US20200159322A1 - Systems, articles, and methods for capacitive electromyography sensors - Google Patents

Abstract

Systems, articles, and methods for improved capacitive electromyography (“EMG”) sensors are described. The improved capacitive EMG sensors include one or more sensor electrode(s) that is/are coated with a protective barrier formed of a material that has a relative permittivity εr of about 10 or more. The protective barrier shields the sensor electrode(s) from moisture, sweat, skin oils, etc. while advantageously contributing to a large capacitance between the sensor electrode(s) and the user's body. In this way, the improved capacitive EMG sensors provide enhanced robustness against variations in skin and/or environmental conditions. Such improved capacitive EMG sensors are particularly well-suited for use in wearable EMG devices that may be worn by a user for an extended period of time and/or under a variety of skin and/or environmental conditions. A wearable EMG device that provides a component of a human-electronics interface and incorporates such improved capacitive EMG sensors is described.

Description

BACKGROUNDTechnical Field
• The present systems, articles, and methods generally relate to electromyography and particularly relate to capacitive electromyography sensors.
Description of the Related ArtWearable Electronic Devices
• Electronic devices are commonplace throughout most of the world today. Advancements in integrated circuit technology have enabled the development of electronic devices that are sufficiently small and lightweight to be carried by the user. Such “portable” electronic devices may include on-board power supplies (such as batteries or other power storage systems) and may be designed to operate without any wire-connections to other electronic systems; however, a small and lightweight electronic device may still be considered portable even if it includes a wire-connection to another electronic system. For example, a microphone may be considered a portable electronic device whether it is operated wirelessly or through a wire-connection.
• The convenience afforded by the portability of electronic devices has fostered a huge industry. Smartphones, audio players, laptop computers, tablet computers, and ebook readers are all examples of portable electronic devices. However, the convenience of being able to carry a portable electronic device has also introduced the inconvenience of having one's hand(s) encumbered by the device itself. This problem is addressed by making an electronic device not only portable, but wearable.
• A wearable electronic device is any portable electronic device that a user can carry without physically grasping, clutching, or otherwise holding onto the device with their hands. For example, a wearable electronic device may be attached or coupled to the user by a strap or straps, a band or bands, a clip or clips, an adhesive, a pin and clasp, an article of clothing, tension or elastic support, an interference fit, an ergonomic form, etc. Examples of wearable electronic devices include digital wristwatches, electronic armbands, electronic rings, electronic ankle-bracelets or “anklets,” head-mounted electronic display units, hearing aids, and so on.
Human-Electronics Interfaces
• A wearable electronic device may provide direct functionality for a user (such as audio playback, data display, computing functions, etc.) or it may provide electronics to interact with, receive information from, or control another electronic device. For example, a wearable electronic device may include sensors that are responsive to (i.e., detect and provide one or more signal(s) in response to detecting) inputs effected by a user and transmit signals to another electronic device based on those inputs. Sensor-types and input-types may each take on a variety of forms, including but not limited to: tactile sensors (e.g., buttons, switches, touchpads, or keys) providing manual control, acoustic sensors providing voice-control, electromyography sensors providing gesture control, and/or accelerometers providing gesture control.
• A human-computer interface (“HCI”) is an example of a human-electronics interface. The present systems, articles, and methods may be applied to HCIs, but may also be applied to any other form of human-electronics interface.
Electromyography Sensors
• Electromyography (“EMG”) is a process for detecting and processing the electrical signals generated by muscle activity. EMG devices employ EMG sensors that are responsive to the range of electrical potentials (typically μV-mV) involved in muscle activity. EMG signals may be used in a wide variety of applications, including: medical monitoring and diagnosis, muscle rehabilitation, exercise and training, prosthetic control, and even in controlling functions of electronic devices.
• There are two main types of EMG sensors: intramuscular EMG sensors and surface EMG sensors. As the names suggest, intramuscular EMG sensors are designed to penetrate the skin and measure EMG signals from within the muscle tissue, while surface EMG sensors are designed to rest on an exposed surface of the skin and measure EMG signals from there. Intramuscular EMG sensor measurements can be much more precise than surface EMG sensor measurements; however, intramuscular EMG sensors must be applied by a trained professional, are obviously more invasive, and are less desirable from the patient's point of view. The use of intramuscular EMG sensors is generally limited to clinical settings.
• Surface EMG sensors can be applied with ease, are much more comfortable for the patient/user, and are therefore more appropriate for non-clinical settings and uses. For example, human-electronics interfaces that employ EMG, such as those proposed in U.S. Pat. Nos. 6,244,873 and 8,170,656, usually employ surface EMG sensors. Surface EMG sensors come in two forms: resistive EMG sensors and capacitive EMG sensors. For both forms of surface EMG sensors, the sensor electrode typically includes a plate of electrically conductive material that is placed against or in very close proximity to the exposed surface of the user's skin. A resistive EMG sensor electrode is typically directly electrically coupled to the user's skin while a capacitive EMG sensor electrode is typically capacitively coupled to the user's skin. In either case, skin and/or environmental conditions, such as hair density, humidity and moisture levels, and so on, can have a significant impact on the performance of the sensor. These parameters are generally controlled for resistive EMG sensors by preparing the user's skin before applying the sensor electrodes. For example, the region of the user's skin where a resistive electrode is to be placed is usually shaved, exfoliated, and slathered with a conductive gel to establish a suitable and stable environment before the resistive electrode is applied. This obviously limits the appeal of resistive EMG sensors to users, in particular for home and/or recreational use. Capacitive EMG sensors are advantageous because they are generally more robust against some skin and environmental conditions, such as hair density, and are typically applied without the elaborate skin preparation measures (e.g., shaving, exfoliating, and applying a conductive gel) that are employed for resistive sensors. However, capacitive EMG sensors are still very sensitive to moisture and performance can degrade considerably when, for example, a user sweats. There is a need in the art for capacitive EMG sensors with improved robustness against variations in skin and/or environmental conditions.
BRIEF SUMMARY
• A capacitive electromyography (“EMG”) sensor may be summarized as including a substrate; a first sensor electrode carried by the substrate, wherein the first sensor electrode comprises an electrically conductive plate having a first surface that faces the substrate and a second surface that is opposite the first surface; circuitry communicatively coupled to the first sensor electrode; and a dielectric layer formed of a dielectric material that has a relative permittivity of at least about 10, wherein the dielectric layer coats the second surface of the first sensor electrode. The first sensor electrode may be formed of a material including copper. The circuitry may include at least one circuit selected from the group consisting of: an amplification circuit, a filtering circuit, and an analog-to-digital conversion circuit. At least a portion of the circuitry may be carried by the substrate. The substrate may include a first surface and a second surface, the second surface opposite the first surface across a thickness of the substrate, and the at least a portion of the circuitry may be carried by the first surface of the substrate and the first sensor electrode may be carried by the second surface of the substrate. The dielectric layer may include a ceramic material. The dielectric layer may include an X7R ceramic material. The substrate, the first sensor electrode, and the dielectric layer may constitute a laminate structure. The capacitive EMG sensor may further include an electrically conductive epoxy sandwiched in between the dielectric layer and the first sensor electrode, wherein the dielectric layer is adhered to the first sensor electrode by the electrically conductive epoxy. Alternatively, the capacitive EMG sensor may further include an electrically conductive solder sandwiched in between the dielectric layer and the first sensor electrode, wherein the dielectric layer is adhered to the first sensor electrode by the electrically conductive solder. The dielectric layer may have a thickness of less than about 10 micrometers. The capacitive EMG sensor may be a differential capacitive EMG sensor that further includes a second sensor electrode carried by the substrate, the second sensor electrode comprising an electrically conductive plate having a first surface that faces the substrate and a second surface that is opposite the first surface across a thickness of the second sensor electrode, wherein the second sensor electrode is communicatively coupled to the circuitry, and wherein the dielectric layer coats the second surface of the second sensor electrode. The dielectric layer may comprise a single continuous layer of dielectric material that coats both the second surface of the first sensor electrode and the second surface of the second sensor electrode. The dielectric layer may comprise a first section that coats the second surface of the first sensor electrode and at least a second section that coats the second surface of the second sensor electrode, wherein the first section of the dielectric layer is physically separate from the second section of the dielectric layer. The first sensor electrode and the second sensor electrode may be substantially coplanar. The capacitive EMG sensor may further include a ground electrode carried by the substrate, the ground electrode comprising an electrically conductive plate having a first surface that faces the substrate and a second surface that is opposite the first surface across a thickness of the ground electrode, wherein the ground electrode is communicatively coupled to the circuitry, and wherein the second surface of the ground electrode is exposed and not coated by the dielectric layer. The capacitive EMG sensor may further include at least one additional layer that is sandwiched in between the first sensor electrode and the substrate.
• A method of fabricating a capacitive EMG sensor may be summarized as including forming at least a portion of at least one circuit on a first surface of a substrate; forming a first sensor electrode on a second surface of the substrate, the second surface of the substrate opposite the first surface of the substrate across a thickness of the substrate, wherein the first sensor electrode comprises an electrically conductive plate; forming at least one electrically conductive pathway that communicatively couples the first sensor electrode and the at least a portion of at least one circuit; and coating the first sensor electrode with a dielectric layer comprising a dielectric material that has a relative permittivity of at least about 10. Coating the first sensor electrode with a dielectric layer may include coating at least a portion of the second surface of the substrate with the dielectric layer. Coating the first sensor electrode with a dielectric layer may include coating the first sensor electrode with a ceramic material. Coating the first sensor electrode with a dielectric layer may include coating the first sensor electrode with an X7R ceramic material. The capacitive EMG sensor may be a differential capacitive EMG sensor and the method may further include forming a second sensor electrode on the second surface of the substrate, wherein the second sensor electrode comprises an electrically conductive plate; forming at least one electrically conductive pathway that communicatively couples the second sensor electrode and the at least a portion of at least one circuit; and coating the second sensor electrode with the dielectric layer. The method may further include forming a ground electrode on the second surface of the substrate, wherein the ground electrode comprises an electrically conductive plate; and forming at least one electrically conductive pathway that communicatively couples the ground electrode and the at least a portion of at least one circuit. Coating the first sensor electrode with a dielectric layer may include selectively coating the first sensor electrode with the dielectric layer and not coating the ground electrode with the dielectric layer. Coating the first sensor electrode with a dielectric layer may include coating both the first sensor electrode and the ground electrode with the dielectric layer, and the method may further include forming a hole in the dielectric layer to expose the ground electrode. Coating the first sensor electrode with a dielectric layer may include depositing a layer of electrically conductive epoxy on the first sensor electrode; and depositing the dielectric layer on the layer of electrically conductive epoxy. Coating the first sensor electrode with a dielectric layer may include depositing a layer of electrically conductive solder on the first sensor electrode; and depositing the dielectric layer on the layer of electrically conductive solder.
• A wearable EMG device may be summarized as including at least one capacitive EMG sensor responsive to (i.e., to detect and provide one or more signal(s) in response to detecting) muscle activity corresponding to a gesture performed by a user of the wearable EMG device, wherein in response to muscle activity corresponding to a gesture performed by a user of the wearable EMG device, the at least one capacitive EMG sensor provides at least one signal, and wherein the at least one capacitive EMG sensor includes: a first sensor electrode comprising an electrically conductive plate; and a dielectric layer formed of a dielectric material that has a relative permittivity of at least about 10, wherein the dielectric layer coats the first sensor electrode; a processor communicatively coupled to the at least one capacitive EMG sensor to in use process signals provided by the at least one capacitive EMG sensor; and an output terminal communicatively coupled to the processor to transmit signals output by the processor. The dielectric layer may include a ceramic material. The ceramic material may include an X7R ceramic material. The wearable EMG device may further include circuitry that mediates communicative coupling between the at least one capacitive EMG sensor and the processor, wherein the circuitry includes at least one circuit selected from the group consisting of: an amplification circuit, a filtering circuit, and an analog-to-digital conversion circuit. The dielectric layer of the at least one capacitive EMG sensor may have a thickness of less than about 10 micrometers. The at least one capacitive EMG sensor may include at least one differential capacitive EMG sensor, and the at least one differential capacitive EMG sensor may further include a second sensor electrode comprising an electrically conductive plate, wherein the dielectric layer coats the second sensor electrode. The at least one capacitive EMG sensor may further include a ground electrode comprising an electrically conductive plate, wherein the ground electrode is exposed and not coated by the dielectric layer.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
• In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.
• FIG. 1 is a cross-sectional view of an improved capacitive EMG sensor that provides enhanced robustness against variations in skin and/or environmental conditions in accordance with the present systems, articles, and methods.
• FIG. 2 is a cross-sectional view of a laminate version of an improved capacitive EMG sensor that provides enhanced robustness against variations in skin and/or environmental conditions in accordance with the present systems, articles, and methods.
• FIG. 3 is a flow-diagram showing a method of fabricating an improved capacitive EMG sensor in accordance with the present systems, articles, and methods.
• FIG. 4 is a perspective view of an exemplary wearable EMG device that includes improved capacitive EMG sensors in accordance with the present systems, articles, and methods.
DETAILED DESCRIPTION
• In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with electric circuits, and in particular printed circuit boards, have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments.
• Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.”
• Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
• As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its broadest sense, that is as meaning “and/or” unless the content clearly dictates otherwise.
• The headings and Abstract of the Disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
• The various embodiments described herein provide systems, articles, and methods for capacitive EMG sensors with improved robustness against variations in skin and/or environmental conditions. In particular, the present systems, articles, and methods describe capacitive EMG sensor designs that employ at least one capacitive electrode having a protective coating that provides a barrier to moisture and a high relative permittivity ε_r. These capacitive EMG sensor designs may be used in any device or method involving capacitive EMG sensing, though they are particularly well-suited for use in applications involving long-term coupling to a user's body over a range of evolving skin and/or environmental conditions. An example application in a wearable EMG device that forms part of a human-electronics interface is described.
• Throughout this specification and the appended claims, the terms “coating” and “coat,” and variants thereof, are used both as nouns and as verbs to indicate a relationship (noun) or the formation of a relationship (verb) in which a layer of material overlies, underlies, or generally “covers” at least a portion of a device or component, either directly or through one or more intervening layers.
• FIG. 1 is a cross-sectional view of an example of an improvedcapacitive EMG sensor100 that provides enhanced robustness against variations in skin and/or environmental conditions in accordance with the present systems, articles, and methods.Exemplary sensor100 is a differential capacitive EMG sensor that includes twocapacitive sensor electrodes121 and131, though the teachings described herein are also applicable to single-ended sensor systems that employ only a single capacitive sensor electrode (i.e., one ofsensor electrodes121 or131).Differential sensor100 comprises asubstrate101 having afirst surface101aand asecond surface101bopposite thefirst surface101aacross a thickness ofsubstrate101.First surface101acarries at least a portion of at least one circuit (generally, circuitry110) andsecond surface101bcarriesfirst sensor electrode121,second sensor electrode131, and aground electrode140. As will be described in more detail later,circuitry110 may include at least a portion of at least one electrical or electronic circuit to process signals provided by first andsecond sensor electrodes121,131, including, for example, at least a portion of at least one amplification circuit, at least a portion of at least one filtering circuit, and/or at least a portion of at least one analog-to-digital conversion circuit.First sensor electrode121 includes an electrically conductive plate formed of an electrically conductive material (such as, for example, copper or a material including copper) and has afirst surface121aand asecond surface121b,second surface121bbeing oppositefirst surface121aacross a thickness ofelectrode121.First sensor electrode121 is carried bysecond surface101bofsubstrate101 such thatfirst surface121aoffirst sensor electrode121 facessecond surface101bofsubstrate101. Throughout this specification and the appended claims, the terms “carries” and “carried by” are generally used to describe a spatial relationship in which a first layer/component is positioned proximate and physically coupled to a surface of a second layer/component, either directly or through one or more intervening layers/components. For example,circuitry110 is carried byfirst surface101aofsubstrate101 andfirst sensor electrode121 is carried bysecond surface101bofsubstrate101.Circuitry110 is directly carried byfirst surface101aofsubstrate101 because there are no intervening layers/components that mediate the physical coupling betweencircuitry110 andfirst surface101aofsubstrate101; however,circuitry110 would still be considered “carried by”first surface101aofsubstrate101 even if the physical coupling betweencircuitry110 andfirst surface101aofsubstrate101 was mediated by at least one intervening layer/component. The terms “carries” and “carried by” are not intended to denote a particular orientation with respect to top and bottom and/or left and right.
• First sensor electrode121 is communicatively coupled tocircuitry110 by at least one electricallyconductive pathway151, which in the illustrated example ofFIG. 1 is realized by a via connection that extends throughsubstrate101.
• In accordance with the present systems, articles, and methods,first sensor electrode121 is coated by adielectric layer123 formed of a material that has a relative permittivity ε_rof at least 10, and by anadhesive layer122 that is sandwiched in betweenfirst sensor electrode121 anddielectric layer123.Adhesive layer122 serves to adhere, affix, or otherwise coupledielectric layer123 to thesecond surface121boffirst sensor electrode121, and may comprise, for example, an electrically conductive epoxy or an electrically conductive solder. In other words,adhesive layer122 mediates physical and electrical coupling betweendielectric layer123 andfirst sensor electrode121. Referring back to the definition of the terms “carries” and “carried by,” bothadhesive layer122 anddielectric layer123 are considered to be carried bysecond surface101bofsubstrate101.
• Dielectric layer123 may comprise any dielectric material that has a large relative permittivity ε_r(e.g., a relative permittivity of about 10 or more, including a relative permittivity of about 10, about 20, about 50, about 100, about 1000, etc.). Advantageously,dielectric layer123 may comprise a ceramic material, such as an X7R ceramic material. Throughout this specification and the appended claims, the term “X7R” refers to the EIA RS-198 standard three-digit code for temperature ranges and inherent change of capacitance. Specifically, the code “X7R” indicates a material that will operate in the temperature range of −55° C. to +125° C. with a change of capacitance of ±15%. A person of skill in the art will appreciate that the X7R EIA code is substantially equivalent to “2×1” under the IEC/EN 60384-9/22 standard.Dielectric layer123 may comprise a resin and/or ceramic powder such as those used in FaradFlex® products available from Oak-Mitsui Technologies.
• Sincecapacitive EMG sensor100 is differential, it includes asecond sensor electrode131.Second sensor electrode131 may be substantially similar tofirst sensor electrode121 in thatsecond sensor electrode131 includes an electrically conductive plate formed of an electrically conductive material (e.g., a material including copper) that has afirst surface131aand asecond surface131b,second surface131bbeing oppositefirst surface131aacross a thickness ofelectrode131.Second sensor electrode131 is carried bysecond surface101bofsubstrate101 such thatfirst surface131aofsecond sensor electrode131 facessecond surface101bofsubstrate101.Second sensor electrode131 is also coated by adielectric layer133 that is substantially similar todielectric layer123, anddielectric layer133 is adhered, affixed, or otherwise coupled tosecond surface131bofsecond sensor electrode131 by anadhesive layer132 that is substantially similar toadhesive layer122.Second sensor electrode131 is communicatively coupled tocircuitry110 by at least one electricallyconductive pathway152, which in the illustrated example ofFIG. 1 is realized by a via connection that extends throughsubstrate101. As is the case for the illustrated example ofFIG. 1,first sensor electrode121 andsecond sensor electrode131 may be substantially coplanar.
• Capacitive EMG sensor100 also includes aground electrode140.Ground electrode140 includes an electrically conductive plate formed of an electrically conductive material (e.g., the same material that makes upfirst sensor electrode121 and second sensor electrode131) that has a first surface141aand a second surface141b, second surface141bbeing opposite first surface141aacross a thickness ofelectrode140.Ground electrode140 is carried bysecond surface101bofsubstrate101 such thatfirst surface140aofground electrode140 facessecond surface101bofsubstrate101.Ground electrode140 is communicatively coupled tocircuitry110 by at least one electricallyconductive pathway153, which in the illustrated example ofFIG. 1 is realized by a via connection that extends throughsubstrate101. Unlikesecond surface121boffirst sensor electrode121 andsecond surface131bofsecond sensor electrode131,second surface140bofground electrode140 is exposed and not coated by a dielectric layer in order thatground electrode140 may advantageously provide a directly electrically coupled (i.e., resistively coupled) path to ground.
• In use,capacitive EMG sensor100 is positioned proximate a user's muscle(s) so thatdielectric layers123,133 andground electrode140 are all in physical contact with the user's skin (or, in some cases, a layer of material such as clothing may mediate physical contact betweensensor100 and the user's skin).Dielectric layers123,133 are advantageously formed of a dielectric material that has a high relative permittivity (e.g., ε_rgreater than or equal to about 10) in order to enhance the capacitive coupling betweensensor electrodes121,131 and the user's body. For each offirst sensor electrode121 andsecond sensor electrode131, the respective capacitance that couples the sensor electrode (121,131) to the user's body (e.g., skin) is at least approximately given by equation 1:
• $\begin{array}{cc}C=\frac{{\varepsilon }_r{\varepsilon }_0A}{d}& \left(1\right)\end{array}$
• where ε_ris the relative permittivity of the dielectric material that coats the sensor electrode (i.e.,dielectric layers123,133), ε₀is the vacuum permittivity (i.e., a constant value of 8.8541878176×10⁻¹²F/m), A is the area of the sensor electrode, and d is the distance between the sensor electrode and the user's body. Thus, if A and d are held constant, ε_r(i.e., the relative permittivity ofdielectric layers123,133) directly influences the capacitance between the user's body and each offirst sensor electrode121 andsecond sensor electrode131. A large ε_rmay enable a capacitive EMG sensor to employ smaller sensor electrode area(s) A and/or greater separation d between the sensor electrode(s) and the user's body.
• Dielectric layers123,133 are advantageously bio-compatible (e.g., non-toxic, etc.) and substantially robust against the corrosive effects of sweat and skin oils.Dielectric layers123,133 are also advantageously non-absorptive and impermeable to water, sweat, and skin oils. Ideally,dielectric layers123,133 provide hermetic barriers between the user's skin and first andsecond sensor electrodes121,131 such that the presence of sweat, water, and/or skin oils does not substantially degrade the performance ofcapacitive EMG sensor100.
• Even thoughdielectric layers123,133 may protectfirst sensor electrode121 and second sensor electrode131 (respectively) from moisture and/or other aspects of the user's skin, such moisture and/or other aspects that may underliedielectric layers123,133 (e.g., sweat or skin oils that may mediate coupling between the user's body anddielectric layers123,133) may still affect the capacitive coupling between the user's body and first andsecond sensor electrodes121,131. This is a further reason why it is advantageous fordielectric layers123,133 to be formed of a dielectric material that has a high relative permittivity (i.e., ε_r≥10): the larger the relative permittivity ofdielectric layers123,133, the larger the capacitance that couples the user's body to first andsecond sensor electrodes121,131 and the smaller the proportionate impact of variations in sweat or skin oil conditions.
• Equation 1 shows that the capacitance C that couples the user's body to first andsecond sensor electrodes121,131 is directly proportional to the relative permittivity ε_rand inversely proportional to the thickness d ofdielectric layers123,133. Thus, while it is advantageous fordielectric layers123,133 to be formed of a dielectric material that has a high relative permittivity ε_r, it is similarly advantageous fordielectric layers123,133 to be relatively thin (i.e., for d to be small). In accordance with the present systems, articles, and methods, the thickness ofdielectric layers123,133 may be, for example, approximately 10 μm or less. Approximately 10 μm or less is sufficiently thick to provide an adequate barrier to moisture (e.g., sweat/oil) and electrical insulation, and sufficiently thin to provide an adequate capacitance C as per equation 1.
• In accordance with the present systems, articles, and methods,ground electrode140 is exposed and not coated by a dielectric layer. This is because it is advantageous forground electrode140 to be resistively coupled to the user's body as opposed to capacitively coupled thereto in order to provide a lower impedance for return currents.
• Even though first andsecond sensor electrodes121,131 are coated bydielectric layers123,133 (respectively) andground electrode140 is not coated by a dielectric layer,dielectric layers123,133 andground electrode140 may all still simultaneously contact a user's skin whencapacitive EMG sensor100 is positioned on the user. This is because the surface of the user's skin may have a curvature and/or the surface of the user's skin (and/or the flesh thereunder) may be elastic and compressible such thatdielectric layers123,133 can be “pressed” into the user's skin with sufficient depth to enable physical contact betweenground electrode140 and the user's skin. While not drawn to scale, in the illustrated example ofFIG. 1,dielectric layers123,133 are still thinner than the electrically conductive plates that form first andsecond sensor electrodes121,131. For example,dielectric layers123,133 may each have a thickness of less than about 10 μm while first andsecond sensor electrodes121,131 may each have a thickness of about 30 μm or more.
• There are many different ways in whichdielectric layers123,133 may be applied to coat first andsecond sensor electrodes121,131 (respectively) and the specific structural configuration of the corresponding capacitive EMG sensor may vary to reflect this. In exemplarycapacitive EMG sensor100,dielectric layers123,133 have been individually and separately deposited on first andsecond sensor electrodes121,131 (respectively). This may be achieved by, for example, brushing a liquid or fluid form of the dielectric material that constitutesdielectric layers123 and133 oversecond surface121boffirst sensor electrode121 andsecond surface131bofsecond sensor electrode131. In this case,dielectric layers123,133 may subsequently be hardened or cured (andadhesive layers122,132 may potentially not be required). Alternatively, individual and separate sections of a substantially solid or non-fluid form of the dielectric material that constitutesdielectric layers123 and133 may be sized and dimensioned to at least approximately match the respective areas of first andsecond sensor electrodes121,131 and then respective ones of such sections may be deposited on first andsecond sensor electrodes121 and131. For example, a first section of a dielectric material (having a high relative permittivity) may be sized and dimensioned to at least approximately match the area offirst sensor electrode121 and this first section of the dielectric material may be adhered, affixed, or otherwise coupled tofirst sensor electrode121 byadhesive layer122 to formdielectric layer123. Likewise, a second section of the dielectric material may be sized and dimensioned to at least approximately match the area ofsecond sensor electrode131 and adhered, affixed, or otherwise coupled tosecond sensor electrode131 byadhesive layer132 to formdielectric layer133.
• As an alternative to the above examples of depositingdielectric layers121,131 as individual, separate sections of dielectric material, a single continuous piece of dielectric material may be deposited oversecond surface101bofsubstrate101, first andsecond sensor electrodes121,131, andoptionally ground electrode140. In this case,substrate101, first andsecond sensors electrodes121,131, anddielectric layers123,133 may together constitute a laminate structure. In other words,dielectric layers123,133 may be applied to first andsecond sensor electrodes121,131 as lamination layers using a lamination process. In fabrication processes in which dielectric materialcoats ground electrode140, the portion of dielectric material that coats ground electrode may subsequently be removed (e.g., by an etching process) to exposesecond surface140bofground electrode140.
• FIG. 2 is a cross-sectional view of an exemplary laminate version of an improvedcapacitive EMG sensor200 that provides enhanced robustness against variations in skin and/or environmental conditions in accordance with the present systems, articles, and methods.Exemplary sensor200 is a differential capacitive EMG sensor that is substantially similar tosensor100 fromFIG. 1 in thatsensor200 includes a substrate201 (substantially similar tosubstrate101 from sensor100), circuitry210 (substantially similar tocircuitry110 from sensor100), first and secondcapacitive sensor electrodes221 and231 (substantially similar to first andsecond sensor electrodes121 and131, respectively, from sensor100), and ground electrode240 (substantially similar toground electrode140 from sensor100).Sensor200 also includes adielectric layer250 that coats first andsecond sensor electrodes221,231 in a similar way todielectric layers123,133 fromsensor100. Likedielectric layers123 and133,dielectric layer250 is formed of a dielectric material that has a large relative permittivity (i.e., ε_rgreater than or equal to about 10). However, unlikedielectric layers123 and133,dielectric layer250 is deposited as a single continuous layer that coats both first andsecond sensor electrodes221,231 and also coats at least a portion ofsubstrate201. For example,sensor200 may be a laminate structure anddielectric layer250 may be deposited using a lamination process. The deposition ofdielectric layer250 may initiallycoat ground electrode240, in whichcase ground electrode240 may subsequently be exposed by forming (e.g., etching) ahole260 indielectric layer250. Otherwise, a temporary mask may coverground electrode240 during deposition ofdielectric layer250 to preventdielectric layer250 from coatingground electrode240 andhole260 may be left as a result when the mask is subsequently removed.
• Dielectric layer250 may be deposited to provide a desired thickness of, for example, less than about 10 μm measured from the interface with first andsecond sensor electrodes221,231. Though not illustrated inFIG. 2, an adhesive layer may be used to adhere, affix, or otherwise coupledielectric layer250 to any or all ofsubstrate201,first electrode221, and/orsecond sensor electrode231.
• Various methods for fabricating an improved capacitive EMG sensor that includes at least one protective, high-ε_rdielectric barrier have been described. These methods are summarized and generalized inFIG. 3.
• FIG. 3 is a flow-diagram showing amethod300 of fabricating an improved capacitive EMG sensor (e.g.,sensor100 and/or sensor200) in accordance with the present systems, articles, and methods.Method300 includes fouracts301,302,303, and304, though those of skill in the art will appreciate that in alternative embodiments certain acts may be omitted and/or additional acts may be added. Those of skill in the art will also appreciate that the illustrated order of the acts is shown for exemplary purposes only and may change in alternative embodiments.
• At301, at least a portion of at least one circuit is formed on a first surface of a substrate. The at least a portion of at least one circuit may include one or more conductive traces and/or one or more electrical or electronic circuits, such as one or more amplification circuit(s), one or more filtering circuit(s), and/or one or more analog-to-digital conversion circuit(s). As examples,sensor100 fromFIG. 1 includescircuitry110 andsensor200 fromFIG. 2 includescircuitry210. Forming at least a portion of at least one circuit may include one or more lithography process(es) and/or soldering one or more component(s) to the substrate.
• At302, a first sensor electrode is formed on a second surface of the substrate. The first sensor electrode may include an electrically conductive plate formed of, for example, a material including copper. As examples,sensor100 fromFIG. 1 includesfirst sensor electrode121 andsensor200 fromFIG. 2 includesfirst sensor electrode221. Forming the first sensor electrode may include, for example, one or more lithography process(es). As previously described, the order of the acts ofmethod300 may change. For example, in some cases it may be advantageous to form the first sensor electrode peract302 prior to forming the at least a portion of circuitry peract301.
• At303, at least one electrically conductive pathway that communicatively couples the at least a portion of at least one circuit and the first sensor electrode is formed. The at least one electrically conductive pathway may include at least one via through the substrate, at least one conductive trace, and/or at least one wiring component. For example,sensor100 includes electricallyconductive pathway151 that communicatively couplescircuitry110 tofirst sensor electrode121. In some implementations, all or a portion of a via (e.g., a hole or aperture with or without electrically conductive communicative path therethrough) may be formed in the substrate before either or both ofacts301 and/or302.
• At304, the first sensor electrode is coated with a dielectric layer comprising a dielectric material that has a relative permittivity ε_rof at least 10. As previously described, the coating may be applied in a variety of different ways, including without limitation: brushing or otherwise applying a fluid form of the dielectric material on the first sensor electrode and curing the dielectric material; adhering, affixing, or otherwise coupling a substantially non-fluid form of the dielectric material to the first sensor electrode using, for example, an adhesive layer such as an electrically conductive epoxy or an electrically conductive solder; or depositing a single continuous layer of the dielectric material over both the first sensor electrode and at least a portion of the substrate using a lamination process or other dielectric deposition process. When an adhesive layer is used, coating the first sensor electrode with a dielectric layer may include depositing a layer of electrically conductive epoxy on the first sensor electrode and depositing the dielectric layer on the layer of electrically conductive epoxy, or depositing a layer of electrically conductive solder on the first sensor electrode and depositing the dielectric layer on the layer of electrically conductive solder. As examples,sensor100 includesdielectric layer123 that is adhered tofirst sensor electrode121 byadhesive layer122 andsensor200 includesdielectric layer250 that is deposited overfirst sensor electrode221 andsubstrate201 to form a laminate structure. The dielectric layer may include a ceramic material, such as an X7R ceramic material.
• In addition toacts301,302,303, and304,method300 may be extended to include further acts in order to, for example, fabricate some of the additional elements and/or features described forsensors100 and200. For example,method300 may include forming a second sensor electrode on the second surface of the substrate, forming at least one electrically conductive pathway that communicatively couples the at least a portion of at least one circuit and the second sensor electrode, and coating the second sensor electrode with the dielectric layer (either with a single continuous dielectric layer or with a separate section of the dielectric layer, as described previously). Either separately or in addition to forming a second sensor electrode,method300 may include forming a ground electrode on the second surface of the substrate and forming at least one electrically conductive pathway that communicatively couples the ground electrode and the at least a portion of at least one circuit. In this case, coating the first sensor electrode with a dielectric layer peract303 may include selectively coating the first sensor electrode with the dielectric layer and not coating the ground electrode with the dielectric layer, or coating both the first sensor electrode and the ground electrode with the dielectric layer and then forming a hole in the dielectric layer to expose the ground electrode.
• The improved capacitive EMG sensors described herein may be implemented in virtually any system, device, or process that makes use of capacitive EMG sensors; however, the improved capacitive EMG sensors described herein are particularly well-suited for use in EMG devices that are intended to be worn by (or otherwise coupled to) a user for an extended period of time and/or for a range of different skin and/or environmental conditions. As an example, the improved capacitive EMG sensors described herein may be implemented in a wearable EMG device that provides gesture-based control in a human-electronics interface. Some details of exemplary wearable EMG devices that may be adapted to include at least one improved capacitive EMG sensor from the present systems, articles, and methods are described in, for example, U.S. Provisional Patent Application Ser. No. 61/903,238; U.S. Provisional Patent Application Ser. No. 61/768,322 (now U.S. Non-Provisional patent application Ser. No. 14/186,889); Provisional Patent Application Ser. No. 61/771,500 (now U.S. Non-Provisional patent application Ser. No. 14/194,252); Provisional Patent Application Ser. No. 61/857,105 (now U.S. Non-Provisional patent application Ser. No. 14/335,668); Provisional Patent Application Ser. No. 61/860,063 (now U.S. Non-Provisional patent application Ser. No. 14/276,575); Provisional Patent Application Ser. No. 61/866,960 (now U.S. Non-Provisional patent application Ser. No. 14/461,044); Provisional Patent Application Ser. No. 61/869,526 (now U.S. Non-Provisional patent application Ser. No. 14/465,194); Provisional Patent Application Ser. No. 61/881,064 (now U.S. Non-Provisional patent application Ser. No. 14/494,274); and Provisional Patent Application Ser. No. 61/894,263 (now U.S. Non-Provisional patent application Ser. No. 14/520,081), all of which are incorporated herein by reference in their entirety.
• Throughout this specification and the appended claims, the term “gesture” is used to generally refer to a physical action (e.g., a movement, a stretch, a flex, a pose, etc.) performed or otherwise effected by a user. Any physical action performed or otherwise effected by a user that involves detectable muscle activity (detectable, e.g., by at least one appropriately positioned EMG sensor) may constitute a gesture in the present systems, articles, and methods.
• FIG. 4 is a perspective view of an exemplarywearable EMG device400 that includes improved capacitive EMG sensors in accordance with the present systems, articles, and methods. Exemplarywearable EMG device400 may, for example, form part of a human-electronics interface. Exemplarywearable EMG device400 is an armband designed to be worn on the forearm of a user, though a person of skill in the art will appreciate that the teachings described herein may readily be applied in wearable EMG devices designed to be worn elsewhere on the body of the user, including without limitation: on the upper arm, wrist, hand, finger, leg, foot, torso, or neck of the user.
• Device400 includes a set of eightpod structures401,402,403,404,405,406,407, and408 that form physically coupled links of thewearable EMG device400. Each pod structure in the set of eightpod structures401,402,403,404,405,406,407, and408 is positioned adjacent and in between two other pod structures in the set of eight pod structures such that the set of pod structures forms a perimeter of an annular or closed loop configuration. For example,pod structure401 is positioned adjacent and in betweenpod structures402 and408 at least approximately on a perimeter of the annular or closed loop configuration of pod structures,pod structure402 is positioned adjacent and in betweenpod structures401 and403 at least approximately on the perimeter of the annular or closed loop configuration,pod structure403 is positioned adjacent and in betweenpod structures402 and404 at least approximately on the perimeter of the annular or closed loop configuration, and so on. Each ofpod structures401,402,403,404,405,406,407, and408 is physically coupled to the two adjacent pod structures by at least one adaptive coupler (not visible inFIG. 4). For example,pod structure401 is physically coupled topod structure408 by an adaptive coupler and topod structure402 by an adaptive coupler. The term “adaptive coupler” is used throughout this specification and the appended claims to denote a system, article or device that provides flexible, adjustable, modifiable, extendable, extensible, or otherwise “adaptive” physical coupling. Adaptive coupling is physical coupling between two objects that permits limited motion of the two objects relative to one another. An example of an adaptive coupler is an elastic material such as an elastic band. Thus, each ofpod structures401,402,403,404,405,406,407, and408 in the set of eight pod structures may be adaptively physically coupled to the two adjacent pod structures by at least one elastic band. The set of eight pod structures may be physically bound in the annular or closed loop configuration by a single elastic band that couples over or through all pod structures or by multiple separate elastic bands that couple between adjacent pairs of pod structures or between groups of adjacent pairs of pod structures.Device400 is depicted inFIG. 4 with the at least one adaptive coupler completely retracted and contained within the eightpod structures401,402,403,404,405,406,407, and408 (and therefore the at least one adaptive coupler is not visible inFIG. 4).
• Throughout this specification and the appended claims, the term “pod structure” is used to refer to an individual link, segment, pod, section, structure, component, etc. of a wearable EMG device. For the purposes of the present systems, articles, and methods, an “individual link, segment, pod, section, structure, component, etc.” (i.e., a “pod structure”) of a wearable EMG device is characterized by its ability to be moved or displaced relative to another link, segment, pod, section, structure component, etc. of the wearable EMG device. For example,pod structures401 and402 ofdevice400 can each be moved or displaced relative to one another within the constraints imposed by the adaptive coupler providing adaptive physical coupling therebetween. The desire forpod structures401 and402 to be movable/displaceable relative to one another specifically arises becausedevice400 is a wearable EMG device that advantageously accommodates the movements of a user and/or different user forms.
• Device400 includes eightpod structures401,402,403,404,405,406,407, and408 that form physically coupled links thereof. Wearable EMG devices employing pod structures (e.g., device400) are used herein as exemplary wearable EMG device designs, while the present systems, articles, and methods may be applied to wearable EMG devices that do not employ pod structures (or that employ any number of pod structures). Thus, throughout this specification, descriptions relating to pod structures (e.g., functions and/or components of pod structures) should be interpreted as being applicable to any wearable EMG device design, even wearable EMG device designs that do not employ pod structures (except in cases where a pod structure is specifically recited in a claim).
• Inexemplary device400 ofFIG. 4, each ofpod structures401,402,403,404,405,406,407, and408 comprises a respective housing having a respective inner volume. Each housing may be formed of substantially rigid material and may be optically opaque. Throughout this specification and the appended claims, the term “rigid” as in, for example, “substantially rigid material,” is used to describe a material that has an inherent tendency to maintain or restore its shape and resist malformation/deformation under the moderate stresses and strains typically encountered by a wearable electronic device.
• Details of the components contained within the housings (i.e., within the inner volumes of the housings) ofpod structures401,402,403,404,405,406,407, and408 are not necessarily visible inFIG. 4. To facilitate descriptions ofexemplary device400, some internal components are depicted by dashed lines inFIG. 4 to indicate that these components are contained in the inner volume(s) of housings and may not normally be actually visible in the view depicted inFIG. 4, unless a transparent or translucent material is employed to form the housings. For example, any or all ofpod structures401,402,403,404,405,406,407, and/or408 may include circuitry (i.e., electrical and/or electronic circuitry). InFIG. 4, afirst pod structure401 is shown containing circuitry411 (i.e.,circuitry411 is contained in the inner volume of the housing of pod structure401), asecond pod structure402 is shown containingcircuitry412, and athird pod structure408 is shown containingcircuitry418. The circuitry in any or all pod structures may be communicatively coupled to the circuitry in at least one other pod structure by at least one communicative pathway (e.g., by at least one electrically conductive pathway and/or by at least one optical pathway). For example,FIG. 4 shows a first set ofcommunicative pathways421 providing communicative coupling betweencircuitry418 ofpod structure408 andcircuitry411 ofpod structure401, and a second set ofcommunicative pathways422 providing communicative coupling betweencircuitry411 ofpod structure401 andcircuitry412 ofpod structure402.
• Throughout this specification and the appended claims the term “communicative” as in “communicative pathway,” “communicative coupling,” and in variants such as “communicatively coupled,” is generally used to refer to any engineered arrangement for transferring and/or exchanging information. Exemplary communicative pathways include, but are not limited to, electrically conductive pathways (e.g., electrically conductive wires, electrically conductive traces), magnetic pathways (e.g., magnetic media), and/or optical pathways (e.g., optical fiber), and exemplary communicative couplings include, but are not limited to, electrical couplings, magnetic couplings, and/or optical couplings.
• Each individual pod structure within a wearable EMG device may perform a particular function, or particular functions. For example, indevice400, each ofpod structures401,402,403,404,405,406, and407 includes a respective improved capacitive EMG sensor410 (only one called out inFIG. 4 to reduce clutter) in accordance with the present systems, articles, and methods. Each improvedcapacitive EMG sensor410 is responsive to muscle activity corresponding to a gesture performed by a user ofwearable EMG device400. Thus, each improvedcapacitive EMG sensor410 is included indevice400 to detect muscle activity of a user and to provide electrical signals in response to the detected muscle activity. Thus, each ofpod structures401,402,403,404,405,406, and407 may be referred to as a respective “sensor pod.” Throughout this specification and the appended claims, the term “sensor pod” is used to denote an individual pod structure that includes at least one sensor to detect muscle activity of a user.
• Pod structure408 ofdevice400 includes aprocessor430 that processes the signals provided by the improvedcapacitive EMG sensors410 ofsensor pods401,402,403,404,405,406, and407 in response to detected muscle activity.Pod structure408 may therefore be referred to as a “processor pod.” Throughout this specification and the appended claims, the term “processor pod” is used to denote an individual pod structure that includes at least one processor to process signals. The processor may be any type of processor, including but not limited to: a digital microprocessor or microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), a graphics processing unit (GPU), a programmable gate array (PGA), a programmable logic unit (PLU), or the like, that analyzes or otherwise processes the signals to determine at least one output, action, or function based on the signals. A person of skill in the art will appreciate that implementations that employ a digital processor (e.g., a digital microprocessor or microcontroller, a DSP, etc.) may advantageously include a non-transitory processor-readable storage medium or memory communicatively coupled thereto and storing processor-executable instructions that control the operations thereof, whereas implementations that employ an ASIC, FPGA, or analog processor may or may optionally not include a non-transitory processor-readable storage medium, or may include on-board registers or other non-transitory storage structures.
• As used throughout this specification and the appended claims, the terms “sensor pod” and “processor pod” are not necessarily exclusive. A single pod structure may satisfy the definitions of both a “sensor pod” and a “processor pod” and may be referred to as either type of pod structure. For greater clarity, the term “sensor pod” is used to refer to any pod structure that includes a sensor and performs at least the function(s) of a sensor pod, and the term processor pod is used to refer to any pod structure that includes a processor and performs at least the function(s) of a processor pod. Indevice400,processor pod408 includes an improved capacitive EMG sensor410 (not visible inFIG. 4) responsive to (i.e., to sense, measure, transduce or otherwise detect and provide one or more signal(s) in response to sensing, measuring, transducing, or otherwise detecting) muscle activity of a user, soprocessor pod408 could be referred to as a sensor pod. However, inexemplary device400,processor pod408 is the only pod structure that includes aprocessor430, thusprocessor pod408 is the only pod structure inexemplary device400 that can be referred to as a processor pod. Theprocessor430 inprocessor pod408 also processes the EMG signals provided by the improvedcapacitive EMG sensor410 ofprocessor pod408. In alternative embodiments ofdevice400, multiple pod structures may include processors, and thus multiple pod structures may serve as processor pods. Similarly, some pod structures may not include sensors, and/or some sensors and/or processors may be laid out in other configurations that do not involve pod structures.
• Indevice400,processor430 includes and/or is communicatively coupled to a non-transitory processor-readable storage medium ormemory440.Memory440 may store processor-executable gesture identification instructions and/or data that, when executed byprocessor430,cause processor430 to process the EMG signals from improvedcapacitive EMG sensors410 and identify a gesture to which the EMG signals correspond. For communicating with a separate electronic device (not shown),wearable EMG device400 includes at least one communication terminal. Throughout this specification and the appended claims, the term “communication terminal” is generally used to refer to any physical structure that provides a telecommunications link through which a data signal may enter and/or leave a device. A communication terminal represents the end (or “terminus”) of communicative signal transfer within a device and the beginning of communicative signal transfer to/from an external device (or external devices). As examples,device400 includes afirst communication terminal451 and asecond communication terminal452.First communication terminal451 includes a wireless transmitter (i.e., a wireless communication terminal) andsecond communication terminal452 includes a tetheredconnector port452.Wireless transmitter451 may include, for example, a Bluetooth® transmitter (or similar) andconnector port452 may include a Universal Serial Bus port, a mini-Universal Serial Bus port, a micro-Universal Serial Bus port, a SMA port, a THUNDERBOLT® port, or the like.
• For some applications,device400 may also include at least one inertial sensor460 (e.g., an inertial measurement unit, or “IMU,” that includes at least one accelerometer and/or at least one gyroscope) responsive to (i.e., to detect, sense, or measure and provide one or more signal(s) in response to detecting, sensing, or measuring) motion effected by a user and provide signals in response to the detected motion. Signals provided byinertial sensor460 may be combined or otherwise processed in conjunction with signals provided by improvedcapacitive EMG sensors410.
• As previously described, each ofpod structures401,402,403,404,405,406,407, and408 may include circuitry (i.e., electrical and/or electronic circuitry).FIG. 4 depictscircuitry411 inside the inner volume ofsensor pod401,circuitry412 inside the inner volume ofsensor pod402, andcircuitry418 inside the inner volume ofprocessor pod418. The circuitry in any or all ofpod structures401,402,403,404,405,406,407 and408 (includingcircuitries411,412, and418) may include any or all of: an amplification circuit to amplify electrical signals provided by at least oneEMG sensor410, a filtering circuit to remove unwanted signal frequencies from the signals provided by at least oneEMG sensor410, and/or an analog-to-digital conversion circuit to convert analog signals into digital signals.Device400 may also include at least one battery (not shown inFIG. 4) to provide a portable power source fordevice400.
• Each ofEMG sensors410 includes a respective improved capacitive EMG sensor per the present systems, articles, and methods, such as forexample sensor100 fromFIG. 1 orsensor200 fromFIG. 2. In particular, eachEMG sensor410 includes a respective first capacitive sensor electrode471 (only one called out to reduce clutter) that is coated with a dielectric layer formed of a dielectric material having a relative permittivity greater than or equal to about 10, a second capacitive sensor electrode472 (only one called out to reduce clutter) that is also coated with a dielectric layer formed of a dielectric material having a relative permittivity greater than or equal to about 10, and a ground electrode473 (only one called out to reduce clutter) that is exposed and not coated by a dielectric layer. Each theelectrodes471,472, and473 of eachEMG sensor410 may be carried by a respective substrate, and the respective circuitry (e.g.,411,412, and418) of eachpod structure401,402,403,404,405,406,407, and408 may be carried by the same substrate. For example, eachrespective EMG sensor410 of eachpod structure401,402,403,404,405,406,407, and408 may include a respective substrate, with thecircuitry411,412,418 of eachpod structure401,402,403,404,405,406,407, and408 carried by a first surface of the substrate and the first andsecond sensor electrodes471,472 and theground electrode473 carried by a second surface of the substrate, the second surface being opposite the first surface.
• The improvedcapacitive EMG sensors410 ofwearable EMG device400 are differential sensors that each implement tworespective sensor electrodes471,472, though the teachings herein may similarly be applied to wearable EMG devices that employ single-ended improved capacitive EMG sensors that each implement a respective single sensor electrode.
• Signals that are provided by improvedcapacitive EMG sensors410 indevice400 are routed toprocessor pod408 for processing byprocessor430. To this end,device400 employs a set of communicative pathways (e.g.,421 and422) to route the signals that are output bysensor pods401,402,403,404,405,406, and407 toprocessor pod408. Eachrespective pod structure401,402,403,404,405,406,407, and408 indevice400 is communicatively coupled to, over, or through at least one of the two other pod structures between which the respective pod structure is positioned by at least one respective communicative pathway from the set of communicative pathways. Each communicative pathway (e.g.,421 and422) may be realized in any communicative form, including but not limited to: electrically conductive wires or cables, ribbon cables, fiber-optic cables, optical/photonic waveguides, electrically conductive traces carried by a rigid printed circuit board, electrically conductive traces carried by a flexible printed circuit board, and/or electrically conductive traces carried by a stretchable printed circuit board.
• Device400 fromFIG. 4 represents an example of a wearable EMG device that incorporates the teachings of the present systems, articles, and methods, though the teachings of the present systems, articles, and methods may be applicable to any wearable EMG device that includes at least one EMG sensor.
• In accordance with the present systems, articles, and methods, a capacitive EMG sensor may be fabricated directly on a substrate that has a high relative permittivity ε_r, such as on a ceramic substrate. For example, referring back tosensor200 ofFIG. 2 using this alternative fabrication approach (which results in re-defining some of the labelled elements ofFIG. 2), acapacitive EMG sensor200 may comprise: asubstrate250 that is formed of a material that has a high relative permittivity (i.e., ε_rgreater than or equal to about 10) such as a ceramic material including but not limited to an X7R ceramic material, at least onesensor electrode221,231 deposited on and carried by thesubstrate250, adielectric layer201 deposited on and carried by the at least onesensor electrode221,231 and thesubstrate250,circuitry210 deposited on and carried by thedielectric layer201, and one or more electrically conductive pathway(s) (e.g., via(s)) that communicatively couple thecircuitry210 to the at least onesensor electrode221,231. In this case, thesubstrate250 may be thin (e.g., with a thickness of about 10 μm or less) and/or the at least onesensor electrode221,231 may be deposited on thesubstrate250 by first etching a trench into the substrate250 (to a depth that leaves a thickness of 10 μm or less ofsubstrate material250 beneath the trench) and then filling the trench with the sensor electrode material. If thesensor200 further includes aground electrode240, ahole260 may be etched in thesubstrate250 to expose theground electrode240.
• Throughout this specification and the appended claims, infinitive verb forms are often used. Examples include, without limitation: “to detect,” “to provide,” “to transmit,” “to communicate,” “to process,” “to route,” and the like. Unless the specific context requires otherwise, such infinitive verb forms are used in an open, inclusive sense, that is as “to, at least, detect,” to, at least, provide,” “to, at least, transmit,” and so on.
• The above description of illustrated embodiments, including what is described in the Abstract, is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Although specific embodiments of and examples are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the disclosure, as will be recognized by those skilled in the relevant art. The teachings provided herein of the various embodiments can be applied to other portable and/or wearable electronic devices, not necessarily the exemplary wearable electronic devices generally described above.
• In the context of this disclosure, a memory is a processor-readable medium that is an electronic, magnetic, optical, or other physical device or means that contains or stores a computer and/or processor program. Logic and/or the information can be embodied in any processor-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions associated with logic and/or information.
• In the context of this specification, a “non-transitory processor-readable medium” can be any element that can store the program associated with logic and/or information for use by or in connection with the instruction execution system, apparatus, and/or device. The processor-readable medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device. More specific examples (a non-exhaustive list) of the processor-readable medium would include the following: a portable computer diskette (magnetic, compact flash card, secure digital, or the like), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM, EEPROM, or Flash memory), a portable compact disc read-only memory (CDROM), digital tape, and other non-transitory media.
• The various embodiments described above can be combined to provide further embodiments. To the extent that they are not inconsistent with the specific teachings and definitions herein, all of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, including but not limited to U.S. Non-Provisional patent application Ser. No. 15/799,621; U.S. Non-Provisional patent application Ser. No. 14/539,773; U.S. Provisional Patent Application Ser. No. 61/903,238; U.S. Provisional Patent Application Ser. No. 61/768,322 (now U.S. Non-Provisional patent application Ser. No. 14/186,889); Provisional Patent Application Ser. No. 61/771,500 (now U.S. Non-Provisional patent application Ser. No. 14/194,252); Provisional Patent Application Ser. No. 61/857,105 (now U.S. Non-Provisional patent application Ser. No. 14/335,668); Provisional Patent Application Ser. No. 61/860,063 (now U.S. Non-Provisional patent application Ser. No. 14/276,575); Provisional Patent Application Ser. No. 61/866,960 (now U.S. Non-Provisional patent application Ser. No. 14/461,044); Provisional Patent Application Ser. No. 61/869,526 (now U.S. Non-Provisional patent application Ser. No. 14/465,194); Provisional Patent Application Ser. No. 61/881,064 (now U.S. Non-Provisional patent application Ser. No. 14/494,274); and Provisional Patent Application Ser. No. 61/894,263 (now U.S. Non-Provisional patent application Ser. No. 14/520,081), are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary, to employ systems, circuits and concepts of the various patents, applications and publications to provide yet further embodiments.
• These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims (7)

1. A method of fabricating an electromyography (“EMG”) sensor, the method comprising:

forming at least a portion of at least one circuit on a first surface of a substrate;

forming a first electrode on a second surface of the substrate, the second surface of the substrate opposite the first surface of the substrate across a thickness of the substrate, wherein the first electrode comprises a first electrically conductive plate;

forming at least a first electrically conductive pathway through the substrate that communicatively couples the first electrode and the at least a portion of at least one circuit;

forming a second electrode on the second surface of the substrate, wherein the second electrode comprises a second electrically conductive plate;

forming at least a second electrically conductive pathway through the substrate that communicatively couples the second electrode and the at least a portion of at least one circuit.

2. The method ofclaim 1 wherein forming a first electrode on a second surface of the substrate includes forming a first sensor electrode on the second surface of the substrate.

3. The method ofclaim 2 wherein forming a second electrode on a second surface of the substrate includes forming a ground electrode on the second surface of the substrate.

4. The method ofclaim 2 wherein forming a second electrode on a second surface of the substrate includes forming a second sensor electrode on the second surface of the substrate.

5. The method ofclaim 4, further comprising:

forming a ground electrode on the second surface of the substrate, wherein the ground electrode comprises a third electrically conductive plate; and

forming at least a third electrically conductive pathway through the substrate that communicatively couples the ground electrode and the at least a portion of at least one circuit.

6. The method ofclaim 1 wherein forming a first electrode on a second surface of the substrate and forming a second electrode on the second surface of the substrate include forming the first electrode and the second electrode coplanar to one another on the second surface of the substrate.

7. The method ofclaim 1 wherein forming at least a portion of at least one circuit on a first surface of a substrate includes forming, on the first surface of the substrate, at least a portion of at least one circuit selected from a group consisting of: an amplification circuit, a filtering circuit, and an analog-to-digital conversion circuit.

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