Patent Description:
Car interiors and cockpits have always been a favorite location for switches and all kinds of input/output (I/O) devices and human machine interfaces (HMI). In recent years, their design and placement have become important due to a number of reasons, in particular the following reasons:.

Traditionally the switches were electro-mechanical devices assembled separately in the interior and cockpit, directly switching the electric load. Recently they have become connected to a microcontroller (via lines or bus systems) and control electronic switch systems.

In order to deeper embed the input devices in the structure of the dashboard, there is a need to do this while manufacturing the structure or the surface of the dashboard and avoid a later assembly process of a separate switch. As a presumption, such devices have to be reliable compact devices being easily to produce.

As customers appreciate an appealing optic and a mechanical/haptic click of a switch device, a haptic feedback is an important principle of good HMI designs. Thus, there is a need to design such devices in a way they can give feedback to users operating the switches in addition to esthetic design requirements.

Among the various sub-classes of electroactive polymers (EAP), dielectric elastomers (DE) are used in products due to their simple operation principle, industrial scale manufacturability and long lifetime. Mechanical sensors, actuators and/or energy generators, even within a single device, each comprise an electrical insulating layer of elastomer, sandwiched between two deformable layers of electrically conductive material providing two electrodes.

A dielectric polymer actuator known from <CIT> comprises a laminate-type actuating part, comprising: at least one dielectric polymer film which has first and second surfaces positioned opposite to each other and a side surface interposed between the first and second surfaces and which includes an incompressible dielectric polymer; and first and second compliant electrodes connected to the first and second surfaces, respectively; and a frame formed along the side surface of the dielectric polymer film so that pre strain applied to the dielectric polymer film is about zero, wherein, when a voltage is applied through the first and second compliant electrodes to the dielectric polymer film, the laminate-type actuating part is warped in any one direction of first and second surface directions to provide displacement corresponding to the voltage applied.

<CIT> refers to an elastomer coating head with a coating nozzle, by means of which an elastomer layer for forming a dielectric layer of a dielectric elastomer stack actuator or sensor can be applied, wherein the coating nozzle is operatively connected to expansion means, so that a nozzle opening of the coating nozzle exiting material jet in a y-direction is expandable during a movement of the elastomer coating head in an x-direction.

<CIT> teaches a method for producing a multilayer dielectric elastomer stack actuator, comprising a plurality of dielectric layers consisting of at least one solidified elastomer which is embedded between a plurality of electrode layers, with the following steps: i) applying a liquid uncrosslinked elastomer to form the dielectric layer with a reproducible layer thickness smaller than <NUM> by means of a grid device on a substrate, followed directly by ii) application of electrically conductive material particles to the surface of the dielectric layer made of liquid elastomer, to form an electrode layer utilizing the surface tension of the elastomer and a finale iii) at least partial crosslinking of the dielectric layer with the electrode layer floating on the surface by thermal treatment and / or irradiation, and repetition of the steps i) to iii), all steps taking place under clean room conditions and with the stationary substrate holder (<NUM>) and substrate held stationary.

<CIT> describes an interconnection electrode structure comprising: a plurality of non-actuating layers comprising polymer layers, extension electrodes disposed at upper surfaces of the polymer layers, and a via hole (H1, H2) which penetrates through the plurality of non-actuating layers and comprises a diameter which increases in a stepwise manner upwards; and a common electrode formed in the via hole to connect the extension electrodes at the via hole to each other.

<CIT> teaches a multi-layer structural component for motor vehicles, which has at least one structural support and a cover film arranged thereon, wherein the cover film is a biopolymer film.

<CIT> refers to a user interface device for manipulation by a user and having an improved haptic effect in response to an output signal, the device comprising: a base chassis adapted to engage a support surface; a housing coupled to the base and having a user interface surface configured to be manipulated by the user; at least one electroactive polymer actuator adjacent to the user interface surface, the electroactive polymer actuator configured to output a haptic feedback force associated with the output signal; where the housing is configured to enhance the haptic feedback force generated by the electroactive polymer actuator.

<CIT> refers to an electronic damping feedback control system for an electroactive polymer module, the system comprising: an electronic damping controller coupled in a feedback loop between a user interface device and an electroactive polymer actuator, wherein the actuator is coupled to the user interface device, and wherein the electronic damping controller is configured to receive an actuation signal from the user interface device in response to a user input and, in response to the actuation signal, the electronic damping controller is to generate an electronic damping signal to drive the actuator and dampen mechanical movement.

The latter two documents also disclose methods according to the preamble of independent claim <NUM>.

It is an object of the present invention to provide a method to operate an electroactive polymer transducer device overcoming the drawbacks of the prior art. The electroactive polymer transducer device is in particular a compact and reliable input/output device, which is easy to produce.

This object is solved by a method to operate an electroactive polymer transducer device as combined actuator and sensing device with good haptic feedback in a click operation as a switch according to independent claim <NUM>, comprising the steps of applying a counter-voltage to electrically conductive layers, having at least one plastic material layer comprising dielectric electroactive polymer material arranged therebetween, by a control unit, in order to hamper a thickness-reduction of an thr active area of the plastic material layer(s) when beginning to apply an external mechanical force to the electroactive polymer transducer device, preferably in at least one actuation area, until a common click-point is reached, and reversing the applied voltage by the control unit after the common click-point is passed to support the click operation.

A counter-voltage denotes voltage applied to the first and second electrodes with a polarity suitable to prevent an electrostrictive effect. Therefore, the external pressure has to overcome a certain threshold to result in a decreased thickness of the stack of layers resulting in a change of voltage to be sensed. The felt mechanical resistance against the applied pressure is high in the beginning and decreases after the click-point, which provides an excellent haptic feedback to the user. The mechanical/haptic click of the resulting switch device is appreciated by customers and haptic feedback is an important principle of good HMI designs provided by the method of operation according to the present invention. This effect is difficult to achieve by the material properties of the plastic layers alone.

According to embodiments, dielectric elastomers are used as sensors. Said sensors can be provided in form a sensor film which can be integrated on or below a surface of a vehicle component. Such a sensor film can comprise a multi sensor area in order to be used for different control approaches. A localized feedback arrangement can be provided by which a person can recognize the boundary of a virtual button and can also guide the finger blindly from one location to another on a surface without the need of a specific shape of said surface. The electroactive polymer transducer device can comprise at least one stack of multiple layers deposited on a base film, plate or wall and/or within a housing with at least one housing wall, preferably extending from the base wall, where the stack comprises an alternating sequence of plastic material layers and electrically conductive layers on top of each other, with at least one plastic material layer, being sandwiched between two electrically conductive layers, wherein each plastic material layer comprises at least one active area made of an elastic polymer providing an electrostrictive effect, with the active area being arranged laterally adjacent to at least one fixation area or at least one housing wall made of solid plastic material in direct contact to the active area, and/or the active area extending across the complete plastic material layer, wherein the electrically conductive layers are arranged in an alternating sequence of first and second electrodes to apply a voltage between first and second electrodes to the respective active area(s) in order to induce or sense the electrostrictive effect of the elastic polymer of the plastic material layer arranged therebetween, and wherein the stack of layers is prepared by three-dimensional printing technology.

In one alternative, with the multiple layers being deposited on a base plate, the first electrode at least partly covers a first fixation area of the fixation area and the active area of the adjacent plastic material layers and the second electrode at least partly covers a second fixation area of the fixation area and the active area of the adjacent plastic material layers. In another alternative, with the multiple layers being deposited within a cavity defined by at least one housing wall, preferably at least one housing wall and a base wall of the housing, all layers are in contact with the at least one wall.

The elastic polymer might be any suitable polymer material showing the electrostrictive effect. Electrostriction is a property of electrical non-conductors, or dielectrics, which causes them to change their shape under the application of an electric field, and is caused by a slight displacement of ions in the crystal lattice upon being exposed to an external electric field. Positive ions will be displaced in the direction of the field, while negative ions will be displaced in the opposite direction. This displacement will accumulate throughout the bulk material and result in an overall strain (elongation) in the direction of the field. The thickness will be reduced in the orthogonal direction of a layer of such material characterized by Poisson's ratio. The area of the layer, where the electrostrictive effect occurs, is denoted as active area. The elastic polymer might be a dielectric elastic polymer, preferably a material with a high dielectric coefficient. The plastic material for the fixation areas might be any plastic material with significant lower elasticity as the material of the active area. In the active area, the material may have a hardness of <NUM> shore-A or more. In the fixation area the material may have a hardness of at least <NUM> shore-A, preferably of <NUM> - <NUM> shore-D. The hardness according to the shore scale measures the resistance of a sample to material deformation due to a constant compression load from a sharp object. The material for the electrically conductive layers might be any material providing a sufficient conductivity to apply a homogeneous voltage across the active area underneath or on top of the electrically conductive layer, e.g. a conductive ink applied during layer preparation.

Active and fixation areas of the plastic material layers of some embodiments are arranged laterally adjacent meaning that the corresponding areas of one layer are located beside each other in a direction parallel to the layer surface. In contrast to that, the electrode layers are arranged underneath and/or on top of each of the plastic material layer. The first and second fixation areas might be arranged on the same side of the device or might be arranged on the left and on the right of the active area, when considering a side view of the layer stack. On the same side denotes an arrangement, where the fixation areas are located either on the right or on the left side of the stack of layers. The first and second fixation areas may also embrace the active area in a circle fully or partly. In case of arranging the fixation areas on the same side of the active area, the resulting device can be manufactured with smaller lateral sizes enabling a placement of more corresponding devices in a given area.

In other embodiments the active area(s) can be embraced by one or more housing side walls. Three-dimensional (3D) printing technology is an excellent solution for depositing many stable layers with good stacking accuracy. 3D Printing is based on a similar number of layers as required for manufacturing the electroactive polymer transducer device according to the present invention. 3D-printing is a technology suitable to provide a layer stack being flexible, e.g. in the middle where the active area(s) is/are arranged, which change its thicknesses due to applied voltage or applied external mechanical force, and being stable at the fixation areas to reliably apply an electrical contact to the electrodes. Alternative technologies such as ablation, milling, sputtering, evaporation, Rakel-printing or centrifugal layer deposition are not suitable to produce as huge amount of electroactive polymer transducer device as required in mass production. The non-suited technologies require a huge amount of time and effort for producing an electroactive polymer transducer device leading to non-acceptable production costs. 3D-Printing is very suited for mass production of the electroactive polymer transducer device according to the present invention. With these technologies it is possible embed the electroactive polymer transducer device as input/output devices in the structure of the dashboard while manufacturing the structure or the surface of the dashboard avoiding a later assembly process of a separate electroactive polymer transducer device.

The resulting electroactive polymer transducer devices can be used as actuator devices and/or sensing devices such as switches. There is an opportunity to combine two devices according to the present invention in one arrangement and operate one of them as sensor or switch and the other one as an actuator and/or acoustic feedback device. In case of a combined sensor/actuator combination, the feedback mechanism can be programmed to mimic key-click characteristics of a mechanical switch over a wide range. Such specified characteristics, where for instance the resistance is high in the beginning and decreased after the click-point in common in the industry and is considered an excellent haptic feedback.

Therefore, the electroactive polymer transducer device provides a compact and reliable input/output device being easily to produce and being appreciated as human machine interface by the users.

In another embodiment the stack of layers comprises <NUM> to <NUM> sequences of plastic material layer and electrically conductive layer. The electrostrictive effect increases proportional to the number of layers comprising active material. The number of <NUM> - <NUM> layers provides an overall electrostrictive effect, which can be used to significantly actuate a component and to sense a pressure applied to the stack of layers with improved accuracy.

In an embodiment, the first electrodes are connected in parallel to be connected to a first polarity of a power supply, while the second electrodes are connected in parallel to be connected to a second polarity of the power supply. The parallel connection of all first and all second electrodes enables to use one simple power supply to supply voltage to all electrodes, where the polarity alternates in a vertical direction through the layer stack in order to achieve a maximum electrostrictive effect.

In another embodiment the first electrodes comprise first contacting areas at least partly covering the first fixation areas and the second electrodes comprise second contacting areas at least partly covering the second fixation areas, where, when projected onto the base plate, the first contacting areas at least do not fully cover the second contacting areas and vice versa. The first and second contacting areas can be used to connect the first and second electrodes to one or more power supplies. The at least partly non-overlapping first and second contacting areas and the resulting vertical coverage of the contacting areas for all first electrodes and separately also for all second electrodes enables to connect all first or all second electrodes together by just providing a vertical conductive path through all the corresponding first or second fixation areas of the layer stack.

In another embodiment the parallel connection of the first electrodes and also of the second electrodes is established by at least two separate conductive pins or vias extending through the stack of layers, of which at least one extending through the first contacting areas and not the second contacting areas and of which at least one extending through the second contacting areas and not the first contacting areas. This electrical connection can simply be established by inserting a pin vertical to the surface of the stack of layers into the already prepared layer stack just penetrating all layers to connect all first or second electrodes without the need of layer structuring during layer preparation. The resulting step for electrically connecting the electrodes is very simple and non-expensive. For example the pin or via may protrude from the layer stack and be connected to the power supply via conducting wires bonded to the protruding pin or via.

In another embodiment, the fixation area comprises separate first and second fixation areas, where the active area of each plastic material layer is arranged laterally between first and second fixation areas in direct contact to the active area. This arrangement provides a resulting electroactive polymer transducer device being mechanically more stable compared to a device where the fixation areas are arranged only on one side of the layer stack, because the active layer is supported by solid plastic material on both sides, or even laterally on all sides.

In another embodiment, the electrically conductive layers have smooth shape in lateral direction without edges at least in the area covering the active areas of the plastic material layers. The shape in lateral direction of a layer is the shape visible when looking on top of the layer in a vertical direction to the layer surface. This smooth lateral shape of the conductive layers avoids sharp edges eventually leading to non-desired peaks in voltage or current between adjacent electrodes and therefore prevent or suppress electrical discharges within the stack of layers. This protects the functionality of the electroactive polymer transducer device and increases its lifetime. In a preferred embodiment, the electrically conductive layers are circular shaped layers when seen in a vertical direction to a surface of the conductive layers. As an example, the shape of the electrically conductive layers may consist of a circle covering the active area completed by two tangential lines touching each of the electrodes in just one point covering the first and second fixation areas, where the electrodes might be connected by a conductive pin.

In another embodiment, the size of the active area decreases from layer to layer starting with the biggest size for the plastic material layer on top of the base plate. This further increases the resistance against electric discharges because the distance between the electrode edges of one electrode and the next electrode underneath is increased. Additionally the stack of layers becomes more elastic and stable. Here the active areas might be arranged symmetrically to the active area underneath, where a center of the active areas coincidence for all active areas. The active areas may also have a circular shape and might be arranged in a concentric way seen in a vertical direction to a surface of the active areas.

In another embodiment, the base plate is made of the solid plastic material also used to prepare the fixation areas. Using the same material as used for the fixation areas in the plastic material layers makes the production process more easily enabling to continue the layer deposition process without an interruption after having prepared the base plate. In another embodiment, <NUM> to <NUM> separate layers applied on top of each other establish the base plate. In case of using 3D printing the thickness of the base layer might be provided by printing <NUM> - <NUM> layers of the same material.

In an alternative embodiment, the base film comprises a stretchable and/or deformable layer, in particular in form of a textile film.

In another embodiment, in the plastic material layer the first and second fixation areas laterally fully embrace the active area. Here the first and second fixation areas give mechanical stability from all sides to the stack of layers, especially to the active area when changing its thickness due to application of voltage or external mechanical forces.

It is also possible that the complete plastic material layer provides an active area.

In other embodiments, the layer stack comprises a protective layer on at least one of its two opposite sides, and/or the layer stack is covered by a solid top cover or a slush skin and/or a décor layer on a side opposite to the base film, plate or wall. The cover can adapt the haptic feeling of the electroactive polymer transducer device by being touch by a user is case of applying the electroactive polymer transducer device as a sensor device. In addition, the cover can be provided with decor features.

The protective layer can be in form of a paint; the slush skin can comprise polyurethane; and the décor layer can be provided as a leather layer. But it is also possible that two or all layers are provided together.

It is possible that the slush skin comprises plastic material, and/or the slush skin is glued and/or mechanically fixed to the housing, with preferably one protective layer and/or a glue layer being interposed, and/or the slush skin or the décor layer can cover more than one layer stack to a provide a multisensor area.

In another embodiment the stack of layers and the base plate are prepared together, with preferably the base plate or wall and/or the protective layer and/or the electrode being arranged thereto being provided as combined component.

In another embodiment the electroactive polymer transducer device is used as an actuator device and/or as a sensor device, further comprising the w control unit connected to the electrically conductive layers. The electroactive polymer transducer device can be operated as an actuator, when applying a suitable voltage to decrease or increase the layer thickness of the active areas via the electrostrictive effect, where so-called electrostrictive forces squeeze the dielectric elastic polymer material of the active area. Typical voltages to be applied to the active area are between 100V and 2000V. With a sufficient number of plastic material layers within the layer stack, a change of thickness of about <NUM>% can be achieve in order to actuate a component connected to the stack of layers. The device can also be used in a sensing mode, where a constant voltage might be applied by a power supply controlled by the control unit to the active areas of the electroactive polymer transducer device and sensing a change of an applied default voltage induced by pressing on top of the stack of layers, for example by a finger touching the top of the layer stack. The default voltage might by applied by a power supply via the control unit also analyzing the induced voltage change due to an applied pressure to the stack of layers. The sensed voltage change can be used as a trigger signal to initiate a certain response or any following action of another component. The control unit may trigger the following actions as a response on the sensed voltage change.

Embodiments can be further characterized in that the slush skin is provided with at least one actuation area, preferably in form of a button, in particular with a first portion projecting from the slush skin away from the stack and/or with a second portion projecting from the slush skin towards the stack.

The invention further is suitable for a vehicle external or internal trim component, like a door trim or a dashboard, and for a vehicle in general.

The following drawings show aspects of the invention for improving the understanding of the invention in connection with some exemplary illustrations, wherein.

<FIG> shows a schematic side view of a layer stack <NUM> of a first electroactive polymer transducer device <NUM> suitable for the present invention. Said stack <NUM> of multiple layers is deposited on a base plate <NUM>. The multiple more than n layers are indicated on the right side with numbers (<NUM>), (<NUM>), (<NUM>). The stack of layers may comprise <NUM> to <NUM> sequences of plastic material layer <NUM> and electrically conductive layer <NUM>. The stack <NUM> comprises an alternating sequence of plastic material layers <NUM> and electrically conductive layers <NUM> on top of each other. The plastic material layers <NUM> each comprise an active area <NUM> made of an elastic polymer providing an electrostrictive effect (gray shaded areas) arranged laterally adjacent beside a first and a second fixation area <NUM>, <NUM> made of solid plastic material in direct contact to the active area <NUM>. The electrically conductive layers <NUM> are arranged in an alternating sequence of first and second electrodes <NUM>, <NUM> to apply a voltage between first and second electrodes <NUM>, <NUM> to the active areas <NUM> in order to induce or sense the electrostrictive effect of the elastic polymer, where the first electrode <NUM> at least partly covers a first fixation area <NUM> of the fixation area and the active area <NUM> of the adjacent plastic material layers <NUM> and the second electrode <NUM> at least partly covers a second fixation area <NUM> of the fixation area and the active area <NUM> of the adjacent plastic material layers.

Here a first electrode <NUM> is deposited on top of the base plate <NUM> followed by a plastic material layer <NUM> with a second electrode <NUM> deposited on top of the plastic material layer <NUM> followed by the next plastic material layer <NUM> on top of the second electrode <NUM> and so on until a second electrode layer <NUM> is deposited as the last layer of the stack of layers <NUM>. The sequence of layers define a vertical direction of the stack <NUM> of layers perpendicular to the base plate <NUM>, here the surface of the base plate <NUM>, where the stack <NUM> is deposited on top. The lateral arrangement of areas <NUM>, <NUM>, <NUM> within one layer <NUM> denotes areas located beside each other in a direction parallel to the surface of the base plate <NUM>, where the stack <NUM> is deposited on top.

The first electrodes <NUM> are connected in parallel to a first polarity of a power supply <NUM>, while the second electrodes <NUM> are connected in parallel to a second polarity of the power supply <NUM> by separate conductive pins <NUM> extending through the stack of layers <NUM>, the left one extending through the first contacting areas <NUM> and not the second contacting areas <NUM> and the right one extending through the second contacting areas <NUM> and not the first contacting areas <NUM>. This simple contacting is enabled by first contacting areas <NUM> of the first electrodes <NUM> partly covering the first fixation areas <NUM> and the second electrodes <NUM> comprise second contacting areas <NUM> at least partly covering the second fixation areas <NUM>, where when projected onto the base plate <NUM> the first contacting areas <NUM> do not or only partly cover the second contacting areas <NUM> and vice versa. Furthermore the size of the active areas <NUM> decreases from layer to layer starting with the biggest size for the plastic material layer <NUM> on top of the base plate <NUM>.

The base plate <NUM> might be made of the solid plastic material also used to prepare the fixation areas <NUM>, <NUM>, preferably, <NUM> to <NUM> separate layers applied on top of each other establish the base plate. In other embodiments, the base plate might be made of other non-conducting materials providing a sufficient flat and smooth (non-rough) surface suitable to deposit the stack of layers on top. The layer stack <NUM> might be covered by a solid top cover <NUM> on a side opposite to the base plate <NUM>. The solid top cover <NUM> might be made of hard plastic, which can be fitted to the top of the assembly providing a desired haptic feeling.

The stack of layers <NUM>, preferably also the base plate <NUM>, might be prepared by three-dimensional printing technology. The electroactive polymer transducer device <NUM> might be used as an actuator device and/or or as a sensor device further comprising a control unit <NUM> connected to the electrically conductive layers <NUM>.

<FIG> shows a schematically top view onto the stacked active areas <NUM> of the plastic material layers <NUM>. For a better overview, only the active areas <NUM> of the plastic material layers <NUM> are shown. Here the size of the active areas <NUM> decreases from layer to layer starting with the biggest size for the plastic material layer <NUM> on top of the base plate <NUM>. The active areas <NUM> are arranged symmetrically to the active area <NUM> underneath, where a center <NUM> of the active areas <NUM> coincidence for all active areas <NUM>. The active areas <NUM> have a circular shape and are arranged in a concentric way seen in a vertical direction to a surface of the active areas <NUM>.

<FIG> shows a schematically top view onto one embodiment of the layer sequence of first electrode <NUM> / plastic material layer <NUM> / second electrode <NUM>. In the plastic material layer <NUM> the first and second fixation areas <NUM>, <NUM> laterally fully embrace the active area <NUM> in this embodiment. The shown layer structure corresponds to the stack of layers <NUM> shown in <FIG>. Here the first and second electrodes <NUM>, <NUM> have smooth circular shape in lateral direction without edges at least in the area covering the active areas of the plastic material layers <NUM> when seen in a vertical direction to a surface of the first and second electrodes <NUM>, <NUM>, where the shape of the electrodes <NUM>, <NUM> is completed by tangential lines touching each of the electrodes <NUM>, <NUM> in just one point. The areas of the electrodes <NUM>, <NUM> outside the active area <NUM> (not covering the active area <NUM>) are the first and second contacting areas <NUM>, <NUM>, where the vertical pin <NUM> is positioned.

<FIG> shows a schematically top view onto another embodiment of the layer sequence of first electrode <NUM> / plastic material layer <NUM> / second electrode <NUM>. Here the plastic material layer <NUM> comprise an active area <NUM> arranged laterally adjacent to the fixation area <NUM>, <NUM> only provided on one side (right side) of the active area <NUM>. Also here the first and second electrodes <NUM>, <NUM> have smooth circular shape in lateral direction without edges at least in the area covering the active areas <NUM> of the plastic material layers <NUM> when seen in a vertical direction to a surface of the first and second electrodes <NUM>, <NUM>, where the shape of the electrodes <NUM>, <NUM> is completed by tangential lines touching each of the electrodes <NUM>, <NUM> in just one point. The areas of the electrodes <NUM>, <NUM> outside the active area <NUM> (not covering the active area <NUM>) are the first and second contacting areas <NUM>, <NUM>, where the vertical pin <NUM> is positioned. The first and second contacting areas are slightly shifted against each other in order to essentially avoid coverage of one of the contacting surfaces <NUM> dedicated to one electrode <NUM> by the other contacting surface <NUM> dedicated to the other electrode <NUM>. As can be seen from <FIG>, the electroactive polymer transducer device <NUM> can be manufactured with smaller lateral sizes compared to the electroactive polymer transducer device <NUM> of <FIG>.

However the mechanical stability of the active area and therefore of the whole electroactive polymer transducer device <NUM> of <FIG> is larger than for the electroactive polymer transducer device <NUM> of <FIG>.

<FIG> shows an embodiment of a vehicle <NUM> comprising at least one electroactive polymer transducer device <NUM> used as an actuator device and/or or as a sensor device. The vehicle <NUM> might be a motorized or non-motorized vehicle. It might be a two-wheel, three-wheel, four-wheel vehicle or a more wheels comprising vehicle <NUM>. The vehicle <NUM> might be used to transport people and/or objects. The vehicle <NUM> might be driven by a driver or an autonomous driven vehicle. The vehicle <NUM> might comprise a door trim or a dashboard with an electroactive polymer transducer device <NUM>.

<FIG> shows a method to produce the electroactive polymer transducer device <NUM> suitable for the present invention, comprising the steps of providing <NUM> a base plate <NUM> for a stack <NUM> of multiple layer to be prepared on top of the base plate <NUM> and preparing <NUM> the stack <NUM> comprising an alternating sequence of plastic material layers <NUM> and electrically conductive layers <NUM> on top of each other by three-dimensional printing technology, where the plastic material layers <NUM> each comprise an active area <NUM> made of an elastic polymer providing an electrostrictive effect arranged laterally adjacent to at least one fixation area <NUM>, <NUM> made of solid plastic material in direct contact to the active area <NUM>, where the electrically conductive layers <NUM> are arranged in an alternating sequence of first and second electrodes <NUM>, <NUM> to apply a voltage between first and second electrodes <NUM>, <NUM> to the active areas <NUM> in order to induce or sense the electrostrictive effect of the elastic polymer, and where the first electrode <NUM> at least partly covers a first fixation area <NUM> of the fixation area and the active area <NUM> of the adjacent plastic material layers <NUM> and the second electrode <NUM> at least partly covers a second fixation area <NUM> of the fixation area and the active area <NUM> of the adjacent plastic material layers. Here also the base plate <NUM> is prepared by three-dimensional printing technology.

<FIG> shows a method to operate the electroactive polymer transducer device <NUM> according to the present invention as combined actuator and sensing device with good haptic feedback in a click operation as a switch, comprising the steps of applying <NUM> a counter-voltage to the electrically conductive layers <NUM> by a control unit <NUM> in order to hamper a thickness-reduction of the active area <NUM> of the plastic material layers <NUM> when beginning to apply an external mechanical force to the electroactive polymer transducer devices <NUM> until a common click-point is reached, and reversing <NUM> the applied voltage by the control unit <NUM> after the common click-point is passed to support the click operation.

<FIG> shows an exploded view of a layer stack <NUM> for a second electroactive polymer transducer device suitable for the present invention. The layer stack <NUM> comprises, on top of each other, a protective layer <NUM>, an electrode layer <NUM>, a dielectric layer <NUM>, a further electrode layer <NUM> and a further protective layer <NUM>. Using three-dimensional printing technology allows serial production.

Said layer stack <NUM> can be inserted into a cavity of a housing <NUM> by providing the same on a thin carrier such as a textile film <NUM> for transfer into the cavity by passing a gap <NUM> as shown in <FIG>. With the carrier the layer stack <NUM>, preferably also being provided in form of a thin film, becomes more stable and more resistant, wherein the thickness of the film can be varied, depending on the desired sensitivity of the electroactive polymer transducer device.

Said cavity is defined by a base wall 1014c and at least one housing wall 1014a, 1014b extending therefrom, in <FIG> upwards. The housing <NUM> can also be formed by injection molding as illustrated via an injection port <NUM>.

As a result of the insertion of the layer stack <NUM> into the cavity, the lower protective layer <NUM> rests on the base wall 1014c, whereas the upper protective layer <NUM> flushes with the upper edge of the housing <NUM>, see <FIG>. Both alternatives of <FIG> further show a glue layer <NUM> on top of the upper edge of the housing <NUM> and the upper protective layer <NUM> to attach a slush skin <NUM> providing a HMI.

In the embodiment of <FIG>, the HMI comprises actuating areas in form of buttons <NUM>, which can be pushed by a finger <NUM> of the hand <NUM> of a user. Said buttons <NUM> each can comprise an upper portion 1011a projecting upwardly and a lower portion 1011b extending downwardly in direction of the layer stack <NUM>.

Mounting a layer stack under a surface or under a liner in form of the slush skin, in addition to or as alternative to the top protective layer, allows to provide a solid button feeling. The attachment of the surface or under a liner, whether it is with glue or mechanical anchoring, further facilitates serial implementation.

Thus, the production of electroactive polymer transducer devices in larger quantities and high accuracy is possible, in particular due to the described manufacturing process of the layer stack. This even allows to produce wearable structures on a carrier as intermediate product, which can be inserted into a cavity provided e.g. in the exterior or interior of a vehicle, like a door trim or a dashboard.

It is to be noted that the layer stack <NUM>, which is based on the principle of a plane-parallel capacitor, and can provide a dielectric elastomer sensor, can simply consist of a flexible and stretchable dielectric polymer layer <NUM> sandwiched between two compliant electrode layers <NUM>, <NUM>, deposited on a textile film <NUM> and covered by a decor layer <NUM>, as shown in <FIG>. This structure is beneficial for providing a flexible and sensitive dielectric elastomer tactile sensor, similar to human skin. Such a sensor can be used for measuring mechanical deformations, such as pressure, strain, shear and torsion and can produce vibration or stroke as confirmation of such a deformation, with an example of such a deformation being shown in <FIG>.

The sensor of <FIG> is in particular suited to be used in a method as described with respect to <FIG> in order to provide a surface feedback or haptic mechanism. The surface feedback mechanism can be the same haptic mechanism which is used for the confirmation of a HMI function with a localized feedback as provided by a conventional push button.

There is no need for positioning the sensor, in particular the layer stack <NUM>, on a surface or make it visible, and there is no need for an additional sensor to provide coordinates of a body part on a surface.

With the described sensor, it is possible to provide blind guidance to a body part, especially a finger <NUM>, to reach a correct location on a surface without having an additional layer providing coordinates or the like. Said correct location is defined by an active area and/or virtual button area described above.

The sensor can detect different signals as pressure, strain, shear and torsion and at the same time can create a movement.

The feedback mechanism to guide said body part only activates after proximity thereof is determined, which results into an optimized system performance. The same function and control mechanism is flexible and applicable to any size of surface without a change of principle method of operation. This provides an optimized solution for different form factors without changing control mechanism.

Claim 1:
A method (<NUM>) to operate an electroactive polymer transducer device (<NUM>) as combined actuator and sensing device with good haptic feedback in a click operation as a switch, characterized in that it comprises the steps of
- applying (<NUM>) a counter-voltage to electrically conductive layers (<NUM>, <NUM>, <NUM>) having at least one plastic material layer (<NUM>, <NUM>) comprising dielectric electroactive polymer material arranged therebetween, by a control unit (<NUM>), in order to hamper a thickness-reduction of an active area (<NUM>) of the plastic material layer(s) (<NUM>, <NUM>) when beginning to apply an external mechanical force to the electroactive polymer transducer device (<NUM>), preferably in at least one actuation area, until a common click point is reached, and
- reversing (<NUM>) the applied voltage by the control unit (<NUM>) after the common click-point is passed to support the click operation.