CN114603873A - Preparation method of variable-rigidity soft driver - Google Patents

Abstract

The invention discloses a preparation method of a variable-stiffness software driver, which is based on polycaprolactone with variable-stiffness ability and ethanol-containing silica gel which can undergo volume expansion by heating as materials, and is formed by a mold to prepare a variable-stiffness layer and a variable-stiffness layer. For the driving layer, the variable stiffness layer and the driving layer are bonded up and down through a silicone adhesive to form a "variable stiffness-drive" double-layer structure, and a variable stiffness software driver with variable stiffness capability is prepared. Application scenarios such as "two-finger gripper", "four-finger gripper", and "artificial muscle" are realized. The variable stiffness software driver prepared by the invention has wide application range, large variable stiffness range, low preparation cost, large bending angle and high self-weight-to-weight ratio, and provides an effective new idea for designing and preparing a software driver with variable stiffness capability. .

Description

A kind of preparation method of variable stiffness software driver

technical field

The invention relates to the field of driver manufacturing, in particular to a preparation method of a variable stiffness soft body driver.

Background technique

Compared with traditional drives with complex mechanical structures, software drives have received great attention due to their high compliance and adaptability to complex environments. They can achieve complex and intelligent mechanical deformation through a simple structure, and have been used for Crawling robots, soft grippers, underwater robots, surgical robots and many other fields. This makes soft actuators ideal materials for designing and manufacturing soft robots and artificial muscles. However, due to the low stiffness properties of the constituent materials, it is difficult for current soft robots to perform some tasks requiring high loads, which greatly limits their wide application. In order to solve this problem, researchers at home and abroad have carried out a lot of research, mainly focusing on adding the function of variable stiffness to the software driver. At present, the main methods of achieving variable stiffness include particle plugging materials; fluid polymer composite materials; electricity and magnetic flow. shape memory materials; thermoplastic materials; liquid crystal elastomers; elastomer composites; phase change composites, etc. Although the above research has achieved certain results, there are still many deficiencies: 1. Most variable stiffness software drives use pneumatic drives, but the volume and mass of the pneumatic devices are too large; There are potential dangers; 3. The preparation process is complicated, the preparation cost is high, and it is not suitable for large-scale application. Therefore, how to prepare a variable stiffness software driver with a wide range of variable stiffness, low cost, simple preparation, low voltage and large deformation needs further research.

From the perspective of material synthesis and structure, the present invention prepares an electrothermally driven variable rigidity ethanol phase-change driven soft driver through mold forming. Polycaprolactone is used as the variable stiffness material, and anhydrous ethanol is used as the phase change material form. The "variable stiffness-driving" double-layer structure in which the "variable stiffness layer" and the "driving layer" are superimposed and does not interfere with each other is innovatively used to realize the variable stiffness. drive design. The preparation method involved in the present invention provides an effective new idea and a new method for improving the load and bending angle of the variable-stiffness software driver.

SUMMARY OF THE INVENTION

The invention prepares an electrothermally driven variable stiffness ethanol phase-change driven soft driver through mold forming, takes silica gel as the matrix, and innovatively adopts a "variable stiffness layer" and a "driving layer" in the form of superimposing each other without interfering with each other. Variable-stiffness drive design, the variable-stiffness layer is adhered to the drive layer to achieve independent electrothermal drive. Combined with the structural design, the variable stiffness drive of the software driver is realized. The invention seeks a method for preparing a variable-stiffness soft-body actuator with a large variable-stiffness range, low cost, simple preparation, low voltage and large deformation, and overcomes the shortcomings of low stiffness, high driving voltage and large driving equipment of traditional flexible actuators. In the fields of soft robots and artificial muscles, the design and development of soft actuators provides a new and effective method.

A preparation method of a variable-stiffness software driver. The technical solution uses polycaprolactone with variable-stiffness capability as a variable-stiffness layer, and an ethanol-containing silica gel that can expand in volume by heating as a driving layer. The layer structure design makes the driver bend at a large angle to the side of the variable stiffness layer when it is working, and controls the stiffness of the driver by regulating the power supply of the variable stiffness layer during operation. stiffness software driver;

The driving layer uses Ecoflex0050 silica gel as the driving layer matrix, anhydrous ethanol as the driving layer phase change material, polycaprolactone as the variable stiffness layer, and 0.15mm diameter silver wire as the electric heating wire. Uniform distribution in the medium, "variable stiffness-drive" double-layer structure can be independently controlled under 2V DC power supply, using the principle of polycaprolactone heating to change stiffness and ethanol heating and evaporation to expand the volume of silica gel, the variable stiffness and bending drive of the actuator are realized. The ability, combined with the structural design, has successfully realized the application scenarios such as "two-finger gripper", "four-finger gripper", and "artificial muscle";

The preparation steps of the variable stiffness soft body actuator are as follows:

1) Preparation of variable stiffness layer:

a) The composition of the original material of the variable stiffness layer: using polycaprolactone as the monomer, silver wire as the heating wire, and 2V DC voltage stabilized power supply as the control source;

b) Ingredients: Weigh the raw materials according to the ingredient ratio in step a), under the condition of 80°C water bath, first put the silver resistance wire into the mold, and add the polycaprolactone to the mold after heating it to a molten state, and then wait for After the mold is cooled, the variable stiffness layer is taken out. So far, the electrothermally driven variable stiffness layer is successfully prepared;

2) Preparation of driving layer:

c) The composition of the original material of the driving layer: take Ecoflex0050 silica gel as the matrix, 99% anhydrous ethanol as the phase change material, the silver wire as the heating wire, and the 2V DC regulated power supply as the control source;

d) Ingredients: At room temperature, the AB components of Ecoflex0050 silica gel were mixed at a mass ratio of 1:1, added with 20% volume fraction of anhydrous ethanol, stirred for 5 minutes, and then added to the mold with silver resistance wire, and cured at room temperature for 4 hours Take out, so far, the electrothermally driven driving layer has been successfully prepared;

3) Preparation of variable stiffness software driver:

e) The variable stiffness layer and the driving layer prepared in steps 1) and 2) are bonded up and down into a "variable stiffness-driving" double-layer structure with a silicone adhesive, and the upper and lower layers are controlled by an independent 2V DC power supply, So far, the preparation of the variable stiffness soft drive is completed.

Beneficial effects of the present invention:

1) The present invention uses polycaprolactone as the variable stiffness layer, Ecoflex0050 silica gel as the matrix, anhydrous ethanol as the phase-change material, silver resistance wire as the electric heating wire, and a 2V DC regulated power supply as the control source, prepared by a mold forming method. An electrothermally driven variable stiffness ethanol phase-change driven soft drive is presented. This type of drive is a layered form of upper and lower layers, which changes the low-stiffness operation mode of the traditional soft drive, and has a low-voltage drive and a wide range of variable stiffness. , the characteristics of large bending angle.

2) The present invention realizes the variable stiffness drive design in the form of superimposing the "variable stiffness layer" and the "driving layer" without interfering with each other, and realizes the low voltage and large variable stiffness range. The principle of volume expansion of silica gel by gasification realizes the variable stiffness and bending driving ability of the driver, and transforms the bionic design into bionic preparation. The preparation process is simple and efficient. After molding, the variable stiffness layer and the driving layer are closely combined. The deformation process is reversible and repeatable.

3) Combined with the structural design, the prepared electrothermally driven variable stiffness ethanol phase change driven software driver has successfully realized the application scenarios such as "two-finger gripper", "four-finger gripper", and "artificial muscle". The variable stiffness software driver prepared by the invention has a wide range of applications, a large variable stiffness range, low manufacturing cost, large bending angle, and high self-weight-to-weight ratio, which can be used for the application of small driver parts and large driver parts. application.

Description of drawings

1 is a schematic diagram of the preparation and assembly of a “variable stiffness layer” and a “driving layer” of the present invention into a variable stiffness software driver;

Fig. 2. is the storage modulus and the tensile strength change diagram of the driver after room temperature and heating of the present invention;

Fig. 3 is the working flow schematic diagram and the physical diagram of the variable stiffness software driver of the present invention;

Fig. 4 is a process diagram of grasping objects by "two-finger gripper" and "four-finger gripper" of the present invention;

Fig. 5 is a process diagram of the "artificial muscle" driving the skeleton model of the present invention.

Detailed ways

A preparation method of a variable stiffness soft body driver, the preparation steps are as follows:

1) Preparation of variable stiffness layer

a) Composition of the original material of the variable stiffness layer:

Polycaprolactone particles 2g, silver wire; glass transition temperature of polycaprolactone is 62°C; silver wire length 30cm, diameter 0.15mm;

b), ingredients:

According to the ingredients in a), the raw materials are taken; under the condition of a water bath at 80 °C, the polycaprolactone particles are first melted to form high elastic polycaprolactone G; then the high elastic polycaprolactone G is placed in a In the mold of the silver wire, it is cooled to a glass state at room temperature;

2) Preparation of driving layer

c) Composition of the original material of the driver layer:

Ecoflex0050 silica gel as the matrix, absolute ethanol as the phase change material, silver resistance wire as electric heating wire; Ecoflex0050 silica gel component A is 10g; Ecoflex0050 silica gel component B is 10g; the volume of absolute ethanol is 4ml; the length of the silver wire is 50cm and the diameter is 0.15 mm;

d) Ingredients:

First, the Ecoflex0050 silica gel AB components were mixed at a volume ratio of 1:1 and stirred at room temperature for 3 minutes to form mixture H; then absolute ethanol was added to mixture H and stirred for 3 minutes; finally, the mixture with absolute ethanol was poured into the mixture with silver Self-made 3D printed PLA mold of wire and cured at room temperature for 4h;

3): Preparation of Variable Stiffness Soft Actuator

e) The variable stiffness layer prepared in step 1) and the driving layer prepared in step 2) are adhered up and down with a silicone adhesive, and cured at room temperature for 1 h; a variable stiffness soft actuator is successfully prepared.

Example 1:

Fabrication of Variable Stiffness Soft Actuators by Molding:

Under the condition of 80 ℃ water bath, first put the silver resistance wire into the mold, and add the polycaprolactone to the mold after heating to a molten state. After the mold is cooled, take out the variable stiffness layer, and at room temperature, put Ecoflex0050 silica gel The AB components were mixed in a mass ratio of 1:1, added with 20% volume fraction of anhydrous ethanol, stirred for 3 minutes, then added to the mold with silver resistance wire, cured at room temperature for 4 hours, and then taken out. As shown in Figure 1, the prepared variable stiffness layer and the driving layer are bonded up and down with a silicone adhesive, so far the preparation of the variable stiffness software driver is completed. The upper and lower layers can be controlled by an independent 2V DC power supply.

Example 2:

Changes in storage modulus and tensile strength of soft-body actuators with variable stiffness at room temperature and after heating:

The storage modulus was tested by dynamic mechanical analysis on a DMA analyzer, increasing the temperature from 35 °C to 100 °C with a heating rate of 3 °C min-1. Due to the glass transition from the rubbery to the glassy state, the storage modulus was The amount increased significantly from ≈ 100 kPa at high temperature to more than 7.263 MPa at room temperature, and the storage modulus decreased by about 72.63 times from room temperature to 70 °C. The change of the tensile strength of the driver with temperature was tested. The tensile strength value at room temperature was 0.403MPa. With the increase of temperature, the tensile strength decreased. At 65℃, the soft driver has the lowest tensile strength, which is higher than room temperature. about 6.4 times lower.

Example 3:

Schematic diagram and physical map of the variable stiffness software driver workflow:

As shown in Figure 3, the variable stiffness soft actuator duty cycle consists of five steps: 1. Softening the actuator by heating the variable stiffness layer with conductive circuits; 2. Bending the actuator by applying current; 3. By cooling it with air Variable stiffness layer to harden the driver; 4. Can withstand heavy loads even after power off; 5. Restore the driver to its original state by heating the variable stiffness layer.

How the drive layer works: Ethanol is dispersed in the bubbles on the inner wall, and the remaining space is occupied by ethanol vapor and air. Liquid ethanol evaporates with temperature, creating internal pressure inside the bubbles, which causes the silicone elastomer matrix to expand. When ethanol passes through the liquid-gas phase transition, extreme volume changes occur and the silicone elastomer matrix swells significantly. As the partial pressure increases, the boiling temperature increases, so it is necessary to continue heating to a temperature slightly above 78.4 °C for further expansion until there is no liquid ethanol in the bubbles.

Example 4:

Process diagram of grasping objects by assembling multiple variable stiffness drivers into "two-finger gripper" and "four-finger gripper":

Under the condition of 80 ℃ water bath, first put the silver resistance wire into the mold, and add the polycaprolactone to the mold after heating to a molten state. After the mold is cooled, take out the variable stiffness layer, and at room temperature, put Ecoflex0050 silica gel The AB components were mixed in a mass ratio of 1:1, added with 20% volume fraction of anhydrous ethanol, stirred for 3 minutes, then added to the mold with silver resistance wire, cured at room temperature for 4 hours, and then taken out. layer, the prepared variable stiffness layer and driving layer are bonded up and down with silicone adhesive, so far the preparation of variable stiffness software driver is completed. The upper and lower layers can be controlled by independent 2V DC power supply. A "two-finger gripper" is assembled on the printing substrate, and four drivers are installed on the 3D printing substrate to assemble a "four-finger gripper". As shown in Figure 4, the fabricated soft gripper can successfully grasp different objects, and the "four-finger gripper" can grasp more stably.

Example 5:

Process diagram of a single variable stiffness actuator driving a bone model as an "artificial muscle":

Under the condition of 80 ℃ water bath, first put the silver resistance wire into the mold, and add the polycaprolactone to the mold after heating to a molten state. After the mold is cooled, take out the variable stiffness layer, and at room temperature, put Ecoflex0050 silica gel The AB components were mixed in a mass ratio of 1:1, added with 20% volume fraction of anhydrous ethanol, stirred for 3 minutes, then added to the mold with silver resistance wire, cured at room temperature for 4 hours, and then taken out. layer, the prepared variable stiffness layer and driving layer are bonded up and down with silicone adhesive, so far the preparation of variable stiffness software driver is completed. The upper and lower layers can be controlled by independent 2V DC power supply, as shown in Figure 5, The variable-stiffness soft actuator is attached to the elbow and, when powered, lifts the arm in a bicep-like action.

Claims (2)

1. A preparation method of a variable-stiffness software driver, characterized in that: this technical scheme uses polycaprolactone with variable-stiffness capability as the variable-stiffness layer, and the ethanol-containing silica gel that can undergo volume expansion when heated is used as the driving layer. The variable-stiffness-drive" double-layer structure design enables the driver to bend at a large angle to the variable-stiffness layer side during operation, and controls the stiffness of the driver by regulating the power supply of the variable-stiffness layer during operation. A low-voltage control system with a large bending angle is fabricated. and variable stiffness software driver with variable stiffness capability; The driving layer uses Ecoflex0050 silica gel as the driving layer matrix, anhydrous ethanol as the driving layer phase change material, polycaprolactone as the variable stiffness layer, and 0.15mm diameter silver wire as the electric heating wire. Uniform distribution in the medium, "variable stiffness-drive" double-layer structure can be independently controlled under 2V DC power supply, using the principle of polycaprolactone heating to change stiffness and ethanol heating and evaporation to expand the volume of silica gel, the variable stiffness and bending drive of the actuator are realized. The ability, combined with the structural design, has successfully realized the application scenarios such as "two-finger gripper", "four-finger gripper", and "artificial muscle". 2. the preparation method of a kind of variable stiffness software driver according to claim 1, is characterized in that: the preparation step of variable stiffness software driver is as follows: 1) Preparation of variable stiffness layer: a) The composition of the original material of the variable stiffness layer: using polycaprolactone as the monomer, silver wire as the heating wire, and 2V DC voltage stabilized power supply as the control source; b) Ingredients: Weigh the raw materials according to the ingredient ratio in step a), under the condition of 80°C water bath, first put the silver resistance wire into the mold, and add the polycaprolactone to the mold after heating it to a molten state, and then wait for After the mold is cooled, the variable stiffness layer is taken out. So far, the electrothermally driven variable stiffness layer is successfully prepared; 2) Preparation of driving layer: c) The composition of the original material of the driving layer: take Ecoflex0050 silica gel as the matrix, 99% anhydrous ethanol as the phase change material, the silver wire as the heating wire, and the 2V DC regulated power supply as the control source; d) Ingredients: At room temperature, the AB components of Ecoflex0050 silica gel were mixed at a mass ratio of 1:1, added with 20% volume fraction of anhydrous ethanol, stirred for 5 minutes, and then added to the mold with silver resistance wire, and cured at room temperature for 4 hours Take out, so far, the electrothermally driven driving layer has been successfully prepared; 3) Preparation of variable stiffness software driver: e) The variable stiffness layer and the driving layer prepared in steps 1) and 2) are bonded up and down into a "variable stiffness-driving" double-layer structure with a silicone adhesive, and the upper and lower layers are controlled by an independent 2V DC power supply, So far, the preparation of the variable stiffness soft drive is completed.

Images