Electrostatic actuator
By integrating a glass cover layer with a higher dielectric constant into the electrostatic actuator, the voltage requirement is reduced, enabling smaller and lighter power supplies while enhancing driving force.
Patent Information
- Application Number
- JP2023189381
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-06
- Publication Date
- 2025-05-19
AI Technical Summary
Conventional electrostatic actuators require high driving voltages exceeding 1 kV, leading to large and heavy power supplies, which is impractical for small and lightweight applications.
The electrostatic actuator incorporates a pair of electrodes with an insulating liquid layer and a cover layer made of glass material with a higher dielectric constant than polyimide, reducing the driving voltage requirement to several hundred volts.
This configuration allows for a significant reduction in driving voltage, enabling the use of small and lightweight drivers while improving the driving force at the same applied voltage.
Smart Images
Figure 2025077298000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an electrostatic actuator.
Background Art
[0002] In recent years, development of an electrostatic actuator that converts energy generated by electrostatic force into power to move an object has been underway. The electrostatic actuator is used, for example, in the optical field such as driving of a variable focus lens and driving of a shutter. Further, application of the electrostatic actuator to artificial muscles of a robot, a prosthetic hand, a prosthetic leg, etc. has been studied. Such an electrostatic actuator requires a thin substrate and is made using FPC (Flexible printed circuits). For example, when using an electrostatic actuator for artificial muscles of a robot or the like, it has been considered to form electrodes by, for example, an additive method (see, for example, Non-Patent Document 1).
Prior Art Documents
Non-Patent Documents
[0003]
Non-Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] When using an electrostatic actuator created by a conventional method as artificial muscle for, e.g., a robot, a high voltage exceeding, e.g., 1 kV is required for driving, and there is a problem that the power supply becomes large-sized.
[0005] The present invention has been made in view of the above problems, and an object thereof is to provide an electrostatic actuator that can be reduced to a driving voltage achievable even with an existing small and lightweight driver of several 100 V.
Means for Solving the Problems
[0006] (1) To achieve the above object, an electrostatic actuator according to one aspect of the present invention is an electrostatic actuator that uses an electrostatic force generated between a pair of electrodes by voltage operation on the pair of electrodes as a driving force, and includes the pair of electrodes, an insulating layer that is a layer of an insulating liquid provided between the pair of electrodes, and a cover layer provided between the pair of electrodes and the insulating layer, where the cover layer is a material having a higher dielectric constant than that of polyimide and a material having low stretchability.
[0007] (2) Further, in the electrostatic actuator according to the one aspect described in (1) above, the cover layer may be a glass material formed at least partially by silicon and oxygen.
[0008] (3) Further, in the electrostatic actuator according to the one aspect described in (2) above, the glass material may be formed by a humidifying and heating manufacturing method after coating with low-temperature sintering coating type silica.
[0009] (4) Further, in the electrostatic actuator according to any one of (1) to (4) above, the thickness from the electrode to the cover layer on the insulating layer side of the cover layer may be 1 μm or less.
[0010] (5) Also, in the electrostatic actuator according to any one of the above (1) to (4), the dielectric constant of the insulating layer may be lower than the dielectric constant of the cover layer.
[0011] (6) Also, in the electrostatic actuator according to any one of the above (1) to (4), the electrode forms a polarity on the substrate on which the electrode is formed to form a high-polarity portion (polarized portion), and a liquid containing a conductive material is applied to the high-polarity portion, and the liquid containing the conductive material is spread by moving on the substrate, and the liquid containing the conductive material may be formed by applying the liquid containing the conductive material on the high-polarity portion by a coating bar.
Advantages of the Invention
[0012] According to the above (1) to (6), an actuator film with a high dielectric constant can be realized, and the driving voltage can be reduced to a value that can be realized even with a small and lightweight existing driver such as several 100 V. According to the above (1) to (6), the driving force can be improved compared with the conventional case at the same applied voltage.
Brief Description of the Drawings
[0013]
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Embodiments for Carrying Out the Invention
[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings used in the following description, the scales of the respective members are appropriately changed in order to make the respective members recognizable in size. In all the drawings for explaining the embodiments, those having the same function are denoted by the same reference numerals, and repeated explanations are omitted. In addition, "based on XX" as used in the present application means "based on at least XX", and includes cases where it is based on another element in addition to XX. Also, "based on XX" is not limited to the case where XX is directly used, and includes cases where it is based on something obtained by performing operations or processing on XX. "XX" is an arbitrary element (for example, arbitrary information).
[0015] (Schematic Configuration Example of Electrostatic Actuator) First, a schematic configuration example of the electrostatic actuator of this embodiment will be described. FIG. 1 is a diagram showing a configuration example of the electrostatic actuator of this embodiment. The electrostatic actuator 1 shown in FIG. 1 is driven using a power supply 19 that generates a three-phase high-voltage alternating current wave so that the movers 11, 13 and the stators 12, 14 maintain the same phase. In the mover and the stator, "1" represents the first phase, "2" represents the second phase, and "3" represents the third phase. In the electrostatic film actuator of FIG. 1, the movers 11, 13 move left and right with respect to the paper surface due to the alternating current wave. The stator and the mover are arranged in parallel via, for example, an insulating layer 15 and a rotatable ball 16.
[0016] In FIG. 1, an example is shown in which there are two stators and two movers, but the number of sets of stators and movers may be one or more. As shown in FIG. 1, when there are two or more sets of stators and movers, for example, the driving force can be increased compared to one set.
[0017] Figure 2 is a view of the electrostatic actuator as seen from above. Image g150 shows the first state. Image g160 shows the second state in which the mover g172 has moved to the right with respect to the stator g171 as indicated by the arrow g173.
[0018] Figure 3 is a schematic diagram of the operating state of Figure 2 as seen from a film cross-section. Image g200 shows an example of the state before the stator g241 and the mover g242 move. Note that the sine wave g251 represents the phase image in the stator g241. The sine wave g252 represents the phase image in the mover g242. Image g210 shows an example of the state in which the mover g242 has started to move to the right with respect to the stator g241. Image g220 shows an example of the state in which the mover g242 has moved to the right by the maximum amount with respect to the stator g241. Note that after image g220, the mover g242 moves to the left with respect to the stator g241 as in image g230. In this way, by means of an alternating current wave, the movement of the mover is controlled, for example, left and right with respect to the stator.
[0019] Figure 4 is a diagram showing a configuration example of the electrostatic actuator of the present embodiment. Note that in Figure 4, one set of stator and mover is shown in the electrostatic actuator 1. The electrostatic actuator 1 includes a substrate 101 of the first electrode, a cover layer 102 of the first electrode, an electrode pattern 103 of the first electrode, an insulating layer 104, a cover layer 105 of the second electrode, an electrode pattern 106 of the second electrode, and a substrate 107 of the second electrode.
[0020] Each of the substrate 101 of the first electrode and the substrate 107 of the second electrode is, for example, an FPC (Flexible printed circuits) film. The cover layer 102 of the first electrode and the cover layer 105 of the second electrode are each a glass film (chemical formula (2)) formed by a humidifying and heating manufacturing method at a low temperature using, for example, low-temperature sintering coating type silica (chemical formula (1)). The relative permittivity of this glass film is, for example, about 60, which is higher than the relative permittivity of 3 of the polyimide that is the cover layer used in a normal FPC. Note that the low-temperature sintering coating type silica may contain contents other than the contents of chemical formula (1). Note that the method for forming the cover layer and the reason why the relative permittivity of the cover layer of the present embodiment can be increased will be described later.
[0021]
Chem.
[0022]
Chem.
[0023] As will be described later, each of the electrode pattern 103 of the first electrode and the electrode pattern 106 of the second electrode is an electrode pattern formed by a method using, for example, silver nanoink. Note that the method for forming the electrodes will be described later.
[0024] The insulating layer 104 is, for example, an insulating liquid such as oil.
[0025] FIG. 5 is a diagram showing a configuration example of an electrostatic actuator of a comparative example. Note that in FIG. 5, in the electrostatic actuator 900 of the comparative example, a set of a stator and a mover is shown. The electrostatic actuator 900 of the comparative example includes a substrate 901 of the first electrode, a cover layer 902 of the first electrode, an electrode pattern 903 of the first electrode, an insulating layer 904, a cover layer 905 of the second electrode, an electrode pattern 906 of the second electrode, and a substrate 907 of the second electrode.
[0026] The difference between the electrostatic actuator 1 (FIG. 4) of the present embodiment and the electrostatic actuator 900 of the comparative example lies in the cover layer 902 of the first electrode and the cover layer 905 of the second electrode.
[0027] Each of the substrate 901 of the first electrode and the substrate 907 of the second electrode is, for example, an FPC film. Each of the cover layer 902 of the first electrode and the cover layer 905 of the second electrode is, for example, polyimide. Each of the electrode pattern 903 of the first electrode and the electrode pattern 906 of the second electrode is an electrode pattern formed by a method using, for example, silver nanoink, as will be described later. The insulating layer 904 is, for example, oil.
[0028] Here, in FIGS. 4 and 5, the number of downward arrows indicates that the stronger the electric field, the more arrows there are, and the weaker the electric field, the fewer arrows there are. As shown in FIGS. 4 and 5, as a result of the simulation, in the configuration of the present embodiment formed of glass, compared with the case where the cover layer is formed of polyimide, the relative permittivity ε rf of the cover layer is high. Therefore, when the same voltage V 0 is applied, the electric field E f generated by the electrodes is lower in the glass cover layer than in the polyimide cover layer. As a result, the electric field E l generated between the first electrode and the second electrode can be increased.
[0029] As a result of the simulation, the thrust f in the case where the cover layer is made of glass is improved compared to the thrust f in the case where the cover layer is made of polyimide having a relative permittivity of 3. That is, according to the present embodiment, by making the cover layer glass, when the applied voltage is the same, the thrust can be improved compared to the configuration where the cover layer is polyimide. Further, according to the present embodiment, when obtaining the same driving force, by making the cover layer glass, the applied voltage can be lowered compared to the configuration where the cover layer is polyimide.
[0030] As described above, the electrostatic actuator 1 of the present embodiment uses the electrostatic force generated between the electrodes by voltage operation on the pair of electrodes as a driving force.
[0031] (Method for Forming Cover Layer) Next, an example of a method for forming a cover layer will be described. FIG. 6 is a diagram showing an example of a method for forming a cover layer according to the present embodiment. In the present embodiment, as shown in FIG. 6, for example, silica (SiNH 3 ) of Chemical Formula (1) is spin-coated, and a cover layer of silica glass SiO 3 of Chemical Formula (2) is formed by a humidifying and heating manufacturing method in which predetermined humidification and predetermined heating are performed for a predetermined time. The reason why the dielectric constant can be increased is that after coating with silica and heating while humidifying, water (H 2 2O) molecules remain in the layer and are polarized, so that a high dielectric constant can be obtained. For example, the relative dielectric constant of glass is about 10 at maximum, and the relative dielectric constant of water is about 80. Note that the cover layer may be a glass material formed of at least a part of silicon and oxygen.
[0032] Note that for normal glass film formation, high-temperature sintering is required, and the film material of the FPC could not withstand it. However, by the low-temperature sintering method as in the present embodiment, it has become possible to form a glass film even on the FPC. Note that in the above example, an example in which the surface of the FPC substrate on which the electrodes are formed is coated with glass has been described. However, the surface on which the electrodes are not formed may also be coated with glass. By coating the surface on which the electrodes are not formed with glass in this way, it is possible to obtain an effect of preventing the surface on which the electrodes are formed from warping.
[0033] In addition, as other high-dielectric-constant materials, for example, there are PVDF (Poly Vinylidene DiFluoride), nematic liquid crystals, and the like. However, such high-dielectric-constant materials cannot be used as the cover layer of the electrostatic actuator because the molecular structure itself is polarized and the material itself is deformed by voltage application. In contrast, in the present embodiment, by using the glass film formation method with humidification heating at a low temperature, a high dielectric constant can be realized to leave water molecules, and a high dielectric constant film that does not deform even when a voltage is applied can be realized.
[0034] As described above, according to the present embodiment, since the dielectric constant of the cover layer is increased, the applied voltage can be lowered, so that the power supply required for driving can be made smaller.
[0035] Note that in the above-described example, an example in which glass is used for the cover layer has been described, but it is not limited thereto. The material used for the cover layer may have a relative dielectric constant greater than 3 times the relative dielectric constant of polyimide and within a predetermined range (for example, 100 or less). The material used for the cover layer may be any other material as long as it can be heated at a low temperature such that the substrate does not deform and water components remain in the cover layer and are polarized by the humidification heat treatment. Or, for example, a material such as a phenolic resin having a relative dielectric constant of about 10 can also improve the driving force compared to conventional materials. Note that a relative dielectric constant and a material are preferably in a range where shrinkage does not occur when a voltage is applied. That is, the cover layer preferably has a material with low stretchability.
[0036] Also, in the above-described example, an example in which the relative dielectric constant of the cover layer is increased has been described, but the relative dielectric constant of the insulating layer may be made higher than before. Note that if the relative dielectric constant of the insulating liquid is too high, the driving force is impaired, so the dielectric constant of the insulating layer may be lower than the dielectric constant of the cover layer.
[0037] (Configuration Example of Electrostatic Actuator Forming Apparatus) Next, a configuration example of the electrostatic actuator forming apparatus 2 will be described. FIG. 7 is a diagram showing a configuration example of the electrostatic actuator forming apparatus according to the present embodiment. As shown in FIG. 7, the electrostatic actuator forming apparatus 2 includes, for example, a control unit 21 and a storage unit 22.
[0038] The control unit 21 includes, for example, an ultraviolet irradiation control unit 211 (high surface energy imparting unit), a bar drive control unit 212 (bar control unit), an ink application control unit 213 (liquid imparting unit), a gas injection control unit 214 (gas injection unit), a coating control unit 215, and a humidification and heating control unit 216.
[0039] Connected to the electrostatic actuator forming apparatus 2 are, for example, an ultraviolet irradiation apparatus 3 (high surface energy imparting unit), a coating bar 4, an ink supply apparatus 5 (liquid imparting unit), a gas injection apparatus 6, a coating apparatus 7, and a humidification and heating apparatus 8.
[0040] The ultraviolet irradiation apparatus 3 irradiates ultraviolet rays in accordance with the control of the electrostatic actuator forming apparatus 2.
[0041] The coating bar 4 smooths, in accordance with the control of the electrostatic actuator forming apparatus 2, the metal nanoink applied, for example, onto the FPC film by the ink supply apparatus 5.
[0042] The ink supply apparatus 5 includes ink 51 (for example, silver nanoink). The ink supply apparatus 5 applies the metal nanoink, for example, onto the FPC film in accordance with the control of the electrostatic actuator forming apparatus 2.
[0043] The gas injection apparatus 6 includes gas 61 (for example, nitrogen). The gas injection apparatus 6 injects gas in accordance with the control of the electrostatic actuator forming apparatus 2. Note that the gas injection is used only when necessary for the print adjustment of the ink. Also, the gas may be any gas other than a gas containing oxygen, and may be argon or the like.
[0044] The coating apparatus 7 spin-coats, for example, silica onto the substrate in accordance with the control of the electrostatic actuator forming apparatus 2 when forming the cover layer.
[0045] The humidification and heating apparatus 8 humidifies and heats in accordance with the control of the electrostatic actuator forming apparatus 2 after spin-coating.
[0046] The control unit 21 controls the ultraviolet irradiation device 3, the coating bar 4, the ink supply device 5, the gas injection device 6, the coating device 7, and the humidifying and heating device 8.
[0047] The storage unit 22 stores the injection direction, injection angle, injection amount, etc. of nitrogen. The storage unit 22 stores the amount of the metal nanoink to be applied.
[0048] The ultraviolet irradiation control unit 211 controls the ultraviolet irradiation device 3 with respect to the irradiation amount, irradiation start, irradiation end, etc. of ultraviolet rays.
[0049] The bar drive control unit 212 controls the start of contact, end of contact, movement, etc. of the coating bar 4 with respect to the film.
[0050] The ink coating control unit 213 controls the ink supply device 5 with respect to the start of ink coating, end of ink coating, coating amount, etc.
[0051] The gas injection control unit 214 controls the gas injection device 6 with respect to the start of injection, end of injection, injection amount, concentration, etc. of the inert gas.
[0052] The coating control unit 215 controls the coating device 7 with respect to, for example, the coating amount of silica on the substrate, the start and end of spin coating, etc.
[0053] The humidifying and heating control unit 216 controls the humidifying and heating device 8 with respect to the humidity to be humidified, the start and end of humidification, the temperature to be heated, the start and end of heating, etc.
[0054] [Method for creating electrode pattern] Next, a method for creating the electrode pattern of the present embodiment will be described. FIG. 8 is a diagram for explaining the procedure for creating the electrode pattern according to the present embodiment. In the formation of the conductive layer in the present embodiment, the silver nanoprint method is used as a basis. As shown by the reference numeral g311 in FIG. 8, the printing direction is the x-axis direction, and the thickness direction of the FPC film is the z-axis direction. Note that the object on which the pattern is formed is not limited to the FPC film. Also, as an example of the metal nanoink applied to the film and used for forming the electrode pattern, silver nanoink will be described as an example.
[0055] (Step S1) As shown by the reference numeral g311, an FPC film 301 on which a pattern is to be formed is set in the electrostatic actuator forming apparatus 2.
[0056] (Step S2) As shown by the reference numeral g312, the electrostatic actuator forming apparatus 2 forms a mask 302 on a portion of the wettability control layer where no pattern is to be formed.
[0057] (Step S3) As shown by the reference numeral g313, the electrostatic actuator forming apparatus 2 controls the ultraviolet irradiation apparatus 3 to perform exposure by irradiating ultraviolet rays having a wavelength of, for example, 300 nm or less. By this exposure, as shown by the reference numeral g314, the pattern formation region 303 of the FPC film 301 that is irradiated with ultraviolet rays not masked by the mask 302 is polarized. Note that in the polarized portions, the ink containing metal is likely to adhere.
[0058] (Step S4) As with reference sign g315, the electrostatic actuator forming apparatus 2 controls the ink supply apparatus 5 to apply the ink 51, and controls the coating bar 4 to level the ink 51 in the x-axis direction. During this printing, the electrostatic actuator forming apparatus 2 may control the gas injection apparatus 6 to perform ink adjustment by injecting, for example, nitrogen 314. As with reference sign g316, as a result of leveling the ink 51 with the coating bar 4 while injecting nitrogen 314, the ink 51 is applied only to the polarized pattern formation region. In this way, the electrostatic actuator forming apparatus 2 prints the ink 51 for forming the electrode pattern on the FPC film 301.
[0059] (Step S5) As with reference sign g17, the electrostatic actuator forming apparatus 2 controls the ultraviolet irradiation apparatus 3 to irradiate ultraviolet rays to cure the ink 51 (or cure it by heating). Thereby, as with reference sign g318, the electrode pattern 305 is formed at a desired position on the FPC film 301.
[0060] Note that for the method of creating the electrode pattern and the like, refer to Japanese Patent Application No. 2022-184225. In the present embodiment, after forming the electrode pattern in this manner, as described above, the cover layer is formed by spin coating and humid heat treatment.
[0061] As described above, according to the conductive layer forming method of the present embodiment, compared with the electrode pattern by a general etching method, the steps and production costs such as copper foil formation, resist coating, resist removal, and etching can be significantly reduced.
[0062] FIG. 9 is a diagram showing a configuration example and a size example of the electrostatic film actuator of the comparative example and the present embodiment. In FIG. 9, the longitudinal direction is the x-axis direction, and the thickness direction is the z-axis direction. The image g400 is an electrostatic film actuator of a comparative example, which is fabricated by an etching method. The electrostatic film actuator of the comparative example has, for example, a distance between the centers of electrode patterns in the x-axis direction of 200 μm, a distance between electrode patterns in the z-axis direction of 70 μm, and a distance between the electrode pattern and the FPC film surface of 25 μm. Also, under these conditions, the applied voltage necessary for increasing the thrust without breaking the film is, for example, 1500 V (1.5 kV), and the relative permittivity ε r is 1.9. The image g410 is an electrostatic film actuator of the present embodiment, which is fabricated by the conductive layer forming method of the present embodiment. The electrostatic film actuator of the present embodiment has, for example, a distance between the centers of electrode patterns in the x-axis direction of about 10 μm, a distance between electrode patterns in the z-axis direction of about 12 μm, and a thickness (gap between films) between the electrode pattern and the FPC film surface of about 1 μm. Note that the gap between films is preferably, for example, 1 μm or less. Also, the necessary applied voltage is several hundreds of V, and the relative permittivity ε r is, for example, 60.
[0063] Here, the force (thrust, driving force) f that acts by applying a voltage is expressed as in the following formula (1).
[0064]
Equation
[0065] In formula (1), p is the electrode pitch, ε is the permittivity between electrodes (the composite permittivity of the cover layer and the insulating layer), S is the overlapping area between the first electrode and the second electrode, d is the gap between films, V is the applied voltage, and E is the applied electric field.
[0066] As described above, in the present embodiment, an actuator film with a high permittivity can be realized, and the driving voltage can be reduced to a value that can be realized even with an existing driver such as several hundreds of V.
[0067] Note that the electrostatic actuator 1 described above can be applied to, for example, artificial muscles such as robots and assistive devices.
[0068] As described above, the embodiments for carrying out the present invention have been described using embodiments. However, the present invention is not limited to such embodiments, and various modifications and substitutions can be made without departing from the gist of the present invention.
Explanation of Reference Numerals
[0069] 1... Electrostatic actuator, 101... Substrate of the first electrode, 102... Cover layer of the first electrode, 103... Electrode pattern of the first electrode, 104... Insulating layer, 105... Cover layer of the second electrode, 106... Electrode pattern of the second electrode, 107... Substrate of the second electrode
Claims
1. An electrostatic actuator that utilizes an electrostatic force generated between a pair of electrodes by applying a voltage to the electrodes as a driving force, The pair of electrodes; an insulating layer which is a layer of insulating liquid provided between the pair of electrodes; a cover layer provided between the pair of electrodes and the insulating layer, The cover layer is made of a material having a higher dielectric constant than that of polyimide and having low elasticity. Electrostatic actuator.
2. The cover layer is a glass material at least partially formed from silicon and oxygen.
2. The electrostatic actuator according to claim 1.
3. The glass material is coated with low-temperature sintering coating type silica and then formed by a humidification and heating method.
3. The electrostatic actuator according to claim 2.
4. The cover layer has a thickness from the electrode to the insulating layer side of the cover layer of 1 μm or less.
2. The electrostatic actuator according to claim 1.
5. The dielectric constant of the insulating layer is lower than the dielectric constant of the cover layer.
2. The electrostatic actuator according to claim 1.
6. The electrode is imparting polarity to the substrate on which the electrodes are formed to form a high polarity portion; Applying a liquid containing a conductive material to the high polarity portion; A liquid containing the conductive material is applied onto the high polarity portion by a coating bar that spreads the liquid containing the conductive material by moving over the substrate, 2. The electrostatic actuator according to claim 1.