FLEXIBLE HAPTIC INTERFACE

Description

Technical field

[0001] The present invention relates to human-machine interfaces, and more particularly those producing haptic effects. Prior art

[0002] A haptic interface allows the user to interact with the environment through the sense of touch. The haptic effect is increasingly used in many applications today, for example on a smartphone, when it generates a slight vibration when a key displayed on the screen is pressed to simulate the impression of pressing a button. Haptic applications also exist for virtual or augmented reality devices, particularly to allow better immersion in video games. Haptic interfaces such as touchscreens, generating a haptic effect on a touch surface when a user contacts it, can be integrated into many technologies such as computers, tablets and / or smartphones.

[0003] It is known to generate varied and relatively complex haptic effects on a rigid tactile surface using ultrasonic transducers emitting ultrasonic waves which propagate on the rigid surface.

[0004] With the emergence of flexible commercial products, such as foldable mobile phones and rollable televisions, there is a desire for flexible haptic interfaces that can be integrated into such products.

[0005] The article by Poncet et. al., "Static and dynamic studies of electro-active polymer actuators and integration in a demonstrator" (Actuators Journal, 2017), describes a device comprising piezoelectric actuators mounted on a flexible substrate to produce vibrotactile buttons. However, to achieve the desired haptic effect, the substrate must be supported by a rigid structure, which substantially limits the flexible nature of the product.

[0006] It is also known to use fluids to generate a haptic effect. Application WO2010078597A1 discloses a tactile haptic interface comprising fluid channels and chambers for generating a button effect.

[0007] Lochtefeld's article "Towards real organic user interfaces - using non-Newtonian fluids for self-actuated displays" (CHI13 workshop, 2013) describes a haptic device using a shear-thickening non-Newtonian fluid sandwiched between two flexible sheets placed on a fixed array of loudspeakers. A finger-perceptible topology is generated when a sound wave propagates through the fluid and locally hardens it. The spatial resolution of the generated haptic effect is, however, relatively low given the bulk of the loudspeakers, and furthermore, such an interface is not completely flexible. Statement of the invention

[0008] There is therefore a need to further improve flexible haptic interfaces, particularly in order to have a relatively simple touch interface to produce and capable of generating varied haptic effects. Summary of the invention

[0009] The invention aims to meet this need, and it achieves this, according to a first of its aspects, thanks to a flexible haptic interface comprising: a chamber containing a non-Newtonian fluid and delimited at least partially by a flexible wall whose outer face defines a touch surface capable of being contacted by a user, a plurality of actuators carried by a flexible support and arranged so as to transmit local mechanical excitation to the fluid, and a control circuit connected to the actuators and configured to modulate the signals sent to the actuators in order to mechanically induce a modification of the rheology of the fluid and generate a haptic sensation perceptible by the user on the touch surface.

[0010] A "non-Newtonian fluid" refers to a fluid whose viscosity is not constant and depends on the mechanical constraints to which it is subjected. Thus, under the vibratory action of the actuators, the viscosity of the fluid undergoes local variations depending on the properties of the fluid; it appears more or less "viscous", or more or less "rigid", when it is stirred, for example. A shear-thickening fluid, for example, will see its viscosity increase in response to mechanical stress. Conversely, a shear-thinning fluid will see its viscosity decrease in response to mechanical stress.

[0011] The invention makes it possible to obtain varied haptic effects on a flexible surface by using a fluid whose viscosity variations induced by the actuators are sufficiently marked to be perceived tactilely by the user, in particular by the user's finger in contact with the tactile surface of the interface, in particular moving in contact with the interface. Such an effect cannot be obtained with Newtonian fluids such as pure water, whose viscosity or "rigidity" is constant regardless of the stress.

[0012] Depending on the number of actuators in operation, it is possible to create the impression of complex rigid shapes. In addition, by varying the stress amplitude of the non-Newtonian fluid, the viscosity variation will be more or less significant, which makes it possible to complicate the generated haptic effect, giving the user the impression of touching a surface with different degrees of hardness.

[0013] The user's contact with the touch-sensitive surface may be direct skin contact with the surface or indirect contact through one or more intermediaries, nevertheless allowing a tactile sensation, for example one or more layers of clothing or a glove. The contact may be made with the finger or with another region of the body. Bedroom

[0014] The chamber preferably has a generally flattened shape. In particular, it can have a parallelepiped shape when the interface is laid flat, which makes it possible to obtain a tablet-type interface if desired.

[0015] The chamber preferably has a substantially constant thickness, ranging from a few hundred µm to a few mm.

[0016] The chamber can be made in several ways. For example, the chamber is formed between at least two opposing flexible walls, at least one of which defines the haptic surface, in particular walls comprising or defined by flexible sheets. The chamber can then be made simply by assembling several flexible sheets, at least one of these sheets being able to be functionalized with the actuators before assembly.

[0017] The interface can be of various shapes, volumes and dimensions, for example from the order of a centimeter to several tens of centimeters, or even a meter. Walls

[0018] The interface according to the invention is flexible as a whole, thanks to the deformability of the walls which delimit the chamber, at least in the areas between the actuators, as well as that of the possible additional wall(s) or layer(s) which are superimposed thereon, at least in the areas between the actuators.

[0019] In particular, the interface may exhibit overall deformability due to the flexibility of both the wall that defines the touch surface and the support that carries the actuators, and which is for example a wall other than that which defines the touch surface or the same wall.

[0020] Preferably, the wall(s) defining the touch surface and serving as support for the actuators allow overall flexion of the chamber around at least one axis, better in all directions.

[0021] The thickness of the wall(s) defining the touch surface and serving as support varies, for example, from a few tens of microns to several mm. This thickness can be substantially constant.

[0022] The wall defining the tactile surface can be opaque, transparent or translucent. It can serve as an optical guide, if desired.

[0023] The tactile surface can be smooth, or have micro-reliefs.

[0024] The wall used as support can be opaque, transparent or translucent.

[0025] The inner faces of the walls defining the touch surface and serving as support may be smooth, or have reliefs. In particular, the walls may have thinnings and / or extra thicknesses, for example to facilitate the mounting of certain elements such as actuators, or to allow the walls to be assembled together, or to create more flexible or, on the contrary, more rigid local areas, particularly at the level of the extra thicknesses.

[0026] The wall defining the touch surface may have a multi-layer structure, in particular when it includes an external detection system and / or a flexible screen. The wall may include an inner layer in contact with the fluid, and one or more outer layers to perform detection and / or display functions. These layers may be assembled in various ways, with or without clearance between them, but their arrangement makes it possible to feel through them, over at least part of their extent, the changes made to the rheology of the fluid by the actuators. Fluid

[0027] The fluid can be opaque, translucent, or transparent. It can be colored or not. It can be a shear-thickening, shear-thinning, viscoplastic, or any other suitable non-Newtonian fluid. This fluid can be electrically conductive or not. Actuators

[0028] The actuators are preferably in contact with the fluid. Thus, their deformation when actuated allows direct mechanical stress on the fluid. In addition, this facilitates the integration of small actuators, which is advantageous for giving the interface the desired flexibility. It can also make it easier to mount the actuators on the supporting wall, and avoid losses in mechanical power and spatial resolution that could be induced by the presence of a more complex mechanical interface between the actuators and the fluid.

[0029] When in contact with the fluid, the actuators are designed in particular so that the fluid does not cause a short circuit.

[0030] The actuators are distributed within the interface according to the haptic effects that are to be generated. The actuators can be distributed without regular spacing between them, but advantageously they are distributed with regular spacing in at least one direction, better in two directions. At least some of the actuators can be arranged in rows and / or columns, preferably in a regular network.

[0031] The density of actuator implantation in one direction varies, for example, from 50 actuators to 1 actuator / cm. This density can be constant or variable, in one direction or in all directions.

[0032] The actuators are for example, for actuators of 1mm diameter, spaced at a distance corresponding to 4mm center to center.

[0033] The interface may comprise at least two sets of actuators on either side of the fluid, arranged opposite each other or offset. Thus, some of the actuators may be carried by the wall that defines the touch surface. The density of implantation of the actuators may be the same on either side of the fluid, or it may be different.

[0034] Using two sets of actuators allows to increase the mechanical effect of the actuators on the fluid, and to obtain a better spatial resolution when the actuators are arranged in an offset manner.

[0035] By modulating the amplitude of each actuator and using or not using opposite actuators, haptic effects giving an impression of relief can be generated, for example with locally rigid zones over the entire thickness of the fluid or only over a part.

[0036] We can also play on the size and shape of the actuators to generate more complex haptic effects.

[0037] Each actuator may be piezoelectric, ferroelectric, electromagnetic, thermal, or ceramic piezoelectric. Preferably, the actuator is a ceramic piezoelectric. For example, commercial piezoelectric ceramics may be used and thinned to the desired thickness before being integrated into the interface.

[0038] The actuators may also have a passivation layer, which covers their piezoelectric material, the passivation layer being in direct contact with the fluid, for example. This prevents the fluid from causing a short circuit in the actuators.

[0039] Each actuator is, for example, glued to the wall serving as a support, but alternatively the fixing can be carried out in other ways, for example by welding, molding or overmolding. Membranes

[0040] The actuator can be integrated into the interface in different ways.

[0041] Preferably, each actuator is carried by an active membrane capable of vibrating under the action of the actuator, the vibration of the membrane mechanically stressing the fluid in the area adjacent to the actuator. The presence of such a membrane makes it possible to increase the surface area accompanying the vibration of the actuator, and to amplify the deformation resulting from the piezoelectric actuation to mechanically stress the fluid.

[0042] The membrane may be defined by a portion of the actuators' support wall, where this support wall may be a chamber wall that defines an outer surface of the interface.

[0043] Alternatively, this support wall is isolated from the exterior of the interface, this wall being for example covered by a counter-wall, which defines for example an exterior surface of the interface.

[0044] The possible counter-wall is flexible to accompany the deformation of the walls delimiting the chamber.

[0045] The interface may include stiffening rings around the membranes carrying the actuators. These rings may have a circular shape or not, and may be independent of each other or have common or linked portions to facilitate their installation, the rings being for example formed by the meshes of a grid.

[0046] Each stiffening ring makes it possible to spatially restrict the extent of the wall vibrated by the actuator to the area of ​​the wall which is inside the ring (i.e. located between the inner contour of the ring and the actuator), and consequently to benefit from a better spatial resolution of the haptic effect generated.

[0047] Each ring can be located on the face of the support wall opposite to that carrying the actuator or on the same face; the presence of the ring on the opposite face can make electrical connections to the actuators easier.

[0048] Each stiffening ring can still be located between the wall which carries the actuator and the aforementioned counter-wall.

[0049] The stiffening ring is preferably made of a material that is more rigid than that of the supporting wall, for example metal, hard plastic, ceramic, glass.

[0050] Alternatively, the ring can be made of the same material as the supporting wall. If necessary, the ring has a thickness that is significantly greater than the supporting wall, in order to have a stiffness greater than that of the wall, for example a stiffness 10 times greater. Detection system

[0051] Preferably, the interface comprises a system for detecting user contact on the touch surface, in particular a capacitive or optical detection system, the control circuit being arranged to control the actuators according to the position thus detected.

[0052] The detection system can also use at least some of the actuators for this detection. In this case, the haptic effect can be generated with only some of the actuators and / or by alternating for at least some of the actuators a detection phase where the actuator is used as a contact sensor, and a phase for producing the haptic effect, where the actuator is used to generate a mechanical stress.

[0053] Thus, when the interface has actuators on the wall defining the touch surface, at least part of these actuators can advantageously be used to detect contact.

[0054] The interface may include a system for superimposing an image, in particular a screen covered by the touch surface, at least partially on the haptic surface. A screen may alternatively be integrated into an ancillary device, for example virtual reality glasses, and the haptic effect generated may be synchronized with the projected or displayed image. Applications

[0055] The invention also relates to an article, in particular an article of clothing, in particular a glove or a jacket, equipped with a haptic interface according to the invention.

[0056] The interface may further comprise at least one actuator for selectively conforming the interface into at least two distinct shapes. Preferably, the interface comprises several actuators. The shape of the interface may be configured to correspond to an object whose image is viewed simultaneously by the user, for example in virtual reality glasses. Haptic effects simulating the texture of the viewed object may then be generated on the touch-sensitive surface of the interface. Tactile perception

[0057] The invention also relates to a method for generating at least one tactile perception capable of being felt by a user in contact with an interface according to the invention, comprising the steps consisting of: detect the position of the user's contact on the flexible touch surface of the interface using a detection system, modulate, using a control circuit, the signals sent to the actuators in order to locally vary the rigidity of the fluid in certain areas of the chamber and generate an effect perceptible tactilely by the user.

[0058] The user's contact on the touch surface can be detected where appropriate, as mentioned above, thanks to at least some of the actuators, in particular by piezoelectric effect when the actuators are piezoelectric actuators.

[0059] The variation in rigidity generating a tactile perception can in certain cases give the user the impression of touching a surface with relief.

[0060] Tactile perception can also be generated in such a way as to give the user the impression of pressing a button. Production of an actuator

[0061] The invention also relates to a method for manufacturing a ceramic piezoelectric actuator usable in an interface according to the invention as defined above, comprising the steps consisting of: depositing at least a first layer of a conductive material on the upper face of a flexible support, preferably a flexible polymer sheet, fixing a piezoelectric ceramic on the conductive layer thus formed, depositing, in particular by inkjet printing, a layer of a conductive material on the piezoelectric ceramic, depositing a layer of an electrical insulator, preferably by printing, on the layers previously deposited.

[0062] The flexible support preferably forms the wall which serves as support for several actuators, for example all of them, and can define an external surface of the interface or be lined externally with a counter-wall.

[0063] The actuators can be made individually, or simultaneously on the same support.

[0064] The insulating layer covering the actuator electrically isolates the actuator from the fluid. It can cover each actuator individually or, alternatively, continuously cover all the actuators fixed on the same support. Creation of the interface

[0065] The invention also relates to a method for manufacturing an interface as defined above, comprising the step consisting of: assembling two flexible walls, in particular by welding or gluing, so as to form a chamber, at least one of the walls having actuators on one of its faces.

[0066] The resulting chamber is filled with a non-Newtonian fluid. For example, a filling opening can be created during assembly, which is then closed, for example by welding or gluing.

[0067] The walls comprise or are, for example, polymer sheets, in particular thermoplastics, elastomers or not. The walls may have a single-material or multi-material structure, this structure being able to be spatially homogeneous or conversely include local thinning, more flexible hinges, etc.

[0068] The wall(s) may have a multi-layer structure in order to integrate a detection system and / or a screen, as mentioned above. Brief description of the drawings

[0069] The invention may be better understood by reading the detailed description which follows, non-limiting examples of its implementation, and by examining the attached drawing, in which: [ Fig 1 ] partially and schematically represents an example of a flexible haptic interface according to the invention, [ Fig 2] partially and schematically represents an example of an interface wall serving as support for the actuators, [ Fig 3 ] illustrates in a partial and schematic manner an example of arrangement of the actuators, [ Fig 4 ] partially and schematically illustrates another example of arrangement of the actuators, [ Fig 5 ] partially and schematically represents an example of a flexible haptic interface equipped with a screen and a speaker, [ Fig 6 ] partially and schematically represents an example of a flexible haptic interface coupled with virtual reality glasses, [ Fig 7A ] partially and schematically represents an example of integration of an actuator into a wall of the interface, [ Fig 7B ] illustrates in a partial and schematic manner the vibration of the wall underlying the actuator of the Figure 7A when activated, [ Fig 8A] partially and schematically represents an example of integration of an actuator into a wall equipped with a stiffening ring, [ Fig 8B ] illustrates in a partial and schematic manner the vibration of the wall underlying the actuator of the Figure 8A when activated, [ Fig 9A ] partially and schematically represents an example of integration of an actuator into a double wall, [ Fig 9B ] illustrates in a partial and schematic manner the vibration of the wall underlying the actuator of the Figure 9A when activated, [ Fig 10 ] partially and schematically represents an example of an interface comprising a network of actuators integrated into a wall according to the integration mode of the Figure 9A , [ Fig 11 ] is a partial and schematic front view of an actuator of the Figure 10 , [ Fig 12] represents in a partial and schematic manner an example of the realization of a matrix of actuators capable of generating different tactile perceptions, [ Fig 13 ] illustrates in a partial and schematic way the possibility of generating a tactile button effect from the actuator matrix of the Figure 12 , [ Fig 14 ] illustrates in a partial and schematic manner the possibility of generating a tactile relief effect from the matrix of the Figure 12 , [ Fig 15 ], [ Fig 16 ], [ Fig 17 ] And [ Fig 18 ] partially and schematically illustrate successive steps of an example of a manufacturing process for a ceramic piezoelectric actuator, [ Fig 19 ] partially and schematically illustrates a step of an example of a method for manufacturing an interface according to the invention, [ Fig 20 ] partially and schematically illustrates another stage of the manufacturing process, [ Fig 21] is a block diagram illustrating an example of operation of the haptic interface according to the invention, [ Fig 22 ] illustrates examples of articles equipped with a flexible haptic interface according to the invention, and [ Fig 23 ] illustrates the possibility of modifying the shape of the interface using actuators. Detailed description

[0070] It has been illustrated at the Figure 1 an example of a flexible interface 1 according to the invention. The interface 1 comprises a chamber 2, of flattened shape in the example considered, delimited mainly by two opposing flexible walls 2a, 2b each defining an external face of the interface.

[0071] The outer face of the upper wall 2a defines a touch surface S on which a user can come into contact, for example with his finger, and perceive a haptic sensation generated by the interface 1.

[0072] In the example considered, the surface S can take a substantially flat or curved configuration.

[0073] The interface comprises a detection system 6, for example a capacitive system known from the state of the art, allowing the detection of at least one point of contact of the user's finger with the surface S.

[0074] The detection system 6 may be part of the wall 2a; it has been shown in Figure 1 schematically in the form of an outer layer of the wall 2a.

[0075] Chamber 2 is closed and filled with a non-Newtonian fluid 3. By "non-Newtonian" is meant a fluid that does not deform proportionally to the force applied to it, in particular a fluid whose viscosity depends on the force exerted. This could be, for example, a shear-thickening fluid, i.e., a fluid whose viscosity increases when a shear stress is applied to it. Alternatively, it could be a shear-thinning fluid, or a viscoplastic fluid. Various types of non-Newtonian fluids can be used. A shear-thickening fluid 3 is, for example, obtained by mixing water and cornstarch in the correct proportions. More generally, many types of fluids with particles suspended in a liquid have non-Newtonian properties.Fluids containing polymers, such as certain shampoos, gels, bleaches, cleaning agents or even multigrade oils to which polymers are added, can also exhibit non-Newtonian rheology.

[0076] The lower wall 2b serves as a support for a plurality of actuators 5 arranged on the inner face of the wall 2b so as to be in contact with the fluid 3. The actuators 5 are connected to a control circuit 4 by wired connections 40.

[0077] The control circuit 4 is configured to modulate the signals sent to the actuators 5 so that they mechanically induce by vibrating a modification of the viscosity of the fluid 3, sufficient to be tactilely perceptible by the user on the surface S. The actuators 5 can be actuated individually, or alternately in groups, depending on the objective pursued.

[0078] The detection system 6 is also connected to the control circuit 4 in order to generate the haptic effect on the detected contact area, if desired.

[0079] In some embodiments, the wall 2b serving as support for the actuators may be defined by a flexible sheet 20 as illustrated in Figure 2 , for example a sheet of a polymer, for example polyethylene naphthalate (PEN) or polycarbonate (PC). The sheet is for example of a thickness equal to approximately 250 µm.

[0080] In the example shown in Figure 2 , the actuators 5 are distributed regularly on the sheet 20 so as to form a regular network, but other distributions are possible, as described below.

[0081] The actuators 5 may all be identical and have the same dimensions, as illustrated, or on the contrary have different dimensions and / or shapes. Depending on the application, large actuators may be provided to simulate large patterns in certain areas and smaller actuators in other areas to have better spatially resolved haptic effects in these other areas.

[0082] The actuators 5 can be arranged within the chamber 2 on several of its walls, and according to various configurations. They can for example be located on the two opposite main walls 2a and 2b of the chamber 2, on either side of the fluid 3 and aligned opposite each other, as illustrated in Figure 3 . Such an arrangement makes it possible to increase the mechanical effect of the actuators 5 on a given volume of fluid 3.

[0083] In the variant illustrated in the Figure 4, the actuators are located on either side of the fluid 3 in an offset manner, which makes it possible to increase the spatial resolution of the haptic interface and / or to generate more complex haptic effects, depending on the actuators used. This offset can be done in such a way that the actuators supported by the wall 2a are centered relative to the middle of the intervals between the actuators of the opposite wall 2b, as illustrated. Alternatively, the pitch between the actuators on the wall 2a is different from that between the actuators of the wall 2b, for example a multiple thereof. The offset can also be done differently.

[0084] The interface 1 may include one or more additional devices making it possible to improve the user experience, in particular to make it a multi-sensory experience.

[0085] In the example shown in Figure 5, the interface comprises a flexible screen 7 which makes it possible to superimpose an image on the touch surface S and for example to give the user the impression of virtually touching what he observes on the screen 7. In the example considered, the screen 7 has been represented schematically as covering the detection system 6, but forming part of the wall 2a. In a variant, the screen 7 and / or the detection system 6 are not integrated into the wall 2a of the chamber 2.

[0086] The interface 1 may further comprise one or more speakers 8 to add a sound effect to the experience. Alternatively, the display screen 7 is attached to a mount M which can be worn by the user, for example virtual reality glasses as illustrated in Figure 6The images displayed on the screen 7 are visible to the user who can simultaneously come into contact with the touch surface S, the control circuit 4 being configured to allow the actuators 5 to generate a haptic effect linked to the image projected or displayed in the frame.

[0087] The actuators 5 are preferably of the piezoelectric type. When an actuator receives an electrical signal from the control circuit 4, it can contract or lengthen by inverse piezoelectric effect, in particular in the direction parallel to the support on which it is fixed. In this case, the piezoelectric material will induce a mechanical torque on the support and therefore by bimetallic effect generate an oscillatory movement.

[0088] The support of each actuator 5 can define an active membrane 21. The latter can be formed by a part of the wall 2b of the chamber 2.

[0089] The vibrational behavior of the actuator 5 and the underlying active membrane 21 depends on how the actuator is integrated into its support. This integration can be done in several configurations, and the corresponding vibrational behavior can be simulated using finite element calculation software, such as COMSOL software, or any other suitable software. Several examples of configurations are described below, as well as the vibrational behavior of the associated membrane.

[0090] In the configuration illustrated in the Figure 7A , the actuator 5 is fixed on a support wall 2b which defines an outer surface of the interface 1.

[0091] In this configuration and as illustrated in the Figure 7B, the vibration of the actuator 5 causes a relatively significant displacement of the membrane 21 in a central zone 210 located under the actuator. A zone 211 surrounding the central zone 210 does not show any particular displacement. On the other hand, parasitic displacements of the wall 2b are visible beyond the zone 211, in distant zones 212. These parasitic displacements are not desirable because they cause a relatively localized stress on the non-Newtonian fluid, and therefore affect the spatial resolution of the haptic effect.

[0092] The addition of a stiffening ring 9 under the wall 2b delimiting the outline of the active membrane 21, as illustrated in the Figure 8A , allows to limit the amplitude of parasitic movements in the 212 zones, even if they still remain visible on the Figure 8B The stiffening ring is made of copper, aluminum, hard plastic, or any other suitable material.

[0093] In the variant illustrated in the Figure 9A , an outer wall 2c is added, also called a counter-wall, the stiffening ring 9 being integral with the walls 2b and 2c and acting as a spacer between them. In this variant, the membrane 21 is kept at a distance from the wall 2c thanks to the stiffening ring 9, and an air gap 90 may be present between the walls 2b and 2c. In this configuration, the movement of the wall 2b under the action of the vibration of the actuator 5 is restricted to the central zone 210 where the actuator is located, and the parasitic movements of the wall 2b are practically absent, as illustrated in Figure 9B .

[0094] For example, for a PEN wall 2b with a thickness of the order of 250 µm and a lead zirconate titanoate (PZT) piezoelectric actuator with a thickness of the order of 30 µm and a radius of approximately 2500 µm, it is possible to obtain a deformation of the membrane 21 of the order of 5 µm when the actuator 5 is subjected to an alternating voltage of 50V at a frequency of 1.82 kHz. At this frequency, the non-Newtonian fluid 3 is stressed locally sufficiently to harden and generate, for example, a perception of “pseudo-relief” on the tactile surface S of the interface 1.

[0095] The parasitic displacements of the wall underlying the actuators can be reduced other than by adding a stiffening element 9 and a counter-wall 2c; this can be achieved in particular by actuating neighboring actuators with a phase shift dependent on the distance between the actuators, in particular in phase opposition.

[0096] We represented at the Figure 10 a plurality of actuators 5 integrated according to the previous configuration with counter-wall 2c. The latter defines in this example an external surface of the interface.

[0097] The thickness of wall 2c is for example 500 µm. A greater thickness makes it possible to substantially limit the parasitic movements of wall 2b mentioned above, but can in turn reduce the overall flexibility of interface 1.

[0098] The thickness of the wall 2c can be chosen when producing the interface 1 according to the application considered and the desired haptic effect.

[0099] For example, the relative thickness of wall 2c compared to wall 2b is a factor of 10

[0100] The actuator 5 may be of different shapes, for example circular, as illustrated in Figure 11. In this example, the actuator 5 comprises a lower electrode 51 connected to the control circuit 4 by a conductive track 41, for example metallic, an active layer 52 for example made of piezoelectric or ferroelectric material, and an upper electrode 53 connected to the control circuit 4 by a conductive track 43, for example metallic. The electrodes 51 and 53 are preferably insulated from each other by a passivation layer (not shown).

[0101] As previously described, the actuator 5 may be supported by an active membrane 21.

[0102] When an actuator 5 receives a signal from the control circuit 4, a potential difference is applied between the electrodes 51 and 53. The signal received by the actuator 5 is for example a complex alternating signal. The applied potential difference causes a deformation of the active layer 52, in particular by inverse piezoelectric effect, which causes a displacement of the active membrane 21.

[0103] We represented at the Figure 12 an example of a matrix 10 of actuators 5. By “matrix”, we mean a single-piece structure carrying several actuators, identical or not. The matrix 10 is for example rectangular and of dimensions for example a few centimeters on each side.

[0104] The actuators 5 are in this example identical, each circular in shape and distributed uniformly over the matrix 10, in a staggered pattern. The active membrane 21 of each actuator 5 is for example circular in shape.

[0105] In other embodiments, the active membrane 21 is of non-circular shape, for example polygonal, in particular square, rectangle, or any other suitable shape, 2D or 3D, the membrane being able to be of convex or concave shape.

[0106] The diameter a of the actuator 5 (i.e. generally its largest dimension) is for example 2500 µm and of the order of 50% of the diameter d of the active membrane 21, this ratio being advantageous for good deformation of the membrane, as described in the article by Casset, F., et al. "Piezoelectric membrane actuator design." (12th Intl. Conf. on Thermal, Mechanical & Multi-Physics Simulation and Experiments (Eurosime) 2011).

[0107] The active membranes 21 are for example separated from each other by a distance equal to the diameter of membrane 21, this separation distance being advantageous for allowing good spatial resolution of the generated haptic effect.

[0108] In other embodiments, the separation distance between the membranes and / or the number of membranes on the matrix 10 are different. It is also possible to have a single isolated membrane.

[0109] The diameter of the membrane 21 is for example of the order of 10 µm to 100,000 µm. The actuators 5 comprise for example an active layer of lead zirconate titanoate (PZT), and their thickness is for example 30 µm.

[0110] In the example shown in figure 13 , a group of actuators 100 arranged on the matrix 10 is actuated by the control circuit 4 in order to generate a tactile perception 60 of a “button effect”, that is to say giving the user the impression of pressing a keyboard key.

[0111] In another example illustrated in the Figure 14, several groups of actuators 101 and 102 are actuated simultaneously or alternately in order to generate tactile perceptions 61 and 62 of a pseudo-relief effect, that is to say giving the impression to the user who moves his finger in contact with the interface of touching reliefs, for example the crest of a mountain on a map displayed on a screen.

[0112] In the examples which have just been described, the actuators 5 of the same group can be modulated according to an actuation amplitude which is identical for all the actuators of the group, or specific to each actuator, depending on the desired effect.

[0113] A piezoelectric actuator 5 can be made following the steps illustrated in figures 15 to 18 .

[0114] First, a first layer 54 of an electrically conductive material, for example silver, is deposited, for example by screen printing, on the upper face of a flexible support 2b in order to form the electrical power supply track of the actuator 5, possibly in the form of a pad. As described previously, the flexible support 2b is for example a sheet of a polymer of the PEN, PC, PMMA, polyamide, SiNR type or any other suitable material. The support 2b may also comprise several layers of several polymers. Its thickness is for example 80 µm. The layer 54 is for example 0.5 µm thick.

[0115] A piezoelectric ceramic comprising a lower electrode 51, a piezoelectric layer 52 and an upper electrode 53 is then deposited on the layer 54. The piezoelectric ceramic is for example a commercial piezoelectric ceramic made of lead zirconate titanoate (PZT). The latter can in particular be thinned and adjusted to a desired thickness.

[0116] As shown in the Figure 15 , the lower electrode 51 of the piezoelectric ceramic can be connected to the track 54 by means of a layer of conductive glue 55, for example a silver paste, for example with a thickness of approximately 40 µm. The deformation of the piezoelectric layer 52 under the effect of a potential difference applied between the electrodes is transmitted to the support 2b by unimorphic effect via the layer 55.

[0117] A portion of the piezoelectric ceramic is then covered with an electrically insulating layer 56, for example made of a polymer cord, as illustrated in figure 16 The insulating layer 56 makes it possible to deposit by inkjet printing or other suitable method, a conductive track 57 connected to the upper electrode 53 while avoiding short circuits, in particular with the electrode 51, as illustrated in Figure 17 . Track 57 may be in the form of a pad, if necessary. Layer 57 is for example 0.5 µm thick.

[0118] Finally, at the step illustrated in the figure 18 , the actuator is electrically isolated from the fluid 3 by means of an insulating layer 58, for example made of silicone. The tracks (not shown) connected to the electrodes 51 and 53 allow the actuation of the actuators 5 by the control circuit.

[0119] A stiffening ring 9 can be added and fixed, in particular by gluing, on the rear face of the flexible support 2b, if desired. The insulation layer 58 can continuously cover all of the actuators supported by the support 2b.

[0120] As described above, it is possible to obtain a haptic interface according to the invention by assembling two flexible sheets 20 respectively forming the two opposite flexible walls 2a and 2b of the chamber 2.

[0121] In the example of manufacturing such an interface illustrated in figure 19 , a filling opening 25 is initially left when assembling the sheets 20. This allows the non-Newtonian fluid 3 to be introduced, for example using a syringe or any other suitable injection means. The opening 25 is then closed, for example by welding or gluing, to obtain the flexible haptic interface illustrated in figure 20 .

[0122] After filling and closing, the thickness of the fluid 3 can be substantially constant in the chamber 2, for example of the order of several hundred µm to several mm, for example 3mm.

[0123] A haptic interface 1 according to the invention can operate according to the steps described in figure 21 .

[0124] At step 81, the haptic interface is in standby, in the absence of a user in contact with the touch surface S, and the non-Newtonian fluid has uniform rheological properties under the entire touch surface S.

[0125] In step 82, the detection system 6, for example produced with a part of the actuators 5 or with any other suitable detection system, for example capacitive, detects at least one point of contact of the user with the surface S and the control circuit 4 determines the place where the haptic effect(s) must be generated.

[0126] In step 83, the control circuit 4 sends the appropriate control signals to actuate at least some of the actuators 5 so as to generate the desired haptic effect.

[0127] At step 84, the actuators 5 concerned contract or lengthen by inverse piezoelectric effect according to an actuation amplitude corresponding to the received signal, driving the active membrane 21 which is underlying them in an oscillatory movement.

[0128] At step 85, the fluid 3 near the membranes 21 sees its viscosity vary as a function of the vibration amplitude, which generates a modification of the rheological properties, for example a local hardening of the fluid, perceptible by the user on the surface S.

[0129] At step 86, the user breaks contact with the touch surface S and the interface can return to standby, if one wishes to save energy for example.

[0130] The interface 1 according to the invention can be integrated into an item of clothing, for example a glove or a vest, as illustrated in figure 22 .

[0131] Of course, the invention is not limited to the examples which have just been described.

[0132] For example, the interface 1 may include a touch surface, and / or a detection system 6, on several of its walls, or even on all of its outer faces. The chamber 2 may have a shape other than that described above; for example, it is spherical or cylindrical in shape, or may change shape depending on the desired haptic effect, the interface 1 being able to be a reconfigurable tangible object, as illustrated in figure 23 . In this figure, we see that the interface can be mechanically coupled to one or more actuators 11 which allow it to be deformed to give it a predefined shape, corresponding to that of the object that we are seeking to simulate tactilely.

[0133] The actuators 5 can be of any size and shape. Sets of actuators of different sizes are, for example, arranged in a concentric distribution on a wall of the interface. Many small actuators, for example about twenty µm wide, can be used in order to obtain high spatial resolution.

[0134] The stiffening ring 9 is not necessarily circular in shape; it can be of any suitable shape chosen according, for example, to the position of the vibration nodes and antinodes of the wall carrying the actuator.

[0135] The interface may operate in ways other than local hardening of the fluid 3 in the areas where the actuators are used; the operation may be adapted to a rheofluidifying fluid, the viscosity of which decreases under the effect of the actuators.

[0136] The actuators may be produced in a manner other than by the manufacturing method described above. For example, the active layer 52 is produced by transferring thin films of piezoelectric or ferroelectric materials, in particular lead zirconate titanoate (PZT), aluminum nitride (AIN) or lithium niobate (LNO), or even in a multilayer of electroactive polymers, such as polyvinylidene fluoride (PVDF).

Claims

1. Flexible haptic interface (1), comprising: - a chamber (2) containing a non-Newtonian fluid (3) and bounded at least partially by a flexible wall (2a) the exterior face of which defines a touch surface (S) capable of being touched by a user, - a plurality of actuators (5) borne by a flexible carrier (2b) and placed so as to transmit a local mechanical excitation to the fluid (3), and - a control circuit (4) connected to the actuators (5) and configured to modulate the signals sent to the actuators in order to mechanically induce a modification of the rheology of the fluid and to generate a haptic sensation perceptible by the user on the touch surface (S) .

2. Interface according to Claim 1, the chamber (2) having a flat general shape.

3. Interface according to either one of Claims 1 and 2, the chamber (2) having a substantially constant thickness.

4. Interface according to any one of the preceding claims, the chamber being formed between at least two opposite flexible walls (2a; 2b), one at least of which walls defines the touch surface (S), and especially walls comprising or defined by flexible sheets (20).

5. Interface according to any one of the preceding claims, the one or more walls (2a, 2b) defining the touch surface (S) and serving as carrier for the actuators (5) allowing the whole chamber (2) to be bent about at least one axis, and better still in every direction.

6. Interface according to any one of the preceding claims, the actuators (5) making contact with the fluid (3).

7. Interface according to any one of the preceding claims, the actuators (5) being distributed with a regular spacing in at least one direction, and better still in two directions.

8. Interface according to one of the preceding claims, each actuator (5) being borne by an active membrane (21) capable of vibrating under the action of the actuator, the vibration of the membrane acting mechanically on the fluid (3) in the region adjacent the actuator, the membrane (21) preferably being defined by at least one portion of a wall (2b) serving as carrier for the actuators (5), said wall defining an exterior surface of the interface (1) or said wall (2b) being covered by a counter-wall (2c), said counter-wall preferably defining an exterior surface of the interface (1).

9. Interface according to Claim 8, comprising stiffening rings (9) around the membranes (21) of the actuators (5), which rings are preferably located on the face of the carrying wall (2b) opposite the face bearing the actuators (5).

10. Interface according to any one of Claims 1 to 9, comprising a system (6) for detecting a touch of the user on the touch surface (S), especially a capacitive or optical detecting system, the control circuit (4) being arranged to control the actuators (5) depending on the position thus detected and / or a system (7), especially a display covered by the touch surface, allowing an image to be at least partially superposed on the haptic surface and / or at least one actuator (11) allowing the interface to be selectively shaped into at least two distinct shapes.

11. Method for generating at least one tactile stimulus capable of being felt by a user touching an interface such as defined in any one of Claims 1 to 10, comprising the steps of: - detecting the position of the touch of the user on the flexible touch surface of the interface by virtue of a detecting system, - modulating, by virtue of a control circuit (4), the signals sent to the actuators (5) in order to make the stiffness of the fluid in certain regions of the chamber vary locally and to generate an effect perceptible tactilely by the user.

12. Method according to the preceding claim, the touch of the user on the touch surface being detected by virtue of at least some of the actuators, especially via a piezoelectric effect.

13. Method according to one of Claims 11 and 12, the stiffness variation generating a tactile stimulus giving the user the impression of touching a surface having a relief.

14. Process for manufacturing an interface such as defined in any one of Claims 1 to 10, comprising manufacture of an actuator, of the plurality of actuators, of piezoelectric ceramic type via the steps of: - depositing at least a first layer (54) of a conductive material on the upper face of a flexible carrier (2b), preferably a flexible polymer sheet, - fastening a piezoelectric ceramic (51) to the conductive layer thus formed, - depositing, especially by inkjet printing, a layer of a conductive material (57) on the piezoelectric ceramic, - depositing a layer of an electrical insulator (58), which is preferably deposited by printing, on the layers deposited beforehand.

15. Process for manufacturing an interface such as defined in any one of Claims 1 to 10, comprising the step of: joining two said flexible walls (2a, 2b), especially by welding or adhesive bonding, so as to form the chamber (2), at least one of the walls having said actuators (5) on one of its faces.