JP5858010B2 - Multilayer polymer actuator and method for manufacturing the same - Google Patents

Description

  The present invention relates to a polymer actuator that bends by an external stimulus and a manufacturing method thereof, and more particularly, a laminated polymer actuator that performs a large bending operation at a low voltage of several volts or less by laminating a polymer film on a substrate, and It relates to the manufacturing method.

  A polymer actuator using a deformation of a polymer film or fiber by external stimulation is disclosed in the following Patent Documents 1 to 3 by Hidenori Okusaki and others of the inventors of the present invention. In the following Patent Documents 1 to 3, a method is disclosed in which a polymer film or fiber is used, and a PEDOT / PSS polymer film or fiber is stretched or bent in a gas by adsorption / desorption of water molecules by electrical stimulation. Yes.

  The stretch rate of the polymer film or fiber disclosed in these patents is approximately 1.5% to 2% from FIG. 3 or FIG. 4 of Patent Document 1 or FIG. 4 and FIG. 5 of Patent Document 2. is there. On the other hand, the polymer film disclosed in Patent Document 3 exhibits a stretch rate of 4% or more at maximum. However, in order to realize an expansion / contraction ratio of 4% or more, the polymer film must be provided in an environment in which humidity and temperature are adjusted. Therefore, there is a problem that the operation of the polymer actuator is not stable depending on the environment (atmosphere) conditions in which the polymer film is provided. The polymer actuators disclosed in these patent documents are so-called direct acting polymer actuators that operate when the polymer film itself is deformed. In the case of such a direct acting polymer actuator, the mechanical strength is the strength of the polymer film itself. Therefore, there is a problem that it is extremely difficult to realize a large mechanical strength.

  On the other hand, as a bending type actuator exhibiting a bending behavior, there is a piezoelectric actuator using a piezoelectric element as shown in Patent Document 4 below, for example. Piezoelectric actuators are actuators that use the properties of piezoelectric materials that generate distortion when an electric field is applied. For example, they are composed of piezoelectric ceramics typified by lead zirconate titanate and lead titanate. Piezoelectric elements are used.

  However, the piezoelectric actuator requires a high voltage with a driving power of 100 V or more, and on the other hand, there is a problem that the displacement is as small as 10 μm or less. In addition, since the laminate of the piezoelectric ceramic layer and the internal electrode layer is used, there is a problem that the actuator is enlarged.

Japanese Patent No. 3131180 Japanese Patent No. 312773 International Publication No. 2008-1114810 Pamphlet JP 2003-338643 A

  As described above, in the polymer actuator, the direct acting polymer actuator operates when the polymer film itself constituting the actuator is deformed. Therefore, the mechanical strength of the direct-acting polymer actuator becomes the strength of the polymer film itself, and it is extremely difficult to realize a large mechanical strength. In addition, a bending type actuator using a piezoelectric element has a problem that the amount of bending displacement is extremely small although a high driving voltage is required. There is also a problem that the actuator becomes larger.

  Accordingly, an object of the present invention is to provide a laminated polymer actuator that is much smaller than a conventional bending actuator and that realizes a bending displacement equivalent to or higher than that of a conventional bending actuator. It is another object of the present invention to provide a laminated polymer actuator that has a remarkably large mechanical strength as compared with a direct acting actuator because power consumption required for bending is remarkably smaller than that of a conventional actuator.

The present invention relates to a laminated polymer actuator in which a re-dissolved polymer thick film that expands and contracts by an external stimulus is laminated on a substrate, and includes a surface active agent on the surface of the substrate that has been subjected to plasma ion treatment. The dissolved polymer thick film is formed in close contact with a film thickness of 1 μm or more.
This is because the addition of the surfactant improves the wettability of the conductive polymer solution. It is possible to use dodecylbenzenesulfonic acid as the surfactant.

  A metal electrode pattern film is formed on the opposite surface (back surface) of the substrate on which the re-dissolved polymer thick film is formed and / or on the surface on which the re-dissolved polymer thick film is formed. And

  The substrate surface is treated with plasma ions, a conductive polymer solution containing a surfactant is applied to the plasma ion-treated substrate surface, and a conductive polymer thick film is formed on the substrate.

  It is preferable to apply the conductive polymer solution on the substrate surface by a bar coating method. Moreover, it is preferable to apply the conductive polymer solution on the substrate surface by a bar coating method with a wet film thickness of 100 μm or more.

  The conductive polymer solution is preferably a poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonic acid) solution. Moreover, it is preferable that ethylene glycol is added in the range of 1% to 20% to the poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonic acid) solution. This is because the addition of ethylene glycol improves conductivity.

  According to the present invention, it is possible to provide a laminated polymer actuator that is much smaller than a conventional bending actuator and realizes a bending displacement equal to or higher than that of a conventional bending actuator. In addition, the power consumption required for bending is remarkably smaller than that of a conventional bending type actuator, and there is a specific effect of having an extremely large mechanical strength compared to a direct acting type actuator.

The flowchart which showed the preparation process of a lamination type polymer actuator. Structural formula of PEDOT and PSS. The figure which showed one Example of the laminated type polymer actuator. The figure which showed the mechanism of the electric contraction of a polymer (PEDOT / PSS) film | membrane. The figure which showed the result of the bar coat by the polymer (PEDOT / PSS) solution from which a density | concentration differs. The graph which showed the sheet resistance of the polymer (PEDOT / PSS) film | membrane with respect to EG density | concentration. The graph which showed the sheet resistance of the polymer (PEDOT / PSS) film | membrane with respect to DBS density | concentration. The graph which showed the relationship between a wet film thickness and a dry film thickness. The graph which showed the sheet resistance with respect to the dry film thickness of a polymer (PEDOT / PSS) film | membrane. The figure which showed the other Example of the lamination type polymer actuator. Graph showing current characteristics and bending behavior of laminated polymer actuator. The figure which showed the lamination type polymer actuator model.

  The present invention has been found, in terms of the principle, to provide a polymer actuator that can be bent repeatedly and stably even at a low voltage by forming a polymer film on a substrate.

  Here, the polymer means a neutral polymer, a polymer electrolyte, or a conductive polymer. The neutral polymer is at least one selected from cellulose, cellophane, nylon, polyvinyl alcohol, vinylon, polyoxymethylene, polyethylene glycol, polypropylene glycol, polyvinyl pyrrolidone, polyvinyl phenol, poly-2-hydroxyethyl methacrylate, and derivatives thereof. One of them.

  Examples of the polymer electrolyte include polycarboxylic acids such as polyacrylic acid and polymethacrylic acid, polysulfonic acids such as polystyrene sulfonic acid, poly-2-acrylamide-2-methylpropane sulfonic acid and Nafion, polyamines such as polyallylamine and polydimethylpropylacrylamide. And at least one selected from quaternized salts thereof and derivatives thereof.

  Conductive polymers include polythiophene, polypyrrole, polyaniline, polyacetylene, polydiacetylene, polyphenylene, polyfuran, polyselenophene, polytellurophene, polyisothianaphthene, polyphenylene sulfide, polyphenylene vinylene, polythienylene vinylene, polynaphthalene, poly And at least one selected from anthracene, polypyrene, polyazulene, polyfluorene, polypyridine, polyquinoline, polyquinoxaline, polyethylenedioxythiophene, and derivatives thereof.

  The polymer film is made of conductive polymer, cast method, bar coat method, spin coat method, spray method, electrolytic polymerization method, chemical oxidative polymerization method, melt spinning method, wet spinning method, solid phase extrusion method, electrospinning. It can be produced by applying at least one method selected from the methods.

  In order to increase the hygroscopicity and electrical conductivity of these polymers, it is preferable to dope a dopant. Examples of the dopant include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, iodine, bromine, arsenic fluoride, perchloric acid, tetrafluoroboric acid, hexafluorophosphoric acid, alkylbenzenesulfonic acid, alkylsulfonic acid, perfluorosulfonic acid, Polystyrene sulfonic acid, trifluoromethane sulfonic acid, trifluoromethane sulfonic imide, oxalic acid, acetic acid, maleic acid, phthalic acid, polyacrylic acid, polymethacrylic acid and their derivatives, carbon black, carbon fiber, carbon nanotube, ethylene glycol, Examples thereof include at least one selected from carbon-based additives such as fullerene and metals such as iron, copper, gold, and silver. Among them, a cast film of poly (3,4-ethylenedioxythiophene) doped with poly (4-styrenesulfonic acid), which is excellent in high electrical conductivity, stability, and reproducibility, is preferable.

  Molecular adsorption / desorption of polymer film by external stimulation includes nichrome wire, torch, burner, infrared irradiation, laser irradiation, heating by microwave irradiation, decompression by vacuum pump or aspirator, DC wave, AC wave, triangular wave, rectangular wave And at least one selected from joule heating by applying a voltage such as a pulse wave. Among these, a DC voltage that is simple and excellent in controllability is preferable.

  The substrates include polyethylene terephthalate, polyethylene naphthalate, nylon, polycarbonate, polyethylene, polypropylene, polyisobutylene, polyisoprene, polybutadiene, polybutene, polypentene, polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinyl fluoride. Vinylidene chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyacrylonitrile, polyvinyl acetate, polyvinyl formal, polystyrene, polyethylene oxide, polyoxymethylene, polystyrene sulfonic acid, polyimide, polyacrylic acid, polymethacrylic acid, polyacrylic acid Stearyl, polystearyl methacrylate, polybutyl acrylate, polybutyl methacrylate, poly Methyl crylate, polymethyl methacrylate, polyacrylamide, polyacrylamide methylpropane sulfonic acid, polyisopropylacrylamide, aromatic polyamide, polydimethylaminopropyl acrylamide, polytrimethylammonium propylacrylamide, polyhydroxy acrylate, polyhydroxy methacrylate, Nafion, Flemion, polyether ether ketone, polyphenylene sulfide, polysulfone, polylactic acid, polyglutamic acid, polycaprolactone, polybutylene succinate, polyethylene succinate, polyvinyl alcohol, polyaspartic acid, starch, cellulose, nitrocellulose, triacetylcellulose, chitosan, Polyhydroxymethyl cellulose, polyhydroxy ester Le cellulose, phenolic resin, silicone rubber, a melamine resin, at least one can be cited selected from epoxy resins and the like.

  FIG. 1 is a flowchart showing a production process of the laminated polymer actuator of the present invention. First, a high concentration polymer (PEDOT / PSS) solution is prepared (step S1). The high-concentration polymer (PEDOT / PSS) solution is obtained by extracting a solid component by freeze-drying the polymer (PEDOT / PSS) solution in a vacuum (step S2), and then lyophilizing the polymer (PEDOT / PSS) solid. It is redissolved in water and adjusted to a predetermined concentration (step S3).

  Separately, a substrate to which a polymer (PEDOT / PSS) solution is applied is prepared (step S1 '). The substrate is manufactured by subjecting the substrate surface to a hydrophilic treatment (step S2 '). For the hydrophilic treatment, a method of irradiating the substrate surface with plasma ions is used. By subjecting the substrate surface to a hydrophilic treatment, a polymer (PEDOT / PSS) film having a uniform film thickness can be obtained.

  The substrate production (step S1 ′) is preferably processed separately from the preparation (step S1 to step S3) of the polymer (PEDOT / PSS) solution, but the PEDOT / PSS solution is lyophilized. You may process in parallel with (step S2).

  Next, a high-concentration re-dissolved polymer (PEDOT / PSS) solution is laminated on the surface of the substrate subjected to the hydrophilic treatment by the bar coating method (step S4), and the polymer (PEDOT / PSS) film is formed on the substrate. A laminated composite element having a two-layer structure is manufactured. Next, this is cut out with a laser as an actuator of a specific size (step S5). Gold (Au) is sputtered on the substrate back side or both ends of the cut out actuator to produce an electrode pattern (step S6), and a laminated polymer actuator is produced (step S7).

  Hereinafter, examples will be described in detail. In the following examples, poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonic acid) (hereinafter, PEDOT / PSS) was used as the material of the polymer film. It is not limited to. In this embodiment, a polymer film (thickness of a certain thickness or more) is used almost synonymously with the polymer film, but basically it is formed on the substrate. One is called a polymer film, and one that is not laminated on a substrate is called a polymer film. The structure of PEDOT / PSS used in this example is shown in FIG. 2A is a structural formula of PEDOT, and FIG. 2B is a structural formula of PSS.

[Production of polymer film by casting method]
3 wt% of ethylene glycol (hereinafter referred to as EG) was added to a 1 wt% PEDOT / PSS solution, and the mixture was stirred with a magnetic stirrer until uniformly mixed. The uniformly mixed solution was pipetted and gently transferred to a Teflon (registered trademark) petri dish so as not to generate bubbles. In order to evaporate the water which is the solvent of PEDOT / PSS and the added EG, drying and heat treatment were performed to produce a polymer (PEDOT / PSS) cast film.

  More specifically, drying was performed at 60 ° C. for 6 hours using a drying oven, and then heat treatment was performed at 160 ° C. for 1 hour in a vacuum using a vacuum oven. Note that the electrical conductivity can be increased from several Siemens (S) / cm to 100 S / cm or more by adding EG.

[Manufacture of laminated polymer actuator by casting method]
FIG. 3 is a view showing an example of the laminated polymer actuator. The laminated polymer actuator 1 was produced by laminating a polymer (PEDOT / PSS) film 11 and a substrate 12 produced by the casting method with an adhesive.

  As the substrate 12, a polyethylene terephthalate (PET) film having a thickness of 100 μm was used. The laminated polymer actuator 1 produced in this example has a two-layer structure in which a PET film (substrate 12) and a polymer (PEDOT / PSS) film 11 (film thickness 14 μm) are bonded together with an adhesive for plastics. It was confirmed that the polymer (PEDOT / PSS) film 11 and the substrate 12 of the multilayer polymer actuator 1 produced in this manner were firmly adhered and did not easily peel off.

[Confirmation of bending motion]
FIG. 4 is a diagram schematically showing the volume variation due to voltage application / cutting of the polymer (PEDOT / PSS) film 11 produced by the casting method. The polymer (PEDOT / PSS) film 11 produced by the casting method contracts and expands when a voltage is applied and cut. That is, the polymer (PEDOT / PSS) film 11 is desorbed and contracted by water molecules 7 existing inside the polymer (PEDOT / PSS) film 11 by Joule heat generated by application of voltage.

  On the other hand, by turning off the voltage, the PSS 6 re-adsorbs water molecules 7 present in the atmosphere. As a result, the polymer (PEDOT / PSS) film 11 extends to the original length. Using the characteristics of the polymer (PEDOT / PSS) film 11 as described above, the bending operation of the multilayer polymer actuator 1 manufactured by the above-described method was verified.

  First, each surface of the upper end of the multilayer polymer actuator 1 is sandwiched between clips having metal electrodes having positive and negative polarities, and a current is applied to the multilayer polymer actuator 1 by applying a voltage to a wiring connected to the metal electrode. Washed away. Then, the displacement of the end of the multilayer polymer actuator 1 at that time was read with a laser displacement meter, and the bending operation was confirmed. As a result, it was confirmed that the multilayer polymer actuator 1 exhibited a bending motion by applying a voltage of several volts.

  However, it has been found that the displacement amount of the bending operation of the multilayer polymer actuator 1 produced by the method of laminating with the above-described adhesive decreases due to repeated voltage response. This is because the polymer (PEDOT / PSS) film 11 of the multilayer polymer actuator 1 gradually shifts from the substrate 12 due to shrinkage. Therefore, it has been found that the adhesion of the polymer (PEDOT / PSS) film 11 and the substrate 12 needs to be improved for the production of the multilayer polymer actuator 1 that operates more stably.

  Therefore, the application of a polymer (PEDOT / PSS) solution directly to a plastic substrate (substrate thickness: 100 μm) by spin coating and bar coating without using an adhesive was investigated.

  A uniform polymer (PEDOT / PSS) film of nanometer order could be obtained on the substrate by spin coating. However, the laminated polymer actuator produced by this method did not show bending motion. This is because the nanometer-order polymer (PEDOT / PSS) film formed on the substrate does not generate enough stress to bend the substrate having a thickness of 100 μm. Even with the spin coating method, a plastic substrate that exhibits a bending action can be produced by thinning the plastic substrate, but on the other hand, the mechanical properties and operability of the multilayer polymer actuator are degraded. Therefore, the production of a multilayer polymer actuator using the bar coat method, which can form a thicker film than the spin coat method, was examined.

  In order to produce a polymer (PEDOT / PSS) film having a thickness of micrometer order, a polymer (PEDOT) is formed on a PET substrate by a bar coating method so that a wet film thickness (hereinafter referred to as a wet film thickness) becomes 100 μm. / PSS) solution was applied. In order to increase the electrical conductivity, 3 wt% EG was added to the polymer (PEDOT / PSS) solution in the same manner as in Example 1.

  In addition, in order to perform bar coating of a uniform polymer (PEDOT / PSS) solution, conditions for performing plasma ion treatment on the substrate in advance using plasma ion bombardment were examined. This is because the plasma ion treatment hydrophilizes the substrate surface and improves the adhesion between the substrate and the polymer (PEDOT / PSS) film. Furthermore, addition of dodecylbenzenesulfonic acid (hereinafter referred to as DBS), which is a surfactant, was also investigated in a polymer (PEDOT / PSS) solution to be bar-coated. This is because DBS can improve the wettability of the polymer (PEDOT / PSS) solution.

  The study conditions are summarized in Table 1. Although a polymer (PEDOT / PSS) thick film could be formed, a completely uniform polymer (PEDOT / PSS) film could not be formed on the substrate under any conditions.

[Production of polymer (PEDOT / PSS) film by bar coating method 2]
The reason why a uniform polymer (PEDOT / PSS) film is not formed on the entire substrate is that the concentration of the polymer (PEDOT / PSS) solution is as low as 1 wt%, and therefore the viscosity is insufficient to adhere to the substrate. I thought it was the cause. Therefore, the conditions for forming a uniform polymer (PEDOT / PSS) thick film of 1 μm or more on the substrate were examined.

  In order to make the substrate surface hydrophilic, plasma ion treatment for 2 minutes was performed by hard ion bombardment capable of plastic ion etching. In addition, a polymer (PEDOT / PSS) solution containing 0.01 wt% DBS and 3 wt% EG was added to a solution obtained by concentrating the mixed solution on a hot plate at 80 ° C. for 1 hour. And applied by bar coating.

  As a result, a polymer (PEDOT / PSS) film having a thickness of about 2 μm was uniformly formed on an 80 mm square PET substrate. That is, in order to create a uniform polymer (PEDOT / PSS) film, it has been found that it is important to define the wet film thickness and the viscosity (concentration) of the polymer (PEDOT / PSS) solution.

  From the above, it was concluded that a polymer (PEDOT / PSS) solution having a higher concentration is necessary to form a polymer (PEDOT / PSS) thick film. Therefore, the optimum concentration conditions for forming a polymer (PEDOT / PSS) thick film by the bar coating method were found by the following experiment.

[Experiment 1: Extraction of polymer (PEDOT / PSS) solid component by vacuum freeze-drying method]
The concentration of the polymer (PEDOT / PSS) solution can be freely defined by making the polymer (PEDOT / PSS) solution once solid and re-dissolving it. Therefore, in order to extract the solid from the polymer (PEDOT / PSS) solution, a vacuum freeze-drying method was used to extract the polymer (PEDOT / PSS) solid component.

  Here, the vacuum freeze-drying method is a method generally called freeze-drying, in which a frozen sample is decompressed and water is sublimated and dried in a vacuum state. In this method, since water is sublimated and removed as ice, it becomes a porous body and has good restorability and solubility. The lyophilization of the polymer (PEDOT / PSS) solution was performed for about 2 days under a vacuum condition (100 Pa) under a freezing condition of −45 ° C. using a vacuum lyophilizer. As a result, about 1 g of a black, sponge-like porous solid component was obtained from 100 g of the polymer (PEDOT / PSS) solution.

[Confirmation of freeze-dried product]
In order to confirm the properties of the freeze-dried polymer (PEDOT / PSS) solid component, the following examination was performed. First, when the polymer (PEDOT / PSS) solid component was redissolved in water as a solvent, the polymer (PEDOT / PSS) was re-dissolved without precipitation or aggregation and recovered to a polymer (PEDOT / PSS) solution state. Next, a polymer (PEDOT / PSS) film was prepared from the re-dissolved 1 wt% polymer (PEDOT / PSS) solution by a casting method, and the electrical conductivity was measured using a resistivity meter. As a result, it was confirmed that there was no electrical deterioration.

  In addition, the electrical contraction behavior was also measured. First, a polymer (PEDOT / PSS) film was cut out and fixed by being sandwiched between gold-plated chucks. Next, a direct current was applied between the chucks using a direct current stabilized power source, and the expansion and contraction behavior was measured with a displacement sensor.

  In the measurement of the electric contraction behavior, in order to keep the environment constant, the measurement was performed in a constant environment of 25 ° C. and an ambient humidity of 50% RH using a constant temperature and humidity chamber. As a result, it was confirmed that there was no decrease in shrinkage of the polymer film prepared from the re-dissolved polymer (PEDOT / PSS) solution.

  As described above, the polymer (PEDOT / PSS) solid component obtained by lyophilization can be redissolved to prepare a polymer (PEDOT / PSS) solution having a desired concentration, and can be obtained by lyophilization and re-dissolution. It was found that the polymer (PEDOT / PSS) solution can be handled in the same manner as the polymer (PEDOT / PSS) solution before lyophilization.

[Experiment 2: Optimization of polymer (PEDOT / PSS) redissolving concentration]
In order to form a polymer (PEDOT / PSS) film as thick as possible on the substrate by the bar coating method, it is preferable that the concentration of the polymer (PEDOT / PSS) solution is high. On the other hand, in order to obtain a uniform polymer (PEDOT / PSS) film, it is necessary that the polymer (PEDOT / PSS) solution does not aggregate. Therefore, the water-soluble concentration of the polymer (PEDOT / PSS) solid component obtained by freeze-drying was examined.

  First, a redissolved polymer (PEDOT / PSS) solution having several concentrations (1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, and 5 wt%) was prepared. Solubility was confirmed visually. As a result, it was found that up to 3.5 wt% or less of the re-dissolved polymer (PEDOT / PSS) solution is solubilized in water, but a semi-solid state remains at a concentration of 4 wt% or more.

  Next, a 1.5-3.5 wt% re-dissolved polymer (PEDOT / PSS) solution confirmed to be dissolved in water is a PET substrate (size 80 mm × 80 mm, film thickness 38 μm) with a wet film thickness of 100 μm. It was applied on top by a bar coat method. The examination conditions are summarized in Table 2. The surface of the PET substrate was subjected to plasma ion treatment for 2 minutes by soft ion bombardment (hereinafter, Soft) used for hydrophilization of a delicate sample such as a support film. Moreover, EG and DBS are not added to the redissolved polymer (PEDOT / PSS) solution.

  FIG. 5 is a diagram showing the results of bar coating under the above conditions. It was found that the higher the concentration of the re-dissolved polymer (PEDOT / PSS) solution, the higher the uniformity of the bar coat and the thicker the film formed. However, bar streaks remained under the condition of 3.5 wt% where the redissolved polymer (PEDOT / PSS) solution concentration was the highest. On the other hand, when the concentration of the redissolved polymer (PEDOT / PSS) solution is 3 wt%, the formed film thickness is the most uniform, and a polymer (PEDOT / PSS) film having a thickness of about 4 μm can be formed. It was.

[Experiment 3: Optimization of electrical conductivity]
The electric conductivity of the redissolved polymer (PEDOT / PSS) film produced under the above conditions is considered to be about several S / cm. However, in order to drive a laminated polymer actuator having a bending behavior of several millimeters or more at a low voltage of several volts, it is necessary to increase the electrical conductivity of the polymer (PEDOT / PSS) film.

  The inventors of the present invention have an electrical conductivity of 100 S / cm or more by adding ethylene glycol (EG) to a polymer (PEDOT / PSS) solution when producing a polymer (PEDOT / PSS) film by a casting method. It has been found that it can rise. Therefore, a mixed solution obtained by adding several concentrations (0, 1, 5, 10, 15, 20, 25 wt%) of EG to the optimized 3 wt% redissolved polymer (PEDOT / PSS) solution by the bar coating method. The polymer (PEDOT / PSS) film was formed by coating on the substrate.

  FIG. 6 is a graph showing the measurement results of the sheet resistance of the formed polymer (PEDOT / PSS) film. The horizontal axis represents the EG concentration (wt%), and the vertical axis represents the sheet resistance (Ω / sq). The sheet resistance of the polymer (PEDOT / PSS) film without addition of EG (0 wt%) was 1877 Ω / sq, and the sheet resistance of the polymer (PEDOT / PSS) film with addition of EG 1 wt% was as high as 1800 Ω / sq. . On the other hand, the sheet resistance decreased with an increase in the EG concentration, and the sheet resistance was the lowest at 32 Ω / sq under the condition where the EG concentration was 15 wt%.

  From the above, as a polymer (PEDOT / PSS) solution to be applied by the bar coating method, a mixed solution in which a 15 wt% EG solution is added to a 3 wt% re-dissolved polymer (PEDOT / PSS) solution is suitable. There was found.

[Experiment 4: Reexamination of hydrophilization conditions]
Furthermore, in order to form a uniform polymer (PEDOT / PSS) thick film, hydrophilization conditions were examined. Specifically, several concentrations (0 wt%, 0.01 wt%, 0.1 wt%, 1 wt%) were added to a mixed solution obtained by adding 15 wt% EG to a 3 wt% redissolved polymer (PEDOT / PSS) solution. ) To which DBS was added. The prepared mixed solution was applied to the substrate by the bar coating method, the properties of the formed polymer (PEDOT / PSS) film were analyzed, and the optimum concentration condition of DBS was examined.

  In addition, for the substrate to which the polymer (PEDOT / PSS) solution is applied, two types of substrates, a plasma ion treatment (Soft, 2 minutes) and an untreated substrate, are used. The necessity of processing was also examined. The substrate used in the experiment is PET (size 80 mm × 80 mm, film thickness 38 μm).

  When the plasma ion treatment was not performed and DBS was not added, the polymer (PEDOT / PSS) solution was repelled on the substrate, and a uniform film was not formed. On the other hand, even under conditions where plasma ion treatment was not performed, formation of a uniform polymer (PEDOT / PSS) film could be confirmed under conditions where DBS was added even at 0.01 wt%. Moreover, when plasma ion treatment was performed, formation of a uniform polymer (PEDOT / PSS) film could be confirmed regardless of the presence or absence of DBS.

  FIG. 7 is a graph showing the relationship between the DBS concentration of the polymer (PEDOT / PSS) film formed under the above conditions and the sheet resistance. As shown in FIG. 7, the sheet resistance does not depend on the presence or absence of plasma ion treatment, but depends on the DBS concentration, and it has been found that the sheet resistance tends to increase as the concentration becomes higher than 0.1 wt%.

  The hydrophilization conditions and sheet resistance results are shown in Table 3. When the plasma ion treatment is not performed and no DBS is added, a uniform film is not formed. On the other hand, even under conditions where plasma ion treatment is not performed, a uniform polymer (PEDOT / PSS) film can be formed when DBS is added. However, in the case of DBS having a concentration of 0.1 wt% or more, the sheet resistance increases. Accordingly, it has been found that it is difficult to form a uniform polymer (PEDOT / PSS) film with high electrical conductivity when plasma ion treatment is not performed.

  On the other hand, when the substrate is subjected to plasma ion treatment, a uniform polymer (PEDOT / PSS) film can be formed even when DBS is not added. In addition, the sheet resistance increases depending on the DBS concentration regardless of the plasma ion treatment. Accordingly, it has been found that in order to form a polymer (PEDOT / PSS) film having a uniform and high electric conductivity, it is preferable to perform plasma ion treatment and not add DBS.

[Experiment 5: Control of dry film thickness]
Under the above conditions, an optimized substrate and a polymer (PEDOT / PSS) solution were used, the wet film thickness was changed, and the relationship between the film thickness of a thick film (dry thick film) obtained by drying it was examined. A glass rod was used for the bar when the polymer (PEDOT / PSS) solution was applied to the substrate, and bar coating was performed by providing a gap with the substrate using shim tape as a spacer. The substrate was PET (size 80 mm × 80 mm, film thickness 38 μm), and this was subjected to plasma ion treatment (Soft, 2 minutes). Moreover, the polymer solution used for the bar coat was a mixed solution obtained by adding 15 wt% EG to a 3 wt% re-dissolved polymer (PEDOT / PSS) solution, and DBS was not added.

  FIG. 8 is a graph showing the relationship between the wet film thickness and the dry film thickness under the above conditions. In any wet film thickness, a dry thick film of a uniform polymer (PEDOT / PSS) film could be formed. For the measurement of the film thickness, a micrometer was used to measure 5 points near the center of each, and the average film thickness was defined as the dry film thickness of the polymer (PEDOT / PSS) film. As shown in FIG. 8, by increasing the wet film thickness, a polymer (PEDOT / PSS) film of several to 10 μm or more was obtained. From this, it was found that the dry film thickness of the polymer (PEDOT / PSS) film increases in proportion to the wet film thickness.

  FIG. 9 is a graph showing measurement results of sheet resistance with respect to the dry film thickness of the formed polymer (PEDOT / PSS) film. As shown in FIG. 9, the thinner the polymer (PEDOT / PSS) film (2 μm), the higher the sheet resistance (20Ω / sq or more), and the thicker the polymer (PEDOT / PSS) film (6 μm or more), the lower the sheet resistance. It can be seen (5Ω / sq or less). That is, it was found that the sheet resistance is inversely proportional to the thickness of the polymer (PEDOT / PSS) film.

  From the above results, it was found that a desired polymer (PEDOT / PSS) film of several to 10 μm or more can be formed by using the shim tape thickness as a specified gap and using it as a spacer with a bar.

[Production of laminated polymer actuator]
FIG. 10 is a view showing another embodiment of the laminated polymer actuator. The laminated polymer actuator 2 produced in this example is composed of a polymer (PEDOT / PSS) film 11, a substrate 12 and an electrode 23 produced by a bar coating method.

  A manufacturing process of the multilayer polymer actuator 2 will be described with reference to the flowchart of FIG. First, a polymer (PEDOT / PSS) solution is prepared by adding 15 wt% EG to a 3 wt% re-dissolved polymer (PEDOT / PSS) solution (FIG. 1, Steps S1 to S3). The substrate 12 was made of PET (80 mm × 80 mm, film thickness 50 μm), and the surface was subjected to plasma ion treatment (Soft, 2 minutes) (FIG. 1, step S2 ′). A polymer (PEDOT / PSS) solution was applied onto the substrate 12 by a bar coating method (FIG. 1, step S4), and a composite element having a two-layer structure of the polymer (PEDOT / PSS) film 11 and the substrate 12 was produced. At this time, the formed polymer (PEDOT / PSS) film thickness was about 4 μm, and the sheet resistance was 8.7 Ω / sq.

  The composite element having the two-layer structure manufactured as described above was cut out as an actuator having an effective length of 10 mm and a width of 1 mm using a laser marker (FIG. 1, step S5). Next, gold (Au) electrode patterns were formed on the back surface and both ends of the actuator by magnetron sputtering (FIG. 1, Step 6), and the laminated polymer actuator 2 was produced.

[Operation check of laminated polymer actuator]
FIG. 11 is a graph showing current characteristics (a) and bending behavior (b) of the multilayer polymer actuator 2. A metal electrode 23 is sputtered on the multilayer polymer actuator 2, and a voltage can be applied to the wiring connected to the metal electrode 23. A voltage was applied to the laminated polymer actuator 2, and the displacement of the end of the laminated polymer actuator 2 at that time was read with a laser displacement meter, and its bending behavior was confirmed.

  In the measurement of the characteristics shown in FIG. 11, the inside of the constant temperature and humidity chamber was controlled at 25 ° C. and 50% RH, and the displacement amount of the multilayer polymer actuator 2 was measured. When a voltage of 1 V was applied, a current of about 6 mA flowed (FIG. 11 (a)), and the laminated polymer actuator 2 was bent toward the polymer (PEDOT / PSS) film 11 side (FIG. 11 (b)). This is because a current flows through the polymer (PEDOT / PSS) film 11, water molecules adsorbed by Joule heating are desorbed, and the polymer (PEDOT / PSS) film 11 contracts. On the other hand, when the voltage is turned off, the original state is restored. This is because water molecules are re-adsorbed on the polymer (PEDOT / PSS) film 11.

  Further, the displacement of the tip of the multilayer polymer actuator 2 of about 1 mm when the applied voltage was 2 V and 2 mm or more when the applied voltage was 3 V was confirmed (FIG. 11B). At that time, there was no deviation between the polymer (PEDOT / PSS) film 11 and the substrate 12 due to repeated voltage application, which was a problem in Example 1.

[Drive model of laminated polymer actuator]
FIG. 12 is a view showing a model of a stacked polymer (PEDOT / PSS) actuator. FIG. 12A shows a state in which no voltage is applied, and FIG. 12B shows a state in which the laminated polymer actuator is bent by the application of voltage. Equations (1) and (2) are theoretical equations of a general bimorph actuator that bends due to the difference in thermal expansion coefficient between the two materials.

  With reference to FIG. 12, the drive mechanism of the laminated polymer actuator will be described below using the mathematical formulas shown in Equations 1 and 2.

  In Equation 1, (αa−αb) ΔT represents a difference in thermal expansion value at a certain temperature between the material a and the material b constituting the bimorph actuator. Here, it is considered that the bending mechanism of the laminated polymer (PEDOT / PSS) actuator is that PEDOT / PSS contracts due to desorption of water molecules due to generation of Joule heat (see FIG. 4).

  Since the shrinkage γ of the polymer (PEDOT / PSS) actuator shown in FIG. 12 is proportional to the temperature, it can be expressed as γ × 10−2 = αΔT (α is a proportional coefficient). Therefore, a model formula of the laminated polymer actuator can be established as expressed by the formulas 3 and 4.

y: Displacement of the tip
ρ: curvature
l: Length of bimorph
ΔT: rising temperature
ta: thickness of material a
Ea: Young's modulus of material a
αa: linear expansion coefficient of material a
tb: thickness of material b
Eb: Young's modulus of material b
αb: Linear expansion coefficient of material b

y: Displacement of the tip
ρ: curvature
l: Length of composite element
γ: PEDOT / PSS shrinkage
ta: PEDOT / PSS thickness
Ea: Young's modulus of PEDOT / PSS
tb: thickness of material b
Eb: Young's modulus of material b

  FIG. 12B shows a bent state when a voltage is actually applied to the laminated polymer (PEDOT / PSS) actuator as described above. In this case, the laminated polymer actuator is made of a material a. Bends to a certain polymer (PEDOT / PSS) film side. This phenomenon is different from the mechanism of a general bimorph structure actuator driven by thermal expansion, and indicates that this actuator is driven by contraction of a polymer (PEDOT / PSS) film.

  In FIG. 11, the curvature ρ of the composite element is obtained from the amount of displacement of the tip when a voltage of 3 V is applied, using the mathematical formulas 3 and 4, and the contraction rate γ of the polymer (PEDOT / PSS) actuator is obtained. When calculated, the value was 1.9%. At this time, the tip displacement y is 2.2 mm, the polymer (PEDOT / PSS) film thickness ta is 4 μm, the substrate thickness tb is 50 μm, the polymer (PEDOT / PSS) film Young's modulus Ea is 4 GPa, The Young's modulus Eb of the substrate was 1 GPa.

  As described above, the inventors have found a phenomenon in which a polymer (PEDOT / PSS) film desorbs and contracts due to Joule heat in air, and measures the contraction behavior of the strip-shaped film in the linear motion direction. The maximum shrinkage of the polymer (PEDOT / PSS) film at that time was 2.4%.

  On the other hand, the contraction rate γ of the polymer (PEDOT / PSS) actuator calculated from the mathematical expressions shown in Equations 3 and 4 is 1.9%, and the polymer (PEDOT / PSS) film is driven by adsorbing and desorbing water molecules. The value was close to the shrinkage rate (2.4%). Further, the bending direction of the laminated polymer actuator was the polymer (PEDOT / PSS) film side. Therefore, it is considered that the laminated polymer actuator is driven by the same mechanism as that of the polymer (PEDOT / PSS) film.

[Features of laminated polymer actuator]
The layered polymer actuator developed in this study, which is composed of a polymer (PEDOT / PSS) film and a substrate, is characterized by being driven by a mechanism different from that of a general bimorph actuator.

  An actuator made of a piezoelectric element, which is a typical example of a bending actuator, requires a high voltage of 100 V or more for driving, and its displacement is as small as a micrometer order or less. On the other hand, the laminated polymer (PEDOT / PSS) actuator developed in this study has a feature that it can generate displacement in the millimeter order at a low voltage of 5 V or less.

  Table 4 compares the direct acting polymer actuator and the laminated polymer actuator of the present invention. Here, the comparison was performed under the conditions in which a displacement of 1 mm was generated in each actuator in an environment of 25 ° C. and 50% RH. As a result, it was found that the actuator size can be reduced to 1/5 or less of the direct acting type in the laminated type. This is probably because the displacement is enlarged by the lever mechanism.

  The power consumption is reduced to nearly one-tenth of that of the direct acting type, thus realizing power saving. In addition, the mechanical strength of the laminated polymer actuator was also improved. The dynamic strength of the direct acting type depends on the strength of the polymer (PEDOT / PSS) film itself. On the other hand, in the laminated type, the polymer (PEDOT / PSS) film is laminated with the substrate, so that the strength is considered to be greatly improved. Furthermore, the response speed when the voltage was turned off was nearly 5 times faster than the direct acting type. This is thought to be because the adsorption rate of water molecules was improved.

  As described above, since the lamination with the substrate has been realized, it has become possible to convert the polymer (PEDOT / PSS) film of several micrometers, which has been difficult from the viewpoint of the strength of the conventional film, into an actuator. In addition, if the polymer (PEDOT / PSS) film is thinned, high-speed response can be expected. This is because the driving mechanism of the laminated polymer actuator is caused by the diffusion of water molecules.

  According to the present invention, it is possible to produce a laminated polymer actuator that utilizes the contraction of a polymer film (film), and such a laminated polymer actuator can be used for motors, solenoids, switches, valves, pumps, and the like. Electronic / mechanical field, optical device field such as lens drive and mirror drive, camera auto-focus, medical field such as guide wire and endoscope, toy / robot field such as biomimetic device and robot finger drive, Braille display, It can be applied to various fields including nursing and welfare as an electronic element such as power assist.

1, 2 Laminated polymer actuator 11 Polymer (PEDOT / PSS) membrane (film)
12 Substrate 5 Poly (3,4-ethylenedioxythiophene) (PEDOT)
6 Poly (4-styrenesulfonic acid) (PSS)
7 Water molecule 23 Electrode

Claims (5)

A method for manufacturing a laminated actuator, in which a conductive polymer solution is applied to a substrate to form a conductive polymer film,
Performing plasma ion treatment for hydrophilizing the surface of the substrate;
The conductive polymer solution is a poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonic acid) redissolved polymer solution having a concentration of 1.5 to 3.5 wt%.
Made by adding ethylene glycol,
The method of manufacturing a laminated polymer actuator, wherein the coating is performed by a bar coating method. The method for producing a laminated polymer actuator according to claim 1 , wherein the ethylene glycol concentration is 5 to 25 wt%. The re-dissolved polymer solution is prepared by re-dissolving a solid component obtained by freeze-drying a 1 wt% solution of poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonic acid) in water. method for producing a laminated polymer actuator according to claim 1 or 2, characterized in that. The method for producing a laminated polymer actuator according to any one of claims 1 to 3 , wherein the conductive polymer film has a thickness of 6 µm or more. Method for producing a laminated polymer actuator according to any one of claims 1 to 4, characterized in that the addition of the re-dissolved polymer solution to 0.01 wt% or less of dodecylbenzenesulfonic acid surfactants.