of the HCNF core gel, respectively, collectively demonstrating the successful construction of an ion / electron hybrid conductive network. The resistance of HCNF at different temperatures was measured, and its conductivity was calculated, yielding... Figure 3 This indicates that HCNF also exhibits good electrical conductivity at low temperatures. The HCNF prepared in Example 1 was connected to the upper and lower mechanical sensors of a universal testing machine at both ends. The program was set at strains of 20%, 40%, 60%, 80%, and 100%, and a constant temperature of 50 mm / min. -1 Under the condition of stretching cycle, the following is obtained Figure 4 A. Then set the program to 50% strain, frequencies of 0.01Hz, 0.05Hz, 0.10Hz, and 0.50Hz, and perform stretching cycles to obtain... Figure 4 B. Figure 4 A-4B indicates that HCNF can operate stably under different strains and frequencies, exhibiting good mechanical properties. The HCNF prepared in Example 1 was placed at -30℃ for 12 hours, and then its ends were connected to the upper and lower mechanical sensors of an electronic universal testing machine. The tensile speed was set to 50 mm / min. -1 Under 50% strain conditions, the cyclic curve of recovery from -20℃ to room temperature was tested, and the results were obtained. Figure 5 ,from Figure 5 It can be seen that HCNF can still work stably at different temperatures, demonstrating excellent stability.

[0050] Example 2

[0051] This embodiment discloses a method for fabricating a strain sensor based on HCNF assembly, including the following steps:

[0052] 1) The HCNF obtained in Example 1 above was cut short to obtain fiber segments X1 with a length of 3cm;

[0053] 2) Insert copper wires coated with conductive adhesive into both ends of fiber segment X1 to obtain fiber segment X2;

[0054] 3) Fix both ends of fiber segment X2 with epoxy resin to obtain device X3, which is a strain sensor based on HCNF assembly.

[0055] The aforementioned device X3 was connected to a combined digital source meter and universal testing machine to control the tensile rate at 50 mm / min. -1 With a tensile strain of 100%, the relative resistance change versus strain curve was obtained, and the corresponding sensitivity was calculated accordingly. Figure 6 The results show that the HCNF strain sensor prepared in this embodiment of the invention has high sensitivity and high linearity over a wide strain range, which is attributed to the successful construction of the ion / electron hybrid conductive network. The tensile rate was controlled at 50 mm / min. -1 By increasing the tensile strain from 10% to 80%, the relative resistance change curve corresponding to the output strain was obtained. Figure 7 The results show that the HCNF strain sensor prepared in this embodiment of the invention can efficiently convert strain stimuli into electrical signals, and has a stable strain stimulus response and a wide strain detection range. After placing the HCNF strain sensor prepared in this embodiment of the invention at -30℃ for 12 hours, it was connected to a combination of a digital source meter and a universal testing machine, and the tensile rate was controlled at 50 mm / min. -1 With a tensile strain of 50%, the relative resistance change was tested as the temperature recovered from -20°C to room temperature. Figure 8 The results show that the HCNF strain sensor prepared in this embodiment of the invention can still work stably under low temperature conditions, has good low temperature tolerance, and the signal output is less affected by temperature, showing potential for use in complex environments.

[0056] Example 3

[0057] This embodiment discloses the fabricated HCNF strain sensor for monitoring human joint bending motion, as detailed below:

[0058] The device X3 prepared in Example 2 above is connected to a digital source meter and the skin of a finger. By controlling the bending of the finger, a series of working curves are obtained. Figure 9 The results show that the HCNF strain sensor prepared in this embodiment can effectively monitor minute bending movements of the fingers. The device X3 prepared in Embodiment 2 was connected to a digital source meter and the skin of the arm. By controlling the bending of the arm, a series of working curves were obtained. Figure 10 The results show that the HCNF strain sensor prepared in this embodiment can effectively monitor wrist flexion movements. The device X3 prepared in Embodiment 2 was connected to a digital source meter and the skin of the knee. By controlling knee flexion, a series of working curves were obtained, such as... Figure 11 As shown, the HCNF strain sensor prepared according to the embodiments of the present invention can effectively monitor knee flexion movements. The above results indicate that the HCNF strain sensor can be used to monitor joint movements in the human body and sense both minute and large deformations during daily activities.

[0059] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A method of making a fiber having a hybrid conductive network, characterized by, Comprising the following steps: (1) 0.1699 g of AgNO3 is added to a PVA solution with a mass fraction of 5 wt% dissolved in EG and deionized water, and mixed for 30 min with a magnetic stirrer to prepare an AgNO3 / PVA / EG core layer spinning solution; (2) TPU is added to DMF and mixed for 12 h by stirring to obtain a TPU / DMF skin layer spinning solution with a mass fraction of 15 wt%; (3) The TPU / DMF skin layer spinning solution obtained in step (2) and the AgNO3 / PVA / EG core layer spinning solution obtained in step (1) are extruded into a deionized water coagulation bath through a coaxial needle with specifications of 17G / 21G at speeds of 400 μL·min -1 and 200 μL·min -1 , respectively, to obtain primary filaments; (4) The primary filament is heated at 40℃ for 10 min, and then subjected to freeze-thaw treatment, the freezing time of the freeze-thaw treatment is 8 h at-24℃, the thawing time is 2 h at room temperature, the freeze-thaw frequency of the freeze-thaw treatment is 3 times, to prepare HCNF with an ion / electron mixed conductive network.

2. Use of a low temperature resistant strain sensing fiber, characterized in that The HCNF prepared by the preparation method of the mixed conductive network fiber in claim 1 is applied to human motion monitoring.

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