TWI485897B - Electrostrictive material and method for making the same and electrothermic type actuator - Google Patents

Description

Electrostrictive material, preparation method thereof and electrothermal actuator

The invention relates to an electrothermal actuator, and to an electrostrictive material and a preparation method thereof.

The working principle of the actuator is to convert other energy into mechanical energy. There are three ways to achieve this conversion: the electrostatic field is converted into electrostatic force, that is, electrostatic drive; the electromagnetic field is converted into magnetic force, that is, magnetic drive; The thermal expansion or other thermal properties enable energy conversion, ie thermal drive.

An electrostatically driven actuator generally comprises two electrodes and an electrostrictive element disposed between the two electrodes, the working process of which is to inject a charge on each of the two electrodes, using mutual attraction and repulsion between the charges, by controlling the charge The quantity and electronegativity are used to control the relative motion of the electrostrictive elements between the electrodes. However, since the electrostatic force is inversely proportional to the square of the distance between the capacitive plates, the electrostatic force is generally significant only when the electrode spacing is small, and the requirements of the distance make the structural design of the actuator more complicated. A magnetically driven actuator generally comprises two magnetic poles and an electrostrictive element disposed between the two magnetic poles, the function of which is to cause relative movement of the electrostrictive elements between the two magnetic poles by mutual attraction and repulsion of the magnetic fields. However, the disadvantage of the magnetic drive is the same as that of the electrostatic drive, that is, due to the limited range of the magnetic field, the upper and lower surfaces of the electrostrictive element must be kept at a small distance. The design of the structure is strict and the actuator is also limited. Application range.

The use of thermally driven actuators overcomes the shortcomings of the above electrostatic drive and magnetic drive actuators, The actuator structure can produce a corresponding deformation as long as it can ensure a certain amount of thermal energy, and the thermal driving force is large with respect to the electrostatic force and the magnetic field force. The prior art discloses an electrothermal actuator, see "Progress in Micro-Electrothermal Actuators Based on Thermal Expansion Effect", Yan Yining et al., Electronic Devices, vol 22, p162 (1999). The electrothermal actuator adopts two pieces of metal with different thermal expansion coefficients to form a two-layer structure as an electrostrictive element. When the current is heated, since the amount of thermal expansion of one piece of metal is larger than the other piece, the bimetal piece will have a small amount of thermal expansion. One side is bent. However, since the above electrostrictive material adopts a metal structure, its flexibility is poor, resulting in a slow thermal response of the entire electrothermal actuator.

In view of the above, it is necessary to provide a flexible electrostrictive material and a method for preparing the same, and an electrothermal actuator having a fast heat response speed.

An electrostrictive material comprising a first material layer and a second material layer, wherein the first material layer and the second material layer are stacked and have different thermal expansion coefficients, wherein the first material layer comprises a first a polymer matrix and a plurality of carbon nanotubes uniformly dispersed in the first polymer matrix, the second material layer comprising a second polymer matrix.

A method for preparing an electrostrictive material, comprising the steps of: providing a plurality of carbon nanotubes and a first polymer monomer solution; mixing the plurality of carbon nanotubes and the first polymer monomer solution to form a mixture a solution; polymerizing the mixed solution to form a first material layer; and forming a second material layer on a surface of the first material layer.

An electrothermal actuator comprising a first material layer, a second material layer and at least two electrodes, the first material layer and the second material layer being stacked and having different coefficients of thermal expansion, the at least two electrodes being spaced apart And electrically connected to the first material layer, wherein the first material layer comprises a first polymer matrix and a plurality of carbon nanotubes dispersed in the first polymer matrix, the second material layer comprises a second polymer matrix.

Compared to the prior art, the electrothermal actuator, the electrostrictive material and the method of preparing the same have the following advantages: since the electrostrictive material in the electrothermal actuator comprises a dispersed carbon nanotube, The carbon nanotube has the properties of low heat capacity, thermal conductivity and electrical conductivity, so that the electrothermal actuator has correspondingly high electrical and thermal conductivity, and the thermal response rate is faster; due to the first material layer and the second material layer The material layers all adopt a polymer matrix, so the electrostrictive material has a certain flexibility, and the preparation method of the electrostrictive material is simple.

10‧‧‧Electrical actuator

12‧‧‧First material layer

122‧‧‧First polymer matrix

124‧‧‧Nanocarbon tube

14‧‧‧Second material layer

16‧‧‧Electrode

1 is a schematic cross-sectional view showing an electrothermal actuator according to an embodiment of the present invention.

Fig. 2 is a comparison diagram of the telescopic characteristics of the electrothermal actuator of the embodiment of the present invention.

3 is a flow chart showing a method of preparing an electrostrictive material according to an embodiment of the present invention.

Hereinafter, an electrothermal actuator and a method of manufacturing the same according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a first embodiment of the present invention provides an electrothermal actuator 10 comprising an electrostrictive material (not shown) and at least two electrodes 16. The electrostrictive material includes a first material layer 12 and a second material layer 14, and the first material layer 12 and the second material layer 14 are stacked and bonded to each other. The surface area and thickness of the first material layer 12 and the second material layer 14 are substantially the same, and the thicknesses of the first material layer 12 and the second material layer 14 can be selected according to actual needs. The first material layer 12 and the second material layer 14 have different coefficients of thermal expansion.

The first material layer 12 is a conductive material layer, and the first material layer 12 includes a first polymer matrix 122 and a plurality of carbon nanotubes 124 uniformly dispersed in the first polymer matrix 122. The tubes 124 overlap each other in the first polymer matrix 122 to form a plurality of conductive networks.

The plurality of carbon nanotubes 124 in the first material layer 12 are arranged in disorder, and the adjacent or adjacent plurality of carbon nanotubes 124 are partially in contact with each other to form a staggered cross-section conductive heat conduction channel. The carbon nanotube The mass percentage of 124 in the first material layer 12 is 10% or less. Preferably, the mass percentage of the carbon nanotubes 124 in the first material layer 12 is 0.5% to 2%. If the content of the carbon nanotubes 124 is too small, it does not constitute a conductive path and the thermal conductivity is not good. If too much, the hardness of the first material layer 12 is increased to deteriorate the flexibility and thermal expansion properties. The carbon nanotubes 124 can be one of a single-walled carbon nanotube, a double-walled carbon nanotube, and a multi-walled carbon nanotube, or any combination thereof. The diameter of the single-walled carbon nanotube is 0.5 nm to 50. Nano, double-walled carbon nanotubes have a diameter of 1.0 nm to 50 nm, and multi-walled carbon nanotubes have a diameter of 1.5 nm to 50 nm. The length of the carbon nanotubes 124 is 0.5 μm to 10 Micron.

The material of the first polymer matrix 122 in the first material layer 12 is a flexible material, including ruthenium rubber, polymethyl methacrylate, polyurethane, epoxy resin, polyethyl acrylate, polybutyl acrylate, A combination of one or more of polystyrene, polybutadiene, polyacrylonitrile, polyaniline, polypyrrole, and polythiophene. The content of the first polymer matrix 122 in the first material layer 12 is 92% to 99.9%.

In this embodiment, the material of the first polymer matrix 122 in the first material layer 12 is polymethyl methacrylate, and the mass percentage of the polymethyl methacrylate in the first material layer 12 is 98.5. %. The carbon nanotubes 124 are multi-walled carbon nanotubes having a mass percentage of 1.5% in the first material layer 12.

The second material layer 14 has a thermal expansion coefficient different from that of the first material layer 12, and the second material layer 14 includes at least a second polymer matrix. The second polymer matrix is made of a flexible material, including ruthenium rubber and polymethyl. One or more of methyl acrylate, polyurethane, epoxy resin, polyethyl acrylate, polybutyl acrylate, polystyrene, polybutadiene, polyacrylonitrile, polyaniline, polypyrrole and polythiophene a combination of species. The second material layer 14 may include only a second polymer matrix, because the carbon nanotubes 124 in the first material layer 12 have less influence on the thermal expansion coefficient of the first material layer 12, so the second polymer at this time The material of the substrate needs to be different from the first polymer matrix 122 in the first material layer 12 The material and the thermal expansion coefficients of the two are different. It can be understood that the second material layer 14 can also include a plurality of carbon nanotubes, and the plurality of carbon nanotubes are uniformly dispersed in the second polymer matrix. Since the carbon nanotubes have good thermal conductivity, the entire electrothermal heating can be further improved. The thermal response speed of the actuator 10. In this embodiment, the second material layer 14 includes only a second polymer matrix, the second polymer matrix is a ruthenium rubber, and the 膨胀 rubber has a thermal expansion coefficient greater than that of the first material layer 12 in the embodiment. The thermal expansion coefficient of the material of the polymer matrix 122, polymethyl methacrylate.

In addition, the first material layer 12 or the second material layer 14 may further include a dopant (not shown) uniformly dispersed in the first polymer matrix 122 or the second polymer matrix, and the dopant may be The coefficient of thermal expansion of the first material layer 12 or the second material layer 14 is adjusted, and the dopant includes ceramic particles, metal particles, bubbles or glass particles, and the like. If the second polymer matrix of the second material layer 14 is the same material as the first polymer matrix 122 of the first material layer 12, the first material layer 12 and the second material layer 14 may each comprise a uniform a dopant dispersed in the first polymer matrix 122 and the second polymer matrix, and the dopants included in the two are different and the coefficient of thermal expansion is also different; and at the same time, only the first material layer 12 or the first One of the two material layers 14 includes a dopant such that the coefficient of thermal expansion of the second material layer 14 is different from the coefficient of thermal expansion of the first material layer 12. The mass percentage of the dopant in the first material layer 12 or the second material layer 14 depends on the magnitude of its thermal expansion coefficient.

The overall thickness of the electrothermal actuator 10 is not limited, and may be determined according to actual needs, generally 0.02 mm to 2 mm, and the thickness of the first material layer 12 is 0.5 mm to 1.5 mm, and the thickness of the second material layer 14 is 0.5 mm to 1.5 mm. In this embodiment, the first material layer is 1 mm and the second material layer is 1 mm.

The at least two electrodes 16 are spaced apart and fixed to both ends or surfaces of the first material layer 12. In this embodiment, the electrodes 16 are two, and the two electrodes 16 are electrically connected to the first material layer 12 for inputting an external current into the first material layer 12. The electrode 16 may be in the form of a rod, a strip, a block or His shape, the shape of its cross section may be a circle, a square, a trapezoid, a triangle, a polygon or other irregular shape. The material of the two electrodes 16 may be selected from gold, copper or iron. In this embodiment, the material of the electrode 16 is copper and is fixed to both ends of the first material layer 12.

The electrothermal actuator 10 applies a voltage to both ends of the first material layer 12 of the electrothermal actuator 10 when applied, and current can be transmitted through the conductive network formed by the carbon nanotubes 124. Since the thermal conductivity of the carbon nanotubes 124 is high, the temperature of the electrothermal actuator 10 is rapidly increased, and heat is rapidly transferred from the periphery of the carbon nanotubes 124 to the entire electric heater in the electrothermal actuator 10. The actuator 10 is diffused, i.e., the first material layer 12 can rapidly heat the second material layer 14. Since the amount of thermal expansion is proportional to the volume of the material and the coefficient of thermal expansion, and the electrothermal actuator 10 of the present embodiment is composed of two layers of the first material layer 12 and the second material layer 14 having different coefficients of thermal expansion, thereby heating The latter electrothermal actuator 10 will bend a layer of material having a small coefficient of thermal expansion. In addition, the electrothermal actuator 10 not only produces a significant linear thermal deformation in the direction in which the current extends, but also a bending deformation perpendicular to the direction in which the current extends. In addition, since the carbon nanotubes 124 have the characteristics of good electrical conductivity and small heat capacity, the thermal response rate of the electrothermal actuator 10 is fast, and only a small amount of carbon nanotubes 124 are added to one of the layers. Larger deformations are obtained, saving the carbon nanotubes 124.

Referring to FIG. 2, in addition, in the embodiment, a power supply voltage is applied to both ends of the electrostrictive material through a wire, and the electrostrictive material is subjected to measurement of a telescopic characteristic.

When not energized, the original length L1 of the electrostrictive material was measured to be 5 cm; after applying a voltage of 40 volts for 2 minutes, the length L2 of the electrostrictive material was measured to be 5.5 cm; In the direction of extension, the displacement ΔS of the electrostrictive material is about 5 mm.

Referring to FIG. 3, a method for preparing an electrostrictive material according to a first embodiment of the present invention includes the following steps:

Step 1: providing a plurality of carbon nanotubes and a first polymer monomer solution; in this embodiment, the carbon nanotubes are obtained by chemical vapor deposition, or by arc discharge or laser cauterization. The first polymer monomer solution may be at least one of methyl methacrylate (MMA), ethyl acrylate, butyl acrylate, styrene, butadiene, acrylonitrile, and methyl methacrylate is used in this embodiment. .

Step 2: mixing the carbon nanotube and the first polymer monomer solution to obtain a first mixed solution; first, mixing the first polymer monomer solution with a carbon nanotube to form a first mixture The solution, the mass percentage of the first polymer monomer in the mixed solution is 92 to 99.8%, and the mass percentage of the carbon nanotube in the mixed solution is 0.2 to 10%; secondly, the ultrasonic oscillation method is used. The first mixed solution is treated such that the carbon nanotubes are uniformly dispersed in the first polymer monomer solution. When the first polymer monomer has volatility, in order to maintain the original mass of the first mixed solution, the first polymer monomer solution volatilized during the ultrasonic vibration may be added after the ultrasonic dispersion process is completed. .

The second step further includes a ball milling process of pouring the first mixed solution into the ball mill tank for a certain period of time before or after the first mixing solution is treated by ultrasonic vibration. Since the carbon nanotubes have a large aspect ratio and are easily agglomerated, the carbon nanotubes are unevenly dispersed in the mixed solution. After the ball milling, the carbon nanotubes can be further broken, thereby reducing the size and The carbon nanotubes are further dispersed in the mixed solution, and the ball milling time may be 1 to 5 hours, and this embodiment is preferably 3 hours.

In addition, the step may further include providing a dopant and adding the dopant to the first polymer monomer solution, and the dopant may be ceramic particles, metal particles, bubbles or glass particles, or the like. The dopant can adjust a coefficient of thermal expansion of the first material layer.

Step 3: polymerizing the first mixed solution to form a first material layer; the reaction method for polymerizing the first mixed solution in the step may include polycondensation reaction, polyaddition reaction, and free radical depending on the type of the first polymer monomer Polymerization, anionic polymerization or cationic polymerization, and the like. For example, polymethyl acrylate, polymethyl methacrylate and polyacrylonitrile are subjected to radical polymerization, and epoxy resin and polyurethane are subjected to polycondensation reaction.

The first polymer monomer solution in this embodiment is methyl methacrylate (MMA), and the specific method for polymerizing the first mixed solution comprises the following steps:

First, a certain proportion of the initiator is added to the first mixed solution to obtain a second mixed solution. The material of the initiator is selected to be related to the material of the first polymer monomer, and the initiator may be at least one of azobisisobutyronitrile (AIBN), benzammonium peroxide and azobisisobutyronitrile. In the examples, azobisisobutyronitrile (AIBN) was used, and the mass percentage of the initiator in the mixture was 0.02 to 2%. The addition of the initiator allows activation of the double bond of the monomer molecule in the polymerization reaction to become a radical, thereby allowing further reaction.

Further, a certain proportion of a plasticizer may be further added to the second mixed solution, and the material of the plasticizer is selected to be related to the material of the first polymer monomer. The plasticizer may be dibutyl phthalate (DBP), cetyltrimethylammonium bromide, polyvinyl acetate, polymethacrylate, C12-C18 higher fatty acid, decane coupling agent, At least one of a titanate coupling agent and an aluminate coupling agent, in this embodiment, dibutyl phthalate (DBP) is used, and the mass percentage in the second mixed solution is 0 to 5%. . The plasticizer acts to weaken the interaction between the polymer molecules, increase the mobility of the polymer molecular chain, and reduce the crystallinity of the polymer molecular chain, thereby increasing the plasticity of the polymer.

Second, the second mixed solution is prepolymerized and a first prepolymerized mixed solution is formed.

The method for forming the first prepolymerized mixed solution specifically includes the following steps: First, the second step The mixed solution is heated to a certain temperature and stirred to cause pre-polymerization of the second mixed solution, and the heating is stopped when the solution reacts to have a certain viscosity. In this embodiment, the second mixed solution is heated to 92 degrees Celsius by a water bath method, after which Stir for 10 minutes and wait until it reacts to have a certain viscosity or glycerin shape to stop heating; secondly, cool and stir the first prepolymerized mixed solution until the prepolymerization reaction is stopped. In this embodiment, the glycerin-like first prepolymerization is mixed. The solution is placed in the air to be naturally cooled.

Thirdly, the first prepolymerized mixed solution is polymerized and a first material layer comprising a plurality of carbon nanotubes and a first polymer matrix is formed; the step is specifically: first, the previously cooled prepolymerized mixed solution Pour into a container and place it in a temperature environment to polymerize the prepolymerized mixed solution in the above container. In this embodiment, the container is placed in a temperature environment of 50 degrees Celsius to 60 degrees Celsius, and the polymerization reaction takes place for 1 hour to 4 hours. Next, the first prepolymerized mixed solution is further heated to a certain temperature to carry out polymerization until complete polymerization, thereby obtaining a polymer film containing a carbon nanotube. In this embodiment, the heating temperature is 70 degrees Celsius to 100 degrees Celsius.

Further, the above-mentioned carbon nanotube-containing polymer film may be immersed in warm water for a certain period of time, and then peeled off from the container to obtain a complete first material layer containing a plurality of carbon nanotubes. In this embodiment, the film is immersed in water of 50 degrees Celsius to 60 degrees Celsius for about 2 minutes, and then the polymer film containing the carbon nanotubes is quickly peeled off from the container, thereby obtaining a complete composite carbon nanotube and polymethyl group. The first material layer of methyl acrylate (PMMA).

Step 4: forming a second material layer on a surface of one of the first material layers, the second material layer comprising a second polymer matrix, the second material layer and the first material layer having different thermal expansion coefficients.

The second material layer is prepared by providing a second polymer monomer solution; polymerizing the second polymer monomer solution to form a second material layer. In addition, the preparation method of the second material layer can be The step of providing a plurality of carbon nanotubes or dopants and mixing the plurality of carbon nanotubes or dopants with the second polymer monomer solution described above. The plurality of carbon nanotubes can further improve the electrical and thermal conductivity of the electrothermal actuator, and the dopant can adjust a thermal expansion coefficient of the second material layer, and the dopant can be ceramic particles, metal particles, bubbles or glass Particles, etc.

The method for bonding the second material layer and the first material layer has the following two types: the first one is that the second material layer which has been prepared is formed on the surface of the first material layer by bonding, pressing, or the like; The second method is to spread the second polymer monomer solution which has not undergone solidification on the surface of the first material layer with its own fluidity, thereby forming a second material layer on the surface of the first material layer. The material of the second polymer matrix included in the second material layer is ruthenium rubber, polymethyl methacrylate, polyethyl acrylate, polybutyl acrylate, polystyrene, polybutadiene, polyacrylonitrile, poly One or more of aniline, polypyrrole and polythiophene.

In this embodiment, the second material layer is formed on one surface of the first material layer by pouring a second polymer monomer solution onto one surface of the first material layer, and utilizing its own fluidity. One of the first material layers is unfolded on the surface, and then left to stand at room temperature for 12 hours to 18 hours to obtain a second material layer. The method provides a good bond between the first material layer and the second material layer, thereby making it easier for the first material layer to diffuse heat to the second material layer, reducing the thermal resistance between the two. In this embodiment, the material of the second polymer matrix in the second material layer is made of ruthenium rubber.

The ruthenium rubber is composed of GF-T2A elastic electronic potting glue A and B components in a ratio of A:B of 100:4~100:8. The specific preparation method is as follows: firstly, thoroughly mixing and stirring the above two components A and B; secondly, pouring the mixed mixture of A and B components on the first material layer to make use of their own flow. Sexually spread on the surface of the first material layer.

This embodiment may further include spacing the two electrodes at both ends or surfaces of the first material layer by a conductive adhesive.

The electrostrictive material described in the embodiments of the present technical solution, the preparation method thereof, and the electrothermal actuator have the following advantages: since the electrostrictive material in the electrothermal actuator includes a dispersed carbon nanotube, The electrothermal actuator has higher electrical and thermal conductivity and a faster thermal response rate; since the first material layer and the second material layer of the electrostrictive material have different coefficients of thermal expansion, the electrostriction When a current passes, the material can not only deform in the direction in which the current flows, but also bend in a direction perpendicular to the current; in the electrostrictive material, only one layer is added with a small amount of nanocarbon. The tube can obtain large deformation, saves carbon nanotubes and saves cost; the electrostrictive material is a flexible material, the material has simple structure, is closer to natural muscle, has good biocompatibility, and can be used as Artificial muscle; the preparation method of the electrostrictive material is simple, suitable for large-scale production integration and the like. In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

10‧‧‧Electrical actuator

12‧‧‧First material layer

122‧‧‧First polymer matrix

124‧‧‧Nanocarbon tube

14‧‧‧Second material layer

16‧‧‧Electrode

Claims (20)

An electrostrictive material comprising a first material layer and a second material layer, the first material layer and the second material layer being stacked and having different coefficients of thermal expansion, wherein the first material layer comprises a first a polymer matrix and a plurality of carbon nanotubes uniformly dispersed in the first polymer matrix, the second material layer comprising a second polymer matrix, and the mass of the plurality of carbon nanotubes in the first material layer The content of the fraction is 0.5% to 2%. The electrostrictive material according to claim 1, wherein the first material layer and the second material layer are overlapped by bonding and pressing. The electrostrictive material according to claim 1, wherein the second material layer further comprises a plurality of carbon nanotubes, the plurality of carbon nanotubes being uniformly dispersed in the second polymer matrix. The electrostrictive material according to claim 1, wherein the first polymer matrix and the second polymer matrix are the same material, and one of the first material layer or the second material layer comprises a dopant. The dopant includes ceramic particles, metal particles, bubbles or glass particles. The electrostrictive material of claim 1, wherein the plurality of carbon nanotubes form a conductive network. The electrostrictive material according to claim 1, wherein the material of the first polymer matrix is a conductive polymer. The electrostrictive material according to claim 6, wherein the plurality of carbon nanotubes are disorderly distributed in the conductive polymer to increase the electrical conductivity of the first material layer. The electrostrictive material according to claim 1, wherein the material of the first polymer matrix or the second polymer matrix is ruthenium rubber, polymethyl methacrylate, polyurethane, epoxy resin, polyacrylic acid One or a combination of ester, polybutyl acrylate, polystyrene, polybutadiene, polyacrylonitrile, polyaniline, polypyrrole, and polythiophene. The electrostrictive material according to claim 1, wherein at least one of the first material layer and the second material layer further comprises a doping body, the doping body being ceramic particles, metal particles, bubbles and One or more of the glass particles. A method for preparing an electrostrictive material, comprising the steps of: providing a plurality of carbon nanotubes and a first polymer monomer solution; mixing the plurality of carbon nanotubes and the first polymer monomer solution to form a mixture a solution, the mass percentage of the plurality of carbon nanotubes in the mixed solution is 0.5% to 2%; polymerizing the mixed solution to form a first material layer; forming a surface of the first material layer a second layer of material. The method for producing an electrostrictive material according to claim 10, wherein the method of forming the mixed solution further comprises: treating the mixed solution by ultrasonic vibration to uniformly disperse the carbon nanotube in the mixed solution. The method for producing an electrostrictive material according to claim 10, wherein the method of forming the mixed solution further comprises subjecting the mixed solution to a ball milling treatment. The method for producing an electrostrictive material according to claim 10, wherein the method for forming the first material layer by the polymerization mixed solution comprises the steps of: adding an initiator to the mixed solution; and mixing the above-mentioned initiator; The solution is prepolymerized and forms a prepolymerized mixed solution; the prepolymerized mixed solution is polymerized and a first material layer comprising a plurality of carbon nanotubes and a first polymer matrix is formed. The method for preparing an electrostrictive material according to claim 10, wherein the method of forming the second material layer comprises: providing a second polymer monomer solution; and polymerizing the second polymer monomer solution to form a second material a layer; the second material layer is disposed on the surface of the first material layer by bonding and pressing. The method for preparing an electrostrictive material according to claim 10, wherein the second material is formed The method of layer includes: providing a second polymer monomer solution; pouring the second polymer monomer solution onto one surface of the first material layer, and utilizing its own fluidity on one surface of the first material layer Expanding; polymerizing the second polymer monomer solution and forming a second material layer. An electrothermal actuator comprising a first material layer, a second material layer and at least two electrodes, the first material layer and the second material layer being stacked and having different coefficients of thermal expansion, the at least two electrodes being spaced apart And electrically connected to the first material layer, wherein the first material layer comprises a first polymer matrix and a plurality of carbon nanotubes dispersed in the first polymer matrix, the second material The layer includes a second polymer matrix, and the mass percentage of the plurality of carbon nanotubes in the first material layer is 0.5% to 2%. The electrothermal actuator of claim 16, wherein the material of the first polymer matrix is a conductive polymer. The electrothermal actuator of claim 17, wherein the plurality of carbon nanotubes are disorderly distributed in the conductive polymer to increase electrical conductivity of the first material layer. The electrothermal actuator of claim 16, wherein the plurality of carbon nanotubes form a conductive network. The electrothermal actuator of claim 19, wherein the electrically conductive network is electrically coupled to the at least two electrodes.