PATENT DOCUMENT

Publication Number: US-10646121-B2
Application Number: US-201615274183-A
Country: US
Kind Code: B2

Title: Pressure measurement designs

Abstract:
The present invention generally relates to the measuring and monitoring of blood pressure. More specifically, embodiments may apply the theory of applanation tonometry for the measurement of blood pressure. Some embodiments provide a method for measuring mean arterial pressure. Some embodiments provide a device that may be worn by a user that may non-invasively measure and monitor blood pressure of a user. In some embodiments, the invention generally relates to sensor arrays for use with a wrist-worn device to measure blood pressure. Embodiments of the sensor array designs described may be configured to improve resolution by decoupling nodes of the sensor array.

Claims:
What is claimed is: 
     
       1. A wrist-worn device configured to measure blood pressure of a user wearing the wrist-worn device, the wrist-worn device comprising:
 a sensor array comprising capacitive nodes configured to measure blood pressure of a user wearing the wrist-worn device, the sensor array comprising one or more distal electrodes and one or more proximal electrodes, wherein each of the capacitive nodes is formed via one of the one or more distal electrodes and one of the one or more proximal electrodes that are separated by a respective gap, wherein each of the one or more distal electrodes is configured to be disposed between a skin of the user and a respective one of the one or more proximal electrodes, and wherein the capacitive nodes are formed at laterally spaced apart locations; 
 a dielectric layer disposed between the one or more distal electrodes and the one or more proximal electrodes; 
 wherein a distal surface of each of the capacitive nodes protrudes toward the skin of the user to form a protrusion individual to the capacitive node; 
 wherein the dielectric layer includes laterally spaced apart pillars, each of the laterally spaced apart pillars being positioned at a respective one of the capacitive nodes and supporting a corresponding one of the one or more distal electrodes relative to a corresponding one of the one or more proximal electrodes of the respective one of the capacitive nodes. 
 
     
     
       2. The wrist-worn device of  claim 1 , wherein:
 one of the one or more distal electrodes is formed by a sheet of conductive material; 
 the one or more proximal electrodes comprise two or more proximal electrodes; and 
 each of two or more of the capacitive nodes comprises a respective one of the two or more proximal electrodes in combination with the distal electrode formed by the sheet of conductive material. 
 
     
     
       3. The wrist-worn device of  claim 2 , wherein the sheet of conductive material comprises a conductive silicone. 
     
     
       4. The wrist-worn device of  claim 1 , wherein the one or more proximal electrodes comprise independent proximal electrodes. 
     
     
       5. The wrist-worn device of  claim 1 , wherein the one or more proximal electrodes comprise proximal electrodes that form strips of the proximal electrodes running parallel with one another. 
     
     
       6. The wrist-worn device of  claim 1 , wherein each of the laterally spaced apart pillars of the dielectric layer has a circular cross-section. 
     
     
       7. The wrist-worn device of  claim 1 , wherein each of the laterally spaced apart pillars of the dielectric layer has a rectangular cross-section. 
     
     
       8. The wrist-worn device of  claim 1 , wherein the dielectric layer includes strips supporting the one or more distal electrodes relative to the one or more proximal electrodes, the strips of the dielectric layer being positioned in spaces between adjacent capacitive nodes of the capacitive nodes. 
     
     
       9. The wrist-worn device of  claim 1 , comprising a device band having a length and a width, wherein:
 the sensor array is supported by the device band; 
 the sensor array comprises primary slits, each of the primary slits being disposed between adjacent capacitive nodes of the capacitive nodes and extending along the width of the device band; and 
 the sensor array comprises secondary lateral slits, each of the secondary lateral slits extending from a corresponding one of the primary slits in a direction transverse to the primary slit, each of the secondary lateral slits at least partially separating adjacent capacitive nodes of the capacitive nodes. 
 
     
     
       10. The wrist-worn device of  claim 1 , wherein:
 the capacitive nodes are arranged in rows and columns; and 
 adjacent rows of the capacitive nodes are staggered. 
 
     
     
       11. The wrist-worn device of  claim 1 , wherein the sensor array is curved. 
     
     
       12. The wrist-worn device of  claim 11 , wherein the sensor array has a radius of curvature between 12 mm and 20 mm. 
     
     
       13. The wrist-worn device of  claim 1 , further comprising pins and a frame, each of the pins coupled with one of the capacitive nodes of the sensor array, wherein the pins are restricted to movement in the a proximal-distal direction by the frame. 
     
     
       14. A wrist-worn device configured to measure blood pressure of a user wearing the wrist-worn device, the wrist-worn device comprising:
 a sensor array comprising capacitive nodes, the sensor array comprising a sheet of conductive material and proximal electrodes that are spaced apart, wherein the sheet of conductive material is separated from each of the proximal electrodes by a respective gap, wherein each of the capacitive nodes is formed at spaced apart locations where the sheet of conductive material overlaps with a respective one of the proximal electrodes, 
 wherein the sensor array comprises primary slits, each of the primary slits being disposed between adjacent capacitive nodes of the capacitive nodes and extending along a width of the device band, and 
 wherein the sensor array comprises secondary lateral slits, each of the secondary lateral slits extending from a corresponding one of the primary slits in a direction transverse to the primary slit, each of the secondary lateral slits at least partially separating adjacent capacitive nodes of the capacitive nodes. 
 
     
     
       15. The wrist-worn device of  claim 14 , wherein:
 the capacitive nodes are arranged in rows and columns; and 
 adjacent rows of the capacitive nodes are staggered. 
 
     
     
       16. The wrist-worn device of  claim 14 , wherein each of the proximal electrodes is configured as an individual electrode. 
     
     
       17. The wrist-worn device of  claim 14 , wherein the sensor array is curved. 
     
     
       18. The wrist-worn device of  claim 17 , wherein the sensor array has a radius of curvature between 12 mm and 20 mm. 
     
     
       19. The wrist-worn device of  claim 14 , further comprising pins and a frame, each of the pins being coupled with one of the capacitive nodes, wherein the pins are restricted to movement in a proximal-distal direction by the frame. 
     
     
       20. The wrist-worn device of  claim 14 , comprising a device band having a length and a width, wherein the sensor array is supported by the device band. 
     
     
       21. The wrist-worn device of  claim 14 , further comprising a dielectric layer disposed between the sheet of conductive material and the proximal electrodes. 
     
     
       22. The wrist-worn device of  claim 21 , wherein the dielectric layer includes pillars that are spaced apart, each of the pillars being disposed at a respective one of the capacitive nodes and supporting the sheet of conductive material relative to one of the proximal electrodes corresponding to the respective one of the capacitive nodes. 
     
     
       23. The wrist-worn device of  claim 22 , wherein each of the pillars has a circular cross-section. 
     
     
       24. The wrist-worn device of  claim 22 , wherein each of the pillars has a rectangular cross-section. 
     
     
       25. The wrist-worn device of  claim 21 , wherein the dielectric layer includes strips supporting the sheet of conductive material relative to the proximal electrodes, the strips of the dielectric layer being positioned in spaces between adjacent capacitive nodes of the capacity nodes. 
     
     
       26. A wrist-worn device configured to measure blood pressure of a user wearing the wrist-worn device, the wrist-worn device comprising:
 a device band having a length and a width; 
 a sensor array supported by the device band and comprising capacitive nodes configured to measure blood pressure of a user wearing the wrist-worn device, the sensor array comprising one or more distal electrodes and one or more proximal electrodes, wherein the distal and proximal electrodes are each of the capacitive nodes is formed via one of the one or more distal electrodes and one of the one or more proximal electrodes that are separated by a respective gap, wherein each of the one or more distal electrodes is configured to be disposed between a skin of the user and a respective one of the one or more proximal electrodes, and wherein the capacitive nodes are formed at laterally spaced apart locations; 
 wherein the sensor array comprises primary slits, each of the primary slits being disposed between adjacent capacitive nodes of the capacitive nodes and extending along the width of the device band, and 
 wherein the sensor array comprises secondary slits, each of the secondary slits extending from a corresponding one of the primary slits in a direction transverse to the primary slit, each of the secondary slits at least partially separating adjacent capacitive nodes of the capacitive nodes. 
 
     
     
       27. The wrist-worn device of  claim 26 , wherein:
 the capacitive nodes are arranged in rows and columns; and 
 adjacent rows of the capacitive nodes are staggered. 
 
     
     
       28. The wrist-worn device of  claim 26 , wherein at least one of:
 the one or more distal electrodes form strips of the one or more distal electrodes that extend parallel to one another; and 
 the one or more proximal electrodes form strips of the one or more proximal electrodes that extend parallel to one another. 
 
     
     
       29. The wrist-worn device of  claim 26 , wherein the sensor array is curved. 
     
     
       30. The wrist-worn device of  claim 29 , wherein the sensor array has a radius of curvature between 12 mm and 20 mm. 
     
     
       31. The wrist-worn device of  claim 26 , further comprising pins and a frame, each of the pins being coupled with one of the capacitive nodes, wherein the pins are restricted to movement in the a proximal-distal direction by the frame. 
     
     
       32. A wrist-worn device configured to measure blood pressure of a user wearing the wrist-worn device, the wrist-worn device comprising:
 a sensor array comprising capacitive nodes configured to measure blood pressure of a user wearing the wrist-worn device, the sensor array comprising: 
 one or more distal electrodes and one or more proximal electrodes, wherein each of the capacitive nodes is formed via one of the one or more distal electrodes and one of the one or more proximal electrodes that are separated by a respective gap, and wherein the capacitive nodes are formed at laterally spaced apart locations; 
 a dielectric layer disposed between the one or more distal electrodes and the one or more proximal electrodes, the dielectric layer including pillars that are spaced apart, each of the pillars being positioned at a respective one of the capacitive nodes and supporting the distal electrode a corresponding one of the one or more distal electrodes relative to a corresponding one of the one or more proximal electrodes of the respective one of the capacitive nodes, 
 wherein a distal surface of each of the capacitive nodes protrudes toward a skin of the user to form a protrusion individual to the capacitive node. 
 
     
     
       33. The wrist-worn device of  claim 32 , wherein each of the pillars has a circular cross-section. 
     
     
       34. The wrist-worn device of  claim 32 , wherein each of the pillars has a rectangular cross-section. 
     
     
       35. A wrist-worn device configured to measure blood pressure of a user wearing the wrist-worn device, the wrist-worn device comprising:
 a sensor array comprising a proximal layer, a distal layer, and a dielectric layer disposed between the proximal layer and the distal layer, the dielectric layer supporting the proximal layer relative to the distal layer, the proximal layer comprising proximal electrodes, the distal layer comprising distal electrodes, and wherein capacitive nodes of the sensor array are formed at locations where a distal electrode of the distal electrodes overlaps with a proximal electrode of the proximal electrodes; 
 wherein the proximal layer comprises cantilevered fingers, each of the cantilevered fingers being separated from an adjacent one of the cantilevered fingers by an intervening slit, and wherein the cantilevered fingers are folded. 
 
     
     
       36. The wrist-worn device of  claim 35 , wherein each of the cantilevered fingers are parallel with one another. 
     
     
       37. The wrist-worn device of  claim 35 , further comprising stiffeners, each of the stiffeners being coupled with one of the cantilevered fingers. 
     
     
       38. The wrist-worn device of  claim 35 , further comprising an actuator sandwiched by the cantilevered fingers. 
     
     
       39. The wrist-worn device of  claim 38 , further comprising stiffeners, each of the stiffeners being coupled with one of the cantilevered fingers adjacent to a free end of the cantilevered finger; and wherein the actuator is coupled with each of the stiffeners.

Description:
CROSS REFERENCE TO RELATED APPLICATION DATA 
     The present application claims the benefit of U.S. Provisional Appln. No. 62/234,510 filed Sep. 29, 2015; the full disclosure which is incorporated herein by reference in its entirety for all purposes. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     The present disclosure generally relates to the measuring and monitoring of pressure (e.g., blood pressure or the like). More specifically, embodiments may utilize applanation tonometry for the measurement of blood pressure. Some embodiments provide a method for measuring mean arterial pressure. Optionally, some embodiments provide for a method of measuring and/or monitoring a blood pressure waveform morphology. Some embodiments provide a device that may be worn by a user that may non-invasively measure and monitor blood pressure of a user. 
     Measuring pressure may be useful in monitoring one or more user parameters. For example, blood pressure measurements may be a helpful user parameter to measure as elevated blood pressure (a.k.a. hypertension) may be an indicator for potential health issues. As a result, blood pressure measurement is a routine test in many medical examinations. Additionally, pressure measurements may also be indicative of a user&#39;s heart rate. Further, in some instances, pressure measurements may provide blood pressure waveform morphologies which may be a useful user parameter to monitor. 
     Embodiments of the present disclosure may provide pressure measurements for monitoring one or more user parameters. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure provides non-invasive devices and methods for determining a blood pressure within a cardiovascular system of a user. In some embodiments, the disclosure generally relates to sensor arrays for use with a wrist-worn device to measure blood pressure. The sensor array may have a plurality of capacitive nodes each formed by an overlapping area of two electrodes. The capacitance at each node may be measured as a representation of the pressure applied at that node. A sensor array may increase the chance of proper placement of at least one pressure sensing node relative to the target artery. Some embodiments reduce the coupling (or cross-talk) between nodes of the sensor array to increase a pressure-sensing resolution of the sensor array. These devices may help reduce issues with signal processing as one or more preferred pressure sensing nodes of the sensor array may be identified and pressure signals received therefrom may require less error correction or processing. Such devices may provide a more convenient and accurate blood pressure monitoring device and may thereby increase the adoption of non-clinical measurements and monitoring of blood pressure by common consumers. 
     Particular embodiments of the sensor array designs described herein may be configured to improve signal resolution by decoupling nodes of the sensor array. The sensor arrays may be provided on a skin-engaging surface of the wrist-worn device and may be coupled with an actuator for urging the sensor array against the artery of a user (e.g., for an applanation tonometry sweep). The nodes of the array may be sized and sensitive enough to detect a heart-beat pulse and/or a blood pressure of a user (e.g., from the user&#39;s radial artery) with minimal adjustment. In some exemplary embodiments, nodes of the array may have a sensing area of approximately 1 mm by 1 mm and the sensor array may define a sensing area of approximately 10 mm×10 mm. 
     The sensor array may include a first layer of parallel electrodes backed by a backing film, such as a polyimide (e.g. Kapton) film and a second layer of parallel electrodes running transverse or perpendicular to the first layer. The intersections of the rows of parallel electrodes with the columns of parallel electrodes may form each of the nodes the sensor array. Put in another way, the intersections of the rows and columns of electrodes may form the active area of each of the capacitive nodes. These two layers of electrodes may be separated by compressible material such as a dielectric material (e.g., silicone or the like). 
     In some embodiments, the dielectric material may form separate pillars that are located in the active area of each node (i.e., at the intersections of the first layer of electrodes and the second layer of electrodes). Pillars of dielectric may be provided at these intersections to support the top electrode strips relative to the bottom electrode strips. The dielectric pillar may reduce cross-talk (also referred to as coupling) between the adjacent nodes so that discrete pressures applied at one node are not detected (or minimally detected) at adjacent nodes. This increase in resolution/granularity for pressure signals from the array may be advantageous for identifying one or more nodes of the sensor array best positioned out of the array of nodes relative to the radial artery for measuring a user&#39;s pulse and/or blood pressure during applanation tonometry. This may be determined, for example, by identifying one or more nodes measuring the greatest pressure change due to the pulse of the user when the sensor array is applied generally to a target artery region. After identifying the one or more nodes best suited for measuring a patient&#39;s pulse, more accurate blood pressure measurements may be performed using the signals from the identified nodes. 
     In additional embodiments, strips of dielectric may run in the gaps between the column and/or row electrodes. In this dielectric strip configuration, an air gap may be disposed in the intersection between the two plates of the capacitive nodes allowing the nodes to be more sensitive to displacements due to outside forces. The electrode backing material (e.g., Kapton film or the like) may be a relatively stiff material and may introduce some cross-talk between adjacent nodes. For example, deformation of the backing material at one point may be detected at adjacent areas. Accordingly, in some embodiments, slits in the backing material may be provided (e.g., via laser cutting or the like) to reduce this coupling introduced by the backing film. The backing film may be cut to include primary slits in the film between the parallel strips of electrodes so as to provide decoupling between the strips of electrodes. Additionally lateral slits from the primary slits may be provided to increase decoupling along the electrode strips. In some embodiments, the lateral slits may be staggered and may extend in a direction transverse to the primary slits (e.g., perpendicular or non-perpendicular to the primary slits). In some embodiments, the wrist-worn device may align the primary slits along the length of the user&#39;s arm such that the distal/top electrode strips are generally parallel to the target artery of the user or aligned with the length of the user&#39;s arm (or within 85% of an axis of the blood flow or length of the user&#39;s arm). The primary slits may be generally transverse or perpendicular to a length of a band of the wrist-worn device or a longitudinal axis of the device (i.e., along the circumference of the wrist-worn device when worn) such that the primary slits are generally along a width of a band of the wrist-worn device. In the implementation where strips of dielectric are provided in the gaps/spaces between the top/distal and bottom/proximal electrode layers, the strips of dielectric may be positioned transverse or perpendicular to the elongate slits and/or parallel with the proximal electrode strips. As used herein, the terms “proximal” and “distal” are to be taken as relative to the skin-engaging surface of the wearable device. For example, “distal” is to be understood as relatively close to the skin-engaging surface of device or toward the skin of the user. “Proximal” is to be understood as relatively further from the skin-engaging surface of the device or a direction away from the skin of the user when the device is coupled with the user. In some embodiments, a display may be provided that is on an outward-facing surface of the device and the sensor array may be provided on an inward-facing surface of the device. 
     In further embodiments, a sensor array may be provided where the top/distal layer and bottom/proximal layer of electrodes are independent or not shared with other nodes of the sensor array (e.g., separate squares or the like versus row/column shared electrode strips). Put in another way, the independent electrodes may form only part of one capacitive node, while shared electrodes may be part of multiple capacitive nodes. The dielectric layer disposed between the top and bottom electrodes may form pillars between the top and bottom independent electrodes such that the dielectric is disposed in the active area of the nodes of the sensor array. In alternative embodiments, the dielectric layer may have a configuration where the dielectric is disposed between the rows and columns of the independent electrodes such that air is primarily disposed between the top and bottom electrodes. 
     In some embodiments, the top layer of electrodes may include spaces that are formed between adjacent top electrodes to further decouple adjacent nodes. For example, the top layer of electrodes may protrude from a surrounding surface or the spaces between adjacent electrodes may be recessed to provide the space or air gap between adjacent top electrodes. The sensor arrays disclosed herein may allow for improved sensing resolution by decoupling of nodes. 
     In some embodiments, a wrist-worn device is provided. The device may be configured to be worn about a wrist of a user and may be further configured to measure a blood pressure of the user from an artery of the user. The wrist-worn device may include a sensor array comprising a plurality of capacitive nodes configured to couple with the skin of the user to measure the blood pressure of the user. The sensor array may include one or more distal electrodes positioned above a plurality of proximal electrodes. The one or more distal electrodes may be separated from the proximal electrodes by a gap. Capacitive nodes of the sensor array may be formed at laterally spaced apart locations where the one or more distal electrodes overlap with a proximal electrode. The distal surface of the laterally spaced apart capacitive nodes may protrude distally to form spaced apart protrusions of the sensor array. The spaced apart protrusions may decrease cross-talk between adjacent capacitive nodes of the sensor array. 
     In some embodiments, a flexible conductive layer, such as a conductive silicone, forms the distal electrode of each of the sensing nodes. The flexible conductive layer may be a skin contact layer of the sensor array. The plurality of proximal electrodes may be independent electrodes in some embodiments. Optionally, the plurality of proximal electrodes may be shared electrodes running parallel with one another. 
     A dielectric layer may be disposed in the gap between the distal electrode(s) and the plurality of proximal electrodes. The dielectric layer may include laterally spaced apart pillars. The laterally spaced apart pillars of the dielectric layer may be positioned at each of the capacitive nodes of the sensor array where the distal electrode overlaps with the proximal electrode. The pillars may support the distal electrode relative to the proximal electrode of each of the capacitive nodes of the sensor array. The laterally spaced apart pillars of the dielectric layer may further reduce cross-talk between adjacent capacitive nodes of the sensor array. In some embodiments, the laterally spaced apart pillars of the dielectric layer have circular cross-sections along a length of the pillars. In some embodiments, the laterally spaced apart pillars of the dielectric layer have rectangular cross-sections along a length of the pillars. 
     Optionally, the dielectric layer may include strips supporting the one or more distal electrodes relative to the plurality of proximal electrodes. The strips of the dielectric layer may be positioned in spaces between adjacent capacitive nodes. 
     In some embodiments, primary slits may be provided between adjacent capacitive nodes that extend in a direction of blood travel through the artery of the user when the wrist-worn device is worn about the wrist of the user. Secondary lateral slits may be provided that extend from the primary slits in a direction perpendicular to the primary slits or otherwise transverse (e.g., with 85% of normal to the primary slits). The secondary lateral slits may at least partially separate adjacent capacitive nodes. 
     The sensor array may include rows and columns of capacitive nodes and adjacent rows of the capacitive nodes of the sensor array may be staggered relative to adjacent rows (e.g., such that nodes are not aligned in uniform columns). Optionally, the sensor array may be curved. For example, the sensor array may have a radius of curvature between 12 mm and 20 mm. 
     The wrist-worn device may further comprise pins and a frame. Each of the pins may be operatively coupled with one of the capacitive nodes of the sensor array such that the pins push against a node of the capacitive sensor array. The pins may be restricted to movement in the proximal-distal direction by the frame (e.g., within 90% of normal to the sensor array). 
     In further aspects of the present disclosure, a wrist-worn device may be provided that is configured to be worn about a wrist of a user. The wrist-worn device may include a sensor array comprising a plurality of capacitive nodes configured to couple with the skin of the user to measure the blood pressure of the user. The sensor array may include a sheet of flexible conductive film, such as a conductive silicone layer, positioned above a plurality of spaced apart proximal electrodes by a gap. The capacitive nodes of the sensor array may be formed at laterally spaced apart locations where the conductive silicone overlaps with a proximal electrode. The sensor array may include rows and columns of capacitive nodes. Adjacent rows of the capacitive nodes of the sensor array may be staggered such that nodes are not aligned in uniform columns. The plurality of proximal electrodes may comprise individual electrodes (i.e., not shared electrodes). Optionally, the sensor array is curved with a radius of curvature between 12 mm and 20 mm. 
     The wrist-worn device may further include pins and a frame. Each of the pins may be coupled with one of the capacitive nodes of the sensor array. The pins may be restricted to movement in the proximal-distal direction by the frame (e.g., within 90% of normal to the sensor array). 
     Primary slits may be provided between adjacent capacitive nodes that extend in a direction of blood travel through the artery of the user when the wrist-worn device is worn about the wrist of the user (e.g., along a width of a device band or transverse to a longitudinal axis of the device). Secondary lateral slits may extend from the primary slits in a direction transverse or perpendicular to the primary slits—the secondary lateral slits may at least partially separate adjacent capacitive nodes. 
     A dielectric layer may be provided that is disposed in the gap between the sheet of flexible conductive film and the plurality of proximal electrodes. The dielectric layer may include laterally spaced apart pillars. The laterally spaced apart pillars of the dielectric layer may be positioned at each of the capacitive nodes of the sensor array where the conductive film overlaps with the proximal electrode. The pillars may support the conductive film relative to the proximal electrode of each of the capacitive nodes of the sensor array. The laterally spaced apart pillars of the dielectric layer may further reduce cross-talk between adjacent capacitive nodes of the sensor array. 
     The laterally spaced apart pillars of the dielectric layer may have circular cross-sections along a length of the pillars. The laterally spaced apart pillars of the dielectric layer may have rectangular cross-sections along a length of the pillars. 
     Optionally, the dielectric layer includes strips supporting the conductive film relative to the plurality of proximal electrodes. The strips of the dielectric layer may be positioned in spaces between adjacent capacitive nodes. 
     In further aspects, a wrist-worn device may be provided with a sensor array comprising a plurality of capacitive nodes configured to couple with the skin of the user to measure the blood pressure of the user. The sensor array may include one or more distal electrodes positioned above a plurality of proximal electrodes and separated by a gap. Capacitive nodes of the sensor array may be formed at laterally spaced apart locations where the one or more distal electrodes overlap with a proximal electrode. Primary slits may be provided between adjacent capacitive nodes that extend in a direction of blood travel through the artery of the user when the wrist-worn device is worn about the wrist of the user. In some embodiments, the primary slits may be transverse to a length or longitudinal axis of a band of the device or generally along a width of the band of the device. Secondary lateral slits may be provided that extend from the primary slits in a direction transverse or perpendicular to the primary slits. The secondary lateral slits may at least partially separate adjacent capacitive nodes. 
     The distal electrode(s) and/or proximal electrodes may be parallel shared electrode strips. The sensor array may be curved with a radius of curvature between 12 mm and 20 mm. 
     The wrist-worn device may further include pins and a frame. Each of the pins may be coupled with one of the capacitive nodes of the sensor array. The pins may be restricted to movement in the proximal-distal direction by the frame. 
     In further aspects, a wrist-worn device may be provided that includes a sensor array comprising a plurality of capacitive nodes configured to couple with the skin of the user to measure the blood pressure of the user. The sensor array may comprise one or more distal electrodes positioned above a plurality of proximal electrodes and separated by a gap. The capacitive nodes of the sensor array may be formed at laterally spaced apart locations where a distal electrode overlaps with a proximal electrode. The sensor array may be curved and may have a radius of curvature between 12 mm and 20 mm. 
     In some aspects, a wrist-worn device may be provided that is configured to measure pressure signals where the wrist-worn device includes a sensor array comprising a proximal layer, a distal layer, and a dielectric layer supporting the proximal layer relative to the distal layer. The proximal layer may include one or more proximal electrodes. The distal layer may include one or more distal electrodes. Capacitive nodes of the sensor array may be formed at locations where a distal electrode overlaps with a proximal electrode. The proximal layer may include a plurality of cantilevered fingers which are each separated from adjacent fingers by a slit. 
     In some embodiments, each of the plurality of cantilevered fingers may be parallel with one another. Optionally, stiffeners may be coupled with a proximal surface of each of the plurality of cantilevered fingers. 
     In certain embodiments, the fingers may be in a folded configuration. An actuator (e.g., fluid bladder or the like) may be sandwiched by the folded plurality of fingers of the proximal layer. Stiffeners may be coupled with a proximal surface of the plurality of fingers that is adjacent to a free end of the plurality of fingers. The actuator may be coupled with a proximal surface of stiffeners in some embodiments. 
     Embodiments of the disclosure covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the disclosure and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this patent, any or all drawings and each claim. 
     The disclosure will be better understood on reading the following description and examining the figures that accompany it. These figures are provided by way of illustration only and are in no way limiting on the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a prior art method of applanation tonometry; 
         FIG. 2  shows the cross section of a wrist; 
         FIG. 3  illustrates an exemplary device according to some embodiments of the present disclosure; 
         FIG. 4  illustrates an exemplary system according to some embodiments of the present disclosure; 
         FIG. 5  illustrates an exemplary device schematic according to some embodiments of the present disclosure; 
         FIG. 6  illustrates components of an exemplary capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 7  illustrates an isometric view of a portion of an exemplary capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 8  illustrates components of another exemplary capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 9  illustrates an isometric view of a portion of an exemplary capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 10  illustrates components of yet another exemplary capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 11  illustrates primary and secondary lateral slits in a backing material of a capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 12  illustrates primary and secondary lateral slits in a backing material of another capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 13  illustrates yet another capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 14  illustrates a cross-sectional view of an exemplary capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 15  illustrates a cross-sectional view of an alternative exemplary capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 16  illustrates another capacitive sensor array according to some embodiments of the present disclosure; 
         FIG. 17  illustrates a side view of the capacitive sensor array of  FIG. 16 ; 
         FIG. 18  illustrates a cross-sectional view of a frame and pin component that may be used with embodiments of the present disclosure; 
         FIG. 19  illustrates a top view of the frame and pin component of  FIG. 19 ; 
         FIG. 20  illustrates a capacitive sensor array protruding from an adjacent contact surface according to some embodiments of the present disclosure; 
         FIG. 21  illustrates curved capacitive sensor arrays according to embodiments of the present disclosure; 
         FIG. 22  illustrates a skin engaging surface or distal surface of an exemplary sensor array according to some embodiments of the present disclosure; 
         FIG. 23  illustrates a back or proximal surface of the exemplary sensor array of  FIG. 22  according to some embodiments of the present disclosure; 
         FIG. 24  illustrates an exemplary proximal layer of a sensor array according to some embodiments of the present disclosure; 
         FIG. 25  illustrates an exemplary system according to some embodiments; 
         FIG. 26  illustrates another exemplary system according to some embodiments of the present disclosure; 
         FIG. 27  illustrates another exemplary proximal layer of another exemplary sensor array according to some embodiments of the present disclosure; 
         FIG. 28  illustrates an exemplary pillar configuration for a sensing element that may be used to support a proximal electrode relative to a distal electrode in any of the herein described embodiments; 
         FIG. 29  illustrates another exemplary pillar configuration for a sensing element that may be used to support a proximal electrode relative to a distal electrode in any of the herein described embodiments; and 
         FIG. 30  illustrates yet another exemplary pillar configuration for a sensing element that may be used to support a proximal electrode relative to a distal electrode in any of the herein described embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure generally relates to pressure measurements which may be helpful in measuring one or more user parameters. In some embodiments, methods and devices for measuring a mean arterial pressure and/or for monitoring blood pressure changes of a user are provided. In particular, the present disclosure provides devices, system, and methods for improved sensing by decoupling nodes of the sensor array so as to provide improved signal resolution and hence more accurate blood pressure measurements. The decoupling of nodes of the sensor array helps reduce cross-talk between adjacent nodes. This may help identify one or more nodes of the sensor array which are better positioned adjacent a target artery for measuring a blood pressure or heart beat pulse of the user. 
     A person&#39;s blood pressure is a continuously changing vital parameter. As a result, blood pressure measurements during intermittent visits to a physician may be insufficient to detect some forms of hypertension. For example, hypertension can occur in a pattern that evades detection during a visit to the physician&#39;s office. Common hypertension patterns include white coat hypertension (elevated only during a limited morning period of time), borderline hypertension (fluctuating above and below definitional levels over time), nocturnal hypertension (elevated only during sleeping hours), isolated systolic hypertension (elevated systolic pressure with non-elevated diastolic pressure), and isolated diastolic hypertension (elevated diastolic pressure with non-elevated systolic pressure). To detect such hypertension patterns, it may be beneficial to perform additional blood pressure measurements over time to obtain a more complete view of a person&#39;s blood pressure pattern and features. Although continuous measurement of blood pressure can be achieved by invasive means, for example, via an intra-arterial pressure sensing catheter, noninvasive blood pressure measurement approaches are more preferable. 
     Current noninvasive blood pressure measurement approaches include ambulatory and home blood pressure measurement strategies. These strategies provide a more complete view of a person&#39;s blood pressure characteristics and are often employed in recommended situations. Ambulatory blood pressure measurement is performed while the person performs daily life activities. Currently, ambulatory blood pressure measurements are typically performed every 20 to 30 minutes using brachial oscillometric blood pressure measurement cuffs. Ambulatory blood pressure measurement may be recommended where there is large variability in in-office blood pressure measurements, where a high in-office blood pressure measurement is measured in a person with otherwise low cardiovascular risk, when in-office and home blood pressure measurements vary, where resistance to drug treatment of high-blood pressure is noted or suspected, where hypotensive episodes are suspected, or where pre-eclampsia is suspected in pregnant women. Home blood pressure measurement includes isolated self-measurements performed by a person at home. Home blood pressure measurements may be recommended where information is desired regarding the effectiveness of blood pressure lowering medication over one or more dose-to-dose intervals and/or where doubt exists as to the reliability of ambulatory blood pressure measurement. 
     Current ambulatory and home blood pressure measurement approaches, however, fail to provide continuous measurement of blood pressure. Additionally, when an oscillometric blood pressure measurement cuff is used to monitor a person&#39;s blood pressure when sleeping, the intermittent inflation and deflation of the cuff can disturb the person&#39;s sleeping pattern, thereby potentially changing the person&#39;s sleeping blood pressure. Thus, convenient and effective approaches for noninvasive continuous measurement of blood pressure remain of interest. 
     In applanation tonometry, the pressure in a superficial artery with sufficient bony support, such as the radial artery, may be accurately recorded during an applanation sweep when the transmural pressure equals zero. An applanation sweep refers to a time period during which pressure over the artery is varied from overcompression to undercompression or vice versa. At the onset of a decreasing applanation sweep, the artery is overcompressed into an occluded state, so that pressure pulses are not recorded. At the end of the sweep, the artery is undercompressed, so that minimum amplitude pressure pulses are recorded. Within the sweep, it is assumed that an applanation occurs where the arterial wall is flattened and transmural pressure turns to zero, and the arterial pressure is perpendicular to the surface and is the only pressure detected by a tonometer sensor. 
       FIG. 1  illustrates a method of measuring blood pressure using applanation tonometry. Here, a pressure transducer  1  is urged against the skin  2  of a user with an applanation force  3 . The applanation force  3  and pressure transducer  1  applanate the target artery  4  such that the arterial wall tension  5  is parallel to the pressure transducer surface  6  and the arterial pressure  7  is perpendicular to the surface  6 . Where the target artery  4  is applanated in such a manner, the arterial pressure may be measured by transducer  1 . The target artery  4  may be supported by bone  8  and adjacent muscle  9 . The target artery  4  may be the radial artery of the user and the bone  8  may be the radial bone. 
       FIG. 2  illustrates an exemplary cross-section of a wrist which may include: palmaris longus tendon  230 , median nerve  232 , flexor dig. sublimis  234 , ulnar artery  236 , ulnar nerve  237 , flexor carp. uln.  238 , flex. dig. profundus  240 , ext. carp. uln.  242 , distal radio-unlar artic.  244 , ext. dig. quinti prop.  246 , ext. dig. commun.  248 , ext. indicis. prop.  250 , ext. poll. long.  252 , ext. carp. rad. brev.  254 , ext. carp. rad. long.  256 , ext poll brev.  258 , abd. poll. long.  260 , radial artery  262 , flex. carp. rad.  264 , and flex. poll. long.  266 . As mentioned above, the radial artery  262  is generally targeted in arterial applanation tonometry given its position adjacent the radial bone (radius). 
     As mentioned above, the radial artery is generally targeted in arterial applanation tonometry given its position adjacent the radial bone (radius). However, finding an ideal or preferred location for applanation of the radial artery can be difficult given its relative size. Compounding this problem is the fact that human anatomy varies from person to person and may change based on a person&#39;s height, weight, gender, etc. Accordingly, targeting the radial artery and identifying a preferred applanation location and orientation can be a challenge. 
     Due to anatomical constrains and variations in sensor placement, it may be difficult to obtain an accurate pressure signal from a target artery. Some blood pressure measurement devices and methods have relied on bulky wrist harnesses to orient a user&#39;s wrist in a preferred orientation to help with sensor placement, however such devices and methods are not practical for daily use by the general public. Additionally, the use of a sensor array to increase the chance that at least one the sensors or sensing nodes of the sensor array is properly placed relative to the target artery comes with its own challenges. 
       FIG. 3  illustrates an exemplary device  10  according to some embodiments of the present disclosure for measuring pressure of a user. Device  10  includes a device body  12  and a device band  14 . An actuator  16  may be supported by device band  14 . A sensor array  18  may be coupled with the actuator  16 . 
     In many embodiments, the device  10  may be a wrist-worn device (e.g., an electronic watch or the like). The device body  12  may house a data processor of device  10 . The device body  12  may also provide a user interface for receiving user input and outputting information to the user (e.g., through a display or integrated audio device or the like). The device band  14  may comprise one or more flexible bands configured to couple the device  10  to the user (e.g., to the user&#39;s wrists). The device body  12  and device band  14  may have an inward-facing skin-engaging surface  20  opposite an outward-facing surface of the device. In some embodiments, it may be preferable if the device  10  does not require a harness for positioning the user&#39;s wrist in a particular manner when measuring a blood pressure of the user. Avoiding a wrist harness may decrease the bulkiness of the device  10  and may increase adoption of the device  10  for blood pressure measurements by general consumers. 
     The actuator  16  may be a linear actuator for driving the sensor array  18  into the skin of the user. For example, the actuator  16  may urge the sensor array  18  against a target artery of the user to conduct an applanation sweep for applanation tonometry. The actuator  16  may be a fluid or air bladder or the like, driven by a pump. The actuator may also be a linear electromagnetic motor. The actuator may be a rotary electromagnetic motor driving a lead screw, or cam, or gears to provide the force and displacement for applanation. The actuator may be driven by piezoelectric, electroactive polymer, or shape memory alloy materials. The sensor array  18  may be an array of capacitive nodes, details of which are described further below. The sensor array  18  may be coupled with the data processor housed in device body  12  or may be operatively coupled with a separate processor that is coupled with the device band  14 . Alternatively, there may be control/processing circuitry in the band  14 , but may use the processor of the device body  12 . 
       FIG. 4  illustrates an exemplary system diagram  22  of the device  10 . The device  10  may include a processor  24 . The processor  24  may be coupled with and may control actuation of the actuator  16 . Additionally, the processor  24  may be further coupled with the sensor array  18 . The processor  24  may be configured to receive signals from each of the nodes of the sensor array  18  and may be further configured to process the signals to determine a pressure sensed by each of the nodes of the array  18 . The processor  24  may detect and compute a pulse rate of the user and/or a blood pressure measurement of the user based on the one or more signals from the sensor array  18 . The processor  24  may then output the measured attribute to the user in a manner perceptible to the user via output  26 . The output  26 , may be an audio output, a display, or the like. In some embodiments, the data may be wirelessly communicated to another electronic device, optionally associated with the user, for further processing and/or output to the user. Accordingly, in some instances, the information may be transmitted to another device (e.g., user device or physician device, etc.) where the information is accessed. 
       FIG. 5  illustrates an exemplary sensor array  28  according to some embodiments of the present disclosure. The array  28  includes bottom/proximal electrodes  30  and top electrodes  32 . Bottom electrodes  30  may be formed of a plurality of conductive strips that are arranged side by side in rows to extend substantially linearly. Top/distal electrodes  32  may be formed of a plurality of conductive strips that are arranged side by side in columns to extend substantially linearly in a direction orthogonal to bottom electrodes  30 . The conductive strips may be a conductive metal, which in some instances may be copper. 
     At each of the intersections of bottom electrodes  30  and upper electrodes  32  arranged in rows and columns, a part of lower electrode  30  and a part of upper electrode  32  face each other with a prescribed distance therebetween. In this manner, capacitive nodes  34  are formed at the intersections and serve as the sensing nodes of the sensor array  28 . 
     Capacitive nodes  34  may be aligned in the form of an array when the pressure detecting portion is seen along the distal-proximal direction. Each capacitive node  34  has its capacitance changed as pressure is applied to upper electrode  32  or lower electrode  30  which causes them to deflect in the direction decreasing the distance therebetween. 
     With lower electrodes  30  and upper electrodes  32  arranged in rows and columns, respectively, a circuit configuration may be provided where one electrode, e.g., the lower electrodes  30  or the upper electrodes  32 , may be connected via a multiplexer  36  to a power source  38  and the other electrodes, e.g., the upper electrodes  32  or the lower electrodes  30 , are connected via multiplexer  36  to a detector  40 . With this configuration, when a particular lower electrode  30  and a particular upper electrode  32  are selected by multiplexer  36 , capacitance of a specific one of the capacitive nodes  34  arranged in the array form can be obtained via detector  40 . For example, in  FIG. 5 , when lower electrode  30  on the second row from the top and upper electrode  32  on the third column from the left are selected, the capacitance of the capacitive node denoted by a reference  42  is output. Thus, it is possible to measure the pressure at a given position on the sensing surface of sensor array  28 . The electrodes connected to the drive signal (i.e., power source  38 ) may be referred to as “drive” electrodes while the electrodes connected to the sensor (i.e., multiplexer  36 ) may be referred to as “sense” electrodes. While  FIG. 5  illustrates a configuration with a single drive source and a single sensor detector, it should be understood that there could be multiple drive sources and/or multiple detectors. Multiple drive sources may allow multiple drive electrodes to be stimulated simultaneously (and thus multiple nodes along a single sense electrode to be measured simultaneously). In these instances, each drive source may stimulate with a different frequency, and the signal sensed from the sense electrode may be demodulated to determine the signal from each node of the sensor array. Multiple detectors may allow nodes across different sense electrodes to be sensed simultaneously. 
     While the sensor array  28  is illustrated as having two parallel lower electrode strips  30  and five parallel upper strips  32  to provide a 2×5 array of capacitive nodes  34 , it should be understood that the sensor array  28  may have other configurations. For example, a 5×5 array, 6×6 array, 6×9 array, or the like may be provided. In some embodiments, the sensor array may be dimensioned to sense pressures from a 10 mm×10 mm area. The capacitive nodes may have a sensing area of approximately 1 mm by 1 mm. 
     For example,  FIG. 6  illustrates components of an exemplary 6×6 sensor array  44  that may be used with device  10  according to some embodiments of the present disclosure. The sensor array  44  is formed by a top layer  46  of six columns of electrode strips  48  and a bottom layer  50  of six rows of electrode strips  52 . The strips of electrodes may have a width between 0.5-1.5 mm, preferably 1 mm. A dielectric layer  54  may be provided between the top layer  46  and the bottom layer  50 . The dielectric layer  54  may include a sheet  55  of dielectric material and strips  56  of dielectric material. In some embodiments, the sheet  55  of dielectric material may have a thickness between 10-50 μm, preferably about 25 μm. The strips  56  of dielectric material may run in the lateral gaps  58  between one of the rows or columns of the electrode strips  48 ,  52 . The lateral gaps  58  may have a width between 150-400 μm and may be filled with a different dielectric material other than air (e.g., a softer dielectric than the dielectric strips  56  or a liquid/gel dielectric). The dielectric strips  56  may act as a spacer member between the top layer  46  and the bottom layer  50  and support the top layer  46  relative to the bottom layer  50  to help maintain a prescribed distance between the two electrode layers  46 ,  50 . The strips  56  of dielectric material may have a 1 mm spacing between adjacent strips  56 . The strips  56  may have a height of approximately 130 μm and a width of approximately 200 μm. While illustrated with a single continuous strips  56  in lateral gaps  58 , other embodiments may utilize a series of strips  56  orientated end-to-end with optional spacing therebetween. In some embodiments the dielectric material may be silicone. 
       FIG. 7  illustrates a schematic diagram of a portion of the array  44  as assembled. As illustrated in  FIG. 7 , the top and bottom layers  46 ,  50  may be coupled with a backing material  60 . The backing material  60  may be a polyimide film or the like. Further, an air gap may be provided in the active area  62  of a capacitive node  64  formed by the electrode strips  48 ,  52 . Further as illustrated, the dielectric strip  55  is disposed in the gap  58  between adjacent bottom electrode strips  52 . In some embodiments, utilizing strips  55 , the active area  62  may be primarily filled with air which may increase the deflection/sensitivity of the capacitive nodes to changes in pressure. 
       FIG. 8  illustrates components of another exemplary capacitive sensor array  66  that may be used with device  10  according to some embodiments of the present disclosure. Similar to array  44 , capacitive sensor array  66  may include a top layer  46  of six columns of electrode strips  48  and a bottom layer  50  of six rows of electrode strips  52 . Each of the strips  48 ,  52  may be separated from adjacent strips by a gap  58 . A dielectric layer  67  may be provided between the top layer  46  and the bottom layer  50 . The dielectric layer  67  may include a sheet  68  of dielectric material and pillars  70  of dielectric material. In some embodiments, the sheet  68  of dielectric material may have a thickness between 10-50 μm, preferably about 25 μm. The pillars  70  of dielectric material may be disposed at the intersection of the electrode strips  48  of the top layer  46  with the electrode strips  52  of the bottom layer  50 . The dielectric pillars  70  may act as a spacer member between the top layer  46  and the bottom layer  50  and support the top layer  46  relative to the bottom layer  50  to help maintain a prescribed distance between the two electrode layers  46 ,  50 . The pillars  70  of dielectric material may have a height of approximately 100-300 μm. The pillars  70  may have a rectangular cross-section or a circular cross-section or the like. A diameter or width of the pillars  70  may range from approximately 200-550 μm, preferably about 350-450 μm. 
       FIG. 9  illustrates an isometric view of a portion of an exemplary capacitive sensor array  66  as assembled, according to some embodiments of the present disclosure. As illustrated in  FIG. 9 , the top and bottom layers  46 ,  50  may be coupled with a backing material  60 . The backing material  60  may be a polyimide film or the like. Further, pillars  70  may be provided in the active area  62  of a capacitive node  64  formed by the electrode strips  48 ,  52 . 
       FIG. 10  illustrates components of yet another exemplary capacitive sensor array  72  that may be used with device  10  according to some embodiments of the present disclosure. The capacitive sensor array  72  may include a top layer  74  of independent electrodes  76  that are laterally spaced from one another. In some embodiments thirty two electrodes  76  may be provided. The electrodes  76  may be arranged in a symmetrical array with a top row of four electrodes; the second-fifth rows including six electrodes; and a sixth row including four electrodes. The electrodes  76  may be sense electrodes. A bottom layer  78  may also include independent electrodes  80 . In some embodiments the bottom layer  78  includes thirty two electrodes  80 , each of which correspond to one of the sense electrodes  76  to form a plurality of capacitive nodes. Accordingly, the electrodes  80  may also be arranged in a symmetrical array with a top row of four electrodes; the second-fifth rows including six electrodes; and a sixth row including four electrodes. The electrodes  80  may be driven separately or, optionally, the electrodes  80  may all be driven together to form a drive layer of the capacitive sensor array  72 . It should be understood that the configuration may be swapped such that the bottom electrodes may be sensed (separately or together) and the top electrodes may be driven (separately or together). A middle layer  82  of dielectric material may be provided to provide the spacing between the top layer  74  and the bottom layer  78 . The dielectric layer  82  may include a sheet  84  of dielectric material and pillars  86  of dielectric material. Similar to the embodiments described above, the sheet  84  may have a thickness between 10-50 μm, preferably about 25 μm. The pillars  86  of dielectric material may be spaced apart from one another by approximately 1 mm so as to be disposed at the capacitive nodes formed by each of the electrodes  76 ,  80 . The dielectric pillars  86  may act as a spacer member between the top layer  74  and the bottom layer  78  and may support the top layer  74  relative to the bottom layer  78  to help maintain a prescribed distance between the two electrode layers  74 ,  78 . The pillars  86  of dielectric material may have a height of approximately 100-300 μm, preferably 200 μm. The pillars  86  may have a rectangular cross-section or a circular cross-section or the like. A diameter or width of the pillars  86  may range from approximately 200-550 μm, preferably about 350-450 μm. While the sensor arrays are illustrated as forming uniform arrays of nodes, it should be understood that the capacitive nodes may be staggered in some embodiments or otherwise offset from one another such that the nodes do not form uniform rows and/or columns. 
     In some embodiments, the electrode backing material (e.g., backing material  60 ) may be a relatively stiff material and may introduce some cross-talk between adjacent nodes. For example, deformation of the backing material at one point may be detected at adjacent areas. Accordingly, in some embodiments, slits in the backing material may be provided (e.g., via laser cutting or the like) to reduce this coupling introduced by the backing material. The slits may decrease mechanical coupling across the slit. For example,  FIG. 11  illustrates primary slits  88  and secondary lateral slits  90  in a backing material  100  of a capacitive sensor array  102  according to some embodiments of the present disclosure. As illustrated, the backing film  100  may be cut to include primary slits  88  in the film  100  between the parallel strips of electrodes  104  so as to provide decoupling between the strips of electrodes  104 . Additionally lateral slits  90  may be cut to extend from the primary slits  88  to increase decoupling along the electrode strips  104 . In some embodiments, the lateral slits  90  may be staggered such that adjacent lateral slits  90  extend in an opposite direction from an adjacent primary slit  88 . In some embodiments, the wrist-worn device may align the primary slits  88  along the length of the user&#39;s arm such that the distal/top electrode strips  104  are generally parallel to the radial artery of the user or aligned with the length of the user&#39;s arm. In the implementation where strips of dielectric are provided in the gaps/spaces between the top/distal and bottom/proximal electrode layers, the strips may be positioned transverse or perpendicular to the elongate slits  88  and parallel with the proximal electrode strips. Alternatively, the strips of dielectric may be positioned parallel to the elongate slits  88  and transverse or perpendicular to the proximal electrode strips. In some embodiments, the lateral slits  90  do not extend across the entire width of the electrode  104 . In other embodiments, a lateral slit  90  may extend across the entire width of the electrode  104  and may join adjacent primary slits  88 . 
     While illustrated with six electrodes  104 , it should be understood that the slits  88 ,  90  may be provided to sensor arrays having alternative configurations. For example,  FIG. 12  illustrates primary  88  and secondary lateral slits  90  in a backing material  100  of another capacitive sensor array  106  according to some embodiments of the present disclosure. The capacitive sensor array  106  may have a 9×6 or 9×9 array of capacitive nodes for example. Additionally, it should be understood that the slits  88 ,  90  in the backing material may be utilized with any of the embodiments described above with reference to  FIGS. 3-10  and below. For example, capacitive sensor arrays utilizing strips of electrodes and strips of dielectric may also take advantage of the slits in the backing material. Similarly, capacitive sensor arrays utilizing strips of electrodes and pillars of dielectric may also benefit from the slits in the backing material. Embodiments utilizing independent electrodes with independent drive electrodes may also benefit from one or more slits in the backing material between adjacent capacitive nodes. 
       FIG. 13  illustrates yet another capacitive sensor array  108  that may be used with device  10  according to some embodiments of the present disclosure. The capacitive sensor array  108  includes a bottom layer  110 , a middle layer  112 , and a top layer  114 . The bottom layer  110  may include an array of independent bottom electrodes  116  (not shared electrodes/electrodes that only form part of a single capacitive node) that are laterally spaced apart. The bottom electrodes  116  may form a 3×9 array, although other array sizes are possible. The electrodes  116  may be a conductive material. In some embodiments, the electrodes  116  may be a conductive metal such as a copper material or the like. The top layer  114  may comprise a sheet of flexible conductive material. In some embodiments the top layer  114  may be conductive silicone. The top layer  114  may form a top shared electrode which cooperates with each of the bottom electrodes  116  to form a plurality of capacitive nodes  118  of the sensor array  108 . In some embodiments, the top layer  114  at each of the nodes  118  may be raised or protruded from a surrounding surface of the top layer  114  as illustrated in the cross-sectional view provided by  FIG. 14 . Accordingly, in some embodiments, lateral air spaces or gaps  119  may be formed between the top layer  114  of adjacent nodes  118  that may further decouple adjacent capacitive nodes  118 . In some embodiments, the interconnecting material  120  between the nodes  118  may be thin to increase flexibility at the interconnections between the nodes  118  so as to increase mechanical decoupling between adjacent nodes  118 . The interconnecting material  120  may have a thickness between 25 μm and 500 μm. Additionally, the slits described above may be used to increase decoupling between adjacent nodes  118 . For example, the slits may be provided in the sheet of flexible conductive material  114 . Primary slits may be provided between adjacent nodes  118  of the array  108 . Lateral slits may also extend from the primary slits and may be staggered to at least partially decouple adjacent nodes. The middle layer  112 , may be a dielectric material such as silicone. The middle layer  112  may include a sheet  121  and an array of spaced apart pillars  122  that correspond to the capacitive nodes  118  of the sensor array  108 . Pillars  122  may support the top layer  114  relative to the bottom layer  116  and bottom electrodes  116 . The pillars  122  may be disposed in the active area of the nodes  118  as illustrated in the exemplary cross-sectional view of  FIG. 14 . The spaced apart pillars  122  may further decouple adjacent capacitive nodes  118  of the array  108 . 
     In alternative embodiments, the middle layer  112  may support the top layer  114  relative to the bottom layer  110  with strips  126  at locations between adjacent electrodes  116  of the array  108  as illustrated in  FIG. 15 . The strips  126  may couple with the interconnecting material  120  between electrodes  118 . It should be understood that strips  126  may run between columns of the array and/or between rows of the array  108 . With such a configuration, the capacitive nodes  118  may be more sensitive to pressure changes as air is primarily disposed in the active area of the nodes  118 . While the array  108  is illustrated and described as protruding the top layer  114  at each of the nodes  118  such that gaps  119  are formed between adjacent nodes  118 , it should be understood that other embodiments of the sensor array may not have the top layer  114  at each of the nodes  118  protruded from an adjacent surface. 
       FIG. 16  and  FIG. 17  illustrate another capacitive sensor array  128  that may be used with device  10  according to some embodiments of the present disclosure.  FIG. 17  illustrates a side view of the capacitive sensor array  128  of  FIG. 16 . The capacitive sensor array includes a top layer  130  comprising a conductive silicone. The top layer  130  forms top electrodes  132  of an array of capacitive nodes. The capacitive nodes form a 5×5 array of capacitive nodes. The bottom layer  134  includes independent bottom electrodes (not shown) corresponding to the top electrodes  132  of the top layer  130 . As illustrated in  FIG. 17 , the top electrodes  132  may be separated by wedge shaped gaps  136  to decouple adjacent nodes. The top layer may have a thickness of 0.3 mm. 
       FIG. 18  illustrates a cross-sectional view of a frame  140  and pin  142  component that may be used with device  10  to further decouple adjacent nodes of the sensor arrays described herein.  FIG. 20  illustrates a top view of the frame  140  and pin  142  component of  FIG. 19 . The frame  140  may have a top surface  143 , a bottom surface  144 , and an array of channels  146  extending between the top surface  143  and the bottom surface  144 . The pins  142  may be disposed in the channels  146  of the frame  140 . The pins may have an elongate body having a proximal end  148  and a distal end  150 . The elongate body may have a cross-section generally matching the channels  146  of the frame  140  and a length of the elongate body of the pin  142  may be greater than a length of the channels  146  such that the distal portion  150  of the pins  142  protrude from the top surface  143  of the frame  140 . In some embodiments, the frame  140  restricts pin  142  movement to the proximal-distal direction only. The proximal end  148  of pins  142  may be enlarged to have a width greater than a width of the channels  146  such that the pins  142  are limited in movement along the distal direction. At the distal range of motion limit of pins  142  relative to frame  140 , the proximal end  148  of pins  142  engages with a bottom surface  144  of frame  140  to restrict further movement of the pin  142  in the distal direction. 
     Each of the pins  142  may be coupled with one of the nodes of an array. For example, the proximal end  148  of the pins  142  may be coupled (directly or indirectly) with a top layer of a capacitive pressure sensor. With the frame  140  restricting pin  142  movement to movement along the proximal-distal direction, the frame  140  and pin  142  component may limit capacitance changes due to shear movements and may further decouple nodes of an array. While illustrated as a 6×6 array of pins  142 , it should be understood that the frame  140  and pins  142  may be adjusted to corresponding with alternative sensor arrays. Additionally, it should be understood that the frame  140  and pin  142  component is optional. 
     In some embodiments, the sensor array may not utilize the frame  140  and pin  142  component and may have a skin-engaging surface. For example,  FIG. 21  illustrates a capacitive sensor array  152  where the backing material  154  (e.g., a Kapton film or the like) of the top/distal layer of the capacitive sensor array  152  protrudes from a surrounding surface or base  156  according to some embodiments of the present disclosure. In some embodiments, if the Kapton film includes slits (e.g., slits  88 ,  90 ) for decoupling nodes of the array  152 , it may be beneficial to provide a flexible coating (e.g., silicone) over the Kapton film for the contact surface of the array  152 . 
     While the capacitive sensor arrays described above are generally planar in configuration (with a flat contact surface), some embodiments of the present disclosure may include sensor arrays with a curvature. For example,  FIG. 22  illustrates a number of curved capacitive sensor arrays that may be used with device  10  according to embodiments of the present disclosure. The capacitive sensor arrays may be any of the arrays described above. The arrays may have a radius of curvature between 12 mm and 20 mm. The curved array may provide increased coupling between the array and a user&#39;s artery when the array is urged against the skin of the user. 
       FIG. 22  illustrates a skin engaging surface of an exemplary sensor array  158  according to some embodiments of the present disclosure.  FIG. 23  illustrates a back or proximal surface of the exemplary sensor array  158  of  FIG. 22  according to some embodiments of the present disclosure. The sensor array  158  may include a plurality of capacitive sensing elements  160 . The capacitive sensing elements  160  may be formed between a proximal layer  162  and a distal layer  164  (illustrated as a transparent layer for illustration purposes only). The proximal layer  162  may be separated from the distal layer  164  by a dielectric material (not shown), similar to embodiments described above. 
     The proximal layer  162  may have a “rake” configuration with a plurality of separated cantilevered fingers  166  extending from a platform  165 . The fingers  166  may be separated in one axis and each finger  166  may move relative to another. While illustrated with ten fingers  166 , it should be understood that more or less fingers  166  may be provided in other embodiments of the disclosure. Each of the fingers  166  may extend from a fixed end  167  to a free end  168  of the fingers  166 . Optionally, the fingers  166  may have a width between 1.5-2.0 mm (e.g., 1.75 mm or the like) and a length between 5-30 mm (e.g., 20 mm or the like). Additionally, each of the fingers  166  may form a proximal portion of one or more sensing elements  160 , e.g., 1-10 sensing elements, 4-6 sensing elements, or the like. The sensing elements  160  may have a sensing area of 1.0-2.0 mm 2  (e.g., 1.5 mm 2  or the like). In some embodiments, the fingers  166  may define rows of the sensing elements  160  of the array  158 . The fingers  166  and/or rows of sensing elements  160  of the sensor array  158  may be separated from adjacent fingers  166  and/or rows of sensing elements  160  by slits  170  between the fingers  166  and/or rows of sensing elements  160  of the sensor array  158 . The slits  170  may decouple sensing elements  160  on one row from sensing elements  160  on adjacent rows of the sensor array  158  and the slits  170  may have a width of 0.1-0.5 mm (e.g., 0.25 mm or the like). 
     In some embodiments, the slits  170  and/or fingers  166  may be parallel to one another. Optionally, the sensing area (generally illustrated as dashed box  172 ) of the sensing array  158  may be toward the free ends  168  of the fingers  166 . The length of finger  166  between the fixed end  167  and the sensing area  172  may limit the strain experienced from the fixed end  167  of a finger  166  from propagating to the sensing area  172 . Optionally, in some embodiments, a stiffener  171  may be provided on a back surface of each finger  166  to further limit the strain experienced from the fix end  167  of a finger  166  from propagating to the sensing area  172 . The stiffener  171  may, in certain embodiments, be a stainless steel material or the like. The stiffener  171  may extend further toward the fixed ends  167  of the fingers  166  than the sensing area  172 . Optionally, the stiffener  171  may have a length between 10-15 mm (e.g., 12.5 mm or the like) and may extend through the sensing area  172  to the free end  168  of a finger  166 . 
     The distal layer  164  may be comprised of a series of separate slats, each associated with one of the fingers  166  of the proximal layer  162 . The distal layer  164  may form a distal portion of the one or more sensing elements  160 . In some embodiments, the distal layer  164  may have one or more slits  174  that extend transverse to a length of the distal layer  164  and that are disposed between adjacent sensing elements  160 . The slits  174  may have a length that is less than a width of the distal layer  164 . Optionally, the slits  174  may extend from an edge of the distal layer  164  and may optionally extend from an edge that is opposite the edge which an adjacent slit extends from. The slits  174  may increase decoupling between a sensing element  160  and an adjacent sensing element  160  in the same row in the array  158 . 
     In some embodiments, the proximal layer  162  and the distal layer  164  may be a polyimide layer supporting one or more electrodes for forming the sensing elements  160 . In some embodiments, the proximal layer  162  may further comprise an integrated circuit  176  on the platform  165 . A trace  178  may be parallel to the fingers  166  and may extend from the platform  165  on a side of the platform  165  that is opposite a side in which the fingers  166  extend from. In some embodiments, the electronics may be on the same side as the active area. 
     Optionally, the trace  178  be perpendicular to the fingers  166 . For example,  FIG. 24  illustrates a proximal layer  180  of a sensor array according to some embodiments of the present disclosure. The proximal layer  180  may include a plurality of separated cantilevered fingers  166  and the fingers  166  may be supported by stiffeners  171 , similar to the array  158  described above. However, with proximal layer  180 , the trace  178  may extend from the platform  165  in a direction transverse to the length of fingers  166  (e.g., perpendicular to fingers  166  in certain embodiments) to define a “comb” configuration. Such a configuration may be beneficial for use in a wrist-worn device, as the trace  178  and electronics (e.g., IC  176 ) may extend along a band (shown in phantom  182 ) of the wrist-worn device. 
     During use with a wrist-worn device, a length of the fingers  166  may be aligned with a length of the arm when the wrist-worn device is attached to the wrist of the user. This alignment and configuration may allow the array  158  to deform in a cylindrical manner to generally match the wrist geometry. In some embodiments, the free ends  168  of the fingers  166  of the array  158  may be positioned toward the hand of the user when the wrist-worn device is attached to the wrist of the user. 
     Optionally, the fingers of a sensor array may be folded. For example,  FIG. 25  illustrates an exemplary system  184  according to some embodiments. The system  184  may comprise a sensor array  186  and an actuator  188 . The sensor array  186  may include a proximal layer  190 , a distal layer  192 , and a dielectric  194  separating the proximal layer  190  and the distal layer  192 . The proximal layer  190  and the distal layer  192  may form the capacitive sensing elements of the sensor array  186 . 
     The proximal layer  190  may include one or more fingers  196 . The finger  196  may have a free end  198  and may include a bend  200  in the fingers  196 . The stiffener  202  may be coupled with a proximal surface of finger  196  that is adjacent the free end  198  of the finger  166 . A length of stiffener  202  may be greater than or equal to the length of a distal layer  192  in certain embodiments. 
     A distal surface of the actuator  188  may be coupled or adhered with the proximal surface of the stiffener  202 . In some embodiments, the actuator  188  is sandwiched by the proximal layer  190  such that the proximal layer  190  is on a proximal and distal side of the actuator  188 . The actuator  188  may be a fluid or air bladder or the like and may be configured for driving the sensing portion of the array  186  into the tissue of the user (e.g., for an applanation sweep, measuring blood pressure morphology, or the like). 
     Optionally, in some embodiments, the actuator  188  may be coupled to a proximal side of sensor array  186 . For example,  FIG. 26  illustrates another exemplary system  204  according to some embodiments of the present disclosure. System  204  includes a sensor array  186  coupled with an actuator  188 , similar to system  184  of  FIG. 25 , however actuator  188  is coupled with a proximal side of the sensor array  186  rather than being sandwiched between the proximal layer  190 . 
       FIG. 27  illustrates another exemplary proximal layer  206  of another exemplary sensor array according to some embodiments of the present disclosure. The proximal layer  206  may comprise a plurality of fingers  208  which form one or more sensing areas  210  of the sensor array. Additionally, the plurality of fingers  208  may each be supported by a stiffener  212 . However, in contrast with the configurations described above, the plurality of fingers  208  may be coupled with one another along a central portion of each finger  208  and the trace  214  may extend from the central portion of the finger  208  at the edge of the proximal layer  206 . The integrated circuit  215  may be coupled with the trace  214  in certain embodiments. 
       FIG. 28  illustrates an exemplary pillar configuration  216  for a sensing element  218  that may be used to separate a proximal layer from a distal layer in any of the above described embodiments. Pillar configuration  216  comprises a two by two array of dielectric pillars  220  for supporting a proximal electrode relative to a distal electrode of a capacitive pressure sensing element. The two by two array of dielectric pillars  220  may be disposed in the sensing area of sensing element  218 . While illustrated as a two by two array of dielectric pillars  220 , larger arrays may be used in other embodiments (e.g., three by three or the like). 
       FIG. 29  illustrates another exemplary pillar configuration  222  for a sensing element  218  that may be used to support a proximal electrode relative to a distal electrode in any of the above described embodiments. Pillar configuration  222  comprises four dielectric strips  224 . The dielectric strips  224  may have a length less than the width of the sensing element  218 . The dielectric strips  224  may be centered and disposed on each edge of the sensing element  218  to support a proximal electrode relative to a distal electrode of a capacitive pressure sensing element. In some embodiments, the dielectric strips  224  may straddle the edge of the sensing element  218 . While illustrated as including four strips  224 , it should be understood that fewer or more strips may be used in other embodiments. For example, in some embodiments, the strips  224  may be disposed only one two of the edges of the sensing element  218 . Optionally, multiple smaller strips may be disposed on a single edge of the sensing element  218 . 
       FIG. 30  illustrates yet another exemplary pillar configuration  226  for a sensing element  218  that may be used to support a proximal electrode relative to a distal electrode in any of the above described embodiments. Pillar configuration  226  may comprise a two by two array of dielectric pillars  228 . The dielectric pillars  228  may be disposed at the corners of the sensing element  218 . In some embodiments, the pillars  228  are only partially disposed within the sensing area of the sensing element  218 . The pillar pattern may also be a mix of side support ( FIG. 29 ), corner support ( FIG. 30 ) and center support ( FIG. 28 ). 
     While the above sensor configurations are described generally for use with capacitive pressure sensors, it should be understood that the configurations described herein may be applicable to other pressure sensors (e.g., piezoresistive pressure sensors or the like). 
     Additionally, in some embodiments, blood pressure morphology and/or absolute pressure measurements. In certain embodiments, peripheral blood pressure waveform (e.g., from radial artery or the like) may be measured with embodiments described above (e.g., with a wrist-worn device or the like). A transfer function may be applied to the blood pressure waveform to calculate a central aortic waveform. From the calculated central aortic waveform, an augmentation index may be calculated which may be equal to the augmentation pressure over the actual left ventricle ejected pressure. The augmentation index may be an indicator for arterial health (e.g., stiffness and/or aging). This arterial health may then be correlated to other physiologies, stress, drug effects, pathophysiologies, etc. 
     It will be appreciated that personal information data may be utilized in a number of ways to provide benefits to a user of a device. For example, personal information such as health or biometric data may be utilized for convenient authentication and/or access to the device without the need of a user having to enter a password. Still further, collection of user health or biometric data (e.g., blood pressure measurements) may be used to provide feedback about the user&#39;s health and/or fitness levels. It will further be appreciated that entities responsible for collecting, analyzing, storing, transferring, disclosing, and/or otherwise utilizing personal information data are in compliance with established privacy and security policies and/or practices that meet or exceed industry and/or government standards, such as data encryption. For example, personal information data should be collected only after receiving user informed consent and for legitimate and reasonable uses of the entity and not shared or sold outside those legitimate and reasonable uses. Still further, such entities would take the necessary measures for safeguarding and securing access to collected personal information data and for ensuring that those with access to personal information data adhere to established privacy and security policies and/or practices. In addition, such entities may be audited by a third party to certify adherence to established privacy and security policies and/or practices. It is also contemplated that a user may selectively prevent or block the use of or access to personal information data. Hardware and/or software elements or features may be configured to block use or access. For instance, a user may select to remove, disable, or restrict access to certain health related applications that collect personal information, such as health or fitness data. Alternatively, a user may optionally bypass biometric authentication methods by providing other secure information such as passwords, personal identification numbers, touch gestures, or other authentication methods known to those skilled in the art. 
     One or more computing devices may be adapted to provide desired functionality by accessing software instructions rendered in a computer-readable form. When software is used, any suitable programming, scripting, or other type of language or combinations of languages may be used to implement the teachings contained herein. However, software need not be used exclusively, or at all. For example, some embodiments of the methods and systems set forth herein may also be implemented by hard-wired logic or other circuitry, including but not limited to application-specific circuits. Combinations of computer-executed software and hard-wired logic or other circuitry may be suitable as well. 
     Embodiments of the methods disclosed herein may be executed by one or more suitable computing devices. Such system(s) may comprise one or more computing devices adapted to perform one or more embodiments of the methods disclosed herein. As noted above, such devices may access one or more computer-readable media that embody computer-readable instructions which, when executed by at least one computer, cause the at least one computer to implement one or more embodiments of the methods of the present subject matter. Additionally or alternatively, the computing device(s) may comprise circuitry that renders the device(s) operative to implement one or more of the methods of the present subject matter. 
     Any suitable computer-readable medium or media may be used to implement or practice the presently-disclosed subject matter, including but not limited to, diskettes, drives, and other magnetic-based storage media, optical storage media, including disks (e.g., CD-ROMS, DVD-ROMS, variants thereof, etc.), flash, RAM, ROM, and other memory devices, and the like. 
     The subject matter of embodiments of the present disclosure is described here with specificity, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described. 
     Different arrangements of the components depicted in the drawings or described above, as well as components and steps not shown or described are possible. Similarly, some features and sub-combinations are useful and may be employed without reference to other features and sub-combinations. Embodiments of the disclosure have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Additionally, it should be understood that the ranges and materials provided herein are exemplary and that the ultimate selection of sizes, materials, etc. may depend on the overall device design and application. Accordingly, the present disclosure is not limited to the embodiments described above or depicted in the drawings, and various embodiments and modifications may be made without departing from the scope of the claims below.

Metadata:
Filing Date: 20160923
Publication Date: 20200512
Grant Date: 20200512
Priority Date: 20150929
Inventors: NARASIMHAN, RAVI K.
ZENG, ZIJING
ZHANG, ZHIPENG
Assignee: APPLE INC
CPC Classifications: [{"code": "A61B2562/046", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B2562/0247", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/02444", "inventive": true, "first": true, "tree": "[]"}, {"code": "A61B5/6831", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/6824", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B2562/0214", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B2562/0214", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B2562/0247", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/6824", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/02141", "inventive": true, "first": true, "tree": "[]"}, {"code": "A61B2562/046", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B2562/0247", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/6824", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B2562/046", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B2562/0214", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/6831", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/02141", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 58406088