TAB STYLE ELECTRODE

Abstract: The present invention discloses a biomedical electrode (10) of low profile, multi-layer construction wherein an electrically conductive tab (18) contacts ionically conductive medium (16) through an aperture (14) of an insulative backing (12).

Description: TAB STYLE ELECTRODE Field ofthe Invention This invention relates to biomedical electrodes having a low profile and a multi-layer construction. Background ofthe Invention Biomedical electrodes are used in the fields of electrocardiography and for transcutaneous electrical nerve stimulation. A number of biomedical electrode constructions have employed an insulative outer layer through which an electrically conductive tab extends to provide a low profile, multi-layer construction Representative examples of such constructions are disclosed in the embodiments shown in U.S. Patent No. 5,012,810 (Strand et al.). Another low profile multi-layer construction employs an electrically conductive tab which remains below the surface ofthe outermost layer but is accessible to the outside through an aperture in the outermost layer. A representative example of this electrode construction is disclosed in U.S. Patent No. 5,215,087 (Anderson et al ). Other biomedical electrode constructions involve an elaborate placement of sponges in apertures to which an electrically conductive tab can contact even though that tab does not extend beneath the surface ofthe outer most layer. Representative examples of this construction is found in U.S. Patent No. 4,522,21 1 (Bare et al.) and U.S. Patent No. 4,838,273 (Cartmell). Another biomedical electrode construction employs a reservoir of conductive gel into which a lead wire can be inserted through an aperture, as disclosed in U.S. Patent No. 4,409,981 (Lundberg). Another biomedical electrode construction employs an aperture in communication with a conductive adhesive into which a lead wire can be inserted through the aperture, as disclosed in U.S. Patent No. 4,715,382 (Strand). Summary ofthe Invention The art needs a low profile multi-layer biomedical electrode that is simplistic in construction and easy to manufacture without losing the advantages of a tab-style biomedical electrode. In one aspect, the invention provides a biomedical electrode that comprises: (a) an insulative backing having opposing major surfaces and an aperture extending between the major surfaces; (b) a field of ionically conductive medium contacting one major surface and extending into the aperture; (c) an electrically conductive tab disposed on the opposing major surface at least partially covering the aperture and having an electrically conductive surface contacting the field of ionically conductive medium at the aperture; and (d) a placement tape having an adhesive major surface covering at least a portion ofthe electrically conductive tab that covers the aperture. A feature ofthe invention is the extremely low profile, multi-layer construction ofthe biomedical electrode in order to maximize flexibility and minimize discomfort during contact with mammalian skin. Another feature ofthe invention is the ability to manufacture the multi-layer construction biomedical electrode by building layers of components of the electrode without requiring any one component to be placed in more than one layer ofthe multi-layer construction An advantage ofthe invention is the ease of manufacture and its consequential low cost for manufacture. Embodiments ofthe invention are explained in relation to the drawings. A Brief Description ofthe Drawings Fig. 1 is an embodiment of a biomedical electrode in an array with other biomedical electrodes after assembly. Fig 2 is a cross-sectional view of a biomedical electrode ofthe present invention as seen in Fig 1 Fig 3 is an alternate embodiment ofthe biomedical electrode, having opposing tab terminii Embodiments ofthe Invention Referring to Fig 1, an array of biomedical electrodes 10 are shown Referring to Fig 2, biomedical electrode 10 comprises a low profile, multi-layer construction comprising a backing 12 having an aperture 14 therein. On one major surface 15 of backing 12 is contacted a field 16 of ionically conductive medium, preferably a conductive pressure sensitive adhesive Field 16 is constructed of an ionically conductive medium that can reside in the aperture 14 of backing 12 Adjacent a second major surface 17 of backing 12 is an electrically conductive tab 18 having an electrically conductive surface 20 which is disposed on surface 17 at least partially covering the aperture 14. Electrically conductive surface 20 contacts field 16 of ionically conductive medium at the aperture 14. Disposed over at least a portion ofthe electrically conductive tab 18 is a placement tape 22 having on a major surface a field 24 of placement adhesive Placement tape 22 and field 24 adhere and restrain electrically conductive tab 18 at that portion of tab 18 covering aperture 14 Protecting field 16 of ionically conductive medium is a release liner 26 until usage of electrode 10 is desired. Optionally, a double-sided adhesive tape 28 can be used to assist in restraining a portion of tab 18 to surface 17 adjacent to aperture 14 The tape 28 places the terminus of tab 18 near, but not adhered to surface 17 of backing 12, to facilitate electrical connection to the terminus of tab 18 Optionally, fields 30 and 32 of biocompatible pressure sensitive adhesive can be applied to surface 15 at locations distant from aperture 14 or completely cover surface 15 to assist in securing electrode 10 to skin and to minimize usage of more expensive ionically conductive medium used in field 16 Optionally, a gripping tab 34 can extend from backing 12 for ease of removal of electrode 10 from liner 26 and for ease of removal of electrode 10 from skin. Backing Backing 12 is insulative, i.e., relatively electrically nonconducting. Backing 12 has an aperture 14 inside of its perimeter. When an optional pressure sensitive adhesive is employed, then the perimeter of backing 12 contacts pressure sensitive adhesive extending beyond the perimeter of medium 16 such that a skirt of pressure sensitive adhesive 12 can be used to adhere electrode 10 to skin of patient Optionally, a pressure sensitive adhesive layer can reside on at least a portion of major surface 15 Nonlimiting examples of a suitable backing for use in the present invention are medical-grade pressure sensitive adhesive tapes such as those commercially available under the brands "Blenderm" or "Durapore" or a melt blown polyurethane material having a pressure sensitive adhesive coating on its major surface, such as that disclosed in U.S. Patent No. 5,230,701 (Riedel). Aperture 14 is constructed within the perimeter of backing 12 to permit contact between electrically conductive tab 18 and ionically conductive medium 16 Aperture 14 can be smaller or larger in any dimension within perimeter of backing 12 so long as there is sufficient area in aperture 14 to provide an interface at which electrically conductive tab 18 and its surface 20 can contact field 16 of ionically conductive medium Backing 12 has a thickness ranging from about 0.02 mm to about 0.89 mm and preferably 0.35 mm in order to provide a low profile layer ofthe multi-layer construction. Ionically Conductive Medium Field 16 of ionically conductive medium can be any ionically conductive electrolyte contacting major surface 15 of backing 12 It is an advantage ofthe invention for performance and manufacturing efficiency that field 16 contacts surface 15 as well as resides in aperture 14 Performance ofthe electrode 10 is enhanced by a larger area of field 16 contacting skin of a patient than the area required in aperture 14 for electrical communication with electrically conductive member 14. Less manufacturing registration is required with larger surface area for field 16 Preferably, field 16 is an ionically conductive pressure sensitive adhesive that can adhere to major surface 15 and reside in aperture 14. If the medium is not inherently adhesive, then at least a portion of major surface 15 of backing 12 should be adhesive to retain a sponge or scrim into which the field of ionically conductive gel is impregnated, such that a portion of field 16 can form a sponge or scrim and enter aperture 14 for interface contact with tab 18 Nonlimiting examples of adhesive for major surface 15 include pressure sensitive adhesives, hot melt adhesives, and hot melt pressure sensitive adhesives. Nonlimiting examples of ionically conductive media useful as field 16 in electrode 10 ofthe present invention include those ionically conductive compositions disclosed in U S Patent Nos 4,524,087 (Engel), 4,539,996 (Engel), 4,848,353 (Engel), 4,846, 185 (Carim); 5,225,473 (Duan), 5,276,079 (Duan et al.), 5,338,490 (Dietz et al ), 5,362,420 (Itoh et al ), 5,385,679 (Uy et al ), copending and coassigned applications PCT Publication Nos WO 95/20634 and WO 94/12585, and PCT Patent Application Serial Nos. US95/17079 (Docket No. 51537PCT6A); US95/16993 (Docket No 51290PCT8 A); and US95/16996 (Docket No 48381PCT1A) Thickness ofthe ionically conductive medium field 16 can range from about 0.25 mm to about 2 5 mm and preferably 0.63 mm in order to maintain a low profile, multi-layer biomedical electrode construction Electrically Conductive Tab Electrically conductive tab 18 has an electrically conductive surface 20 which contacts field 16 of ionically conductive medium When used for electrocardiography, electrically conductive surface 20 preferably is non-polarizable to enhance recovery of performance after defibrillation events At least a portion of conductive tab 18 is placed over aperture 14 of backing 12 so that tab 18 can contact field 16 of ionically conductive medium in aperture 14 At least a portion of tab 18 can be contacted by a clamp or connector for electrical communication with electrical instrumentation, either to transmit energy into a body such as that used in transcutaneous electrical nerve stimulation or for receiving electrical signals from the body such as that used in electrocardiography. Electrically conductive tab 18 can be a tab/pad construction comparable to that disclosed in U S Patent Nos 5,012,810 and 5,215,087 Tab 18 comprises an electrically nonconductive sheet of plastic coated with silver/silver chloride on surface 20 facing aperture 14 and field 16 Alternatively, electrically conductive surface 20 can be constructed from materials disclosed in PCT Publications WO 94/26950 and WO 95/20350 Alternatively, surface 20 can be constructed from graphite materials disclosed in U S Patent No 5,215,087 Optionally, surface 20 can reside on both major surfaces of electrically conductive tab 18 An advantage of multiple conductive surfaces 20 is the ease of electrical connection of electrode 10 to a biomedical connector regardless of the orientation ofthe connector to electrode 10 during connection To permit both opposing major surfaces of tab 18 to be electrically conductive surfaces 20, tab 18 is perforated between its major surfaces to permit a coating forming surface 20 to cover surfaces lining such perforations to provide at least one electrical pathway between opposing major surfaces of tab 18 Preferably, surface 20 is constructed of a silver/silver chloride ink commercially available as R301 MPK (+240) brand ink from Ercon, Inc of Waltham, Massachusetts Tab 18 preferably has a shape that it may either cover all of aperture 14 and is larger than aperture 14 with a portion extending beyond aperture 14 so that it can be connected to the electrical instrument. If tab 18 covers all of aperture 14, then a hot melt adhesive or a pressure sensitive adhesive can be applied as a skirt around aperture 14 to adhere tab 18 over aperture 14 Alternatively, tab 18 can be not as wide as aperture 1 and cover only a portion of aperture 14 In another embodiment seen in Fig. 3, tab 18 can extend from aperture 14 in different, preferably opposite, directions to provide at least two points of electrical contact to biomedical instrumentation. Preferably, tab 18 is positioned over aperture 14 such that nearly equal portions of tab 18 extend toward opposing edges of electrode 10 with tape 22 restraining tab 18 over aperture 14. The thickness of tab 18 and surface 20 can range from about 0.025 mm to about 0.5 mm in order to maintain a low profile, multi-layer biomedical construction. Placement Tape Placement tape 22 having an adhesive field 24 on its major surface is one of several means for restraining at least a portion of electrically conductive tab 18 over that portion which covers aperture 14. Other means of securing tab 18 positioned over or in aperture 14 to contact field 16 of ionically conductive medium include mechanical anchoring such as staples, ultrasonic bonding, or variety of tapes having a variety of pressure sensitive, hot melt, or other adhesives or glues necessary to adhere tape 22 over tab 18. Another method of anchoring tab 18 to backing 12 is to have a pressure sensitive adhesive or hot melt adhesive field on surface 20 on areas not in contact with field 16, for example, around the aperture 14. Preferably, the adhesive field as a skirt around aperture 14 also provides a hermetical seal. Preferably tape 22 is moisture impervious and has a pressure sensitive adhesive which can cover tab 18 and anchor it to the major surface 17 of backing 12. A moisture impervious tape 22 minimizes loss of moisture from ionically conductive medium that is exposed at the interface in aperture 14 and also prevents conductive tab 18 from separating from the remainder of electrode 10 when it is connected to an electronic instrument during usage. Further, tape 22 imparts to electrode 10 a distribution of mechanical forces from any wire connection between electrode 10 and electronic instrumentation. Preferably, tape 22 has elastic properties sufficient to resist delamination caused by mechanical forces of strain on wires connecting electrode 10 to instrumentation. Tape 22 can have dimensions that can control forces from tugging of a connector and lead wire to the biomedical electrode and also to provide conformance ofthe electrode to skin stretched beneath the electrode on the body of a patient. Nonlimiting examples of placement tape suitable for those features described above include Scotch™ Magic™ brand tape and Blenderm™ brand surgical tape, both commercially available from Minnesota Mining and Manufacturing Company Optionally, such tape 22 can have trademark or other branding indica to identify the manufacturer ofthe electrode or provide other informational or regulatory markings for patient and practitioner usage. Tape 22 and adhesive field 24 can have a thickness ranging from about 0.03 mm to about 0.38 mm and preferably 0.2 mm in order to maintain a low profile, multi-layer construction for electrode 10 Release liner Release liner 28 can be any construction suitable for protecting the ionically conductive medium from contamination or loss of adhesion prior to usage. Commercially available release liners include "Polyslik" release liners commercially available from Rexam Release of Oakbrook, Illinois. Release liner 28 also provides a surface to prevent a dry out of ionically conductive medium field 16 when such medium is a polyelectrolyte Thickness of release liner 28 can range from about 0.03 mm to about 0.20 mm again to maintain a low profile, multi-layer biomedical electrode construction Optional Adhesiveness Double-sided tape 28 can be any tape conventionally used to restrain a tab in a biomedical electrode construction. Fields 30 and 32 of skin adhesive can be any conventional biocompatible pressure sensitive adhesive Typically, acrylate ester adhesives will be preferred Acrylate ester copolymer adhesives are particularly preferred. Such material are generally described in U.S. Pat. Nos 2,973,826; Re 24,906; Re 33,353; 3,389,827, 4,1 12,213, 4,3 10,509, 4,323,557, 4,732,808, 4,917,928, 4,917,929, and European Patent Publication 0 051 935 In particular, an adhesive copolymer having from about 95 to about 97 weight percent iso-octyl acrylate and from about 5 to about 3 percent acrylamide and having an inherent viscosity of 1 1-1 25 dl/g is presently preferred Adhesive useful for double-sided tape 28 can be any ofthe acrylate ester adhesives described above used in double stick tape form. A presently preferred adhesive is the same adhesive as presently preferred for the skin adhesive except having an inherent viscosity of about 1 3-1 45 dl/g Method of Making Biomedical Electrode Construction of electrode 10 is simplified over electrode constructions previously known in the art One can begin with release liner 28 and form ionically conductive medium thereon, followed by placement of backing 12 with a prior punching of aperture 14 over the field 16 of ionically conductive medium Thereafter, a registration placement of conductive tab 18 over aperture 14, followed by placement of tape 22 over tab 18 completes electrode construction from bottom to top. When fields 30 and 32 are included in electrode 30, such fields 30 and 32 must be placed prior to placement of backing 12 using a pattern coating of adhesives such as that disclosed in copending, co-assigned PCT Patent Application Serial No US95/14291 When double-sided tape 28 is included in electrode 30, such tape 28 is placed on backing 12 before tab 18 is placed over aperture 14 Equipment such as that shown in U S Patent Nos 4,795,516 and 4,798,642 disclose processes and equipment useful for dispensing strips of material from rolls and overlaying such strips in a registered, continuous manner in order to prepare electrode 10 ofthe present invention, either in the construction identified in Fig 2 or in the construction identified in Fig 1 For an additional appreciation ofthe scope ofthe invention, the claims follow

Claims: What is claimed is 1 A biomedical electrode, comprising: (a) an insulative backing having opposing major surfaces and an aperture extending between the major surfaces; (b) a field of ionically conductive medium contacting one major surface and extending into the aperture, (c) an electrically conductive tab disposed on the opposing major surface at least partially covering the aperture and having an electrically conductive surface contacting the field of ionically conductive medium at the aperture, and (d) means for restraining at least a portion ofthe electrically conductive tab that covers the aperture 2 The biomedical electrode, according to Claim 1, wherein the electrode further comprises means for adhering the tab adjacent the aperture 3 The biomedical electrode, according to Claim 1 , further comprising fields of biocompatible pressure sensitive adhesive at locations distant from aperture 14 4 The biomedical electrode, according to Claim 1 , wherein ionically conductive medium comprises a sponge into which a field of ionically conductive gel is impregnated 5 The biomedical electrode, according to Claim 1, wherein ionically conductive medium comprises an ionically conductive pressure sensitive adhesive 6 The biomedical electrode, according to Claim 1 , wherein the electrically conductive tab is perforated and has a second electrically conductive surface wherein an electrical pathway exists between the first and the second electrically conductive surface 7 The biomedical electrode, according to Claim 1, wherein the electrically conductive tab is perforated and extends in different directions to provide at least two points of electrical contact to biomedical instrumentation 8 A biomedical electrode, comprising (a) a field of an ionically conductive medium and (b) an electrically conductive tab having an electrically conductive surface contacting the field of ionically conductive medium, wherein the electrically conductive tab is perforated and has a second electrically conductive surface wherein an electrical pathway exists between the first and second electrically conductive surface 9 A biomedical electrode, comprising (a) a field of an ionically conductive medium and (b) an electrically conductive tab having an electrically conductive surface contacting the field of ionically conductive medium, wherein the electrically conductive tab extends in different directions to provide at least two points of electrical contact to biomedical instrumentation

Inventors: CARIM HATIM M, CARIM, HATIM, M.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1996
Main classification: A61B5
IPC codes: A61B5, A61N1