US20210041287A1 - On-Bed Differential Piezoelectric Sensor - Google Patents

Abstract

A sensor system includes a sensor stack, a differential amplifier, an analog-to-digital converter, and a processor. The sensor stack includes a piezoelectric material having a first side opposing a second side, a first electrode connected to the first side, and a second electrode connected to the second side. The differential amplifier is coupled to the first and second electrodes and is configured to generate a differential output indicative of vibrations sensed by the piezoelectric material. The analog-to-differential converter is configured to digitize the differential output. The processor is configured to identify a type of biological vibration included in the digitized differential output.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a nonprovisional of and claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application No. 62/885,028, filed Aug. 9, 2019, and U.S. Provisional Patent Application No. 62/891,195, filed Aug. 23, 2019, the contents of which are incorporated herein by reference as if fully disclosed herein.
FIELD
• The described embodiments relate generally to an on-bed differential piezoelectric sensor, or to a sensor system including such a sensor. The sensor or sensor system can be used on a bed or elsewhere to sense vibrations, including sounds. The sensed vibrations or sounds may include biological vibrations or sounds made by a user, such as heart vibrations or sounds, lung vibrations or sounds, nasal vibrations or sounds, or digestive vibrations or sounds.
BACKGROUND
• A device such as a smartphone or electronic watch may include various health sensors. The health sensors may be capable of monitoring a user's heart rate, heart rhythm, steps taken, calories burned, and so on as the user carries the smartphone or wears the electronic watch during the day. However, at night, the user may place (or couple) the smartphone and electronic watch on (or to) one or more chargers. The user's nighttime health may therefore not be monitored, or may be monitored to a lesser extent than the user's daytime health. Although the user may place the smartphone on their bed or wear the electronic watch while sleeping, these options may not be comfortable or convenient, and may interfere with charging these devices.
SUMMARY
• Embodiments of the systems, devices, methods, and apparatus described in the present disclosure are directed to sensors and sensor systems for differentially sensing vibrations, such as biological vibrations or sounds made by a user. Biological vibrations and sounds include, for example, heart vibrations or sounds, lung vibrations or sounds, nasal vibrations or sounds, and digestive vibrations or sounds. Vibrations and sounds are collectively referred to herein as vibrations, and may include audible sounds (e.g., sounds heard by a person) and inaudible sounds (e.g., sounds experienced as vibrations and not heard by a person, or sounds heard or sensed by a device configured to listen or monitor for such sounds). In some embodiments, a sensor may be placed on a user's bed, or otherwise positioned on or near the user's torso. The sensor may include a piezoelectric material or element having electrodes connected to opposite sides thereof. Vibration-induced waveforms (e.g., waveforms associated with biological vibrations or sounds) may impinge on the piezoelectric material and impart forces on the piezoelectric material, which forces cause the piezoelectric material to change shape and vibrate. The electrodes connected to the piezoelectric material may differentially sense these vibrations (i.e., the electrodes may produce out-of-phase signals in response to the vibrations, as a result of the electrodes being connected to opposite sides of the piezoelectric material). When the signals generated by the electrodes are differentially amplified and subtracted, the out-of-phase signals combine to produce an amplified waveform (e.g., an amplified vibratory or audio output). In contrast, electromagnetic noise sensed by the electrodes (e.g., AC line noise) may induce in-phase signals that combine with out-of-phase signals. However, when the signals generated by the electrodes are differentially amplified and subtracted, the in-phase noise signals cancel out, leaving only an amplified signal (e.g., an amplified vibratory or audio output).
• In a first aspect, the present disclosure describes a sensor system that includes a sensor stack, a differential amplifier, an analog-to-differential converter, and a processor. The sensor stack may include a piezoelectric material having a first side opposing a second side, a first electrode connected to the first side, and a second electrode connected to the second side. The differential amplifier may be coupled to the first and second electrodes and be configured to generate a differential output indicative of vibrations sensed by the piezoelectric material. The analog-to-differential converter may be configured to digitize the differential output. The processor may be configured to identify a type of biological vibration included in the digitized differential output.
• In another aspect, the present disclosure describes a sensor system that includes a sensor, an electrical interconnect, and a differential amplifier. The sensor may include a piezoelectric element, and first and second electrodes that are respectively connected to first and second opposing surfaces of the piezoelectric element. The electrical interconnect may include first and second conductors, respectively connected (or connectable) to the first and second electrodes. The differential amplifier may be connected (or connectable) to the first and second conductors and provide a differential output indicative of vibrations sensed by the piezoelectric element.
• In another aspect of the disclosure, the present disclosure describes a method of monitoring biological vibrations of a user. The method may include receiving a pair of signals from a pair of electrodes connected to opposite sides of a piezoelectric element; differentially amplifying the pair of signals to generate a differential output; identifying a type of biological vibration included in the differential output; and outputting an indicator of the type of biological vibration.
• In addition to the aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
• The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:
• FIG. 1 shows an example of a sensor system that may be used to sense biological vibrations;
• FIG. 2 shows an alternative embodiment of the vibration sensor described with reference toFIG. 1;
• FIG. 3 shows examples of some different types of biological vibrations that can be sensed by the vibration sensors described with reference toFIG. 1 or 2, and the approximate frequency ranges of such vibrations;
• FIG. 4 shows example vibration patterns for ballistocardiography (BCG)/seismocardiography (SCG) vibrations or sounds; S1, S2, S3, and S4 heart sounds; heart murmurs; normal lung sounds; wheeze sounds; crackle sounds; snore sounds; cough sounds; and respiration sounds;
• FIG. 5 shows an example embodiment of various components included in the sensor system described with reference toFIG. 1;
• FIG. 6 illustrates how measured vibrations, including biological vibrations, may be amplified by the processing circuitry described with reference toFIGS. 1 and 5, while an AC line frequency or other background noise may be canceled by the processing circuitry;
• FIG. 7A shows, in exploded form, an example more detailed cross-section of the sensor stack described with reference toFIG. 5;
• FIG. 7B shows the cross-section ofFIG. 7A in assembled form;
• FIG. 7C shows, in exploded form, an example of the sensor interface described with reference toFIG. 5, in the context of the sensor stack described with reference toFIG. 7A;
• FIG. 8A shows an example more detailed cross-section of the sensor stack described with reference toFIG. 7A;
• FIGS. 8B-8D show various examples of the sensor interface described with reference toFIG. 5, in the context of the sensor stack described with reference toFIG. 8A; and
• FIG. 9 illustrates a method of monitoring biological vibrations of a user.
• The use of cross-hatching or shading in the accompanying figures is generally provided to clarify the boundaries between adjacent elements and also to facilitate legibility of the figures. Accordingly, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, element proportions, element dimensions, commonalities of similarly illustrated elements, or any other characteristic, attribute, or property for any element illustrated in the accompanying figures.
• Additionally, it should be understood that the proportions and dimensions (either relative or absolute) of the various features and elements (and collections and groupings thereof) and the boundaries, separations, and positional relationships presented therebetween, are provided in the accompanying figures merely to facilitate an understanding of the various embodiments described herein and, accordingly, may not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for an illustrated embodiment to the exclusion of embodiments described with reference thereto.
DETAILED DESCRIPTION
• Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims.
• Described herein are techniques that enable the high-fidelity collection of biological vibrations, such as heart vibrations or sounds, lung vibrations or sounds, nasal vibrations or sounds, or digestive vibrations or sounds. The collection of chest cavity vibrations, in particular, such as heart and lung vibrations or sounds, typically requires a sensing bandwidth of at least 500 Hertz (Hz). Unfortunately, the bandwidth includes typical AC line frequencies, which are in the range of 50/60 Hz, and which can have second harmonics in the range of 100/120 Hz (e.g., due to rectification of the AC line frequencies in power supplies). To provide high-fidelity sensing of chest cavity vibrations (and/or other biological vibrations), while mitigating the effects of line noise interference, the techniques described herein employ differential sensing. Differential sensing is useful in that it produces out-of-phase signals corresponding to mechanical vibrations, such as biological vibrations, and the out-of-phase signals constructively interfere and amplify mechanical vibrations (e.g., biological vibrations) when subtracted. In contrast, electromagnetic noise (e.g., AC line noise) that may interfere with the sensing process produces in-phase signals (i.e., common mode signals). When subtracted, the in-phase signals cancel out (through destructive interference), leaving an amplified output corresponding to the sensed mechanical vibrations.
• These and other techniques are described with reference toFIGS. 1-9. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting.
• Directional terminology, such as “top”, “bottom”, “upper”, “lower”, “front”, “back”, “over”, “under”, “left”, “right”, etc. is used with reference to the orientation of some of the components in some of the figures described below. Because components in various embodiments can be positioned in a number of different orientations, directional terminology is used for purposes of illustration only and is in no way limiting. The directional terminology is intended to be construed broadly, and therefore should not be interpreted to preclude components being oriented in different ways. The use of alternative terminology, such as “or”, is intended to indicate different combinations of the alternative elements. For example, A or B is intended to include, A, or B, or A and B.
• FIG. 1 shows an example of asensor system100. Thesensor system100 may be used to sense biological vibrations (e.g., chest cavity vibrations or sounds, nasal cavity vibrations or sounds, abdominal cavity vibrations or sounds, and so on) made by a person laying on abed102, a couch, an examination table, or the like. Alternatively, thesensor system100 may be used by a person sitting in a chair, or by a person who has attached part or all of the sensor system100 (e.g., the sensor package104) to their torso, or to an object in contact with their torso. In addition to biological vibrations, thesensor system100 may sense other mechanical vibrations.
• In some embodiments, thesensor system100 may include avibration sensor110 that is coupled toprocessing circuitry114 by anelectrical interconnect108. In some embodiments, thevibration sensor110 may be housed in asensor package104, theprocessing circuitry114 may be housed in a processing module106 (e.g., a separate physical package, such as a dongle), and theelectrical interconnect108 may take the form of an electrical cord or cable that connects thevibration sensor110 to theprocessor114. Alternatively, theelectrical interconnect108 may take the form of wires, conductive traces, or other conductive elements, which conductive elements may be routed within one or more connectors, on one or more substrates (e.g., on or in a printed circuit board (PCB) or integrated circuit (IC)), or on or within thevibration sensor110. In some embodiments, thevibration sensor110,electrical interconnect108, andprocessing circuitry114 may all be housed within thesensor package104 and, in some of these embodiments, there may not be a separate housing for theprocessing circuitry114 or electrical interconnect108 (e.g., there may not be a physicallyseparate processing module106 or electrical cord).
• Thesensor package104, including thevibration sensor110, may be flexible, so that it is more or less unnoticeable to a person laying on thebed102. Theelectrical interconnect108 may also be flexible, and/or theprocessing circuitry114 may be flexible (e.g., theprocessing circuitry114 may be formed on or in a flexible substrate). In some embodiments, one or more of thevibration sensor110,electrical interconnect108,processing circuitry114, orsensor package104 may not be flexible.
• Theprocessing circuitry114 may receive and process signals received from the vibration sensor110 (e.g., signals received via the electrical interconnect108). For example, theprocessing circuitry114 may amplify and digitize signals received from thevibration sensor110. In some embodiments, theprocessing circuitry114 may include a communications interface for communicating digitized signals or other information to another device112 (e.g., a remote device), such as a smartphone or electronic watch. The communications interface may also receive from theother device112. For example, the communications interface may receive instructions, control signals, settings, or queries from theother device112. The communications interface may be wireless (e.g., a Wi-Fi or Bluetooth interface) or wired (e.g., a universal serial bus (USB) interface). In some cases, theprocessing circuitry114 may include a processor (e.g., a microprocessor, a microcontroller, an application-specific integrated circuit (ASIC), or a field-programmable gate array (FPGA)). The processor may control operation of other circuitry, such as the circuity that processes signals received from thevibration sensor110, or the communications interface. In some cases, theprocessing circuitry114 may additionally or alternatively include circuits that do not rise to the level of a processor. Theprocessing circuitry114 may be housed separately from thevibration sensor110, such as in aprocessing module106. Alternatively, theprocessing circuitry114 may be housed with thevibration sensor110 in thesensor package104, or components of theprocessing circuitry114 may be distributed between different physical locations (e.g., a portion of theprocessing circuitry114 may be housed with thevibration sensor110 and a portion of theprocessing circuitry114 may be housed in a separate processing module106). In some cases, part or all of theprocessing circuitry114 may be integrated with thevibration sensor110 on a shared substrate. In some embodiments, components or functions of theprocessing circuitry114 may be housed by, or provided by, theremote device112, and theelectrical interconnect108 may terminate at a connector that plugs into theremote device112. Theelectrical interconnect108 may also terminate at a connector that plugs into theprocessing module106.
• Thesensor package104 may variously enclose thevibration sensor110, and/or protect thevibration sensor110 from dust, oil, moisture, or liquid spills, and/or electrically insulate thevibration sensor110 from a user. In some embodiments, thesensor package104 may be made of natural or synthetic cloth, plastic, or other materials, and may include a sealed or accessible pouch configured to hold thevibration sensor110. In some cases, thesensor package104 may be a pocket included in (or attachable to) a bed sheet, mattress, cushion, or seating surface. In some embodiments, thesensor package104 may include a polymer, thermoplastic polymer, resin, or other material that is applied to, encapsulates, or is molded around thevibration sensor110. In some embodiments, thesensor package104 may include both an inner package (e.g., a material that is applied to, encapsulates, or is molded around the vibration sensor110) and an outer package (e.g., a cloth or plastic sleeve or cover). When theelectrical interconnect108 is packaged in an electrical cord, thesensor package104 may have an opening through which the electrical cord may pass. When part or all of theprocessing circuitry114 is separately housed in theprocessing module106, theprocessing module106 may be constructed similarly to, or different from, thesensor package104. In some embodiments, theprocessing module106 may take the form of a polymer (e.g., plastic) housing.
• FIG. 2 shows an alternative embodiment of the vibration sensor described with reference toFIG. 1. In particular, thevibration sensor200 shown inFIG. 2 includes a plurality of vibration sensors202-1,202-2,202-3,202-4, each of which may be configured similarly to thevibration sensor100. The vibration sensors202-1,202-2,202-3,202-4 may be encapsulated in aflexible material204 at predefined positions (e.g., in an array or other distribution pattern); held in different pockets of a sensor package (e.g., a sensor package having multiple pockets for the multiple vibration sensors202-1,202-2,202-3,202-4); or arbitrarily positioned on a bed or other surface by their user or an aide (e.g., a partner, caretaker, or nurse). In use, each vibration sensor202-1,202-2,202-3,202-4 may be positioned at a different location and/or oriented in a different direction with respect to a user's torso.
• Each vibration sensor202-1,202-2,202-3,202-4 may be positioned or used to sense the same or different biological vibrations (e.g., chest cavity vibrations or sounds, nasal cavity vibrations or sounds, abdominal cavity vibrations or sounds, and so on). For example, two or more vibration sensors202-1,202-2,202-3,202-4 may be positioned to sense the same biological vibrations (e.g., lung vibrations or sounds), and their outputs may be compared or combined. Additionally or alternatively, and by way of example, one or more of the vibration sensors202-1,202-2,202-3,202-4 may be positioned to sense chest cavity vibrations or sounds (e.g., one or more vibration sensors may be positioned closer to a user's chest cavity), and one or more different vibration sensors202-1,202-2,202-3,202-4 may be positioned to sense abdominal cavity vibrations or sounds (e.g., one or more vibration sensors may be positioned closer to a user's abdomen). Or, for example, one or more vibration sensors202-1,202-2,202-3,202-4 may be positioned to sense heart vibrations or sounds (e.g., one or more vibration sensors may be positioned closer to a user's heart), and one or more other vibration sensors202-1,202-2,202-3,202-4 may be positioned to sense lung vibrations or sounds (e.g., one or more vibration sensors may be positioned closer to a user's lungs). In some embodiments, the vibration sensors202-1,202-2,202-3,202-4 may all have the same configuration, and may simply be placed closer to, or farther from, different portions of a user's torso. In other embodiments, different vibration sensors may be longer, wider, or differently shaped, to improve their sensitivity to particular types of vibration, or to improve their sensitivity to vibrations originating from particular regions of a user's torso.
• The vibration sensors described with reference toFIGS. 1 and 2 can be used to differentially sense various types of biological sounds. As previously discussed, the sensing of biological sounds using differential sensing can enable the sensing of sounds having a frequency bandwidth that includes (e.g., intersects or crosses) an alternating current (AC) line frequency, or sounds on both sides of an AC line frequency (e.g., low-frequency vibrations and higher frequency audible sounds).
• The biological vibrations sensed by the vibration sensors described with reference toFIGS. 1 and 2 may include vibrations or sounds that propagate through a person and/or other objects that are directly or indirectly in contact with the vibration sensors. In this manner, ambient sounds may not be sensed, as might be the case with a typical diaphragm-type microphone included in a smartphone or electronic watch.
• FIG. 3 shows examples of some different types of biological vibrations that can be sensed by the vibration sensors described with reference toFIGS. 1 and 2, and the approximate frequency ranges of such vibrations.
• A first set of biological vibrations that can be sensed are heart vibrations or sounds. Heart vibrations and sounds include, for example, BCG/SCG vibrations and sounds300 extending from about 5 Hz-50 Hz; S1, S2, S3, and S4 heart sounds302 extending from about 25 Hz-250 Hz; and heart murmurs304 (including different types of heart murmurs) extending from about 100 Hz-1 kilohertz (kHz). Both the BCG/SCG vibrations and sounds and S1, S2, S3, and S4 heart sounds may have frequency bandwidths that intersect or cross an AC line frequency (e.g., 50/60 Hz). A differential sensor can subtract out the AC line frequency during signal amplification, as discussed with reference toFIG. 7.
• A second set of biological vibrations that can be sensed are lung vibrations or sounds. Lung vibrations and sounds include, for example, normal lung sounds, wheeze sounds, crackle sounds, and cough sounds, which generally have frequency bandwidths above AC line frequencies, and respiration vibrations, which generally have frequency bandwidths below AC line frequencies. Normal lung sounds306 (e.g., vesicular sounds) may generally extend from about 100 Hz-1 kHz; wheeze sounds308 may generally extend from about 100 Hz-5 kHz; crackle sounds310 may generally extend from about 300 Hz-700 Hz; and cough sounds312 may generally extend from about 275 Hz-600 Hz. Respiration vibrations (e.g., inspiration and expiration vibrations)314 are generally in the 1 Hz-2 Hz range, and are typically not audible to the human ear.
• A third set of biological vibrations that can be sensed are nasal vibrations or sounds. Nasal vibrations and sounds include, for example, snore sounds. Snore sounds316 may generally extend from about 130 Hz-1250 Hz.
• In some cases, a type of biological vibration that is sensed by a differential sensor (or different types of biological vibrations) can be distinguished by virtue of the frequency bandwidth in which it resides. Alternatively, biological vibration types can be distinguished by their vibration patterns; by a combination of their frequency bandwidth and vibration pattern; or using alternative or additional parameters (e.g., peak-to-peak timings, peak-to-peak intensities, and so on).FIG. 4 showsexamples vibration patterns400 for BCG/SCG vibrations; S1, S2, S3, and S4 heart sounds; heart murmurs; normal lung sounds; wheeze sounds; and crackle sounds. As shown, the vibration patterns for the different biological sound types typically vary, and sometimes substantially.
• FIG. 5 shows an example embodiment of various components included in the sensor system described with reference toFIG. 1. In particular,FIG. 5 shows examples of thevibration sensor110,electrical interconnect108, andprocessing circuitry114.
• As shown, thevibration sensor110 may include a sensor stack500 (e.g., a plurality of elements or layers, such as a plurality of planar elements or layers, stacked one on top of the other). At its core, thesensor stack500 may include a piezoelectric material502 (e.g., a piezoelectric element). In some embodiments, thepiezoelectric material502 may include a polyvinylidene difluoride (PVDF) material, such as a PVDF film, a PVDF-copolymer, a PVDF/poly-L-lactide (PLLA) blend, and so on. Thepiezoelectric material502 may alternatively include a PLLA material or other material. Thepiezoelectric material502 may have first and second opposing sides504-1,504-2 and surfaces that extend in a plane perpendicular to thestack500.
• A first electrode506-1 (e.g., a positive electrode) may be connected to the first side504-1 or surface of thepiezoelectric material502, and a second electrode506-2 (e.g., a negative electrode) may be connected to the second side506-2 or surface of thepiezoelectric material502. The first and second electrodes506-1,506-2 may terminate at asensor interface508 that passively outputs a pair of signals obtained from thepiezoelectric material502 by the first and second electrodes506-1,506-2. Theelectrical interconnect108 may be permanently or detachably connected to thesensor interface508.
• Optionally, thesensor stack500 may further include a first electromagnetic noise shield510-1 (e.g., a first ground layer) disposed on the first side504-1 of thepiezoelectric material502. The first electromagnetic noise shield510-1 may be electrically insulated from both thepiezoelectric material502 and the first electrode506-1, with the first electrode506-1 disposed between thepiezoelectric material502 and the first electromagnetic noise shield510-1. Thesensor stack500 may also include a second electromagnetic noise shield510-2 (e.g., a second ground layer) disposed on the second side504-2 of thepiezoelectric material502. The second electromagnetic noise shield510-2 may be electrically insulated from both thepiezoelectric material502 and the second electrode506-2, with the second electrode506-2 disposed between thepiezoelectric material502 and the second electromagnetic noise shield510-2.
• In some embodiments, a first thermoplastic polymer resin512-1 (e.g., a first layer of polyethylene terephthalate (PET) or biaxially-oriented PET (BoPET)) may be disposed between the first electrode506-1 and the first electromagnetic noise shield510-1, and a second thermoplastic polymer resin512-2 (e.g., a second layer of PET or BoPET) may be disposed between the second electrode506-2 and the second electromagnetic noise shield512-2.
• In some embodiments, the outermost or exterior layers (and in some cases sides) of thestack500 may include a third thermoplastic polymer resin514-1 (e.g., a third layer of PET or BoPET) disposed on or over the first electromagnetic noise shield510-1, and a fourth thermoplastic polymer resin514-2 (e.g., a fourth layer of PET or BoPET) disposed on or over the second electromagnetic noise shield510-2. The third and fourth thermoplastic polymer resins514-1,514-2 may be considered first and second non-conductive stack covers for thevibration sensor110. In other embodiments, the electromagnetic noise shields510-1,510-2 may be the outermost or exterior layers of thestack500, or the first and second thermoplastic polymer resins512-1,512-2 may be the outermost or exterior layers of thestack500.
• The first and second thermoplastic polymer resins512-1,512-2 may be coupled to the first and second electrodes506-1,506-2 using a pressure-sensitive adhesive (PSA) (e.g., a PSA deposited on each of the first and second electrodes506-1,506-2, or on each of the first and second thermoplastic polymer resins512-1,512-2, and/or between corresponding ones of the first and second electrodes506-1,506-2 and first and second thermoplastic polymer resins512-1,512-2). Similarly, the third and fourth thermoplastic polymer resins514-1,514-2 may be coupled to the first and second electromagnetic noise shields510-1,510-2 using a PSA (e.g., the same type of PSA used to couple the first and second thermoplastic polymer resins512-1,512-2 to the first and second electrodes506-1,506-2, or a different type of PSA), which PSA may be deposited on each of the first and second electromagnetic noise shields510-1,510-2, or on each of the third and fourth thermoplastic polymer resins514-1,514-2, and/or between corresponding ones of the first and second electromagnetic noise shields510-1,510-2 and third and fourth thermoplastic polymer resins514-1,514-2).
• Any of the thermoplastic polymer resins512-1,512-2,514-1,514-2 may alternatively be replaced with a different type of electrical insulator.
• In some embodiments, the elements or layers stacked on either side of thepiezoelectric material502 may be symmetric or nearly symmetric on opposite sides504-1,504-2 of the piezoelectric material502 (e.g., the silhouettes of corresponding elements or layers may have a symmetric projection over 90% or more of their circumference). For example, the first and second electrodes506-1,506-2 may be symmetric or nearly symmetric, the electromagnetic noise shields510-1,510-2 may be symmetric or nearly symmetric, the thermoplastic polymer resins512-1,512-2 may be symmetric or nearly symmetric, and the thermoplastic polymer resins514-1,514-2 may be symmetric or nearly symmetric. In addition, the electromagnetic noise shields510-1,510-2 may have surface areas that are greater than the surface areas of the electrodes506-1,506-2. In some embodiments, the electromagnetic noise shields510-1,510-2 may completely cover the surface areas of the electrodes506-1,506-2. In some embodiments, the electromagnetic noise shields510-1,510-2 may cover most of the surface areas of the electrodes506-1,506-2, but nonetheless have surface areas that are greater than the surface areas of the electrodes506-1,506-2. This helps to mitigate or eliminate the inducement of common mode noise in the electrodes506-1,506-2.
• Theelectrical interconnect108 may mechanically and electrically connect to thesensor interface508, and may include first and second conductors516-1,516-2 that connect to the first and second electrodes506-1,506-2 at or via thesensor interface508. The first and second conductors516-1,516-2 may be surrounded by insulation, and may be twisted to form a twisted pair within theelectrical interconnect108. The first and second electromagnetic noise shields510-1,510-2 may be connected to each other and to an electromagnetic noise shield518 (e.g., a metal or conductive sheath) that surrounds the first and second conductors516-1,516-2, thereby forming a shielded twisted pair (STP). Theelectromagnetic noise shield518 may be surrounded by a non-conductive sheath (not shown). In alternative embodiments, the first and second conductors516-1,516-2 may be routed on a substrate as conductive traces, with a noise shield being formed by conductive traces or planes coupled to the first and second electromagnetic noise shields510-1,510-2.
• Theprocessing circuitry114 may include components that form part of an analog front end (AFE) and/or data acquisition (DAQ) circuit. For example, theprocessing circuitry114 may include adifferential amplifier520, a differential analog-to-digital converter (ADC)522, acommunications interface524, aprocessor526, and/or other circuitry. Thedifferential amplifier520 may be connected to the first and second conductors516-1,516-2 of theelectrical interconnect108. For example, the first and second conductors516-1,516-2 may be electrically connected to input nodes or terminals of thedifferential amplifier520. Thedifferential amplifier520 may provide amplified differential output528 (e.g., an amplification of the pair of signals obtained from the piezoelectric material502). The differential output may include biological vibrations sensed by thepiezoelectric material502. As discussed with reference toFIGS. 1 and 3, the differential output may have a frequency bandwidth that includes (e.g., intersects or crosses) an AC line frequency.
• In some embodiments, thedifferential amplifier520 may be a differential charge amplifier. In other embodiments, thedifferential amplifier520 may be a transimpedance amplifier (TIA). When using a TIA, thepiezoelectric material502 may be considered a current source instead of a charge source. A TIA may provide a flatter response over a greater range of frequencies than a differential charge amplifier (i.e., a TIA may provide satisfactory amplification over a greater frequency bandwidth).
• In general, the more symmetry that can be maintained in the physical layout of thesensor system500, from the first and second electrodes506-1,506-2 through the output of thedifferential amplifier520, the better fidelity of the amplified output.
• Thedifferential ADC522 may be configured to digitize the differential output of thedifferential amplifier520. Thedifferential ADC522 may combine (subtract) the differential signals or differential output of thedifferential amplifier520. The digitized differential output may be stored in an optional memory on-board theprocessing module106 and/or transmitted (e.g., streamed) to another device via thecommunications interface524. In some cases, thecommunications interface524 may include a Wi-Fi and/or Bluetooth interface. Anoptional processor526 or other circuitry may control operation of thedifferential amplifier520,differential ADC522,communications interface524, memory, and/or other components of theprocessing module106.
• In some embodiments, theprocessor526 of theprocessing circuitry114, a processor of the device112 (see,FIG. 1), or a processor of yet another device may identify at least a first vibration included in the digitized differential output of thedifferential ADC522. The same or a different processor may then pattern match the first vibration to any of a number of known biological vibrations, including, for example, any of the biological vibrations described with reference toFIGS. 3 and 4.
• FIG. 6 illustrates how measured vibrations, including biological vibrations, may be amplified by the processing circuitry described with reference toFIGS. 1 and 5, while an AC line frequency or other background noise may be canceled by the processing circuitry. In particular, afirst graph600 shows how AC line noise may be sensed by a differential piezoelectric sensor, such as one of the vibration sensors described with reference toFIG. 1, 2, or5. As shown, first and second electrodes of the vibration sensor may sense the AC line noise in-phase, such that a subtraction of one signal from the other results in no signal or a direct current (DC) signal being output from a differential ADC, as shown in asecond graph610.
• Athird graph620 shows how a vibration (e.g., a biological vibration) may be measured or sensed by the same differential piezoelectric sensor. As shown, the first and second electrodes may sense the vibration out-of-phase, such that a subtraction of one electrode's signal from the other results in an amplified signal being output from the differential ADC, as shown in athird graph630.
• FIG. 7A shows, in exploded form, an example more detailed cross-section of the sensor stack described with reference toFIG. 5. Like components are therefore referred to by like reference numerals inFIGS. 5 and 7A.FIG. 7B shows the cross-section ofFIG. 7A in assembled form.
• Similar to the sensor stack described with reference toFIG. 5, thesensor stack700 includes apiezoelectric material502; first and second electrodes506-1,506-2 connected to opposite sides504-1,504-2 of thepiezoelectric material502; first and second electromagnetic noise shields510-1,510-2; and first, second, third, and fourth thermoplastic polymer resins512-1,512-2,514-1,514-2. Thesensor stack700 also includes various PSAs.
• A first PSA702-1 may be disposed on the first electrode506-1, or between the first electrode506-1 and the first thermoplastic polymer resin512-1. The first thermoplastic polymer resin512-1 may be disposed on the first PSA702-1, and may be coupled to the first electrode506-1 (and in some areas, to the piezoelectric material502) by the first PSA702-1. A second PSA702-2 may be disposed on the second electrode506-2, or between the second electrode506-2 and the second thermoplastic polymer resin512-2. The second thermoplastic polymer resin512-2 may be disposed on the second PSA702-2, and may be coupled to the second electrode506-2 (and in some areas, to the piezoelectric material502) by the second PSA702-2.
• A third PSA702-3 may be disposed on the first electromagnetic noise shield510-1, or between the first electromagnetic noise shield510-1 and the third thermoplastic polymer resin514-1. The third thermoplastic polymer resin514-1 may be disposed on the third PSA702-3, and may be coupled to the first electromagnetic noise shield510-1 (and in some areas, to the first thermoplastic polymer resin512-1) by the third PSA702-3. A fourth PSA702-4 may be disposed on the second electromagnetic noise shield510-2, or between the second electromagnetic noise shield510-2 and the fourth thermoplastic polymer resin514-2. The fourth thermoplastic polymer resin514-2 may be disposed on the fourth PSA702-4, and may be coupled to the second electromagnetic noise shield510-2 (and in some areas, to the second thermoplastic polymer resin512-2) by the fourth PSA702-4.
• In some alternative embodiments, the third thermoplastic polymer resin514-1 and third PSA702-3 may be combined, and/or the fourth thermoplastic polymer resin514-2 and fourth PSA702-4 may be combined.
• As shown inFIG. 7A, the various conductive elements of thesensor stack700 may have different widths. They may also have different lengths. In some cases, the electrodes506-1,506-2 may have widths and/or lengths that are narrower than those of the electromagnetic noise shields510-1,510-2, so that the electrodes506-1,506-2 are better shielded by the electromagnetic noise shields510-1,510-2. In other cases, the electromagnetic noise shields510-1,510-2 may have widths and/or lengths that are the same as those of the electrodes506-1,506-2.
• FIG. 7C shows an example of the sensor interface described with reference toFIG. 5, in the context of the sensor stack described with reference toFIGS. 7A-7B. Although the electrodes506-1,506-2 and first electromagnetic noise shield510-1 are shown adjacent to one another in theplan view710, the electrodes506-1,506-2 and electromagnetic noise shields510-1,510-2 may be stacked as shown inFIG. 7A and theplan view712. In theplan view712, the second electromagnetic noise shield510-2 is not illustrated because it is stacked directly under the first electromagnetic noise shield510-1.
• In thesensor interface714, each of the first and second electrodes506-1,506-2 are re-routed (to the left or to the right), so that the signals they carry are also routed to the left and right, and so that the conductors of an electrical interconnect may be soldered or otherwise connected to the first and second electrodes506-1,506-2. The electromagnetic noise shields510-1,510-2 may extend between the re-routed electrodes506-1,506-2, and may widen to extend over portions of the re-routed electrodes506-1,506-2. The symmetry of the sensor interface714 (at least from a plan perspective) can help maintain the differential integrity of the signals carried on the first and second electrodes506-1,506-2. In some cases, the end portions of the electrodes506-1,506-2 and/or electromagnetic noise shields510-1,510-2 may be raised or lowered to a common plane, using vias or other conductive transitions. The common plane may be variously defined by the first or second thermoplastic polymer resin512-1,512-2, a flex circuit, a printed circuit board (PCB), or other non-conductive element.
• FIG. 8A shows, in exploded form, an example more detailed cross-section of the sensor stack described with reference toFIG. 7A. Like components are therefore referred to by like reference numerals inFIGS. 7A and 8A.
• Similar to the sensor stack described with reference toFIG. 7A, thesensor stack800 includes all of the elements described with reference toFIG. 7A. However, thesensor stack800 also includes a capacitivetouch sensor electrode802. The capacitivetouch sensor electrode802 may be disposed in a same layer of thesensor stack800 as the first electromagnetic noise shield510-1, but may be electrically insulated from the first electromagnetic noise shield510-1.
• Thesensor stack800 also includes a thirdelectromagnetic noise shield804, which may be positioned between thepiezoelectric material502 and capacitive touch sensor electrode802 (or more specifically, between thepiezoelectric material502 and the first PSA702-1). The thirdelectromagnetic noise shield804 may be electrically insulated from thepiezoelectric material502 and the capacitivetouch sensor electrode802. The first and third electromagnetic noise shields510-1,804 provide at least some noise mitigation between thepiezoelectric material502 and the capacitivetouch sensor electrode802, and at least some noise mitigation between the electrode506-1 and the capacitivetouch sensor electrode802.
• In some embodiments, a self-capacitance of theelectrode802 may be sensed to determine whether a user's finger, torso, or other body part is proximate to the exterior surface of the third thermoplastic polymer resin514-1. In some embodiments, a determination that a user is proximate to the capacitivetouch sensor electrode802 can be used to enable thedifferential amplifier520 and downstream circuitry described with reference toFIG. 5.
• FIGS. 8B-8D show various examples of the sensor interface described with reference toFIG. 5, in the context of the sensor stack described with reference toFIG. 8A. In contrast to the sensor interface described with reference toFIG. 7C, the sensor interfaces described with reference toFIGS. 8B-8D passively output a touch indication obtained from the capacitivetouch sensor electrode802, in addition to a pair of signals obtained from the piezoelectric material by the first and second electrodes506-1,506-2.
• FIG. 8B shows a non-stacked,plan view810 of the electrodes506-1,506-2 and first electromagnetic noise shield510-1. Although the electrodes506-1,506-2 and first electromagnetic noise shield510-1 are shown adjacent to one another in theplan view810, the electrodes506-1,506-2 and electromagnetic noise shields510-1,510-2 may be stacked as shown inFIG. 8A and theplan view812. In theplan view812, the second electromagnetic noise shield510-2 is not illustrated because it is stacked directly under the first electromagnetic noise shield510-1.
• In thesensor interface814, each of the first and second electrodes506-1,506-2 are re-routed (to the left or to the right), so that the signals they carry are also routed to the left and right, and so that the conductors of an electrical interconnect may be soldered or otherwise connected to the first and second electrodes506-1,506-2. The electromagnetic noise shields510-1,510-2 may extend between the re-routed electrodes506-1,506-2.
• The capacitivetouch sensor electrode802 and itselectromagnetic noise shield804 may also extend into thesensor interface814, with theelectromagnetic noise shield804 positioned between the second electrode506-2 and the capacitive touch sensor electrode802 (at least in the plan view812). In this manner, each of the electrodes506-1,506-2,802 is separated from adjacent electrodes by an electromagnetic noise shield510-1,510-2, or804.
• In some embodiments, the stacked portions of the first and second electrodes506-1,506-2 and first and second electromagnetic noise shields510-1,510-2 may be shifted off-center from the end portions of these elements, so that the majority of the first and second electrodes506-1,506-2 and first and second electromagnetic noise shields510-1,510-2 are farther away from the capacitivetouch sensor electrode802 and itselectromagnetic noise shield804. This can reduce interference between the sound (vibratory and audio) and touch sensors included in thesensor stack800.
• In some cases, the end portions of the electrodes506-1,506-2,802 and/or electromagnetic noise shields510-1,510-2,804 may be raised or lowered to a common plane, using vias or other conductive transitions. The common plane may be variously defined by the first or second thermoplastic polymer resin512-1,512-2, a flex circuit, a PCB, or other non-conductive element.
• FIG. 8C shows a non-stacked,plan view820 of the electrodes506-1,506-2 and first electromagnetic noise shield510-1. Although the electrodes506-1,506-2 and first electromagnetic noise shield510-1 are shown adjacent to one another in theplan view820, the electrodes506-1,506-2 and electromagnetic noise shields510-1,510-2 may be stacked as shown inFIG. 8A and theplan view822. In theplan view822, the second electromagnetic noise shield510-2 is not illustrated because it is stacked directly under the first electromagnetic noise shield510-1.
• In thesensor interface824, each of the first and second electrodes506-1,506-2 are re-routed to one side of the electromagnetic noise shields510-1,510-2, so that the signals they carry are also routed to one side of the electromagnetic noise shields510-1,510-2, and so that the conductors of an electrical interconnect may be soldered or otherwise connected to the first and second electrodes506-1,506-2. The electromagnetic noise shields510-1,510-2 may extend adjacent the re-routed electrodes506-1,506-2.
• The capacitivetouch sensor electrode802 and itselectromagnetic noise shield804 may also extend into thesensor interface824, and may be routed as described with reference toFIG. 8B. In this manner, the electrodes506-1 and506-2 may be bordered by electromagnetic noise shields510-1,510-2, and804, and the capacitivetouch sensor electrode802 may be separated from the other electrodes by theelectromagnetic noise shield804.
• In some cases, the end portions of the electrodes506-1,506-2,802 and/or electromagnetic noise shields510-1,510-2,804 may be raised or lowered to a common plane, using vias or other conductive transitions. The common plane may be variously defined by the first or second thermoplastic polymer resin512-1,512-2, a flex circuit, a PCB, or other non-conductive element.
• FIG. 8D shows a non-stacked,plan view830 of the electrodes506-1,506-2 and first electromagnetic noise shield510-1. Although the electrodes506-1,506-2 and first electromagnetic noise shield510-1 are shown adjacent to one another in theplan view830, the electrodes506-1,506-2 and electromagnetic noise shields510-1,510-2 may be stacked as shown inFIG. 8A and theplan view832. In theplan view832, the second electromagnetic noise shield510-2 is not illustrated because it is stacked directly under the first electromagnetic noise shield510-1.
• In thesensor interface834, the second electrode506-2 is re-routed to one side of the first electrode506-1, and each of the first and second electromagnetic noise shields510-1,510-2 is re-routed to extend adjacent and between end portions of the first electrode506-1 and the re-routed second electrode506-2. The electromagnetic noise shields510-1,510-2 may also be routed to extend over the transverse portion of the second electrode506-2.
• The capacitivetouch sensor electrode802 and itselectromagnetic noise shield804 may also extend into thesensor interface834, and may be routed as described with reference toFIG. 8B. In this manner, each of the electrodes506-1,506-2,802 is separated from adjacent electrodes by an electromagnetic noise shield510-1,510-2, or804.
• In some cases, the end portions of the electrodes506-1,506-2,802 and/or electromagnetic noise shields510-1,510-2,804 may be raised or lowered to a common plane, using vias or other conductive transitions. The common plane may be variously defined by the first or second thermoplastic polymer resin512-1,512-2, a flex circuit, a PCB, or other non-conductive element.
• In the various embodiments described herein, it was indicated that the various thermoplastic polymer resins could be formed as a layer of PET or BoPET. Alternatively, the thermoplastic polymer resins may take other forms, or the thermoplastic polymer resins may be replaced by other materials. Some suitable materials include polyurethane (PU) or thermoplastic polyurethane (TPU) substrates. The PU or TPU substrates may be selected to have relatively less hysteresis and relatively elastic strain when undergoing deformation or strain cycling. In some cases, the substrates may be or include shape memory polymer (SMP) substrates (i.e., PU substrates having properties such as good shape recovery, shape retention, and shock absorption over a wide temperature range of interest). One useful SMP is poly(urethane-oxazolidone) (PUO, also known as oxazolidone-modified PU), which has a relatively linear E_g/E_rratio over a wide temperature range, where E_gis a glassy state modulus of the PUO, and E_ris a rubber modulus of the PUO. The E_g/E_rratio and shape recovery of a PUO substrate are generally proportional to the PUO's oxazolidone content.
• The various electrodes described herein may include silver (Ag), and in some cases may be or include silver/silver sulfate or silver/silver chloride electrodes. The electrodes may also or alternatively include copper (copper/copper sulfate, copper nickel), mercury (calomel), aluminum, gold (AgNW), or other materials. The electromagnetic noise shields described herein may be formed using the same materials used to form the electrodes, or different materials. In some examples, an electromagnetic noise shield may include silver (Ag) printed on a thermoplastic polymer resin, PU, TPU, SMP, and/or PUO substrate. In some examples, an electromagnetic noise shield may include aluminum (Al) and/or copper (Cu), and/or another metal, sputtered on a thermoplastic polymer resin, PU, TPU, SMP, and/or PUO substrate. An electromagnetic noise shield may also be provided by a conductive fabric.
• In some embodiments, all of the thermoplastic polymer resins, electrodes, and electromagnetic noise shields may be selected to have characteristics such as great flexibility, and resilience to fatigue, during repeated use of a device.
• FIG. 9 illustrates amethod900 of monitoring biological vibrations of a user. Themethod900 may be performed using a vibration sensor, vibration sensor module, or sensor stack described with reference toFIG. 1, 2, 5, 7A, or8A, and the processing module or other device described with reference toFIG. 1 or 5.
• Atblock902, themethod900 may include receiving a pair of signals from a pair of electrodes connected to opposite sides of a piezoelectric element, as further described herein.
• Atblock904, themethod900 may include differentially amplifying the pair of signals to generate a differential output, as further described herein. In some cases, the differential amplification may be performed using a differential charge amplifier or a TIA.
• Atblock906, themethod900 may include identifying a type of biological vibration included in the differential output, as further described herein. The biological vibration may be any of the biological vibrations described with reference toFIGS. 3 and 4, or some other biological vibration.
• Atblock908, themethod900 may include outputting an indicator of the type of biological vibration. In some cases, the indicator may be a text alert presented on a display screen, or a haptic or audible notification that a user needs to review further details of the biological vibration or discuss the biological vibration with their doctor.
• In some cases, the vibration sensors described herein may be used to opportunistically monitor a user's heart rhythm, by sensing basic heart vibrations (S1 and S2 heart sounds) and/or BCG/SCG vibrations. An irregular rhythm may be detected by pattern matching S1/S2 and/or BCG/SCG heart vibrations to known (possibly learned) arrhythmia vibration patterns.
• In some cases, the vibration sensors described herein may be used to classify a user's heart rhythm (e.g., as regular (a sinus rhythm (SR)), irregular (e.g., atrial fibrillation detected, etc.), or inconclusive).
• In some cases, the vibration sensors described herein may be used to generate a report of a user's heart rate variability (HRV).
• In some cases, the vibration sensors described herein may be used to monitor symptoms associated with asthma (e.g., coughs, wheezes, or nighttime awakenings) and generate, for example, a nightly index, trends by week, month, or other time period, and so on. In some cases, incidences of a particular biological vibration or event may be counted. For example, a number of cough sounds, wheeze sounds, or snoring episodes may be counted by a processor or other circuit as a user sleeps.
• The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art, after reading this description, that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art, after reading this description, that many modifications and variations are possible in view of the above teachings.
• As described above, one aspect of the present technology is the gathering and use of data available from various sources, including data that may be indicative of a user's biological vibrations or sounds, and/or data that may identify the person from which such biological vibrations or sounds were obtained. The present disclosure contemplates that, in some instances, this gathered data may include personal information data that uniquely identifies a user or can be used to identify, diagnose, classify, locate, or contact a specific person. Such personal information data can include demographic data, location-based data, telephone numbers, email addresses, home addresses, data or records relating to a user's health or level of fitness (e.g., vital sign measurements, medication information, exercise information), date of birth, or any other identifying or personal information.
• The present disclosure recognizes that the use of such personal information data, in the present technology, can be used to the benefit of users. For example, the personal information data can be used to activate or deactivate various functions of a user's device, or gather health, medical, or fitness information that may be used to diagnose or assist the user. Further, other uses for personal information data that benefit the user are contemplated by the present disclosure. For instance, health, medical, and fitness data may be used to provide insights into a user's general wellness, or may be used as positive feedback to individuals using technology to pursue wellness goals.
• The present disclosure contemplates that the entities responsible for the collection, analysis, disclosure, transfer, storage, or other use of such personal information data will comply with well-established privacy policies and/or privacy practices. In particular, such entities should implement and consistently use privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining personal information data private and secure. Such policies should be easily accessible by users, and should be updated as the collection and/or use of data changes. Personal information from users should be collected for legitimate and reasonable uses of the entity and not shared or sold outside of those legitimate uses. Further, such collection/sharing should occur after receiving the informed consent of the users. Additionally, such entities should consider taking any needed steps for safeguarding and securing access to such personal information data and ensuring that others with access to the personal information data adhere to their privacy policies and procedures. Further, such entities can subject themselves to evaluation by third parties to certify their adherence to widely accepted privacy policies and practices. In addition, policies and practices should be adapted for the particular types of personal information data being collected and/or accessed and adapted to applicable laws and standards, including jurisdiction-specific considerations. For instance, in the US, collection of or access to certain health data may be governed by federal and/or state laws, such as the Health Insurance Portability and Accountability Act (HIPAA); whereas health data in other countries may be subject to other regulations and policies and should be handled accordingly. Hence different privacy practices should be maintained for different personal data types in each country.
• Despite the foregoing, the present disclosure also contemplates embodiments in which users selectively block the use of, or access to, personal information data. That is, the present disclosure contemplates that hardware and/or software elements can be provided to prevent or block access to such personal information data. For example, in the case of advertisement delivery services, the present technology can be configured to allow users to select to “opt in” or “opt out” of participation in the collection of personal information data during registration for services or anytime thereafter. In another example, users can select not to provide health, medical, or fitness data to targeted content delivery services. In yet another example, users can select to limit the length of time personal information data is maintained or entirely prohibit the development of a diagnosis based on such personal information data. In addition to providing “opt in” and “opt out” options, the present disclosure contemplates providing notifications relating to the access or use of personal information. For instance, a user may be notified upon downloading an app that their personal information data will be accessed and then reminded again just before personal information data is accessed by the app.
• Moreover, it is the intent of the present disclosure that personal information data should be managed and handled in a way to minimize risks of unintentional or unauthorized access or use. Risk can be minimized by limiting the collection of data and deleting data once it is no longer needed. In addition, and when applicable, including in certain health related applications, data de-identification can be used to protect a user's privacy. De-identification may be facilitated, when appropriate, by removing specific identifiers (e.g., date of birth, etc.), controlling the amount or specificity of data stored (e.g., collecting location data at a city level rather than at an address level), controlling how data is stored (e.g., aggregating data across users), and/or other methods.
• Therefore, although the present disclosure broadly covers use of personal information data to implement one or more various disclosed embodiments, the present disclosure also contemplates that the various embodiments can also be implemented without the need for accessing such personal information data. That is, the various embodiments of the present technology are not rendered inoperable due to the lack of all or a portion of such personal information data. For example, content can be selected and delivered to users by inferring preferences based on non-personal information data or a bare minimum amount of personal information, such as the content being requested by the device associated with a user, other non-personal information available to the content delivery services, or publicly available information.

Claims (20)

What is claimed is:

1. A sensor system, comprising:

a sensor stack, including,

a piezoelectric material having a first side opposing a second side;

a first electrode connected to the first side; and

a second electrode connected to the second side;

a differential amplifier coupled to the first and second electrodes and configured to generate a differential output indicative of vibrations sensed by the piezoelectric material;

an analog-to-digital converter configured to digitize the differential output; and

a processor configured to identify a type of biological vibration included in the digitized differential output.

2. The sensor system ofclaim 1, wherein:

the sensor stack further includes,

a first electromagnetic noise shield disposed on the first side of the piezoelectric material and electrically insulated from the piezoelectric material and the first electrode, with the first electrode disposed between the piezoelectric material and the first electromagnetic noise shield; and

a second electromagnetic noise shield disposed on the second side of the piezoelectric material and electrically insulated from the piezoelectric material and the second electrode, with the second electrode disposed between the piezoelectric material and the second electromagnetic noise shield.

3. The sensor system ofclaim 2, wherein:

the sensor stack further includes,

a capacitive touch sensor electrode, disposed in a same layer of the sensor stack as the first electromagnetic noise shield, and electrically insulated from the first electromagnetic noise shield; and

a third electromagnetic noise shield positioned between the piezoelectric material and the capacitive touch sensor electrode, and electrically insulated from the piezoelectric material and the capacitive touch sensor electrode.

4. The sensor system ofclaim 3, further comprising:

a sensor interface disposed between the sensor stack and the differential amplifier and configured to passively output a pair of signals obtained from the piezoelectric material by the first and second electrodes, and a touch indication obtained from the capacitive touch sensor electrode.

5. The sensor system ofclaim 2, wherein:

the sensor stack further includes,

a first pressure-sensitive adhesive (PSA) disposed on the first electrode;

a first thermoplastic polymer resin disposed on the first PSA;

a second PSA disposed on the second electrode; and

a second thermoplastic polymer resin disposed on the second PSA;

the first electromagnetic noise shield is disposed on the first thermoplastic polymer resin; and

the second electromagnetic noise shield is disposed on the second thermoplastic polymer resin.

6. The sensor system ofclaim 5, wherein:

the sensor stack further includes,

a first non-conductive sensor stack cover disposed on the first electromagnetic noise shield; and

a second non-conductive sensor stack cover disposed on the second electromagnetic noise shield.

7. The sensor system ofclaim 1, further comprising a sensor interface, disposed between the sensor stack and the differential amplifier, that re-routes at least one of: the first electrode or the second electrode.

8. The sensor system ofclaim 1, further comprising a sensor interface, disposed between the sensor stack and the differential amplifier, that re-routes at least one signal received from at least one of the first electrode or the second electrode.

9. The sensor system ofclaim 1, wherein the piezoelectric material comprises a polyvinylidene difluoride (PVDF) material.

10. The sensor system ofclaim 1, wherein the first and second electrodes are configured to generate a pair of signals having a frequency bandwidth including an alternating current (AC) line frequency.

11. A sensor system, comprising:

a sensor, including:

a piezoelectric element; and

first and second electrodes, respectively connected to first and second opposing surfaces of the piezoelectric element;

an electrical interconnect, including:

first and second conductors, respectively connected to the first and second electrodes; and

a differential amplifier connected to the first and second conductors and providing a differential output indicative of vibrations sensed by the piezoelectric element.

12. The sensor system ofclaim 11, wherein the differential amplifier is a differential charge amplifier.

13. The sensor system ofclaim 11, wherein the differential amplifier is a transimpedance amplifier.

14. The sensor system ofclaim 11, wherein the differential output has a frequency bandwidth including an alternating current (AC) line frequency.

15. The sensor system ofclaim 11, further comprising:

an analog-to-digital converter configured to digitize the differential output; and

a communications interface configured to transmit the digitized differential output to a remote device.

16. The sensor system ofclaim 11, further comprising:

an analog-to-digital converter configured to digitize the differential output; and

a processor configured to:

pattern match a vibration pattern in the digitized differential output to one of: a crackle sound, or a wheeze sound, or a cough sound, or a snore sound, or a respiration sound.

17. The sensor system ofclaim 11, further comprising:

an analog-to-digital converter configured to digitize the differential output; and

a processor configured to:

pattern match a vibration pattern in the digitized differential output to one of: a type of heart murmur, or a S1, S2, S3, or S4 heart sound.

18. A method of monitoring biological vibrations of a user, comprising:

receiving a pair of signals from a pair of electrodes connected to opposite sides of a piezoelectric element;

differentially amplifying the pair of signals to generate a differential output;

identifying a type of biological vibration included in the differential output; and

outputting an indicator of the type of biological vibration.

19. The method ofclaim 18, wherein the type of biological vibration is a crackle sound or a wheeze sound.

20. The method ofclaim 18, wherein the differential amplification is performed using a transimpedance amplifier.

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