SKIN SCREW ELECTRODES
Electrodes providing excellent recording and physical stability. Electrodes are disclosed that may include a plurality of small teeth that possess a novel design shape and orientation. The shallow and relatively long teeth run parallel to the rim of the electrode that presses against the patient’s skin. When the electrode is twisted onto skin, the tiny teeth penetrate the stratum corneum and move nearly horizontally under the stratum corneum, thus anchoring the electrode securely to the skin. The electrodes cause minimal discomfort to the patient since the small teeth do not extend to the pain fibers which are located in deeper layers of the skin. The electrodes may be fabricated in a variety of geometries including cylindrical, disk, and blunt bullet or top shapes. In some instances, the electrodes may be connected to detachable leads having magnetic properties.
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This application is a divisional of U.S. Pat. Application No. 15/360,880 filed Nov. 23, 2016, which is a continuation-in-part of U.S. Pat. Application No. 15/282,828, filed Sep. 30, 2016 and U.S. Pat. Application No. 14/359,904, filed Aug. 26, 2014, which is a U.S. National Stage of International Patent Application No. PCT/US2012/024010, filed Feb. 6, 2012, which was published in English under PCT Article 21(2), which is a continuation-in-part of U.S. Pat. Application No. 12/012,607 (now U.S. Pat. No. 8,112,139), filed Feb. 4, 2008, and also claims the benefit of U.S. Provisional Pat. Application No. 61/562,483, filed Nov. 22, 2011. The entire disclosures of these applications are incorporated herein by referenced.FIELD OF THE INVENTION
The present invention relates to electrodes that are adapted for fast installation and stable implantation into the skin of a subject. The electrodes are useful for a variety of physiological recording and stimulation applications.ACKNOWLEDGMENT OF GOVERNMENT SUPPORT
This invention was made with government support under grant number EB013174 awarded by the National Institutes of Health. The government has certain rights in the invention.BACKGROUND OF THE INVENTION
The electrical nature of physiological processes has been known for over a century. The electrical components of neuronal activity and the contraction of muscles may be recorded using electrodes placed onto the surface or just below the surface of the skin. Furthermore, excitable tissues, such as nerves and muscles, may be stimulated electrically to achieve various physiological effects.
The electroencephalogram (EEG), as a commonly-utilized diagnostic tool, provides a unique window to observe the functional activity within the brain. Recent technological advances in electronic and computer systems have allowed over one-hundred EEG channels to be recorded simultaneously and modern signal and data processing techniques have provided new insights into the recorded data, both in the temporal and spatial domains. Similar advances have affected the techniques used to record other electrophysiological events in the body, such as electromyograhy (EMG). Recording of electrophysiological events in the body may be useful in diagnosing a variety of physiological disorders. For example, EEG allows for the non-invasive measurement of the electrical activity of the brain to diagnose epilepsy, sleep disorders, or determine the state of the brain during coma. By assessing the entry of a patient into a sleep state, EEG may also be used to maintain a state of arousal in a patient. EEG in the form of event related potentials (ERPs) is also commonly used in clinical neurophysiology to evaluate the functional or cognitive response of the central nervous system to a certain stimulus. Finally, EEG is currently being employed within systems that establish communication between the brain and an external device - so called brain-computer interfaces.
Despite the recent technological advances and the large number of potential applications, affixing EEG recording electrodes onto the scalp of a subject requires a manual procedure which is a long, difficult process for both the EEG technician as well as the subject. Hair on skin will hinder the ability of the electrode to adhere to the patient. Because of body heat drying the electrolytic gel, the electrode impedance will increase over time. In addition, due to body motion, snagging of the wire leads, and deterioration of the adhesive, electrodes will often disengage. In light of these difficulties, the labor and facility usage costs for electrode installation have been a significant portion of the total cost of clinical EEG studies and have significantly hindered the acceptance of large-array EEG in clinical applications. In addition, some applications require improved electrical access that may be obtained chiefly through the insertion of needle electrodes under the skin. The insertion may be quite painful for the patient and is accompanied by a variety of concerns regarding the safety of the patient.
An additional difficulty encountered during EEG is in the stability of electrode attachment to the body. The electrode is connected to a wire lead which in turn runs to the signal recording device. Because of the natural movements of the patient, the wire leads will often become tangled and pulled by the patient. The electrode will subsequently be pulled off of the skin and require reattachment. The wire leads of common EEG electrodes can also act as tethers which limit the movement of the patient, which in turn limits the potential application of EEG and EMG.
Prior work has attempted to address some of the deficiencies of EEG electrodes. For example, U.S. Pat. Nos. 6,175,753 and 6,201,982 to Menkes et al. discloses quick-placement EEG electrodes. The electrodes disclosed in those patents attempt to avoid the problems associated with hair on the patient by actually attaching the electrode to the hair of the patient, thereby stabilizing the electrode. The electrodes disclosed by Menkes et al. also include a sponge that replenishes the electrolytic gel for prolonged applications. Nevertheless, the electrodes would still suffer from some of the shortcomings of the prior art, including inconsistent electrical contact with the skin due to eventual drying of the electrolyte solutions, physical instability of the electrode, and clinical feasibility of allowing a large number of electrodes to be affixed to the scalp rapidly.
Thus, there has been a long-standing need for electrodes that may be quickly and securely placed on a patient without requiring shaving of the skin or administration of adhesive. In addition, typical electrode administration often employs an abrasion step where a layer of the skin is worn off to improve the signal. Such procedures are time consuming and are often uncomfortable for the patient. The electrodes would preferably be stable after implantation and provide excellent electrical contact to the skin for both recording and stimulation of the tissue in the area of the electrode, with or without the use of electrolytic gels.
For the present invention to be clearly understood and readily practiced, the present invention will be described in conjunction with the following figures, wherein like reference characters designate the same or similar elements, which figures are incorporated into and constitute a part of the specification, wherein:
The present invention is directed to recording and stimulating electrodes that are easily and stably attached to the skin. The present invention provides a simple, effective, and low-cost design that solves many of the traditional problems associated with the installation of an electrode onto the hairy skin of human and animal patients. The electrodes of the present invention may include small teeth that possess a novel design shape and orientation. The teeth may be fabricated from a hard metal or other material, as well as be coated or electroplated with a conductive metal or other material to promote effective electrical access through the patient’s skin. The electrodes of the present invention may optionally include a rubber ring that covers and protects the electrode teeth when the electrode is not in use.
The plurality of shallow and relatively long teeth preferably runs parallel to the rim or surface of the electrode so that they are able to penetrate the patient’s skin effectively, but only to a relatively shallow depth. When the electrode is twisted onto skin, the tiny teeth penetrate the stratum corneum and move nearly horizontally with respect to the skin surface under the stratum corneum, thus anchoring the electrode securely to the skin. As such, the electrodes of the present invention preferably do not cause pain because the small teeth do not extend to the pain fibers which are located in a deeper layer of the skin, yet the electrodes provide for excellent electrical access to the interior of the body as well as tremendous physical stability. The electrodes of the present invention may be cylindrical, disc-shaped, or shaped in the form of a blunt bullet or top.
In some embodiments, magnetic leads are used to connect the electrodes electrically with signal processing equipment. The magnetic leads may connect to the cap of the electrodes of the present invention that are fabricated from a metal having magnetic properties. In some embodiments, the cap of the electrode may include a socket where a circular magnetic lead may be inserted to establish electrical connection between the lead and the electrode. The circular magnet lead may be fabricated from a metal or ceramic material. If the material is ceramic, it is preferably coated with a metal, such as gold, to ensure adequate electrical contact between the electrode and the lead.
Because of their superior physical stability, the electrodes of the present invention are well suited to house electronic components that may accomplish a wide variety of tasks. For example, the electrodes of the present invention may include sensors designed to measure blood oxygenation, blood glucose levels, or other common physiological variables. The electrodes the present invention may also be used wirelessly either singularly or as an array so that no electrode leads extend away from the patient’s body, thereby reducing the annoyance of the electrode assembly for the patient. Implementation of the present invention is particularly appropriate for situations where numerous electrodes are commonly used, such as EEG or EMG recordings.
The electrodes of the present invention may be fabricated either as a single integrated unit or as a multi-component system depending on the specific demands of the application. In certain embodiments, the electrodes of the present invention may be fabricated using precision photo-chemical etching techniques that are well known in the art.DETAILED DESCRIPTION
It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the invention, while eliminating, for purposes of clarity, other elements that may be well known. The detailed description will be provided hereinbelow with reference to the attached drawings.
The present invention provides electrodes that may be quickly and stably attached to a patient’s skin. The electrodes of the present invention do not require any pre-treatment of the skin to be applied and as such represent a significant improvement over the prior art. In addition, the electrodes of the present invention may be applied to hairy skin (e.g., scalp) of a patient. Insofar as the present invention has general applicability, as used herein, “patient” refers to both human and animal subjects who either have a medical condition or are healthy. The electrodes of the present invention provide superior physical stability and electrical access to the skin of the patient, thus representing a significant improvement over the prior art. The electrodes of the present invention may be employed both as stimulating electrodes and recording electrodes as detailed hereinbelow.
The electrodes may possess a variety of shapes and geometrical configuration of the teeth. The general structure of an electrode 100 of the present invention is shown in
A higher resolution of the proximal rim of the electrodes of the present invention is shown in
As seen in
The teeth 116 may be of a length and angle such that they are capable of penetrating the epidermis to just past the level of the stratum corneum. The specific length, shape, and angle of the teeth 116 of the electrodes of the present invention may be varied widely, with embodiments where the teeth 116 penetrate the epidermis past the stratum corneum, though preferably not to the level of pain fibers. Orientation at such a slight angle from the surface of the electrode limits the penetration depth of the teeth 116 of the present invention is limited, thereby drastically reducing discomfort for the patient. Additionally, the plurality of teeth 116 forms a sturdy attachment to the skin through the interaction with the stratum corneum. When piercing the skin (particularly the scalp), the electrodes of the present invention should be applied quickly to minimize the discomfort to the patient.
By piercing the stratum corneum and reaching the water-containing portions of the epidermis below, the electrodes of the present invention also provide excellent electrical access to the patient with electrode impedance on the order of 5 kΩ being commonly observed without use of any electrolytic gels. The electrodes of the present invention may also be used with electrolytic gels to improve impedance as the particular situation warrants. In those instances where an electrolytic gel is used, the electrodes of the present invention may be pressed and turned lightly into a sheet of hydrogel that contains an amount of ionic electrolyte compound
The shape, size, and material properties of the teeth may be varied in the design of the electrodes of present invention. Since the teeth are typically very small, the material from which the teeth are fabricated is preferably be both sufficiently hard and stress resistant so that the teeth will not bend or break off during electrode installation. Stainless steel alloy may be effectively employed in fabricating the electrodes of the present invention in that it achieves an appropriate hardness after annealing. In certain embodiments, the steel alloy includes a sufficient amount of iron to achieve magnetic permissibility for lead wire connection as described below. In other embodiments, the teeth may be coated or electrochemically plated with a conductive metal (e.g., gold or silver) to improve the electrical properties of the electrodes.
In order to improve performance, the electrode teeth may be coated or electroplated with a material of low half-cell potential (e.g., silver-silver chloride), an anti-oxidation metal (e.g., gold), or a high electron-transfer material (e.g., iridium). The electrodes may be fabricated as a single unit made entirely from one type of material. In other embodiments described below, the body of the electrode may be made of multiple components including plastic or other non-conductive materials. In some embodiments, the teeth of the electrode may include a nickel-containing alloy (e.g., stainless steel). To reduce the likelihood or severity of reactions in patients who are allergic to nickel, the teeth of the electrodes of the present invention may be coated with a metal or conductive metal oxide. The electrodes of the present invention may be synthesized from a material that is either disposable or autoclavable, thus eliminating cross-infection potential in human applications.
In some embodiments of the present invention, the electrodes possess the approximate external dimensions of prior art EEG electrodes (on the order of 1 centimeter). However, alternative dimensions that are tailored to the specific application may also be employed. For example, if electrodes are to be used on a small patch of skin, a small animal, or applied using an automatic tool, the diameter of the electrode could be reduced.
The application of the electrode to a patient’s skin may be made by slightly pressing towards the body while turning the electrode 100 clockwise as shown in
In many prior art electrodes, the electrode lead is permanently connected to the electrode. As the number of electrodes installed on the scalp, for example, increases, the space above the head becomes cluttered with wires. In addition, when an electrode lead is accidentally pulled, the electrodes may separate from the scalp requiring a complete re-installation. The present invention overcomes these limitations. In certain embodiments, a magnetic disk glued to a brass plate makes electrical contact between the wire lead (which may be soldered to the brass plate) and the electrode as shown in
The electrodes of the present invention may also implement a magnetic lead 400 in a different manner. The wire lead 404 may be soldered 406 to a magnetic sphere 408 as shown in
The electrodes of the present invention may also include a rubber ring 460 that surrounds the base of the electrode as shown for a disk-like electrode body in
An additional embodiment of the electrodes of the present invention is shown in
The “blunt bullet” type electrodes may be formed using a single strip of metal. For example, a strip of metal 570 that includes the electrode teeth may be fabricated using the commonly known technique of photochemical etching (or photochemical milling). After a protection film is formed on desired portions of the sheet, a series of chemical etching will be utilized to form the microscopic teeth of all electrodes simultaneously. Next, each strip 570 will be peeled from the sheet and rolled precisely together with a spacer sheet 574 (which has the same shape but no teeth), as shown in
Since the electrode design of the present invention provides an electrically-shielded space inside the electrode, electronic circuits may be placed within this space, converting the passive electrode into an active device. The signal may be amplified through an amplifier within the interior of the electrode where the outer rim is grounded, thus providing an ideal shield from exterior interference. The interior space may also contain a small battery and a telemetric circuit (e.g., RF, infrared, or BLUETOOTH), providing power and transmitting a single channel to a nearby receiver (e.g., a cell phone, PDA, other hand-held electronic device, or receiver attached to a recording device). An example of the circuitry that made be used with the electrodes of the present invention is shown in
While the implementation of the present invention shown in
In other configurations, electrodes 620 could be placed in a star pattern (
As described above for the blunt bullet-shaped electrode, cylindrical electrodes may also be fabricated using a similar technique. The electrode rim that includes the electrode teeth 704 may be fabricated using the commonly known technique of photochemical etching (or photochemical milling). The repeating pattern of teeth 804 (as also shown in
In other embodiments, the constraining wall may be formed from a plastic mold. In those embodiments, the metallic strip may include holes in the body of the strip where plastic could flow during molding, thereby forming a strong connection between the two components once the plastic dries. One of skill in the art will recognize variations of these methods for the fabrication of the electrodes of the present invention, such as negative etching or standard high-precision machining.
Although the electrodes of the present invention may be applied manually, in cases where a large number of electrodes need to be installed, the electrode technician might hand-pick individual electrodes from a container which takes a significant amount of time. In addition, it is often desirable to know the exact coordinates of the electrodes on the patient’s body (e.g., scalp) relative to a known reference point. Although these coordinates can be acquired using a Polhemus sensor, such processes are time consuming for the administration of a large number of electrodes. In order to address these issues, the present invention may also include a “volley gun″-like electrode installation device. Since the electrodes of the present invention need not have leads attached prior to installation, a pack of electrodes of identical size may be loaded into the electrode installation device, greatly reducing the time between electrode installations. The electrode installation device may also be equipped with a coordinate sensor, e.g., similar to a Polhemus sensor, to record the coordinates of each electrode as it is installed on the patient’s skin, taking little extra time during operation.
An example of the electrode installation device 900 is shown in
The electrodes of the present invention may be used for various physiological recording techniques such as traditional EEG, EKG, EMG, and other electrophysiological applications. The present invention may also be used in other applications where the device is not used as an electrode. Because of the strength with which the electrodes may be attached to the skin, they may be used to anchor another device onto the skin more securely than by employing standard adhesive tape. For example, when equipped with the appropriate electronic components, the electrodes of the present invention may be used to assess a variety of additional physiological measures such as blood oxygenation and blood glucose levels. With a leak-preventive seal, a liquid-form drug may be stored within the chamber of the device and delivered transcutaneously. Drug delivery may also benefit from electrically induced and controlled electroporation in which a transcutaneous current is utilized to open microscopic channels through which drug may be delivered through the skin in a desired amount.
The electrodes of the present invention may also be used to stimulate muscle tissue. Microcurrent stimulation of muscles may be employed to treat age-related macular degeneration, wound healing, tendon repair, and ruptured ligament recovery. Further, the present invention may be used to stimulate muscle to improve their strength such as in patients suffering from osteoarthritis or to preserve muscle tone and mass during extended periods of disuse such as coma or surgery recovery. Electric simulation of muscles may also be utilized to mimic the effect of exercise in weight management.
The electrodes of the present invention may be connected to a variety of electronic components to enable a diversity of technical and medical implementations. Examples include: 1) a game system controlled by the EEG patterns of the player, where those EEG signals are measured using electrodes of the present invention; 2) a robotic system that serves a paralyzed patient by employing measurements of patients’ EEG and EMG signals assessed through the electrodes of the present invention; 3) an ambulatory EEG recorder employing electrodes of the present invention for emergency medical care; 4) an automatic drowsiness monitor for motor vehicle drivers; and 5) a diagnostic tool for animals in a veterinary setting. The wireless design of the present invention greatly facilitates a number of specialized experimental applications, such as unconstrained neurophysiological monitoring during behavior, where it is preferred for animal or human subjects to have free range of motion within an environment. Those of skill in the art will recognize that numerous modifications of the above-described process can be performed without departing from the present invention. For example, modification of the specific geometry and spacing of the teeth of the electrodes and variation of the electronic components coupled to the present invention are considered to be within the scope of the present invention.Example Flexible Electrode
In typical applications, electrodes are applied to rough, curved, or other non-planar surfaces and some flexing of the electrodes or the support to which electrodes are mounted is desirable. With some flexibility, electrodes can be better secured to a patient, achieve low electrical resistances, and reduce any tendency for the electrodes to break.
With respect to
As shown in
In another example shown in
Representative fine teeth or hooks for connection to a top layer of skin (stratum corneum) or other surface are shown in
In the example of
With respect to
Only two teeth are shown in
In another example shown in
1. A method, comprising
- applying an etchant-resistant chemical to a surface of a sheet of conductive material in a pattern that includes a plurality of flexible electrode extensions and a plurality of teeth on the flexible electrode extensions, wherein each of the teeth face a first direction; and
- etching the patterned sheet of conductive material so as to define an electrode so that the plurality of flexible electrode extensions and the plurality of teeth on the flexible electrode extensions are situated on and extend outward from a distal edge of the electrode.
2. The method of claim 1, wherein the patterned sheet of conductive material is etched so that a proximal edge of the electrode is planar.
3. The method of claim 1, wherein the flexible electrode extensions are boot shaped portions of the conductive sheet that face a second direction.
4. The method of claim 3, wherein the first direction is opposite the second direction.
5. The method of claim 3, wherein the first direction is the same as the second direction.
6. The method of claim 2, further comprising forming the etched and patterned conductive material into a cylindrical section about an axis such that a surface of the proximal edge is perpendicular to the axis.
7. The method of claim 6, wherein first direction is a first azimuthal direction with respect to the axis with the etched and patterned conductive material formed into the cylindrical section.
8. The method of claim 7, wherein the flexible electrode extensions are boot shaped portions of the conductive sheet and face a second azimuthal direction with respect to the axis with the etched and patterned conductive material formed into the cylindrical section.
9. The method of claim 8, wherein the first azimuthal direction is opposite the second azimuthal direction.
10. The method of claim 8, wherein the first azimuthal direction is the same as the second azimuthal direction.
11. The method of claim 1, wherein each of the flexible electrode extensions defines a first open-ended gap and a second open-end gap facing opposite directions.
12. The method of claim 1, wherein electrode extensions are arc-shaped and define and surround respective apertures.
13. The method of claim 1, wherein electrode extensions are arc-shaped and define and surround an open-ended gap.
14. The method of claim 1, wherein the flexible electrode extensions face outward from the distal edge and along the distal edge at an angle of between 0 and 10 degrees with respect to the distal edge.
15. The method of claim 14, wherein each of the plurality of flexible electrode extensions includes a respective arcuate distal surface having a plurality of teeth.
16. The method of claim 1, wherein the etching the patterned sheet of conductive defines a plurality of electrodes having flexible electrode extensions and respective pluralities of teeth on the flexible electrode extensions.
17. The method of claim 6, further comprising securing the cylindrical section to a disk substrate at the proximal edge.
18. The method of claim 17, wherein the teeth are between 30 µm and 50 µm high at are at an angle of between 2 degrees and 5 degrees with respect to the disk substrate.
19. The method of claim 17, wherein the teeth have a depth of less than 1.0 mm.
20. The method of claim 11, wherein at least one conductive nanowire is situated on each of the teeth.
Filed: Apr 24, 2023
Publication Date: Aug 17, 2023
Applicant: University of Pittsburgh - Of the Commonwealth System of Higher Education (Pittsburgh, PA)
Inventors: Mingui Sun (Pittsburgh, PA), Wenyan Jia (Wexford, PA), Robert Joseph Sclabassi (Gibsonia, PA)
Application Number: 18/306,164