Patent Publication Number: US-2020278748-A1

Title: Integrated systems with force or strain sensing and haptic feedback

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional patent application No. 62/555,238, filed on Sep. 7, 2017, and entitled “A FORCE-HAPTIC SYSTEM INTEGRATION,” the disclosure of which is expressly incorporated herein by reference in its entirety. 
    
    
     FIELD OF TECHNOLOGY 
     The present disclosure relates to integrated systems with force or strain sensing and haptic feedback functionality. 
     BACKGROUND 
     Force sensing buttons are gaining attraction due to their intrinsic benefits of sensing through any different surface, ease of water and moisture proofing, and ability to work with multiple force level thresholds. The force sensing buttons are therefore promising in a number of applications including, but not limited to, mobile, automotive, and industrial applications. 
     In many applications, the trend of implementing force sensing buttons aligns with a trend toward a single sensing surface that does not accommodate mechanical buttons. Without mechanical buttons, however, the natural haptic feedback users are normally expecting from operating mechanical buttons is eliminated. In order to mimic a similar user experience, the industry has been implementing haptic actuation functionality with force sensing buttons. However, the conventional approach is to have the sensor signal processed through an application processor before sending out an excitation signal to initiate the haptic excitation. This leads to latency in the system that can negatively affect the user experience. 
     SUMMARY 
     Described herein are integrated systems that have force or strain sensing, force level calibration, force threshold detection, and haptic excitation functionalities. Two types of sensors, force sensors and strain gauges, are considered with different implementations with respect to a sensing surface. Additionally, haptic actuator implementations and force-haptic system partition implementations are also described herein. In some implementations, full haptic feedback logic is implemented on a sensor chip. In other implementations, partial haptic feedback logic is implemented on the sensor chip. 
     An example force-haptic system is described herein. The force-haptic system can include a sensor chip configured to receive an applied force, a haptic actuator configured to convert an electrical excitation signal into mechanical vibration, and a circuit board. The sensor chip can include at least one sensing element and an integrated circuit. Additionally, the sensor chip and the haptic actuator can be electrically and mechanically coupled to the circuit board, and the integrated circuit can be configured to process an electrical signal received from the at least one sensing element and to output the electrical excitation signal. 
     In some implementations, processing the electrical signal received from the at least one sensing element can include performing calibration and force threshold detection. In other implementations, processing the electrical signal received from the at least one sensing element can include generating the electrical excitation signal. 
     Alternatively or additionally, the at least one sensing element can be a force sensor or a strain gauge sensor. 
     Alternatively or additionally, in some implementations, the haptic actuator can be a piezoelectric haptic actuator. 
     Optionally, the piezoelectric haptic actuator can be implemented with a bulk piezoelectric substrate. For example, the piezoelectric haptic actuator can include a bulk piezoelectric substrate having top and bottom surfaces; top and bottom electrodes disposed on the top and bottom surfaces of the bulk piezoelectric substrate, respectively; top and bottom passivation layers disposed on the top and bottom electrodes, respectively; a via configured to provide an electrical connection to the bottom electrode; and a plurality of pad openings configured to provide electrical and mechanical connection between the haptic actuator and the circuit board. The piezoelectric substrate can be made of lead zirconate titanate (PZT), lithium niobate (LiNbO 3 ), barium titanate (BaTiO 3 ), or sodium potassium niobate (KNN). 
     Optionally, the piezoelectric haptic actuator can be implemented with a thin film piezoelectric substrate. For example, the piezoelectric haptic actuator can include a thin film piezoelectric substrate having top and bottom surfaces; top and bottom electrodes disposed on the top and bottom surfaces of the thin film piezoelectric substrate, respectively; a passivation layer disposed on the top electrode; a via configured to provide an electrical connection to the bottom electrode; a semiconductor substrate and a dielectric layer, wherein the dielectric layer is arranged between the semiconductor substrate and the bottom electrode; and a plurality of pad openings configured to provide electrical and mechanical connection between the haptic actuator and the circuit board. The piezoelectric substrate can be made of lead zirconate titanate (PZT), lithium niobate (LiNbO 3 ), barium titanate (BaTiO 3 ), or sodium potassium niobate (KNN). 
     Alternatively or additionally, in other implementations, the haptic actuator can be an eccentric rotating mass (ERM) vibration motor or a linear resonance actuator (LRA). 
     Alternatively or additionally, the circuit board can be a flexible circuit board. 
     Another example force-haptic system is described herein. The force-haptic system can include a sensor chip configured to receive an applied force, an integrated circuit chip, a haptic actuator configured to convert an electrical excitation signal into mechanical vibration, and a circuit board. The sensor chip can include at least one sensing element and an integrated circuit. Additionally, the sensor chip, the integrated circuit chip, and the haptic actuator can be electrically and mechanically coupled to the circuit board. The integrated circuit can be configured to process an electrical signal received from the at least one sensing element, and the integrated circuit chip can be configured to output the electrical excitation signal. 
     Other systems, methods, features and/or advantages will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  illustrates an example integrated force-haptic system including a force sensor configured to implement the full functionality of haptic feedback logic. 
         FIG. 2  illustrates another example force-haptic system including a force sensor configured to execute partial functionality of haptic feedback logic. 
         FIG. 3  illustrates an example force-haptic system including a strain gauge sensor configured to execute the full functionality of haptic feedback logic. 
         FIG. 4  illustrates another example force-haptic system including a strain gauge sensor configured to execute partial functionality of haptic feedback logic. 
         FIG. 5  is a block diagram of an example complementary metal-oxide-semiconductor (CMOS) integrated force or strain sensor with internal haptic drive. 
         FIG. 6  is a block diagram of an example CMOS integrated force or strain sensor with external haptic drive. 
         FIG. 7  illustrates a cross sectional view of an example piezoelectric haptic actuator implemented on bulk piezoelectric substrate. 
         FIG. 8  illustrates a cross sectional view of an example piezoelectric haptic actuator implemented on thin film piezoelectric on silicon substrate. 
         FIG. 9  illustrates a top view of a foot print of an example piezoelectric haptic actuator. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure can be understood more readily by reference to the following detailed description, examples, drawings, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this disclosure is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, and, as such, can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. 
     The following description is provided as an enabling teaching. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made, while still obtaining beneficial results. It will also be apparent that some of the desired benefits can be obtained by selecting some of the features without utilizing other features. Accordingly, those skilled in the art will recognize that many modifications and adaptations may be possible and can even be desirable in certain circumstances, and are contemplated by this disclosure. Thus, the following description is provided as illustrative of the principles and not in limitation thereof. 
     As used throughout, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a force sensing element” can include two or more such force sensing elements unless the context indicates otherwise. 
     The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. 
     Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. 
     As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. 
     The present disclosure relates to the system integration of force sensing and haptic feedback. In some implementations, the force sensing is realized with a force sensor. In other implementations, the force sensing is realized with a strain gauge sensor. 
     Referring now to  FIG. 1 , an example force-haptic system  101  is shown. The force-haptic system  101  shown in  FIG. 1  includes a force sensor  103  (sometimes referred to herein as “sensor chip”) that includes at least one sensing element and digital circuitry (sometimes referred to as “integrated circuit”) configured to fully implement the haptic feedback logic. Haptic feedback logic can include, but is not limited to, analog-to-digital conversion (ADC), force level calibration, force threshold detection, and/or haptic excitation functions. The digital circuitry can be configured to perform various signal conditioning functions and/or other operations as described herein. In other words, the force sensor  103  can include digital circuitry for receiving and processing the force signal detected by the sensing element(s) of the force sensor  103  and providing a control signal for driving a haptic actuator  108 . By implementing haptic feedback logic with the force sensor  103 , the force-haptic system&#39;s latency is reduced and therefore the user&#39;s experience is improved. Force sensors having both sensing elements and integrated circuitry are known in the art. For example, integrated force sensor chips having both sensing elements (e.g., piezoresistive and/or piezoelectric elements) and digital circuitry (e.g., integrated circuitry or CMOS circuitry) are described in WO2018/148503, published Aug. 16, 2018 and entitled “INTEGRATED DIGITAL FORCE SENSORS AND RELATED METHODS OF MANUFACTURE,” and WO2018/148510, published Aug. 16, 2018 and entitled “INTEGRATED PIEZORESISTIVE AND PIEZOELECTRIC FUSION FORCE SENSOR,” the disclosures of which are expressly incorporated herein by reference in their entireties. Other example integrated force sensors having both sensing elements and digital circuitry are described in PCT/US2018/042883, filed Jul. 19, 2018 and entitled “STRAIN TRANSFER STACKING IN A MEMS FORCE SENSOR,” and PCT/US2018/044049, filed Jul. 27, 2018 and entitled “A WAFER BONDED PIEZORESISTIVE AND PIEZOELECTRIC FORCE SENSOR AND RELATED METHODS OF MANUFACTURE.” 
     As discussed above, the force-haptic system  101  includes the force sensor  103  and the haptic actuator  108 . The haptic actuator  108  is configured to provide haptic feedback such as mechanical vibration when activated. In some implementations, the haptic actuator  108  can be a piezoelectric haptic actuator. It should be understood that piezoelectric haptic actuators are only provided as examples and that the haptic actuator  108  can be an Eccentric Rotating Mass (ERM) vibration motor, a Linear Resonance Actuator (LRA), or other actuator that generates vibration in response to electrical excitation. The force-haptic system  101  also includes a sensing surface  102  to which the external force is applied. As shown in  FIG. 1 , the force sensor  103  is attached to the sensing surface  102  through a tolerance absorption layer  104  and an adhesive  105 . This disclosure contemplates that the tolerance absorption layer  104  can be made of rubber or other suitable material, and that the adhesive  105  can be epoxy, tape, glue, or other suitable material. In addition, the haptic actuator  108  is attached to the sensing surface  102  with adhesive  105  and can provide haptic feedback at the sensing surface  102 . Further, as shown in  FIG. 1 , the force-haptic system  101  can include a circuit board such as printed circuit board (PCB)  107 . Optionally, the PCB  107  is a flexible PCB as shown in  FIG. 1 . Each of the force sensor  103  and the haptic actuator  108  are mechanically and electrically coupled to the PCB  107  through one or more metal layers  106  such as a solder bump. This disclosure contemplates that the metal layers  106  can be made of any suitable conductive material such as aluminum, copper, or gold for example. The haptic actuator  108  is electrically coupled to the force sensor  103  through the PCB  107  such that the haptic actuator  108  can receive control signals (e.g., an electrical activation signal) from the force sensor  103 . A mechanical anchor  109  is attached to the PCB  107 , which provides a reaction force to the force sensor  103 . 
     Referring now to  FIG. 2 , another example force-haptic system  201  is shown. The force-haptic system  201  shown in  FIG. 2  includes a sensing surface  102 , a force sensor  103 , a printed circuit board (PCB)  107 , and a haptic actuator  108 . The force sensor  103  and the haptic actuator  108  are attached to the sensing surface  102  as described above, for example, using adhesive  105  and/or a tolerance absorption layer  104 . Additionally, the force sensor  103  and the haptic actuator  108  are attached to the PCB  107  as described above, for example, using one or more metal layers  106 . A mechanical anchor  109  is attached to the PCB  107 , which provides a reaction force to the force sensor  103 . These features are described in detail above with regard to  FIG. 1  and are therefore not described in further detail below. 
     The force-haptic system  201  shown in  FIG. 2  also includes an integrated circuit (IC) chip  210 . As shown in  FIG. 2 , the IC chip  210  is mechanically and electrically coupled to the PCB  107  through one or more metal layers  106 . The IC chip  210 , the haptic actuator  108 , and the force sensor  103  are electrically coupled to one another through the PCB  107  such that the IC chip  210 , the haptic actuator  108 , and/or the force sensor  103  can transmit/receive electrical signals. The IC chip  210  can be configured to partially implement the haptic feedback logic. This is different than the force-haptic system described with regard to  FIG. 1 , where the force sensor includes the digital circuitry for implementing all of the haptic feedback logic. By implementing at least some of the haptic feedback logic with the force sensor  103 , the force-haptic system&#39;s latency is reduced and therefore the user&#39;s experience is improved. For example, the force sensor  103  can include digital circuitry for receiving and processing the force signal detected by the sensing element(s) of the force sensor  103 . This can include performing force level calibration and/or force threshold detection algorithms. In other words, the digital circuitry on the force sensor  103  includes the sensor feedback circuitry. The force sensor  103  can be configured to transmit the processed force signal to the IC chip  210 , which can be configured to perform haptic excitation algorithms. The IC chip  210  can be configured to generate and transmit a control signal (e.g., an electrical excitation signal) to the haptic actuator  108 . In other words, the IC chip  210  includes the haptic driver circuitry. It should be understood that the specific algorithms performed by the force sensor  103  and the IC chip  210  are provided only as examples. 
     Referring now to  FIG. 3 , another example force-haptic system  301  is shown. The force-haptic system  301  shown in  FIG. 3  includes a strain gauge sensor  303  (sometimes referred to herein as “sensor chip”) that includes at least one sensing element and digital circuitry (sometimes referred to as “integrated circuit”) configured to fully implement the haptic feedback logic. As described above, haptic feedback logic can include, but is not limited to, analog-to-digital conversion (ADC), force level calibration, force threshold detection, and/or haptic excitation algorithms. The digital circuitry can be configured to perform various signal conditioning functions and/or other operations as described herein. In other words, the strain gauge sensor  303  can include digital circuitry for receiving and processing the signal detected by the sensing element(s) of the strain gauge sensor  303  and providing a control signal for driving a haptic actuator  308 . By implementing haptic feedback logic with the strain gauge sensor  303 , the force-haptic system&#39;s latency is reduced and therefore the user&#39;s experience is improved. Sensor chips having both sensing elements and integrated circuitry are known in the art. For example, integrated force sensors having both sensing elements (e.g., piezoresistive and/or piezoelectric elements) and digital circuitry (e.g., integrated circuitry or CMOS circuitry) are described in WO2018/148503, published Aug. 16, 2018 and entitled “INTEGRATED DIGITAL FORCE SENSORS AND RELATED METHODS OF MANUFACTURE,” and WO2018/148510, published Aug. 16, 2018 and entitled “INTEGRATED PIEZORESISTIVE AND PIEZOELECTRIC FUSION FORCE SENSOR,” the disclosures of which are expressly incorporated herein by reference in their entireties. Other example integrated force sensors having both sensing elements and digital circuitry are described in PCT/US2018/042883, filed Jul. 19, 2018 and entitled “STRAIN TRANSFER STACKING IN A MEMS FORCE SENSOR,” and PCT/US2018/044049, filed Jul. 27, 2018 and entitled “A WAFER BONDED PIEZORESISTIVE AND PIEZOELECTRIC FORCE SENSOR AND RELATED METHODS OF MANUFACTURE.” 
     As discussed above, the force-haptic system  301  includes the strain gauge sensor  303  and the haptic actuator  308 . The haptic actuator  308  is configured to provide haptic feedback such as mechanical vibration when activated. In some implementations, the haptic actuator  308  can be a piezoelectric haptic actuator. It should be understood that piezoelectric haptic actuators are only provided as examples and that the haptic actuator  308  can be an Eccentric Rotating Mass (ERM) vibration motor, a Linear Resonance Actuator (LRA), or other actuator that generates vibration in response to electrical excitation. The force-haptic system  301  also includes a sensing surface  302  to which the external force is applied. As shown in  FIG. 3 , the force-haptic system  301  can also include a circuit board such as printed circuit board (PCB)  307 . Optionally, the PCB  307  is a flexible PCB as shown in  FIG. 3 . The PCB  307  can be attached to the sensing surface  302  through an adhesive  305 . This disclosure contemplates that the adhesive  305  can be epoxy, tape, glue, or other suitable material. Each of the strain gauge sensor  303  and the haptic actuator  308  are mechanically and electrically coupled to the PCB  307  through one or more metal layers  306  such as a solder bump. This disclosure contemplates that the metal layers  306  can be made of any suitable conductive material such as aluminum, copper, or gold for example. The haptic actuator  308  is electrically coupled to the strain gauge sensor  303  through the PCB  307  such that the haptic actuator  308  can receive control signals (e.g., an electrical excitation signal) from the strain gauge sensor  303 . 
     Referring now to  FIG. 4 , another example force-haptic system  401  is shown. The force-haptic system  401  shown in  FIG. 4  includes a sensing surface  302 , a strain gauge sensor  303 , a printed circuit board (PCB)  307 , and a haptic actuator  308 . The strain gauge sensor  303  and the haptic actuator  308  are attached to the PCB  307  as described above, for example, using one or more metal layers  306 . Additionally, the PCB  307  is attached to the sensing surface  302  as described above, for example, using adhesive  305 . These features are described in detail above with regard to  FIG. 3  and are therefore not described in further detail below. 
     The force-haptic system  401  shown in  FIG. 4  also includes an integrated circuit (IC) chip  409 . As shown in  FIG. 4 , the IC chip  409  is mechanically and electrically coupled to the PCB  307  through one or more metal layers  306 . The IC chip  409 , the haptic actuator  308 , and the strain gauge sensor  303  are electrically coupled to one another through the PCB  307  such that the IC chip  409 , the haptic actuator  308 , and/or the strain gauge sensor  303  can transmit/receive electrical signals. The IC chip  409  can be configured to partially implement the haptic feedback logic. This is different than the force-haptic system described with regard to  FIG. 3 , where the strain gauge sensor includes the digital circuitry for implementing all of the haptic feedback logic. By implementing at least some of the haptic feedback logic with the strain gauge sensor  303 , the force-haptic system&#39;s latency is reduced and therefore the user&#39;s experience is improved. For example, the strain gauge sensor  303  can include digital circuitry for receiving and processing the signal detected by the sensing element(s) of the strain gauge sensor  303 . This can include performing force level calibration and/or force threshold detection algorithms. In other words, the digital circuitry on the strain gauge sensor  303  includes the sensor feedback circuitry. The strain gauge sensor  303  can be configured to transmit the processed signal to the IC chip  409 , which can be configured to perform haptic excitation algorithms. The IC chip  409  can be configured to generate and transmit a control signal (e.g., an electrical excitation signal) to the haptic actuator  308 . In other words, the IC chip  409  includes the haptic driver circuitry. It should be understood that the specific algorithms performed by the strain gauge sensor  303  and the IC chip  409  are provided only as examples. 
     Referring now to  FIG. 5 , a block diagram of an example CMOS integrated sensor (sometimes referred to as a force-haptic system) with internal haptic drive is shown. The integrated sensor can include at least one sensing element such as piezoresistive and/or piezoelectric sensing elements, which is shown as the force/strain sensor in  FIG. 5 . Additionally, the integrated sensor can also include CMOS circuitry (e.g., digital circuitry or integrated circuit) on the same chip. The CMOS circuitry can be configured to fully implement the haptic feedback logic as shown in  FIG. 5 . Haptic feedback logic can include, but is not limited to, analog-to-digital conversion (ADC), force calibration, force threshold detection, and haptic excitation functions. In  FIG. 5 , the CMOS circuitry includes both the sensor feedback circuitry and the haptic driver circuitry. This is different than the conventional approach because the force sensor/strain gauge sensor signal is fully processed by digital circuitry on the integrated sensor chip itself. This has advantages including, but not limited to, reducing system latency and/or improving the user&#39;s experience. For example, as shown in  FIG. 5 , the force sensor or strain gauge outputs an analog electrical signal when force is applied to the system. The analog signal can be converted to a digital signal with the digital circuitry. This signal is then processed by the calibration algorithm, which can include eliminating offset, temperature, and/or drift effects from the system. This disclosure contemplates that functions other than those described above can be included as part of the calibration algorithm. Following calibration, the calibrated signal is then processed by the force threshold detection algorithm. For example, the force threshold detection algorithm can determine whether the calibrated signal is equal to or exceeds a threshold value. This disclosure contemplates that the threshold value can have any value selected by the user. If not, the calibrated signal can be ignored by the system. On the other hand, when the calibrated signal is equal to or exceeds the threshold (e.g., not noise), then the calibrated signal is transmitted to the haptic driver. This disclosure contemplates that functions other than those described above can be included as part of the force threshold detection algorithm. The haptic driver can be configured to generate the electrical activation signal and transmit the electrical activation signal to the haptic actuator, for example, an actuator described above with regard to  FIGS. 1 and 3 . This disclosure contemplates that functions other than those described above can be included as part of the haptic driver algorithm. As described above, it should be understood that the sensing elements can be provided on the same chip (e.g., the force sensor  103  or strain gauge sensor  303  shown in  FIGS. 1 and 3 , respectively) as the CMOS circuitry (e.g., digital circuitry) configured to implement the above-described algorithms. 
     Referring now to  FIG. 6 , a block diagram of an example CMOS integrated sensor (sometimes referred to as a force-haptic system) with external haptic drive is shown. The integrated sensor can include at least one sensing element such as piezoresistive and/or piezoelectric sensing elements, which is shown as the force/strain sensor in  FIG. 6 . Additionally, the integrated sensor can also include CMOS circuitry (e.g., digital circuitry or integrated circuit) on the same chip. The CMOS circuitry on the sensor chip can be configured to partially implement the haptic feedback logic as shown in  FIG. 6 . For example, the CMOS circuitry on the sensor chip can be configured to implement force calibration and force threshold detection algorithms. The remaining logic (e.g., haptic driver) can be implemented by an external chip such as IC chip  210  shown in  FIG. 2  or IC chip  409  shown in  FIG. 4 . In other words, in  FIG. 6 , the CMOS circuitry on the sensor chip includes the sensor feedback circuitry, while the external chip includes the haptic driver circuitry. This is different than the conventional approach because the force sensor/strain gauge sensor signal is partially processed by digital circuitry on the integrated sensor chip itself. This has advantages including, but not limited to, reducing system latency and/or improving the user&#39;s experience. For example, as shown in  FIG. 6 , the force sensor or strain gauge outputs an analog electrical signal when force is applied to the system. The analog signal can be converted to a digital signal with the digital circuitry. This signal is then processed by the calibration algorithm, which can including eliminating offset, temperature, and/or drift effects from the system. This disclosure contemplates that functions other than those described above can be included as part of the calibration algorithm. Following calibration, the calibrated signal is then processed by the force threshold detection algorithm. For example, the force threshold detection algorithm can determine whether the calibrated signal is equal to or exceeds a threshold value. This disclosure contemplates that the threshold value can have any value selected by the user. If not, the calibrated signal is ignored by the system. On the other hand, when the calibrated signal is equal to or exceeds the threshold (e.g., not noise), then the calibrated signal is transmitted from the sensor chip to an external chip (e.g., IC chip  210  or  409  shown in  FIG. 2 or 4 ), which implements the haptic driver. This disclosure contemplates that functions other than those described above can be included as part of the force threshold detection algorithm. The haptic driver can be configured to generate the electrical activation signal and transmit the electrical activation signal to the haptic actuator, for example, an actuator described above with regard to  FIGS. 2 and 4 . This disclosure contemplates that functions other than those described above can be included as part of the haptic driver algorithm. As described above, it should be understood that the sensing elements can be provided on the same chip (e.g., the force sensor  103  or strain gauge sensor  303  shown in  FIGS. 1 and 3 , respectively) as the CMOS circuitry (e.g., digital circuitry) configured to implement the calibration and/or force threshold detection algorithms, while the haptic driver algorithm can be implemented on an external chip. 
     Referring now to  FIG. 7 , a cross sectional view of an example piezoelectric haptic actuator implemented on bulk piezoelectric substrate is shown. As described above, a piezoelectric haptic actuator can optionally be used with a force-haptic system described above with regard to any one of  FIGS. 1-6 . It should be understood that piezoelectric haptic actuators are only provided as one example haptic actuator. This disclosure contemplates using other types of actuators that generate vibration in response to electrical excitation including, but not limited to, an Eccentric Rotating Mass (ERM) vibration motor or a Linear Resonance Actuator (LRA). In  FIG. 7 , the piezoelectric haptic actuator  701  is implemented with a bulk piezoelectric substrate  702 . As used herein, the term “bulk” means that the thickness of the piezoelectric substrate  702  is about 90% or more of the piezoelectric haptic actuator&#39;s thickness after fabrication. The piezoelectric substrate  702  can optionally be made of lead zirconate titanate (PZT), lithium niobate (LiNbO 3 ), barium titanate (BaTiO 3 ), or sodium potassium niobate (KNN). As shown in  FIG. 7 , opposing electrodes—bottom electrode  703  and top electrode  705 —are disposed on opposite surfaces of the piezoelectric substrate  702 . Additionally, a via  707  provides an electrical connection to the bottom electrode  703 . This disclosure contemplates that the electrodes and via can be made of any suitable conductive material such as aluminum, copper, or gold for example. Passivation layers—bottom passivation layer  704  and top passivation layer  706 —are disposed on the opposing electrodes  703 ,  705  as shown in  FIG. 7  and provide protection to the electrodes. This disclosure contemplates that the passivation layers can be made of any suitable passivation material such as silicon oxide, silicon nitride, or polymer for example. Further, as shown in  FIG. 7 , under bump metallization (UBM)  708  and metal contact layer  709  can be arranged in pad openings  710 . This disclosure contemplates that the UBM and metal layer can be made of any suitable conductive material such as aluminum, copper, or gold for example. It should be understood that the number, shape, size, and/or arrangement of the pad openings are provided only as examples. This disclosure contemplates that the electrical activation signal (e.g., the signal output by the force-haptic system of any one of  FIGS. 1-6 ) can be provided to the piezoelectric haptic actuator  701  through the metal contact layer  709 . For example, that piezoelectric haptic actuator  701  can be soldered to the circuit board as shown in any one of  FIGS. 1-4  at the metal contact layer  709 . 
     Referring now to  FIG. 8 , a cross sectional view of an example piezoelectric haptic actuator implemented on thin film piezoelectric on silicon substrate is shown. As described above, a piezoelectric haptic actuator can optionally be used with a force-haptic system described above with regard to any one of  FIGS. 1-6 . It should be understood that piezoelectric haptic actuators are only provided as one example haptic actuator. This disclosure contemplates using other types of actuators that generate vibration in response to electrical excitation including, but not limited to, an Eccentric Rotating Mass (ERM) vibration motor or a Linear Resonance Actuator (LRA). In  FIG. 8 , the piezoelectric haptic actuator  801  is implemented with a thin film piezoelectric substrate  802 . The piezoelectric substrate  802  can optionally be made of lead zirconate titanate (PZT), lithium niobate (LiNbO 3 ), barium titanate (BaTiO 3 ), or sodium potassium niobate (KNN). As used herein, the term “thin film” means that the thickness of the piezoelectric substrate  802  is about 10% or less of the piezoelectric haptic actuator&#39;s thickness after fabrication. As shown in  FIG. 8 , opposing electrodes—bottom electrode  703  and top electrode  705 —are disposed on opposite surfaces of the piezoelectric substrate  802 . Additionally, a via  707  provides an electrical connection to the bottom electrode  703 . This disclosure contemplates that the electrodes and via can be made of any suitable conductive material such as aluminum, copper, or gold for example. The piezoelectric substrate  802  and electrodes  703 ,  705  are arranged on a semiconductor (e.g., silicon) substrate  811  with a dielectric layer  804  arranged there between. This disclosure contemplates that the dielectric layer can be made of any suitable insulation material such as silicon oxide, silicon nitride or polymer. A passivation layer—top passivation layer  706 —is disposed on the top electrode  705  as shown in  FIG. 8  and provides protection to the electrode. This disclosure contemplates that the passivation layer can be made of any suitable passivation material. Further, as shown in  FIG. 8 , under bump metallization (UBM)  708  and metal contact layer  709  can be arranged in pad openings  710 . This disclosure contemplates that the UBM and metal layer can be made of any suitable conductive material such as aluminum, copper, or gold for example. It should be understood that the number, shape, size, and/or arrangement of the pad openings are provided only as examples. This disclosure contemplates that the electrical activation signal (e.g., the signal output by the force-haptic system of any one of  FIGS. 1-6 ) can be provided to the piezoelectric haptic actuator  801  through the metal contact layer  709 . For example, that piezoelectric haptic actuator  801  can be soldered to the circuit board as shown in any one of  FIGS. 1-4  at the metal contact layer  709 . 
     Referring now to  FIG. 9 , a top view of a foot print of the piezoelectric haptic actuator shown in either  FIG. 7  or  FIG. 8  is shown. In the example layout  901 , the bottom electrode pins  902  provide the electrical connection to the bottom electrodes (e.g., electrode  703  shown in  FIGS. 7 and 8 ) through vias (e.g., via  707  shown in  FIGS. 7 and 8 ). The pins  902  are placed at the corners of the piezoelectric haptic actuator to minimize the non-actuation electrode area ratio. The majority of the top electrode (e.g., electrode  705  shown in  FIGS. 7 and 8 ) is patterned for the actuation pin(s)  903 . The shape of the actuation pin(s)  903  can vary depending on the shape of the piezoelectric haptic actuator and/or the desire for maximum actuation. As shown in  FIG. 9 , both the bottom electrode pins  902  and actuation pin(s)  903  can be formed using two layers, e.g., electrode layer  904  and passivation layer  905 . 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.