PATENT DOCUMENT

Publication Number: US-10026721-B2
Application Number: US-201615295480-A
Country: US
Kind Code: B2

Title: Electronic devices with soft input-output components

Abstract:
An electronic device may have control circuitry coupled to input-output devices such as a display. A flexible input-output device may be formed from an elastomeric substrate layer. The substrate layer may have signal paths to which components are mounted. Openings may be formed in the elastomeric substrate layer between the signal paths to create a stretchable mesh-shaped substrate. The electrical components may each include an interposer having solder pads soldered to the elastomeric substrate. Electrical devices such as micro-light-emitting diodes may be soldered to the interposers. The electrical components may also include electrical devices such as sensors and actuators. A stretchable lighting unit may have a stretchable light guide illuminated by a stretchable light source.

Claims:
What is claimed is: 
     
       1. A stretchable display, comprising:
 a stretchable substrate having a mesh shape, wherein the stretchable substrate comprises a first region having a first thickness and a second region having a second thickness and wherein the first thickness is greater than the second thickness; and 
 an array of components mounted on the stretchable substrate in the first region, each component forming a pixel that includes subpixels of different colors formed from respective crystalline semiconductor light-emitting diodes, wherein the array of components is interconnected using signal paths in the first region of the stretchable substrate; and 
 thin-film circuitry in the stretchable substrate that is configured to supply signals to the components. 
 
     
     
       2. The stretchable display defined in  claim 1  wherein the thin-film circuitry comprises a pixel circuit associated with each of the pixels that supplies independently adjustable diode drive currents to each of the crystalline semiconductor light-emitting diodes. 
     
     
       3. The stretchable display defined in  claim 2  wherein the subpixels of different colors in each pixel include first, second, and third subpixels with respective first, second, and third crystalline semiconductor light-emitting diodes. 
     
     
       4. The stretchable display defined in  claim 3  wherein at least the first and second subpixels include photoluminescent material. 
     
     
       5. The stretchable display defined in  claim 4  wherein the third light-emitting diode is a blue light-emitting diode that is not covered with photoluminescent material. 
     
     
       6. The stretchable display defined in  claim 5  wherein the first and second light-emitting diodes are blue light-emitting diodes, wherein the photoluminescent material in the first subpixel comprises red phosphorescent material that is configured to emit red light in response to receiving blue light from the first light-emitting diode and wherein the photoluminescent material in the second subpixel comprises green phosphorescent material that is configured to emit green light in response to receiving blue light from the second light-emitting diode. 
     
     
       7. The stretchable display defined in  claim 3  wherein at least one of the first, second, and third crystalline semiconductor light-emitting diodes comprises an ultraviolet light-emitting diode. 
     
     
       8. The stretchable display defined in  claim 3  wherein at least the first and second subpixels include quantum dots. 
     
     
       9. The stretchable display defined in  claim 3  wherein the first subpixel includes red phosphor and wherein the second subpixel includes green phosphor. 
     
     
       10. The stretchable display defined in  claim 3  wherein each component includes an interposer substrate on the stretchable substrate, wherein the crystalline semiconductor light-emitting diodes in each component are mounted to the interposer substrate. 
     
     
       11. The stretchable display defined in  claim 10  wherein the interposer substrate is soldered to pads on the stretchable substrate. 
     
     
       12. The stretchable display defined in  claim 10  wherein the interposer substrate is a polymer layer formed directly on the stretchable substrate. 
     
     
       13. The stretchable display defined in  claim 1  wherein the thin-film circuitry includes semiconducting-oxide thin-film transistors. 
     
     
       14. A stretchable display, comprising:
 a mesh-shaped stretchable substrate layer having an array of openings and having serpentine signal paths that extend between and along at least one peripheral portion of each of the openings, wherein the mesh-shaped stretchable substrate layer has interconnects that are coupled to the serpentine signal paths; 
 a plurality of pixels in an array on the mesh-shaped elastomeric substrate layer, wherein each pixel is electrically coupled to the interconnects and has first, second, and third subpixels and wherein at least the first and second subpixels include photoluminescent material, wherein each pixel includes a semiconductor die and wherein the first, second, and third subpixels of the pixel include first, second, and third respective blue light-emitting diodes formed in the semiconductor die of the pixel; and 
 thin-film transistor circuitry in the mesh-shaped stretchable substrate layer, wherein the thin-film transistor circuitry is coupled to the interconnects and is configured to supply signals to the pixels. 
 
     
     
       15. The stretchable display defined in  claim 14  further comprising red photoluminescent material in the first subpixel that receives blue light from the first blue light-emitting diode and green photoluminescent material in the second subpixel that receives blue light from the second blue light-emitting diode. 
     
     
       16. A stretchable display, comprising:
 a mesh-shaped stretchable substrate layer having an array of openings and having serpentine signal paths that run between and along edges of the openings; 
 a plurality of pixels arranged in an array on the mesh-shaped stretchable substrate layer, wherein each pixel has first, second, and third subpixels of different colors with respective first, second, and third crystalline semiconductor light-emitting diodes; and 
 thin-film transistor circuitry in the mesh-shaped stretchable substrate layer that supplies drive currents to the first, second, and third crystalline semiconductor light-emitting diodes in each pixel. 
 
     
     
       17. The stretchable display defined in  claim 16  wherein each pixel includes red photoluminescent material in the first subpixel that emits red light in response to light received from the first crystalline semiconductor light-emitting diode in that pixel. 
     
     
       18. The stretchable display defined in  claim 17  wherein each pixel further includes green photoluminescent material in the second subpixel that emits green light in response to light received from the second crystalline semiconductor light-emitting diode in that pixel. 
     
     
       19. The stretchable display defined in  claim 18  wherein the first, second, and third crystalline semiconductor light-emitting diodes comprise blue light-emitting diodes and wherein the stretchable display further comprises an interposer substrate in each pixel that is coupled between the first, second, and third crystalline semiconductor light-emitting diodes in that pixel and the mesh-shaped stretchable substrate layer.

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 15/068,372, filed Mar. 11, 2016, which claims the benefit of provisional patent application No. 62/186,785 filed on Jun. 30, 2015, both of which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and, more particular, to input-output components for electronic devices. 
     Electronic devices such as cellular telephones, computers, and other electronic devices contain integrated circuits and other electrical components. Input-output devices such as displays and touch sensors can be used in an electronic device to provide output to a user and to gather input from a user. 
     It can be challenging to incorporate input-output devices into an electronic device. Form factor considerations, reliability considerations, and various other factors may make it difficult or impossible for conventional input-output components to be used in certain devices. As an example, if an electronic device has bendable portions, traditional displays and touch sensors mounted in the device may be subject to stress-induced failures. 
     It would therefore be desirable to be able to provide electronic devices with improved input-output devices. 
     SUMMARY 
     An electronic device may have control circuitry coupled to input-output devices. A flexible input-output device such as a display or a display with integrated sensors and haptic output may be formed from an elastomeric substrate layer. The substrate layer may have signal paths to which an array of electrical components may be mounted. Openings or thinned areas may be formed in the elastomeric substrate layer between the signal paths. An array of through-hole openings may be formed in the substrate to create a mesh-shaped substrate that can be stretched in one or more dimensions. The signal paths that extend between the openings to interconnect the electrical components may have serpentine shapes that help to accommodate stretching. 
     The electrical components may each include an interposer having solder pads soldered to the elastomeric substrate. Electrical devices such as micro-light-emitting diodes may be soldered to the interposers. The electrical components may also include electrical devices such as sensors and actuators. An array of components on the mesh-shaped substrate may include light-emitting components such as components containing micro-light-emitting diodes and/or laser diodes, sensor components such as touch sensors, force sensors, temperature sensors, accelerometers, and other sensors, and vibrators or other devices for providing haptic feedback. An input-output device may have transparent components such as a transparent substrate to allow light to pass through the input-output device. 
     A display or other component in an electronic device may have stretchable lighting structures. A stretchable lighting unit may, for example, have a stretchable light guide formed from a sheet of elastomeric material and a stretchable light source. The stretchable light source may be formed from light-emitting diodes that are coupled to each other using stretchable signal paths such as signal paths formed from serpentine signal lines. 
     Thin-film circuitry may be incorporated onto a stretchable substrate for controlling light-emitting diodes in the pixels of a stretchable display or for controlling other components in an input-output device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device having input-output devices in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative flexible input-output device having an array of components in accordance with an embodiment. 
         FIG. 3  is a perspective view of an illustrative flexible input-output device that has been deformed into a dome shape in accordance with an embodiment. 
         FIG. 4  is a front perspective view of an illustrative component that has been formed by mounting electrical devices on an interposer in accordance with an embodiment. 
         FIG. 5  is a rear view of the component of  FIG. 4  in accordance with an embodiment. 
         FIG. 6  is a top view of an array of components that have been joined using straight signal path segments in accordance with an embodiment. 
         FIG. 7  is a top view of an array of components that have been joined using serpentine signal paths that extend past thinned or opened areas in a substrate in accordance with an embodiment. 
         FIG. 8  is a top view of an illustrative array of components on a substrate with serpentine path segments for joining adjacent components in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of components and a substrate of the type shown in  FIG. 8  in accordance with an embodiment. 
         FIG. 10  is a top view of an illustrative array of components having different types of components arranged in a checkerboard pattern in accordance with an embodiment. 
         FIG. 11  is a top view of another illustrative array of components having different types of components in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of a flexible input-output device being supported by a temporary carrier during manufacturing in accordance with an embodiment. 
         FIG. 13  is a cross-sectional side view of the flexible input-output device of  FIG. 12  after embedding the components and substrate of the input-output device in polymer in accordance with an embodiment. 
         FIG. 14  is a cross-sectional side view of the flexible input-output device of  FIG. 12  after mounting the components and substrate of the input-output device to a support structure in accordance with an embodiment. 
         FIG. 15  is a cross-sectional side view of the flexible input-output device of  FIG. 12  after coating the components and substrate of the input-output device with an encapsulating layer such as a layer of polymer in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of the flexible input-output device of  FIG. 12  after laminating the components between layers of material in accordance with an embodiment. 
         FIG. 17  is a schematic diagram of illustrative input-output devices for an electronic device that include a stretchable lighting unit and other structures in accordance with an embodiment. 
         FIG. 18  is a perspective view of an illustrative stretchable lighting unit in accordance with an embodiment. 
         FIG. 19  is a perspective view of a stretchable lighting unit showing how a lighting unit may be stretched by a user in accordance with an embodiment. 
         FIG. 20  is a top view of a stretchable lighting unit being stretched horizontally in accordance with an embodiment. 
         FIG. 21  is a top view of a stretchable lighting unit being stretched vertically in accordance with an embodiment. 
         FIG. 22  is a cross-sectional side view of an illustrative stretchable lighting unit showing how light from a stretchable light source may be guided within a stretchable light guide layer by total internal reflection and can be scattered by light scattering structures in accordance with an embodiment. 
         FIG. 23  is a cross-sectional side view of an illustrative stretchable lighting unit with a cladding layer in accordance with an embodiment. 
         FIGS. 24, 25, and 26  are diagrams of illustrative stretchable light sources with light-emitting components joined by stretchable serpentine signal paths in accordance with embodiments. 
         FIG. 27  is a cross-sectional side view of the light source of  FIG. 25  in accordance with an embodiment. 
         FIG. 28  is a cross-sectional side view of the light source of  FIG. 24  in accordance with an embodiment. 
         FIG. 29  is a perspective view of a portion of a stretchable light guide layer into which a stretchable light source is emitting light of multiple colors in accordance with an embodiment. 
         FIG. 30  is a top view of an illustrative light-emitting component having an interposer and a single light-emitting diode in accordance with an embodiment. 
         FIGS. 31 and 32  are top views of illustrative light-emitting components each having an interposer and multiple light-emitting diodes of different colors in accordance with embodiments. 
         FIGS. 33, 34, 35, 36, 37, 38, and 39  are top views of illustrative stretchable light guides having light guide layers formed from elastomeric sheets of different shapes and having stretchable light sources mounted in different locations in accordance with embodiments. 
         FIGS. 40, 41, and 42  are diagrams that show how stretchable light guides may be formed by stretching together multiple light guide layers with bonding material in accordance with embodiments. 
         FIG. 43  is a perspective view of an illustrative stretchable light guide that is conforming to a curved surface of an object in accordance with an embodiment. 
         FIG. 44  is a top view of an illustrative stretchable lighting unit having a light source mounted on an exterior edge surface of a stretchable light guide layer in accordance with an embodiment. 
         FIG. 45  is a top view of an illustrative stretchable lighting unit having a light source embedded within a stretchable light guide layer in accordance with an embodiment. 
         FIG. 46  is a cross-sectional side view of an illustrative stretchable lighting unit having a light downconversion layer in accordance with an embodiment. 
         FIG. 47  is a cross-sectional side view of an illustrative stretchable lighting unit having light extraction structures such as a patterned coating or layer of material attached to a surface of a light guide layer with adhesive in accordance with an embodiment. 
         FIGS. 48 and 49  are cross-sectional side views of stretchable lighting units having multiple stretchable light guide layers in accordance with embodiments. 
         FIGS. 50, 51, and 52  are cross-sectional side views of stretchable light guide structures with deformable surfaces that allow the structures to serve as sensors that detect pressure from a finger in accordance with embodiments. 
         FIG. 53  is a cross-sectional side view of a device that has components such as pixels formed from crystalline semiconductor light-emitting diodes on a stretchable substrate of the type shown in  FIG. 8  and that has thin-film circuitry in the stretchable substrate that is coupled to an interposer in accordance with an embodiment. 
         FIG. 54  is a cross-sectional side view of a device that has components such as pixels formed from crystalline semiconductor light-emitting diodes formed directly on a stretchable substrate of the type shown in  FIG. 8  and that has thin-film circuitry in the substrate coupled to the pixels in accordance with an embodiment. 
         FIG. 55  is a cross-sectional side view of a device that has components such as pixels formed from crystalline semiconductor light-emitting diodes on a common die on a substrate of the type shown in  FIG. 8  and that has thin-film circuitry in the substrate coupled to the pixels in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with flexible input-output devices is shown in  FIG. 1 . As shown in  FIG. 1 , electronic device  10  may have control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  22  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  22  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators (e.g., piezoelectric vibrating components, etc.), cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  22  and may receive status information and other output from device  10  using the output resources of input-output devices  22 . 
     Input-output devices  22  may include one or more displays such as display  14 . Display  14  may be a touch screen display that includes a touch sensor for gathering touch input from a user or display  14  may be insensitive to touch. A touch sensor for display  14  may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. If desired, display  14  may include actuators to provide haptic feedback for a user. 
     Sensors  18  in input-output devices  22  may include strain gauge sensors, proximity sensors, ambient light sensors, touch sensors, force sensors, temperature sensors, pressure sensors, magnetic sensors, accelerometers, gyroscopes and other sensors for measuring orientation (e.g., position sensors, orientation sensors), microelectromechanical systems sensors, and other sensors. Sensors  18  may be light-based sensors (e.g., proximity sensors or other sensors that emit and/or detect light), capacitive sensors (e.g., sensors that measure force and/or touch events using capacitance measurements). Strain gauges, piezoelectric elements, capacitive sensors, and other sensors may be used in measuring applied force and can therefore be used to gather input from a user&#39;s fingers or other external source of pressure. Capacitive touch sensors may make capacitance measurements to detect the position of a user&#39;s finger(s). If desired, sensors  18  may include microphones to gather audio signals. Sensors  18  may be incorporated into display  14 . For example, display  14  may have an array of light-emitting diodes and sensors  18  and/or actuator components may be incorporated into the array to provide display  14  with the ability to sense user input and provide haptic feedback in addition to the ability to display images for the user. 
     Control circuitry  16  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  16  may be used in gathering user input and making environmental measurements using sensors  18  and may be used in providing output to a user with display  14  and other output resources in input-output devices  22 . 
     Device  10  may form all or part of a tablet computer, laptop computer, a desktop computer, a monitor that includes an embedded computer, a monitor that does not include an embedded computer, a display for use with a computer or other equipment that is external to the display, a cellular telephone, a media player, a wristwatch device or other wearable electronic equipment, equipment that is integrated into furniture, equipment that is integrated into a vehicle, equipment that is built into windows or architectural elements in a building, a kiosk, seating, clothing, a strap for a bag or watch, a lanyard or other structure for supporting a pendant device, a cover or other enclosure for a portable device (e.g., a bag, a computer case, a phone case, a tablet computer cover, etc.), or other suitable device. 
     Display  14  may include light-emitting pixels based on organic light-emitting diodes, discrete crystalline light-emitting diode dies (sometimes referred to as micro-light-emitting diodes or micro-LEDs), or other suitable pixel elements. Sensors  18  may include discrete sensors and sensors that are formed from arrays of elements (e.g., arrays of strain sensors, arrays of light-based sensors, etc.). 
     If desired, input-output devices  22  may include flexible devices (sometimes referred to as soft or bendable devices) that have the ability to be bent or otherwise deformed into a variety of non-planar shapes. These devices may be displays such as display  14 , sensor panels, and/or displays that incorporate sensors  18  and/or actuators. 
     Illustrative flexible input-output devices are shown in  FIGS. 2 and 3 . As shown in  FIG. 2 , flexible input-output device  20  may be flexed (bent) about various bend axes  26  to form a wavy planar shape.  FIG. 3  shows how flexible input-output device  20  may be sufficiently flexible to deform in multiple dimensions. Deformations of the type shown in  FIGS. 2 and 3  may allow input-output devices  20  to conform to a human body part such as the wrist or chest of a user. 
     As shown in  FIGS. 2 and 3 , a flexible input-output device may contain an array of one or more different types of electrical components  24 . Components  24  may include light-emitting diodes (e.g., micro-light-emitting diodes), organic light-emitting diodes, vibrators or other electrically controlled actuators, sensors  18 , sound-producing components, and/or other electrical devices. 
     Components  24  may include circuitry mounted in plastic packages, ceramic packages, packages with solder pads and other contacts to couple components  24  to metal traces on flexible printed circuit substrates and other electrical paths, and/or other packaging. With one illustrative configuration, which is shown in  FIG. 4 , a component such as component  24  may include multiple electrical devices  30  mounted on a substrate such as substrate  32 . Substrate  32  may be formed from molded plastic, rigid printed circuit board material (e.g., a fiberglass-filled epoxy material such as FR4 or other printed circuit board dielectric), flexible printed circuit board material (e.g., a sheet of polyimide or a flexible layer of other polymer), a ceramic substrate, and/or other substrate material. Substrate  32  may include one or more layers of metal traces separated by layers of dielectric. The layers of metal traces may form signal interconnect paths. These paths may couple components such as electrical devices  30  to each other and to contact pads on substrate  32 . Electrical devices  30  may, if desired, be encapsulated in a polymer (e.g., a clear polymer) or other encapsulant such as encapsulating layer  38 . 
     Electrical devices  30  may include, for example, components  34  and one or more integrated circuits such as integrated circuit  36 . Integrated circuits  36  may be coupled to components  34  using the interconnects in each substrate  32 . Integrated circuits  36  may also be coupled to signal paths in input-output device  20  using interposer contacts such as contacts  56 ′ (shown in the rear perspective view of component  24  in  FIG. 5 ). There may be any suitable number of contacts  56 ′ for each component  24  (e.g., 2-10, 4-20, 2-8, fewer than 10, more than 10, fewer than 20, more than 5, etc.). Integrated circuits  36  may use these signal paths to receive information from control circuitry  16  that is to be output to a user using components  24  (e.g., image data to display using an array of light-emitting components  24 ). Integrated circuits  36  may also use these signal paths to provide sensor data or other input that has been captured using components  24  to control circuitry  16  (e.g., user touch sensor and force sensor input that has been gathered with sensors in components  24 ). 
     Components  34  may be electrical devices such as light-emitting diodes (e.g., micro-light-emitting diodes), sensors  18 , vibrators, other actuators, and/or other circuitry. If desired, components  24  may include both output devices (e.g., light-emitting diodes, actuators, etc.) and input components (force sensors, touch sensors, temperature sensors, accelerometers, etc.). Components  34  (and/or circuits  36 ) may be radio-frequency communications circuits (e.g., radio-frequency transceiver circuits, radio-frequency identification (RFID) chips, or other integrated circuits capable of handling wireless communications). Configurations in which each component  24  contains either a set of one or more output devices (e.g., light-emitting diodes) or a set of one or more input devices (e.g., a sensor) may sometimes be described herein as an example. With one suitable arrangement, components  24  each include a set of multiple micro-light-emitting diodes (e.g., red, green, and blue light-emitting diodes). Redundant light-emitting diodes may be included in component  24  and may be switched into use in response to detection of a faulty light-emitting diode during testing. There may be one, two, three, or more than three redundant sets of light-emitting diodes on each interposer substrate  32 . 
     If desired, components  24  that contain faulty circuitry can be replaced during manufacturing rework operations. For example, a pick and place tool (e.g., a tool based on an elastomeric or electromagnetic pick heads), a tool with a laser, hot bar, infrared heating element, or other heating device to heat solder joints, thermocompression bonding equipment, or other equipment may remove a faulty component by melting solder connections between the faulty component and the signal paths in input-output device  20 . Once the faulty component has been removed, the pick and place tool or other equipment may be used to solder a replacement component onto the signal paths in place of the removed faulty component. 
     To accommodate deformation (e.g., bending and/or stretching in one or more dimensions), input-output device  20  may be formed by mounting an array of components  24  to a flexible substrate. The flexible substrate may have signal paths that accommodate deformation of the substrate without cracking. 
       FIGS. 6 and 7  are illustrative top views of device  20  showing how device  20  may contain an array of components  24  interconnected by corresponding signal paths  42 . Paths  42  may have segments that extend between respective pairs of components  24 . The overall shape of paths  42  may form a mesh (i.e., a grid). The signal paths may be straight (see, e.g., paths  42  of  FIG. 6 ), may be serpentine to help accommodate stretching (see, e.g., paths  42  of  FIG. 7 ), may have vertical undulations (in and out of the page of  FIG. 7 ), or may have other suitable shapes. 
     The arrays of components  24  that are used in forming device  20  may have rows and columns. Components  24  may also be organized in other patterns (e.g., hexagonal patterns, arrays with triangular elements, Penrose tiling, pseudorandom patterns, etc.). In the examples of  FIGS. 6 and 7 , input-output device  20  has rectangular arrays of components  24  and paths  42  run horizontally and vertically. Other configurations may be used, if desired. 
     Signal paths  42  may include one or more signal lines. For example, each signal path  42  may contain 2-10 signal lines, may contain fewer than 10 signal lines, may contain 5-20 signal lines, or may contain more than 4 signal lines. Dielectric (e.g., organic thin films such as insulating polymers, inorganic films such as silicon oxide, silicon nitride, metal oxides, etc.) may be used to electrically isolate the signal lines in paths  42  from each other. 
     The conductive lines that make up signal paths  42  may be formed from conductive materials such metal (e.g., aluminum, copper, etc.), transparent conductive material (e.g., indium tin oxide), carbon nanotubes or other nanotubes, silver nanowires, carbon nanowires, or other nanowires, graphene and derivatives of graphene, or other conductive trace materials. These conductive traces may be formed from stretchable material such as conductive ink (e.g., conductive particles such as silver particles, copper particles, nickel particles, or other metal particles, nanotubes, or nanowires that are supported using a polymer matrix such as a stretchable polymer matrix). 
     During deformation of the substrate of input-output device  20 , serpentine paths such as paths  42  of  FIG. 7  may serve as springs that can deform to accommodate stretching without cracking the conductive material that forms the serpentine paths. Accordingly, serpentine paths or other undulating paths (paths that meander back and forth within the plane of the array of components  24  and/or that meander back and forth out of the plane of the array of components  24  in device  20 ) may tend to accommodate more deformation than straight line paths. 
     To provide serpentine paths and other paths such as straight paths with enhanced stretchability, it may be desirable to from straight and serpentine paths  42  from stretchable conductive materials and stretchable dielectrics. As an example, the dielectric that is used in isolating the conductive lines in paths  42  from each other may be formed from a stretchable polymer such as silicone, polyurethane, acrylic, or other elastomeric (low modulus) polymer that can stretch without failing. If desired, the stretchable dielectric may be a composite material (e.g., a polymer filled with inorganic particles or other particles) or a hybrid material (e.g., a material including combinations of polymer and fiber). Stretchable conductive materials for forming the signal lines of paths  42  may include stretchable conductive inks (e.g., conductive particles in a stretchable polymer matrix). In situations in which the serpentine shape or other stretch-accommodating shape of paths  42  can accommodate stretching without significantly stretching the material that makes up the signal lines in paths  42 , the dielectric and conductive line materials of paths  42  may be formed from materials that exhibit reduced stretchability (e.g., metals, inorganic dielectrics, etc.). 
     To enhance the flexibility of input-output device  20 , it may be desirable to mount components  24  on a substrate with thinned portions or openings. For example, before or after soldering or otherwise mounting components  24  to a flexible polymer substrate layer, portions of the polymer substrate layer may be removed using die cutting, laser cutting, etching, or other processing techniques. This will provide the substrate layer with a mesh (grid) shape that can accommodate deformation. The removed portions of the polymer substrate layer may be rectangular, circular, or oval, may have other shapes with straight and/or curved edges, may all be the same shape, may have a variety of different shapes, may all have the same size, may have multiple different sizes, may have a mixture of shapes and/or sizes that create an irregular mesh, may have portions that pass entirely through the substrate (i.e., to form through-hole openings) and/or that thin the substrate without passing entirely through the substrate, or may have other suitable configurations to enhance flexibility of input-output device  20 . 
     The portions of the substrate for input-output device  20  that have not been thinned or removed to form openings for the mesh (i.e., the portions of the mesh that remain attached to components  24 ) may be used in forming signal paths  42 . This type of arrangement is shown in  FIG. 8 .  FIG. 8  is a top view of a portion of input-output device  20  showing how components  24  (e.g. electrical devices mounted on interposers) may be mounted to substrate such as substrate  44 . Segments of substrate  44  extend between respective components  24  and contain signal lines formed from metal traces and/or conductive inks, transparent conductors, nanowires, nanotubes, graphene, and/or other conductive materials. These signal lines may be insulated from each other using dielectric material  52  of substrate  44  (e.g., silicone, polyurethane, acrylic, or other elastomeric polymer, composite materials, hybrid materials, inorganic materials, etc.) and may form signal paths  42  that interconnect components  24  to form the component array of  FIG. 8 . Signal paths  42  may have serpentine shapes (as shown in the example of  FIG. 8 ) or other suitable shapes. 
     To promote flexibility of substrate  44 , portions  46  of substrate  44  that are not used in forming signal paths  42  may be thinner than the portions of substrate  44  that form paths  42 . For example, portions  46  may be thinned or removed completely to form openings in substrate  44 . After components  24  have been mounted to substrate  44  and after processing substrate  44  to form a mesh with an array of through-hole openings extending between paths  42  (or after forming a substrate with thinned portions), components  24  and substrate  44  may be mounted on a support structure, may be embedded within or coated by a layer of polymer or other material, or may be laminated between layers of material or otherwise incorporated into structures to complete formation of device  20 . Device  20  may then be assembled into electronic device  10 . 
     If desired, mesh-shaped substrates  44  and substrates  44  with locally thinned portions  46  may be formed using an additive process (e.g., by building up signal paths  42  from conductive and/or dielectric layers that are added to substrate  44  in addition to or instead of removing material from substrate  44  in regions  46 ). Techniques that may be used to remove or thin regions  46  and/or to build up regions  42  include laser ablation (e.g., using a pulsed laser or other suitable laser), photolithography with dry or wet etching, sand blasting, water jet cutting, or other physical removal techniques, die cutting, printing (e.g., ink jet printing, flexographic printing, gravure, stencil printing etc.), blanket deposition of photosensitive polymer layers followed by exposure to light through a mask and subsequent development, shadow mask deposition, etc. 
       FIG. 9  is a cross-sectional side view of a portion of input-output device  20  showing how components  20  may be mounted on substrate  44 . As shown in  FIG. 9 , substrate  44  may include one or more layers of patterned metal traces or other conductive lines that form interconnects  50 . The metal traces or other conductive structures of substrate  44  may include contacts such as substrate solder pads  50 ′. Components  24  may have interposer substrates  32 . Substrates  32  may include metal traces or other structures for forming interconnects  56 . Interconnects  56  may include interposer contacts such as solder pads  56 ′. Solder  54  (e.g., reflowed solder or solder that forms a joint when subjected to thermocompression bonding techniques or other soldering techniques) may be used to couple pads  56 ′ to pads  50 ′ on substrate  44 . Polymer underfill may be placed under interposer  32  to provide solder  54  with environmental protection. Interconnects  56  may include portions that form contacts such as solder pads  56 ″ on the upper surface of interposer substrate  32 . Components  30  (e.g., semiconductor devices such as light-emitting diode dies or other electrical devices) may have solder pads  60 . Solder  58  may be used to couple pads  60  to pads  56 ″ on substrate  32 . Encapsulant  38  may be formed on top of substrate  32  to encapsulate components  30 . 
     It may be desirable to enhance the transparency of input-output device  20 . Transparency may be enhanced by forming structures of the type shown in  FIG. 9  from transparent materials. As an example, substrates  44  and  32  may be formed from transparent dielectrics (e.g., transparent polymers, glass, transparent ceramic, etc.). Conductive lines for signal paths  42 , interconnects  50 , and/or interconnects  56  may be formed from indium tin oxide, transparent conductive polymers, or other transparent conductive materials. Transparent material such as transparent conductive adhesive may be used in place of solder  58  and/or solder  54 . Encapsulant  38  may be formed from a transparent polymer or other transparent dielectric. When integrating components  24  and substrate  44  with additional structures to form input-output device  20 , the additional structures (e.g., plastic layers, fabric layers, etc.) may also be transparent. Transparent structures may be highly transparent (e.g., having a transmission of more than 90% or may be partly transparent (e.g., having a transmission of more than 50% or other lower value). 
     It may be desirable to provide input-output device  20  with more than one type of component  24 . For example, some of components  24  may be light-emitting components such as interposers populated with micro-light-emitting diodes (e.g., red, green, and blue diodes and redundant sets of red, green, and blue diodes), whereas other components  24  may be sensors (e.g., force sensors, touch sensors, temperature sensors, accelerometers, etc.). Yet other components  24  may be vibrators or other actuators for providing tactile feedback or other mechanical output to a user. In this type of arrangement, input-output device  20  may be a display (with pixels formed by light-emitting diodes) having an integrated touch sensor (formed from the force and/or touch sensors) and may have optional tactile feedback (from the actuating components). Other arrangements for combination multiple types of components  24  into device  20  may be used, if desired. The use of light-emitting diodes and sensors to form a touch sensing display device with optional force feedback is merely illustrative. 
     One way in which to incorporate sensors and light-emitting diodes into the array of components forming device  20  involves incorporating both light-emitting diodes and sensors onto a common interposer (e.g., by mounting multiple different types of components  34  onto interposer  32 ). Another illustrative technique for incorporating different types of devices into input-output device  20  involves mounting different types of components  24  onto substrate  44 . Examples of configurations for device  20  in which the array of components  24  on substrate  44  includes two different types of components (e.g., components  24 A and components  24 B) are shown in  FIGS. 10 and 11 . 
     Components  24 A may be micro-light-emitting diodes or other light-emitting diodes (as an example). Components  24 B may be sensors and/or mechanical actuators. In the example of  FIG. 10 , components  24 A are interspersed with components  24 B in a checkerboard pattern. The array of components in  FIG. 11  has a rectangular subarray of components  24 B surrounded by components  24 A. Other patterns of intermingled components  24  of different types may be used, if desired. The arrangements of  FIGS. 10 and 11  are merely illustrative. 
     The mesh formed by thinning or removing portions  46  from substrate  44  and/or by building up paths  42  may make it challenging to handle substrate  44  during manufacturing.  FIG. 12  shows how a temporary carrier layer such as a transfer tape or other carrier (carrier  62 ) may be used to hold components  24  and substrate  44  in place after portions  46  have been thinned and/or removed from substrate  44 . Carrier  62  may be used to help peel substrate  44  from a glass carrier or other temporary support structure that is used in forming and patterning substrate  44  and in mounting components  24  to substrate  44  with solder or other conductive material. 
     After forming the structures of  FIG. 12  (e.g., after forming a mesh substrate with attached components  24 ), the mesh substrate may be combined with other structures to form input-output device  20 , as shown by illustrative input-output devices  20  of  FIGS. 13, 14, 15, and 16 . 
     In the example of  FIG. 13 , input-output device  20  has been formed by encasing substrate  44  and devices  24  in a cast polymer resin, thereby forming a polymer encapsulation layer such as polymer layer  64  in which substrate  44  and components  24  are embedded. Polymer  64  may be transparent silicone, polyurethane, acrylic, composite material, hybrid material, or other transparent elastomeric material to permit light to pass to and/or from components  24 . 
     In the example of  FIG. 14 , substrate  44  and components  24  have been mounted on support structure  66 . Structure  66  may be a layer of plastic, metal, glass, sapphire or other crystalline material, ceramic, fabric, or other material. Adhesive may be used in attaching substrate  44  to layer  66  or substrate  44  may be attached to layer  66  using heat and/or pressure. 
       FIG. 15  shows how an encapsulating layer such as layer  68  may be deposited as a coating over components  24  and the upper surface o substrate  24 . Some of layer  68  may penetrate into openings  46 . Layer  68  may be formed from a clear polymer such as transparent silicone, polyurethane, acrylic, composite material, hybrid material, or other elastic polymer (as an example). Covering layers such as layer  68  may also be formed from fabric or other suitable materials. 
       FIG. 16  is a cross-sectional side view of an illustrative configuration for input-output device  20  in scenario in which upper and/or lower layers of material  72  have been laminated to substrate  44  (e.g. to cover components  24  on the upper surface of substrate  44 ). Adhesive  70  may be interposed between each of layers  72  and substrate  44  to help attach layers  72  to substrate  44 . Each of layers  72  may be a layer of plastic, metal, glass, sapphire or other crystalline material, ceramic, fabric, or other material. 
     If desired, openings such as openings aligned with openings  46  in substrate  44  may be formed in layers  64 ,  66 ,  68 , and/or one or both of layers  72 . Openings may also be formed in layers  64 ,  66 ,  68 , and/or  72  that are aligned with some or all of components  24 . As an example, perforations may be formed in one or more layers of material overlapping components  24  to allow light to be emitted from components  24 . Components  24  may be formed on one or both sides of substrate  44 . 
     After forming input-output device  20 , input-output device  20  may be integrated with other devices such as driving and sensing systems. Connections may be formed between device  20  and other resources in device  10  using anisotropic conductive film bonding, soldering, welds, crimped connections, connections formed by using these techniques to mount one or more connectors to substrate  44 , etc. Signal paths for interconnecting device  20  with other circuitry in device  10  may include ribbon cables, flexible printed circuit cables, coaxial cables and other radio-frequency transmission lines, and other signal paths. 
     The materials that are added to substrate  44  and components  24  in configurations of the type shown in  FIGS. 13, 14, 15, and 16  may provide environmental protection and may help ensure that the neutral stress plane of input-output device  20  is brought into alignment with the signal lines in paths  42  and components  24 , thereby reducing stress on components  24  and the interconnects of substrate  44 . These added materials may also serve as stress limiter structures that help prevent excess stress from being imposed on device  20  due to bending of device  10 . 
     Input-output device  20  may be used in forming some or all of electronic device  10 . Because of the flexibility provided by the openings in substrate  44 , the shape of paths  42  (e.g., serpentine shapes that form springs between respective components  24 ), and the stretchable materials used in forming interconnects  50  in substrate  44  (e.g., interconnects in paths  42 ), device  20  may be deformed into a wide range of shapes. Flexing of device  20  may take place along one dimension (e.g., device  20  may be bent along a bend axis) or may take place along multiple dimensions (e.g., device  20  may be deformed to follow compound curves in a device housing or support structure or may otherwise be deformed in multiple dimensions). Device  20  may, if desired, be deformed along one or more dimensions without buckling. 
     Following removal of regions  46 , substrate  44  may form a mesh. The mesh may contain traces  50  that run under components  24  (and that are coupled to components  24  via pads  50 ′) and traces  50  that extend along paths  42  between components  24 . Components  24  (sometimes referred to as electrical units or islands) may be interconnected using serial and/or parallel signals conveyed over the conductive lines of paths  42 . 
     The use of serpentine structures for paths  42  may allow otherwise rigid thin-film metals and dielectric materials to deform sufficiently in two or three dimensions to accommodate mechanical stresses produced during deformation of input-output device  10 . The strain induced in the thin films during deformation may be relatively low. Paths  42  may have accordion shapes, zig zag shapes, figure eight shapes, or other shapes that accommodate deformation. 
     Components  24  may be individually addressable by sending data and control signals to components  24  over paths  42 . By mounting potentially small components such as light-emitting diodes, other semiconductor die, and other components  30  on interposer  32 , the size of the pads that are soldered to substrate  44  can be effectively increased from the smaller size associated with pads  60  (e.g., less than 5-10 microns, less than 15 microns, etc.) to the larger size associated with interposer pads  56 ′ (e.g., 50 microns, more than 25 microns, less than 100 microns, etc.) 
     If desired, each component  24  may be addressable to emit red, green, and/or blue light in response to image data or other pixel data supplied to that component by control circuitry  16 . Testing and selective replacement of defective components  24  during manufacturing may enhance yield. Haptic systems and touch sensing systems may be incorporated into input-output device  20  by incorporating sensing and/or actuation components in the components  24  that are mounted on substrate  44 . Components  24  may, in general, include components that sense touch, force, temperature, acceleration, that generate haptic feedback, or that have other types of sensing and actuation capabilities. Components  24  such as these may be formed from devices  30  that are mounted on a common interposer substrate  32  with light-emitting diodes or may be formed from devices  30  that are mounted on separate interposer substrates  32  from the substrates used for mounting the light-emitting diodes. 
     Components  24  may be relatively small. For example, components  30  may have dimensions of about 10 by 10 microns (or other dimensions in the range of 2-100 microns or other suitable size). The outline of integrated circuits such as illustrative integrated circuit  36  of  FIG. 4  may be about 150 by 50 microns (or other suitable dimensions in the range of 2-500 microns, above 10 microns, or below 100 microns). Interposers  32  (and therefore components  24 ) may have dimensions of about 200 by 500 microns, above 100 microns, below 1000 microns, or other suitable size). The potentially small size of components  24  may help ensure that only small amounts of light are blocked by opaque structures in components  24 , thereby helping ensure that input-output device  20  is sufficiently transparent for desired applications (e.g., transparent display and/or sensor applications). The small size of components  24  may also allow large densities of components  24  to be formed (e.g., components may be mounted with dot-per-inch values of 100 or more, 10 or more, 300 or more, 50-500, etc.). 
     If desired, input-output devices  22  may include lighting structures for device  10  such as display backlight units, structures that supply patterned light that serves as decorative trim or that forms characters or symbols (e.g., for a keyboard), light-based sensor structures, lighting for an enclosure, or other lighting structures based on stretchable light guide layers. As shown in  FIG. 17 , input-output devices  22  may include stretchable lighting structures such as stretchable lighting unit  100 . 
     Stretchable lighting unit  100  may include components (e.g., components  24 ) that form a stretchable light source such as light source  102  that produces light. The light may be infrared light, ultraviolet light, or visible light. Examples in which the light is visible light may sometimes be described herein as an example. The light from light source  102  may be provided to a stretchable light guide structure such as a stretchable light guide layer  104 . Layer  104  may be formed from one or more layers of material (e.g., sheets of transparent elastomeric materials such as stretchable polymer layers, layers with light scattering features, layers that serve as cladding layers, spacer layers, encapsulant layers, and other layers of material). Signal paths  42  (e.g., stretchable serpentine metal lines) may be formed within light source  102  and may be coupled to components  24  to provide signals to components  24 . 
     After light has been launched into stretchable light guide  104 , the light may propagate within the interior of light guide  104  (e.g., between upper and lower surfaces of a sheet of clear elastomeric material) due to the principle of total internal reflection. Light scattering features or local deformation due to application of pressure from a user&#39;s finger or other external object may cause the light within light guide  104  to be scattered out of light guide  104 . The scattered light may be used as backlight for a flexible display (e.g., display layers that form an array of pixels for displaying images for a user), may be used to form a decorative illuminated trim structure, may form part of a finger sensor (e.g., a light-based touch sensor and/or a light-based force sensor, etc.), may form part of a label (e.g., an icon, an alphanumeric character, a logo, etc.), may serve as a source of illumination for a flashlight or ambient lighting structure, may serve as a flash for a camera, or may form other suitable illuminated structure for device  10 . 
     If desired, device  10  and/or input-output devices  22  may include additional structures such as illustrative optical components  106  (e.g., a light diffuser, a prism, lenses, etc.), mechanical structures  108  (e.g., strain-limiting membranes, protective coating layers, housing structures, etc.), and electronic components (e.g., control circuits, sensors, batteries, energy sources based on energy harvesting systems, solar cells, etc.), and other structures. 
       FIG. 18  is a perspective view of an illustrative stretchable lighting structure. As shown in  FIG. 18 , stretchable light unit (structure)  100  may include stretchable light source  102  and stretchable light guide  104 . Stretchable light guide  104  may be formed from a stretchable transparent layer such as layer  112 . Layer  112  may be formed from a sheet of transparent elastomer such as a stretchable clear plastic (e.g., silicone, etc.). Light may be emitted into the interior of layer  112  along the edge (edge surface)  116  of layer or may be otherwise launched into layer  112 . In the example of  FIG. 18 , light source  102  has a plurality of light-emitting components  24  (e.g., components containing light-emitting diodes and/or other circuitry) on edge  116  that are electrically connected to control circuitry  16  and/or each other using paths  42  (e.g., stretchable serpentine signal paths or other stretchable signal paths). Light from components  24  in source  102  is launched into layer (light guide layer)  112  and is distributed throughout layer  112  by total internal reflection. 
     All or selected parts of layer  112  may be provided with light scattering structures such as light scattering features  114  of  FIG. 18 . Light scattering features  114  may be formed from protrusions, recesses, patterned coating material on the surfaces of layer  112 , embedded microbeads, other light-scattering particles, or other embedded structures, and/or other structures that scatter light out of layer  112  (e.g., out of the plane of layer  112 ). As shown in  FIG. 18 , light scattering features  114  may include features  114  on the front surface of layer  112 , features  114  that are embedded within layer  112 , and/or features  114  that are formed on rear surface  112 R of layer  112 . 
     Because stretchable light source  102  is formed using stretchable signal paths  42 , stretchable light source  102  can stretch to accommodate stretching of layer  112 .  FIG. 19  shows how a user&#39;s hands and fingers  118  may be used to stretch layer  112 .  FIG. 20  shows how layer  112  may be stretched horizontally.  FIG. 21  shows how layer  112  may be stretched vertically. Layer  112  may also be stretched diagonally and/or may be stretched to cover surfaces with compound curves (as examples). Layer  112  may be stretched during manufacturing and subsequently maintained in a fixed position within device  10  or layer  112  may be stretched dynamically by a user during operation of device  10 . 
       FIG. 22  is a cross-sectional side view of an illustrative stretchable lighting unit. As shown in  FIG. 22 , lighting unit  100  may have stretchable light source  102  and stretchable light guide  104 . Stretchable light source  102  may be formed from light-emitting diodes or other light-emitting components  24  that emit light  124  into stretchable layer  112  of light guide  104 . Light  124  may propagate within layer  112  due to total internal reflection. Light scattering features  114  may be used to scatter light  124  out of layer  112  at desired areas of layer  112 .  FIG. 23  shows how a stretchable light guide layer  112  may have a core layer  112 - 1  and a cladding layer  112 - 2 . Core layer  112 - 1  may have an index of refraction that is higher than that of the coating formed from layer  112 - 2  to promote total internal reflection. Layers  112 - 1  and  112 - 2  may be formed from clear elastomeric polymers (as an example). 
       FIGS. 24 and 25  show how components  24  may include light-emitting diodes or other light-emitting components  34  mounted on substrates such as interposers  32 . Components  24  may be electrically coupled to each other and to control circuitry  16  by stretchable signal paths such as serpentine paths  42 - 1  ( FIG. 24 ) and serpentine paths  42 - 2  ( FIG. 25 ). The structures of  FIGS. 24 and 25  may be stacked to form a two-layer stretchable light source such as light source  102  of  FIG. 26 .  FIG. 27  is a side view of the upper layer of light source  102  of  FIG. 26  (i.e.,  FIG. 27  is a side view of the structures of  FIG. 25 ) and  FIG. 28  is a side view of the lower layer of light source  102  of  FIG. 26  (i.e.,  FIG. 28  is a side view of the structures of  FIG. 24 ). 
       FIG. 29  is a perspective view of an edge portion of stretchable layer  112  showing how light-emitting components in light source  102  may emit light of different colors. Red light may be emitted by red light-emitting components  24 R, green light may be emitted by green light-emitting components  24 G, and blue light may be emitted by blue light-emitting components  24 B. Components such as components  24 R,  24 G, and  24 B may be coupled in any suitable order using serpentine paths  42 . Other colors of light may be emitted by components  24 , if desired. 
       FIG. 30  is a top view of an illustrative light-emitting component  24  showing how a light-emitting diode or other light-emitting component  34  may be mounted on a substrate such as interposer  32 . Component  34  of  FIG. 30  may be a single-color light-emitting diode (as an example). In the arrangement of  FIG. 31 , red light-emitting diode  34 R, green light-emitting diode  34 G, and blue light-emitting diode  34 B have been mounted on interposer  32 . In the arrangement of  FIG. 32 , red light-emitting diode  34 R, green light-emitting diode  34 G, blue light-emitting diode  34 B, and white light-emitting diode  34 W have been mounted on interposer  32 . Control circuitry may also be mounted on the interposers. 
       FIGS. 33, 34, 35, 36, 37, 38, and 39  are top views of illustrative stretchable light guide units  100  having various light guide and light source configurations. In the example of  FIG. 33 , layer  112  is rectangular and light source  102  is located along one of the edges of layer  112 . In the example of  FIG. 34 , light source  102  includes arrays of components  24  along opposing edges of layer  112 . Three edges of layer  112  have been provided with light-emitting components  24  in the example of  FIG. 35  and four edges of layer  112  have been provided with light-emitting components  24  in the example of  FIG. 36 .  FIG. 37  shows how layer  112  may be circular and how light source  102  may have light-emitting components  24  that run around the circumference of layer  112 .  FIG. 38  shows how layer  112  may be octagonal and how each of the eight sides of layer  112  may have light-emitting components  24 .  FIG. 39  shows how some of light-emitting components  24  of light source  102  may be embedded within layer  112  and some of light-emitting components  24  of light source  102  may be mounted on exposed external edge surfaces of layer  112 . In general, layer  112  may have any suitable shape (i.e., a shape with one or more curved edges and/or one or more straight edges, etc.) and components  24  may be mounted one or within any suitable portions of layer  112 . Layer  112  may or may not include light extraction features  114 . 
     As shown in the illustrative configurations of  FIGS. 40, 41, and 42 , stretchable light source  100  may have a stretchable light guide layer  112  that is formed by stitching together multiple smaller areas of light guide material (e.g., rectangular sheets or sheets of other shapes) using bonding material  128  (e.g., clear elastomeric adhesive such as silicone adhesive or other suitable bonding layer). Bonding material  128  may have an index of refraction that matches that of layer  112  (e.g., that is within +/−0.1 of that of layer  112 ) to suppress reflections. Panels of layer  112  may be stitched together linearly ( FIG. 40 ), in a rectangular tiled configuration ( FIG. 41 ), or in other suitable shapes (see, e.g., the illustrative layout of  FIG. 42 ). 
     As shown by illustrative stretchable light guide unit  100  of  FIG. 43 , layer  112  may be stretched to conform to a curved surface such as the surface of spherical object  130  or other surface with compound curves (e.g., layer  112  may be stretched in directions  132  by hands  118 ). Adhesive or other attachment structures may be used to attach unit  100  to structure  130  (i.e., structure  130  may serve as a support structure in device  10 ) or unit  100  may be stretched dynamically during use of device  10 . 
       FIG. 44  shows how components  24  and stretchable signal paths  42  may be mounted on an edge surface of layer  112 . As shown in  FIG. 45 , some or all of components  24  may be embedded within layer  112 . 
     If desired, light  124  may be downconverted in frequency (e.g., converted from a shorter wavelength to a longer wavelength). For example, light  124  may be downconverted by forming a downconversion layer by incorporating downconverting agent into elastomeric material in stretchable light guide unit  100 . As shown in  FIG. 46 , downconverting agent  138  may be incorporated into an encapsulating layer such as layer  136  on layer  112  to form a downconversion layer. Downconversion material for unit  100  such as agent  138  may include phosphors, quantum dots, or other agents for downconverting light  124 . For example, agent  138  may include red and green quantum dots so that blue light  124  from light-emitting component  24  may be converted to red, green, and glue light when emitted by unit  100  or may include phosphors that convert blue light into white light (as examples). If desired, downconverting agent  138  may be incorporated into layer  112 , may be incorporated into light-emitting diode structures in components  24 , and/or may be incorporated into other coatings, layers of material in unit  100 , or other structures in device  10 . The illustrative configuration of  FIG. 46  in which layer  136  (e.g., a clear elastomeric polymer or other encapsulation layer) has been provided with downconverting material such as agent  138  is merely illustrative. 
       FIG. 47  is a side view of unit  100  in an illustrative configuration in which light scattering features  114  include surface-mounted structures. The surface mounted structures on layer  112  may be formed by printing or otherwise patterning a coating layer on layer  112  (see, e.g., patterned light-scattering coating  114 C), may be formed by attaching light-scattering structures such as structure  114 A to layer  112  using adhesive  114 A′, or may be formed by attaching other light-scattering structures to layer  112 . Light-extraction structures may be permanently attached to light guide layer  112 , may be temporary attached using a pressure sensitive adhesive or other temporary bonding agent, or may be attached using other mounting techniques. Light-extraction structures such as features  114  of  FIG. 47  may include optical structures that form lenses, diffusive light-scattering structures (e.g., hazy material or textured material), or colored material for coloring light  24 . Structures  114  of the type shown in  FIG. 47  or other light extraction features may be patterned to form characters, logos, icons, other symbols, or other patterns. This type of light-scattering feature may be selectively applied to areas of layer  112  for functional purposes (e.g., to scatter backlight for a display where desired), for decorative purposes (e.g., to form a decorative trim), or to form a symbol or other label that informs a user of the location of an input-output device such as the location of a button, force sensor, touch sensor, etc. 
       FIGS. 48 and 49  show how multiple stretchable light guide layers may be used in forming stretchable lighting unit  100 . As shown in the example of  FIG. 48 , separation layer  140  may be interposed between upper light guide layer  112 T and lower light guide layer  112 B. Layer  140  may have an index of refraction that is lower than that of layers  112 T and  112 B so that layer  140  serves as an optical cladding layer. Optional spacers  142  (e.g., microspheres, columns of polymer, or other spacer structures) may be incorporated into layer  140  to ensure that the gap between layers  112 T and  112 B is even. Layers  112 T and  112 B may each have a respective array of light-emitting components  24  and stretchable paths  42 . The light-emitting components may emit light  124  into each of layers  112 T and  112 B that is scattered out of unit  100  by light scattering structures  114 . In the example of  FIG. 49  two of cladding layers  140  are used in separating light guide layers  112 A,  112 B, and  112 C. 
     Layers  140  of  FIGS. 48 and 49  may be formed from a deformable material such as a liquid, a gel (e.g., a deformable sol-gel material), or other suitable material that can be compressed by external pressure (as an example). Spacers  142  may have an index of refraction that is matched to that of layers  140  (e.g., spacers  142  may have an index that deviates by less than +/−0.1 or other suitable amount from the index of layers  140 ). If desired, layers  140  may be formed from clear elastomeric polymer. 
       FIG. 50  is a cross-sectional side view of unit  100  in an illustrative configuration that includes light-scattering material such as light-scattering agent  144 . Light-scattering agent  144  may include light-scattering particles, light-scattering microspheres, microvoids (e.g., bubbles of air or other gas), or other features that enhance light scattering. Agent  144  may be embedded within a stretchable clear polymer layer (e.g., a silicone layer or other elastomeric polymer layer) such as encapsulation layer  146 . Separation layers such as layers  140  with optional spacers  142  may be use to separate stretchable encapsulation layers  146  from light guide layer  112 ′ of light guide layer  112 . 
     Structures such as structure  100  of  FIG. 50  may deform when pressure is applied by a finger (finger  118 ) of a user or by other external objects. Emitted light created when structure  100  is deformed may provide a user with visual feedback or may be detected (e.g., when structure  100  is used as part of a light-based structure in a pressure sensor, force sensor, touch sensor, button, or other sensor responsive to applied force). 
     The deformation of structure  100  when pressure is applied by finger  118  is illustrated in  FIG. 51 . Layer(s)  140  may have a lower index than layer  112 ′. Layer  146  may have an index that matches that of layer  112 ′ to encourage light leakage when layer  146  contacts layer  112 ′ or may have other suitable index values. 
     As shown in  FIG. 51 , the layers that make up structure  100  such as layer  146  may and  140  may be deformed by pressure from finger  118 , thereby locally defeating total internal reflection of light  124  and locally allowing light  124  to escape from layer  112 ′ of layer  112  and unit  100 . The light that is extracted from layer  112  in this way may create a glowing effect around the point of contact between finger  118  and layer  112  due to light scattering in layer  148  by light-scattering structures  144  or may otherwise be visible to a user of device  10 . If desired, light extraction features  114  may be incorporated into this type of stretchable lighting unit (see, e.g.,  FIG. 52 ). 
     If desired, thin-film circuitry can be formed in substrate  44 . As shown in  FIG. 53 , for example, substrate  44  may include thin-film circuitry  36 ′ (sometimes referred to as thin-film transistor circuitry). Thin-film circuitry  36 ′ may include circuits for supplying components  34  such as light-emitting diodes (e.g., light-emitting diodes formed from crystalline semiconductor dies) with image data (e.g., signals such as drive currents that direct light-emitting diodes or other light-emitting components  34  to emit light to display images for a user of a stretchable display or other input-output device  20  and/or other signals of the type handled by integrated circuits  36  of  FIG. 4 ). Thin-film circuitry  36 ′ may include thin-film transistors such as polysilicon thin-film transistors and/or semiconducting oxide (e.g., indium gallium zinc oxide) thin-film transistors. Thin-film circuitry  36 ′ may also include other thin-film components such as thin-film capacitors, resistors, inductors, etc. Thin-film circuitry  36 ′ may be formed using photolithography, deposition techniques such as physical vapor deposition and chemical vapor deposition, and/or other fabrication techniques. 
     Thin-film circuitry  36 ′ may be formed by depositing and patterning semiconductor layers, metal layers, and dielectric layers on a stretchable polymer substrate such as substrate  44  (e.g., a stretchable mesh-shaped substrate having an array of openings and/or thinned areas and serpentine interconnection paths or other paths that enhance flexibility for substrate  44 ). Thin-film layers of patterned metal for forming interconnects  50  and thin-film layers of dielectric (e.g., organic layers such as polymer layers and/or inorganic layers such as layers of silicon oxide, silicon nitride, etc.) may be formed over the thin-film transistors and other circuitry  36 ′. 
     Interconnects  50  may have pads (contacts) or other structures that are soldered or otherwise connected to corresponding pads (contacts) on the lower surface of interposer  32 . The pad structures on the lower surface of interposer  32  may be formed from interconnects  56  in interposer  32 . Interconnects  56  may also form pads on the upper surface of interposer  32  to which the terminals of light-emitting diodes  34 - 1 ,  34 - 2 , and  34 - 3  or other components  34  may be coupled (e.g., using solder and/or other conductive materials). During operation, thin-film circuitry  36 ′ (e.g., pixel control circuits formed from silicon thin-film transistors and/or semiconducting-oxide thin-film transistors in circuitry  36 ′) may supply drive currents to light-emitting diodes  34 - 1 ,  34 - 2 , and  34 - 3  via signal paths in interconnects  50  and interconnects  56 . 
     Light-emitting diodes  34 - 1 ,  34 - 2 , and  34 - 3  may be crystalline semiconductor die. Component  24  may form a pixel for a pixel array in a stretchable display (e.g., device  20  may be a stretchable display). Each diode in component  24  may be associated with a subpixel of a different color. As an example, each pixel may have red, green, and blue subpixels formed respectively by diodes  34 - 1 ,  34 - 2 , and  34 - 3 . 
     With one illustrative configuration, diode  34 - 1  may be a red light-emitting diode (e.g., a AlInGaP diode), diode  34 - 2  may be a green light-emitting diode (e.g., an InGaN diode), and diode  34 - 3  may be a blue light-emitting diode (e.g., an InGaN diode). Red diodes may require more drive current than green and blue diodes. To help equalize and lower the drive current requirements for the diodes in component  24 , it may be desirable to form red subpixels (and, if desired, green and/or blue subpixels) from short wavelength diodes (blue or ultraviolet) that are provided with downconverters to generate longer-wavelength light. 
     For example, at least some of the light-emitting diodes in each pixel may provide blue or ultraviolet light to photoluminescent material  200  such as phosphors or quantum dots. The photoluminescent material may include phosphors such as K 2 SiF 6 :Mn 4++  or other red phosphor particles, SrGa 2 Sr 4 :Eu 2++ , B—SiAlON or other green phosphor particles, or other phosphors and/or may include quantum dots such as red quantum does having CdSe cores and CdS/ZnS shells or InP cores and ZnSeS shells, or other red quantum dots and/or green quantum dots such as quantum dots having CdSe cores and CdS/ZnS shells, having InP cores and ZnSeS shells, or other green quantum dots. If desired, infrared subpixels may be formed by pumping infrared quantum dots with blue light or ultraviolet light or other light. Illustrative configurations for device  20  in which the subpixels of each component (pixel)  24  are visible-light subpixels may sometimes be described herein as an example. Downconverting material such as photoluminescent material  200  may be patterned using photolithography, screen printing, transfer printing, embossing, or other suitable fabrication techniques. 
     Photoluminescent material  200  may convert blue or ultraviolet light to red and/or green light. For example, a red subpixel may be formed by illuminating red photoluminescent material with blue or ultraviolet light (e.g., from diode  34 - 1 , which may be a blue or ultraviolet light diode), a green subpixel may be formed by illuminating green photoluminescent material with blue or ultraviolet light (e.g., from diode  34 - 2 , which may be a blue or ultraviolet light diode), and a blue subpixel may be formed by illuminating clear (non-photoluminescent) material with blue light (e.g., blue light from diode  34 - 3  in a configuration in which diode  34 - 3  is a blue diode) or a blue pixel may be formed by illuminating blue photoluminescent material with ultraviolet light (e.g., ultraviolet light from diode  34 - 3  in a configuration in which diode  34 - 3  is an ultraviolet light diode). Encapsulant  38  (e.g., clear polymer) may be used to cover photoluminescent material  200  on diodes  34 - 1 ,  34 - 2 , and  34 - 3 . If desired, black polymer or other opaque material may be interposed between adjacent diodes to help reduce stray light. 
     In the illustrative configuration of  FIG. 54 , diodes  34 - 1 ,  34 - 2 , and  34 - 2  have been mounted directly to substrate  44  (e.g., the terminals of diodes  34 - 1 ,  34 - 2 , and  34 - 3  may be soldered to pads formed from portions of interconnects  50  in substrate  44  or may be coupled to contacts in interconnects  50  using conductive adhesive or other coupling mechanisms). As in the arrangement of  FIG. 53  that includes interposer  32 , pixel control circuitry formed from thin-film transistors in thin-film circuitry  36 ′ may be used to supply independently adjustable currents to diodes  34 - 1 ,  34 - 2 , and  34 - 3  to illuminate the red, green, and blue subpixels by desired amounts. 
       FIG. 55  is a cross-sectional side view of a portion of a stretchable display or other input-output device  20  in an illustrative configuration in which light-emitting diodes  34 - 1 ,  34 - 2 , and  34 - 3  have been formed from a common substrate 34SUB (e.g., an InGaN die). Diodes  34 - 1 ,  34 - 2 , and  34 - 3  of  FIG. 55  may be independently driven and may each emit blue light. Diode  34 - 1  may be covered with red photoluminescent material  200  to form a red subpixel, diode  34 - 2  may be covered with green photoluminescent material  200  to form a green subpixel, and diode  34 - 3  may be covered clear material, so that blue light from diode  34 - 3  may be used in forming a blue subpixel for component (pixel)  24 . In general, the diodes  34 - 1 ,  34 - 2 , and  34 - 3  in each pixel may be crystalline semiconductor light-emitting diodes formed from one semiconductor die, two semiconductor dies, or more than two semiconductor dies. 
     Any suitable fabrication process may be used in forming stretchable displays or other input-output devices  20  of the type shown in  FIGS. 53, 54, and 55 . With one illustrative arrangement, a sacrificial layer may be formed on a support structure, a mesh-shaped stretchable substrate  44  (e.g., a polymer layer with an array of openings and/or thinned areas and serpentine paths or other paths) may be formed on the sacrificial layer, and thin-film transistor circuitry  36 ′ may be formed on substrate  44 . An interlayer dielectric layer and interconnects  50  may be formed over circuitry  36 ′. Optional interposer  32  may be soldered to pads in interconnects  50  or diodes  34  may be coupled to pads in interconnects  50  using other techniques (e.g., direct soldering, conductive adhesive, etc.). If desired, interposer  32  may be a “printable” interposer formed from a layer of polymer that is patterned directly on the surface of substrate  44  to form interposer  32  on substrate  44 . Printable interposers may be formed by screen printing, photolithography (e.g., using photoimagable polymer material), or using other suitable techniques. 
     After coupling diodes  34  to thin-film circuitry  36 ′ in substrate  44  (with or without an interposer), photoluminescent material  200  and encapsulant  38  may be formed over diodes  34  (and/or material  200  may be formed over diodes  34  before attaching diodes  34 ). If not previously formed, openings (or thinned areas)  42  may be formed in substrate  44  to provide clear apertures through which light may pass and/or to enhance the stretchability of input-output device (display)  20 . Device  20  may then be released from the support structure, residual sacrificial layer material may be removed, and an elastomer (e.g., a silicone or other elastomeric material) may be applied to device  20  to enhance the durability of device  20 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20161017
Publication Date: 20180717
Grant Date: 20180717
Priority Date: 20150630
Inventors: KIM, HOON SIK
HSU, YUNG-YU
DRZAIC, PAUL S.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/181", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1652", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0065", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1652", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0073", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/15192", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/16225", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L25/0753", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10166", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L25/167", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0065", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04109", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/15192", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/15311", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L25/167", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2924/15311", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0283", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/16225", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L25/0753", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/49894", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10128", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04109", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/4985", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/4985", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L33/62", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10128", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10166", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L27/1218", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/1225", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/15192", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/49894", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L25/0753", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1652", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04109", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L25/167", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K1/0283", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/16225", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L29/7869", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L33/502", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0073", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/181", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/15311", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0065", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10D86/423", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/411", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D30/6755", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10H20/8512", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10H20/857", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10H20/857", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10H20/8512", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 58053073