WO2014176420A1 - Apparatus, systems, and methods for detecting or stimullating muscle activity - Google Patents

Apparatus, systems, and methods for detecting or stimullating muscle activity Download PDF

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Publication number
WO2014176420A1
WO2014176420A1 PCT/US2014/035291 US2014035291W WO2014176420A1 WO 2014176420 A1 WO2014176420 A1 WO 2014176420A1 US 2014035291 W US2014035291 W US 2014035291W WO 2014176420 A1 WO2014176420 A1 WO 2014176420A1
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muscles
electrodes
array
subject
method
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PCT/US2014/035291
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French (fr)
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Cinzia METALLO
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Tufts University
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Priority to US61/815,440 priority
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Publication of WO2014176420A1 publication Critical patent/WO2014176420A1/en

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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/04Measuring bioelectric signals of the body or parts thereof
    • A61B5/0488Electromyography
    • A61B5/0492Electrodes specially adapted therefor, e.g. needle electrodes
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/0033Features or image-related aspects of imaging apparatus classified in A61B5/00, e.g. for MRI, optical tomography or impedance tomography apparatus; arrangements of imaging apparatus in a room
    • A61B5/004Features or image-related aspects of imaging apparatus classified in A61B5/00, e.g. for MRI, optical tomography or impedance tomography apparatus; arrangements of imaging apparatus in a room adapted for image acquisition of a particular organ or body part
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/103Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/107Measuring physical dimensions, e.g. size of the entire body or parts thereof
    • A61B5/1077Measuring of profiles
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/103Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/107Measuring physical dimensions, e.g. size of the entire body or parts thereof
    • A61B5/1079Measuring physical dimensions, e.g. size of the entire body or parts thereof using optical or photographic means
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/103Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
    • A61B5/1126Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb using a particular sensing technique
    • A61B5/1128Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb using a particular sensing technique using image analysis
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/68Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813Specially adapted to be attached to a specific body part
    • A61B5/6814Head
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/02Details of sensors specially adapted for in-vivo measurements
    • A61B2562/0209Special features of electrodes classified in A61B5/04001, A61B5/0408, A61B5/042, A61B5/0478, A61B5/0492 or A61B5/053
    • A61B2562/0215Silver or silver chloride containing
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/02Details of sensors specially adapted for in-vivo measurements
    • A61B2562/0209Special features of electrodes classified in A61B5/04001, A61B5/0408, A61B5/042, A61B5/0478, A61B5/0492 or A61B5/053
    • A61B2562/0217Electrolyte containing
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/04Arrangements of multiple sensors of the same type
    • A61B2562/046Arrangements of multiple sensors of the same type in a matrix array
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/16Details of sensor housings or probes; Details of structural supports for sensors
    • A61B2562/164Details of sensor housings or probes; Details of structural supports for sensors the sensor is mounted in or on a conformable substrate or carrier
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/16Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state
    • A61B5/165Evaluating the state of mind, e.g. depression, anxiety
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/16Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state
    • A61B5/167Personality evaluation
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/40Detecting, measuring or recording for evaluating the nervous system
    • A61B5/4076Diagnosing or monitoring particular conditions of the nervous system
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00Electrotherapy; Circuits therefor
    • A61N1/02Details
    • A61N1/04Electrodes
    • A61N1/0404Electrodes for external use
    • A61N1/0408Use-related aspects
    • A61N1/0452Specially adapted for transcutaneous muscle stimulation [TMS]
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00Electrotherapy; Circuits therefor
    • A61N1/18Applying electric currents by contact electrodes
    • A61N1/32Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/36014External stimulators, e.g. with patch electrodes

Abstract

One aspect of the invention provides an apparatus including: a mechanically flexible substrate conformable to a subject's skin and an array of electrodes embedded within the mechanically flexible substrate. At least a first subset of the array of electrodes are arranged in a pattern associated with a first predetermined set of muscles. Another aspect of the invention provides a system for making a multi-electrode array. The system includes: an imaging device programmed to scan a portion of a body and generate a topology of the portion of the body; a memory device adapted and configured to store the topology; and a processor adapted and configured to load and execute computer program instructions to generate data representative of the apparatus described herein. The predetermined set of muscles can be a set of muscles in the portion of the body.

Description

APPARATUS, SYSTEMS, AND METHODS FOR

DETECTING OR STIMULATING MUSCLE ACTIVITY

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of the following U.S. Provisional Application No. 61/815,440, filed April 24, 2013, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Facial muscles carry out an extensive range of functions, from speech production to emotional expression. Despite the importance of facial electromyography (EMG) in both research and clinical settings, a reliable and stable method for detecting high resolution activity from facial muscles remains a challenging technical problem. Surface or implanted electrodes are typically used to detect or induce muscle activity. Their performance is highly dependent on their recording or stimulation capabilities, as well as on their position with respect the target muscles. The ability to extract fine-scale electrical information from signals recorded from any muscle is also dependent on the detection capabilities of the electrodes. The use of conventional surface electrodes on facial muscles is severely limited by the lack of an appropriate

spatiotemporal resolution and the lack of the necessary signal sensitivity and selectivity. As a result, the fine motor coordination required to carry out the sophisticated movements underlying speech production and facial expressions is not amenable to detection with conventional EMG electrodes.

Similarly, the effectiveness of the stimuli delivered using conventional electrodes is significantly limited by the low signal selectivity of these electrodes. As a consequence, the contraction of particular sets of muscles necessary to recapitulate specific facial movements cannot be reliably induced.

The ability to coordinate or activate facial muscles is frequently lost due to ischemic events, neurodegenerative diseases, trauma, or a host of other insults. Conventional, one-size- fits-all recording and stimulating electrodes lack the sensitivity and selectivity necessary to characterize and quantify these deficits in particular facial muscles. SUMMARY OF THE INVENTION

As described below, the present invention features a flexible electrode array capable of stimulating and/or recording from particular facial muscles and methods of using this device.

One aspect of the invention provides an apparatus including: a mechanically flexible substrate conformable to a subject's skin and an array of electrodes embedded within the mechanically flexible substrate. At least a first subset of the array of electrodes are arranged in a pattern associated with a first predetermined set of muscles.

This aspect of the invention can have a variety of embodiments. The first subset of the array of electrodes can be independently addressable from a second subset of the array of electrodes. The second subset of the array of electrodes can be arranged in a pattern associated with a second predetermined set of muscles.

The first subset of the array of electrodes can have a first spacing and the second subset of the array of electrodes can have a second spacing. The first spacing can be different than the second spacing.

The first subset of the array of electrodes can have a first density characteristic and the second subset of the array of electrodes can have a second density characteristic. The density characteristics can describe a quantity of electrodes within a defined area. The first density characteristic can be different than the second density characteristic.

The mechanically flexible substrate can include: a first region associated with the first subset of the array of electrodes and having a first flexibility characteristic; and a second region associated with the second subset of the array of electrodes and a having a second flexibility characteristic. The first flexibility characteristic can be different than the second flexibility characteristic.

The mechanically flexible substrate can include one or more selected from the group consisting of: poly(p-xylylene) polymer and polyimide.

The apparatus can further include a controller. The controller can include a signal processor programmed to receive signals from the array of electrodes. The controller can include a recording device. The controller can include a signal generator programmed to provide signals to the array of electrodes. The controller can include a biofeedback module programmed to generate and communicate signals to the array of electrodes based on others signals received from the array of electrodes. The first predetermined set of muscles can be facial muscles selected from the group consisting of depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and sternocleidomastoid. The electrodes can be configured to record from one or more muscle fibers within said set of muscles.

Another aspect of the invention provides a system for making a multi-electrode array. The system includes: an imaging device programmed to scan a portion of a body and generate a topology of the portion of the body; a memory device adapted and configured to store the topology; and a processor adapted and configured to load and execute computer program instructions to generate data representative of the apparatus described herein. The predetermined set of muscles can be a set of muscles in the portion of the body.

This aspect of the invention can have a variety of embodiments. The computer program instructions can include instructions for generating data specifying inter-spacing of the electrodes. The computer program instructions can include instructions for generating data specifying density of the electrodes.

Another aspect of the invention provides a method of making a multi-electrode array. The method includes: scanning a portion of a subject's body to generate a topology of the portion of the body; and generating data representative of the apparatus as described herein. The predetermined set of muscles can be a set of muscles in the portion of the body.

This aspect of the invention can have a variety of embodiments. The method can further include fabricating a device based on the generated data. The step of scanning the portion of the subject's body can further include moving the portion of the subject's body to identify muscles associated with the portion of the body.

The portion of the subject's body can be a facial region of the subject. The muscles can be selected from the group consisting of depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and

sternocleidomastoid.

Another aspect of the invention provides a method for selectively stimulating or recording from a muscle. The method includes applying the apparatus as described herein to a subject's skin so that the first subset of the array of electrodes lies over the first predetermined set of muscles.

This aspect of the invention can have a variety of embodiments. The method can further include receiving signals from the at least first subset of the array of electrodes. The method can further include recording the signals.

The method can further include providing signals to the at least first subset of the array of electrodes sufficient to stimulate the first predetermined set of muscles. The array of electrodes can be configured to selectively stimulate muscle fibers within a muscle selected from the group consisting of depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and sternocleidomastoid.

The subject can be in need of treatment for a disorder relating to the central nervous system. The subject can be in need of treatment for a disorder selected from the group consisting of: stroke-related facial paralysis, facial droop, synkinesis, facial nerve paralysis, peripheral nerve injury, Bell's palsy, Parkinson's facial masking, dysphagia, speech impediments, myasthenia gravis, facial paralysis due to trauma, viral or infectious diseases, chronic tension headaches, and chronic pain.

The first predetermined set of muscles can include facial muscles. The method can further include: exposing the subject to a product or an advertisement; receiving signals from the apparatus associated with the facial muscles; and correlating the signals with an emotional response to the product or an advertisement.

The method can further include providing audio or visual feedback to the subject regarding signals received from the apparatus. The method can further include instructing the subject to move one or more muscles. Another aspect of the invention provides a system including: the apparatus as described herein; and a feedback device communicatively coupled to the apparatus.

This aspect of the invention can have a variety of embodiments. The feedback device can include an audiovisual display. The feedback device can be programmed to provide quantified feedback regarding detected signals.

Another aspect of the invention provides a method of treating a subject diagnosed with a disorder. The method includes: applying the apparatus as described herein to the subject's skin so that the first subset of the array of electrodes lies over the first predetermined set of muscles; instructing the subject to move the first predetermined set of muscles; measuring electrical signals at the first predetermined set of muscles using the device; and providing feedback to the subject regarding the electrical signals.

This aspect of the invention can have a variety of embodiments. The method can further include applying an electrical signal to the first subset of electrodes sufficient to stimulate the first predetermined set of muscles. The disorder can relate to the central nervous system. The disorder can be selected from the group consisting of: stroke-related facial paralysis, facial droop, synkinesis, facial nerve paralysis, peripheral nerve injury, Bell's palsy, Parkinson's facial masking, dysphagia, chronic tension headaches, and chronic pain.

Another aspect of the invention provides a method of improving the appearance of a subject. The method includes: applying the apparatus as described herein to the subject's skin so that the first subset of the array of electrodes lies over the first predetermined set of muscles; instructing the subject to move, and thereby tone, the first predetermined set of muscles;

measuring electrical signals at the first predetermined set of muscles using the device; and providing feedback to the subject regarding the electrical signals.

This aspect of the invention can have a variety of embodiments. The method can further include applying an electrical signal to the first subset of electrodes sufficient to stimulate the first predetermined set of muscles.

The muscles can be facial muscles selected from the group consisting of depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and sternocleidomastoid.

Another aspect of the invention provides a device for facilitating placement of the apparatus as described herein. The device includes: a mask having a shape complimentary to at least a portion of a human face and one or more markings specifying a proper position of one or more of the apparatus as described herein.

Other features and advantages of the invention will be apparent from the detailed description, and from the claims.

DEFINITIONS

Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which this invention belongs. The following references provide one of skill with a general definition of many of the terms used in this invention: Singleton et al., Dictionary of Microbiology and Molecular Biology (2nd ed. 1994); The Cambridge Dictionary of Science and Technology (Walker ed., 1988); The Glossary of Genetics, 5th Ed., R. Rieger et al. (eds.), Springer Verlag (1991); and Hale & Marham, The Harper Collins Dictionary of Biology (1991). As used herein, the following terms have the meanings ascribed to them below, unless specified otherwise.

By "ameliorate" is meant decrease, suppress, attenuate, diminish, arrest, or stabilize the development or progression of a disease.

In this disclosure, "comprises," "comprising," "containing" and "having" and the like can have the meaning ascribed to them in U.S. patent law and can mean " includes," "including," and the like; "consisting essentially of" or "consists essentially" likewise has the meaning ascribed in U.S. patent law and the term is open-ended, allowing for the presence of more than that which is recited so long as basic or novel characteristics of that which is recited is not changed by the presence of more than that which is recited, but excludes prior art embodiments.

By "disease" is meant any condition or disorder that damages or interferes with the normal function of a cell, tissue, or organ. Examples of diseases include any condition that interferes with the normal function or coordination of facial muscles. For example, an ischemic event, such as a stroke, can affect the facial muscle control. Other examples include peripheral nerve injuries, facial nerve paralysis due to viral or infectious diseases such as Herpes Zoster and Lyme disease, Bell's palsy, Myasthenia Gravis, and trauma affecting one or more nerves innervating the face (e.g., trigeminal nerve Cranial nerve V, facial nerve cranial nerve VII). Patients affected by facial paralysis resulting from stroke, injury or viral causes experience weakness, paralysis, and abnormal involuntary movements (synkinesis) of facial muscles.

By "reduces" is meant a negative alteration of at least 10%, 25%, 50%, 75%, or 100%.

By "reference" is meant a standard or control condition.

By "subject" is meant a mammal, including, but not limited to, a human or non-human mammal, such as a bovine, equine, canine, ovine, or feline.

Ranges provided herein are understood to be shorthand for all of the values within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group consisting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50.

As used herein, the terms "treat," treating," "treatment," and the like refer to reducing or ameliorating a disorder and/or symptoms associated therewith. It will be appreciated that, although not precluded, treating a disorder or condition does not require that the disorder, condition or symptoms associated therewith be completely eliminated.

Unless specifically stated or obvious from context, as used herein, the term "or" is understood to be inclusive. Unless specifically stated or obvious from context, as used herein, the terms "a", "an", and "the" are understood to be singular or plural.

Unless specifically stated or obvious from context, as used herein, the term "about" is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. About can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from context, all numerical values provided herein are modified by the term about.

Any compositions or methods provided herein can be combined with one or more of any of the other compositions and methods provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1(a) is a flexible electromyography device positioned on a face of a subject according to embodiments of the invention. FIG. 1(b) is a flexible electromyography device positioned on a face of a subject with the underlying facial musculature of the subject shown according to embodiments of the invention.

FIG. 2 is a detailed view of the electrodes of the device positioned over individual muscle fibers of a facial muscle according to embodiments of the invention.

FIG. 3 is an electromyography system including a flexible electromyography device according to embodiments of the invention.

FIG. 4 is a system for designing a custom electrode array for a flexible electromyography device according to embodiments of the invention.

FIG. 5 is a method for fabricating an electrode array of a flexible electromyography device according to embodiments of the invention.

FIG. 6 is a cross sectional view of a pre-gelled electrode according to embodiments of the invention.

FIG. 7(a)-7(d) are diagrams showing the muscles of the face according to embodiments of the invention.

FIG. 8 depicts the form factor of electrode arrays according to embodiments of the invention.

FIG. 9 compares the form factor of electrode arrays according to embodiments of the invention with conventional electrodes.

FIG. 10 depicts the pairing of electrodes to measure voltage in a channel according to embodiments of the invention.

FIG. 11 depicts the coupling of an electrode array to an amplifier via a flexible cable and a zero insertion force (ZIF) connector according to embodiments of the invention.

FIG. 12 depicts the removal and reapplication of an array according to embodiments of the invention. Although medical tape is visible at the edges of the device, the medical tape is not necessary for adhesion.

FIG. 13 depicts the application of an electrode array with medical tape according to embodiments of the invention. Although medical tape is visible at the edges of the device, the medical tape is not necessary for adhesion.

FIG. 14 depicts the ability of the electrode assemblies to provide conformal coverage of the skin surface according to embodiments of the invention. FIGS. 15(a)- 15(d) depict voltages captured from an electrode array during various facial expressions according to embodiments of the invention.

FIG. 16 depicts voltage signals obtained from electrodes positioned over the wrist flexor muscles according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As described below, the present invention features devices useful for stimulating or recording from particular facial muscles, and methods of using these devices.

The invention is based, at least in part, on the discovery of a novel low profile multi- electrode array that exploits the properties of its structural substrate, parylene C (poly(p- xylylene) polymer), to provide a customizable electrode capable of recording EMG signals with an unparalleled signal-to-noise ratio, which makes it particularly suitable for use in recording signals from facial electromyography (fEMG).

Devices intended for surface fEMG recordings must meet several key requirements: (1) high mechanical flexibility and minimal thickness to facilitate conformal coverage of the skin surface as depicted in FIG. 14, maintain stable and uniform electrical contact, and enhance the signal to noise ratio (SNR); (2) mechanical strength; (3) configurable and customizable size and overall arrangement of the recording electrodes to ensure optimal placement in correspondence of different muscle groups; (4) configurable and customizable electrode density to facilitate signal decomposition into constituent components; (5) lightweight and minimally obstructive connection system. The present invention provides a novel low profile multi-electrode array that satisfies all of the above requirements.

As reported in detail below, a parylene C array has been produced that conforms to the muscle anatomy of the human face. For example, initial prototypes were designed to record from forehead muscles (corrugator supercilii, procerus, and occipitofrontalis), as well as eye muscles (depressor supercilii and orbicularis oculi).

The fabrication process can include standard photolithographic techniques, parylene C vapor-deposition, metal sputtering deposition and reactive ion etching in oxygen plasma. Metal recording sites and interconnecting traces are sandwiched between two insulating layers of parylene C, which serves both as an insulator and as a structural substrate. If desired, the output of the electrode array can be fed to an amplifier through a lightweight zero insertion force (ZIF) connector and a flex cable as depicted in FIG. 11. To minimize skin-electrode impedance, a conductive gel can be applied on the skin corresponding to the recording sites. If desired, medical tape can be custom-cut to match the final openings of the recording electrodes to provide a mask through which the gel can be selectively applied. In other embodiments, a biocompatible adhesive can be applied to the substrate of the array, either during manufacture or prior to application to the subject.

The devices described herein (particularly those with a final thickness in the range of 15 to 30 μπι) are extremely flexible and able to conform to the skin surface, reducing possible motion artifacts. Since parylene C can be deposited in very thin layers without compromising its ability to minimize the capacitive crosstalk between adjacent metal lines, flexible high-density arrays can be easily fabricated. Different recording configurations can be generated to optimize the spatial resolution and the overall recording capabilities of the arrays. For instance, in some of the current prototypes, the recording electrodes have a radius ranging from about 50 μπι to about 4 mm (e.g., about 5 mm), whereas the interspacing between electrodes ranges from about 300 μπι to about 7 mm. Devices with different shapes can be customized to target specific muscles. In one working example, concave-shaped arrays have been designed to record from the orbicularis oculi, the muscle responsible for closing the eyelid. Furthermore, since parylene C is optically transparent, the position of the recording sites can be visually monitored throughout the entire duration of each recording session. The design parameters of the arrays presented here can be easily modified not only to fine-tune their recording capabilities, but also to match the anatomy of different facial muscles and, potentially, any other muscle throughout the body.

Applications

Every year, 800,000 people suffer a stroke in the U.S. alone. Approximately 25% of stroke survivors have a second stroke within 5 years, bringing the total number of Americans that at any given time live with post-stroke effects to 4 million. Since a stroke can compromise the ability of the brain to communicate with the rest of the body, loss of muscle control and paralysis represent two of the most disabling symptoms. Facial paralysis, in particular, is one of the most frequent complications. It results not only in speech impediments and swallowing problems, but also in a reduced ability to communicate feelings and emotions through facial expressions, which often leads to a deep sense of isolation and depression. Facial rehabilitation exercises are often prescribed, but the lack of a technique or mechanism to precisely quantify the activation levels of the small and overlapping facial muscles significantly limits effectiveness and delays recovery.

Aspects of the invention provide a novel flexible electromyographic (EMG) electrode specifically designed for facial muscle rehabilitation. Unlike traditional one-size-fits-all electrodes, the electrodes described herein can be shaped to match the muscle anatomy of the face, enhancing signal selectivity and enabling the use of muscle biofeedback or myofeedback. By responding to a series of audio-visual cues (feedback), patients are able to monitor their own muscle activity, identify the muscles that are not functioning correctly, track their progress over time and, ultimately, learn how to regain control of their face. The high signal selectivity and signal sensitivity provided by aspects of the invention significantly simplifies muscle

biofeedback interpretation and is especially valuable when recording from weakened or paralyzed muscles.

The timing, specificity and frequency of muscle retraining exercises are extremely important in post-stroke rehabilitation. Aspects of the invention provide the first clinically proven EMG device specifically designed to effectively retrain facial muscles. Regaining control of a patient' s face will help stroke survivors improve their quality of life and reestablish their role in society.

In the case of peripheral nerve injuries, aspects of the invention can be used to monitor motor unit re-innervation and assess the recovery of motor unit functionality. Aspects of the invention can also be used to determine with extreme precision the location of motor endplate zones in specific muscles prior to botulinum toxin (botox) injections to maximize the

effectiveness of the treatment.

In addition to treating stroke-related facial paralysis and any other type of facial paralysis, aspects of the invention can be applied to the field of facial aesthetics to restore muscle tone and treat age-related facial laxity. Additionally, the store-and-forward capabilities and wireless technology described herein will also meet the growing demand of EMG sensors compatible with mobile applications.

Facial Muscles

The coordinated contraction of facial muscles is required for the generation of a variety of facial expressions and for speech. The invention provides devices capable of selectively recording from and/or selectively stimulating one or more of the following facial muscles:

depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and sternocleidomastoid as depicted in Figures 7(a)-7(d). In particular embodiments, an electrode of the invention is configured in a branching pattern that provides for the selective stimulation of muscle fibers within the depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and

sternocleidomastoid. In another embodiment, the electrode is configured in a branching pattern that provides for a high degree of sensitivity and selectivity in recording from muscle fibers within a facial muscle that is one or more of the depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and

sternocleidomastoid.

In particular embodiments, the invention provides methods for stimulating or recording from particular muscles in the upper face. For example, stimulating the frontalis pulls the eyebrows up; stimulating the temporalis elevates the jaw and moves it forward; stimulating the orbicularis oculi squints the eyes; stimulating the procerus pulls the skin between the eyebrows downwards, which assists in flaring the nostrils; stimulating the depressor supercilii moves the eyebrows and the skin of the glabella; stimulating the corrugator supercilii lowers and pulls the eyebrows together; stimulating the medial palpebral ligament contracts a small muscle at the corner of the eye; stimulating the levator of the upper eyelid raises the upper eyelid; stimulating the nasalis, which includes the transverse (compressor naris) and alar (pars alaris) dilator nasalis, flares the nostrils; stimulating the depressor septi draws the ala of the nose downward, and constricts the aperture of the nares; stimulating the pyramidalis - lowers the glabella and helps wrinkle the nose.

In other embodiments, invention provides methods for stimulating or recording from particular muscles in the lower face. For example, stimulating the zygomaticus including the zygomaticus minor retracts and pulls the lip corners upwards; stimulating the zygomaticus major retracts and pulls the lip corners upwards; stimulating the risorius retracts the lip corners;

stimulating the orbicularis oris constricts and deforms the lips and mouth opening; stimulating the incisivus labii superioris part of the orbicularis oris.

The quadratus labii superioris is a muscle in the medial cheek and nose that has multiple strands; stimulating the levator labii superius alaeque nasi (or caput angulare) wrinkles the nose; stimulating the levator labii superius (or caput infraobitalis) pulls the upper lip upwards;

stimulating the depressor anguli oris pulls the corners of the mouth downwards; stimulating the depressor labii inferioris pulls the lower lip down; stimulating the caninus (levator anguli oris) elevates the lateral parts of the lips; stimulating the mentalis (transversus menti) pushes chin up and wrinkles the chin; stimulating the sternocleidomastoid, which is a ribbon-like muscle running along the side of the neck, tilts the head right or left; stimulating the buccinator compresses the cheek towards the teeth; stimulating the masseter closes the jaw; the platysma is a large muscle that lies under the jaw and runs down the neck to the upper chest; stimulating the omohyoid depresses the hyoid; stimulating the sternohyoid depresses the hyoid; stimulating the stylohyoid draws the hyoid bone backwards and elevates the tongue; stimulating the digastric elevates the hyoid bone. If the hyoid is held in place by the infrahyod muscles, it will depress the mandiblele and open the mouth. Stimulating the mylohyoid elevates the hyoid and the tongue, which functions during swallowing and speaking.

In addition the exemplary muscles listed above, one of skill in the art can readily identify other muscles for monitoring or treatment from a variety of resources, such as Henry Gray, Gray's Anatomy (1901).

Therapeutic Methods

As discussed herein, aspects of the invention can be utilized to address one or more conditions such as stroke-related facial paralysis, facial droop, synkinesis, facial nerve paralysis, Bell's Palsy, Parkinson's facial masking, dysphagia, speech impediments, myasthenia gravis, facial paralysis due to trauma, viral or infectious diseases, chronic tension headaches, and chronic pain. Aspects of the invention can be used to monitor the re-innervation and the functional recovery of motor units following peripheral nerve injuries. To maximize the effectiveness of injections of botulinum toxin, aspects of the invention can also be used to determine with extreme precision the location of motor endplate zones in specific muscles prior to injection. Aspects of the invention can enable the subject or a care-giver to detect which muscles the subject is attempting to move or which muscles are not being properly activated, detect when the subject is actuating the correct muscle(s) for a desired expression or movement, quantify muscle activation, and strengthen individual underperforming muscles. By using aspects of the invention in stimulating mode, it is also possible to enable the subject or a care-giver to stimulate specific individual muscles to accelerate recovery.

Cosmetic Methods

In addition to rehabilitative treatment of clinically-diagnosed conditions, aspects of the invention can also be used to enhance the appearance of the face, to tone muscles, particularly in the face, and/or to prevent or reduce wrinkles, sagging, and other undesirable effects of aging. For example, aspects of the invention can be provided with instructions (printed or computer- generated) to perform various facial exercises (e.g. , smiling, raising eyebrows, blinking, squinting, and the like) to isolate and exercise particular muscles within the face. The

instructions can specify and provide feedback on the particular numbers of sets and repetitions of each exercise as well as performance speed, rest, and the like. Aspects of the invention will also enable the subject to quantify progress over time. Various exercise regimens include so-called "facial yoga".

Flexible Electromyography Device

Referring to FIGs. 1(a) and 1(b), one example of a flexible electromyography device 100 is positioned on the face of a subject 102. The flexible electromyography device 100 includes an electrode array 101 and a signal processing and transmission module 103. The electrode array 101 includes a flexible substrate 105, which is described in greater detail below, for supporting a number of electrodes 104. The flexible nature of the electrode array 101 firmly maintains the position of the electrodes 104 on the surface of the subject's skin in the presence of small movements of the subject' s face. The signal processing and transmission module 103 includes circuitry (e.g. , transmitter, antenna 107) for wirelessly communicating data between the device 100 and a computer of an electromyography system (not shown).

In general, the electrodes 104 are arranged on the flexible substrate 105 in one or more patterns. In one example of an electrode array 101 of the flexible electromyography device 100 of FIG. 1, the electrodes 104 are arranged in three distinct electrode patterns: a first electrode pattern 108, a second electrode pattern 110, and a third electrode pattern 112. The

electrodes 104 of each individual pattern are arranged such that when the device 100 is positioned on the subject' s face, the electrodes 104 are aligned with certain facial muscles 106 of interest beneath the subject's skin.

In the examples described herein, the flexible substrate 105 is fabricated out of Parylene C material. Parylene C is a crystalline thermoplastic polymer that has a unique combination of physical, chemical and mechanical properties. Parylene C is intrinsically flexible and

mechanically strong, having a tensile modulus of 3.2 GPa. Parylene C is also chemically inert and is not subject to hydrolytic degradation, having a water absorption of about 0.01% for 0.019 inches, and about 0.06% for 0.029 inches, after 24 hours and a water vapor transmission rate of 0.0004 ng/Pa sm2 at 37 °C. Parylene C meets the highest biocompatibility standards for plastic materials (i.e., ISO 10993 and USP Class VI). Furthermore, due to its low dielectric constant of -3.1 at 1 kHz, the use of Parylene C minimizes capacitive crosstalk between adjacent metal lines even when deposited in very thin layers. Finally, Parylene C is optically transparent, allowing tissues to be seen through the array and, therefore, facilitating the correct positioning of the device on the skin corresponding to underlying target muscles. Taken together, all of these properties make Parylene C exceptionally well suited for use as a substrate material in the fabrication of devices for EMG recordings.

In some examples, the flexible substrate 105 has a thickness in the range of 10 to 100 μπι.

In some examples, the substrate 105 has different thicknesses at different points on the substrate. For example, portions of the substrate 105 which interact with areas of the subject's face that frequently move can be thinner than portions of the substrate 105 which interact with areas of the subject' s face which infrequently move.

In some examples, the electrodes 104 are fabricated using gold or silver due to their biocompatibility and electrochemical stability. In general, the diameter of the electrodes 104 can be specified to match a range of widths of the muscle fibers that are measured. For example, electrodes can have a diameter of: between about 30 μπι and about 50 μπι, between about 50 μπι and about 75 μπι, between about 75 μπι and about 100 μπι, between about 100 μπι and about 125 μη , between about 125 μπι and about 150 μη , between about 150 μπι and

about 175 μπι, between about 175 μπι and about 200 μπι, between about 200 μηι and

about 225 μπι, between about 225 μπι and about 250 μπι, between about 250 μπι and

about 275 μπι, between about 275 μπι and about 300 μπι, between about 300 μπι and

about 325 μπι, between about 325 μπι and about 350 μπι, between about 350 μπι and

about 375 μπι, between about 375 μπι and about 400 μπι, between about 400 μπι and

about 425 μπι, between about 425 μπι and about 450 μπι, between about 450 μπι and

about 475 μπι, between about 475 μπι and about 500 μπι, between about 500 μπι and

about 525 μπι, between about 525 μm and about 550 μπι, between about 550 μπι and

about 575 μπι, between about 575 μm and about 600 μπι, between about 600 μπι and

about 625 μπι, between about 625 μm and about 650 μπι, and the like. Specifying the diameter in this way yields high signal selectivity and an electrode array that is capable of resolving electromyography signals in individual muscles with single fiber resolution. In particular embodiments, the electrode provides a method for resolving signals from a facial muscle that is any one or more of an electrode of the invention is configured in a branching pattern that provides for the selective stimulation of muscle fibers within the depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and sternocleidomastoid. In another embodiment, the electrode is configured in a branching pattern that provides for a high degree of sensitivity and selectivity in recording from muscle fibers within a facial muscle that is one or more of the depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and

sternocleidomastoid. Generally speaking, larger electrodes are preferred for electrical stimulation of muscles, while smaller electrodes are preferred for detection of muscle activity. Larger electrodes generate electrical currents that more effectively penetrate the subject's skin to reach the underlying muscles. For example, relatively larger muscles such as the trapezius muscle in the neck can be effectively stimulated using electrodes having a diameter between about 2 mm and about 3 mm.

In some examples, the longitudinal spacing between the electrodes 104 is selected to distribute different recording sites on distinct fibers of the same muscle. In some examples, the transverse spacing between the electrodes 104 defines the final width of the device and determines the area of the muscle that is ultimately covered by the electrode array 101 of the flexible electromyography device 100. In some examples, interconnecting traces connected to the electrodes 104 are routed among the electrodes and terminate into output pads.

Referring to FIG. 2, a detailed view of one of the facial muscles 106 of the subject 102 shows the individual muscle fibers 207 of the muscle 106. The detailed view also illustrates that the electrodes 104 of the electrode array 101 are specifically patterned such that they are aligned with the individual fibers 207 of the muscle 106. In this way, bipolar electrodes (i.e., pairs of electrodes that are differentially connected to reduce noise) can be aligned parallel to the direction of the muscle fibers.

Overall Electromyo raphy System

Referring to FIG. 3, an electromyography system 200 includes the flexible

electromyography device 100, which is in wireless communication with an electromyography workstation 215. The electromyography workstation 215 includes a computer 214 including a display device 216, and signal processing and communication module 218 for receiving data from and transmitting data to the flexible wireless electromyography device 100.

The electromyography system 200 is configured to operate in two modes: an

electromyography measurement mode and an electrical muscle stimulation mode. Very generally, in the measurement mode, the flexible electromyography device 100 is used to sense electrical signals emitted by muscle fibers using its electrodes 104 and to communicate the sensed signals to the electromyography workstation 215 where the sensed electrical signals are processed and analyzed. In the muscle stimulation mode, the flexible electromyography device 100 is used to electrically stimulate muscle fibers by transmitting electrical impulses, which are communicated from the electromyography workstation 215 through the electrodes and into the subject' s muscle fibers.

Electromyography Measurement Mode

In the electromyography measurement mode, the electrodes 104 of the flexible electromyography device 100 measure electrical activity (e.g., the electrical currents generated by activated muscle fibers) of the subject' s facial muscles. The signals measured by each of the electrodes 104 can be maintained as a separate channel or be differentially connected in order to isolate and reduce noise as depicted in FIG. 10. Electrical signals representative of the measured electrical activity are provided to the signal processing and communication module 103, which amplifies and processes (e.g., using signal processing algorithms or signal processing circuitry) the electrical signals to produce a useful representation of the measured electrical activity. In some examples, electrical signals are first amplified by a preamplifier in the signal processing and communication module 103 and are again amplified (e.g., using a differential or a non- differential amplifier) in the signal processing and communication module 103. The signal processing and communication module 103 then wirelessly transmits (e.g., using a wireless microtransmitter) the representation of the measured electrical activity to the electromyography workstation 215.

The signal processing and communication module 218 of the electromyography workstation 215 receives transmission from the flexible electromyography device 100 and optionally applies additional signal processing algorithms to the representation of the measured electrical activity before providing the electrical signals to the computer 214. The computer 214 presents the representation of the measured electrical activity on a display device 216 (e.g., a computer monitor).

In some examples, an electromyography technician views and analyzes the representation of the measured electrical activity (e.g. , a graph of the measured voltages) on the display 216 to detect medical abnormalities, a level of activation of muscles, an order of muscle activation, or to analyze biomechanical features of movement. In other examples, the measurement mode of the electromyography system 200 can be used as a biofeedback (e.g., myofeedback) tool to help patients regain control of their muscles for a vast range of muscle disorders (e.g., post-stroke facial paralysis). In such a system, a simplified version (e.g., audio-visual cues or graphical elements such as bars or an animated representation of the face illustrating where electrical signals are detected or which muscles are being moved) of the representation of the measured electrical activity is displayed to the subject 102 to provide real-time assistance to the

subject 102 in learning how to control their own muscle activity as they attempt to contract specific muscles. In some examples, myofeedback is used to achieve rehabilitative goals such as improving, restoring, or maintaining the functionality of the musculature being measured. In other examples, the electromyography system 200 is used as a biofeedback tool to improve physiological relaxation responses and reduce pain or for diagnosing myophaties that involve damage to a subset of fibers and result in reduced muscle activity. In some examples, clinical and non-clinical indications for facial myofeedback include stroke-related facial paralysis, facial droop, synkinesis, Bell's palsy, Parkinson's facial masking, dysphagia, chronic tension headaches, chronic pain, relaxation, facial muscle exercises (e.g., facial yoga or other approaches to tighten and lift facial muscles and thus skin), lie detection, emotion detection (e.g., through the detection of zygomatic muscle activity), market and advertising research studies (e.g. , through the detection of zygomatic muscle activity in response to products or advertisements), biomechanics, and gaming. In some examples, myofeedback is used on muscles other than facial muscles. In some examples, representation is displayed to the user on other types of computing devices such as tablet, smart phone, or cell phone screens. Data regarding a treatment session can also be transmitted to a remote computer for storage and viewing by a healthcare professional.

One advantage of aspects of the system is the ability to quantify a subject' s improvement. For example, the intensity of the electrical signals that the subject applies to a particular muscle can be audio-visually displayed, stored in computer-readable memory, and/or compared between treatment sessions.

In some examples, one or both of the signal processing and communication

modules 103, 218 are configured to amplify the representation of the measured electrical activity (e.g., a 10,000x amplification), high pass filter the representation of the measured electrical activity (e.g., a high pass filter with a 10 Hz cutoff frequency), and low pass filter the

representation of the measured electrical activity (e.g., a low pass filter with a cutoff frequency at 10 kHz). Muscle Stimulation Mode

In the muscle stimulation mode, a technician working at the electromyography workstation 215 can use the computer 214 to specify one or more muscle stimulation signals, which are applied to the facial muscles of the subject 102 through one or more of the

electrodes 104 of the flexible electromyography device 100. For example, the technician can specify that one muscle stimulation signal be applied to all of the electrodes in a given pattern of electrodes 104 on the electrode array 101 of the device 100 and that another muscle stimulation signal be applied to another, different pattern of electrodes 104 of the electrode array 101. The technician can also specify stimulation frequencies for each stimulation signal.

The signal processing and communication module 218 of the electromyography workstation 215 wirelessly transmits the specification of one or more muscle stimulation signals to the flexible electromyography device 100. The signal processing and communication module 103 of the flexible electromyography device 100 receives the specification of one or more muscle stimulation signals and converts the specification (e.g., through signal generation and amplification) to an electrical signal that is applied with the appropriate stimulation frequency to the appropriate facial muscles of the subject through the appropriate electrodes 104 of the electrode array 101. To guarantee patient comfort, several parameters can be set by the therapist depending on the target muscles and the type of treatment (e.g., muscle strengthening, rehabilitation, pain relief) and then used at home by the patient. Parameters that can be adjusted include ramp time (e.g., 1-5 s), waveforms (e.g., symmetric, asymmetric, biphasic), amplitude (e.g., 0-300mA), voltage (e.g., 100- 300V), pulse width (e.g., 0-400 μ8), pulse frequency (e.g., 10-50 pps).

Upon application of the electrical signal, the targeted facial muscles contract. This type of electrical muscle stimulation is useful, for example, as a strength training tool, a rehabilitation tool for immobilized patients, and a post-exercise recovery tool.

Electrode Array Design and Fabrication Process

Referring to FIG. 4, an electrode array specification and fabrication system 400 analyzes a three dimensional topology of a subject's face to generate an electrode array specification. The system then fabricates the electrode array 101 of the flexible electromyography device 100 based on the array specification. The specification and fabrication system 400 includes a three dimensional scanner 420, a computer-implemented electrode array specification generation module 422, and an electrode array fabrication system 424. The three dimensional scanner 420 performs a scan of the subject' s face and generates a data representation of the topology of the subject' s face. Such a topology can be derived from a 3D photograph or video and can produced using commercially available cameras or smart phones such as the IPHONE® smart phone available from Apple Inc. of Cupertino, California. The data representation of the topology of the subject' s face is provided to a computer running the electrode array specification generation module 422. The electrode array specification generation module 422 generates a specification of the electrode array 101 based on the data representation of the topology of the subject' s face and models of underlying muscle locations. The generated specification is passed to the electrode array fabrication system 424, which generates the electrode array 101 according to the specification.

In some examples, the system 400 of FIG. 4 can be configured to fabricate a device that simplifies proper positioning and re-positioning of the flexible electromyography device 100 on the subject's face in order to ensure accurate EMG measurements or muscle stimulation. For example, the data representation of the topology of the subject' s face can be used to fabricate a three dimensional facial mask that has openings at specific locations. The openings in the three dimensional mask indicate where the flexible electromyography device (or any other

electromyography electrodes) should be placed on the subject' s face. The openings simplify device placement for subjects who need to place the flexible electromyography device 100 on their face when they are not in the presence of medical professionals. For example, the mask can be used by a patient at the beginning of each rehabilitation session to ensure that the electrodes are positioned at exactly the same location for each session. This allows for a more precise comparison with past data (e.g., from previous rehabilitation sessions) and a more accurate progress report.

In another example, the mask can include printed outlines approximating the positions of one or more electromyography device. The subject can either place the devices within the mask (e.g., when the mask is lying on table or other surface) and then place the mask on the subject' s face (e.g. , by lowering the subject's face into the mask) or place the mask over the subject's face after application of the devices to confirm proper positioning. Such a mask can be transparent or translucent and can be fabricated using a variety of techniques including 3D printing. In still another example, a transparent or translucent mask substantially conforming the subject's face can be provided. After placement of the array(s) on the subject' s face during a first session, the mask can be placed on the subject' s face over the array(s), and the locations of the arrays can be drawn on the mask using marking pen in order to facilitate proper placement in later sessions. The locations and shapes of one or more muscles can be preprinted on the mask so that the subject knows which muscles she is activating.

The masks described herein can include one or more marks adapted and configured to facilitate proper placement of the mask and the underlying arrays. Examples of such markings include one or more lines connecting the eyes or printed quadrants.

In some examples, use of such a mask allows for standardization of the shape of the electrode array 101 for each muscle group (e.g., muscle groups of FIGS. 1(a), 1(b),

and 7(a)-7(d)) so that the layout of the electrodes closely tracks the shape and size of any muscle targeted by a subject of activated electrodes. With standardized electrode arrays, only the angle and/or the orientation of the array needs to be adjusted to accommodate different facial features. It is also possible to only use a subset of electrodes within an array so that only the electrodes that are aligned with the muscle fibers of a specific muscle are used. Such an approach would reduce muscle cross talk, enhance muscle selectivity, and minimize adjustments to the arrays.

Referring to FIG. 5, one example of the electrode array fabrication system 424 performs a number of steps to fabricate an electrode array according to the specification. In general, the electrode array fabrication system 424 follows a fabrication protocol including a two mask photolithography process, a vapor deposition of Parylene C, a sputtering deposition, and a reactive ion etching.

In step (A), 5- 100 μπι of Parylene C vapor is deposited from a monomer (e.g., a wafer made of silicon or another substrate compatible with photolithographic processing) 526 at room temperature. The resulting layer of Parylene C 528 is an optically transparent, flexible and insulating base for the devices, on top of which the metallic structures can be patterned.

In step (B), a thin layer (e.g. , about 3 μπι) of positive photoresist is spun over the

Parylene C layer 528. Portions of the photoresist are exposed to a light pattern which is specified by the device specification, causing the exposed portions of photoresist to degrade. The photoresist is then developed, stripping the degraded portions of photoresist to expose the underlying Parylene C layer 528. A thin film (e.g. , about 30 nm) of chromium or other metals and a thin film of a conductive metal (e.g., gold, titanium, platinum, or silver) 530 are then sputtered onto the wafer. The chromium layer is deposited to promote adhesion between

Parylene C layer and the metal 530. In some examples, no additional adhesion treatment is required. The wafer is then sonicated in an acetone bath until the metal lifts off, delineating the geometry of the device (i.e. recording electrodes, conductive lines, and connection pads). Step (B) shows the resulting wafer after sonication. The metal layer can, in some embodiments, have a thickness between about 100 nm and about 150 nm, between about 150 nm and about 200 nm, between about 200 nm and about 250 nm, between about 250 nm and about 300 nm, between about 300 nm and about 350 nm, between about 350 nm and about 400 nm, and the like.

In step (C), a second insulating layer (e.g., about 1 μπι or more) of Parylene C 532 is deposited on the whole wafer to encapsulate all of the patterned metallic structures. In step (D), portions of Parylene C on the wafer are selectively removed from the areas of the wafer corresponding to the electrode sites and the connection pads, while leaving the conductive traces coated. To do so, another photoresist layer is spun onto the second insulating layer of

Parylene C 532. Portions of the photoresist are exposed to a light pattern, which is specified by the device specification, causing the exposed portions of the photoresist to degrade. The photoresist is then developed, stripping the degraded portions of photoresist to the underlying second insulating layer of Parylene C 532. Next, a thin layer (e.g., about 150 nm) of copper (or another suitable metal) 534 is sputter deposited over the pattern defined by photolithography. Once the photoresist is stripped in an acetone bath, the copper layer 534 acts as an excellent etch mask.

In step (E), the wafer is subjected to a reactive ion etch in oxygen plasma. The plasma etch is carried out until Parylene C is completely removed not only from the recording electrodes and the connection pads, but also from the area surrounding the devices to define their final shape. After a quick copper wet etch in standard acid metal etching chemistries, the devices are ready to be manually peeled off the wafer as is shown in step (F). In some examples, no additional sacrificial release layer is needed; adhesion of the Parylene C to the silicon is sufficient for processing, but the devices can be manually peeled from the surface without damage. In some examples, the exposed area of the gold electrodes is designed to be slightly smaller than that patterned via photolithography to guarantee an effective Parylene C

encapsulation.

In another example of the electrode array fabrication system 424, rather than depositing metal(s) after defining the geometry of the devices via photolithography, a thin, pre-fabricated parylene or metal mask is placed on the substrate before sputter deposition, directly defining the geometry of the devices and eliminating the need of the photolithography step. Similarly, rather than creating a metal etch mask using photoresist and sputter deposition, a thin, pre-fabricated and custom made metal etch mask is placed on the substrate before the reactive ion etch in oxygen plasma is performed.

In some examples, the plasma etch is performed only until Parylene C material is removed from the recording and interconnecting pads. In this case, the devices can be laser or manually cut out of the substrate. For example, a plurality of arrays can be fabricated in single substrate, before the substrate is cut to form a plurality of devices. Additionally, the shape of the substrate can be modified at any point to fit the particular anatomy of the subject (e.g., with scissors).

Referring to FIG. 6, one example of a fabricated electrode array 101 includes a

Parylene C layer 638 in which electrodes 104 are embedded. In some examples, a conductive gel 640 is placed on an exposed portion of the electrodes 104 to minimize skin-electrode impedance. In some examples, an adhesive layer 642 is disposed on an outer surface of the

Parylene C layer 638 to guarantee adhesion to a subject's skin, (self-adhesive electrode arrays)

As depicted in FIG. 12, the electrode array can be removed and reapplied to the subject to enable repositioning. Although medical tape is visible at the edges of the device, the medical tape is not necessary for adhesion. Form Factor

Referring now to FIGS. 8 and 9, the form factor of an electrode array and an individual electrode is depicted. As can be seen, the electrode arrays can have a variety of configurations with respect to the lead wires connecting each electrode to a controller. For example, electrodes can have a branched pattern with respect to lead wires extending laterally from the center of the array as seen in the left panel. In another example, the electrodes extend substantially laterally to each side of the wires as seen in the top and bottom panels on the right side of FIG. 8. In still another example, the electrode can extend to one side of the lead wires as seen in the right center panel of FIG. 8. In FIG. 9, embodiments of the invention are depicted in panels (B) and (D) and contrasted with conventional electrodes depicted in panels (A) and (C).

Detection of Various Facial Expressions

Referring now to FIGS. 15(a)-15(d), EMG signals captured from an electrode array placed on the subject's forehead are provided. The voltages generated during upward movements of the eyebrows in FIG. 15(a), surprised expressions in FIGS. 15(b) and 15(c), and low intensity upward movements of the eyebrows in FIG. 15(d) are visibly distinct.

Non-Facial Applications

Although aspects of the invention are described primarily in the context of facial electrodes, aspects of the invention can also be applied to monitor and stimulate other muscles throughout the body. For example, FIG. 16 depicts voltage signals obtained from electrodes positioned over the wrist flexor muscles.

Alternatives

In some examples, the substrate material is a material other than Parylene C but still having suitable mechanical, electrical, and chemical properties. One exemplary material is polyimide.

In some examples, the electrodes are fabricated using materials other than gold, such as silver or platinum, which still have suitable properties for use as an EMG electrode.

In some examples, wired, and not wireless communication is used to communicate between the flexible electromyography device and the electromyography workstation.

In some examples, the electromyography system used above can be used for other application such as lie detection and biomechanics research.

Implementations

Systems that implement the techniques described above or portions of the techniques described above can be implemented in software, in firmware, in digital electronic circuitry, or in computer hardware, or in combinations of them. The system can include a computer program product tangibly embodied in a machine-readable storage device for execution by a programmable processor, and method steps can be performed by a programmable processor executing a program of instructions to perform functions by operating on input data and generating output. The system can be implemented in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language. Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, a processor will receive instructions and data from a readonly memory and/or a random access memory. Generally, a computer will include one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application- specific integrated circuits).

It is to be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention, which is defined by the scope of the appended claims. Other embodiments are within the scope of the following claims.

Other Embodiments

From the foregoing description, it will be apparent that variations and modifications may be made to the invention described herein to adopt it to various usages and conditions. Such embodiments are also within the scope of the following claims.

The recitation of a listing of elements in any definition of a variable herein includes definitions of that variable as any single element or combination (or subcombination) of listed elements. The recitation of an embodiment herein includes that embodiment as any single embodiment or in combination with any other embodiments or portions thereof. All patents and publications mentioned in this specification are herein incorporated by reference to the same extent as if each independent patent and publication was specifically and individually indicated to be incorporated by reference.

Claims

1. An apparatus comprising:
a mechanically flexible substrate conformable to a subject's skin; and
an array of electrodes embedded within the mechanically flexible substrate, at least a first subset of the array of electrodes arranged in a pattern associated with a first predetermined set of muscles.
2. The apparatus of claim 1, wherein the first subset of the array of electrodes is
independently addressable from a second subset of the array of electrodes.
3. The apparatus of claim 2, wherein the second subset of the array of electrodes is arranged in a pattern associated with a second predetermined set of muscles.
4. The apparatus of claim 2, wherein the first subset of the array of electrodes have a first spacing and the second subset of the array of electrodes have a second spacing, the first spacing being different than the second spacing.
5. The apparatus of claim 2, wherein the first subset of the array of electrodes have a first density characteristic and the second subset of the array of electrodes have a second density characteristic, the density characteristics describing a quantity of electrodes within a defined area, the first density characteristic being different than the second density characteristic.
6. The apparatus of claim 2, wherein the mechanically flexible substrate includes:
a first region associated with the first subset of the array of electrodes and having a first flexibility characteristic; and
a second region associated with the second subset of the array of electrodes and a having a second flexibility characteristic, the first flexibility characteristic being different than the second flexibility characteristic.
7. The apparatus of claim 1, wherein the mechanically flexible substrate comprises one or more selected from the group consisting of: poly(p-xylylene) polymer and polyimide.
8. The apparatus of claim 1 further comprising:
a controller.
9. The apparatus of claim 8, wherein the controller includes a signal processor programmed to receive signals from the array of electrodes.
10. The apparatus of claim 8, wherein the controller includes a recording device.
11. The apparatus of claim 8, wherein the controller includes a signal generator programmed to provide signals to the array of electrodes.
12. The apparatus of claim 8, wherein the controller includes a biofeedback module programmed to generate and communicate signals to the array of electrodes based on others signals received from the array of electrodes.
13. The apparatus of any of claims 1-12, wherein the first predetermined set of muscles are facial muscles selected from the group consisting of depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and
sternocleidomastoid, and the electrodes are configured to record from one or more muscle fibers within said set of muscles.
14. A system for making a multi-electrode array, the system comprising:
an imaging device programmed to scan a portion of a body and generate a topology of the portion of the body;
a memory device adapted and configured to store the topology; and
a processor adapted and configured to load and execute computer program instructions to generate data representative of the apparatus according to claim 1, wherein the predetermined set of muscles is a set of muscles in the portion of the body.
15. The system of claim 14, wherein the computer program instructions include instructions for generating data specifying inter-spacing of the electrodes.
16. The system of claim 14, wherein the computer program instructions include instructions for generating data specifying density of the electrodes.
17. A method of making a multi-electrode array, the method comprising:
scanning a portion of a subject's body to generate a topology of the portion of the body; and
generating data representative of the apparatus according to claim 1, wherein the predetermined set of muscles is a set of muscles in the portion of the body.
18. The method of claim 17, further comprising:
fabricating a device based on the generated data.
19. The method of claim 17, wherein scanning the portion of the subject's body further comprises moving the portion of the subject's body to identify muscles associated with the portion of the body.
20. The method of claim 17, wherein the portion of the subject's body is a facial region of the subject.
21. The method of claim 20, wherein the muscles are selected from the group consisting of depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and sternocleidomastoid.
22. A method for selectively stimulating or recording from a muscle, the method comprising: applying the apparatus of claim 1 to a subject's skin so that the first subset of the array of electrodes lies over the first predetermined set of muscles.
23. The method of claim 22, further comprising:
receiving signals from the at least first subset of the array of electrodes.
24. The method of claim 23, further comprising:
recording the signals.
25. The method of claim 22, further comprising:
providing signals to the at least first subset of the array of electrodes sufficient to stimulate the first predetermined set of muscles.
26. The method of claim 22, wherein the array of electrodes is configured to selectively stimulate muscle fibers within a muscle selected from the group consisting of depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and sternocleidomastoid.
27. The method of claim 26, wherein the subject is in need of treatment for a disorder relating to the central nervous system.
28. The method of claim 26, wherein the subject is in need of treatment for a disorder selected from the group consisting of: stroke-related facial paralysis, facial droop, synkinesis, facial nerve paralysis, peripheral nerve injury, Bell's palsy, Parkinson's facial masking, dysphagia, speech impediments, myasthenia gravis, facial paralysis due to trauma, viral or infectious diseases, chronic tension headaches, and chronic pain.
29. The method of claim 22, wherein the first predetermined set of muscles include facial muscles.
30. The method of claim 29, wherein the method further comprises:
exposing the subject to a product or an advertisement; receiving signals from the apparatus associated with the facial muscles; and correlating the signals with an emotional response to the product or an advertisement.
31. The method of claim 22, further comprising:
providing audio or visual feedback to the subject regarding signals received from the apparatus.
32. The method of claim 31, further comprising:
instructing the subject to move one or more muscles.
33. A system comprising:
the apparatus of claim 1 ; and
a feedback device communicatively coupled to the apparatus.
34. The system of claim 33, wherein the feedback device includes an audiovisual display.
35. The system of claim 33, wherein the feedback device is programmed to provide quantified feedback regarding detected signals.
36. A method of treating a subject diagnosed with a disorder, the method comprising:
applying the apparatus of claim 1 to the subject's skin so that the first subset of the array of electrodes lies over the first predetermined set of muscles;
instructing the subject to move the first predetermined set of muscles; and
measuring electrical signals at the first predetermined set of muscles using the device; and
providing feedback to the subject regarding the electrical signals.
37. The method of claim 36, further comprising:
applying an electrical signal to the first subset of electrodes sufficient to stimulate the first predetermined set of muscles.
38. The method of claim 36, wherein the disorder relates to the central nervous system.
39. The method of claim 36, wherein the disorder is selected from the group consisting of: stroke-related facial paralysis, facial droop, synkinesis, facial nerve paralysis, peripheral nerve injury, Bell's palsy, Parkinson's facial masking, dysphagia, chronic tension headaches, and chronic pain.
40. A method of improving the appearance of a subject, the method comprising:
applying the apparatus of claim 1 to the subject's skin so that the first subset of the array of electrodes lies over the first predetermined set of muscles;
instructing the subject to move, and thereby tone, the first predetermined set of muscles; measuring electrical signals at the first predetermined set of muscles using the device; and
providing feedback to the subject regarding the electrical signals.
41. The method of claim 40, further comprising:
applying an electrical signal to the first subset of electrodes sufficient to stimulate the first predetermined set of muscles.
42. The method of any of claims 36-41, wherein the muscles are facial muscles selected from the group consisting of depressor supercilii, corrugator supercilii, medial palpebral ligament, nasalis, zygomaticus minor, zygomaticus major, masseter, buccinator, risorius, platysma, omohyoid superior belly, sternohyoid, frontalis, temporalis, procerus, orbicularis oculi, levator labii superius alaeque nasi, levator labii superius, depressor septi, orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis, and sternocleidomastoid.
43. A device for facilitating placement of the apparatus of claim 1, the device comprising: a mask having a shape complimentary to at least a portion of a human face; and one or more markings specifying a proper position of one or more of the apparatus of claim 1.
PCT/US2014/035291 2013-04-24 2014-04-24 Apparatus, systems, and methods for detecting or stimullating muscle activity WO2014176420A1 (en)

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