Multifunctional sensing PDMS (Polydimethylsiloxane) / liquid metal composite fiber as well as preparation method and application thereof

Abstract

The invention discloses a multifunctional sensing PDMS (Polydimethylsiloxane) / liquid metal composite fiber as well as a preparation method and application thereof, and belongs to the technical field of functional materials. A PDMS spinning solution containing thermochromic microcapsules is used as a skin layer spinning solution, nitrogen is used as a middle layer, a liquid metal spinning solution is used as a core layer spinning solution, and three-layer coaxial spinning is performed to obtain the PDMS / liquid metal composite fiber. The composite fiber prepared by the invention has strain sensing, magnetic driving and thermochromic sensing functions, and can be applied to the fields of wearable equipment, flexible robots, biomedical monitoring and the like; and moreover, the preparation process is high in controllability, the interface structure is stable, and continuous batch production is supported.

Description

TECHNICAL FIELD

[0001] The present application relates to a multifunctional sensing PDMS / liquid metal composite fiber and a preparation method and application thereof, and belongs to the technical field of functional materials. BACKGROUND

[0002] Strain sensing technology and magnetic actuation technology have important application value in the field of smart materials and structures. Strain sensors can monitor the deformation of materials or structures in real time and are widely used in health monitoring, motion tracking, intelligent robots and other fields. Magnetic actuation technology uses magnetic field to exert force on materials to achieve deformation or movement of materials, which can be used in micro-electro-mechanical systems (MEMS), flexible robots, biomedical devices, etc. Thermochromic sensing is a technology that uses the color change of thermochromic materials at different temperatures to monitor temperature changes, which can be used in industrial, medical and environmental monitoring fields. However, current sensors mostly rely on different material and structure systems, making it difficult to realize strain sensing, magnetic actuation and thermochromic sensing functions in a single material, limiting their integration and multifunctional development in complex application scenarios.

[0003] PDMS (polydimethylsiloxane) is a high polymer material with good flexibility, biocompatibility and chemical stability, which is widely used in flexible electronic devices, biomedical engineering and other fields. Liquid metal (such as gallium-based alloy) has unique physical and chemical properties, such as high electrical conductivity, high thermal conductivity, low melting point and good fluidity, which has shown broad application prospects in flexible electronics, smart materials and biomedical engineering in recent years. By combining PDMS and liquid metal, it is expected to combine the advantages of both and develop new composite materials with multifunctional properties.

[0004] Currently, although there have been studies on the preparation of fibers by combining PDMS and liquid metal, most of these fibers only focus on the realization of single function, such as simple strain sensing or simple electrical conductivity. For example, by embedding liquid metal channels in the PDMS matrix to prepare conductive fibers for strain sensing, but lack of magnetic actuation function; while some magnetic actuation materials mostly rely on the dispersion of magnetic nanoparticles, making it difficult to achieve high-precision strain monitoring. In addition, existing composite fibers have many problems in the preparation process, such as poor uniformity of liquid metal dispersion, insufficient stability of fiber structure, poor combination of the two, complex preparation process, etc., which limits the further improvement of their performance and the expansion of their practical application.

[0005] With the continuous development of smart material and structure technology, the market demand for composite materials with multiple functions is increasing. Especially in the fields of wearable devices, flexible robots, biomedical monitoring, etc., a composite material capable of realizing strain sensing, magnetic driving, and thermochromic sensing at the same time is needed to meet the multifunctional integration requirements in complex application scenarios. For example, in wearable health monitoring devices, it can monitor the human motion state (strain sensing, thermochromic sensing) in real time and adaptively adjust according to the external magnetic field signal (magnetic driving) to improve the comfort and functionality of the device; in the field of flexible robots, functional materials with strain sensing, magnetic driving, and thermochromic sensing can be used to build intelligent joints or actuators to achieve precise motion control and state feedback. SUMMARY

[0006] [Technical problem]

[0007] It is difficult to realize strain sensing, magnetic driving, and thermochromic sensing in a single material at the same time;

[0008] Although there have been studies on the preparation of fibers by combining PDMS with liquid metal, most of these fibers only focus on the realization of a single function, such as simple strain sensing or simple electrical conductivity;

[0009] The uniform dispersion of liquid metal in the composite fiber is poor, the fiber structure stability is insufficient, and the preparation process is complex.

[0010] [Technical solution]

[0011] To solve the above problems, the present application uses PDMS spinning solution containing thermochromic microcapsules as the skin layer spinning solution, nitrogen as the intermediate layer, and liquid metal spinning solution as the core layer spinning solution to obtain PDMS / liquid metal composite fiber by three-layer coaxial spinning. The composite fiber prepared by the present application has strain sensing, magnetic driving, and thermochromic sensing functions, and can be used in wearable devices, flexible robots, biomedical monitoring, etc. Moreover, the preparation process has strong controllability, stable interface structure, and supports continuous batch production.

[0012] The first object of the present application is to provide a method for preparing PDMS / liquid metal composite fiber with strain sensing, magnetic driving, and thermochromic sensing, comprising the following steps:

[0013] (1) uniformly mix polydimethylsiloxane prepolymer PDMS184, PDMS186, and curing agent to obtain a mixed solution; then add thermochromic microcapsules to the mixed solution, continue to mix, degas, and stand for crosslinking to obtain PDMS spinning solution containing thermochromic microcapsules;

[0014] (2) using the PDMS spinning solution containing thermochromic microcapsules as the sheath layer spinning solution, nitrogen as the intermediate layer, and liquid metal as the core layer spinning solution, three-layer coaxial spinning, preliminary crosslinking at 85-95℃ for 20-40s, and deep crosslinking at 130-140℃ for 80-100s to obtain the PDMS / liquid metal composite fiber.

[0015] In an embodiment of the present application, the mass ratio of the polydimethylsiloxane prepolymer PDMS184 and PDMS186 in step (1) is 1-3:7-9, and is further preferably 2:8.

[0016] In an embodiment of the present application, the mass ratio of the polydimethylsiloxane prepolymer PDMS184, PDMS186 and the curing agent in step (1) is 10:0.8-1.2, and is further preferably 10:1; the curing agent and the polydimethylsiloxane prepolymer are purchased as a set.

[0017] In an embodiment of the present application, the mass concentration of the thermochromic microcapsules in step (1) in the mixed solution is 0.5-1.5%.

[0018] In an embodiment of the present application, the liquid metal in step (2) is liquid metal alloy eutectic gallium-indium (EGaIn).

[0019] In an embodiment of the present application, the defoaming in step (1) is vacuum defoaming.

[0020] In an embodiment of the present application, the standing crosslinking in step (1) is standing crosslinking at 25-35℃ for 20-40min.

[0021] In an embodiment of the present application, the spinning speed of the sheath layer spinning solution in step (2) is 0.65-0.75mm / min, the flow rate of the intermediate layer is 0.3-0.5mL / min, and the spinning speed of the core layer spinning solution is 0.4-0.6mm / min.

[0022] In an embodiment of the present application, the crosslinking in step (2) is crosslinking in an oil bath environment.

[0023] In an embodiment of the present application, after the formation of the composite fiber in step (2), the surface residues are removed by silicon oil cleaning, and automatic winding collection is performed.

[0024] A second object of the present application is the PDMS / liquid metal composite fiber prepared by the method of the present application, which has strain sensing, magnetic driving and thermochromic sensing.

[0025] A third object of the present application is the use of the PDMS / liquid metal composite fiber described in the present application in wearable devices, flexible robots, biomedical monitoring.

[0026] A fourth object of the present application is to provide a functional fabric knitted with the PDMS / liquid metal composite fiber described in the present application.

[0027] In an embodiment of the present application, the knitting can be knitting, weaving, etc.

[0028] In an embodiment of the present application, the functional fabric includes a smart mattress.

[0029] A fifth object of the present application is to provide a smart knee pad knitted with the PDMS / liquid metal composite fiber described in the present application.

[0030] In an embodiment of the present application, the smart knee pad is obtained by sewing the PDMS / liquid metal composite fiber in a serpentine line into the smart knee pad.

[0031] A sixth object of the present application is to provide a method for improving the strain sensing, magnetic actuation, and thermochromic sensing performance of the PDMS / liquid metal composite fiber, comprising the following steps:

[0032] (1) uniformly mixing polydimethylsiloxane prepolymer PDMS184, PDMS186, and a curing agent to obtain a mixed solution; then adding thermochromic microcapsules to the mixed solution, continuing to mix, degassing, and standing for crosslinking to obtain a PDMS spinning solution containing thermochromic microcapsules;

[0033] (2) using the PDMS spinning solution containing thermochromic microcapsules as the skin layer spinning solution, nitrogen as the intermediate layer, and liquid metal spinning solution as the core layer spinning solution, three-layer coaxial spinning, preliminary crosslinking at 85-95℃ for 20-40s, and then deep crosslinking at 130-140℃ for 80-100s to obtain the PDMS / liquid metal composite fiber.

[0034] A seventh object of the present application is to provide a method for improving the spinning stability of the PDMS / liquid metal composite fiber, comprising the following steps:

[0035] (1) uniformly mixing polydimethylsiloxane prepolymer PDMS184, PDMS186, and a curing agent to obtain a mixed solution; then adding thermochromic microcapsules to the mixed solution, continuing to mix, degassing, and standing for crosslinking to obtain a PDMS spinning solution containing thermochromic microcapsules;

[0036] (2) The PDMS spinning solution containing thermochromic microcapsules is used as the skin layer spinning solution, nitrogen is used as the intermediate layer, and the liquid metal spinning solution is used as the core layer spinning solution. The three-layer coaxial spinning is carried out, and then the preliminary crosslinking is carried out at 85-95 DEG C for 20-40 s, and then the deep crosslinking is carried out at 130-140 DEG C for 80-100 s, so as to obtain the PDMS / liquid metal composite fiber.

[0037] [Advantages]

[0038] (1) The differential temperature two-stage curing strategy is adopted, the bubble and uneven crosslinking phenomenon are significantly reduced, the elongation at break of the composite fiber is increased by about 25%, and the thermochromic response speed is accelerated to within 18 seconds.

[0039] (2) The three-layer coaxial spinning is adopted, the interface performance is improved, and the conductivity stability is obviously improved.

[0040] (3) The two-stage curing treatment and the microstructure interface enhancement technology are adopted, and the liquid metal leakage and delamination are effectively avoided.

[0041] (4) The present application can be continuously formed stably, supports nanoscale production, the interface adhesion of the composite fiber is enhanced, there is no delamination phenomenon, the microcapsules are uniformly distributed, the color change threshold error is <±1.5 DEG C, and it is suitable for industrial large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is the process flow chart (A), the thermochromic principle diagram (B) and the screenshot mechanism diagram (C) of the PDMS / liquid metal composite fiber of Example 1.

[0043] Figure 2 It is the strain-induced color change principle of the PDMS / liquid metal composite fiber of Example 1.

[0044] Figure 3 It is the relationship curve between the core layer flow rate and the resistance (A) and the diameter (B) of the PDMS / liquid metal composite fiber of Example 1.

[0045] Figure 4 It is the color response photo of the pressure sensing grid of the PDMS / liquid metal composite fiber of Example 1.

[0046] Figure 5 It is the three-color fiber fabric temperature control display and infrared thermal imaging of the PDMS / liquid metal composite fiber of Example 1.

[0047] Figure 6 It is the magnetic driving bending experiment and the angle-voltage relationship of the PDMS / liquid metal composite fiber of Example 1. DETAILED DESCRIPTION

[0048] The following describes preferred embodiments of the present application, and it should be understood that the embodiments are for better explaining the present application and are not intended to limit the present application.

[0049] Test method:

[0050] 1. Fiber morphology and structure characterization

[0051] The cross-sectional morphology of the fiber was observed using a scanning electron microscope (SEM, ZEISS Sigma 300) to confirm the structural integrity of the fiber; spatial distribution analysis of the skin-core interface elements (Ga, In) was performed using energy dispersive spectroscopy (EDS) to determine the adhesion quality of the interface.

[0052] 2. Mechanical property testing

[0053] A uniaxial tensile test was performed on a 5 cm long fiber sample using a tensile testing machine (Instron 5943, 5N sensor); the stress-strain curve was recorded to obtain the elongation at break and the maximum stress; each group of samples was tested 5 times, and the average value and standard deviation were taken.

[0054] 3. Electrical property and core diameter consistency testing

[0055] The fiber resistance was measured using a precision multimeter (Keysight 34460A).

[0056] The test voltage was 0.5V, and the fiber length was 5cm; the fiber core diameter was measured using a laser diameter measuring instrument (Keyence LS-9000) with a sampling interval of 1mm, and 10 consecutive points were measured; the core diameter standard deviation σ reflects the consistency of preparation.

[0057] 4. Thermochromic response testing

[0058] A power supply (DC, LW-K305D) was used to apply different voltages to the fiber, and the thermochromic phenomenon induced by heating was observed; an infrared thermal imager (FLIR E54) was used to record the temperature change process, and the time required to reach the color change threshold and the cooling recovery time were measured; color change was measured by CIE Lab system to measure color difference ΔE*ab (color difference meter: 3nh NR200).

[0059] 5. Magnetic driving performance testing

[0060] The fiber was fixed on a flexible support and placed in a neodymium magnetic field with a strength of 450mT; the power range was 0-0.6V, and a high-speed camera (Phantom VEO710) was used to record the bending angle and response time of the fiber; at the same time, the driving clamping force was measured by a tension sensor.

[0061] 6. Interface adhesion strength testing

[0062] 180° peeling test was used to test the adhesion between electrode and skin; the electrode was packaged with 0.2mm copper wire and Sil-Poxy glue, and the maximum peeling force was tested by a tensile testing machine.

[0063] 7. Pressure mapping array response test

[0064] A plurality of fibers were woven into a 3x3 orthogonal array, and the resistance and color response under different point pressures (0.5-5N) were tested; the pressure-color mapping matrix was established by combining color change and resistance value, and the response uniformity and positioning accuracy were evaluated.

[0065] Raw materials used in the examples:

[0066] Polydimethylsiloxane prepolymer PDMS184, PDMS186, curing agent: purchased from Dow Corning Company;

[0067] Thermochromic microcapsules: reversible thermochromic pigments, purchased from Shenzhen Qiansai Pigment Co., Ltd.;

[0068] Liquid metal: liquid metal alloy eutectic gallium-indium (EGaIn): purchased from Dongguan Dingguan Metal Co., Ltd. in Guangdong.

[0069] Example 1

[0070] A method for preparing PDMS / liquid metal composite fibers with strain sensing, magnetic driving, and thermochromic sensing, comprising the following steps:

[0071] (1) Mix polydimethylsiloxane prepolymer PDMS184, PDMS186, and curing agent in a mass ratio of 2:8:1 to obtain a mixed solution; then add thermochromic microcapsules with a mass concentration of 1% to the mixed solution, continue to mix, vacuum degassing, and stand at 30°C for 30min to crosslink to obtain a PDMS spinning solution containing thermochromic microcapsules;

[0072] (2) Use the PDMS spinning solution containing thermochromic microcapsules as the skin spinning solution, nitrogen as the intermediate layer, and liquid metal as the core spinning solution; the spinning speed of the skin spinning solution is 0.7mm / min, the flow rate of the intermediate layer is 0.4mL / min, and the spinning speed of the core spinning solution is 0.5mm / min; three-layer coaxial spinning is carried out, followed by preliminary crosslinking at 90°C oil bath for 30s, and then deep crosslinking at 135°C oil bath for 90s; remove the surface residue by silicone oil cleaning, and automatically wind and collect to obtain PDMS / liquid metal composite fibers (fineness of 420±10μm).

[0073] The obtained composite fibers were tested for performance, and the test results are as follows:

[0074] Figure 2To demonstrate the strain-induced color change principle of the PDMS / liquid metal composite fiber of Example 1. From Figure 2 It can be seen that: under 60% uniaxial strain, with the decrease of the diameter of the liquid metal core, the fiber changes from green to blue (therefore, the resistance increases, and the Joule heat also increases); at 100% strain, the color completely fades, and when this force is removed, the fiber quickly returns to the original color, indicating that the process is completely reversible. When a local pressure is applied to the fiber, a local heat-induced color change effect is also exhibited. The electromechanical-thermal coupling behavior reveals unique dynamic response characteristics.

[0075] Example 2

[0076] Adjust the mass ratio of polydimethylsiloxane prepolymer PDMS184, PDMS186, curing agent in step (1) of Example 1 to 0:10:1, 1:9:1, 3:7:1, 10:0:1, and keep the rest the same as Example 1, to obtain a composite fiber.

[0077] The obtained fiber is tested for performance, and the test results are as follows:

[0078] Table 1

[0079] Proportion Elongation at break (%) Thermal response time (s) 2:8:1 (Example 1) 145 18 1：9：1 138 22 3：7：1 131 26 0：10：1 129 25 10：0：1 101 32

[0080] Example 3

[0081] Adjust the mass concentration of the thermochromic microcapsule in step (1) of Example 1 to 0.5, 1.5%, and keep the rest the same as Example 1, to obtain a composite fiber.

[0082] The obtained fiber is tested for performance, and the test results are as follows:

[0083] Table 2

[0084] Concentration Thermal response time (s) Color difference standard deviation (ΔΕ*abσ) 1 (Example 1) 18 2.1 0.5 28 4.2 1.5 30 5.6

[0085] Example 4

[0086] Adjust the flow rate of the intermediate layer in step (2) of Example 1 to 0.3, 0.5, 0.7 mL / min, and keep the rest the same as Example 1, to obtain a composite fiber.

[0087] The obtained fiber is tested for performance, and the test results are as follows:

[0088] Table 3

[0089] Flow rate Core diameter consistency (σ, μm) Resistance stability (ΔR / R0, %) 0.3 ±3.4 3.8 0.4 (Example 1) ±3.1 2.6 0.5 ±7.4 6.2 0.7 ±10.2 10.1

[0090] Example 5

[0091] The spinning speed of the core layer spinning solution of step (2) of Example 1 was adjusted to 0.2-1.2 mm / min, and the other conditions were the same as those of Example 1 to obtain the composite fiber.

[0092] The obtained fiber was subjected to performance test, and the test results were as follows:

[0093] Table 4

[0094] Flow rate Core diameter consistency σ (μm) Steady-state resistance (Ω) 0.5 (Example 1) ±3.1 19.8 0.2 ±9.6 28.5 0.4 ±3.4 22.4 0.6 ±5.6 17.2 0.8 ±6.1 16.4 1.0 ±9.2 16 1.2 ±10.4 15.3

[0095] Figure 3 The core layer flow rate and resistance / diameter relationship curve of the PDMS / liquid metal composite fiber of Example 1.

[0096] From Figure 3 It can be seen that the relationship among the extrusion speed, fiber diameter and resistance is very obvious. With the increase of the core extrusion speed, the core diameter increases and the resistance decreases, which confirms the proportional relationship between the core speed and the diameter and the inverse relationship with the resistance.

[0097] Comparative Example 1

[0098] In Example 1, step (2) was omitted, and the PDMS spinning solution containing thermochromic microcapsules was directly subjected to deep crosslinking at 135°C for 120 s. The other conditions were the same as those of Example 1 to obtain the composite fiber.

[0099] Comparative Example 2

[0100] In Example 1, step (2) was omitted, and the PDMS spinning solution containing thermochromic microcapsules was directly subjected to crosslinking at 90°C for 120 s. The other conditions were the same as those of Example 1 to obtain the composite fiber.

[0101] Comparative Example 3

[0102] In Example 1, the intermediate layer in step (2) was omitted, and the other conditions were the same as those of Example 1 to obtain the composite fiber.

[0103] Comparative Example 4

[0104] In Example 1, the coaxial spinning in step (2) was omitted, and the liquid metal was directly added to the PDMS spinning solution containing thermochromic microcapsules for spinning. The other conditions were the same as those of Example 1 to obtain the composite fiber.

[0105] Comparative Example 5

[0106] In Example 1, step (2) was adjusted as follows:

[0107] The PDMS spinning solution containing thermochromic microcapsules was used as the skin layer spinning solution, and nitrogen was used as the core layer for coaxial spinning to form a hollow fiber, and then the liquid metal was filled in the middle.

[0108] Other conditions are the same as Example 1, and the composite fiber is obtained.

[0109] The obtained fiber is subjected to performance test, and the test results are as follows:

[0110] Table 5

[0111] Example Bubble rate (%) Elongation at break (%) Thermal response time (s) Example 1 2.1 145 18 Comparative Example 1 9.8 105 38 Comparative Example 2 7.6 131 24 Comparative Example 3 5.7 124 22 Comparative Example 4 15.3 76 15 Comparative Example 5 17.2 113 31

[0112] As can be seen from Table 5, the double-temperature-zone differential temperature curing strategy can significantly improve the interface quality, reduce bubble generation, improve mechanical flexibility and response speed, and is suitable for high stability application scenarios.

[0113] Comparative Example 6

[0114] The liquid metal (EGaIn) in Example 1 is replaced by carbon nanotube conductive paste;

[0115] The preparation method of the carbon nanotube conductive paste is as follows:

[0116] Multi-walled carbon nanotubes (MWCNT, diameter 8-15 nm, length 50 μm) are dispersed in deionized water at 5 wt%, 0.5 wt% sodium dodecyl sulfate (SDS) is added as a dispersant, ultrasonic treatment is performed for 2 hours, 2 wt% hydroxyethyl cellulose (HEC) is added to thicken to a viscosity of 320±20 mPa·s (determined by a rotary viscometer), and the rheological properties of EGaIn are matched;

[0117] Other conditions are the same as Example 1, and the fiber is obtained.

[0118] The obtained fiber is subjected to performance test, and the test results are as follows:

[0119] Table 6

[0120] Test index Comparative Example 6 Example 1 Magnetic drive function Failure (no magnetic response) Magnetic drive function flexibility Strain sensitivity (GF) 1.8 12.5 Thermal response time (s) 35 18

[0121] Comparative Example 7

[0122] The amount of thermochromic microcapsules in Example 1 is increased from 1% to 5%, and other conditions remain unchanged. The obtained fiber is subjected to performance test, and the test results are as follows:

[0123] Table 7

[0124] Test index Comparative Example 7 Example 1 Fiber formability Poor (surface roughness break) Smooth continuous Color difference standard deviation (ΔΕ*abσ) 9.4 2.1 Elongation at break (%) 82 145

[0125] Example 6

[0126] A 3×3 sensing grid is constructed using the composite fiber of Example 1 for spatial pressure mapping, as follows:

[0127] (1) 6 composite fibers are woven orthogonally with a spacing of 5 mm;

[0128] (2) Apply 0.5 / 1.0 / 2.0N point pressure (diameter 2mm pressure head), record resistance change and thermal image;

[0129] (3) Generate pressure-color mapping matrix by current re-distribution algorithm;

[0130] Results are shown in Figure 4 .

[0131] It can be seen from Figure 4 that: pressure sensitivity: ΔR / R0=10478.9% at 5N (linearity R 2 =0.998); positioning accuracy: ±0.8mm (lower than fiber spacing); color development response time: 1.2s (from pressurization to complete color change). It can be used for smart mattress monitoring sleep posture pressure distribution.

[0132] Example 7

[0133] The multifunctional drive is prepared by using the composite fiber of Example 1, and the specific process is as follows:

[0134] (1) The composite fiber is sewn in a serpentine line in the elastic knee pad (spandex content 80%);

[0135] (2) Apply 0.35V voltage to realize 38℃ constant temperature thermotherapy (infrared thermal imager calibration).

[0136] (3) Influence of distance between magnet and fiber on bending angle

[0137] Results are shown in Figure 5 and 6 .

[0138] It can be seen from Figure 5 and Figure 6 that:

[0139] (1) Thermotherapy performance: the fiber is rapidly heated to 30±1℃ and 41±1℃ by applying 0.2V and 0.4V;

[0140] (2) Magnetic drive performance: the driving effect is closely related to the distance between the magnet and the fiber and the applied voltage, the distance between the magnet and the fiber is 1, 2, 3, 4, 5cm, and the voltage of 0.1-0.6V is applied at each distance, with a gradient of 0.1V, it is found that the farther the distance, the smaller the bending angle when the voltage is unchanged; on the contrary, when the distance is unchanged, the greater the voltage, the greater the bending angle.

[0141] Example 8

[0142] The present application and the conventional process for preparing PDMS fiber have great differences.

[0143] The specific process is as follows:

[0144] Table 8

[0145]

[0146] While the application has been disclosed in its preferred embodiments with reference to specific details, it is to be understood that various modifications and substitutions can be made by one skilled in the art without departing from the spirit and scope of the application as defined by the claims.

Claims

1. A method for preparing a PDMS / liquid metal composite fiber with strain sensing, magneto-actuation, and thermochromic sensing, characterized in that: The steps include: (1) uniformly mixing polydimethylsiloxane prepolymers PDMS184, PDMS186, and a curing agent to obtain a mixed solution; then adding thermochromic microcapsules to the mixed solution, continuing to mix, degas, and allow to stand for crosslinking to obtain a PDMS spinning solution containing thermochromic microcapsules; (2) Using PDMS spinning solution containing thermochromic microcapsules as the skin spinning solution, nitrogen as the middle layer, and liquid metal as the core layer spinning solution, three layers were coaxially spun, first preliminarily crosslinked at 85-95°C for 20-40s, and then deeply crosslinked at 130-140°C for 80-100s to obtain PDMS / liquid metal composite fibers.

2. The method according to claim 1, characterized in that In step (1), the mass ratio of polydimethylsiloxane prepolymer PDMS184 to PDMS186 is 1-3:7-9.

3. The method according to claim 1, characterized in that The mass concentration of the thermochromic microcapsules in step (1) in the mixed solution is 0.5-1.5%.

4. The method according to claim 1, wherein In step (2), the spinning speed of the cortex spinning solution is 0.65-0.75 mm / min, the flow rate of the middle layer is 0.3-0.5 mL / min, and the spinning speed of the core layer spinning solution is 0.4-0.6 mm / min.

5. A PDMS / liquid metal composite fiber having strain sensing, magneto-actuation, and thermochromic sensing properties, prepared by the method according to any one of claims 1 to 4.

6. Application of the PDMS / liquid metal composite fiber according to claim 5 in the fields of wearable devices, flexible robots, and biomedical monitoring.

7. A functional fabric, characterized in that: It is obtained by weaving the PDMS / liquid metal composite fiber described in claim 5.

8. An intelligent kneepad, characterized in that: It is obtained by weaving the PDMS / liquid metal composite fiber described in claim 5.

9. A method for improving the strain sensing, magneto-actuation, and thermochromic sensing performance of PDMS / liquid metal composite fibers, characterized in that: The steps include: (1) uniformly mixing polydimethylsiloxane prepolymers PDMS184, PDMS186, and a curing agent to obtain a mixed solution; then adding thermochromic microcapsules to the mixed solution, continuing to mix, degas, and allow to stand for crosslinking to obtain a PDMS spinning solution containing thermochromic microcapsules; (2) Using PDMS spinning solution containing thermochromic microcapsules as the skin spinning solution, nitrogen as the middle layer, and liquid metal as the core layer spinning solution, three layers were coaxially spun, first preliminarily crosslinked at 85-95°C for 20-40s, and then deeply crosslinked at 130-140°C for 80-100s to obtain PDMS / liquid metal composite fibers.

10. A method for improving the spinning stability of PDMS / liquid metal composite fibers, characterized in that: The steps include: (1) uniformly mixing polydimethylsiloxane prepolymers PDMS184, PDMS186, and a curing agent to obtain a mixed solution; then adding thermochromic microcapsules to the mixed solution, continuing to mix, degas, and allow to stand for crosslinking to obtain a PDMS spinning solution containing thermochromic microcapsules; (2) Using PDMS spinning solution containing thermochromic microcapsules as the skin spinning solution, nitrogen as the middle layer, and liquid metal as the core layer spinning solution, three layers were coaxially spun, first preliminarily crosslinked at 85-95°C for 20-40s, and then deeply crosslinked at 130-140°C for 80-100s to obtain PDMS / liquid metal composite fibers.

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