Preparation method of carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristic

Abstract

The invention provides a preparation method of high-response-characteristic high-thermal-conductivity particle / liquid crystal elastomer bionic muscle fibers, and belongs to the technical field of functional materials. According to the method, the surface of the liquid crystal elastomer preform is coated with the high-thermal-conductivity particles, the heat conduction capability of the high-thermal-conductivity particles is utilized, so that the heated part of the liquid crystal elastomer preform can be uniformly stretched when the liquid crystal elastomer preform is drawn by adopting a hot drawing forming method, and the liquid crystal elastomer preform is partially or completely immersed in the suspension during soaking, so that the liquid crystal elastomer preform is completely immersed in the suspension; and the bionic muscle fiber subjected to hot drawing molding shows a differential hot bending characteristic. The method can realize continuous processing and is suitable for large-scale production. The prepared bionic muscle fiber keeps the characteristic of high indirect thermal stimulation response, and has important application value in the fields of medical devices, motion assistance, bionic materials and the like in the aspects of controlling elbow parts with loads, clamping devices and the like as a flexible driver.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and in particular relates to a carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristics, a preparation method and a solution for improving the performance of a flexible actuator. Background Art

[0002] Artificial muscles are key components of flexible actuators in the next generation of soft robots. They can imitate the complex movements of the human body. Compared with traditional rigid actuators, they have superior flexibility, operational safety, and environmental adaptability.

[0003] Liquid crystal elastomer is a kind of high molecular polymer formed by appropriate cross-linking of liquid crystal polymers. It has the orderliness and fluidity of liquid crystals and the soft elasticity of elastomers. It can show obvious reversible deformation (such as stretching, rotation, bending) under external stimuli (such as heat, light, electricity, pH value), and is considered to be one of the most promising artificial muscle materials. In particular, indirect thermal stimulation can convert external energy such as light and electricity into thermal energy, and achieve remote and non-contact precise driving in selected areas through local thermal response, so that liquid crystal elastomers can complete complex movement patterns. However, there are key problems in the indirect thermal stimulation driving pure liquid crystal elastomers, such as low heat diffusion and heat dissipation efficiency, which seriously limit the response time and movement bandwidth of flexible actuators.

[0004] Light-driven core-shell fiber actuator based on carbon nanotubes / liquid crystal elastomer for artificial muscle and phototropic locomotion.[J]Carbon 187 (2022)97~107. A light-driven core-shell fiber artificial muscle and photoactuator based on carbon nanotubes / liquid crystal elastomer is disclosed, which is a CNTs@LCE fiber structure composed of a liquid crystal elastomer (LCE) fiber and a carbon nanotube (CNTs) shell wrapped on the outside, which can act as an artificial muscle. The preparation method adopted in the article is to first prepare an oriented liquid crystal elastomer fiber, and then immerse the oriented liquid crystal elastomer fiber in a CNTs / CH2Cl2 dispersion (0.5 mg / mL) for ultrasonic treatment, and evaporate the CH2Cl2 solvent in a vacuum at room temperature to obtain a CNTs@LCE fiber structure.

[0005] Since this method first prepares liquid crystal elastomer fibers and then immerses them in ultrasonic compounding, it is difficult to use them for large-scale production due to the limitation of the ultrasonic immersion container. In addition, this method cannot selectively compound one side of the fiber, and cannot prepare various muscle fibers with different stretching direction restrictions. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a method for preparing carbon nanomaterial / liquid crystal elastomer bionic muscle fibers with high response characteristics, and the specific steps of the method are: Step 1: immersing one side or the entire liquid crystal elastomer preform in a carbon nanomaterial / dichloromethane suspension, and ultrasonically treating for 1 to 2 hours; the concentration of the carbon nanomaterial / dichloromethane suspension is 5 to 15 mg / mL; the carbon nanomaterial is selected from one of graphene and carbon nanotubes, preferably multilayer graphene; Step 2: placing the liquid crystal elastomer preform rod treated in step 1 in a vacuum drying oven and vacuum drying at 25° C. for 2 to 4 hours to evaporate the dichloromethane; Step 3: Hang a 20g weight at the bottom of the liquid crystal elastomer preform rod processed in step 2, place it in the center of a heating furnace, and heat it to a deformed state; the temperature of the heating furnace is determined according to the rheological properties of the liquid crystal elastomer preform rod; Step 4: The bottom of the liquid crystal elastomer preform rod forms a necking area under the action of the load, and is slowly pulled to form a fiber; Step 5: Turn on the stepper motor at the upper end of the heating furnace to continuously feed the preform into the heating zone, clamp the fiber on a pair of constant speed rollers under the heating furnace, and draw the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristics; Furthermore, the method also includes step 6: twisting the carbon nanomaterial / liquid crystal elastomer bionic muscle fibers drawn in step 5 into bundles to produce higher mechanical properties.

[0007] Since the shape of the final carbon nanomaterial / liquid crystal elastomer bionic muscle fiber is the same as that of the preform, the shape of the liquid crystal elastomer preform in step 1 can be selected according to the shape of the final carbon nanomaterial / liquid crystal elastomer bionic muscle fiber, preferably a cylinder or a cuboid.

[0008] The duration of the ultrasonic treatment in step 1 is proportional to the thickness of the carbon nanomaterial coated on the surface of the liquid crystal elastomer preform rod, until a stable saturation thickness is reached.

[0009] The heating temperature of the heating furnace in step 3 is preferably 300-350°C.

[0010] The diameter of the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber in step 5 is related to the preform diameter, the preform feeding speed and the constant speed roller drawing speed, which is obtained by the following relationship.

[0011] In the formula, Diameter / width of carbon nanomaterial / liquid crystal elastomer bionic muscle fiber (mm), is the diameter / width of the liquid crystal elastomer preform rod (mm), Preform feeding speed (mm / min), is the constant speed roller drawing speed (mm / min).

[0012] Beneficial effects of the present invention: 1. The present invention prepares a carbon nano / liquid crystal elastomer bionic muscle fiber with excellent response characteristics very similar to skeletal muscle fibers. Its significant advantage is that the bionic muscle fiber can fully combine the thermal conductivity of carbon nanomaterials with the thermal contraction characteristics of liquid crystal elastomers, and has important application value in realizing rapid thermal response and thermal movement as an artificial muscle fiber with bionic characteristics, and as a flexible actuator to control loaded elbows and clamps.

[0013] 2. The present invention first coats the carbon nanomaterial on the surface of the liquid crystal elastomer preform rod, and utilizes the high thermal conductivity of the carbon nanomaterial to evenly distribute the heat of the carbon nano / liquid crystal elastomer preform rod when heated, so that when the carbon nano / liquid crystal elastomer preform rod is drawn by the hot drawing method, it can be ensured that the stretched carbon nano / liquid crystal elastomer bionic muscle fiber has the same shape as the preform rod without change.

[0014] 3. The method of the present invention can make the bionic muscle fibers after heat drawing show differential thermal bending characteristics by partially or completely immersing the liquid crystal elastomer preform rod in the suspension during immersion. The carbon nanomaterial adsorbed on the surface of the liquid crystal elastomer preform rod can significantly improve the response characteristics of the liquid crystal elastomer under indirect thermal stimulation, achieving a response time of ≤0.5 seconds and a motion bandwidth of ≥0.2 Hz.

[0015] 4. As the preferred graphene of the present invention, graphene also has excellent mechanical properties, so that the load / self-weight of the bionic muscle fiber prepared by the method of the present invention is ≥3000 times, and the cycle life is ≥500 times.

[0016] 5. The preparation process of carbon nano / liquid crystal elastomer bionic muscle fibers does not require secondary complex processing such as surface modification. It can be formed by hot drawing in one time, with a short preparation cycle and simple steps. It can realize continuous processing and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the steps of the method of the present invention.

[0018] Figure 2 This is a real picture of the graphene / liquid crystal elastomer bionic muscle fiber in Example 1.

[0019] Figure 3 Schematic diagram of thermal bending of graphene / liquid crystal elastomer bionic muscle fibers in Example 1.

[0020] Figure 4 This is a real picture of the thermal bending of graphene / liquid crystal elastomer bionic muscle fibers in Example 1.

[0021] Figure 5 Schematic diagram of the thermal movement of graphene / liquid crystal elastomer bionic muscle fibers in Example 1.

[0022] Figure 6 This is a real picture of the graphene / liquid crystal elastomer bionic muscle fiber in Example 2.

[0023] Figure 7 Schematic diagram of graphene / liquid crystal elastomer bionic muscle fibers used as flexible actuators to control loaded elbow motion in Example 2. DETAILED DESCRIPTION

[0024] The technical solution adopted by the present invention is further explained and illustrated in the form of specific embodiments below.

[0025] Example 1 (bending and moving toward heat) First, immerse all the cylindrical liquid crystal elastomer preform rods with a diameter of 20 mm in a multilayer graphene / dichloromethane suspension, ultrasonically treat for 1.5 hours, and then put the treated liquid crystal elastomer preform rods into a vacuum drying oven and vacuum dry them at 25°C for 3 hours. Next, hang a 20g weight at the bottom of the liquid crystal elastomer preform rod, place it in the center of the heating furnace, select a heating temperature of 310°C, heat it until the preform rod is deformed, and then slowly pull it to form a fiber. At the same time, turn on the stepper motor at the upper end of the heating furnace, set the feed speed of the preform rod into the heating zone to 0.5 mm / min, and clamp the fiber on the fixed speed roller. The wire drawing speed of the fixed speed roller is set to 200 mm / min, and a cylindrical graphene / liquid crystal elastomer bionic muscle fiber with a diameter of 1 mm with high response characteristics is obtained.

[0026] like Figure 2 The figure shows the actual image of the high-response graphene / liquid crystal elastomer bionic muscle fiber prepared in this embodiment. Figure 3 is a schematic diagram of thermal bending, Figure 4 This is a real picture of thermal bending. Figure 5 Schematic diagram of thermotropic movement. Under the condition of heat source heating, the graphene / liquid crystal elastomer bionic muscle fiber responds thermally within 0.5 seconds. Under the condition of alternating heat source heating, the movement bandwidth is 0.25 Hz. Compared with pure liquid crystal elastomer fibers under the same heating conditions, the response time is shortened by 2 / 3 and the movement bandwidth is increased by 3 times. It can be seen that through remote and non-contact indirect thermal stimulation in the selected area, the rapid thermal response and thermotropic movement of graphene / liquid crystal elastomer muscle fibers with bionic characteristics are achieved.

[0027] Example 2 (Controlling Loaded Elbow Movement) First, immerse a 20 mm wide cube-shaped liquid crystal elastomer preform in a multilayer graphene / dichloromethane suspension, with the immersion area being 10 mm high on one side of the preform, and ultrasonically treat for 1 hour, then place the treated liquid crystal elastomer preform in a vacuum drying oven and vacuum dry at 25°C for 2 hours. Next, hang a 20g weight at the bottom of the liquid crystal elastomer preform, place it in the center of the heating furnace, select a heating temperature of 330°C, heat it to a semi-molten state, and slowly pull it to form a fiber. At the same time, turn on the stepper motor at the upper end of the heating furnace, set the feed speed of the preform into the heating zone to 1 mm / min, and clamp the fiber on a fixed-speed roller, and set the fixed-speed roller drawing speed to 100 mm / min to obtain a 2 mm wide cube-shaped graphene / liquid crystal elastomer bionic muscle fiber with high response characteristics.

[0028] like Figure 6 The figure shows the actual image of the high-response graphene / liquid crystal elastomer bionic muscle fiber prepared in this embodiment. Figure 7 Schematic diagram of the flexible actuator controlling the elbow motion with load. Under the condition of heat source heating, the graphene / liquid crystal elastomer bionic muscle fiber responded thermally within 0.5 seconds, lifted a load of 3200 times its own weight, and did not break after 500 cycles. It can be seen that through remote and non-contact indirect thermal stimulation in the selected area, the graphene / liquid crystal elastomer muscle fiber was realized as a flexible actuator to control the elbow motion with load.

Claims

1. A method for preparing a carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristics, characterized in that: The specific steps of this method are: Step 1: immersing one side or the entire liquid crystal elastomer preform in a carbon nanomaterial / dichloromethane suspension, and ultrasonically treating for 1 to 2 hours; the concentration of the carbon nanomaterial / dichloromethane suspension is 5 to 15 mg / mL; the carbon nanomaterial is selected from one of graphene and carbon nanotubes, preferably multilayer graphene; Step 2: placing the liquid crystal elastomer preform rod treated in step 1 in a vacuum drying oven and vacuum drying at 25° C. for 2 to 4 hours to evaporate the dichloromethane; Step 3: Hang a 20g weight at the bottom of the liquid crystal elastomer preform rod processed in step 2, place it in the center of a heating furnace, and heat it to a deformed state; the temperature of the heating furnace is determined according to the rheological properties of the liquid crystal elastomer preform rod; Step 4: The bottom of the liquid crystal elastomer preform rod forms a necking area under the action of the load, and is slowly pulled to form a fiber; Step 5: Turn on the stepper motor at the upper end of the heating furnace to continuously feed the preform rod into the heating zone, clamp the fiber on a pair of constant speed rollers under the heating furnace, and draw carbon nanomaterial / liquid crystal elastomer bionic muscle fibers with high response characteristics.

2. The method for preparing the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristics according to claim 1, characterized in that: The method also includes step 6: twisting the carbon nanomaterial / liquid crystal elastomer bionic muscle fibers drawn in step 5 into bundles to produce higher mechanical properties.

3. The method for preparing the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristics according to claim 1, characterized in that: The shape of the liquid crystal elastomer preform in step 1 is selected according to the shape of the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber finally obtained.

4. The method for preparing the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristics according to claim 1, characterized in that: The shape of the liquid crystal elastomer preform is a cylinder or a cuboid.

5. The method for preparing the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristics according to claim 1, characterized in that: In the step 1, the thickness of the carbon nanomaterial coated on the surface of the liquid crystal elastomer preform is controlled by the duration of ultrasonic treatment.

6. The method for preparing the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristics according to claim 1, characterized in that: The heating temperature of the heating furnace in step 3 is 300-350°C.

7. The method for preparing the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber with high response characteristics according to claim 1, characterized in that: The diameter of the carbon nanomaterial / liquid crystal elastomer bionic muscle fiber in step 5 is related to the preform diameter, the preform feeding speed and the constant speed roller drawing speed, which is obtained by the following relationship:

8. In the formula, Diameter / width of carbon nanomaterial / liquid crystal elastomer bionic muscle fiber (mm), is the diameter / width of the liquid crystal elastomer preform rod (mm), is the preform feeding speed (mm / min), is the constant speed roller drawing speed (mm / min).

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