Abstract:
The present disclosure describes pressure sensitive keys with a single-sided direct conduction sensor that includes a sensor substrate, a conductive layer formed on an underside of a contact layer, and a force sensing layer formed on the underside of the contact layer substantially surrounding the conductive layer. The contact layer, the conductive layer, and the force sensing layer are configured to cooperatively flex in response to an application of pressure to contact the sensor substrate.

Description:
RELATED APPLICATIONS 
       [0001]    The present is related to each of the following applications, which are incorporated herein by reference in their entirety: 
         [0002]    U.S. Provisional Patent Application No. 61/606,321, filed Mar. 2, 2012, Attorney Docket Number 336082.01, and titled “Screen Edge;” 
         [0003]    U.S. Provisional Patent Application No. 61/606,301, filed Mar. 2, 2012, Attorney Docket Number 336083.01, and titled “Input Device Functionality;” 
         [0004]    U.S. Provisional Patent Application No. 61/606,313, filed Mar. 2, 2012, Attorney Docket Number 336084.01, and titled “Functional Hinge;” 
         [0005]    U.S. Provisional Patent Application No. 61/606,333, filed Mar. 2, 2012, Attorney Docket Number 336086.01, and titled “Usage and Authentication;” 
         [0006]    U.S. Provisional Patent Application No. 61/613,745, filed Mar. 21, 2012, Attorney Docket Number 336086.02, and titled “Usage and Authentication;” 
         [0007]    U.S. Provisional Patent Application No. 61/606,336, filed Mar. 2, 2012, Attorney Docket Number 336087.01, and titled “Kickstand and Camera;” and 
         [0008]    U.S. Provisional Patent Application No. 61/607,451, filed Mar. 6, 2012, Attorney Docket Number 336143.01, and titled “Spanaway Provisional;” 
         [0009]    U.S. patent application Ser. No. 13/468,882, filed May 10, 2012, Attorney Docket Number 336559.01, and titled “Pressure Sensitive Keys;” 
         [0010]    U.S. patent application Ser. No. 13/471,393, filed May 14, 2012, Attorney Docket Number 336554.01, and titled “Key Strike Determination For Pressure Sensitive Keyboard.” 
         [0011]    U.S. patent application Ser. No. 13/470,633, filed May 14, 2012, Attorney Docket Number 336554.01, and titled “Flexible Hinge and Removable Attachment;” and 
         [0012]    U.S. patent application Ser. No. 13/471,186, filed May 14, 2012, Attorney Docket Number 336563.01, and titled “Input Device Layers and Nesting.” 
     
    
     TECHNICAL FIELD 
       [0013]    The present disclosure pertains to pressure sensitive keys with a single-sided direct conduction sensor. 
       BACKGROUND 
       [0014]    Mobile computing devices have been developed to increase the functionality that is made available to users in a mobile setting. For example, a user may interact with a mobile phone, tablet computer, or other mobile computing device to check email, surf the web, compose texts, interact with applications, and the like. Traditional mobile computing devices often employed a virtual keyboard that was accessed using touchscreen functionality of the device. This approach was generally employed to maximize an amount of display area of the computing device. 
         [0015]    Use of the virtual keyboard, however, could be frustrating to a user that desired to provide a significant amount of inputs, such as to enter a significant amount of text to compose a long email, document, and the like. Thus, conventional mobile computing devices were often perceived to have limited usefulness for such tasks, especially in comparison with ease at which users could enter text using a conventional keyboard, e.g., of a conventional desktop computer. Use of the conventional keyboards, though, with the mobile computing device could decrease the mobility of the mobile computing device and thus could make the mobile computing device less suited for its intended use in a mobile setting. 
       SUMMARY 
       [0016]    This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
         [0017]    The present disclosure presents pressure sensitive keys with a single-sided direct conduction sensor. In an implementation, the pressure sensitive keys include a single-sided direct conduction sensor that, in turn, includes a sensor substrate, a conductive layer fabricated on a bottom surface of a contact layer, and a force sensing layer fabricated on the bottom surface of the contact layer substantially surrounding the conductive layer. The contact layer, the conductive layer, and the force sensing layer may be configured to cooperatively flex in response to an application of pressure to contact the sensor substrate. In an implementation, the sensor substrate may include a first conductor or a second conductor or a combination of both. The contact layer, the conductive layer, and the force sensing layer may be configured to cooperatively flex in response to the application of pressure to contact the first conductor or the second conductor or a combination of both the first conductor and the second conductor. In an implementation, the single-sided direct conduction sensor further includes a carbon layer fabricated to substantially surround the first conductor or the second conductor. A spacer layer may be configured to space apart the contact layer from the sensor substrate in an absence of the application of pressure. The force sensing layer may include a force sensing ink having a first conductivity under the application of pressure and the conductive layer may include a second conductivity higher than the first conductivity. 
         [0018]    Additional aspects and advantages of exemplary pressure sensitive keys with a single-sided direct conduction sensor will be apparent from the following detailed description that proceeds with reference to the accompanying drawings. 
     
    
     
       DRAWINGS DESCRIPTION 
         [0019]    In the drawings, the left-most digit(s) of a reference number identifies the drawing figure in which the reference number first appears. The use of the same reference numbers in different instances in the description and the drawing figures may indicate similar or identical items. Entities represented in the figures may be indicative of one or more entities and thus reference may be made interchangeably to single or plural forms of the entities in the discussion. 
           [0020]      FIG. 1  is an illustration of an environment in an example implementation that is operable to employ the techniques described herein. 
           [0021]      FIG. 2  depicts an example implementation of an input device of  FIG. 1  as showing a flexible hinge in greater detail. 
           [0022]      FIG. 3  depicts an example implementation showing a perspective view of a connecting portion of  FIG. 2  that includes mechanical coupling protrusions and a plurality of communication contacts. 
           [0023]      FIG. 4  depicts an example of a cross-sectional view of a pressure sensitive key of a keyboard of the input device of  FIG. 2 . 
           [0024]      FIG. 5  depicts an example of a pressure sensitive key of  FIG. 4  as having pressure applied at a first location of a flexible contact layer to cause contact with a corresponding first location of a sensor substrate. 
           [0025]      FIG. 6  depicts an example of the pressure sensitive key of  FIG. 4  as having pressure applied at a second location of the flexible contact layer to cause contact with a corresponding second location of the sensor substrate. 
           [0026]      FIG. 7  depicts an example of a cross-sectional view of a pressure sensitive key of a keyboard of the input device of  FIG. 2 . 
           [0027]      FIG. 8A  depicts an example of a cross-sectional view of a pressure sensitive key of  FIG. 4  including force sensitive ink and conductors exaggerated to explain its operation. 
           [0028]      FIG. 8B  depicts an example of a cross-sectional view of the pressure sensitive key of  FIG. 7  including conductive layer and force sensitive ink exaggerated to explain its operation. 
           [0029]      FIG. 9  depicts an example layout of conductors. 
           [0030]      FIG. 10  illustrates an example system including various components of example pressure sensitive keys that can be implemented as any type of computing device as described with reference to  FIGS. 1-9  to implement embodiments of the techniques described herein. 
       
    
    
     DETAILED DESCRIPTION 
     Overview 
       [0031]    Pressure sensitive keys may be used as part of an input device to support a relatively thin form factor, such as less than approximately 3.0 millimeters. However, pressure sensitive keys may not provide a degree of feedback that is common with conventional mechanical keyboards and therefore may result in missed hits and partial hits to intended keys of the keyboard. Further, conventional configuration of the pressure sensitive keys often resulted in different sensitivities due to the flexibility of the material being deflected, e.g., greater deflection is generally observed at a central area of the key as opposed to an edge of the key. Therefore, conventional pressure sensitive keys could result in an inconsistent user experience with a device that employs the keys. 
         [0032]    Pressure sensitive key techniques are described. In one or more implementations, a pressure sensitive key is configured to provide a normalized output, e.g., to counteract differences in the flexibility at different positions of the pressure sensitive key. For example, sensitivity at an edge of a key may be increased in comparison with the sensitivity at a center of the key to address the differences in flexibility of the key at those positions. 
         [0033]    The sensitivity may be adjusted in a variety of ways. For example, sensitivity may be adjusted by increasing an amount of force sensitive ink at the edges of a flexible contact layer as opposed to a center of the flexibility contact layer. In another example, an amount of conductors available to be contacted in a sensor substrate may be increased. This may be performed in a variety of ways, such as through arrangement of gaps, amount of conductive material, surface area, and so on at an edge of a sensor substrate that is contacted by the flexible contact layer as opposed to at a center of the sensor substrate. 
         [0034]    Sensitivity may also be adjusted for different keys. For example, keys that are more likely to receive a lighter pressure (e.g., a key at a bottom row, positioned near the edges of a keyboard, and so on) may be configured to have increased sensitivity in comparison with a key that is likely to receive a higher amount of pressure, e.g., such as keys in a home row. In this way, normalization may also be performed between keys of a keyboard as well as at the keys themselves. Further discussion of these and other features may be found in relation to the following sections. 
         [0035]    In the following discussion, an example environment is first described that may employ the techniques described herein. Example procedures are then described which may be performed in the example environment as well as other environments. Consequently, performance of the example procedures is not limited to the example environment and the example environment is not limited to performance of the example procedures. 
       Example Environment 
       [0036]      FIG. 1  is an illustration of an environment  100  in an example implementation that is operable to employ the techniques described herein. The illustrated environment  100  includes an example of a computing device  102  that is physically and communicatively coupled to an input device  104  via a flexible hinge  106 . The computing device  102  may be configured in a variety of ways. For example, the computing device  102  may be configured for mobile use, such as a mobile phone, a tablet computer as illustrated, and so on. Thus, the computing device  102  may range from full resource devices with substantial memory and processor resources to a low-resource device with limited memory and/or processing resources. The computing device  102  may also relate to software that causes the computing device  102  to perform one or more operations. 
         [0037]    The computing device  102 , for instance, is illustrated as including an input/output module  108 . The input/output module  108  is representative of functionality relating to processing of inputs and rendering outputs of the computing device  102 . A variety of different inputs may be processed by the input/output module  108 , such as inputs relating to functions that correspond to keys of the input device  104 , keys of a virtual keyboard displayed by the display device  110  to identify gestures and cause operations to be performed that correspond to the gestures that may be recognized through the input device  104  and/or touchscreen functionality of the display device  110 , and so forth. Thus, the input/output module  108  may support a variety of different input techniques by recognizing and leveraging a division between types of inputs including key presses, gestures, and so on. 
         [0038]    In the illustrated example, the input device  104  is configured as a keyboard having a QWERTY arrangement of keys although other arrangements of keys are also contemplated. Further, other non-conventional configurations are also contemplated, such as a game controller, configuration to mimic a musical instrument, and so forth. Thus, the input device  104  and keys incorporated by the input device  104  may assume a variety of different configurations to support a variety of different functionality. 
         [0039]    As previously described, the input device  104  is physically and communicatively coupled to the computing device  102  in this example through use of a flexible hinge  106 . The flexible hinge  106  is flexible in that rotational movement supported by the hinge is achieved through flexing (e.g., bending) of the material forming the hinge as opposed to mechanical rotation as supported by a pin, although that embodiment is also contemplated. Further, this flexible rotation may be configured to support movement in one direction (e.g., vertically in the figure) yet restrict movement in other directions, such as lateral movement of the input device  104  in relation to the computing device  102 . This may be used to support consistent alignment of the input device  104  in relation to the computing device  102 , such as to align sensors used to change power states, application states, and so on. 
         [0040]    The flexible hinge  106 , for instance, may be formed using one or more layers of fabric and include conductors formed as flexible traces to communicatively couple the input device  104  to the computing device  102  and vice versa. This communication, for instance, may be used to communicate a result of a key press to the computing device  102 , receive power from the computing device, perform authentication, provide supplemental power to the computing device  102 , and so on. The flexible hinge  106  may be configured in a variety of ways, further discussion of which may be found in relation to the following figure. 
         [0041]      FIG. 2  depicts an example implementation  200  of the input device  104  of  FIG. 1  as showing the flexible hinge  106  in greater detail. In this example, a connection portion  202  of the input device is shown that is configured to provide a communicative and physical connection between the input device  104  and the computing device  102 . In this example, the connection portion  202  has a height and cross section configured to be received in a channel in the housing of the computing device  102 , although this arrangement may also be reversed without departing from the spirit and scope thereof. 
         [0042]    The connection portion  202  is flexibly connected to a portion of the input device  104  that includes the keys through use of the flexible hinge  106 . Thus, when the connection portion  202  is physically connected to the computing device the combination of the connection portion  202  and the flexible hinge  106  supports movement of the input device  104  in relation to the computing device  102  that is similar to a hinge of a book. 
         [0043]    For example, rotational movement may be supported by the flexible hinge  106  such that the input device  104  may be placed against the display device  110  of the computing device  102  and thereby act as a cover. The input device  104  may also be rotated so as to be disposed against a back of the computing device  102 , e.g., against a rear housing of the computing device  102  that is disposed opposite the display device  110  on the computing device  102 . 
         [0044]    Naturally, a variety of other orientations are also supported. For instance, the computing device  102  and input device  104  may assume an arrangement such that both are laid flat against a surface as shown in  FIG. 1 . In another instance, a typing arrangement may be supported in which the input device  104  is laid flat against a surface and the computing device  102  is disposed at an angle to permit viewing of the display device  110 , e.g., such as through use of a kickstand disposed on a rear surface of the computing device  102 . Other instances are also contemplated, such as a tripod arrangement, meeting arrangement, presentation arrangement, and so forth. 
         [0045]    The connecting portion  202  is illustrated in this example as including magnetic coupling devices  204 ,  206 , mechanical coupling protrusions  208 ,  210 , and a plurality of communication contacts  212 . The magnetic coupling devices  204 ,  206  are configured to magnetically couple to complementary magnetic coupling devices of the computing device  102  through use of one or more magnets. In this way, the input device  104  may be physically secured to the computing device  102  through use of magnetic attraction. 
         [0046]    The connecting portion  202  also includes mechanical coupling protrusions  208 ,  210  to form a mechanical physical connection between the input device  104  and the computing device  102 . The mechanical coupling protrusions  208 ,  210  are shown in greater detail in the following figure. 
         [0047]      FIG. 3  depicts an example implementation  300  shown a perspective view of the connecting portion  202  of  FIG. 2  that includes the mechanical coupling protrusions  208 ,  210  and the plurality of communication contacts  212 . As illustrated, the mechanical coupling protrusions  208 ,  210  are configured to extend away from a surface of the connecting portion  202 , which in this case is perpendicular although other angles are also contemplated. 
         [0048]    The mechanical coupling protrusions  208 ,  210  are configured to be received within complimentary cavities within the channel of the computing device  102 . When so received, the mechanical coupling protrusions  208 ,  210  promote a mechanical binding between the devices when forces are applied that are not aligned with an axis that is defined as correspond to the height of the protrusions and the depth of the cavity. 
         [0049]    For example, when a force is applied that does coincide with the longitudinal axis described previously that follows the height of the protrusions and the depth of the cavities, a user overcomes the force applied by the magnets solely to separate the input device  104  from the computing device  102 . However, at other angles the mechanical coupling protrusion  208 ,  210  are configured to mechanically bind within the cavities, thereby creating a force to resist removal of the input device  104  from the computing device  102  in addition to the magnetic force of the magnetic coupling devices  204 ,  206 . In this way, the mechanical coupling protrusions  208 ,  210  may bias the removal of the input device  104  from the computing device  102  to mimic tearing a page from a book and restrict other attempts to separate the devices. 
         [0050]    The connecting portion  202  is also illustrated as including a plurality of communication contacts  212 . The plurality of communication contacts  212  is configured to contact corresponding communication contacts of the computing device  102  to form a communicative coupling between the devices. The communication contacts  212  may be configured in a variety of ways, such as through formation using a plurality of spring loaded pins that are configured to provide a consistent communication contact between the input device  104  and the computing device  102 . Therefore, the communication contact may be configured to remain during minor movement of jostling of the devices. A variety of other examples are also contemplated, including placement of the pins on the computing device  102  and contacts on the input device  104 . 
         [0051]      FIG. 4  depicts an example of a cross-sectional view of a pressure sensitive key  400  of a keyboard of the input device  104  of  FIG. 2 . The pressure sensitive key  400  in this example is illustrated as being formed using a flexible contact layer  402  (e.g., Mylar) that is spaced apart from the sensor substrate  404  using a spacer layer  406 ,  408 , which may be formed as another layer of Mylar, formed on the sensor substrate  404 , and so on. In this example, the flexible contact layer  402  does not contact the sensor substrate  404  absent application of pressure against the flexible contact layer  402 . 
         [0052]    The flexible contact layer  402  in this example includes a force sensitive ink  410  disposed on a surface of the flexible contact layer  402  that is configured to contact the sensor substrate  404 . The force sensitive ink  410  is configured such that an amount of resistance of the ink varies directly in relation to an amount of pressure applied. The force sensitive ink  410 , for instance, may be configured with a relatively rough surface that is compressed against the sensor substrate  404  upon an application of pressure against the flexible contact layer  402 . The greater the amount of pressure, the more the force sensitive ink  410  is compressed, thereby increasing conductivity and decreasing resistance of the force sensitive ink  410 . Other conductors may also be disposed on the flexible contact layer  402  without departing form the spirit and scope therefore, including other types of pressure sensitive and non-pressure sensitive conductors. 
         [0053]    The sensor substrate  404  includes one or more conductors  412  disposed thereon that are configured to be contacted by the force sensitive ink  410  of the flexible contact layer  402 . When contacted, an analog signal may be generated for processing by the input device  104  and/or the computing device  102 , e.g., to recognize whether the signal is likely intended by a user to provide an input for the computing device  102 . A variety of different types of conductors  412  may be disposed on the sensor substrate  404 , such as formed from a variety of conductive materials (e.g., silver, copper), disposed in a variety of different configurations as further described below. 
         [0054]      FIG. 5  depicts an example  500  of the pressure sensitive key  400  of  FIG. 4  as having pressure applied at a first location of the flexible contact layer  402  to cause contact of the force sensitive ink  410  with a corresponding first location of the sensor substrate  404 . The pressure is illustrated through use of an arrow in  FIG. 5  and may be applied in a variety of ways, such as by a finger of a user&#39;s hand, stylus, pen, and the like. In this example, the first location at which pressure is applied as indicated by the arrow is located generally near a center region of the flexible contact layer  402  that is disposed between the spacer layers  406 ,  408 . Due to this location, the flexible contact layer  402  may be considered generally flexible and thus responsive to the pressure. 
         [0055]    This flexibility permits a relatively large area of the flexible contact layer  402 , and thus the force sensitive ink  410 , to contact the conductors  412  of the sensor substrate  404 . Thus, a relatively strong signal may be generated. Further, because the flexibility of the flexible contact layer  402  is relatively high at this location, a relatively large amount of the force may be transferred through the flexible contact layer  402 , thereby applying this pressure to the force sensitive ink  410 . As previously described, this increase in pressure may cause a corresponding increase in conductivity of the force sensitive ink and decrease in resistance of the ink. Thus, the relatively high amount of flexibility of the flexible contact layer at the first location may cause a relatively stronger signal to be generated in comparison with other locations of the flexible contact layer  402  that located closer to an edge of the key, an example of which is described in relation to the following figure. 
         [0056]      FIG. 6  depicts an example  600  of the pressure sensitive key  400  of  FIG. 4  as having pressure applied at a second location of the flexible contact layer  402  to cause contact with a corresponding second location of the sensor substrate  404 . In this example, the second location of  FIG. 6  at which pressure is applied is located closer to an edge of the pressure sensitive key (e.g., closer to an edge of the spacer layer  406 ) than the first location of  FIG. 5 . Due to this location, the flexible contact layer  402  has reduced flexibility when compared with the first location and thus less responsive to pressure. 
         [0057]    This reduced flexibility may cause a reduction in an area of the flexible contact layer  402 , and thus the force sensitive ink  410 , that contacts the conductors  412  of the sensor substrate  404 . Thus, a signal produced at the second location may be weaker than a signal produced at the first location of  FIG. 5 . 
         [0058]    Further, because the flexibility of the flexible contact layer  402  is relatively low at this location, a relatively low amount of the force may be transferred through the flexible contact layer  402 , thereby reducing the amount of pressure transmitted to the force sensitive ink  410 . As previously described, this decrease in pressure may cause a corresponding decrease in conductivity of the force sensitive ink and increase in resistance of the ink in comparison with the first location of  FIG. 5 . Thus, the reduced flexibility of the flexible contact layer  402  at the second location in comparison with the first location may cause a relatively weaker signal to be generated. Further, this situation may be exacerbated by a partial hit in which a smaller portion of the user&#39;s finger is able to apply pressure at the second location of  FIG. 6  in comparison with the first location of  FIG. 5 . 
         [0059]    However, as previously described techniques may be employed to normalize outputs produced by the switch at the first and second locations. This may be performed in a variety of ways, such as through configuration of the flexible contact layer  402  having various specialized zones, use of a plurality of sensors, and combinations thereof. 
         [0060]      FIG. 7  depicts an example of a cross-sectional view of a pressure sensitive key  700  of a keyboard of the input device  104  shown in  FIG. 2 . The pressure sensitive key  700  in this example is illustrated as being fabricated, formed, or otherwise manufactured using a flexible contact layer  702  (e.g., Mylar) that is spaced apart from the sensor substrate  704  using a spacer layer  706 ,  708 , which may be formed as another layer of Mylar, formed on the sensor substrate  704 . In this example, the flexible contact layer  702  does not contact the sensor substrate  704  absent application of pressure against the flexible contact layer  702 . 
         [0061]    The flexible contact layer  702  includes a conductive layer  714  disposed or otherwise fabricated, formed, or manufactured on a surface of the flexible contact layer  702 . In the example shown in  FIG. 7 , the conductive layer  714  is disposed on a bottom surface of the flexible contact layer  702  that makes contact with the substrate  704  under the application of pressure against a top surface of the flexible contact layer  702 . 
         [0062]    The conductive layer  714  may be fabricated using silver, copper, or any other conductive material known to a person of ordinary skill in the art using any known process known to a person of ordinary skill in the art. The conductive layer  714  may be screened, coated, sprayed, printed or applied in other conventional ways to the contact layer  702 . The conductive layer  714  may be deposited as a thin layer or in a predetermined pattern. The term “layer” as used herein may include shapes such as cylinders, rectangles, squares or other shapes as may be required for a specific application. The conductive layer  714  may include a conductivity (or resistivity) that, unlike force sensitive ink  710 , does not change with the application of pressure. Put differently, the conductive layer  714  may include a conductivity that is nearly constant under the application of pressure or in the absence of the application of pressure. 
         [0063]    A force sensitive ink  710  may be disposed or otherwise fabricated, formed, or manufactured on a surface of the flexible contact layer  702 . In the example shown in  FIG. 7 , the force sensitive ink  710  is fabricated on the bottom surface of the flexible contact layer  702 . The force sensitive ink  710  may be fabricated to substantially enclose or surround the conductive layer  714  to avoid the conductive layer  714  contacting the conductors  712 . The force sensitive ink  710  is configured such that a resistance of the ink varies directly in relation to an amount of pressure applied. Similar to the force sensitive ink  410 , the force sensitive ink  710  may be configured with a relatively rough surface that is compressed against the sensor substrate  704  upon the application of pressure against the flexible contact layer  702 . The greater the amount of pressure, the more the force sensitive ink  710  is compressed, thereby increasing conductivity and decreasing impedance of the force sensitive ink  710 . Other conductors may also be disposed on the flexible contact layer  702  without departing form the spirit and scope therefore, including other types of pressure sensitive and non-pressure sensitive conductors. The force sensitive ink  710  may be screened, coated, sprayed, printed or applied in other conventional ways to the flexible contact layer  702 . The force sensitive ink  710  may be deposited as a thin layer or in a predetermined pattern. 
         [0064]    The sensor substrate  704  includes one or more conductors  712  disposed thereon that are configured to be contacted by the conductive layer  714  and by the force sensitive ink  710  of the flexible contact layer  402 . Upon the application of pressure, the flexible contact layer  702 , the conductive layer  714 , and the force sensitive ink  710  may cooperatively flex in the direction of the pressure to contact the sensor substrate  704  generally and the conductors  712  specifically. When contacted, an analog signal may be generated for processing by the input device  104  and/or the computing device  102 , e.g., to recognize whether the signal is likely intended by a user to provide an input for the computing device  102 . A variety of different types of conductors  712  may be disposed on the sensor substrate  704 , such as formed from a variety of conductive materials (e.g., silver, copper), disposed in a variety of different configurations. 
         [0065]      FIG. 9  depicts an example of conductors  712  of a sensor substrate  704 . Referring to  FIG. 9 , a first conductor  902  is inter-digitated or interlocked to a second conductor  904 . Surface area, amount of conductors, and gaps between the conductors may be used to adjust sensitivity at different locations of the sensor substrate  704 . 
         [0066]    Referring back to  FIG. 7 , the sensor substrate  704  may optionally include a carbon layer  716  disposed to substantially cover the one or more conductors  712 . The carbon layer  716  may be screened, coated, sprayed, printed, or applied in other conventional ways to the substrate  704 . The carbon layer  716  may be deposited as a thin layer or in a predetermined pattern. The carbon layer  716 , as the name implies, may comprise carbon or any other material known to a person of ordinary skill in the art applied in any manner to the substrate  704  known to a person of ordinary skill in the art. The carbon layer  716  smooths rough edges in the conductors  712  that may deteriorate the force sensitive ink  710  to thereby improve the general life and/or performance of pressure sensitive key  700 . 
         [0067]      FIG. 8A  depicts an example of a cross-sectional view of the pressure sensitive key  400  shown with the force sensitive ink  410  and the conductors  412  exaggerated to explain its operation. In  FIG. 8A , the application of pressure is illustrated through the use of an arrow and may be applied in a variety of ways, such as by a user&#39;s hand, stylus, pen, and the like. The force sensitive ink  410  is configured such that an amount of resistance of the ink varies directly in relation to an amount of pressure applied. As explained previously, the greater the amount of pressure, the more the force sensitive ink  410  is compressed increasing contact surface area between the granules suspended in the force sensitive ink  410 . The greater contact surface area between granules creates more efficient paths for electrical flow between conductors  412 . The force sensitive ink  410 , therefore, increases its conductivity and decreases its impedance Ri between conductors  412 . The signal created using the pressure sensitive key  400  is dependent on area and pressure because the impedance Ri varies dependent on area and pressure as we explained above relative to  FIGS. 5 and 6 . 
         [0068]      FIG. 8B  depicts an example of a cross-sectional view of the pressure sensitive key  700  shown with the conductive layer  714  and the force sensitive ink  710  exaggerated to explain its operation. As explained above, the conductive layer  714  may include an impedance Rc that, unlike force sensitive ink  710 , remains constant with the application of pressure. As explained above, the greater the amount of pressure applied to the contact layer  702 , the more the force sensitive ink  710  is compressed, thereby increasing the conductivity and decreasing the impedance Ri1 and impedance Ri2. Unlike the pressure sensitive key  400 , the pressure sensitive key  700  is less dependent on the area and pressure because the impedance Rc of the conductive layer  714  is substantially constant, remaining unaffected with changes in the area or amount of pressure applied. The result is that the pressure sensitive key  700  presents impedance Ri1+Rc+Ri2 to electrical flow that is less dependent on the variations of the force sensitive ink  710  to improve accuracy and increase linearity of the resulting signal. The pressure sensitive key  700 , like key  400 , is considered single-sided because the conductors  712  are on a single side of the force sensitive ink  710  and  410 , respectively. The pressure sensitive key  400  operates in a shunt mode where the electrical path is formed between the conductors  412  through the impedance Ri of the force sensitive ink  410 . By contrast, the addition of conductive layer  714 , allows the pressure sensitive key  700  to operate in a hybrid shunt/thru mode where the electrical path includes the conductors  712  through the impedance Rc of the conductive layer  714  as well as impedances Ri1 and Ri2 of the force sensitive ink  710 . The pressure sensitive key  700 , therefore, relies primarily on the ink impedance Ri1 and Ri2 for varied signal response while the pressure sensitive key  400  relies on primarily on the ink impedance Ri plus the area of activation and position for varied signal response. The addition of the conductive layer  714  applied directly under the force sensitive ink layer  710  used with shunt sensor design ( FIG. 9 ) avoids the additional cost and manufacturing complexity associated with double-sided devices that include conductors on both sides of the force sensitive ink  710 , which typically require interconnection therebetween. 
       Example System and Device 
       [0069]      FIG. 10  illustrates an example system generally at  1000  that includes an example computing device  1002  that is representative of one or more computing systems and/or devices that may implement the various techniques described herein. The computing device  1002  may be, for example, be configured to assume a mobile configuration through use of a housing formed and size to be grasped and carried by one or more hands of a user, illustrated examples of which include a mobile phone, mobile game and music device, and tablet computer although other examples are also contemplated. 
         [0070]    The example computing device  1002  as illustrated includes a processing system  1004 , one or more computer-readable media  1006 , and one or more I/O interface  1008  that are communicatively coupled, one to another. Although not shown, the computing device  1002  may further include a system bus or other data and command transfer system that couples the various components, one to another. A system bus can include any one or combination of different bus structures, such as a memory bus or memory controller, a peripheral bus, a universal serial bus, and/or a processor or local bus that utilizes any of a variety of bus architectures. A variety of other examples are also contemplated, such as control and data lines. 
         [0071]    The processing system  1004  is representative of functionality to perform one or more operations using hardware. Accordingly, the processing system  1004  is illustrated as including hardware element  1010  that may be configured as processors, functional blocks, and so forth. This may include implementation in hardware as an application specific integrated circuit or other logic device formed using one or more semiconductors. The hardware elements  1010  are not limited by the materials from which they are formed or the processing mechanisms employed therein. For example, processors may be comprised of semiconductor(s) and/or transistors (e.g., electronic integrated circuits (ICs)). In such a context, processor-executable instructions may be electronically-executable instructions. 
         [0072]    The computer-readable storage media  1006  is illustrated as including memory/storage  1012 . The memory/storage  1012  represents memory/storage capacity associated with one or more computer-readable media. The memory/storage component  1012  may include volatile media (such as random access memory (RAM)) and/or nonvolatile media (such as read only memory (ROM), Flash memory, optical disks, magnetic disks, and so forth). The memory/storage component  1012  may include fixed media (e.g., RAM, ROM, a fixed hard drive, and so on) as well as removable media (e.g., Flash memory, a removable hard drive, an optical disc, and so forth). The computer-readable media  1006  may be configured in a variety of other ways as further described below. 
         [0073]    Input/output interface(s)  1008  are representative of functionality to allow a user to enter commands and information to computing device  1002 , and also allow information to be presented to the user and/or other components or devices using various input/output devices. Examples of input devices include a keyboard, a cursor control device (e.g., a mouse), a microphone, a scanner, touch functionality (e.g., capacitive or other sensors that are configured to detect physical touch), a camera (e.g., which may employ visible or non-visible wavelengths such as infrared frequencies to recognize movement as gestures that do not involve touch), and so forth. Examples of output devices include a display device (e.g., a monitor or projector), speakers, a printer, a network card, tactile-response device, and so forth. Thus, the computing device  1002  may be configured in a variety of ways to support user interaction. 
         [0074]    The computing device  1002  is further illustrated as being communicatively and physically coupled to an input device  1014  that is physically and communicatively removable from the computing device  1002 . In this way, a variety of different input devices may be coupled to the computing device  1002  having a wide variety of configurations to support a wide variety of functionality. In this example, the input device  1014  includes one or more keys  1016 , which may be configured as pressure sensitive keys, mechanically switched keys, and so forth. 
         [0075]    The input device  1014  is further illustrated as include one or more modules  1018  that may be configured to support a variety of functionality. The one or more modules  1018 , for instance, may be configured to process analog and/or digital signals received from the keys  1016  to determine whether a keystroke was intended, determine whether an input is indicative of resting pressure, support authentication of the input device  1014  for operation with the computing device  1002 , and so on. 
         [0076]    Various techniques may be described herein in the general context of software, hardware elements, or program modules. Generally, such modules include routines, programs, objects, elements, components, data structures, and so forth that perform particular tasks or implement particular abstract data types. The terms “module,” “functionality,” and “component” as used herein generally represent software, firmware, hardware, or a combination thereof. The features of the techniques described herein are platform-independent, meaning that the techniques may be implemented on a variety of commercial computing platforms having a variety of processors. 
         [0077]    An implementation of the described modules and techniques may be stored on or transmitted across some form of computer-readable media. The computer-readable media may include a variety of media that may be accessed by the computing device  1002 . By way of example, and not limitation, computer-readable media may include “computer-readable storage media” and “computer-readable signal media.” 
         [0078]    “Computer-readable storage media” may refer to media and/or devices that enable persistent and/or non-transitory storage of information in contrast to mere signal transmission, carrier waves, or signals per se. Thus, computer-readable storage media refers to non-signal bearing media. The computer-readable storage media includes hardware such as volatile and non-volatile, removable and non-removable media and/or storage devices implemented in a method or technology suitable for storage of information such as computer readable instructions, data structures, program modules, logic elements/circuits, or other data. Examples of computer-readable storage media may include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, hard disks, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or other storage device, tangible media, or article of manufacture suitable to store the desired information and which may be accessed by a computer. 
         [0079]    “Computer-readable signal media” may refer to a signal-bearing medium that is configured to transmit instructions to the hardware of the computing device  1002 , such as via a network. Signal media typically may embody computer readable instructions, data structures, program modules, or other data in a modulated data signal, such as carrier waves, data signals, or other transport mechanism. Signal media also include any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media include wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, and other wireless media. 
         [0080]    As previously described, hardware elements  1010  and computer-readable media  1006  are representative of modules, programmable device logic and/or fixed device logic implemented in a hardware form that may be employed in some embodiments to implement at least some aspects of the techniques described herein, such as to perform one or more instructions. Hardware may include components of an integrated circuit or on-chip system, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), and other implementations in silicon or other hardware. In this context, hardware may operate as a processing device that performs program tasks defined by instructions and/or logic embodied by the hardware as well as a hardware utilized to store instructions for execution, e.g., the computer-readable storage media described previously. 
         [0081]    Combinations of the foregoing may also be employed to implement various techniques described herein. Accordingly, software, hardware, or executable modules may be implemented as one or more instructions and/or logic embodied on some form of computer-readable storage media and/or by one or more hardware elements  1010 . The computing device  1002  may be configured to implement particular instructions and/or functions corresponding to the software and/or hardware modules. Accordingly, implementation of a module that is executable by the computing device  1002  as software may be achieved at least partially in hardware, e.g., through use of computer-readable storage media and/or hardware elements  1010  of the processing system  1004 . The instructions and/or functions may be executable/operable by one or more articles of manufacture (for example, one or more computing devices  1002  and/or processing systems  1004 ) to implement techniques, modules, and examples described herein. 
       CONCLUSION 
       [0082]    Although the example implementations have been described in language specific to structural features and/or methodological acts, it is to be understood that the implementations defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as example forms of implementing the claimed features. 
         [0083]    A person of ordinary skill in the art will recognize that they may make many changes to the details of the above-described exemplary systems and methods without departing from the underlying principles. Only the following claims, therefore, define the scope of the exemplary systems and methods.