JP2007318960A - Integrated soft actuator with sensor function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an integrated soft actuator with sensor function which can be driven with low voltage, can stably be operated in air and vacuum without charging electroyte from outside, can easily be manufactured, has high responsiveness to an input signal from outside, and can detect displacement. <P>SOLUTION: The actuator is provided with an actuator 12 and a sensor 14 which have ion conduction layers 4 comprising ionic liquid and have non-volatility, flexibility, and insulation; and electrode layers 3 comprising ionic liquid and having non-volatility, flexibility, and conductivity. In the actuator 12, the ion conduction layer 4 is inserted between the two electrode layers 3, and a voltage signal is inputted between them. In the sensor 14, the ion conduction layer 4 is inserted between the two electrode layers 3, and the voltage signal is output from a part between them. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an integrated soft actuator with a sensor function that is displaced in response to an external input signal and detects the displacement.

  In recent years, attention has been focused on polymer actuators capable of soft biological movement in various fields such as medical care, welfare, robots, and entertainment industries. A polymer actuator refers to an actuator that is mainly composed of a polymer material and utilizes the deformation of the polymer material itself in response to some stimulus. Such a polymer actuator is disclosed in Non-Patent Document 1, for example.

  Currently, an ion conductive polymer film (ICPF) shown in FIG. 13 is known as one of polymer actuator materials that have been developed to near practical use. This polymer film is provided with electrodes 52a and 52b on both surfaces of the ion conductive polymer film 51, and is also called an ion conductive polymer metal composite (IPMC). Hereinafter, this is called an IPMC film (or ICPF).

  In the IPMC film, when a voltage is applied between the electrodes, ions in the polymer film move in the film thickness direction, and accordingly, the solvent in the resin moves in the film thickness direction. It has the property of bending when the surface is extended and the other surface is contracted. As for the response characteristics of this bending motion, the response speed is relatively fast (for example, 10 ms) and the deformation is large in low voltage driving (3 V or less). It is also known to be excellent in mechanical, thermal and chemical durability.

However, since the polymer actuator using the IPMC film utilizes the swelling and shrinkage phenomenon of the electric field responsive polymer film, it is necessary to always keep the electric field responsive polymer film in an aqueous solution or in a wet state.
In order to solve this problem, for example, Non-Patent Document 2 and Patent Document 1 have been proposed.

Non-Patent Document 2 discloses an actuator element shown in FIG. This actuator element is composed of three layers in which electrodes 63 are laminated on both surfaces of an electrolyte film 61 obtained by gelling an ionic liquid with a base polymer, and is bent by applying a potential difference between the electrodes 63. The electrode 63 is formed by molding a gel material (referred to as “bucky gel”) in which single-walled carbon nanotubes 62 are dispersed in an ionic liquid, with a base polymer.
The single-walled carbon nanotube 62 is a cylindrical substance formed by winding one surface of graphite, and has a diameter of about 1 nm and a length of several μm.

  As shown in FIG. 15, the “actuator element” of Patent Document 1 is a gel-like composition of carbon nanotubes, an ionic liquid, and a polymer on the surface of an ion conductive layer 71 made of a gel-like composition of an ionic liquid and a polymer. The electrode layer 72 made of is formed in an insulated state from each other, and can be bent and deformed by applying a potential difference between the electrodes 72.

Satoshi Azumi, “Polymer Actuator”, Journal of the Robotics Society of Japan, Vol. 21 No. 7, pp. 708-712, 2003 Satoshi Azumi, Takanori Fukushima, Takuzo Aida “Development of Printable Polymer Actuator Materials”, Future Materials, Vol. 5, No. 10

JP 2005-176428 A, “Actuator element”

The above-described IPMC film is an ion conductive polymer / metal joined body obtained by plating a noble metal on a fluorine-based ion exchange resin. This material can be used as an actuator that deforms when a voltage is applied, but moisture is necessary for the ion exchange resin to be driven. For this reason, it has been necessary to perform coating in order to prevent underwater operation and moisture evaporation.
In addition, for plating precious metals, it is necessary to use a complicated means called electroless plating.

On the other hand, the ionic liquid used in Non-Patent Document 2 and Patent Document 1 is also referred to as a normal temperature molten salt, and exhibits a molten state in a wide temperature range including normal temperature (room temperature), and the vapor pressure is so low that it can be ignored. There is a feature that can prevent the solvent from drying due to volatilization.
Therefore, the actuators disclosed in Non-Patent Document 2 and Patent Document 1 (hereinafter referred to as “Bucky Gel Actuator”) have an electrolyte (an ionic liquid) for canceling out the charge injected into the nanotubes previously contained in the film. In addition, since it is not necessary to replenish the electrolyte from the outside, it can be operated in the air.
Therefore, the bucky gel actuator has (1) aerial operability by integrating the non-volatile electrolyte and the electrode, (2) excellent formability to which the printing method can be applied, and (3) responsiveness to deform large and flexibly. It has excellent characteristics such as.

  However, the bucky gel actuator can be driven at a low voltage, but there is a problem that its displacement (for example, bending angle) cannot be detected.

  The present invention has been made to solve such problems. That is, the object of the present invention is that it can be driven at a low voltage, can be stably operated in the air and in a vacuum without replenishing the electrolyte from the outside, is extremely easy to manufacture, and is responsive to an input signal from the outside. An object of the present invention is to provide an integrated soft actuator with a sensor function that is high and can detect the displacement.

The present invention is based on the discovery that the actuator element disclosed in Patent Document 1 has a reverse operation characteristic in which a voltage is generated when it is deformed and can be used as a displacement sensor.
Based on this discovery, it became possible to realize an integrated soft actuator with a sensor function that integrated an actuator and a displacement sensor, and it became possible to control a biocompatible soft device.

That is, according to the present invention, a non-volatile, flexible and insulating ion conductive layer containing an ionic liquid;
Comprising an actuator unit and a sensor unit comprising a non-volatile, flexible and conductive electrode layer containing the ionic liquid;
The actuator unit is configured to sandwich an ion conductive layer between two electrode layers and input a voltage signal therebetween,
An integrated soft actuator with a sensor function is provided, wherein the sensor unit is configured to sandwich an ion conductive layer between two electrode layers and output a voltage signal therebetween.

  According to a preferred embodiment of the present invention, the two electrode layers constituting the actuator portion and the two electrode layers constituting the sensor portion are four electrode layers spaced apart from each other, and the same It is the parallel arrangement which pinches | interposes the different part of the ion conduction layer of this.

  According to another preferred embodiment of the present invention, the two electrode layers constituting the actuator part and the two electrode layers constituting the sensor part are sandwiched between two ion conductive layers. In addition, there are a total of three electrode layers sharing one sheet, and a stacked arrangement in which the same positions of the two ion conductive layers are sandwiched.

The ion conductive layer is a gel composition composed of an ionic liquid and a polymer,
The electrode layer is a gel composition composed of carbon nanotubes, an ionic liquid, and a polymer.

  According to the configuration of the present invention described above, the actuator unit is configured to sandwich the non-volatile ion conductive layer between the non-volatile electrode layers and input a voltage signal therebetween, so the electrolyte is replenished from the outside. It can operate stably in air and in vacuum.

  In addition, since the ion conductive layer and the electrode layer contain the ionic liquid and are flexible, the ion conductive layer and the electrode layer can be driven at a low voltage and can be highly responsive to an input signal from the outside.

  In addition, the actuator unit and the sensor unit are provided, and the sensor unit is also configured to sandwich the ion conductive layer between the two electrode layers and output a voltage signal therebetween. Can be directly detected by the sensor unit.

Furthermore, the actuator part and the sensor part can be formed by performing the electrode layer forming process and the conductive layer forming process simultaneously or sequentially, and both processes can be performed by coating, printing, extrusion, casting or injection. Since it can be produced, it is very easy to manufacture.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a first embodiment of an integrated soft actuator with a sensor function according to the present invention. In this figure, an integrated soft actuator 10 with a sensor function of the present invention (hereinafter simply referred to as “soft actuator”) includes an actuator unit 12 and a sensor unit 14.

  The actuator unit 12 includes two electrode layers 3 and one ion conductive layer 4, and the ion conductive layer 4 is sandwiched between the two electrode layers 3. In addition, a signal input line 13 is attached to each of the two electrode layers 3, and a voltage signal is input from the outside between them.

  The sensor unit 14 also includes two electrode layers 3 and one ion conductive layer 4, and the ion conductive layer 4 is sandwiched between the two electrode layers 3. In addition, a signal output line 15 is attached to each of the two electrode layers 3, and a voltage signal is output to the outside from between the signal output lines 15.

  The ion conductive layer 4 is a gel composition composed of an ionic liquid and a polymer, and is a thin film layer that contains the ionic liquid and is non-volatile, flexible, and insulating.

  The electrode layer 3 is a gel composition composed of carbon nanotubes, an ionic liquid, and a polymer, and is a thin film layer that contains the ionic liquid and is nonvolatile, flexible, and conductive.

FIG. 1 shows an example of parallel arrangement of soft actuators 10 of the present invention.
In this figure, two electrode layers 3 constituting the actuator section 12 and two electrode layers 3 constituting the sensor section 14 are four electrode layers 3 spaced apart from each other, and have the same ion conduction. Different parts of the layer 4 are sandwiched.
Note that the parallel arrangement is not limited to this example, and either one or both of the actuator unit 12 and the sensor unit 14 may be configured by a plurality of pairs of electrode layers 3.

FIG. 2 is a diagram showing a second embodiment of the soft actuator 10 of the present invention. This figure shows an example of the laminated arrangement of the soft actuators of the present invention.
In this figure, two electrode layers 3 constituting the actuator section 12 and two electrode layers 3 constituting the sensor section 14 share one sheet sandwiched between two ion conductive layers 4. It is a total of three electrode layers, and sandwiches the same position of the two ion conductive layers 4.

In this example, the signal line 16 attached to the intermediate electrode layer 3 is grounded in this example, and is configured to serve as a two-terminal pair for both the signal input line 13 and the signal output line 15. However, the signal line 16 may be replaced with two of the signal input line 13 and the signal output line 15.
The stacking arrangement is not limited to this example, and three or more ion conductive layers 4 and four or more electrode layers 3 are alternately stacked, and the actuator unit 12 and the sensor unit 14 are configured by a plurality of pairs of electrode layers 3. May be.

  Further, the present invention is not limited to the parallel arrangement or the stacked arrangement, and may be a structure in which both are combined. The shape, size, and orientation of the actuator unit 12 and the sensor unit 14 are the same in this example, but may be different.

FIG. 3 is a flowchart showing a method for manufacturing the soft actuator of the present invention.
As shown in this figure, the manufacturing method of the soft actuator of the present invention includes electrode layer precursor liquid preparation step S1, conductive layer precursor liquid preparation step S2, electrode layer formation step S3, and conductive layer formation step S4. .

In the electrode layer precursor liquid preparation step S1, an electrode layer precursor liquid 1 containing carbon nanotubes, an ionic liquid, a polymer and a solvent is prepared. When single-walled carbon nanotubes are mixed with an ionic liquid, the nanotubes are dispersed and the liquid is gelled to form a gel material. Therefore, it can be formed into an arbitrary shape by adding a polymer thereto.
Moreover, after adding the carbon nanotube, the ionic liquid, the polymer and the solvent and preparing the electrode layer precursor liquid 1 without the gelation process, it can be formed into an arbitrary shape.
In the conductive layer precursor liquid preparation step S2, a conductive layer precursor liquid 2 containing an ionic liquid, a polymer and a solvent is prepared. By adding a polymer to the ionic liquid, it can be formed into an arbitrary shape.

Ionic liquids, in the Examples below, ethyl methyl imidazolium tetrafluoroborate (EMIBF ₄₎ or butyl methylimidazolium tetrafluoroborate (BMIBF _4). The ionic liquid is preferably common to both the ion conductive layer 4 and the electrode layer 3.
The polymer is a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF (HFP)) (III) in Examples described later. The polymer should be common to both the ion conductive layer 4 and the electrode layer 3.
The carbon nanotube is a high-purity single-walled carbon nanotube (SWNT) in Examples described later.
In the examples described later, the solvent is 4-methylpentan-2-one (MP) and propylene carbonate (PC).

In the electrode layer forming step S3, the electrode layer precursor liquid 1 is formed in a thin film shape, and the solvent is removed to form the thin film electrode layer 3. This step S3 can be performed by coating, printing, extrusion, casting, or injection.
In the conductive layer forming step S4, the conductive layer precursor liquid 2 is formed into a thin film and the solvent is removed to form the thin film ion conductive layer 4. This step S4 can also be performed by coating, printing, extrusion, casting, or injection.

The electrode layer forming step S3 and the conductive layer forming step S4 are performed simultaneously or sequentially to form the actuator unit 12 and the sensor unit 14 with the ion conductive layer 4 sandwiched between the electrode layers 3.
The actuator unit 12 is configured to sandwich the ion conductive layer 4 between the two electrode layers 3 and input a voltage signal therebetween. A signal input line 13 is attached to each of the two electrode layers 3.
The sensor unit 14 is configured to sandwich the ion conductive layer 4 between the two electrode layers 3 and output a voltage signal therebetween. A signal output line 15 is attached to each of the two electrode layers 3.
Examples of the present invention will be described below.

A sensor film corresponding to the sensor portion 14 of the soft actuator of the present invention was produced by the following method.
The chemicals and materials used are as follows.
1 Ionic liquid (IL)
A. Ethylmethylimidazolium tetrafluoroborate (EMIBF ₄ )
B. Butylmethylimidazolium tetrafluoroborate (BMIBF ₄ )
2 Carbon nanotubes High purity single-walled carbon nanotubes (SWCNT)
Product name: HiPco (manufactured by Carbon Nanotechnology Inc.)
3 Polymer Polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF (HFP))
4 Solvent A: 4-Methylpentan-2-one (MP)
B: Propylene carbonate (PC)

(Production method)
1 Preparation of electrode layer precursor liquid (electrode casting liquid) The above-mentioned materials are mixed at a ratio of SWNT / PVDF (HFP) / IL / PC / MP = 3/8/12/24/300 (weight ratio) and subjected to ultrasonic cleaning. A dispersion was prepared by dispersing in the machine for 1 hour or longer. Thereafter, the liquid temperature was raised to 80 ° C. and stirred for 30 minutes or more.
As the ionic liquid (IL), both A (EMIBF ₄ ) and B (BMIBF ₄ ) were used.
2 Preparation of conductive layer precursor liquid (electrolyte casting liquid) The above materials are mixed at a ratio of IL / PVDF (HFP) / PC / MP = 12/20/24/300 (weight ratio), and the liquid temperature is raised to 80 ° C. , Stirred for 30 minutes or more.
3 Production of Sensor Film Casting was performed in the order of the electrode casting solution, the electrolyte casting solution, and the electrode casting solution, and the solvent was sufficiently dried to produce two types of sensor films in a three-layer form.

Hereinafter, a film using A (EMIBF ₄ ) as the ionic liquid (IL) is referred to as “sensor film A”, and a film using B (BMIBF ₄ ) as the ionic liquid (IL) is referred to as “sensor film B”.

  The following verification tests were performed on the sensor functions of the sensor film A and the sensor film B obtained in Example 1. The dimensions of the tested sensor films A and B were 20 mm long × 2.5 mm wide × 130 μm thick.

FIG. 4 is a configuration diagram of the test apparatus used. In this figure, 20 is a sensor film (A or B), 22 is a laser displacement meter, and 24 is a voltmeter with a built-in voltage amplification amplifier.
In this test, the lateral displacement due to the bending deformation of the sensor film 20 and the voltage generated between the electrodes on both sides of the film were measured.
The sensor film 20 was positioned vertically on both sides, positioned horizontally in the length direction, and fixed and held at one end. For deformation of the sensor film 20, the tip portion was manually moved in the horizontal direction, and a lateral displacement at a position of about 12 mm from the fixed portion was measured using a laser displacement meter 22.
The voltage generated between the electrode layers 3 of the sensor film 20 was amplified about 500 times with a voltage amplification amplifier and measured through a primary low-pass filter.

5 and 6 are test results of the sensor film A. FIG. 5 shows a relatively slow deformation (period of about 1 second and about 5 seconds), and FIG. This is the case of vibration. In each figure, the horizontal axis indicates time, the vertical axis indicates voltage change, and (B) indicates displacement.
5A and 5B, it can be seen that the voltage change agrees well with the displacement in the period of about 1 second, but the deviation between the voltage change and the displacement is large in the period of about 5 seconds.
Also, from FIGS. 6A and 6B, the voltage change and the displacement agree well with each other in the damping free vibration.

7 and 8 are test results of the sensor film B. FIG. 7 shows a case of relatively slow deformation (period of about 1 second and about 5 seconds), and FIG. This is the case of vibration. In each figure, the horizontal axis indicates time, the vertical axis indicates voltage change, and (B) indicates displacement.
7A and 7B, the voltage change agrees well with the displacement in both periods of about 1 second and about 5 seconds.
Also, from FIGS. 8A and 8B, the voltage change and the displacement agree well even with the damped free vibration.

The sensor film B using BMIBF ₄ is a film having slightly larger positive ions than the sensor film A using EMIBF ₄ .
Comparing FIGS. 5 and 6 with FIGS. 7 and 8, it can be confirmed that the generated voltage is larger in the sensor film B having a slightly larger positive ion.
That is, it can be seen that the sensor characteristics greatly change due to the difference in ions, as in the case of Na ⁺ and TEA ^{+ in} IPMC.

Moreover, from the test result of Example 2,
1 Sensor film A and sensor film B generate a potential approximately proportional to deformation, but the generated voltage is about 0.01 to 0.1 mV, which is lower than IPMC.
2 Sensor characteristics change due to ions in the membrane.
It was confirmed that it has a sensor function.

About the sensor function of the sensor film B obtained in Example 1, the verification test was performed again using the same apparatus as Example 1. The dimensions of the tested sensor film B were 20 mm long × 2.5 mm wide × 130 μm thick.
9, 10, and 11 show the test results. In each figure, the horizontal axis represents time, the vertical axis represents voltage change, and (B) represents displacement.

9 and 10 show the response results for a relatively fast operation with a period of 1 to 5 seconds. From these figures, it can be confirmed that for a relatively fast deformation with a period of 1 to 5 seconds, a potential substantially proportional to the displacement is generated.
FIG. 11 shows a response result when the actuator is stopped at a fixed position, and it can be confirmed that the output voltage slowly decays.
In comparison with Example 2, the behavior differs depending on the ion species in the polymer, and the sensor film A using EMIBF ₄ (in the case of small positive ions) has a behavior that attenuates in the sensor film B using BMIBF _4. You can see that it is faster.

FIG. 12 shows the reproducibility / quantitative test results performed at intervals of several days with the same settings as in Example 3.
12A, 12B, and 12C show the results of tests performed on different days. In this figure, the horizontal axis represents the deformation amount, and the vertical axis represents the output voltage, which is a test result when a relatively fast deformation is applied in 40 seconds. It can be seen that in the fast operation, the influence of the slow dynamics that attenuates is small, and the displacement and the potential response have a substantially proportional relationship.
In addition, from FIG. 12, it was confirmed that the same results were obtained in tests performed on different days, and that there was reproducibility.

  As described above, according to the apparatus and method of the present invention, the actuator unit 12 is configured to sandwich the nonvolatile ion conductive layer 4 between the nonvolatile electrode layers 3 and input a voltage signal therebetween. Therefore, it can operate stably in air and vacuum without replenishing the electrolyte from the outside.

  Moreover, since the ion conductive layer 4 and the electrode layer 3 contain an ionic liquid and are flexible, they can be driven at a low voltage and can be highly responsive to an input signal from the outside.

  Further, the actuator unit 12 and the sensor unit 14 are provided, and the sensor unit 14 is also configured to sandwich the ion conductive layer 4 between the two electrode layers 3 and output a voltage signal therebetween. The displacement of the ion conductive layer by the part can be detected by the sensor part.

Furthermore, by performing the electrode layer forming step S3 and the conductive layer forming step S4 simultaneously or sequentially, the actuator portion 12 and the sensor portion 14 can be formed, and both steps are applied, printed, extruded, cast or injected. Therefore, manufacturing is extremely easy.

In addition, by using the soft actuator 10 of the present invention, it is possible to operate in the air, and by using the feedback function by the sensor unit 14, it is possible to partially change the rigidity in a spatial manner, and more various tactile sensations. You can create a given device.
In addition, by using a similar mechanism as a sensor, it is possible to construct a sensor that can detect contact on the surface, such as skin (growth), and it is expected to be used as artificial skin for robots that come into contact with caregivers. it can. In addition, by utilizing the advantage that it can be driven at a low voltage, and constructing a miniaturized flagella propulsion mechanism, development of a device that moves inside the human body such as blood vessels can be expected.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.

It is a 1st embodiment figure of an integrated type soft actuator with a sensor function of the present invention. It is 2nd Embodiment figure of the soft actuator of this invention. It is a flowchart which shows the manufacturing method of the soft actuator of this invention. It is a block diagram of the used test apparatus. It is a test result of sensor film A. It is another test result of the sensor film A. It is a test result of sensor film B. It is another test result of the sensor film B. It is a response result to a relatively fast operation of the sensor film B. It is another response result with respect to the comparatively quick operation | movement of the sensor film B. FIG. This is a response result when the sensor film B is stopped at a certain position. It is a test result of reproducibility / quantitative property. 1 is a schematic diagram of an IPMC film of Non-Patent Document 1. FIG. 10 is a schematic diagram of an actuator element of Non-Patent Document 2. FIG. 2 is a configuration diagram of an “actuator element” in Patent Document 1. FIG.

Explanation of symbols

1 electrode layer precursor liquid, 2 conductive layer precursor liquid,
3 electrode layer, 4 ion conductive layer,
10 Integrated soft actuator with sensor function (soft actuator),
12 Actuator section, 13 Signal input line,
14 sensor units, 15 signal output lines, 16 signal lines,
20 sensor film (A or B),
22 Laser displacement meter,
24 Voltmeter with built-in voltage amplifier

Claims (4)

A non-volatile, flexible and insulating ion conductive layer containing an ionic liquid;
Comprising an actuator unit and a sensor unit comprising a non-volatile, flexible and conductive electrode layer containing the ionic liquid;
The actuator unit is configured to sandwich an ion conductive layer between two electrode layers and input a voltage signal therebetween,
An integrated soft actuator with a sensor function, wherein the sensor unit is configured to sandwich an ion conductive layer between two electrode layers and output a voltage signal therebetween.   The two electrode layers constituting the actuator part and the two electrode layers constituting the sensor part are four electrode layers spaced apart from each other, and sandwich different portions of the same ion conductive layer. The integrated soft actuator with sensor function according to claim 1, wherein the integrated soft actuator has a sensor function.   The two electrode layers constituting the actuator part and the two electrode layers constituting the sensor part are a total of three electrode layers sharing one sheet sandwiched between two ion conductive layers. The integrated soft actuator with a sensor function according to claim 1, wherein the integrated soft actuator has a sensor function and has a stacked arrangement that sandwiches the same position of two ion conductive layers. The ion conductive layer is a gel composition composed of an ionic liquid and a polymer,
The integrated soft actuator with a sensor function according to claim 1, wherein the electrode layer is a gel composition composed of carbon nanotubes, an ionic liquid, and a polymer.

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