JP2698716B2 - Fast response gel actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed responsive gel actuator utilizing the electric field orientation of a dielectric of a general-purpose polymer material.

[0002]

2. Description of the Related Art Attempts to utilize physical property changes under a DC electric field have been around for a long time. For example, a patent by Winslow was already proposed in 1947. Proposals concerning so-called electrorheological fluids or electroviscoelasticity, which have been increasing recently, conform to this.
That is, in each case, the origin of the substance change is a structure formation induced by applying an electric field to a polymer or a particle having a property of being ionized by an ionic or electric field. The term “structural formation” as used herein refers to a macroscopic meaning, and as a result, changes from physical properties in a liquid state to those in a solid state. In each case, a structure in which charged molecules or particles are one-dimensionally oriented in the direction of the electric field is observed, and it is considered that such an oriented structure induces a change in physical properties.

[0003]

However, since the conventional electrorheological fluid described above is basically a fluid, it requires a highly confidential packing in processing and manufacturing, and is difficult to be a flexible machine or device. Had. For example, Japanese Patent Laid-Open Publication No.
Water / diluted solution of vinyl alcohol and polyacrylic acid
Freeze and thaw the methylsulfoxide mixed solution several times, and
The product is immersed in aqueous sodium hydroxide solution to polymer gel
Is formed as a mechanochemical actuator.
Although it has been proposed to use the polymer gel,
Since the drive is attenuated due to evaporation of the minute,
Highly confidential film as revealed in terms
It was necessary to pack in.

[0004] The present invention is directed to a system including a dielectric medium using an uncharged polymer material to solve the above-mentioned problems of the prior art. It is possible to change the shape of the gel-like polymer molded article only by molecular orientation in a close state, and to use mechanical deformation energy generated at the time of this shape change for actuation.

[0005]

In order to achieve the above object, a high-speed response gel actuator according to the present invention comprises a three-dimensional network comprising a dielectric polymer or a polymer having a substituent having a relatively strong dipole moment. This is a polymer gel in which a non-ionic dielectric solvent is added to the gel formed to form a gel, and when a DC electric field is applied, the dielectric molecules or substituents are oriented in the direction of the electric field. Structure changes anisotropically and its response speed is approximately milliseconds
It is on the order of 10 milliseconds .

[0006]

According to the configuration of the present invention described above, an anisotropic force is generated at an extremely high speed, and a significant work can be performed using the generated anisotropic force, so that it can be applied as an actuation. That is, the mechanism in which deformation or actuation occurs in the present invention is based on the orientation of the dielectric molecule by the electric field and the change in the conformation of the polymer induced by the orientation. This is the reason for the term “induced orientation”. Therefore, a higher-order structure such as anisotropy of the aggregate state of the polymer chains constituting the gel is one of the factors that determine the magnitude of actuation. Here, unlike the conventional electrorheological fluid, there is no extreme change in physical properties from liquid-like to solid-like. The structural change occurs continuously and linearly by the electric field, so that the generated force and deformation can be linearly controlled by the electric field. This also means that the action is constant, independent of the current, even when measured under conditions where current is passed through the system, and so is the fact. In effect, under conditions where no current flows (eg, 1
Being able to actuate the gel at (mA or less) means that energy can be thermally dissipated, suggesting that electrical energy can be converted to mechanical energy with high efficiency. As a result, it is possible to change the shape of the gelled polymer molded article only by molecular orientation in a state where the effective current is practically close to zero.
The mechanical deformation energy generated at the time of this shape change can be used for actuation.

Further, the gel of the present invention has a fixed shape,
It has the function of no or very low fluidity. Therefore, packing with high secrecy, which is required when a conventional electrorheological fluid is used, is not particularly necessary. This function has the advantage that it is easy to become a flexible machine or device.

[0008]

The present invention will be described more specifically with reference to the following examples. In addition, this invention is not limited to a following example.

As described above, the actuation mechanism of the present method is derived from the conformational change of the polymer chain, and the response of the action is extremely fast since the induction by the orientation of the medium is required to be triggered. The response speed depends on the inductivity of the gel and the strength of the medium, but is generally on the order of milliseconds to 10 milliseconds. The amount of displacement largely depends on the structure and physical properties of the gel derived from the degree of crosslinking inherent to the gel.

As a polymer material which can be actuated by the present method, polyvinyl alcohol, methylcellulose, hydroxymethylcellulose, polyacrylic acid, carboxymethylcellulose, casein, alginic acid, polyvinylpyrrolidone and the like can be mentioned. Further, a rubber-like material having a structure similar to this and containing no solvent but having sufficient elasticity, such as chloroprene, polyvinylidene chloride, nylon, and polyacrylamide, is also possible. In the case of a polymer or rubber having an oleyl group or the like in the side chain, actuation can be caused independently without requiring a medium. The medium that can be used is not particularly limited as long as it has a suitable permittivity that is compatible with the polymer.
For example, dimethyl sulfoxide, tetrahydrofuran, dimethylformamide, water, alcohol, acetone, and the like, and a mixed solvent thereof can be used.
However, those having too high a volatility are not preferable because they are inconvenient for maintaining the properties of the gel at a constant level and have a danger of ignition.

Since the gel actuator obtained by the present invention can be micromachined by microfabrication, it can be applied to manipulators and the like which are also used in microsurgeries requiring high precision, soft and fine action.

A specific embodiment will be described below. Example 1 A 10 wt% dimethylsulfoxide (DMSO) solution of polyvinyl alcohol (PVA) having an average degree of polymerization of 1700 and a degree of saponification of 99.0 mol% or more was spread on a petri dish so as to have a predetermined thickness, and the temperature was lowered at -20 ° C. Store refrigerated and PVA-D
An MSO gel was made. This gel was immersed in an aqueous glutaraldehyde solution, and reacted with the hydrochloric acid as a catalyst at 30 ° C. for a predetermined time in a state in which the glutaraldehyde had penetrated into the gel, thereby chemically crosslinking the gel. This gel was thoroughly washed with water and then boiled in water. Furthermore, what was desolvated in acetone and dried was immersed in DMSO to re-swell. This de-swelling-re-swelling operation was repeated to produce a PVA-DMSO gel from which water in the gel had been removed. The degree of swelling decreased with increasing degree of crosslinking.

The upper and lower surfaces of the PVA-DMSO gel sheet thus produced were sandwiched between electrode plates, and a voltage was applied. The change in the thickness of the gel was observed with a displacement sensor, and the effects of potential, current, etc. were measured. The dimensions, shape and measurement conditions of the gel are as follows. Actual dimensions of the gel: 25 mm long x 25 mm wide x 7 mm thick. Gel shape: flat, plate-like, with rubber-like elasticity. Applied voltage: 100 V to 1000 V, changed current value: 1 mA to 10 mA. When the applied voltage was less than 100 V, no deformation of the gel was observed. The amount of gel shrinkage in the direction of the electric field observed at a voltage of 100 V or higher is 1 μm to 26 μm.
At μm, it increased monotonically with increasing voltage. At a voltage of 1000 V and a current of 1 mA, the gel shrinkage in the direction of the electric field was 26 μm. Heat generation could not be observed under the condition of 3 mA or less. The temperature of the gel was measured with a thermocouple inserted into the gel.

As a result, the gel contracted instantaneously in the direction of the electric field by application of the electric field and expanded in the direction perpendicular to the direction of the gel, showed a deformation behavior in a different direction due to the electric field, and no heat generation was observed in this process.

When a small amount of ionic species was added to this gel and an electric current was applied, Joule heat was generated and the temperature of the gel increased. In this case, the gel swelled isotropically, and the above-described anisotropic displacement behavior could not be observed.

This suggests that the above-described anisotropic displacement behavior is not due to thermal inducement but to the dipole orientation due to the electric field. The action induced by the electric field was dependent on the electric field strength, but not on the current.

In the above case, the electric field causing displacement is 40 V /
cm · cm ² or more. The stress generated by the application of the electric field reached the maximum value in the range of milliseconds to ten milliseconds, and the value also changed almost in proportion to the electric field. The amount of displacement is as small as about 1% of the thickness of the gel, which depends on the chemical structure and network structure of the gel, and the orientation structure of molecules, and can be further increased by modifying them. However,
Even with this degree of displacement, its high-speed response and the fact that the displacement can be controlled by an electric field can be applied to a microactuator by a method such as integration.

As described above, according to the present embodiment, when viewed as a gel actuator, a speedup of about 1000 times compared with the conventional driving method can be achieved.

[0019]

As described above, the present invention utilizes the fact that the application of a DC electric field causes the dielectric molecules or substituents to be oriented in the direction of the electric field, and the gel structure to be changed anisotropically. Then, the shape of the gel-like polymer molded body can be changed only by the molecular orientation in a state where the effective current is practically close to zero (that is, while minimizing the heat generation). The resulting mechanical deformation energy can be effectively applied to actuation. Ma
In addition, when viewed as a gel actuator, the conventional driving method
About 1000 times as fast as the above.

The gel of the present invention has a fixed shape,
Since it exhibits the function of no fluidity or extremely low fluidity, packing with high confidentiality, which is required when a conventional electrorheological fluid is used, is not particularly necessary.
This feature has the advantage of being easy to incorporate into flexible machines and devices.

Claims (1)

(57) [Claims] 1. A polymer comprising a dielectric polymer or a polymer having a substituent having a relatively strong dipole moment.
This is a polymer gel formed by adding a nonionic dielectric solvent to a gel formed with a three-dimensional network structure, and the dielectric molecules or substituents are oriented in the direction of the electric field by applying a DC electric field. then, the structure of the gel is changed anisotropically, the response
A high response gel actuator, characterized in that the response speed is on the order of milliseconds to 10 milliseconds .