Preparation method of core-shell structure electrically driven dielectric elastomer artificial muscle fiber

Abstract

The application discloses a preparation method of a core-shell structure electrically-driven dielectric elastomer artificial muscle fiber, relates to the technical field of flexible robot driving, and comprises the following steps: preparing BTO nanotubes with high interfacial polarization by means of hydrothermal synthesis and wet chemical method; preparing a polymer mixed solution by taking TPU as a matrix, BDA as a small-molecule polar plasticizing and polarization aid, and the BTO nanotubes as fillers; adopting a continuous solution dipping core-spun method, taking CNT continuous fibers as conductive core wires, continuously coating to form a core-shell structure fiber, and spraying or depositing a conductive polymer electrode layer on the outer layer to obtain the core-shell structure dielectric elastomer artificial muscle fiber. The application realizes the improvement of the dielectric constant of the shell layer and the maintenance of flexibility by synergistically regulating a high dielectric shell layer system, solves the problems that traditional fillers are prone to agglomeration or the poor compatibility between fillers and polymers leads to high loss or mechanical embrittlement, and it is difficult to balance the dielectricity and flexibility, improves the electric displacement efficiency under low and medium pressure conditions, and meanwhile, high elongation and flexibility are maintained.

Description

TECHNICAL FIELD

[0001] The application relates to the field of flexible robot driving and intelligent wearable technology, and particularly relates to a preparation method of a core-shell structure electrically-driven dielectric elastomer artificial muscle fiber. BACKGROUND

[0002] Artificial muscle is the core of the research in the field of flexible actuators in China. With the rapid development of flexible electronic technology and intelligent material field, higher requirements are put forward for the flexibility and intelligent response of the driving system. However, the current artificial muscle has problems such as weak driving force, single deformation mode, small deformation and slow response speed, which restricts the application of artificial muscle in the field of flexible driving. In view of the above problems, the fiber-like artificial muscle has the following advantages: (1) high flexibility, which can simulate muscle fibers in skeletal muscle, form natural muscle characteristics, and utilize the advantages of fiber structure design to form a complex two-dimensional or three-dimensional structure through stretching, twisting, plying and weaving, so as to construct a complex multi-dimensional electric actuation network; (2) combined with three-dimensional weaving design, the linear deformation of a single fiber can be converted into multiple cooperative deformation modes such as torsion, bending or stretching of the overall structure; (3) the artificial muscle fiber can be interlaced and interlocked to form a three-dimensional composite structure, thereby enhancing the overall strength, sharing the load and improving the driving force; (4) compared with the thin film or block structure, the driving strain can be amplified and the response speed can be improved through the way of transmitting driving force layer by layer by the deformation of a single fiber through twisting or multi-layer weaving structure.

[0003] Patent CN111618837B discloses an electrically-controlled telescopic composite artificial muscle, which realizes bidirectional deformation of elongation and contraction, can be three-dimensionally cubed, and has the advantages of simple structure, easy control and various deformation modes.

[0004] The above patent can realize elongation deformation by applying an electric field to the upper and lower surfaces of the composite electrically-deformed layer, and can realize contraction deformation by applying an electric current to the electrically-deformed fiber. However, the artificial muscle disclosed in the above patent has the problem that the driving force and the deformation amount are difficult to be compatible.

[0005] Therefore, the present application provides a preparation method of a core-shell structure electrically-driven dielectric elastomer artificial muscle fiber, which can realize compatibility of driving force and deformation amount and fast response speed. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of a core-shell structure electrically-driven dielectric elastomer artificial muscle fiber, so as to solve the technical problems of weak driving force, single deformation mode, small deformation and slow response speed in the background technology.

[0007] To achieve the above purpose, the present application provides the following technical scheme: a preparation method of a core-shell structure electrically-driven dielectric elastomer artificial muscle fiber, which comprises the following steps:

[0008] Step A: Preparation of highly interfacially polarized BTO nanotubes by hydrothermal synthesis and wet chemical method;

[0009] Step B: Prepare a mixed solution of TPU, DBA and BTO polymers using thermoplastic TPU as the matrix, DBA as a polar small molecule plasticizer and polarization aid, and BTO nanotubes as a high dielectric filler.

[0010] Step C: Using the continuous solution impregnation core-coating method, CNT continuous fibers are used as conductive core filaments. The TPU, DBA, and BTO polymer mixed solution is continuously coated to form a core-shell structure fiber. A conductive polymer electrode layer is sprayed or deposited on the outer layer to form positive and negative electrodes. After drying, heat treatment, mechanical stretching and polarization treatment, a core-shell structure dielectric elastomer artificial muscle fiber with electric drive and thermal response shape memory functions is obtained.

[0011] Preferably, the hydrothermal synthesis and wet chemical preparation process in step A includes:

[0012] Add 0.8g of titanium dioxide powder to 50mL of sodium hydroxide solution, stir magnetically at room temperature for 8 hours, and then place in a high-pressure reactor at 130℃ for 5 hours to react.

[0013] After the reaction, the mixture was washed with deionized water until neutral and dried at 40°C to obtain a nanotube mixture.

[0014] Barium hydroxide octahydrate was added to the nanotube mixture, and a low-temperature displacement reaction was carried out in a 50°C water bath.

[0015] After the reaction was completed, the powder was washed with anhydrous ethanol and deionized water and dried at 40°C for 12 hours to obtain BTO nanotube powder.

[0016] Preferably, the preparation of the TPU, DBA, and BTO polymer mixed solution in step B is as follows:

[0017] Add 10g of TPU particles to the THF solution and stir magnetically for 12 hours at room temperature until completely dissolved;

[0018] Slowly add DBA liquid molecules dropwise to the solution, with DBA content ranging from 1 wt% to 20 wt% based on the mass of TPU;

[0019] Simultaneously, 0.5 wt% of ultrasonically dispersed BTO nanotubes were added, and the mixture was ultrasonically dispersed and degassed under reduced pressure to obtain a uniform TPU, DBA, and BTO polymer mixture solution.

[0020] Preferably, the continuous solution impregnation core-wrapping method in step C includes:

[0021] Oriented CNT continuous fibers are fixed on a winding and traction device and passed through TPU, DBA, and BTO solutions at a constant linear speed, and excess solution is removed by a precision metering roller or spray.

[0022] The shell thickness is controlled by single or multiple immersion-intermittent drying cycles.

[0023] The core-spun fibers are heat-treated at 40-120℃ to promote interfacial bonding and solvent evaporation.

[0024] Preferably, the outer positive electrode is a PEDOT:PSS conductive liquid, which forms a continuous conductive layer on the surface of the core-shell fiber by spraying, dipping or in-situ polymerization.

[0025] PEDOT:PSS formulations include DMSO or surfactants to improve conductivity and wettability, and heat treatment at 80-140℃ to form a conductive layer and enhance conductivity.

[0026] Preferably, the post-processing steps after core-shell fiber forming also include the following:

[0027] The fibers are subjected to thermomechanical stretching to orient BTO nanotubes and polymer segments in the shell, with a pre-stretching rate preferably of 100-300%.

[0028] Electrode polarization or electric field polarization is performed under pre-stretched conditions to enhance dielectric polarization response. The polarization conditions are to apply a DC electric field of 10kV / mm-50kV / mm at 40-100℃ for 10-60 min. After completion, the device is cooled and the pre-stretched state is released to program the shape memory network.

[0029] Preferably, to improve the core-shell interface adhesion and the surface wettability of the CNT core wire, the CNT core wire is subjected to plasma treatment, oxidation treatment or polymer grafting treatment before continuous coating to introduce nucleophilic groups or interfacial binders; coupling agents or surface modifiers such as silane coupling agents or carboxyl functionalized molecules are added to the TPU solution to improve the compatibility and mechanical strength of the BTO, TPU and CNT three-phase interface.

[0030] Preferably, the BTO nanotubes in step A are further subjected to surface functionalization treatment to introduce carboxyl, amino, or organic coating layers. Surface functionalization is achieved by chemical grafting with alcohol solution or in-situ silanization, thereby improving the dispersibility of BTO in TPU and DBA matrices and reducing the tendency to aggregate.

[0031] Preferably, several core-shell structured fibers are twisted, plyed, woven, or braided into multi-strand composite yarns or fabric structures, and multi-channel independent driving units are formed on the composite structure by selective cluster electrode deposition or segmental polarization, thereby realizing fabric-level and modular multi-degree-of-freedom electro-temperature composite actuators.

[0032] Preferably, the quality control and performance adjustment of the preparation method include:

[0033] The dielectric constant, Young's modulus, and driving strain of the fiber are controlled by adjusting the DBA content, BTO nanotube loading, shell thickness, and pre-stretching rate. The fabrication process is monitored by online detection methods such as online impedance spectroscopy, optical measurement of core-shell thickness, and fiber DC conductivity measurement. This ensures that the final artificial muscle fiber can achieve reversible stretching, torsion, and bending multi-mode deformation under electric field drive and temperature response, making it suitable for flexible robot drive and smart wearable fields.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. This invention achieves improved dielectric constant and maintained flexibility by synergistically regulating the high dielectric shell system of BTO nanotubes and DBA. It solves the problems of high loss or mechanical embrittlement caused by the easy agglomeration of traditional fillers or poor compatibility between fillers and polymers, making it difficult to balance dielectric and flexibility. It improves the electro-displacement efficiency under low and medium pressure conditions, while retaining high elongation and flexibility, which is convenient for wearable and soft applications.

[0036] 2. This invention achieves efficient electric field loading, good electrode contact, and a flexible surface conductive layer by combining a core-shell core structure with an oriented CNT core and a PEDOT outer electrode in a layered electrode system. This solves the problems that thin film and bulk electrodes often have, such as limited flexibility, interface detachment between the conductive layer and the elastomer, high electrode contact impedance, and poor cycle stability. It ensures effective coupling of the electric field in the shell, reduces contact impedance, and improves cycle stability and electro-driven repeatability.

[0037] 3. This invention improves the dispersion and interfacial adhesion of BTO in the matrix through surface functionalization of BTO and interface modification strategies, solves the problems of uneven dielectric properties and stress concentration caused by nanofiller agglomeration, increases the dielectric constant while reducing loss, and improves mechanical strength and fatigue life.

[0038] 4. This invention achieves rapid response and reversible shape reprogramming of a single fiber through a dual electro-thermal stimulation reversible drive and modular fabric integration scheme. This solves the problem that a single stimulation method cannot simultaneously meet the requirements of short-term high response and long-term shape programming memory, thereby improving the applicability of the system and expanding the output force and motion complexity. Attached Figure Description

[0039] Figure 1 These are schematic diagrams illustrating the fabrication of dielectric elastomer artificial muscle fiber actuators with different DBA contents in Examples 1-3 of the present invention.

[0040] Figure 2 This is a comparison chart of the driving performance of time-displacement cycle curves with different DBA contents in Examples 1-3 of the present invention;

[0041] Figure 3 This is a schematic diagram of the temperature response shape memory function in Embodiment 3 of the present invention. Detailed Implementation

[0042] 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 some embodiments of the present invention, and not all embodiments. 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. Example

[0043] Please see Figure 1 , Figure 2 and Figure 3 A method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers involves the following steps: 0.8 g of titanium dioxide powder is magnetically stirred with 50 mL of high-concentration sodium hydroxide solution at room temperature for 8 hours, followed by heating in a 130°C autoclave for 5 hours. The mixture is then washed with deionized water until neutral and dried in a 40°C oven to obtain a nanotube mixture. Barium hydroxide octahydrate is added to the nanotube mixture, and the mixture is reacted at a low temperature in a 50°C water bath. After the reaction is complete, the mixture is washed with anhydrous ethanol and deionized water, and finally dried in a 40°C oven for 12 hours to obtain BTO nanotubes. 10 g of TPU particles are poured into a THF solution and magnetically stirred at room temperature for 12 hours until the particles are completely dissolved. Then, 5 wt% DBA liquid molecules and 0.5 wt% BTO nanotubes are slowly added dropwise to prepare a TPU / DBA / BTO solution. Oriented carbon nanotube continuous fibers were used as conductive negative electrodes. TPU / DBA / BTO solution was coated onto the surface of CNT fibers using a continuous solution impregnation core-coating method to form core-shell structured fibers. Finally, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) conductive liquid was sprayed onto the surface of the core-shell structured fibers as the outer positive electrode, thus preparing high-performance flexible high-dielectric polymer elastomer artificial muscle fiber T-5D-0.5B with electro-driven and thermally responsive shape memory functions. Example

[0044] Please see Figure 1 , Figure 2 and Figure 3A method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers involves the following steps: 0.8 g of titanium dioxide powder is magnetically stirred with 50 mL of high-concentration sodium hydroxide solution at room temperature for 8 hours, followed by heating in a 130°C autoclave for 5 hours. The mixture is then washed with deionized water until neutral and dried in a 40°C oven to obtain a nanotube mixture. Barium hydroxide octahydrate is added to the nanotube mixture, and the mixture is reacted at a low temperature in a 50°C water bath. After the reaction is complete, the mixture is washed with anhydrous ethanol and deionized water, and finally dried in a 40°C oven for 12 hours to obtain BTO nanotubes. 10 g of TPU particles are poured into a THF solution and magnetically stirred at room temperature for 12 hours until the particles are completely dissolved. Then, 10 wt% DBA liquid molecules and 0.5 wt% BTO nanotubes are slowly added dropwise to prepare a TPU / DBA / BTO solution. Oriented carbon nanotube continuous fibers were used as conductive negative electrodes. TPU / DBA / BTO solution was coated onto the surface of CNT fibers using a continuous solution impregnation core-coating method to form core-shell structured fibers. Finally, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) conductive liquid was sprayed onto the surface of the core-shell structured fibers as the outer positive electrode, thus preparing high-performance flexible high-dielectric polymer elastomer artificial muscle fiber T-10D-0.5B with electro-driven and thermally responsive shape memory functions. Example

[0045] Please see Figure 1 , Figure 2 and Figure 3 A method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers involves the following steps: 0.8 g of titanium dioxide powder is magnetically stirred with 50 mL of high-concentration sodium hydroxide solution at room temperature for 8 hours, followed by heating in a 130°C autoclave for 5 hours. The mixture is then washed with deionized water until neutral and dried in a 40°C oven to obtain a nanotube mixture. Barium hydroxide octahydrate is added to the nanotube mixture, and the mixture is reacted at a low temperature in a 50°C water bath. After the reaction is complete, the mixture is washed with anhydrous ethanol and deionized water, and finally dried in a 40°C oven for 12 hours to obtain BTO nanotubes. 10 g of TPU particles are poured into a THF solution and magnetically stirred at room temperature for 12 hours until the particles are completely dissolved. Then, 20 wt% DBA liquid molecules and 0.5 wt% BTO nanotubes are slowly added dropwise to prepare a TPU / DBA / BTO solution. Oriented carbon nanotube continuous fibers were used as conductive negative electrodes. TPU / DBA / BTO solution was coated onto the surface of CNT fibers by continuous solution impregnation core-coating method to form core-shell structured fibers. Finally, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) conductive liquid was sprayed onto the surface of the core-shell structured fibers as the outer positive electrode, and finally, high-performance flexible high-dielectric polymer elastomer artificial muscle fiber T-20D-0.5B with electro-driven and thermally responsive shape memory functions was prepared. Example

[0046] Please seeFigure 1 , Figure 2 and Figure 3 A method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers involves dispersing BTO nanotube powder obtained in Example 2 with anhydrous ethanol, sonicating for 10 min, adding APTES to the dispersion at 2wt%-5wt% of the BTO mass, stirring at room temperature for 30 min, and then reacting at 60°C for 2 h to allow silane grafting onto the BTO surface. After the reaction, the surface is washed three times alternately with ethanol and deionized water, and dried at 40°C for 12 h to obtain functionalized BTO (denoted as BTO-Si) with surface grafted amino and silane groups. 10 g of TPU particles are added to a THF solution, and 10 wt% DBA and the sonicated BTO-Si are slowly added to the TPU solution. 1.0 wt% was ultrasonically dispersed for 10-30 min and degassed under reduced pressure to obtain a uniform TPU / DBA / BTO-Si solution. Oriented CNT continuous fibers were used as the core, and coating was performed using a continuous solution impregnation core-shell method. After each impregnation, the core was rapidly pre-dried in a 60℃ hot air drying chamber, and this process was repeated three times to control the shell film thickness to approximately 5-20 μm. The core-shell fibers were placed in an aqueous phase mixture of EDOT monomer and surfactant, and an appropriate amount of FeCl3 was added for in-situ chemical polymerization, allowing PEDOT to polymerize in situ on the fiber surface to form a tightly bonded conductive layer. After polymerization, the fibers were washed with deionized water and ethanol and dried at 80℃ to obtain a core-shell fiber named T-10D-1.0BS. The obtained fiber was pre-stretched by 180%, and a DC polarization field of 30 kV / mm was applied at 80℃ and maintained for 30 min before cooling and setting. Example

[0047] Please see Figure 1 , Figure 2 and Figure 3 A method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers involves dissolving 10g of TPU in THF, adding 20wt% DBA and 0.2wt% BTO nanotubes to the solution, with the DBA content of 20wt% aimed at improving segment plasticity and the activity of the shape memory network; using the same continuous core-wrapping impregnation method, controlling the wet film thickness to achieve a dry film thickness of approximately 3-10μm to reduce rigidity and improve flexibility and deformability; each fiber is pre-stretched by 200% after drying and held under tension, then cross-linked and programmably cooled at 60℃; the outer layer is coated with PEDOT:PSS conductive liquid, and after spraying, treated at 100℃ for 10min to remove the solvent and form a conductive layer; in the pre-stretched state, a DC polarization field of 40kV / mm is applied at 90℃ for 20-40min, and after cooling, the pre-stretch is released and the shape memory properties are recorded. Example

[0048] Please see Figure 1 , Figure 2 andFigure 3 A method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers, using the formulation of Example 2 to prepare core-shell fibers in batches, with the diameter of a single fiber controlled in the range of 100μm-1mm, selected according to the application;

[0049] Twelve single fibers are twisted into multi-strand yarns at a given twist angle and twist length, or several twisted yarns are woven into unidirectional or bidirectional fabrics through warp knitting, weft knitting, and plain weave. Segmented drive units are achieved in different areas of the fabric by doping with different polarization directions or by local electrode patterning. Multiple independent positive electrodes are formed on the fabric surface using selective spraying and screen printing of PEDOT:PSS or vapor deposition and spraying of metal nanomaterials. CNT core fibers or bottom conductors form electrode pairs for each unit with the outer electrodes, enabling multi-channel PWM and DC control. The fabric sample is fabricated into bending, twisting, and elongation actuators and tested on an independent electronic control platform.

[0050] Cyclic electric drive test: Perform ≥10,000 cycles at a set voltage and frequency, and periodically record displacement and strain decay and current changes;

[0051] Thermal response cycling: Perform ≥1000 shape memory cycles under set heating conditions and monitor recovery rate and mechanical property retention rate;

[0052] Environmental stability: The electrode driving and shape memory performance were tested after being exposed to 35℃, 85%RH and -20℃ for 100h.

[0053] The performance of the artificial muscle fibers prepared in Examples 1-6 was tested as follows:

[0054] Instruments and Measurements:

[0055] SEM / TEM: Morphology of the nanotube-core-shell interface;

[0056] XRD / FTIR: Crystal phase and functionalization verification;

[0057] Broadband dielectric spectrum (1Hz-1MHz), reporting dielectric constant ε' and dielectric loss tanδ at 1kHz;

[0058] Tensile testing machine (standard clamping and speed): Young's modulus E, breaking strength αb, elongation at break εb;

[0059] Dielectric breakdown tester: Breakdown field strength (kV / mm);

[0060] Electro-driven (bending displacement) test platform: sample field 35mm, one end fixed, one end free, laser displacement sensor records displacement and response time; reference voltage 300V DC;

[0061] Thermomechanical analysis (TMA / DMTA): Shape memory cycle (heating rate 5℃ / min, programmed temperature example 80℃), record Rf, Rr;

[0062] Cyclic fatigue test bench: electrically driven for 10,000 cycles (1Hz) to record displacement decay;

[0063] PEDOT layer resistance (four probes) and electrode-fiber contact resistance (for Examples 4 and 6).

[0064] Sample replication: at least 3 samples for each test, report the mean ± standard deviation (n=3);

[0065] Electric drive test procedure: Power on and off at 300V DC, record the maximum static bending displacement and response time t90, and perform 10,000 cycles (1Hz) to monitor the displacement retention rate;

[0066] Shape memory test procedure: (1) Heat to the programmed temperature and apply load to the target strain εm; (2) After holding at high temperature, cool to below the transition temperature and unload and record εu; (3) Reheat and record εp; calculate Rf and Rr.

[0067] The test results are as follows:

[0068] 1. Shell dry film thickness (μm): Example 1: 8±0.6; Example 2: 12±0.9; Example 3: 10±0.7; Example 4: 5±20; Example 5: 3±10; Example 6: Single fiber homology;

[0069] 2. BTO content (wt%): Example 1: 0.5; Example 2: 0.5; Example 3: 0.5; Example 4: 1.0 (BTO-Si); Example 5: 0.2; Example 6: Same as reference fiber;

[0070] 3. ε': Example 1: 12.5±0.4; Example 2: 14.8±0.5; Example 3: 17.2±0.6; Example 4: 18.5±0.6; Example 5: 13.2±0.5; Example 6: ~14.8 (average of fabric);

[0071] 4. tanδ: Example 1: 0.035±0.002; Example 2: 0.038±0.002; Example 3: 0.045±0.003; Example 4: 0.032±0.002; Example 5: 0.052±0.003; Example 6: 0.04±0.003;

[0072] 5. E (MPa): Example 1: 28±1.2; Example 2: 22±1.0; Example 3: 15±0.8; Example 4: 24±1.1; Example 5: 10±0.6; Example 6: Depends on twisting and tension;

[0073] 6. αb (MPa): Example 1: 18±0.8; Example 2: 15±0.7; Example 3: 10.2±0.6; Example 4: 16.5±0.7; Example 5: 8.0±0.5; Example 6: N / A (structured);

[0074] 7. εb (%): Example 1: 420±18; Example 2: 520±22; Example 3: 700±30; Example 4: 560±25; Example 5: 800±35; Example 6: The fabric can achieve higher macro elongation;

[0075] 8. Dielectric breakdown strength (kV / mm): Example 1: 60±3; Example 2: 55±3; Example 3: 45±3; Example 4: 58±3; Example 5: 42±3; Example 6: Affected by fabric structure;

[0076] 9. Electroinduced bending displacement (mm): Example 1: 2.1±0.08; Example 2: 3.6±0.12; Example 3: 6.8±0.2; Example 4: 5.2±0.18; Example 5: 8.4±0.25; Example 6: End-to-end contraction 15.2±0.5;

[0077] 10. t90(s): Example 1: 0.95±0.05; Example 2: 0.7±0.04; Example 3: 0.45±0.03; Example 4: 0.55±0.04; Example 5: 0.35±0.03; Example 6: System response is affected by driving strategy;

[0078] 11. Displacement retention rate (%): Example 1: 92±2; Example 2: 95±1.5; Example 3: 97±1.0; Example 4: 96±1.0; Example 5: 90±1.8; Example 6: Fabric 92±2;

[0079] 12. Rf (%): Example 1: 96±1.0; Example 2: 94±1.2; Example 3: 91±1.5; Example 4: 95±1.0; Example 5: 93±1.3; Example 6: ~95%;

[0080] 13. Rr (%): Example 1: 98±0.5; Example 2: 96±0.8; Example 3: 94±1.0; Example 4: 97±0.6; Example 5: 92±1.0; Example 6: ~94-96%.

[0081] in conclusion:

[0082] The dielectric constant is determined by the DBA content, BTO morphology, and surface treatment. A higher dielectric constant corresponds to a larger electroinduced displacement under the same voltage. Example 4 achieves higher cycle stability while balancing dielectric constant and low loss. As the DBA content increases, the material modulus decreases and the elongation increases, enabling engineering choices for high displacement / low force and high force / medium displacement. APTES-functionalized BTO-Si and in-situ polymerized PEDOT conductive layer significantly reduce electrode contact resistance and dielectric loss, while improving cycle life. Through twisting, plying, and weaving, the driving capability of single fibers can be amplified and multi-channel, segmented driving can be achieved.

[0083] The core-shell structured electro-driven dielectric elastomer artificial muscle fiber prepared in this application exhibits the following characteristics: When a voltage is applied to the elastomer fiber, equal amounts of opposite charges accumulate on the upper and lower electrodes, establishing an electric field perpendicular to the film surface between the two electrodes. This causes the polar groups inside the elastomer to rearrange their orientation, increasing the charge density and enhancing the material's electrostatic response. Macroscopically, this manifests as overall dielectric polarization of the material, leading to thickness compression and in-plane expansion of the fiber actuator, resulting in macroscopic electroinduced bending, stretching, and coiling deformations. Furthermore, the stationary phase in the polymer network of the fiber actuator can remember a permanent shape, while its reversible phase can freeze and release a temporary shape, giving it temperature-responsive shape memory capabilities. This has broad application prospects in robotics, flexible actuators, and other fields.

[0084] Working principle: The shell of the core-shell fiber is a composite dielectric elastomer with a high dielectric constant. When a voltage is applied, the dipoles in the shell and the interface polarization enhance the overall dielectric constant. The electric field generates Maxwell stress inside the dielectric. This stress causes compression and tension coupling on the elastic shell, which in turn drives the fiber to undergo mechanical deformations such as bending, stretching, and torsion. The oriented CNT core, as the negative electrode, and the outer PEDOT:PSS positive electrode form a compact conductive system, ensuring effective electric field loading and reducing electrode contact loss.

[0085] TPU matrix features microphase separation and reversible phase transition between soft and hard segments. The addition of small molecules such as DBA can regulate the flexibility and shape memory transition temperature of polymer chain segments. Through thermomechanical programming, the system maintains a temporary state at low temperatures. When heated above the transition temperature, the polymer chain segments regain their mobility, release the stored internal stress, and achieve shape recovery. The dual stimulation of electricity and temperature can achieve a composite driving capability of electro-induced rapid response and thermal reprogramming.

[0086] BTO nanotubes with a large aspect ratio provide high dielectric constant and interfacial polarization sites. Functionalizing the BTO surface can significantly improve compatibility with TPU and DBA matrices, reduce agglomeration and dielectric loss. The core-shell structure optimizes electric field distribution, mechanical stress transmission and electrode contact through structured layering, taking into account both high dielectric response and flexible mechanical properties, and improving cycle stability and durability.

[0087] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers, characterized in that: The preparation method includes the following steps: Step A: Preparation of highly interfacially polarized BTO nanotubes by hydrothermal synthesis and wet chemical method; Step B: Prepare a mixed solution of TPU, DBA and BTO polymers using thermoplastic TPU as the matrix, DBA as a polar small molecule plasticizer and polarization aid, and BTO nanotubes as a high dielectric filler. Step C: Using the continuous solution impregnation core-coating method, CNT continuous fibers are used as conductive core filaments. The TPU, DBA, and BTO polymer mixed solution is continuously coated to form a core-shell structure fiber. A conductive polymer electrode layer is sprayed or deposited on the outer layer to form positive and negative electrodes. After drying, heat treatment, mechanical stretching and polarization treatment, a core-shell structure dielectric elastomer artificial muscle fiber with electric drive and thermal response shape memory function is obtained. The outer positive electrode is a PEDOT:PSS conductive liquid, which forms a continuous conductive layer on the surface of the core-shell fiber by spraying, dipping or in-situ polymerization. PEDOT: PSS formulations include DMSO or surfactants to improve conductivity and wettability, and heat treatment at 80-140℃ to form a conductive layer and enhance conductivity. In step A, the BTO nanotubes are further subjected to surface functionalization to introduce carboxyl, amino, or organic coating layers. Surface functionalization is achieved through alcohol solution chemical grafting or in-situ silanization.

2. The method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers according to claim 1, characterized in that: The hydrothermal synthesis and wet chemical preparation process in step A includes: Add 0.8g of titanium dioxide powder to 50mL of sodium hydroxide solution, stir magnetically at room temperature for 8 hours, and then place in a high-pressure reactor at 130℃ for 5 hours to react. After the reaction, the mixture was washed with deionized water until neutral and dried at 40°C to obtain a nanotube mixture. Barium hydroxide octahydrate was added to the nanotube mixture, and a low-temperature displacement reaction was carried out in a 50°C water bath. After the reaction was completed, the powder was washed with anhydrous ethanol and deionized water and dried at 40°C for 12 hours to obtain BTO nanotube powder.

3. The method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers according to claim 1, characterized in that: The preparation of the TPU, DBA, and BTO polymer mixed solution in step B is as follows: Add 10g of TPU particles to the THF solution and stir magnetically for 12 hours at room temperature until completely dissolved; Slowly add DBA liquid molecules dropwise to the solution, with DBA content ranging from 1 wt% to 20 wt% based on the mass of TPU; Simultaneously, 0.5 wt% of ultrasonically dispersed BTO nanotubes were added, and the mixture was ultrasonically dispersed and degassed under reduced pressure to obtain a uniform TPU, DBA, and BTO polymer mixture solution.

4. The method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers according to claim 1, characterized in that: The continuous solution impregnation core-wrapping method in step C includes: The oriented CNT continuous fibers are fixed on the winding and traction device and passed through TPU, DBA, and BTO solutions at a constant linear speed and then removed by a precision metering roller or spray to remove excess solution. The shell thickness is controlled by a single or multiple immersion-intermittent drying cycle. The core-spun fibers are heat-treated at 40-120℃ to promote interfacial bonding and solvent evaporation.

5. The method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers according to claim 1, characterized in that: The following post-processing steps are included after core-shell fiber forming: The fibers are subjected to thermomechanical stretching to orient BTO nanotubes and polymer segments in the shell, with a pre-stretching rate of 100-300%. Electrode polarization or electric field polarization is performed under pre-stretched conditions to enhance dielectric polarization response. The polarization conditions are to apply a DC electric field of 10kV / mm-50kV / mm at 40-100℃ for 10-60 min. After completion, the device is cooled and the pre-stretched state is released to program the shape memory network.

6. The method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers according to claim 1, characterized in that: To improve the core-shell interface adhesion and the surface wettability of CNT core wires, the CNT core wires are subjected to plasma treatment, oxidation treatment, or polymer grafting treatment before continuous coating to introduce nucleophilic groups or interfacial binders; coupling agents or surface modifiers are added to the TPU solution to improve the compatibility and mechanical strength of the BTO, TPU and CNT three-phase interface.

7. The method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers according to claim 1, characterized in that: Several core-shell structured fibers are twisted, plyed, woven, or braided into multi-strand composite yarns or fabric structures. Multi-channel independent driving units are formed on the composite structure by selective cluster electrode deposition or segmental polarization, realizing fabric-level and modular multi-degree-of-freedom electro-temperature composite actuators.

8. The method for preparing core-shell structured electrically driven dielectric elastomer artificial muscle fibers according to claim 1, characterized in that: The quality control and performance adjustment of the preparation method include: The dielectric constant, Young's modulus, and driving strain of the fiber are controlled by adjusting the DBA content, BTO nanotube loading, shell thickness, and pre-stretching rate. The preparation process is monitored by online detection to ensure that the final artificial muscle fiber can achieve reversible stretching, torsion, and bending multi-mode deformation under electric field driving and temperature response. It is suitable for flexible robot driving and smart wearable fields.

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