CN113802294A

CN113802294A - Preparation method of polymer fiber artificial muscle based on hydrophilic and hydrophobic driving

Info

Publication number: CN113802294A
Application number: CN202111161418.7A
Authority: CN
Inventors: 胡兴好; 赵凯; 程广贵; 丁建宁; 张忠强
Original assignee: Jiangsu University
Current assignee: Jiangsu University
Priority date: 2021-09-30
Filing date: 2021-09-30
Publication date: 2021-12-17

Abstract

The invention belongs to the technical field of material science, and particularly relates to a preparation method of an artificial muscle based on hydrophilic and hydrophobic driving polymer fibers. The invention provides a composite fiber, which comprises a carbon nanotube fiber and a polymer material which is coated on the surface of the carbon nanotube fiber and has hydrophilic and hydrophobic characteristics and can be volatilized by heating, then the composite fiber is twisted, and a certain load is applied, so that a spiral structure is formed. Finally, the shrinkage of the film is controlled in a water drop driving mode. Due to the poisson effect, the hydrophilic and hydrophobic driving polymer fiber artificial muscle can contract longitudinally when absorbing water to expand in volume. When the shrinkage peak value is reached, the moisture on the surface of the fabric is dried by using a blower, and the original length is recovered. The whole process achieves the purposes of water drop driving, large strain, environmental protection, no toxicity and the like.

Description

Preparation method of polymer fiber artificial muscle based on hydrophilic and hydrophobic driving

Technical Field

The invention belongs to the technical field of material science, and particularly relates to a novel solvent adsorption driven artificial muscle fiber, in particular to a preparation method and driving performance of a water-soluble polymer composite fiber artificial muscle.

Background

The artificial muscle is a novel bionic flexible driver, is similar to biological muscle, and has the characteristics of large contraction stress, high power density, high energy conversion efficiency and the like. In the last two decades, artificial muscles have also developed rapidly with the continued development of smart materials. The artificial muscle generates the motion forms of stretching, torsion, bending and the like when being subjected to external stimulation (such as voltage, fluid temperature, pH, pressure, light, moisture/solvent and the like), and has important application prospect in the fields of soft robots, artificial limbs, exoskeletons, temperature regulation fabrics and the like. Among the numerous driving methods, moisture/solvent adsorption-desorption driving has led to extensive research due to its advantages of low cost, no significant thermal effect, etc.

Smart materials currently available for use as artificial muscles include shape memory alloys, electroactive polymers, carbon nanotube fibers, nylon threads, polyethylene fibers, and the like. The carbon nanotube fiber is used as one of various macroscopic assemblies of the Carbon Nanotube (CNT), and inherits the characteristics of the carbon nanotube such as excellent electrical conductivity, thermal conductivity, high mechanical strength and the like. However, it is found that, under the stimulation of different humidity environments, the corresponding portion of a single carbon nanotube fiber expands or contracts to different degrees, i.e., the structure generates a tensile and compressive gradient, thereby causing the deformation of the single carbon nanotube fiber. However, the single carbon nanotube fiber has the disadvantages of small deformation amount and slow response speed, which leads us to further research. Researchers prepare the carbon nanotube yarn actuator by compounding poly (diallyldimethylamine) chloride ions (PDDA) and carbon nanotube fibers, so that the response speed of the carbon nanotube yarn actuator is improved, and the driving strain of the carbon nanotube yarn actuator is also greatly improved. However, if the prepared yarn is immersed in liquid water, the highly soluble PDDA may dissolve, causing its degradation. This is because the interaction between pure PDDA and non-oxidized carbon nanotubes is very weak. And the CNT/PDDA mixed yarn is soaked in water for a long time, and the performance is obviously reduced. To solve this series of problems, the present invention constructs a composite yarn artificial muscle by infiltrating CNT yarn with hygroscopic and more stable poly (sodium p-styrenesulfonate) (PSS). The invention adds poly (sodium p-styrenesulfonate) (PSS) into the carbon nano tube twisted yarn with high specific strength uniformly, and the prepared artificial muscle can provide larger stroke and reversible drive under the stimulation of different humidity environments.

The artificial muscle may be actuated by a variety of drive means. For example, the pneumatic artificial muscles are deformed by uneven volume expansion caused by embedding gas into a cavity, have the characteristics of quick driving, large contraction stroke, programmability and the like, but need a pressure pump and are inconvenient to carry and use. The main disadvantage of temperature driven artificial muscles is the need for a complex heating and cooling system. Light-driven artificial muscles have limited their use due to the relatively small contraction strain and slow response. Therefore, water and solvents are widely used in industry and daily life, compared to other stimulating media. The water/solvent adsorption can cause volume expansion of certain materials, such as graphene (-oxide) fibers, carbon nanotube fibers, and the like. Compared with organic solvents, water is cheap, convenient to supply, environment-friendly and nontoxic. The invention prepares a novel polymer composite fiber artificial muscle driven by water/solvent adsorption and shows excellent mechanical properties. The artificial muscle with the driving mode can show good application potential in future life bodies, such as self-healing of wounds, wearable exoskeleton muscles and the like. The artificial muscle driven by water may be driven by water in a living body. Water/solvent driven artificial muscles have therefore required further exploration to pursue greater breakthroughs.

In conclusion, the invention aims to improve the output strain, response rate, reversible driving and other performances of the current water/solvent driven artificial muscle. A method for preparing fiber artificial muscle by mixing humidity response material and carbon nano tube fiber is provided, and the method is applied to the fields of intelligent fabrics and intelligent robots. Specifically, a 5 wt% aqueous solution of PSS was prepared and stirred thoroughly with a magnetic stirrer at room temperature for one and a half hours. Then the prepared carbon nano tube fiber capable of spinning is fully and uniformly mixed with a polymer with humidity response by a dripping coating method or an immersion method, and then twisting is carried out to make the carbon nano tube fiber have a spiral structure; then, the driving principle, the mechanical property and the like of the fiber artificial muscle are further researched.

Disclosure of Invention

The invention mainly aims at the defects of the prior art, provides a preparation method of the polymer fiber artificial muscle based on hydrophilicity and hydrophobicity driving, and researches the driving performance.

The invention relates to a design method of polymer fiber artificial muscle based on hydrophilic and hydrophobic driving, which comprises the following contents and principles:

the invention provides a composite fiber, which comprises a carbon nanotube fiber and a polymer material which is coated on the surface of the carbon nanotube fiber and has hydrophilic and hydrophobic characteristics and can be volatilized by heating, then the composite fiber is twisted, and a certain load is applied, so that a spiral structure is formed. Finally, the shrinkage of the film is controlled in a water drop driving mode.

Secondly, the working principle of the hydrophilic and hydrophobic driving polymer fiber artificial muscle prepared by the invention is as follows: the poly (sodium p-styrenesulfonate) (PSS) is taken as a typical hydrophilic polyelectrolyte containing sulfonic acid groups, and has strong hygroscopicity, so that the composite yarn has excellent hydrophilic and hydrophobic regulation driving capability. After being compounded with the carbon nanotube fiber, a certain volume expansion and more permeability expansion occur with the change of humidity. In addition to the high moisture sensitivity and water collection capacity of the selected materials, the reversibly twisted yarns forming the helical structure and the large specific surface area provided by the nano-pores and channels provide a large number of sites for water absorption and diffusion. According to the characteristics, the mixed yarn absorbs certain water and generates volume expansion when sensing the water, and further converts the free energy of the whole system into mechanical energy. Due to the poisson effect, the hydrophilic and hydrophobic driving polymer fiber artificial muscle can contract longitudinally when absorbing water to expand in volume. When the shrinkage peak value is reached, the moisture on the surface of the fabric is dried by using a blower, and the original length is recovered. The whole process achieves the purposes of water drop driving, large strain, environmental protection, no toxicity and the like.

And thirdly, the driving performance mainly depends on factors such as torsional density, moment of inertia and applied stress of the composite yarn. In particular, the application of large torsional stresses has a large effect on the output strain. Here we compare the magnitude of the output strain under different twisting loads, as shown in the figure. Under a load of 1.06MPa, the maximum output strain can reach 54.8 percent.

And fourthly, the spinnable carbon nanotube array can be prepared by a Chemical Vapor Deposition (CVD) method in the prior art. First, methane is used as a carbon source, and ferrocene and thiophene vapor are respectively used as a catalyst and a growth promoter. Helium is used as carrier gas to introduce the gaseous raw materials into the reactor. The synthesis of carbon nanotubes is carried out at high temperatures (above 700 ℃). And the reaction is carried out in a hydrogen atmosphere. Thereby, a multi-wall carbon nano vertical tube array can be manufactured.

And fifthly, the carbon nanotube film can be continuously drawn out from the multi-wall carbon nanotube vertical array by a printed special die, and the two ends of the carbon nanotube film are fixed by double faced adhesive tapes, so that the length of the special die can be controlled at will. The width of the prepared carbon nano tube film is 6.3cm, and the number of preparation layers is 6-9. And then rolled into a cylindrical shape.

The preparation method for preparing the composite artificial muscle fiber provided by the invention specifically comprises the following steps:

the method comprises the following steps: a5 wt% aqueous solution of poly (sodium p-styrenesulfonate) (PSS) was prepared, and since poly (sodium p-styrenesulfonate) (PSS) was powdery, the aqueous solution was stirred in a magnetic stirrer at room temperature for 1.5 hours to dissolve it sufficiently and uniformly in water, and the PSS solution was successfully prepared.

Step two: soaking the prepared carbon nanotube film in a PSS aqueous solution, or uniformly dripping the PSS solution on the surface of the carbon nanotube film by using a liquid transfer gun to fully soak the carbon nanotube film so as to obtain the CNT/PSS composite fiber, then placing the CNT/PSS composite fiber which is well dipped and coated at room temperature for 40 minutes to completely air-dry the CNT/PSS composite fiber, and then fixing two ends of the CNT/PSS composite fiber by using a clip for later use.

Step three: and suspending the prepared CNT/PSS composite fiber on a twisting device for twisting, wherein one end of the CNT/PSS composite fiber is fixed with an output shaft of a motor, and the other end of the CNT/PSS composite fiber is suspended with a weight of 2g or 5g respectively for comparison experiments. Then, the Arduino is used for controlling a single chip microcomputer to enable a motor to twist the composite fibers at the speed of 200 rpm. In the twisting process, a process of dripping and twisting the composite fiber is adopted until a spiral structure is formed. Specifically, the prepared CNT/PSS composite fiber sample is dripped from the top to the bottom by using a dropper, or sprayed by using a spray. The suspended weight cannot rotate along with the motor, so that twisting is prevented from influencing the formation of the spiral structure. Wherein the twist of the weight can be avoided by using a twist tie.

The composite fiber artificial muscle prepared by the invention adopts the following steps to test the driving performance:

step four: and testing the prepared sample through an optical microscope to further obtain the diameter of the prepared sample.

Step five: and (3) dripping water on the composite fiber artificial muscle forming the spiral structure by using a liquid transfer gun to enable the composite fiber artificial muscle to be completely contracted, and then drying the composite fiber artificial muscle by using a blower to recover the original length. And further suspending different loads to perform stress-strain test. As shown in fig. 5.

Step six: and (4) testing time and displacement by using a displacement sensor and Labview software. And further obtaining a graph of the relationship between the strain and the time. As shown in fig. 6.

The invention has the advantages that:

the design method of the polymer fiber artificial muscle based on hydrophilic and hydrophobic driving is based on the fact that the carbon nanotube fibers are used as raw materials, the PSS solution is uniformly dripped on the surface layers of the carbon nanotube fibers, the surface is smooth, the nano-scale pores are contained, the defect that the interface of a double-layer composite structure of a traditional driver is weak in combination is overcome, and a structural foundation guarantee is provided for the driver to have sensitive responsiveness.

The design method of the carbon nanotube fiber composite yarn artificial muscle with large strain, quick response and humidity stimulation response and the performance test thereof provided by the invention are simple and convenient to operate, economic and environment-friendly, high in mechanical strength and high in stability, when 1.06MPa of stress is applied, the shrinkage strain can reach 54.8%, and the mixed yarn shows approximately linear response to the change of humidity. The method has great application prospect in the fields of humidity switches, intelligent fabrics, microfluid mixers and the like.

Drawings

FIGS. 1 and 2 are optical microscope images of droplet-driven artificial muscle of CNT/PSS composite fiber under different twisting loads; FIG. 1 twisting load was 2 g; the twisting load of fig. 2 was 5 g.

The dimensions indicated therein are the diameter of the fiber in μm.

FIG. 3 is a graph showing a comparison of shrinkage before and after dropping water, where Δ l is the magnitude of the shrinkage.

FIG. 4 is a schematic diagram of the operation of a droplet driven CNT/PSS fiber artificial muscle;

wherein 1 is the CNT/PSS fiber artificial muscle before contraction; 2 is a pipette; 3 is a blower; 4 is a clip fixed at both ends of the CNT/PSS fiber artificial muscle; 5 is the CNT/PSS fiber artificial muscle after contraction; and 6 is the suspended weight.

Fig. 5 is a graph showing the results of stress-strain testing of artificial muscles prepared by the method of the present invention.

FIG. 6 is a graph showing the results of a strain-time test on an artificial muscle prepared by the method of the present invention.

The invention aims to improve the output strain, response rate, reversible driving and other performances of the current moisture/solvent driven artificial muscle. Provides a method for preparing fiber artificial muscle by mixing hydrophilic and hydrophobic polymers and carbon nanotube fibers, and applies the method to the fields of intelligent fabrics and intelligent robots. Specifically, the carbon nanotube fiber capable of being spun is compounded with hydrophilic polyelectrolyte poly (sodium p-styrenesulfonate) (PSS) by an immersion method or a dropping coating method. The composite carbon nanotube fiber artificial muscle driven by the large strain water drop with quick response is prepared, and the driving principle and the mechanical property of the artificial muscle are further researched and tested.

Detailed Description

In view of the defects of the prior art, the invention provides a technical scheme through long-term research and a great deal of practice of the inventor. The technical solution, implementation process and driving principle are further explained below.

The method comprises the following steps: firstly, the patent provides a preparation method of CNT/PSS composite fiber artificial muscle driven by hydrophilic and hydrophobic water drops, and the preparation method has the advantages of simple and convenient operation, environmental protection and stronger stability. Here, we use a carbon nanotube film made by carbon nanotube vertical array spinning as a raw material, and pull the carbon nanotube film out of the carbon nanotube forest using a dedicated die. To ensure that the sample has a certain strength, we set the width of the carbon nanotube film to 6.3cm and the number of layers to 6-9. Then, the two ends of the carbon nanotube film are fixed by using double-sided adhesive tape, and then the carbon nanotube film is wound into a cylindrical shape so as to be twisted conveniently.

Step two: subsequently, a 5 wt% aqueous solution of poly (sodium p-styrenesulfonate) (PSS) was prepared, and since poly (sodium p-styrenesulfonate) (PSS) was powdery, the aqueous solution was stirred in a magnetic stirrer at room temperature for 1.5 hours to be sufficiently and uniformly dissolved in water. The PSS solution was successfully prepared.

Step three: and soaking the prepared carbon nanotube film sample subjected to a series of treatments in the prepared PSS solution. Or the PSS solution is fully and uniformly dripped on the surface of the carbon nano tube film by using a liquid transfer gun and a dripping method. The purpose is to sufficiently complex the carbon nanotubes with the material PSS convertible by humidity change and then control the shrinkage thereof by controlling the humidity change.

The working principle of the invention patent is as follows: poly (sodium p-styrene sulfonate) (PSS) as a typical hydrophilic polyelectrolyte contains sulfonic acid groups, and the composite yarn has excellent hydraulic driving capability due to strong hygroscopicity. After being compounded with the carbon nanotube film, a certain volume expansion and more permeability expansion occur with the change of humidity. In addition to the high moisture sensitivity and water collection capacity of the selected materials, the reversibly twisted yarns forming the helical structure and the large specific surface area provided by the nano-pores and channels provide a large number of sites for water absorption and diffusion. When water drops are dripped on the CNT/PSS composite fiber yarns forming the spiral structure, certain shrinkage is generated, and then the yarns are dried by a blower, so that the original length of the yarns can be quickly recovered, and the purposes of large strain and quick response are achieved.

The spinnable carbon nanotube array may be prepared by a conventional Chemical Vapor Deposition (CVD) method. First, methane is used as a carbon source, and ferrocene and thiophene vapor are respectively used as a catalyst and a growth promoter. The synthesis of carbon nanotube is carried out at high temperature (above 700 deg.C). And the reaction is carried out in a hydrogen atmosphere. Thereby obtaining the multi-wall carbon nano-tube array.

Step four: the carbon nanotube fiber on which the PSS is sufficiently and uniformly applied by drops is left to dry at room temperature for 40 minutes, and after the carbon nanotube fiber is completely dried, both ends of the carbon nanotube fiber are fixed by a clip. Then the sample is hung on a twisting device, wherein one end of the sample is fixed with an output shaft of a motor, and weights of 2g and 5g are respectively hung at the other end of the sample for comparison experiment. Then, the Arduino is used for controlling a single chip microcomputer to enable a motor to twist the composite fibers at the speed of 200 rpm. In the twisting process, a process of dripping water and twisting is adopted until a spiral structure is formed. The suspended weight cannot rotate along with the motor, so that twisting is prevented from influencing the formation of the spiral structure. Wherein the twist of the weight can be avoided by using a twist tie.

Step five: the prepared sample is placed on an optical microscope to observe the microstructure, as shown in the attached figures 1 and 2, and the diameters of different samples can be measured through the optical microscope. And the size of the load can be indirectly calculated through the diameter and the hung weight. Here, we will utilize the iron stand platform to build test platform, hang the artificial muscle of composite fiber who prepares on the iron stand platform, and one end is fixed, and the other end hangs the weight of different heavy objects respectively, and wherein usable bundle brings the rotation of control weight and then avoids this artificial muscle who forms helical structure to move back to twist with fingers. Then, the shrinkage of the sample was observed by dropping a drop of water, and as shown in FIG. 3, the sample was shrunk to some extent under the condition that a weight of 1g was suspended, where Δ l is the magnitude of the shrinkage and 40% -50% of strain was clearly seen with the naked eye.

Step six: according to the driving principle schematic diagram shown in fig. 4, a corresponding test platform can be built for testing. In order to test a strain-stress image in more detail, the specific scheme is that two ends of a sample are tied to two clip needles respectively, then one clip needle is fixed, the other clip needle is hung with different weights respectively, and then loads are calculated correspondingly. Further, a certain amount of water drops are uniformly dropped on the sample by using a pipette gun, and after the sample is completely contracted, the size of the contraction amount is measured by using a vernier caliper. And calculating the magnitude of the strain by using a strain calculation formula. The measured results are shown in fig. 5, and it can be clearly seen that the heavier the weight is hung during twisting, the larger the total strain is obtained. We have used a 5g twist weight and the maximum shrinkage strain can have reached 54.8% at a load of 1.06 MPa. Thereby realizing breakthrough of large strain.

Step seven: besides the strain-stress relationship image, we also need to test the response time-strain relationship. Firstly, a platform is well built, and a displacement sensor with relatively high precision is used for testing the time-displacement relation by combining Labview software. The schematic diagram of the testing principle is shown in the attached figure 4, and the specific steps are that a sample is fixed at two ends of a clip, connected and hung on a fixed pulley through a thin 0.1mm nylon wire, and then a certain weight is tied at the other end of the nylon wire and aligned with a displacement sensor. Before the test is started, a displacement sensor is firstly switched on, then a Labview control switch is utilized, and after an image curve is stabilized, a liquid transfer gun or spray is used for enabling a sample to be in a wet state. Then, the sample can be gradually shrunk along with the increase of the humidity, after the sample is completely shrunk, the sample is aligned to the sample by using a blower, the sample is dried by blowing, and the sample can recover the corresponding original length after being dried by blowing. The tested result is shown in fig. 6, and we can find that the artificial muscle can reach the optimal contraction state within one minute and more, and can rapidly recover the original length within one minute after complete contraction, thereby achieving the purpose of quick response.

The invention aims to provide a preparation method of the artificial muscle fiber, which is simple and convenient to operate, high in stability, green and environment-friendly, and provides a novel driving method. Compared with traditional pneumatic, electric heating, electrochemical and other driving modes, the humidity stimulation response driving has inherent advantages, and a water drop driving mode is adopted. Because it is inexpensive, convenient to supply, environmentally friendly and non-toxic, it can provide a large stroke and reversible actuation. The invention can show a certain application prospect in the fields of humidity switches, intelligent fabrics, soft robots and the like.

Claims

1. A preparation method of polymer fiber artificial muscle based on hydrophilic and hydrophobic driving is characterized by comprising the following specific steps:

the method comprises the following steps: preparing an aqueous solution of poly (sodium p-styrenesulfonate) (PSS);

step two: soaking the prepared carbon nanotube film in a PSS aqueous solution, or uniformly dripping the PSS solution on the surface of the carbon nanotube film by using a liquid transfer gun to fully soak the carbon nanotube film so as to obtain the CNT/PSS composite fiber, then placing the CNT/PSS composite fiber which is well dipped at room temperature to completely air-dry the CNT/PSS composite fiber, and then fixing two ends of the CNT/PSS composite fiber for later use;

step three: suspending the prepared CNT/PSS composite fiber on a twisting device for twisting, wherein one end of the CNT/PSS composite fiber is fixed with an output shaft of a motor, and the other end of the CNT/PSS composite fiber is suspended with a weight for carrying out a comparison experiment; then, the Arduino is used for controlling the single chip microcomputer to enable the motor to twist the composite fibers, and the process of dripping and twisting the composite fibers is adopted in the twisting process until a spiral structure is formed; the suspended weight cannot rotate along with the motor, so that twisting is prevented from influencing the formation of the spiral structure.

2. The method for preparing artificial muscle based on hydrophilic and hydrophobic driving polymer fibers according to claim 1, wherein in the first step, the concentration of the aqueous solution of poly (sodium p-styrenesulfonate) (PSS) is 5 wt%.

3. The method for preparing the artificial muscle based on the hydrophilic and hydrophobic driving polymer fibers as claimed in claim 1, wherein in the second step, the CNT/PSS composite fibers are placed at room temperature for 40min, and the two ends of the CNT/PSS composite fibers are fixed by a clip for standby.

4. The preparation method of the hydrophilic and hydrophobic driving polymer fiber based artificial muscle according to the claim 1, wherein in the third step, the weight of the suspended weight is 2g or 5g, and the rotation speed of the motor is 200 rpm; the process of dripping and twisting the composite fiber comprises the following steps: the prepared CNT/PSS composite fiber sample is dripped from the top to the bottom by a dropper, or sprayed by a spray.