CN110861119A - A kind of polydimethylsiloxane/liquid metal composite material and its preparation method and application - Google Patents

Abstract

The invention relates to a polydimethylsiloxane/liquid metal composite material and a preparation method and application thereof, belonging to the technical field of composite materials. The technical problems that the existing magnetorheological material is in a viscous state, does not bear load and cannot be applied to a magnetorheological variable stiffness mechanism are solved. The composite material consists of a core body and a shell; the shell is of a cylindrical structure and is made of polydimethylsiloxane; the core body is of a solid structure, the size of the outer contour of the core body is matched with that of the cavity of the shell, the core body can be just embedded into the cavity, and the shell is made of a magnetorheological material consisting of iron particles and gallium indium tin liquid metal. The composite material can adjust the stiffness range of the composite material by adjusting the percentage of iron particles and the magnetic field intensity, has a large adjustment range and a high response speed, requires only millisecond time, can rapidly realize reversible change, and is suitable for preparing magnetorheological stiffness joints.

Description

A kind of polydimethylsiloxane/liquid metal composite material and preparation method thereof application

technical field

The invention belongs to the technical field of composite materials, in particular to a polydimethylsiloxane/liquid metal composite material, a preparation method and application thereof, and in particular to the magnetorheological properties of the polydimethylsiloxane/liquid metal composite material. Applications in variable stiffness joints.

Background technique

With the increasing maturity of robotics technology, there are more and more human-centered robot applications such as wearable robots, rehabilitation robots, and prosthetics, and the physical human-machine interaction between users and the robot body also increases. Flexible robots have also become an important development direction of future robots. As an important part of robot motion, variable stiffness joints have also become a hot research field at home and abroad.

In order to improve the safety of human-computer interaction and improve the motion performance of flexible robots, there are various driving methods in the existing technology that can change the joint stiffness, such as mechanical variable stiffness mechanism, particle filling variable stiffness mechanism, layer interference variable stiffness mechanism, rope Drive flexible variable stiffness mechanism, low melting point polymer variable stiffness mechanism, shape memory alloy polymer variable stiffness mechanism, electrorheological variable stiffness mechanism and magnetorheological variable stiffness mechanism. The mechanical variable stiffness mechanism is simple in principle, easy to process, easy to control, and has a strong bearing capacity, but has a small adjustable range, large volume, and low efficiency; the particle-filled variable stiffness mechanism has a complicated design due to the interference of auxiliary equipment such as pumps and valves; The layer interference variable stiffness mechanism is compact in structure, light in weight, and has the disadvantages of small stiffness range and low load; the rope-driven flexible stiffness variable mechanism has complex control, limited space and flexibility; the liquid state of the low melting point polymer variable stiffness mechanism needs to be considered tightness. The solid-state to liquid state takes a long time; the stiffness range of the shape memory alloy polymer variable stiffness mechanism is small, and the impact on joint motion is small; the electrorheological variable stiffness mechanism is time-consuming to manufacture and the process is relatively strong; and the magnetorheological variable stiffness mechanism has a reversible change in stiffness. The speed is fast, the stiffness range is wide, and the external magnetic field can be precisely adjusted. It is a relatively ideal driving method that can change the stiffness of the joint.

Liquid metal refers to an amorphous metal that can be seen as a mixture of positive ionic fluid and free electron gas. In the prior art, the liquid metal is mainly composed of gallium indium tin alloys in different proportions, and the melting points of the gallium indium tin alloys in different proportions are different. Gallium indium tin liquid metal can be fused with magnetic particles to form magnetorheological materials, which can change the physical properties of materials under the action of a magnetic field, and have a wide range of research and applications in the fields of electronic circuits, flexible electronic devices and medicine. However, since the magnetorheological material is in a viscous state and cannot withstand loads, it cannot be used in a magnetorheological variable stiffness mechanism.

SUMMARY OF THE INVENTION

In view of this, in order to solve the technical problem that the existing magnetorheological material is in a viscous state and cannot withstand load, and cannot be applied to a magnetorheological variable stiffness mechanism, the present invention provides a polydimethylsiloxane/liquid metal Composite materials and preparation methods and applications thereof.

The technical solutions adopted by the present invention to solve the above technical problems are as follows.

The invention provides a polydimethylsiloxane/liquid metal composite material, which is composed of a core and a shell;

The outer shell has a cylindrical structure, and the material of the outer shell is polydimethylsiloxane (PDMS);

The core is a solid structure, the size of the outer contour matches the size of the cavity of the shell, and can be embedded in the cavity, and the shell is made of a magnetorheological material composed of iron particles and gallium indium tin liquid metal.

Preferably, the outer shell is a square cylinder, and the core body is a solid cube.

Preferably, the wall thickness of the casing is 1 mm.

Preferably, in the magnetorheological material, the mass percentage of iron particles is 10wt%-50wt%.

Preferably, the particle size of the iron particles is 50 nanometers to 100 micrometers.

Preferably, the composition of the gallium indium tin liquid metal is: 68.5 wt % of gallium, 21.5 wt % of indium and 10 wt % of tin.

The preparation method of the above-mentioned polydimethylsiloxane/liquid metal composite material, the steps are as follows:

Step 1: Weigh the iron particles and the gallium indium tin liquid metal according to the ratio, dissolve them in an ethanolic hydrochloric acid solution, stir at a speed of 800-1000rpm for 5-8min, and filter to obtain a magnetorheological material;

Step 2: Embed the magnetorheological material into the cavity of the shell to obtain the polydimethylsiloxane/liquid metal composite material.

Preferably, in the hydrochloric acid ethanol solution, the concentration of hydrochloric acid is 1 mol/L.

The present invention also provides the application of the above polydimethylsiloxane/liquid metal composite material in the preparation of magnetorheological stiffness joints.

Preferably, the polydimethylsiloxane/liquid metal composite material further includes two lids, the two lids are respectively covered on both ends of the outer casing and are in interference fit with the barrel opening of the outer casing, and the material of the lids is polydimethylsiloxane siloxane.

The inventive principle of the present invention is shown in Figure 1-3:

Let the Young's modulus, Poisson's ratio, width and thickness of the core be E ₁ , v ₁ , a and 2h ₁ respectively, and the Young's modulus, Poisson's ratio and thickness of the shell be E ₂ , v ₂ , b respectively and 2h ₂ , and the lengths of the core and the shell are the same, according to the mechanical formula, it can be obtained that the stiffness k of the composite material satisfies the following formula:

It can be seen from this formula that if the Young's modulus E ₁ of the core changes, the stiffness k of the composite material will change accordingly. After the gallium indium tin liquid metal and the iron particles are mixed, the hydrochloric acid ethanol solution is used as a solvent, and under the stirring action of a high-speed mixer, the gallium indium tin and the iron particles can be uniformly mixed and are in a viscous state to form a magnetorheological material. In the absence of a magnetic field, the magnetic particles (iron particles) in the magnetorheological material are arranged in disorder and have low stiffness; under the action of a magnetic field, the magnetic particles (iron particles) in the magnetorheological material can be chained along the direction of the magnetic field. It is arranged in the shape of a magneto-rheological material and has a large stiffness. After testing, the Young's modulus of the magnetorheological material can be expanded by 10,000 times under the action of a magnetic field. On the other hand, iron particles with different particle sizes have different solubility in gallium indium tin liquid metal, and the percentage of iron particles can affect the Young's modulus of magnetorheological materials. Therefore, by controlling the percentage of iron particles and the strength of the magnetic field, the Young's modulus of the magnetorheological material can be controlled, and then the stiffness of the composite material can be controlled to realize the magnetorheological variable stiffness mechanism. On the other hand, because the magnetorheological material itself is in a viscous state and cannot be used alone, the magnetorheological material is encapsulated in polydimethylsiloxane, which can withstand external loads and seal well magnetorheological materials.

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

The polydimethylsiloxane/liquid metal composite material of the present invention adopts magnetorheological material as the core body, and can adjust its own stiffness range by adjusting the percentage of iron particles and the magnetic field strength, and has a large adjustment range, fast response speed, and needs The time is only milliseconds, enabling rapid reversible changes.

The polydimethylsiloxane/liquid metal composite material of the present invention adopts polydimethylsiloxane as a shell, which can withstand external loads.

The polydimethylsiloxane/liquid metal composite material of the present invention can be used to prepare a magnetorheological variable stiffness joint, and the stiffness can be adjusted by realizing the Young's modulus of the cavity magnetorheological material, and the polydimethylsilicon After the two ends of the oxane/liquid metal composite material are covered with lids, the magnetorheological material can be sealed to prevent the liquid metal from flowing out.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

Fig. 1 is the structural representation of the polydimethylsiloxane/liquid metal composite material of the present invention;

In Figure 1, 1, the shell, 2, the core.

FIG. 2 is a schematic diagram showing that the polydimethylsiloxane/liquid metal composite material of the present invention can be applied in a magnetorheological stiffness joint.

In FIG. 3 , (a) and (b) are schematic diagrams of the arrangement of magnetic particles of the magnetorheological material of the present invention not under the action of a magnetic field and under the action of a magnetic field, respectively.

In Fig. 4, (a) and (b) are the effect diagrams of the magnetorheological material of the present invention.

In Figure 5, (a), (b), (c), (d), (e), (f), (g), (h) are the polydimethylsiloxanes of Examples 1-8, respectively Young's modulus curves of liquid metal composites under different magnetic field strengths.

Detailed ways

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with specific embodiments, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent requirements of the present invention.

As shown in Figure 1, the polydimethylsiloxane/liquid metal composite material of the present invention is composed of a shell 1 and a core 2;

The outer shell 1 is a cylindrical structure, and the material of the outer shell 1 is polydimethylsiloxane; the core body 2 is a solid structure, and the size of the outer contour is matched with the size of the cavity of the outer shell 1, and can be just embedded in the cavity, The material of the shell 1 is a magnetorheological material composed of iron particles and gallium indium tin liquid metal.

In the above technical solution, it is preferred that the outer shell 1 is a square cylinder, and the core body 2 is a solid cube; the sizes of the outer shell 1 and the core body 2 are not particularly limited, and can be set according to actual needs. The thinner the wall thickness of the outer shell 1, the better, usually is 1 mm.

In the above technical solution, the particle size of the iron particles is preferably 50 nanometers to 100 microns, and the mass percentage of the iron particles in the magnetorheological material is preferably 10 wt % to 50 wt %. There is mutual influence between the particle size of iron particles and the mass percentage of iron particles. As the particle size decreases, the upper limit of mass percentage becomes smaller and smaller. The particle size is 500 nanometers to 1000 nanometers, and the upper limit of the mass percentage is 30 wt %. Specifically, it is determined according to the maximum dissolution percentage of iron particles of different particle sizes in the liquid metal.

In the above technical solution, the composition of the gallium indium tin liquid metal is: 68.5% by weight of gallium, 21.5% by weight of indium and 10% by weight of tin.

The preparation method of the above-mentioned polydimethylsiloxane/liquid metal composite material, the steps are as follows:

Step 1: Weigh the iron particles and the gallium indium tin liquid metal according to the ratio, dissolve them in an ethanolic hydrochloric acid solution, stir at a speed of 800-1000rpm for 5-8min, and filter to obtain a magnetorheological material, the effect diagram is shown in Figure 4;

Step 2: Embed the magnetorheological material in the cavity of the shell 1 to obtain a polydimethylsiloxane/liquid metal composite material.

In the above technical scheme, the preferred stirring speed is 1000rpm, and the stirring time is 6min; the stirring equipment usually adopts a high-speed mixer.

In the above technical solution, the ethanolic hydrochloric acid solution can be obtained commercially, and the concentration of the hydrochloric acid is 1 mol/L.

The present invention also provides the application of the above-mentioned polydimethylsiloxane/liquid metal composite material in the preparation of magnetorheological variable stiffness joints. During the application, the polydimethylsiloxane/liquid metal composite material further includes two covers, The two covers can be respectively covered on both ends of the shell, and are in interference fit with the barrel opening of the shell, and the cover material is polydimethylsiloxane.

The present invention is further described below in conjunction with the examples.

Example 1

The polydimethylsiloxane/liquid metal composite material consists of a shell 1 and a core 2; the shell 1 is a rectangular tube (length, width and thickness are: 100mm, 20mm, 8mm respectively), and the material of the shell 1 is polyamide. Dimethylsiloxane; the core 2 is a solid cube (length, width and thickness are: 100mm, 16mm, 6mm respectively), the size of the outer contour is matched with the size of the cavity of the shell 1, and it can fit into the cavity. , the material of shell 1 is magnetorheological material, by dissolving iron particles (100 microns) and gallium indium tin liquid metal (gallium 68.5%wt, indium 21.5wt% and tin 10wt%) in hydrochloric acid ethanol solution, stirring at 1000rpm for 6min , filter, get;

In the magnetorheological material, the iron particles are respectively 10wt%, 20wt%, 30wt%, 40wt% and 50wt%.

Example 2

The polydimethylsiloxane/liquid metal composite material consists of a shell 1 and a core 2; the shell 1 is a rectangular tube (length, width and thickness are: 100mm, 20mm, 8mm respectively), and the material of the shell 1 is polyamide. Dimethylsiloxane; the core 2 is a solid cube (length, width and thickness are: 100mm, 16mm, 6mm respectively), the size of the outer contour is matched with the size of the cavity of the shell 1, and it can fit into the cavity. , the material of shell 1 is magnetorheological material, by dissolving iron particles (75 microns) and gallium indium tin liquid metal (gallium 68.5%wt, indium 21.5wt% and tin 10wt%) in hydrochloric acid ethanol solution, stirring at 1000rpm for 5min , filter, get;

In the magnetorheological material, the iron particles are respectively 10wt%, 20wt%, 30wt%, 40wt% and 50wt%.

Example 3

The polydimethylsiloxane/liquid metal composite material consists of a shell 1 and a core 2; the shell 1 is a rectangular tube (length, width and thickness are: 100mm, 20mm, 8mm respectively), and the material of the shell 1 is polyamide. Dimethylsiloxane; the core 2 is a solid cube (length, width and thickness are: 100mm, 16mm, 6mm respectively), the size of the outer contour is matched with the size of the cavity of the shell 1, and it can fit into the cavity. , the material of shell 1 is magnetorheological material, by dissolving iron particles (50 microns) and gallium indium tin liquid metal (gallium 68.5%wt, indium 21.5wt% and tin 10wt%) in hydrochloric acid ethanol solution, stirring at 1000rpm for 6min , filter, get;

In the magnetorheological material, the iron particles are respectively 10wt%, 20wt%, 30wt%, 40wt% and 50wt%.

Example 4

The polydimethylsiloxane/liquid metal composite material consists of a shell 1 and a core 2; the shell 1 is a rectangular tube (length, width and thickness are: 100mm, 20mm, 8mm respectively), and the material of the shell 1 is polyamide. Dimethylsiloxane; the core 2 is a solid cube (length, width and thickness are: 100mm, 16mm, 6mm respectively), the size of the outer contour is matched with the size of the cavity of the shell 1, and it can fit into the cavity. , the material of shell 1 is magnetorheological material, by dissolving iron particles (30 microns) and gallium indium tin liquid metal (gallium 68.5%wt, indium 21.5wt% and tin 10wt%) in hydrochloric acid ethanol solution, stirring at 900rpm for 7min , filter, get;

In the magnetorheological material, the iron particles are respectively 10wt%, 20wt%, 30wt%, 40wt% and 50wt%.

Example 5

The polydimethylsiloxane/liquid metal composite material consists of a shell 1 and a core 2; the shell 1 is a rectangular tube (length, width and thickness are: 100mm, 20mm, 8mm respectively), and the material of the shell 1 is polyamide. Dimethylsiloxane; the core 2 is a solid cube (length, width and thickness are: 100mm, 16mm, 6mm respectively), the size of the outer contour is matched with the size of the cavity of the shell 1, and it can fit into the cavity. , the material of shell 1 is magnetorheological material, by dissolving iron particles (1000 nanometers) and gallium indium tin liquid metal (gallium 68.5%wt, indium 21.5wt% and tin 10wt%) in hydrochloric acid ethanol solution, stirring at 800rpm for 8min , filter, get;

In the magnetorheological material, 8 iron particles are respectively used in 10wt%, 20wt%, and 30wt%.

Example 6

The polydimethylsiloxane/liquid metal composite material consists of a shell 1 and a core 2; the shell 1 is a rectangular tube (length, width and thickness are: 100mm, 20mm, 8mm respectively), and the material of the shell 1 is polyamide. Dimethylsiloxane; the core 2 is a solid cube (length, width and thickness are: 100mm, 16mm, 6mm respectively), the size of the outer contour is matched with the size of the cavity of the shell 1, and it can fit into the cavity. , the material of shell 1 is magnetorheological material, by dissolving iron particles (500 nanometers) and gallium indium tin liquid metal (gallium 68.5%wt, indium 21.5wt% and tin 10wt%) in hydrochloric acid ethanol solution, stirring at 800rpm for 7min , filter, get;

In the magnetorheological material, the iron particles are respectively 10wt%, 20wt%, and 30wt%.

Example 7

The polydimethylsiloxane/liquid metal composite material consists of a shell 1 and a core 2; the shell 1 is a rectangular tube (length, width and thickness are: 100mm, 20mm, 8mm respectively), and the material of the shell 1 is polyamide. Dimethylsiloxane; the core 2 is a solid cube (length, width and thickness are: 100mm, 16mm, 6mm respectively), the size of the outer contour is matched with the size of the cavity of the shell 1, and it can fit into the cavity. , the material of shell 1 is magnetorheological material, by dissolving iron particles (100 nanometers) and gallium indium tin liquid metal (gallium 68.5%wt, indium 21.5wt% and tin 10wt%) in hydrochloric acid ethanol solution, stirring at 1000rpm for 6min , filter, get;

In the magnetorheological material, the iron particles are respectively 10wt% and 20wt% of the iron particles.

Example 8

The polydimethylsiloxane/liquid metal composite material consists of a shell 1 and a core 2; the shell 1 is a rectangular tube (length, width and thickness are: 100mm, 20mm, 8mm respectively), and the material of the shell 1 is polyamide. Dimethylsiloxane; the core 2 is a solid cube (length, width and thickness are: 100mm, 16mm, 6mm respectively), the size of the outer contour is matched with the size of the cavity of the shell 1, and it can fit into the cavity. , the material of shell 1 is magnetorheological material, by dissolving iron particles (50 nanometers) and gallium indium tin liquid metal (gallium 68.5%wt, indium 21.5wt% and tin 10wt%) in hydrochloric acid ethanol solution, stirring at 1000rpm for 6min , filter, get;

In the magnetorheological material, the iron particles are respectively 10wt% and 20wt% of the iron particles.

The magnetic field strengths of 0T, 0.1T, 0.2T, 0.3T, 0.4T, 0.5T, 0.6T, and 0.7T were added to the magnetorheological materials used in Examples 1-8 respectively, and the Young's modes of the magnetorheological materials were detected. The detection equipment adopts a uniform magnetic field generator, and the detection results are shown in Figure 5. It can be seen from FIG. 5 that the magnetorheological material used in the polydimethylsiloxane/liquid metal composite material of the present invention can improve its physical properties under the action of a magnetic field. When the magnetic field strength reaches 0.4T, the magnetization of iron particles reaches saturation, and the Young's modulus can be expanded by a maximum of 10,000 times; iron particles with different particle sizes have different solubility in gallium indium tin liquid metal, and iron particles with different diameters The percentage of particles reaching saturation in the gallium indium tin liquid metal varies. Therefore, by adjusting the percentage of iron particles and the strength of the magnetic field, the stiffness range of the composite material can be adjusted, and the adjustment range is large, the response speed is fast, and the required time is only milliseconds, and the reversible change can be quickly realized.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. polydimethylsiloxane/liquid metal composite material, is characterized in that, is made up of core and shell; The shell is a cylindrical structure, and the material of the shell is polydimethylsiloxane; The core is a solid structure, the size of the outer contour matches the size of the cavity of the shell, and can be embedded in the cavity, and the shell is made of a magnetorheological material composed of iron particles and gallium indium tin liquid metal. 2 . The polydimethylsiloxane/liquid metal composite material according to claim 1 , wherein the outer shell is a square cylinder, and the core body is a solid cube. 3 . 3 . The polydimethylsiloxane/liquid metal composite material according to claim 1 , wherein the shell has a wall thickness of 1 mm. 4 . 4. The polydimethylsiloxane/liquid metal composite material according to claim 1, wherein, in the magnetorheological material, the mass percentage of iron particles is 10wt%-50wt%. 5 . The polydimethylsiloxane/liquid metal composite material according to claim 1 , wherein the iron particles have a particle size of 50 nanometers to 100 micrometers. 6 . 6 . The polydimethylsiloxane/liquid metal composite material according to claim 1 , wherein the composition of the gallium indium tin liquid metal is: gallium 68.5wt%, indium 21.5wt% and tin 10wt% . 7. the preparation method of the polydimethylsiloxane/liquid metal composite material described in any one of claim 1-6, is characterized in that, step is as follows: Step 1: Weigh the iron particles and the gallium indium tin liquid metal according to the ratio, dissolve them in an ethanolic hydrochloric acid solution, stir at a speed of 800-1000rpm for 5-8min, and filter to obtain a magnetorheological material; Step 2: Embed the magnetorheological material into the cavity of the shell to obtain the polydimethylsiloxane/liquid metal composite material. 8 . The method for preparing a polydimethylsiloxane/liquid metal composite material according to claim 7 , wherein, in the ethanolic hydrochloric acid solution, the concentration of hydrochloric acid is 1 mol/L. 9 . 9. The application of the polydimethylsiloxane/liquid metal composite material according to any one of claims 1 to 6 in the preparation of magnetorheological stiffness joints. 10. The application of the polydimethylsiloxane/liquid metal composite material according to claim 9 in the preparation of a magnetorheological stiffness joint, wherein the polydimethylsiloxane/liquid metal composite material It also includes two covers, the two covers are respectively covered on both ends of the shell and are in interference fit with the barrel mouth of the shell. The material of the covers is polydimethylsiloxane.

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