Membrane actuator and methods for manufacturing a membrane actuator

Abstract

Membrane actuator (10) comprising a first frame part (12) and a second frame part (14), between which at least two membrane layers (16) are stacked and designed as electroactive polymer layers, wherein the first frame part (12) abuts a first surface (17a) of the at least two membrane layers (16) and the second frame part (14) abuts a second surface (17b) of the at least two membrane layers (16) opposite the first surface (17a), such that the membrane layers (16) are clamped in a single frame comprising both frame parts (12, 14), wherein the at least two membrane layers (16) each have at least one electrode (20, 22) and the electrodes (20, 22) of directly adjacent membrane layers (16) are arranged offset from each other.

Description

The invention relates to a membrane actuator and a method for manufacturing a membrane actuator. The term "actuator," as used here, refers to a component or assembly that converts electrical energy into mechanical energy, thereby generating movement in a part of the actuator that can be transferred to an element to be actuated. Such an actuator can be advantageously used, among other things, in fluid valve technology, for example, to actuate a valve. A membrane actuator is characterized by a membrane layer that converts electrical energy into mechanical energy. Typically, this membrane layer is made of an electroactive polymer that expands or contracts when a voltage is applied. This process converts the applied electrical energy into mechanical energy, resulting in the movement of an output component of the actuator. Suitable electroactive polymers include, for example, silicone, polyurethane, and acrylate. It is known from the prior art to stack several such membrane actuators on top of each other to form a stacked membrane actuator, the available force of which is thereby increased. For example, such a stacked membrane actuator is known from WO 2008 / 083 325 A1, in which a membrane layer is clamped between two frame parts. Several of these membrane actuators are stacked on top of each other to form the stacked membrane actuator. US Patent 2009 / 0236939A1 discloses a membrane actuator with multiple frame parts and membrane layers, wherein electrodes are arranged on the membrane layers, and wherein the membrane layers are arranged between the frame parts. US patent 8,797,654 B2 discloses an optical device in which an electroactive element is arranged on a flexible lens. US patent 2013 / 0207793A1 discloses a membrane actuator with multiple electroactive layers, each associated with electrodes, and connecting layers arranged between them which, together with contact pins, serve to connect the electrodes. A passive layer is arranged on both the top and bottom of the stack. WO 2013 / 192 143 A1 describes an electroactive component and a method for manufacturing such a component. US 7 049 732 B2 discloses an actuator in which several layers of membrane with electrodes arranged on them are clamped vertically between two frame parts. A disadvantage of such stacked membrane actuators is their large space requirement, as the individual actuators rest on top of each other via their frame components. However, the frames are taller than the active areas of the membrane layers that generate the movement—that is, the areas of the membrane layers located between the electrode layers. This results in a significant waste of installation space. The object of the invention is to design a membrane actuator that can exert a high force and yet requires little installation space. The problem is solved according to the invention by a membrane actuator comprising a first frame part and a second frame part, between which at least two membrane layers are stacked and arranged as electroactive polymer layers. The first frame part rests against a first surface of the at least two membrane layers, and the second frame part rests against a second surface of the at least two membrane layers, which is opposite the first surface, such that the membrane layers are clamped in a single frame that encompasses both frame parts. The at least two membrane layers each have at least one electrode, and the electrodes of directly adjacent membrane layers are arranged offset from one another. The basic idea of ​​the invention is to reduce the space requirement of the membrane actuator by eliminating the need to clamp each individual membrane layer in its own frame. Therefore, such a membrane actuator can also be called a multilayer membrane actuator, since several membrane layers are arranged within a single actuator, particularly within a single frame. Despite this, the multiple membrane layers can still provide a significant force, enabling such a membrane actuator to generate forces comparable to those of stacked membrane actuators known from the prior art, but with a lower overall height. In particular, the membrane actuator can be a dielectric elastomer actuator. A dielectric elastomer actuator generally works by placing a large-area electrode on each of two opposite sides of a dielectric polymer film. When a sufficiently strong electrical voltage is applied to the electrodes, they attract each other, compressing the intervening polymer film. Since the dielectric polymer film used is nearly incompressible, reducing the distance between the electrodes results in a change in shape. For example, in the case of a membrane, the central section of a circular membrane can be deflected axially relative to the outer edge when an electrical voltage is applied to the electrodes on both sides of the membrane; the reduction in the thickness of the dielectric polymer film is, in simplified terms, translated into a greater axial length of the membrane. The electrode ensures that the membrane layers can be subjected to an electrical voltage. The electroactive membrane layers can thus expand or contract when subjected to an electrical voltage. By arranging the electrodes offset from one another, a membrane actuator with stacked membrane layers ensures that an electric field forms between directly adjacent membrane layers. The offset membrane layers are assigned to different poles of a voltage source. Therefore, a single voltage source can be sufficient to electrically stimulate all membrane layers. One aspect of the invention provides that the at least two active membrane layers are in direct contact with each other. This significantly reduces the space required for the membrane actuator, since the individual membrane layers are very thin and no further component is arranged between them. The first frame section can form the lower end of the membrane actuator, while the second frame section forms the upper end. This ensures that the membrane layers located between the frame sections are held securely and firmly in place. According to a first embodiment of the membrane actuator according to the invention, a first connecting part is provided which rests against the first surface of the at least two membrane layers, and / or a second connecting part is provided which rests against the second surface of the at least two membrane layers, wherein, in particular, the first connecting part and / or the second connecting part rests or rests centrally against the respective surface. The membrane actuator can interact with an actuated element via the first or the second connecting part. This can be achieved, for example, by connecting the membrane actuator to the respective part to be moved via the first and / or the second connecting part. Alternatively, the connecting parts can also serve as stop elements that engage with an actuated element when the actuator moves. Furthermore, each of the two connecting parts can be assigned an actuated element.The central arrangement of the first and / or second connecting part ensures that the connecting parts experience a homogeneous adjustment movement when the membrane actuator is activated. According to a second embodiment of the invention, the at least two membrane layers each have an opening located centrally within the respective membrane layer, and in particular, this opening is circular. In such a membrane actuator, it can be provided, for example, that the membrane layers expand or contract mechanically when a voltage is applied, such that the opening within the membrane layers changes. For instance, the opening can contract when an electrical voltage is applied, thereby reducing its size. The opening can be circular or substantially rectangular. Furthermore, the at least two membrane layers can be circular or substantially rectangular. Different mechanical movements of the membrane actuator can be achieved by varying the shape of the membrane layers when the actuator is electrically actuated. In particular, the first frame part and / or the second frame part can be circular or essentially rectangular. The frame parts are designed according to the respective membrane layers to ensure that they can hold the membrane layers securely at their outer edges or are attached to the membrane layers via these edges. The area of ​​the membrane layers not fixed by the frame parts serves as the active area, which translates the movement when the membrane actuator is stimulated. Another aspect of the invention provides that the first frame part and / or the second frame part are at least partially flexible. The partially flexible design of the frame parts allows for the creation of a membrane actuator capable of assuming various shapes and performing movements, since the frame itself can deform due to the at least partially flexible frame parts. The membrane actuator can have or be formed from a DEMES structure. A DEMES structure (Dielectric Elastomer Minimum Energy Structure) is a structure that assumes an energetically favorable state (equilibrium state). By activating the membrane layers, energy can be introduced into the membrane actuator, which is at least partially formed from a DEMES structure, causing it to deform from its energetically favorable equilibrium state.In particular, the membrane actuator can also be designed to be completely flexible, i.e., to consist entirely of a DEMES structure. A further aspect of the invention provides that the first frame part has a first connection and / or the second frame part has a second connection. The membrane layers, in particular their electrodes, are supplied with a voltage via these connections. The frame parts, which serve to fix the individual membrane layers, thus simultaneously ensure the indirect electrical supply to the individual membrane layers as well as the edge fixation of the membrane layers. In particular, the electrodes of the at least two membrane layers are electrically contacted, with the electrodes of every second membrane layer being coupled to the first terminal and the other membrane layers to the second terminal. This results in an asymmetrical contacting of the stacked membrane layers, since an electric field always forms between two adjacent membrane layers, which is required to generate a voltage in the respective membrane layers. The object of the invention is further achieved by a method for manufacturing a membrane actuator, comprising the following steps: a) providing a first tool part, a first frame part and a polymer film made of an electroactive material, b) arranging the first frame part on the first tool part, c) clamping the polymer film, d) mechanically stretching the polymer film, e) fixing the polymer film, in particular on the first tool part, and f) cutting the polymer film so that a membrane layer is formed. The method according to the invention ensures that the required preload of the membrane layer can be achieved. Due to the preload, the available force of the membrane actuator can be increased. By stretching or extending the membrane layer, a preferred direction of the actuator is defined. According to one aspect of the invention, step g) is performed in which at least one electrode is applied to the membrane layer, wherein step g) is performed particularly after steps c) to e). Applying the electrode is important so that the membrane layer can be subjected to a voltage. The electrode should be applied particularly after the mechanical stretching in step d) to prevent damage to the electrode. The at least one electrode can be applied by means of a wet chemical process such as spraying, stamping, printing, or screen printing. In general, a wide variety of electrode patterns can be realized using this method. Furthermore, steps c) to e) are repeated to form multiple membrane layers. Depending on the number of repetitions, a multilayer membrane actuator is created, possessing membrane layers corresponding to the number of repetitions. This increases the available force of the membrane actuator. In particular, the electrodes of directly adjacent membrane layers are arranged at least partially offset from each other. This ensures that directly adjacent membrane layers can be supplied or coupled with different voltages or connections, so that an electric field can form between directly adjacent membrane layers when a voltage is applied to the membrane actuator. Furthermore, a second frame part is provided, which is arranged on the side of the at least one membrane layer opposite the first frame part. The second frame part thus forms the end of the membrane actuator opposite the first frame part, ensuring that the at least one membrane layer is positioned between the two frame parts. The at least one membrane layer is therefore securely clamped. Furthermore, it is provided that the polymer film is stretched unidirectionally or radially in step d), in particular uniformly. This stretching allows for the creation of a multilayer membrane actuator with pre-stretched membrane layers, which delivers high force in a compact design. Radial stretching is particularly important for circular membrane layers. Uniform radial stretching ensures that a circular membrane layer clamped in a circular frame, for example, when the electrodes are actuated, is compressed in its active area between the electrodes, thus reducing the wall thickness there. Since the membrane layer material is incompressible, it "elongates," allowing the center of the membrane to be deflected relative to its initial state.When the voltage is removed from the electrodes, the actuator returns to its initial state; the wall thickness of the membrane layers increases again, thereby pulling the center back into its original position. In general, pre-stretching allows for a defined movement of the membrane actuator with greater force. In particular, the first tool part is moved in step d) to mechanically stretch the polymer film. The first tool part thus serves not only to fix the polymer film in order to form the membrane layer, but also to stretch the polymer film. This results in a simple method for manufacturing the membrane actuator, especially a membrane actuator with pre-stretched membrane layers. Furthermore, a second tool component can be provided, which is also moved to stretch the polymer film. This second tool component can be provided particularly when radial stretching of the polymer film or membrane layer is required. According to one aspect of the invention, the second tool part has a structure that essentially corresponds to the first frame part and / or the second tool part is positioned opposite the first frame part. Due to the positioning and / or design of the second tool part, the polymer film can be radially stretched. For this purpose, the second tool part is, in particular, movable such that it can be moved in the direction of the first tool part, on which the first frame part is arranged. The appropriately designed structure ensures that the polymer film is radially stretched to form the radially pre-stretched membrane layer. According to a further aspect of the invention, the first membrane layer is attached to the first frame part, in particular by gluing or welding. This ensures that there is a firm connection between the frame part and the edge of the first membrane layer, so that no relative movement can occur between the first frame part and the first membrane layer. Furthermore, the subsequent membrane layers can also be connected to the first frame part or the previous membrane layer. The connection is made at the edge. In particular, the first tool component is a worktable or a work drum with multiple working surfaces. This enables a very economical manufacturing process that can be carried out in a very small space. In particular, the first tool component, designed as a working drum, is rotated around an axis of rotation, so that a polymer film section assigned to a work surface is fed to different work stations. This allows for the highly efficient production of a multilayer membrane actuator, as the respective membrane layer being processed passes through several stations sequentially. Furthermore, the rotation of the working drum around its axis of rotation minimizes the required space. Simultaneously, other multilayer membrane actuators can be subjected to different process steps on the other work surfaces. In general, the work surfaces can be designed such that several membrane actuators are produced simultaneously. Accordingly, a batch of membrane actuators is manufactured on one work surface. A matrix can be arranged on the corresponding work surface for this purpose. Further advantages and features of the invention will become apparent from the following description and the drawings, to which reference is made. The drawings show: - Fig. 1a a sectional view through a membrane actuator according to a first embodiment of the invention, - Fig. 1b a top view of the membrane actuator according to Fig. 1a, - Fig. 1c a cross-section through the membrane actuator according to Fig. 1a at a first electrode, - Fig. 1d a cross-section through the membrane actuator according to Fig. 1a at a second electrode, - Figs. 2a to 2c a representation of the membrane actuator according to the invention from Fig. 1a in a top view, a sectional view in the initial state and a sectional view in the activated state, - Figs. 3a to 3c a representation of a membrane actuator according to the invention according to a second embodiment in a top view, a sectional view in the initial state and a sectional view in the activated state, - Fig.3d a top view of the membrane actuator according to the second embodiment,- Fig. 3e a cross-section through the membrane actuator according to the second embodiment at a first electrode,- Fig. 3f a cross-section through the membrane actuator according to the second embodiment at a second electrode,- Figs. 4a to 4c a representation of a membrane actuator according to the invention according to a third embodiment in a top view, a sectional view in the initial state and a sectional view in the activated state,- Figs. 5a to 5c an overview view of a membrane actuator according to the invention according to a fourth embodiment,- Fig. 6a a top view of an electrode pattern of a membrane actuator according to the invention according to a fifth embodiment,- Fig. 6b a top view of an electrode pattern of a membrane actuator according to the invention according to a sixth embodiment,- Fig.Fig. 6c shows a top view of an electrode pattern of a membrane actuator according to a seventh embodiment according to the invention, Fig. 6d shows a top view of an electrode pattern of a membrane actuator according to an eighth embodiment according to the invention, Fig. 7 shows a top view of a matrix membrane actuator according to the invention, Figs. 8a to 8c show a representation of a membrane actuator according to the invention according to a ninth embodiment in a top view in the activated state, a sectional view in the initial state and a sectional view in the activated state, Figs. 9a to 9c show a representation of a membrane actuator according to the invention according to a tenth embodiment in a top view in the activated state, a sectional view in the initial state and a sectional view in the activated state, Fig. 10a shows a top view of a membrane actuator according to the invention according to an eleventh embodiment, Fig.Fig. 10b a top view of a membrane actuator according to the invention according to a twelfth embodiment, Fig. 10c a top view of a membrane actuator according to the invention according to a thirteenth embodiment, Fig. 10d a top view of a membrane actuator according to the invention according to a fourteenth embodiment, Fig. 10e a top view of a membrane actuator according to the invention according to a fifteenth embodiment, Figs. 11a to 11c a representation of a membrane actuator according to the invention according to a sixteenth embodiment in a top view, a sectional view in the initial state and a sectional view in the activated state, Fig. 12a a schematic representation of a first process step of the manufacturing process according to the invention according to a first variant, Fig. 12b a schematic representation of a second process step of the manufacturing process according to the invention according to a first variant, Fig.Fig. 12c a schematic representation of a third process step of the manufacturing process according to a first embodiment, Fig. 12d a schematic representation of a fourth process step of the manufacturing process according to a first embodiment, Fig. 12e a top view of Fig. 12d, Fig. 13a a schematic representation during the manufacturing process at a first time point according to a first embodiment, Fig. 13b the representation according to Fig. 13a at a second time point, Fig. 14a a schematic representation during the manufacturing process at a first time point according to a second embodiment, Fig. 14b the representation according to Fig. 14a at a second time point, Fig. 15a a schematic representation of a first process step in the manufacturing process according to a second embodiment, Fig.Fig. 15b a schematic representation of a second process step in the manufacturing process according to a second variant of the invention,- Fig. 15c a schematic representation of a third process step in the manufacturing process according to a second variant of the invention,- Fig. 16 a detailed view of Fig. 15c,- Fig. 17 a flow chart of the manufacturing process according to a second variant of the invention,- Fig. 18 a schematic overview of the manufacturing process according to a third variant of the invention,- Fig. 19 a perspective view of the first tool part designed as a tool drum, which is used in the process shown in Fig. 18,- Fig. 20a a first process step of the manufacturing process according to the invention according to the third variant,- Fig. 20b a second process step of the manufacturing process according to the invention according to the third variant,- Fig.Fig. 20c a third process step of the manufacturing process according to the invention according to the third variant,- Fig. 20d a fourth process step of the manufacturing process according to the invention according to the third variant,- Fig. 20e a fifth process step of the manufacturing process according to the invention according to the third variant,- Fig. 20f a sixth process step of the manufacturing process according to the invention according to the third variant,- Fig. 20g a seventh process step of the manufacturing process according to the invention according to the third variant,- Fig. 20h an eighth process step of the manufacturing process according to the invention according to the third variant,- Fig. 21a a first alternative embodiment of the first tool part,- Fig. 21b a second alternative embodiment of the first tool part,- Fig. 21c a third alternative embodiment of the first tool part,- Fig.Fig. 22a shows another membrane actuator produced by the manufacturing process according to the invention in an overview view, Fig. 22b shows another membrane actuator produced by the manufacturing process according to the invention in an overview view, Fig. 22c shows another membrane actuator produced by the manufacturing process according to the invention in an overview view, Fig. 22d shows another membrane actuator produced by the manufacturing process according to the invention in an overview view, Fig. 22e shows another membrane actuator produced by the manufacturing process according to the invention in an overview view, Fig. 22f shows another membrane actuator produced by the manufacturing process according to the invention in an overview view, Fig. 22g shows another membrane actuator produced by the manufacturing process according to the invention in an overview view. Fig. 1a shows a membrane actuator 10 which has a first frame part 12 and a second frame part 14. In the illustrated embodiment, five membrane layers 16 are arranged between the two frame parts 12, 14. Accordingly, the membrane actuator 10 is a multi-layer membrane actuator that has several membrane layers 16 in a frame 15, which is formed by the frame parts 12, 14. In general, the membrane layers 16 are made of a dielectric elastomer or an electroactive polymer, so that they can convert an electrical excitation into a mechanical movement. The individual membrane layers 16 can in particular be pre-stretched, as will be explained below with reference to Fig. 12 , Fig. 13 , Fig. 14 , Fig. 15 , Fig. 16 , Fig. 17 , Fig. 18 , Fig. 19 to Fig. 20. The membrane layers 16 lie directly against each other and form a stack 17, which has a first surface 17a and a second surface 17b. The second surface 17b is arranged opposite to the first surface 17a, with the first frame part 12 abutting the first surface 17a and the second frame part 14 abutting the second surface 17b. The frame parts 12, 14 are located directly adjacent to the first membrane layer 16a and the last membrane layer 16e in a first edge area 18 and a second edge area 19 of the membrane layers 16. Each of the membrane layers 16 is preferably assigned two electrodes 20, 22, wherein a first electrode 20 and a second electrode 22 are provided which differ in their corresponding assigned polarity, as explained below. In general, the electrodes 20, 22 are assigned to the membrane layers 16 such that two directly adjacent membrane layers 16 have a different electrode application or a different electrode pattern. Electrodes 20 and 22 can, for example, be made of metal. Alternatively, electrodes 20 and 22 can be based on carbon, nanoparticles, or an ICP (intrinsically conducting polymer). For contacting the electrodes 20, 22, the frame parts 12, 14 have a first connection 24, which is assigned to the first edge region 18, and a second connection 25, which is assigned to the second edge region 19. The two connections 24, 25 differ in their polarity. Each membrane layer 16 therefore has at least one electrode 20, 22 which is assigned either to the first terminal 24 or to the second terminal 25. The through-hole plating of the electrodes 20, 22 of the membrane layers 16 and the contact with the terminals 24, 25 can be effected via contacting elements 26, 27, which are designed, for example, as rivets, push pins and / or made of an elastically conductive elastomer. The openings provided for receiving the contacting elements 26, 27 can be formed, for example, by punching. The connections 24, 25 can be integrated into the respective frame parts 12, 14 and can also be designed as plugs or sockets to enable simple electrical contacting of the membrane actuator 10. The membrane actuator 10 can be supplied with a voltage via the connections 24, 25, so that the electroactive membrane layers 16 expand or contract, thereby converting the electrical energy into mechanical kinetic energy. The structure of the individual membrane layers 16 is explained below by way of example with reference to Figs. 1a to 1d: For example, the first or lowest membrane layer 16a, which rests directly on the first frame part 12, has a first electrode 20a, which is provided on the upper side of the membrane layer 16a. The first electrode 20a is electrically coupled to the first terminal 24. Such an electrode 20a is shown in Fig. 1c, which represents a cross-section. For contacting the first terminal 24, the first electrode 20a has a lateral projection which is provided in the first edge area 18. In contrast, the second membrane layer 16b, which is arranged directly on the side of the first membrane layer 16a opposite the first frame part 12, has a second electrode 22b on its upper side. Such a second electrode 22 is shown by way of example in Fig. 1d. The second electrode 22b extends to the second edge 19, so that the second electrode 22b of the second membrane layer 16b is electrically coupled to the second terminal 25. This structure is repeated several times. Accordingly, the third membrane layer 16c also has a first electrode 20c on its upper surface, which has a projection extending to the first edge region 18. In contrast, the fourth membrane layer 16d has a second electrode 22d on its upper surface, which is coupled to the second connection 25. The final membrane layer 16e, on the other hand, has a first electrode 20e which is electrically coupled to the first terminal 24. As a result, the stack 17 of the membrane layers 16 has an asymmetrical electrode pattern in cross-section, since a first electrode 20 ( Fig. 1c) and a second electrode 22 ( Fig. 1d) are provided alternately. Accordingly, on the respective upper surface of each second membrane layer 16 of the stack 17 either a first or a second electrode 20, 22 is applied, with a second or a first electrode 22, 20 being applied accordingly on the upper surfaces of the other membrane layers 16. This ensures that each membrane layer 16b to 16e is assigned a first electrode 20 and a second electrode 22 with opposite polarities. When a voltage is applied, these membrane layers 16b to 16e are compressed in the direction of the electric field and, due to the incompressibility of the membrane layers 16, expand perpendicular to the direction of the electric field to maintain a constant volume. The expansion of the membrane layers 16b to 16e is then used for the mechanical adjustment movement. In the sectional view shown in Fig. 1a, the first membrane layer 16a has a second electrode 22a on its underside, which is optional. This merely ensures that the first membrane layer 16a can also be used to generate the mechanical adjustment movement. Without the second electrode 22a on its underside, the first membrane layer 16a would only function as a support layer for the first electrode 20a on its top side, without contributing to the adjustment movement; it would be passively adjusted when the other membrane layers "work". If the second electrode 22a on the underside of the first membrane layer 16a were omitted, then each membrane layer 16 would only have one electrode 20, 22 on its respective top side. Alternatively, all membrane layers 16 can have an electrode 20, 22 on both their upper and lower surfaces, with the electrodes 20, 22 having correspondingly different polarities. For example, a first electrode 20 is provided on the upper surface, whereas a second electrode 22 is provided on the lower surface. The membrane layer 16 located on the upper surface must then also have a first electrode 20 on its lower surface, so that no insulation between adjacent membrane layers 16 is necessary. However, this may be provided for in certain cases. A comparison of Figures 1b to 1d further shows that the two electrodes 20, 22 differ only in their projections, via which they are coupled to the respective terminals 24, 26. Otherwise, they have the same base area, which corresponds in particular to almost the entire area of ​​the respective membrane layer 16. This results in the electrodes 20, 22 having a large surface area opposite each other. The membrane actuator 10 can be installed with preload, so that, for example, the central region of the membrane layers 16 can be preloaded into a deflected (conical) state by means of a spring. By applying a tension, the deflection of the central region can then be controlled very precisely as desired. Furthermore, the membrane actuator 10 shown in Fig. 1a has a first connecting part 28 and a second connecting part 30. The first connecting part 28, like the first frame part 12, is arranged on the first surface 17a of the stack 17, whereas the second connecting part 30 is arranged on the second surface 17b of the stack 17. The two connecting parts 28, 30 are each attached centrally to the stack 17 and, in particular, have a height that corresponds to the two frame parts 12, 14. This creates a compact membrane actuator 10. Figure 1a further shows that the respective electrodes 20, 22 of the membrane layers are designed such that they do not cover the central area where the connecting elements 28, 30 are provided. The spring mentioned above can act on the connecting elements 28, 30. The connecting elements can also be used as the actuator's output to transfer the generated stroke to another component (for example, a valve element). Figure 2 shows an overview of the membrane actuator 10 from Figure 1. The overview includes a top view of the inactive membrane actuator 10 (Figure 2a), as well as a sectional view of the membrane actuator 10 in an inactive position (Figure 2b) and in a deflected position (Figure 2c). As can be seen in Fig. 2a, the membrane actuator 10 is circular, since both the first frame part 12 and the second frame part 14 are circular. Furthermore, the individual membrane layers 16 and the connecting parts 28, 30 are also circular. In the initial state (Fig. 2b) the membrane layers 16 are stretched tightly between the frame parts, so that the connecting parts 28, 30 are in an initial position in the central plane. When a voltage is applied to the membrane actuator 10 via the two electrical connections 24, 25 (not shown here), an electric field forms between directly adjacent membrane layers 16 of the stack 17, since the directly adjacent membrane layers 16 are alternately contacted with one of the connections 24, 25. The membrane layers 16, made of electroactive polymer, are compressed due to the attractive force between the electrodes, thus reducing their wall thickness. Since the material of the membrane layers is (almost) incompressible, the material becomes "longer." This allows the central section of the membrane layers 16 to be deflected relative to its initial state. In Fig. 2c, the central section is deflected upwards. This can be achieved by means of a spring (not shown) that can adjust the connecting parts 28, 30 upwards when the membrane layers between the electrodes 20, 22 are compressed and therefore "lengthen." If there were no spring or other component to adjust the central section upwards with respect to Fig. 2c, the central section could also sag downwards under the influence of gravity when a tension is applied. Regardless of the installation position and an element that prestresses the central section, it can be seen that the applied electrical energy is converted into mechanical energy, resulting in the deflection of the connecting parts 28, 30, as can be seen from the lower illustration in the overview. The connecting parts 28, 30 can in particular interact with at least one element to be adjusted, so that when the membrane actuator 10 is activated a mechanical adjustment of the element to be moved is achieved. The frame parts 12, 14 may be provided with means by which the membrane actuator 10 can be mechanically fastened. These means may be bores or slots or fastening elements. Figures 3a to 3c also show a second embodiment of the membrane actuator 10 in an overview view. The second embodiment of the membrane actuator 10 differs from the first embodiment in that the frame parts 12, 14, the membrane layers 16 and the connecting parts 28, 30 are essentially rectangular (see Fig. 3a). Only the corners are rounded. Otherwise, the structure and function of the membrane actuator 10 are the same. The advantage of the second embodiment is that several actuators can be arranged close together without wasting space between them. In Figs. 3d to 3f, the membrane actuator 10 from Fig. 3 is shown in a top view (Fig. 3d) and two cross-sectional views (Fig. 3e and Fig. 3f) in different planes to illustrate the design of the two electrodes 20, 22 according to the second embodiment. Figures 3d to 3f are to be understood in an analogous manner to Figures 1b to 1d, so that in particular the extent of the respective electrode 20, 22 can be seen from Figures 3e and 3f. Fig. 4 shows a third embodiment of the membrane actuator 10 in an overview view, which at first glance resembles the first embodiment. The difference between the third embodiment and the first embodiment, however, is that each of the membrane layers 16 has an opening 32 which is formed in the middle of the respective membrane layer 16 (see Fig. 4a and Fig. 4b). The openings 32 of the respective membrane layers 16 are also circular in the embodiment shown. As can be seen from the overview in Fig. 4, activation of the membrane actuator 10 according to the third embodiment causes the individual membrane layers 16 to contract in such a way that the diameter of the openings 32 is reduced. In the illustrated embodiment, the openings 32 can contract so far that they close relative to an initial state (see Fig. 4a and Fig. 4b) (see Fig. 4c). In this way, for example, a flow cross-section can be controlled directly without having to transmit the movement of the actuator to a valve element. Fig. 5 shows a fourth embodiment of the membrane actuator 10, which essentially corresponds to the third embodiment, wherein the frame parts 12, 14, the membrane layers 16 and the openings 32 are not circular, but essentially rectangular. However, the overall structure and operation of the membrane actuator 10 do not differ from the third embodiment; here too, the openings 32 can be closed from an initial state (see Fig. 5a and Fig. 5b) (see Fig. 5c) by applying a voltage to the electrodes. Figures 6a to 6e show further embodiments of the membrane actuator 10, showing the arrangement of the electrodes 20, 22 and the electrode pattern, respectively. Different movements of the membrane actuator 10 according to the invention can be achieved by varying the arrangement and design of the electrodes 20, 22. In particular, asymmetrical electrodes can be used to obtain asymmetrical deformations of the membrane layers. Fig. 7 shows a top view of a matrix membrane actuator 34. The matrix membrane actuator 34 has a circumferential frame 35 with intermediate webs 36 arranged between it, which form a matrix 37. This matrix 37 contains several segments 38, each containing a membrane actuator 10. The membrane actuators 10 are each configured according to the second embodiment shown in Fig. 3. Each individual segment 38 is also assigned the connections 24, 25, so that the individual membrane actuators 10 of the matrix membrane actuator 34 can be electrically actuated independently of each other. The matrix membrane actuator 34 can also be configured with the membrane actuators 10 of the other embodiments. In particular, mixtures of the embodiments can also be provided in a matrix membrane actuator 34. Fig. 8 shows a ninth embodiment of the membrane actuator 10 in an overview view, with the top view (Fig. 8a) and the lower sectional view (Fig. 8c) now showing the electrically excited position of the membrane actuator 10. In contrast to the previous embodiments, the frame parts 12, 14 of the membrane actuator 10 are designed to be flexible. For this purpose, the membrane actuators 10 and, in particular, the frame parts 12, 14 can be formed from a DEMES structure. As can be seen from the overview shown in Fig. 8, the individual membrane layers 16 and thus the stack 17 contract when a voltage is applied. This causes the membrane actuator 10 and in particular its frame 15 to transition from its energetically favorable equilibrium state (Fig. 8b) to an excited state (Fig. 8c). In the embodiment shown, this reduces the height of the membrane actuator 10, as can be seen in particular from a comparison of Fig. 8b and Fig. 8c. In the illustrated embodiment, the frame parts 12, 14 and the membrane layers 16 are each circular in shape. Fig. 9 shows a further embodiment of the membrane actuator 10, in which the frame parts 12, 14 are designed flexibly analogous to the previous embodiment. In contrast to the previous embodiment, the frame parts 12, 14 and the membrane layers 16 are essentially rectangular. A comparison of the two embodiments shown in Figs. 8 and 9 further illustrates that the frame parts 12, 14 can be configured differently with respect to their initial energy state. This manifests itself in the fact that the frame parts contract to different degrees when no stress is applied (and consequently deform to different degrees when a stress is applied). The frame 15 of the embodiment in Fig. 9 contracts more in the relaxed state than the frame 15 of the embodiment in Fig. 8. Figures 10a to 10e show further embodiments of the membrane actuator 10, each of which is shown in a top view. In this case, both the geometry of the flexible frames 15 and that of the electrode pattern can be designed accordingly to realize a wide variety of movements of the membrane actuator 10. Fig. 11 shows another embodiment of the membrane actuator 10 in an overview view, in which the top view (Fig. 11a) shows the excited position of the membrane actuator 10 (Fig. 11c). In this embodiment, features of the third embodiment are combined with features of the ninth embodiment: the actuator has a central opening 32, and DEMES structures are used. The central opening 32 is located in the initial state (Fig. 11b) between quarter-circle membrane layers. These are bent in the same direction due to the prestressing of their frame parts, so that their tips are spaced apart. When a voltage is applied to the electrodes, they deform into a stretched state (see Fig. 11c), in which their tips are (almost) touching each other. The opening 32 is now (almost) closed. This is possible because the frame 15 is partially flexible. The frame 15 has a flexible frame part 14a, which has an annular section and four sections surrounding the quadruple-circular membrane layers, projecting inwards from the annular section. The semi-flexible frame part 14a is fixedly arranged on the rigid frame part 14 via its ring-shaped section, whereas the inwardly projecting sections are free so that they can deform due to their flexible design, as a comparison of Figs. 11a to 11c illustrates. In general, 15 different mechanical movement patterns and very different geometries of the membrane actuators 10 can be realized via the semi-flexible frame. Instead of the second frame part 14 and in particular section 14a, a first or second connecting part can also be used, which is designed to be correspondingly flexible. The manufacturing process according to the invention, with which the membrane actuator 10 according to the invention can be manufactured, is described with reference to Figs. 12a to 12e. For the production of the membrane actuator 10, a polymer film 40 is provided which is clamped between a first pair of rollers 42 and a second pair of rollers 44. Furthermore, a first tool part 46 is provided, which in the illustrated embodiment is designed as a worktable. The first frame part 12 is arranged on a first surface 46a on the first tool part 46, but this is not shown in the figures for the sake of clarity. The polymer film 40 is transferred via the first pair of rollers 42, which rotates at a first speed, to the second pair of rollers 44, which rotates at a second speed. If the two pairs of rollers 42 and 44 move at the same speed, no pre-tension is generated on the polymer film 40, so that only clamping occurs. However, if the second pair of rollers 44 has a higher rotational speed than the first pair of rollers 42, the polymer film 40 between the two pairs of rollers 42, 44 is already mechanically prestressed. The first tool part 46 is moved linearly and translationally in the direction of the polymer film 40 with the first frame part 12 arranged on it (see Fig. 12b), so that the polymer film 40 clamped between the two pairs of rollers 42, 44 is mechanically stretched. This results in a uniaxial elongation of the polymer film 40, i.e., a mechanical elongation in one direction. An alignment grid can be provided, which is previously applied to the unstretched polymer film 40. The deformation of the alignment grid indicates whether the desired elongation of the polymer film 40 has been achieved. The alignment grid can, for example, be detected and monitored electronically. Furthermore, openings can be provided in the first surface 46a of the tool part 46 through which an overpressure or underpressure can be generated, so that the polymer film 40 either slides well over the first surface 46a when air or gas is blown between the film and the tool, or adheres to it when the film is sucked against the surface with underpressure. The tool part 46 can be made of a sintered metal or at least have a sintered metal plate forming the first surface 46a, such that the first surface 46a is permeable to air. The first surface 46a generally has a high surface quality, as it comes into contact with the polymer film 40. Subsequently, the two pairs of rollers 42, 44 are moved around the first tool part 46, in particular translationally, until they are opposite the second surface 46b of the first tool part 46, which is opposite to the first surface 46a (see Fig. 12c). This coats the first tool part 46 with the polymer film 40. Now the polymer film 40 is attached to the first tool part 46, in particular to the second surface 46b of the first tool part 46. The polymer film 40 is then cut in the area of ​​the two roller pairs 42, 44 by cutting means 48, in particular in an area between the fixed points on the first tool part 46 and the roller pairs 42, 44 (see Fig. 12d). The cutting means 48 can be knives or metal plates. After the polymer film 40 has been cut off, the two pairs of rollers 42, 44 can move freely again and return to their starting position. This places the first membrane layer 16a on the first frame part 12. Subsequently, the first electrode 20 or the second electrode 22 can be applied to the first membrane layer 16a. The steps described above can now be repeated to apply further membrane layers 16 in an analogous manner, applying the electrodes 20, 22 alternately, so that a multilayer membrane actuator 10 is formed. It may also be provided that the first membrane layer 16a is attached to the first frame part 12, in particular by gluing or welding. UV-curing silicone or a thermal ultrasonic compression welding process can be used for this purpose. Figure 12e shows a top view of the representation shown in Figure 12d. The top view reveals that a batch of membrane actuators 10 was manufactured simultaneously. For this purpose, several first frame parts 12 or a continuous part were arranged on the first tool part 46, which encompasses several first frame parts 12 in a matrix-like manner. This could, for example, be an injection-molded matrix. After all membrane layers 16 have been arranged on the respective membrane actuator 10, the second frame part 14 is placed on the last or uppermost membrane layer 16. All membrane layers 16 are thus arranged between the first frame part 12 and the second frame part 14, which form the frame 15. The individual membrane layers 16 are then connected via a contact element such as a rivet or a push pin. The contact element can also be made of an elastically conductive elastomer. In this case, it is advantageous to additionally arrange rigid fastening elements between the two frame parts to ensure the membrane layers are reliably held in place. Alternatively, the contact elements can be used to fix the membrane layers radially to the frame parts 12, 14. Generally, contact can be made by punching or by pressing in contact elements. If the first membrane layer 16a is to have an electrode 20, 22 on its underside, this can be applied before the first membrane layer 16a is placed on the first frame part 12 or afterwards, although this makes contacting more difficult. Thus, a membrane actuator 10 according to the invention is created, which is a multilayer membrane actuator. Such manufacturing processes can produce a unidirectional or uniaxial pre-stretch of the polymer film 40, which is particularly important for an essentially rectangular membrane actuator 10. Figure 13a shows the two pairs of rollers 42, 44 in their initial position, in which the polymer film 40 is fed to the first pair of rollers 42. As the first pair of rollers 42 rotates, the introduced polymer film 40 is transferred to the second pair of rollers 44, so that the polymer film 40 is clamped between the two pairs of rollers 42, 44. Subsequently, the second pair of rollers 44 moves away from the first pair of rollers 42, whereby, depending on the movement of the second pair of rollers 44 and its rotational speed, a pre-stretching of the polymer film 40 may or may not occur. The roller pairs 42, 44 can in particular be driven and controlled individually to ensure defined movements. Furthermore, the roller pairs 42, 44 can have a surface hardening or coating, giving them non-stick properties. Alternatively, a rubber coating can also be provided. Figures 14a to 14b show an alternative embodiment of the manufacturing process in which the second pair of rollers has been replaced by a gripper 50 which is moved linearly at a defined speed. Depending on the speed of the gripper 50, a pre-stretch of the polymer film 40 can be set. Figures 15a to 15c show an alternative embodiment of the manufacturing process in which a radial elongation of the polymer film 40 and thus of the individual membrane layers 16 is produced. In an analogous manner to the first manufacturing variant, the polymer film 40 is clamped, in particular pre-tensioned, between the first pair of rollers 42 and the second pair of rollers 44. Furthermore, the first tool part 46 is also designed as a worktable on which the first frame part 12 is arranged, which, however, is not shown for the sake of clarity. The first tool part 46 differs from that of the first embodiment in that it has projections 52 that protrude from the first surface 46a of the tool part 46. The projections 52 are arranged at the outer edges of the tool part 46. The function of these projections 52 is clearly shown in Fig. 15b, since the clamped polymer film 40 comes to rest on the projections 52 when the first tool part 46 has been moved linearly and translationally in the direction of the polymer film 40 in order to mechanically clamp or stretch the polymer film 40. The projections 52 extend from the first surface 46a of the first tool part 46 in such a way that the polymer film 40 does not contact the first frame part 12 arranged on the first surface 46a. As shown in Fig. 15c, the mechanically stretched polymer film 40 is now acted upon by a second tool part 54, which contacts the side of the polymer film 40 opposite to the first tool part 46. The second tool part 54 can also be moved linearly and translationally to contact the polymer film 40. In Fig. 16, the area circled with dashed lines in Fig. 15 is shown in detail. Figure 16 shows that the second tool part 54 has at least one punch arrangement 56 on its side associated with the polymer film 40. Via the punch arrangement 56, the second tool part 54 has a structure corresponding to the first frame part 12 and the first connecting part 28, both of which are arranged on the first surface 46a of the first tool part 46. The stamp arrangement 56 accordingly has a central pin 58 which is assigned to the first connecting part 28, as well as two outer pins 60, 62 which can interact with the first frame part 12. Before the punch assembly 56 is activated, the polymer film 40 is attached to the first tool part 46 in a manner analogous to the embodiment described above. For this purpose, the two pairs of rollers 42, 44 are moved around the tool part 46 so that they are opposite the second surface 46b. The polymer film 40 is attached there in an analogous manner, so that the stamp arrangement 56 can now be activated. As can be seen from the course of Fig. 17, the desired symmetrical and radial elongation of the polymer film 40 is achieved via the punch arrangement 56, since first the middle pin 58 of the punch arrangement 56 is adjusted, thereby pressing the polymer film 40 down onto the first connecting part 28. Subsequently, the two outer pins 60, 62 are also adjusted linearly, so that the polymer film 40 is pressed onto the first frame part 12. The stamp arrangement 56 thus represents an adjustable structure with which the symmetrical and radial elongation of the polymer film 40 is ensured. It can also be provided that the polymer film 40 is additionally attached to the second tool part 54 to achieve additional fixation. Attachment to the second tool part 54 can also be an alternative to attachment to the first tool part 46. The polymer film 40 can then be attached to the first frame part 12, either by bonding with, for example, UV-curable silicone or by thermal ultrasonic compression welding. The second tool part 54 can include the corresponding tools for attachment. In general, the second tool part 54 has several such punch arrangements 56, so that several membrane actuators 10 can be manufactured simultaneously. This is particularly important for the batch production of the membrane actuators 10. After the mechanical stretching of the polymer film 40 has taken place, the polymer film 40 attached to the first tool part 46 can be cut off in an analogous manner to the first embodiment of the manufacturing process, so that the first membrane layer 16a is formed. If the polymer film 40 has only been attached to the second tool part 54, the polymer film 40 will be cut off accordingly. Following this, the first electrode 20 or the second electrode 22 is also applied to the first membrane layer 16a. The steps described above are now repeated so that several membrane layers 16 are applied to form the multilayer membrane actuator 10. The electrodes 20, 22 applied to the upper surfaces of the membrane layers 16 alternate, so that each membrane layer 16 is assigned a first electrode 20 and a second electrode 22. As a final step, the second frame part 14 is placed on the last membrane layer 16 and the individual membrane layers 16 are connected via plated through to establish an electrical connection and to mechanically couple the individual membrane layers 16 with the frame parts 12, 14. Furthermore, the second tool part 54 can have cutting means 64 with which the polymer film 40 attached to the first tool part 46 can be cut directly in the area of ​​the first frame part 12 or the membrane actuator 10. This can be done after the respective membrane layer 16 has been attached or after all membrane layers 16 have been arranged. The first tool part 46, designed as a worktable, can be designed analogously to the embodiment previously described in Figs. 12a to 12e. The radial elongation of the polymer film 40 is particularly suitable for the membrane actuators 10, which are circular in shape. Fig. 18 schematically shows a third embodiment of the manufacturing process according to the invention for producing the membrane actuator 10 according to the invention. In this embodiment of the manufacturing process, the first tool part 46 is a working drum, which is shown in perspective in Fig. 19. The first tool part 46, designed as a working drum, has in the embodiment shown eight working surfaces 66, each of which is assigned to one of eight work stations 68, as can be seen from Fig. 18. As already indicated by the arrows in Fig. 18, the first tool part 46, designed as a working drum, can be moved rotationally and linearly translationally, whereby one of the eight working surfaces 66 is progressively positioned opposite one of the work stations 68. For this purpose, the tool part 46 rotates 45° about its axis of rotation A each time. The workstations 68 generally also have at least one degree of freedom, so that they can be adjusted linearly. The manufacture of the membrane actuator 10 is described with reference to Figs. 20a to 20h based on the third embodiment of the manufacturing process according to the invention. In the first process step, the polymer film 40 is introduced between the two pairs of rollers 42, 44 into a system 70 formed by the workstations 68 and the first tool part 46. The polymer film 40 is clamped between the two pairs of rollers 42, 44, and in particular slightly pre-tensioned. The first tool part 46 is in a position that is translationally offset from the center. In the first process step, the first workstation 68a is moved linearly towards the polymer film 40 in a translational manner, so that it almost comes into contact with the polymer film 40. The first workstation 68a can measure the thickness of the polymer film 40, which can be adjusted by the movement of the roller pairs 42, 44. In particular, a greater prestress of the polymer film 40 can be generated by the different speeds of the roller pairs 42, 44 and the resulting stretching. The thickness can be measured in particular using optical techniques such as white light interferometry, transmission spectroscopy or laser profilometry. Once the desired thickness of the polymer film 40 is reached, the second process step is carried out (see Fig. 20b). In this process, the first tool part 46, designed as a working drum, is moved translationally, whereby it is brought against the polymer film 40 with a first working surface 66a and mechanically stretches it. The first frame part 12 is placed on the first working surface 66a, so that it is positioned between the first working surface 66a and the polymer film 40. The polymer film 40 can slide along the first working surface 66a of the first tool part 46, provided that the surface of the first working surface 66a is designed accordingly. In this position, the first workstation 68a again measures the thickness of the polymer film 40 and attaches the polymer film 40 to the first tool part 46. Subsequently, the polymer film 40 is cut in an area between the second pair of rollers 44 and the attachment point, as schematically shown by the arrow. For attaching the polymer film 40 to the first tool part 46, the first work station 68a can be designed essentially analogously to the second tool part 54 according to the second embodiment of the manufacturing process. The first tool part 46, designed as a working drum, is now rotated 45° about its axis of rotation A, so that the first working surface 66a is opposite the second working station 68b (Fig. 20c). This marks the beginning of the third process step. In the second workstation 68b, a surface treatment of the polymer film 40 is carried out. This could, for example, involve plasma activation, which increases the adhesion of the electron layer. At the same time, a second batch of membrane actuators 10 is prepared in the first workstation 68a, since the same steps are carried out as in Fig. 20b. In general, the elongation of the polymer film 40 should remain constant, which is why the thickness of the polymer film 40 is constantly monitored in the first workstation 68a. After the surface treatment has been carried out, the first tool part 46, designed as a working drum, rotates again by 45° so that the first working surface 66a is opposite the third working station 68c (see Fig. 20d ). In the third workstation 68c, the first electrode 20 or the second electrode 22 is applied to the treated surface of the polymer film 40, so that the corresponding electrode 20, 22 is later applied to the top of the membrane layer 16. At the same time, a third batch of membrane actuators 10, which is arranged on the third work surface 66c, is prepared in the first work station 68a, while the second batch undergoes surface treatment in the second work station 68b. In a fourth process step, the first tool part 46, designed as a working drum, rotates again by 45° (see Fig. 20e), so that the first working surface 66a of the first tool part 46 is opposite the fourth work station 68d. At the fourth workstation 68d, another surface treatment is carried out, which may be a corona treatment intended to prevent the formation of bubbles during lamination. In workstations 68a to 68c, the further batches of the membrane actuators 10 are treated accordingly. The first tool part 46 now rotates further in 45° increments, whereby the fifth to eighth working surfaces 66e to 66h are supplied with a batch and the process steps provided in the first four work stations 68a to 68d have been carried out. When the first work surface 66a returns to the first work station 68a, a second membrane layer 16 is applied. The steps are now repeated several times, so that each batch of membrane actuators 10 is provided with several membrane layers 16 (see Fig. 20f). The individual membrane layers 16 are laminated together to form a composite. Workstations 5 to 8 are only used when the membrane actuators 10 have all membrane layers 16. If this is the case, the second frame part 14 is arranged and attached to the uppermost membrane layer 16 in the fifth work station 68e (see Fig. 20g). Simultaneously, the polymer film 40 is separated in the area of ​​the first workstation 68a. The remaining batches of the membrane actuators 10 are further processed in the preceding workstations 68a to 68d. The first tool part 46 then rotates again by 45°, whereby the individual membrane layers 16 of the membrane actuators 10 are connected in the sixth work station 68f. After a further rotation of the first tool part 46 by 45°, the batch of completed membrane actuators 10 is tested in the seventh workstation 68g. After a further rotation of 45°, the membrane actuator 10 reaches the eighth workstation 68h, in which the batch of membrane actuators 10 are punched or cut out to form the individual membrane actuators 10. Figures 21a to 21c show alternative embodiments of the first tool part 46 which can be used in the manufacturing process according to the third embodiment variant. The tool parts 46 shown have fewer work surfaces 66, so that several workstations 68 can be assigned to one work surface 66. Furthermore, Figures 22a to 22g show various embodiments of the membrane actuator 10, which can also be manufactured using the manufacturing process according to the invention in accordance with one of the three embodiment variants. These correspond essentially to the embodiment described above, with the difference that the membrane actuators 10 are designed as single-layer membrane actuators. In general, the manufacturing process according to the invention creates a membrane actuator 10 according to the invention which can provide large forces and yet has a small structure.

Claims

Membrane actuator (10) comprising a first frame part (12) and a second frame part (14), between which at least two membrane layers (16) are stacked and designed as electroactive polymer layers, wherein the first frame part (12) abuts a first surface (17a) of the at least two membrane layers (16) and the second frame part (14) abuts a second surface (17b) of the at least two membrane layers (16) opposite the first surface (17a), such that the membrane layers (16) are clamped in a single frame comprising both frame parts (12, 14), wherein the at least two membrane layers (16) each have at least one electrode (20, 22) and the electrodes (20, 22) of directly adjacent membrane layers (16) are arranged offset from each other. Membrane actuator (10) according to claim 1, characterized in that the at least two membrane layers (16) are directly adjacent to each other. Membrane actuator (10) of claim 1 or 2, characterized in that a first connecting part (28) is provided which abuts the first surface (17a) of the at least two membrane layers (16) and / or that a second connecting part (30) is provided which abuts the second surface (17b) of the at least two membrane layers (16), wherein in particular the first connecting part (28) and / or the second connecting part (30) abuts the respective surface (17a, 17b) centrally. Membrane actuator (10) according to one of the preceding claims, characterized in that the at least two membrane layers (16) each have an opening (32) which is provided centrally in the respective membrane layer (16) and is in particular circular in shape. Membrane actuator (10) according to one of the preceding claims, characterized in that the at least two membrane layers (16) are circular or substantially rectangular. Membrane actuator (10) according to one of the preceding claims, characterized in that the first frame part (12) and / or the second frame part (14) are circular or substantially rectangular in shape. Membrane actuator (10) according to one of the preceding claims, characterized in that the first frame part (12) and / or the second frame part (14) are at least partially flexible. Membrane actuator (10) according to one of the preceding claims, characterized in that the first frame part (12) has a first connection (24) and / or the second frame part (14) has a second connection (25). Membrane actuator (10) according to claim 8, characterized in that the electrodes (20, 22) of the at least two membrane layers (16) are electrically contacted, wherein the electrodes (20, 22) of each second membrane layer (16) are coupled to the first terminal (24) and the other membrane layers (16) to the second terminal (25). Method for manufacturing a membrane actuator (10), comprising the following steps: a) providing a first tool part (46), a first frame part (12) and a polymer film (40) made of an electroactive material, b) arranging the first frame part (12) on the first tool part (46), c) clamping the polymer film (40), d) mechanically stretching the polymer film (40) by linearly and translationally moving the first tool part (46) with the first frame part (12) arranged thereon in the direction of the polymer film (40), e) fixing the polymer film (40), in particular on the first tool part (46), and f) cutting the polymer film (40) so that a membrane layer (16) is formed. Method according to claim 10, characterized in that a step g) is carried out in which at least one electrode (20, 22) is applied to the membrane layer (16), wherein in particular step g) is carried out after steps c) to e). Method according to claim 11, characterized in that steps c) to g) are carried out repeatedly to form several membrane layers (16). Method according to claim 11 or 12, characterized in that the electrodes (20, 22) of directly adjacent membrane layers (16) are arranged offset from each other. Method according to one of claims 10 to 13, characterized in that a second frame part (14) is provided which is arranged on the side of the at least one membrane layer (16) opposite the first frame part (12). Method according to one of claims 10 to 14, characterized in that the polymer film is stretched unidirectionally or radially in step d), in particular is stretched uniformly. Method according to one of claims 10 to 15, characterized in that the first tool part (46) is moved in step d) to mechanically stretch the polymer film (40). Method according to one of claims 10 to 16, characterized in that a second tool part (54) is provided which is also moved to stretch the polymer film (40). Method according to claim 17, characterized in that the second tool part (54) has a structure (56) which is essentially the same as the first frame part (12) and / or that the second tool part (54) is positioned opposite the first frame part (12). Method according to one of claims 10 to 18, characterized in that the first membrane layer (16a) is attached to the first frame part (12), in particular by gluing or welding. Method according to one of claims 10 to 19, characterized in that the first tool part (46) is a work table or a work drum having several work surfaces (66). Method according to one of claims 10 to 20, characterized in that the first tool part (46) designed as a working drum is rotated about an axis of rotation (A) so that a polymer film section of the polymer film (40) assigned to a working surface (66) is supplied to different work stations (68).

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