Systems, articles, and methods for capacitive electromyography sensors
View Patent ↗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 ε r 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.
1. A capacitive electromyography (“EMG”) sensor comprising:
a substrate, wherein the substrate includes a first surface and a second surface, the second surface opposite the first surface across a thickness of the substrate;
a first sensor electrode carried by the second surface of 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, wherein at least a portion of the circuitry is carried by the first surface of the substrate;
at least one electrically conductive pathway, wherein the first sensor electrode is communicatively coupled to the circuitry by the at least one electrically conductive pathway and wherein the at least one electrically conductive pathway passes through the substrate; 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.
2. The capacitive EMG sensor of claim 1 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.
3. The capacitive EMG sensor of claim 1 wherein the dielectric layer includes a ceramic material.
4. The capacitive EMG sensor of claim 1 , further comprising:
an electrically conductive adhesive 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 adhesive, and wherein the electrically conductive adhesive is selected from the group consisting of: electrically conductive epoxy and electrically conductive solder.
5. The capacitive EMG sensor of claim 1 wherein the dielectric layer has a thickness of less than about 10 micrometers.
6. The capacitive EMG sensor of claim 1 wherein the capacitive EMG sensor is a differential capacitive EMG sensor that further comprises:
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.
7. The capacitive EMG sensor of claim 6 wherein the dielectric layer comprises either 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, or 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.
8. The capacitive EMG sensor of claim 6 wherein the first sensor electrode and the second sensor electrode are substantially coplanar.
9. The capacitive EMG sensor of claim 1 , further comprising:
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.
10. A wearable electromyography (“EMG”) device comprising:
at least one capacitive EMG sensor responsive to muscle activity corresponding to a gesture performed by a user of the wearable EMG device, wherein in response to muscle activity corresponding to the gesture performed by the user 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.
11. The wearable EMG device of claim 10 wherein the dielectric layer includes a ceramic material.
12. The wearable EMG device of claim 10 , further comprising:
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.
13. The wearable EMG device of claim 10 wherein the dielectric layer of the at least one capacitive EMG sensor has a thickness of less than about 10 micrometers.
14. The wearable EMG device of claim 10 wherein the at least one capacitive EMG sensor includes at least one differential capacitive EMG sensor, and wherein the at least one differential capacitive EMG sensor further comprises:
a second sensor electrode comprising an electrically conductive plate, wherein the dielectric layer coats the second sensor electrode.
15. The wearable EMG device of claim 10 wherein the at least one capacitive EMG sensor further comprises:
a ground electrode comprising an electrically conductive plate, wherein the ground electrode is exposed and not coated by the dielectric layer.