PATENT DOCUMENT

Publication Number: US-11592946-B1
Application Number: US-202117481122-A
Country: US
Kind Code: B1

Title: Capacitive gap force sensor with multi-layer fill

Abstract:
A capacitive gap force sensor includes a first electrode, a second electrode spaced apart from the first electrode, a first layer of dielectric material positioned between the first electrode and the second electrode, and a second layer of conductive material positioned between the first layer and the second electrode. The first layer has a first compression resistance less than a second compression resistance of the second layer. An effective capacitive sensing gap is defined between the first electrode and the second layer. The first layer is configured to compress or deform and alter the effective capacitive sensing gap when a force is received at the first electrode or the second electrode.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a capacitive gap force sensor, comprising:
 a first electrode; 
 a second electrode spaced apart from the first electrode; 
 a first layer of dielectric material positioned between the first electrode and the second electrode; and 
 a second layer of conductive material positioned between the first layer and the second electrode; and 
 
 a housing having a force input surface; wherein, 
 the first layer has a first compression resistance less than a second compression resistance of the second layer; 
 an effective capacitive sensing gap is defined between the first electrode and the second layer; 
 the capacitive gap force sensor is positioned near or against an interior surface of the housing, under the force input surface; and 
 the first layer is configured to compress or deform and alter the effective capacitive sensing gap when a force is received on the force input surface. 
 
     
     
       2. The electronic device of  claim 1 , wherein the first layer and the second layer are part of a multi-layer fill that spans an entirety of a space between the first electrode and the second electrode. 
     
     
       3. The electronic device of  claim 1 , wherein the first layer comprises a polymer foam. 
     
     
       4. The electronic device of  claim 1 , wherein each of the first layer and the second layer comprises a polymer foam. 
     
     
       5. The electronic device of  claim 1 , wherein the housing comprises acrylonitrile butadiene styrene (ABS). 
     
     
       6. The electronic device of  claim 5 , wherein a first stiffness of the first electrode and a second stiffness of the first layer are at least an order of magnitude less stiff than a third stiffness of the force input surface. 
     
     
       7. The electronic device of  claim 1 , wherein the capacitive gap force sensor defines an air gap between one of:
 the first electrode and the first layer; or 
 the first layer and the second layer. 
 
     
     
       8. The electronic device of  claim 1 , further comprising:
 a capacitive force sensing circuit coupled to at least one of the first electrode or the second electrode. 
 
     
     
       9. A capacitive gap force sensor, comprising:
 a first electrode; 
 a second electrode spaced apart from the first electrode; 
 a first layer of dielectric material positioned between the first electrode and the second electrode; and 
 a second layer of conductive material positioned between the first layer and the second electrode; wherein, 
 the first layer has a first compression resistance less than a second compression resistance of the second layer; 
 an effective capacitive sensing gap is defined between the first electrode and the second layer; and 
 the first layer is configured to compress or deform and alter the effective capacitive sensing gap when a force is received at the first electrode or the second electrode. 
 
     
     
       10. The capacitive gap force sensor of  claim 9 , wherein each of the first layer and the second layer comprises a hydrophobic material. 
     
     
       11. The capacitive gap force sensor of  claim 9 , wherein each of the first layer and the second layer comprises a closed cell foam. 
     
     
       12. The capacitive gap force sensor of  claim 9 , wherein the second layer comprises an open cell foam. 
     
     
       13. The capacitive gap force sensor of  claim 9 , further comprising:
 an adhesive attaching the first layer to the second layer. 
 
     
     
       14. The capacitive gap force sensor of  claim 9 , wherein the second layer comprises a polymer foam at least partially coated with a metal. 
     
     
       15. A method of constructing a capacitive gap force sensor, comprising:
 constructing a stack of materials, the constructing including,
 attaching a first electrode to a first surface of a first layer of dielectric material; 
 attaching a second electrode to a first surface of a second layer of conductive material; and 
 attaching a second surface of the first layer to a second surface of the second layer; 
 
 compressing the stack of materials; and 
 structurally modifying the second layer, after compressing the stack of materials; wherein, 
 the second surface of the first layer is opposite the first surface of the first layer; 
 the second surface of the second layer is opposite the first surface of the second layer; and 
 the stack of materials defines an effective capacitive sensing gap between the first electrode and the second layer of conductive material; 
 after constructing the stack of materials, the first layer has a first compression resistance greater than a second compression resistance of the second layer; and 
 the structural modification of the second layer transitions the second compression resistance to a compression resistance greater than the first compression resistance. 
 
     
     
       16. The method of  claim 15 , wherein structurally modifying the second layer comprises:
 heating the second layer. 
 
     
     
       17. The method of  claim 15 , wherein structurally modifying the second layer comprises:
 exposing the second layer to a predetermined wavelength or wavelengths of light. 
 
     
     
       18. The method of  claim 15 , wherein structurally modifying the second layer comprises:
 exposing the second layer to oxygen or removing oxygen from an environment of the second layer. 
 
     
     
       19. The method of  claim 15 , wherein structurally modifying the second layer comprises:
 chemically treating the second layer. 
 
     
     
       20. The method of  claim 15  further comprising:
 positioning the stack of materials within an electronic device; wherein, 
 the compressing occurs at least partially during the positioning. 
 
     
     
       21. The method of  claim 15 , further comprising:
 positioning the stack of materials within an electronic device; wherein, 
 the compressing occurs at least partially after the positioning.

Description:
FIELD 
     The described embodiments relate to sensors for determining the presence of a force, or an amount of force, on a force input surface. More particularly, the described embodiments relate to capacitive gap force sensors. 
     BACKGROUND 
     Sensors are included in many of today&#39;s electronic devices, including electronic devices such as smartphones, computers (e.g., tablet computers or laptop computers), wearable electronic devices (e.g., electronic watches, smart watches, or health or fitness monitors), game controllers, navigation systems (e.g., vehicle navigation systems or robot navigation systems), earbuds, headphones, and so on. Sensors may variously sense the presence of objects, forces applied by objects, distances to objects, proximities of objects, movements of objects (e.g., whether objects are moving, or the speed, acceleration, or direction of movement of objects), compositions of objects, and so on. One useful type of sensor is the capacitive gap force sensor. 
     Given the wide range of sensor applications, any new development in the configuration or operation of a sensor can be useful. New developments that may be particularly useful are developments that reduce the cost, size, complexity, part count, or manufacture time of a sensor, or developments that improve the sensitivity or speed of sensor operation. 
     SUMMARY 
     Embodiments of the systems, devices, methods, and apparatus described in the present disclosure are directed to capacitive gap force sensors. 
     In a first aspect, the present disclosure describes an electronic device. The electronic device may include a capacitive gap force sensor and a housing. The capacitive gap force sensor may include a first electrode, a second electrode spaced apart from the first electrode, a first layer of dielectric material positioned between the first electrode and the second electrode, and a second layer of conductive material positioned between the first layer and the second electrode. The housing may have a force input surface. The first layer may have a first compression resistance that is less than a second compression resistance of the second layer. An effective capacitive sensing gap may be defined between the first electrode and the second layer. The capacitive gap force sensor may be positioned near or against an interior surface of the housing, under the force input surface. The first layer may be configured to compress or deform and alter the effective capacitive sensing gap when a force is received on the force input surface. 
     In a second aspect, the present disclosure describes a capacitive gap force sensor. The capacitive gap force sensor may include a first electrode, a second electrode spaced apart from the first electrode, a first layer of dielectric material positioned between the first electrode and the second electrode, and a second layer of conductive material positioned between the first layer and the second electrode. The first layer may have a first compression resistance that is less than a second compression resistance of the second layer. An effective capacitive sensing gap may be defined between the first electrode and the second layer. The first layer may be configured to compress or deform and alter the effective capacitive sensing gap when a force is received at the first electrode or the second electrode. 
     In a third aspect, the present disclosure describes a method of constructing a capacitive gap force sensor. The method may include constructing a stack of materials. Constructing the stack of materials may include attaching a first electrode to a first surface of a first layer of dielectric material, attaching a second electrode to a first surface of a second layer of conductive material, and attaching a second surface of the first layer to a second surface of the second layer. The second surface of the first layer may be opposite the first surface of the first layer, and the second surface of the second layer may be opposite the first surface of the second layer. The stack of materials may define an effective capacitive sensing gap between the first electrode and the second layer of conductive material. 
     In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG.  1    shows an example of a capacitive gap force sensor; 
         FIGS.  2 A- 2 C  show various examples of a capacitive gap force sensor having a multi-layer fill; 
         FIG.  3    shows an electrical block diagram of a capacitive gap force sensor and circuitry for sensing a capacitance of the sensor and generating an indication of a force presence of an amount of force; 
         FIG.  4    shows a first example method of constructing a capacitive gap force sensor; 
         FIG.  5    shows a second example method of constructing a capacitive gap force sensor; 
         FIG.  6    shows an example of an earbud having a capacitive gap force sensor; 
         FIG.  7    shows an example of an electronic device that includes a capacitive gap force sensor; 
         FIG.  8    shows another example of an electronic device that includes a capacitive gap force sensor; and 
         FIG.  9    shows a sample electrical block diagram of an electronic device. 
     
    
    
     The use of cross-hatching or shading in the accompanying figures is generally provided to clarify the boundaries between adjacent elements and also to facilitate legibility of the figures. Accordingly, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, element proportions, element dimensions, commonalities of similarly illustrated elements, or any other characteristic, attribute, or property for any element illustrated in the accompanying figures. 
     Additionally, it should be understood that the proportions and dimensions (either relative or absolute) of the various features and elements (and collections and groupings thereof), and the boundaries, separations, and positional relationships presented therebetween, are provided in the accompanying figures merely to facilitate an understanding of the various embodiments described herein and, accordingly, may not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for an illustrated embodiment to the exclusion of embodiments described with reference thereto. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     Capacitive gap force sensing uses a capacitor to sense a presence of a force or an amount of force. In particular, when an amount of force is applied to a capacitive gap force sensor, the force changes a spacing between the capacitor&#39;s electrodes, thus changing the capacitor&#39;s capacitance. The capacitance, or change in capacitance, can be sensed and correlated to an amount of force. 
     Described herein is a capacitive gap force sensor having a multi-layer fill. The multi-layer fill includes a layer of conductive material that decreases the effective capacitive sensing gap between the sensor&#39;s electrodes. The multi-layer fill also includes a layer of dielectric material, which increases the dielectric constant of the effective capacitive sensing gap, thus increasing the sensor&#39;s capacitance, force sensitivity and, ultimately, the force signal that can be obtained from the sensor. 
     In some cases, a first electrode, a first layer of dielectric material, a second layer of conductive material, and a second electrode may be assembled to form a capacitive gap sensor having a multi-layer fill. During and after assembly, the second layer may have a compression resistance that is less than the compression resistance of the first layer. This enables the conductive material to compress more than the dielectric material (and preferably much more) when the sensor is positioned in a particular application. After the sensor is positioned, the conductive material can be structurally modified through heating, exposure to light, or other means. The structural modification of the conductive material sets the nominal extent of the conductive material (defining a fixed capacitive sensing gap between the first electrode and the layer of conductive material), and also increases its compression resistance so that the compression resistance of the conductive material is greater than the compression resistance of the dielectric material. Thus, when used to sense an applied force, the dielectric material compresses more than the conductive material (and preferably much more). 
     Providing the layer of conductive material in an initial state that allows it to compresses much more than the dielectric material 1) limits the amount of compression that occurs within the dielectric material during install, and 2) substantially confines the compression that occurs during install to the layer of conductive material. As a result, like sensors that are installed in spaces of differing size are likely to have structurally modified conductive layers having different thicknesses, but have effective capacitive sensing gaps that are the same (or very similar). Like sensors that are installed in different locations, or used in different applications, are therefore likely to produce both higher and more uniform signals (i.e., more uniform signals or responses from sensor to sensor, or device to device, given equivalent applications of force). 
     The above and other embodiments and techniques are described with reference to  FIGS.  1 - 9   . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
     Directional terminology, such as “top”, “bottom”, “upper”, “lower”, “front”, “back”, “over”, “under”, “above”, “below”, “left”, “right”, etc. is used with reference to the orientation of some of the components in some of the figures described below. Because components in various embodiments can be positioned in a number of different orientations, directional terminology is used for purposes of defining relative positions of various structures, and not absolute positions. For example, a first structure described as being “above” a second structure and “below” a third structure is also “between” the second and third structures, and would be “above” the third structure and “below” the second structure if the stack of structures were to be flipped. Also, as used herein, the phrase “at least one of” preceding a series of items, with the term “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list. The phrase “at least one of” does not require selection of at least one of each item listed; rather, the phrase allows a meaning that includes at a minimum one of any of the items, and/or at a minimum one of any combination of the items, and/or at a minimum one of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; any combination of A, B, and C; and/or one or more of each of A, B, and C. Similarly, it may be appreciated that an order of elements presented for a conjunctive or disjunctive list provided herein should not be construed as limiting the disclosure to only that order provided. 
       FIG.  1    shows an example of a capacitive gap force sensor  100 . The sensor  100  includes a first electrode  102  and a second electrode  104  (e.g., metal plates, conductive traces, or other conductive elements). The second electrode  104  is spaced apart from the first electrode  102  by a capacitive sensing gap  106 . The electrodes  102 ,  104  may be attached to various structures that preserve the capacitive sensing gap  106  absent a force  108  applied to the sensor  100 . In some cases, the electrodes  102 ,  104  may be attached to different surfaces of a capacitive sensing module, or to different components that have a fixed relationship absent a force  108  applied to the sensor  100 . The capacitive sensing gap  106  may be filled with air or a dielectric material. 
     When a force  108  is applied to the first electrode  102 , or to a surface (e.g., a surface of a housing) that the first electrode  102  is placed near or adjacent, the first electrode  102  may deform or move toward the second electrode  104 , thereby compressing, deforming, and/or altering (e.g., changing the profile of) the capacitive sensing gap  106  and, as a result, changing a capacitance of the sensor  100 . Alternatively, the second electrode  104  may be positioned near or adjacent a force input surface, and a force may be applied to the second electrode  104 ; or the capacitive gap force sensor  100  may be positioned between a pair of force input surfaces and a force may be applied to one or both of the first and second electrodes  102 ,  104  via one or both of the force input surfaces (e.g., with a pinching-type application of force). A capacitive force sensing circuit coupled to one of the electrodes  102 ,  104  (in the case of a self-capacitance sensor) or both of the electrodes  102 ,  104  (in the case of a mutual capacitance sensor), and an analog-to-digital converter (ADC) and processor may be used to convert the capacitance (or change in capacitance) to an amount of force (or to a change in an amount of force). The capacitive force sensing circuit (in some cases in combination with the ADC and processor) may also be used to detect a presence of a force on the first electrode  102  (i.e., in a binary detect/no detect mode of operation). 
       FIGS.  2 A- 2 C  show various examples of a capacitive gap force sensor  200  having a multi-layer fill. As shown in  FIG.  2 A , the sensor  200  includes a first electrode  202  and a second electrode  204 . The second electrode  204  is spaced apart from the first electrode  202  by a space  206 . The space  206  may be filled with a multi-layer fill including a first layer  208  of a dielectric material and a second layer  210  of a conductive material. The first layer  208  may be positioned between the first electrode  202  and the second electrode  204 , and the second layer  210  may be positioned between the first layer  208  and the second electrode  204 . 
     The first layer  208  may have a first compression resistance that is less than a second compression resistance of the second layer  210 . In other words, the first layer  208  may be softer than the second layer  210 . In some embodiments, the compression resistance of the first layer  208  may be much less than (e.g., an order of magnitude or more less than) the compression resistance of the second layer  210 . When the compression resistance of the first layer  208  is much less than the compression resistance of the second layer  210  (and likewise, when the compression resistance of the second layer  210  is much greater than the compression resistance of the first layer  208 ), an effective capacitive sensing gap  214  that is smaller than the space  206  may be defined between the first electrode  202  and the second layer  210 . A smaller capacitive sensing gap provides the sensor  200  with a greater sensitivity for detecting forces applied to the first electrode  202  (e.g., as compared to the sensor described with reference to  FIG.  1   , and assuming that the electrodes of each sensor are equally spaced). 
     In some cases, the first and second layers  208 ,  210  may be or include polymers, such as polymer foams. In the case of polymer foams, each of the first and second layers  208 ,  210  may be or include an open cell polymer foam and/or a closed cell polymer foam. In some cases, the first or second layer  208 ,  210  may be or include other types of foams, such as other types of open and/or closed cell polymer foams. In some cases, each of the first and/or second layer  208 ,  210  may be a hydrophobic material. When both of the layers  208 ,  210  are hydrophobic, capacitive sensing may be less susceptible to variation due to moisture. In some cases, the dielectric material may have a dielectric constant of about 2-4. In some cases, the dielectric material may have a dielectric constant of 3 or about 3 (e.g., 3±10%). One or both of the first and second layers  208 ,  210  may in some cases include a composite material (i.e., a material having two or more constituent materials). 
     In some embodiments, the second layer  210  may be or include a foam (e.g., a polymer foam) that is at least partially coated with a metal. For example, the second layer  210  may be or include an electroplated polyurethane. In some embodiments, the second layer  210  may be or include a foam that includes metal or other conductive particles embedded in a polymer matrix. For example, the second layer  210  may be or include a porous first polymer having a conductive second polymer embedded in its pores. 
     In some cases, the first and second layers  208 ,  210  may be part of a multi-layer fill that spans an entirety of the space  206  between the first and second electrodes  202 ,  204 . In some embodiments, the multi-layer fill may include other layers, such as an adhesive that attaches the first layer  208  to the second layer  210 , an adhesive that attaches the first electrode  202  to the first layer  208 , and/or an adhesive that attaches the second electrode  204  to the second layer  210 . 
     In some cases, an air gap may be provided between the first and second layers  208 ,  210 , or between the first electrode  202  and the first layer  208 . If an air gap is provided, each of the first and second electrodes  202 ,  204  may need to be attached to a structure to preserve a fixed effective capacitive sensing gap  214  absent a force  212  on the first electrode  202 . 
     When a force  212  is applied to the first electrode  202 , or to a surface (e.g., a surface of a housing) that the first electrode  202  is placed near or adjacent, the first electrode  202  may deform or move toward the second electrode  204 , thereby compressing, deforming, and/or altering (e.g., changing the profile of) the effective capacitive sensing gap  214  and, as a result, changing a capacitance of the sensor  200 . Alternatively, the second electrode  204  may be positioned near or adjacent a force input surface, and a force may be applied to the second electrode  204 ; or the capacitive gap force sensor  200  may be positioned between a pair of force input surfaces and a force may be applied to one or both of the first and second electrodes  202 ,  204 , via one or both of the force input surfaces (e.g., with a pinching-type application of force). A capacitive force sensing circuit coupled to one of the electrodes  202 ,  204  (in the case of a self-capacitance sensor) or both of the electrodes  202 ,  204  (in the case of a mutual capacitance sensor) may detect the capacitance (or change in capacitance), and an ADC and processor may be used to convert the capacitance (or change in capacitance) to an amount of force (or to a change in an amount of force). The capacitive force sensing circuit (in some cases in combination with the ADC and processor) may also be used to detect a presence of a force on the first electrode  202  (i.e., in a binary detect/no detect mode of operation). 
     The electrodes  202 ,  204  and layers  208 ,  210  may be assembled in various ways. For example, in some cases, it may be advantageous to attach the first layer  208  to the second layer  210  before attaching an electrode  202  or  204  to either the first layer  208  or the second layer  210 . In some cases, it may be advantageous to attach the first electrode  202  to the first layer  208 , or to attach the second electrode  204  to the second layer  210 , before the first layer  208  is attached to the second layer  210 . 
     Regardless of the order in which the electrodes  202 ,  204  and layers  208 ,  210  are assembled, it can be advantageous to assemble the electrodes  202 ,  204  and layers  208 ,  210  while the first layer  208  has a compression resistance that is greater than the compression resistance of the second layer  210 . This is the opposite of the finished, usable sensor  200 , in which the compression resistance of the first layer  208  is less than the compression resistance of the second layer  210 . 
     Starting with a sensor  200  in which the first layer  208  has a greater compression resistance than the compression resistance of the second layer  210 , the sensor  200  can be positioned in a space of arbitrary size. If the space is narrower than the height of the sensor (i.e., a dimension perpendicular to the first and second layers  208 ,  210  and extending from an exterior surface of the first electrode  202  to an exterior surface of the second electrode  204 ), the sensor  200  can be compressed to fit. The sensor  200  can be compressed before or during the positioning of the sensor  200  in the installation space. After the sensor  200  is compressed, or in cases where the sensor  200  does not need to be compressed, the second layer  210  may be structurally modified to transition the compression resistance of the second layer  210  to a compression resistance that is greater than the compression resistance of the first layer  208 . 
     When the compression resistance of the second layer  210  starts out being less than the compression resistance of the first layer  208 , the second layer  210  can compress to a greater degree than the first layer  208  and, in some embodiments, can absorb all, or substantially all (e.g., 90% or more), of the compression that occurs during assembly, installation, and so on. After the second layer  210  is structurally modified to increase its compression resistance, the first layer  208  can absorb all, or substantially all (e.g., 90% or more), of the compression caused by application of a force  212  to the first electrode  202 . 
     The second layer  210  (i.e., the layer of conductive material) may be structurally modified in various ways, depending on the composition of the second layer  210 . In some cases, the second layer  210  may be structurally modified by heating the second layer  210  (or otherwise thermally triggering a structural modification). In some cases, the second layer  210  may be structurally modified by exposing the second layer  210  to a predetermined wavelength or wavelengths of light (or other optically triggering a structural modification). In some cases, the second layer  210  may be structurally modified by exposure to oxygen or removal of oxygen. In some cases, the second layer  210  may be structurally modified by a chemical reaction (e.g., the second layer  210  may include an epoxy (e.g., a two-part epoxy) that is cured and hardened; or the second layer  210  may include a resin or other material that is in the form of a liquid or gel carried by a foam or other material, and the resin or other material may be cured and hardened). 
       FIGS.  2 A,  2 B, and  2 C  show the sensor  200  as it might exist, in different installation environments, after structurally modifying the second layer  210  to increase its compression resistance.  FIG.  2 A  shows the sensor  200  with no compression of the second layer  210 .  FIG.  2 B  shows the sensor  200  after the second layer  210  has experienced moderate compression.  FIG.  2 C  shows the sensor  200  after the second layer  210  has experienced more extreme compression. In all of these cases ( FIGS.  2 A- 2 C ), the first layer  208  remains uncompressed or very mildly compressed, and the compression is entirely or substantially absorbed by the second layer  210 , thus maintaining an equal or approximately equal effective capacitive sensing gap in all of the installation environments, and providing uniformity (or substantial uniformity) of operation of the sensor  200  in all of the installation environments. The variation in thickness of the second layer  210  (i.e., the layer of conductive material) will often have a negligible impact on how the different embodiments of the sensor  200  operate. 
     In some embodiments, the first layer  208  may compress to a greater degree during compression and installation of the sensor  200 . However, this need not be the case. 
       FIG.  3    shows an electrical block diagram  300  of a capacitive gap force sensor  302  and circuitry for sensing a capacitance of the sensor  302  and generating an indication of a force presence or an amount of force. In some embodiments, the sensor  302  may be the sensor described with reference to  FIGS.  2 A- 2 C . The circuitry may include a capacitive force sensing circuit  304 , which in some cases may include one or more amplifiers or filters. The capacitive force sensing circuit  304  may operate in an analog domain. An ADC  306  may receive an output of the capacitive force sensing circuit  304  and convert it to a digital domain. A processor  308  may receive an output of the ADC  306  directly, or may retrieve an output of the ADC  306  from a memory, and may translate the output of the ADC  306  from a raw value to an amount of force applied to the sensor  302 . In some cases, the processor  308  may index a lookup table using the output of the ADC  306  or apply a conversion function to the output of the ADC  306 . 
       FIG.  4    shows a first example method  400  of constructing a capacitive gap force sensor. In some embodiments, the capacitive gap force sensor may be the sensor described with reference to  FIGS.  2 A- 2 C . 
     At block  402 , the method  400  may include constructing a stack of materials. Constructing the stack of materials may include attaching a first electrode to a first surface of a first layer of dielectric material (at block  404 ); attaching a second electrode to a first surface of a second layer of conductive material (at block  406 ); and attaching a second surface of the first layer to a second surface of the second layer (at block  408 ). The second surface of the first layer may be opposite the first surface of the first layer, and the second surface of the second layer may be opposite the first surface of the second layer. The stack of materials may define an effective capacitive sensing gap between the first electrode and the second layer of conductive material. 
       FIG.  5    shows a second example method  500  of constructing a capacitive gap force sensor. In some embodiments, the capacitive gap force sensor may be the sensor described with reference to  FIGS.  2 A- 2 C . 
     At block  502 , the method  500  may include constructing a stack of materials. The stack of materials may include a first electrode, a first layer of dielectric material, a second layer of conductive material, and a second electrode, and may be constructed as described with reference to any of  FIGS.  2 A- 2 C and  4   . After constructing the stack of materials, the first layer may have a first compression resistance that is greater than a second compression resistance of the second layer (e.g., the layer of conductive material may be softer than the layer of dielectric material). 
     At block  504 , the method  500  may include compressing the stack of materials. 
     At block  506 , the method  500  may include structurally modifying the second layer of the stack of materials. Structurally modifying the second layer may transition the second compression resistance to a compression resistance greater than the first compression resistance (e.g., the second layer of conductive material may be made harder than the first layer of dielectric material). The structurally modification may include one or more treatments of the second layer, as described below. 
     In some embodiments, structurally modifying the second layer may include heating the second layer. In some embodiments, structurally modifying the second layer may include exposing the second layer to a predetermined wavelength or wavelengths of light. In some embodiments, structurally modifying the second layer may include exposing the second layer to oxygen or, conversely, removing oxygen from the second layer&#39;s environment. In some embodiments, structurally modifying the second layer may include chemically treating the second layer or otherwise initiating a chemical reaction in the second layer. In some embodiments, structurally modifying the second layer may include increasing an extent of crosslinking of a polymer or polymer foam. In embodiments in which the second layer includes a foam that includes metal or other conductive particles embedded in a polymer matrix, such as a porous first polymer having a conductive second polymer embedded in its pores, structurally modifying the second layer may include hardening the first polymer and/or the second polymer. 
     In some embodiments, the method  500  may include positioning the stack of materials within an electronic device. In these embodiments, the compressing performed at block  504  may occur at least partially before the positioning, at least partially during the positioning, and/or at least partially after the positioning. In some embodiments, the structural modification may include partially curing the second layer before the stack of materials is positioned within an electronic device, and completing the cure after positioning the stack of materials within the electronic device. 
     The first layer may or may not be structurally modified as the second layer is structurally modified. 
       FIGS.  6 - 8    show various example electronic devices in which one or more capacitive gap force sensors, such as the sensor described with  FIGS.  2 A- 2 C , may be incorporated. 
       FIG.  6    shows an example of an earbud  600  (an electronic device) that includes a capacitive gap force sensor  608 . The earbud  600  may include a housing  610  (i.e., an earbud housing). The housing  610  may hold a speaker  602  that can be inserted into a user&#39;s ear, an optional microphone  604 , and circuitry  606  that can be used to acquire audio from the microphone  604  (if provided), transmit audio to the speaker  602 , and communicate audio between the speaker  602 , the microphone  604 , and one or more remote devices. The circuitry  606  may communicate with a remote device wirelessly (e.g., via a wireless communications interface, using a Wi-Fi, BLUETOOTH®, or cellular radio communications protocol, for example) or via one or more wires (e.g., via a wired communications interface, such as a Universal Serial Bus (USB) communications interface). In addition to communicating audio, the circuitry  606  may transmit or receive instructions and so on. 
     The capacitive gap force sensor  608  may be used, for example, to receive a force input (e.g., a button press) from a user. In some cases, the capacitive gap force sensor  608  may be positioned near or against an interior surface of the housing  610 , under a force input surface on an exterior of the housing  610 . The sensor  608  may have a stack of materials including a first electrode, a first layer of dielectric material, a second layer of conductive material, and a second electrode, as described with reference to  FIGS.  2 A- 2 C,  4 , and  5   . In these latter cases, the first electrode or the second electrode may be positioned near or against an interior surface of the housing  610 , or the first and second electrodes may be positioned between opposing first and second force input surfaces on the exterior of the housing  610 . 
     In some embodiments, the housing  610  may be formed of acrylonitrile butadiene styrene (ABS). In these and other embodiments, a stiffness of the first electrode and first layer of the sensor  608  may be much less than a stiffness of the housing  610 , such as an order of magnitude or more less stiff. This may enable relatively small amounts of force on the force input surface to be registered by the sensor  608 . 
     The circuitry  606  may include a processor and/or other components that are configured to determine an amount of force, or identify the presence of a force, received on the force input surface. In some cases, the circuitry  606  may include the components described with reference to  FIG.  3    and the processor may be the processor described with reference to  FIG.  3   . In some embodiments, the circuitry  606  may adjust a volume of the speaker  602  in response to a received amount of force. In some embodiments, the earbud  600  may have a pair of capacitive gap force sensors, and one of the sensors may be used to turn the volume of the speaker  602  up, and the other may be used to turn the volume of the speaker  602  down. The circuitry  606  may also maintain or alter one or more other settings, functions, or aspects of the earbud  600 . 
       FIG.  7    shows an example of a device  700  (an electronic device). The device  700  may include a body  702  (e.g., a watch body) and a band  704 . The body  702  may include an input or selection device, such as a crown  706  or a button  708  that are attached to a housing  710  of the body  702 . The band  704  may be attached to the housing  710  and may be used to attach the body  702  to a body part (e.g., an arm, wrist, leg, ankle, or waist) of a user. The body  702  may include a housing  710  that at least partially surrounds a display  712 . In some embodiments, the housing  710  may include a sidewall  714 , which sidewall  714  may support a front cover  716 . The front cover  716  may be positioned over the display  712  and may provide a window through which the display  712  can be viewed. In some embodiments, the display  712  may be attached to (or abut) the sidewall  714  and/or the front cover  716 . In alternative embodiments of the device  700 , the display  712  may not be included and/or the housing  710  may have an alternative configuration. 
     The display  712  may include one or more light-emitting elements including, for example, light-emitting elements that define a light-emitting diode (LED) display, organic LED (OLED) display, liquid crystal display (LCD), electroluminescent (EL) display, or other type of display. In some embodiments, the display  712  may include, or be associated with, one or more touch and/or force sensors that are configured to detect a touch and/or a force applied to a surface of the front cover  716 . 
     In some embodiments, the sidewall  714  of the housing  710  may be formed using one or more metals (e.g., aluminum or stainless steel), polymers (e.g., plastics), ceramics, or composites (e.g., carbon fiber). The front cover  716  may be formed, for example, using one or more of glass, a crystal (e.g., sapphire), or a transparent polymer (e.g., plastic) that enables a user to view the display  712  through the front cover  716 . In some cases, a portion of the front cover  716  (e.g., a perimeter portion of the front cover  716 ) may be coated with an opaque ink to obscure components included within the housing  710 . In some cases, all of the exterior components of the housing  710  may be formed from a transparent material, and components within the device  700  may or may not be obscured by an opaque ink or opaque structure within the housing  710 . 
     The front cover  716  or a back cover (not shown) may be mounted to the sidewall  714  using fasteners, adhesives, seals, gaskets, or other components. 
     A display stack or device stack (hereafter referred to as a “stack”) including the display  712  may be attached (or abutted) to an interior surface of the front cover  716  and extend into an interior volume of the device  700 . In some cases, the stack may include a touch sensor (e.g., a grid of capacitive, resistive, strain-based, ultrasonic, or other type of touch sensing elements), or other layers of optical, mechanical, electrical, or other types of components. In some cases, the touch sensor (or part of a touch sensor system) may be configured to detect a touch applied to an outer surface of the front cover  716  (e.g., to a display surface of the device  700 ). 
     In some cases, a force sensor (or part of a force sensor system) may be positioned within the interior volume below and/or to the side of the display  712  (and in some cases within the device stack). In some cases, the force sensor may include one or more of the capacitive gap force sensors described with reference to  FIGS.  2 A- 2 C,  4 , and  5   . The force sensor (or force sensor system) may be triggered in response to the touch sensor detecting one or more touches on the front cover  716  (or a location or locations of one or more touches on the front cover  716 ), and may determine an amount of force associated with each touch, or an amount of force associated with the collection of touches as a whole. The force sensor (or force sensor system) may alternatively trigger operation of the touch sensor (or touch sensor system), or may be used independently of the touch sensor (or touch sensor system). 
     The device  700  may include various sensors. In some embodiments, the device  700  may have a port  718  (or set of ports) on a side of the housing  710  (or elsewhere), and an ambient pressure sensor, ambient temperature sensor, internal/external differential pressure sensor, gas sensor, particulate matter concentration sensor, or air quality sensor may be positioned in or near the port(s)  718 . 
     In some embodiments, the device  700  may include a capacitive gap force sensor  720 . The capacitive gap force sensor  720  may be constructed as described with reference to any of  FIGS.  2 A- 2 C,  4 , and  5   , and may be positioned to sense a force applied to the button  708  (i.e., with the button  708  providing a force input surface). The sensor  720 , or an additional capacitive gap force sensor, may also or alternatively be positioned elsewhere on the device  700 . 
     In some embodiments, the processor  722  may be configured to change a state of the device  700  in response to a press on the button  708 , a press on the crown  706 , or a rotation of the crown  706 . For example, the processor  722  may change what is displayed on the display  712 , adjust a volume of a local (internal to the device) or remote speaker, activate or deactivate a function or mode of the device  700 , turn the device  700  on or off, and so on. 
       FIG.  8    shows another example of a device  800  (an electronic device) that includes a capacitive gap force sensor  816 . The device&#39;s dimensions and form factor, including the ratio of the length of its long sides to the length of its short sides, suggest that the device  800  is a mobile phone (e.g., a smartphone). However, the device&#39;s dimensions and form factor are arbitrarily chosen, and the device  800  could alternatively be any portable electronic device including, for example a mobile phone, tablet computer, portable computer, portable music player, portable terminal, vehicle navigation system, robot navigation system, or other portable or mobile device. The device  800  could also be a device that is semi-permanently located (or installed) at a single location (e.g., a door lock, thermostat, refrigerator, or other appliance). 
     The device  800  may include a housing  802  that at least partially surrounds a display  804 . The housing  802  may include or support a front cover  806  or a rear cover  808 . The front cover  806  may be positioned over the display  804 , and may provide a window through which the display  804  (including images displayed thereon) may be viewed by a user. In some embodiments, the display  804  may be attached to (or abut) the housing  802  and/or the front cover  806 . 
     The display  804  may include one or more light-emitting elements or pixels, and in some cases may be an LED display, an OLED display, an LCD, an EL display, a laser projector, or another type of electronic display. In some embodiments, the display  804  may include, or be associated with, one or more touch and/or force sensors that are configured to detect a touch and/or a force applied to a surface of the front cover  806 . 
     The various components of the housing  802  may be formed from the same or different materials. For example, a sidewall  818  of the housing  802  may be formed using one or more metals (e.g., stainless steel), polymers (e.g., plastics), ceramics, or composites (e.g., carbon fiber). In some cases, the sidewall  818  may be a multi-segment sidewall including a set of antennas. The antennas may form structural components of the sidewall  818 . The antennas may be structurally coupled (to one another or to other components) and electrically isolated (from each other or from other components) by one or more non-conductive segments of the sidewall  818 . The front cover  806  may be formed, for example, using one or more of glass, a crystal (e.g., sapphire), or a transparent polymer (e.g., plastic) that enables a user to view the display  804  through the front cover  806 . In some cases, a portion of the front cover  806  (e.g., a perimeter portion of the front cover  806 ) may be coated with an opaque ink to obscure components included within the housing  802 . The rear cover  808  may be formed using the same material(s) that are used to form the sidewall  818  or the front cover  806 , or may be formed using a different material or materials. In some cases, the rear cover  808  may be part of a monolithic element that also forms the sidewall  818  (or in cases where the sidewall  818  is a multi-segment sidewall, those portions of the sidewall  818  that are non-conductive). In still other embodiments, all of the exterior components of the housing  802  may be formed from a transparent material, and components within the device  800  may or may not be obscured by an opaque ink or opaque structure within the housing  802 . 
     The front cover  806  may be mounted to the sidewall  818  to cover an opening defined by the sidewall  818  (i.e., an opening into an interior volume in which various electronic components of the device  800 , including the display  804 , may be positioned). The front cover  806  may be mounted to the sidewall  818  using fasteners, adhesives, seals, gaskets, or other components. 
     A display stack or device stack (hereafter referred to as a “stack”) including the display  804  (and in some cases the front cover  806 ) may be attached (or abutted) to an interior surface of the front cover  806  and extend into the interior volume of the device  800 . In some cases, the stack may also include a touch sensor (e.g., a grid of capacitive, resistive, strain-based, ultrasonic, or other type of touch sensing elements), or other layers of optical, mechanical, electrical, or other types of components. In some cases, the touch sensor (or part of a touch sensor system) may be configured to detect a touch applied to an outer surface of the front cover  806  (e.g., to a display surface of the device  800 ). 
     In some cases, a force sensor (or part of a force sensor system) may be positioned within the interior volume below and/or to the side of the display  804  (and in some cases within the stack). In some cases, the force sensor may include one or more of the capacitive gap force sensors described with reference to  FIGS.  2 A- 2 C,  4 , and  5   . The force sensor (or force sensor system) may be triggered in response to the touch sensor detecting one or more touches on the front cover  806  (or indicating a location or locations of one or more touches on the front cover  806 ), and may determine an amount of force associated with each touch, or an amount of force associated with the collection of touches as a whole. 
     The device  800  may include various other components. For example, the front of the device  800  may include one or more front-facing cameras  810  (including one or more image sensors), speakers  812 , microphones, or other components  814  (e.g., audio, imaging, and/or sensing components) that are configured to transmit or receive signals to/from the device  800 . In some cases, a front-facing camera  810 , alone or in combination with other sensors, may be configured to operate as a bio-authentication or facial recognition sensor. 
     The device  800  may also include buttons or other input devices positioned along the sidewall  818  and/or on a rear surface of the device  800 . For example, a volume button or multipurpose button  820  may be positioned along the sidewall  818 , and in some cases may extend through an aperture in the sidewall  818 . In some cases, the button  820  may include one or more of the capacitive gap force sensors described with reference to  FIGS.  2 A- 2 C,  4 , and  5   , or a capacitive gap force sensor  816  may be positioned under a surface (i.e., a force input surface) of the housing  802  or sidewall  818 . The sidewall  818  may in some cases include one or more ports  822  that allow air, but not liquids, to flow into and out of the device  800 . In some embodiments, one or more sensors may be positioned in or near the port(s)  822 . For example, an ambient pressure sensor, ambient temperature sensor, internal/external differential pressure sensor, gas sensor, particulate matter concentration sensor, or air quality sensor may be positioned in or near a port  822 . 
     In some embodiments, the processor  824  may be configured to change a state of the device  800  in response to a press of the button  820  or a press on the capacitive gap force sensor  816 . For example, the processor  824  may change what is displayed on the display  804 , adjust a volume of a local (internal to the device) or remote speaker, activate or deactivate a function or mode of the device  800 , turn the device  800  on or off, and so on. 
       FIG.  9    shows a sample electrical block diagram of an electronic device  900 , which electronic device may in some cases be the device described with reference to one of  FIGS.  6 - 8   . The electronic device  900  may include an optional electronic display  902  (e.g., a light-emitting display), a processor  904 , a power source  906 , a memory  908  or storage device, a sensor system  910 , or an input/output (I/O) mechanism  912  (e.g., an input/output device, input/output port, or haptic input/output interface). The processor  904  may control some or all of the operations of the electronic device  900 . The processor  904  may communicate, either directly or indirectly, with some or all of the other components of the electronic device  900 . For example, a system bus or other communication mechanism  914  can provide communication between the electronic display  902 , the processor  904 , the power source  906 , the memory  908 , the sensor system  910 , and the I/O mechanism  912 . 
     The processor  904  may be implemented as any electronic device capable of processing, receiving, or transmitting data or instructions, whether such data or instructions is in the form of software or firmware or otherwise encoded. For example, the processor  904  may include a microprocessor, a central processing unit (CPU), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a controller, or a combination of such devices. As described herein, the term “processor” is meant to encompass a single processor or processing unit, multiple processors, multiple processing units, or other suitably configured computing element or elements. In some cases, the processor  904  be the processor described with reference to  FIG.  3   . 
     It should be noted that the components of the electronic device  900  can be controlled by multiple processors. For example, select components of the electronic device  900  (e.g., the sensor system  910 ) may be controlled by a first processor and other components of the electronic device  900  (e.g., the electronic display  902 ) may be controlled by a second processor, where the first and second processors may or may not be in communication with each other. 
     The power source  906  can be implemented with any device capable of providing energy to the electronic device  900 . For example, the power source  906  may include one or more batteries or rechargeable batteries, or one or more contacts or housings for contacting or supporting the battery(ies). Additionally or alternatively, the power source  906  may include a power connector or power cord that connects the electronic device  900  to another power source, such as a wall outlet. 
     The memory  908  may store electronic data that can be used by the electronic device  900 . For example, the memory  908  may store electrical data or content such as, for example, audio and video files, documents and applications, device settings and user preferences, timing signals, control signals, and data structures (e.g., instructions) or databases. The memory  908  may include any type of memory. By way of example only, the memory  908  may include random access memory, read-only memory, Flash memory, removable memory, other types of storage elements, or combinations of such memory types. 
     The electronic device  900  may also include a sensor system  910 , including sensors positioned almost anywhere on the electronic device  900 . In some cases, the sensor system  910  may include one or more capacitive gap force sensors, positioned and/or configured as described with reference to any of  FIGS.  2 A- 8   . The sensor system  910  may be configured to sense one or more type of parameters, such as but not limited to, motion; relative motion; vibration; light; touch; force; heat; biometric data (e.g., biological parameters) of a user; air quality; proximity; position; connectedness; matter type; and so on. By way of example, the sensor system  910  may include one or more of (or multiple of) a heat sensor, a position sensor, a proximity sensor, a light or optical sensor (e.g., a light emitter and/or detector), an accelerometer, a pressure transducer, a gyroscope, a magnetometer, a health monitoring sensor, an air quality sensor, and so on. Additionally, the sensor system  910  may utilize any suitable sensing technology, including, but not limited to, interferometric, magnetic, pressure, capacitive, ultrasonic, resistive, optical, acoustic, piezoelectric, or thermal technologies. 
     The I/O mechanism  912  may transmit or receive data from a user or another electronic device. The I/O mechanism  912  may include the electronic display  902 , a touch sensing input surface, a crown, one or more buttons (e.g., a graphical user interface “home” button), one or more cameras (including an under-display camera), one or more microphones or speakers, one or more ports, such as a microphone port, and/or a keyboard. Additionally or alternatively, the I/O mechanism  912  may transmit electronic signals via a communications interface, such as a wireless, wired, and/or optical communications interface. Examples of wireless and wired communications interfaces include, but are not limited to, cellular and Wi-Fi communications interfaces. 
     The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art, after reading this description, that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art, after reading this description, that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20210921
Publication Date: 20230228
Grant Date: 20230228
Priority Date: 20210921
Inventors: BECHSTEIN, DANIEL J.
HARJEE, Nahid
OWENS, TRAVIS N.
Assignee: APPLE INC
CPC Classifications: [{"code": "G01L1/142", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 85289373