Patent Publication Number: US-8538502-B1

Title: Method and device for quick press on EEG electrode

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The Present Application is a divisional application of U.S. patent application Ser. No. 13/607,693, filed on Sep. 8, 2012, which is a continuation application of U.S. patent application Ser. No. 13/475,890, filed on May 18, 2012, now U.S. Pat. No. 8,271,065, issued on Sep. 18, 2012, which is a continuation application of U.S. patent application Ser. No. 13/366,331, filed on Feb. 5, 2012, now U.S. Pat. No. 8,185,183, issued on May 22, 2012, which is a continuation application of U.S. patent application Ser. No. 12/125,802, filed on May 22, 2008, now U.S. Pat. No. 8,112,141, issued on Feb. 7, 2012, which claims priority to U.S. Provisional Application No. 60/939,523, filed May 22, 2007, now abandoned, all of which are hereby incorporated by reference in their entireties. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to methods and systems for monitoring bioelectric potentials. In some instances, an electrode is applied to a patient&#39;s skin. The electrode may be at least partly inserted into the patient&#39;s skin, such as by inserting at least part of one or more teeth underneath the skin. 
     2. Description of the Related Art 
     The prior art discusses Electroencephalography (EEG), a major clinical diagnostic tool used to evaluate cerebral function in humans. Briefly, one or more electrodes placed on the scalp detect electrical activity produced by the brain. This activity is transmitted to amplification and/or recording devices. The electrical activity is produced by the summation of neural activity across a plurality of neurons. Thus, monitoring of the amplitude and temporal dynamics of the electrical signals provides information about underlying neural activity and medical conditions associated with this activity. 
     For example, EEGs are commonly used to evaluate seizures, such as determining whether a seizure is an epileptic seizure or to localize the place of origin of the seizure within the brain. In another example, EEGs can be used to monitor sleep states or anesthesia depths. The neurobiological sciences are also using EEGs as a non-invasive research tool. 
     It may be necessary to keep the electrodes on for significant periods of time, such as during sleep monitoring. Additionally, because EEG monitoring usually comprises signals from multiple electrodes, each of a plurality of electrodes may need to be simultaneously secured to a patient&#39;s scalp. Furthermore, in some instances, the electrodes should maintain contact with the patient&#39;s scalp despite movement, such as that which may occur during a seizure. Therefore, there is a need to ensure that the EEG monitoring systems are stable and easy to use. 
     BRIEF SUMMARY OF THE INVENTION 
     In some embodiments, an electrode is provided, the electrode comprising a main portion; a plurality of legs extending from said main portion; and a plurality of protrusions extending from each of said legs. 
     In some embodiments, an electrode system is provided, the system comprising: a plurality of electrodes, each of the electrodes comprising a main portion; a plurality of legs extending from said main portion; and a plurality of protrusions extending from each of said legs; and support structure to support the plurality of electrodes, wherein said system is configured to be worn on a patient&#39;s head. 
     In some embodiments, a kit is provided, the kit comprising a plurality of electrodes, each of the electrodes comprising a main portion; a plurality of legs extending from said main portion; and a plurality of protrusions extending from each of said legs; support structure to support the plurality of electrodes; a wireless transmitter; and a receiver configured to receive signals from the wireless transmitter, wherein said system is configured to be worn on a patient&#39;s head. 
     In some embodiments a method for recording biopotentials is provided, the method comprising: inserting part of an electrode into a patient&#39;s skin; and receiving a plurality of biopotentials by the electrode. 
     In some embodiments, an electrode is provided, the electrode comprising a plurality of protruding portions configured to stabilize the electrode upon attaching the electrode to a patient, wherein the electrode comprises a shape-memory material. 
     In some embodiments, an electrode system is provided, the system comprising: an applicator; and the electrode comprising a plurality of protruding portions configured to stabilize the electrode upon attaching the electrode to a patient, wherein the electrode comprises a shape-memory material. 
     Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a top view of an example of an electrode according to one embodiment. 
         FIG. 2  is a top view of the electrode of  FIG. 1  inserted in skin of a human. 
         FIG. 3  is a top view further illustrating the teeth of an electrode such as illustrated in  FIG. 1 . 
         FIG. 4  is a bottom view further illustrating one embodiment of an electrode such as illustrated in  FIG. 1  in a device for applying the electrode. 
         FIG. 5  is a top view of another example of an electrode according to one embodiment. 
         FIG. 6  illustrates a process for recording biopotentials. 
         FIG. 7  shows a system for recording biopotentials. 
         FIG. 8A  illustrates a biopotential recording system and electrode components in the system. 
         FIG. 8B  illustrates a front view of a biopotential recording system and electrode components in the system worn on a user&#39;s head. 
         FIG. 8C  illustrates a top perspective front view of a biopotential recording system and electrode components in the system worn on a user&#39;s head. 
         FIG. 8D  illustrates a top perspective rear view of a biopotential recording system and electrode components in the system worn on a user&#39;s head. 
         FIG. 8E  illustrates a top perspective front view of a biopotential recording system and electrode components in the system worn on a user&#39;s head. 
         FIG. 8F  illustrates an isolated exploded view of an electrode component of a biopotential recording system and electrode components in the system. 
         FIG. 8G  illustrates an isolated view of an electrode component of a biopotential recording system and electrode components in the system. 
         FIG. 8H  illustrates an isolated view of an electrode component of a biopotential recording system and electrode components in the system. 
         FIG. 9A  illustrates an example of an electrode and an applicator according to one embodiment. 
         FIG. 9B  illustrates an example of an electrode and an applicator according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Typically, an EEG is made in contact with the scalp by first abrading the scalp with a gritty paste in order to lessen the skin&#39;s intrinsic electrical impedance, and then applying a conductive gel-containing or gel-filled electrode to the scalp. The electrode is then held in place by an adhesive. However, obtaining a stable electrode interface with good recording properties is a technically demanding process, a process that has required a trained EEG technologist in order to obtain recordings of satisfactory quality for clinical interpretation. Also, the successful application of EEG recoding electrodes is a time-consuming and thus expensive process, even for highly skilled EEG technologists. Small needles placed just under the skin (subdermal needles) have also been used for EEG recordings, but these too are time consuming to place, and their insertion induces a moderate amount of discomfort in patients who are not deeply obtunded or comatose. The difficulties involved in obtaining a satisfactory EEG electrode connection to the patient have limited the settings and scope of EEG recording, and in particular have limited the presence of EEG recording in intensive care units, emergency rooms, and emergent field settings, all locations in which evaluations of brain activity can provide diagnostically and therapeutically useful information. 
     Embodiments disclosed herein relate to electrodes that penetrate into the patient&#39;s skin in order to both provide attachment of the electrode to the patient and enhance transmission of biopotentials to external amplification and recording devices. Embodiments further provide a recording electrode which is durable and can be applied without skin preparation and without the use of conductive electrolyte gels. 
     The quality of EEG recordings (and biopotential recordings in general) can be degraded due to properties of the skin. The skin is composed of two primary layers, the dermis and epidermis; the hypodermis, a region of loose connective and adipose tissues connecting the epidermis and dermis to the underlying structures, is also sometimes considered as the third and deepest layer of the skin. 
     The epidermis, or outmost layer, is only, on average, about 50 microns thick on the scalp and consists of several stacked layers: deepest is the stratum basale, over which lies, in ascending order towards the surface, the stratum spinosum, stratum granulosum, stratum lucidum, and finally, abutting air, the stratum corneum. 
     The most superficial layer—the stratum corneum—has a high electrical impedance, which can act to reduce the amplitude of potentials recorded for an EEG. The stratum corneum (and the stratum lucidum) do not contain living cells and are largely responsible for the protection of the underlying skin layers from damage. Additionally, when a patient moves, the electrically charged nature of the skin can cause fluctuations in the skin&#39;s intrinsic electrical potential, thereby interfering with the signals of interest. The skin layer associated with movement-related alterations of the skin&#39;s electrical potential appears to be in the region of the thin stratum granulosum. 
     The dermis lies beneath the epidermis, and, at 1,000-2,000 microns thick, accounts for most of the mass of the skin. The dermis can be subdivided into two layers: the papillary layer and the reticular layer. The thin papillary layer sits just beneath the epidermis, and is composed of many connective tissue cells, blood-conveying microscopic capillaries, and collagen fibers. It is of note that the overlying epidermis does not contain blood-conveying vessels. Deep to the dermal papillary layer is the reticular layer of the dermis, a thicker and less cellular region that contains abundant collections of collagen fibers as well as the blood-conveying capillaries, arterioles, and venules. Nerve fiber endings mediating the sensations of touch, vibration, temperature sensation, and pain are present in both the dermis and in the epidermis. These nerve endings extend to about the boundary between the stratum granulosum and the stratum corneum (i.e., nerve endings are not evident in the most superficial layer of dead cells forming the skin&#39;s outermost surface). 
     Reduction in the skin&#39;s electrical impedance can be accomplished through abrasion of the skin with sandpaper, through puncturing the skin with a very short (500 micron) stylet, or thorough abrading of the skin with a gritty abrasive paste (the latter being the most commonly used clinical procedure). Common to these procedures is a relative breach of the superficial stratum corneum layer of the epidermis. All of these methods can cause skin irritation, and, if vigorous, a very small amount of localized transient bleeding. However, virtually all clinical EEG recording utilizes one of these methods to reduce the skin&#39;s impedance. 
       FIG. 1  shows a top view of an embodiment of an electrode  100 . The electrode  100  comprises four legs  102  extending from a main portion of the electrode  100 . The main portion may comprise a central portion of the electrode  100  and/or a portion from which all legs  102  extend. Each leg comprises one or more teeth  104  or protrusions that are configured to penetrate a patient&#39;s skin as described herein. The illustrated embodiment of the electrode  100  includes five teeth  104 . Other embodiments may include any other suitable number of teeth. The teeth may have sharp points as illustrated in  FIG. 1  or the teeth may have other shapes or wider or shallower points. The electrode may include one or more slots  106  for use in conjunction with an applicator, as shown, for example, in  FIG. 4 . Each leg  102  may also have one or more score lines  108  to facilitate even bending of the legs  102 . In some embodiments, a diameter or length of the main body of the electrode  100  is at least about 0.1, 0.2, 0.3, 0.4 or 0.5 cm and may be less than or equal to about 3, 2.5, 2, 1.5 or 1 cm. Smaller size electrodes may be suitable for, for example, very young children. The length of the teeth  104  may be at least 50, 100, 200, 300 400 or 500 microns and may be less than or equal to about 1000, 900, 800, 700, 600 or 500 microns. The teeth may be long enough to extend through the epidermis and anchor the electrode when it is flattened. The length and width of the legs  102  relative to the diameter of the electrode  100  may vary, for example, so that the legs  102  be bent to an angle of at least about 20, 25, or 35 degrees and/or less than or equal to about 60, 55, 50, 45 or 40 degrees. The angle may be an angle relative to the surface of the main body and/or to the position of the unbent legs. The angle may also be an insertion or an attack angle, describing the angle at which the legs are relative to a patient&#39;s skin upon insertion of the electrode  100 . The electrode  100  may be substantially flat in shape when ultimately residing on the skin. The electrode  100  may be manufactured using, for example, electroetching and/or microlaser manufacturing procedures. 
     The electrode  100  may comprise a thin metal, such as a moderately electrically conductive alloy. In one embodiment, the electrode  100  comprises a nitinol or other suitable shape memory material, metal or alloy. An electrode comprising one or more of these materials, metals or alloys may be bendable or deformable but may subsequently move towards its initial shape. For example, legs of an electrode comprising a shape memory metal may be configured to bend upon application of a force (e.g., a force applied by a human or machine prior to insertion of the electrode into a patient&#39;s skin) and to return towards an initial configuration upon release of said force (e.g., after the electrode has been inserted into the patient&#39;s skin). The legs may be bent away from the plane of an electrode body prior to insertion into a patient and may return towards this plane, such that the legs lie substantially parallely under a patient&#39;s skin after insertion, securing the position and insertion of the electrode. 
     In some instances (e.g., when the electrode comprises a shape memory alloy), the electrode may be compatible with computerized tomographic (CT) and magnetic resonance (MR) imaging studies; such that a patient wearing the electrode (e.g. a critically ill or unstable patient) does not need to remove the electrode before undergoing such studies. In one embodiment, the metal is at least about 0.0005, 0.001, 0.002 or 0.003 inches in thickness and/or less than or equal to about 0.020, 0.015, 0.010, 0.008, 0.007, 0.006, 0.005 or 0.004 inches in thickness. The natural or “remembered” shape of the electrode  100  in such an embodiment is a flat, substantially planar geometry. To apply the electrodes, the legs  102  may be each bent at an angle (e.g., about 25, 30, 40, 45 or 50 degrees) and pressed into the skin of the patient so that the teeth  104  enter the skin at a shallow angle (e.g. about 0 to about 45.degree.). Once inserted, the memory properties of the electrode  100  tend to force the legs  102  back into their planar position, thus causing the surface of the teeth  104  to push out against the skin. This force helps to hold the electrode  102  in place. 
     In another embodiment, the electrode  100  comprises stainless steel. The legs  102  of the steel electrode  100  are bent at an angle (e.g., about 25, 30, 40, 45 or 50 degrees) and pushed into the skin with enough force to at least partly flatten the legs  100  and affix the electrode  100 . In other embodiments, the electrode may be formed of any suitable conductive material, or combination of materials, with at least a portion of the electrode being formed of a conductive material. For example, other embodiments may comprise a nonconductive material with a conductive outer material. 
     The electrode  100  may be used to record EEG data from a human or an animal patient. The electrode  100  may be used to record other bioelectric potentials accessible at the skin, including the electrocardiogram. In some embodiments, the electrode  100  can be successfully and painlessly placed on hair-containing or hairless skin within seconds, establishes a long-lasting and stable electrical connection, does not require conductive gel for stable recording, and/or is self-anchoring. 
       FIG. 2  is a top view of the electrode  100  inserted in skin of a human. The teeth  104  are partly under the skin thereby affixing the electrode  100 . 
       FIG. 3  is a top view illustrating the teeth  104  of the electrode  100 . In the illustrated embodiment, a portion  302  of the teeth  104  has been etched to form thin, sharp edges and points along the edge of the etched portion  302  to easier insertion of the electrode  100  into the skin. 
       FIG. 4  is a bottom view the electrode  100  positioned in a device or applicator  400  configured to apply or affix the electrode  100  to a medium (e.g., a patient&#39;s skin). The illustrated applicator  400  comprises one or more sides  401  that each have a radially extending flange or tab  402  configured to fit into the slots  108  of the legs  102  of the electrode  100  when the legs  102  are bent for insertion. The applicator  400  may include an insertion triggering component, such as a button or actuator, (not shown) on the opposite side of the applicator  400  that is configured to eject an electrode  100  (e.g., upon depression of a button) from the applicator  400 , for example into a patient&#39;s skin. In the illustrated applicator  400 , the applicator  400  includes a recess  406  into which the electrode  100  is forced, bending the legs  102 , until the tabs  402  engage the slots  108 . This action helps to bend the legs  102  to a selected angle for insertion. The electrode  100  and/or applicator  400  are configured such that when the electrode  100  is applied to the patient&#39;s skin, the electrode  100  depresses (e.g., via the button or actuator) so that the teeth  104  are forced into the patient&#39;s skin and so that the legs  102  bend sufficiently for the legs  102  to be released from the tabs  402 . The applicator  400  can thus allow easier and/or more consistent bending of the legs  102  for insertion and application of pressure to insert the electrode  100 . 
       FIG. 5  is a top view of another example of the electrode  100 . In the embodiment illustrated in  FIG. 5 , the electrode has two legs  102  (instead of 4 legs of the example of the electrode  100  illustrated in  FIGS. 1-4 . It is to be recognized that other embodiments may have different numbers of legs  102  and/or teeth  104 . 
     As illustrated in  FIG. 1 , the electrode  100  comprises a small central planar metallic portion from which several in-plane extensions (legs)  102  protrude outward. These legs  102  are tipped by a row of several small sharp beveled teeth  104  oriented outwards from the electrode&#39;s center. Initially, the peripheral portion of the electrode&#39;s legs  102  are bent symmetrically out of plane with the electrode&#39;s center, either with a physical bend or utilizing the flexible properties of shape memory alloys. This allows the leg&#39;s terminal teeth  104  to approach the skin at an angle of attack of, for example, 30-45 degrees relative to the skin&#39;s surface. When the electrode  100  is pressed downward with an application device or by hand, its teeth penetrate the skin in an orientation roughly parallel to the skin&#39;s surface to a depth of, for example, approximately 100-330 .mu.m, and the overall electrode configuration flattens onto the skin&#39;s surface. The embedded teeth can form the point of electrical contact between the patient and an amplification and recording system. Because of the radial orientation of the legs  102  and teeth  104 , this insertion process deforms the skin very slightly in a radial direction compared to the electrode&#39;s center and so anchors the electrode due to both the elasticity of the skin pressing back against the electrode&#39;s teeth  104  and rigid body, as well as by the resistance of the very thin superficial layer of skin lying directly over the electrode&#39;s multiple teeth. The electrode&#39;s electrical impedance may be, for example, at least about 1, 2, 3, 4, 5, 7 or 10 kΩ and/or may be less than or equal to about 50, 40, 30, 25, 20, 19, 18, 17, 16, 15, 12 or 10 kΩ. The electrode may also have substantially stable electrical interface resistance. EEG recordings attained through using an electrode  100  described herein may comprise fewer skin movement-related electrical artifacts. Though not wishing to be bound to any particular theory, this may be because it barely penetrates the barrier layer of epidermis to a sufficient depth. The electrode  100  may be relatively inexpensive and/or disposable (e.g., in embodiments in which the electrode comprises stainless steel). The electrode  100  may be durable and/or reusable (e.g., in embodiments in which the electrode  100  comprises nitinol and/or stainless steel). Reusable electrodes  100  may be configured to be disinfected across uses. The electrode  100  may be used, for example, in computed tomography and magnetic resonance imaging devices. Metals of the electrode  100  may be electroplated with silver or gold to increase conductivity. Further, in one embodiment in which the electrode  100  is electroplated with silver, the electrode  100  may be coated with silver-chloride (AgCl), which may optimize the transduction of Cl ions from the scalp to the electrons in the metal. Electrodes may be mass produced using, for example, photo chemical etching. 
       FIG. 6  shows a process  600  for recording biopotentials, and  FIG. 7  shows a system  700  for recording biopotentials. Process  600  begins at step  605  with the positioning of an electrode  705  over a sample. The electrode  705  may comprise any electrode  100  as described herein. The positioning of the electrode  705  may comprise inserting at least part of the electrode  705  into the sample. For example, at least part of one or more teeth of the electrode  705  may be inserted to be underneath a surface of the sample. At least part of the electrode  705  (e.g., a sharp end of one or more teeth) may puncture a surface of the sample. Teeth of the electrode  705  may be inserted into the sample such that the positions of the teeth once the electrode is positioned are approximately parallel and/or close to the surface of the sample. This may be possible due to a radial orientation of the teeth. In embodiments in which at least part of the electrode  705  punctures a sample surface, the puncturing (and the positioning of the electrode  705 ) may be associated with an acceptable amount, a negligible amount or no pain. 
     The positioning of the electrode  705  may comprise physically attaching the electrode  705  to the sample, such as by anchoring the electrode  705  to the sample using part of the electrode  705 . The positioning of the electrode  705  may be such that the electrode  705  is then configured to remain substantially stationary relative to the sample, for example, throughout a sustained duration (e.g., about 15 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 4 hours, 6 hours or 8 hours) or during movement of the sample or part of the sample (e.g., the patient&#39;s skin). In one instance, penetrations of electrode teeth into the epidermal layer reduce skin movement artifacts. The electrode  700  may remain more stationary as compared to other electrodes that are not at least partly inserted into the sample. In some embodiments, only a single electrode  700  is positioned, while in other embodiments a plurality of electrodes  700  are positioned. At least one of the plurality of electrodes may serve as a reference electrode, such that signals of other (signal) electrodes may be compared to signals of the reference electrode. The electrode  705  may be configured to be stably positioned to be substantially stationary relative to the sample within less than about 30, 20, 10, 5, 3, 2 or 1 second. 
     The electrode  705  may be positioned such that it lies substantially flat again a surface of the sample. In one instance, teeth of the electrode may be inserted through the sample&#39;s surface and the portion of the electrode  705  not inserted into the sample lies flat against the surface. This may reduce or eliminate cutaneous pressure points related to electrode  705  protrusions when head weight is applied to the flat electrode surface. 
     In some embodiments, the electrode  705  is positioned over the sample without the use of or with reduced use of a conductive gel or paste. For example, in one embodiment, the surface of the sample is not coated with a conductive gel or paste before the electrode  705  is positioned. In another embodiment, the surface of the sample is coated with less conductive gel or paste than would otherwise be used with a standard disc electrode. In some embodiments, no secondary adhesive is used to further stabilize the electrode  705  over the sample. 
     The sample may comprise a patient or a patient&#39;s skin. In some embodiments, the sample comprises a region of the patient of a patient&#39;s skin, such as the head or the scalp. For example, teeth of an electrode may be partly inserted into the scalp&#39;s skin of a patient, thereby puncturing a top layer or a surface of the skin and anchoring the electrode  705  to the patient. The sample may comprise hair. For example, the electrode  705  may be positioned over a region of a patient&#39;s scalp, that region containing hair. The small size and shape of the electrode  705  may enable hair to pass around the edges of the device. A large intra-cutaneous electrode recording surface may, in some embodiments, be provided by superficial skin penetration of multiple teeth of the electrode. 
     In some embodiments, the sample is not abraded. For example, in some embodiments, no skin abrasive has been used to prepare a surface of the sample for the positioning of the electrode  705 . 
     The patient may comprise a mammal, such as a human. The patient may be suffering from a disease or medical condition or may be substantially healthy. The disease or medical condition may comprise an insomnia, sleep disorder, migraines, epilepsy, multiple sclerosis, schizophrenia, auditory neuropathy, a heart disease, muscular dystrophy, or a psychiatric condition. 
     Process  600  continues with step  610  with the receiving of a plurality of biopotentials by the positioned electrode  705 . The electrodes  705  may be used in connection with, for example, ECG, EEG or EMG recordings to receive biopotentials of the heart, the brain or the muscle, respectively. Biopotentials may be received during a predefined time interval or during one or more tasks. For example, biopotentials may be received while a patient reads an eye chart, sleeps or exercises. 
     Next, at step  615  of process  600 , the received biopotentials are amplified. The biopotentials may be amplified by an amplifier  710 . The amount of amplification may depend on, for example, the signal being measured and/or noise. 
     Continuing to step  620  of process  600 , the amplified biopotentials are filtered by one or more filters  715 . The filters used in the filtering may depend on signal and/or noise properties. The amplifier  710  may comprise a filtering component to filter the biopotentials. 
     Moving to step  625  of process  600 , the filtered biopotentials are converted to a digital format. Any appropriate A/D convertor  720  may be used to perform this conversion. The amplifier  710  may comprise a conversion component to convert the biopotentials to a digital format. 
     Proceeding to step  630  of process  600 , the converted biopotentials are analyzed. In one embodiment, the converted biopotentials are input to a computer  725 . The computer  725  may then analyze the converted biopotentials and/or may store or output biopotential data (e.g., on a screen or a printer) to allow a user to analyze the data. The biopotential data may comprise one or more time-varying voltage traces or frequency spectra obtained from the converted biopotentials. The analysis may comprise a diagnosis or evaluation of a disease or medical condition. The analysis may comprise a state determination (e.g., a sleep state or an anesthesia state) of a patient. The analysis may comprise an evaluation of an organ or a patient, such as the health of a heart or of a human. In some embodiments, the converted biopotentials are used to produce electroencephalograph, electrocardiograph, or electromyograph data. 
     Steps of the process  600  may be added, deleted, combined, or rearranged. For example, in some embodiments, the filtering step  620  is deleted. In some embodiments, the amplifying and filtering steps are combined or reversed with respect to each other. Similarly, system  700  may have fewer or more components than as presented here, and separate components may be combined. 
       FIG. 8A  shows a biopotential recording system  800  comprising a plurality of electrode components  805 . The system shown in  FIG. 8  may be configured to be worn by a patient, as shown in  FIG. 8B-E . The system may be configured such that parts of the electrode components of the system can be inserted into the skin of a patient&#39;s head. The system may comprise a headpiece, at least one head bands and/or at least one strap.  FIGS. 8A-E  show an embodiment where the system comprises a headpiece comprising three straps  810   a - c . Two straps  810   a - b  are configured to wrap around a patient&#39;s head, while a third strap  810   c  is configured to be positioned on top of a patient&#39;s head. The straps may be connected by a strap securing component  815 . In some embodiments, each strap  810  snaps into the strap securing component  815 . The system  800  may comprise a size-adjusting mechanism. The size-adjusting mechanism may be configured to change the length of a band, a circumference of a headpiece of another dimension of the system. The size-adjusting mechanism may include, for example, a belt with a number of holes, such that a lock could be secured through one of the holes to adjust a size of the system  800 . 
     The system  800  may comprise flexible material and/or rigid material. For example, straps  810   a - c  may be flexible in order to bend around a patient&#39;s head. The system may comprise support structure (e.g., straps  810   a - c ) to support electrode components to maintain specific spacing between electrode components or positions of the electrode components. The support structure may also house wiring or connections, such as that between electrode components and/or between electrode components and another device. 
     The system  800  may comprise a power supply  820 . The power supply  820  may include, for example, one or more batteries or a connection to an external power source. In some embodiments (e.g., ones which utilize battery power) the system  800  is portable. The system  800  may include one or more controls, such as a power control  825 . The power control  825  or other controls may, in some embodiments, also be used to perform other functions, such as specifying active electrodes or a recording type. The system may include one or more indicators  830 . The indicator may indicate, for example, that the system is powered and/or that electrodes are properly positioned and/or inserted. The indicator may be a visual indicator and may, for example, a light source. 
       FIGS. 8F-H  show exploded expanded views of an electrode component  805 . The electrode component comprises an electrode  835 , such as an electrode described herein. The electrode  835  shown in  FIG. 8F  comprises two legs and five protrusions extending from each leg. An electrode connector  840  is connected to the electrode  835 . The electrode connector  840  may comprise a conductive material, such as copper foil. The electrode connector  840  may connect the electrode to wiring  845 . The wiring  845  may serve to transmit signals between electrodes and/or from the system  800 . The electrode  835  may be positioned within a suspension structure  850  or another support. The suspension structure  850  or support may support the electrode  835  within the system  800 . For example, the suspension support  850  is configured to fit within a ring  855  in order to securely support the electrode  835  within the system  800 . The suspension structure may be configured to support the electrode  835  when the electrode  835  is bent or in an unrelaxed state. However, in some instances, the suspension structure  850  is configured such that movement of the electrode  835  from an unrelaxed state towards a relaxed state causes the electrode  835  to be ejected from the suspension structure  850 . 
     A flexible conductive piece  860  may be positioned within the ring. The piece  860  may comprise, for example, a metal or alloy, such as nitinol. The piece  860  may provide electrical contact from the electrode  835  with the wiring  845 . A material that doesn&#39;t fatigue after repeated bending may be used in the piece  860  to ensure that strong contact will be maintained after repeated electrode replacements. 
     The electrode component may also include an applicator  865 . The applicator may comprise, for example, a button or a switch. Triggering of the applicator  865  (e.g., by pushing a button) may cause at least part of the electrode  835  to be inserted in a patient (e.g., a patient&#39;s scalp). 
     In some embodiments parts or all of the electrode component  805  are removable from the system  800 . Thus, between patients or recording periods, new electrodes may be inserted into the electrode component or the electrodes may be positioned into a compressed, unrelaxed state, such that the electrodes  835  are again ready to be attached to the patient. 
       FIG. 8H  shows a compressed, unrelaxed electrode. Upon pressure on the button, the electrode may be forced at least partly out of the suspension support  850 , the protrusions of the electrode  835  piercing a patient&#39;s skin. The electrode  835  may then return towards a relaxed state, in which both legs are substantially in the same plane. 
     The system  800  may be lightweight, weighing less than about 10, 5, 4, 3, 2, 1, ½ or ¼ pounds. The system  800  may include a transmitter. The transmitter may be a physical connection or a wireless transmitter. The transmitter may transmit data to a receiver (e.g., a digital, USB-powered receiver), which may be connected to, for example, to a computer. The receiver may be small, such as less than about 5, 4, 3, 2, 1, ½ or a ¼ inch in its largest dimension. The receiver and/or transmitter may be configured such that the wireless operating range is at least about 0, ¼, ½, 1, 2, 3, 4, 5, 8, 10 or 20 meters and/or no greater than about 100, 50, 30, 20, 15 or 10 meters. 
     The system  800  may comprise a storage component or a memory in order to store biopotential recording data. The system  800  may comprise an amplifier, a filter and/or an A/D converter. 
     In some embodiments, a kit may comprise an electrode or system  800  described herein. The kit may further comprise leads and/or connectors. The leads and/or connectors may be configured to connect the electrode to an electronic device, such as an amplifier. The kit may comprise an amplifier, filter and/or A/D converter. The kit may comprise a computer (e.g., a portable computer). The computer may comprise software for analyzing biopotential recordings. 
     As described above, an electrode may be configured such that the electrode expands following the initial insertion of the electrode (upon a release of an applied force). Alternatively, the electrode may be configured to contract following the initial insertion of the electrode. For example, as shown in  FIGS. 9A-B , an electrode  900  may be configured such that the electrode  900  is expanded upon application of a force (e.g., prior to inserting the electrode in a patient) and is compressed upon removal of the force (e.g., after the insertion). The electrode  900  comprises a plurality of protruding portions  905  or teeth. The protruding portions  905  may have characteristics of protrusions or teeth as described herein. For example, the length of the protruding portions  905  may be at least 50, 100, 200, 300 400 or 500 microns and may be less than or equal to about 1000, 900, 800, 700, 600 or 500 microns. The protruding portions  905  may be configured to stabilize, position and/or anchor the electrode  900  after at least part of the electrode has been inserted into a sample or patient or after the electrode has been attached to a sample or patient. In some embodiments, two or more segments  910  comprise the protruding portions  905 . The segments  910  may be positioned substantially symmetrically around a central portion of the electrode  900 . For example, in  FIG. 9B , two segments  910  are shown to be positioned on opposite sides of a central curved portion  915 . The protruding portions  905  may be positioned on the inner surface of the segments  910 , as shown in  FIG. 9B , such that the protruding portions  905  of multiple segments  910  are facing each other and pointing towards a central portion of the electrode  900 . 
     The electrode  900  may comprise a deformable, flexible and/or shape memory material. As used herein, a shape memory material refers to a material that can be deformed from an initial state to a deformed state upon application of a force between but returns towards the initial state upon release of the force. In  FIG. 9A-B , the electrode  900  comprises a central curved portion  915  which is deformable. Application of force may cause the radius of the curved portion  915  to expand. For example, a downward force may be applied to the central curved portion  915  while an upward force is applied to the sides of the electrode  900 . In some embodiments, at least one force is applied to the electrode  900  prior to the application, attachment and/or insertion of the electrode  900  in a patient. When the electrode contacts a patient, the at least one force may be released, which may reduce the radius of curvature of the central curved portion  915 , thereby reducing the separation between the segments  910 , and puncturing the patient&#39;s skin with the protruding portions  905 . Thus, the protruding portions  905  may then anchor or stabilize the electrode  900  in the patient. Notably, the electrode  900  may be configured such that following application of the electrode, portions of the electrode  900  (e.g., the protruding portions  905 ) are inserted into a patient, while other portions (e.g., the curved circular portion  915 ) are not. 
     In some embodiments, the electrode is made of only a single material, whereas in other embodiments, the electrode comprises a plurality of materials. The electrode may comprise, for example, stainless steel or an alloy. The electrode  900  may be manufactured by an assembly line. For example, a stainless steel electrode may be cut, stamped and sharpened on an assembly line. The electrode  900  may comprise one or more removal tool contact portions  920 . The removal tool contact  920  may comprise, for example, a groove, to maintain stable contact between a removal tool  930  and the electrode  900 . 
     The removal tool  930  may be configured to apply force to the electrode  900  and/or to change the distance between at least two of the protruding portions  905  and/or at least two of the segments  910 . In one instance, when force is applied to the removal tool  930 , force is also applied to at least two applicator contact removal tool contact portions  920 , which then increases the separation between at least two segments  910  and increases a radius of curvature of the central curved portion  915 . This may cause protruding portions  905  or portions of the protruding portions  905  that are in a patient (e.g., punctured through a patient&#39;s scalp) to be removed from the patient, thereby unattaching the electrode  900  and the patient. 
     In one embodiment, the removal tool  930  comprises at least one pivot point  935 . The removal tool  930  may comprise at least one force application component  940  and at least one or at least two electrode contact components  945 . The force application components  940  may be configured such that force may be applied to one or all of the components by an operator (e.g., a human) or a machine. In some embodiments, such as the embodiment shown in  FIGS. 9A-B , the force application components  940  comprise a curved surface. The force application components  940  may be configured such that the distance between at least two force application components  940  decreases upon application of a force. The electrode contact components  945  may be configured such that a distance between the electrode positioning components is at least partly dependent on force applied to the at least one force application component. For example, application of a force on the force application components  940  may increase the separation distance between the electrode contact components. In some embodiments, the applicator  930  is separable from the electrode  900 . 
     Embodiments of the electrode include an easily applied self-anchoring electrode for recording bioelectric potentials present at the skin&#39;s surface. In some embodiments, an electrode as described herein may serve as a replacement for a standard EEG disc recording electrode, a subdermal needle EEG electrode, and/or a subdermal wire EEG electrode. Moreover, the infection risk associated with such electrodes that penetrate the epidermis or superficially into the dermis would not be expected to be greater than with standard disc EEG electrodes (a risk which is very low, and which is minor in severity when a rare case of superficial skin infection does occur). 
     Embodiments of an electrode as described herein may be used for applications that include: any suitable applications and settings in which EEG might be performed (EEG laboratory, epilepsy monitoring unit, intensive care unit, operating room, emergency room, emergency field settings, and ambulatory EEG monitoring); any suitable applications and settings in which cerebral evoked potentials or event-related potentials might be performed, including for psychiatric and psychological studies; use as the point of person-machine contact in a device acting as a brain-machine interface; and settings in which EEG or evoked potentials might be performed on animals. 
     From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes modification and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claim. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.