Abstract:
An electrode and a method for measuring bio-electric waves are provided in which the electrode comprises a support member, a piece of absorbent fiber projecting from the support member and a non-corrosive lead coupled to the piece of absorbent fiber. Improved electrical contact between the electrode and the subject&#39;s skin is provided by allowing the piece of absorbent fiber to absorb an electrically conductive fluid.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to electrodes. The present invention is primarily intended for use with live subjects and has application in, for example, the recordation of bio-electric waves such as electroencephalographic (&#34;EEG&#34;) brain waves. 
     Heretofore, most electrodes used for measuring brain waves have required the application of some kind of paste or gel to establish electrical contact between the electrode and the scalp. After measurement, the paste or gel remains on the patient&#39;s scalp and in his hair and must be washed off. The process of applying and washing the paste or gel is an added burden for patients, especially those who may be suffering from dementia, for example. In addition, the paste or gel which adhere to the patient&#39;s scalp and hair can increase his stress level, thereby interfering with brain wave measurements. 
     In view of the foregoing, it would be desirable to provide an electrode which does not require the use of paste or gel to establish electrical contact. 
     It would also be desirable to provide an electrode which is easy to use. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an electrode which does not require the use of paste or gel to establish electrical contact. 
     It is also an object of the present invention to provide an electrode which is easy to use. 
     These and other objects are accomplished by electrode comprising a support member, a piece of absorbent fiber projecting from the support member and a non-corrosive lead coupled to the piece of absorbent fiber. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     The above and other objects and advantages of the invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which reference characters refer to like parts throughout and in which: 
     FIG. 1 is an exterior view of the head of a patient wearing a headpiece which incorporates an implementation of the electrode of the present invention; 
     FIG. 2 is a angle view of an implementation of the electrode of the present invention; 
     FIG. 3 is a cross-section view of an implementation of the electrode of the present invention; 
     FIG. 4 is a cross-section view of another implementation of the electrode of the present invention; 
     FIG. 5 is a cross-section view of yet another implementation of the electrode of the present invention; 
     FIG. 6 is an exterior view of the head of a patient wearing a modified headpiece which incorporates an imolementation of the electrode of the present invention; 
     FIGS. 7A and 7B show the component parts of the headpiece of FIG. 6; and 
     FIGS. 8A and 8B show angle views of another implementation of the piece of absorbent fiber and the electrode of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows an exterior view of head 1 of a patient wearing headpiece 2 which includes net cap 3 and incorporates a plurality of electrodes 4. Net cap 3 can be made of an elastic material and can, therefore, fit various sized heads. Electrode 4 is shown with insertion hole 7, which allows electrically conductive fluid to be introduced into electrode 4, both before and during use, without removing electrode 4 from contact with the patient&#39;s skin. Also shown are leads 5 coupled between each electrode 4 and connector 6. Connector 6 is used to correct leads 5 to external processing equipment (not shown in FIG. 1). 
     FIG. 2 is a angle view of an implementation of electrode 4 comprising disk-shaped support member 4a with concentric cylindrical projection 4b and a non-through hole. Piece of absorbent fiber 4c is mounted in the non-through hole. 
     FIG. 8A is an angle view of another implementation of piece of absorbent fiber 4c which comprises bundle of hard felt rods 10 (preferably of diameter of about 2 mm and with rounded tips for making contact with a patient&#39;s skin 11). Hard felt rods 10 may be impregnated with carbon powder for increased conductivity. FIG. 8B shows electrode 4 coupled to net cap 3. Electrode 4 comprises support member 4a, projection 4b and piece of absorbent fiber 4c. Also shown are leads 5 which may be coupled to piece of absorbent fiber 4c. 
     Support member 4a and projection 4b are fabricated of insulating materials (such as ceramics) and/or preferably materials which are also light-weight, such as plastics. Also, synthetic fibers and felt which have had their surfaces heat treated may be used. 
     Piece of absorbent fiber 4c may be, for example, felt. One reason why felt is preferred as piece of absorbent fiber 4c is that, along with its high absorption, it prevents evaporation and drying out of the electrically conductive fluid during measurement. In addition to felt, cotton and synthetic fibers may be used. 
     The electrically conductive fluid may also comprise various skin conditioners, such as menthol, counterirritant materials such as Frescolat, anti-inflammatory agents such as Candilla wax and astringents such as zinc sulfate. 
     Saline solution is preferably used as the electrically conductive fluid because, in addition to greatly increasing the electrical conductivity, saline solution is basically the same as sweat and therefore the need for the patient to wash his hair after removal of the electrodes is eliminated. 
     FIG. 3 is a cross-section view along line I--I of an implementation of electrode 4 shown in FIG. 2. Projection 4b is shown with non-through hole 4d. Insertion hole 7 goes through support member 4a and reaches non-through hole 4d. Electrode 4 may be fastened to net cap 3 by adhesive 8. 
     Leads 5 may, for example, comprise insulator 5a surrounding bundle 5b of conductors, such as carbon fibers, which make electrical contact with the bottom of non-through hole 4d through support member 4a. 
     FIG. 4 is a cross-section view of another implementation of electrode 4 of the present invention. 
     In FIG. 4, electrode 4 is shown without absorbent fiber 4c. Bundle 5b of conductors project from a wall of non-through hole 4d. 
     FIG. 5 is a cross-section view of yet another implementation of electrode 4. Here, bundle 5b of conductors is molded to and projects from the surface of non-through hole 4d. 
     In use, after piece of absorbent fiber 4c is inserted into non-through hole 4d in projection 4b, electrically conductive fluid is allowed to be absorbed by piece of absorbent fiber 4c. As can be seen from FIG. 3, for example, the depth of non-through hole 4d is less than the length of piece of absorbent fiber 4c , which projects from non-through hole 4d. Thus, projection 4b does not come in direct contact with the patient&#39;s skin and does not cause any unpleasant sensation. Piece of absorbent fiber 4c swells as it absorbs the electrically conductive fluid and therefore does not easily fall out of non-through hole 4d , even when electrode 4 is suspended upside down. An increased density of piece of absorbent fiber 4c also contributes to making it difficult for piece of absorbent fiber 4c to fall out of non-through hole 4d. 
     Because bundle 5b of conductors projects from a wall of non-through hole 4d , a signal strong enough for further processing can be obtained from the patient&#39;s brain waves when electrode 4 is brought into contact with the patient&#39;s scalp as the signal travels the low resistance path through the electrically conductive fluid absorbed in piece of absorbent fiber 4c. Bundle 5b of conductors in leads 5 is preferably fabricated from carbon fibers, which are strong and resistant to corrosion by electrically conductive fluids such as saline solution. 
     As shown in FIG. 5, bundle 5b of conductors is molded to and projects from the surface of non-through hole 4d , which provides better electrical conduction between piece of absorbent fiber 4c and bundle 5b of conductors. 
     FIG. 6 is an exterior view of the head of a patient wearing modified headpiece 9 which incorporates an implementation of electrode 4. Headpiece 9 is comprised of headband 9a and umbrella frame bands 9b to which electrodes 4 are coupled. 
     FIGS. 7A and 7B show the component parts (i.e., headband 9a and umbrella frame bands 9b) of headpiece 9 of FIG. 6. Also shown are fasteners 9c and 9d, such as Velcro tape, at the ends of headband 9a and umbrella frame bands 9b. Using fasteners 9c and 9d, it is possible to assemble headband 9a and umbrella frame bands 9b into headpiece 9 of FIG. 6. 
     To provide greater freedom of movement, the electrodes may be coupled to a wireless transmitter. The wireless transmitter may, for example, be located on the headpiece or net cap. Thus, the electric signals produced on the electrodes may be transmitted to external processing equipment through the wireless transmitter.