Patent Publication Number: US-2021181846-A1

Title: Apparatus for providing a tactile output

Description:
TECHNOLOGICAL FIELD 
     Examples of the disclosure relate to an apparatus for providing a tactile output. In particular, they relate to an apparatus for providing a tactile output in a wearable device. 
     BACKGROUND 
     Apparatus for providing tactile outputs to a user may be arranged to provide outputs which a user can perceive via their sense of touch. Such apparatus may be provided within a wearable electronic device which can be positioned in close proximity to the user&#39;s skin. Such apparatus may be arranged to vibrate and/or deform so that the user can sense these vibrations and/or deformations. 
     BRIEF SUMMARY 
     According to various, but not necessarily all, examples of the disclosure there is provided an apparatus comprising: an actuator arranged to move in a first direction and a second direction in response to an electrical input signal; at least one member, coupled to the actuator and arranged to extend towards the second direction; and wherein the actuator is arranged relative to the at least one member so that displacement of the at least one member caused by movement of the actuator in the first direction is restricted and displacement of the at least one member caused by movement of the actuator in the second direction provides a tactile output. 
     The apparatus may comprise at least one deformable substrate wherein the at least one member may be coupled to the deformable substrate so that displacement of the at least one member, caused by the movement of the actuator in the second direction, deforms the deformable substrate to provide a tactile output for a user. 
     The at least one member may be unattached at a first end and coupled to the deformable substrate at a second end so that when the actuator moves in the first direction the first end of the at least one member moves towards the first direction but the second end does not move. 
     The displacement of the at least one member may be restricted so as to prevent a tactile output being provided to the user when the actuator moves in the first direction. 
     The actuator may be arranged relative to the at least one member so that movement of the actuator in the first direction does not cause a displacement of the at least one member that provides a tactile output. 
     The second direction may be orthogonal to the first direction. 
     The apparatus may comprise a plurality of members. 
     The plurality of members may be parallel to each other. 
     The apparatus may comprise a coupling member arranged to couple the plurality of members together. 
     The actuator may be coupled to the at least one member so that when the actuator moves in the second direction the at least one member also moves in the second direction. 
     The apparatus may be arranged to be coupled to a user&#39;s body so that the user can feel the tactile output provided by the displacement of the at least one member. 
     The apparatus may comprise at least one member coupled to a first side of the actuator and at least one member coupled to an opposing side of the actuator. 
     The at least one member may comprise an elastic material. 
     The apparatus may comprise a plurality of actuators arranged in a matrix arrangement. 
     The apparatus may comprise a cavity and the actuator is provided within the cavity. The cavity may be, at least partially formed, by an elastomeric member. The actuator may be free to move within the cavity. 
     The actuator may be mounted on a structured membrane. The structured membrane may enables movement in the second direction. 
     The electronic signal may provide an indication of a biosignal of a user. 
     According to various, but not necessarily all, examples of the disclosure there may be provided a wearable device comprising an apparatus as described in this application. 
     According to various, but not necessarily all, examples of the disclosure there may be provided an apparatus comprising: an actuator arranged to move in a first direction and a second direction in response to an electrical input signal; means for providing a tactile output; and wherein the actuator is arranged relative to the means for providing a tactile output so that displacement of the means for providing a tactile output caused by movement of the actuator in the first direction is restricted and displacement of the means for providing a tactile output caused by movement of the actuator in the second direction provides a tactile output. 
     The means for providing the tactile output may comprise one or more members. 
     The means for providing the tactile output may comprise a cavity formed by an elastomeric member. 
     The means for providing the tactile output may comprise a deformable membrane. 
     According to various, but not necessarily all, examples of the disclosure there is provided examples as claimed in the appended claims. 
    
    
     
       BRIEF DESCRIPTION 
       For a better understanding of various examples that are useful for understanding the detailed description, reference will now be made by way of example only to the accompanying drawings in which: 
         FIGS. 1A to 1C  illustrate an apparatus; 
         FIG. 2  illustrates an apparatus; 
         FIG. 3  illustrates an apparatus; 
         FIGS. 4A and 4B  illustrate an apparatus; 
         FIGS. 5A and 5B  illustrate an apparatus; and 
         FIG. 6  illustrates an example wearable device comprising an apparatus. 
     
    
    
     RECTIFIED SHEET (RULE 91) ISA/EP 
     DETAILED DESCRIPTION 
     The figures and description relate to an apparatus  1  which can be arranged to provide a tactile output to a user. The apparatus  1  may be provided within a wearable electronic device. In some examples the apparatus could be arranged to provide an output indicative of a bio signal or other biometric parameter of the user. For instance, the apparatus  1  could be arranged to provide a tactile output indicative of a user&#39;s heart rate. 
     The example apparatus  1  are arranged to transfer multi-directional motion of an actuator  3  into a displacement or deformation in a given direction. The given direction could be perpendicular, or substantially perpendicular, to the surface of the apparatus  1  so that the energy used by the actuator  3  is efficiently used for displacement or deformation which can be detected by the user. 
     The Figures illustrate example apparatus  1  comprising: an actuator  3  arranged to move in a first direction and a second direction in response to an electrical input signal; at least one member  5 , coupled to the actuator  3  and arranged to extend towards the second direction; wherein the actuator  3  is arranged relative to the at least one member  5  so that displacement of the at least one member  5  caused by movement of the actuator  3  in the first direction is restricted and displacement of the at least one member  5  caused by movement of the actuator  3  in the second direction, provides a tactile output. 
       FIGS. 1A to 1C  illustrate a first example apparatus  1 . The example apparatus  1  comprises an actuator  3 , a plurality of members  5  and a deformable substrate  7 .  FIG. 1A  illustrates a cross section of the example apparatus  1 ,  FIG. 1B  illustrates a plurality of members  5  which may be provided within the apparatus  1  and  FIG. 1C  illustrates a plan view of the plurality of members  5 . 
     The actuator  3  may comprise any means which may be arranged to move in response to an electrical input signal. The actuator  3  may be arranged so that the movement of the actuator  3  corresponds to the input electrical signal. For example, the speed and/or amplitude of the movement of the actuator  3  may be controlled by the electrical input signal. Other parameters of the movement of the actuator  3  may be controlled by the electrical input signal in other examples of the disclosure. 
     The actuator  3  is positioned within the apparatus  1  so that the actuator  3  can move in both a first direction and a second direction. In  FIG. 1A  the first direction is indicated by the arrow  9  and the second direction is indicated by the arrow  11 . The first direction and the second direction are orthogonal to each other. The movement of the actuator  3  may comprise linear motion, rotational motion or a combination of both linear and rotational motion. The movement of the actuator  3  may comprise components in both the first direction and the second direction. 
     The actuator  3  may comprise any suitable type of actuator  3 . In some examples the actuator  3  may comprise an eccentric rotating mass (ERM) actuator, a linear resonant actuator (LRA) or any other suitable type of actuator. The actuator  3  may be arranged to be driven by a small voltage. The small voltage could be a voltage which would not be harmful to a user. The small voltage could be  5 V or below. This may ensure that the actuator  3  is suitable for use in a wearable electronic device. 
     The apparatus  1  also comprises a plurality of members  5 . In the example of  FIGS. 1A to 1C  a plurality of members  5  are provided. In other examples a single member could be provided.  FIG. 1B  shows a side view of the plurality of members  5  and  FIG. 1C  shows a plan view of the plurality of members. 
     The plurality of members  5  are positioned adjacent to the actuator  3 . The plurality of members  5  are positioned adjacent to the actuator  3  in the second direction. In the example of  FIGS. 1A to 1C  the plurality of members  5  are provided overlaying the actuator  3  and the also underneath the actuator  3 . 
     The plurality of members  5  comprise a plurality of elongate members. The elongate members may be elongate so that the length of the member is several times larger than the width of the member. As shown in  FIG. 1C  the plurality of members are arranged in an array. The array comprises a plurality of rows and columns with members  5  provided along the rows and columns. In the example of  FIG. 1C  the array is a circular array. Other shapes of the array could be provided in other examples of the disclosure. 
     The plurality of members are aligned to be parallel with each other so that the lengths of the members  5  extend in the same direction or substantially the same direction. In the example of  FIGS. 1A to 1C  the each of the plurality of members extend toward the second direction. 
     The plurality of members  5  may be rigid or at least partially rigid. The plurality of members may be sufficiently rigid so that when a force in the second direction is applied by the actuator  3  this causes displacement of the member  5  rather than deformation of the member  5 . 
     In the example of  FIGS. 1A to 1C  a coupling member  13  is provided. The coupling member  13  may comprise any means which may enable the plurality of members  5  to be coupled together. The coupling member  11  may be arranged to ensure that the plurality of members  5  remain aligned in a parallel or substantially parallel direction. In some examples the coupling member  13  may act to increase the rigidity of the plurality of members  5  and reduce deformation when a force is applied in a second direction. 
     The coupling member  13  may be a thin polymeric layer. The coupling member  13  may be arranged to allow movement of the members  5  relative to each other in the second direction. This may allow different members  5  in the array to have different displacements in the second direction. The coupling member  13  may be arranged to restrict movement of the members  5  relative to each other in the first direction That is, the coupling member  13  may prevent the members from becoming spaced from each other in the first direction. 
     In some examples the coupling member  13  may comprise a plurality of holes. One or members  5  may be positioned within each hole so that the members  5  can move relative to the coupling member  13  and/or each other in the second direction but the edges of the holes may restrict movement of the members  5  in the second direction. 
     In some examples the coupling member  13  could comprise a rubber film, silicone deformable layer or other suitable member. In the example of  FIGS. 1A to 1C  the rubber film extends over a surface which extends orthogonal, or substantially orthogonal to, the second direction of movement of the actuator  3 . The rubber film extends over a surface which extends parallel, or substantially parallel to, the first direction of movement of the actuator  3 . In the example of  FIGS. 1A to 1C  the rubber film is provided at a midpoint along the length of the plurality of members  5 . In other examples the rubber film could be provided at a different position. 
     The apparatus  1  also comprises a deformable substrate  7 . The deformable substrate may be flexible and/or stretchable. The deformable substrate  7  could comprise any suitable fabric or elastomeric material. The deformable substrate  7  may be deformable enough so that it will deform when one or more of the members  5  are moved in the second direction. This deformation may provide a tactile output which can be detected by a user when the device is in contact with the user&#39;s skin. 
     In some examples the deformable substrate  7  could provide the outer surface of a wearable electronic device. For instance the deformable substrate  7  could be provided as the outer surface in an item of clothing or in a wearable pendant or necklace. In use, the deformable substrate  7  could be positioned adjacent to the user&#39;s skin so that the user can detect the deformation of the deformable substrate  7  using their sense of touch. The deformable substrate  7  may be arranged so that the user can detect the displacement of one or more members  5  through the deformable substrate  7 . 
     In the example of  FIGS. 1A to 1C  a first deformable substrate  7  is provided overlaying a first plurality of members  5  and a second deformable substrate  7  is provided underneath the second plurality of members  5 . 
     The deformable substrates  7  may comprise any suitable material. In some examples the deformable substrates  7  may comprise a fabric or an elastomeric material. 
     In the example of  FIG. 1  the apparatus  1  comprises two deformable substrates  7 . In other examples the apparatus  1  could comprise only one deformable substrate  7 . In other examples the apparatus  1  could be arranged without the deformable substrates  7 . In such examples the tactile output detected by the user could be the displacement of one or more members  5 . 
     Each of the plurality of members  5  has a first end  15  and a second end  19 . The first ends  15  are unattached. The first ends  15  are positioned adjacent to the actuator  3 . The first ends  15  may be touching, or in close proximity, to the actuator  3 . The second ends  19  are coupled to the deformable substrate  7 . The second ends  19  may be coupled to the deformable substrate  7  so that if the seconds ends  19  of the members  5  are moved this causes the deformable substrate  7  to be moved. The second ends  19  may be coupled to the deformable substrate  7  via any suitable means. 
     When the actuator  3  moves in the first direction this movement does not cause a force to be applied to the plurality of members  5 . As the first ends  15  of the members  5  are unattached this allows movement of the actuator  3  in the first direction without causing a movement of the members  5 . This restricts the displacements of the plurality of members  5  when the actuator  3  moves in the first direction. In some examples movement of the actuator  3  in the first direction could cause a small displacement of the first ends  15  of the members  5 . However, as the members  5  are fixed at the second end  19  this may restrict the movement of the members  5 . In such examples the first ends of the members  5  may damp the movement of the actuator  3  in the first direction. In some examples the members  5  may be arranged within the apparatus  1  so that movement of the actuator  3  in the first direction does not cause any displacement of the members  5 . The restriction of the movement of the members  5  may ensure that the movement of the actuator  3  in the first direction does not cause a tactile output to be provided by the apparatus  1 . 
     In some examples the restriction of the movement of the members  5  may ensure that the movement of the actuator  3  in the first direction is small enough so that any tactile output that is provided is very small. A very small tactile output may be one that may be perceptible to a user but may be gentle enough so that it can be easily ignored. 
     When the actuator  3  moves in the second direction this causes a force to be applied to the first end  15  of the members  5 . The force may extend towards the second direction. The force may be applied because the actuator  3  is positioned adjacent to the plurality of members in the second direction. The force applied by the actuator  3  causes movement of one or more of the members  5  towards the second direction. As the deformable substrate  7  is deformable this movement of the one or more members  5  causes the deformation of the deformable substrate  7 . This deformation provides a tactile output for the user. 
     In the example of  FIGS. 1A to 1C  the apparatus  1  comprises two sets of members  5  and two sets of deformable substrates  7 . The different sets of members  5  and deformable substrates  7  are provided on opposing sides of the actuator  3 . In this example the apparatus  1  may therefore be arranged to provide a tactile output on two different surfaces. It is to be appreciated that in other examples the apparatus  1  could comprise just one set of members  5  and one deformable substrate  3  which could be provided on just one side of the actuator  3 . 
     In the example of  FIGS. 1A to 1C  the plurality of members  5  extend in a direction which is parallel to, or substantially parallel to, the second direction. In other examples the plurality of members could extend in a different angle. This may enable the movement of the actuator  3  in the second direction to be translated into a tactile output at an angle different to the second direction. 
     In the example of  FIG. 1  the apparatus  1  comprises a single actuator  3 . In some examples the apparatus  1  may comprise a plurality of actuators  3 . The plurality of actuators  3  could be arranged in a matrix arrangement or any other suitable arrangement. In such examples the members  5  damp the movements of the actuators in the first direction which reduces vibrational cross talk between the actuators  3 . This reduction in cross talk makes it possible to increase the density of the actuators  3  and have adjacent actuators  3  positioned closer to each other while still enabling different tactile outputs to be detectable by a user. This provides for improved granularity of the tactile outputs. 
       FIG. 2  illustrates another example apparatus  1  according to examples of the disclosure. In the example of  FIG. 2  the apparatus  1  comprises an actuator  3 , a plurality of members  5  and a deformable substrate  7 . These may be as described above and corresponding reference numerals are used for corresponding features. 
     In the example of  FIG. 2  the apparatus  1  also comprises a cavity  23  where the actuator  3  is provided within the cavity  23 . In the example of  FIG. 2  the cavity  23  is formed by an elastomeric member  21 . The elastomeric member  21  may form an enclosing wall around the actuator  3 . In some examples the elastomeric member  21  may be formed into a ring shape. Other shapes of elastomeric member  21  could be used in other examples of the disclosure. 
     The actuator  3  is positioned within the cavity  23 . The cavity  23  and the actuator  3  are sized so that the actuator  3  fits entirely within the cavity  23 . The cavity  23  is larger than the actuator  3  so that the actuator  3  can move within the cavity  3  along the first direction as indicated by arrow  9 . The cavity  23  may be slightly larger than the actuator  3  to allow for small movements of the actuator  3  in the first direction. This may enable the actuator  3  to move in both the first direction and the second direction within the cavity  13 . The possible movements in the first direction are smaller than the possible movements in the second direction. 
     The elastomeric member  21  provides a wall of the cavity  23  which is positioned adjacent to the actuator  3  in the first direction. This restricts the movement of the actuator  3  in the first direction. This allows the actuator  3  to move up to the walls in the first direction but restricts further motion in that direction. 
     In the example of  FIG. 2  the cavity does not have any walls overlaying or underlying the actuator  3 . This allows the actuator  3  to move in the second direction. The plurality of members  5  are provided overlaying and underlying the cavity  23  so that when the actuator  3  moves in the second direction this causes displacement of one or more of the plurality of members  5 . 
     The cavity  23  therefore restricts the movement of the apparatus  1  in the first direction but enables the actuator  3  to move freely in the second direction and so enables the plurality of members  5  to be used to provide a tactile output to a user. 
     In the example of  FIG. 2  the actuator  3  is provided within the cavity  23 . In other examples of the disclosure other components of the apparatus  1  could also be provided within the cavity  23 . For example, the plurality of members  5 , or at least part of the plurality of members  5  could also be provided within the cavity  23 . 
       FIG. 3  illustrates another example apparatus  1  according to examples of the disclosure. In the example of  FIG. 3  the apparatus  1  comprises an actuator  3 , a plurality of members  5  and a deformable substrate  7 . These may be as described above and corresponding reference numerals are used for corresponding features. 
     In the example of  FIG. 3  the apparatus  1  comprises a structured membrane  31 . The structured membrane  31  may be a deformable membrane or an at least partially deformable membrane. This may enable the structured membrane  31 , or at least parts of the structured membrane  31  to move. 
     The structured membrane  31  may be structured so as to provide localized elasticity. The membrane  31  may comprise any suitable structures. The structures may comprise a three dimensional pattern on the surface of the membrane  31  which adjusts the elasticity of the membrane  31 . In some examples the structures could be arranged in a zig-zag pattern. Other arrangements and types of structures could be used in other examples of the disclosure. 
     In the example of  FIG. 3  the structured membrane  31  is mounted over a discontinuity  33  in the deformable substrate  7 . The structured membrane  31  is arranged over the discontinuity  33  so that the edges of the structured membrane  33  are fixed to the deformable substrate  7  around the edge of the discontinuity  33 . This prevents the edges of the structured membrane  31  from moving relative to the deformable substrate  7 . This may prevent movement of the structured membrane  31  in the first direction. The discontinuity  33  provides a gap within the deformable substrate  7  which the structured membrane  31  can move into. This therefore enables movement of the structured membrane  31  in the second direction. 
     In the example of  FIG. 3  the actuator  3  is mounted on the structured membrane  31 . The actuator  3  may be mounted on the structured membrane  31  so that the structured membrane  31  bears the weight, or at least part of the weight, of the actuator. The actuator  3  is mounted on the structured membrane  31  so that movement of the actuator  3  causes movement of, at least part of, the structured membrane  31 . 
     The plurality of members  5  are provided overlaying the actuator  3 . The plurality of members  5  are provided on the opposing side of the actuator  3  to the structured membrane  31 . This enables movement of the structured membrane  31  in the second direction to cause the displacement of the plurality of members  5  in the second direction. 
     When the actuator  3  moves in the first direction this does not cause any displacement of the structured membrane  31  as the structured membrane  31  is fixed in position in the first direction. However, when the actuator  3  moves in the second direction this causes movement of the structured membrane  31  in the second direction. This may cause the structured membrane  31  to move in and out of the discontinuity  33  of the deformable substrate  7 . This also causes displacement of the plurality of members  5  which therefore provides a tactile output for the user. Therefore the apparatus  1  provides a tactile output when the actuator  3  is moving in the second direction but not when the actuator  3  is moving in the first direction. 
     In some examples the frequency of the structured membrane  31  may be tuned to a resonant frequency of the actuator  3 . This may enable the movement of the actuator  3  to be enhanced so as to provide a larger tactile output for the user. The frequency of the structured membrane  31  may be tuned using any suitable means. In some examples the structures on the membrane  31  may be used to tune the structured membrane  31 . For example the thickness and spacing of the zig-zag structures could be used to tune the membrane. 
       FIGS. 4A and 4B  illustrate another apparatus  1  according to examples of the disclosure.  FIG. 4A  illustrates a plan view of a part of the apparatus  1  and  FIG. 4B  illustrates a cross section of the apparatus  1 . The example apparatus  1  comprises an actuator  3 , a cavity  23 , an elastomeric member  21 , and two deformable substrates  7 . 
     In the example of  FIG. 2  the apparatus  1  also comprises a cavity  23  where the actuator  3  is provided within the cavity  23 . In the example of  FIG. 2  the cavity  23  is formed by an elastomeric member  21 . The elastomeric member  21  may form an enclosing wall around the actuator  3 . In some examples the elastomeric member  21  may be formed into a ring shape. Other shapes of elastomeric member  21  could be used in other examples of the disclosure. 
     The apparatus  1  is arranged so that the actuator  3  is positioned within the cavity  23 . The cavity  23  and the actuator  3  are sized so that the actuator  3  fits entirely within the cavity  23 . In the examples of  FIGS. 4A and 4B  the cavity  23  has a diameter R 1  and the actuator  3  has a diameter R 2  where R 2  is smaller than R 1 . This leaves a gap between the edges of the actuator  3  and the walls of the cavity  23 . The cavity  23  is larger than the actuator  3  so that the actuator  3  can move within the cavity  3 . This may enable the actuator  3  to move in both the first direction and the second direction within the cavity  23 . 
     The elastomeric member  21  provides a wall of the cavity  23  which is positioned adjacent to the actuator  3  in the first direction. This restricts the movement of the actuator  3  in the first direction. This allows the actuator  3  to move up to the walls in the first direction but restricts further motion in that direction. 
     In the example of  FIG. 2  the cavity does not have any walls overlaying or underlying the actuator  3 . This allows the actuator  3  to move in the second direction. The plurality of members  5  are provided overlaying and underlying the cavity  23  so that when the actuator  3  moves in the second direction this causes displacement of the deformable substrates  7  overlaying the cavity  23 . 
     The cavity  23  therefore restricts the movement of the apparatus  1  in the first direction but enables the actuator  3  to move freely in the second direction and so enables the deformable substrates  7  to be deformed so as to provide a tactile output to a user. 
       FIGS. 5A and 5B  illustrate another apparatus  1  according to examples of the disclosure.  FIG. 5A  illustrates a plan view of a part of the apparatus  1  and  FIG. 5B  illustrates a cross section of the apparatus  1 . The example apparatus  1  comprises an actuator  3 , a structured membrane  31  and a deformable substrate  7 . 
     The structured membrane  31  is mounted over a discontinuity  33  in the deformable substrate  7 . The structure membrane  31  is arranged so that the edges of the structured membrane are fixed to the deformable substrate around the edge of the discontinuity  33 . The discontinuity provides a gap within the deformable substrate  7  which the structured membrane  31  can move into. 
     In the example of  5 A and  5 B the apparatus  1  comprises a structured membrane  31 . The structured membrane  31  may be a deformable membrane or an at least partially deformable membrane. This may enable the structured membrane  31 , or at least parts of the structured membrane  31  to move. 
     The structured membrane  31  may be structured so as to provide localized elasticity. The membrane  31  may comprise any suitable structures. The structures may comprise a three dimensional pattern on the surface of the membrane  31  which adjusts the elasticity of the membrane  31 . In some examples the structures could be arranged in a zig-zag pattern. Other arrangements and types of structures could be used in other examples of the disclosure. 
     In the example of  5 A and  5 B the structured membrane  31  is mounted over a discontinuity  33  in the deformable substrate  7 . The structured membrane  31  is arranged over the discontinuity  33  so that the edges of the structured membrane  33  are fixed to the deformable substrate  7  around the edge of the discontinuity  33 . This prevents the edges of the structured membrane  31  from moving relative to the deformable substrate  7 . This may prevent movement of the structured membrane  31  in the first direction. The discontinuity  33  provides a gap within the deformable substrate  7  which the structured membrane  31  can move into. This therefore enables movement of the structured membrane  31  in the second direction. 
     In the example of  5 A and  5 B the actuator  3  is mounted on the structured membrane  31 . The actuator  3  may be mounted on the structured membrane  31  so that the structured membrane  31  bears the weight, or at least part of the weight, of the actuator. The actuator  3  is mounted on the structured membrane  31  so that movement of the actuator  3  causes movement of, at least part of, the structured membrane  31 . 
     When the actuator  3  moves in the first direction this does not cause any displacement of the structured membrane  31  as the structured membrane  31  is fixed in position in the first direction. However, when the actuator  3  moves in the second direction this causes movement of the structured membrane  31  in the second direction. This may cause the structured membrane  31  to move in and out of the discontinuity  33  of the deformable substrate  7 . This also causes displacement of the plurality of members  5  which therefore provides a tactile output for the user. Therefore the apparatus  1  provides a tactile output when the actuator  3  is moving in the second direction but not when the actuator  3  is moving in the first direction. 
     In some examples the frequency of the structured membrane  31  may be tuned to a resonant frequency of the actuator  3 . This may enable the movement of the actuator  3  to be enhanced so as to provide a larger tactile output for the user. The frequency of the structured membrane  31  may be tuned using any suitable means. In some examples the structures on the membrane  31  may be used to tune the structured membrane  31 . For example the thickness and spacing of the zig-zag structures could be used to tune the membrane. 
       FIG. 6  schematically illustrates an example wearable device  61  which may comprise one or more apparatus  1  as described above. 
     The wearable device  61  is arranged to be coupled to a user&#39;s body  63 . The wearable device  61  can be arranged to be coupled to the user&#39;s body  63  via any suitable means. The wearable device  61  is arranged to be coupled to a user&#39;s body so that the user can feel the deformations of the deformable substrate  7  or other parts of the apparatus  1 . This may require the wearable device  61  to be coupled to the user&#39;s body  63  so that the apparatus  1  is in close proximity to the user&#39;s skin. 
     The wearable device  61  may comprise means for enabling the wearable device  61  to be coupled to the user&#39;s body  63 . The means for coupling the wearable device  61  to the user&#39;s body  63  could comprise a necklace or lanyard which could be worn around the neck of the user. In some examples the means for coupling the wearable device  61  to the user&#39;s body  63  could comprise an item of clothing such as a shirt into which the apparatus  1  and other components of the wearable device  61  could be integrated. In some examples the means for coupling the wearable device  61  to the user&#39;s body  63  could comprise a strap or a sleeve which could be attached to a user&#39;s torso or any other suitable part of the user&#39;s body  63 . 
     The wearable device  61  comprises one or more sensors  65 . The sensors may  65  may comprise means for detecting a biosignal from the user&#39;s body  63  and converting the biosignal into an electrical output. The sensors  65  may be arranged to detect any suitable biosignal. The biosignal that is sensed by the sensors  65  could be any signal that is generated by the user&#39;s body  63 . In some examples the biosignal may comprise an autonomic signal which may be controlled subconsciously by the user. The biosignal may comprise signals which are generated by autonomic bodily functions such as the user&#39;s heartbeat. In some examples the biosignal could comprise a bioelectrical signal such as a biopotential signal. 
     The one or more sensors  65  are coupled to the apparatus  1  so that the electrical output of the sensors  65  is provided to the apparatus  1 . The electrical output may be used to drive the actuator  3  and cause movement of the actuator  3 . This movement is then converted to a tactile output as described above which can be sensed by the user via their sense of touch. 
     In the example of  FIG. 6  wearable device  61  is arranged to sense a biosignal and enable an output indicative of the sensed signal to be provided to the user. This may be useful in monitoring health applications. For instance it may enable a user&#39;s heart rate or respiration rate to be monitored and provide haptic feedback to the user. It is to be appreciated that the apparatus  1  could also be used in other types of wearable devices. For instance the apparatus  1  could be provided within a wearable communication device and arranged to provide a tactile output in response to trigger events associated with the communication functions. For instance, the tactile output could be provided in response to an incoming message or telephone call. 
     The apparatus allow the actuators  3  to move in a first direction but do not transfer this movement to the user as a tactile output. The apparatus  1  may emphasise the movement in the second direction so as to provide an enhanced tactile output in that second direction. This minimises the spread of the tactile output in the first direction and so provides for an improved granularity of the tactile output. This may make it easier for the user to sense the tactile output. This may also reduce the energy requirements of the apparatus  1  as it reduces the energy that is spread in the first direction. 
     In this description the term coupled means operationally coupled. It is to be appreciated that any number or combination of intervening elements may be providing, including no intervening elements. 
     The term “comprise” is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use “comprise” with an exclusive meaning then it will be made clear in the context by referring to “comprising only one . . . ” or by using “consisting”. 
     In this brief description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term “example” or “for example” or “may” in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus “example”, “for example” or “may” refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example but does not necessarily have to be used in that other example. 
     Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For instance, in the examples described above the apparatus  1  comprises a plurality of members  5 . It is to be appreciated that any number of members  5  could be provided including a single member. 
     Features described in the preceding description may be used in combinations other than the combinations explicitly described. 
     Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. 
     Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. 
     Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.