PATENT DOCUMENT

Publication Number: US-10180721-B2
Application Number: US-201815940876-A
Country: US
Kind Code: B2

Title: Fabric-based devices with force sensing

Abstract:
A fabric-based item such as a fabric glove may include force sensing circuitry. The force sensing circuitry may include force sensor elements formed from electrodes on a compressible substrate such as an elastomeric polymer substrate. The fabric may include intertwined strands of material including conductive strands. Signals from the force sensing circuitry may be conveyed to control circuitry in the item using the conductive strands. Wireless circuitry in the fabric-based item may be used to convey force sensor information to external equipment. The compressible substrate may have opposing upper and lower surfaces. Electrodes for the force sensor elements may be formed on the upper and lower surfaces. Stiffeners may overlap the electrodes to help decouple adjacent force sensor elements from each other. Integrated circuits can be attached to respective force sensing elements using adhesive.

Claims:
What is claimed is: 
     
       1. Apparatus, comprising:
 fabric containing conductive strands of material that form signal paths; 
 control circuitry coupled to the signal paths; and 
 a force sensor coupled to the control circuitry, wherein the force sensor has a force sensor element and capacitive force sensor circuitry that is electrically coupled to the force sensor element through the signal paths and wherein the force sensor element includes a compressible substrate and first and second electrodes that are respectively located on first and second opposing surfaces of the compressible substrate. 
 
     
     
       2. The apparatus defined in  claim 1  wherein the compressible substrate is an elastomeric polymer layer and wherein the force sensor element further comprises first and second stiffeners respectively on the first and second electrodes. 
     
     
       3. The apparatus defined in  claim 2  wherein the elastomeric polymer layer is characterized by a first modulus of elasticity and wherein the stiffeners are characterized by a second modulus of elasticity that is greater than the first modulus of elasticity. 
     
     
       4. The apparatus defined in  claim 3  wherein the compressible substrate has an elongated shape and forms a strand of material in the fabric. 
     
     
       5. The apparatus defined in  claim 4  wherein the force sensor element comprises one of multiple force sensor elements in an array of force sensor elements on the compressible substrate. 
     
     
       6. The apparatus defined in  claim 5  wherein the array is a one-dimensional array formed from a row of the force sensor elements. 
     
     
       7. The apparatus defined in  claim 1  wherein the force sensor element comprises metal shielding layers on the compressible substrate. 
     
     
       8. The apparatus defined in  claim 1  wherein the force sensor comprises a metal layer on the compressible substrate having serpentine signal lines. 
     
     
       9. A fabric force-sensing glove, comprising:
 glove fingers formed from fabric that has intertwined strands; 
 control circuitry; and 
 a force sensor coupled to the control circuitry, wherein the force sensor is formed from force sensor elements on an elongated strip-shaped polymer substrate that forms one of the intertwined strands. 
 
     
     
       10. The fabric force-sensing glove defined in  claim 9  wherein the strip-shaped polymer substrate is formed from an elastomeric polymer and wherein the force senor elements extend in a row along the strip-shaped polymer substrate. 
     
     
       11. The fabric force-sensing glove defined in  claim 10  wherein each force sensor element includes first and second electrodes and wherein each force sensor element includes a stiffener on the first electrode of that force sensor element. 
     
     
       12. The fabric force-sensing glove defined in  claim 11  wherein there are openings in the polymer substrate surrounding the first electrode of each force sensor element. 
     
     
       13. The fabric force-sensing glove defined in  claim 12  wherein the control circuitry includes wireless communications circuitry and wherein the control circuitry is configured to gather force sensor measurements from the force sensor and to wirelessly transmit the force sensor measurements with the wireless communications circuitry. 
     
     
       14. The fabric force-sensing glove defined in  claim 9  wherein each force sensor element has electrodes on opposing surfaces of the strip-shaped polymer substrate. 
     
     
       15. The fabric force-sensing glove defined in  claim 14  wherein each force sensor element has stiffeners on the electrodes. 
     
     
       16. The fabric force-sensing glove defined in  claim 15  wherein the polymer substrate is characterized by a first elastic modulus and wherein the stiffeners are characterized by a second elastic modulus that is greater than the first elastic modulus. 
     
     
       17. A fabric-based item, comprising:
 fabric formed from intertwined strands of material including conductive strands; and 
 force sensor circuitry in the fabric that is coupled to the conductive strands, wherein the force sensor circuitry includes integrated circuits containing capacitive force sensor circuitry and includes respective force sensor elements electrically coupled to the integrated circuits, wherein each force sensor element has capacitive force sensor electrodes on an elastomeric substrate that is attached to the integrated circuit. 
 
     
     
       18. The fabric-based item defined in  claim 17  wherein the intertwined strands of material are configured to form glove fingers and wherein the force sensor elements are located on the glove fingers. 
     
     
       19. The fabric-based item defined in  claim 18  wherein each force sensor element has a via that passes through the elastomeric substrate of that force sensor element and that shorts one of the capacitive force sensor electrodes of that force sensor element to the integrated circuit that is attached to that elastomeric substrate. 
     
     
       20. The fabric-based item defined in  claim 19  wherein the conductive strands include first strands and second strands that cross the first strands at intersections and wherein the integrated circuits are coupled to the conductive strands at the intersections. 
     
     
       21. A fabric-based item, comprising:
 fabric formed from intertwined strands of material; 
 control circuitry; and 
 a force sensor coupled to the fabric and electrically coupled to the control circuitry, wherein the force sensor has a force sensor element and capacitive force sensor circuitry and wherein the force sensor element includes an elastomeric material, first and second electrodes separated by the elastomeric material, an electrical shield on the elastomeric material, and conductive traces on the elastomeric material that couple the first and second electrodes to the capacitive force sensor circuitry. 
 
     
     
       22. The fabric-based item defined in  claim 21  wherein the electrical shield on the elastomeric material is electrically isolated from the first and second electrodes. 
     
     
       23. The fabric-based item defined in  claim 21  wherein the conductive traces include sense and drive lines and wherein the electrical shield overlaps and electrically shields the sense line. 
     
     
       24. The fabric-based item defined in  claim 23  wherein the elastomeric material forms a substrate having first and second elastomeric layers, wherein the first electrode is a sense electrode between the first and second elastomeric layers and wherein the second electrode is a drive electrode on the first elastomeric layer and separated from the first electrode by the first elastomeric layer. 
     
     
       25. The fabric-based item defined in  claim 24  wherein the electrical shield includes a metal trace separated from the first electrode by the first elastomeric layer. 
     
     
       26. The fabric-based item defined in  claim 25  wherein the electrical shield includes an additional metal trace separated from the first electrode by the second elastomeric layer. 
     
     
       27. The fabric-based item defined in  claim 21  further comprising additional force sensor elements coupled to the capacitive force sensor circuitry with additional conductive traces on the elastomeric material. 
     
     
       28. The fabric-based item defined in  claim 21  further comprising a stiffener on the first electrode. 
     
     
       29. The fabric-based item defined in  claim 28  further comprising an additional stiffener on the second electrode.

Description:
This patent application claims the benefit of provisional patent application No. 62/519,564, filed on Jun. 14, 2017, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to force sensing and, more particularly, to items such as fabric-based items with force sensing capabilities. 
     BACKGROUND 
     It may be desirable to form items using materials such as fabric. For example, wearable items may be formed from fabric. Some wearable items may include sensing circuitry. Electronic equipment may use information from the sensing circuitry in controlling a system or performing other tasks. 
     If care is not taken, fabric-based items such as these may not offer desired features. For example, a fabric-based item with sensing circuitry may be awkward to use, may not have an attractive appearance, or may not gather measurements accurately. 
     SUMMARY 
     A fabric-based item such as a fabric glove may include force sensing circuitry. The force sensing circuitry may include force sensor elements formed from electrodes on a compressible substrate such as an elastomeric polymer substrate. The fabric may include intertwined strands of material including conductive strands. Signals from the force sensing circuitry may be conveyed to control circuitry in the item using the conductive strands. Wireless circuitry in the fabric-based item may be used to convey force sensor information to external equipment. 
     The compressible substrate may have opposing upper and lower surfaces. Electrodes for the force sensor elements may be formed on the upper and lower surfaces. Stiffeners may overlap the electrodes to help decouple adjacent force sensor elements from each other. In some configurations, integrated circuits can be attached to respective force sensing elements using adhesive. 
     Force sensing elements may have sets of electrodes that are arranged in an array on the compressible substrate such as a one-dimensional array. The compressible substrate may be formed from an elongated strip of the elastomeric polymer and may be sufficiently elongated to serve as a strand that is intertwined with the conductive strands and other intertwined strands of material in the fabric. 
     To facilitate deformation of the compressible substrate, the compressible substrate may be provided with openings surrounding the electrodes of each force sensor element. Electrodes, signal traces for conveying capacitive force sensor signals, shield structures, and other conductive signal paths in the force sensing circuitry may be formed from structures that resist cracking when flexed such as mesh structures with serpentine line segments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative fabric-based item in accordance with an embodiment. 
         FIG. 2  is a side view of illustrative woven fabric in accordance with an embodiment. 
         FIG. 3  is a top view of illustrative knit fabric in accordance with an embodiment. 
         FIG. 4  is a diagram of an illustrative fabric-based item such as a glove with sensor circuitry coupled to an electronic device in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative glove finger with sensor circuitry such as force sensors in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative capacitive force sensor in accordance with an embodiment. 
         FIGS. 7 and 8  are diagrams of illustrative arrays of electrodes for capacitive force sensors in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of an illustrative capacitive force sensor in accordance with an embodiment. 
         FIG. 10  is a top view of an illustrative strip-shaped substrate and associated array of force sensor elements incorporated into fabric in accordance with an embodiment. 
         FIG. 11  is a top view of an illustrative force sensor in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of the force sensor of  FIG. 11  in accordance with an embodiment. 
         FIG. 13  is a diagram of an illustrative conductive mesh structure of the type that may be used in forming conductive paths in force sensor circuitry in accordance with an embodiment. 
         FIG. 14  is a top view of an illustrative force sensor formed from metal traces on an elastomeric layer having through-holes or other openings to facilitate deformation of the elastomeric layer in accordance with an embodiment. 
         FIG. 15  is a top view of illustrative fabric having an array of force sensors in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of an illustrative force sensor formed from an integrated circuit that is coupled to signal lines such as conductive strands in a fabric layer and that is attached to an elastomeric layer with capacitive electrodes that are separated by the elastomeric layer in accordance with an embodiment. 
         FIG. 17  is a cross-sectional side view of another illustrative force sensor formed from an integrated circuit and capacitive electrodes separated by an elastomeric layer that is attached to the integrated circuit in accordance with an embodiment. 
         FIG. 18  is a cross-sectional side view of an illustrative force sensor being molded into a finger shape in accordance with an embodiment. 
         FIG. 19  is a cross-sectional side view of an illustrative yarn-based force sensor in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A schematic diagram of an illustrative item that contains force sensors is shown in  FIG. 1 . Item  10  may be an electronic device or an accessory for an electronic device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a remote control, a navigation device, an embedded system such as a system in which item  10  is mounted in a kiosk, in an automobile, airplane, or other vehicle, other electronic equipment, or may be equipment that implements the functionality of two or more of these devices. If desired, item  10  may be a removable external case for electronic equipment, may be a strap, may be a wrist band or head band, may be a removable cover for a device, may be a case or bag that has straps or that has other structures to receive and carry electronic equipment and other items, may be a necklace or arm band, may be a wallet, sleeve, pocket, or other structure into which electronic equipment or other items may be inserted, may be part of a chair, sofa, or other seating (e.g., cushions or other seating structures), may be part of an item of clothing or other wearable item (e.g., a hat, belt, wrist band, headband, sock, glove, shirt, pants, etc.), or may be any other suitable item. Configurations in which item  10  is a glove or other wearable item may sometimes be described herein as an example. This is, however, merely illustrative. Item  10  may be any suitable device. 
     Item  10  may include intertwined strands of material that form fabric  12 , so items such as item  10  may sometimes be referred to as fabric-based items or fabric-based electronic devices. Fabric  12  may form all or part of a housing wall or other layer in an electronic device (e.g., when item  10  is a glove or other flexible device worn by a user), may form an outer covering for a housing wall structure, may form internal structures in an electronic device, or may form other fabric-based structures. Item  10  may be soft (e.g., item  10  may have a fabric surface that yields to a light touch), may have a rigid feel (e.g., the surface of item  10  may be formed from a stiff fabric), may be coarse, may be smooth, may have ribs or other patterned textures, and/or may be formed as part of a device that has portions formed from non-fabric structures of plastic, metal, glass, crystalline materials, ceramics, or other materials. 
     The strands of material in fabric  12  may be single-filament strands (sometimes referred to as fibers or monofilaments), may be yarns or other strands that have been formed by intertwining multiple filaments (multiple monofilaments) of material together, or may be other types of strands (e.g., tubing). Monofilaments for fabric  12  may include polymer monofilaments and/or other insulating monofilaments and/or may include bare wires and/or insulated wires. Monofilaments formed from polymer cores with metal coatings and monofilaments formed from three or more layers (cores, intermediate layers, and one or more outer layers each of which may be insulating and/or conductive) may also be used. 
     Yarns in fabric  12  may be formed from polymer, metal, glass, graphite, ceramic, natural materials as cotton or bamboo, or other organic and/or inorganic materials and combinations of these materials. Conductive coatings such as metal coatings may be formed on non-conductive material. For example, plastic yarns and monofilaments in fabric  12  may be coated with metal to make them conductive. Reflective coatings such as metal coatings may be applied to make yarns and monofilaments reflective. Yarns may be formed from a bundle of bare metal wires or metal wire intertwined with insulating monofilaments (as examples). 
     Strands of material may be intertwined to form fabric  12  using intertwining equipment such as weaving equipment, knitting equipment, or braiding equipment. Intertwined strands may, for example, form woven fabric, knit fabric, braided fabric, etc. Conductive strands and insulating strands may be woven, knit, braided, or otherwise intertwined to form contact pads that can be electrically coupled to conductive structures in item  10  such as the contact pads of an electrical component. The contacts of an electrical component may also be directly coupled to an exposed metal segment along the length of a conductive yarn or monofilament. 
     Conductive and insulating strands may also be woven, knit, or otherwise intertwined to form conductive paths. The conductive paths may be used in forming signal paths (e.g., signal buses, power lines, etc.), may be used in forming part of a capacitive touch sensor electrode, a resistive touch sensor electrode, a force sensor electrode, or other input-output device, or may be used in forming other patterned conductive structures. Conductive structures in fabric  12  may be used in carrying power signals, digital signals, analog signals, sensor signals, control signals, data, input signals, output signals, or other suitable electrical signals. 
     Item  10  may include mechanical structures in addition to fabric  12  such as polymer binder to hold strands in fabric  12  together, support structures such as frame members, housing structures (e.g., an electronic device housing), and other mechanical structures. 
     Item  10  may include circuitry  30 . Circuitry  30  may include electrical components that are coupled to fabric  12 , electrical components that are housed within an enclosure formed by fabric  12  and/or an enclosure formed using other housing structures such as housing walls formed from plastic, metal, glass, ceramic, or other materials, electrical components that are attached to fabric  12  using welds, solder joints, adhesive bonds (e.g., conductive adhesive bonds such as anisotropic conductive adhesive bonds or other conductive adhesive bonds), crimped connections, or other electrical and/or mechanical bonds. Circuitry  30  may include metal structures for carrying current, electrical components such as integrated circuits, discrete components (e.g., capacitors, resistors, and inductors), and/or other circuitry. 
     As shown in  FIG. 1 , circuitry  30  may include input-output circuitry  26  and control circuitry  16 . Input-output circuitry  26  may include force sensors  14  (sometimes referred to as pressure sensors) and other sensors and input-output devices  18 . Devices  18  may include light-emitting diodes, displays, speakers, microphones, buttons, tone generators, haptic output devices such as vibrators, and sensors (e.g., gas sensors, gas pressure sensors, temperature sensors, strain gauges, accelerometers, proximity sensors, touch sensors, ambient light sensors, digital image sensors, fingerprint sensors, gaze detection and eye and face sensing devices, and/or other sensors). 
     Control circuitry  16  may be formed from one or more integrated circuits such as microprocessors, microcontrollers, application-specific integrated circuits, digital signal processors, and/or other circuits. Control circuitry  16  may be used to gather information from user input circuitry, sensing circuitry such as touch sensors, proximity sensors, and other sensing circuitry, and other input-output devices  18  and may be used in gathering and processing force sensor information from force sensors  14 . Control circuitry  16  may be used to control the operation of item  10  based on this gathered information and/or based on other information by controlling electrically controllable (electrically adjustable) components in circuitry  16 . The control circuitry may have wireless communications circuitry and other communications circuitry and may be used in supporting communications with external equipment. Using wireless communications or wired communications, control circuitry in item  10  may, if desired, provide information such as force sensor information and/or other information gathered using input-output devices  18  to external equipment. 
     External equipment that communicates with item  10  may include separate items that are configured to operate with each other. For example, item  10  may be a case that operates with a device that fits within the case. As another example, item  10  may be a force sensing glove or other wearable device and may be used in controlling an electronic device that is using information such as force sensor measurements from force sensors in item  10 . Devices that may be controlled using force sensor information from a force sensing glove or other item  10  include a gaming unit, a computer, a set-top box, a television, and or other electronic equipment. 
     To supply force sensor measurements (e.g., raw measurements or commands or other information derived from raw measurements) to external equipment, circuitry  16  may include wireless communications circuitry such as antennas, wireless radio-frequency transceivers (e.g., transceivers operating at 2.4 GHz, 5 GHz, and/or other wireless communications frequencies) and other electrical components for supporting wireless communications with external electronic devices. If desired, the wireless communications circuitry may be based on infrared transmitters such as infrared light-emitting diodes or lasers for transmitting infrared commands to electronic equipment. 
     Fabric  12  may be used in forming a force sensing glove or other electronic device. The fabric may serve as a supporting structure for the body of the glove or other device or, in some configurations, may serve as an inner liner, outer covering, or other portion of a supporting structure that also includes other structural components. Fabric  12  may be formed from strands that are intertwined using any suitable intertwining equipment. With one suitable arrangement, which may sometimes be described herein as an example, fabric  12  may be woven fabric formed using a weaving machine. In this type of illustrative configuration, fabric  12  may have a plain weave, a basket weave, a satin weave, a twill weave, or variations of these weaves, may be a three-dimensional woven fabric, or may be other suitable fabric. With other suitable arrangements, fabric  12  may be knit or braided. If desired, signal paths formed from conductive yarns and monofilaments (e.g., insulated and bare wires) may be used to route signals within item  10  and may be used to route signals between item  10  and external devices. 
     A cross-sectional side view of illustrative woven fabric  12  is shown in  FIG. 2 . As shown in  FIG. 2 , fabric  12  may include strands  20  such as warp strands  20 A and weft strands  20 B. In the illustrative configuration of  FIG. 2 , fabric  12  has a single layer of woven strands  20 . Multi-layer fabric constructions may be used for fabric  12  if desired. 
     As shown in  FIG. 3 , fabric  12  may be a knit fabric. In the illustrative configuration of  FIG. 3 , fabric  12  has a single layer of knit strands  20  that form horizontally extending rows of interlocking loops (courses  22 ) and vertically extending wales  24 . Other types of knit fabric may be used in item  10 , if desired. 
     Item  10  may include non-fabric materials (e.g., structures that are formed from plastic, metal, glass, ceramic, crystalline materials such as sapphire, leather, etc.). These materials may be formed using molding operations, extrusion, machining, laser processing, and other fabrication techniques and may be used in forming housing structures, internal mounting structures, buttons, portions of display components and other electronic components, and/or other structures in item  10 . In some configurations, item  10  may include one or more layers of material. The layers in item  10  may include layers of polymer, metal, glass, fabric, leather, adhesive, crystalline materials, ceramic, substrates on which components have been mounted, patterned layers of material, layers of material containing patterned metal traces, thin-film devices such as transistors, and/or other layers. 
     As shown in  FIG. 4 , item  10  may include a layer of fabric  12  and/or other layers of material shaped in the form of a glove. Force sensing circuitry such as force sensors  14  may be located on one or more fingers  38  of the glove (e.g., on the top, bottom, and/or sides of fingers  38 ) and/or on other areas of the glove such as on palm  40  or the top surface of the glove that covers the back of a user&#39;s hand. Signal paths  32  may be used in electrically coupling force sensors  14  to control circuitry  16 . Signal paths  32  may be formed from conductive strands  20  in fabric  12  and/or separate conductive strands (wires, traces on printed circuits, etc.). Control circuitry  16  may have wired or wireless communications circuitry for supporting communications over communications link  36  between item  10  and external electronic devices such as electronic device  34 . Device  34  may be a computer, cellular telephone, a head-mounted device, a display, a gaming unit, a set-top box, a system including two or more of these devices, or other electronic equipment. During operation, control circuitry  16  may use force sensors  14  to gather force sensor measurements and may, as an example, provide this information to electronic device  34  for controlling device  34 . If desired, control circuitry in external equipment  34  may be used in processing sensor data (e.g., to minimize the amount of circuitry in item  10 ). Force sensor measurements may be used in a glove or other input device, in clothes, as part of a heart rate sensor, blood pressure sensor, respiration sensor, etc. 
       FIG. 5  is a cross-sectional side view of an illustrative portion of item  10  (e.g., a glove) such as a finger portion. As shown in  FIG. 5 , glove finger  38  may include fabric  12  that has been woven, knit, braided and/or sewn to form a shape appropriate for receiving a user&#39;s finger (e.g., finger  42 ). When the user presses glove finger  38  in direction  46  towards surface  44  with finger  42 , a compressive force will be applied to fabric  12  and force sensors  14  between finger  42  and surface  44 . Surface  44  may be an external surface such as a table top or may be an inner surface of a glove-shaped outer shell (housing) against which the user may press. Control circuitry  16  ( FIG. 4 ) can measure this force using force sensors  14 . 
     An illustrative force sensor is shown in  FIG. 6 . Force sensor  14  may include capacitive force sensor processing circuitry such as circuitry  48  and a capacitive force sensor element such as force sensor element  50 . Capacitive force sensor circuitry  48  may be implemented using one or more integrated circuits and may be used to apply alternating current signals to elements such as element  50  (e.g., drive signals D) while monitoring resulting signals (sense signals S). By processing the D and S signals, circuitry  48  can measure the capacitance of element  50  and can detect any changes to this capacitance due to applied force. Any suitable capacitance sensing techniques may be used in processing capacitance measurements (e.g., mutual capacitance or self capacitance). 
     Element  50  may include capacitive force sensing electrodes  52  and  54 . Conductive strands in fabric  12  and/or other signal paths may be used in electrically coupling capacitive force sensor circuitry  48  to electrodes  52  and  54 . Electrodes  52  and  54  may be separated by substrate  56 . Substrate  56  may be formed from an elastomeric polymer such as silicone or other compressible material. Elastomeric polymer substrate  56  may be insulating. When no force is applied to element  50 , electrodes  52  and  54  will be separated by a distance D 1 . When force is applied to element  50  in directions  58  and  59 , elastomeric polymer substrate  56  will deform inwardly and the distance between electrodes  52  and  54  will decrease to distance D 2 . This will cause the capacitance between electrodes  52  and  54  to rise, which can be detected by capacitive force sensor circuitry  48 . 
     There may be any suitable number of elements  50  and any suitable number of integrated circuits for implementing circuitry  48  in item  10 .  FIG. 7  is a diagram of an illustrative force sensor formed from multiple vertical strip-shaped electrodes  52  that carry drive signal D and multiple horizontal strip-shaped electrodes  54  that provide sense signals S to circuitry  48 . Electrodes  52  and  54  may run perpendicular to each other and may be formed form metal traces on opposing sides of an elastomeric layer such as elastomeric polymer substrate  56  of  FIG. 6 . The electrode pattern of  FIG. 7  allows two-dimensional force measurements (in dimensions X and Y) to be gathered by circuitry  16 . In the illustrative configuration of  FIG. 8 , drive electrodes  52  receive a common drive signal D and each sense electrode  54  is coupled to an independent sense signal line for providing a respective independent sense signal to circuitry  48 . In configurations such as these, each intersection between drive and sense electrodes serves as a separate element  50 . Electrodes  52  and  54  of  FIGS. 7 and 8  may be separated by a compressible material such as an elastomeric material (e.g., substrate  56 ). If desired, other electrode patterns may be used in forming force sensor  14 . The configurations of  FIGS. 7 and 8  are merely illustrative. 
       FIG. 9  is a cross-sectional side view of an illustrative capacitive force sensor element. As shown in  FIG. 9 , element  50  may have a compressible layer such as elastomeric polymer substrate  56  that separates electrodes  52  and  54  as described in connection with  FIG. 6 . When polymer substrate  56  is compressed, the separation distance T 1  between electrodes  52  and  54  decreases to a distance D 2  that is less than distance T 1  as illustrated by compressed electrode positions  52 ′ and  54 ′. This changes the capacitance between electrodes  52  and  54 , which can be measured and used in determining how much force has been applied to element  50 . 
     Optional stiffeners  60  may be formed on top of electrodes  52  and  54  to help decouple sensor element  50  from adjacent sensor elements  50  (e.g., to help reduce cross-talk). If desired, there may be multiple stiffener structures over each pair of electrodes (e.g., stiffener  60  of  FIG. 9  may be segmented by forming gaps  61  that divide stiffeners  60  to form smaller stiffener segments). In some arrangements, only one stiffener  60  is used (e.g., lower stiffener structures may be omitted from electrode  52  so that only the stiffener structure on electrode  54  is present). 
     The thickness T 1  of the layer of elastomeric polymer substrate  56  in element  50  may be, for example, 20-100 microns, at least 3 microns, at least 15 microns, at least 40 microns, less than 400 microns, less than 200 microns, or other suitable thickness. The thickness T 2  of stiffeners  60  may be, for example, 50-300 microns, at least 10 microns, at least 25 microns, less than 1000 microns, less than 500 microns, or other suitable thickness. Stiffeners  60  may be formed form a polymer, metal, or other material that is more rigid than elastomeric polymer substrate  56 . For example, elastomeric polymer substrate  56  may be formed from an elastomeric polymer characterized by a first modulus of elasticity (e.g., a Young&#39;s modulus or other elastic modulus) and stiffeners  60  may be characterized by a second modulus of elasticity that is greater than the first modulus of elasticity. The Young&#39;s modulus of elasticity of polymer substrate  56  may be 0.1 MPa to 10 MPa, greater than 0.2 MPa, less than 5 MPa, etc. The Young&#39;s modulus of elasticity of stiffeners  60  may be 100 MPa to 200 GPa, more than 150 MPa, less than 150 GPa, etc. The thickness of electrodes  52  and  54  may be less than 20 microns, less than 10 microns, less than 3 microns, less than 0.5 microns, more than 0.01 microns, more than 0.2 microns, or other suitable thickness. Electrodes  52  and  54  may be formed from metal traces (e.g., metal traces deposited using physical vapor deposition, electroplating, etc.) and/or may be formed form patterned conductive structures such as patterned metal ink (e.g., printed silver paint or other metal paint, graphene, graphite, silver particles, or other conductive material in a polymer such as silicone, PEDOT:PSS or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate conductive polymer, etc.). The width WD of stiffeners  60  and electrodes  54  and  52  (e.g., the diameter or other lateral dimension in the XY plane of  FIG. 9 ) may be 2-3 mm, at least 0.1 mm, at least 0.5 mm, at least 1 mm, less than 10 mm, less than 4 mm, or other suitable dimension. Stiffeners  60  help translate applied pressure on the surface of stiffeners  60  into compression of the elastomeric material directly between the stiffeners, thereby helping to avoid undesired coupling between adjacent elements  50  that could reduce measurement accuracy. The use of locally stiff areas (e.g., stiffeners  60 ) and the use of a flexible substrate that allows individual sensors to be compressed without crosstalk helps to accommodate variations in fabric morphology and finger curvature while minimizing longitudinal substrate stress. 
     To facilitate incorporation of force sensor  14  into fabric  12 , sensor elements  50  may be formed on an elongated strip-shaped flexible substrate such as elastomeric polymer substrate  56  of  FIG. 10 . The aspect ratio of substrate  56  (length over width) may be at least 10, at least 25, at least 100, less than 1000, or other suitable aspect ratio. Sensor elements  50  may, in general, be arranged in a two-dimensional array (e.g., extending across both the X and Y dimensions when sensor  14  lies in an XY plane) or a one-dimensional array. Sensor  14  of  FIG. 10  has a one-dimensional array configuration in which substrate  56  is elongated along the Y axis and in which sensor elements  50  are arranged in a single row extending along the Y axis. If desired, narrow strip-shaped sensors can be formed using multiple closely spaced rows of elements  56  (e.g., a 2×N arrangement in which N is the number of elements  50  that extend along the longitudinal axis of the sensor substrate). The use of a narrow sensor substrate arrangement with a single one-dimensional array of elements  50  and/or a relatively narrow two-dimensional array of elements  50  allows sensor  14  to form a strand of material that can be incorporated into fabric  12  amongst other strands  20  as shown in  FIG. 10 . Strands formed from elongated compressible substrates and narrow arrays of force sensor elements  50  may serve as warp strands or weft strands in woven fabric or may be incorporated into knit or braided fabric. 
     If desired, electrical shielding structures may be incorporated into sensors  14 . For example, grounded conductive layers may be formed above and/or below sensor signal paths. This type of arrangement is shown in the top view of sensor element  50  in  FIG. 11  and the corresponding side view of  FIG. 12 . As shown in  FIGS. 11 and 12 , sensor element  50  may include electrodes  54  and  52  that are located on opposing surfaces of an substrate  56  Grounded shielding structures such as shield layer G 2  and shield layer G 1  may help shield signal paths in element  50 . For example, shield G 1  may be formed on the upper surface of substrate  56  and shield G 2  may be formed on the opposing lower surface of substrate  56  so that these shield layers overlap portions of electrodes  52  and  54 . Substrate  56  may be formed from multiple elastomeric layers such as layer  56 A and  56 B. Layers  56 A and  56 B may be coupled together (e.g., using a layer of adhesive). Electrode  52  may be formed between layers  56 A and  56 B (as an example). Optional stiffeners  60  may be formed on both electrode  54  and the opposing side of substrate  56  (e.g., on shield G 2  where shield G 2  overlaps electrode  54 ) and/or one or both of these stiffeners may be omitted. If desired, shields can be formed around drive electrode  54 . In some configurations, conductive strands in fabric can form shields. 
     To prevent cracks from forming in the conductive layers of sensor  14 , one or more of these conductive layers may be formed using serpentine lines. As an example, one or more conductors in sensor  14  such as electrodes  52  and  54  and shielding layers G 1  and G 2  may be formed using a mesh of serpentine lines (see, e.g., serpentine lines  72  of mesh  70  in the example of  FIG. 13 ). Isolated (non-mesh-shaped) paths formed from serpentine lines may also be used (e.g., to convey signals between force sensor elements  50  and force sensor processing circuitry). Lines  72  may be formed from metal traces deposited and patterned on substrate  56  using photolithography and/or may be metal layers formed from metal paint or other conductive materials. 
     To enhance the flexibility of substrate  56 , one or more areas of substrate  56  may be provided with openings. The openings may be recesses that pass partially through substrate  56  and/or may be through holes that pass between opposing surfaces of substrate  56 . Flexibility-enhancement structures such as these may, if desired, be concentrated around electrodes  52  and  54  to facilitate compression of the portion of substrate  56  that overlaps electrodes  52  and  54 . As shown in  FIG. 14 , for example, openings  74  that pass partly or entirely through substrate  56  may be arranged in a ring-shaped pattern such as a circular ring surrounding electrodes  52  and  54 . This may facilitate compression of the portion of substrate  56  that is interposed between electrodes  52  and  54  when a user compresses force sensing element  50  during use of item  10 . 
     In the arrangement of  FIG. 15 , fabric  12  includes woven strands such as warp strands  20 A and weft strands  20 B. Force sensing elements  50  may be formed at intersections  76  of strands  20 A and  20 B (e.g., at the intersections of conductive strands among strands  20 A and  20 B) and may be electrically coupled to these strands. This allows signals for the force sensor elements to be routed through the conductive strands of fabric  12 . Signals can also be routed through signal paths (wires, flexible printed circuits, etc.) that are separate from fabric  12 , if desired. 
       FIG. 16  is a cross-sectional side view of an illustrative force sensor that includes an integrated circuit. As shown in  FIG. 16 , electrodes  52  and  54  of force sensing element  50  may be formed on opposing sides of substrate  56 . Integrated circuit  80  may have terminals such as contacts  82  and  86 . Contact  82  may be shorted to electrode  54 . Via  78  may be formed from a conductor such as metal to short electrode  52  to contact  86 . If desired, adhesive  88  (e.g., a polymer layer) may be used to attach integrated circuit  80  to substrate  56 . Integrated circuit  80  may be a bare integrated circuit die (e.g., a silicon die) or may be a packaged integrated circuit (e.g., an integrated circuit die or dies mounted in package formed of plastic, ceramic, and/or other materials). 
     Integrated circuit  80  may include capacitive force sensor circuitry  48  of  FIG. 6  and may analyze capacitive electrode measurements made using electrodes  54  and  52  to produce force sensor readings for use by control circuitry  16 . Optional stiffener structures such a structure  60  may be placed on electrode  52 . Integrated circuit  80  may serve as a stiffener for electrode  54 . Integrated circuit  80  may be coupled to control circuits in item  10  (e.g., control circuitry  16  of  FIG. 4 ) using conductive paths such as conductive strands in fabric  12  or other conductive paths in item  10 . Conductive strands of fabric  12  may be electrically coupled to integrated circuit terminals such as contacts  90  and  92  using solder, conductive adhesive, or other conductive material. 
     The signal paths in fabric  12  or other signal paths in item  10  that couple each integrated circuit  80  to control circuitry  16  may be used in conveying force measurements from force sensor elements  50  to control circuitry  16 . One or more force sensor elements  50  may be coupled to each integrated circuit  80  to form force sensor circuitry for item  10 . For example, there may be only a single element  50  coupled to each integrated circuit  80  or multiple elements  50  may be coupled to a given integrated circuit  80 . Fabric  12  may be formed above and/or below force sensor components such as integrated circuit  80  and force sensor element(s)  50 . For example, force sensor  14  may be embedded within fabric  12 . 
     In the illustrative configuration of  FIG. 17 , electrodes  52  and  54  have been placed on integrated circuit  80 . Force sensor electrode  94  may be capacitively coupled to electrode  52  through substrate  56  and may be capacitively coupled to electrode  54  through substrate  56 . Optional stiffener  60  may be formed on electrode  94 . When the substrate material between electrode  94  and electrodes  52  and  54  is compressed by an applied force, the capacitive force sensor circuitry in integrated circuit  80  can detect the resulting capacitance change between electrode  52  and  54  to measure the applied force. 
       FIG. 18  shows how sensor  50  may be molded into the shape of a finger. After forming sensor elements  50  on substrate  56 , heat and pressure may be applied to substrate  56  using finger-shaped molds  150 . After molds  150  are removed, substrate  56  retains its molded shape, thereby producing force sensor circuitry in which substrate  56  and the array of elements on substrate  56  have compound curvature configured to receive a finger of a user. If desired, circuitry such as sensor elements  50  may be formed after substrate  56  has been molded into its desired shape (e.g., a finger shape having surfaces with compound curvature). 
       FIG. 19  shows how force sensor circuitry may be integrated into a yarn. Shield SH, sense line S, and drive line D may be formed from conductive strands of material. Portions of sense line S and drive line D and/or conductive traces on elastomeric substrate  56  (covered with optional stiffeners  60 ) may be used in forming electrodes for force sensing element  50 . Shield SH may be braided with sense line S and drive line D. With one illustrative configuration, shield line SH may be twisted around sense line S to shield sense line S from interference with drive line D and drive line D may be loosely wrapped around both sense line S and shield line SH. In this way, a braided yarn with integral force sensing elements  50  along its length may be formed. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20180329
Publication Date: 20190115
Grant Date: 20190115
Priority Date: 20170614
Inventors: HOEN, STORRS T.
SUNSHINE, Daniel D.
ZIMMERMAN, AIDAN N.
PODHAJNY, DANIEL A.
May, Maurice P.
Assignee: APPLE INC
CPC Classifications: [{"code": "A61B5/0816", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/021", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/024", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/024", "inventive": false, "first": false, "tree": "[]"}, {"code": "D10B2401/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "D10B2401/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/014", "inventive": true, "first": true, "tree": "[]"}, {"code": "A41D1/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "A41D31/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/6806", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/163", "inventive": false, "first": false, "tree": "[]"}, {"code": "A41D1/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "D03D1/0088", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04883", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/021", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/6806", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/0816", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/163", "inventive": false, "first": false, "tree": "[]"}, {"code": "D10B2401/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01L1/146", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "D10B2401/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "D02G3/441", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01L1/146", "inventive": true, "first": false, "tree": "[]"}, {"code": "D10B2501/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/6843", "inventive": false, "first": false, "tree": "[]"}, {"code": "D03D1/0082", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/014", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/045", "inventive": true, "first": false, "tree": "[]"}, {"code": "D10B2501/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/6843", "inventive": false, "first": false, "tree": "[]"}, {"code": "D03D1/0088", "inventive": true, "first": false, "tree": "[]"}, {"code": "D03D1/0088", "inventive": true, "first": false, "tree": "[]"}, {"code": "A41D31/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "D10B2401/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "D02G3/441", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "D03D1/0082", "inventive": true, "first": false, "tree": "[]"}, {"code": "A41D1/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "D10B2401/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04883", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0414", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/6843", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/6806", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/014", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/163", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/045", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01B5/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/163", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01L1/146", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 64658022