A cable-free flexible actuator with gradient distribution of low-boiling-point liquid and its preparation method

Abstract

The present invention relates to a cable-free flexible actuator with a gradient distribution of low-boiling-point liquid and a preparation method thereof. The method comprises the following steps: mixing a low-boiling-point liquid with a silicone rubber prepolymer to obtain a first mixture; mixing the low-boiling-point liquid with a silicone rubber prepolymer curing agent to obtain a second mixture; mixing the first mixture with the second mixture to obtain a composite slurry; pouring the composite slurry into a mold and first curing it at a temperature of 15 to 25°C and an absolute pressure of 0.064 to 0.090 MPa for 5 to 10 minutes, and then curing it at room temperature and pressure for 1 to 50 hours to obtain a cable-free flexible actuator with a gradient distribution of low-boiling-point liquid. The method of the present invention has a simple process and low cost. The obtained flexible actuator has the advantages of simple configuration and controllable bending degree. It can achieve predetermined deformation under external heat radiation and does not require external circuit drive or complex structural design, which greatly simplifies the structural configuration, preparation process and assembly complexity.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible actuators, and in particular relates to a cable-free flexible actuator with a gradient distribution of a low-boiling-point liquid and a preparation method thereof. Background Art

[0002] Flexible actuators, due to their excellent properties such as continuous deformation with multiple degrees of freedom, high adaptability, and interactive safety, have found applications in soft robotics, medical devices, artificial muscles, and other fields. Currently, most flexible actuators are pneumatic or voltage-driven, driven by flexible materials connected to external circuits (e.g., air pipes or wires). These actuators are limited in scope and require additional energy supply equipment. Furthermore, to achieve deformation along a preset path, complex geometric design and circuit connections are required, leading to complex manufacturing processes and assembly, and the inability to miniaturize the actuators. In addition, in order to achieve bending, the flexible actuators in the prior art need to achieve different deformation stiffness characteristics at different positions through heterogeneous material stacking or heterogeneous design; for example, Chinese patent application CN113736262A provides a light-responsive liquid-gas phase change composite material and its preparation method and application. The light-responsive liquid-gas phase change composite material provided can be used to prepare light-responsive devices, such as flexible actuator grippers, but its flexible actuator is composed of two layers of materials, one of which is an active layer, which is composed of the liquid-gas phase change composite material prepared in this patent application, and the other layer is ordinary silicone rubber. When exposed to light, the active layer will extend, and due to the limitation of the passive layer, the double-layer structure will bend, so the actuator will bend to one side to grasp the object.

[0003] Therefore, it is very necessary to provide an integrated cable-free flexible actuator and a preparation method thereof. Summary of the Invention

[0004] To address one or more technical problems existing in the prior art, the present invention provides a cable-free flexible actuator with a gradient distribution of low-boiling-point liquid and a method for preparing the same. The present invention provides an integrated cable-free flexible actuator containing a low-boiling-point liquid with a gradient distribution characteristic in the direction of gravity (thickness direction). This actuator can achieve predetermined deformation under external thermal radiation and can achieve deformations such as bending without the need for external circuit drive or complex structural design. This greatly simplifies the flexible actuator's structural configuration, preparation process, and assembly complexity, and provides adjustable deformation response.

[0005] In a first aspect, the present invention provides a method for preparing a cable-free flexible actuator with a gradient distribution of a low-boiling-point liquid, the method comprising the following steps:

[0006] (1) mixing a low-boiling-point liquid with a silicone rubber prepolymer to obtain a first mixture;

[0007] (2) mixing the low boiling point liquid with the silicone rubber prepolymer curing agent to obtain a second mixture;

[0008] (3) mixing the first mixture with the second mixture to obtain a composite slurry;

[0009] (4) The composite slurry is poured into a mold and first cured for 5 to 10 minutes at a temperature of 15 to 25°C and an absolute air pressure of 0.064 to 0.090 MPa, and then cured at a temperature of 15 to 25°C and normal pressure for 1 to 50 hours to obtain a cable-free flexible actuator with a low-boiling-point liquid gradient distribution.

[0010] Preferably, the composite slurry is poured into a mold and first cured at a temperature of 15-22° C. and an absolute pressure of 0.064-0.076 MPa for 5-8 minutes, and then cured at a temperature of 15-25° C. and normal pressure for 1-50 hours.

[0011] Preferably, the normal pressure curing time is 4 to 50 hours.

[0012] Preferably, the low-boiling-point liquid is an ethanol solution, a tetrahydrofuran solution, an electronic fluorinated liquid, a trichlorotrifluoroethane solution or an ethyl acetate solution.

[0013] Preferably, the low-boiling-point liquid is an ethanol solution, and the volume fraction of ethanol in the ethanol solution is 15-35%.

[0014] Preferably, the silicone rubber prepolymer is Ecoflex 00-50 prepolymer, Ecoflex 00-30 prepolymer, Dragon skin 30 prepolymer or Sylgard 184 prepolymer; and the silicone rubber prepolymer curing agent is Ecoflex 00-50 prepolymer curing agent, Ecoflex 00-30 prepolymer curing agent, Dragon skin 30 prepolymer curing agent or Sylgard 184 prepolymer curing agent.

[0015] Preferably, in the first mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber prepolymer is (16-25):100; in the second mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber prepolymer curing agent is (16-25):100; and / or the volume ratio of the first mixture to the second mixture is 100:(10-100).

[0016] Preferably, in step (1) and / or step (2), the mixing method is: stirring for 1 to 3 minutes at normal temperature and pressure, and the stirring speed is 1000 to 1500 r / min.

[0017] Preferably, in step (3), the mixing method is: stirring at room temperature and pressure for 5 to 10 minutes, and the stirring speed is 1000 to 1500 r / min.

[0018] In the second aspect, the present invention provides a cable-free flexible actuator with a gradient distribution of low-boiling-point liquid, which is prepared by the preparation method described in the first aspect of the present invention. The cable-free flexible actuator with a gradient distribution of low-boiling-point liquid comprises silicone rubber and a low-boiling-point liquid, and the low-boiling-point liquid is gradiently dispersed in the silicone rubber in the form of droplets in the direction of gravity.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] (1) The present invention produces an integrated cable-free flexible actuator, which has the characteristics of a simple configuration to achieve preset geometric deformation, adjustable volume thickness and deformation, and controllable bending degree, and does not require a complex geometric configuration and external circuit connection.

[0021] (2) The low-boiling-point liquid contained in the cable-free flexible actuator obtained by the present invention has a gradient distribution characteristic in the form of droplets in the direction of gravity (thickness direction), that is, the distribution of the low-boiling-point liquid decreases from one side to the other side in the thickness direction. It is precisely because the cable-free flexible actuator obtained by the present invention has this characteristic of gradient distribution of low-boiling-point liquid that the flexible actuator can be made to have a larger expansion coefficient under external heat radiation due to the distribution of more low-boiling-point liquid on one side. The side with more low-boiling-point liquid will have a large expansion deformation degree, which is the active side, while the other side has a small expansion coefficient and a small expansion deformation degree due to the less distribution of low-boiling-point liquid, which can limit the expansion deformation and is the passive side. As a result, the cable-free flexible actuator obtained by the present invention can achieve bending deformation, that is, it can achieve predetermined deformation under external heat radiation, and can complete deformation such as bending without the need for external circuit drive and complex structural design, which greatly simplifies the structural configuration, preparation process and assembly complexity of the flexible actuator, and has the ability to adjust the deformation response.

[0022] (3) The method of the present invention adjusts the pressure, time and temperature of the curing environment to form an integrated cable-free flexible actuator with a low-boiling-point liquid gradient distribution. The process is simple and the cost is low. The cable-free flexible actuator has the advantages of simple configuration, controllable thickness, controllable bending degree, and recyclability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a process preparation flow chart of the present invention.

[0024] Figure 2 It is a schematic diagram of the cable-free flexible actuator with gradient distribution of low-boiling-point liquid prepared by the present invention.

[0025] Figure 3 This is a physical picture of the cable-free flexible actuator with gradient distribution of low-boiling-point liquid prepared in Example 3 of the present invention (unheated).

[0026] Figure 4 This is a real picture of the cable-free flexible actuator with a gradient distribution of low-boiling-point liquid prepared in Example 3 of the present invention after being heated by radiation at 90°C and normal pressure for 7 minutes and then the heating bending deformation is stabilized.

[0027] Figure 5 These are pictures of samples obtained from Examples 1 to 4 of the present invention and Comparative Examples 1 and 4; in the figures, (a) to (d) are all photographed along the thickness of the samples, and the samples are milky white as a whole; in the process of pouring the mixed slurry into a cylindrical mold for integrated molding, there is a wall hanging phenomenon, so when the obtained cylindrical sample is photographed from the thickness, there are corners on the upper side of the sample, which does not represent the effective part of the sample. Taking the cylindrical sample shown in Figure (a) as an example, the position of the top of the cylindrical sample is approximately the position shown by the dotted line in Figure (a); in the figures, (a) is the sample obtained from Example 1 of the present invention, (b) is the sample obtained from Example 2 of the present invention; (c) is the sample obtained from Example 3 of the present invention; (d) is the sample obtained from Comparative Example 1 of the present invention; (e) is the sample obtained from Example 4 of the present invention; and (f) is the sample obtained from Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] In the first aspect, the present invention provides a method for preparing a cable-free flexible actuator with a low-boiling-point liquid gradient distribution, and the process flow chart thereof is as follows, for example: Figure 1 As shown; the method comprises the following steps:

[0030] (1) mixing a low-boiling-point liquid (also referred to as a low-boiling-point solution) with a silicone rubber prepolymer (also referred to as silicone rubber component A) to obtain a first mixture;

[0031] (2) mixing the low-boiling-point liquid with a silicone rubber prepolymer curing agent (also referred to as silicone rubber component B) to obtain a second mixture;

[0032] (3) mixing the first mixture with the second mixture to obtain a composite slurry;

[0033] (4) The composite slurry is poured into a mold at a temperature of 15 to 25°C (e.g., 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C or 25°C) and an absolute pressure of 0.064 to 0.090 MPa (e.g., 0.064, 0.065, 0.066, 0.067, 0.068, 0.069, 0.070, 0.071, 0.072 , 0.073, 0.074, 0.075, 0.076, 0.077, 0.078, 0.079, 0.080, 0.081, 0.082, 0.083, 0.084, 0.085, 0.086, 0.087, 0.088, 0.089 or 0.090 MPa) for 5 to 10 minutes (e.g., 5, 6, 7, 8, 9 or 10 minutes), and then at a temperature of Curing is carried out at 15-25°C at normal pressure for 1-50h (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46 , 47, 48, 49 or 50h), to obtain a cable-free flexible actuator with a gradient distribution of low-boiling-point liquid; the cable-free flexible actuator with a gradient distribution of low-boiling-point liquid comprises a dispersion medium and a dispersed phase, the dispersed phase is gradiently dispersed in the dispersion medium along the direction of gravity (thickness direction), the dispersion medium is silicone rubber, the dispersed phase is a low-boiling-point liquid, and the low-boiling-point liquid is gradiently dispersed in the silicone rubber along the direction of gravity in the form of droplets, for example, Figure 2 As shown; the present invention does not make any specific limitation on the configuration of the mold, and it can be designed according to actual needs. By selecting molds of different configurations, cable-free flexible actuators of different configurations can be cast; in the present invention, the mold can be, for example, a cylindrical mold, which can be integrated to obtain a cable-free flexible actuator of equal thickness block type; in the present invention, curing for 5 to 10 minutes will be carried out at a temperature of 15 to 25°C and an absolute air pressure of 0.064 to 0.090 MPa, which is simply referred to as low-pressure curing; in the present invention, absolute air pressure refers to the absolute air pressure of the curing environment; in the present invention, curing will be carried out at 15 to 25°C and normal pressure (atmospheric pressure) of 0.1 MPa, which is simply referred to as normal temperature and normal pressure curing. Preferably, curing at normal temperature and normal pressure is carried out for 4 to 50 hours (for example, 4, 5, 10, 15, 20, 24, 30, 35, 40, 45, 48 or 50 hours).

[0034] Before curing the mixed slurry at room temperature and pressure, the present invention first cures the mixed slurry in a low-pressure environment lower than atmospheric pressure for 5 to 10 minutes, specifically, curing at low pressure for 5 to 10 minutes under an absolute pressure of 0.064 to 0.090 MPa. As the pressure of the curing environment decreases while the pressure inside the mixed slurry remains unchanged, the internal and external pressure difference increases, and the low-boiling-point liquid moves in the form of micro-droplets to the side with low pressure, that is, toward the top side of the mixed slurry, thereby forming a cable-free flexible actuator with a gradient distribution of low-boiling-point liquid. In addition, for the present invention, it is necessary to reasonably control the temperature, absolute pressure and time of the low-pressure curing. If the temperature of the low-pressure curing is too high, the absolute pressure is too low, or the low-pressure curing time is too long, All of these will cause the low-boiling-point liquid to volatilize, and it will be impossible to form a phase change driving material, let alone the cable-free flexible actuator described in the present invention; and if the absolute air pressure of the low-pressure curing is too high or the low-pressure curing time is too short, the low-boiling-point liquid will not move significantly to one side, and the low-boiling-point liquid will not be able to form an obvious gradient distribution along the thickness direction in the silicone rubber dispersion medium; the method of the present invention adjusts the pressure, time and temperature of the low-pressure curing environment to integrate and form a cable-free flexible actuator with a gradient distribution of low-boiling-point liquid, thereby achieving a simple configuration of the flexible actuator to achieve a preset geometric deformation; the method of the present invention has a simple process and low cost, and the cable-free flexible actuator obtained has the advantages of simple configuration, controllable thickness, adjustable deformation, controllable bending degree, and recyclability.

[0035] The low-boiling-point liquid contained in the cable-free flexible actuator obtained by the present invention has a gradient distribution characteristic in the form of droplets in the direction of gravity (thickness direction). In the thickness direction of the cable-free flexible actuator body, the low-boiling-point liquid is not evenly dispersed, but the distribution of the low-boiling-point liquid decreases successively from one side to the other side in the thickness direction. It is precisely because the cable-free flexible actuator obtained by the present invention has the characteristic of gradient distribution of low-boiling-point liquid that the flexible actuator can be subjected to external heat radiation. Since there is more low-boiling-point liquid distributed on one side, the expansion coefficient will be greater. The side with more low-boiling-point liquid distribution will have a greater degree of expansion and deformation, which is the active side, while the other side has less low-boiling-point liquid distribution, a small expansion coefficient, and a small degree of expansion and deformation, and can limit expansion and deformation, which is the passive side, thereby enabling the cable-free flexible actuator obtained by the present invention to achieve Bending deformation, that is, predetermined deformation can be achieved under external heat radiation, and bending and other deformations can be completed without external circuit drive and complex structural design, which greatly simplifies the structural configuration, preparation process and assembly complexity of the flexible actuator, and has the ability to adjust the deformation response, that is, by regulating the temperature, absolute air pressure and time of the low-pressure curing of the present invention, the degree of bending deformation of the cable-free flexible actuator can be controlled. For the first time, the present invention obtains an integrated cable-free flexible actuator by making the low-boiling point liquid in the form of droplets gradiently distributed in the direction of gravity (thickness direction) in the silicone rubber; while the phase change composite material with uniformly distributed low-boiling point liquid in the prior art has the same expansion coefficient in all directions. When subjected to external heat radiation, it will only expand and deform as a whole. Since it is not restricted or restrained, it is basically impossible to achieve bending deformation.

[0036] According to some preferred embodiments, the composite slurry is poured into a mold at a temperature of 15 to 22° C. (e.g., 15° C., 16° C., 17° C., 18° C., 19° C., 20° C., 21° C., or 22° C.) and an absolute pressure of 0.064 to 0.076 MPa (e.g., 0.064, 0.065, 0.066, 0.067, 0.068, 0.069, 0.070, 0.071, 0.072, 0.073, 0.074, 0.075, or 0.076 MPa). 6MPa) for 5 to 8 minutes (for example, 5, 6, 7 or 8 minutes), and then cured at normal pressure at a temperature of 15 to 25°C for 1 to 50 hours; in the present invention, it is preferred to first cure at a temperature of 15 to 22°C and an absolute air pressure (absolute air pressure of the curing environment) of 0.064 to 0.076MPa for 5 to 8 minutes, which is conducive to obtaining the cable-free flexible actuator with an obvious gradient distribution of low-boiling-point liquid, which can enable the cable-free flexible actuator to achieve a larger angle of bending deformation.

[0037] According to some preferred embodiments, the normal pressure curing time is 4 to 50 hours (e.g., 4, 5, 10, 15, 20, 24, 30, 35, 40, 45, 48 or 50 hours). In the present invention, the normal pressure curing time is selected according to the type of silicone rubber. For example, when the silicone rubber prepolymer is Ecoflex 00-50 prepolymer or Ecoflex 00-30 prepolymer, and the corresponding silicone rubber prepolymer curing agent is Ecoflex 00-50 prepolymer curing agent or Ecoflex 00-30 prepolymer curing agent, the normal pressure curing time may be 4 to 5 hours; when the silicone rubber prepolymer is Dragon skin 30 prepolymer, and the corresponding silicone rubber prepolymer curing agent is Dragon skin 30 prepolymer curing agent, the normal pressure curing time may be 16 to 17 hours; when the silicone rubber prepolymer is Sylgard 184 prepolymer, and the corresponding silicone rubber prepolymer curing agent is Sylgard When 184 prepolymer curing agent is used, the normal pressure curing time can be 48 to 50 hours.

[0038] According to some preferred embodiments, the low-boiling-point liquid is an ethanol solution, a tetrahydrofuran solution, an electronic fluoridation liquid, a trichlorotrifluoroethane solution or an ethyl acetate solution; in the present invention, the ethanol solution, the tetrahydrofuran solution, the trichlorotrifluoroethane solution or the ethyl acetate solution can, for example, use deionized water as a solvent. Preferably, the low-boiling-point liquid is an ethanol aqueous solution. In the present invention, preferably, the low-boiling-point liquid selected in step (1) and step (2) is of the same type; the electronic fluoridation liquid is a commercially available product, for example, Novec 7000 electronic fluoridation liquid; preferably, the boiling point of the low-boiling-point liquid is less than 90°C.

[0039] According to some preferred embodiments, the low boiling point liquid is an ethanol solution, and the volume fraction of ethanol in the ethanol solution is 15-35% (for example, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%); In the present invention, preferably, the low boiling point liquid is an ethanol aqueous solution, and the ethanol aqueous solution is a mixture of anhydrous ethanol and deionized water. And preferably, the volume fraction of ethanol contained in the ethanol aqueous solution is 15-35%. Taking Ecoflex silicone rubber material as an example, pure anhydrous ethanol or other organic liquids may dissolve with the material. Ethanol and deionized water form an ethanol aqueous solution containing ethanol with a volume fraction of 15-35%, which can prevent ethanol and silicone rubber material from dissolving and form tiny droplets inside. This is conducive to obtaining the cable-free flexible actuator with a low-boiling-point liquid gradient distribution, and can enable the cable-free flexible actuator to achieve large-angle bending deformation.

[0040] According to some preferred embodiments, based on the performance requirements of the cable-free flexible actuator, conductive materials such as graphite, graphene or metal powder may be added to the low-boiling-point liquid in steps (1) and (2).

[0041] In the present invention, the side chain groups of the silicone rubber prepolymer and the silicone rubber prepolymer curing agent can react with each other to form a silicone rubber having a three-dimensional network macromolecular structure; the present invention does not specifically limit the selection of the silicone rubber prepolymer and the silicone rubber prepolymer curing agent. Preferably, the silicone rubber prepolymer and the silicone rubber prepolymer curing agent should have the characteristics of low modulus, stretchability, easy doping and low cost.

[0042] According to some preferred embodiments, the silicone rubber prepolymer is Ecoflex 00-50 prepolymer, Ecoflex 00-30 prepolymer, Dragon skin 30 prepolymer or Sylgard 184 prepolymer, but is not limited thereto; the silicone rubber prepolymer curing agent is Ecoflex 00-50 prepolymer curing agent, Ecoflex 00-30 prepolymer curing agent, Dragon skin 30 prepolymer curing agent or Sylgard 184 prepolymer curing agent, but is not limited thereto.

[0043] According to some preferred embodiments, the dispersion medium (silicone rubber) included in the cable-free flexible actuator with gradient distribution of low-boiling-point liquid is one or more of Ecoflex 00-50, Ecoflex 00-30, Dragon skin 30, and Sylgard 184, but is not limited thereto.

[0044] According to some preferred embodiments, in the first mixture, the volume ratio of the low boiling point liquid to the silicone rubber prepolymer is (16-25):100 (e.g., 16:100, 17:100, 18:100, 19:100, 20:100, 21:100, 22:100, 23:100, 24:100 or 25:100); in the second mixture, the volume ratio of the low boiling point liquid to the silicone rubber prepolymer curing agent is (16-25):100 (e.g., 16:100, 17:100, 18:100, 19:100, 20:100, 21:100, 22:100, 23:100, 24:100 or 25:100). 23:100, 24:100 or 25:100); and / or the volume ratio of the first mixture to the second mixture is 100:(10-100) (e.g., 100:10, 100:15, 100:20, 100:25, 100:30, 100:35, 100:40, 100:45, 100:50, 100:55, 100:60, 100:65, 100:70, 100:75, 100:80, 100:85, 100:90, 100:95 or 100:100); in the present invention, for example, when the silicone rubber material is Ecoflex or Dragon skin, that is, when the silicone rubber prepolymer is Ecoflex 00-50 prepolymer, Ecoflex 00-30 prepolymer or Dragon skin 30 prepolymer, and the corresponding silicone rubber prepolymer curing agent is Ecoflex 00-50 prepolymer curing agent, Ecoflex 00-30 prepolymer curing agent or Dragonskin 30 prepolymer curing agent, the volume ratio of the first mixture to the second mixture is, for example, 1:1; when the silicone rubber material is Sylgard 184, that is, when the silicone rubber prepolymer is Sylgard 184 prepolymer and the corresponding silicone rubber prepolymer curing agent is Sylgard 184 prepolymer curing agent, the volume ratio of the first mixture to the second mixture is, for example, 10:1.

[0045] In the present invention, preferably in the first mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber prepolymer is (16-25):100, and preferably in the second mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber prepolymer curing agent is (16-25):100. If the amount of low-boiling-point liquid used is too much, it will lead to incomplete mixing, resulting in the presence of large liquid droplets inside the sample, affecting the uniformity of the material, and thus affecting the bending deformation performance of the cableless flexible actuator.

[0046] According to some preferred embodiments, the volume ratio of the low-boiling-point liquid to the dispersion medium (silicone rubber) in the cable-free flexible actuator with a gradient distribution of the low-boiling-point liquid is (16-25):100 (for example, 16:100, 17:100, 18:100, 19:100, 20:100, 21:100, 22:100, 23:100, 24:100 or 25:100).

[0047] According to some preferred embodiments, in step (1) and / or step (2), the mixing method is: stirring at room temperature and pressure for 1 to 3 minutes (for example, 1, 2 or 3 minutes), and the stirring speed is 1000 to 1500 r / min (for example, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450 or 1500 r / min); and / or in step (3) In the mixing method, the mixing is carried out at room temperature and pressure for 5 to 10 minutes (for example, 5, 6, 7, 8, 9 or 10 minutes), and the stirring speed is 1000 to 1500 r / min (for example, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450 or 1500 r / min); in the present invention, room temperature refers to, for example, room temperature of 15 to 25°C.

[0048] In the present invention, step (3) is preferably: stirring the first mixture and the second mixture at room temperature and pressure with a rotation speed of 1000-1500 r / min for 5-10 minutes to obtain the composite slurry, which is conducive to fully mixing and dispersing the low-boiling-point liquid into the silicone rubber material without agglomeration; if the stirring time of step (3) is insufficient, for example, only stirring for 1-3 minutes, the stirring time is too short, resulting in insufficient mixing and dispersion of the liquid droplets; if the stirring time is too long, the material will solidify during the stirring process. Whether the stirring time is too short or too long, the low-boiling-point liquid will not be able to move in an orderly manner in the form of droplets during the subsequent low-pressure curing process, thereby failing to form a cable-free flexible actuator with a significant gradient distribution of the low-boiling-point liquid, resulting in a small degree of bending deformation of the cable-free flexible actuator.

[0049] According to some specific embodiments, the preparation of the cable-free flexible actuator with gradient distribution of low-boiling-point liquid comprises the following steps:

[0050] S1. Prepare a certain volume fraction of low-boiling-point liquid;

[0051] S2. The low-boiling point liquid is uniformly dispersed in the silicone rubber prepolymer by mechanical stirring to obtain a first mixture;

[0052] S3. The low-boiling point liquid is uniformly dispersed in the silicone rubber prepolymer curing agent by mechanical stirring to obtain a second mixture;

[0053] S4. Mixing the first mixture and the second mixture by mechanical stirring to obtain a composite slurry;

[0054] S5. Pour the composite slurry into a mold, first cure it at low pressure (absolute pressure 0.064-0.090 MPa) at 15-25°C for 5-10 minutes, and then cure it at normal pressure at room temperature 15-25°C for 1-50 hours to obtain a cable-free flexible actuator with a low-boiling-point liquid gradient distribution.

[0055] In the second aspect, the present invention provides a cable-free flexible actuator with a gradient distribution of low-boiling-point liquid, which is prepared by the preparation method described in the first aspect of the present invention. The cable-free flexible actuator with a gradient distribution of low-boiling-point liquid comprises silicone rubber and a low-boiling-point liquid, and the low-boiling-point liquid is gradiently dispersed in the silicone rubber in the form of droplets in the direction of gravity (thickness direction).

[0056] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these examples. The present invention may also have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, and such corresponding changes and modifications shall fall within the scope of protection of the claims appended hereto.

[0057] Example 1

[0058] S1. Prepare anhydrous ethanol and deionized water in a volume ratio of 1:4 to a 20% ethanol aqueous solution to obtain a low-boiling-point liquid;

[0059] S2. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component A (Ecoflex 00-50 prepolymer) was added to 2.5 mL of a 20% by volume ethanol aqueous solution and mechanically stirred at 1500 rpm for 2 minutes at 18°C ​​and 0.1 MPa to obtain a first mixture; in the first mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber component A was 2.5:15;

[0060] S3. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component B (Ecoflex 00-50 prepolymer curing agent) was added to 2.5 mL of a 20% volume fraction ethanol aqueous solution and mechanically stirred at 1500 rpm for 2 minutes at 18°C ​​and 0.1 MPa to obtain a second mixture; in the second mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber component B was 2.5:15;

[0061] S4. The first mixture and the second mixture were added to a beaker in a volume ratio of 1:1 and mechanically stirred at 1500 r / min for 5 min at 18 ° C and 0.1 MPa to obtain a composite slurry;

[0062] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.076 MPa and 18°C ​​for curing for 5 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a low-boiling-point liquid gradient distribution with a thickness of 5 mm.

[0063] Example 2

[0064] Example 2 is basically the same as Example 1, except that:

[0065] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.070 MPa and 18°C ​​for curing for 5 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a low-boiling-point liquid gradient distribution with a thickness of 5 mm.

[0066] Example 3

[0067] Example 3 is basically the same as Example 1, except that:

[0068] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.064 MPa and 18°C ​​for curing for 5 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a low-boiling-point liquid gradient distribution with a thickness of 5 mm.

[0069] Example 4

[0070] Example 4 is basically the same as Example 3, except that:

[0071] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.064 MPa and 18°C ​​for curing for 10 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a low-boiling-point liquid gradient distribution with a thickness of 5 mm.

[0072] In this embodiment, since the low-pressure curing time is as long as 10 minutes, part of the low-boiling-point liquid evaporates. Compared with the curing for 5 minutes in an environment with an absolute air pressure of 0.064 MPa and 18°C, the gradient distribution layer moves upward as a whole, and the result is a cable-free flexible actuator with a relatively less obvious gradient distribution of the low-boiling-point liquid.

[0073] Example 5

[0074] Example 5 is basically the same as Example 3, except that:

[0075] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.090 MPa and 18°C ​​for curing for 5 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a low-boiling-point liquid gradient distribution with a thickness of 5 mm.

[0076] Example 6

[0077] S1. Prepare anhydrous ethanol and deionized water in a volume ratio of 1:9 to obtain a 10% ethanol aqueous solution to obtain a low-boiling-point liquid;

[0078] S2. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component A (Ecoflex 00-50 prepolymer) was added to 2.5 mL of a 10% ethanol aqueous solution and mechanically stirred at 1500 rpm for 2 minutes at 18°C ​​and 0.1 MPa to obtain a first mixture; in the first mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber component A was 2.5:15;

[0079] S3. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component B (Ecoflex 00-50 prepolymer curing agent) was added to 2.5 mL of a 10% ethanol aqueous solution and mechanically stirred at 1500 rpm for 2 minutes at 18°C ​​and 0.1 MPa to obtain a second mixture; in the second mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber component B was 2.5:15;

[0080] S4. The first mixture and the second mixture were added to a beaker in a volume ratio of 1:1 and mechanically stirred at 1500 r / min for 5 min at 18 ° C and 0.1 MPa to obtain a composite slurry;

[0081] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.064 MPa and 18°C ​​for curing for 5 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a thickness of 5 mm.

[0082] Example 7

[0083] S1. Prepare anhydrous ethanol and deionized water in a volume ratio of 4:6 to obtain a 40% ethanol aqueous solution to obtain a low-boiling-point liquid;

[0084] S2. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component A (Ecoflex 00-50 prepolymer) was added to 2.5 mL of a 40% by volume ethanol aqueous solution and mechanically stirred at 1500 rpm for 2 minutes at 18°C ​​and 0.1 MPa to obtain a first mixture; in the first mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber component A was 2.5:15;

[0085] S3. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component B (Ecoflex 00-50 prepolymer curing agent) was added to 2.5 mL of a 40% by volume ethanol aqueous solution and mechanically stirred at 1500 rpm for 2 minutes at 18°C ​​and 0.1 MPa to obtain a second mixture; in the second mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber component B was 2.5:15;

[0086] S4. The first mixture and the second mixture were added to a beaker in a volume ratio of 1:1 and mechanically stirred at 1500 r / min for 5 min at 18 ° C and 0.1 MPa to obtain a composite slurry;

[0087] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.064 MPa and 18°C ​​for curing for 5 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a thickness of 5 mm.

[0088] Example 8

[0089] S1. Take anhydrous ethanol as the low-boiling-point liquid;

[0090] S2. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component A (Ecoflex 00-50 prepolymer) was measured and mixed with 2.5 mL of a low-boiling liquid (anhydrous ethanol). The mixture was mechanically stirred at 1500 rpm at 18°C ​​and 0.1 MPa for 2 minutes to obtain a first mixture. In the first mixture, the volume ratio of the low-boiling liquid to the silicone rubber component A was 2.5:15.

[0091] S3. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component B (Ecoflex 00-50 prepolymer curing agent) was added to 2.5 mL of a low-boiling-point liquid (anhydrous ethanol) and mechanically stirred at 1500 rpm for 2 minutes at 18°C ​​and 0.1 MPa to obtain a second mixture; in the second mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber component B was 2.5:15.

[0092] S4. The first mixture and the second mixture were added to a beaker in a volume ratio of 1:1 and mechanically stirred at 1500 r / min for 5 min at 18 ° C and 0.1 MPa to obtain a composite slurry;

[0093] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.064 MPa and 18°C ​​for curing for 5 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a thickness of 5 mm.

[0094] Comparative Example 1

[0095] Comparative Example 1 is substantially the same as Example 3, except that:

[0096] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.044 MPa and 18°C ​​for curing for 5 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a thickness of 5 mm.

[0097] In this comparative example, since the low-pressure curing pressure of the composite slurry is too low, the low-boiling-point liquid evaporates, and a phase-change composite material cannot be formed, and a cable-free flexible actuator with a gradient distribution of the low-boiling-point liquid cannot be formed.

[0098] Comparative Example 2

[0099] Comparative Example 2 is substantially the same as Example 3, except that:

[0100] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment of absolute air pressure 0.064 MPa and 18°C ​​for curing for 3 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a low-boiling-point liquid gradient distribution with a thickness of 5 mm.

[0101] Comparative Example 3

[0102] Comparative Example 3 is substantially the same as Example 3, except that:

[0103] S5. The composite slurry was cast into a cylindrical mold (inner diameter 86 mm, thickness 10 mm), placed in an environment with an absolute air pressure of 0.064 MPa and 37°C for curing for 5 minutes, and then cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 hours to obtain a cable-free flexible actuator with a thickness of 5 mm.

[0104] Comparative Example 4

[0105] S1. Prepare anhydrous ethanol and deionized water in a volume ratio of 1:4 to a 20% ethanol aqueous solution to obtain a low-boiling-point liquid;

[0106] S2. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component A (Ecoflex 00-50 prepolymer) was added to 2.5 mL of a 20% by volume ethanol aqueous solution and mechanically stirred at 1500 rpm for 2 minutes at 18°C ​​and 0.1 MPa to obtain a first mixture; in the first mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber component A was 2.5:15;

[0107] S3. 15 mL of Ecoflex 00-50 platinum-catalyzed silicone rubber component B (Ecoflex 00-50 prepolymer curing agent) was added to 2.5 mL of a 20% volume fraction ethanol aqueous solution and mechanically stirred at 1500 rpm for 2 minutes at 18°C ​​and 0.1 MPa to obtain a second mixture; in the second mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber component B was 2.5:15;

[0108] S4. The first mixture and the second mixture were added to a beaker in a volume ratio of 1:1 and mechanically stirred at 1500 r / min for 5 min at 18 ° C and 0.1 MPa to obtain a composite slurry;

[0109] S5. The composite slurry was poured into a cylindrical mold (inner diameter 86 mm, thickness 10 mm) and directly cured at room temperature 18°C ​​and normal pressure 0.1 MPa for 5 h to obtain a cable-free flexible actuator with a thickness of 5 mm.

[0110] The low-boiling-point liquid contained in the sample obtained in this comparative example is uniformly dispersed in the silicone rubber in the form of droplets in the direction of gravity.

[0111] The present invention conducted a performance test on the samples finally prepared in each embodiment and each comparative example. The samples were made into specimens with a length of 40 mm, a width of 20 mm, and a thickness of 5 mm for bending test. The test environment was a radiation environment at 90°C, normal pressure, and 0.1 MPa (radiation power density 0.4 W / cm 2 ) under heating conditions, the bending deformation stabilized after heating for 7 minutes, and the average curvature was measured. The larger the average curvature, the greater the degree of bending deformation of the sample.

[0112] The formula for calculating the mean curvature is: The results are shown in Table 1.

[0113] Table 1

[0114]

[0115] In the present invention, the sample obtained in Example 3 is heated in a radiation environment at 90°C, normal pressure, and 0.1 MPa for 7 minutes, and the heating bending deformation is stabilized. After the average curvature is measured, the sample is cooled at room temperature to restore to its original shape, and then heated again in a radiation environment at 90°C, normal pressure, and 0.1 MPa for 7 minutes, and the heating bending deformation is stabilized. The average curvature is measured, and the results are shown in Table 2; after the sample obtained in Example 3 is heated for the second time and the average curvature is measured, the sample is cooled at room temperature again to restore to its original shape, and then heated for the third time in a radiation environment at 90°C, normal pressure, and 0.1 MPa for 7 minutes, and the heating bending deformation is stabilized. The average curvature is measured, and the results are shown in Table 2.

[0116] Table 2

[0117] Example 3 <![CDATA[Mean curvature (cm -1 )]]> Curvature recovery rate (%) Secondary heating 0.6608 98.03％ Three heating 0.6118 90.76％

[0118] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a cable-free flexible actuator with a gradient distribution of low-boiling-point liquid, characterized in that: The method comprises the following steps: (1) mixing a low-boiling-point liquid with a silicone rubber prepolymer to obtain a first mixture; (2) mixing the low boiling point liquid with the silicone rubber prepolymer curing agent to obtain a second mixture; (3) mixing the first mixture with the second mixture to obtain a composite slurry; (4) The composite slurry is poured into a mold and first cured for 5-10 min at a temperature of 15-25 °C and an absolute pressure of 0.064-0.090 MPa, and then cured at a temperature of 15-25 °C and normal pressure for 1-50 h to obtain a cable-free flexible actuator with a low-boiling-point liquid gradient distribution; The low-boiling-point liquid is an ethanol aqueous solution, wherein the volume fraction of ethanol in the ethanol aqueous solution is 15-35%; In the first mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber prepolymer is (16-25): 100; In the second mixture, the volume ratio of the low-boiling-point liquid to the silicone rubber prepolymer curing agent is (16-25): 100; The volume ratio of the first mixture to the second mixture is 100:(10~100).

2. The preparation method according to claim 1, wherein: The composite slurry is poured into a mold and first cured at a temperature of 15-22°C and an absolute air pressure of 0.064-0.076 MPa for 5-8 minutes, and then cured at a temperature of 15-25°C and normal pressure for 1-50 hours.

3. The preparation method according to claim 1, wherein: The normal pressure curing time is 4 to 50 hours.

4. The preparation method according to claim 1, wherein: The silicone rubber prepolymer is Ecoflex 00-50 prepolymer, Ecoflex 00-30 prepolymer, Dragon skin 30 prepolymer or Sylgard 184 prepolymer; The silicone rubber prepolymer curing agent is Ecoflex 00-50 prepolymer curing agent, Ecoflex 00-30 prepolymer curing agent, Dragon skin 30 prepolymer curing agent or Sylgard 184 prepolymer curing agent.

5. The preparation method according to claim 1, wherein: In step (1) and / or step (2), the mixing method is: stirring for 1 to 3 minutes at normal temperature and pressure, and the stirring speed is 1000 to 1500 r / min.

6. The preparation method according to claim 1, wherein: In step (3), the mixing method is: stirring at room temperature and pressure for 5 to 10 minutes, and the stirring speed is 1000 to 1500 r / min.

7. A cable-free flexible actuator with a gradient distribution of a low-boiling-point liquid prepared by the method according to any one of claims 1 to 6, characterized in that: The cable-free flexible actuator with gradient distribution of low-boiling-point liquid comprises silicone rubber and low-boiling-point liquid. The low-boiling-point liquid is gradiently dispersed in the silicone rubber in the form of droplets in the direction of gravity.

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