PATENT DOCUMENT

Publication Number: US-9781984-B2
Application Number: US-201514691217-A
Country: US
Kind Code: B2

Title: Dynamic fit adjustment for wearable electronic devices

Abstract:
Systems and methods for dynamically adjusting the fit of a wearable electronic device are disclosed. In many embodiments, a tensioner associated with a wearable electronic device can control one or more actuators that are mechanically coupled to either the housing or to a band attached to the wearable electronic device. In one example, in response to a signal to increase the tightness of the band, the tensioner can cause the actuator(s) to increase the tension within the band.

Claims:
We claim: 
     
       1. A method of adjusting a fit of a watch band of a watch, the method comprising:
 receiving, with a processor of the watch, an electronic instruction to obtain biometric data; 
 in response to the receiving, electronically actuating a tensioner coupled to the watch band to increase a tightness of the watch band on a wrist of a user; and 
 after the actuating and with a biometric sensor of the watch, obtaining the biometric data from the wrist of the user. 
 
     
     
       2. The method of  claim 1 , further comprising: after obtaining the biometric data, deactivating the tensioner. 
     
     
       3. The method of  claim 1 , further comprising:
 receiving a user input from an input mechanism; and 
 in response to receiving the user input, generating the electronic instruction. 
 
     
     
       4. The method of  claim 1 , further comprising:
 accessing a user setting; and 
 in response to accessing the user setting, generating the electronic instruction. 
 
     
     
       5. The method of  claim 1 , wherein obtaining the biometric data comprises receiving an output from the biometric sensor. 
     
     
       6. The method of  claim 1 , wherein electronically actuating the tensioner comprises electronically actuating the tensioner to adjust a dimension of the watch band. 
     
     
       7. The method of  claim 1 , wherein electronically actuating the tensioner comprises adjusting a coupling between the watch band and a wearable electronic device connected to the watch band. 
     
     
       8. The method of  claim 1 , wherein electronically actuating the tensioner comprises adjusting, by operation of the tensioner, a coupling between a first portion and a second portion of the watch band. 
     
     
       9. The method of  claim 1 , wherein obtaining the biometric data comprises optically interacting between the biometric sensor and skin of a user. 
     
     
       10. A watch comprising:
 a housing; 
 a processor within the housing; 
 a strap coupled to the housing, the strap configured to hold the housing against a wrist of a user; 
 a tensioner operably coupled to the processor and configured to, in response to an electronic signal from the processor, adjust a tightness of the strap; and 
 a biometric sensor operably coupled to the processor, wherein the processor is configured, in response to receiving an instruction to obtain biometric data, to send a signal to the tensioner to tighten the strap prior to obtaining the biometric data from the biometric sensor. 
 
     
     
       11. The watch of  claim 10 , wherein the biometric sensor obtains the biometric data via optical interaction with skin of the user. 
     
     
       12. The watch of  claim 10 , wherein the strap comprises a material configured to change shape in response to an electronic signal; and
 wherein the tensioner is configured to provide an electronic signal to the material in order to adjust the tightness of the strap. 
 
     
     
       13. The watch of  claim 10 , wherein the tensioner is configured to extend a first portion of the housing outward from a second portion of the housing and toward the user. 
     
     
       14. The watch of  claim 10 , wherein the tensioner is configured to retract a first portion of the housing into a second portion of the housing. 
     
     
       15. The watch of  claim 10 , wherein the processor is configured to receive an instruction to adjust a tightness of the strap from a portable electronic device in communication with the watch. 
     
     
       16. The watch of  claim 10 , further comprising a sensor coupled to the processor and configured to detect motion of the watch; and
 wherein the processor is configured to send a signal to the tensioner to tighten the strap upon receiving an indication of motion from the sensor. 
 
     
     
       17. The watch of  claim 10 , wherein the biometric sensor comprises a temperature sensor, an electrodermal sensor, a blood pressure sensor, a heart rate sensor, a respiration rate sensor, an oxygen saturation sensor, a plethysmographic sensor, a blood glucose sensor, a body weight sensor, a body fat sensor, a blood alcohol sensor, or a dietary sensor. 
     
     
       18. A watch comprising:
 a housing; 
 a watch band connected to the housing and configured to hold the housing against a wrist of a user; 
 a biometric sensor; 
 a tensioner coupled to the watch band; and 
 a processor programmed to:
 receive an electronic instruction to obtain biometric data; 
 in response to the electronic instruction and prior to obtaining the biometric data, send a first signal to the tensioner to adjust a tightness of the watch band; and 
 send a second signal to the biometric sensor to obtain the biometric data. 
 
 
     
     
       19. The watch of  claim 18 , wherein watch band comprises a material configured to change shape in response to an electronic signal; and
 wherein the tensioner is configured to provide an electronic signal to the material in order to adjust the tightness of the watch band. 
 
     
     
       20. The watch of  claim 18 , further comprising a housing, wherein the tensioner is configured to extend a first portion of the housing outward away from a second portion of the housing. 
     
     
       21. The watch of  claim 18 , further comprising a housing, wherein the tensioner is configured to retract a first portion of the housing into a second portion of the housing. 
     
     
       22. The watch of  claim 18 , further comprising a motion sensor coupled to the processor and configured to detect motion of the watch; and
 wherein the processor is configured to send a signal to the tensioner to adjust the tightness of the watch band upon receiving an indication of motion from the motion sensor. 
 
     
     
       23. The watch of  claim 18 , wherein the biometric sensor comprises a temperature sensor, an electrodermal sensor, a blood pressure sensor, a heart rate sensor, a respiration rate sensor, an oxygen saturation sensor, a plethysmographic sensor, a blood glucose sensor, a body weight sensor, a body fat sensor, a blood alcohol sensor, or a dietary sensor. 
     
     
       24. The watch of  claim 18 , wherein the biometric sensor obtains the biometric data via optical interaction with skin of a user.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a nonprovisional patent application of and claims the benefit of U.S. Provisional Patent Application No. 62/129,950, filed Mar. 8, 2015 and titled “Dynamic Adjustment for Wearable Electronic Devices,” the disclosure of which is hereby incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments described herein relate to systems and methods for affixing an electronic device to an object and, more particularly, to systems and methods for dynamic adjustment of the fit of wearable electronic devices. 
     BACKGROUND 
     Some electronic devices may be removably attached to a user. For example, a wristwatch or fitness/health tracking device can be attached to a user&#39;s wrist by joining free ends of a watch band together. 
     In many cases, watch bands may have limited fit adjustment increments available. For example, some bands have an incrementally user-adjustable size (e.g., a buckling clasp, pin and eyelet, etc.) whereas other bands have a substantially fixed size, adjustable only with specialized tools and/or expertise (e.g., folding clasp, deployment clasp, snap-fit clasp, etc.). Still other bands may be elasticated expansion-type bands that stretch to fit around a user&#39;s wrist. 
     In many cases, conventional watch bands may catch, pinch, or pull a user&#39;s hair or skin during use if the band is overly tight. In other cases, watch bands may slide along a user&#39;s wrist, turn about a user&#39;s wrist, or may be otherwise uncomfortable or bothersome to a user if the band is overly loose. These problems can be exacerbated during periods of heightened activity, such as while running or playing sports. Furthermore, adjusting the size or fit of conventional watch bands often requires multiple steps, specialized tools, and/or technical expertise. In other cases, sizing options available to a user may be insufficient to obtain a proper fit. In still further examples, the fit may be different and/or may be perceived to be different given certain environmental (e.g. temperature, humidity) or biological conditions (e.g., sweat, inflammation). As a result, users of conventional wristwatches and/or fitness/health tracking devices may select a tolerable (although not optimally comfortable) fit, reserving tight bands for fitness/health tracking devices and loose bands for conventional wristwatches. 
     However, some wearable electronic devices (such as smart watches) may be multi-purpose devices, providing in one example both fitness/health tracking and timekeeping functionality. Accordingly, a user may prefer the fit of a smart watch to vary with use. For example, a user may prefer a looser fit in a timekeeping mode and a tighter fit in a fitness/health tracking mode. 
     Accordingly, there may be a present need for systems and methods for dynamic adjustment of the fit of wearable electronic devices. 
     SUMMARY 
     Embodiments described herein may relate to, include, or take the form of a method of adjusting the fit of a wearable electronic device secured by a band to a user, the method including at least the operations of receiving a signal with an instruction to adjust the fit of the band, selecting an operational mode (e.g., tightening mode, loosening mode, flexibility mode, rigid mode, etc.) of a tensioner coupled to electronic device, and actuating the tensioner based on the instruction. 
     Further embodiments described herein may relate to, include, or take the form of a method of soliciting attention of a user by adjusting the fit of a wearable electronic device secured to the user by a band, the method including at least the operations of receiving an instruction to solicit attention of the user, and in response, actuating a tensioner coupled to the wearable electronic device to cause an increase in the tightness of the band. 
     Other embodiments described herein may relate to, include, or take the form of a method of restraining a wearable electronic device secured by a strap to a user engaged in physical activity, the method including at least the operations of receiving an indication that the user may be engaged in physical activity, and in response, actuating a tensioner coupled to the wearable electronic device to increase the tightness of the strap. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to representative embodiments illustrated in the accompanying figures. It should be understood that the following descriptions are not intended to limit the disclosure to one preferred embodiment. To the contrary, each is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the described embodiments as defined by the appended claims. 
         FIG. 1A  depicts a perspective view of an example wearable electronic device loosely attached by a band to a user. 
         FIG. 1B  depicts a perspective view of an example wearable electronic device tightly attached by a band to a user. 
         FIG. 2A  depicts a top plan view of an example wearable electronic device with a two-piece band system for attaching to a user. 
         FIG. 2B  depicts a side plan view of an example wearable electronic device with an overlapping two-piece band system for attaching to a user. 
         FIG. 2C  depicts a side plan view of an example wearable electronic device with a mortise-tenon band system for attaching to a user. 
         FIG. 2D  depicts a side plan view of an example wearable electronic device with an interlacing band system for attaching to a user. 
         FIG. 3A  depicts a simplified block diagram of a wearable electronic device. 
         FIG. 3B  depicts a perspective view of an example wearable electronic device depicting a user instructing the wearable electronic to adjust the fit of the band. 
         FIG. 4A  depicts a top plan view of an example wearable electronic device with a two-piece band system configured to contract along its length in response to an electrical signal from a tensioner. 
         FIG. 4B  depicts a top plan view of the example wearable electronic device of  FIG. 4A , showing the two-piece band system in a contracted configuration. 
         FIG. 4C  depicts a top plan view of another example wearable electronic device with a two-piece band system configured to partially contract along its length in response to an electrical signal from a tensioner. 
         FIG. 4D  depicts a side plan view of another example wearable electronic device with a two-piece band system configured to contract along its thickness in response to an electrical signal from a tensioner. 
         FIG. 5A  depicts a top plan view of an example wearable electronic device with a two-piece band system configured to retract into the body of the wearable electronic device in response to an electrical signal from a tensioner. 
         FIG. 5B  depicts a side plan view of the example wearable electronic device of  FIG. 5A  showing a lug-based band attachment system. 
         FIG. 5C  depicts another side plan view of the example wearable electronic device of  FIG. 5A  showing a channel-based attachment system. 
         FIG. 5D  depicts another side plan view of the example wearable electronic device of  FIG. 5A  showing a permanent attachment system. 
         FIG. 6A  depicts a top plan view of an example wearable electronic device with a segmented band system configured to contract along its length in response to an electrical signal from a tensioner. 
         FIG. 6B  depicts a top plan view of the example wearable electronic device of  FIG. 6A , showing the segmented band system in a contracted configuration. 
         FIG. 7A  depicts a top plan view of an example wearable electronic device with a woven band system configured to contract along its length and/or width in response to an electrical signal from a tensioner. 
         FIG. 7B  depicts a detail view of the example wearable electronic device of  FIG. 7A . 
         FIG. 7C  depicts a detail view of the example wearable electronic device of  FIG. 7A , showing the woven band system in a contracted configuration. 
         FIG. 8A  depicts a top plan view of an example wearable electronic device with a two-part band system, each band configured to slide relative to the other band in response to an electrical signal from a tensioner. 
         FIG. 8B  depicts a side plan view of the example wearable electronic device of  FIG. 8A . 
         FIG. 8C  depicts a side plan view of the example wearable electronic device of  FIG. 8A  in a contracted configuration. 
         FIG. 9  depicts a side plan view of an example wearable electronic device with a bracelet-style band system configured to rotate the housing of the wearable electronic device toward or away from a user&#39;s wrist in response to an electrical signal from a tensioner. 
         FIG. 10  depicts a side plan view of an example wearable electronic device with a loop-style band system configured to tighten or loosen the loop in response to an electrical signal from a tensioner. 
         FIG. 11A  depicts a side plan view of an example wearable electronic device with a bladder-style band system configured to increase or decrease pressure within one or more bladders in response to an electrical signal from a tensioner. 
         FIG. 11B  depicts a side plan view of the example wearable electronic device of  FIG. 11A , depicting inflated bladders. 
         FIG. 12A  depicts a side plan view of an example wearable electronic device with another bladder-style band system configured to increase or decrease pressure within one or more bladders in response to an electrical signal from a tensioner. 
         FIG. 12B  depicts a side plan view of the example wearable electronic device of  FIG. 12A , depicting inflated bladders. 
         FIG. 13A  depicts a side plan view of an example wearable electronic device with an extendable housing portion configured to extend toward or retract from a user&#39;s skin in response to an electrical signal from a tensioner. 
         FIG. 13B  depicts a side plan view of the example wearable electronic device of  FIG. 13A , depicting an extended housing portion. 
         FIG. 14A  depicts a side plan view of an example wearable electronic device with an extendable buckle portion configured to extend toward or retract from a user&#39;s skin in response to an electrical signal from a tensioner. 
         FIG. 14B  depicts a side plan view of the example wearable electronic device of  FIG. 14A  depicting an extended buckle portion. 
         FIG. 15A  depicts a side plan view of an example wearable electronic device with another extendable housing portion configured to extend toward or retract from a user&#39;s skin in response to an electrical signal from a tensioner. 
         FIG. 15B  depicts a side plan view of the example wearable electronic device of  FIG. 15A , depicting an extended housing portion. 
         FIG. 16  depicts a top plan view of an example wearable electronic device with another two-piece band system configured to retract toward the body of the wearable electronic device in response to an electrical signal from a tensioner. 
         FIG. 17  depicts a top plan view of an example wearable electronic device with another two-piece band system configured to retract into the body of the wearable electronic device in response to an electrical signal from a tensioner. 
         FIG. 18  depicts a top plan view of an example wearable electronic device with another two-piece band system configured to retract toward the body of the wearable electronic device in response to an electrical signal from a tensioner. 
         FIG. 19A  depicts a top plan view of an example wearable electronic device with another two-piece band system configured to contract along its length in response to an electrical signal from a tensioner or in response to a user input. 
         FIG. 19B  depicts a side plan view of the example wearable electronic device of  FIG. 19A  in a closed configuration. 
         FIG. 20A  depicts a side plan view of an example wearable electronic device with a movable housing configured to move toward or away from a user&#39;s skin in response to an electrical signal from a tensioner. 
         FIG. 20B  depicts a side plan view of the example wearable electronic device of  FIG. 20A , depicting the movable housing in an elevated position. 
         FIG. 21A  depicts a top plan view of an example wearable electronic device with a pin and eyelet and interlacing band system configured such that the pin moves along the longitudinal axis of the band system in response to an electrical signal from a tensioner. 
         FIG. 21B  depicts a side plan view of the example wearable electronic device of  FIG. 21A . 
         FIG. 22  is a flow chart that depicts example operations of a method of tightening the fit of a wearable electronic device. 
         FIG. 23  is a flow chart that depicts example operations of a method of dynamically adjusting the fit of a wearable electronic device. 
         FIG. 24  is a flow chart that depicts example operations of a method of dynamically adjusting the fit of a wearable electronic device prior to obtaining biometric data with a biometric sensor. 
         FIG. 25  is a flow chart that depicts example operations of a method of dynamically adjusting the fit of a wearable electronic device as a means of soliciting a user&#39;s attention. 
         FIG. 26  is a flow chart that depicts example operations of a method of dynamically adjusting the fit of a wearable electronic device in response to heightened user activity. 
     
    
    
     The use of the same or similar reference numerals in different drawings can indicate similar, related, or identical items. 
     DETAILED DESCRIPTION 
     Embodiments described herein relate to systems and methods for dynamic adjustment of the fit of wearable electronic devices. It should be appreciated that the various embodiments described herein, as well as functionality, operation, components, and capabilities thereof may be combined with other elements, embodiments, structures and the like, and so any physical, functional, or operational discussion of any element or feature is not intended to be limited solely to a particular embodiment to the exclusion of others. 
     As noted above, many portable electronic devices may be removably attached to a user. In some examples, a heart rate sensor may be attached to a user&#39;s chest by a strap. In another example, a portable audio player may be secured to a user&#39;s arm by inserting the player into an armband case. In another example, a wearable electronic device such as a smart watch or a fitness device can be attached to a user&#39;s wrist by joining free ends of a conventional watch band together. In other examples, a clasp or an elasticated band may be used to secure the wearable electronic device. 
     Although many embodiments are described herein with reference to wrist bands for attaching a wrist-worn electronic device to a user, one may appreciate that other form factors may be favored in other embodiments. In other words, the methods, systems, and techniques described herein with illustrative reference to wrist-worn devices may be equally applied to non-wrist worn devices. For example, in other embodiments, devices may be configured to attach to other limbs or body portions (e.g., necklaces, arm bands, waistbands, ear hooks, finger rings, anklets, toe rings, chest wraps, head bands, etc.). Furthermore, other embodiments described herein may be applied to dynamically adjust the fit of an electronic device to a non-user object such as a charging stand or station. In other embodiments, an electronic device can be fit to another biological subject such as an animal (e.g., pet collar). 
     As noted above, many conventional watch bands may be uncomfortable, painful, or bothersome if improperly fit to a user. For example, a user&#39;s skin and/or hair may be pinched or pulled if a conventional watch band is improperly fit. In another example, a user may be irritated by a watch that slides up and down a user&#39;s wrist and/or rotates about the user&#39;s wrist during use. 
     In other cases, the fit of a conventional watch band may be different and/or may be perceived to be different given different situations. For example, in humid conditions, the fit of a band may be perceived to be tighter. In another example, a user who is sweating may perceive the fit of a band to be looser. In many cases, these problems can be exacerbated during periods of heightened activity, such as while running or playing sports. 
     Despite the prevalence of issues associated with improperly fit bands, adjusting the size or fit of conventional watch bands often requires multiple steps, specialized tools, and/or technical expertise. For example, a metal link band may require specialized tools to remove one or more links of the band to resize the band. In other cases, a leather band with a deployment clasp may need to be physically cut to size in order to resize the band. 
     In other cases, watch bands may have limited fit adjustment increments available. For example, a conventional watch band may space sizing eyelets approximately 8 mm apart. In some cases, a user may prefer a fit corresponding to a location between two eyelets. In some examples, especially for users having relatively small wrists, an error of ±4 mm (e.g., example of error halfway between “too tight” and “too loose”) can correspond to an error upwards of ±5% of the circumference of that user&#39;s wrist, which, for many users, may be intolerable. 
     As a result, users of conventional wristwatches and/or fitness/health tracking devices may select a tolerable (although not optimally comfortable) fit, reserving tighter bands for fitness/health tracking devices and looser bands for conventional wristwatches. 
     However, as noted above, some wearable electronic devices, such as smart watches, may be multi-purpose devices. For example, many smart watches provide both fitness/health tracking and timekeeping functionality. Thus, many users may wear a smart watch exclusively, instead of periodically switching between wearing a traditional wristwatch and a separate fitness/health tracking device. In these examples, a user may prefer the fit of a smart watch to vary with use. For example, a user may prefer a looser fit in a timekeeping mode and a tighter fit in a fitness/health tracking mode. 
     As may be appreciated, the inconvenience associated with repeated resizing and reattachment of a conventional watchband may contribute to diminishing use of a wearable electronic device, which may, in turn, precipitate a customer retention problem for the manufacturer thereof. In other examples, such as for wearable electronic devices configured to collect health-related information (e.g., pulse rate, blood oxygen saturation, blood pressure, insulin levels, etc.) or to provide health-related notifications (e.g., prescription timing reminders, medical alerts, medical identification numbers, etc.), discontinued use of the wearable electronic device may lead to more serious consequences such as health problems, medical emergencies, and/or incomplete or inconsistent medial data collection. 
     Accordingly, many embodiments described herein relate to systems and methods for dynamic adjustment of the fit of the wearable electronic devices. 
     For example, certain embodiments described herein take the form of methods for adjusting the fit of a wearable electronic device secured by a band to a user, the method including the operations of receiving a signal with an instruction to adjust the fit of the band, selecting an operational mode (e.g., tightening mode, loosening mode, flexibility mode, rigid mode, etc.) of a tensioner coupled to electronic device, and actuating the tensioner based on the instruction. 
     In some embodiments, the signal received in the course of operating methods described herein may be generated within the wearable electronic device itself. For example, a wearable electronic device such as a smart watch may periodically adjust its own fit. In other examples, the wearable electronic device can generate the signal in response to input from a user. For example, a user can provide input to a touch screen of the wearable electronic device to indicate to the wearable electronic device the user&#39;s desire for the fit of the device to change, either with increased tightness or decreased tightness. 
     In another example, the signal received may be generated by a secondary electronic device in communication with the wearable electronic device. For example, in some embodiments, a personal cellular phone in communication with a wearable electronic device can provide a signal to the wearable electronic device to adjust the fit thereof. In still further embodiments, the signal received may be generated by a network device such as a server. In these examples, the server in communication with the wearable electronic device can provide a signal to the wearable electronic device to adjust the fit thereof. 
     In many cases, the instruction associated with the signal received in the course of operating methods described herein may include one or more values that correspond to a mode with which the fit of the wearable electronic device should be changed. For example, in some embodiments, the instruction can include a value or pointer (e.g., selection bit, function name, etc.) that indicates the tightness of the fit of the wearable electronic device should increase, corresponding to a tightening mode. In another example, the instruction can include a value or pointer that indicates the tightness of the fit of the wearable electronic device should decrease, corresponding to a loosening. 
     In further examples, the instruction can also include a value or pointer corresponding to an amount or magnitude of change, either relative or absolute. For example, an instruction as described above can include a value or pointer indicating that the fit should be changed by 5%. In another example, an instruction as described above can include a value or pointer indicating that the fit should be changed by shortening a band by 1 mm. In another example, an instruction as described above can include a value or pointer indicating that the fit should be changed by extending a portion of the housing of the wearable electronic device by 3 mm. In another example, an instruction as described above can include a value or pointer indicating that the fit should be change by applying a force of 0.1 Newtons to the band. In other embodiments, other values and/or pointers may be used. 
     In further examples, the instruction can include a value or pointer corresponding to a threshold of change. For example, an instruction as described above can include a value or pointer indicating that the fit should be changed by extending a portion of the housing of the wearable electronic device until the portion comes into contact with the user&#39;s skin and applies pressure of 1,000 N/m 2  (e.g., 0.15 psi). In other embodiments, other threshold values and/or pointers may be used. 
     In many cases, and as described above, the instruction may be subdivided into multiple parts (or subcomponents) including, in some examples, a mode, a magnitude, and/or a threshold. In this manner, a variety of functions can be performed. For example, a band can tighten or loosen without a target (e.g., “become generally tighter” or “become generally looser”), can tighten or loosen by an increment (e.g., “become X tighter” or “become X looser”), can tighten or loosen until a threshold is reached (e.g., “become tighter until” or “become looser until”), apply a specific value of greater or less tightness (e.g., “apply tightness X”), apply a tightness or looseness as a function of time (e.g., “become tighter for 1 second, then loosen”). 
     As noted above, a tensioner can be coupled to the wearable electronic device. In many cases, a tensioner can be an analog, digital, or integrated circuit configured to apply an electrical signal to cause tension (either directly or indirectly) to be applied to, or relieved form, the band. In other cases, a tensioner can be a physical apparatus such as a motor, electromagnetic coil, or solenoid that can be actuated to cause tension (either directly or indirectly) to be applied to, or relieved form, the band. Accordingly, the term “tensioner” and related phrases and terminology is used herein to generally refer to a circuit, apparatus, controller, or program code executed by a processor, that is configured to cause, either directly or indirectly, tension in a band or strap coupled to an electronic device housing to increase or decrease. 
     In some examples, a tensioner associated with and/or coupled to the wearable electronic device can also be coupled to a portion of the band that is configured to compress in response to an electrical signal. For example, a shape memory wire such as Nitinol can be formed in a longitudinal serpentine pattern within one or more portions of a band. The tensioner can increase a current (or voltage) applied to the Nitinol in response to an instruction to increase the tightness of the band or can decrease a current (or voltage) applied to the Nitinol in response to an instruction to decrease the tightness of the band. In response to the increase or decrease in the length of the longitudinal and serpentine Nitinol, the band can experience an increase or decrease in length which, in turn, can cause an increase or decrease the tightness of the fit of the band. 
     In other examples, Nitinol can be formed in a serpentine pattern through the thickness or width of one or more portions of a band. In these embodiments, the tensioner can increase a current (or voltage) applied to the Nitinol in response to an instruction to decrease the tightness of the band and, correspondingly, can decease a current (or voltage) applied to the Nitinol in response to an instruction to increase the tightness of the band. In response to the increase or decrease in the width and/or thickness of the band, the band can experience a respective decrease or increase in length which, in turn, decreases or increases the tightness of the fit of the band. 
     In some examples, one or more portions of a band can include a bladder in communication with a pump or actuator disposed within the housing of the wearable electronic device. The tensioner may be configured to control the pressure applied by the pump to a fluid in communication with the bladder. In some cases the fluid can be a gas or a liquid. For example, in some embodiments, air can be used as the fluid in communication with the bladder. In other cases, a liquid with a low viscosity such as oil or water can be used as the fluid in communication with the bladder. In these embodiments, the tensioner can increase the pressure applied by the pump to the fluid in response to an instruction to increase the tightness of the band or can decrease the pressure applied by the pump in response to an instruction to decrease the tightness of the band. In response to the increase or decrease in pressure, the bladder can experience an increase or decrease in volume, which, in turn, increases or decreases the tightness of the band. 
     In another embodiment, the tensioner can be connected to a coupling that joins the band at one or more points to the housing of the wearable electronic device. In some examples, the coupling can be a lug that extends from the housing of the wearable electronic device. In such an embodiment, the tensioner can withdraw the coupling into the housing of the wearable electronic device in response to an instruction to increase the tightness of the band or can extend the coupling from the housing of the wearable electronic device in response to an instruction to decrease the tightness of the band. 
     In another embodiment, the tensioner can be connected to an extendable portion of the housing of the wearable electronic device oriented to extend toward (or retract from) the user&#39;s skin. For example, in certain embodiments the extendable portion can extend toward a user&#39;s wrist or, in other examples, the extendable portion can retract from the user&#39;s wrist. In such an embodiment, the tensioner can extend the extendable portion in response to an instruction to increase the tightness of the band or can withdraw the extendable portion into the housing of the wearable electronic device in response to an instruction to decrease the tightness of the band. 
     In other embodiments, the tensioner may be coupled to, or configured to control the operation of, one or more mechanisms, components, or apparatuses capable to reduce or increase one or more dimensions of the band. For example, in some cases, the tensioner can be coupled to an apparatus capable to increase or decrease the length of the band. In another example, the tensioner can be coupled to an apparatus capable to increase or decrease the thickness of the band. In other examples, the tensioner can be coupled to an apparatus capable to increase or decrease the width of the band. In still further examples, the tensioner can be coupled to an apparatus capable to increase or decrease the rigidity of the band. 
     In other embodiments, the tensioner may be coupled to, or configured to control the operation of, one or more mechanisms, components, or apparatuses capable to reduce or increase one or more dimensions of the housing of the wearable electronic device. For example, as noted above, in some cases the tensioner can be coupled to an extendable portion that can extend toward or retract from a user&#39;s skin. In other examples, the tensioner can be coupled to a portion of the wearable electronic device housing that is configured to couple to the band itself. For example, as noted above, the tensioner of some embodiments can be coupled to an apparatus capable to withdraw into the housing of the wearable electronic device and also configured to extend from the housing of the wearable electronic device. In still further embodiments, alternative tensioner, band, and/or housing configurations, topologies, and interactions are contemplated. 
     For example, some embodiments may include a configuration in which the instruction received in the course of operating methods described herein may be based on a user input to the wearable electronic device. For example, a user may provide input to the wearable electronic device via one or more input mechanisms such as a touch screen to indicate the user&#39;s preference for the fit of the wearable electronic device to tighten. In other examples, a user can provide input to the wearable electronic device to indicate the user&#39;s preference for the fit of the wearable electronic device to loosen. 
     Still further embodiments may include a configuration in which the instruction received in the course of operating methods described herein may be based on a user setting accessible to the wearable electronic device. For example, in some cases the wearable electronic device may access a secondary portable electronic device, a remote server, or a memory within the wearable electronic device itself to obtain an indication of a user&#39;s preference for the fit of the wearable electronic device. In some cases, a wearable electronic device can query a portable electronic device in communication therewith for a value corresponding to a user&#39;s preference for the tightness of the fit of the wearable electronic device. After obtaining the value from the portable electronic device, the wearable electronic device can provide the value to the tensioner in order to obtain or maintain the user&#39;s preferred fit. 
     Still further embodiments may include a configuration in which the instruction received in the course of operating methods described herein may be based on an output from a sensor in communication with the wearable electronic device. For example, in some embodiments, the wearable electronic device can include a tension sensor that can be configured to obtain a measurement or an approximation of the tightness of the band. In response to a tightness measurement above a selected threshold, the tension sensor can provide a signal to the wearable electronic device that the wearable electronic device can provide to the tensioner in order to loosen the fit of the band. Conversely, in response to a tightness measurement below a selected threshold, the tension sensor can provide a signal to the wearable electronic device that the wearable electronic device can provide to the tensioner in order to tighten the fit of the band. In still further examples, in response to a tightness measurement between selected thresholds, the tension sensor can provide a signal to the wearable electronic device that the wearable electronic device can use to determine that an adjustment of the fit of the wearable electronic device is not required. 
     Still further embodiments may include a configuration in which the instruction received in the course of operating methods described herein may be based on an operational state of the wearable electronic device. For example, if a wearable electronic device is operated in a fitness mode, the tensioner can tighten the band to fit more snugly about the user&#39;s wrist. In other examples, if a wearable electronic device is operated in a non-fitness mode, the tensioner can loosen the band. 
     Still further embodiments may include a configuration in which the instruction received in the course of operating methods described herein may be based on an operational state of a biometric sensor in communication with the wearable electronic device. For example, some biometric sensors may obtain more accurate or precise biometric data if said biometric sensor is positioned within a certain distance of a user&#39;s skin. 
     For example, a photoplethysmographic (“PPG”) sensor may obtain more accurate and precise volumetric data if positioned in close proximity to a user&#39;s skin. In these embodiments, a biometric sensor in communication with the wearable electronic device may request an increase in tightness of the fit of the wearable electronic device prior to obtaining data. Similarly, after obtaining biometric data, the biometric sensor may request to return the fit of the wearable electronic device to the user&#39;s preferred fit. 
     In many cases, other embodiments described herein relate to methods of using a wearable electronic device having a dynamically adjustable fit. For example, some embodiments described herein relate to a method of soliciting attention (e.g., notifying by providing haptic output) of a user by adjusting the fit of a wearable electronic device secured to the user by a band. The method can begin by receiving an instruction to solicit attention of the user of some event, condition, data, or other information, and in response, actuate a tensioner coupled to the wearable electronic device to cause an increase in the tightness of the band. For example, a user may desire to be notified of an incoming email message. Upon receiving an indication that a new email message is received (or is being received), the wearable electronic device can increase the tightness of the band so as to quietly and discretely notify the user of the message. 
     In other cases, embodiments described herein relate to other methods of using a wearable electronic device having a dynamically adjustable fit. For example, a wearable electronic device can be used to provide haptic feedback for a cinema patron or a video game participant. In other examples, a wearable electronic device can be connected to home automation equipment. In such a case, a user may receive a notification of a knock on the front door via a tightening of the wearable electronic device. In another case, a user may receive a notification of a crying child in another room via a tightening of the wearable device. 
     In still other examples, a wearable electronic device having a dynamically adjustable fit can be used as an authentication device in a two-factor authentication system. For example, if a user wishes to access financial details hosted on a banking website, the banking website may require both the user&#39;s credentials and a verification of a number of tightening-loosening patterns sent to a wearable electronic device previously authenticated by the banking website. For example, a user can enter the user&#39;s credentials (e.g., username and password). Thereafter, the banking website can send a tactile pattern to a wearable electronic device previously authenticated by the banking website. In one example, a tactile pattern may be a series of five squeezes of the user&#39;s wrist (e.g., tighten and loosen in sequence). The user may thereafter enter “5” to gain access to the banking website. 
     In another embodiment, the wearable electronic device may be operated in a fitness/health tracking mode. In these embodiments, the wearable electronic device may tighten the fit of the band to count repetitions while the user is weight lifting. In another embodiment the wearable electronic device may tighten the fit of the band to notify a running user of certain distance intervals (e.g., every kilometer). In another embodiment, the wearable electronic device may notify a swimmer of an upcoming turn. 
     In still further embodiments, the wearable electronic device, operating as a navigation assistant, may tighten the fit of the band to notify a user to turn a certain direction. In these embodiments, the wearable electronic device can tighten a right portion of a band to indicate a right turn and can tighten a left portion of a band to indicate a left turn. In other embodiments, the wearable electronic device can tighten a band in order to wake a user from sleep. In another embodiment, the electronic device can tighten based on the user&#39;s geographic location. For example, if a user arrives at a fitness center, the wearable electronic device can tighten. Upon leaving the fitness center, the wearable electronic device can loosen. 
     Also described herein are methods of restraining a wearable electronic device secured by a strap to a user engaged in physical activity. For example, upon receiving an indication that the user may be engaged in physical activity (e.g., via output from a motion and/or acceleration sensor), a wearable electronic device can actuate a tensioner coupled to the wearable electronic device to increase the tightness of the strap. In one example, when a user begins a physical activity such as running, the wearable electronic device can respond by tightening around the user&#39;s wrist in order to prevent undesirable motion of the wearable electronic device about or along the user&#39;s wrist. 
     In many cases, other embodiments described herein relate to methods of using one or more wearable electronic devices having a dynamically adjustable fit as accessibility tools. For example, a user with sight impairment may operate a wearable electronic device as a means for discretely navigating an unknown environment. For example, a sight-impaired user may receive a notification via tightening of the wearable electronic device if the sight-impaired user is approaching an obstacle. In other examples, a hearing-impaired user may be notified when a loud sound is present of which the hearing-impaired user may not be aware (e.g., knock at a door). In other embodiments, a wearable electronic device such as described herein can provide compression therapy for a user with venous disorders. In some embodiments, a wearable electronic device such as described herein can be used as an emergency immobilization cuff, tightening around an injury to prevent movement or blood loss. 
       FIG. 1A  depicts a perspective view of an example wearable electronic device loosely attached by a band to a user. In the illustrated embodiment, the wearable electronic device  100  is implemented as a portable electronic device that is worn on the wrist of a user  102 . Other embodiments can implement the wearable electronic device differently. For example, the wearable electronic device can be a smart phone, a gaming device, a digital music player, a sports accessory device, a medical device, navigation assistant, accessibility device, a device that provides time and/or weather information, a health assistant, and other types of electronic device suitable for attaching to a user. 
     The wearable electronic device  100  includes a housing  104  and a display  106 . In many examples, the display  106  may incorporate an input device configured to receive user input. For example, a user can provide input to the display  106  to indicate the user&#39;s intention to increase the tightness of the fit of the wearable device. In other examples, the user can provide a force input to the display  106 , the magnitude of which can correspond to the magnitude of tightness increase in the fit the user desires to be implemented by the wearable electronic device  100 . 
     The housing  104  can form an outer surface or partial outer surface and protective case for one or more internal components of the wearable electronic device  100 . In the illustrated embodiment, the housing  104  is formed into a substantially rectangular shape, although this configuration is not required and other shapes are possible in other embodiments. 
     The housing  104  can be formed of one or more components operably connected together, such as a front piece and a back piece or a top clamshell and a bottom clamshell. Alternatively, the housing  104  can be formed of a single piece (e.g., uniform body or unibody). 
     The display  106  can be implemented with any suitable technology, including, but not limited to, a multi-touch sensing touchscreen that uses liquid crystal display (LCD) technology, light emitting diode (LED) technology, organic light-emitting display (OLED) technology, organic electroluminescence (OEL) technology, or another type of display technology. In many embodiments, the display  106  can have a resolution beyond 200 pixels per inch. In many embodiments, the display  106  can be disposed below a protective cover glass formed from a rigid and scratch resistant material such as ion-implanted glass, laminated glass, or sapphire. 
     As noted above, the display  106  can incorporate or be disposed proximate to an input sensor. For example, in some embodiments, the display  106  can also include one or more contact sensors to determine the position of one or more contact locations on a top surface of the display  106 . For example, a contact sensor (such as a touch sensor or touch sensor array) can detect the location of one or more objects engaging the display  106 , such as a stylus or a user&#39;s finger. In certain embodiments, a contact sensor can monitor an electrical property, such as conductance or capacitance. Upon detecting that the electrical property has changed at a location or area of the display  106 , the contact sensor can report that an object is contacting the input surface at the specified location or area. In many cases, contact sensors may report the locations of all objects engaging the input surface. For example, a contact sensor may report two independent contact locations when a user positions two fingers on the display  106 . 
     In some embodiments, the display  106  can also include one or more force-sensitive elements (not shown) to detect a magnitude of force applied to the top surface of the display  106 . In some examples, the force-sensitive elements can be mechanically coupled to the underside of the display  106 . In other examples, force-sensitive elements can be disposed around the perimeter of the display  106 . 
     A force-sensitive element associated with the display  106  may be formed from a material or formed into a structure, such that upon application of a force (e.g., compression, expansion, tension, strain), one or more electrical properties of the material or structure can measurably change. Force-sensitive electrical properties can include conductance, accumulated charge, inductance, magnetic field strength, electrical field strength, capacitance, and so on. For example, a force-sensitive element formed from a piezoelectric material can accumulate charge in response to an applied force. In another example, a force-sensitive element can be formed as a structure (such as a number of layered materials) having a capacitance that measurably varies with force. In another example, a force-sensitive element can be formed from a strain-sensitive material that may measurably change in conductance (e.g., resistance) in response to a force. In these and some embodiments, a known relationship (e.g., linear, exponential, and so on) between the electrical property or properties and force applied can be used to determine an amount of force applied to display  106 . 
     The wearable electronic device  100  can include within the housing  104  a processor, a memory, a power supply and/or battery, network communications, sensors, display screens, acoustic elements, input/output ports, haptic elements, digital and/or analog circuitry for performing and/or coordinating tasks of the wearable electronic device  100 , and so on. In some examples, the wearable electronic device  100  can communicate with a separate electronic device via one or more proprietary and/or standardized wired and/or wireless interfaces. For simplicity of illustration, the wearable electronic device  100  is depicted in  FIG. 1A  without many of these elements, each of which may be included, partially, optionally, or entirely, within the housing  104 . 
     The wearable electronic device  100  can be coupled to the user  102  via a band  108  that loops around the user&#39;s wrist. The band  108  can be formed from a compliant material, or into a compliant structure, that is configured to easily contour to a user&#39;s wrist, while retaining stiffness sufficient to maintain the position and orientation of the wearable electronic device on the user&#39;s wrist. The material selected for the band  108  may vary from embodiment to embodiment. For example, in certain cases, the band  108  can be formed from metal, such as a band formed into a metal mesh. In other embodiments, the band  108  can be formed from an organic material such as leather. In further examples, the band  108  can be formed from an inorganic material such as nylon. In still further embodiments, materials such as plastic, rubber, or other fibrous, organic, polymeric, or synthetic materials may be used. 
     As can be appreciated, the relative stiffness of a band can impact the tightness with which the band may be fit to a user&#39;s wrist. For example, the more flexible the band  108 , the tighter the band should be secured to prevent the wearable electronic device  100  from sliding, rotating, or otherwise displacing on the user&#39;s wrist. 
     In some embodiments, the band  108  can be formed from a polymer, such as a fluoroelastomeric polymer, having a Shore durometer selected for having flexibility suitable for easily contouring to a user&#39;s wrists while maintaining sufficient stiffness to maintain support of the wearable electronic device  100  when attached to the wrist of user  102 . For example, bands of certain embodiments may have a Shore A durometer ranging from 60 to 80 and/or a tensile strength greater than 12 MPa. 
     In some embodiments, a fluoroelastomeric polymer (or other suitable polymer) can be doped or treated with one or more other materials. For example, the polymer can be doped with an agent configured to provide the polymer with a selected color, odor, taste, hardness, elasticity, stiffness, reflectivity, refractive pattern, texture and so on. In other examples, the doping agent can confer other properties to the fluoroelastomeric polymer including, but not necessarily limited to, electrical conductivity and/or insulating properties, magnetic and/or diamagnetic properties, chemical resistance and/or reactivity properties, infrared and/or ultraviolet light absorption and/or reflectivity properties, visible light absorption and/or reflectivity properties, antimicrobial and/or antiviral properties, oleophobic and/or hydrophobic properties, thermal absorption properties, pest repellant properties, colorfast and/or anti-fade properties, deodorant properties, antistatic properties, medicinal properties, liquid exposure reactivity properties, low and/or high friction properties, hypoallergenic properties, and so on. 
     In some embodiments, one or more doping agents may be used. In further embodiments, the doping agents associated with one area of the band  108  may be different from the doping agents associated with another area of the bands. In one example, a band may have a low friction dopant added to the portion of a band that faces a user&#39;s wrist (e.g., bottom surface) while having a high reflectivity dopant added to the portion of the band that faces outwardly (e.g., top surface). 
     In some embodiments, one or more doping agents may be used to intentionally increase the elasticity of one or more portions of the band  108 . For example, in some embodiments, a band  108  may include a compressible region having a greater elasticity than other regions of the band  108 . This region can be configured to compress in response to an electrical signal from the wearable electronic device  100 . In other examples, the compressible region can also be configured to expand in response to an electrical signal from the wearable electronic device  100 . 
     In some examples, more than one compressible region can be used. In these cases, the several compressible regions of the band  108  can be independently, sequentially, or simultaneously compressed or expanded in response to an electrical signal from the wearable electronic device. 
     In some embodiments, as noted above, the compressible regions can be formed via doping the material selected for the band  108  with a dopant that increases the elasticity and/or compressibility of that selected region. In other examples, the compressible region(s) can be formed by hollowing a portion of the band  108 . In other examples, the compressible region(s) can be formed by partially thinning a portion of the band  108 . In still further examples, the compressible region(s) can be formed by causing macroscopic, microscopic, or nanoscopic pockets to form within the band  108 . For example, in one embodiment, pockets of gas can be injected into a portion of the band. In another example, a portion of the band  108  can be intentionally weakened by microscopic perforations (e.g., via laser and/or water jet). In still further embodiments, a portion of the band can be formed as a foam, including many nano or microscopic cavities. 
     Other embodiments described herein include configurations in which the band  108  is formed from a non-compliant material into a compliant structure. For example, a metallic mesh can be used to form band  108 . In other embodiments, the band can be formed by joining a number of metal links. In other embodiments, the band can be formed by joining a number of glass or crystal links. 
     In other embodiments, the band  108  can be formed form a combination of complaint and non-compliant materials. 
     In many examples, the band  108  can be removably coupled to the housing  104 . For example, in certain embodiments, the band  108  can be at least partially looped around a watch pin that is configured to insert within lugs extending from the body of the housing  104 . In other examples, the band  108  can be configured to slide within and be retained by two or more channels within external sidewalls of the housing  104 . In other examples, the band  108  can be looped through and aperture in the housing  104 . In other cases, the band  108  can be riveted, screwed, or otherwise attached to the housing  104  via one or more mechanical fasteners. In still further embodiments, additional removable couplings between the band  108  and the housing  104  are possible. 
     In other examples, the band  108  can be permanently coupled to the housing  104 . For example, in some cases, the band  108  may be formed as an integral portion of the housing  104 . In other cases, the band  108  can be rigidly adhered to the housing  104  via an adhesive. In still further embodiments, the band  108  can be welded, soldered, or chemically bonded to the housing  104 . In other embodiments, additional permanent couplings between the band  108  and the housing  104  are possible. 
     As noted above, the housing  104  may be rigid and can be configured to provide structural support and impact resistance for electronic or mechanical components contained therein. A rigid housing is not necessarily required for all embodiments and, in some examples, the wearable electronic device  100  can have a housing may be flexible. Furthermore, although wearable electronic device housings are typically formed to take a rectangular shape, this is not required and other shapes are possible. For example, certain housings may take a circular shape. 
     In other embodiments, the wearable electronic device  100  can include one or more sensors (not shown) positioned on a bottom surface of the housing  104 . Sensors utilized by the wearable electronic device  100  can vary from embodiment to embodiment. Suitable sensors can include temperature sensors, electrodermal sensors, blood pressure sensors, heart rate sensors, respiration rate sensors, oxygen saturation sensors, plethysmographic sensors, activity sensors, pedometers, blood glucose sensors, body weight sensors, body fat sensors, blood alcohol sensors, dietary sensors, and so on. 
     In many cases, sensors such as biometric sensors can collect certain health-related information non-invasively. For example, the wearable electronic device  100  can include a sensor that is configured to measure changes in (or an amount of) light reflected from a measurement site (e.g., wrist) of the user  102 . In one embodiment, the biometric sensor such as a PPG sensor can include a light source for emitting light onto or into the wrist of the user  102  and an optical sensor to detect light exiting the wrist of the user  102 . Light from the light source may be scattered, absorbed, and/or reflected throughout the measurement sight as a function of various physiological parameters or characteristics of the user  102 . For example, the tissue of the wrist of the user  102  can scatter, absorb, or reflect light emitted by the light source differently depending on various physiological characteristics of the surface and subsurface of the user&#39;s wrist. 
     In many cases a PPG sensor can be used to detect a user&#39;s heart rate and blood oxygenation. For example, during each complete heartbeat, a user&#39;s subcutaneous tissue can distend and contract, alternatingly increasing and decreasing the light absorption capacity of the measurement site. In these embodiments, the optical sensor of the PPG can collect light exiting the measurement site and generate electrical signals corresponding to the collected light. Thereafter, the electrical signals can be conveyed as raw data to the wearable electronic device  100 , which in turn can process the raw data into health data  110 . The raw data can be based on information about the collected light, such as the chromaticity and/or luminance of the light. In some cases, the health data  110  can be shown on the display  106  as biometric feedback to the user  102 . 
     However, certain sensors such as PPG sensors may be susceptible to noise associated with ambient light, surface conditions of the measurement site (e.g., cleanliness, hair, perspiration, etc.), proximity of the optical sensor and/or light source to the measurement site, and motion artifacts caused by the relative motion between the wearable electronic device  100  and the user  102 . As a result, if the wearable electronic device  100  is not snugly fit to the user  102  (at least while the PPG sensor is obtaining a measurement), for example as illustrated in  FIG. 1A , the health data  110  obtained from the sensor may be sub-optimal (e.g., insufficient or insignificant magnitude) as a direct result of the improper fit. Alternatively, if the wearable electronic device  100  is snugly fit to the user  102 , for example as illustrated in  FIG. 1B , the health data  110  obtained from the sensor may be of substantially improved quality, magnitude, and clarity. 
     Although  FIGS. 1A-1B  are sequentially illustrated to show an improvement in the quality of health data  110  obtained by tightening the band  108 , one can appreciate that in certain embodiments, the wearable electronic device  100  may dynamically resize the band  108  and/or the fit of the wearable electronic device  100  for reasons unrelated to sensor data quality. 
     For example, as mentioned above, a tensioner (not shown) can be coupled to the wearable electronic device  100 . In some examples, the tensioner can be included within the housing  104 . In other examples, the tensioner can be included within the band  108 . In still further examples, a portion of the tensioner can be included within the housing  104  and a portion of the tensioner can be included within the band  108 . In some examples, the tensioner can be coupled to the band  108  and to the housing  104 . For example, the tensioner can take the form of a coupling and/or a lug by which the band  108  couples to the housing  104 . 
     In many cases, a tensioner can be an analog, digital, or integrated circuit configured to apply an electrical signal to cause tension (either directly or indirectly) to be applied to, or relieved form, the band  108 . In other cases, a tensioner can be a physical apparatus such as a motor, electromagnetic coil, or solenoid that can be actuated to cause tension (either directly or indirectly) to be applied to, or relieved form, the band  108 . 
     For example, in some embodiments, a tensioner can apply an electrical current or voltage to an element that contracts or expands in the presence of an electrical current (e.g., piezoelectric materials, memory wire, electroactive polymers, etc.). In other examples, the tensioner can apply a current to an electromagnetic coil positioned proximate to a ferromagnetic material within the band. An increase in the current applied to the electromagnetic coil can cause a corresponding increase in the magnetic flux produced and, thus, an increase in the attractive force between the coil and the ferromagnetic material. In other embodiments, a permanent magnet can be disposed within the band such that the electromagnetic coil can be actuated to either repel or attract the permanent magnet. In still further examples, the tensioner can be implemented as a motor geared to a worm gear that either extends or retracts the band. In other examples, the tensioner can be implemented as a linear actuator. In other examples, the tensioner can be implemented as a fluid control system that is configured to increase or decrease the pressure and/or volume of a fluid within a particular portion of the band  108  or the housing  104 . In other embodiments, the tensioner can be implemented as a combination of cooperating systems. 
       FIG. 2A  depicts a top plan view of an example wearable electronic device  200  with a two-piece band system for attaching to a user. The wearable electronic device  200  can include a tensioner (not illustrated) in order to provide dynamic adjustment of the fit of the wearable electronic device  200 . As with other embodiments described herein, the tensioner may alter the fit of the wearable electronic device  200  in a number of ways. For example, the tensioner can adjust one or more dimensions of a band coupled to the wearable electronic device. In another example, the tensioner can adjust a coupling between a band and the wearable electronic device. In another example the tensioner can adjust the position of the housing of the wearable electronic device relative to the band. In still other embodiments, other adjustments are possible. 
     In the illustrated embodiment, the wearable electronic device  200  is implemented as a portable electronic device that is adapted to be worn by a user, such as shown in  FIGS. 1A-1B . Other embodiments can implement the wearable device differently. For example, the wearable device can be a smart phone, a gaming device, a digital music player, a sports accessory device, a medical device, a device that provides time and/or weather information, a health assistant, and other types of electronic device suitable for attaching to a user. 
     As with the embodiments depicted in  FIGS. 1A-1B , the wearable electronic device  200  can include a housing and a display. In many examples, the display may incorporate an input device configured to receive touch input, force input, or other input from a user. The wearable electronic device  200  may also include one or more buttons or input ports (not shown). The housing can form a protective case for the internal components of the wearable electronic device  200 . In the illustrated embodiment, the housing is formed into a substantially rectangular shape, although this configuration is not required. 
     The wearable electronic device  200  can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  202  and a second band  204 . In some embodiments, when attaching to a user&#39;s wrist, the first band  202  can be configured to overlap the second band  204 , for example as depicted in  FIG. 2B . In other embodiments, the first band  202  can be configured in a mortise-tenon relationship with the second band  204 , such as depicted in  FIG. 2C . In still further embodiments, the first band  202  can be configured to insert within an aperture of the second band  204  such that the first band  202  and the second band  204  interlace, such as depicted in  FIG. 2D . In other embodiments, other relationships between the first band  202  and the second band  204  can be established. 
     The initial attachment between the first band  202  and the second band  204  (regardless whether the interaction is overlapping, interlacing, mortise-tenon or otherwise) is referred to herein as a “coarse” fit. A coarse fit may not provide users of the wearable electronic device  200  with a sufficiently many increments to find an optimally comfortable or preferred fit. For example, a coarse fit for the wearable electronic device  200  may be different when the user is operating the wearable electronic device  200  as a fitness/health tracker than when the same user is operating the wearable electronic device  200  as a conventional timekeeping device. 
     As with the embodiment depicted in  FIGS. 1A-1B , the first band  202  and the second band  204  can each be formed from a compliant material or into a compliant structure that is configured to easily contour to a user&#39;s wrist, while retaining stiffness sufficient to maintain the position and orientation of the wearable electronic device on the user&#39;s wrist. In some embodiments, the first band  202  and the second band  204  may be formed from the same material, but this is not necessarily required. For example, in some embodiments the first band  202  can be formed from a leather material and the second band  204  can be formed from a metal material. In certain embodiments, the first band  202  and the second band  204  are each formed from a fluoroelastomeric polymer. In still further embodiments, materials such as plastic, rubber, or other fibrous, organic, polymeric, or synthetic materials may be used. 
     As noted above, the relative stiffness of the first band  202  and the second band  204  can impact the tightness with which the band may be fit to a user&#39;s wrist. Accordingly, in many embodiments, the wearable electronic device  200  may be configured to adjust one or more dimensions of the first band  202  or the second band  204 . In other embodiments, the wearable electronic device  200  may be configured to adjust the coupling between the first band  202 , the second band  204  and the housing of the wearable electronic device. In other embodiments, the wearable electronic device may be configured to adjust the housing itself. 
     For example, in some embodiments, the length of the first band  202  can be increased or decreased in order to adjust the fit of the wearable electronic device  200 . In these embodiments, the shorter the length of the first band  202 , the tighter the fit of the wearable electronic device  200  may be. Similarly, the longer the length of the first band  202 , the looser the fit of the wearable electronic device  200  may be. Length adjustments to the first band  202  are shown in  FIG. 2A  with a bi-directional arrow labeled as adjustment A 1 . 
     In some embodiments, the length of the second band  204  can be increased or decreased in order to adjust the fit of the wearable electronic device  200 . In these embodiments, the shorter the length of the second band  204 , the tighter the fit of the wearable electronic device  200  may be. Similarly, the longer the length of the second band  204 , the looser the fit of the wearable electronic device  200  may be. Length adjustments to the second band  204  are shown in  FIG. 2A  with a bi-directional arrow labeled as adjustment A 2 . 
     In some embodiments the adjustments A 1 , A 2  can be carried out simultaneously, sequentially, or individually. For example, in some embodiments, the adjustment A 1  can be carried out independent of the adjustment A 2 . In other words, the length of the first band  202  can be increased or decreased independent of any change in the length of the second band  204 . In other embodiments, the adjustment A 1  can be carried out to a greater degree than the adjustment A 2 . In other words, the length of the first band  202  can be increased or decreased by a greater amount than the any increase or decrease in the length of the second band  204 . 
     In some embodiments, the width of the first band  202  can be increased or decreased in order to adjust the fit of the wearable electronic device  200 . In these embodiments, the wider the first band  202 , the tighter the fit of the wearable electronic device  200  may be. Similarly, the thinner the first band  202 , the looser the fit of the wearable electronic device  200  may be. Width adjustments to the first band  202  are shown in  FIG. 2A  with a bi-directional arrow labeled as adjustment A 3 . 
     In some embodiments, the width of the second band  204  can be increased or decreased in order to adjust the fit of the wearable electronic device  200 . In these embodiments, the wider the second band  204 , the tighter the fit of the wearable electronic device  200  may be. Similarly, the thinner the second band  204 , the looser the fit of the wearable electronic device  200  may be. For illustrative simplicity, width adjustments to the second band  204  are not illustrated in  FIG. 2A . 
     In some embodiments width adjustments to the first band  202  and the second band  204  can be carried out simultaneously, sequentially, or individually. For example, in some embodiments, the adjustment A 3  can be carried out independent of any width adjustment to the second band  204 . In other embodiments, the adjustment A 3  can be carried out to a greater degree any width adjustment to the second band  204 . 
     In some embodiments, the relationship between the housing of the wearable electronic device  200  and the first band  202  and the second band  204  can be retracted or extended in order to adjust the fit of the wearable electronic device  200 . In these embodiments, the more the first band  202  and/or the second band  204  are retracted into the housing of the wearable electronic device, the tighter the fit of the wearable electronic device  200  may be. Similarly, the more the first band  202  and/or the second band  204  are extended from the housing of the wearable electronic device  200 , the looser the fit of the wearable electronic device  200  may be. Adjustments to the coupling between first band  202 , the second band  204  and the housing of the wearable electronic device are shown in  FIG. 2A  with a bi-directional arrow labeled as adjustment A 4 . 
       FIG. 2B  depicts a side plan view of an example wearable electronic device, such as shown in  FIG. 2A , with an overlapping two-piece band system for attaching to a user. As with the embodiment depicted in  FIG. 2A , the wearable electronic device  200  can include a tensioner to provide dynamic adjustment of the fit of the wearable electronic device  200 . The wearable electronic device  200  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  202  and a second band  204 . 
     As illustrated, the first band  202  and the second band  204  can be overlapped in order to form a closed loop around a user&#39;s wrist. In some examples, the first band  202  and the second band  204  can be affixed together with a traditional or conventional attachment mechanism. For example, in some embodiments, a buckling clasp can be used. In other examples a pin and eyelet attachment mechanism can be used. 
     Accordingly, and as with other embodiments described herein, the coarse fit of a wearable electronic device, such as the wearable electronic device  200  depicted in  FIG. 2B  can be adjusted by actuating a tensioner to adjust (or cause to be adjusted) one or more dimensions of the first band  202 , the second band  204 , the housing of the wearable electronic device  200 , or the coupling between them. For example, as described above, a tensioner may be configured to carry out the adjustments A 1 , A 2 , A 3  and/or A 4 . 
     In addition, in some embodiments, the height of the wearable electronic device  200  can be increased or decreased in order to adjust the fit of the wearable electronic device  200  when attached to a user. In these embodiments, the higher the housing of the wearable electronic device  200  is with respect to the user&#39;s wrist, the looser the fit of the wearable electronic device  200  may be. Similarly, the lower the housing of the wearable electronic device  200  is with respect to the user&#39;s wrist, the tighter the fit of the wearable electronic device  200  may be. Height adjustments to the housing of the wearable electronic device  200  are shown in  FIG. 2B  with a bi-directional arrow labeled as adjustment A 5 . 
     Furthermore, in some embodiments, the thickness of the first band  202  can be increased or decreased in order to adjust the fit of the wearable electronic device  200 . In these embodiments, the thicker the first band  202 , the shorter the first band  202 , and thus the tighter the fit of the wearable electronic device  200  may be. Similarly, the thinner the first band  202 , the looser the fit of the wearable electronic device  200  may be. Width adjustments to the first band  202  are shown in  FIG. 2B  with a bi-directional arrow labeled as adjustment A 6 . 
     Furthermore, in some embodiments, the thickness of the second band  204  can be increased or decreased in order to adjust the fit of the wearable electronic device  200 . In these embodiments, the thicker the second band  204 , the shorter the second band  204 , and thus the tighter the fit of the wearable electronic device  200  may be. Similarly, the thinner the second band  204 , the looser the fit of the wearable electronic device  200  may be. For illustrative simplicity, thickness adjustments to the second band  204  are not illustrated in  FIG. 2B . 
     As with other adjustments described herein, in some embodiments, thickness adjustments to the first band  202  and the second band  204  can be carried out simultaneously, sequentially, or individually. For example, in some embodiments, the adjustment A 6  can be carried out independent of any thickness adjustment to the second band  204 . In other embodiments, the adjustment A 6  can be carried out to a greater degree any thickness adjustment to the second band  204 . 
     In addition, in some embodiments, the relative alignment of the first band  202  and the second band  204  can be changed in order to adjust the fit of the wearable electronic device  200 . For example, the farther along the second band  204  the first band  202  is disposed, the tighter the fit of the wearable electronic device  200  may be. Relative alignment adjustments are shown in  FIG. 2C  with a bi-directional arrow labeled as adjustment A 7 . 
       FIG. 2C  depicts a side plan view of an example wearable electronic device with a mortise-tenon band system for attaching to a user. As with the embodiment depicted in  FIG. 2A , the wearable electronic device  200  can include a tensioner to provide dynamic adjustment of the fit of the wearable electronic device  200 . The wearable electronic device  200  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  202  and a second band  204 . As illustrated, the first band  202  can be inserted into a cavity opened within the second band  204  in order to form a coarse fit of closed loop around a user&#39;s wrist. 
     Accordingly, and as with other embodiments described herein, the coarse fit of a wearable electronic device, such as the wearable electronic device  200  depicted in  FIG. 2C  can be adjusted by actuating a tensioner to adjust (or cause to be adjusted) one or more dimensions of the first band  202 , the second band  204 , the housing of the wearable electronic device  200 , or the coupling between them. For example, as described above, a tensioner may be configured to carry out the adjustments A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , and/or A 7 . 
       FIG. 2D  depicts a side plan view of an example wearable electronic device with an interlacing band system for attaching to a user. As with the embodiment depicted in  FIG. 2A , the wearable electronic device  200  can include a tensioner to provide dynamic adjustment of the fit of the wearable electronic device  200 . The wearable electronic device  200  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  202  and a second band  204 . As illustrated, the first band  202  can be inserted into an aperture of the second band  204  in order to form a coarse fit of closed loop around a user&#39;s wrist. 
     In many examples, the first band  202  can include one or more sizing eyelets into which a pin associated with the second band  204  can be inserted. In many examples, more than one eyelet can be formed within the first band  202 , distributed at uniform or semi-uniform intervals across the length of the band. In some examples, the eyelets may be distributed in a logarithmic or exponential distribution, or any other suitable distribution. In these embodiments, the distribution of the eyelets may be based, at least in part, on the average wrist size of the expected user. Some embodiments may not follow any mathematical distribution. 
     As illustrated, the second band  204  can include a concealment aperture (not visible) having a greater width than the first band  202 . In some embodiments, the concealment aperture may be formed to have a width approximately equal to the width of the first band  202 . The concealment aperture may be configured to receive the first band  202  through it, thereby concealing a portion of the first band  202  between the second band  204  and the user&#39;s wrist. In many embodiments, the concealment aperture is formed to have the shape of a rounded rectangle (e.g., “pill” shaped or “lozenge” shaped), although this shape is not required. 
     In many examples, the second band  204  can also include a pin (not illustrated) configured to be inserted in a selected eyelet of the first band  202 . Upon insertion into the eyelet, the pin can resist unintended separation of the first band  202  and the second band  204 . In many cases, the pin may be formed from metal, ceramic, or plastic and/or may include at least one surface finish configured to increase friction between the pin and the first band  202 . 
     In many examples, the second band  204  can also incorporate a recessed guide bed (not visible) to receive and guide the inserted length of first band  202 . In many cases, the guide bed can be longitudinally centered along the bottom surface of the second band  204 . For these embodiments, the combined thickness of the overlapping portions of the sizing and second band  204  may be reduced. In addition, the guide bed may at least partially retain the inserted length of the first band  202  in place behind the second band  204 . 
     To attach the portable electronic device around a user&#39;s wrist, the end of the first band  202  can be fed around the wrist and through the concealment aperture of the second band  204  so that the two bands interlace to form a closed loop. In many examples, the material selected for each band may have a low coefficient of friction such that the insertable end of the first band  202  can slide into the concealment aperture and against or past the user&#39;s skin without substantial resistance that might cause discomfort to the user. After insertion of the band-insertable end through the concealment aperture, the user can apply pressure to the first band  202  to push the first band  202  further along the guide bed of the second band  204  in order to adjust the tightness against the limb. When an acceptable tightness is reached, the user can push the pin of the second band  204  through the most proximate eyelet of the first band  202 . In many embodiments, the process of inserting the band-insertable end and tightening the first band  202  and the second band  204   s  may be comfortably and conveniently accomplished with the user&#39;s free hand. 
     To detach the portable electronic device from the wrist, the pin can be withdrawn from the eyelet and the insertable end of the first band  202  can be withdrawn from the concealment aperture. The process of removing the insertable end and loosening the first band  202  and the second band  204  may be comfortably and conveniently accomplished with the user&#39;s free hand. 
     As with other embodiments described herein, the coarse fit of a wearable electronic device, such as the wearable electronic device  200  depicted in  FIG. 2D  can be adjusted by actuating a tensioner to adjust (or cause to be adjusted) one or more dimensions of the first band  202 , the second band  204 , the housing of the wearable electronic device  200 , or the coupling between them. For example, as described above, a tensioner may be configured to carry out the adjustments A 1 , A 2 , A 3 , A 4 , A 5 , A 6  and/or A 7 . 
     One can appreciate that although many embodiments are described herein with reference to two-part bands for attaching wearable electronic devices to users, that other bands are contemplated. For example, in some embodiments, a single-part band may be used. In other cases, a segmented band can be used. 
     Similarly, one may appreciate that the adjustments A 1 , A 2 , A 3 , A 4 , A 5 , A 6  and/or A 7  (and other adjustments) may apply equally or equivalently to other band and/or wearable electronic device embodiments described herein. More generally, it should be appreciated that the various examples and embodiments presented herein can apply equally or equivalently to many band and/or wearable device embodiments and no single embodiment, or adjustments thereto by a tensioner or the wearable electronic device itself, should be considered as limited to that single embodiment. 
       FIG. 3A  depicts a simplified block diagram of a wearable electronic device  300  configured to be coupled to a user by joining a first band  302  with a second band  304  about the user&#39;s wrist. The wearable electronic device  300  can one or more processing devices  306 , memory  308 , one or more input/output (I/O) devices or sensors  310  (e.g., biometric sensors, environmental sensors, etc.), one or more displays  312 , one or more power source(s) (not shown), one or more physical and/or rotary input devices  314 , one or more touch and/or force input device(s)  316 , one or more acoustic input and/or output devices  318 , one or more haptic output device(s)  320 , one or more a network communication interface(s)  322 , and one or more tensioner  324 . Some embodiments can also include additional components. 
     The display  312  may provide an image or video output for the wearable electronic device  300 . The display  312  may also provide an input surface for one or more input devices such as a touch sensing device  316 , force sensing device, temperature sensing device, and/or a fingerprint sensor. The display  312  may be any size suitable for inclusion at least partially within the housing of the wearable electronic device  300  and may be positioned substantially anywhere on the wearable electronic device  300 . In some embodiments, the display  312  can be protected by a cover glass formed from a scratch-resistant material (e.g., sapphire, zirconia, glass, and so on) that may form a substantially continuous external surface with the housing of the wearable electronic device  300 . 
     The processing device(s)  306  can control or coordinate some or all of the operations of the wearable electronic device  300 . The processing device  306  can communicate, either directly or indirectly with substantially all of the components of the wearable electronic device  300 . For example, a system bus or signal line or other communication mechanisms can provide communication between the processing device  306 , the memory  308 , the I/O device(s)  310 , the power source(s), the network communication interface  322 , and/or the haptic output device  320 . 
     The one or more processing devices  306  can be implemented as any electronic device capable of processing, receiving, or transmitting data or instructions. For example, the processing device(s)  306  can each be a microprocessor, a central processing unit (CPU), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), or combinations of such devices. As described herein, the term “processing device” is meant to encompass a single processor or processing unit, multiple processors, multiple processing units, or other suitably configured computing element or elements. 
     The memory  308  can store electronic data that can be used by the wearable electronic device  300 . For example, a memory can store electrical data or content such as, for example, audio and video files, documents and applications, device settings and user preferences, timing and control signals or data for the haptic output device  320 , data structures or databases, and so on. The memory  308  can be configured as any type of memory. By way of example only, the memory can be implemented as random access memory, read-only memory, Flash memory, removable memory, or other types of storage elements, or combinations of such devices. 
     The one or more I/O device(s)  310  can transmit and/or receive data to and from a user or another electronic device. The I/O device(s)  310  can include a touch sensing input surface such as one or more buttons, one or more microphones or speakers, and/or one or more ports such as a microphone port. 
     The wearable electronic device  300  may also include one or more sensors  310  positioned substantially anywhere on the wearable electronic device  300 . The sensor or sensors  310  may be configured to sense substantially any type of characteristic such as, but not limited to, images, pressure, light, touch, force, temperature, position, motion, and so on. For example, the sensor(s)  310  may be an image sensor, a temperature sensor, a light or optical sensor, an atmospheric pressure sensor, a humidity sensor, a magnet, a gyroscope, an accelerometer, and so on. In other examples, the wearable electronic device  300  may include one or more health sensors. In some examples, the health sensors can be disposed on a bottom surface of the housing of the wearable electronic device  300 . 
     The power source can be implemented with any device capable of providing energy to the wearable electronic device  300 . For example, the power source can be one or more batteries or rechargeable batteries, or a connection cable that connects the remote control device to another power source such as a wall outlet. In other examples, wireless power can be used. 
     The network communication interface  322  can facilitate transmission of data to or from other electronic devices across standardized or proprietary protocols. For example, a network communication interface can transmit electronic signals via a wireless and/or wired network connection. Examples of wireless and wired network connections include, but are not limited to, cellular, Wi-Fi, Bluetooth, infrared, and Ethernet. 
     The haptic output device  320  can be implemented as any suitable device configured to provide force feedback, vibratory feedback, tactile sensations, and the like. For example, in one embodiment, the haptic output device  320  may be implemented as a linear actuator configured to provide a punctuated haptic feedback, such as a tap or a knock. 
     As noted above, the wearable electronic device  300  can include a tensioner  324 . In many cases, a tensioner can be an analog, digital, or integrated circuit configured to apply an electrical signal to cause tension (either directly or indirectly) to be applied to, or relieved form, the first band  302  and the second band  304 . In other cases, a tensioner can be a physical apparatus such as a motor, electromagnetic coil, or solenoid that can be actuated to cause tension (either directly or indirectly) to be applied to, or relieved form, the first band  302  and/or the second band  304 . 
     In response to a signal from the wearable electronic device, the tensioner can cause the first band  302  or the second band  304  to tighten and or loosen. In other embodiments, in response to a signal from the wearable electronic device  300 , the tensioner can cause the housing of the wearable electronic device  300  to shift its position relative to the first band  302  or the second band  304 . 
     As noted above, the signal to change the fit of the wearable electronic device  300  can be received from any number of sources. For example, in certain embodiments, the signal can be received from secondary electronic device through the network communication interface  322 . In other embodiments, the signal can be received as direct user input. For example, a user can provide input to the touch sensing device  316  of the wearable electronic device  300  to indicate to the wearable electronic device  300  and/or the tensioner  324  the user&#39;s desire for the fit of the device to change, either with increased tightness or decreased tightness. For example,  FIG. 3B  depicts in perspective view a user providing an indication to the wearable electronic device  300 , via a display  312 , to decrease the tightness of the band. 
       FIG. 4A  depicts a top plan view of an example wearable electronic device with a two-piece band system configured to contract along its length in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  400  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  402  and a second band  404 . In the illustrated embodiment, a first actuator  406  can be disposed within the first band  402  and a second actuator  408  can be disposed within a second band  404 . Both the first actuator  406  and the second actuator  408  can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  400 . 
     In the illustrated example, the first actuator  406  and the second actuator  408  can be formed in a longitudinal serpentine pattern and can be configured to contract or expand in response to an electrical signal from the tensioner. For example, in some embodiments, the first actuator  406  and the second actuator  408  can be formed from a shape memory wire such as Nitinol. In these embodiments, the tensioner can increase a current (or voltage) applied to the Nitinol in response to an instruction to increase the tightness of the band or can decrease a current (or voltage) applied to the Nitinol in response to an instruction to decrease the tightness of the band. In many cases, an increase in current applied to the Nitinol can cause the temperature of the Nitinol to increase, which can cause the Nitinol to contract. 
     In response to the increase or decrease in the length of the longitudinal and serpentine Nitinol, the band can experience an increase or decrease in length which, in turn, can cause an increase or decrease the tightness of the fit of the band, for example as illustrated in  FIG. 4B . In this manner, the first actuator  406  and the second actuator  408  can achieve the adjustment A 1  and/or the adjustment A 2  discussed with respect to  FIGS. 2A-2D . 
     In other embodiments, the first actuator  406  and the second actuator  408  can be formed from another shape-memory wire, such as a copper-based shape memory alloy. In other examples, another material can be used such as electroactive polymer (either dielectric or ionic). In response to an electrical signal from the tensioner, electroactive polymer can contract and/or expand to achieve the adjustments A 1  and A 2 . 
     Although illustrated with a serpentine pattern, in other embodiments, other patterns can be used. For example, in other cases, a series of parallel actuators can be included within either or both the bands. In other examples, one or both of the actuators can be disposed along the entire length of one or both of the bands. 
     In other cases, the first actuator  406  and the second actuator  408  can be disposed only through a portion of the first band  402  and the second band  404 . For example,  FIG. 4C  depicts the first actuator  406  as disposed only along a portion of the length of the first band  402 . Although illustrated to abut the housing of the wearable electronic device  400 , one can appreciate that the first actuator  406  can be positioned anywhere along the length of the first band  402 . For example, in some embodiments, the first actuator  406  can be disposed in a middle portion of the first band  402 . In other embodiments, the first actuator  406  can be disposed in an end portion of the first band  402 . In still further embodiments, more than one actuator can be disposed within the first band  402 . For example, one actuator can be placed within an end portion of the first band  402  and a second actuator can be positioned to abut the housing of the wearable electronic device  400 . 
     In some embodiments, the first actuator  406  and the second actuator  408  can be insert molded into the first band  402  and the second band  404  respectively. In some cases, the first actuator  406  and the second actuator  408  can be insert molded closer to a bottom surface of the first band  402  and the second band  404 . In other cases, the first actuator  406  and the second actuator  408  can be insert molded closer to a top surface of the first band  402  and the second band  404 . In still further examples, the first actuator  406  and the second actuator  408  can be insert molded into the center of the first band  402  and the second band  404 . 
     In other cases, the first actuator  406  and the second actuator  408  can be inserted into the first band  402  and the second band  404  after the molding of the first band  402  and the second band  404 . For example, after molding, an incision path can be cut into the first band  402  and the second band  404  that is shaped to fit the shape of the first actuator  406  and the second actuator  408 . In a subsequent manufacturing step, the first actuator  406  and the second actuator  408  can be inserted into the incision. 
     In other examples, the first actuator  406  and the second actuator  408  can be formed with selective placement of dopants during the formation of the first band  402  and the second band  404 . 
     In other examples, the first actuator  406  and the second actuator  408  can be disposed on an exterior surface of the first band  402  and the second band  404 . For example, in certain embodiments, the first actuator  406  and the second actuator  408  can be disposed around the perimeter of the first band  402  and the second band  404 . 
     In still further examples, one or both of the first actuator  406  and the second actuator  408  can be disposed or formed along an axis that is not parallel to the length of the first band  402  or the second band  404 . For example, as illustrated in  FIG. 4C , the second actuator  408  can be disposed parallel to the width of the second band  404 . In this example, contraction of the second actuator  408  can achieve an adjustment A 3 . In other words, contraction of the second actuator  408  can cause the width of the second band  404  to contract. 
     As may be appreciated, contraction of the width of the second band  404  can cause the second band  404  to lengthen. In other words, by achieving the adjustment A 3 , the adjustment A 2  can also be achieved. 
     Similarly, and as depicted in the side plan view of  FIG. 4D , some embodiments can dispose either or both the first actuator  406  and the second actuator  408  as a serpentine pattern through the thickness of the first band  402  or the second band  404 . For example, as illustrated, the first actuator  406  can be disposed through the thickness of the first band  402 . As may be appreciated, contraction of the thickness of the first band  402  can cause the first band  402  to lengthen. In other words, by achieving the adjustment A 6 , the adjustment A 1  can also be achieved. 
       FIG. 5A  depicts a top plan view of an example wearable electronic device with a two-piece band system configured to retract into the body of the wearable electronic device in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  500  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  502  and a second band  504 . In the illustrated embodiment, a first actuator  506  can be partially disposed within the first band  502  and partially disposed within the housing of the wearable electronic device. Similarly, a second actuator  508  can be partially disposed within a second band  504  and partially within the housing of the wearable electronic device. Both the first actuator  506  and the second actuator  508  can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  500 . 
     In the illustrated example, the first actuator  506  and the second actuator  508  can be formed in a longitudinally-oriented serpentine pattern and can be configured to contract or expand in response to an electrical signal from the tensioner. For example, as with the embodiment depicted in  FIGS. 4A-4D , the first actuator  506  and the second actuator  508  can be formed from a shape memory wire such as Nitinol. 
     In response to the increase or decrease in the length of the longitudinal and serpentine Nitinol, the band can experience an increase or decrease the tension with which the first band  502  and the second band  504  are coupled to the housing of the wearable electronic device  500 , which, in turn, can cause an increase or decrease the tightness of the fit of the band. In this manner, the first actuator  506  and the second actuator  508  can achieve the adjustment A 4 . 
     In another embodiment, the tensioner can be connected to a coupling that joins the first band  502  and the second band  504  at one or more points to the housing of the wearable electronic device  500 . In some examples, such as that depicted in  FIG. 5B , the coupling can be a first lug  510  and a second lug  512 , associated with the first band  502  and the second band  504  respectively, that each extend from the housing of the wearable electronic device  500 . In such an embodiment, the tensioner can withdraw the first lug  510  and a second lug  512  into the housing of the wearable electronic device  500  by applying an electrical signal to the first actuator  506  and the second actuator  508  (shown in  FIG. 5A ). 
     In other examples, the first band  502  and the second band  504  can be configured to slide within (and be retained by) two or more channels within external sidewalls of the housing. In such an embodiment, such as that depicted in  FIG. 5C , the tensioner can withdraw first channel  514  and a second channel  516 , associated with the first band  502  and the second band  504  respectively, further into the housing of the wearable electronic device  500  by applying an electrical signal to the first actuator  506  and the second actuator  508 . In another case, the tensioner can withdraw the portions of the first band  502  and the second band  504  that are inserted into the channels further into the housing of the wearable electronic device  500  by applying an electrical signal to the first actuator  506  and the second actuator  508 . 
     In other examples, the first band  502  and the second band  504  can be looped through and aperture in the housing. In such an embodiment, the tensioner can withdraw the aperture further into the housing of the wearable electronic device  500  by applying an electrical signal to the first actuator  506  and the second actuator  508 . In other cases, the first band  502  and the second band  504  can be riveted, screwed, or otherwise attached to the housing via one or more mechanical fasteners. In such an embodiment, the tensioner can withdraw the one or more mechanical fasteners further into the housing of the wearable electronic device  500  by applying an electrical signal to the first actuator  506  and the second actuator  508 . 
     In other examples, the first band  502  and the second band  504  can be permanently coupled to the housing, such as depicted in  FIG. 5D . For example, in some cases, the first band  502  and the second band  504  may be formed as an integral portion of the housing. In other cases, the first band  502  and the second band  504  can be rigidly adhered to the housing via a first adhesive  520  and a second adhesive  522 , associated with the first band  502  and the second band  504  respectively. In still further embodiments, the first band  502  and the second band  504  can be welded, soldered, or chemically bonded to the housing. In other embodiments, additional permanent couplings between the first band  502  and the second band  504  and the housing of the wearable electronic device  500  are possible. In these embodiments, the tensioner can apply a withdrawing force to the first band  502  and the second band  504  such that the first band  502  and the second band  504  contract at their interface with the housing. 
       FIG. 6A  depicts a top plan view of an example wearable electronic device with a segmented band system configured to contract along its length in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  600  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  602  and a second band  604 . In the illustrated embodiment, the first band  602  and a second band  604  can each be formed as a group of metallic links. In other embodiments other materials can be used. For example, in some embodiments, glass, crystal, or rigid plastic can be used. In other examples, compliant materials can be used. In many cases, each link can be coupled to adjacent links via a hinging attachment. In other examples, each link can be coupled to adjacent links via an elasticated band. 
     In the illustrated embodiment, a first actuator  606  can be coupled to the first band  602 . Similarly, a second actuator  608  coupled to the second band  604 . Both the first actuator  606  and the second actuator  608  can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  600 . 
     In the illustrated example, the first actuator  606  and the second actuator  608  can be configured contract or expand the first and/or second band in response to an electrical signal from the tensioner. For example, upon receiving a signal to contract (e.g., increase the tightness of the fit of the wearable electronic device  600 , the links of each of the first band  602  and the second band  604  can be collapsed together, for example as shown in  FIG. 6B   
     In one embodiment, the first actuator  606  can be formed as a series of electromagnetic coils disposed within each link of the first band  602  and the second band  604 . In this example, in response to an instruction to tighten the fit of the band, the tensioner can apply a current to each of the electromagnetic coils so that the band collapses into the configuration shown in  FIG. 6B . 
     In another embodiment, as with the embodiment depicted in  FIGS. 4A-4D , the first actuator  606  and the second actuator  608  can be formed from a shape memory wire such as Nitinol. The Nitinol wire can be fed through each of the links of each of the first band  602  and the second band  604 . In some examples, the Nitinol can be fed through more than once, for example in a serpentine pattern. In this example, in response to an instruction to tighten the fit of the band, the tensioner can apply a current to the Nitinol wire so that the band collapses into the configuration shown in  FIG. 6B . 
     In response to the increase or decrease in the length of the first band  602  and the second band  604 , tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the first actuator  606  and the second actuator  608  can achieve the adjustment A 1  and the adjustment A 2 . 
       FIG. 7A  depicts a top plan view of an example wearable electronic device with a woven band system configured to contract along its length and/or width in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  700  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  702  and a second band  704 . In the illustrated embodiment, the first band  702  and a second band  704  can each be formed from a woven material. In many examples, a woven material can be made from a material that can be threaded, such as, but not limited to, plastic, rubber, nylon, cotton, or other fibrous, organic, polymeric, or synthetic materials. In many cases, a woven material can be formed by drawing a weft thread  708  through substantially parallel warp threads  710  in an patterned manner (e.g., alternating, alternating every other warp, alternating every third warp, etc.), for example as shown in the detail view of  FIG. 7B . Nominally, one weft thread can be separated from adjacent weft threads by a distance  712  that defines the tightness of the woven material. 
     In the illustrated embodiment, a first actuator can be coupled to the first band  702 . Similarly, a second actuator coupled to the second band  704 . Both the first actuator  706  and the second actuator can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  700 . 
     In the illustrated example, the first actuator and the second actuator can be configured contract or expand the first and/or second band in response to an electrical signal from the tensioner. 
     As with the embodiment depicted in  FIGS. 4A-4D , the first actuator  706  and the second actuator can be formed from a shape memory wire such as Nitinol. In some cases the Nitinol wire can be threaded into the woven material forming the first band  702  and the second band  704 . For example, in certain embodiments, the Nitinol wire can be one or more warps of the woven material. In another example, the Nitinol wire can be one or more wefts of the woven material. In this example, in response to an instruction to tighten the fit of the band, the tensioner can apply a current to the Nitinol wire so that the band collapses into the configuration shown in  FIG. 7C . In other embodiments, the first actuator and the second actuator can be formed from another material, such as an electroactive polymer. 
     In response to the increase or decrease in the length of the first band  702  and the second band  704 , tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the first actuator and the second actuator can achieve the adjustment A 1  and the adjustment A 2 . 
       FIG. 8A  depicts a top plan view of an example wearable electronic device with a two-part band system, each band configured to slide relative to the other band in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  800  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  802  and a second band  804 . In the illustrated embodiment, a first actuator  806  can be partially disposed within the first band  802  and partially disposed within the housing of the wearable electronic device. Similarly, a second actuator  808  can be partially disposed within a second band  804  and partially within the housing of the wearable electronic device. Both the first actuator  806  and the second actuator  808  can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  800 . 
     In the illustrated example, the first actuator  806  can be formed as a permanent magnet. The permanent magnet can be formed of any number of suitable magnetic materials. For example, in some embodiments, the first actuator  806  can be formed from rare earth metals. In other examples, the first actuator  806  can be formed as a ceramic magnet. 
     In the illustrated example, the second actuator  808  can be formed as a series of electromagnetic coils, illustrated as the coils  806   a - 806   e . Upon overlapping the first band  802  with the second band  804 , the tensioner can send an electrical signal to one of the coils  806   a - 806   e  in order to attract the permanent magnetic the first actuator  806 . For example, as shown in  FIG. 8B , the coil  808   b  is activated by the tensioner so as to attract the permanent magnet of the first actuator  806 . 
     In response to a signal to tighten the fit of the band, the tensioner can apply an electrical signal to one or more adjacent of the coils adjacent to the coil  808   b , or whichever coil  808   a - e  was activated upon overlapping the first band  802  with the second band  804 . For example, as shown in  FIG. 8C , coil  808   d  can be activated so as to attract the permanent magnet of the first actuator  806 . 
     In this manner, in response to the increase or decrease in the length of the first band  802  and the second band  804 , tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the first actuator  806  and the second actuator  808  can achieve the adjustment A 7 . 
       FIG. 9  depicts a side plan view of an example wearable electronic device with a bracelet-style band system configured to rotate the housing of the wearable electronic device toward or away from a user&#39;s wrist in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  900  can include a housing at that can be permanently or removably attached to a two-part band system including a rigid bracelet-style band  902 . In the illustrated embodiment, the housing of the wearable electronic device  900  can be configured to rotate about a pivot point to which the rigid bracelet-style band  902  is coupled. For example, the wearable electronic device  900  can include an actuator (not shown) within the housing of the wearable electronic device  900  that can be electrically coupled to a tensioner (not shown) also disposed within the housing of the electronic device. In some embodiments, the actuator can be an electrical motor. In other examples, the actuator can be an electrical motor that, in other modes, is used to provide haptic feedback to the user. For example, the actuator may be a vibration motor. 
     In response to a signal to increase the tightness of the fit, the tensioner can cause the actuator to rotate the rigid bracelet-style band  902  relative to the housing of the wearable electronic device  900 . By rotating the rigid bracelet-style band  902  toward the housing, the tightness of the fit can increase. By rotating the rigid bracelet-style band  902  away from the housing, the tightness of the fit can decrease. 
     In this manner, in response to the increase or decrease relative positioning of the rigid bracelet-style band  902  and the housing of the wearable electronic device  900 , the tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the actuator can achieve the adjustment A 5 . 
       FIG. 10  depicts a side plan view of an example wearable electronic device with a loop-style band system configured to tighten or loosen the loop in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1000  can include a housing at that can be permanently or removably attached to a two-part band system including a complaint loop-style band  1002 . In the illustrated embodiment, the housing of the wearable electronic device  1000  can be configured to insert through about an aperture within the housing through which the complaint loop-style band  1002  can be inserted, and folded back on itself. In some examples, the complaint loop-style band  1002  can be formed from a metallic mesh. In some of these examples, the metallic mesh can be formed from a ferromagnetic material such as steel. In these examples, the complaint loop-style band  1002  can also include a permanent magnet, such as a bar magnet along the free end of the complaint loop-style band  1002 . In this manner, after the complaint loop-style band  1002  is inserted and folded back upon itself, the permanent magnet can attract the complaint loop-style band  1002  itself in order to hold its position. 
     In some embodiments, the wearable electronic device  1000  can include an actuator (not shown) at least partially within the housing of the wearable electronic device  1000  that can be electrically coupled to a tensioner (not shown) also disposed within the housing of the electronic device. In some embodiments, the actuator can be an electrical motor that includes a gear or high-friction portion that is configured and oriented to feed the complaint loop-style band  1002  through the aperture in the housing in response to a signal from the tensioner. In some examples, the actuator can be an electrical motor that, in other modes, is used to provide haptic feedback to the user. For example, the actuator may be a vibration motor or a linear actuator. 
     In response to a signal to increase the tightness of the fit, the tensioner can cause the actuator to feed the complaint loop-style band  1002  through the aperture in the housing of the wearable electronic device  1000 . By feeding the complaint loop-style band  1002  through the aperture in the housing, the tightness of the fit can be increased or decreased, depending upon the direction of the feed. 
     In this manner, in response to the increase or decrease relative positioning of the complaint loop-style band  1002  and the housing of the wearable electronic device  1000 , the tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the actuator can achieve the adjustment A 5 . 
       FIG. 11A  depicts a side plan view of an example wearable electronic device with a bladder-style band system configured to increase or decrease pressure within one or more bladders in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1100  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  1102  and a second band  1104 . In the illustrated embodiment, the first band  1102  and a second band  1104  can each be formed with one or more bladders that are in communication with an actuator such as a pump that is disposed within the housing of the wearable electronic device  1100 . 
     In the illustrated embodiment, a first actuator can be associated with the first band  1102 . Similarly, a second actuator can be associated with the second band  1104 . Both the first actuator and the second actuator can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  1100 . 
     The tensioner may be configured to control the pressure applied by the actuators to a fluid in communication with the bladders. In some cases the fluid can be a gas or a liquid. For example, in some embodiments, air can be used as the fluid in communication with the bladder. In other cases, a liquid with a low viscosity such as oil or water can be used as the fluid in communication with the bladder. In these embodiments, the tensioner can increase the pressure applied by the pump to the fluid in response to an instruction to increase the tightness of the band or can decrease the pressure applied by the pump in response to an instruction to decrease the tightness of the band. In response to the increase or decrease in pressure, the bladder can experience an increase or decrease in volume, which, in turn, increases or decreases the tightness of the band, for example as depicted in  FIG. 11B . 
     In response to the increase or decrease in the length of the first band  1102  and the second band  1104 , tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the first actuator and the second actuator can achieve the adjustment A 1  and the adjustment A 2 . 
       FIG. 12A  depicts a side plan view of an example wearable electronic device with another bladder-style band system configured to increase or decrease pressure within one or more bladders in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1200  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  1202  and a second band  1204 . In the illustrated embodiment, the first band  1202  and a second band  1204  can each be formed with a first bladder  1206  and a second bladder  1208 , respectively, that each are in communication with an actuator such as a pump that is disposed within the housing of the wearable electronic device  1200 . 
     In the illustrated embodiment, a first actuator can be associated with the first band  1202 . Similarly, a second actuator can be associated with the second band  1204 . Both the first actuator and the second actuator can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  1200 . 
     The tensioner may be configured to control the pressure applied by the actuators to a fluid in communication with the first bladder  1206  and a second bladder  1208 . As with the embodiment depicted in  FIGS. 11A-11B , the fluid can be any suitable fluid. In response to a request to increase or decrease the tightness of the fit of the band of the wearable electronic device  1200 , the tensioner can cause the actuators to increase or decrease the pressure of the first bladder  1206  and a second bladder  1208 . In response to the increase or decrease in pressure, the first bladder  1206  and a second bladder  1208  can experience an increase or decrease in volume, which, in turn, increases or decreases the tightness of the band, for example as depicted in  FIG. 12B . 
     In response to the increase or decrease in the length of the first band  1202  and the second band  1204 , tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the first actuator and the second actuator can achieve the adjustment A 1  and the adjustment A 2 . 
       FIG. 13A  depicts a side plan view of an example wearable electronic device with an extendable housing portion configured to extend toward or retract from a user&#39;s skin in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1300  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  1302  and a second band  1304 . In the illustrated embodiment, the housing of the wearable electronic device  1300  can include an extendable portion that can be configured to extend from a bottom surface of the housing toward the user&#39;s wrist. 
     In the illustrated embodiment, an actuator  1306  can be configured to extend the extendable portion. The actuator can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  1300 . 
     In this embodiment, the actuator  1306  can cause the extendable portion of the housing of the wearable electronic device  1300  to extend toward or retract from the user&#39;s skin. For example, in certain embodiments the extendable portion can extend toward a user&#39;s wrist (see, e.g.,  FIG. 13B ) or, in other examples, the extendable portion can retract from the user&#39;s wrist. In such an embodiment, the tensioner can cause the actuator  1306  to extend the extendable portion in response to an instruction to increase the tightness of the band or the tensioner can cause the actuator  1306  to withdraw the extendable portion into the housing of the wearable electronic device in response to an instruction to decrease the tightness of the band. 
     In some embodiments, the extendable portion can be formed from a material that contracts or expands in the presence of an electrical current (e.g., piezoelectric materials, memory wire, electroactive polymers, etc.). In other examples, the extendable portion can be formed as an electromagnetic coil positioned proximate to a permanent magnet (or other electromagnetic coil) coupled to a bottom surface of the housing of the wearable electronic device  1300 . An increase in the current applied to the electromagnetic coil can cause a corresponding increase in the magnetic flux produced and, thus, an increase in the attractive or repulsive force between the coil and the permanent magnetic material. 
     In still further examples, the extendable portion can be extended with a motor geared to a worm gear that either extends or retracts the extendable portion. In other examples, the extendable portion can be implemented as a linear actuator that extends or retracts the extendable portion. In other examples, the extendable portion can be implemented as a fluid pressure control system such as a pump that is configured to increase or decrease the pressure and/or volume of a fluid that then causes the extendable portion of the housing to extend or contract. In some examples, the extendable portion can be mechanically biased by a spring. In some cases, the bias can cause the extendable portion to be biased inwardly, in other cases, the bias spring can cause the extendable portion to be biased outwardly. 
     Furthermore, although illustrated as a large portion of the bottom surface of the wearable electronic device  1300 , one can appreciate that in other embodiments, smaller extendable portions are possible. For example, in certain embodiments, an optical biometric sensor coupled to the bottom surface of the housing of the wearable device (e.g., PPG sensor) may require one or more transparent or semi-transparent lenses such that optical components of the sensor can be exposed to conditions external to the housing of the wearable electronic device  1300 . In some embodiments, these lenses can be extendable portions. For example, one or more sensor lenses can extend or withdraw from contact with the user&#39;s skin. 
     In this manner, in response to the increase or decrease in the height of the housing relative to the first band  1302  and the second band  1304 , tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the actuator can achieve the adjustment A 5 . 
       FIG. 14A  depicts a side plan view of an example wearable electronic device with an extendable buckle portion configured to extend toward or retract from a user&#39;s skin in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1400  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  1402  and a second band  1404 . The first band  1402  and the second band  1404  can be joined by a buckle that can include an extendable portion that can be configured to extend from a top surface of the buckle toward the user&#39;s wrist. 
     In the illustrated embodiment, an actuator  1406  can be configured to extend the extendable portion. The actuator can be in electrical communication, either wireless or wired, with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  1400 . 
     In this embodiment, the actuator  1406  can cause the extendable portion of the buckle to extend toward or retract from the user&#39;s skin. For example, in certain embodiments the extendable portion can extend toward a user&#39;s wrist (see, e.g.,  FIG. 14B ) or, in other examples, the extendable portion can retract from the user&#39;s wrist. In such an embodiment, the tensioner can cause the actuator  1406  to extend the extendable portion in response to an instruction to increase the tightness of the band or the tensioner can cause the actuator  1406  to withdraw the extendable portion into the buckle in response to an instruction to decrease the tightness of the band. 
     As with the extendable portion described with respect to the embodiment depicted in  FIGS. 13A-13B , the extendable portion of the buckle can be implemented using piezoelectric materials, electroactive polymers, pumps and fluids, electromagnetic attraction and repulsion, and so on. 
     In this manner, in response to the increase or decrease in the height of the housing relative to the first band  1402  and the second band  1404 , tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the actuator  1406  can achieve the adjustment A 5 . 
       FIG. 15A  depicts a side plan view of an example wearable electronic device with another extendable housing portion configured to extend toward or retract from a user&#39;s skin in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1500  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  1502  and a second band  1504 . In the illustrated embodiment, the housing of the wearable electronic device  1500  can include a deformable portion that can be configured to deform away from a bottom surface of the housing toward the user&#39;s wrist. 
     In the illustrated embodiment, an actuator  1506  can be configured to deform the deformable portion. The actuator can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  1500 . 
     In this embodiment, the actuator  1506  can cause the deformable portion of the housing of the wearable electronic device  1500  to deform toward or deform away from the user&#39;s skin. For example, in certain embodiments the deformable portion can deform toward a user&#39;s wrist (see, e.g.,  FIG. 15B ) or, in other examples, the deformable portion can deform away from the user&#39;s wrist. In such an embodiment, the tensioner can cause the actuator  1506  to deform the deformable portion in response to an instruction to increase the tightness of the band or the tensioner can cause the actuator  1506  to withdraw the deformable portion toward the housing of the wearable electronic device in response to an instruction to decrease the tightness of the band. 
     In addition, although the deformable portion is illustrated with an arcuate deformation, such a deformation is not required. For example, in other embodiments, other deformations are possible. 
     As with the deformable portion described with respect to the embodiment depicted in  FIGS. 13A-13B , the deformable portion of the buckle can be implemented using piezoelectric materials, electroactive polymers, pumps and fluids, electromagnetic attraction and repulsion, and so on. 
     In this manner, in response to the increase or decrease in the height of the housing relative to the first band  1502  and the second band  1504 , tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the actuator  1506  can achieve the adjustment A 5 . 
       FIG. 16  depicts a top plan view of an example wearable electronic device with another two-piece band system configured to retract toward the body of the wearable electronic device in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1600  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  1602  and a second band  1604 . In the illustrated embodiment, a first actuator  1606  can be partially disposed within the first band  1602  and partially disposed within the housing of the wearable electronic device. Similarly, a second actuator  1608  can be partially disposed within a second band  1604  and partially within the housing of the wearable electronic device. Both the first actuator  1606  and the second actuator  1608  can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  1600 . 
     In response to the increase or decrease in the size of the first actuator  1606  and the second actuator  1608 , the band can experience an increase or decrease the tension with which the first band  1602  and the second band  1604  are coupled to the housing of the wearable electronic device  1600 , which, in turn, can cause an increase or decrease the tightness of the fit of the band. In this manner, the first actuator  1606  and the second actuator  1608  can achieve the adjustment A 4 . 
       FIG. 17  depicts a top plan view of an example wearable electronic device with another two-piece band system configured to retract into the body of the wearable electronic device in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1700  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  1702  and a second band  1704 . In the illustrated embodiment, an actuator  1706  can be formed as spring can be coupled between the first band  1702  and the second band  1704  through the housing of the wearable electronic device  1700 . In some embodiments, the spring can be a passive spring. In other embodiments, the spring can be an active spring. For example, the spring can be made from a shape-memory material such as Nitinol. In such an embodiment, the tightness of a fit of the wearable electronic device  1700  can be maintained by the tensioner by applying an electrical current to the Nitinol. 
     In response to the increase or decrease in the tautness of the spring of the actuator  1706 , can cause an increase or decrease the tightness of the fit of the band. In this manner, the actuator  1706  can achieve the adjustment A 4 . 
       FIG. 18  depicts a top plan view of an example wearable electronic device with another two-piece band system configured to retract toward the body of the wearable electronic device in response to an electrical signal from a tensioner. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1800  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  1802  and a second band  1804 . In the illustrated embodiment, a first actuator  1806  can be partially disposed within the first band  1802  and partially disposed within the housing of the wearable electronic device. Similarly, a second actuator  1808  can be partially disposed within a second band  1804  and partially within the housing of the wearable electronic device. Both the first actuator  1806  and the second actuator  1808  can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  1800 . In these examples, the first actuator  1806  and the second actuator  1808  can be worm gears (or other linear gears) that are in communication with a gear disposed within the housing of the wearable electronic device  1800 . 
     In this manner, rotation of the gear can cause the first actuator  1806  and the second actuator  1808  to either extend or to retract into the housing. In many embodiments the gear can be coupled to electrical motor. In other examples, the gear can be coupled to a haptic feedback device disposed within the housing of the wearable electronic device  1800 . As a result, the first band  1802  and the second band  1804  can extend or retract. In this manner, the first actuator  1806  and the second actuator  1808  can achieve the adjustment A 4 . 
       FIG. 19A  depicts a top plan view of an example wearable electronic device with another two-piece band system configured to contract along its length in response to an electrical signal from a tensioner or in response to a user input. In many cases the tensioner can be coupled to one or more actuators that, in response to a signal from the tensioner, adjust the fit of the wearable electronic device. 
     The wearable electronic device  1900  can include a housing at that can be permanently or removably attached to a band that is illustrated as a two-part band system including a first band  1902  and a second band  1904 . In the illustrated embodiment, a first actuator  1906  can be disposed within the first band. Similarly, a second actuator  1908  can be disposed within a second band  1904 . The first actuator can be configured to be inserted into a buckle  1910 , for example as shown in  FIG. 19B . 
     Both the first actuator  1906  and the second actuator  1908  can be in electrical communication with a tensioner (not visible), which may be disposed within the housing of the wearable electronic device  1900 . 
     In these examples, the first actuator  1906  and the second actuator  1908  can be worm gears (or other linear gears) that are in communication with a gear  1912  disposed within the buckle  1910 . In this manner, rotation of the gear can cause the first actuator  1906  and the second actuator  1908  to either extend or to retract into the housing. In many embodiments the gear can be coupled to electrical motor. In other examples, the gear  1912  may be turned manually by a user. As a result, the first band  1902  and the second band  1904  can extend or retract. In this manner, the first actuator  1906  and the second actuator  1908  can achieve the adjustment A 7 . 
       FIG. 20A  depicts a side plan view of an example wearable electronic device with a movable housing configured to move toward or away from a user&#39;s skin in response to an electrical signal from a tensioner. The wearable electronic device  2000  can include a housing at that can be permanently or removably attached to a two-part band system. In the illustrated embodiment, the housing of the wearable electronic device  2000  can be configured to change the height of the housing of the wearable electronic device  2000  relative to a user&#39;s wrist and to the band, such as shown by the relative difference between  FIG. 20A  and  FIG. 20B . In this manner, in response to the increase or decrease relative positioning of the band and the housing of the wearable electronic device  2000 , the tightness of the fit of the wearable electronic device can respectively increase or decrease. In this manner, the wearable electronic device  2000  can achieve the adjustment A 5 . 
       FIG. 21A  depicts a top plan view of an example wearable electronic device with a pin and eyelet and interlacing band system configured such that the pin moves along the longitudinal axis of the band system in response to an electrical signal from a tensioner. As illustrated, a first band  2102  and a second band  2104  can be overlapped in order to form a closed loop around a user&#39;s wrist. The first band  2102  can be coupled to the second band  2104  via a pin and eyelet attachment mechanism as substantially described herein. In this embodiment, an actuator  2108  can be coupled to the eyelet, which itself can be coupled to the tensioner. In response to an instruction to loosen or tighten the fit of the wearable electronic device  2100 , the tensioner can cause the actuator  2108  to move the eyelet along the longitudinal axis of the second band  2104 . In this manner, the actuator  2108  to can achieve the adjustment A 7 , as shown for example in  FIG. 21B . 
       FIG. 22  is a flow chart that depicts example operations of a method of tightening the fit of a wearable electronic device. The method can begin at operation  2202  in which a command is received to tighten a band of a wearable electronic device by a selected amount. In some examples, the selected amount can be a value or pointer corresponding to an amount or magnitude of tightness change, either relative or absolute. For example, the value or pointer can indicate that the fit should be tightened by 5%. 
     In another example, the value or pointer can indicate that the fit should be tightened by shortening a band by 1 mm. In another example, the value or pointer can indicate that the fit should be tightened by applying a force of 0.1 Newtons to the band. In other embodiments, other values and/or pointers may be used. 
     The method can continue to operation  2204  in which a tensioner is activated to begin tightening the band. Next, at operation  2206 , tightening can be discontinued after the selected amount of tightness increase is obtained. In other embodiments, the method depicted in  FIG. 22  can be implemented by first received a command to loosen the band by a particular amount. 
       FIG. 23  is a flow chart that depicts example operations of a method of dynamically adjusting the fit of a wearable electronic device. The method can begin at operation  2302  during which a signal can be received that indicates the band tightness has changed from a previously obtained or determined user-selected tightness. For example, in some embodiments, a sensor coupled to a band of the wearable electronic device can periodically, continuously, or on request measure the strain within the band. Thereafter, the strain measurement can be correlated to (via a formula, algorithm output, or look-up table) what degree of tightness the measured strain corresponds to. In some examples strain can be measured with a piezoresistive strain sensor. Upon determining that the current tightness of the band does not match (or has been measured to be outside a threshold range of tightnesses), the method can continue to operation  2304  in which the tightness of the band can be adjusted by either activating or deactivating a tensioner mechanism such as an actuator that is mechanically coupled to the band itself. Thereafter, tightening or loosening can be terminated at operation  2306 , once the necessary tightness is obtained. 
     In many cases the threshold, threshold range, and/or other user-selected setting for tightness of the band can be obtained from a memory associated with the wearable electronic device. In other examples, the user setting can be obtained from a third-party device, or a separate electronic device in communication with the wearable electronic device. 
       FIG. 24  is a flow chart that depicts example operations of a method of dynamically adjusting the fit of a wearable electronic device prior to obtaining biometric data with a biometric sensor. The method can begin at operation  2402  in which a command is received to obtain biometric data, such as a user&#39;s pulse. Next, at operation  2404 , a tightening mechanism associated with the wearable electronic device can be activated in order to increase the tightness of the wearable electronic device against the measurement site for obtaining a biometric data measurement. Next, at operation  2406 , tightening can be discontinued once it is determined that a tightness sufficient for obtaining biometric data is obtained. Next, at operation  2408 , biometric data can be obtained. Finally, at operation  2410 , the previously-applied tension can be released, and the band can be restored to its original tightness. 
       FIG. 25  is a flow chart that depicts example operations of a method of dynamically adjusting the fit of a wearable electronic device as a means of soliciting a user&#39;s attention. The method can begin at operation  2502  by receiving a command to notify a wearer of the wearable electronic device. Next, at operation  2504 , the wearable electronic device can be tightened. 
       FIG. 26  is a flow chart that depicts example operations of a method of dynamically adjusting the fit of a wearable electronic device in response to heightened user activity. The method can begin at operation  2602  by receiving an indication that the user is engaged in heighted activity. For example, in some embodiments, heighted user activity can be detected by monitoring the output from one or more accelerometers, gyroscopes, inertial measurement units, global positioning sensors, proximity sensors, and the link. Next, at operation  2604 , the wearable electronic device can be tightened to prevent sliding during the heightened activity. 
     Many embodiments of the foregoing disclosure may include or may be described in relation to various methods of operation, use, manufacture, and so on. Notably, the operations of methods presented herein are meant only to be exemplary and, accordingly, are not necessarily exhaustive. For example an alternate operation order, or fewer or additional steps may be required or desired for particular embodiments. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art 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 meant 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 that many modifications and variations are possible in view of the above teachings. In particular, any features described with respect to one embodiment may also be used in other embodiments, where compatible. Likewise, the features of the different embodiments may be exchanged, substituted, or omitted where compatible and appropriate.

Metadata:
Filing Date: 20150420
Publication Date: 20171010
Grant Date: 20171010
Priority Date: 20150308
Inventors: BARANSKI ANDRZEJ T.
ISIKMAN SERHAN O.
BUSHNELL TYLER S.
MARTISAUSKAS STEVEN J.
NAZZARO DAVID I.
Assignee: APPLE INC
CPC Classifications: [{"code": "A44C5/0069", "inventive": true, "first": false, "tree": "[]"}, {"code": "A44C5/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "A44C5/2071", "inventive": true, "first": true, "tree": "[]"}, {"code": "A44C5/2071", "inventive": true, "first": true, "tree": "[]"}, {"code": "A44C5/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "A44C5/0069", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/681", "inventive": false, "first": false, "tree": "[]"}, {"code": "A44C5/0053", "inventive": false, "first": false, "tree": "[]"}, {"code": "A45F2005/008", "inventive": false, "first": false, "tree": "[]"}, {"code": "A45F2005/008", "inventive": false, "first": false, "tree": "[]"}, {"code": "A44C5/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "A44C5/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "A44C5/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "A45F2005/008", "inventive": false, "first": false, "tree": "[]"}, {"code": "A44C5/0053", "inventive": false, "first": false, "tree": "[]"}, {"code": "A44C5/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/681", "inventive": false, "first": false, "tree": "[]"}, {"code": "A44C5/0069", "inventive": true, "first": false, "tree": "[]"}, {"code": "A44C5/2071", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 56850275