Stacked electrostatic actuator

1. A stacked electrostatic actuator comprising a plurality of electrode films each including a three-layer structure including a first insulating layer, a conductor layer, and a second insulating layer, wherein

each of the electrode films includes, on the first insulating layer of the electrode film, a bonding region P subjected to surface processing so as to be bonded to another electrode film and a non-bonding region Q not bonded to the another electrode film, and a boundary C between the bonding region P and the non-bonding region Q has a wavy pattern that can be defined using at least one curvature radius of a finite value, and

the bonding region P of a first electrode film and the bonding region P of a second electrode film immediately below the first electrode film are stacked and arranged such that the bonding regions do not overlap each other in a stacking direction and that an axis of the wavy pattern of the boundary C of the first electrode film and an axis of the wavy pattern of the boundary C of the second electrode film are parallel to each other, and the first electrode film and the second electrode film are bonded by the bonding region P of the first insulating layer of the second electrode film,

so that the plurality of electrode films has electrode portions where the two electrode films are bonded and hinge portions where the two electrode films are not bonded when viewed from the stacking direction, and

when the stacked electrostatic actuator is pulled in the stacking direction by an external force, the hinge portions are elastically deformed to separate the electrode portions from each other and the stacked electrostatic actuator extends in the stacking direction, and

when a voltage is applied between the conductor layers of the plurality of electrode films, a distance between the electrode portions separated from each other is reduced by electrostatic force so that the stacked electrostatic actuator contracts in the stacking direction.

2. A stacked electrostatic actuator comprising a plurality of electrode films each including a three-layer structure including a first insulating layer, a conductor layer, and a second insulating layer, wherein

each of the electrode films includes, on the first insulating layer of the electrode film, a bonding region P subjected to surface processing so as to be bonded to another electrode film and a non-bonding region Q not bonded to the another electrode film, and the bonding region P is formed in a weight connection pattern including weight shapes separated from each other on the first insulating layer, and

the weight shapes on the first insulating layer of a first electrode film and the weight shapes on the first insulating layer of a second electrode film immediately below the first electrode film are stacked and arranged such that the weight shapes do not overlap each other in a stacking direction and that the weight shapes and in orientations such that the weight shapes are rotated by 90 degrees from each other, and the first electrode film and the second electrode film are bonded by the bonding region P of the first insulating layer of the second electrode film,

so that the plurality of electrode films has electrode portions where the two electrode films are bonded and hinge portions where the two electrode films are not bonded when viewed from the stacking direction, and

when the stacked electrostatic actuator is pulled in the stacking direction by an external force, the hinge portions are elastically deformed to separate electrode portions from each other and the stacked electrostatic actuator extends in the stacking direction, and

when a voltage is applied between the conductor layers of the plurality of electrode films, a distance between electrode portions separated from each other is reduced by electrostatic force so that the stacked electrostatic actuator contracts in the stacking direction.

3. The stacked electrostatic actuator according to claim 1 , wherein

the hinge portions of each of the electrode films are formed as arcuate regions having a curvature radius R e of an outer periphery and a curvature radius R i of an inner periphery, and

the arcuate regions each have a shape in which arcs are continuously connected while changing a curvature orientation for each opening angle θ OA of the arcuate region.

4. The stacked electrostatic actuator according to claim 1 , wherein

the hinge portions of each of the electrode films are formed as arcuate regions having a curvature radius R e of an outer periphery and a curvature radius R i of an inner periphery, and

an opening angle θ OA of the arcuate region is 180 degrees or more.

5. The stacked electrostatic actuator according to claim 1 , wherein

with definition of a movement amount of one boundary C of each of the hinge portion with respect to another boundary C of the hinge portion in an extension/contraction direction of the stacked electrostatic actuator as a displacement of the hinge portion, and definition of a displacement of the hinge portion corresponding to a maximum allowable distance between the facing electrode portions defined by a generated force of the actuator as a maximum displacement, the maximum displacement of the hinge portions is √2 times or more a thickness of each of the electrode films.

6. The stacked electrostatic actuator according to claim 1 , wherein

the hinge portions have a uniform width.

7. The stacked electrostatic actuator according to claim 6 , wherein

a ratio of the width of the hinge portions to a thickness of the electrode films is 5 or more.

8. The stacked electrostatic actuator according to claim 1 , wherein

a space formed between two of the electrode films by the corresponding hinge portion is in fluid communication with an outside, and

fluid is allowed to flow in and out between the space and the outside when the stacked electrostatic actuator extends and contracts.